Effects of varying material properties on the load deformation characteristics of heel cushions.
Various insole materials were used in attenuation of heel-strike impact. This study presented a compression test to investigate the deformation characteristics of common heel cushions. There were two materials (thermoplastic elastomer "TPE" and silicone) with three hardness and six thickness being analyzed. They underwent consecutive loading-unloading cycles with a load control mode. The displacement of material thickness was recorded during cyclic compression being applied and released from 0 to 1050 N. The energy input, return and dissipation were evaluated based on the load deformation curves when new and after repeated compression. The TPE recovered more deformed energy and thickness than the silicone after the first loading cycle. The silicone would preserve more strain energy with increasing its hardness for the elastic recovery in the unloading process. The deformed energy was decreased as the original thickness did not completely recover under cyclic tests. The reduction in hysteresis area was gradually converged within 20 cycles. The silicone attenuated more impact energy in the initial cycles, but its energy dissipation was reduced after repeated loading. To increase hardness or thickness should be considered to improve resilience or accommodate persistent compression without flattening. The careful selection of cushion materials is imperative to meet individual functional demands.
Sun
Pi-Chang
PC
Orthopedic Biomechanics Laboratory, Institute of Rehabilitation Science and Technology, National Yang Ming University, No. 155, Sec. 2, Li-Nung St, Taipei 11221, Taiwan.
Wei
Hung-Wen
HW
Chen
Chien-Hua
CH
Wu
Chun-Hao
CH
Kao
Hung-Chan
HC
Cheng
Cheng-Kung
CK
D001696:Biomechanical Phenomena; D019245:Compressive Strength; D020724:Elastomers; D006365:Heel / Q000502:physiology*; D006801:Humans; D007869:Leg Injuries / Q000517:prevention & control; D010969:Plastics; D012420:Running; D012775:Shoes; D012828:Silicones; D013314:Stress, Mechanical; D016138:Walking
D020724:Elastomers; D010969:Plastics; D012828:Silicones