As I have written on frettingwear.com, electrical contacts are one of the major technologies affected by fretting wear and fretting corrosion.  Hsu and Liao wrote a paper in 2012 in which they conducted a three-dimensional fretting wear analysis of an audio-jack electronic connector.  While most analyses of electronic contacts looked at their ability to continue carrying an electronic signal, this study checked for mechanical failure of the component.  Consequently, it is closer to a traditional fretting wear analysis.  Both a numerical and experimental set of tests were carried out in this study.

The audio-jack was modeled using five terminals and a rigid male terminal was inserted into the model.  The ABAQUS finite element software was used for the numerical calculations.  The force was measured during insertion of the male terminal and corresponded with my expectations:  the force increased for the first half of the halfway process and then dropped as the rigid terminal clicked into place.

The wear model was programmed similarly to the previous models I am studied as was illustrated by a flow chart.  First, a single fretting cycle was modeled.  The contact data from this cycle was used to calculate the wear rate at each node.  The wear rate was assumed to remain constant over an increment of cycles which were modeled as a single block.  The finite element geometry was updated to reflect the new worn geometry and another cycle was run.  This process was repeated until the simulation was complete. 

Both the experimental and numerical results demonstrated that the insertion and withdrawal forces declined throughout the tests.  The greatest reduction in force occurred during the first 4000 cycles.  The model was better at predicting withdrawal forces than input forces which it consistently under predicted. 

The wear scars calculated are shown in the illustration below.  Notice that the wear scar depth is significant with regard to part thickness and dimensions.  No wear scar profiles were taken to show a comparison of the shape of wear scars from the field data or experiments with the numerical model.  However, this is listed as future work by the authors. 

The parts were tested for 20,000 cycles until long past fatigue failure (failure was defined as either the insertion force or withdrawal force going outside of design specifications).  In the experimental study and numerical analysis failure occurred at 7,000 and 9,000 cycles respectively.  This difference corresponds to differences in strength of about 3%. 

Overall this was an interesting study and it demonstrated that fretting wear analyses can be carried out on a complex multi-part geometries.  Before most analyses have been 2-D and simple geometries although there have been a few with tougher 3-D geometries.

• Hsu, S., Liao, K., 2012, “Wear analysis and verification of metallic terminals for electronic connectors,” Engineering Failure Analysis, Vol. 25, pp. 71-80.