Stress-strain relation simulation method, springback-amount prediction method, and springback analyzer

Patent metadata

Field	Value
Publication number	US-10089422-B2
Application number	US-201414765208-A
Country	US
Kind code	B2
Filing date	Feb 10, 2014
Priority date	Mar 14, 2013
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

Displacement or a load is applied to an elastic-plastic material to deform the elastic-plastic material plastically to acquire experimental values of a stress-strain relation. With a kinematic-hardening incremental vector dα ij of a yield surface in an elastic-plastic constitutive model as a predetermined first equation, the elastic-plastic constitutive model being defined as a function of stress and back stress, a computer identifies material constants contained in the elastic-plastic constitutive model with the acquired experimental values. The computer identifies material constants contained in a predetermined second equation on the basis of the acquired experimental values and the predetermined first equation into which the identified material constants are substituted. The computer simulates the stress-strain relation of the elastic-plastic material with the predetermined first equation, the predetermined second equation, and the elastic-plastic constitutive model into which the identified material constants are substituted.

First claim

The invention claimed is:

1. A springback-amount prediction method comprising:
determining a spring-back amount of a press-formed product including:
(i) an experimental-value acquisition step of plastically deforming an elastic-plastic material to acquire experimental values of a stress-strain relation;
(ii) a first material-constant identification step of, by a computer, with a kinematic-hardening incremental vector dα ij of a yield surface in an elastic-plastic constitutive model as Equation (1), the elastic-plastic constitutive model being defined as a function of stress and back stress, identifying material constants contained in the elastic-plastic constitutive model using the experimental values acquired at the experimental-value acquisition step;
(iii) a second material-constant identification step of, by the computer, based on the Equation (1) into which the material constants identified at the first material-constant identification step are substituted and based on the experimental values acquired at the experimental-value acquisition step, identifying material constants contained in Equation (2); and
(iv) a step of, by the computer, predicting the springback amount with the Equation (1) and the Equation (2) into which the material constants identified are substituted, and the elastic-plastic constitutive model,

modifying a die based upon the determined spring-back amount, and
pressing the die onto a metal sheet to produce the press-formed product,
wherein Equation (1) is defined as follows:

d
⁢

⁢

α

i
⁢

⁢
j

=

[

C
⁡

(

a
Y

)

⁢

(

σ

i
⁢

⁢
j

-

α

i
⁢

⁢
j

)

-

C
0

⁢
ρ
⁢

⁢

X

i
⁢

⁢
j

]

⁢
d
⁢

⁢

ɛ
eq
p

Equation (2) is defined as follows:

C
=

C
a

+

C
c

⁢

exp
⁡

(

-

X
eq
n

A

)

⁢

where:
a: maximum value of movement of yield surface
Y: yield stress
α ij : movement vector of yield surface
σ ij : stress vector
X ij : yield—surface kinematic—hardening amount after stress reversal
X eq : equivalent value of X ij
dε p eq : equivalent plastic—strain increment
C 0 , C C , A, n: material constants
ρ: variable such that ρ=1 or ½.

2. The springback-amount prediction method according to claim 1 , wherein variables X ij , ρ, A, and n in the Equations (1) and (2) are represented by Equation (3), wherein Equation (3) is defined as follows:

If
⁢

⁢

σ
eq

≥

σ

eq
⁢

⁢
max

,

σ
eq

=

σ

eq
⁢

⁢
max

⁢

Assignees

• Jfe Steel Corp

Inventors

• Sumikawa Satoshi
• Ishiwatari Akinobu

Classifications

• G01N2203/0092

  Visco-elasticity, solidification, curing, cross-linking degree, vulcanisation or strength properties of semi-solid materials · CPC title

• G01N3/08 Primary

  by applying steady tensile or compressive forces (G01N3/28 takes precedence) · CPC title

• G01N2203/0075

  Strain-stress relations or elastic constants · CPC title

• G01N33/442

  Resins; Plastics · CPC title

• G06F17/16

  Matrix or vector computation {, e.g. matrix-matrix or matrix-vector multiplication, matrix factorization (matrix transposition G06F7/78)} · CPC title