Weight optimization and fatigue design of a welded bogie beam structure in a construction equipment

A welded bogie beam in an articulated hauler has been designed, analyzed, produced and fatigue tested in order to demonstrate the features of the research project LOST (Lightweight Optimized welded STructures). The results from LOST, e.g. a new weld class system, effect of using high strength steel and post treatment, were applied. The general goal was achieved by 20% weight reduction compared with existing component and at the same time a decrease of the production cost. This was accomplished mainly due to less material usage and cutting cost, but also due to a more efficient design, which decreased the production time by 30 min. Reduced weight also causes less environmental impact and lower fuel costs during the operation of the hauler. The demonstrator was produced with welds in as-welded condition where TIG treatment and weld preparation were needed in a couple of welds. A major conclusion was that the inspection of the weld quality after production needs to be improved so that the demands are secured and later failures in service can be avoided. Another conclusion was made during the fatigue test due to a multi axial stress state, which will affect the design in future projects. The requirements on the static and fatigue strengths are fulfilled in the new bogie beam design. However, some fatigue improvement effects have not been incorporated in the analysis of the new design, e.g. compressive residual stresses.