Establishment of the thermo-mechanical coupling model of axle box bearings with track irregularity excitation and analysis of its temperature characteristics

As an important component of the running gear of high-speed trains,axle box bearings can cause lubricating grease failure and damage to bearing components under continuous high-temperature operation,which will affect the normal operation of highspeed trains.Therefore,bearing temperature is one of the key parameters to be monitored in the online monitoring system for trains.Based on the thermal network method,this paper establishes a thermal network model for the axle box bearing,considering the radial thermal deformation of the double-row tapered roller bearing components caused by the oil film characteristics and the temperature variations of the lubricating grease.A thermo-mechanical coupling model for the grease-lubricated double-row tapered roller axle box bearing of high-speed trains with track irregularity excitation is established.The correctness of the model is verified using the test bench data,and the temperature of the bearing at different rotational speeds,loads,fault sizes,and ambient temperatures are investigated.

Instrumented oscillographic study on impact toughness of an axle steel DZ2 with different tempering temperatures

Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.

Optimal allocation method of electric/air braking force of high-speed train considering axle load transfer

Reasonable distribution of braking force is a factor for a smooth,safe,and comfortable braking of trains.A dynamic optimal allocation strategy of electric-air braking force is proposed in this paper to solve the problem of the lack of consideration of adhesion difference of train wheelsets in the existing high-speed train electric-air braking force optimal allocation strategies.In this method,the braking strategy gives priority to the use of electric braking force.The force model of a single train in the braking process is analyzed to calculate the change of adhesion between the wheel and rail of each wheelset after axle load transfer,and then the adhesion of the train is estimated in real time.Next,with the goal of maximizing the total adhesion utilization ratio of trailer/motor vehicles,a linear programming distribution function is constructed.The proportional coefficient of adhesion utilization ratio of each train and the application upper limit of braking force in the function is updated according to the change time point of wheelset adhesion.Finally,the braking force is dynamically allocated.The simulation results of Matlab/Simulink show that the proposed algorithm not only uses the different adhesion limits of each trailer to reduce the total amount of braking force undertaken by the motor vehicle,but also considers the adhesion difference of each wheelset.The strategy can effectively reduce the risk and time of motor vehicles during the braking process and improve the stability of the train braking.

Effect of Seasonal Variations on the Behavior of Flexible Pavements in Burkina Faso: Towards Alternating and Periodic Loading of Multi-Axle Heavy Goods Vehicles for Road Durability

Bituminous materials are heat-sensitive, and their mechanical properties vary with temperature. This variation in properties is not without consequences on the performance of flexible road structures under the repeated passage of multi-axles. This study determines the influence of seasonal variations on the rate of permanent deformation, the rut depth of flexible pavements and the effect of alternating loading of heavy goods vehicles following the temperature variations on the durability of roads. Thus, an ambient and pavement surface temperature measurement was carried out in 2022. The temperature profile at different layers of the modelled pavement, the evaluation of deformation rates and rutting depth were determined using several models. The results show that the permanent deformation and rutting rates are higher at the level of the bituminous concrete layer than at the level of the asphalt gravel layer because the stresses decrease from the surface to the depth of the pavement. On the other hand, the variations in these rates, permanent deformations and ruts between the hot and so-called cold periods are more pronounced in the bitumen gravel than in bituminous concrete, showing that gravel bitumen is more sensitive to temperature variations than bituminous concrete despite its higher rigidity. Of these results, we suggested a periodic and alternating loading of the different types of heavy goods vehicles. These loads consist of fully applying the WAEMU standards with a tolerance of 15% during periods of high and low temperatures. This regulation has increased 2 to 3 times in the durability of roadways depending on the type of heavy goods vehicle.

