Recessed Joining Structure for Small-Hole Weld Strength
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Solution Overview
Problem
Existing joining structures face insufficient joining strength due to a small welding area of the filler material, particularly when the hole diameter of the penetrating part is small.
Innovation Solution
A joining structure is developed where a first member with a recess formed by press molding is used, allowing a third member with a flange to be arc-welded towards the bottom of the recess via a penetrating part of a second member, increasing the welding area and securing the joining strength by solidification contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a small hole diameter penetrating part is used, then the device complexity is reduced, but the welding area of the filler material becomes small resulting in insufficient joining strength
Solution Approach 1:
The recess transforms the flat welding surface into a three-dimensional cavity structure. By creating a recess with depth and volume in the first member, the welding area is expanded from a two-dimensional surface to a three-dimensional space, allowing the filler material to be deposited throughout the recess volume and increasing the total welding area without increasing the hole diameter of the penetrating part.
Solution Approach 2:
The recess creates a nested structure where the filler material is deposited within the cavity formed by the recess. The filler material nestles into the recess space, maximizing the contact area between the filler material, first member, and second member, thereby increasing the welding area and joining strength within the constrained hole diameter.
2Area of stationary object
If a recess is formed by press molding, then the welding area is increased, but the manufacturing process becomes more complex
Solution Approach 1:
The recess is formed by press molding during the initial manufacturing of the first member, before the welding process. This preliminary formation of the recess structure allows the welding area to be increased without adding separate manufacturing steps for creating the cavity, as the recess is integrated into the first member's production process.
3Area of stationary object
If the filler material is arc-welded toward the bottom of the recess, then the welding area is increased, but the heat input and welding time increase
Solution Approach 1:
The welding process is segmented into two distinct stages: first, arc welding to deposit the filler material into the recess and form the joint; second, solidification contraction to compress and fix the second member between the flange and first member. This segmentation allows the welding area to be maximized in the recess while the fixation process occurs during solidification, optimizing both welding area and process efficiency.
Solution Approach 2:
The joining process utilizes the phase transition of the filler material from molten to solid state. During arc welding, the filler material melts and fills the recess; during solidification, the filler material contracts and generates compressive force to fix the second member. This phase transition enables increased welding area while utilizing the solidification contraction for fixation rather than requiring additional welding time.
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 increased welding area of the filler material enhances the joining strength between the first, second, and third members, improving mechanical stability even with thin first member plates.
Implementation Method 1
The second member is compressed by the flange and the first member by solidification contraction of the third member, and the second member is therefore fixed between the flange of the third member and the first member.
Implementation Method 2
The third member includes a flange that presses a peripheral edge of the penetrating part, and is arc-welded toward at least a bottom of the recess via the penetrating part.
Data Source
Figure 1
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Figure 3
AI summary
Second member 20 includes a material that is difficult to weld to first member 10. In first member 10, recess 11 is formed by press molding such that a lower surface of first member 10 opposite to second member 20 protrudes. Third member 30 is arc-welded toward at least a bottom of recess 11 via penetrating part 21 of second member 20. Second member 20 is compressed by flange 31 and first member 10 by solidification contraction of third member 30, and second member 20 is therefore fixed between flange 31 of third member 30 and first member 10.