Aiming at the dynamic mechanical system with multiple failure correlation, the copula function is used to describe the correlation of failure modes among units, and a reliability model of dynamic mechanical system with multiple failure correlations is proposed. The reliability problem of complex system is transformed into multiple two-dimensional pair copula functions by using R-Vine copula function. The optimal R-Vine structure is selected by using MST algorithm. The time-varying parameters in the model are described by nonparametric kernel density estimation(KDE). The common series parallel system(hybrid system) in mechanical system is modeled and analyzed. Finally, the effectiveness of the model is verified by an example of spacecraft open and close shafting.

In order to explore the effects of material properties, filling density, support structure and other parameters on mechanical properties and strength characteristics of 3 D printed products, an optimization design method of 3 D printed configuration based on strength requirements was proposed. The mechanical properties of the products were obtained through the simulation calculation of the finite element structure strength and the comparative analysis of the tensile test of the characteristic samples. The tensile strength of 3 D printed products with different internal structures has great differences when the packing density is the same. In theoretical analysis and experimental test, the tensile strength of concentric structures is higher, while that of folded lines and spirals is lower. The results have guiding significance for in-depth analysis of the relationship between the strength of 3 D printing parts and the filling structure, and provide research data support for the optimization design of 3 D printing parameters based on strength demand.

Hertz contact is a ideal contact status which supposes the contact surfaces as not moving, completely smooth and no lubricant, but real surfaces of meshing gears are rude, exiting relative motion and lubricating, and which is a kind of non-Hertz contact. Based on EHL theory, this paper proposes a new gear design theory and method, called gear design theory and method of non-Hertz contact. The new theory and method comprehensive considers every factors of influencing strength and lubrication of gears, and which can ensure the designed gears meet the dual requirements of strength and elastic hydrodynamic lubrication. Specific formulas of are given out and a large number of engineering examples are used to verify the new theory and method proposed in the paper, and the results show that the conformity of new design theory and method and the actual engineering examples are very well, and which can directly apply to practical engineering design to meet the requirement of engineering design. In particular, to design of high speed and heavy duty gear transmission, the new theory and method of this paper has important theoretical significance and practical value.

In order to study the torsional vibration problem of the transmission system of a front-rear-drive MPV model, a 21-degree-of-freedom transmission system torsional vibration equivalent model was established based on AMEsim software, and the torsional vibration analysis of the established model was carried out through free vibration calculation and forced vibration calculation. The torsional vibration test of the vehicle transmission system is carried out, the simulation results are compared with the experimental results, and the accuracy of the simulation model is verified in two aspects: Modal frequency and torsional vibration response. Based on the established vehicle transmission system model, the moment of inertia, torsional stiffness and damping in the model are analyzed through sensitivity analysis. The conclusions obtained show that the six system parameters have a greater impact on the transmission system.The multi-parameter adjustment based on MATLAB genetic algorithm is adopted for these parameters. After adjustment, the torsion amplitude values at the transmission and final reducer are reduced by 20.16% and 23% respectively, which greatly reduces the torsion amplitude of the transmission system.

Micro-milling can fabricate 3D free-form surface and complex components and has a promising prospect. However, due to sharp decreases of the tool scale and machining parameters, micro-milling process shows remarkable differences from traditional milling, thus researchers conduct broad studies on micro-milling technology recent years. The process of micromilling is complicated and involves many aspects, the domestic and overseas researches in micro-milling are summed up in this paper, the development of minimum chip thickness, cutting force, surface roughness, tool wear, and other aspects of researches are summarized. The development trend of micro-milling and the application prospect are discussed.

In order to solve the reliability evaluation of small samples for the high reliability, long-life products and to improve the accuracy of reliability evaluation, the Bayesian reliability evaluation model of multiple information source data fusion was carried out. First, a set of data as the initial prior information of another information source in this model was selected, by using the posterior density according to Bayesian estimation. Then, it as the prior distribution of the next information source was used. Through iteration, the joint posterior density and reliability index data of multi-source heterogeneous data are obtained, and the corresponding reliability analysis is completed. Finally, a simulation example verifies the rationality and effectiveness of the model.

