Press-Formed Weld Joint Structure for Higher Fatigue Strength
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Solution Overview
Problem
Current welding methods for structural parts, such as suspension arms and chassis frames, face fatigue damage due to stress concentration at the weld boundary, leading to reduced fatigue strength, and existing solutions increase the number of steps and costs without effectively addressing this issue.
Innovation Solution
A welding structure is developed where two press-formed parts with openings are joined using a step portion formed by a bent projection on one part, which is fitted into the opening of the other part and linearly welded, reducing stress concentration and preventing damage by shaping the weld metal to alleviate stress concentration factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two press-formed parts are joined by fillet welding to form a closed cross-section, then structural strength is improved, but fatigue strength is reduced due to stress concentration at the weld boundary
Solution Approach 1:
A step portion is formed on one of the press-formed parts before welding to pre-shape the weld metal deposition area. This preliminary geometric modification ensures that when arc welding is performed, the weld metal naturally forms a smooth transition zone that reduces stress concentration at the weld boundary, thereby improving fatigue strength while maintaining structural strength
Solution Approach 2:
The invention changes the geometric parameters of the joint interface by introducing a step portion with specific height and width dimensions. This parameter modification alters the weld metal distribution pattern, creating a more favorable stress distribution profile that reduces peak stresses at the weld boundary and improves fatigue performance
2Reliability
If multiple layering or complex welding methods are used to improve fatigue strength, then fatigue strength is improved, but the number of steps and manufacturing costs increase
Solution Approach 1:
The step portion is formed during the press-forming process itself, before welding takes place. This preliminary action eliminates the need for multiple welding layers or post-welding treatments, as the pre-formed step portion directly guides the arc welding to produce optimal weld geometry in a single pass, thereby improving fatigue strength without increasing process complexity
Solution Approach 2:
The invention merges the step portion formation into the press-forming process, combining two operations (step formation and part shaping) into one integrated process. This consolidation eliminates the need for separate operations to create the step portion, reducing the total number of manufacturing steps while achieving the desired fatigue strength improvement through optimized weld geometry
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 enhances fatigue strength by reducing stress concentration, improving weld stability, and increasing the cross-section modulus, resulting in longer fatigue life and increased stiffness without increasing the number of steps or costs.
Implementation Method 1
the step portion of the one part and a tip end of a side wall portion of the other part are linearly joined by arc welding... shaped so as to prevent a stress concentration factor
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4(a)~4(b)
AI summary
A welding structure of a press-formed part according to the present invention is a welding structure of a press formed part made by combining and joining two parts formed by press-forming and each having an opening portion on at least one side of a cross-section, while the opening portions face each other. A step portion 7 is provided by forming a bent projection 5 projecting outwardly on a tip end portion of a side wall portion 3a of a lower side part 3, partially or entirely on a joining surface. A tip end side of the step portion 7 is fitted into the opening portion of an upper side part 9, and the step portion 7 of the lower side part 3 and the tip end of a side wall portion 9a of the upper side part 9 are linearly joined by arc welding.