The process of deformation of twinned ferromagnetic martensite under a combined action of slowly increasing magnetic field (or mecha
nical stress) and oscillatory mecha
nical stress has been studied theoretically in the framework of a statistical model of magnetically/mecha
nically induced deformation. The dependencies of magnetically/mecha
nically induced deformation on time, oscillatory stress amplitude and magnetic field (or mecha
nical stress) has been modeled. The additional deformation of a Ni
x2013;Mn
x2013;Ga specimen activated by a superimposed oscillatory stress has been computed for the case of resonant longitudinal ultraso
nic waves with several realistic values of strain amplitudes using the typical values of Young
x2019;s modulus, specimen length, and threshold field/stress (i.e. the field/stress, which triggers the process of magnetically/mecha
nically induced deformation). Quantitative estimations show, in particular, that the ultraso
nic wave with a strain amplitude of 4 × 10
−5 causes a
30%decrease of the threshold field/stress value; the additional deformation induced by the ultrasound reaches its maximal value ≈2.8%when the field/stress reaches the i
nitial (i.e. observed in the absence of ultrasound) threshold value.