Bearing is one of the most critical and the most vulnerable parts of mechanical transmission system,Accurate identification of its faults is the key to achieve stable operation of equipment. The five degree of freedom dynamic model of rolling bearing system with local fault is established by considering the nonlinear factors such as oil film and the sliding of rolling element. An improved model of pitting failure is proposed, and the corresponding models of different fault parameters are analyzed. The system vibration signal of the inner ring and the outer ring with pitting fault is simulated, and the corresponding fault characteristics are analyzed. Through the comparative analysis of the simulation signal and experimental signal, the correctness of the model is verified, which can help to realize the early diagnosis of bearing fault.

Split Hopkinson pressure bar(SHPB) tests are widely used for testing material mechanism behavior under high strain rates, A series of SHPB numerical tests were done based on K&C local concrete damage model, The stress-strain curves of the concrete specimens were reconstructed with the two-wave theory, and the damage of the concrete was analyzed. According to the comparison between the numerical and the test results, Proving K&C model can simulate concrete in concrete under high strain rate compressive mechanical behavior. Proving the increase of dynamic strength of concrete under the influence of structural effects.

binocular photogrammetry vibration measurement method for considering the radial and tangential distortion parameters calibration by using the Levenberg-Marquardt algorithm based nonlinear optimization was proposed. As an example, the modal frequency identified of a wind turbine blade. The vibration images sequence of the blade was acquired synchronously by two cameras and the target was segmented by adaptive binary dynamic threshold method, the direction with fastest grayscale gradient of the coding point as the edge,the circle curve was fitted by the least squares and iterative method, and the precise sup-pixel central coordinates of the coding point in the dynamic consecutive images were obtained by the gray square centroid method. Each coding point is similar to a small "displacement transducer" that reflects the blade's time domain vibration response. Finally, the blade's natural modal frequency was obtained from the time domains response, and compared with the results of the finite element and Laser Doppler Vibrometry, the relative error of vibration frequencies less than 5%, which verified the reliability and effectiveness of binocular photogrammetry method.

Counterbalanced forklifts is a kind of industrial vehicles specially used for handling, loading and unloading, having a wide range of uses, and the working environment is becoming more and more complex. Research on the stability of counterbalanced forklifts is becoming more and more important, but stability has attracted less attention in the academic community. The deflection of portal frame channel steel is a key parameter of stability that cannot be ignored. Domestic design of portal frame channel steel is based on analogy, which leads to its high safety factor, waste of raw materials, and weak theory and computer assistance. This paper analyzes the influence on safety and stability of the counterbalance forklift, and studies the longitudinal stacking stability of the forklift. Through the force and deformation analysis of the forklift channel beam, a model of the longitudinal stability and deflection deformation of the channel steel is established. Verify the correctness of the model through experiments. Research on the stability of counterbalanced forklifts provides theoretical basis and guidance for enterprises in the design and development of forklifts, which is conducive to saving materials, improving the energy efficiency of forklifts and ensuring their safety and reliability. It has certain theoretical significance and engineering value.

In the field of low-frequency vibration isolation research, the proposed quasi-zero stiffness provides people with new solutions. This paper systematically summarizes the structure and characteristics of various quasi-zero stiffness isolators. The control method and engineering application examples of quasi-zero stiffness isolator are described in detail. The research status of quasi-zero stiffness isolator at home and abroad is compared and analyzed. And look forward to the future development trend of quasi-zero stiffness isolators. Finally, the existing problems and corresponding solutions of the quasi-zero stiffness isolator are described.

The dynamic mechanical properties of aluminum honeycomb sandwich panels were investigated under low velocity drop weight impact test. The failure behaviors, destruction process and typical force-displacement curves were analyzed. The impact velocities and panel thickness have influence on ultimate impact force and energy absorption was analyzed respectively. The mechanical properties of sandwich panels with corresponding panel thickness under quasi-static test were compared. The tests result show that typical impact load-displacement curve of aluminum honeycomb sandwich panels presents five stages. The ultimate impact force and energy absorption of sandwich panels under different impact velocities are basically identical. With the panel thickness increasing, ultimate impact force and energy absorption of sandwich panels increase. Compared with quasi-static experiment, the ultimate impact force and energy absorption of sandwich panels with three kinds surface thickness under low velocity drop weight impact tests are improved.

