To connect an electrical wire to a socket, crimping is widely used for a wide range of applications. Especially when considering high-reliability electrical connections (e.g., for aerospace or automotive applications), a detailed assessment of the crimp joint is required to ensure the proper functionality. The most commonly used method to assess the quality of crimp joints involves the metallographic investigation of the cross-section as described in the ESA-standard ECSS-Q-ST-70-26C.
Crimp assessment according to ECSS-Q-ST-70-26C
A metallographic cross-section is prepared through the crimp joint revealing the area of the maximal compression. The cross-section is assessed to evaluate the following acceptance criteria
• The cross-section is free from contaminations.
• The crimp barrel is evenly deformed.
• Voids occupy less than 10 % of the cross sectioned area of the wire volume.
• All strands are deformed from their circular cross section approaching a hexagonal shape.
• No indentations or fracturing of the deformed barrel are detected.
It is obvious, that not every single crimp joint can be assessed as described above. The scope is, to prepare reference crimp contact samples representative for the applied methodology. Those samples are investigated to qualify the used materials, tools and procedures.
Results obtained by AAC
The microstructural analysis group at AAC has the expertise and equipment to carry out professional assessment of crimp connections according to ECSS-Q-ST-70-26C: A metallographic cross-cut is prepared as described above and refined by target sample preparation to obtain the appropriate position of the cross-section. After proper polishing, the position of the cross-cut is verified and light-microscopic images are recorded. Those images are used to identify the different parts of the crimp: The compressed strands, the coating of the strands (if any), the crimp barrel and the voids between the strands.
As a final result of the investigation, the single components are shown as color-coded overlays on the cross-section image to obtain a high-quality representation of the crimp joint allowing to assess the acceptance criteria. Furthermore, the area fractions of the single components and the voids are evaluated and compared to the requirements defined by the standard.
As the assessment of crimp joints is frequently performed at AAC we can offer high-quality investigations leading to representative results with fast processing times at moderate costs.
Interested in more information? Get in touch with our team of experts at office@aac-research.at or visit us at Aerospace & Advanced Composites: Space Engineering & Technology
