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Spatial Distribution of Hip Capsule Structural and Material Properties
ARTICLE IN PRESS
Journal of Biomechanics 36 (2003) 1403
Letter to the editor Spatial Distribution of Hip Capsule Structural and Material Properties Mechanical properties, such as Young’s modulus, ultimate strength, yield strength, modulus of resilience, modulus of toughness and density, are traditionally key factors involved in the understanding, evaluation or analysis of subjects (Ding et al., 1997; Juvinall, 1983; Wang and Dixon, 1997a,b; Wang and Dixon, 1997a,b; Wang et al., 2000). However, the properties of human subject are various and difficult to built up due to the availability of donors. For many years, researchers have been pursuing the mechanical properties for human beings. Recently, Stewart et al. (Journal of Biomechanics 35 (2002) 1491–1498) add to our armamentarium of the properties of hip capsule. The authors presented the typical force–displacement relationships of experimental data in Figs. 2 and 6 of the original paper. However, as the authors might be aware, the displacement of a substance due to loading could not present its material property in that the dimensional factor, such as length, will affect its experimental measurement. The longer the material, the easier deformation under loading. Instead of force and displacement, the stress as well as strain is introduced to describe the mechanical properties of a substance (Popov, 1999; Ross, 1996; Wang et al., 1997; Wang et al., 2000). The authors used digital vernier caliper to measure the specimen and stated that the repeatability of the cross-sectional area with 3%. However, the more detail how to control the caliper for the soft tissues was not
stated. Furthermore, the slippage of cryo-clamps was note either to re-clamp or discard the data. However, the visual inspection seems not able to detect the minor slippage.
References Ding, M., Dalstra, M., Danielsen, C.C., Kabel, J., Hvid, I., Linde, F., 1997. Age variations in the properties of human tibial trabecular bone. Journal of Bone and Joint Surgery 79 (B), 995–1002. Juvinall, R.C., 1983. Fundamentals of Machine Component Design. Wiley, New York, pp. 157–172. Popov, E.P., 1999. Engineering Mechanics of Solids. Prentice-Hall, Englewood Cliffs, NJ, pp. 70–71. Ross, C.T.F., 1996. Mechanics of Solids. Prentice-Hall, London, pp. 67–69. Wang, S.J., Dixon, M.W., 1997a. A new static failure criterion for ductile materials. Journals of Strain Analysis 32, 345–350. Wang, S.J., Dixon, M.W., 1997b. A new criterion for positive mean stress fatigue design. ASME Journal of Mechanical Design 119, 135–137. Wang, S.J., Dixon, M.W., Huey, C.H., 2000. The Clemson limit stress diagram for ductile parts subjected to positive mean fatigue loading. Journal of Mechanical Design 122 (1), 143–146.
Shyh-Jen Wang Division of Experimental Surgery, Department of Surgery, Veterans General Hospital-Taipei, Institute of Bio-Engineering, National Yang-Ming University, No 201 Sec. II ShihPai Road, Taipei 11217, Taiwan, ROC E-mail address: [email protected]
0021-9290/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0021-9290(03)00184-2
Journal of Biomechanics 36 (2003) 1403
Letter to the editor Spatial Distribution of Hip Capsule Structural and Material Properties Mechanical properties, such as Young’s modulus, ultimate strength, yield strength, modulus of resilience, modulus of toughness and density, are traditionally key factors involved in the understanding, evaluation or analysis of subjects (Ding et al., 1997; Juvinall, 1983; Wang and Dixon, 1997a,b; Wang and Dixon, 1997a,b; Wang et al., 2000). However, the properties of human subject are various and difficult to built up due to the availability of donors. For many years, researchers have been pursuing the mechanical properties for human beings. Recently, Stewart et al. (Journal of Biomechanics 35 (2002) 1491–1498) add to our armamentarium of the properties of hip capsule. The authors presented the typical force–displacement relationships of experimental data in Figs. 2 and 6 of the original paper. However, as the authors might be aware, the displacement of a substance due to loading could not present its material property in that the dimensional factor, such as length, will affect its experimental measurement. The longer the material, the easier deformation under loading. Instead of force and displacement, the stress as well as strain is introduced to describe the mechanical properties of a substance (Popov, 1999; Ross, 1996; Wang et al., 1997; Wang et al., 2000). The authors used digital vernier caliper to measure the specimen and stated that the repeatability of the cross-sectional area with 3%. However, the more detail how to control the caliper for the soft tissues was not
stated. Furthermore, the slippage of cryo-clamps was note either to re-clamp or discard the data. However, the visual inspection seems not able to detect the minor slippage.
References Ding, M., Dalstra, M., Danielsen, C.C., Kabel, J., Hvid, I., Linde, F., 1997. Age variations in the properties of human tibial trabecular bone. Journal of Bone and Joint Surgery 79 (B), 995–1002. Juvinall, R.C., 1983. Fundamentals of Machine Component Design. Wiley, New York, pp. 157–172. Popov, E.P., 1999. Engineering Mechanics of Solids. Prentice-Hall, Englewood Cliffs, NJ, pp. 70–71. Ross, C.T.F., 1996. Mechanics of Solids. Prentice-Hall, London, pp. 67–69. Wang, S.J., Dixon, M.W., 1997a. A new static failure criterion for ductile materials. Journals of Strain Analysis 32, 345–350. Wang, S.J., Dixon, M.W., 1997b. A new criterion for positive mean stress fatigue design. ASME Journal of Mechanical Design 119, 135–137. Wang, S.J., Dixon, M.W., Huey, C.H., 2000. The Clemson limit stress diagram for ductile parts subjected to positive mean fatigue loading. Journal of Mechanical Design 122 (1), 143–146.
Shyh-Jen Wang Division of Experimental Surgery, Department of Surgery, Veterans General Hospital-Taipei, Institute of Bio-Engineering, National Yang-Ming University, No 201 Sec. II ShihPai Road, Taipei 11217, Taiwan, ROC E-mail address: [email protected]
0021-9290/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0021-9290(03)00184-2