The accuracy of traditional milling force prediction model is low, and it is difficult to provide effective support for the reasonable selection of process parameters in practical production, by synthetically considering the equivalent turning force model of working angle, cutting edge arc and radius of tool tip arc, in this model, the actual turning tool is equivalent to the ideal turning tool model to identify the material constant, the chip flow angle and the average friction angle in the material constitutive equation, according to the oblique cutting model, the shear stress on the main shear plane and the F₀ vector of the unit cutting force at different cutting speeds are calculated, thus the instantaneous cutting force on the front face of the end mill can be calculated, the three-dimensional cutting force of end mill in X-Y-Z coordinate system is obtained by coordinate transformation.The prediction of the cutting force model is verified by simulation and experiment.

When mechanical components are subjected to multiaxial cyclic loading during operation,the additional strengthening effect is easy to occur.Using uniaxial fatigue life calculation formula to predict their life will produce large errors.However,the existing multiaxial fatigue life prediction models are not convenient for engineering applications because it contains a large number of material constants.To solve the above problems,based on the initiation and promotion mechanism of fatigue microcracks under different stresses,combined with the shear damage model,a new expression of damage parameters is proposed,and the corresponding multiaxial fatigue life prediction model is derived combined with the Manson-Coffin-Basquin equation.The test data of two materials under the non-proportional loading and proportional loading path are used to verify the proposed life prediction model,and compared with the prediction results of the FS model.The results show that the proposed model has a good prediction effect.Finally,the model is applied to the fatigue life prediction of a big pendulum boom,and the results show that the boom meets the fatigue life requirements.

To reduce the raw material waste problems and repeated trial production in the matching process of rubber parts hardness and stiffness,the correlation analysis of rubber parts stiffness and hardness was carried out.Based on a rectangular rubber spring cushion,with uniaxial compression and tensile tests,the theoretical parameters of the Mooney-Rivlin model were calculated,and the results were verified by the least square method.The stiffness of the rectangular rubber spring pad increases nonlinearly with the increase of deformation,which Abaqus calculated.Based on the experimental data of rubber hardness,the exponential quadratic nonlinear function of hardness and Mooney-Rivlin model parameters was established.As a result,the hardness of rubber was positively correlated with the material parameters.The relationship between elastic modulus and hardness was transformed into elastic modulus and material parameters C₂ and C₁.Furthermore,the stiffness displacement curve of rubber material was obtained by simulation analysis to find the relationship between rubber material parameters and stiffness.Finally,with Mooney-Rivlin model parameters as the bridge,the correlation conclusion between stiffness and hardness of rubber parts was obtained.

To obtain the filling material with good compression mechanical properties,two kinds of orthogonal trapezoidal honeycomb aluminum with different structures were manufactured (90° orthogonal trapezoidal honeycomb aluminum and 45° orthogonal trapezoidal honeycomb aluminum),the mechanical properties of the material under quasi-static axial loading was analyzed.Two kinds of orthogonal trapezoidal honeycomb aluminum were filled with polyurethane foam,and the effect of polyurethane filling on the orthogonal trapezoidal honeycomb aluminum was analyzed.The results show that compared with 45° orthogonal trapezoidal aluminum honeycomb,the performance of 90° orthogonal trapezoidal honeycomb aluminum is better,and the peak stress,plateau stress and unit volume absorption energy of the two kinds of orthogonal trapezoidal honeycomb aluminum are improved after polyurethane filling.However,the energy absorption efficiency is not significantly improved after being filled with polyurethane,and the strain corresponding to the maximum energy absorption efficiency decreases.