Simulation Research on Stress Intensity Factors of Different Crack Aspect Ratios on Hollow Axles

Because of the wicked service environment of the high speed train, it is possible that the hollow axle of the train may encounter the foreign object damage and form a sharp notch. Under the fatigue loading a crack can initiate from the notch and propagate to failure. It is noted that the stress intensity factor is the control parameter of the crack propagating, for the purpose of getting the more exact propagation characteristics, the stress intensity factor is studied mainly. The service loads of hollow axles are defined, and the stress distribution of hollow axles is obtained according to the load spectrum. The semi-ellipse crack configuration is defined with three parameters： the aspect ratio, the relative depth and the relative location along the crack front. Quarter point 20-node isoparametric degenerate singular elements are used for the region near the crack tip. The finite element model of crack extension of hollow axle is created, and the crack front is dispersed which can realize orthogonal extension. Based on this the stress intensity factors of crack front were calculated, and the distribution rules of the stress intensity factors of different initial crack shapes are obtained. The conclusions are compared with that of the analytic method and they agree with each other very well, and the calculating results show that there is a close relationship between the stress intensity factor and the initial crack shape. For a round crack the stress intensity factor at the surface point increases faster than the one at the center point with the crock propagation. However, for a narrow crack, the results are in contrast with that of a round one. So, all the cracks with different shapes propagate toward to a similar shape, and they grow at this shape to end. The study may contribute to the crack propagate characteristics research.

Analysis of Quenching Stresses in 35CrMo Axle

By using the finite element method （FEM）, we comprehensively analyzed the fields of temperature, organization, and stress in 35CrMo train axles during the quenching process is conducted, and experimentally studied the formation and evolution of inner stresses in axles during the quenching process. The results show that in the quenching process, stresses on the axle surface change from tensile to compressive gradually, while stresses in the axle core change from compressive to tensile gradually. Heat stresses and the amount of martensitic transformation are all increased with the increase of cooling rate. As a result, the maximmn instantaneous stresses in the axle are increased greatly when the cooling rate is increased with brine quenching. Large instantaneous tensile stress in the axle core with brine quenching is very likely to cause quench cracking and should be avoided.

Analysis and Optimization on Factors Affecting Forming Quality of Half Axle Gears Warm Precision Forging

Half axle gears is produced by precision forging popularly because of the advantages in minimum machining allowances, lower material consumption and good service properties. But the forming quality of precision forging is difficult to control. Many simulations and analysis of precision forging process were taken by previous researchers. But no concrete method is proposed to evaluate and optimize the forming quality of half axel gears. The primary purpose of this work is improving the forming quality of half axel gears by analyzing and optimizing the affected factors of forming quality. The enclosed-die warm forging process of half axle gears was developed, and a new type of die-set used on double action hydraulic press was brought forward. The main influential factors of precision forming quality were analyzed after the forming process had been simulated by using finite element method（FEM）. These factors include die structure, web thickness and web position. A method used to evaluate the forming quality was established, which investigated the maximal forming load, the metal filling rate and the material damage factor. The FEM simulations of half axle gears precision forging were evaluated by this method. The results show that the best forming quality can be achieved when the punches were added with bosses, the web located at the middle plant of the gear, and the web thickness was 30 percent of the inner hole diameter. Verification experiments taking the above optimized parameters were performed on a 7.8 MN double action hydraulic press. The trial products were formed well. And their geometric precision meets the demand. The verification result shows that the optimization of the influential factors, according to the simulations and the evaluation method, can improve the forming quality. The new structure of precision forging die-set and the new evaluation method guarantee a high forming quality ofhalfaxel gears.

