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Springback Analysis of the Stiffened Panel Milling from the Bent Plate

  • Chun-Guo LiuEmail author
  • Tao Yue
  • Xiao-Tong Yu
Regular Paper

Abstract

An analytical method considering the redistribution of residual stress in the bent plate is proposed to predict the springback of the stiffened panel when milling the panel layer by layer. Two types of stiffened panel, namely, a panel with crosswise stiffeners and a panel with lengthwise stiffeners, were selected as examples and were analyzed during the removal of each layer. Moreover, a finite-element simulation of the milling process was conducted to make comparisons with the analytical results, which demonstrates similar stress distribution and springback values. The maximum stress variation and springback value appeared when the milling depth reached the initial neutral surface. When the plate thickness decreased, the errors between analytical results and FEM results increased, and the lengthwise-stiffened panel was less affected by errors than the crosswise-stiffened panel because of a larger moment of inertia. The effects of different milling thicknesses per layer, initial plate thickness, and bending radius were also analyzed. Moreover, the milling experiment was performed to make verification. The results suggest that the analytical method can predict the springback of the stiffened panel effectively. The proposed method can also be applied to other similar forming conditions.

Keywords

Residual stress Springback Milling Bent plate FE simulation 

List of symbols

t

Half of the plate thickness

\(\Delta t\)

The thickness of removed layer

t1, t2

The thickness of the stiffer and the plate

h

The height of the stiffener

Zc

The centroid of the cross section

E

The elastic modulus

σx

The stress in x-direction

σs*

The principal stress

σs

The initial yield stress

\(\sigma_{\text{x}}^{\prime }\)

The residual stress in the lengthwise stiffeners

ε

The strain

εe

The strain caused by milling after springback

m

Hardening index

A

Hardening coefficient

μ

Poisson ratio

b

The width of the plate

\(\kappa\)

The curvature of the plate

n

The times of milling

ys

Distance between initial yield surface and the neutral surface

M

The bending moment

Mbend

The bending moment in the bending process

Me

The bending moment when the surface of the plate starts to yield

\(\varPhi (\kappa )\)

The function of the bending moment and the curvature

\(\kappa_{f}\)

The curvature after springback

\(\upalpha,\upalpha^{\prime }\)

The bending angle of the plate before and after springback,

\(y,y^{\prime }\)

The y coordinate before and after springback

\(\Delta L,\Delta L^{\prime }\)

The elongation of the y-th layer before and after springback

\(r,r^{\prime }\)

The radius of the neutral surface before and after springback

I

The moment of inertia

I1, I2

The moment of inertia of the stiffer and the plates

Iz

The moment of inertia of the plate after milling

\(\eta\)

The springback ratio

\(\lambda\)

The ratio of ys and t

σres

The residual stress after springback

σres1

The stress after the first layer is milled

σresn

The stress after the n-th layer is milled

σress

The residual stress in the plate of the stiffened panels after springback

Fm

The stress released after milling

Mm

The bending moment released after millng

Fmn, Mmn

The stress and the bending moment caused by the removal of the n-th layer

Ffin, Mfin

The total stress and bending moment caused by milling process

k1, k2

The coefficients of the stress increment increment for the upper and lower sides

k1n, k2n

The coefficients of linear stress increments after the n-th layer is milled

Notes

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Copyright information

© Korean Society for Precision Engineering 2019

Authors and Affiliations

  1. 1.Roll Forging Research InstituteJilin University (Nanling Campus)ChangchunPeople’s Republic of China
  2. 2.College of Materials Science and EngineeringJilin University (Nanling Campus)ChangchunPeople’s Republic of China

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