Title of Invention	"AN IMPROVED IMPLANT TEST APPARATUS FOR QUANTITATIVE ASSESSMENT OF HYDROGEN INDUCED COLD CRACKING (HICC) SUSCEPTIBILITY OF HIGH STRENGTH STEEL WELDMENTS"
Abstract	This invention relates to an improved implant test apparatus for quantitative assessment of hydrogen induced cold cracking (HICC) susceptibility of high strength steel weldments characterised in that the system has a plurality of independent test rigs, each with its own loading mechanism which enable simultaneous testing of several samples under different load conditions and wherein each test rig comprises: (a) loading structure for holding a test sample, (b) load cell disposed below of loading structure, (c) double cantilever mechanism held to said load cell, (d)servo controlled load positioner held to said cantilever mechanism, (e) weld temperature sensors as herein described, (f) data acquisition system to record the temperature changes, (g)Linearly Variable Displacement Transducer (LVDT) for strain measurement.

Title of Invention

"AN IMPROVED IMPLANT TEST APPARATUS FOR QUANTITATIVE ASSESSMENT OF HYDROGEN INDUCED COLD CRACKING (HICC) SUSCEPTIBILITY OF HIGH STRENGTH STEEL WELDMENTS"

Abstract

This invention relates to an improved implant test apparatus for quantitative assessment of hydrogen induced cold cracking (HICC) susceptibility of high strength steel weldments characterised in that the system has a plurality of independent test rigs, each with its own loading mechanism which enable simultaneous testing of several samples under different load conditions and wherein each test rig comprises: (a) loading structure for holding a test sample, (b) load cell disposed below of loading structure, (c) double cantilever mechanism held to said load cell, (d)servo controlled load positioner held to said cantilever mechanism, (e) weld temperature sensors as herein described, (f) data acquisition system to record the temperature changes, (g)Linearly Variable Displacement Transducer (LVDT) for strain measurement.