This paper analyses the vibration modes of a simply supported beam with vibration table. Firstly, the one dimensional vibration theory is used to acquire the beam vibration mathematical model. Following to use Bernoulli Euler beam theory to calculate the beam vibration differential equation, in addition to the beam set specific boundary constraint conditions to calculate each order modal parameters, using the Workbench beam finite element simulation analysis for the first five order natural frequency and vibration mode. In the end, the experimental modal algorithm based on Poly IIR is applied to identify the modal parameters of simply supported beam. The modal frequencies and mode shapes are obtained in this paper. It is keeping 3% about the consistency of the simulation value and experiment result, Which can subsequent beam or plate and so on EMA elastomer complex structure analysis and research to provide certain reference.

The lubrication state of wire rope has an important influence on the working characteristics and fatigue life of wire rope.6X19 steel wire rope is taken as the research object, and three kinds of steel wire rope without grease lubrication, partially lubrication and fully lubrication are selected.The bending fatigue tests are carried out on the bending fatigue test machine under different tension states, and the fatigue damage states of each specimen in different stages are statistically analyzed and microscopic studied.Under good lubrication condition, between wire rope and pulley rope groove of the oil film to improve the contact state, reduce the friction coefficient between steel wire rope, steel wire surface is not easy to wear and tear scratches, delay the formation and extension of cracks and improve the steel wire rope section stress distribution and reduce the stress concentration phenomenon, make more effective load effect on the number of steel wire.The steel wire in the rope is fully drawn, and the proportion of necked broken wire in the total broken wire is higher than that of the wire rope with poor lubrication condition.For the wire rope with poor lubrication condition, the proportion of flush fracture is high, and the steel wire in the rope is not fully drawn, resulting in wire breakage due to local damage.Under the same lubrication condition, the increase of tension force destroys the lubricating oil film between the wire rope and pulley groove on the one hand, on the other hand, under the action of compressive stress, the lubricating oil in the rope core is not easy to infiltrate into the side of the wire rope and pulley groove, which deteriorates the lubrication state.

A method about fatigue strength analysis of high-strength joint bolts was proposed on the background of gearbox housing joint design of the wind turbine. The method was based on the theory of multi-axial fatigue. And the calculation process of the method described as following:first, the multi-axial non-proportional loads, which loading on the hub blade because of natural wind, were transformed into corresponding stress spectrum after the process of the stress calculation of housing FE model and the stress treated according to the rain-flow counting rules. Second, the Mises stress was synthesized at the calculation nodal location of the bolt cross section from the multi-axial stress spectrum. And third, the fatigue damage of the nodal location was calculated according to the VDI2230 standard under the consideration of the bolt material S-N curve. Finally, the fatigue safety factor of the joint bolts was obtained according to the theory of Palmgren-Miner. Application software was programmed according to the method. With the software, a case of high-strength joint bolt fatigue strength was analyzed, and the fatigue safety factor is 1.819 within the design life of 20 years. The paper proposes a new way to evaluate the fatigue strength of high-strength joint bolts under complex loading condition.

In order to study the dynamic mechanical properties of SUS304 stainless steel commonly used in rail vehicles, tensile tests under wide strain rates of 0.000 2 s^-1~500 s^-1 were carried out respectively. The test results show that SUS304 stainless steel exhibits strain hardening during dynamic stretching. As the strain rate increases, the material exhibits a strain rate strengthening effect. At the same time, a certain thermal softening effect is produced. To accurately describe the dynamic mechanical properties of the material, the Johnson-Cook model of the material at room temperature was first established. On this basis, adiabatic temperature rise is introduced, and a modified Johnson-Cook model considering plastic strain and strain rate correlation is established. The modified Johnson-Cook model can better describe the dynamic mechanical characteristics of SUS304 stainless steel, which is the characteristic that the stress gradually weakens with the increase of strain and strain rate. This modified model provides a basic basis for the crashworthiness analysis of the rail vehicle body structure.

Aiming at the problem of thermal fatigue of solder joints for airborne electronic equipment, the evaluation method of thermal fatigue life of solder joints suitable for engineering application was studied, considered that the empirical equation based on strain energy was suitable for multiple components on PCBA. The accelerated test method of thermal fatigue life of solder joints was discussed, the accelerated test case proved that the test was feasible, and the simulation was credible. The results indicated that the simulation and accelerated test method of thermal fatigue life of solder joints were suitable for engineering application.

