In order to study the flexible dynamic vibration characteristics of railway freight cars, a rigid-flexible coupling dynamic model of railway freight cars C80 was established by joint simulation of NASTRAN and SIMPACK. The model was verified by modal test and dynamic calculation, in which the maximum error of mode is 9.70

Improving the strength of face-centered cubic CoCrFeNi-based high-entropy alloys remains challenging because conventional precipitation strengthening often incurs a pronounced strength-ductility trade-off. In Nb-Mo-alloyed CoCrFeNi systems, micron-scale Laves phases can be retained to provide strength, yet further optimization critically depends on how Nb and Mo are partitioned and retained as effective solutes in the face-centered cubic matrix to promote nanoscale precipitation and atomic-scale short-range ordering. In this study, CoCrFeNiNbxMo0.4-x alloys with different Nb/Mo ratios (ANM13, ANM22, and ANM31) were annealed at 700 degrees C for 24 h to clarify solute-concentration-controlled microstructural evolution and its correlation with tensile behavior. The results show that all alloys develop a hierarchical microstructure consisting of micron-scale Laves phases, nanoscale Cr2Nb-type Laves precipitates, and atomic-scale short-range order within the face-centered cubic matrix. Varying the Nb/Mo ratio produces a clear solute-partitioning effect, leading to a systematic redistribution of Nb and Mo between the matrix and Laves phases and thereby altering the effective matrix supersaturation for nanoscale precipitation and short-range ordering. As a consequence, ANM13 achieves the most favorable strength-ductility balance, with a yield strength of similar to 751 MPa, an ultimate tensile strength of similar to 1100 MPa, and a tensile elongation of similar to 15.1%, whereas ANM31 exhibits the highest yield strength of similar to 860 MPa but with reduced ductility. Quantitative strengthening analysis further reveals a composition-dependent redistribution of strengthening contributions across different length scales. Strain-hardening analysis indicates that ANM13 maintains a broader strain-hardening plateau and a slower decay of strain-hardening rate, consistent with its enhanced uniform deformation capability. These findings demonstrate that regulating matrix solute availability via Nb/Mo-controlled partitioning provides an effective route to couple Laves-phase retention with nanoscale precipitation and atomic-scale short-range ordering, enabling compositional tuning of the microstructural hierarchy and strength-ductility synergy in CoCrFeNi-based high-entropy alloys.

Post-welded geometric treatment(PWGT) can effectively mitigate or eliminate weld defects and improve the fatigue performance of weldments. However, quantitatively evaluating the fatigue improvement resulting from PWGT is still a challenge in engineering practice. In this study, finite element-based averaged elastic strain energy (SED) evaluation approaches for both 2D and 3D joints are proposed and validated in advance. The impact of PWGT on fatigue behaviors is investigated utilizing the SED method. More than 300 fatigue data with detailed information provided in the literature, such as joint types, shapes of geometric treatments, and base materials, were collected and analyzed. It turns out that SED, as an effective parameter, is capable of quantitatively characterizing fatigue improvements from PWGT compared to as-welded conditions. The analysis results indicate that the strength of the base material has a significant impact on the fatigue improvement from PWGT. Then, fatigue design curves are proposed corresponding to the strength of base materials and validated by a set of fatigue data of gusset joints.

In order to describe the local cyclic behavior of welds during low cycle fatigue of welded structures, so as to effectively assess the low cycle fatigue of structures, a structural strain numerical method is proposed. Based on the plate and shell theory and elastic-plastic theory, the numerical method of equivalent structural strain parameter is derived, and the UMAT subroutine of ABAQUS software is used to solve the structural strain parameters directly. The fatigue life of the welded specimens of different materials was evaluated, and the predicted life was basically the same as the test life, among which the maximum error of the predicted life of structural steel was 12%, the maximum error of the predicted life of aluminum alloy was 15.7%, and the maximum error of the predicted life of titanium alloy was 7.3%. The fatigue data of different materials were analyzed by using the master E-N curve, and the results showed that all the evaluated fatigue data were distributed in the same narrow band of the master E-N curve, which proved the effectiveness of the equivalent structural strain range for the evaluation of low cycle fatigue of welded specimens.

