Optical Stress Imaging for Orthopedic Biomechanics – Comparison of Thermoelastic Stress Analysis and Developed Mechanoluminescent Method

Thermoelastic stress analysis, which utilizes the thermoelastic properties of materials, is a full-field, noncontact technique for surface stress mapping of materials and structures. Unlike the conventional technique such as strain gauge method, the unique advantage of the method is its ability to image whole-surface stress (Δ(

σ

1 + 

σ

2)) distribution in specimens. An experimental system using the thermoelastic stress analysis method and a synthetic femur was utilized to perform reliable and convenient mechanical biocompatibility evaluation of hip prosthesis design. In addition, the mechanoluminescent materials, the author (Xu) developed, are novel inorganic materials that can luminesce in response to applied mechanical energy. A prosthetic device in which these mechanoluminescent materials are applied to a synthetic bone is a “mechanoluminescent synthetic bone.” Since the region subjected to load emits high intensity light in the visible region, the device has allowed high-definition and high-speed visualization of the mechanical dynamic environment using conventional image sensors such as CCDs. Thermoelastic stress analysis and mechanoluminescent method have mutual, supplementary advantages. It is confirmed that they are very effective techniques in vitro biomechanics research and to contribute to a variety of biomechanical analyses and thus support the practical implementation of prosthetic devices.