Based on linear materials, two kinds of equivalent tire models were proposed, which are single solid element structure and solid element + beam element mixed structure, taking TBR tire 11.00R20 18RP as the research object. The impact of different elastic modulus of each layer on the static stiffness of two equivalent models was analyzed using ANSYS. And on this basis, the parameter optimization analysis of elastic modulus of materials was carried out. Based on the optimization results, the modal property of the two equivalent models were studied, and the effective range of the equivalent models was analyzed by comparison with the experimental results. The was shown that the tire equivalent model composed of solid element + beam element mixed structure based on linear material can better simulate the static stiffness, tangential mode and axial mode of tire, but the radial mode frequency is relatively low; in the study in which only the radial property is concerned, such as in a vehicle-road coupling simulation, the radial mode frequency can be improved by reducing the density of the bundle layer, so that the equivalent model is more effective.

In order to solve the optimization design problem of complex shape of underwater glider and improve the optimization efficiency of Kriging surrogate model while improving its lift drag ratio, an adaptive surrogate optimal algorithm is proposed.The proposed improved parallel expectation improvement(PEI) criterion and probability of improvement(PI) criterion are used for global exploration, and the minimizing surrogate prediction(MSP) criterion is used for local exploration.The switching between global exploration and local exploration is realized according to the relationship between new sample points and known sample points.The proposed algorithm, the maximum expected improvement(EI) criterion multiple expectation of improvement(q-EI) and the improved probability improvement(IPI) are combined through a mathematical example.The result shows that the proposed algorithm converges faster and has higher accuracy.Finally, the optimal algorithm is used to optimize the shape of the underwater glider, and the maximum lift drag ratio is increased by 19.37%.

Aiming at the low accuracy with unbalanced data sets in existing bearing fault diagnosis methods,we proposed a bearing fault diagnosis method based on importance weighted auto-encoder (IWAE) in unbalanced data sets.It was trained by minority samples,and the generated samples were added into original data sets to obtain balanced data sets.Then,deep learning method was used as diagnose network,and the balanced data sets were fed into it as input,so as to adaptively learn fault characteristics and realize fault classification.A large number of qualitative experiments showed that when the imbalance rate was 1 ∶7,the method could correctly classify the balanced samples,and the accuracy rate was 98.90%.Based on various imbalance ratios,the proposed method had better convergence and generalization than other existing models.

The background of fault diagnosis is from the prevention of accidents, and from the reverse progression of accidents to the fault subdivision of the failure stage.By studying the single fault and the coupled fault separately, this paper demonstrates that the current theory of fault diagnosis has been intervened and developed in the fault stage, and it is a rule method of subdividing the fault models into opposite and parallel layers. This method makes the research object a divergent system and cannot be solved.The whole process of laboratory experiments and field failures is tracked, and data analysis proves that failures are dynamic links that build each other in the rotor system, and show the corresponding “homogeneous“characteristics with the change of the “forward” phase of the fault state time, and expand the process layer by layer.Therefore, the application of fault diagnosis theory should be restored to the unified whole and the whole process system, which requires changing the direction of fault diagnosis, reversing the horizon, and mastering the main law of fault development in the unified whole and the whole process based on the "forward" and "homogeneous" methods of time history and fault nature, so as to lay a more solid theoretical basis for intelligent diagnosis.