Full Text	AN IMPROVED APPARATUS FOR QUANTITATIVE DETERMINATION OF HYDROGEN INDUCED COLD CRACKING SUSCEPTIBILITY OF HIGH STRENGTH STEEL WELDMENTS Field of Invention This invention relates to an improved apparatus for quantitative determination of Hydrogen Induced Cold Cracking (HICC) susceptibility of high strength steel weldments which is of vital importance in fabrication of high strength steel structures like pressure vessels, bridges, ship-building etc. Prior Art HICC remains a major problem to fabricators of high strength structural steels and their weldments. It is associated with a decrease in tensile ductility and tensile strength. Weldments certified as sound by the most exhaustive non-destructive evaluation often exhibit extensive cracking after few days, weeks or months after entering service. This type of cracks can virtually destroy the effectiveness of the load carrying capability of the weldment and also act as potential sites for initiation of a brittle fracture. It is often difficult to detect them as the cracks are hidden in the weld toes, root of the welds ,or at the underbed position. Three interrelated factors are responsible for this crack formation, namely:- a) presence of critical concentration of hydrogen b) constraints due to a critical level of applied/ residual stress c) a susceptible microstructure. Hydrogen embrittlement in steel is inhibited by fast strain rate and low temperatures which is in direct contrast with conventional behaviour of steels where embrittlement is enhanced by fast strain rate and low temperature. It is, therefore, essential and very important for the fabricators of high strength structural steels to know in a quantitative manner, the susceptibility of steel to HICC under various welding conditions using different types of welding consumables. For fabrication of critical components like bridges and other structural components, a knowledge of the HICC sesceptibility will help the designer, in formulating the correct welding practices and procedures and ensure safety from catastrophic failure. For the purpose of investigation of the phenomenon of HICC and for proper selection of welding -consumables and welding parameters to avoid HICC, a number of test systems have been developed and are presently commercially available. These test systems are either of self-restraint type or of external-restraint type. Though the former type of test system simulates the HICC in a weld more accurately, stress in required in a weld for HICC to occur can be obtained only in the external-restraint "type test systems. Thus the external restraint type test systems can determine susceptibility to HICC in a quantitative manner. One of the most important and widely accepted test system for quantitative determination of HICC susceptibility is implant testing system. Generally, Implant testing systems involve loading a helically notched specimen, positioned in flush with the surface of its supporting plate through a hole in it, immediately after welding, to a pre-set dead weight. The welded specimen is kept in the loaded condition for 24 hours. If the sample fails within that time frame, the time taken to fail is noted down and the next test is carried out at lower stress. If at a particular stress level, failure does not. occur with in that time frame of 24 hours, the test specimen is unloaded -and that particular stress is taken to be the lower critical stress (LCS). For determination of the lower critical stress (LCS) level, below which a sample will not fail within 24 hours. At least 4 tests are required to be done at different stress levels but keeping other welding parameters same. This consume a lot of time to generate realistic data when different type of weld consumables are used and various weld conditions are employed. As the known systems have only one test rig, the test of sample has to wait till the completion of the test on the preceding sample. The known system therefore had the disadvantage that these being based on usage of single test rig, the determination of LCS is time consuming. In the available Implant test systems, discrete weights are used which are unsuitable for getting an accurate LCS value, as few intermediate stress levels may often get missed inadvertently and so the intermediate stress levels cannot be ascertained with this system. Also the initiation of hydrogen cracks is a temperature dependent process between -1000C to + 100'C. Hence, the application of load in the proper temperature range is very crucial in obtaining not only an accurate LCS value but also in producing the repeatability of the test results. These available Implant test systems have further drawback that there is no provision in the system for automatic triggering of a pre-set load when the preset load when the pre-set temperature of the weld is reached. Due to this, it is not possible to obtain accurate values and repeatability of results. Object of the present invention The primary object of the present invention is to propose an improved implant testing system which enables quantitative determination of HICC susceptibility of high strength steel weldments in a reasonably shorter time. Another object of the present invention is to propose an improved implant system which enables quantitative determination of HICC suspectibi1ity with higher accuracy as compared with known implant test systems. Still another object of the present invention is to propose an improved implant test system with four independent test rigs each with its own loading mechanisms which enable simultaneous testing of four samples under different load conditions. Further object of the present invention is to propose an improved implant test system which incorporates an improved servo controlled load positioner which enables automatic application of pre-set load in the continuous range upto 50KN in place of manual application of discrete weights in the known system. Still further object of the present invention is to propose an improved implant test system which incorporates a thermocouple which enables automatic triggering of the loading mechanisms at a pre-set load level as soon as present : temperature of the weld is sensed by the thermocouple. Yet further object of the present invention is to propose an improved implant test system which incorporates double lever cant lever loading mechanism which enables a 100 fold load multiplication. Still further object of the present invention is to propose an improved implant test system when incorporates a data acquisition system which collects real time load and weld-temperature data and feeds to the main controller. Yet further object of the present invention is to propose an improved implant test system when incorporates LVDT to measure the strain in the welded sample to order to few hundred microns. STATEMENT OF INVENTION According to this invention there is provided an improved implant test apparatus for quantitative assessment of hydrogen induced cold cracking (HICC) susceptibility of high strength steel weldments characterised in that the system has a plurality of independent test rigs, each with its own loading mechanism which enable simultaneous testing of several samples under different load conditions and wherein each test rig comprises: (a) loading structure for holding a test sample, (b) load cell disposed below of loading structure, (c) double cantilever mechanism held to said load cell, (d) servo controlled load positioner held to said cantilever mechanism, (e) weld temperature sensors as herein described, (f) data acquisition system to record the temperature changes, (g) Linearly Variable Displacement Transducer (LVDT) for strain measurement. The proposed system considerably reduces the total time of testing by providing four independent test rigs, each with its own loading mechanism. This make is possible to test four different samples simultaneously by loading each test rig with different sample to desired load levels. A servo controlled load positioner is provided which enables automatic application of pre-set load. This servo controlled load positioner moves on a rotary to line converter in the horizontal direction and enables use * of continuous range of load upto 50KN in place of manual application of discrete weights in the earlier test systems. This enable precision in