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1. Study on Rollover Index and Stability for a Triaxle Bus
Zhilin Jin, Jingxuan Li, Yanjun Huang, Amir Khajepour
Chinese Journal of Mechanical Engineering    2019, 32 (4): 64-64.   DOI: 10.1186/s10033-019-0376-0
摘要138)      PDF(pc) (1818KB)(0)    收藏
Vehicle rollover, and its resulting fatalities, is an actively researched topic especially for multi-axle vehicles in the field of vehicle dynamics and control. This paper first presents a new rollover index for a triaxle bus to accurately evaluate its rollover possibility and then discusses the influence laws of the vehicle rollover dynamics to explore the mechanism of its stability. First, a six degree of freedom rollover model of the triaxle bus is developed, including lateral, yaw, roll motion of the sprung mass of the front/rear axle, and roll motion of the unsprung mass of the front/rear axle. Next, some key parameters of the vehicle rollover model are identified. A new rollover index is deduced according to the basics of vehicle dynamics, to predict vehicle rollover risk for the triaxle bus, which is verified by TruckSim. Furthermore, the influence laws of vehicle rollover dynamics by vehicle parameters and road parameters are discussed based on the simulation results. More importantly, the results show that the new method of modeling can precisely describe the rollover dynamics of the studied bus, and the proposed new index can effectively evaluate the rollover possibility. Therefore, this study provides a theoretical basis to improve anti-rollover ability for triaxle buses.
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2. Grinding Chatter Detection and Identifcation Based on BEMD and LSSVM
Huan-Guo Chen, Jian-Yang Shen, Wen-Hua Chen, Chun-Shao Huang, Yong-Yu Yi, Jia-Cheng Qian
Chinese Journal of Mechanical Engineering    2019, 32 (1): 1-1.   DOI: 10.1186/s10033-018-0313-7
摘要19)      PDF(pc) (1765KB)(0)    收藏
Grinding chatter is a self-induced vibration which is unfavorable to precision machining processes. This paper proposes a forecasting method for grinding state identification based on bivarition empirical mode decomposition (BEMD) and least squares support vector machine (LSSVM), which allows the monitoring of grinding chatter over time. BEMD is a promising technique in signal processing research which involves the decomposition of two-dimensional signals into a series of bivarition intrinsic mode functions (BIMFs). BEMD and the extraction criterion of its true BIMFs are investigated by processing a complex-value simulation chatter signal. Then the feature vectors which are employed as an amplification for the chatter premonition are discussed. Furthermore, the methodology is tested and validated by experimental data collected from a CNC guideway grinder KD4020X16 in Hangzhou Hangji Machine Tool Co., Ltd. The results illustrate that the BEMD is a superior method in terms of processing non-stationary and nonlinear signals. Meanwhile, the peak to peak, real-time standard deviation and instantaneous energy are proven to be effective feature vectors which reflect the different grinding states. Finally, a LSSVM model is established for grinding status classification based on feature vectors, giving a prediction accuracy rate of 96%.
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3. Remaining Useful Life Model and Assessment of Mechanical Products: A Brief Review and a Note on the State Space Model Method
Yawei Hu, Shujie Liu, Huitian Lu, Hongchao Zhang
Chinese Journal of Mechanical Engineering    2019, 32 (1): 15-15.   DOI: 10.1186/s10033-019-0317-y
摘要40)      PDF(pc) (1762KB)(0)    收藏
The remaining useful life (RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety (safety awareness and safety improvement). These studies incorporated many different models, algorithms, and techniques for modeling and assessment. In this paper, methods of RUL assessment are summarized and expounded upon using two major methods: physics model based and data driven based methods. The advantages and disadvantages of each of these methods are deliberated and compared as well. Due to the intricacy of failure mechanism in system, and difficulty in physics degradation observation, RUL assessment based on observations of performance variables turns into a science in evaluating the degradation. A modeling method from control systems, the state space model (SSM), as a first order hidden Markov, is presented. In the context of non-linear and non-Gaussian systems, the SSM methodology is capable of performing remaining life assessment by using Bayesian estimation (sequential Monte Carlo). Being effective for non-linear and non-Gaussian dynamics, the methodology can perform the assessment recursively online for applications in CBM (condition based maintenance), PHM (prognostics and health management), remanufacturing, and system performance reliability. Finally, the discussion raises concerns regarding online sensing data for SSM modeling and assessment of RUL.
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4. Modelling of the Infuence of Tool Runout on Surface Generation in Micro Milling
Wanqun Chen, Yazhou Sun, Dehong Huo, Xiangyu Teng
Chinese Journal of Mechanical Engineering    2019, 32 (1): 2-2.   DOI: 10.1186/s10033-019-0318-x
摘要22)      PDF(pc) (2668KB)(0)    收藏
Micro milling is a flexible and economical method to fabricate micro components with three-dimensional geometry features over a wide range of engineering materials. But the surface roughness and micro topography always limit the performance of the machined micro components. This paper presents a surface generation simulation in micro end milling considering both axial and radial tool runout. Firstly, a surface generation model is established based on the geometry of micro milling cutter. Secondly, the influence of the runout in axial and radial directions on the surface generation are investigated and the surface roughness prediction is realized. It is found that the axial runout has a significant influence on the surface topography generation. Furthermore, the influence of axial runout on the surface micro topography was studied quantitatively, and a critical axial runout is given for variable feed per tooth to generate specific surface topography. Finally, the proposed model is validated by means of experiments and a good correlation is obtained. The proposed surface generation model offers a basis for designing and optimizing surface parameters of functional machined surfaces.
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5. Infuence of Cross-Sectional Flow Area of Annular Volute Casing on Transient Characteristics of Ceramic Centrifugal Pump
Yi Tao, Shouqi Yuan, Jianrui Liu, Fan Zhang
Chinese Journal of Mechanical Engineering    2019, 32 (1): 4-4.   DOI: 10.1186/s10033-019-0319-9
摘要51)      PDF(pc) (3835KB)(0)    收藏
The annular volute is typically used in a slurry pump to reduce the collisions between solid particles and the volute tongue and to achieve a better resistance to blocking. However, only limited studies regarding annular volutes are available, and there is no systematic design method for annular volutes. In this study, the influence of volute casing cross-sectional flow area on the hydraulic loss, pressure pulsations, and radial force under varying working conditions in a centrifugal ceramic pump are discussed in detail. Experimental tests were conducted to validate the numerical results. The results indicated that, when the volute casing flow area increases, the hydraulic performance decreases marginally under the rated working conditions, but increases at the off-design points, specifically under large flow condition. However, the volute casing with a larger flow area has a wider high-efficiency region. In addition, the increase in the volute casing flow area will decrease the pressure pulsations in the volute, regardless of the working condition, and decrease the radial force on the shaft, therefore, providing an improved pump operational stability. It is anticipated that this study will be of benefit during the design of annular volutes.
