Patent ID: 7543732

Claim:
An evaluation method for a spot welded portion for evaluating a strength of a welded portion of a plurality of panels joined together by spot welding, comprising: a first step of dividing each of the panels into a plurality of elements; a second step of calculating a stress value at the welded portion of each of the panels by a stress analysis according to a finite element method using the elements obtained by the first step; and a third step of evaluating a strength of the welded portion based on the stress value at the welded portion obtained by the second step; the first step being performed such that a portion in a proximity of the spot welded portion is divided, with a central portion of the spot welded portion being determined as a nodal point of the elements, into a central element and a plurality of concentric ring-like elements including first and second ring-like elements from a center side provided by the central portion of the spot welded portion, whereafter the plural concentric ring-like elements are individually divided in a circumferential direction each into a plurality of portions to form the elements; the second step being performed such that an analysis being performed assuming the central element corresponding to the central portion of the spot welded portion as a rigid element; the third step being performed such that the strength of the welded portion being evaluated based on the stress value of the second ring-like element by eliminating a stress value of the first ring-like element from the evaluation, the second ring-like element neighboring the central portion through the first ring-like element; wherein an outer diameter of the central element is set smaller than an outer diameter of a nugget portion of the spot welded portion, and the first ring-like element has an outer diameter that coincides with the outer diameter of the nugget portion, such that the second ring-like element substantially coincides with a circumferential portion of the nugget portion.