$q$	Heat flux density
$\mathsf{\eta }$	Welding thermal efficiency
$U$	Welding voltage
$I$	Welding current
$V$	Heat source effective volume
$Q_m$	Welding heat input
$\rho$	Filler wire density
$r_w$	Filler wire radius
$\omega$	Wire feed speed
$H_d$	Filler wire fusion enthalpy
$\rho (T)$	Temperature-dependent density
$c_p(T)$	Temperature-dependent specific heat
$k(T)$	Temperature-dependent thermal conductivity
$f_r$	Energy distribution fraction in the front half of the ellipsoidal heat source
$a_2$	Length of the back half of the ellipsoidal heat source
$c$	Depth of the ellipsoidal heat source
${\sigma }_{1,2,3}$	The normal stresses acting along three directions that are orthogonal to each other, respectively
${\left\{d\epsilon \right\}}_p$	Plastic strain increment
${\displaystyle \frac{\partial \overline{\sigma }}{\partial \left\{\sigma \right\}}}$	Partial derivative of the scalar function $\overline{\sigma }$ with respect to the vector function $\left\{\sigma \right\}$
$t$	Welding time
$Q_v$	Heat source energy density
$h_c$	Heat transfer coefficient
$\epsilon$	Emissivity
${\sigma }_B$	Stefan–Boltzmann constant
$T_0$	Initial environmental temperature
${\mathsf{\epsilon }}_{\mathrm{total}}$	Total strain
${\mathsf{\epsilon }}_{\mathrm{elastic}}$	Elastic strain
${\mathsf{\epsilon }}_{\mathrm{plastic}}$	Plastic strain
${\mathsf{\epsilon }}_{\mathrm{thermal}}$	Thermal strain
${\mathsf{\epsilon }}_{\mathrm{creep}}$	Creep strain
${\mathsf{\epsilon }}_{\mathrm{phase}}$	Phase transformation strain
$f_f$	Energy distribution fraction in the rear half of the ellipsoidal heat source
$a_1$	Length of the front half of the ellipsoidal heat source
$b$	Width of the ellipsoidal heat source
$\overline{\sigma }$	Equivalent stress
${\sigma }_s$	Uniaxial tensile yield limit
$d\lambda$	Plastic multiplier