最新刊期
期 2 ， 2023
- 摘要：Aiming at the low accuracy and efficiency of stochastic model updating, a stochastic finite element model updating method based on the Kriging model and wavelet packet energy spectrum was proposed. Firstly, assume that the parameters and response characteristics of the model to be updated obey normal distributions, the uncertainty model updating was transformed into the updating of mean and standard deviation. Secondly, the parameters to be updated were taken as inputs of Kriging model, the node energies extracted by the acceleration frequency response function after wavelet packet decomposition were taken as the outputs, the political optimizer algorithm was introduced to optimize the correlation coefficient to construct Kriging model. Then, minimize the absolute value of the difference between the test response and the predicted response as the objective function for updating mean, and minimize the cross entropy as the objective function for updating standard deviation, and updated the parameters mean and standard deviation through the political optimizer algorithm. Finally, taking a space truss structure as the example, the elastic modulus and density were selected as the parameters to be updated to verify the feasibility of the proposed method. The results show that the proposed method can effectively update the mean and standard deviation of structural parameters, and errors of the updated mean and standard deviation are less than 0.1% and 3.5%, respectively.关键词：Model updating;Acceleration frequency response function;Cross entropy;Wavelet packet energy spectrum;Kriging model
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发布时间：2023-06-09 - 摘要：The data-driven intelligent diagnosis of rolling bearing status suffers from low recognition rate due to the poor quality of learning samples in the process of identification model construction. To address this problem, a method is proposed to improve the recognition rate of the rolling bearing intelligent diagnosis model by selecting learning samples using the deep belief neural network. First, aiming at the time-varying modulation characteristics of the rolling bearing vibration signal, a finite number of intrinsic mode function components were decomposed using variational mode decomposition, which represents different components of the original signal. Secondly, according to the fault energy fluctuations and correlation of each component, the proportion of fault information in each intrinsic mode function components is quantitatively evaluated. On the basis of this, the vibration signal is screened and reconstructed to obtain learning samples. Finally, the obtained samples are used as the input of the deep belief network, and the fault identification model of the rolling bearing is constructed accordingly. Experimental results show that the proposed method is capable of screening out the intrinsic mode function components of the rolling bearing vibration signal, which contains the main components of the fault and realizes the construction of learning sample sets. Moreover, it improves the fault recognition rate of the rolling bearing state identification model based on vibration data.关键词：Learning sample screening;Correlation energy fluctuation evaluation;Rolling bearing;Deep belief neural network;Fault recognition rate
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发布时间：2023-06-09 - 摘要：A bistable-nonlinear energy sink（BNES） is designed to control the vibration of the main system in a wide frequency range. The spatial magnetic force of cantilever structure system is analyzed based on the magnetizing current theory, and the influences of magnetic spacing and cantilever length on stability point of BNES are studied. The dynamic equations of main system coupling BNES are established to study the stability of transient performance of BNES under different excitation intensities. The effect of magnetic spacing on the steady-state vibration reduction performance of the BNES is studied through the amplitude frequency characteristics, and the stability performance of the BNES with the change of excitation intensity at 0.5 times, 1 times and 1.5 times resonant excitation frequency is studied. The analysis results show that the proposed BNES has good transient and steady-state vibration reduction performance and good robustness.关键词：Vibration suppression;Magnetizing current;Bistable-nonlinear energy sink;Magnetic distance;Robustness
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发布时间：2023-06-09 - 摘要：Based on the crow search algorithm（CSA）, by the adaptive crow search algorithm（ACSA） the adaptive value strategy of sensing probability and flight distance, which effectively enhanced the performance of the algorithm is designed. In view of the fact that the selection of deep belief network（DBN） model parameters has great influence on the engine fault diagnosis results, ACSA is used to optimize the selection of its model parameters, and an engine fault diagnosis method based on DBN improved by ACSA is proposed. The Engine fault diagnosis example results show that the ACSA algorithm can obtain better DBN model parameters, and obtain higher engine fault diagnosis accuracy in less time than other methods.关键词：Deep belief network;Crow search algorithm;Adaptive parameter;Engine;Fault diagnosis