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6. Broken Rotor Bar Fault Detection of Induction Motors Using a Joint Algorithm of Trust Region and Modifed Bare-bones Particle Swarm Optimization
Panpan Wang, Liping Shi, Yong Zhang, Yifan Wang, Li Han
Chinese Journal of Mechanical Engineering    2019, 32 (1): 10-10.   DOI: 10.1186/s10033-019-0325-y
摘要44)      PDF(pc) (1261KB)(0)    收藏
A precise detection of the fault feature parameter of motor current is a new research hotspot in the broken rotor bar (BRB) fault diagnosis of induction motors. Discrete Fourier transform (DFT) is the most popular technique in this field, owing to low computation and easy realization. However, its accuracy is often limited by the data window length, spectral leakage, fence effect, etc. Therefore, a new detection method based on a global optimization algorithm is proposed. First, a BRB fault current model and a residual error function are designed to transform the fault parameter detection problem into a nonlinear least-square problem. Because this optimization problem has a great number of local optima and needs to be resolved rapidly and accurately, a joint algorithm (called TR-MBPSO) based on a modified bare-bones particle swarm optimization (BPSO) and trust region (TR) is subsequently proposed. In the TR-MBPSO, a reinitialization strategy of inactive particle is introduced to the BPSO to enhance the swarm diversity and global search ability. Meanwhile, the TR is combined with the modified BPSO to improve convergence speed and accuracy. It also includes a global convergence analysis, whose result proves that the TR-MBPSO can converge to the global optimum with the probability of 1. Both simulations and experiments are conducted, and the results indicate that the proposed detection method not only has high accuracy of parameter estimation with short-time data window, e.g., the magnitude and frequency precision of the fault-related components reaches 10-4, but also overcomes the impacts of spectral leakage and non-integer-period sampling. The proposed research provides a new BRB detection method, which has enough precision to extract the parameters of the fault feature components.
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7. Structural Design and Dynamic Characteristics of Overloaded Horizontal Servo Cylinder for Resisting Dynamic Partial Load
Linan Ma, Qingxue Huang, Lifeng Ma, Qiangjun Ma, Wenze Zhang, Heyong Han
Chinese Journal of Mechanical Engineering    2019, 32 (1): 11-11.   DOI: 10.1186/s10033-019-0326-x
摘要32)      PDF(pc) (1481KB)(0)    收藏
When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly affects the frequency response and control accuracy of the servo cylinder. Based on this partial load, increased friction can lead to cylinder bore scuffing, leakage, lack of output power, or even system failure. In this paper, a novel asymmetric static-pressure support structure is proposed based on the principle of hydrostatic support. The radial component force of a dynamic partial load is balanced by cooperation between the support oil cushion of the variable hydraulic pressure support structure, oil cushion of the supportive force, and the damper. Adaptive control of the servo cylinder piston rod, guide sleeve, and piston, as well as the cylinder oil film friction between lubricated surfaces is achieved. In this paper, theoretical design and analysis of the traditional hydrostatic bearing structure and novel structure are presented. A hydraulic dynamic shear scissor is used as a research target to derive a structural dynamic model. Comparative simulations are performed using Matlab Simulink. Additionally, flow field analysis of the novel structure is performed, which verifies the rationality and feasibility of the proposed structure and system.
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8. A Novel Integrated Stability Control Based on Diferential Braking and Active Steering for Four-axle Trucks
Buyang Zhang, Changfu Zong, Guoying Chen, Yanjun Huang, Ting Xu
Chinese Journal of Mechanical Engineering    2019, 32 (1): 12-12.   DOI: 10.1186/s10033-019-0323-0
摘要25)      PDF(pc) (3741KB)(0)    收藏
Differential braking and active steering have already been integrated to overcome their shortcomings. However, existing research mainly focuses on two-axle vehicles and controllers are mostly designed to use one control method to improve the other. Moreover, many experiments are needed to improve the robustness; therefore, these control methods are underutilized. This paper proposes an integrated control system specially designed for multi-axle vehicles, in which the desired lateral force and yaw moment of vehicles are determined by the sliding mode control algorithm. The output of the sliding mode control is distributed to the suitable wheels based on the abilities and potentials of the two control methods. Moreover, in this method, fewer experiments are needed, and the robustness and simultaneity are both guaranteed. To simplify the optimization system and to improve the computation speed, seven simple optimization subsystems are designed for the determination of control outputs on each wheel. The simulation results show that the proposed controller obviously enhances the stability of multi-axle trucks. The system improves 68% of the safe velocity, and its performance is much better than both differential braking and active steering. This research proposes an integrated control system that can simultaneously invoke differential braking and active steering of multi-axle vehicles to fully utilize the abilities and potentials of the two control methods.
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9. Trajectory Tracking of Autonomous Vehicle with the Fusion of DYC and Longitudinal–Lateral Control
Fen Lin, Yaowen Zhang, Youqun Zhao, Guodong Yin, Huiqi Zhang, Kaizheng Wang
Chinese Journal of Mechanical Engineering    2019, 32 (1): 16-16.   DOI: 10.1186/s10033-019-0327-9
摘要52)      PDF(pc) (1934KB)(0)    收藏
The current research of autonomous vehicle motion control mainly focuses on trajectory tracking and velocity tracking. However, numerous studies deal with trajectory tracking and velocity tracking separately, and the yaw stability is seldom considered during trajectory tracking. In this research, a combination of the longitudinal-lateral control method with the yaw stability in the trajectory tracking for autonomous vehicles is studied. Based on the vehicle dynamics, considering the longitudinal and lateral motion of the vehicle, the velocity tracking and trajectory tracking problems can be attributed to the longitudinal and lateral control. A sliding mode variable structure control method is used in the longitudinal control. The total driving force is obtained from the velocity error in order to carry out velocity tracking. A linear time-varying model predictive control method is used in the lateral control to predict the required front wheel angle for trajectory tracking. Furthermore, a combined control framework is established to control the longitudinal and lateral motions and improve the reliability of the longitudinal and lateral direction control. On this basis, the driving force of a tire is allocated reasonably by using the direct yaw moment control, which ensures good yaw stability of the vehicle when tracking the trajectory. Simulation results indicate that the proposed control strategy is good in tracking the reference velocity and trajectory and improves the performance of the stability of the vehicle.
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10. Topological and Shape Optimization of Flexure Hinges for Designing Compliant Mechanisms Using the Level Set Method
Benliang Zhu, Xianmin Zhang, Min Liu, Qi Chen, Hai Li
Chinese Journal of Mechanical Engineering    2019, 32 (1): 13-13.   DOI: 10.1186/s10033-019-0332-z
摘要50)      PDF(pc) (1871KB)(0)    收藏
A flexure hinge is a major component in designing compliant mechanisms that offers unique possibilities in a wide range of application fields in which high positioning accuracy is required. Although various flexure hinges with different configurations have been successively proposed, they are often designed based on designers' experiences and inspirations. This study presents a systematic method for topological optimization of flexure hinges by using the level set method. Optimization formulations are developed by considering the functional requirements and geometrical constraints of flexure hinges. The functional requirements are first constructed by maximizing the compliance in the desired direction while minimizing the compliances in the other directions. The weighting sum method is used to construct an objective function in which a self-adjust method is used to set the weighting factors. A constraint on the symmetry of the obtained configuration is developed. Several numerical examples are presented to demonstrate the validity of the proposed method. The obtained results reveal that the design of a flexure hinge starting from the topology level can yield more choices for compliant mechanism design and obtain better designs that achieve higher performance.
