Terminal Fitting Through Hole Contour for Ultrasonic Welding Stress
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Solution Overview
Problem
Ultrasonic welding of electric wire conductors to terminal fittings can cause stress resonance in the mounting parts, leading to cracks or breaks due to uneven cross-sectional area changes, particularly near the welded area and the periphery of the through hole.
Innovation Solution
The terminal fitting design incorporates a through hole with a contour featuring a large radius circle and smaller radius circles connected by tangent lines, with the smaller radius circle closer to the welded part to reduce stress concentration, and an additional configuration with a first and second small radius circle to manage stress distribution across the mounting part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic welding is performed on the conductor part, then electrical connection is achieved, but stress resonance causes cracks or breaks in the mounting part
Solution Approach 1:
The through hole contour is designed with different radius circles at different locations: a large radius circle at the distal end and small radius circles at the proximal end near the welded part. This local variation in curvature radius creates gradual cross-sectional area changes specifically where stress concentration occurs, while maintaining the overall structural integrity needed for electrical connection.
Solution Approach 2:
The through hole contour uses multiple circular arcs with different radii instead of straight lines or sharp corners. The curved surfaces, particularly the small radius circles near the welded part, eliminate abrupt geometric discontinuities that would cause stress concentration, allowing stress to distribute more uniformly throughout the mounting part.
2Ease of manufacture
If the through hole has a standard circular shape, then manufacturing is simple, but stress concentrates at the periphery causing cracks
Solution Approach 1:
Rather than making the entire through hole complex, only specific portions (the proximal end with small radius circles) are modified to reduce stress concentration. The distal end maintains a simple large radius circle shape that is easy to manufacture, achieving a balance between stress distribution and manufacturing simplicity.
Solution Approach 2:
The through hole contour is formed using multiple circular arcs that are relatively easy to manufacture with standard machining or punching operations. The curved geometry eliminates sharp corners while remaining compatible with conventional manufacturing processes for metal plates.
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 design prevents sudden changes in cross-sectional area, alleviating stress resonance and reducing the risk of cracks or breaks in the mounting part, thereby enhancing the durability of the terminal fitting during ultrasonic welding.
Implementation Method 1
By applying ultrasonic vibration to the core wire 53 while the horn 63 is pressed against the core wire 53, the core wire 53 is ultrasonically welded to the welded part 55
Implementation Method 2
When the horn ultrasonically vibrates in this way, vibration energy of the horn spreads from the welded part, and the mounting part may resonate
Data Source
AI summary
A terminal fitting (17) includes a welded part (26) to which the conductor part of an electric wire is ultrasonically welded, and a board-like mounting part (23) which is formed integrally with the welded part in the axial direction and which a through hole (21) penetrates in the thickness direction. A contour, when viewed from the penetration direction, of the through hole (21) is formed of a large radius circle (31), a small radius circle (33) whose radius is smaller than that of the large radius circle, and two tangent lines (35, 37) which respectively connect the two circles, and the small radius circle is located closer to the welded part than the large radius circle.