Finite element modeling and validation of a four-bar linkage prosthetic knee under static and cyclic strength tests

Figures & data

Figure 1.  Prosthetic knee with defined reference planes and loading line. (a) Condition I. (b) Condition II.

Table 1. P4 loading level for static and cyclic strength test

Loading condition	Static test force (N)	Cyclic test force (N)
I	2,065	1,230
II	1,811	1,085

Figure 2.  Model of a prosthetic knee. (a) CAD model. (b) Finite element model.

Table 2. Mechanical properties of materials

	Stainless steel	Plastic	Aluminum
Modulus of elasticity (GPa)	200	110	70
Poisson ratio	0.30	0.42	0.33
Density (kg/m^3)	7,850	950	2,800

Figure 3.  Prosthetic knee instrumented with strain gauges.

Figure 4.  Experimental setup.

Figure 5.  Stress distributions on a prosthetic knee under static strength test. (a) Loading condition I. (b) Loading condition II.

Figure 6.  Stress distributions on a prosthetic knee under one loading cycle of cyclic strength test. (a) Loading condition I. (b) Loading condition II.

Figure 7.  Fatigue strength prediction of a prosthetic knee. (a) Loading condition I. (b) Loading condition II.

Figure 8.  Comparisons of strains obtained from experiments and finite element model under static strength test. (a) Loading condition I. (b) Loading condition II.

Figure 9.  Comparisons of strains obtained from experiments and finite element model under cyclic strength test. (a) Loading condition I. (b) Loading condition II.