Experimental and numerical study on fretting wear and fatigue of full-scale railway axles

This study investigated the fretting wear and fatigue of full-scale railway axles.Fatigue tests were conducted on full-scale railway axles,and the fretting wear and fretting fatigue in the fretted zone of the railway axles were analysed.Three-dimensional finite element models were established based on the experimental results.Then,multi-axial fatigue parameters and a linear elastic fracture mechanics-based approach were used to investigate the fretting fatigue crack initiation and propagation,respectively,in which the role of the fretting wear was taken into account.The experimental and simulated results showed that the fretted zone could be divided into zones I-III according to the surface damage morphologies.Fretting wear alleviated the stress concentration near the wheel seat edge and resulted in a new stress concentration near the worn/unworn boundary in zone II,which greatly promoted the fretting crack initiation at the inner side of the fretted zone.Meanwhile,the stress concentration also increased the equivalent stress intensity factor range DKeq below the mating surface,and thus promoted the propagation of fretting fatigue crack.Based on these findings,the effect of the stress redistribution resulting from fretting wear is suggested to be taken into account when evaluating the fretting fatigue in railway axles.

DAMAGE TOLERANCE ANALYSIS ON HOLLOW AXLES OF HIGH SPEED MOTOR TRAINS

According to the rules of UIC515-3, the service loads of the axles are defined, which include some different loads cases as follows： the static loads; the impact loads resulted from running through the rail joints and unevenness rails; the loads through curves and from braking. Through the calculating and analysis, the stress distribution of the hollow axles is obtained for 200 km/h high speed motor trains used in China. At the same time, the fatigue crack growth of hollow axles is studied, and the initial surface cracks of 2 mm depth caused by hard objects strike or the other causes are discussed. On the basis of the linear elastic fracture mechanics theory, the stress intensity factor of the crack of the geometry transition outside the wheel seat is also studied. Associated with fatigue crack propagation equation and the corresponding crack propagation threshold, the crack propagation characteristics under different shapes are calculated. Then the running distances are educed with different shapes propagating to the critical length, and the estimation of the residual lives about hollow axles which are the reference values of examine and repair limit of the hollow axle is given.

Seismic and Geological Model of Jura Sedimentation from the South-West Part of Tarskii Axle Part

Seismic attributes have proliferated in the last three decades at a rapid rate and have helped interpreters in making accurate predictions in hydrocarbon exploration and development.Attributes sensitive to amplitude, such as impedance inversion and AVO,are widely used for lithological and petrophysical prediction of reservoir properties.Other attributes,such as coherence and curvature,are particularly useful

Dynamic Characteristics Analysis on Truck Drive Axle Assembly

A kind of single impulse welding drive axle used in a truck was selected as research object.The dynamic characteristic simulation of the drive axle was analyzed through building the vehicle dynamics simulation model in virtual software.Comparison between different speeds and different roads were made to get the corresponding dynamics of drive axle.

可溶性Axl受体酪氨酸激酶在老年急性失代偿性心力衰竭患者短期预后中的价值

目的 探讨急性失代偿性心力衰竭(ADHF)患者血清可溶性Axl受体酪氨酸激酶(sAxlTK)水平在评估短期预后中的临床价值。方法 选择2018年1月1日至2021年10月1日亳州市人民医院收治的老年ADHF患者238例,根据随访90 d内复合事件发生情况分为预后不良组45例和预后良好组193例。又根据血清sAxlTK最佳截断值分为高水平组80例和低水平组158例。检测血清sAxlTK、肌钙蛋白I(cTnI)和N末端B型钠尿肽前体(NT-proBNP)水平。结果 预后不良组血清sAxlTK水平明显高于预后良好组[43.89(33.95,51.44)μg/L vs 23.89(18.73,33.92)μg/L,P<0.01]。多因素logistic回归分析显示,血清cTnI和sAxlTK是ADHF患者短期预后不良的独立危险因素(OR=1.922,95%CI:1.035~3.568,P=0.039;OR=1.021,95%CI:1.008~1.034,P=0.001)。ROC曲线分析显示,血清sAxlTK、cTnI和NT-proBNP联合预测短期预后不良的曲线下面积为0.836(95%CI:0.778~0.895)。高水平组90 d内复合事件发生率明显高于低水平组(45.0%vs 5.7%,P<0.05)。Kaplan-Meier曲线分析显示,高水平组复合事件累积发生率较低水平组更高(χ^(2)=66.991,P_(log rank)<0.01)。高水平组总生存率较低水平组更低,生存预后更差(χ^(2)=16.899,P_(log rank)<0.01)。结论 老年ADHF患者入院时高血清sAxlTK水平与短期预后不良高风险有关。血清sAxlTK有希望成为短期预后不良早期预测的有用工具,且其与cTnI、NT-proBNP联合使用可进一步提高预后预测准确性。

