title: A Nondestructive Evaluation Method: Measuring the Fixed Strength of Spot-Welded Joint Points by Surface Electrical Resistivity.
abstract: Destructive tests are generally applied to evaluate the fixed strength of spot-welding nuggets of zinc-plated steel (which is a widely used primary structural material for automobiles). These destructive tests, however, are expensive and time-consuming. This paper proposes a nondestructive method for evaluating the fixed strength of the welded joints using surface electrical resistance. A direct current nugget-tester and probes have been developed by the authors for this purpose. The proposed nondestructive method uses the relative decrease in surface electrical resistance,α. The proposed method also considers the effect of the corona bond. The nugget diameter is estimated by two factors:RQuota, which is calculated from variation of resistance, and a constant that represents the area of the corona bond. Since the maximum tensile strength is correlated with the nugget diameter, it can be inferred from the estimated nugget diameter. When appropriate measuring conditions for the surface electrical resistance are chosen, the proposed method can effectively evaluate the fixed strength of the spot-welded joints even if the steel sheet is zinc-plated.
authors.affiliation: e-mail:  shimamot@sit.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Shimamoto
authors.affiliation: e-mail:  yamashita-kn@nifty.com High-Tech Research Center , Saitama Institute of Technology , 1690 Fusaiji Fukaya , Saitama 369-0293 , Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yamashita
authors.affiliation: Mito Industry Co., Ltd. , 6 Kandakitanorimonocho, Chiyoda , Tokyo 101-0036 , Japan e-mail:  hi_inoue@mitokogyo.co.jp.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Division of Mechanical & Advanced Materials Engineering , Chonbuk National University , 664-14 Duckjin-dong , Jeonju 561-756 , Korea e-mail:  yangsm@moak.chonbuk.ac.kr.
authors.forename: Sung-Mo
authors.initials: SM
authors.lastname: Yang
authors.affiliation: e-mail:  rd@emic-jp.com.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iwata
authors.affiliation: e-mail:  et.factory@emic-jp.com Densijiki Industry Co., Ltd. , 1-13-10 Funado, Itabashi , Tokyo 174-0041 , Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Ike