Hollow Axle Research Articles

Fatigue life prediction of a railway hollow axle with a tapered bore surface

This paper aims to evaluate the fatigue life of railway hollow axles with tapered bore surfaces (hereinafter indicated as RATB) that have a different inner shape than the shape of existing hollow axles. The fatigue strength evaluation method is identified in accordance with European Standards EN13103 and EN13261; the fatigue strength is also evaluated by finite element analysis of a full-scale axle test piece by way of applying an S–N curve that was identified through fatigue tests of high strength axle materials. Furthermore, a fatigue life analysis of the wheel–rail contact force was conducted using dynamic simulation results of a Korean Electric Multiple Unit (K-EMU) multi-body dynamics model. As a result of the fatigue life evaluation, the RATB for metro vehicles satisfied the fatigue strength requirements of EN, and the fatigue life by wheel–rail contact force was predicted to be safe within a standard axle replacement cycle.

Potential improvements of the presently applied in-service inspection of wheelset axles

Wheelset axles are safety relevant components because they are subject to high dynamic and static loads during operation. Therefore, they have to undergo periodic non-destructive examination to find potential defects before they can lead to failure. Minimizing the risk of fatigue failure for 3.5million axles, potentially in service in Europe, was the objective of the 3.5years R&D project EURAXLES which ended in April 2014. EURAXLES aimed to propose a global concept approach for axles design, production, and maintenance. An important objective within Work Package 5 was the analysis of the present status of in-service inspections. The strengths and weaknesses of the presently applied inspection systems and practices were evaluated with the aim to identify potential improvements provided by new technologies. That evaluation was firstly based on the results of a questionnaire which was distributed to the main European railway operators with the request to describe the testing procedures and equipment applied in their maintenance facilities. Secondly, the results of benchmark tests with presently applied ultrasonic inspection equipment were exploited for the analysis. These tests were performed at hollow axles and solid axles with implemented artificial defects.

Advanced ultrasonic “Probability of Detection” curves for designing in-service inspection intervals

In order to ensure the safe service of modern railway vehicles, safety critical components are subjected to a dedicated maintenance and inspection plan. Railways axles, in particular, are periodically inspected by the ultrasonic testing method during maintenance interruptions in first level workshops, while the magnetic particles test is carried out in second level workshops. The reliability of such inspections is quantified in terms of “Probability of Detection” curves, which are traditionally related to a specific linear dimension of the defect to be detected. Actually, a fatigue crack is known to change its shape under cyclic loading, so affecting its detectability.In the present paper, a novel approach to “Probability of Detection” takes into account of this effect, introducing a “Master” probability of detection curve, which is a function of the reflecting area of the crack. A comparative applicative example between standard and such advanced probabilities of detection curves is then presented considering high-speed railway applications, whose hollow axles are made of the medium strength EA4T steel grade.

Equivalent Rigidity at the Minor Axis of Concrete Hollow Slab Based on Continuity Analysis

Basic assumptions are proposed for the continuity model of a tubular hollow slab combined with continuity analysis and calculation of a finite-element model; the continuity Equation of a tubular hollow slab at the minor axis supported at two ends of the hollow axle under a vertical even load is determined and solved. The overall equivalent flexural rigidity is then determined, which provides important conditions for the continuity analysis of tubular hollow floor supported along four sides.

