material elastic [
	 name = steel
	 rho = 10   # density
	 E   = 10   # young's modulus
	 nu  = 0.1 # poisson's ratio
]

material cohesive_bilinear [
	 name = cohesive
	 sigma_c = 1
	 beta = 1.5
	 G_c = 1
	 kappa = 1.2
	 delta_0 = 0.1
#	 penalty = 1e10
]