Necking failure limiting strain detection method based on DIC

A technology of ultimate strain and detection method, which is applied in the direction of applying stable tension/pressure to test the strength of materials, can solve problems such as unfavorable engineering applications, lengthy and cumbersome processes, and achieve accurate and reliable results, clear physical meaning, and good universality. sexual effect

Active Publication Date: 2019-03-15
SHANGHAI JIAO TONG UNIV
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Problems solved by technology

Although the forming limit curves obtained by this method and other existing time-correlation detection methods are relatively accurate, differential operations are generally required, which have high requirements for data continuity and smoot

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  • Necking failure limiting strain detection method based on DIC
  • Necking failure limiting strain detection method based on DIC
  • Necking failure limiting strain detection method based on DIC

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Embodiment Construction

[0027] The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0028] Physically, sudden changes in thickness in critical localized areas of the sheet indicate the onset of localized necking. The strain on the sheet before local necking begins depends on the geometry of the punch and the shape of the sheet itself. After the local necking begins, all the strains are concentrated in this local area, which is the instability zone. The strain rate of the sheet outside the instability region thereafter decreases rapidly until deformation finally stops. The present inv...

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Abstract

The invention provides a necking failure limiting strain detection method based on DIC. The method comprises the following steps: S1, based on a DIC technique, selecting data points in a plurality ofsections vertical to a crack direction to draw a curve of primary and secondary strains varying along with time; S2, determining the limiting primary strain and the limiting secondary strain of the sections vertical to the crack direction based on the curve of primary and secondary strains varying along with time; and S3, based on the limiting primary strain and the limiting secondary strain of the sections vertical to the crack direction, drawing the limiting primary strain and the limiting secondary strain as vertical axis and cross axis in a coordinate map to obtain a formed limiting curveof a metal panel material, wherein necking failure limiting strain detection of the metal panel material is achieved. The method is quick, direct, concise and effective, and has very good universality.

Description

technical field [0001] The invention relates to the technical field of plate formability testing, in particular to a DIC-based necking failure limit strain detection method, especially a rapid detection method. Background technique [0002] When sheet metal is formed, the deformation process includes several stages of uniform deformation, diffusive instability, concentrated instability, and fracture failure. Among them, diffuse instability and concentrated instability can also be called dispersed necking and local necking respectively. Sheet metal forming must exceed the elastic limit, but not beyond the necking stage, especially the local necking stage. Because once the deformation exceeds this stage, the strength of the material cannot be guaranteed, and a slight force may cause rupture and failure in the subsequent process or during use. Therefore, although the desired shape can be obtained by large deformation, necking of the sheet must be avoided in the actual process...

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Application Information

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IPC IPC(8): G01N3/08
CPCG01N3/08
Inventor 何霁冯怡爽李淑慧
Owner SHANGHAI JIAO TONG UNIV
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