Press Forming Analysis for Springback Estimation
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Solution Overview
Problem
Existing methods for estimating springback in press-formed parts using high-strength steel sheets struggle to accurately evaluate the influence of residual stress in each region after the part is released from the press die, leading to difficulties in achieving dimensional accuracy and requiring repeated corrections to the press die.
Innovation Solution
A method using a finite element method analysis system that calculates and transforms stress distributions before and after the part's release, determining springback effective stress and evaluating its influence by changing or removing stress in specific regions, allowing for a more accurate assessment of stress impact on the part's shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional finite element method is used to estimate springback, then springback analysis can be performed, but it is difficult to estimate which region has residual stress having dominant influence on springback
Solution Approach 1:
The patent divides the press-formed part into multiple analysis target regions and performs separate springback analyses for each region by changing or removing stress in each specific region. This segmentation allows identification of which region has residual stress having dominant influence on springback, resolving the difficulty of detecting and measuring the dominant stress region while maintaining accurate springback estimation.
2Productivity
If stress is changed only before releasing from press die, then springback analysis can be performed, but it may be difficult to accurately evaluate the influence of stress in each region
Solution Approach 1:
The patent performs preliminary springback analysis to calculate the distribution of residual stress after releasing from the press die before performing the actual influence evaluation. This preliminary action ensures that both stress states (before and after release) are considered, enabling accurate evaluation of stress influence in each region while maintaining analysis efficiency through a systematic two-stage approach.
3Manufacturing precision
If repeated correction of press die is performed, then dimensional accuracy can be achieved, but the burden for correction increases
Solution Approach 1:
The patent provides a feedback mechanism by quantifying the degree of influence of stress in each analysis target region on springback through separate springback analyses. This feedback information allows engineers to predict the effect of stress changes before actual die correction, reducing the need for repeated trial-and-error corrections and thereby reducing the time and burden associated with press die correction while maintaining dimensional accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise evaluation of stress influence on springback without overestimation or underestimation, allowing for effective measures to reduce springback and improve dimensional accuracy in press-formed parts.
Implementation Method 1
This invention relates to a method for press forming analysis, and particularly to a method that quickly and accurately analyzes a degree of influence of stress in each region of a press-formed part on the springback
Implementation Method 2
Since the degree of an elastic recovery (hereinafter referred to as a springback, or may be abbreviated as SB) of high strength steel sheets after a press forming is greater than that of mild steel sheets
Data Source
AI summary
A method for press forming analysis is provided which can accurately estimate a degree of influence of stress in each region of a press-formed part on a springback. The method for press forming analysis includes the steps of (1) calculating a data representing a shape of and a distribution of residual stress in a press-formed part before the release, and performing a coordinate transformation on a basis of the data before the release to calculate a distribution of stress (a) before the release in a local coordinate system; (2) performing a springback analysis on the basis of the data before the release which includes (i) calculating a distribution of residual stress in the press-formed part after the release and performing the coordinate transformation to calculate a distribution of residual stress (b) in the press-formed part in the local coordinate system, and (ii) calculating shape data (d) of the press-formed part after the release; (3) calculating a difference (a - b) between the distributions of stress (a) and (b) as springback effective stress (SB effective stress), performing a coordinate transformation to calculate a distribution of SB effective stress in a global coordinate system, changing or removing the SB effective stress in an analysis target region in the distribution of SB effective stress to calculate a distribution of SB effective stress in the press-formed part, and performing the springback analysis to calculate a shape data (c) of the press-formed part after the release; and (4) calculating a difference (c - d) between the shape data (c) and the shape data (d) to determine a degree of influence of the analysis target region on the overall shape.