Biomedical Engineering Reference
In-Depth Information
Table 8.3 Mechanical properties of wrought titanium 6-aluminium 4-vanadium
alloy in annealed condition (ISO, 1996)
Form of alloy
Tensile
Proof stress of
Percentage
Mandrel
strength
nonproportional
elongation
diameter for
R
m
min
elongation
after
bend test
fracture
a
(MPa)
R
0:2
min
(MPa)
A min
10
b
Sheet and strip
860
780
8
Bar
c
860
780
10
Not applicable
Gauge length 5:65
p
a
S
0
or 50mm, where S
0
is the original cross-sectional area, in square
millimeters.
b
thickness of the sheet or strip.
c
Maximum diameter or thickness75mm.
ISO 5832 Implants for surgery ± Metallic materials, Part 3: Wrought titanium 6-
aluminium 4-vanadium alloy (ISO, 1996) provides details of the mechanical
properties and corresponding test methods for Ti-6Al-4V. The ISO standard for
Ti-6Al-4V is depicted in Tables 8.3 and 8.4 (ISO, 1996) in terms of mechanical
properties and test methods in annealed condition respectively.
Dion et al. (1993a) evaluated in vitro haemocompatibility tests for surface
portion of Ti-6Al-4V and compared with Scurasil, silicone elastomer. Scanning
electron microscopy (SEM) observations and R
a
roughness criterion indicated
that titanium alloy is a suitable biocompatible material for orthopaedic and
cardiovascular medical devices. In addition, Grade 4, CP Ti, is also used as an
implant biomaterial (Brunski, 2004).
Shape memory nickel±titanium (nitinol) has also been considered for intra-
vascular devices. For example, it is the most common material used for stents
Table 8.4 Test methods (ISO, 1996)
Parameter
Relevant part
Test methods
Chemical composition
3
Recognized analytical procedures
(ISOmethods where these exist)
Microstructure
4
ETTC 2
Mechanical properties
5
Tensile strength
ISO 6892
Proof stress of
ISO6892
nonproportional elongation
Percentage elongation
ISO 6892
Bending
ISO 7438
Bend the sheet or strip through an
angle of 105ë around a mandrel of
the diameter specified in Table 8.3
