Evaluation method of plastic material and evaluation method of deformation processing of plastic material

Patent metadata

Field	Value
Publication number	US-2017191915-A1
Application number	US-201515308680-A
Country	US
Kind code	A1
Filing date	May 8, 2015
Priority date	May 8, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

An evaluation method of a plastic material includes: a first shearing process of performing simple shearing deformation with respect to a first plastic sheet; a second shearing process of performing simple shearing deformation with respect to a second plastic sheet; a first partial stress-strain curve data obtaining process of obtaining first partial stress-strain curve data; a second partial stress-strain curve data obtaining process of obtaining second partial stress-strain curve data; and a synthesized stress-strain curve data obtaining process of obtaining synthesized stress-strain curve data based on the first partial stress-strain curve data and the second partial stress-strain curve data.

First claim

1 . An evaluation method of a plastic material comprising:
a first shearing process of performing simple shearing deformation with respect to a first plastic sheet by dividing the first plastic sheet having a first strain amount which includes 0 into two regions by a virtual section perpendicular to a surface thereof, and by applying a shear stress to the first plastic sheet so as to make relative positions of the two regions shifted along the virtual section be on the same surface; a second shearing process of performing simple shearing deformation with respect to a second plastic sheet by dividing the second plastic sheet having a second strain amount which is different from the first strain amount and includes 0 into two regions by a virtual section perpendicular to a surface thereof, and by applying a shear stress to the second plastic sheet so as to make relative positions of the two regions shifted along the virtual section be on the same surface; a first partial stress-strain curve data obtaining process of obtaining first partial stress-strain curve data from a relationship between the shear stress applied to the first plastic sheet in the first shearing process, and a total strain amount which is a sum of a shear strain amount which is applied to the first plastic sheet in the first shearing process and the first strain amount, by measuring the shear stress and the shear strain which are applied to the first plastic sheet in the first shearing process; a second partial stress-strain curve data obtaining process of obtaining second partial stress-strain curve data from a relationship between the shear stress applied to the second plastic sheet in the second shearing process, and a total strain amount which is a sum of a shear strain amount which is applied to the second plastic sheet in the second shearing process and the second strain amount, by measuring the shear stress and the shear strain which are applied to the second plastic sheet in the second shearing process; and a synthesized stress-strain curve data obtaining process of obtaining synthesized stress-strain curve data based on the first partial stress-strain curve data and the second partial stress-strain curve data.

2 . The evaluation method of a plastic material according to claim 1 , further comprising:
an outer form removing process of obtaining the second plastic sheet by removing an outer form part of the first plastic sheet after unloading the shear stress applied in the first shearing process.

3 . The evaluation method of a plastic material according to claim 2 ,
wherein, in the outer form removing process, the outer form part is removed across the two regions of the first plastic sheet along the surface direction perpendicularly intersecting the virtual section and a flat surface of the first plastic sheet.

4 . The evaluation method of a plastic material according to claim 1 ,
wherein the first plastic sheet and the second plastic sheet are individual plastic sheets different from each other.

5 . The evaluation method of a plastic material according to claim 4 ,
wherein the second strain amount is greater than the first strain amount, and is equal to or less than the strain amount applied to the first plastic material in the first shearing process.

6 . The evaluation method of a plastic material according to claim 4 ,
wherein, in the synthesized stress-strain curve data obtaining process, the synthesized stress-strain curve data is obtained by combining the curve data of a strain region other than a part which receives the influence of a cross-over effect from the first partial stress-strain curve data and the second partial stress-strain curve data.

7 . The evaluation method of a plastic material according to claim 4 , further comprising:
an outer form removing process of obtaining a third plastic sheet having a third strain amount different from the first strain amount and the second strain amount by removing an outer form part formed by the simple shearing deformation in the first plastic sheet; a third shearing process of performing simple shearing deformation with respect to the third plastic sheet by dividing the third plastic sheet into two regions by a virtual section perpendicular to the surface thereof, and by applying a shear stress to the third plastic sheet so as to make relative positions of the two regions shifted along the virtual section be on the same surface; and a third partial stress-strain curve data obtaining process of obtaining third partial stress-strain curve data from a relationship between the shear stress applied to the third plastic sheet in the third shearing process, and a total strain amount which is a sum of a shear strain amount which is applied to the third plastic sheet in the third shearing process and the third strain amount, by measuring the shear stress and the shear strain which are applied to the third plastic sheet in the third shearing process, wherein, in the synthesized stress-strain curve data obtaining process, the synthesized stress-strain curve data is obtained based on the first partial stress-strain curve data, the second partial stress-strain curve data, and the third partial stress-strain curve data.

8 . The evaluation method of a plastic material according to claim 1 ,
wherein, in the synthesized stress-strain curve data obtaining process, the synthesized stress-strain curve data is obtained by approximating the first partial stress-strain curve data and the second partial stress-strain curve data based on a work hardening law.

9 . The evaluation method of a plastic material according to claim 1 ,
wherein, in the synthesized stress-strain curve data obtaining process, the synthesized stress-strain curve data is obtained by approximating the first partial stress-strain curve data and the second partial stress-strain curve data by a relational equation expressed by the following equation (1).
σ= K (ε p +a ) m   (1)

m=n*+ 1 /{b (ε p +c )}  (2)

here, in equation (1), σ is an equivalent stress, K (MPa) and a are material factors of the plastic material, ε p is an equivalent plastic strain, and m is as illustrated in the above-described equation (2), and in equation (2), n* is a convergence value of a work hardening coefficient, b is a parameter indicating the rate of convergence of the work hardening coefficient, and c is a parameter indicating the rate of development of the work hardening coefficient.

10 . The evaluation method of a plastic material according to claim 1 ,
wherein the application direction of the shear stress in the first shearing process and the application direction of the shear stress in the second shearing process are opposite to each other.

11 . The evaluation method of a plastic material according to claim 1 ,
wherein, in the first shearing process, the application direction of the shear stress is reversed in the middle.

12 . The evaluation method of a plastic material according to claim 10 ,
wherein, in the synthesized stress-strain curve data obtaining process, the synthesized stress-strain curve data is obtained by approximating the first partial stress-strain curve data and the second partial stress-strain curve data based on a kinematic hardening law.

13 . The evaluation method of a plastic material according to claim 1 ,
wherein the first plastic sheet and the second plastic sheet have a shape of a rectangular flat surface.

14 . The evaluation method of a plastic material according to claim 1 ,
wherein, in the first shearing process and the second shearing process, the largest amount of change in the sheet thickness of the f

Assignees

• Nippon Steel & Sumitomo Metal Corp

Inventors

• Shirakami Satoshi
• Yoshikawa Nobuo
• Yoshida Tohru
• Yoshida Hiroshi

Classifications

• G01N2203/0216

  Finite elements · CPC title

• G06F2111/10

  Numerical modelling · CPC title

• G01N2203/0025

  Shearing · CPC title

• G01N2203/0282

  Two dimensional, e.g. tapes, webs, sheets, strips, disks or membranes · CPC title

• G01N3/00

  Investigating strength properties of solid materials by application of mechanical stress · CPC title