Analysis of an Intermediate Rear Axle Shaft Failure

Subrata Kr Mandal,Palash Kr Maji S Karmakar

doi:10.4172/2167-7670.1000114

Abstract

This paper describes the failure analysis of an intermediate shaft used in a prototype, which had been failed during the trial run of the prototype. The shaft was found to be bending. The investigation was carried out in order to establish whether the failure was the cause or a consequence of the accident. A study of the bend shaft shows how vulnerable such a rotating component can be to failure by fatigue, even when operating under steady conditions, if basic preventative design actions are not taken. The analysis considers the effects of both transmission torque and weight (thus bending) upon stress levels and assesses their individual affect on the breakage and upon any subsequent modifications needed to improve the design. Results indicate that the axle shaft bends due to fatigue as a result of improper design. The drive shaft arrangement is compared with the feasible alternative of using a driven wheel arrangement rotating on a stationary axle. Findings confirm the importance of recognizing in advance the salient factors leading to fatigue and the necessity in paying adequate attention to detail during design and manufacture if long service life is to be achieved.

Highlights

Having a wheel shaft which is directly driven from a power source using a timing belt transmission is a common means for driving small, relatively low cost vehicles
Results of Fatigue Tests of Steel Specimens Subjected to Combined Bending and Torsion [6]
According to American Society of Mechanical Engineers code for the Design of transmission of shafts, the maximum permissible working stress in tension or compression may be taken as: a) 112 M Pa for shafts without allowance for keyway b) 84 M Pa for shafts with allowance for keyway The maximum permissible shear stress may be taken as: a) 56 M Pa for shafts without allowance for keyway b) 42 M Pa for shafts with allowance for keyway Calculations show that the bending stress magnitude is much greater than the shear stress caused by torsion due to accelerating and braking

Summary

Introduction

Having a wheel shaft which is directly driven from a power source (in this case, the engine of a motorcycle) using a timing belt transmission is a common means for driving small, relatively low cost vehicles. The attraction of a rotating wheel shaft is that it can be made very simple because it can accommodate the driven pulley, be used to mount the bearings and attach a pair of wheels all on a single component Such a design has undoubted advantages compared to the alternative of using a driven wheel hub arrangement located on an axle; as occurs, for example, with a chain sprocket on a bicycle wheel. The design requirement is further complicated by additional factors, many of which are of a variable nature These include the effect of changing torque transmitted during acceleration of the vehicle from start up to full speed and abrupt breaking (these effects will result in torsion and changing shear stresses), traveling over uneven terrains without suspension will contribute shock loading (further adding to fluctuating bending stresses). The vulnerability to fatigue damage is clearly very real and so it is essential to realize this and identify weak locations and take preventative steps at the design and manufacturing stages [2]

Results

Discussion

Conclusion