Biomedical Engineering Reference
In-Depth Information
120
110
Longitudinal
100
90
80
70
60
Transverse
50
40
30
20
10
0
0
5000
10000
15000
20000
Strain [ μ ]
FIGURE 4.14 Tensile stress-strain curves for longitudinal and transverse sections of bone. Adapted from [2].
TABLE 4.2
Tensile Yield and Ultimate Stresses, and Elastic Moduli E for Some Common Orthopedic
Materials
Material
s yield [MPa]
s ultimate [MPa]
E [GPa]
Stainless steel
700
850
180
Cobalt alloy
490
700
200
Titanium alloy
1,100
1,250
110
Bone
85
120
18
PMMA (fixative)
35
5
UHMWPE (bearing)
14
27
1
Patellar ligament
58
Data from [2].
bone. Taking the longitudinal curve first, from 0 to 7,000m, bone behaves as a purely elastic
solid, with E
12 GPa. At a tensile stress of approximately 90 MPa, the stress-strain curve
becomes nonlinear, yielding into the plastic region of deformation. This sample ultimately
fails around 120 MPa. Table 4.2 shows elastic moduli, yield stresses, and ultimate stresses
for some common orthopedic materials, both natural and implant.
Figure 4.14 also shows that the elastic properties of bone differ depending on whether
the sample is cut in the longitudinal or transverse direction—that is, bone is anisotropic.
Bone is much weaker and less stiff in the transverse compared to the longitudinal direction,
as is illustrated by the large differences in the yield and ultimate stresses and the slopes of
the stress-strain curves for the two samples.
Search WWH ::




Custom Search