if i don't have any experimental results, i am doing computational analysis and providing contact. Ansys provides a set of contact parameter. You get the converged results for a set of range of these parameters. But the variation in results is considerable. So which results is close to actual results.
As the only parameter for frictional contact which is may be known as per the material properties. But, How are the parameters like FKT,FKN,COHE etc dependent on the material property ? If they are independent then how can we judge the solutriuon?
Today, one of my PG student presented ANSYS analysis for vibration effects on PCB Boards and components. In that, capacitor failure was maching 100% with actual failure. That means, perfect prediction of failure.
It is hypothetical question ... Frictional contact is not possible for independent of material properties.....
FKN is a scaled paramater for the normal penalty - theoretically FKN should be infinity in order to reach the perfect non-penetration condition. In practice, it is just about 1 to 10 of E modulus - afterwards in many cases it will cause disconvergence.
FKT is a scaled parameter for the tangential penalty - again FKT is infty in order to reach the perfect sticking condition. The same practical advice.
Both parameters should be studied in separated examples - first example in order to check non-penetration and second example in order to enforce the perfect sticking. If the first example is just geometrical check - if the user is satisfied with the level of non-penentration. However the second example is critical in order to estimate the stick-slip transition
The big problem is convergence - that is why the values are usually set by default such small that convergence is reached - but computation may lead to large penetration and totally wrong stick-slip transition.
The summary - the perfect analysis requrires quite a number of computations with increasing FKN and FKT in order to show the result is converging.
S . Sathishkumar ,Alexender
Sir,
as per my understanding, Value of friction coefficient can be given in ansys as per your material behavior in actual in order to define contact.
But until and unless we do not have experimental results, the other parameters value like FKT,FKN,COHE etc can be taken only on your understanding.
Is these values can be estimated exactly before performing experimental validation?
Ya sure but I can't get exact value some tolerance should there because regarding upon your material condition, environment issues and machining performance etc.....
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