Dangerous associations of differement metals in car seats heating structures
Example of dangerous mistake leading to major hot spot risk
During the conference, mr Tiberghien has presented the following example:
In some case people are willing to increase the strength of highly conductive materials as copper by example because they find that a stainless steel based multifilament yarn is not conductive enough for their application.
Therefore they try to associate by twisting of binding a copper yarn with a fine stainless steel yarn of 35 to 100 microns by example.
consequences in Real applications as car seat heaters by example:
- Of course the tenacity of the copper yarn will be improoved with the stainless steel reinforcment and the breaking load will be much higher
- At first the product will work perfectly, ... but with the time, the multiple bending strain applied on the structure will lead to a weakening point on the copper part
- This process will even be worsened by the relative stifness of the stainless steel: the copper yarn will progresively be damaged against the stainless steel thread
- As consequence , all the power fed through the yarn will concentrate very locally on the very fine, but very strong, semi resistive stainless steel yarn , creating a very strong teperature rise... weakening even further the remaining strength of the copper part... until the stainless steel ultra fine wire becomes incandecent and ... set the close by sythetics parts of the car seat on fire!
* Abstact of the conference on hot spots risks of G tiberghien
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