Press-Formed Lower Arm Wall Forming With Reduced Springback
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Solution Overview
Problem
Conventional press forming methods for manufacturing automobile lower arms result in products with low fatigue resistance due to residual tensile stress and springback, especially in components with inward curving vertical walls, which are prone to cracking under repeated loads.
Innovation Solution
A pressing machine and method that control the motion and pressure of multiple dies to form the concavity and vertical wall in a specific sequence, ensuring the material flows into the concavity and reduces compressive stress, thereby minimizing springback and residual tensile stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional press forming method is used to form vertical walls, then the vertical wall shape is achieved, but springback occurs and fatigue resistance decreases
Solution Approach 1:
The patent applies preliminary action by forming the concavity in the blank before forming the vertical wall. This preliminary concavity formation allows the material to be pre-positioned and pre-stressed in a way that compensates for the springback that will occur during subsequent vertical wall formation, thereby maintaining both shape accuracy and fatigue resistance
Solution Approach 2:
The patent applies preliminary anti-action by creating compressive stress in the blank through concavity formation before the vertical wall forming process. This pre-applied compressive stress counteracts the tensile springback forces that will occur during vertical wall formation, effectively preventing the springback deformation and maintaining fatigue resistance
2Manufacturing precision
If the vertical wall is formed first, then the shape is achieved, but residual tensile stress increases and causes cracking
Solution Approach 1:
The patent applies preliminary action by forming the concavity in the blank before forming the vertical wall. This preliminary concavity formation allows the material to be pre-positioned and pre-stressed in a way that compensates for the springback that will occur during subsequent vertical wall formation, thereby maintaining both shape accuracy and fatigue resistance
Solution Approach 2:
The patent converts the harmful effect of stress concentration into a beneficial pre-compressive stress state. By forming the concavity first, the material is subjected to compressive stress that will counteract the tensile stresses generated during vertical wall formation, effectively converting what would be harmful tensile residual stress into beneficial compressive pre-stress
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 approach effectively suppresses the decrease in fatigue resistance of press-formed products, enhancing their durability and reliability by reducing residual stress and springback.
Implementation Method 1
In press forming, after the second die reaches a bottom dead point for forming, the first die reaches a bottom dead point for forming
Implementation Method 2
the vertical wall is subjected to bending and is apt to warp due to its restoration behavior (that is, springback is apt to occur)
Data Source
AI summary
A method for manufacturing a press-formed product includes a first step and a second step. In the first step, a concavity is press formed in a blank by use of a punch and a first die. The punch has a shape corresponding to the shape of the entire press-formed product. The first die has a shape corresponding to at least the shape of the concavity. In the second step, a vertical wall and an edge portion are press formed in the blank by use of the punch and a second die. The second die is located adjacent to the first die. The second die has a shape corresponding to at least the shape of the vertical wall and the edge portion. The first step is completed after the second step is completed. The method allows production of a press-formed product which is excellent in fatigue resistance.