Mass adjust verification

Using mass adjustment to define the total mass of an element set in a model is tested. The analyses consist of a set of reference elements and another set of test elements whose material density is different from that of the reference elements. Mass adjustment is applied to the test elements to make the total mass equal those of the reference elements. The response of the test elements should be identical to that of the reference elements. Several element types are tested in each input file, with two elements in the model for each element type. Each element pair is subjected to equivalent displacements (and rotations in the case of beams and shells) such that their response is dynamic. Tests of membranes and shells are performed with and without the specification of nodal thickness. The reaction forces for the constrained nodes of each pair of elements are output for comparison purposes.

Using mass adjustment to define the total mass of an element set is tested, with redistribution of the element masses to satisfy the minimum stable element time increment requirement. A circular plate subject to blast loading is considered for the test. Considering symmetry, a quarter of the plate is meshed with square elements in an inner region and non-square elements in the outer region. The elements in the inner region are smaller in size than those in the outer region and have a lower material density. In a reference analysis, fixed mass scaling is specified and the mass addition in the inner region due to mass scaling is noted. There is no mass scaling in the outer region. In the test, first the mass of the outer region is adjusted to include the additional mass of the inner region noted in the reference analysis. Next, the mass of the whole model is adjusted to the total mass (including mass scaling) of the whole model of the reference, with the same minimum element stable time increment used for mass scaling. Thus, in the test analysis, the mass added to the outer region from the first mass adjust data entry will be redistributed in its entirety to the inner region as a result of the second. The resulting masses of the inner and outer regions in the test should be identical to those in the reference. The dynamic response of the test should also be the same as the reference.