TWI Industrial Member Report Summary 91/1979
By T R Gurney
The report gives the results of finite element analyses of transverse fillet welded joints in which both the thickness of the attachment and the size of the fillet welds were varied. It is shown that the value of Mk (the factor by which the stress concentration at the weld tow increases K) can be expressed by means of a relatively simple formula which takes account both of the size of the attachment and of the weld size.
Using the calculated values of Mk a limited theoretical study has been made of the effect of continuous and semi-elliptical toe cracks on fatigue strength. As in the case of joints with relatively thick attachments there is a region over which the initial defect size necessary to cause through thickess cracks in a given life tends to decrease rapidly with increasing plate thickness. This critical region is shifted to greater thickness by the use of thinner attachments. As far as fatigue strength is concerned it is shown that strength tends to decrease with increasing thiclmess of either the main or attachment plates or with increasing weld size.