Magnus Andersson, Volvo Construction Equipment (since 2006). I have been a specialist in structural dynamics and vibration induced fatigue for over 10 years. This means that I am developing methods within strength, structural dynamics, fatigue, and other failure modes. I also conduct training and support the product development within Volvo CE globally. I have a Master of Science degree in engineering physics (1987) from Lund university (LTH). I have previously worked with structural integrity of submarines at Kockums AB, Malmö for 8 years. I then moved to Stockholm and worked for Det Norske Veritas/Inspecta (today Kiwa) as a senior consultant. For 11 years I worked with different assignments, education, and research mainly within the nuclear power industry. For the last 17 years I have been employed by Volvo CE in Braås.
Volvo CE currently uses the effective notch stress method for assessing fatigue life in welded structures. For large structures such as frames, a sub modelling technique with a very fine mesh is necessary using millions of DOF. Stress tensors from unit load cases, estimated with FEA, are combined with time history loading from Multi Body Simulations of the complete machine operating on digitized test tracks. A critical plane approach (the Modified Wöhler Curve Method) is used to estimate the fatigue life. The usage of the effective notch method implies a very time-consuming design process.
An LEFM approach for weld roots would be even more time-consuming but would be a more natural approach since the weld root consists of crack like defects. To overcome the drawbacks with the current design process that involves usage of the effective notch method, a hybrid method is defined using pre-calculated geometry factors for different crack sizes and weld geometries. The geometry factors as a function of crack size, and the weld geometry, are stored in a database. From the unit load cases the structural stress using a coarse mesh in the weld is extracted. Together with the geometry factors, the stress intensity factors may be estimated and used with Paris law to calculate the fatigue life of welds.
A comparison between the effective notch method, LEFM and the new hybrid method is carried for typical fillet welds are presented in this paper.
|Thursday 30th November
S07-3 Experimental and numerical design and validation methods
39 - A Simplified Fracture Mechanics Method for fatigue life analysis of weld roots