Tapered Rivet Hole Geometry to Prevent Block Cracking
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Solution Overview
Problem
When attempting to fasten a plate member to a block member using a rivet, there is a risk of cracking in the block member, leading to leaks, especially when the block member has a large thickness.
Innovation Solution
A riveting method involving a metal rivet with a tapered shaft portion and a prepared hole with a cone-shaped inner wall surface, where the rivet is driven into the members in a specific order to minimize interference and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rivet is driven from the front surface of the plate member into the block member, then the members can be fastened together, but cracking occurs in the block member leading to leaks
Solution Approach 1:
Instead of driving the rivet from the front surface of the plate member into the block member, the rivet is driven from the front surface of the block member into the plate member. This inversion of the fastening direction prevents cracking in the block member while still achieving secure fastening of both members together.
2Strength
If the interference between the rivet and hole is increased to improve fastening strength, then the connection becomes stronger, but cracking in the block member is more likely to occur
Solution Approach 1:
The interference between the rivet and hole is controlled within a specific range (3-13%) rather than maximizing it. This parameter optimization ensures sufficient fastening strength while preventing excessive stress that would cause cracking in the block member. The interference fit is carefully calibrated to balance strength and reliability.
Data Source
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AI summary
The present invention includes: a preparation step in which a back surface (50a) of a second fastenable member (50) is overlaid on a front surface (40a) of a first fastenable member (40) that has a lower hole (41); and a riveting step in which a rivet (1a) that is made of metal and has been set in a location distanced from a front surface (50b) of the second fastenable member (50) is moved toward the location of the lower hole (41), and the rivet (1a) is driven, in order, through the second fastenable member (50) and the first fastenable member (40), and made to arrive in the the lower hole (41). The lower hole (41) comprises a hole section (43) that has an inner wall surface with a tapering substantially conical shape or substantially truncated conical shape, the rivet (1a) comprises a first shaft section (3) with a tapered shape, the first shaft section (3) has a tip end section (3a1) that becomes narrower in diameter toward the tip end side, a helical groove (3b) is carved into the peripheral surface of the first shaft section (3) from the base end side to the tip end side, and the maximum interference is 3-13%.