Press Forming of Concave Curved Panels Without Fractures or Wrinkles
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Solution Overview
Problem
Press forming high-strength metal sheets for automotive parts with concave curved shapes faces challenges such as fractures and wrinkles due to stretch flange deformation, particularly in the flange and top portions, which existing methods struggle to prevent effectively without increasing die size or cost.
Innovation Solution
A press forming method that increases the bending radius of the punch shoulder portion from the center to the ends of the curve, decreases the bending radius of the die shoulder portion, and incorporates rotational motion restraining shapes or wider flange widths to guide material flow, preventing fractures and wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional press forming is used for high-strength metal sheets with concave curved shapes, then manufacturing cost and time are reduced, but fractures occur in the flange portion and wrinkles occur in the top and punch shoulder portions
Solution Approach 1:
The invention applies different bending radii to different regions of the punch shoulder portion. Specifically, the bending radius is made larger at the end sides of the curve and smaller at the center, creating local variations in geometry that control material flow differently across regions. This local quality differentiation prevents both fractures in the flange portion and wrinkles in the top and punch shoulder portions simultaneously
Solution Approach 2:
The invention changes the geometric parameter (bending radius) of the punch shoulder portion to optimize material flow. By increasing the bending radius at end sides and decreasing it at the center, the material flow characteristics are modified to prevent stretch flange deformation, thereby preventing fractures and wrinkles without requiring additional pressure devices
Data Source
AI summary
A press forming method includes: press forming a press formed product including a top portion, a side wall portion continuous from the top portion through a punch shoulder portion, and a flange portion continuous from the side wall portion through a die shoulder portion, the press formed product including a curved portion that is concave and curved in a top view; and increasing a bending radius of the punch shoulder portion in the curved portion from a center of a curve toward an end side of the curve.