Experimental Determination of the Structural Hot-Spot Stress

Structural hot-spot stresses can be determined experimentally by measuring the strain on the surface in the vicinity of the hot-spot. On a plate surface, i. e. at a type “a” hot-spot, the nonlinear stress increase caused by the notch of the weld toe vanishes in a distance of about 0.4t from the weld toe, so that the strain outside this region is used for extrapolating the structural strain to the hot-spot. Usually, a linear extrapolation over points 0.4t and 1.0t in front of the weld toe are used. Alternatively, a quadratic extrapolation can be used, recommended in case of a strongly nonlinear structural stress increase. When converting the hot-spot strain into stress, the biaxial strain state can be considered by appropriate formulae. Because plate thickness is no more relevant for type “b” hot spots, quadratic extrapolation over points in fixed distances is recommended.