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发布时间：2023-06-09 - 摘要：The contact ratio is an important performance index in the design of gear transmission, and it directly affects the load-bearing capacity and transmission stability of herringbone gears. The requirements of contact ratio must be met when designing gear pairs. Firstly, the stiffness excitation and meshing impact excitation of herringbone gear system are introduced, and a bending-torsion-axis coupling model of a pair of herringbone gear transmission system is established by means of lumped-mass method. Then, the influence of contact ratio on time-varying meshing stiffness and meshing impact force is analyzed. Finally, the influence of contact ratio on the dynamic meshing performance of herringbone gear pairs is studied. The results show that when the contact ratio increases from 2.72 to 3.08, the peak-to-peak value of time-varying meshing stiffness is reduced from 4.653 3×10~8 N/mm to 3.229 9×10~8 N/mm, and the maximum meshing impact force is reduced from 2.23×10~3 N to 1.92×10~3 N, and dynamic meshing force curve of the gear pair becomes smooth, and the dynamic load factor is also reduced from 1.23 to 1.18. It is concluded that the increase of contact ratio can achieve the effect of system vibration reduction, noise reduction and transmission stability.关键词：Contact ratio;Herringbone gear transmission system;Lumped-mass method;Vibration characteristics
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发布时间：2023-06-09 - 摘要：A dynamic model of rotor system with loosening and rubbing multiple faults coupling was established. Fourth-order Runge-Kutta method was used for numerical simulation. Periodic bifurcation diagram of rotor system, maximum rub-impact force diagram, amplitude diagram of loose bearing support, phase diagram as well as Poincaré map of the rotor system were obtained. The analysis was focused on the influence of loose mass on the dynamic characteristics of the system.The research shows that the looseness fault makes the rotor system enter the rub-impact motion at low speed. The rotational speed range of subharmonic motion, almost periodic motion and chaotic motion increases. At the same time, the corresponding maximum friction force and loose support amplitude are larger. The large loose mass can reduce the vibration amplitude of the loose bearing support. At the same time, it can make the system in the periodic motion without rub-impact in the long range of low speed, which is conducive to the stable state of the system under fault conditions.关键词：Rotor;Loose;Rubbing;Coupling faulty
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发布时间：2023-06-09 -
RESEARCH OF DETECTING DEFECTS IN POLYUREA ANTI-CORROSIVE PIPES BY USING ULTRASONIC GUIDED WAVES (MT)
摘要：In recent years, as a new type of anti-corrosion material, polyurea coatings have been widely applied to the protection of internal and external walls for pipes. In order to overcome the shortage of traditional ultrasonic testing with low efficiency, the imagine of detecting some cracks in polyurea anti-corrosive pipes was proposed, which based on ultrasonic guided wave detection technology, and it would be studied by numerical simulation. By analyzing the analytical model in the polyurea anti-corrosion pipes, established the three-dimensional cylindrical model of the viscoelastic-elastic composite material by finite element software Abaqus, and simulated the propagation state in which the L（0,2） modal guided wave with the different excited frequencies. Combined with the study of its dispersion and attenuation for selecting optimize frequency, and the analysis of defect detection for the model were accomplished the simulated. The results of research show that the results of numerical simulation are basically consistent with experimental verification, which show that it is effective to use the ultrasonic guided waves for detecting defects of polyurea anti-corrosion pipes and realizing the location of defects.关键词：Ultrasonic guided waves;Polyurea anti-corrosion pipes;Numerical simulation;Optimize frequency;Defect detection- 8
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发布时间：2023-06-09 - 摘要：In order to explore the effect of the specimen size on results of small punch test（SPT）, SPT was conducted on Incoloy 800H and low alloy steel 3Cr1MoV using various specimen thicknesses of 100～500 μm, and a database of force-deflection curves and true stresses were created for various specimen thicknesses by Ludwig hardening model and finite element method. True stress-plastic strain curves of different specimen sizes were acquired based on the database and SPT experimental curves. The strength properties of the studied materials were predicted through these true stress-plastic strain curves. Meanwhile, the relationship between flow stresses, strength properties and specimen size was obtained. The results show that tensile properties of Incoloy 800H increase gradually with the decrease of sample thicknesses, while sample sizes have a slightly influence on tensile properties of 3Cr1MoV. The different responses of tensile properties to thicknesses were discussed, which provides a basis for the selection and design of sample thickness when SPT is employed to predict tensile properties.关键词：Small punch test;Size effect;Tensile properties;Finite element method;Database
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发布时间：2023-06-09 - 摘要：The performance of the aramid III composite product is affected by the molding process parameters. Through the analysis of the prepreg molding process, it is found that the prepreg placement time is the main parameter that affects the interlaminar shear strength（ILSS） of the aramid III composite. In order to study the influence and sensitivity of the prepreg placement time on the ILSS of the aramid III composite material, the short beam method interlaminar shear experiment method was used to obtain the corresponding strength values of the prepreg under different placement time. According to the experimental data, the regression model of the process parameters on the ILSS was established, and the reliability and validity of the regression model were verified by the residual error, the comparison between the predicted value and the actual value. Using this regression model can accurately give the ILSS of the aramid III composite under different storage time of the prepreg, and obtain a single parameter sensitivity curve. Through the analysis of the sensitivity curve, the stability and instability range of the parameters can be determined. The experimental results show that as the placement time increases, the ILSS of the aramid III composite material increases first and then decreases. The optimal prepreg placement time corresponding to 0°/0°, 0°/90°, ±45° layup is within the range of 10～22 h. Within this range of process parameters, the aramid III composite material can be guaranteed to have the maximum ILSS.关键词：Composite material;ILSS;Prepreg placement time;Sensitivity analysis;Stable range
