Hollow Axle Research Articles

Application of hollow billets for the production of railway wheels and hollow car axles by screw piercing method

Application of hollow billets for the production of railway wheels and hollow car axles by screw piercing method

Gradient residual strain determination of surface impacted railway S38C axles by neutron Bragg-edge transmission imaging

Non-destructive and quantitative mapping of gradient residual strain distribution in surface-hardened railway S38C axles could provide a positive reference for determining service lifetime and maintenance strategy. To tackle this concern, time-of-flight neutron Bragg-edge transmission imaging was employed by real axle samples with and without impacted crater. A novel and simple procedure to formulate the residual strain field was also developed in this work, with the transmission batch code in Appendix A. By mapping the global two- dimensional residual strains, it can be verified that the residual strains into the axle are uniformly distributed in the hoop direction. Subsequently, it was revealed that the axial and hoop residual strains, respectively in the cylinder and the long strip samples prepared from a real S38C hollow axle, indicated a gradient evolution distribution with a depth of ∼ 8 mm, covering a range of −5500 ∼ 1000 με for axial strains and −6500 ∼ 1000 με for hoop strains. More importantly, the maximum compressive lattice strain of the cylinder sample was increased by 15.61 %, and 22.35 % at the impacting speeds of 100, and 125 m/s, respectively; and that of the long strip sample increased by 29.17 %, and 43.70 %, respectively. It can thus be concluded that lattice strains have redistributed around the impact crater, demonstrating the local alteration of the residual strain field. These new findings suggest the localized variation in residual strains should be taken into account while evaluating the service damage evolution of railway axles, especially those affected by high-speed impacts during operation.

Study of CNC skew rolling of hollow rail axles with a mandrel

The manuscript presents a new manufacturing technology for the production of hollow railway axle forgings. The manufacturing technology analyzed is based on three-roll skew rolling (TRSR) using a computer numerically controlled (CNC) rolling mill. The study focused on comparing the rolling capability of hollow products without and with a mandrel calibrating the hole of the forging. The influence of tube billet size on the rolling process was also analyzed. FE analysis and experimental studies were carried out. An analysis of the accuracy of the internal hole of the forging depending on the adopted parameters of the rolling process was carried out. Based on numerical simulations, the state of strain and the flow pattern of the material and temperature distribution during rolling were determined. The force parameters of the rolling process of hollow forgings were also analyzed. Based on the research, a two-stage rolling technology for rolling hollow railway axle forgings was proposed. The results obtained indicate the suitability of using a calibrating mandrel to improve hole accuracy in hollow forgings rolled from a tubular billet. The gap c between the bore diameter of the forging and the diameter of the mandrel was measured. Increasing the tubular billet dimensions from Ø42.4 × 10 mm to Ø48.3 × 12.5 mm reduced the gap c by 49.8%. Rolling the billet Ø51 × 14.2 mm in two passes compared to rolling in one pass reduced the gap c by 45.5%.

Gradient residual stress and fatigue life prediction of induction hardened carbon steel S38C axles: Experiment and simulation

Gradient distribution of triaxial residual stresses to a depth of several millimeters is retained in middle carbon steel S38C axles after high-frequency induction hardening, which has become a critical concern for fatigue structural integrity. To address this, the axial, hoop, and radial gradient residual strains inside the axles were measured for the first time by advanced neutron diffraction. The SIGINI Fortran subroutine was then adopted to reconstruct the global initial residual stress field from the measured data. Experimental and simulation results show that residual stresses of about −520 MPa (axial), −710 MPa (hoop), and −40 MPa (radial) residual stress were retained below the axle surface. Subsequently, the fatigue crack propagation behavior of S38C axles was numerically investigated in the framework of fracture mechanics. The calculated results clearly show that the compressive residual stresses at a depth of 0–3 mm from the axle surface lead to a low crack growth driving force, and that fatigue cracks do not propagate as long as the crack depth is less than 3.7 mm for hollow S38C axles. These results further indicate that the maximum defect size allowed in routine inspections is acceptable from a safety and economic point of view. Accurate measurement and characterization of the global gradient residual stress field through experiments and simulations can provide an important reference for optimizing the mileage intervals of nondestructive testing (NDT) of surface defects in these surface-strengthened railway axles.