WHEELSET AXLE WITH THE CAVITY OF UNIFORM CROSS SECTION

Purpose. Due to operation in complex loading conditions, the rolling stock wheelsets should provide high reliability, since the train traffic safety largely depends on them. Design and technical condition of wheelsets affect the smoothness, intensity of forces generated by the interaction between the car and track, and the motion resistance. Specificity of the axle operation consists in the fact that it undergoes the bending stresses under loading. These stresses are unevenly distributed along the cross-sectional area, reaching the highest values in the outer fibers and the minimal values in the internal ones. This aspect sets the problem of replacement of the uniform cross section with the hollow cross section. The disadvantages of hollow axle design, which are used at the present time, should include a significant manufacturing complexity of the variable section cavity. The purpose is to develop a modernized design of the wheelset axle. Methodology. A construction of the hollow axle having an inner longitudinal cylindrical through hole of the constant diameter throughout its length was proposed. The item is made of steel seamless tube. The inner surface of the tube is treated by mechanical means to remove the voltage concentrations in the internal longitudinal cylindrical through hole, which has a constant diameter along the entire length of the axle. Findings. Application of this design will facilitate manufacturing of the hollow axle and the machining of the inner longitudinal through hole, while retaining all the use advantages of the hollow axle in the rolling stock wheel pairs. Another use advantage of the hollow axle of this design is the absence of partial heterogeneity of the metal, which is inevitably, occurs during the solid axles blanking. Originality. A new design of the wheelset hollow axle of railway rolling stock was proposed. Practical value. Introduction of the new design simplifying the manufacture and mechanical treatment of the inner cavity of the wheel pair axle will bring significant economic benefits. According to preliminary calculations, the use of the axle with the uniform cross section cavity will reduce the metal consumption by 100-110 kg.

Billet Preparation Method for Railcar Hollow Axle Production

A method is considered for preparing a hollow billet for producing a railcar hollow axle based on piercing in a two-roll screw rolling mill. A deformation regime and alignment of the screw rolling mill deformation zone are proposed in order to prepare a high quality especially thick-walled billet. Results are given for prior study of especially thick-walled pipe preparation for railcar hollow axles in the VMZ 70-270 pipe rolling unit.

Experimental investigation by laser ultrasonics for high speed train axle diagnostics

The present paper demonstrates the applicability of a laser-ultrasonic procedure to improve the performances of train axle ultrasonic inspection. The method exploits an air-coupled ultrasonic probe that detects the ultrasonic waves generated by a high-power pulsed laser. As a result, the measurement chain is completely non-contact, from generation to detection, this making it possible to considerably speed up inspection time and make the set-up more flexible. The main advantage of the technique developed is that it works in thermo-elastic regime and it therefore can be considered as a non-destructive method.The laser-ultrasonic procedure investigated has been applied for the inspection of a real high speed train axle provided by the Italian railway company (Trenitalia), on which typical fatigue defects have been expressly created according to standard specifications. A dedicated test bench has been developed so as to rotate the axle with the angle control and to speed up the inspection of the axle surface. The laser-ultrasonic procedure proposed can be automated and is potentially suitable for regular inspection of train axles.The main achievements of the activity described in this paper are:–the study of the effective applicability of laser-ultrasonics for the diagnostic of train hollow axles with variable sections by means of a numerical FE model,–the carrying out of an automated experiment on a real train axle,–the analysis of the sensitivity to experimental parameters, like laser source – receiving probe distance and receiving probe angular position,–the demonstration that the technique is suitable for the detection of surface defects purposely created on the train axle.

Development of a Numerical Chain to Optimize Railway Axles with Respect to Fatigue Damage

In today's competitive business environment, it has become increasingly important to reduce manufacturing and raw materials cost. For this purpose, an innovative process of design and manufacturing railway axles is developed. It is based on forging hollow axles which allows a significant reduction in steel consumption. In this work, we tried to analyze how these modifications induced by this new process and design impact the service behavior and particularly the durability face to cyclic loadings that can lead to fatigue failure. In the present study, a numerical chain has been developed going from the simulation of the manufacturing process up to the analysis in fatigue. In the first step, the forging process is modeled in order to predict the residual stress field and the initial plastic strain. From this initial condition, the assembly operation of the wheel on the axle is simulated before the redistribution of stresses and strains under cyclic load. The final objective is to obtain the cyclic loadingpaths, in order to provide the data needed for the analysis of fatigue.

