Blind Rivet Mandrel Segmentation for Secure Fastening
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Solution Overview
Problem
Peel type blind rivets face issues with breakage, mandrel head falling off, and limited thickness range due to variable cutting edge length and high stress application, making controlled fastening and securing of workpieces challenging, especially with varying thicknesses.
Innovation Solution
A blind rivet design featuring a sleeve with thick and thin portions and a mandrel with distinct diameter portions and a securing groove, allowing controlled metal flow and secure attachment, preventing breakage and mandrel head detachment, while accommodating a wide range of workpiece thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cutting edges are used to expand the sleeve diameter by cutting, then the fastening capability is greatly improved, but the mandrel shaft may break and the mandrel head may fall off due to excessive stress
Solution Approach 1:
The mandrel shaft is segmented into multiple diameter portions (first large diameter portion, second large diameter portion, intermediate portion, small diameter portion) with different cross-sectional areas. This segmentation allows different portions to serve different functions: the larger diameter portions provide structural support and prevent breakage, while the smaller intermediate portion allows controlled deformation and metal flow into the securing groove, enabling reliable fastening without mandrel failure
Solution Approach 2:
Different portions of the mandrel shaft are given different local qualities through varying diameters. The first and second large diameter portions have high strength to prevent breakage, the intermediate portion has reduced diameter to enable metal flow and securing groove filling, and the small diameter portion is designed for breaking at a controlled location. This local quality variation resolves the contradiction between strength and reliability
2Force
If the mandrel is pulled out strongly to expand the sleeve, then the fastening force is improved, but the mandrel head may fall off and the rivet body may break
Solution Approach 1:
The intermediate portion of the mandrel shaft is preliminarily designed with a reduced diameter and a securing groove before the fastening operation. During mandrel extraction, this pre-configured intermediate portion automatically deforms and causes metal from the sleeve to flow into the groove, creating a locking action that secures the mandrel head to the rivet body before the final breaking occurs. This preliminary action prevents mandrel head detachment and rivet body breakage
Solution Approach 2:
The intermediate portion of the mandrel shaft acts as an intermediary element between the large diameter portions and the small diameter breaking portion. It mediates the stress distribution during extraction, enabling controlled metal flow into the securing groove without transmitting excessive stress to the mandrel head or rivet body, thus preventing their failure
3Length of moving object
If cutting edges cut into the sleeve, then the sleeve diameter is expanded, but the cutting length is variable and may cause excessive cutting and mandrel breakage
Solution Approach 1:
The mandrel shaft parameters are changed along its length, with the intermediate portion having a specifically reduced diameter compared to the large diameter portions. This parameter change creates a controlled deformation zone that limits the cutting depth to a precise value determined by the geometry of the intermediate portion and securing groove, eliminating the variability and excessive cutting problems
4Strength
If great stresses are applied to expand the sleeve by cutting, then the fastening capability is improved, but the mandrel head may fall off due to stress
Solution Approach 1:
The mandrel shaft is segmented into portions with different diameters, where the first and second large diameter portions provide high strength to withstand extraction forces, while the intermediate portion with reduced diameter is designed to deform and secure metal into the groove. This segmentation distributes stress appropriately, preventing mandrel head detachment while maintaining fastening capability
Solution Approach 2:
The securing groove is preliminarily formed in the intermediate portion of the mandrel shaft. During extraction, this pre-configured groove automatically receives flowing metal from the sleeve, creating a mechanical interlock that secures the mandrel head before final breaking occurs. This preliminary action reduces the stress required to prevent mandrel head detachment
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
Ensures stable, defect-free fastening of workpieces across a broad thickness range without mandrel head loss or breakage, with reduced operational stress and improved load requirements.
Implementation Method 1
the middle diameter portion of the mandrel causes the material of the thick portion to undergo metal flow and enter into the securing and attaching groove
Implementation Method 2
the cutting edges expand the diameter of one end of the sleeve of the rivet body by cutting it
Data Source
AI summary
A blind rivet including a sleeve and a flange on one end of the sleeve, and a mandrel including a shaft and a head, the head having a cutting edge for cutting open the sleeve. The sleeve of the rivet body has a thick portion, and a thin which has an inner diameter larger than the thick portion. The shaft of the mandrel has a large diameter portion, a middle diameter portion, a small diameter portion having an outer diameter smaller than the middle diameter portion, and a securing and attaching groove which is between the middle diameter portion and the small diameter portion. When the blind rivet is fastened, the middle diameter portion of the mandrel causes the material of the thick portion to undergo metal flow and to flow into the securing and attaching groove, enabling the mandrel to be tightly secured to the rivet body.