Ms. Jensen, HIGH CONVERGENCE ORDER FINITE-ELEMENTS WITH LUMPED MASS MATRIX, International journal for numerical methods in engineering, 39(11), 1996, pp. 1879-1888
A method for deriving hexahedral finite elements with lumped mass matr
ices for 3-D-problems is presented. These elements meet the theoretica
l conditions for high order convergence, and two numerical examples ba
sed on the 3-D scalar wave equation show that this is also the case in
practice and that their accuracy is comparable to elements with consi
stent mass matrices.