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11. Safety Assessment of Aircraft Fuel Tank Access Cover under the Impact Load by Tire Fragments
Shile Yao, Zhufeng Yue, Xiaoliang Geng, Peiyan Wang
Chinese Journal of Mechanical Engineering    2019, 32 (1): 14-14.   DOI: 10.1186/s10033-019-0330-1
摘要25)      PDF(pc) (4074KB)(0)    收藏
According to relevant airworthiness standards, the aircraft fuel tank access cover must withstand the impact by tire fragments, and minimize the penetration and deformation, which is critical for flight safety. To assess the safety of an aircraft fuel tank access cover subjected to tire fragments, a study of dynamic response was presented in this paper using the Finite element (FE) software ANSYS/LS-DYNA. To obtain the reliable mechanical characteristics of tire tread rubber, a series of material tests have been conducted. Then the proposed rubber material model is validated by comparing the numerical simulations with the experimental results of aluminium alloy plate impact. The simulation results indicate that the rubber fragment and alloy plate will undergo the largest deformation when impact angle is equal to 90°. Finally, the proposed FE model and modelling approaches are extended to the numerical simulation of a full-scale aircraft fuel tank access cover impact. The numerical simulations are carried out with impact velocity of 71.1 m/s and impact angle of 40.5°. The simulation results indicate that the aluminium alloy by precision casting is more likely to rupture, and the middle region of the access cover is vulnerable to fragment impact. This research proposes a reliable rubber model applying to various strain rates. Considering the influence of impact regions, the dynamic response and various failure patterns of fuel tank access cover are acquired. The findings of this paper can be used to improve the future aircraft safety design.
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12. Unsteady Flow and Structural Behaviors of Centrifugal Pump under Cavitation Conditions
Denghao Wu, Yun Ren, Jiegang Mou, Yunqing Gu, Lanfang Jiang
Chinese Journal of Mechanical Engineering    2019, 32 (1): 17-17.   DOI: 10.1186/s10033-019-0328-8
摘要36)      PDF(pc) (2383KB)(0)    收藏
Cavitation has a significant effect on the flow fields and structural behaviors of a centrifugal pump. In this study, the unsteady flow and structural behaviors of a centrifugal pump are investigated numerically under different cavitation conditions. A strong two-way coupling fluid-structure interaction simulation is applied to obtain interior views of the effects of cavitating bubbles on the flow and structural dynamics of a pump. The renormalization-group k-ε turbulence model and the Zwart-Gerbe-Belamri cavitation model are solved for the fluid side, while a transient structural dynamic analysis is employed for the structure side. The different cavitation states are mapped in the head-net positive suction head (H-NPSH) curves and flow field features inside the impeller are fully revealed. Results indicate that cavitating bubbles grow and expand rapidly with decreasing NPSH. In addition, the pressure fluctuations, both in the impeller and volute, are quantitatively analyzed and associated with the cavitation states. It is shown that influence of the cavitation on the flow field is critical, specifically in the super-cavitation state. The effect of cavitation on the unsteady radial force and blade loads is also discussed. The results indicate that the averaged radial force increased from 8.5 N to 54.4 N in the transition progress from an onset cavitation state to a super-cavitation state. Furthermore, the structural behaviors, including blade deformation, stress, and natural frequencies, corresponding to the cavitation states are discussed. A large volume of cavitating bubbles weakens the fluid forces on the blade and decreases the natural frequencies of the rotor system. This study could enhance the understanding of the effects of cavitation on pump flow and structural behaviors.
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13. Effects of Flexibility and Suspension Configuration of Main Shaft on Dynamic Characteristics of Wind Turbine Drivetrain
Jianjun Tan, Caichao Zhu, Chaosheng Song, Huali Han, Yao Li
Chinese Journal of Mechanical Engineering    2019, 32 (2): 36-36.   DOI: 10.1186/s10033-019-0348-4
摘要21)      PDF(pc) (7231KB)(0)    收藏
The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attention is paid to the effects of these suspension configurations on the dynamic responses of wind turbine gearbox. This paper investigates the influences of suspension configurations of main shaft on the dynamic characteristics of drivetrain. For evaluating the dynamic behaviors of drivetrain with multi-stage transmission system more realistically, a dynamic modeling approach of drivetrain is proposed based on Timoshenko beam theory and Lagrange's equation. Considering the flexibility and different suspension configurations of main shaft, time-varying mesh stiffness excitation, time-varying transmission error excitation and gravity excitation, etc., a three-dimensional dynamic model of drivetrain is developed, and the dynamic responses of drivetrain are investigated. Results show that with the one-point suspension of main shaft, the resonance frequencies in gearbox, especially at the low-speed stage, obviously shift to the higher frequency range compared to the gearbox without main shaft, but this trend could be inversed by increasing main shaft length. Meanwhile, the loads in main shaft, main shaft bearing and carrier bearing are greatly sensitive to the main shaft length. Hence, the load sharing is further disrupted by main shaft, but this effect could be alleviated by larger load torque. Comparing to the one-point suspension of main shaft, there occurs the obvious load reduction at the low-speed stage with two-point suspension of main shaft. However, those advantages greatly depend on the distance between two main bearings, and come at the expense of increased load in upwind main shaft unit and the corresponding main bearing. Finally, a wind field test is conducted to verify the proposed drivetrain model. This study develops a numerical model of drivetrain which is able to evaluate the effects of different suspension configurations of main shaft on gearbox.
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14. Vibration Performance Analysis of a Mining Vehicle with Bounce and Pitch Tuned Hydraulically Interconnected Suspension
Jie Zhang, Yuanwang Deng, Nong Zhang, Bangji Zhang, Hengmin Qi, Minyi Zheng
Chinese Journal of Mechanical Engineering    2019, 32 (1): 5-5.   DOI: 10.1186/s10033-019-0315-0
摘要29)      PDF(pc) (1546KB)(0)    收藏
The current investigations primarily focus on using advanced suspensions to overcome the tradeoff design of ride comfort and handling performance for mining vehicles. It is generally realized by adjusting spring stiffness or damping parameters through active control methods. However, some drawbacks regarding control complexity and uncertain reliability are inevitable for these advanced suspensions. Herein, a novel passive hydraulically interconnected suspension (HIS) system is proposed to achieve an improved ride-handling compromise of mining vehicles. A lumped-mass vehicle model involved with a mechanical-hydraulic coupled system is developed by applying the free-body diagram method. The transfer matrix method is used to derive the impedance of the hydraulic system, and the impedance is integrated to form the equation of motions for a mechanical-hydraulic coupled system. The modal analysis method is employed to obtain the free vibration transmissibilities and force vibration responses under different road excitations. A series of frequency characteristic analyses are presented to evaluate the isolation vibration performance between the mining vehicles with the proposed HIS and the conventional suspension. The analysis results prove that the proposed HIS system can effectively suppress the pitch motion of sprung mass to guarantee the handling performance, and favorably provide soft bounce stiffness to improve the ride comfort. The distribution of dynamic forces between the front and rear wheels is more reasonable, and the vibration decay rate of sprung mass is increased effectively. This research proposes a new suspension design method that can achieve the enhanced cooperative control of bounce and pitch motion modes to improve the ride comfort and handling performance of mining vehicles as an effective passive suspension system.
