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.

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.

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.

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.

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.

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.

DEVELOPMENT OF MATERIAL USED FOR AVIATION APPARATUS AXLE JOURNALS

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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.

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.

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.

A hybrid ensemble deep reinforcement learning model for locomotive axle temperature using the deterministic and probabilistic strategy

This paper proposes a hybrid deep reinforcement learning framework for locomotive axle temperature by combining the wavelet packet decomposition(WPD),long short-term memory(LSTM),gated recurrent unit(GRU)reinforcement learning and generalized autoregressive conditional heteroskedasticity(GARCH)algorithms.The WPD is utilized to decompose the raw nonlinear series into subseries.Then the deep learning predictors LSTM and GRU are established to predict the future axle temperatures in each subseries.The Q-learning could generate optimal ensembleweights to integrate the predictors to finish the deterministic forecasting and GARCH is used to conduct the deterministic forecasting based on the deterministic forecasting residual.These parts of the hybrid ensemble structure contributed to optimal modelling accuracy and provided effective support in the real-time monitoring and fault diagnosis of transportation.

益肾化湿颗粒联合达格列净治疗糖尿病肾病脾肾气虚证临床研究

目的:观察益肾化湿颗粒联合达格列净治疗糖尿病肾病(DN)脾肾气虚证的临床疗效及对血小板反应蛋白1 (TSP-1)、可溶性Axl受体酪氨酸激酶(sAxl)水平的影响。方法:采用随机数字表法将88例DN脾肾气虚证患者分为对照组与观察组各44例。对照组给予单纯达格列净治疗,观察组给予益肾化湿颗粒联合达格列净治疗。比较2组治疗前后中医证候积分、肾脏功能指标、血糖指标、TSP-1、sAxl水平,评估2组临床疗效及不良反应发生情况。结果:治疗后,观察组总有效率93.18%,高于对照组77.27%(P<0.05)。治疗后,2组中医证候积分、尿白蛋白/肌酐比值(UACR)、尿白蛋白排泄率(UAER)、空腹血糖(FBG)、餐后2 h血糖(P2hBG)、糖化血红蛋白(HbA1c)、 TSP-1、 sAxl水平均低于治疗前(P<0.05),肾小球滤过率(eGFR)水平高于治疗前(P<0.05),且观察组治疗后UACR、UAER、TSP-1、sAxl水平及血糖指标均低于对照组(P<0.05),eGFR水平高于对照组(P<0.05)。2组不良反应发生率比较,差异无统计学意义(P>0.05)。结论:益肾化湿颗粒联合达格列净治疗DN脾肾气虚证疗效显著,能有效改善患者肾脏功能,控制血糖,降低TSP-1、sAxl水平,安全性较高。

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。

Vibration of Axle Box from Wheel Diameter Difference in Vehicle

The wheel diameter difference would worsen the dynamic performance and affect the safety of the rail vehicle.Therefore,it is necessary to detect wheel diameter difference while the train is operating.However,several existing detection methods can’t accurately detect and diagnose the wheel diameter difference under highspeed running environment.In this study,a new method of detecting wheel diameter difference was proposed for high speed rail vehicle.The wheel diameter difference would be diagnosed by the amplitude and frequency of vibration impact on the axle box.Firstly,the dynamic model with varying wheel diameters was established in SIMPACK,and LMA tread was used in high-speed rail vehicles.Then,the simulation results of rail vehicle dynamic performance were compared under different wheel diameter differences.After that,the relationship between axle box vibration and wheel diameter difference was used to demonstrate the feasibility of this detection technology.Finally,comparing and analyzing the simulation results of vibration obtained by matching treads with different wheel diameters,it shows that by increasing the wheel diameter difference,the longitudinal and lateral impacts on axle boxes increase asymmetrically,and the amplitude and the frequency become more evident.Therefore,this paper presents a technical scheme of online measuring wheel diameter difference by monitoring the vibration of the axle box.

Hierarchical methodology to evaluate the quality of disparate axle load data sources for pavement design

Axle load data are an essential input for pavement design,yet for most North American agencies,there is uncertainty about the quality of axle load data obtained from weigh-inmotion(WIM)systems,the applicability of these data for pavement design,and potential opportunities to integrate axle load data from disparate sources.This article presents a novel and practical methodology to evaluate the quality of axle load data from WIM systems and roadside weigh scales through a series of hierarchical analyses designed to test data validity.When applied using data from Manitoba,Canada,the methodology quantified the uncertainty of axle loads measured at the weigh scales and piezo-quartz WIM,concluding that both could be used for pavement design applications.Data collected at piezo-polymer WIM sites exhibited poorer data validity;however,application of site-specific temperature correction factors significantly improved data validity at these sites.The article describes how other data quality dimensions,including spatial coverage,temporal coverage,and long-term data availability,could be considered when determining the suitability of disparate axle load data sources for pavement design.Application of the methodology enables a pragmatic evaluation of the quality and limitations of commonlyavailable axle load data,revealing uncertainties and data needs relevant for pavement design practice.

Effect of Nb addition on microstructure and mechanical properties of 25CrNiMoV(DZ2)steel for high-speed railway axles

The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back-scattering diffraction,transmission electron microscopy and physicochemical phase analysis.The results show that the grain size of the original austenite of the test steels decreases from 20.5 to 14.2 and 10.8μm after adding 0.026 and 0.039 wt.%Nb to a 25CrNiMoV steel,respectively.Moreover,the block width of the tempered martensite in the test steels is refined from 1.91 to 1.72 and 1.60µm,respectively.MC-type precipitates in 25CrNiMoV steel are mainly VC,while(Nb,V)C gradually precipitates when Nb is microalloyed,and the amount of precipitates increases with increasing Nb content.Through strengthening mechanism analysis,it is found that grain refinement strengthening is the primary way to increase the strength.The improvement in the yield strength with increasing Nb content is attributed to a significant increase in precipitation strengthening,grain refinement strengthening and dislocation strengthening.