Online Quality Determination in Self-Piercing Riveting
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Solution Overview
Problem
Current quality control methods for punch riveting processes, particularly for semi-tubular and solid rivets, are inefficient as they require destructive testing and are not suitable for series production, as they rely on external geometry inspection and force-displacement data that need to be measured individually after each process.
Innovation Solution
An online method for determining the compression dimension and rivet head end position using force-displacement data recorded during the punch riveting process, where the path covered by the punch and the force applied are monitored, and specific points in the data are identified to calculate these parameters, allowing for real-time evaluation and reducing the need for destructive testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visual inspection and external geometry measurement are used for quality control, then the inspection can be performed non-destructively and on a large scale, but only general information about external features is obtained without detailed internal quality data
Solution Approach 1:
The patent replaces mechanical measurement systems (visual inspection, external geometry measurement) with a field-based detection system using force-displacement data. By monitoring the force-displacement characteristics during the punch riveting process, the system obtains information about internal quality parameters such as rivet head end position and compression dimension without physical contact or destruction of the joint.
2Measurement precision
If destructive testing with macrosections and strength tests is performed, then detailed quality parameters such as evenness, gap formation, flushness, undercut, and cracks can be evaluated, but the process is time-consuming and not suitable for series production
Solution Approach 1:
The patent performs quality assessment during the punch riveting process itself by monitoring force-displacement data, rather than after the process is complete. The starting point and relief point are identified during the forming process, allowing quality parameters to be determined in real-time without requiring subsequent destructive testing or waiting for post-process measurements.
Solution Approach 2:
The patent creates a digital copy of the quality parameters by analyzing force-displacement data that replicates the information obtained from destructive testing. The force-displacement curve serves as a digital representation of the joint quality, allowing parameters like compression dimension and rivet head end position to be determined without physically destroying the joint for macrosection analysis.
3Ease of manufacture
If reference values for rivet head end position and compression dimension are determined in preliminary tests and used for random control, then the effort for destructive quality testing is reduced, but individual measurement after each joining process is still required which involves a lot of time
Solution Approach 1:
The patent implements continuous quality monitoring during the punch riveting process by continuously recording force-displacement data. Rather than performing discrete measurements after each joint is formed, the system continuously captures data throughout the forming process, allowing quality parameters to be extracted in real-time without interrupting the production flow or requiring separate measurement steps.
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
Enables the automatic documentation of quality parameters, facilitating process capability studies and quality control charts, and providing insights into geometric parameters and load-bearing behavior previously only determinable through destructive testing, thus improving the efficiency of quality control in punch riveting processes.
Implementation Method 1
recording a path covered by the movable punch during the punch riveting process using a displacement transducer
Implementation Method 2
recording a force applied by the movable punch to the semi-tubular punch rivet during the punch riveting process as a function of the path covered
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention discloses a method for the online determination of the upsetting dimension XST and the rivet head end position K of a rivet 3 with a length L during a self-piercing riveting process using a movable punch 10 and a rigid die 20. During the joining process, the distance traveled by the punch 10 and the force applied by it are recorded and evaluated online. Using defined threshold values or a graphical evaluation of force-displacement data from the joining process, the quality parameters of the joint can be determined.