Metodik för utmattningsberäkning av svets i vibrationsmiljö
In this work, a method was developed and evaluated for calculating the life of welds under the influence of fatigue loads from a vibration environment. Typically, a shaker table is used for testing a component against vibration loads. The shaker table creates a vibration environment that is defined in the frequency domain by a power spectrum.Similarly, a virtual vibration table can be used to calculate the same type of load environment, which can then be used to calculate the expected lifetime. The benefit of this method is that it can be used in design, as well as in simulation of tests before physical verification tests are carried out.Today there are methods for calculating fatigue life of non-welded base material, but since many components contain welded joints, there is a need to apply this method to those types as well. To achieve this, the thesis combines two different areas, which together provide a method for fatigue assessment of welds using a virtual shaker table.The methodology is carried out by modeling the component, and its welded joints, in a finite element program. The weld is modeled with the effective notch method. The model is then processed though a virtual shaker simulation. The stresses provided by the virtual shaking table are then evaluated with the software DesignLife by nCode, which provides a calculated life for all areas of interest in the model. For evaluation of the method, the results of the calculation are compared with a physical test performed on a shaker table with 15 similar samples.The calculated life of the component was found to be conservative compared to the results from the shaker table test. The estimation error turned out to be quite small, only 8.5% difference between test and calculation. Additionally, the area of crack propagation was found to be a good match between calculation and test.Despite the good correlation between calculations and shaker table tests there is still a need for further evaluation of the method. Since this work only evaluated one component, there is no way to know for certain how general the method is. Hence, there is a need for more comprehensive studies on other component types, and with different load cases. The conclusion, therefore is that the method shows good potential, but needs to be further evaluated, in able to be used for life calculation of welded joints in vibration environments.