New support roller profile design for railway wheel re-profiling process by under-floor lathes with a single cutting tool

The wheel re-profiling is an important part of railway wheelset maintenance. Researchers and railway operators have been very concerned about how to minimize the loss of time during wheel re-profiling without decreasing safety. Avoiding wheelset disassembly means considerable time savings, while reducing wheel damage during operation. Underfloor wheel lathes are the most appropriate tool to achieve this double objective, and therefore the most used nowadays. Multi-cut tool lathes have the disadvantage of being extremely expensive. On the other hand, with single tool lathes, re-profiling is not smooth or safe enough when current convex profile support rollers are used. It is well known by the companies that during reprofiling the wheel suffers impacts/damaged. In this article, a methodology to optimize the profile of the support rollers used in underfloor single tool lathes for railway wheel re-profiling is proposed. This novel profile design will minimize damage and increase the safety of such lathes, since it proposes a greater smoothness in the process. Simulations of re-profiling process have been carried out by the finite element method showing that the designed roller profile reduces drastically the impact/damage during the operation. The impact generated between the re-profiling wheel and the rollers is avoided. Profile-optimized support rollers have been used in a real underfloor wheel lathe, showing good results.

The effect of the roller profile oncave-in defect in reshaping processby considering nonlinear combine strain hardening

The reshaping process of pipes is an important method in producing non-circular pipes. Desired profile products are produced by passing round pipe through the rotating rollers. Cave-in defect is one of the common defects in the reshaping process. Roller design issues can decrease this kind of defect. In this paper, a method based on the slab method and the incremental plasticity has been presented to the numerical study of a 2D reshaping process. For investigating the Cave-in defect, the contact model has been developed. The concept of element elongation has been introduced to increase the accuracy of the contact model. Based on the presented method, numerical software has been developed to simulate the 2D reshaping process. Elastic-plastic equations for this subject have been driven based on the incremental method, J yielding criterion, and non-linear combined hardening. The effects of the radius of the roller profile on cave-in defects have been investigated by using the presented software (DARF). A set of experiments has been conducted in a forming station to verify the results. Results show that the presented model has higher accuracy than the Abaqus commercial software in predicting the cave-in defect. Based on the results of the model, the local increase of yielding stress directly affects the cave-in defect. Also, a meaningful relationship between the radius of the roller and the amount of the cave-in has been observed.

Tool profile stationarity while simulating surface plastic deformation by rolling as a process of flat periodically reproducible deformation

Introduction. Surface plastic deformation is an effective way to improve the operating performance of machine parts. One of the promising approaches to the design of surface hardening technological processes is the technological inheritance mechanics. To calculate the hereditary parameters characterizing the accumulated deformation and damage to the metal, it is possible to simulate spinning as a process of plane fractional deformation, which significantly reduces the time required for modeling the process. However, upon rotation of the plane in which the stress-strain state is considered, the roller profile changes. The aim of the work is to assess the magnitude of the change in the roller profile in the deformation plane during deformation as an important factor ensuring the accuracy of the solution obtained. Research methods. The roll profile in the warp plane is defined by the intersection line of the roll surface and this plane. The paper presents the procedure for calculating the coordinates of the points of intersection lines, which are curves of the fourth order, depending on the geometric dimensions of the roller and the part, as well as the angle of inclination of the deformation plane. Results and discussion. To estimate the value of the roller profile change, the coordinates of the points of the intersection lines of the roller surface and the deformation plane are determined for the rolling modes corresponding to a sufficiently developed plastic deformation, the obtained lines are approximated in the coordinate system associated with the deformation plane, and the relative change in the coordinates of the intersection lines when the plane was rotated are estimated. As a result of the conducted analytical studies, it is found that even with developed plastic deformation, the relative change in the coordinates of the points of intersection lines does not exceed 0.1%. This indicates the possibility of using a stationary roller profile when simulating rolling using the plane fractional deformation model.

Design of logarithmic crowned roller for tapered roller bearings based on the elastohydrodynamic lubrication model

Purpose The purpose of this paper is to study the film-forming capacity of logarithmic crowned roller for tapered roller bearing (TRB) and to design a tapered roller profile based on an elastohydrodynamic lubrication model. Design/methodology/approach A coupled model, incorporating a quasi-static model of TRBs and an elastohydrodynamic lubrication model was developed to investigate the load distribution of TRB and to evaluate the lubrication state of tapered roller/raceway contact. Findings The model is verified with published literature results. Parametric analysis is conducted to investigate the effect of crown drop on azimuthal load distribution of the roller, film thickness and pressure distribution in the contact area. The result shows that crown drop has little influence on the azimuthal load distribution; also, the film thickness and the pressure distribution are asymmetric. When the tapered roller is designed and manufactured, the crown drop of the small end should be larger than that in the large end. Originality/value Precise roller profile design is conducive to improve the fatigue life of TRBs. Currently, most crown design methods neglect the influence of lubrication, which can lead to a non-suitable roller profile. Therefore, the present work is undertaken to optimize roller profiles based on lubrication theory.

