material CustomGurson (1) (2) (3) (4) [5] [6] [7] [8] [9] [10]
# (1) int, unique material tag
# (2) int, expression tag
# (3) double, elastic modulus
# (4) double, poissons ratio
# [5] double, q1, default: 1.0
# [6] double, q2, default: 1.0
# [7] double, fn, default: 0.0
# [8] double, sn, default: 1.0
# [9] double, en, default: 0.0
# [10] double, density, default: 0.0