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15. Application of Instantaneous Rotational Speed to Detect Gearbox Faults Based on Double Encoders
Lin Liang, Fei Liu, Xiangwei Kong, Maolin Li, Guanghua Xu
Chinese Journal of Mechanical Engineering    2019, 32 (1): 9-9.   DOI: 10.1186/s10033-019-0324-z
摘要22)      PDF(pc) (2477KB)(0)    收藏
Considerable studies have been carried out on fault diagnosis of gears, with most of them concentrated on conventional vibration analysis. However, besides the complexity of gear dynamics, the diagnosis results in terms of vibration signal are easily misjudged owing to the interference of sensor position or other components. In this paper, an alternative gearbox fault detection method based on the instantaneous rotational speed is proposed because of its advantages over vibration analysis. Depending on the timer/counter-based method for the pulse signal of the optical encoder, the varying rotational speed can be obtained effectively. Owing to the coupling and meshing of gears in transmission, the excitations are the same for the instantaneous rotational speed of the input and output shafts. Thus, the differential signal of instantaneous rotational speeds can be adopted to eliminate the effect of the interference excitations and extract the associated feature of the localized fault effectively. With the experiments on multistage gearbox test system, the differential signal of instantaneous speeds is compared with other signals. It is proved that localized faults in the gearbox generate small angular speed fluctuations, which are measurable with an optical encoder. Using the differential signal of instantaneous speeds, the fault characteristics are extracted in the spectrum where the deterministic frequency component and its harmonics corresponding to crack fault characteristics are displayed clearly.
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16. On Generating Expected Kinetostatic Nonlinear Stiffness Characteristics by the Kinematic Limb-Singularity of a Crank-Slider Linkage with Springs
Baokun Li, Guangbo Hao
Chinese Journal of Mechanical Engineering    2019, 32 (3): 54-54.   DOI: 10.1186/s10033-019-0369-z
摘要112)      PDF(pc) (3671KB)(0)    收藏
Being different from avoidance of singularity of closed-loop linkages, this paper employs the kinematic singularity to construct compliant mechanisms with expected nonlinear stiffness characteristics to enrich the methods of compliant mechanisms synthesis. The theory for generating kinetostatic nonlinear stiffness characteristic by the kinematic limb-singularity of a crank-slider linkage is developed. Based on the principle of virtual work, the kinetostatic model of the crank-linkage with springs is established. The influences of spring stiffness on the toque-position angle relation are analyzed. It indicates that corresponding spring stiffness may generate one of four types of nonlinear stiffness characteristics including the bi-stable, local negative-stiffness, zero-stiffness or positive-stiffness when the mechanism works around the kinematic limb-singularity position. Thus the compliant mechanism with an expected stiffness characteristic can be constructed by employing the pseudo rigid-body model of the mechanism whose joints or links are replaced by corresponding flexures. Finally, a tri-symmetrical constant-torque compliant mechanism is fabricated, where the curve of torque-position angle is obtained by an experimental testing. The measurement indicates that the compliant mechanism can generate a nearly constant-torque zone.
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17. Analysis of the Internal Characteristics of a Deflector Jet Servo Valve
Hao Yan, Yukai Ren, Lei Yao, Lijing Dong
Chinese Journal of Mechanical Engineering    2019, 32 (2): 31-31.   DOI: 10.1186/s10033-019-0345-7
摘要34)      PDF(pc) (3760KB)(0)    收藏
In current research on deflector jet servo valves, the receiver pressure estimated using traditional two-dimensional simulation and theoretical calculation is always lower than the experimental data; therefore, credible information about the flow field in the prestage part of the valve can hardly be obtained. To investigate this issue and understand the internal characteristics of the deflector jet valve, a realistic numerical model is constructed and a three-dimensional simulation carried out that displays a complex flow pattern in the deflector jet structure. Then six phases of the flow pattern are presented, and the defects of the two-dimensional simulation are revealed. Based on the simulation results, it is found that the jet in the deflector has a longer core area and the fluid near the shunt wedge cannot resist the impact of the high-speed fluid. Therefore, two assumptions about the flow distribution are presented by which to construct a more complete theoretical model. The receiver pressure and prestage pressure gain are significantly enhanced in the calculations. Finally, special experiments on the prestage of the servo valve are performed, and the pressure performance of the numerical simulation and the theoretical calculation agree well with the experimental data. Finally, the internal mechanism described by the theoretical and numerical models is verified. From this research, more accurate numerical and theoretical models are proposed by which to figure out the internal characteristics of the deflector jet valve.
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18. Force Analysis and Curve Design for Laying Pipe in Loop Laying Head of Wire Rod Mills
Shuangji Yao, Marco Ceccarelli, Giuseppe Carbone, Bin Ma
Chinese Journal of Mechanical Engineering    2019, 32 (2): 32-32.   DOI: 10.1186/s10033-019-0344-8
摘要23)      PDF(pc) (2921KB)(0)    收藏
Laying head is a high-precision engineering device in hot-rolled high speed wire rod production line. Previously research works are focused on the laying pipe wear-resisting. Laying pipe curve design method based on wire rod kinematics and dynamics analyses are not reported before. In order to design and manufacture the laying pipe, the motion and force process of the wire rod in the laying pipe should be studied. In this paper, a novel approach is proposed to investigate the force modeling for hot-rolled wire rod in laying pipe. An idea of limited element method is used to analysis and calculates the forces between laying pipe inner surface and wire rod. The design requirements of laying pipe curve for manufacturing are discussed. The kinematics and dynamics modeling for numerical calculation are built. A laying pipe curve equation is proposed by discussing design boundary conditions. Numerical results with different laying pipe curves design parameters are plotted and compared. The proposed approach performs good result which can be applied for laying pipe curve design and analysis for engineering application.
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19. Reliability and Availability Models of Belt Drive Systems Considering Failure Dependence
Peng Gao, Liyang Xie, Jun Pan
Chinese Journal of Mechanical Engineering    2019, 32 (2): 30-30.   DOI: 10.1186/s10033-019-0342-x
摘要21)      PDF(pc) (2356KB)(0)    收藏
Conventional reliability models of belt drive systems in the failure mode of fatigue are mainly based on the static stress strength interference model and its extended models, which cannot consider dynamic factors in the operational duration and be used for further availability analysis. In this paper, time-dependent reliability models, failure rate models and availability models of belt drive systems are developed based on the system dynamic equations with the dynamic stress and the material property degradation taken into account. In the proposed models, dynamic failure dependence and imperfect maintenance are taken into consideration. Furthermore, the issue of time scale inconsistency between system failure rate and system availability is proposed and addressed in the proposed system availability models. Besides, Monte Carlo simulations are carried out to validate the established models. The results from the proposed models and those from the Monte Carlo simulations show a consistency. Furthermore, the case studies show that the failure dependence, imperfect maintenance and the time scale inconsistency have significant influences on system availability. The independence assumption about the belt drive systems results in underestimations of both reliability and availability. Moreover, the neglect of the time scale inconsistency causes the underestimate of the system availability. Meanwhile, these influences show obvious time-dependent characteristics.
