A Forming Limit Test Method

Abstract

The invention relates to a forming limit testing method, comprising the following steps: S1, designing the stamping deformation structure on the metal pole plate, including three types of straight channel structure, circular truncated structure and bulging structure, and determining the key dimension parameters; S2, respectively selecting Determine the radius r of the inner circle of the upper corner 1 and the radius r of the inner circle of the lower corner 2 As the calculation base value, several groups of key dimension parameters are selected, and the maximum thinning rate is obtained through finite element simulation; the ratio α of the secondary strain to the principal strain is determined; S3, using the stamping device to stamp the sample plate to form the corresponding stamping deformation structure, to obtain the forming limit sample; S4, observe and measure the section of the stamping deformation structure on the forming limit sample, judge whether there is cracking or necking or local thinning, and calculate the strain parameter group, and obtain the cracking point, Necking or local thinning points and safety points; S5, drawing all cracking points, necking or local thinning points, and safety points to obtain a forming limit diagram.

Description

technical field [0001] The invention relates to the field of forming property testing of metal sheet materials, in particular to a forming limit testing method. Background technique [0002] Forming limit is a quantitative description of sheet forming performance. Accurately characterizing the forming limit is the key to solving sheet stamping problems, judging the quality of stamping process, and is of great significance for optimizing stamping process. The forming limit diagram is usually used to characterize the forming limit of the sheet. The forming limit curve is obtained by connecting the forming limit points of the sheet under various stress states into a curve. Drawing the forming limit curve in the strain space is called the forming limit diagram. [0003] Now the test method to obtain the forming limit diagram of sheet metal is to test according to the national standard: GB / T15825.8-2008 "Forming Properties and Test Methods of Sheet Metal Part 8: Guidelines for De...

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Problems solved by technology

The main difficulties that this method often faces when testing ultra-thin metal plate substrate FLD are: 1. The thickness of the ultra-thin metal plate substrate is usually 0.05-0.1mm, and the characteristic size of the plate is usually below 1mm. It is difficult to print a precise grid (such as a diameter of less than 0.2mm) on a metal sheet; 2. The size (diameter or side length) of the sample used in the Nakazima and Marciniak tests is 180mm, and the test results cannot accurately reflect ultra-thin metal poles. Forming limit of small-scale forming (≤1mm) of plate substrate; 3. Traditional forming limit test method, one test can only obtain data under one strain path, and obtaining a complete forming limit diagram requires a large number of tests, which is inefficient

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