New Support Roller Profile Design for Railway Wheel Re-profiling Process by Under-floor Lathes With a Single Cutting Tool

The wheel re-profiling is an important part of railway wheelset maintenance. Researchers and railway operators have been very concerned about how to minimize the loss of time during wheel re-profiling without decreasing safety. Avoiding wheelset disassembly means considerable time savings, while reducing wheel damage during operation. Underfloor wheel lathes are the most appropriate tool to achieve this double objective, and therefore the most used nowadays.Multi-cut tool lathes have the disadvantage of being extremely expensive. On the other hand, with single tool lathes, re-profiling is not smooth or safe enough when current convex profile support rollers are used.In this article, a methodology to optimize the profile of the support rollers used in underfloor single tool lathes for railway wheel re-profiling is proposed. This novel profile design will minimize damage and increase the safety of such lathes, since it proposes a greater smoothness in the process. Simulations of re-profiling process have been carried out by the finite element method showing that the designed roller profile reduces drastically the impact/damage during the operation. Profile-optimized support rollers have been used in a real underfloor wheel lathe, showing good results.

Quality Evaluation of Wind Turbine Roller Bearing Profile in the Ultra-long Flexible Blade

In order to accurately measure and evaluate the quality of the roller profile of the ultra-long flexible blade bearing, an error evaluation model is established for the arc segment and the straight segment of the roller based on the least square method, and then an overall quality evaluation model is proposed based on these two error models. Through the simulation of a standard wind turbine cylindrical roller bearing, it is found that the quality evaluation model established in this work can effectively measure and evaluate the contour line of the wind turbine bearing’s roller. The overall absolute error is 0.0319 mm, which is consistent with the set random error. The overall quality evaluation model is also valid for other types of bearings commonly used in the wind turbine, which include arc and straight segments, and can be used to evaluate the error quality of the roller profile of wind turbine bearings.

Lubrication and Fatigue Life Evaluation of High-Speed Cylindrical Roller Bearing under Misalignment

This paper developed a coupled model, incorporating the quasistatic model, fatigue life model, and mixed lubrication model, to investigate the effect of misalignment angle on high-speed cylindrical roller bearings. The model is verified by comparing with the published literature results. Then, a parametric analysis is carried out. The results show that as the misalignment increases, the load distribution is basically unchanged, but the fatigue life of the roller bearing decreases due to the variation of contact pressure, and the skewing moment of single roller contact pair increases. Furthermore, the optimal design of roller profile needs to consider the effect of lubrication in order to improve the fatigue life of roller bearings. In general, the optimal crown drop is too small according to the design from the slicing technique.

Optimization Design of RV Reducer Crankshaft Bearing

The crankshaft bearing is the key component of a rotate vector (RV) reducer. However, owing to the harsh working load and restricted available space, the bearing often suffers from fatigue failure. Therefore, this study proposes a novel optimization method for RV reducer crankshaft bearings. A nonlinear constraint optimization model for the design of the bearing considering the crowned roller profile is formulated and is solved by using a crow search algorithm. The goal of the optimization is to maximize the fatigue life of the bearing. The design variables corresponding to the bearing geometry and crowned roller profile are considered. The load working conditions of the bearing and structure of the RV reducer are analyzed. Various constraints, including geometry, lubrication, strength of the bearing, and structure of the RV reducer, are established. Through the optimization design, the optimum crowned roller profile suitable for the working load of the bearing is obtained, and the stress concentration between the roller and raceway is eliminated. Taking the crankshaft bearing of RV-20E and RV-110E type reducers as examples, the bearings were optimized by the proposed method. After optimization, the bearing life of the RV-20E type reducer is increased by 196%, and the bearing life of the RV-110E type reducer is increased by 168%.

Study on Logarithmic Crowning of Tapered Roller Profile Considering Angular Misalignment

The angular misalignment of the tapered roller contact pair aggravates the stress edge effect and the stress concentration effect at the contact field, which in turn would affect bearing capacity and fatigue life of the contact pair. In this paper, based on the angular misalignment, the geometric interference model of the tapered roller contact pair was established. And two types of logarithmic crowning models for the roller profile design were theoretically deduced, in which design redundancy was considered through the quadratic processing of the pre-pressure. Then, with the discrete convolution and fast Fourier transform (DC-FFT) method and the conjugate gradient method (CGM), contact characteristics of the tapered roller with these two logarithmic profiles were verified. The results show that two profiles can effectively prevent the stress edge/concentration effect, improve contact pressure distribution and stress field of the roller in misalignment state, and ensure that the contact condition in alignment state is not greatly affected. The logarithmic crowning scheme is also suitable for the profile design of heavy-duty tapered rollers and can provide a reference for the crowning of other finite-line contact pairs under angular misalignment.