Patent ID: 9421735
Filing Date: 2016-08-23
CPC Classification: B21D,B32B,Y10T

Claim Text:
1. A method for joining at least two metal sheets together, comprising: forming projections in each of the overlapping metal sheets; forming holes in each of the overlapping metal sheets; and forming a joint between the overlapping metal sheets and between each projection and each hole of each overlapping metal sheet, wherein the projections are formed by pressing and thus cutting the overlapping metal sheets along two cutting lines relative to a same uncut reference line such that each cutting line extends from and communicates with the reference line, each projection having a portion whose width is wider than a length of the uncut reference line, each hole is formed by further pressing each cut projection relative to the uncut reference line and toward one of the overlapping metal sheets, the joint is formed between an outer peripheral cutting face of the projection of first metal sheet and an inner peripheral cutting face of the hole of a second metal sheet the joint is formed by the pressing so as to increase a normal load and a friction distance to increase an amount of the adhesion, and the pressing is a single operation, the adhesion follows a formula as depicted: in above formula, A a is an adhesion surface area when two solid objects are contacted with each other, ζ is a surface coefficient, P is a normal load, and P m is a plastic flow pressure of material.