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发布时间：2023-06-09 - 摘要：In order to effectively evaluate the grinding performance of CBN（Cubic Boron Nitride） grinding wheel in the grinding process, a monitoring method of CBN grinding wheel performance was proposed based on Shannon entropy theory and acoustic emission signal. Firstly, the acoustic emission signal of CBN grinding wheel was collected by an acoustic emission sensor. Then, the probability density and distribution of acoustic emission signal of CBN grinding wheel was estimated by using the maximum information entropy. In addition, the characteristics of acoustic emission signals of CBN grinding wheel during cyclic grinding after dressing and residual grinding with different diameters were analyzed and discussed. Subsequently, the relationship between the maximum entropy probability density distribution of acoustic emission signals and the different grinding performance of CBN grinding wheel was established according to the cross entropy principle. Finally, a large number of experiments verified the availability above mentioned estimation method. The CBN grinding wheel wear status and the remaining life of CBN grinding wheel can be monitored.关键词：Grinding performance of CBN wheel;Acoustic emission signal;Shannon entropy;Maximum information entropy;Cross entropy
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发布时间：2023-06-09 - 摘要：In order to meet the demand of three-way vibration reduction of metal rubber, a pot-shaped metal rubber was designed and prepared via introducing spatial configuration. The method of controlling variables to study the effect of preparation process parameters such as relative density, forming angle, wire diameter and compression on the static mechanics of pot-shaped metal rubber was investigated, and the influence of three preparation process parameters on the pot-shaped metal rubber axial and radial static mechanics was revealed by orthogonal test method. The results show that the sequence that affects the axial static mechanical properties of the test piece is forming angle, relative density, and wire diameter; the sequence that affects the radial static mechanical properties of the test piece is relative density, wire diameter, and the forming angle.关键词：Pot-shaped metal rubber;Three-way vibration reduction;Quasi-static test;Control variable method;Orthogonal analysis
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发布时间：2023-06-09 - 摘要：To meet the requirements of equipment performance optimization in the intelligent environment of mining machinery, a solution model of excavator resistance with wide applicability is established, which made the solution model of excavation resistance have high efficiency and accuracy. The theoretical equation of excavation force is established and solved based on d′Alembert′s principle, and its accuracy is verified by dynamic simulation. The precise soil parameters are calibrated with theoretical results, and a simulation model is constructed by coupling drive of Adams-EDEM to obtain the precise solution of excavation resistance. The accuracy of the method is verified by the measured stress. In addition, the influence of different soil parameters on simulated excavation resistance is analyzed. The results show that compared with the traditional theoretical equation, the proposed model has advantages in precision and computational efficiency. The excavation resistance output from the theoretical model is used as the standard to modify the simulated soil model. The stress output from the modified simulation model is consistent with the measured stress, which verified the accuracy of the proposed method. This method provides an important basis for the calibration of complex soil parameters and the establishment of accurate soil model.关键词：Excavation resistance;EDEM;Coupling simulation;Soil model;Data driven
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发布时间：2023-06-09 - 摘要：The mesh stiffness calculation and load distribution among teeth of helical gear are the basis of its dynamics analysis and strength calculation. Aiming at the accuracy of approximate replacement method of mesh stiffness of helical gear, the quasi-static elastic model of helical gear was established based on the change rule of contact length, quasi-parabolic model of single tooth mesh stiffness per unit of contact length and ISO6336-1 standard, and a comparative study was conducted with the approximate replacement method based on quasi-static rigid model and ISO6336-1 standard. The results showed that the results calculated by quasi-static elastic model were in good agreement with the ISO standard results when the ratio of the minimum stiffness to the maximum stiffness of single tooth αk is 0.55, and the errors of the quasi-static rigid model and ISO standard were large. Based on the quasi-static elastic model, the effects of geometric parameters and broken teeth failure on meshing stiffness and load distribution coefficient of helical gear were analyzed and discussed, which provided a basis for the study of fault dynamics.关键词：Helical gear;Mesh stiffness;Load distribution among teeth;Broken tooth fault