In order to explore the influence of different TPMS pore structures on the mechanical properties of the porous scaffold, TPMS expressed by implicit function was used as the basic pore unit to construct the micro-porous structure. TPMS porous scaffolds with different structural characteristics were constructed by defining the distance function, And AlSi10 Mg porous scaffolds were prepared by SLM. Finite element Method(FEM) analysis and mechanical test method were used to study the influence of different pore structure characteristics on mechanical performance of porous TPMS scaffolds and analyze the influence law of different distance function k values on porosity, elastic modulus, yield strength and failure of Primitive(P) and F-RD porous structure scaffolds. Finite element analysis and experimental results show that with the increase of distance function k, the elastic modulus and yield strength of the P unit porous scaffold presented an increasing trend, However, the elastic modulus and yield strength of the FRD unit porous scaffold showed a downward trend, Moreover, Comparing to FRD unit, P unit porous scaffolds were more likely to be crushing, through the control of the TPMS types and the distance function k value, the porosity, elastic modulus and yield strength of the porous scaffold can be effectively adjusted. The results provide a basis for the design of tissue-engineered bone scaffolds.

According to the working process and fault characteristics of belt conveyor, a safe and reliable intelligent control system solution is proposed. The solution consists of centralized control system and field control system. It adopts the control mode of PLC and host computer. PLC is used to collect and control the data of the equipment in the whole belt conveyor. The intelligent control of belt conveyor is realized by issuing control commands to the system equipment through the interface of the upper computer and displaying the operation status and fault alarm information of each equipment intuitively and dynamically. The main technical points of the system are introduced from the aspects of overall solution, hardware selection, software design and control flow.

Taking the rotary worktable of a gantry machining center as the research object, the static and dynamic characteristics analysis and optimization design are carried out by using the finite element method. In order to increase the stiffness and reduce the weight of rotary worktable, the main design parameters are tested by Box-Behnken experiment design. Based on the design of experiment, sensitivity analysis is carried out for design parameters and the response surface model is established. Then, the multi-objective optimization algorithm is adopted to optimize the response surface model and combined with the production technique to determine the best optimization scheme. The results of optimization show that the maximum deformation is reduced by 36.8%, the first natural frequency is increased by 5.4% and the weight is decreased by 2.6% by using above method to optimize the rotary worktable, which providing a new idea for the design and optimization of the rotary worktable.

Due to low adsorption efficiency of magnetic adsorption unit (MAU) of crawler wall-climbing robot,the parameters analysis and structural optimization design are carried out based on DOE,RSM and sensitivity analysis method.The functional relationship between the parameters of the MAU and the magnetic force is obtained by the finite element simulation model,DOE and RSM.The sensitivity of parameters of the MAU to the magnetic adsorption force is determined by the sensitivity analysis.The length,the width,the height of the permanent magnet,the thickness of the yoke and the distance between the permanent magnet and the wall are selected as the design variables.After the optimized design,the adsorption efficiency of the MAU is increased from 2.029 7 to 3.938 1.

Aiming at the mutation in demodulation of the envelope estimation function,a local mean decomposition method for singular interval envelope reconstruction is proposed.This method determines that the reason for the sudden change in the demodulation of the envelope estimation function is the intersection of the envelopes,and defines the local area where the intersection exists as a singular interval.Combined with the extreme value symmetry theory,the interpolation points in this interval are expanded,and the cubic Hermitian interpolation is used to perform local reconstruction.A singular interval envelope reconstruction algorithm is formed.The simulation signal and the application of fault diagnosis of reciprocating compressor bearing prove that the proposed method solves the envelope crossing problem,suppresses the demodulation mutation phenomenon,and the decomposition result has more obvious fault characteristics.

In order to research the influence of the web deflection on the bend-twist coupling characteristics of large wind turbine blades, the CAD model of NREL 5 MW blade is established based on NX secondary development, the aerodynamic loads of the blade are obtained by CFD method, the blade bendind angle and twisting angle are solved by the node displacement method to analyze the influence of web deflection for bend-twist coupling blade.The results show that the offset web helps to achieve the bend-twist coupling of blades.Under the action of aerodynamic load, the bending and twisting angle both increase along spanwise direction of blade gradually, and reach the magnitude at the tip of the blade; in forward bias, negative correlation between twist angle and offset, reverse bias is the opposite; positive bias blades bend-twist coupling coefficient is decreasing trend with the increase of deflection angle, reverse bias blade are greater than the conventional blade.

