Discussion Forum

Yasemin,

Line integration - integrates the expression over the line
Line max/min - returns the maximum or minimum of the expression over the line
Line average - integrates the expression over the line and divides by the length of the line

The simplest way to calculate reaction forces is to use the predefined reaction force variables that can be found by clicking on the "Replace Expression" icon and browsing under the Solid Mechanics section. In 3D with cartesian coordinates the names will be solid.RFx, solid.RFy, and solid.RFz. If you want the total reaction force along a line for example, then use the Line integration to integrate the reactions force variables over the line. COMSOL will automatically detect that the reaction forces are discrete nodal values and apply a summation instead of an integration. The same holds true for integrating over a surface.

As far as when to choose linear or quadratic discretization, it depends. The discretization refers to the order of the approximation functions used to approximate the solution variable (disp.) across each element. If you expect the displacement field to vary linearly across each element use linear. If you expect a quadratic variation of displacement across each element use quadratic, etc. In beam bending problems, strains vary linearly through the thickness of beams which means that displacements vary quadratically. So, if you expect bending, it's a good idea to use quad. discretization. Although, you can always just use a large number of linear elements to capture the variation of your dependent variables. If you doing contact modeling, linear elements can be more stable during the solution process.

Hope this helps.

Regards,
Josh Thomas
AltaSim Technologies

Many thanks.

The answer is very helpful.