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发布时间：2023-06-09 - 摘要：To study the stability of the over-pressure reinforcement effect of the copper tube at room temperature, the burst tests for the small diameter soft TP2 copper tube at room temperature during the natural aging time of 0, 6, 12 and 24 months were carried out respectively. These results indicated that: the mean of the measured burst pressure did not change significantly for small diameter soft TP2 copper bare tube and rifled tube at the same pretreatment pressure during the natural aging time of 0, 6, 12 and 24 months, respectively. The standard deviation was gradually smaller and the over-pressure strengthening effect was obvious. The measured burst pressure was different obviously for small diameter soft TP2 copper tube at the pretreatment pressure was 4.60 MPa and 16.50 MPa respectively during the same natural aging time, the mean was significantly larger and standard deviation was significantly smaller for measured burst pressure with the increase of pretreatment pressure, the results showed that pretreatment pressure had a great influence on strengthening effect, and higher pretreatment pressure could get better strengthening effect. The burst pressure conforms to the normal distribution for the same small diameter soft TP2 copper tube at the same over-pressure reinforcement during the natural aging time shall not exceed 24 months. Over-pressure reinforcement at room temperature was a suitable method to increase burst pressure of soft TP2 copper tube, and the method could be used in engineering.关键词：Natural aging;Small diameter;TP2 copper pipe;Over-pressure reinforcement;Burst pressure;Stability
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发布时间：2023-06-09 - 摘要：To efficiently evaluate the dynamic reliability of the impeller structure in cross-flow fans, its probability density function of maximal stress is established using the probability density evolution theory（PDEM）. The stochastics in structure and surroundings are considered and the finite element analysis model is used. On the basis, the structural failure probability and time-dependent reliability at different operation times are given. The Abaqus finite element analysis software is developed again. Through the joint simulation of Matlab and Abaqus, the whole process batch simulation analysis of model building, stress analysis, result extraction and probability density evolution is realized. By comparing with the agent model method and the Monte-Carlo model from the perspectives of calculation efficiency and accuracy, the practicability of PDEM in evaluating the dynamic reliability of impeller structure is further validated.关键词：PDEM;Time-dependent reliability;Impeller;Cross-flow fan;Agent model
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发布时间：2023-06-09 - 摘要：In order to estimate the mechanical components′ response reliability under interference of dynamic correlative stress-strength, the Copula function and random process theory were introduced to establish dynamic reliability model. Due to the complexity of random integral, the random process degenerates into random variable, and then the reliability at a fixed time was calculated based on the discretization thought. Furthermore, the function fitting optimization method was adopted to make the reliability value continuous. At the same time, according to model complexity and fitting residual, the optimal reliability function fitting method was selected. Finally, the typical verified example indicates the effectiveness and feasibility of this method.关键词：Stress-strength interference;Correlation;Dynamic Copula;Reliability;Monte Carlo;Fitting optimization
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发布时间：2023-06-09 - 摘要：To improve estimating accuracy in the traditional mean rank or median rank estimation method, an improved mean rank is proposed in the correction principle of rank estimation function as the cumulative distribution function of samples by adjusting the applicable points of natural mean rank. Then a least squares estimation is performed by directly fitting the cumulative distribution function. Based on the hypothesis of Weibull distribution under small sample, the parameter estimations under different ranks are calculated by Monte Carlo simulation. The results indicate that the relative error on calculating scale parameter using the improved mean rank method for the Weibull distribution with different parameters is less than 9.5% under the condition of sample size not less than 4. Furthermore, the relative error on calculating mean time between failures using the improved mean rank method is less than 8.7%, while the relative errors using traditional methods are higher than 16%. From calculated results, proposed method can effectively improve the parameter estimation accuracy for Weibull distribution.关键词：Improved mean rank;Least square method;Weibull distribution;Mean time between failures;Small sample;Monte Carlo simulation
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发布时间：2023-06-09 - 摘要：Automobile front axle structure is one of the core components of an automobile, which plays a decisive role in the automobile design. In order to improve the convergence speed and accuracy of the automobile front axle lightweight, an improved manta ray algorithm based on manta ray self-defense strategy is proposed. Six classical benchmark functions are used to verify the performance of the improved manta ray algorithm. Results show that the improved manta ray algorithm has competitive convergence speed and convergence accuracy. On this basis, the improved manta ray algorithm is used to optimize the lightweight design of the automobile front axle. The optimization results show that the optimal solution can be obtained after 94 iterations, and the total mass of the automobile front axle after optimization is reduced from 51.95 kg to 43.24 kg, a decrease of 16.75%. By analyzing the results of classical benchmark functions and automobile front axle cases, it can be seen that the improved manta ray algorithm is an efficient optimization algorithm, which provides reference for future engineering optimization problems and algorithm improvements.关键词：Manta ray foraging algorithm;Automobile front axle;Benchmark functions;Engineering optimization;Optimization algorithm