受体酪氨酸激酶AXL在肿瘤生物学中的作用研究进展

AXL是一种受体酪氨酸激酶(receptor tyrosine kinase,RTK),属于TAM(TYRO3-AXL-MER)家族。在生理条件下,AXL表达于人体的心脏、骨骼肌、甲状腺中。AXL通过调控多条信号通路介导了肿瘤细胞的血管生成、迁移、侵袭、增殖与转移等过程。此外,AXL在多种癌症中高表达,对于肿瘤患者的预后评价具有重要意义,并极有可能成为一种新的诊断及预后生物标志物和治疗靶点。本文就近年来AXL在肿瘤生物学中的作用研究进展进行综述。

DEVELOPMENT OF MATERIAL USED FOR AVIATION APPARATUS AXLE JOURNALS

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FLEXIBLE 2-DOF STEERING MODEL OF MULTI-AXLE HEAVY-DUTY VEHICLE

A flexible two degrees of freedom (2-DOF) steering model of multi-axlevehicle (MAV) is presented with considering the effect of frame flexibility based on the classic2-DOF model. A method to calculate the frame flexibility is derived by using three moments equation.The steering stability of MAV is analyzed. The steering performance of MAV is also researched infrequency domain. Simulation results show that the dynamic effects of flexible model are more severethan rigid model and the flexible effect of frame will weaken the steering stability of MAV.Different disposals of steering axles lead to different steering characteristics of MAV. Thein-phase steering mode improves the steering characteristics and stability at high speed. Theanti-phase steering mode increases the steering mobility at low vehicle speed.

血清Occludin、Axl水平与急性缺血性脑卒中溶栓后出血转化的关系

目的探讨血清闭合蛋白(Occludin)、Axl水平与急性缺血性脑卒中(AIS)溶栓治疗后出血转化(HT)的关系。方法选取2019年1月至2022年1月该院AIS患者126例为研究对象,根据是否发生HT分为HT组(43例)和非HT组(83例)。比较两组一般资料及血清Occludin、Axl水平,采用多因素Logistic回归分析AIS患者发生HT的影响因素,采用受试者工作特征(ROC)曲线分析血清Occludin、Axl对AIS患者发生HT的预测价值,并分析血清Occludin、Axl预测HT发生的交互作用。结果两组心房颤动、入院时美国国立卫生研究院卒中量表(NIHSS)评分及血清Occludin、Axl水平比较,差异有统计学意义(P<0.05);多因素Logistic回归分析显示,心房颤动、入院时NIHSS评分高、血清Occludin高水平、Axl低水平均为AIS患者发生HT的独立危险因素(P<0.05);ROC曲线结果显示,血清Occludin、Axl预测AIS患者溶栓治疗后HT风险均有较高价值,二者联合预测的曲线下面积(AUC)、灵敏度、特异度分别为0.742、70.73%、66.93%。Occludin和Axl对HT发生存在负向交互作用。结论AIS患者血清Occludin、Axl均异常表达,可作为HT的预测指标,且二者对HT发生存在负向交互作用。

NEW TECHNOLOGY AND MACHINE TOOL FOR THE FORMING OF THE REAR AXLE SHAFT OF LIGHT TRUCK

A new technology of forward extrusion and cross rolling has been developed to process the rear axle shaft sleeve of light truck with the use of tube billets. This technology is characterized by large reductions of material, energy and cost of production and has significant economical benefits. This technology is stable and reliable. The three rolls transverse rolling mill built based on this technology has novelty construction, higher production efficiency, non-vibration and noise. The research results have been extensively applied to light trucks and farm transport with load of 1 to 3 tones.

