J t
ð Þ ¼ A t
ð Þ= 1 À ν
ð
ÞP 0 tan θ
ð7:2Þ
In Eq. (7.2) A(t) is the contact area, P 0 constant applied load, θ is the effective cone angle which is 70.3
for a Berkovich
indenter and the Poisson’s ratio ν is assumed to be 0.3.
This approach takes into account how the contact area under the Berkovich tip alters while displacement into the surface
changes.
The strain versus time behaviour during creep is characterized by a high strain rate in the primary stage of creep and then in
the secondary, steady state stage of creep, the strain rate is given in Eq. (7.3) can be written as
_
ε ¼ Kσ
n
ð7:3Þ
where K is a constant and n is the stress exponent. The strain rate is calculated in the software and in turn n is obtained from the
log-log plot of strain rate versus stress in the secondary stage of creep.
The materials under consideration are heterogeneous in nature and the fact that the nanoindentation test is carried out over a
small area/volume, a large scatter in the data is observed and to overcome this sampling number was taken as large as possible.
Figure 7.6 shows the displacement-time graphs for indents 3 and 12 on the sinter + forged specimen. These curves are
typical for the other indents on both sinter and sinter + forged specimens in that no significant creep was observed, and hence
the creep exponents were not calculated.
The modulus and hardness of the composites as measured during the unloading phase of the creep tests and their standard
deviations are presented in Table 7.4.
Figure 7.7 depicts the maximum wear track deformation measured as the area between the initial profile and the final
(residual) profile of the wear track. These are the averages of the 10 wear tests for each type of manufacturing. The sinter +
forged samples resulted to be more resistant to wear. Also shown in this figure is 5 of the wear tracks for 500 μm long wear
path for the sinter + forged specimen.
7.3.4 Low Velocity or Dynamic Compression (Drop Weight) Test Results
Low velocity (drop weight) or dynamic compression tests results were presented in the Fig. 7.8 for two process; sintered and
sintered + forged specimens. Maximum force was evaluated there by the values from both support data points. Here, a series
of impact tests were performed at room temperature at the centre of cylindrical specimens using the instrumented drop weight
Fig. 7.6 Typical displacement into surface vs time curves during creep tests and a micrograph of the indents
Table 7.4 Modulus and
hardness from unload data
Composition name
Modulus (GPa)
Hardness (MPa)
FASIO (Sintering)
118.93 Æ 15.84
1.81 Æ 0.63
50
H. M. Enginsoy et al.
ð Þ ¼ A t
ð Þ= 1 À ν
ð
ÞP 0 tan θ
ð7:2Þ
In Eq. (7.2) A(t) is the contact area, P 0 constant applied load, θ is the effective cone angle which is 70.3
for a Berkovich
indenter and the Poisson’s ratio ν is assumed to be 0.3.
This approach takes into account how the contact area under the Berkovich tip alters while displacement into the surface
changes.
The strain versus time behaviour during creep is characterized by a high strain rate in the primary stage of creep and then in
the secondary, steady state stage of creep, the strain rate is given in Eq. (7.3) can be written as
_
ε ¼ Kσ
n
ð7:3Þ
where K is a constant and n is the stress exponent. The strain rate is calculated in the software and in turn n is obtained from the
log-log plot of strain rate versus stress in the secondary stage of creep.
The materials under consideration are heterogeneous in nature and the fact that the nanoindentation test is carried out over a
small area/volume, a large scatter in the data is observed and to overcome this sampling number was taken as large as possible.
Figure 7.6 shows the displacement-time graphs for indents 3 and 12 on the sinter + forged specimen. These curves are
typical for the other indents on both sinter and sinter + forged specimens in that no significant creep was observed, and hence
the creep exponents were not calculated.
The modulus and hardness of the composites as measured during the unloading phase of the creep tests and their standard
deviations are presented in Table 7.4.
Figure 7.7 depicts the maximum wear track deformation measured as the area between the initial profile and the final
(residual) profile of the wear track. These are the averages of the 10 wear tests for each type of manufacturing. The sinter +
forged samples resulted to be more resistant to wear. Also shown in this figure is 5 of the wear tracks for 500 μm long wear
path for the sinter + forged specimen.
7.3.4 Low Velocity or Dynamic Compression (Drop Weight) Test Results
Low velocity (drop weight) or dynamic compression tests results were presented in the Fig. 7.8 for two process; sintered and
sintered + forged specimens. Maximum force was evaluated there by the values from both support data points. Here, a series
of impact tests were performed at room temperature at the centre of cylindrical specimens using the instrumented drop weight
Fig. 7.6 Typical displacement into surface vs time curves during creep tests and a micrograph of the indents
Table 7.4 Modulus and
hardness from unload data
Composition name
Modulus (GPa)
Hardness (MPa)
FASIO (Sintering)
118.93 Æ 15.84
1.81 Æ 0.63
50
H. M. Enginsoy et al.