Occurrence of reflected wave in Split Hopkinson Pressure Bar (SHPB) method had caused the limitation of deformation time, which is considered to be insufficient for the high-strain foam material. A new device has been proposed for foam material as an alternative to SHPB method. This device has a small detection part designed for the reflected wave to be very small and negligible by creating a big surface area ratio at the detected section and stress transmitted bar. Besides, the ability to detect small strain had been improved due to the small thickness of the device's neck part. We found that an unexpected vibration had appeared in the detection part due to the small thickness of the neck which will influence the data obtained during the impact compression. As a countermeasure, we study the optimum size of detection part by numerical analysis of two different sizes. The comparison of the numerical analysis showed that the shorter neck's length is better for vibration suppression. We did quasi-static and impact load experiments and compared the two.
