Transient Dynamic Analysis of a Linear Model of a Bus

Transient analysis of a linear model of a bus was performed. In the experiment the right front wheel of the bus rolled over a bump and one acceleration, two axil forces in the wheel suspension and two bending moments in the frame of the bus were measured. The different parts of the bus were modelled by uniform Rayleigh-Timoshenko beams and rigid bodies. This beam element has a uniformly distributed stiffness, inertia and viscous and/or hysteretic damping along its axis. The loading of the bus due to the bump was in the theoretical analysis modelled by a prescribed transient displacement of the model of the wheel. The fast Fourier transform technique was utilized. Fairly good agreement between calculated and measured values was obtained.     

Residual stresses at a longitudinal stiffener — Web frame intersection and their effects on crack growth

Stress coining at geometrical discontinuities may introduce compressive residual stresses which will lower the propagation of surface cracks and thus increase the fatigue life. In a non-linear finite element analysis, the residual stresses after welding of a transverse web-frame to a ship hull plating is first estimated. Stress coining of one corner of a longitudinal cut-out in a transverse web-frame is then simulated in detail. The calculated residual compressive tangential stresses in the corner of the cut-out is seen to lower the propagation of edge cracks. Experiments performed on web-frames taken from a shipyard after manufacturing show indeed that large tensile residual stresses exist in the web-frame after welding. Stress coining is therefore believed to have a beneficial effect on the fatigue life.