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发布时间：2023-06-09 - 摘要：A reliability analysis of medical equipment is implemented based on the q-Weibull distribution to provide a basis for healthcare organizations to revise their operational maintenance management strategies. The Weibull distribution failure rate function is monotonic and cannot fully describe the full life cycle operation of complex medical equipment. Therefore, this study introduces the q-Weibull distribution to predict the remaining life of medical equipment, uses a method based on the contour error function to simplify the q-Weibull distribution parameter estimation process, and verifies the validity and feasibility of the method using a hemofiltration apparatus and a lamp-holder of surgical shadowless lamp as examples, and compares the advantages and disadvantages of the two distributions by mean square error（MSE）, the Akaike information criterion（AIC） and the coefficient of determination R~2. Both distributions for the hemofiltration apparatus and lamp-holder of surgical shadowless lamp show the same predictive trend, but the R~2 and MSE comparisons show that the q-Weibull distribution had a better fit accuracy, especially the MSE(2.818 1×10-3)for the hemofiltration apparatus based on the q-Weibull distribution is much smaller than the MSE（9.465） for the Weibull distribution. When the hemofiltration apparatus and lamp-holder of surgical shadowless lamp are operated for 50 days, their estimated remaining life is 254.390 9 days and 291.011 1 days respectively. The above data verifies the validity and fitting accuracy of the q-Weibull distribution, which is worthy of further research and promotion in the reliability research of medical equipment.关键词：Medical equipment;Life prediction;Weibull distribution;q-Weibull distribution
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发布时间：2023-06-09 - 摘要：By designing structures with different gradients, the strength of lattice structure can be improved, and its mechanical properties such as impact resistance, energy absorption and vibration reduction can be improved. The Voronoi method was used to generate random points in the Eulerian space domain to form the basic unit cell of lattice structure. The distribution forms of different gradient unit cell structure were set, and finally the lattice structures with different gradient were generated. In this experiment, “inward” gradient and “outward” gradient were designed, and five different lattice structures with gradient grades of 0.5, 0.6, 0.7, 0.8 and 0.9 were designed for “inward” and “outward” structures, respectively. And gradient level of the uniform lattice structure was 1.0. The finite element analysis software Abaqus was used to simulate the mechanical properties of lattice structures with different gradients. The lattice structures were fabricated by 3D printing technology, and the mechanical compression experiment was carried out to verify the finite element analysis results. The results of finite element analysis and experiments show that the mechanical properties of lattice structures with different gradients generated by Voronoi method are better than that of the uniform lattice structure; in the “inward” gradient lattice structures, the mechanical properties of the lattice structure with gradient grade 0.6 are the best, with good shock resistance and vibration reduction; in the “outward” gradient lattice structures, the mechanical properties of the lattice structure with gradient grade 0.8 is the best. The overall performance of “outward” gradient lattice structure is better than that of “inward” gradient lattice structure. The gradient lattice structures based on Voronoi method have good mechanical properties such as high strength, vibration resistance and energy absorption. The mechanical properties of lattice structures are closely related to the gradient grade.关键词：Voronoi;Lattice structure;Gradient;Finite element analysis;Impact resistance;Energy absorption and vibration reduction
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发布时间：2023-06-09 - 摘要：In order to study the influence of warhead shape on the impact performance of polycarbonate（PC） plate against rod projectile, the impact tests of flat-head, hemispherical-head and ogival-head rod projectile with 12.6 mm diameter were carried out by gas gun. The relationship of initial-residual velocity and ballistic limit were obtained, and the deformation and failure mode of PC plate were analyzed in detail. The results show that in the velocity range of 30～120 m/s, the PC plate has the strongest resistance to hemispherical-nosed projectile, followed by flat-nosed projectile, and the weakest resistance to ogival-nosed projectile. The failure modes of PC plate are different after the three kinds of projectiles impact. The plat-bulge and plug failure occur after impacted by flat-nosed projectile, the cap-bulge and petal failure occur after the impact of hemispherical projectile, however, petal failure always occurs after the impact of ogival-nosed projectile. It is found that the energy consumption by crack propagation of PC thin plate is less, and the main reason for the great difference of ballistic performance is the difficulty in producing initial damage of PC plate for different projectiles.关键词：Polycarbonate;Impact test;Ballistic performance;Ballistic limit;Failure modes
