Springback Stress Difference Analysis for Press-Formed Parts
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Solution Overview
Problem
Existing methods fail to analyze the specific portions in press forming parts that cause variations in springback amount due to scattering or variation in press forming conditions, such as material properties, tool temperature, and environmental changes, which affect shape accuracy in mass production.
Innovation Solution
A method involving finite element analysis to calculate stress distribution differences at the press forming bottom dead center under varying conditions, followed by springback analysis to identify areas contributing to springback variation, by altering stress differences and analyzing resulting displacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional springback analysis methods are used to evaluate springback behavior, then the overall springback amount can be assessed, but the specific portions causing springback variation due to press forming condition scattering cannot be identified
Solution Approach 1:
The press forming part is divided into multiple small regions, and stress difference distributions are calculated for each region separately. This segmentation allows identification of specific portions contributing to springback variation, enabling targeted analysis rather than evaluating the entire part as a single unit.
Solution Approach 2:
The analysis focuses on local stress difference distributions in specific regions of the press forming part. By evaluating stress differences in divided small regions and comparing them with springback amounts, the method identifies which local portions cause springback variation, providing localized insights for quality improvement.
2Reliability
If finite element analysis is performed under multiple press forming conditions to capture condition variation, then the influence of condition scattering can be evaluated, but the computational complexity and analysis time increase significantly
Solution Approach 1:
Stress distributions under multiple press forming conditions are calculated in advance before the actual springback analysis. These pre-calculated stress distributions are then used to compute stress difference distributions, avoiding the need to perform multiple complete springback simulations and significantly reducing computational time.
Solution Approach 2:
The method extracts only the essential stress difference information from multiple press forming conditions, separating the stress distribution calculation from the springback analysis. This extraction allows using pre-computed stress data for efficiency while maintaining the ability to evaluate condition variation effects.
3Manufacturing precision
If stress distribution differences under multiple conditions are calculated to identify variation causes, then specific portions causing springback variation can be analyzed, but the complexity of data processing and interpretation increases
Solution Approach 1:
The method changes the evaluation parameter from absolute stress values to stress difference values between multiple press forming conditions. This parameter transformation simplifies the identification of variation causes, as the stress difference directly indicates which regions are sensitive to condition changes and contribute to springback variation.
Solution Approach 2:
The stress difference distribution in each small region is compared with the actual springback amount to establish a relationship. This feedback mechanism allows identifying which specific portions cause springback variation by correlating stress differences with observed springback behavior, simplifying the interpretation process.
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
Accurately identifies portions requiring countermeasures for shape stability in press forming parts, reducing springback variation and enhancing shape accuracy in mass production.
Implementation Method 1
Springback is the behavior of elastic recovery, which is generated when internal stress in a press forming part at the time of completion of sandwiching by upper and lower tools of press forming (bottom dead center) (bottom dead center stress) is released at the time of die release.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A springback variation cause analysis method according to the present invention includes the steps of: calculating stress distributions at a press forming bottom dead center under first press forming conditions and second press forming conditions set in advance (S21, S23); determining a stress difference distribution as a difference between the stress distributions under the first press forming conditions and the second press forming conditions (S25), and setting the stress difference distribution to a press forming part at the press forming bottom dead center; changing a value of stress difference in a part of the press forming part for which the stress difference distribution has been set; calculating springback amount of the press forming part for which the value of the stress difference has been changed; and analyzing, based on the springback amount calculated by changing the stress difference, a portion that is a cause of variation in springback amount due to scattering in press forming conditions (S33).