Corrosion fatigue behavior and life prediction of railway axle EA4T alloy steel with artificial indentation

The combined effects of aggressive media and artificial surface indentation on the fatigue behaviours were investigated to evaluate the defect tolerance of high-speed hollow railway EA4T steel axles. Corrosive rotating-bending fatigue tests were performed on both smooth and notched specimens to assess their fatigue strengths and failure mechanisms. Based on the corrosion testing campaign, which mainly included examinations of the microstructure, residual stress, and fatigue crack resistance, material deformation underneath the bottom of indentations triggered corrosion fatigue cracks. The results also showed that the corrosive media was responsible for the decrease in fatigue strength, and notched specimens were more sensitive to 3.5 wt% NaCl solution than to air. The fracture surface indicated that cracks were mainly initiated from the notch of specimens in air, whereas cracks were formed from multiple sources in specimens in the corrosive medium. Finally, a three-parameter Kitagawa-Takahashi diagram was established to correlate the threshold stress range (Δσth) and critical defect size (a) with the corrosion fatigue life (N) in terms of the El-Haddad model, thus providing a scientific reference for the service safe region identification of high-speed railway axles subjected to corrosive environments.

Study on the method of establishing the probability of detection curve for ultrasonic detection on railway hollow axle cracks

Obtaining the ultrasonic probability of the detection (POD) curve of railway hollow axle cracks through experiments in an effective way has always been a pending issue. A new method of obtaining ultrasonic testing data for railway hollow axles crack is proposed, which can obtain a large amount of detection data from a small number of specimens. A new equivalent crack parameter which can characterize the location, area and direction of cracks is proposed, and the POD curve is analyzed by using this parameter, quantifying the crack detection capability of ultrasonic detection equipment for the first time. The range of POD for different crack depths under in-service detection methods was calculated using semi-circular crack and chordal crack as the critical state of semi-elliptical crack, respectively. When the crack depth reaches 10 mm, the POD can reach more than 80% regardless of the shape of the crack.

Research on monitoring method for crack depth of railway hollow axle during bench test

AbstractHollow axles are critical safety components for high‐speed trains, and the operational safety of the axle is ensured by combining infinite life design and damage tolerance analysis based on ultrasonic testing. The establishment of the ultrasonic inspection interval requires the axle bench test, but it has been a challenge to obtain the initial crack at a determined depth. This paper proposes a method for predicting the transverse crack depth of axles by combining a full‐scale axle bench test with simulation analysis. The monitoring of crack depth is achieved by measuring the cracks on the axle surface. The crack propagation test was conducted to validate the prediction method with good results. The test results demonstrate the potential of crack monitoring methods in axle crack monitoring and provide new ideas for axle safety monitoring.

Investigation on smoothed finite element methods using linear tetrahedral elements for high-speed train hollow axle strength analysis

PurposeThis paper aims to investigate the performance of two novel numerical methods, the face-based smoothed finite element method (FS-FEM) and the edge-based smoothed finite element method (ES-FEM), which employ linear tetrahedral elements, for the purpose of strength assessment of a high-speed train hollow axle.Design/methodology/approachThe calculation of stress for the wheelset, comprising an axle and two wheels, is facilitated through the application of the European axle strength design standard. This standard assists in the implementation of loading and boundary conditions and is exemplified by the typical CRH2 high-speed train wheelset. To evaluate the performance of these two methods, a hollow cylinder cantilever beam is first used as a benchmark to compare the present methods with other existing methods. Then, the strength analysis of a real wheelset model with a hollow axle is performed using different numerical methods.FindingsThe results of deflection and stress show that FS-FEM and ES-FEM offer higher accuracy and better convergence than FEM using linear tetrahedral elements. ES-FEM exhibits a superior performance to that of FS-FEM using linear tetrahedral elements, showing accuracy and convergence close to FEM using hexahedral elements.Originality/valueThis study channels the novel methods (FS-FEM and ES-FEM) in the static stress analysis of a railway wheelset. Based on the careful testing of FS-FEM and ES-FEM, both methods hold promise as more efficient tools for the strength analysis of complex railway structures.