철도차량용 중공차축 설계에 관한 연구

철도차량용 중공차축 설계에 관한 연구

The Strain Analysis at the Broadening Stage of the Hollow Railway Axle by Multi-Wedge Cross Wedge Rolling

The paper is based on the newest hollow railway axle, which utilizes the Pro/E designed multi-wedge cross wedge rolling (MCWR) model, utilizes the finite element analysis software DEFORM-3D to complete the numerical simulation about the whole stage of the hollow railway axle forming process, and analyzes the strain rule at the broadening stage of the hollow railway axle, especially conducts a detailed research on forming character into the strain rule at the multi-wedge transition stage, and finally gets the strain forming mechanism of the hollow railway axle at the broadening stage. The result of the research on the strain rule poses great scientific significance on enhancing the product quality and the production efficiency of the hollow railway axle, and improving the theory of multi-wedge cross wedge rolling.

Ultrasonic and electromagnetic inspections of railway hollow axles

Ultrasonic and electromagnetic inspections of railway hollow axles

Variation of Flaw Echo Height at Wheel Seat of Hollow Railway Axle in Cyclic Rotating Bending

For a full-sized wheelset with a hollow axle having machined artificial flaws at the fitting part (wheel seat), the variation of flaw echo heights due to cyclic rotating bending was investigated experimentally. The flaw echo heights were measured at different stages of cyclic loading with bending moment applied to the wheelset. The influence of the direction of bending moment as well as the incident direction of ultrasound on the echo-height variation was examined for each flaw. The flaw echo heights varied significantly during the cyclic loading and by the applied bending moment in spite that the size of each flaw was almost constant. The observed echo-height variations are discussed from the viewpoint of the change of contact condition of the axle-wheel interface by the fretting wear during the cyclic loading. The experimental results indicate that the progress of wear at the axle-wheel interface changes the ultrasound reflectivity and influences the measured echo heights. The wear at the interface can also amplify the effect of axis bending moment on the reflectivity and the echo heights. Some implications of the present finding to the ultrasonic testing of axles are also provided.

Research on the Manufacturing Process of the Whole Fiber Hollow the Trailer Axle

With the rapid development of road transport enterprise and the popularity of car trailer transport, semi-trailer has become the main means of transport of road freight. So the semi-trailer manufacturing has become an important component part of the auto industry. Speed and heavy duty are the long-term pursuit of the High-speed transport, the key to solving this problem is a component of lightweight, while the hollow axle is the important one. The hollow axle manufacturing process, with many process factors, is more complex than the solid one. Therefor, the research on the hollow axle manufacturing process is very necessary.

Smart hot stamping of ultra-high strength steel parts

Smart hot stamping processes of ultra-high strength steel parts have been developed to overcome difficulties in the present hot stamping process. Using rapid resistance heating, the stamping equipment became considerably simpler than that using furnace heating. The formability was improved by high speed hot stamping using a mechanical servo press in comparison with the conventional process using a hydraulic press. Parts having a different distribution of strength were produced by tailored die quenching using local bypass resistance heating. Die-quenched steel parts and ultra-high strength steel sheets were sheared by reducing the flow stress in the shearing zone using local resistance heating. An ultra-high strength steel gear drum was produced by hot spline forming using resistance heating of side wall of a cup. V-shaped hot forming using sealed air was developed to produce ultra-high strength hollow axle beams used for suspensions of automobiles. A one shot hot stamping process consisting of resistance heating, forming, shearing and die quenching was applicable to comparatively small high strength steel parts.

Feasibility Study on Forming Hollow Axle with Multi-Wedge Synchrostep by Cross Wedge Rolling

One direction of the cross wedge rolling technology is to realize high-efficiency, precise and near-net-shape forming hollow axle with multi-wedge synchrostep cross wedge rolling. This paper deduced the rotated condition of forming hollow shaft with multi-wedge cross wedge rolling (MCWR) base on forming solid shaft with single-wedge cross wedge rolling, and analyzed technics parameters on the influence of rotated conditions. Through the finite element simulation we got rolling technics parameters on the effect of rolled piece and selecting principle, and then created the 3D model of the equal diameter period of hollow axle with the MCWR. By using DEFORM-3D software, the process of rolling equal diameter period was simulated. The result indicated that it is feasible to roll hollow axle with multi-wedge synchrostep by cross wedge rolling.

