Friction Stir Weld Seam Root Defect Detection via Tensile Stress
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Solution Overview
Problem
Detecting root fusion defects in friction stir weld seams is challenging due to the smooth surface and 'cold welded' nature of the joints, which makes it difficult to identify cracks and ensures only low mechanical strength, posing safety risks in critical sectors like aviation and power station technology.
Innovation Solution
Generating tensile stress in the vicinity of the friction stir weld seam to open up any joint defects, followed by testing using methods like dye penetration, pattern comparison, or shearography, ensuring the stress does not exceed the metal's elastic limit, allowing for the detection of defects through dye penetration or image analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between the welding nib and backing is increased, then the material is completely plasticised and stirred, but root fusion defects occur due to incomplete welding penetration
Solution Approach 1:
The patent applies preliminary action by generating tensile stress in the weld seam before final inspection to open up potential root fusion defects. This pre-stressing action reveals hidden defects that would otherwise remain undetected, allowing for their identification and remediation before the weld is put into service, thus preventing future failures.
Solution Approach 2:
The patent changes the physical state of the weld seam by applying tensile stress, which transforms the closed-state defects into open-state defects. This parameter change (from stress-free to stressed state) enables the detection methods to visualize defects that are otherwise invisible on the smooth weld surface.
2Shape
If the surface is made smooth for aesthetic and protective purposes, then the appearance and protection are improved, but defect detection becomes difficult
Solution Approach 1:
The patent applies preliminary action by generating tensile stress in the weld seam before final inspection to open up potential root fusion defects. This pre-stressing action reveals hidden defects that would otherwise remain undetected, allowing for their identification and remediation before the weld is put into service, thus preventing future failures.
Solution Approach 2:
The patent introduces an intermediary substance (dye) that penetrates into the opened defects. This dye acts as a mediator between the inspection system and the hidden defects, making them visible through color contrast on the otherwise smooth surface, thus solving the contradiction between surface smoothness and defect detectability.
3Ease of operation
If conventional inspection methods are used on smooth surfaces, then the inspection process is simple, but root fusion defects remain undetected
Solution Approach 1:
The patent applies preliminary action by generating tensile stress in the weld seam before final inspection to open up potential root fusion defects. This pre-stressing action reveals hidden defects that would otherwise remain undetected, allowing for their identification and remediation before the weld is put into service, thus preventing future failures.
Solution Approach 2:
The patent changes the physical state of the weld seam by applying tensile stress, which transforms the closed-state defects into open-state defects. This parameter change (from stress-free to stressed state) enables the detection methods to visualize defects that are otherwise invisible on the smooth weld surface.
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 method allows for reliable, quick, and accurate detection of root fusion defects, preventing potential failures by identifying cracks that would otherwise be hidden, ensuring the welds meet safety standards.
Implementation Method 1
The friction heat generated plasticises the metal in the butt joint region and enables firstly the introduction of the rotating welding nib and subsequently its ongoing movement along the joint to form the friction stir welding seam
Implementation Method 2
The friction heat generated plasticises the metal in the butt joint region
Implementation Method 3
a) Generation of a tensile stress in the vicinity of the friction stir weld seam in the elastic range
Implementation Method 4
Generation of a tensile stress in the vicinity of the friction stir weld seam in the elastic range
Implementation Method 5
testing is undertaken in step b) by means of a dye penetration test
Data Source
AI summary
The disclosure provides methods for the detection of a possible joint defect, in particular a root fusion defect, in a friction stir weld seam, wherein two members are joined together and the methods include generating of a tensile stress in the region of the friction stir weld seam in the elastic range, and testing in at least some regions of a lower face of the friction stir weld seam, in order to detect any joint defect.