There are two methods to verify the durability characteristics of a new designed leafspring, there are physical test which takes more time and cost and CAE simulation which is time-saving and cost-saving.Aiming at coming up an effective CAE simulation of the leafspring life, the CAE simulation for stiffness and strength with rig test is validated.Base on the validated CAE method, with material property from test, CAE fatigue simulation is conducted with different surface treatment factor and validated with rig test to find out the best parameter for good life correlation.Finally, an effective CAE life prediction of automotive leafspring is provided, and the solution can serve as a good reference for the industry.

Based on random vibration theory and fatigue analysis method in frequency domain, with finite element software to construct the battery pack failure model of random vibration fatigue analysis and to calculate the fatigue life of the structure, the analysis results are in good agreement with the test results. Analyze the failure mechanism of the structure and carry out structural design improvement, the simulation and test results show that the fatigue life of the improvement scheme is significantly improved, and it has better anti vibration durability.

To quickly evaluate the safety of damaged bridge structures in the service process of cranes,a real-time prediction method for the fatigue life of bridge structures based on the optimal additive agent model is proposed.Based on the measured load data,the randomness of the relevant parameters of the service conditions is characterized by the combination of the working cycle process.In line with the most unfavorable service conditions,the stress weak position of the bridge structure is determined through finite element statics analysis and failure case statistics.And the structure finite element model is established for fatigue damage and life prediction.The MSC.Fatigue's S-N module and crack propagation module are employed to simulate the residual life of the structure under random working conditions,and the influence of different crack depths on the residual life of the structure is analyzed.The Kriging model for the life prediction of the bridge structure that is optimized by the Pelican Optimization Algorithm and additive point criterion is created by the Latin Hypercube Sampling method and the black box theory.The real-time fatigue life prediction of bridge structures during trolley movement with load by Miner linear cumulative damage theory.The bridge structure of QD20/10 t × 43 m × 12 m general bridge crane is taken as an example to verify the feasibility of the proposed method.Comparing the proposed method with the traditional fatigue life calculation method based on finite element simulation,the results show that it can accurately assess the remaining life of the damaged bridge structure with fewer simulation calls and shorter simulation time,which can provide some reference significance for crane maintenance cycle formulation and scrapping decisions.

Based on the theory of rigid-flex coupled multi-body system dynamics, systematic research has conducted on transmission system of a coal winning machine's cutting part. By using the software of RecurDyn,the model was established including transmission gears, drive shaft and bearing. Considering the flexible characteristics of drive shaft, the rigid-flexible coupled model was built.Transmission system of a coal winning machine's cutting part was simulated dynamics analysis before contact parameter setting on the parts of transmission system. The working process of shearer transmission system was described intuitively and dynamically. Results showed that 11th gear mesh together is the biggest, 11272634.4N.4th. The maximum strain, measured at the axes of 4, is 0.081. It reveals the difference of Gear meshing force curve and its frequency-domain information between Rigid-flexible coupling system and Stiff systems. Results provide a basis for optimum design of the transmission system and prediction of fatigue life.

Rotor blades are one of the most important parts of helicopter, and its can be used as lifting surface, pulling surface and control surface in flight. The fatigue life evaluation of rotor blades is the very important problem in helicopter engineering development. The history on fatigue life evaluation for helicopter composite blades is simple reviewed in this paper. Then, the main methods of fatigue life evaluation for composite blades are introduced in detail, including to damage tolerance method, flaw tolerance method and its flow chart, practical application, key problems etc. Furthermore, aim to the practical engineering application, existing problems in the three methods are analysed in-depth. Next, the unconventionality fatigue life evaluation methods are introduced, including to residual strength method, progressive damage method, the method based on dynamic characteristic, and the examples of these methods are presented. At last, based on personal knowledge, the authors summarize some thinking to the fatigue life prediction for composite blades, and these thinking is perhaps helpful to related researcher.

