Self-Piercing Rivet Joining Conditions to Prevent Plate Cracking
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Solution Overview
Problem
Existing methods for joining plate materials using self-piercing rivets often result in cracking of the second plate material due to inadequate setting of joining conditions, despite efforts to set conditions based on tensile elongation measurements.
Innovation Solution
A method involving a test step to measure physical value information of the second plate material by plastic deformation in the plate thickness direction, followed by setting the joining conditions to minimize cracking, using a die with a concave portion of specific dimensions to support the back surface and drive the rivet, thereby reducing the likelihood of cracking during the joining process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If joining conditions are set based on tensile elongation measurement, then the joining process can be standardized, but the second plate material still cracks during joining
Solution Approach 1:
The invention changes the test parameter from tensile elongation (uniaxial tension) to compression test with lateral expansion measurement. This parameter change better represents the actual joining condition where the plate material is compressed and expands laterally, leading to accurate determination of joining conditions that prevent cracking while enabling standardization
Solution Approach 2:
The invention performs preliminary compression tests on the second plate material before actual joining to measure lateral expansion characteristics. Based on these preliminary test results, the optimal joining conditions (punch force, die geometry, rivet specifications) are determined in advance, preventing cracks during the actual joining process
2Strength
If the cylinder portion is driven deeply into the plate materials to ensure strong joining, then joining strength is improved, but the back surface of the second plate material is more likely to crack
Solution Approach 1:
The invention uses compression test results (lateral expansion measurement) as feedback to determine optimal joining conditions. The measured expansion characteristics guide the selection of punch force, die concavity depth, and rivet dimensions, creating a closed-loop system that achieves strong joining without back surface cracking
Solution Approach 2:
The invention applies different geometric characteristics to different parts of the die: a concave portion at the bottom and a flange at the top. The concave portion controls local deformation at the joining point to prevent cracking, while the flange provides overall support. This localized quality optimization enables deep rivet insertion with strong joining strength without causing back surface cracks
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 accurately sets joining conditions to prevent cracking in the second plate material, as the test step simulates the deformation state of the material during joining, ensuring the back surface is less likely to crack, and allows for further reduction in cracking likelihood by optimizing the concave portion dimensions.
Implementation Method 1
a test step of plastically deforming the second plate material by a load in a plate thickness direction to measure physical value information of the second plate material
Implementation Method 2
the cylinder portion passes through the first plate material, and a radially expanded and deformed distal end of the cylinder portion bites into the second plate material to join the first plate material and the second plate material together
Data Source
AI summary
A method for manufacturing a joined body includes at least one first plate material, one second plate material, and a self-piercing rivet where a cylinder portion projects from a head. The method includes: a test step of plastically deforming the second plate material by a load in a plate thickness direction to measure physical value information of the second plate material; a setting step of setting a joining condition based on the physical value information by the test step; and a joining step of supporting a back surface of the second plate material having a front surface on which the first plate material is stacked with a die and driving the cylinder portion from the front surface side toward a concave portion provided in the die to join the first plate material and the second plate material together based on the joining condition set by the setting step.