Study on forming quality of three-roll skew rolling hollow axle

Study on forming quality of three-roll skew rolling hollow axle

Dynamic analysis for high-speed train hollow power axle

Dynamic analysis for high-speed train hollow power axle

Bumble Bee Colony Maintains Nest Site despite High Disturbance Level

During the 2021 spring a Bombus terricola Kirby queen initiated a nest in the hollow iron front axle of a 1950 John Deere 40U tractor that was being repaired outside in Bowdoinham, Maine. The tractor was not moved during the lengthy repair period, from 15 April–10 June. Seven workers were observed flying out from the tractor axle upon starting it up on 10 June. The tractor was used 1–3 times a week between 15 June and 15 August, usually for 15–90 min at a time. The tractor was always returned to the same location after use. Based upon observed adults issuing from the tractor upon startup throughout the summer, the colony appeared to have survived long enough to produce gynes (next year’s queens).

Analysis and Prospect of Precision Plastic Forming Technologies for Production of High-Speed-Train Hollow Axles

The hollow axle is the key basic component of high-speed trains. How to realize its production with short process and high-quality precision plastic forming is the frontier of current research and a major problem to be solved. On the basis of analyzing the advantages and disadvantages of the existing forging process of the hollow axle, this paper expounds the principles and characteristics of multi-wedge synchrostep cross-wedge rolling (MSCWR) technology, multi-roll cross-wedge rolling (MCWR) technology, three-roll skew rolling (TRSR) technology, and tandem flexible skew rolling (TFSR) technology in detail, and discusses the feasibility and key technical problems of these technologies to form the hollow axle. It is concluded that tandem flexible skew rolling (TFSR) technology has the advantages of short process, high quality, high efficiency, energy saving, and material saving, and this technology is the development direction of precision plastic forming of the hollow axle. The research results provide technical guidance and research directions for promoting global high-speed rail development.

Research on variation law of workpiece temperature of three roll skew rolling hollow axle

To explore the variation law of workpiece temperature in the process of three roll skew rolling (TRSR) hollow axle, the process of TRSR hollow axle is tested and simulated in this paper. Firstly, the working principle of TRSR hollow axle is described; Then the blank and rolling process parameters are selected according to the actual performance of TRSR mill; Next, the finite element model is established, and the changes of workpiece temperature are studied; Finally, the simulation results are verified by experiments. The results show that the simulation results are basically consistent with the experimental results. The temperature change of workpiece in the rolling process is very small as a whole, and the temperature drop will be greater only at the place in contact with the die.

Effect of process parameters on forming quality of hollow axle blank with rotary piercing

At present, hollow axles are mostly manufactured by precision forging and then deep processing, which has long technological process and high cost. In order to realize the integrated forming of hollow axles with short process and low cost piercing and skew rolling, a method of piercing billet by two-roll skew rolling is proposed in this paper, and the finite element model of the forming process is established by using SimufactForming software. The effects of roll feed angle, roll speed and plug advance on the wall thickness uniformity of piercing tube billet are explored, and the process parameters with the best wall thickness uniformity are obtained. It lays a technical foundation for the blank guarantee and the realization of the integrated forming process of hollow axle.