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20. Development and Analysis of the Magnetic Circuit on Double-Radial Permanent Magnet and Salient-Pole Electromagnetic Hybrid Excitation Generator for Vehicles
Xueyi Zhang, Qinjun Du, Jinbin Xu, Yuzhen Zhao, Shilun Ma
Chinese Journal of Mechanical Engineering    2019, 32 (2): 33-33.   DOI: 10.1186/s10033-019-0334-x
摘要22)      PDF(pc) (2005KB)(0)    收藏
With the improvement of vehicles electrical equipment, the existing silicon rectification generator and permanent magnet generator cannot meet the requirement of the electric power consumption of the modern vehicles electrical equipment. It is difficult to adjust the air gap magnetic field of the permanent magnet generator. Consequently, the output voltage is not stable. The silicon rectifying generator has the problems of low efficiency and high failure rate. In order to solve these problems, a new type of hybrid excitation generator is developed in this paper. The developed hybrid excitation generator has a double-radial permanent magnet, a salient-pole electromagnetic combined rotor, and a fractional slot winding stator, where each rotor pole corresponds to 4.5 stator teeth. The equivalent magnetic circuit diagram of permanent magnet rotor and magnetic rotor is established. Magnetic field finite element analysis (FEA) software is used to conduct the modeling and simulation analysis on double-radial permanent magnet magnetic field, salient-pole electro-magnetic magnetic field and hybrid magnetic field. The magnetic flux density mold value diagram and vector diagram are obtained. The diagrams are used to verify the feasibility of this design. The designed electromagnetic coupling regulator controller can ensure the stable voltage export by changing the magnitude and direction of the excitation current to adjust the size of the air gap magnetic field. Therefore, the problem of output voltage instability in the wide speed range and wide load range of the hybrid excitation generator is solved.
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21. Indirect Adaptive Robust Trajectory Tracking Control of Hard Rock TBM with Load Variation of Tunneling Face
Chengjun Shao, Jianfeng Liao, Zhitao Liu, Hongye Su
Chinese Journal of Mechanical Engineering    2019, 32 (2): 34-34.   DOI: 10.1186/s10033-019-0347-5
摘要29)      PDF(pc) (2810KB)(0)    收藏
Posture adjustment of open-type hard rock tunnel boring machine (TBM) can be achieved by properly adjusting the hydraulic pressure of gripper cylinder and torque cylinders. However, the time-varying inhomogeneous load acting on tunneling face of TBM and complex stratum working condition can cause the trajectory deviation. In this paper, the position and posture rectification kinematics and dynamics models of TBM have been established in order to track the trajectory. Moreover, there are uncertain parameters and uncertain loads from complex working conditions in the dynamic model. An indirect adaptive robust control strategy is applied to achieve precise position and posture trajectory tracking control. Simulation results show when the position deviation only occurs in Y-axis and the current orientation is parallel with the designed axis, the deviation can be corrected by controlling the pressure of gripper cylinder and the actual trajectory meets the designed axis when TBM is pushed forward 0.14 m in X-axis. If the deviation only occurs in Z-axis, then the deviation can be corrected by controlling torque cylinders. If the position deviation occurs both in Y-axis and Z-axis at the same time, the pressure of gripper cylinder and torque cylinders should be controlled at the same time to rectify the deviation. Simulation results are shown to illustrate the effectiveness and robustness of the proposed controller. This research proposes an indirect adaptive robust controller that can track the planned tracking trajectory smoothly and rapidly.
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22. Frequency Loss and Recovery in Rolling Bearing Fault Detection
Aijun Hu, Ling Xiang, Sha Xu, Jianfeng Lin
Chinese Journal of Mechanical Engineering    2019, 32 (2): 35-35.   DOI: 10.1186/s10033-019-0349-3
摘要25)      PDF(pc) (3115KB)(0)    收藏
Rolling element bearings are key components of mechanical equipment. The bearing fault characteristics are afected by the interaction in the vibration signals. The low harmonics of the bearing characteristic frequencies cannot be usually observed in the Fourier spectrum. The frequency loss in the bearing vibration signal is presented through two independent experiments in this paper. The existence of frequency loss phenomenon in the low frequencies, side band frequencies and resonant frequencies and revealed. It is demonstrated that the lost frequencies are actually suppressed by the internal action in the bearing fault signal rather than the external interference. The amplitude and distribution of the spectrum are changed due to the interaction of the bearing fault signal. The interaction mechanism of bearing fault signal is revealed through theoretical and practical analysis. Based on mathematical morphology, a new method is provided to recover the lost frequencies. The multi-resonant response signal of the defective bearing are decomposed into low frequency and high frequency response, and the lost frequencies are recovered by the combination morphological flter (CMF). The efectiveness of the proposed method is validated on simulated and experimental data.
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23. Type Synthesis of Lower Mobility Parallel Mechanisms: A Review
Wei Ye, Qinchuan Li
Chinese Journal of Mechanical Engineering    2019, 32 (2): 38-38.   DOI: 10.1186/s10033-019-0350-x
摘要35)      PDF(pc) (1087KB)(0)    收藏
Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on different theories were proposed for type synthesis of lower mobility parallel mechanisms in past decades. However, there does not exist a comprehensive review on these approaches. Therefore, the goal of this paper is to give such a review, classifying the approaches proposed in the literature into three groups, namely, motion-based methods, constraint-based methods, and other methods. The motion-based methods include the Lie group based method, the GF set method, the linear transformation method, the POC set method, and the finite screw method. The constraint-based methods involve the screw theory-based method, the virtual chain method, the method based on Grassmann line geometry and line graphs, and the motion constraint generator method. Other methods contain the enumeration approach based on the general CGK mobility formula and the graph theory method. Upon thoroughly analyzing the characteristics and/or limitations of each method, this review provides a well reference to help researchers find an effective synthesis method for innovative design and further scientific investigations for mechanisms.
