48  ! Materials implemented:
  49  !
  50  !    1 --> plane strain (or 3d) compressible neo-Hookean
  51  !    2 --> plane stress compressible neo-Hookean (*)
  52  !    3 --> plane strain (or 3d) hyperelastic in principal directions
  53  !    4 --> plane stress hyperelastic in principal directions
  54  !    5 --> plane strain (or 3d) nearly incompressible neo-Hookean
  55  !    6 --> plane stress incompressible neo-Hookean
  56  !    7 --> plane strain (or 3d) nearly incompressible in principal
  57  !          directions
  58  !    8 --> plane stress incompressible in principal directions

1588  !
1589  !     For incompressible types of elements finds the volumetric
1590  !     component of the tangent matrix
1591  !
1592          IF (  (mat == 5) .or. (mat == 7)  ) then
1593            xkapp = props (4, im)
1594            CALL kvolume (ndime, nnode, ngaus, xkapp, vinc, elecd, &
1595                          elacd, lnods (1, ie), ldgof, kprof, stifd, &
1596                          stifp)
1597          END IF

1955  !
1956  !     For incompressible types of elements finds the volumetric
1957  !     component of the tangent matrix, theta (the volume ratio)
1958  !     and the element pressure. First for nearly incompressible
1959  !     neo-Hookean materials.
1960  !
1961          IF ( mat == 5 ) then
1962            CALL getheta (ngaus, vol0 (ie), vinc, theta)
1963            xkapp = props (4, im)
1964            press = xkapp * (theta - 1.d0)
1965            xkapp = xkapp * theta
1966            CALL kvolume (ndime, nnode, ngaus, xkapp, vinc, elecd, &
1967                          elacd, lnods (1, ie), ldgof, kprof,      &
1968                          stifd, stifp)

2022  !
2023  !     Material 5 nearly incompressible neo-Hookean
2024  !
2025            ELSEIF ( mat == 5 ) then
2026              xmu = props (2, im)
2027              CALL stress5 (ndime, xmu, detf, btens, sigma) ! Eq (5.51)
2028              CALL addpres (ndime, press, sigma)            ! Eq (5.51)
2029              CALL cdevia (ndime, xmu, detf, btens, ctens) ! Eq (5.55a)
2030              CALL cvolum (ndime, press, ctens)            ! Eq (5.55b)