In times of energy scarcity and global warming, simple but efficient smart processes are needed to reduce the need for natural resources and the production of climate-changing gases. Therefore, ultrasonic vibrations (UV) in deformation processes could be a possibility because UV can reduce the flow stresses, decrease friction, increase the forming limit, produce heat, and increase the process efficiency of metallic materials. Furthermore, it can modify the material’s strengthening behavior during the superimposed UV in tensile and compression loadings. This effect is called ultrasonic softening and it is known since the mid-1950s by Blaha and Langenecker but the influences and mechanisms are still not understood completely up to this day.

For this purpose, a UV compression test was developed to investigate ultrasonic softening. Analyses with UV during the plastic flow of the steels C15E and X6CrNiMoTi17-12-2 were carried out. Softening by UV reduces the flow stress proportional to the increase of the UV amplitude. In this presentation, we will discuss the influence of the specimen size scale effect on the UV compression tests with different amplitudes and specimen sizes with variable height diameter ratios. The stress reduction is linear to the ultrasonic energy for all height-diameter ratios. An approximation of the geometrical dimensionless stress drop is found to describe the ultrasonic softening for both steels. Temperature increases of more than 100 K are measured depending on the UV amplitude for both steels.