Với dữ liệu từ một thí nghiệm căng thẳng, thư giãn, vật liệu hệ số B, C, τ1 và τ2 có thể được xác định bởi một đường cong phù hợp, phi tuyến, ít nhất là vuông thủ tục (88). Liên tục có thể được tính bằng cách sử dụng một trong hai EQS. 5 hoặc 6. | 194 Hartright et al. With data from a stress-relaxation experiment the material coefficients B C T1 and t2 can be determined by a nonlinear least-square curve-fitting procedure 88 . Constant A can be then computed by using either Eqs. 5 or 6. For a known strain history these five constants together with G t and ơe e can be then used to determine the stress at any time t ơ t by using Eq. 3. COMBINED ROBOTIC UNIVERSAL FORCE SENSOR ASSESSMENT OF TENDONS AND LIGAMENTS A recent advance in biomechanical testing techniques and understanding of the properties of tendons ligaments and their reconstruction comes once again from the work of Professor Savio Woo and colleagues 44 50 89 . The use of robotic technology and a universal force sensor that combines a six-degree freedom robotic manipulator and a six-degree freedom force-moment sensor and control system represents a new era in biomechanical testing of tendons and ligaments 44-46 48-51 53 58 89-102 . Along with providing information about the passive knee flexion path for controlling the knee flexion positions and straining specific knee structures it can be used to measure the in situ forces in tendons and ligaments. These forces are measured by recording differences in forces and moments when repeating a prerecorded movement before and after the removal of the ligament or tendon to be tested. The testing of ligaments and tendons is relatively easy in principle. Yet with the unique biological properties of the tissues the inaccuracies of clinical assessment the difficulties with experimental apparatus and sample maintenance in vitro testing of these tissues is far from straightforward. Indeed there is uncovered ground in this area with exciting work still to be done. REFERENCES 1. Kastelic J Galeski A Baer E. The multicomposite structure of tendon. Connect Tissue Res 1978 6 11-23. 2. Silver FH Freeman JW Seehra GP. Collagen self-assembly and the development of tendon mechanical properties. J Biomech 2003 36 1529-1553.
