constraint_eqn_072 Subroutine

   subroutine constraint_eqn_072(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
      !! Central Solenoid Tresca yield criterion
      !! author: P B Lloyd, CCFE, Culham Science Centre
      !! args : output structure : residual error; constraint value;
      !! residual error in physical units; output string; units string
      !! Central Solenoid Tresca yield criterion
      !! #=# pfcoil
      !! #=#=# foh_stress, alstroh
      !! In the case if the bucked and wedged option ( i_tf_bucking >= 2 ) the constrained
      !! stress is the largest the largest stress of the
      !!  - CS stress at maximum current (conservative as the TF inward pressure is not taken
      !!    into account)
      !!  - CS stress at flux swing (no current in CS) from the TF inward pressure
      !! This allow to cover the 2 worst stress scenario in the bucked and wedged design
      !! Otherwise (free standing TF), the stress limits are only set by the CS stress at max current
      !! Reverse the sign so it works as an inequality constraint (tmp_cc > 0)
      !! This will have no effect if it is used as an equality constraint because it will be squared.
      !! and hence also optional here.
      !! Logic change during pre-factoring: err, symbol, units will be assigned only if present.
      !! foh_stress : input real : f-value for Tresca yield criterion in Central Solenoid
      !! alstroh : input real :  allowable hoop stress in Central Solenoid structural material (Pa)
      !! s_tresca_oh : input real : Maximum shear stress coils/central solenoid (Pa)
      !! sig_tf_cs_bucked : input real : Maximum shear stress in CS case at flux swing (no current in CS)
      !!                       can be significant for the bucked and weged design
      !! i_tf_bucking : input integer : switch for TF structure design
      use constraint_variables, only: foh_stress
      use pfcoil_variables, only: alstroh, s_tresca_oh
      use tfcoil_variables, only: sig_tf_cs_bucked, i_tf_bucking
      use build_variables, only: tf_in_cs
      implicit none
            real(dp), intent(out) :: tmp_cc
      real(dp), intent(out) :: tmp_con
      real(dp), intent(out) :: tmp_err
      character(len=1), intent(out) :: tmp_symbol
      character(len=10), intent(out) :: tmp_units

      ! bucked and wedged desing (see subroutine comment)
      if ( i_tf_bucking >= 2 .and. tf_in_cs == 0 ) then
         tmp_cc = 1.0d0 - foh_stress * alstroh / max(s_tresca_oh, sig_tf_cs_bucked)
         tmp_err = alstroh - max(s_tresca_oh, sig_tf_cs_bucked)
      ! Free standing CS
      else
         tmp_cc = 1.0d0 - foh_stress * alstroh / s_tresca_oh
         tmp_err = alstroh - s_tresca_oh
      end if

      tmp_con = alstroh
      tmp_symbol = '<'
      tmp_units = 'Pa'

   end subroutine constraint_eqn_072