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Mechanical Baseline

Pressure components

axisymmetric_pressure_breakdown() keeps the following components explicit:

  • steady deformation pressure;
  • billet-container friction increment;
  • breakthrough increment;
  • peak pressure;
  • force obtained from peak pressure and container-bore area.

The billet contact length and friction factor are caller-supplied model inputs. PyExtrusion does not infer either value from a profile name or die type.

When obtaining the initial billet length from production calculations, pass the corrected full-precision billet_length_mm to upset_billet_length_mm(). The existing geometric relation L_upset = L_billet * (D_B / D_C)**2 is unchanged. Do not add another butt or apply another area-ratio conversion in the pressure chain. See physical butt and coefficient semantics, including the measured-coefficient limitation.

Force naming

The force returned by pressure.required_force_mn must be interpreted as:

\[ F_{baseline}=p_{peak}A_C \]

F_baseline is an equivalent-axisymmetric mechanical screening baseline. The Python attribute retains the public name required_force_mn, but that name does not make the value a final prediction for a real shaped, bridge or porthole die.

It does not include a shaped-section correction, bridge/porthole pressure correction, die-specific calibration, transient stroke reconstruction or tooling-response model.

Press comparison

When a configured scalar press limit is compared with the baseline, the arithmetic difference may be written as:

\[ F_{reserve}=F_{press}-F_{baseline} \]

check_force_capacity() and check_press_force_capacity() expose this difference as margin_mn, together with utilization and within_limit. Public interpretation should call the difference reserve, not safety margin.

F_reserve is only a screening indicator. It is not:

  • available hydraulic capacity or a certified hydraulic reserve;
  • guaranteed remaining press capacity;
  • a safety margin or safety factor;
  • force available for a porthole die;
  • a prediction of the real die load.

A positive reserve means only that the equivalent-axisymmetric baseline is below the configured scalar used in that comparison.