def true_stress(tech_stress, tech_strain):
    """
     Calculate the true stress data from technical data

    Parameters
    ----------
    tech_stress : array-like float
        stress data from tensile experiments
    tech_strain : list of float
        strain data from tensile experiments

    Returns
    -------
    true_stress : array-like float

    """
    return tech_stress * (1. + tech_strain)