Stress concentrations associated with circular holes in cylinders and bone in torsion
- 190 Downloads
Experimental studies were undertaken to determine the torsional stress concentration factors (Kt) associated with circular holes in bone. Reflective photoelasticity was used to determine the stress field around a circular hole through one wall of the bone. A single adult sheep femur was used as the torsional model, in which six circular holes were concentrically machined through the posterior cortex. These holes ranged from 10.4 percent to 66.4 percent of the mediolateral bone diameter. From the photoelastic data, a stress concentration curve was developed for bone. The maximum stress location on the boundary of the hole was found to shift from the previously expected 45-deg location.
Studies on tubes made of steel and plastic, both coated with photoelastic coating, were also performed. Three different pieces of steel tubing with similar inner to outer diameters were coated with different thicknesses of photoelastic coating. The variation in coating thickness did not appear to influence the stress-concentration factors in steel. TheKt in steel for 10 percent and 20 percent defects agreed with theKt associated with similar defects in bone. A single piece of plastic tubing was used in which six holes from 10 percent to 60 percent of the tube's outer diameter were concentrically machined through one wall. The location of the maximum stress around the boundary of the hole was found to shift, and this agreed with the maximum stress shift found in the bone.
KeywordsStress Concentration Outer Diameter Maximum Stress Circular Hole Stress Concentration Factor
Unable to display preview. Download preview PDF.
- 1.Burstein, A.H., Currey, J., Frankel, V.H., Heiple, K.G., Lunseth, P. andVessely, J.C., “Bone Strength-The Effect of Screw Holes,”The J. Bone and Joint Surgery,54-A (6),1143–1156 (1972).Google Scholar
- 2.Books, D.B., Burstein, A.H. andFrankel, V.H., “The Biomechanics of Torsional Fractures,”The J. Bone and Joint Surgery,52-A (3),507–514 (1970).Google Scholar
- 3.Peterson, R.E., Stress Concentration Factors, John Wiley & Sons, New York (1974).Google Scholar
- 4.Heywood, R.B. Photoelasticity for Designers, Pergamon Press, Oxford (1969).Google Scholar
- 5.Savin, G.N., Stress Concentrations Around Holes, 234–300, Pergamon Press, New York (1961).Google Scholar
- 6.Jessop, H.T., Snell, C. and Allison, I.M., “Stress Concentration Factors in Cylindrical Tubes with Transverse Circular Holes,” Aeronautical Quarterly, 326–344 (1959).Google Scholar
- 7.Kuo, R.F., “Stress Concentration and Torsional Strength of Tubular Structure with Circular Defect,” Proc. 36th Annual Mtg. Orthopaedic Res. Soc., (1989).Google Scholar
- 8.Bartlett, J.P., “Finite Element Modeling of Circular Cortical Defects in Bone,”MS Thesis, North Dakota State University, Fargo, ND (1989).Google Scholar
- 9.Ashman, R.B., Cowin, S.C., Van Buskirk, W.C. andRice, J.C., “A Continuous Wave Technique for the Measurement of the Elastic Properties of Cortical Bone,”J. Biomechanics,17 (5),349–361 (1984).Google Scholar
- 10.Harms, M.R., “Photoelastic Determination of Stress Concentrations Associated with Circular Defects in Bone,”MS Thesis, North Dakota State University, Fargo, ND (1992).Google Scholar