US 7,543,732 B2
Evaluation method and evaluation apparatus for spot welded portion
Eiichi Kobayashi, Aichi (Japan); Yusuke Kondo, Aichi (Japan); Hisayuki Ishizu, Aichi (Japan); Nobutaka Oda, Gifu (Japan); and Kazuo Ao, Aichi (Japan)
Assigned to Mitsubishi Jidosha Kogyo Kabushiki Kaisha, Tokyo (Japan)
Filed on May 20, 2004, as Appl. No. 10/849,140.
Claims priority of application No. 2003-146373 (JP), filed on May 23, 2003; and application No. 2003-146374 (JP), filed on May 23, 2003.
Prior Publication US 2004/0262365 A1, Dec. 30, 2004
Int. Cl. B23K 31/12 (2006.01)
U.S. Cl. 228—103  [219/110; 148/500] 8 Claims
OG exemplary drawing
 
1. 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.