def METHOD_NAME(self, variables):
    domain, Domain = self.domain_Domain
    phase_name = self.phase_name
    l_cr = variables[f"{Domain} particle crack length [m]"]
    a = variables[
        f"{Domain} electrode {phase_name}surface area to volume ratio [m-1]"
    ]
    rho_cr = self.domain_param.rho_cr
    w_cr = self.domain_param.w_cr
    roughness = 1 + 2 * l_cr * rho_cr * w_cr  # ratio of cracks to normal surface
    a_cr = (roughness - 1) * a  # crack surface area to volume ratio
    roughness_xavg = pybamm.x_average(roughness)
    variables = {
        f"{Domain} crack surface to volume ratio [m-1]": a_cr,
        f"{Domain} electrode roughness ratio": roughness,
        f"X-averaged {domain} electrode roughness ratio": roughness_xavg,
    }
    return variables