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Welded joint manufactured with a complex and expendable joint preparation are not always safer .The result of the tests and analyses showed no significant influence of the weld shape preparation on the fatigue strength in the HV and HY fillet-welded joints subjected to torsion and bending loads.The accomplished finite element analyses in joining welds indicate similar result ,i.e.,no influence on the fatigue strength in bending and torsion loads.
The welded joints in the analyses were generally accepted as failure –free and the joint transiton regions included in the calculations are negligibly small. However,the harmonious forms of the stress distributions and are diverted in the notching locations and in joint transion regions of coat and root layers.Thus , the harmonious forms of the stress distributions and the material attenuation in the welded joints as a notch with internal imperfections such as residual stresses,hardening regions,coarse formations,occluded gases,then joint geometry(weld shape ,thick- ness ) has an influence on the distribution of stresses as well as on the fatigue strength in thick sheet metal joints with butt-joint and fillet welds.In this case,welded joint with smaller volume are more favorable.A qualitative comparision of GMAW and laser beam welds shows that the fatigue strength of laser welds is larger due to smaller weld joint volume and insignificant stress concentratins.For a detailed comparision of weleed shapes ,the centers of gravity of surfaces and volumes as well as moments of inertia of th welded joints should be considered.In a rough comparition, one can regard the first two parameters mentioned above.
In order to improve the computational life assessment of welded joints subjected to alternate loads,results obtained should be compared with the test data. However,there is still a lack of data on welded joints with other notch factors.The test results represented in this study as Wohler’s and Gassner’s curves contribute to this aim.For dimensioning joints to be welded,the diagrams are made available in directions of ⅡW recommendations with a ptobability of survival of Ps= 97.7%.
The inclination coefficients of the regression lines were selected for the bending and torsion loads to k=3 and k=5, respectively. For determining fatigue strength ,the extension of the straight lines change up to cycles of 10 and 10 in terms of the type of loads and welded joints.
With the joint preparation (primarily joint shape and orifice angle),the needed accessibility and the welding process can be improved in conventional welding methods.However,in today’s state of the art such as with laser beam welding ,one can join thick sheet metals without joint preparation and be failure-free.◆