As railway freight technology advances towards heavy-load, high-speed capabilities, the design of liquid tank products is evolving to prioritize high load capacity, lightweight, high-strength materials, low structural rigidity, and thin-walled construction. These changes result in pronounced nonlinear low-frequency vibrations during rail operation. Addressing these complex liquid-solid coupled vibrations requires accurate dynamic modeling of the structural system. This paper introduces a novel dynamic modeling method for liquid tank products based on acousto-elastic coupling. This approach considers the swaying of the free liquid surface and liquid-solid interactions, enabling precise characterization of these dynamics in a unified model. Specifically, it tackles the challenge of uneven node swaying forces caused by non-uniform liquid surface meshing, presenting a technique and program to adjust swaying recovery forces based on nodes’ actual coverage area. This method’s liquid sway frequency calculations showed a 10% precision increase over traditional methods, more accurately reflecting liquid vibration states. The paper applies these techniques to a single tank container and an LNG tank container on a flatbed trailer. Through theoretical, simulation, and experimental comparisons, the model’s accuracy and reasonableness were validated. This low-dimensionality, high-precision dynamic model is universally applicable, especially valuable in modeling complex engineering structures.

The main S-N curve method is a new method for fatigue calculation,which is widely used in fatigue analysis of welded structures.In order to predict the fatigue life of welded structures under the test load,firstly,the bench model is taken as the boundary condition to make the test load become the input of simulation analysis,and the more accurate dynamic response of weld is obtained through steady-state dynamic calculation.Second,in the master S-N curve method of quasi static calculation process,based on the introduction of dynamic structural stress based on modal structural stress superposition calculation method,the method to obtain the modal coordinates and calculated by the dynamic welding structure modal stress superposition structure,structure dynamic stress and the equivalent stress calculation,the method adopts the Lord S-N curve forecasting life assessment.Finally,the fatigue evaluation software of welded structure modal structure stress method is developed.The software is used to carry out the fatigue evaluation and fatigue test comparison.The results show that:this method can effectively identify the fatigue failure parts of the car body under dynamic loading,which verifies the effectiveness and superiority of this method in fatigue evaluation of welded structures under dynamic loading,and provides a technical basis for the study of fatigue life evaluation of welded structures and the expansion of the main S-N curve method.

This work provides a post-processing procedure to predict the high- and low-cycle fatigue life of welded structures. The post-processor calculates the equivalent structural strain range, given the traction stress state at the weld notch, by enforcing the equilibrium condition and Navier's hypothesis. The return mapping algorithm is applied to deal with the low-cycle fatigue condition in which through-thickness plastic deformation develops. The proposed method predicts the fatigue life of 793 welded joints of different configurations made from steel, magnesium, titanium, and aluminum alloy. The predicted high- and low-cycle fatigue lives agree equally well with the experimental result.

The averaged elastic strain energy density (SED) within a characteristic volume radius R has been investigated and applied for characterizing the fatigue strength of welded joints for decades. However, engineering applications are still relatively rare. The main reason is that the calculation process is cumbersome due to fine mesh size and circular pattern requirements. This study proposes a novel approach of SED without requiring special finite element size and special layout requirements. First, a novel approach of the notch stress solution is presented. As a result, the present solution differs from the conventional approach which has been focused on notch tip singular stress field. Then, an averaged strain energy density can be obtained analytically by taking advantage of the new notch stress solutions presented in this study. Both the closed-form notch stress solutions and resulting expression for average strain energy density have been validated by FEA results. Subsequently, a large number of fatigue tests published in the literature are selected to examine the effectiveness of the evaluation approach of SED on interpreting fatigue behaviors of welded joints. Finally, a procedure for practical engineering application is established and verified by a group of fatigue tests of 3D gusset welded components.

轻量化车体具有线弹振动属性,但是其响应特性则要真实地反映轮轨接触与转向架悬挂两大非线性影响.轨道车辆刚柔耦合关系会因复杂约束奇异性而变得难以确定,使既有振动疲劳评估方法丧失了应用前提.利用刚柔耦合仿真技术,在多轴激励下构建一种基于动态质量阵的刚柔耦合关系,使柔性车体动态响应特性更加真实地反映相关非线性影响,实现与董氏结构应力恢复及焊缝疲劳损伤评估方法之间的无缝对接操作.应用这一新方法,某运煤敞车刚柔耦合仿真分析表明:在特定的直线扭曲激励输入下,车体摇晃迫使约6.10 Hz空车扭曲模态产生耦合共振,使钩缓冲击座附近焊缝最短寿命降低至30余万km.相应的下边去除修复方案也仅使最短疲劳寿命延长至50余万km.

In this work, load-controlled low-cycle fatigue tests of butt and lap joints are conducted, and a structural strain range parameter is proposed to characterize the fatigue behavior of weldment. A new scheme to calculate the structural strain range is formulated, which can deal with arbitrary material elastic–plastic behavior. The method captures the lateral structural constraint effect through the stress triaxiality parameter. The new fatigue parameter shows superior data transferability, which correlates high and low-cycle fatigue data of steel, aluminum, titanium, and magnesium weldments into one master E-N curve.

