Evaluation method and evaluation apparatus for spot welded portion

• US 7,543,732 B2
• Filed: 05/20/2004
• Issued: 06/09/2009
• Est. Priority Date: 05/23/2003
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Kondo, Yusuke, Kobayashi, Eiichi, Oda, Nobutaka, Ishizu, Hisayuki, Ao, Kazuo
• Primary Examiner(s): Ward; Jessica L
• Assistant Examiner(s): Aboagye; Michael
• Application Number:
  US10/849,140
• Publication Number:
  US 20040262365A1
• Time in Patent Office: 1,846 Days
• Field of Search: 228/103, 148/500, 148/503, 700/145, 219/110, 219/109, 219/130.01
• US Class Current: 228/103
• CPC Class Codes: B23K 11/11 Spot welding
• CPC Class Codes: B23K 31/12 relating to investigating the properties, e.g. the weldability, of materials
• CPC Class Codes: G01N 2203/0216 Finite elements
• CPC Class Codes: G01N 2203/0296 Welds
• CPC Class Codes: G01N 3/00 Investigating strength properties of solid materials by application of mechanical stress

Abstract

A technique for evaluation of the strength of a spot welded portion of a panel is provided. A stress value at the welded portion of the panel is calculated by a stress analysis according to a FEM using the elements, and then the strength of the welded portion is evaluated based on the stress value at the welded portion. A portion in the proximity of the spot welded portion is divided, with a central portion of the spot welded portion registered with a nodal point of the elements, into a central element and plural concentric ring-like elements from the center side provided by the central portion of the spot welded portion. Thereafter, the plural concentric ring-like elements are individually divided in a circumferential direction each into a plurality of portions to form the elements. Then, the strength is evaluated based on the stress value of the second ring-like element.

Claims

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.

2. The evaluation method for a spot welded portion as claimed in claim 1, wherein a width of the second ring-like element in a diametrical direction is set to a size substantially equal to a strain detection width of a strain gauge.

3. The evaluation method for a spot welded portion as claimed in claim 1, wherein each of the plural concentric ring-like elements is divided into 4 to 8 portions in the circumferential direction.

4. The evaluation method for a spot welded portion as claimed in claim 1, wherein the elements are formed as rectangular elements except those which are in the proximity of the spot welded portion.

5. 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 plurality of concentric ring-like elements around the central portion, whereafter the plural concentric ring-like elements are further divided in a circumferential direction each into a plurality of portions to form the elements;

the second step being performed such that only for an outermost ring-like element positioned on a most outside from among the concentric ring-like elements obtained by the division in the proximity of the spot welded portion, the stress value being calculated by a P method finite element method which uses a high-order coordinate function, and

the second step being configured such that, for the elements other than the outermost ring-like element and a ring-like element closest to the central portion, the stress value is calculated by an H method finite element method which uses a low-order coordinate function,

wherein the ring-like element closest to the central portion has an outer diameter that coincides with an outer diameter of a nugget portion of the spot welded portion, such that one of the concentric ring-like elements positioned immediately outside the ring-like element closest to the central portion substantially coincides with a circumferential portion of the nugget portion.

6. The evaluation method for a spot welded portion as claimed in claim 5, wherein the elements are formed as rectangular elements except that which is positioned in the proximity of the spot welded portion.

7. The evaluation method for a spot welded portion as claimed in claim 5, wherein the division into the plural concentric ring-like elements is performed such that a ring is divided in a radial direction from a center into three or four layers from a first layer of an innermost layer corresponding to the spot welded portion to a third or fourth layer of an outermost layer.

8. The evaluation method for a spot welded portion as claimed in claim 5, wherein each of the plural concentric ring-like elements is divided into 4 to 8 portions in the circumferential direction.