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发布时间：2023-06-09 - 摘要：The research progress of designing and optimization of milling tool is summarized. The design process of cutting tools has greatly improved and optimized according to the existing problems in the field of cutting and manufacturing. The research progresses of the improvement and optimization of the milling tool in five aspects, such as: Machining quality, tool wear, machining vibration, chip removal performance and machining efficiency are mainly described and summarized. Finally, it analyzes the existing technical problems, and puts forward the corresponding prospects for the later research of NC milling tool technology.关键词：Milling tool;Design;Optimization;Machining
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发布时间：2023-06-09 - 摘要：The single layer re-entrant honeycomb cylindrical shell with different angles is established in this paper. Based on the single layer re-entrant honeycomb cylindrical shell with different angles, a novel composite re-entrant honeycomb cylindrical shell is proposed. The deformation behavior of single and multi-layer re-entrant honeycomb cylindrical shells under axial impact was studied by numerical simulation. By comparing and analyzing the plateau stress and specific energy absorption of single and multi-layer re-entrant honeycomb cylindrical shells under different impact velocities. The following conclusions can be obtained: compared with the single-layer re-entrant honeycomb cylindrical shell, the energy absorption capacity of the multi-layer re-entrant honeycomb cylindrical shell is significantly improved under the same density and size. The deformation position of re-entrant honeycomb cylindrical shell is changed with different impact velocities.The multi-layer re-entrant honeycomb cylindrical shell doesn′t show negative Poisson’s ratio.关键词：Re-entrant honeycomb;Composite material;Cylindrical shell;Impact velocities;Energy absorption
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发布时间：2023-06-09 - 摘要：Based on the three-dimensional fractal theory, a fractal model of normal contact stiffness and contact damping of joint surfaces considering simultaneously the influence of the friction and the asperity interaction was established. Through the simulation of the built model, the influence of friction coefficient, fractal dimension, fractal roughness parameter and contact load on contact stiffness and contact damping was analyzed. The results show that the contact stiffness and contact damping of this model increase with the increase of normal load and fractal dimension, and decrease with the increase of the fractal roughness parameter; and the contact stiffness decreases with the increase of friction coefficient, but contact damping increases first and then decreases with the increase of friction coefficient. In addition, the cases of interaction only considering the asperity and interaction without the friction and the asperity are compared and analyzed, and it is concluded that the interaction of asperities can slightly increase the contact stiffness when the fractal dimension D=2.4, and at that time D≥2.5, the asperity interaction can reduce the contact stiffness, and the degree of reduction can become larger and larger. At that time2.4≤D≤2.9, the asperity interaction can reduce the contact damping. In addition, the simulation calculation results of the built model are compared with the experimental data to verify the correctness of the built model.关键词：Friction;Interaction;Joint surfaces;Stiffness;Damping
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发布时间：2023-06-09 - 摘要：In order to study the dynamics of a very large monopile offshore wind turbine under emergency shutdown, the DTU 10 MW monopile offshore wind turbine is used as the research object to establish a turbulent wind-wave-earthquake load multi-physics field model with wind and wave correlation and construction of soil-structure coupling model by p-y curve method, Q-z curve method and Winkler model. The dynamics of the wind turbine under normal operation, shutdown and emergency shutdown were studied. The results show that the wind turbine is most affected by the seismic load under the shutdown condition, and the extreme differences of the forward-backward and lateral displacements of the tower top increase by 249.22% and 1 869.14%, respectively, and the peak shear stress of the support structure increases by 333.33% compared with that without the earthquake. During the emergency shutdown operation, the shear stress of the support structure and the strain energy of the tower were greater than the normal operation at the same time due to the blade pitch effect. The emergency shutdown operation increased the displacement range of the tower top and shifted the vibration center to the direction of turbulent wind flow, and effectively relieved the shear force surge of the support structure and the strain energy gathering in the front and rear of the tower caused by the external load.关键词：Emergency shutdown;Offshore wind turbine;Seismic load;Wind and wave related;Soil-structure coupling effect