On the one hand, considering that the traditional fatigue method of railway freight cars is based on damage as a parameter, the influence of stress waveform cannot be considered. On the other hand, physical experiments have the characteristics of lag, long period, and high cost. The full-scale physical test and virtual test of car body are carried out. First of all, the data processing method of small deletion and the inverse problem load acquisition method based on data to data are proposed. Secondly, the dynamic stress calculation method with the bench as the boundary is proposed. Finally, taking the obtained load as the input of the physical and virtual bench, a new fatigue test method for simulating the running attitude of the car body line is completed. The acceleration RMS error of the C70E gondola body is less than 6%, the stress RMS is less than 13%, and the equivalent mileage is 3.125 million highway test results show that the car meets the life requirements of the car body. The inverse problem analysis results of virtual and physical tests are basically consistent, and the study of this method provides a basis for improving the fatigue reliability of freight car bodies.

For the locomotive with axle suspension, the driven gear is pressed-fit and integrated with the wheel into a whole. The helix angle can improve step characteristics of meshing stiffness for the gear transmission system which dynamic performance has a direct effect on the locomotive and its components. This paper proposes a gear-axle suspension locomotive coupled system dynamic 3D model, the gear transmission is coupled with a traditional locomotive dynamics system via the gear mesh interface. The influence of helix angle in the range of 0 degrees similar to 20 degrees on dynamic behavior of locomotive traction gear transmission system is investigated in detail, the peak acceleration trend indicated that the helix angle of 8 degrees minimizes vibration acceleration in three directions. The vibration acceleration peak value on the vertical, lateral, and rotational direction with the helix angle of 8 degrees is compared with the helix angle of 0 degrees, the three values decreased approximately 29.8%, 29.8%, and 29.6%, and the amplitude-frequency characteristic indicated that high frequency harmonic components of gear transmission system can be obviously improved by the helix angle. The results verify that helix angle have effect on the lateral dynamic responses of wheel in the coupled system.

Purpose The purpose of this paper is to propose an improved method which can shorten the calculation time and improve the calculation efficiency under the premise of ensuring the calculation accuracy for calculating the response of dynamic systems with periodic time-varying characteristics. Design/methodology/approach An improved method is proposed based on Runge–Kutta method according to the composition characteristics of the state space matrix and the external load vector formed by the reduction of the dynamic equation of the periodic time-varying system. The recursive scheme of the holistic matrix of the system using the Runge–Kutta method is improved to be the sub-block matrix that is divided into the upper and lower parts to reduce the calculation steps and the occupied computer memory. Findings The calculation time consumption is reduced to a certain extent about 10–35% by changing the synthesis method of the time-varying matrix of the dynamics system, and the method proposed of paper consumes 43–75% less calculation time in total than the original Runge–Kutta method without affecting the calculation accuracy. When the ode45 command that implements the Runge–Kutta method in the MATLAB software used to solve the system dynamics equation include the time variable which cannot provide its specific analytic function form, so the time variable value corresponding to the solution time needs to be determined by the interpolation method, which causes the calculation efficiency of the ode45 command to be substantially reduced. Originality/value The proposed method can be applied to solve dynamic systems with periodic time-varying characteristics, and can consume less calculation time than the original Runge–Kutta method without affecting the calculation accuracy, especially the superiority of the improved method of this paper can be better demonstrated when the degree of freedom of the periodic time-varying dynamics system is greater.

Modeling of vibration fatigue of welded structures in the frequency domain can be particularly challenging. For instance, the stress singularity at weld locations causes finite element size sensitivity in stress determination. Furthermore, the interactions of multiple vibration modes at a weld location can generate non-proportional multiaxial stresses. Here we present a comprehensive procedure for modeling multiaxial fatigue behaviors of welded structures in the frequency domain to address some of these issues. The procedure utilizes a robust mesh-insensitive method and modal decomposition approach to determine the normal and shear traction stress responses. We proposed a non-proportionality correlation function to interrelate the resulting power spectrum density (PSD) of normal and shear traction stresses and their cross-PSD (CPSD) for establishing an effective stress parameter. The correlation function is determined and validated based on the well-established time-domain path-dependent maximum range (PDMR) method through a small-scale data-driven approach.

