Loading ramp effects in uniaxial compression creep device

Tissue viscoelastic properties measured by uniaxial compression creep ultrasound method have shown correlation with tissue state. The majority of creep studies assume step-loading conditions, which are analytically convenient but experimentally impossible to implement. The goals of the study were to compare global creep response using a conventional mechanical testing machine to a prototype compression device as well as studying the effects of loading rate in the creep response. A 10% gelatin phantom was tested with the prototype compression device and a commercial mechanical testing machine with a 3 N force held for 30 seconds and loading rates of 3 N/s and 20 N/s. Additionally a Dynamic Mechanical Analysis (DMA) was used to characterize the phantom viscoelastic properties. The measured loss tangent with prototype compression device and commercial mechanical testing machine were similar and converged to DMA results as the loading rate was increased.