FIELD OF INVENTION
The invention generally relaters to a low temperature arrangement for
measurement of crack tip opening displacement in metallic materials. More
particularly, the invention relates to a device in a testing machine to determine
crack tip opening displacement (CTOD) parameter of a metallic component at
sub-zero temperature. The invention further relates to a process in a testing
machine for measurement of crack tip opening displacement parameter of a
metallic component at sub-zero temperature.
BACKGROUND OF THE INVENTION
The fracture mechanics testing of metallic specimens has emerged as a major
tool for the analysis of integrity of metallic materials containing growing cracks.
The fracture mechanics is concerned solely with the condition prevailing at the
tip of a crack. When the conditions at the tip of the crack are such that the size
of the plastic zone is considerably larger, then the integrity analysis is of elastic
plastic type. Accordingly, the value of a crack tip opening displacement (CTOD) is
determined to characterize the ability of the material to resist the growing
cracks. The evaluation of crack tip opening displacement is carried out as per the
procedures given in various standards like ASTM E 1820 and BS 7448.
When the material is operating at subzero conditions, the CTOD needs to be
evaluated at lower temperatures up to minus 60°C. For testing the specimen
under subzero temperatures, the specimen needs to be immersed in a low
temperature bath for a period of at least 45 minutes and tested under an
immersed condition.
This requires the construction of a device which enables the testing under
immersed conditions at sub-zero temperature level. The device should be
mountable on a standard testing machine.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device in a testing machine
to determine crack tip opening displacement (CTOD) parameter of a metallic
component at sub-zero temperature.
Another object of the invention is to propose a device in a testing machine to
determine crack tip opening displacement (CTOD) parameter of a metallic
component at sub-zero temperature, which allows mounting of a CTOD test
specimen.
A still another object of the invention is to propose a device in a testing machine
to determine crack tip opening displacement (CTOD) parameter of a metallic
component at sub-zero temperature, which is additionally enabled to fill-up a
bath.
A further object of the invention is to propose a device in a testing machine to
determine crack tip opening displacement (CTOD) parameter of a metallic
component at sub-zero temperature, which is mountable on a standard testing
machine.
A still further object of the invention is to propose a process in a testing machine
for measurement of crack tip opening displacement parameter of a metallic
component at sub zero temperature.
These and other objects and advantages of the invention will be apparent from
the ensuing description.
SUMMARY OF THE INVENTION
Accordingly, there is provided in a first aspect of the invention a device in a
testing machine to determine crack tip opening displacement (CTOD) parameter
of a metallic component at sub-zero temperature, the testing machine
comprising at least one top jaw and a bottom jaw each having clamping
surface, the device comprising a vessel having one each top and bottom
member, and at least two side members forming an enclosure, the top and
bottom members each respectively having at least one input port and output
port, the side members including the bottom member jacketted with a first
insulation cover which comprises a central hole in registration with said output
port of the vessel, the top member being substantially similarly provided with a
second insulation cover configured with an opening corresponding to said input
port; a liquid bath enabled to maintain a liquid therein at a subzero temperature
level formed within the vessel; a top adapter disposed at an upper external
location of the vessel, and having at a first end a clamping means which is
clamped to the top jaw of the testing machine, the top adapter comprising at a
second end a male threaded portion; a bottom adapter located at a low external
position in relation to the vessel, and having a clamping means at a distal end
for clamping with the bottom jaw , a proximal end of the bottom adapter
configured with a male threaded portion; Characterized by comprising a top
clevis grip having a female threaded portion corresponding to the male threaded
portion of the top adapter arranged inside the liquid bath, and releasably joined
through said input port of the vessel to the top adapter ; a bottom clevis grip
comprising a female threaded portion corresponding to said male threaded
portion of the bottom adapter, the top and bottom clevis grips are enabled to
mount and hold a CTOD specimen inside the liquid bath maintained at the sub-
zero temperature level to allow measurement of the CTOD parameter of the
specimen by operably connecting the vessel with the testing machine.
