Hat-Section Press Forming With Initial Deflection Against Springback
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Solution Overview
Problem
High-strength steel sheets used in automobile bodies face challenges in press forming due to reduced formability, leading to spring back and dimensional inaccuracies, particularly in manufacturing components like side sills with hat-shaped cross sections, which affects subsequent welding procedures and requires suppression of angular changes and wall warps.
Innovation Solution
A press forming method and apparatus with specific configurations, including a punch and die design with recessed portions and adjustable blank holding surfaces, allow for controlled deflection and residual deflection management, ensuring dimensional accuracy by maintaining a gap between the punch, die, and workpiece, thereby suppressing moment fluctuations and enlarging the allowable range of initial deflection amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press forming is performed on high-strength steel sheet to manufacture hat-shaped cross section, then strength and fuel economy are improved, but spring back and dimensional accuracy deteriorate
Solution Approach 1:
The invention applies preliminary action by creating an initial deflection in the steel sheet before the main forming operation. The die pad is positioned to contact the steel sheet at a specific location, causing a predetermined amount of deflection to occur during the pressing process. This preliminary deflection counteracts the spring back that would otherwise occur after forming, thereby improving dimensional accuracy of the press-formed article while maintaining the use of high-strength steel sheets
2Strength
If press forming is performed on high-strength steel sheet, then strength is improved, but formability deteriorates
Solution Approach 1:
The invention applies parameter changes by modifying the positioning parameters of the die pad relative to the punch. Specifically, the die pad is positioned to contact the steel sheet at a location that is a predetermined distance from the punch contact point. This parameter adjustment changes the forming mechanism to accommodate high-strength steel sheets with reduced formability, enabling successful manufacturing of hat-shaped cross sections without excessive forming forces or defects
3Manufacturing precision
If angular change in ridgeline is suppressed, then dimensional accuracy is improved, but wall warp occurs
Solution Approach 1:
The invention applies the intermediary principle by introducing the die pad as a mediating element between the punch and the steel sheet. The die pad contacts the steel sheet at a specific intermediate location and applies a controlled deflection that indirectly influences both the ridgeline angle and the vertical wall shape. This intermediary action allows suppression of angular change in the ridgeline while minimizing wall warp through proper positioning of the die pad
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
The method effectively suppresses spring back and ensures dimensional accuracy of press-formed articles by managing residual deflections and bending tendencies, enhancing the stability of the forming process and allowing for a broader range of initial deflection settings within tolerance.
Implementation Method 1
a spring back tends to occur in the obtained press-formed article
Implementation Method 2
the workpiece sheet is press-formed
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2E
AI summary
This press forming method is a press forming method of manufacturing a press-formed article from a workpiece sheet using a press forming apparatus including a punch, a die, a punch pad, and a die pad, in which, when the workpiece sheet is clamped between the die and the punch, a surface of the workpiece sheet on a die side in a section between a point in contact with a die bottom end shoulder portion and a point in contact with the die pad is in non-contact with the die and the die pad, and an end surface of a punch side blank holding surface adjacent to a punch shoulder portion is flush with the punch shoulder portion or located on a more inner side of the punch than the punch shoulder portion.