Nawal K. Prinja, Joseph M. Bushell, AMEC Nuclear UK Ltd.
R. Chandwani, C. Timbrell, Zentech International Ltd.

NAFEMS World Congress 2009, Crete, Greece, Jun 16-19 2009

Abstract:
This paper explains how the general purpose FE code Abaqus was combined with Zencrack to predict 3D crack growth as part of an investigation conducted to explain failure of single cylinder bridge roller bearings. Finite Element analyses were conducted to gain an understanding of the stresses caused during operation and explain the possible cause of crack growth resulting in failure. It was important to predict sub-surface crack growth in the rollers induced by repeated rolling as the bridge expands due to daily and seasonal temperature cycles. Models of the bearings were required to represent the contact between the roller and plates, daily movement of the load and the non-linear behaviour of the material. A band of pressure due to contact with the plates traverses back and forth over the roller as it rotates. The ambient temperature changes were such that the roller would experience at least one stress cycle per day of operation. A number of initial crack scenarios are studied, based on crack initiation sites identified during inspections of the failed rollers. Stress intensity factors (SIFs) for all three modes of cracking (KI, KII and KIII) are plotted against angle of roll bearing is misaligned, the roller is subjected to additional twist. The Abaqus and Zencrack analyses showed that in the absence of any twist, the load cycling caused by the rotation of the roller propagates initial end cracks along the roller axis which can lead to the roller splitting in half. Twisting of the roller due to bearing misalignment causes out of plane growth of the crack indicating that a part of the roller can break away.