.. _auto_johnson_cook_parameter_fit:

*JOHNSON-COOK PARAMETER FIT*
============================

Fit the Johnson-Cook flow-stress constants A, B, n, C, m by sequential closed-form least squares. A, B, n come from the quasi-static effective-plastic hardening curve; C from optional higher-strain-rate curves; m from optional elevated-temperature curves.

When to use
-----------

Tagged: ``johnson-cook``, ``material-calibration``, ``curve-fitting``, ``plasticity``, ``strain-rate``, ``thermal-softening``, ``hardening``, ``flow-stress``.

Inputs
------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20 20 20

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Quasi-Static Hardening Curve
     - quasi_static_curve
     - vector
     - —
     - ✓
     - Effective plastic strain (X) vs effective stress (Y) at the reference strain rate and room temperature. The only required input; A, B, n are fit from it.
   * - Reference Strain Rate
     - reference_strain_rate
     - scalar
     - 1.0
     - 
     - Quasi-static strain rate used to normalize rate_star (same units as strain_rates).
   * - Evaluation Plastic Strain
     - eval_plastic_strain
     - scalar
     - 0.1
     - 
     - Plastic strain at which the rate and temperature ratios are evaluated for the C and m fits.
   * - Plastic Strain Threshold
     - plastic_strain_threshold
     - scalar
     - 1e-06
     - 
     - Points at or below this plastic strain are excluded from the A,B,n log-fit.
   * - Room Temperature
     - room_temperature
     - scalar
     - 293.0
     - 
     - Reference temperature for Tstar.
   * - Melt Temperature
     - melt_temperature
     - scalar
     - 0.0
     - 
     - Melt temperature for Tstar. Leave <= room_temperature to skip the m fit.
   * - Strain-Rate Curves
     - rate_curves
     - vector
     - —
     - 
     - Optional CurveGroup of effective-plastic curves at higher strain rates, in the same order as strain_rates. Needed (with strain_rates) to fit C.
   * - Strain Rates
     - strain_rates
     - text
     - —
     - 
     - Comma-separated strain rates matching rate_curves in order.
   * - Temperature Curves
     - temperature_curves
     - vector
     - —
     - 
     - Optional CurveGroup of effective-plastic curves at elevated temperatures, in the same order as temperatures. Needed (with temperatures + melt_temperature) to fit m.
   * - Temperatures
     - temperatures
     - text
     - —
     - 
     - Comma-separated temperatures matching temperature_curves in order.

Outputs
-------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20

   * - Label
     - ID
     - Type
     - Description
   * - A (Yield Stress)
     - a
     - scalar
     - 
   * - B (Hardening Coefficient)
     - b
     - scalar
     - 
   * - n (Hardening Exponent)
     - n
     - scalar
     - 
   * - C (Strain-Rate Coefficient)
     - c
     - scalar
     - 
   * - m (Thermal Softening Exponent)
     - m
     - scalar
     - 
   * - R2 (A,B,n fit)
     - r2_abn
     - scalar
     - 
   * - R2 (C fit)
     - r2_c
     - scalar
     - 
   * - R2 (m fit)
     - r2_m
     - scalar
     - 
   * - All JC Parameters
     - parameters
     - keyvalue
     - 
   * - Fit Summary (per bracket)
     - fit_summary
     - dataset
     - 

Disciplines
-----------

- engineering.material.calibration
- engineering.material.characterization
- data.curve.transform

Runnable example
----------------

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=johnson_cook_parameter_fit <https://www.d3view.com/api/workflow/example?id=johnson_cook_parameter_fit>`_

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