In a second aspect of the invention there is provided a process to determine
crack tip opening parameter of a metallic component with crack in a device of
the invention. The process comprising the steps of mounting the specimen in
between the top clevis grip and the bottom clevis grip ; placing the specimen
inside the vessel ; fastening the top clevis grip with the top adopter and the
bottom clevis grip with the bottom adopter; mounting the top adopter with the
top jaw of the testing machine and mounting the bottom adopter with the
bottom jaw of the machine; pouring a sub-zero temperature liquid coolant into
the vessel for complete immersion of the specimen ; adding dry ice to the liquid
coolant for further cooling to achieve a temperature equal to or less than - 60°
C; allowing the CTOD specimen for a duration of 45 to 60 minutes for soaking
inside the liquid bath ; and carrying out the CTOD testing of the specimen by
adapting the testing machine being operably connected to the device.
At the outset of the description, which follows, it is to be understood that the
ensuring description only illustrates a particular form of this invention. However,
such a particular form is only an exemplary embodiment and the teaching of the
invention is not intended to be taken restrictively.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 schematically shows the invented device.
Figure 2 shows embodiments of the top and bottom clevis grips of the device of
Figure 1.
Figure 3 shows embodiments of top and bottom adopters of the device of
Figure 1.
Figure 4 shows a rubber washer adaptable to a liquid alcohol bath for immersing
the device of Figure 1.
Figure 5 shows a lock nut adaptable to the bottom adapter and the bottom clevis
grip of the device of Figure-1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION.
The inventive device is enabled to act as an in-situ container surrounding the
CTOD test specimen so that the testing can be carried out at subzero
temperatures upto - 60°C. As shown in Figure 1, the device comprises a
stainless steel vessel (9) housing a low temperature alcohol bath (12). The
stainless steel vessel (9) is first inserted into an insulated side cover (10) which
fits the vessel (9) without leaving any gap. A CTOD specimen (13) is immersed in
the alcohol bath (12) contained in the stainless steel vessel (9) during the test.
At least two adopters, one at the top (3) and one at the bottom (4) are used for
holding the stainless steel vessel (9) around the specimen (13). A male threaded
portion of the bottom adopter (4) is inserted through a central hole in the
bottom of the stainless steel container (9) including the insulation cover (10) as
shown in Figure 1. The bottom clevis grip (6) which contains a female threaded
portion is then tightened after inserting a washer (7) using a lock nut means (8).
The washer (7) at the bottom prevents any leakage from the alcohol bath (12)
during the entire duration of the test. The washer at the bottom (7) is tightly
cemented to the stainless steel vessel (9) using adhesives. In the same way, the
male threaded portion in the top adopter (3) is passed through the insulation top
cover (11) and the female threaded portion in the top clevis grip (5) is tightened.
After the device being assembled, the CTOD specimen (13) is mounted between
the top clevis grip (5) and bottom clevis grip (6). Subsequently, the device with
the specimen (13) is carefully mounted on the testing machine. The top adopter
(3) is clamped to a top jaw (1), and the bottom adopter (4) is clamped on the
bottom jaw (2) of the testing machine respectively. The correct mounting of the
various components is then checked and a liquid alcohol (12) is poured into the
stainless steel vessel (9) so that the CTOD specimen (13) is completely
submerged in the alcohol bath (12). The alcohol bath (12) is cooled using dry
ice to the required temperature. Once the desired temperature is reached, the
CTOD specimen (13) is soaked for a duration of at least 45 minutes before the
commencement of the test. The leak tightness of the stainless steel vessel (9) is
maintained during the entire testing period.
