basic question about gap element stiffness

[madg1]

if I selected two surfaces 1 inch apart and both surfaces having say 100 nodes.

I select draw-design-contact eleemnts and pick the two surfaces.say i am able to create 100 elements.

now in the tree....element type would be  gap and we give stiffness in the definition.

my question is the stiffness value is for each gap element or the all 100 elemets combined?

[John_Holtz]

Hi magd1,

The entered stiffness is for each element.

It sounds like you are setting up a linear static stress analysis. You example is probably just a hypothetical example; otherwise, a 1 inch gap sounds large for a linear analysis in which all of the displacements are assumed to be small. Small is relative to the size of the model, too.

[madg1]

if I can give maximum stiffness(allowable in software)....what difference does the gap size can make?afterall its closing and opening gaps right?

[John_Holtz]

Sorry, for some reason I assumed the gap type was "compression with gap". I have no idea where I got that idea because you did not mention what type of gap elements you were setting up.

If you are using "compression without gap", then I agree with you completely that the size of the gap is not a factor. I

f they are "compression with gap", then the two parts connected by the gap elements must move a relative distance of 1 inch toward each other before contact occurs. Depending on the geometry of the model, 1 inch could be ok (large physical size of thing being analyzed, small strain in parts) or stretching the accuracy of linear stress (small physical size, large strain in parts).