Research on fatigue evaluation method of high-speed train axle based on axle box acceleration

As a key safety component of the high-speed train, fatigue fracture of the axle would lead to major accidents such as derailment or overturning. The complexity of the axle dynamic stress test seriously enhances the difficulty of axle fatigue damage analysis. In this paper, the dynamic stress test of the high-speed train axle was carried out,the axle box acceleration was monitored on-track during the test, and the relationship between the axle stress spectrum and acceleration was analyzed on-track. The results show that the relationships between the axle equivalent stresses and the Root Mean Square(RMS) values of the axle box vertical acceleration and lateral acceleration exhibit a strong joint probability density distribution. The concept of the virtual surface density of wheel-rail contact is also proposed to realize the purpose of using axle box acceleration to deduce axle equivalent force. The results quantify the relationship between axle box acceleration and axle equivalent force, provide a new method for predicting the axle damage using the acceleration RMS values, and open up a new approach for structural health monitoring of high-speed train axles.

Development of a Test Machine for IVECO Drive Axle

To improve the automation level of the vehicle drive axle test and better simulate a vehicle＇s actual operation, an advanced test machine has been developed. The load system of the machine consists of hand brakes and electric cylinders. It is simple-structured and low-cost. The major motor of the machine is controlled by a transducer and its speed can be adjusted easily. In addition, the programmed machine can automatically test such parameters as the grinding condition, the differential speed, the noise level, etc. It can also adjust the test procedures according to different requirements. Detailed discussion of the structure and mechanism of the test machine is given in this paper.

血清Decorin、sAxl和CYTL1水平与膝骨关节炎患者K-L分级的关系研究

目的探讨血清核心蛋白聚糖(Decorin)、可溶性Axl(sAxl)和细胞因子样蛋白1(CYTL1)水平与膝骨关节炎患者Kellgren-Lawrence(K-L)分级的关系。方法选取2021年8月至2023年5月该院收治的膝骨关节炎患者328例作为研究组,另选取同期体检健康者328例作为对照组。采用酶联免疫吸附试验检测血清Decorin、sAxl和CYTL1水平,西安大略和麦克马斯特大学骨性关节炎调查量表(WOMAC)评估患者临床症状。采用Spearman法分析血清Decorin、sAxl和CYTL1与K-L分级和WOMAC评分的相关性,Logistic回归分析膝骨关节炎的影响因素,绘制受试者工作特征(ROC)曲线分析血清Decorin、sAxl和CYTL1对膝骨关节炎Ⅰ~Ⅱ级、Ⅲ~Ⅳ级的诊断价值。结果研究组血清Decorin、sAxl水平显著高于对照组,CYTL1显著低于对照组,差异均有统计学意义(P<0.05)。K-L分级Ⅰ级、Ⅱ级、Ⅲ级、Ⅳ级血清Decorin、sAxl水平和WOMAC评分依次升高(P<0.05),CYTL1水平依次降低(P<0.05)。Spearman相关性分析显示,血清Decorin、sAxl与K-L分级和WOMAC评分均呈正相关(P<0.05),CYTL1与K-L分级和WOMAC评分呈负相关(P<0.05)。Decorin、sAxl高水平、CYTL1低水平为膝骨关节炎的危险因素(P<0.05)。血清Decorin、sAxl和CYTL1水平对膝骨关节炎Ⅰ~Ⅱ级、Ⅲ~Ⅳ级有一定诊断价值。结论血清Decorin、sAxl和CYTL1水平与膝骨关节炎K-L分级密切相关,均可用于膝骨关节炎Ⅰ~Ⅱ级、Ⅲ~Ⅳ级的辅助诊断。