The experiments under the coupling of the multi-physics field don't have the conditions to be carried out in the heat exchange tubes fouling test. And it's very important to establish the accurate ultrasonic propagation model for achieving the numerical simulation of selecting the detection frequency. Based on the finite element method, the three-dimension model with different heat exchange tubes had been established under the COMSOL Multiphysics condition. The varied relationship of the ultrasonic wave propagation, the different heat exchange tubes and echo exciting frequency were discussed respectively. The characteristic frequency and echo vibration mode of multi-layer tubes were found. The results show that the relationship between different characteristics of the heat exchange tubes (material and wall thickness) and pressure load is similar. The ultrasonic time-domain reflectometry technology to detect the thickness of the tube fouling needs to select 5 MHz echo exciting frequency at least for inhibiting the pseudo-Gibbs oscillation. The optimal detection frequency is 10 MHz, and the detection effect is the best when the thickness at 3 mm~5 mm. The numerical simulation agrees with the test results, and ultrasonic detection produces an error around ±5% in examining tube fouling deposit. These results provide a basis for quantitative detecting basis to select the characteristic frequency under the different tubes.

The complex and changeable working conditions of mechanical equipment in industrial field lead to uneven distribution of fault samples,which brings great trouble to traditional machine learning.In order to solve this problem,proposes a bearing fault transfer diagnosis method based on domain adaptive neural network and balanced dynamic distribution adaptive.Firstly,According to the characteristics of bearing vibration fault samples,the convolution layer of convolutional neural network is improved by wavelet transform,and the characteristics of bearing samples are extracted adaptively.Then,Maximum Mean Discrepancy measure and weight regularization are used to process the generated features in the loss function to reduce the difference in sample distribution and obtain the domain adaptive neural network model.Finally,A-distance is used to improve the equilibrium distribution adaptive to make it have dynamic characteristics,further improve the difference of sample distribution,and realize bearing transfer diagnosis by KNN classifier.Through experimental verification,the proposed method can accurately migrate the bearing fault state in the same bench rig cases and cross bench rig cases,proving that the method can effectively solve the problem of uneven distribution of unlabeled samples under variable working conditions,and has the effectiveness and robustness.

The vehicle body is an important bearing structure of railway vehicles, which can bear dynamic loads from passengers and bogies. The reliability of the structure is directly related to the service safety of the vehicle.Based on the existing vehicle body standard EN12663, this paper firstly studies the static strength and fatigue strength of the vehicle body, and identifies the static weak position of the vehicle body under standard load.In order to further identify the weak position of the vehicle body under service conditions, a rigid-flexible coupling dynamic model of subway vehicle is established based on the rigid-flexible coupling dynamic theory and finite element method.Using the modal stress recovery method, the dynamic weak positions in various service modes are identified, and the vehicle modes which contribute a lot to each weak position are analyzed.Finally, based on the subway rigid-flexible coupling dynamic model, the dynamic stress characteristic of vehicle body weak position under various service conditions is analyzed, and the service life of key welds of vehicle body structure is predicted based on monte Carlo sampling and Miner linear cumulative damage theory.

Turbulent winds and earthquakes are the two main factors that lead to the vibration of the wind turbine tower. In order to study the dynamic response characteristics and anti-seismic of wind turbine structure under wind-earthquake coupling condition, NREL 5MW wind turbine is studied. A soil-structure interaction model was established by Wolf Method, and based on the multi body dynamics simulation and open source software FAST, the seismic load calculation module is developed. The structural control of the wind turbine tower under the seismic condition is carried out by configuring a tuned mass damper (Tuned Mass damper, TMD) at the top of the tower by self-compiling program. The results show that the seismic load greatly increases the lateral vibration of the tower, and the excitation frequency is the first-order lateral natural frequency of the tower. Under the control of TMD, the dynamic response of tower and nacelle are obviously reduced, where the amplitude of lateral displacement of the tower top is reduced by 18%, the standard deviation is reduced by 67%, and the response amplitude of the first order natural frequency of tower is greatly reduced, as high as 90%. Additionally, the variation of the lateral acceleration of the tower top is reduced by 4%, the standard deviation is reduced by 61%, and the peak vibration of the first-order natural frequency decreases by 88%. Therefore, the TMD can be used for anti-seismic of wind turbines in extreme environments such as earthquakes, and improve the stability of wind turbines.