WE CLAIM :
1. A device in a testing machine to determine crack tip opening
displacement (CTOD) parameter of a metallic component at sub-zero
temperature, the testing machine comprising at least one top jaw (1)
and a bottom jaw (2) each having clamping surface, the device
comprising :-
a vessel (9) having one each top and bottom member, and at
least two side members forming an enclosure, the top and
bottom members each respectively having at least one input
port and output port, the side members including the bottom
member jacketted with a first insulation cover (10) which
comprises a central hole in registration with said output port of
the vessel, the top member being substantially similarly provided
with a second insulation cover (11) configured with an opening
corresponding to said input port;
a liquid bath (12) enabled to maintain a liquid therein at a
subzero temperature level formed within the vessel (9);
a top adapter (4) disposed at an upper external location of the
vessel, and having at a first end a clamping means which is
clamped to the top jaw(l) of the testing machine, the top
adapter (4) comprising at a second end a male threaded portion;
a bottom adapter (4) located at a low external position in
relation to the vessel (9), and having a clamping means at a
distal end for clamping with the bottom jaw (2), a proximal end
of the bottom adapter (4) configured with a male threaded
portion; Characterized by comprising :
a top clevis grip (5) having a female threaded portion
corresponding to the male threaded portion of the top adapter
(3) arranged inside the liquid bath, and releasably joined
through said input port of the vessel (9) to the top adapter (3);
a bottom clevis grip (6) comprising a female threaded portion
corresponding to said male threaded portion of the bottom
adapter (4), the top and bottom clevis grips (5,6) are enabled to
mount and hold a CTOD specimen (13) inside the liquid bath
(12) maintained at the sub-zero temperature level to allow
measurement of the CTOD parameter of the specimen (13) by
operably connecting the vessel (9) with the testing machine.
2. The device as claimed in claim 1, comprising a lock nut means (8)
including a washer (7) to form a leak proof sealing between the output
port of the vessel (9) and the bottom clevis grip (6), wherein the
washer (7) is further provided with a sealing adhesive to strengthen
the joint between the output port and the bottom clevis grip (6).
3. The device as claimed in claim 1, wherein the vessel (9), and the top
and bottom clevis grips (5,6) comprise anti-corrosive material for
example, stainless steel.
4. A process to determine crack tip opening parameter of a metallic
component with crack in a device as claimed in claim. 1, the process
comprising the steps of:
mounting the specimen (13) in between the top clevis grip (5)
and the bottom clevis grip (6);
placing the specimen inside the vessel (9);
fastening the top clevis grip (5) with the top adopter (3) and the
bottom clevis grip with the bottom adopter (4);
mounting the top adopter (3) with the top jaw (1) of the testing
machine and mounting the bottom adopter (4) with the bottom
jaw (2) of the machine;
pouring a sub-zero temperature liquid coolant into the vessel (9)
for complete immersion of the specimen (13);
adding dry ice to the liquid coolant for further cooling the liquid
to achieve a temperature equal to or less than - 60° C;
allowing the CTOD specimen (13) for a duration of 45 to 60
minutes for soaking inside the liquid bath (12); and
Carrying out the CTOD testing of the specimen by adapting the
testing machine being operably connected to the device.
5. The process as claimed in claim 4, wherein the sub-zero temperature
coolant can be selected from a group consisting of alcohol, liquid
nitrogen, liquid oxygen.
6. A device in a testing machine to determine crack tip opening
displacement (CTOD) parameter of a metallic component at sub-zero
temperature, as substantially described and illustrated herein with
reference to the accompanying drawings.
7. A process to determine crack tip opening parameter of a metallic
component with crack as substantially described and illustrated herein
with reference to the accompanying drawings.

The invention relates to The invention relates to a device in a testing machine to
determine crack tip opening displacement (CTOD) parameter of a metallic
component at sub-zero temperature, the testing machine comprising at least one
top jaw (1) and a bottom jaw (2) each having clamping surface, the device
comprising a vessel (9) having one each top and bottom member, and at least
two side members forming an enclosure, the top and bottom members each
respectively having at least one input port and output port, the side members
including the bottom member jacketted with a first insulation cover (10) which
comprises a central hole in registration with said output port of the vessel, the
top member being substantially similarly provided with a second insulation cover
(11) configured with an opening corresponding to said input port; a liquid bath
(12) enabled to maintain a liquid therein at a subzero temperature level formed
within the vessel (9); a top adapter (4) disposed at a upper external location of
the vessel, and having at a first end a clamping means which is clamped to the
top jaw(l) of the testing machine, the top adapter (4) comprising at a second
end a male threaded portion; a bottom adapter (4) location at a low external
position in relation to the vessel (9), and having a clamping means at a distal
end for clamping with the bottom jaw (2), a proximal end of the bottom adapter
(4) configured with a male threaded portion; Characterized by comprising a top
clevis grip (5) having a female threaded portion corresponding to the male