PurposeIn this paper, the C80 special coal gondola car was taken as the subject, and the load test data of the car body at the center plate, side bearing and coupler measured on the dedicated line were broken down to generate the random load component spectrums of the car body under five working conditions, namely expansion, bouncing, rolling, torsion and pitching according to the typical motion attitude of the car body.Design/methodology/approachOn the basis of processing the measured load data, the random load component spectrums were equivalently converted into sinusoidal load component spectrums for bench test based on the principle of pseudo-damage equivalence of load. Relying on the fatigue and vibration test bench of the whole railway wagon, by taking each sinusoidal load component spectrum as the simulation target, the time waveform replication (TWR) iteration technology was adopted to create the drive signal of each loading actuator required for the fatigue test of car body on the bench, and the drive signal was corrected based on the equivalence principle of measured stress fatigue damage to obtain the fatigue test loads of car body under various typical working conditions.FindingsThe fatigue test results on the test bench were substantially close to the measured test results on the line. According to the results, the relative error between the fatigue damage of the car body on the test bench and the measured damage on the line was within the range of −16.03%–27.14%.Originality/valueThe bench test results basically reproduced the fatigue damage of the key parts of the car body on the line.

The design idea of express wagon is to ensure that the car-body has the characteristics of hi-cube capacity and easy loading and unloading which indirect causes the stiffness of car-body is changed with uncertain factors, such as the full sliding side covered and other forms of design, thus the running stability of the vehicle operation is affected and the risk of the transported goods is damaged will be increased. The random dynamic analysis for the express wagon is operated with the railway vehicles random analysis procedure (RVRAP) according to the analysis process firstly, then the uncertain stiffness is described by random variable and the modified stochastic perturbation method is employed to establish a deterministic approach. In this paper, the random variable parameter of side post stiffness for the express wagon is selected and the running stability index at three positions on the underframe are calculated. The result shows that the parameter uncertainty of stiffness of the side post has a greater impact on the vertical running stability than the lateral and ignoring the uncertainty of the parameter will result in a higher stability evaluation result.

为解决全尺寸车体疲劳试验周期长、成本高等问题,基于刚柔耦合多体动力学理论,依托铁路货车全尺寸车体疲劳试验台架,开展了台架试验仿真模拟关键技术研究.首先建立由虚拟刚性试验台架与柔性车体组成的刚柔耦合多体动力学试验模型,然后通过侧滚、浮沉等典型工况完成虚拟试验系统的理论验证,最后,将试验的随机驱动载荷作为仿真输入,开展虚拟试验台架上的车体动态响应计算与试验对比.结果表明:车体枕梁加速度仿真与试验结果吻合较好,加速度的频谱形状一致;关键部位动应力仿真结果与试验测试结果波形一致,验证了虚拟试验方法的合理性.该虚拟试验台架模型的建立为提升铁路货车产品疲劳可靠性提供了有力依据.

某轨道车辆的一个横向减振器座的焊缝在服役过程中出现了疲劳裂纹.?为了找到疲劳开裂的原因,在获得疲劳载荷谱的情况下,分别采用名义应力法、热点应力法以及结构应力法对开裂焊缝进行了疲劳寿命数值仿真计算.?数值仿真计算的结果表明,与名义应力和热点应力法相比较,结构应力法的计算结果最符合实际情况,且在焊缝应力集中的识别能力上,结构应力法也明显优于其它两种方法.?结合具体的工程实例,进一步讨论了3种方法的本质差异,得出在焊接结构抗疲劳设计的过程中,结构应力法最值得在应用中普遍推广.

In this paper, the discrepancy between the calculated and actual fatigue life distribution trend of the axles of railway vehicle structures is corrected. The calculations were made using the traditional fixed-axle model in which the wheelset rotation is neglected in random vibration analysis. A correction method is proposed, which is based on the original methods of fatigue life analysis of the axle structure of railway vehicles (i.e. the pseudo-excitation method and finite element model) and according to the characteristics of the symmetrical axle structure and the actual rotational operation state of the railway vehicle wheelset. Taking a locomotive system as an example, the minimum fatigue life calculated by the fixed-axle model is only 0.81 million km. In contrast, the minimum fatigue life calculated by the proposed method is 5.85 million km, which is consistent with the actual fatigue life of the axle. The position of the minimum fatigue life is also consistent with the actual position. The reliability of the proposed method for calculating the random fatigue life of the axle structure is illustrated. The influence and contribution of the prestress generated by axle press-fitting and vehicle serving weight of the railway vehicle acting on the axle on the axle fatigue life were studied. The results show that the prestress has a different influence on the fatigue life reduction of the wheelset. The minimum fatigue life reduction can reach 16.68% when all the prestresses are considered. Therefore, the influence of prestress should be considered in the design of railway vehicle axle structures. The idea of considering prestress should be proposed when revising axle standards.