US2005066702A1PendingUtilityA1
Method for measuring elastic properties
Priority: Nov 20, 2001Filed: Aug 13, 2004Published: Mar 31, 2005
Est. expiryNov 20, 2021(expired)· nominal 20-yr term from priority
G01N 3/42G01N 2203/0286B82Y 35/00
44
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Claims
Abstract
This invention relates to a method for measuring elastic modulus of a sample object. This invention also relates to a method for correcting creep effects in the modulus measurement. The error due to creep in the apparent contact compliance is equal to the ratio of the indenter displacement rate at the end of the load hold to the unloading rate. Determination of this error term and deduction of it from the measured contact compliance can be easily done at a low cost by modifying the data analysis software in any commercial depth-sensing indentation system.
Claims
exact text as granted — not AI-modified1 . A method for measuring a material property, comprising:
obtaining a correction term; and determining the material property using the correction term; wherein the correction term reduces a measurement error occurred during the measurement of the material property.
2 . The method of claim 1 , wherein the correction term comprises one or more of the following: a contact stiffness, a contact area, and a contact depth.
3 . The method of claim 1 , wherein the correction term comprises a contact stiffness S.
4 . The method of claim 1 , wherein the correction term is based on one or more of the indenter displacement drift rate {dot over (h)} h , the apparent contact stiffness S u , and {dot over (P)}; wherein:
the indenter displacement drift rate {dot over (h)} h is measured prior to the unload process; the apparent contact stiffness S u is measured at the onset of the unloading process; and {dot over (P)} is the imposed unloading rate at the onset of the unload process.
5 . The method of claim 4 , wherein the correction term comprises a contact stiffness S determined by the following equation:
1
S
=
1
S
u
+
h
.
h
P
.
.
6 . The method of claim 5 , wherein the correction term further comprises a contact depth h c determined as follows:
h
c
=
h
max
-
ɛ
P
max
S
wherein h max is the maximum indenter displacement, P max is the maximum load imposed, and ε is a constant.
7 . The method of claim 5 , wherein the correction term is a contact area A c determined as follows:
A
c
=
f
(
h
c
)
,
h
c
=
h
max
-
ɛ
P
max
S
wherein h c is a contact depth, h max is the maximum indenter displacement, P max is the maximum load imposed, and ε is a constant.
8 . The method of claim 7 , wherein the material property obtained is a reduced modulus E r determined by the following equation:
E
r
=
π
2
S
A
c
9 . The method of claim 1 , wherein a crystal material is measured.
10 . The method of claim 9 , wherein the crystal material comprises one of the following: a single crystal of Ni 3 Al, a single crystal of copper, or a polycrystalline Al.
11 . A method for correcting a measurement error in measuring a material property during an unloading process in the depth-sensing indentation, comprising:
obtaining a correction term based on one or more of the indenter displacement drift rate {dot over (h)} h , the apparent contact stiffness S u , and {dot over (P)}; and correcting the measurement error using the correction term; wherein the indenter displacement drift rate {dot over (h)} h is measured prior to the unloading process; the apparent contact stiffness S u is measured at the onset of the unloading process; and {dot over (P)} is the imposed unloading rate at the onset of the unload process.
12 . The method of claim 11 , wherein the correction term comprises a contact stiffness S.
13 . The method of claim 12 , wherein the contact stiffness S is determined according to the following equation:
1
S
=
1
S
u
+
h
.
h
P
.
.
14 . The method of claim 11 , wherein the correction term comprises a contact depth h c based on the following:
h
c
=
h
max
-
ɛ
P
max
(
1
S
u
+
h
.
h
P
.
)
wherein h max is the maximum indenter displacement, P max is the maximum load imposed, ε is a constant.
15 . The method of claim 11 , wherein the correction term comprises a contact area A c determined as follows:
A
c
=
f
(
h
c
)
,
h
c
=
h
max
-
ɛ
P
max
(
1
S
u
+
h
.
h
P
.
)
wherein h c is a contact depth, h max is the maximum indenter displacement, P max is the maximum load imposed, and ε is a constant.
16 . The method of claim 11 , wherein the indenter displacement drift rate {dot over (h)} h is obtained by curve fitting of the data of indenter displacement-time h-t curve prior to the unloading process by the following equation:
h ( t )= h i +β( t−t i ) 1/3 +Kt
wherein h i , β, t i , and K are fitting constants.
17 . The method of claim 11 , wherein the indenter displacement drift rate {dot over (h)} h is obtained by differentiating the following equation:
h ( t )= h i +β( t−t i ) 1/3 +Kt
wherein h i , β, t i , and K are fitting constants.
18 . The method of claim 11 , wherein the indenter displacement drift rate {dot over (h)} h is obtained by the following equation:
{dot over (h)}
h
=dh/dt|
h
wherein h denotes the end of the load holding period.
19 . The method of claim 11 , wherein the apparent contact stiffness S u is obtained by curve fitting of the data of load-indenter displacement P-h curve during an initial part of the unloading process by the following equation:
h=h
o
±A
1
P
m
+A
2
P
n
wherein h o , A 1 , A 2 , m, and n are fitting constants.
20 . The method of claim 11 , further comprising obtaining a second correction term, wherein the second correction term is based in part on one or more of the following: the maximum indenter displacement, the indenter geometry, the contact depth, the maximum load imposed, the apparent contact stiffness measured at the onset of the unloading process, the indenter displacement drift rate measured prior to the unloading process, and the imposed unloading rate measured at the onset of the unloading process.Join the waitlist — get patent alerts
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