In mechanical components like those designed and produced in Magneti Marelli Powertrain S.p.A., very often it’s important to have a correct value of driving load for interference couplings.
In particular temperature variations are important, due to the typical installation under the hood (generally between -30°C in winter and really hard conditions up to more than 150°C in very tough situations in summer).
Parts coupled by means of pure interference could have problems if involved materials are different (i.e. different coefficients of linear thermal expansion): from one side the clamping load could become too high, causing failure due to excessive stress. On the other side, especially at high temperatures, clamping load could become not enough to grant working conditions.
In this scenario, Magneti Marelli Powertrain S.p.A. decided to create a procedure for simulating the interference clamping, and in particular with the aim of having a good correlation between experimental test and calculations in term of friction coefficient.
In this paper, the main phases of the above described activity are presented, applied to a real case:
- Creation of FEM model suitable for analysis and its solution with a “first attempt” value for friction coefficient
- Execution of lab tests to have a “real” value of driving load
- Correlation with simulation to have a corrected value for friction coefficient
- New solution of the same model with updated coefficient.
At the end of presented activity, an usable value of friction coefficient for considered materials has been obtained; the same value has been used in different applications to see if it was not dependent from the specific application.
Once verified this item (and so the correctness of described methodology), the same activity was performed (and it is still running) on various coupling with other material couples normally used in Magneti Marelli Powertrain S.p.A. |