Press Forming Springback Analysis by Regional Young's Modulus Variation
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Solution Overview
Problem
Conventional methods for identifying the cause of springback in press forming products, particularly those using high-strength steel sheets, struggle to accurately pinpoint the region and direction of residual stress, leading to inconsistent calculations and ineffective die correction.
Innovation Solution
A method involving a press forming analysis followed by a springback analysis, where the press forming product is divided into regions, and the Young's modulus is selectively changed in designated directions to identify the region and direction contributing most to springback by comparing springback amount differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the residual stress is changed in a press forming simulation to identify springback cause, then the springback amount can be evaluated, but the calculation may crash or wrong calculation may be performed when using high accurate material models with history variables
Solution Approach 1:
The patent introduces Young's modulus as an intermediary parameter to indirectly identify the cause of springback. Instead of directly changing residual stress which causes calculation crashes, the method changes Young's modulus in specific regions and directions, which serves as a mediator to achieve the same identification purpose while maintaining calculation stability. This intermediary approach allows the springback cause identification to proceed without the numerical instability issues associated with direct residual stress modification in kinematic hardening models.
2Weight of moving object
If high-strength steel sheets are used for weight saving, then the automotive body weight is reduced, but the degree of springback increases
Solution Approach 1:
The patent divides the press forming product into multiple regions and further segments the Young's modulus modification into specific directions within each region. By segmenting the analysis into regional and directional components, the method can identify the specific location and orientation of residual stress causing springback, enabling targeted die corrections rather than blanket approaches, thus improving manufacturing precision for high-strength steel applications.
Solution Approach 2:
The patent applies local quality by modifying Young's modulus in specific regions and directions rather than uniformly across the entire part. This localized approach allows for precise identification of springback causes in specific areas, enabling targeted die corrections that address the actual problem locations while leaving other regions unaffected, thereby improving overall manufacturing precision for weight-reduced automotive bodies.
3Measurement precision
If the yield surface is moved in plastic deformation as in kinematic hardening model, then the prediction accuracy of springback is improved, but the calculation complexity increases due to history variables
Solution Approach 1:
The patent uses Young's modulus as an intermediary parameter that bypasses the need to directly manipulate history variables in the kinematic hardening model. By changing Young's modulus in specific regions and directions, the method achieves springback cause identification without directly interfering with the complex history variable updates required by the kinematic hardening model, thus maintaining prediction accuracy while avoiding calculation crashes.
Solution Approach 2:
The patent changes the physical parameter of Young's modulus instead of modifying the complex history variables or residual stress parameters directly. This parameter change approach allows the method to work with high-accuracy kinematic hardening models without introducing the numerical instability that arises from direct manipulation of stress or history variables, effectively managing the complexity of advanced material models.
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 allows for accurate identification of the residual stress region and direction causing springback without calculation crashes, providing reliable data for die correction and improved springback suppression.
Implementation Method 1
a press forming analysis step of acquiring a shape, a residual stress distribution, and a strain distribution of the press forming product before a die release by performing a press forming analysis
Implementation Method 2
a press forming analysis step of acquiring a shape, a residual stress distribution, and a strain distribution of the press forming product before a die release by performing a press forming analysis
Implementation Method 3
a springback analysis step of acquiring a springback amount of the press forming product after the die release by performing a springback analysis
Implementation Method 4
a Young's modulus changing unit that selects regions of the press forming product divided by the region dividing unit and changes Young's modulus in a designated direction in each of the selected regions
Data Source
Figure 1
Figure 2
Figure 3A~4B
AI summary
A method of identifying a cause of springback includes a step of performing a press forming analysis, a step of performing a springback analysis on the basis of information acquired by the press forming analysis, a step of dividing a shape of a press forming product acquired by the press forming analysis into a plurality of regions, a step of changing Young's modulus in a designated direction in any region of the divided regions, a step of performing the springback analysis on the press forming product whose Young's modulus is changed, a step of acquiring springback amount differences on the basis of multiple springback, analysis results, and a step of identifying the cause of the springback on the basis of the acquired springback amount differences.