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24. Experimental Study on Influences of Surface Materials on Cavitation Flow Around Hydrofoils
Jiafeng Hao, Mindi Zhang, Xu Huang
Chinese Journal of Mechanical Engineering    2019, 32 (3): 45-45.   DOI: 10.1186/s10033-019-0355-5
摘要25)      PDF(pc) (2945KB)(0)    收藏
In order to resist on the cavitation erosion, many researchers try to change the solidity and tenacity of the coatings, but ignore the influence of surface characteristics of materials on cavitation flow and the interaction with each other. In this paper, high speed visualization system is used to observe the cavitation flow patterns in different stage. After comparing the characteristics of cavitation flow around hydrofoils made of aluminum (Foil A), stainless steel (Foil B) and the hydrofoil painted with epoxy coating (Foil C), the study shows that material has a significant effect on the cavitation flow. Firstly, when the incipient cavitation occurs, cavitation number of Foil A is highest among three hydrofoils, generating horseshoe vortex randomly. For Foil B and Foil C, it shows in the form of free bubbles. When the sheet cavitation occurs, Foil A has the highest cavitation number and shortest period, which is contrary to Foil C. And cavity consists of lots of small finger-like cavities. For Foil B and Foil C, it both constitutes with many bubbles. Compared with the high-density and small-scale cavities over surface of Foil C, the cavity of Foil B has larger scale and less density, which causes a minimal scope of influence of the re-entrant jet and strong randomness. When the cloud cavitation occurs, Foil C has the lowest cavitation number and shortest period. Secondly, compared with aluminum, both of stainless steel and epoxy coating restrains the occurrence and development of cavitation, and stainless steel and epoxy coating performs better than aluminum. For inception and sheet cavitation, stainless steel performs better than epoxy coating and aluminum. For cloud cavitation, epoxy coating performs better than stainless steel and aluminum. The objective of this paper is applied experimental method to investigate the effect of surface materials on cavitation around Clark-Y hydrofoils.
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25. Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data
Guangxue Yang, Meng Wang, Qiang Li, Ran Ding
Chinese Journal of Mechanical Engineering    2019, 32 (3): 51-51.   DOI: 10.1186/s10033-019-0365-3
摘要19)      PDF(pc) (2087KB)(0)    收藏
The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.
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26. Modified Pre-stretching Assembly Method for Cable-Driven Systems
Guokai Zhang, Xuyang Ren, Jinhua Li, Kang Kong, Shuxin Wang, Jingchao Shen
Chinese Journal of Mechanical Engineering    2019, 32 (3): 48-48.   DOI: 10.1186/s10033-019-0362-6
摘要17)      PDF(pc) (1615KB)(0)    收藏
Soft cable-driven systems have been employed in many assembled mechanisms, such as industrial robots, parallel kinematic mechanism machines, medical devices, and humaniform hands. A pre-stretching process is necessary to guarantee the quality of cable-driven systems during the assembly process. However, the stress relaxation of cables becomes a critical concern during long-term operation. This study investigates the effects of non-uniform deformation and long-term stress relaxation of the driven cables owing to moving parts in the system. A simple closed-loop cable-driven system is built and an alternating load is applied to it to replicate the operation of transmission cables. Under different experimental conditions, the cable tension is recorded and the boundary data are selected to be curve-fitted. Based on the fitted results, a formula is presented to estimate the stress relaxation of cables to evaluate the assembly performance. Further experimental results show that the stress relaxation is mainly caused by cable creep and the assembly procedure. To remove the influence of the assembly procedure, a modified pre-stretching assembly method based on the stress relaxation theory is proposed and verification experiments are performed. Finally, the assembly performance is optimized using a cable-driven surgical robot as an example. This paper proposes a dual stretching method instead of the pre-stretching method to assemble the cable-driven system to improve its performance and prolong its service life.
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27. Design and Manufacturing Strategies for Fused Deposition Modelling in Additive Manufacturing: A Review
Hugo I. Medellin-Castillo, Jorge Zaragoza-Siqueiros
Chinese Journal of Mechanical Engineering    2019, 32 (3): 53-53.   DOI: 10.1186/s10033-019-0368-0
摘要32)      PDF(pc) (1654KB)(0)    收藏
Although several research works in the literature have focused on studying the capabilities of additive manufacturing(AM) systems, few works have addressed the development of Design for Additive Manufacturing (DfAM) knowledge, tools, rules, and methodologies, which has limited the penetration and impact of AM in industry. In this paper acomprehensive review of design and manufacturing strategies for Fused Deposition Modelling (FDM) is presented.Consequently, several DfAM strategies are proposed and analysed based on existing research works and the operation principles, materials, capabilities and limitations of the FDM process. These strategies have been divided into fourmain groups: geometry, quality, materials and sustainability. The implementation and practicality of the proposedDfAM is illustrated by three case studies. The new proposed DfAM strategies are intended to assist designers andmanufacturers when making decisions to satisfy functional needs, while ensuring manufacturability in FDM systems.Moreover, many of these strategies can be applied or extended to other AM processes besides FDM.
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28. Effect of Heat Sink and Cooling Mediums on Ferrite Austenite Ratio and Distortion in Laser Welding of Duplex Stainless Steel 2205
P. Dinesh Babu, P. Gouthaman, P. Marimuthu
Chinese Journal of Mechanical Engineering    2019, 32 (3): 50-50.   DOI: 10.1186/s10033-019-0363-5
摘要9)      PDF(pc) (1682KB)(0)    收藏
In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.
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29. Crosswind Stability Evaluation of High-Speed Train Using Different Wind Models
Mengge Yu, Rongchao Jiang, Qian Zhang, Jiye Zhang
Chinese Journal of Mechanical Engineering    2019, 32 (3): 40-40.   DOI: 10.1186/s10033-019-0353-7
摘要15)      PDF(pc) (2166KB)(0)    收藏
Different wind models are being used for the operational safety evaluation of a high-speed train exposed to crosswinds. However, the methodology for simulating natural wind is of substantial importance in the wind-train system, and different simplified forms of natural wind result in different levels of accuracy. The purpose of the research in this paper is to investigate the effects of different wind models on the operational safety evaluation of high-speed trains. First, three wind models, namely, steady wind model, gust wind model, and turbulent wind model, are constructed. Following this, the algorithms for computing the aerodynamic loads using the wind models are described. A multi-body dynamic model of a vehicle is then set up using the commercial software "Simpack" for investigating the dynamic behavior of a railway vehicle exposed to wind loads. The rollover risks corresponding to each wind model are evaluated by applying the definition of characteristic wind curves (CWC). The results indicate that the CWC computed using the gust wind model is marginally higher than that computed using the turbulent wind model; the difference is less than 1%. With regard to the steady wind model, the assurance coefficient substantially affects the final CWC. A reasonable agreement of CWC between the steady wind model and turbulent wind model can be obtained by applying an "appropriate value" of the assurance coefficient. This study included a systematic analysis of the operational safety evaluation results using different wind models; the analysis can serve as a reference basis for different engineering accuracy requirements.
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30. Symmetric Equations for Evaluating Maximum Torsion Stress of Rectangular Beams in Compliant Mechanisms
Gui-Min Chen, Larry L.Howell
Chinese Journal of Mechanical Engineering    2018, 31 (1): 14-14.   DOI: 10.1186/s10033-018-0214-9
摘要27)      PDF(pc) (1567KB)(0)    收藏
There are several design equations available for calculating the torsional compliance and the maximum torsion stress of a rectangular cross-section beam, but most depend on the relative magnitude of the two dimensions of the crosssection (i.e., the thickness and the width). After reviewing the available equations, two thickness-to-width ratio independent equations that are symmetric with respect to the two dimensions are obtained for evaluating the maximum torsion stress of rectangular cross-section beams. Based on the resulting equations, outside lamina emergent torsional joints are analyzed and some useful design insights are obtained. These equations, together with the previous work on symmetric equations for calculating torsional compliance, provide a convenient and efective way for designing and optimizing torsional beams in compliant mechanisms.
