Springback Analysis via Stress Decomposition

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Solution Overview

Problem

Current methods for analyzing springback in press-formed products are inadequate, making it difficult to accurately determine the cause of springback during the design stage, leading to increased time and costs in determining a suitable forming process.

Innovation Solution

A method involving numerical simulation that decomposes stress data into in-plane stress and bending moment components, allowing for the calculation and analysis of springback configurations, and the use of a coefficient to evaluate the influence of stress on deformation in specific areas, enabling more accurate identification of springback causes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If high-strength steel plates are used to provide thin and lightweight products, then weight reduction is achieved, but deformation resistance increases leading to greater springback

Engineering Contradiction:
Improveproduct weightVSAvoiddeformation resistance
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The patent segments the stress analysis by dividing the formed product into multiple areas and decomposing stress into in-plane stress components and bending moment components. This allows separate evaluation of different stress contributions to springback in different regions, enabling targeted analysis without requiring physical testing of the entire product.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent creates a virtual copy of the formed product through numerical simulation (finite element method) to analyze springback causes. By simulating the forming process and stress distribution in a virtual model, the invention eliminates the need for repeated physical testing with actual steel plates and dies, reducing development time while maintaining analysis accuracy.

Inventive Principle:
Principle #26Copying

2Loss of time

If numerical analysis is performed to estimate springback and correct die configuration, then die design time is reduced, but complete analysis of springback causes remains difficult due to nonlinear problem complexity

Engineering Contradiction:
Improvedie design timeVSAvoidspringback analysis accuracy
Core Design Contradiction:
Loss of timeVSMeasurement precision

Solution Approach 1:

The patent divides the formed product into multiple areas and separately analyzes in-plane stress components and bending moment components. This segmentation allows the complex nonlinear springback problem to be broken down into manageable parts, improving analysis precision while maintaining computational efficiency for timely die design.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent changes the analysis parameters by decomposing stress into different components (in-plane stress and bending moment) and evaluating them separately in different areas. This parameter transformation enables more precise identification of springback causes compared to conventional holistic numerical analysis, while still completing the analysis within acceptable timeframes for die design.

Inventive Principle:
Principle #35Parameter changes

3Stress or pressure

If openings or slits are provided in the formed product to remove residual stress, then springback is reduced, but product rigidity decreases leading to greater springback from slight residual stress

Engineering Contradiction:
Improveresidual stressVSAvoidproduct rigidity
Core Design Contradiction:
Stress or pressureVSStrength

Solution Approach 1:

The patent replaces physical modification methods (cutting or punching openings) with a numerical simulation approach. By using finite element analysis to evaluate stress components and their contribution to springback, the invention identifies the root causes without physically altering the product, thereby maintaining product rigidity while achieving springback reduction through die configuration correction.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If actual testing with test dies and steel plates is conducted to determine countermeasures, then accurate springback analysis is achieved, but development man-hours and costs increase

Engineering Contradiction:
Improvespringback analysis accuracyVSAvoiddevelopment man-hours
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent creates virtual copies of the forming process and product through numerical simulation. By analyzing stress components and springback causes in a virtual model, the invention achieves accurate analysis results without requiring repeated physical testing, significantly reducing development man-hours and costs while maintaining measurement precision.

Inventive Principle:
Principle #26Copying

Data Source

PatentEP2371464B1Method, device, program and recording medium of analyzing cause of springback
Publication Date: 2018.12.05 NIPPON STEEL CORPORATION
  • EP2371464B1 patent drawingFigure 1
  • EP2371464B1 patent drawingFigure 2
  • EP2371464B1 patent drawingFigure 3

AI summary

A method of analyzing a cause of springback of the invention includes: performing a forming analysis to calculate forming data of a formed product; decomposing a component into an in-plane stress component and a bending moment component; generating a before-calculation individual decomposition forming data; performing a calculation to generate an after-calculation individual decomposition forming data; analyzing a first springback configuration and a second springback configuration; obtaining a degree of influence of a stress in each of the areas with respect to springback deformation; and displaying the degree of influence with respect to the springback deformation.