Mean Displacement Computation

Possibility of the user to choose between average over an area and average over a curve.

Computation of the mean displacement (see equation (24) DamageBand for Beginners V3) in DamageGrowth- Base::measureMeanDisplacement in DamageGrowthBase.ipp

How it is currently done: Current implementation: "xFilteredRegion<xIter,FILTER> filtered_boundary(all.begin(1), all.end(1), filter);" The mean displacement u ̄ is computed by integrating the displacement field over the edges of the element of Γd, even if Γd is a 2D surface in a 3D computation. In this way, u ̄ can be computed in 3D, even if Γd is a line. How it should be done: Possible improvement: add a parameter "dim" to specify the dimensions of the finite elements in Γd, to be able to integrate over faces in 3D for instance. Current implementation: "xFilteredRegion<xIter,FILTER> filtered_boundary(all.begin(dim), all.end(dim), filter);" For instance, in a 3D computation, if Γ_d is a line, "dim =1"; if Γd is a surface, "dim =2"