determination of lower critical stress (LCS) value. Double lever cantilever mechanism has been provided which enables 100 fold load multiplication. A thermocouple has been provided in the apparatus which enables automatic triggering of the loading mechanism at a pre-set load level as soon as the pre-set temperature of the cooling weld is sensed by thermocouple. This adds to the accuracy and enables repeatability of results. The •precision strain gauge based load cells, measure the effective loading on each specimen throughout the entire testing period. "The system also makes it possible to measure the magnitude of strain due to hydrogen cracking in the test system during the entire test range by suitable Linearly Variable Displacement Transducer (LVDT). Using this test system, a lower critical stress (LCS) is obtained, below which a given weldment will not fail, at a constant diffusible hydrogen level. A comparison of the LCS values of various steels welded under identical conditions, gives a relative ranking of these steels with -respect of their "susceptibility to- HICC. Susceptibility to HICC of various high strength structural steels like HY-80, HSLA-80 have been carried out. When welded at a heat input of 2Kj/mm, HY-80 steel was observed to have LCS values varied from 565 N/mm2 to 309 N/mm2 at diffusible hydrogen levels of 3ml/lOO gm to 16ml/100 gm respectively. Description of figures The preferred embodiment of present invention will now be illustrated with the following figures which are intended to illustrate an embodiment of the proposed apparatus, without intending to limit in any way, the scope of the present invention, wherein:- Fig.l - Shows the complete apparatus for Implant Test System Fig.2 - Shows front-view and top-view of the implant test system for four samples Fig.3 - Shows Servo controlled load positioner Description with respect to drawings Referring to fig(l), the specimen (3) whose HICC susceptibility is to be determined, is placed between the specimen holder (4) and the backing plate(1). The specimen (3) is held in position by passing it through a hole at the middle of both bearing plate (2) and backing plate(1). The spring (5) provides the support to the specimen holder(4) The specimen holder (4) and the spring (5) are housed in a holder(6). The specimen (3) is held in position with the help of spring(5) till the actual load is transmitted-to the specimen(3) after being welded to the backing plate(1). The load cell (7) measures the actual load being transmitted to for example the specimen (3) . The load cell has a capacity of/ 50 KN. As the load is applied over a period of 24 hours or more. The load cell has a very high degree of accuracy over the entire time frame in the measurement of load being applied to the sample. The primary fixed load(14) is multiplied twice by the primary lever(18) and secondary lever (17) arms through cantilever mechanism. The arms X1 and X2 of. secondary lever (17) are preferably in the ratio 1:10 and the arms L1 and L2 of the primary lever (18) are preferably in the ratio 10:1. Knife edge bearings(9) are provided to minimise the loss of load when being transferred from one member to another and also at the lever fulcrums. The actuator servo motor(10) controls the movement of the load positioner (15) so that the effective arm length of the primary lever is changed accordingly and the desired load is actually applied to the test sample (3). The hydraulic dampers (11) make the movement of the primary lever smooth during loading/unloading. Provisions for Linearly Variable Displacement Transducer(16) are kept to measure the actual strain occuring in the test sample prior to failures, if any. The strain measured is of the order of few hundred microns. The poise 8 (a) is positioned at the lower end of primary lever arm(18) and poise 8 (b) is positioned at the lower end of secondary arm (17) makes .sure that the lever arms are free from any stress before a new experiment is carried out. The load cell guides (12) maintain proper alignment of the load cell(7) during up and down movement of the load cell(7) during-loading and unloading. The lifting cylinder(13) keeps the primary lever arm(18) in position so that the load applied on- the primary lever (18) is not transmitted to the test sample in the beginning. Immediately after welding, when the load is required to be transmitted to the test sample, the lifting cylinder comes down .and - gets detached from the primary lever. At this condition, the test sample is. fully under the applied load. If sample fails during experimentation, the primary lever (18) arm comes down and rests on the lifting cylinder(13) . - . The weld temperature sensors used are preferably -K type chromel- (+)-Alumel(-) thermocouple having ;high sensitivity (10 to 55 nv/°C), high accuracy (ii2.2°C) within a range of -18 to 12.00°C. The one end of thermocouple is properly placed ' in the vicinity of weld being made to measure ti.e temperature of the cooling weld. The other end is fed into the central controller having a data acquisition system which records the temperature changes as experienced by the tip of the thermocouple. The fig 2 shows the front view and top-view of the apparatus for four, test samples. The figure (3) gives -the details of .Servo Controlled load positioner. the servo controlled load positioner basically consists of a load mover, (15) (fig 1) , a helically threaded power screw(19) (fig 3) and a arctuator servo motor(lO) (fig 1). The motor rotates the screw to which the load positioner is held and brings the load positioner to the desired place on the primary lever(: 8) arm. Subsequently the load positioner is separated from the screw and the load positioner rests only on the primary lever (18) arm. It is to be understood that the above description of the present invention is susceptible to considerable modifications, change and adapations by those skilled in the art, such modifications and adaptations are intended to be considered to be within the scope of the present invention, which is set forth by the following claims:- WE CLAIM; 1. An improved implant test apparatus for quantitative assessment of hydrogen induced cold cracking (HICC) susceptibility of high strength steel elements characterised in that the system has a plurality of independent test rigs, each with its own loading mechanism which enable simultaneous testing of several samples under different load conditions and wherein each test rig comprises: (a) loading structure for holding a test sample, (b) load cell disposed below of loading structure, (c) double cantilever mechanism held to said load cell, (d) servo controlled load positioner held to said cantilever mechanism, (e) weld temperature sensors as herein described, (f) data acquisition system to record the temperature changes, (g) Linearly Variable Displacement Transducer (LVDT) for strain measurement. 2. An improved implant test apparatus as claimed in claim 1 wherein the said loading structure comprises of backing plate (1) supported on a bearing plate (2), sample holder (4) held to said sample, spring (5) disposed within a holder (6) and between holder (4) and holder (6) (fig. 1). 3. An improved implant test apparatus as claimed in claim 1 wherein the said load cell (7) is held to holder (6) and measures the actual load being transmitted to the test sample. 4. An improved implant test apparatus as claimed in claim 1 wherein the said double-cantilever mechanism has primary lever (18) with arms L1, L2 in the ratio of 10:1 and secondary lever arms (17) with arms X1, X2 ratio of 1:10 which enable multiplication the load twice upto a total of 100 times and hydraulic damper (11) provides smooth loading/unloading. 5. An improved implant test apparatus as claimed in claim 1 wherein the said servo controlled load positioner comprises of a load positioner (15), a helically threaded power screw (19) (fig.3) and actuator servo motor (10). 6. An improved implant test apparatus as claimed in claim 5 wherein the said servo controlled load positioner 5 enables automatic application of pre-set load in a continuous range of load upto 50 KN in place of conventional manual application of discrete weight. 7. An improve implant test, apparatus for quantitative . assessment of hydrogen induced cold cracking substantially as herein described and illustrated.