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发布时间：2023-06-09 - 摘要：Aiming at the problem of failure strength analysis and prediction of bolted composite connection, the strong nonlinear mapping ability of deep learning neural network was used to non-linear fit the influence of different parameters on the failure load of composite bolting, and the influence weight of each parameter was allocated. A prediction model was constructed based on limited training samples to predict the peak failure load of bolted composite joints. Using finite element software, the data set of peak failure load of bolted laminates was calculated to construct the deep learning neural network. Through the test, it is determined that the development effect of deep learning model is the best when the number of hidden layers is two. The mean square error between the predicted value and the finite element simulation value is taken as the loss function, and the learning rate is set at 0.01. When the mean square error is the minimum, the training is stopped, and the best deep learning prediction model is obtained. The model is used to predict the maximum value of all the prediction results of peak load failure and the corresponding parameter combination, and compared with the simulation results of the same parameters, the difference between them is 1.4%. Compared with the prediction methods of finite element simulation and empirical formula fitting, the deep learning prediction method has obvious advantages in time efficiency.关键词：Carbon fiber composites;Bolted connection;Peak failure load;Deep learning;Neural network
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发布时间：2023-06-09 - 摘要：In engineering practice, due to various functional requirements, structures with geometric discontinuities occur widely; in addition, most structures undergo complex multiaxial loads, which drives the development of relevant theories. As a result, to provide reference for structural anti-fatigue design and ensuring their operation safety, the establishment of fatigue lifing methods for notched components under multiaxial loads is critical and indispensable. In this paper, by combining the popular Fatemi-Socie critical plane model with the critical distance theory, a fatigue lifing model for notched structures under multiaxial loads was established, and its effectiveness was verified with the fatigue test data of TC4 stepped shaft specimens. Results show that the proposed model can overcome the conservative estimation problem when performing fatigue lifing based on the stress-strain data of critical points, with all predicted fatigue lives within two-time error bands. Finally, the method was applied to the fatigue life prediction of a turbine compressor disc.关键词：Fatigue;Notch;Compressor disc;Critical plane;Critical distance;Life prediction
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发布时间：2023-06-09 - 摘要：Leakage occurred on a company′s waste heat recovery unit after short-term operation of it. In order to determine the cause of the leak and take effective countermeasures, the reasons for the failure of the waste heat recovery device were analyzed. Firstly, the stress level of the waste heat recovery device under working condition was calculated by Ansys simulation software, and the maximum stress point was found at the tube sheet, and the stress value at the joint of tube sheet and heat exchange tube was larger.Then, macro-corrosion morphology analysis, metallographic microstructure analysis, micro-hardness test, scanning electron microscope（SEM） analysis of corrosion micro-morphology and EDS micro-area composition analysis of corrosion products were carried out on the sampling site of tube bundle leakage.The results show that, because of high temperature, increasing alkali concentration occurs at the crack of tube bundle. And welding cracks exist there, which eventually leads to alkali stress corrosion cracking at the weld of tube sheet and tube bundle.关键词：Waste heat recovery device;Leakage;Finite element simulation;Stress analysis;Failure analysis;Alkali stress corrosion
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发布时间：2023-06-09 - 摘要：In order to ensure safety and efficient state of nuclear power plant in the long time operation, it is necessary to figure out the acceptance table of defects of the primary loop to meet the requirement of rapid assessment in engineering. It is necessary to do the fracture mechanics and plastic limit load analysis for the cracked pipe. Through numerical simulation analysis, the rationality of adopting plastic limit load as the critical state of austenitic stainless steel structure with good fracture toughness is demonstrated. Based on the criterion of non-decreasing the plastic limit load in design state, the acceptance standard of defects for the austenitic stainless steel pipe is established in this paper. The results show that the defect acceptance size of the primary circuit pipe is close to that in the ASME code, but much larger than that of the RSE-M code, and the RSE-M code is too conservative.关键词：Pressure piping;Austenitic stainless steel;Limit load;Service induced defects;Acceptance criteria
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发布时间：2023-06-09 - 摘要：42CrMo is a kind of ultra-high strength steel, which has high strength, good hardenability and small deformation after quenching. It is widely used in driving materials such as large gears, bearing spindle and connecting rod used in traction. Bending fatigue test is of great significance for fatigue life prediction of gears. First of all, the bending fatigue test data of gear under alternating load at stress ratio R=0.1 were obtained, the P-S-N curve of gear bending fatigue strength and the fitting curve relation were obtained, and the fatigue limit value of gear under different reliability was obtained. Then the finite element method was used to simulate the bending fatigue test of gear. The static strength at the root of the gear tooth is compared with the theoretical value, and the analysis shows that the numerical simulation results are basically consistent with the theoretical analysis results, which can be used as the basis of fatigue life simulation of bending fatigue test. Finally, the experimental values of the bending fatigue life test are compared with the numerical simulation results. The results show that the fatigue life test values are basically consistent with the numerical simulation results when the reliability is 84.1%, which verifies the accuracy of the numerical simulation and can effectively predict the bending fatigue life of 42CrMo gear.关键词：Gear;Bending fatigue;Fatigue life;P-S-N curve