EN 규격에 기반한 도시철도차량 차축의 경량화

Weight reduction of a railway axle, which is one of heaviest parts in an urban railway vehicle, is discussed in this paper. A wheelset of a railway vehicle is very important with regard to railway safety, and its structural strength should always be considered when attempting to reduce the railway axle weight. In this work, the weight of the axles of a trailer bogie and a motor bogie of the Korean EMU was reduced by replacing solid axles with hollow axles. On the basis of the EN standard for railway axle design, the strength of existing solid axles was analyzed and the required bore size of a hollow axle was determined. It is shown that the weight of the concurrent axle of the Korean EMU can be reduced by up to 20% with a very small decrease in the structural strength. Finite element analyses were also carried out to verify the design result for lightweight hollow axles.

Numerical Simulation for Thick-Walled Hollow Axle during Cross Wedge Rolling

The paper investigates a process of cross wedged rolling (CWR) for manufacturing thick-walled hollow axles. A finite element numerical model coupled deformation and heat transfer of CWR is established using commercial finite element software DEFORM-3D. The rolling process of hollow axle during CWR is simulated successfully. The stress, strain and temperature distributions of workpiece are obtained and analyzed. The simulation results show that forming thick-walled hollow axles through CWR is feasible.

Ultrasonic measurement of railway wheel hub–axle press-fit contact pressures

Railway wheels are secured onto the axle by means of an interference fit. The wheel is either shrink fitted or press fitted onto a pre-lubricated axle, and the resulting interference fit induces a contact pressure at the interface. Occasionally railway axles fail by fatigue, with the initiation point for the failure frequently traced to the interference fit. In this study, the reflection of ultrasound was used to determine contact conditions in the interference fit. It is a non-intrusive technique preserving the mechanics of the contact. The concept is simple; an acoustic wave bounces back from an incomplete interface. The higher the contact load, the more conformal the contact and hence more of the wave will be transmitted. A spring model is used to determine maps of contact stiffness from ultrasonic reflection data. A calibration procedure is then used to determine the pressure. Two types of wheelsets were used for the measurements, both with a hollow axle that was used as an access point for the ultrasonic transducer. The wheels differed in the design of their web sections. Variations were detected in the determined interface pressure profiles, due to both surface roughness effects and discontinuities in the fit geometry. When comparing the two fits, it was found that material removal from the web of the wheel in the second fit reduced the interface pressure distribution.

A Study on Radial Curtain Plybamboo Form

Plybamboo is commonly made using chordwise bamboo strips. Previous studies have indicated that the bamboo utilization rate and the processing efficiency are low in manufacturing chordwise curtain Plybamboo. This paper presents a study on the manufacturing technology of radial curtain plybamboo form. Radial strips cut from bamboo were glued on the radial faces. The results showed: (1) the bamboo utilization rate of radial cutting strips was 15-20% higher than chordwise cutting strips, and the resin consumption was only approximately 50% of chordwise bamboo strips; (2) however, radial bamboo strips were more subject to lengthwise bending deformation than chordwise strips during drying. This lengthwise bending deformation can be effectively reduced or prevented by placing a hollow rigidity axle in the radial bamboo curtain rolls when using the bound drying method; (3) the hot pressing time of the radial curtain plybamboo form was approximately 50% of the chordwise composite plastic curtain plybamboo.

Investigations on fatigue crack growth under variable amplitude loading in wheelset axles

The present paper summarizes the results of fatigue crack growth simulations for hollow wheelset axles. Within the scope of this paper different influencing factors of the remaining lifetime have been identified. Therefore different simulations using NASGRO have been performed with different initial crack depth as well as aspect ratios. Moreover the influence of press fitting on the remaining lifetime has been pointed out. Preliminary experimental studies using standardized fracture mechanical specimens have been used in order to optimize time- and cost-consuming component testing.