Well‐known models for rubberlike elasticity with strain‐stiffening effects provide good predictions for unlimitedly, rapidly growing stress in a process of approaching a very large strain limit. According to such models, however, unbounded elastic strain energy would be generated as the strain limit is approached. To resolve this issue, a new, explicit approach is proposed to obtain multi‐axial elastic potentials based on uniaxial data and shear data. Then, a strain‐stiffening elastic potential is given to always yield bounded strain energy. Good agreement is achieved with a number of test data.
Multi-axial elastic potentials for isotropic, incompressible elastomeric solids are constructed based solely on uniaxial potentials by means of direct, explicit procedures. Results are presented for the purpose of meeting the following three requirements: (i) the strain-stiffening effect is represented with rapidly growing stress at certain strain limits, (ii) the strain energy never grows to infinity but is always bounded, and (iii) the stress is also bounded and asymptotically tends to vanish with increasing strain up to failure. As such, a realistic simulation of rubberlike elasticity with the strain-stiffening effect up to failure is proposed for the first time. Numerical examples show good agreement with a number of test data. Motivation and introductionIn the past decades, various expressions for elastic potentials for isotropic, incompressible rubberlike solids have been derived from either the statistical or the phenomenological approach or other approaches. In the statistical respect, reviews of earlier results may be found in the monograph by Treloar [35], and some recent results have been presented by Arruda and Boyce [4], Boyce [7], Boyce and Arruda [8], Diani and Gilormini [10], Drozdov and Gottlieb [11], Edwards and Vilgis [12], Fried [14], Heinrich and Kaliske [17], Heinrich et al. [18], Kaliske and Heinrich [26], Miehe et al. [30], Ogden, et al. [33], and the relevant references therein. In the phenomenological respect, representative results may be found in the monograph by Ogden [32] and Saccomandi and Ogden [34] as well as the review articles by Vahapoglu and Karadenitz [36] and the references therein. Further references will be indicated later on.Rubberlike materials exhibit complex nonlinear features coupled with large deformations, as exemplified by the well-known S-shaped stress-stretch curve in the uniaxial case (cf., e.g., Treloar [35]; Arruda and Boyce [4]). In fact, from small to moderate deformation emerges a mild turn and then follows a sharp turn with rapidly growing stress at a certain large strain limit, and, eventually, failure is expected at a point beyond the strain limit. Of them, the rapid growing of stress at a strain limit is known as the strain-stiffening effect and represents an essential feature of the nonlinear complexity of rubberlike elasticity, with the micro-structural origin of limiting extensibility of long chain-like macromolecules.In the study of rubberlike elasticity, much attention has been directed to modeling the nonlinear features indicated above. Early studies provided reasonable results from small to moderate deformation. Most recent results have shown considerable progresses in further representing the strain-stiffening effect up to large strain limits. Of them, the pioneering results are the two-parameter elastic potentials with the strain-stiffening effect, presented by Arruda and Boyce [4] and Gent [15] from statistical and phenomenological approaches, separately, and shown to be in good accord with test data at very large stretch close to 800 %. Furth...
To investigate the efficacy of a fast rehabilitation program for the recovery of knee joint function after arthroscopic autologous hamstring tendon transplantation for reconstruction of the anterior cruciate ligament (ACL), from January 1, 2017, to March 31, 2019, a total of 65 patients with ACL injury were randomly divided into a study group and a control group. Both groups were treated with autologous hamstring tendon to reconstruct the anterior cruciate ligament, arthroscopic transplantation, and decompression techniques. The research group was treated with a fast rehabilitation program. The control group was treated with traditional rehabilitation program. Knee flexion angles were measured at 2, 4, and 8 weeks postoperatively. KT-1000 knee anterior stability was measured at 3, 6, and 12 months after operation. Knee function was assessed by subjective knee function assessment scale (IKDC) and Lysholm knee score. The knee curvature, KT-1000 measurement, IKDC score, and Lysholm score were compared between the two groups before and after treatment. KT-1000 measured value, IKDC score, and Lysholm score in 2 groups were significantly improved 3, 6, and 12 months compared with those before treatment, and the difference was statistically significant ( P < 0.001 ). Comparison between the two groups: 2 weeks, 4 weeks, and 8 weeks after treatment, the knee curvature in the study group was better than that in the control group, and the difference was statistically significant ( P < 0.001 ); there was no significant difference in the measured values of KT-1000 between the two groups 3, 6, and 12 months after treatment ( P > 0.05 ); IKDC score and Lysholm score in the study group 3 and 6 months after treatment were significantly better than those in the control group, with statistical significance ( P < 0.001 ); there was no significant difference in IKDC score and Lysholm score between the two groups 12 months after treatment (P >0.05). Autograft hamstring tendon transplantation and tense-reducing technique for anatomical reconstruction of anterior cruciate ligament under arthroscopy combined with rapid rehabilitation program can quickly, safely, and effectively restore the knee function of patients, greatly shortening the rehabilitation period of patients.
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