Numerical prediction of ductile damage evolution of 40CrNiMo railway axle steel during hot cross wedge rolling

Ductile damage formed by hot forming seriously affects the railway axle fatigue. It is vital to study the damage evolution mechanism of the 40CrNiMo steel during the high-temperature cross wedge rolling for the manufacturing of the high-speed railway axles. In the current study, the ductile damage model was established and verified. The specimens of the 40CrNiMo steel were subjected to the high-temperature tensile test using a Gleeble-3800 thermal simulation testing machine. Three deformation temperatures (1223 K, 1323 K, and 1423 K) and four strain rates (0.5 s -1 , 1.0 s -1 , 5.0 s -1 , and 10 s -1 ) were set. The deformation temperature, the strain rate, and the stress state were quantified by the Z parameter, the stress triaxiality, and Lode parameter, respectively. These were considered in the Bai & Wierzbicki (B&W) fracture strain equation to establish the fracture strain expression for the 40CrNiMo steel, and then the relevant parameters were solved. The secondary development route was used to embed the model into the Deform-3D software to simulate the distribution characteristics of the ductile damage as well as the evolution of the stress state and the Z parameter when the 40CrNiMo steel was rolled into the high-speed rail axle at the high-temperature. The simulation results were studied, and the direction of the process improvement was proposed. The results show that the damage could be decreased by reducing the forming angle, increasing the broadening angle, maintaining the section shrinkage at 35%, machining the hollow axle, and setting the roll speed and the rolling temperature at 8 r/min and 1273–1323 K, respectively.

Forming Quality Research on the Variable-Diameter Section of the Hollow Axle in Three-Roll Skew Rolling.

The hollow axle is the key component of the high-speed train, and the realization of high-quality forming is the key to ensure the safety of train operation. In this paper, the specimen of the variable-diameter section of the hollow axle is taken as the research object, and the generation mechanism of surface spiral mark defects and the formula of spiral mark depth of variable-diameter section in the TRSR (three-roll skew rolling) process with variable roll spacing are explored. The external roundness error and the function C to measure the wall thickness uniformity of the cross-section were taken as the evaluation indexes and the single-factor simulation experiment was established and simulated in the software Simufact.forming16.0 to obtain the influence law of each process parameter on the external roundness error and wall thickness uniformity of the rolled piece. Orthogonal tests were designed and the order and optimal combination of process parameters on the forming quality were obtained by range analysis and ANOVA analysis. The research results provide theoretical guidance for improving the forming quality of the variable-diameter section of the hollow axle in three-roll skew rolling, and promote the transformation of the TRSR process to high performance and accurate forming.

Microstructure evolution of three-roll skew-rolling formed hollow axles with uniform wall thickness

The uniform thickness hollow axle is one of the lightest weight axles in the high-speed rail industry. It can effectively reduce unsprung mass and further improve the train speed. Therefore, due to its importance and significance, it is crucial to research and develop the uniform thickness hollow axle. To understand the microstructural evolution during three-roll skew-rolling (TRSR) forming, 30CrMoA alloy steel was used in this study. A constitutive model of 30CrMoA was established by SIMUFACT FORMING finite element software and utilized to simulate the deformation, heat transfer, and microstructure coupling during TRSR. Via analyzing the influence of process parameters on the average grain size, the microstructural evolution of the forming part at each deformation stage is revealed. The result shows that the dynamic recrystallization of the rolled piece produces a fine and uniform grain structure during the forming process. The refinement level is enhanced with the increase of the radial compression; the grain size is gradually increased from the outer surface to the inner surface of the rolled piece. At a higher rolling temperature, it was found the initial grain size and final average grain size were larger compared to the lower temperature. By increasing the axial traction speed, not only can the rolling time be shortened, but also the appearance of coarse grains can be avoided. Therefore, the mechanical properties can be improved.

Simulation Analysis of Fretting Wear and Fatigue of Press-fitted Structure of Hollow Axle and Solid Axle

Simulation Analysis of Fretting Wear and Fatigue of Press-fitted Structure of Hollow Axle and Solid Axle

Research on microstructure evolution of the three-roll skew rolling hollow axle

Research on microstructure evolution of the three-roll skew rolling hollow axle

Conception of Hollow Axles Forming by Skew Rolling with Moving Mandrel

Conception of Hollow Axles Forming by Skew Rolling with Moving Mandrel