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31. Fuzzy Sliding Mode Control for the Vehicle Height and Leveling Adjustment System of an Electronic Air Suspension
Xiao-Qiang Sun, Ying-Feng Cai, Chao-Chun Yuan, Shao-Hua Wang, Long Chen
Chinese Journal of Mechanical Engineering    2018, 31 (2): 25-25.   DOI: 10.1186/s10033-018-0223-8
摘要22)      PDF(pc) (2351KB)(0)    收藏
The accurate control for the vehicle height and leveling adjustment system of an electronic air suspension (EAS) still is a challenging problem that has not been effectively solved in prior researches. This paper proposes a new adaptive controller to control the vehicle height and to adjust the roll and pitch angles of the vehicle body (leveling control) during the vehicle height adjustment procedures by an EAS system. A nonlinear mechanism model of the full-car vehicle height adjustment system is established to reflect the system dynamic behaviors and to derive the system optimal control law. To deal with the nonlinear characters in the vehicle height and leveling adjustment processes, the nonlinear system model is globally linearized through the state feedback method. On this basis, a fuzzy sliding mode controller (FSMC) is designed to improve the control accuracy of the vehicle height adjustment and to reduce the peak values of the roll and pitch angles of the vehicle body. To verify the effectiveness of the proposed control method more accurately, the full-car EAS system model programmed using AMESim is also given. Then, the co-simulation study of the FSMC performance can be conducted. Finally, actual vehicle tests are performed with a city bus, and the test results illustrate that the vehicle height adjustment performance is effectively guaranteed by the FSMC, and the peak values of the roll and pitch angles of the vehicle body during the vehicle height adjustment procedures are also reduced significantly. This research proposes an effective control methodology for the vehicle height and leveling adjustment system of an EAS, which provides a favorable control performance for the system.
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32. Type Synthesis of Walking Robot Legs
Da Xi, Feng Gao
Chinese Journal of Mechanical Engineering    2018, 31 (1): 15-15.   DOI: 10.1186/s10033-018-0216-7
摘要20)      PDF(pc) (2009KB)(0)    收藏
Walking robots use leg structures to overcome obstacles or move on complicated terrains. Most robots of current researches are equipped with legs of simple structure. The specifc design method of walking robot legs is seldom studied. Based on the generalized-function (GF) set theory, a systematic type synthesis process of designing robot legs is introduced. The specifc mobility of robot legs is analyzed to obtain two main leg types as the goal of design. Number synthesis problem is decomposed into two stages, actuation and constraint synthesis by name, corresponding to the combinatorics results of linear Diophantine equations. Additional restrictions are discussed to narrow the search range to propose practical limb expressions and kinematic-pair designs. Finally, all the ffty-one leg structures of four subtypes are carried out, some of which are chosen to make up robot prototypes, demonstrating the validity of the method. This paper proposed a novel type synthesis methodology, which could be used to systematically design various practical robot legs and the derived robots.
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33. Active Profling and Polishing Model and Validation Based on Rotor Spiral Groove
Guo Yu, Feng Li, Yong-Min Yu, Shou-Xiang Zai
Chinese Journal of Mechanical Engineering    2018, 31 (2): 28-28.   DOI: 10.1186/s10033-018-0225-6
摘要23)      PDF(pc) (2163KB)(0)    收藏
When a spiral groove is formed using superplastic molding, precision casting, additive manufacturing, or other non-mechanical processing technology, it is difficult to meet the molding precision required for direct use, and the surface quality and accuracy of the shape need to be improved through a finishing process. In view of the poor reachability of the current tool-based polishing process, a tool-less polishing method using free-abrasive grains for complex spiral grooves is proposed. With this method, by controlling the movement of the workpiece, the design basis and relative motion of the abrasive particles along a helical path remain consistent, resulting in a better polishing profile. A spiral groove of a revolving body is taken as the research object; the influence of the installation method and the position of the parts, as well as the effect of the rotational speed of the abrasive ball on its relative motion along a helical trajectory, are studied, and the polishing cutting process of an abrasive ball is reasonably simplified. A consistent mathematical model of the trajectory of an abrasive ball relative to the design helix is constructed. The grooved drum parts are verified through a polishing experiment. The spiral groove of the revolving body is modified and polished. Experiments show that the process not only corrects the shape a spiral groove error, but also reduces the surface roughness of a spiral groove. This study provides a theoretical basis for achieving free-abrasive, tool-free polishing.
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34. Conclusions in Theory and Practice for Advancing the Applications of Cable-Driven Mechanisms
Bin Zi, Yuan Li
Chinese Journal of Mechanical Engineering    2017, 30 (4): 763-765.   DOI: 10.1007/s10033-017-0148-7
摘要21)      PDF(pc) (3087KB)(0)    收藏
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35. Advances in Valveless Piezoelectric Pump with Cone-shaped Tubes
Jian-Hui Zhang, Ying Wang, Jun Huang
Chinese Journal of Mechanical Engineering    2017, 30 (4): 766-781.   DOI: 10.1007/s10033-017-0151-z
摘要34)      PDF(pc) (12769KB)(0)    收藏
This paper reviews the development of valveless piezoelectric pump with cone-shaped tube chronologically, which have widely potential application in biomedicine and micro-electro-mechanical systems because of its novel principles and deduces the research direction in the future. Firstly, the history of valveless piezoelectric pumps with cone-shaped tubes is reviewed and these pumps are classified into the following types: single pump with solid structure or plane structure, and combined pump with parallel structure or series structure. Furthermore, the function of each type of cone-shaped tubes and pump structures are analyzed, and new directions of potential expansion of valveless piezoelectric pumps with cone-shaped tubes are summarized and deduced. The historical argument, which is provided by the literatures, that for a valveless piezoelectric pump with cone-shaped tubes, cone angle determines the flow resistance and the flow resistance determines the flow direction. The argument is discussed in the reviewed pumps one by one, and proved to be convincing. Finally, it is deduced that bionics is pivotal in the development of valveless piezoelectric pump with cone-shaped tubes from the perspective of evolution of biological structure. This paper summarizes the current valveless piezoelectric pumps with cone-shaped tubes and points out the future development, which may provide guidance for the research of piezoelectric actuators.