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发布时间：2023-06-09 - 摘要：In order to solve the problem that the reliability analysis of special semitrailer frame depends heavily on the sample vehicle, a calculation method of structural vibration fatigue estimation based on random load history in frequency domain is proposed. Firstly, the correctness of the frame analysis model is verified through the comparative analysis of the frame modal and static load test; Then the frequency response is calculated to obtain the transfer function, and the stress power spectral density of the structure is obtained by combining with the dynamic load power spectral density of the frame; Finally, according to the material parameters, the appropriate fatigue damage model is selected, and the frequency domain method is used to predict the fatigue defect location and life of the frame structure. Through the fatigue test, the predicted results are credible, which provides a more credible scheme for the design and improvement of special frame structure.关键词：Frame;Multibody dynamics;Frequency domain;Fatigue life;Test
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发布时间：2023-06-09 - 摘要：The new rigid-flexible coupling system for vehicle-beam expansion joints is proposed in the context of all-steel load-bearing radial tire by using the RecurDyn multi-body system dynamics simulation platform, the system is used to simulate the whole contact process of 1/4 car body through expansion joint, and the dynamic response of car body and beam body expansion joint is compared with the traditional simulation results. The results show that the simulation waveform of the new coupling system is consistent with the traditional method and the waveform is sensitive to the two influence factors in the coupling system, which verifies the good contact dynamic characteristics of the coupling system, the contact stability of the beam body can be improved by strengthening the connection between the side beam and the beam body and the end structure, the car with the new type of tire should not exceed 80 km/h when passing the seam. The coupling system provides a new and effective method for joint dynamic simulation of vehicle-beam expansion joint.关键词：Expansion joint;Rigid-flexible coupling system;Vibration response;Dynamics;RecurDyn
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发布时间：2023-06-09 - 摘要：In order to study the influence of pitting defect on the contact stress of face gear, a face gear of helicopter transmission system was taken as the research object, the defect shape was assumed to be spherical and the solid model was built by UG and Catia software. Using the finite element loading tooth contact analysis method（LTCA）, the contact stress distribution and variations of maximum contact stress value and its position are obtained when the defect is in different position on the tooth surface. The results show that the introduction of pitting defect can increase the maximum contact stress of tooth surface by 21%. When the defect is close to the contact trace line and tooth tip, the maximum contact stress is greater than that of other positions. The maximum contact stress occurs near the middle or upper part of the defect, its position is on the right of the defect while the defect is outside the contact trace line, and it is the opposite when the defect is inside the contact trace line. The maximum contact stress near the defect increases with the increase of defect radius gradually. The influence of defect depth on contact stress is small.关键词：Face gear;Contact stress;Defect;Finite element method
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发布时间：2023-06-09 - 摘要：In order to solve the problem of low connection strength between elastic skin and honeycomb sandwich of composite flexible skin for variant aircraft, a “two-step bonding” connection scheme is proposed. Firstly, the polyurethane fiber cloth and honeycomb are bonded by epoxy resin structural adhesive, then the silicone rubber sheet and the spandex fiber cloth are bonded by the silicone rubber adhesive, and the manufacturing method is given. Finally, “two-step bonding” experimental piece and “direct bonding” experimental piece were prepared respectively, and the bonding strength experiment and comparative analysis were carried out, The results show that the bonding strength of the “two-step bonding” experimental piece is five times that of the “direct bonding” experimental piece.关键词：Flexible skin;Elastic skin;Honeycomb structure;Two-step bonding;Direct bonding
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发布时间：2023-06-09 - 摘要：When the BP neural network model is used to predict the reliability of the grain dryer, the model has problems such as slow convergence speed and easy to fall into local optimum. An improved particle swarm algorithm is used to optimize the BP neural network model and establish the PSO＿BP neural network The reliability prediction model of grain dryer is compared with MAERMSEMAPE index obtained by BP network model and GA＿BP network model. The research results show that when the improved PSO＿BP network model is used for forecasting, the three indicators are reduced by 0.051 8, 0.047 9 and 28.04% respectively compared with the BP network model; the three indicators are reduced by 0.000 4, 0.000 2 and 0.61% respectively compared with the GA＿BP network model, Which shows that it has smaller errors and better predictive ability. The methods and ideas for realizing accurate prediction of the reliability of grain dryers are provided.关键词：Grain dryer;Particle swarm algorithm;BP neural network;Reliability prediction
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发布时间：2023-06-09
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