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36. Comprehensive Overview on Computational Intelligence Techniques for Machinery Condition Monitoring and Fault Diagnosis
Wan Zhang, Min-Ping Jia, Lin Zhu, Xiao-An Yan
Chinese Journal of Mechanical Engineering    2017, 30 (4): 782-795.   DOI: 10.1007/s10033-017-0150-0
摘要36)      PDF(pc) (3067KB)(0)    收藏
Computational intelligence is one of the most powerful data processing tools to solve complex nonlinear problems, and thus plays a significant role in intelligent fault diagnosis and prediction. However, only few comprehensive reviews have summarized the ongoing efforts of computational intelligence in machinery condition monitoring and fault diagnosis. The recent research and development of computational intelligence techniques in fault diagnosis, prediction and optimal sensor placement are reviewed. The advantages and limitations of computational intelligence techniques in practical applications are discussed. The characteristics of different algorithms are compared, and application situations of these methods are summarized. Computational intelligence methods need to be further studied in deep understanding algorithm mechanism, improving algorithm efficiency and enhancing engineering application. This review may be considered as a useful guidance for researchers in selecting a suitable method for a specific situation and pointing out potential research directions.
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37. Load Sharing Behavior of Star Gearing Reducer for Geared Turbofan Engine
Shuai MO, Yidu ZHANG, Qiong WU, Feiming WANG, Shigeki MATSUMURA, Haruo HOUJOH
Chinese Journal of Mechanical Engineering    2017, 30 (4): 796-803.   DOI: 10.1007/s10033-017-0096-2
摘要22)      PDF(pc) (6920KB)(0)    收藏
Load sharing behavior is very important for power-split gearing system, star gearing reducer as a new type and special transmission system can be used in many industry fields. However, there is few literature regarding the key multiple-split load sharing issue in main gearbox used in new type geared turbofan engine. Further mechanism analysis are made on load sharing behavior among star gears of star gearing reducer for geared turbofan engine. Comprehensive meshing error analysis are conducted on eccentricity error, gear thickness error, base pitch error, assembly error, and bearing error of star gearing reducer respectively. Floating meshing error resulting from meshing clearance variation caused by the simultaneous floating of sun gear and annular gear are taken into account. A refined mathematical model for load sharing coefficient calculation is established in consideration of different meshing stiffness and supporting stiffness for components. The regular curves of load sharing coefficient under the influence of interactions, single action and single variation of various component errors are obtained. The accurate sensitivity of load sharing coefficient toward different errors is mastered. The load sharing coefficient of star gearing reducer is 1.033 and the maximum meshing force in gear tooth is about 3010 N. This paper provides scientific theory evidences for optimal parameter design and proper tolerance distribution in advanced development and manufacturing process, so as to achieve optimal effects in economy and technology.
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38. Numerical Prediction of Tip Vortex Cavitation for Marine Propellers in Non-uniform Wake
Zhi-Feng Zhu, Fang Zhou, Dan Li
Chinese Journal of Mechanical Engineering    2017, 30 (4): 804-818.   DOI: 10.1007/s10033-017-0145-x
摘要15)      PDF(pc) (10479KB)(0)    收藏
Tip vortex cavitation is the first type of cavitation to take place around most marine propellers. But the numerical prediction of tip vortex cavitation is one of the challenges for propeller wake because of turbulence dissipation during the numerical simulation. Several parameters of computational mesh and numerical algorithm are tested by mean of the predicted length of tip vortex cavtiation to validate a developed method. The predicted length of tip vortex cavtiation is on the increase about 0.4 propeller diameters using the developed numerical method. The predicted length of tip vortex cavtiation by RNG k - ε model is about 3 times of that by SST k - ω model. Therefore, based on the validation of the present approach, the cavitating flows generated by two rotating propellers under a non-uniform inflow are calculated further. The distributions of axial velocity, total pressure and vapor volume fraction in the transversal planes across tip vortex region are shown to be useful in analyzing the feature of the cavitating flow. The strongest kernel of tip vortex cavitation is not at the position most close to blade tip but slightly far away from the region. During the growth of tip vortex cavitation extension, it appears short and thick, and then it becomes long and thin. The pressure fluctuations at the positions inside tip vortex region also validates the conclusion. A key finding of the study is that the grids constructed especially for tip vortex flows by using separated computational domain is capable of decreasing the turbulence dissipation and correctly capturing the feature of propeller tip vortex cavitation under uniform and non-uniform inflows. The turbulence model and advanced grids is important to predict tip vortex cavitation.
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39. Impact Fretting Wear Behavior of Alloy 690 Tubes in Dry and Deionized Water Conditions
Zhen-Bing Cai, Jin-Fang Peng, Hao Qian, Li-Chen Tang, Min-Hao Zhu
Chinese Journal of Mechanical Engineering    2017, 30 (4): 819-828.   DOI: 10.1007/s10033-017-0147-8
摘要18)      PDF(pc) (34831KB)(0)    收藏
The impact fretting wear has largely occurred at nuclear power device induced by the flow-induced vibration, and it will take potential hazards to the service of the equipment. However, the present study focuses on the tangential fretting wear of alloy 690 tubes. Research on impact fretting wear of alloy 690 tubes is limited and the related research is imminent. Therefore, impact fretting wear behavior of alloy 690 tubes against 304 stainless steels is investigated. Deionized water is used to simulate the flow environment of the equipment, and the dry environment is used for comparison. Varied analytical techniques are employed to characterize the wear and tribochemical behavior during impact fretting wear. Characterization results indicate that cracks occur at high impact load in both water and dry equipment; however, the water as a medium can significantly delay the cracking time. The crack propagation behavior shows a jagged shape in the water, but crack extended disorderly in dry equipment because the water changed the stress distribution and retarded the friction heat during the wear process. The SEM and XPS analysis shows that the main failure mechanisms of the tube under impact fretting are fatigue wear and friction oxidation. The effect of medium(water) on fretting wear is revealed, which plays a potential and promising role in the service of nuclear power device and other flow equipments.
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40. Theoretical Investigation of the Viscous Damping Coefficient of Hydraulic Actuators
Ming-Hui Huang, Qing Pan, Yi-Bo Li, Peng-Da Ma, Jun Ma
Chinese Journal of Mechanical Engineering    2017, 30 (4): 829-842.   DOI: 10.1007/s10033-017-0153-x
摘要12)      PDF(pc) (7190KB)(0)    收藏
The viscous damping coefficient (VDC) of hydraulic actuators is crucial for system modeling, control and dynamic characteristic analysis. Currently, the researches on hydraulic actuators focus on behavior assessment, promotion of control performance and efficiency. However, the estimation of the VDC is difficult due to a lack of study. Firstly, using two types of hydraulic cylinders, behaviors of the VDC are experimentally examined with velocities and pressure variations. For the tested plunger type hydraulic cylinder, the exponential model B = αv-β, (α > 0, β > 0) or B = α1e-β1v + α2e-β2v(α1, α2 > 0, β1, β2 > 0), fits the relation between the VDC and velocities for a given pressure of chamber with high precision. The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa. Furthermore, the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types. In order to investigate the VDC of a plunger type hydraulic actuator drastically, a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrication, back-up ring related friction behaviors and shear stress of fluid. It is shown that the simulated results of VDC agree with the measured results with a good accuracy. The proposed method provides an instruction to predict the VDC in system modeling and analysis.
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