Full Text

AN IMPROVED APPARATUS FOR QUANTITATIVE DETERMINATION
OF HYDROGEN INDUCED COLD CRACKING SUSCEPTIBILITY
OF HIGH STRENGTH STEEL WELDMENTS
Field of Invention
This invention relates to an improved apparatus for
quantitative determination of Hydrogen Induced Cold Cracking
(HICC) susceptibility of high strength steel weldments which
is of vital importance in fabrication of high strength steel
structures like pressure vessels, bridges, ship-building
etc.
Prior Art
HICC remains a major problem to fabricators of high strength structural steels and their weldments. It is associated with a decrease in tensile ductility and tensile strength. Weldments certified as sound by the most
exhaustive non-destructive evaluation often exhibit extensive cracking after few days, weeks or months after entering service. This type of cracks can virtually destroy the effectiveness of the load carrying capability of the weldment and also act as potential sites for initiation of a brittle fracture. It is often difficult to detect them as the cracks are hidden in the weld toes, root of the welds ,or at the underbed position. Three interrelated factors are
responsible for this crack formation, namely:-
a) presence of critical concentration of hydrogen
b) constraints due to a critical level of applied/
residual stress
c) a susceptible microstructure.
Hydrogen embrittlement in steel is inhibited by fast strain rate and low temperatures which is in direct contrast with conventional behaviour of steels where embrittlement is enhanced by fast strain rate and low temperature. It is,

therefore, essential and very important for the fabricators of high strength structural steels to know in a quantitative manner, the susceptibility of steel to HICC under various welding conditions using different types of welding consumables. For fabrication of critical components like bridges and other structural components, a knowledge of the HICC sesceptibility will help the designer, in formulating the correct welding practices and procedures and ensure safety from catastrophic failure.
For the purpose of investigation of the phenomenon of HICC and for proper selection of welding -consumables and welding parameters to avoid HICC, a number of test systems have been developed and are presently commercially
available.
These test systems are either of self-restraint type or of external-restraint type. Though the former type of test system simulates the HICC in a weld more accurately, stress in required in a weld for HICC to occur can be obtained only in the external-restraint "type test systems. Thus the external restraint type test systems can determine susceptibility to HICC in a quantitative manner. One of the most important and widely accepted test system for quantitative determination of HICC susceptibility is implant testing system.
Generally, Implant testing systems involve loading a helically notched specimen, positioned in flush with the surface of its supporting plate through a hole in it, immediately after welding, to a pre-set dead weight. The welded specimen is kept in the loaded condition for 24 hours. If the sample fails within that time frame, the time taken to fail is noted down and the next test is carried out at lower stress. If at a particular stress level, failure does not. occur with in that time frame of 24 hours, the test specimen is unloaded -and that particular stress is taken to be the lower critical stress (LCS). For determination of the lower critical stress (LCS) level, below which a sample will not fail within 24 hours. At least 4 tests are required to be done at different stress levels but keeping other

welding parameters same. This consume a lot of time to generate realistic data when different type of weld consumables are used and various weld conditions are employed. As the known systems have only one test rig, the test of sample has to wait till the completion of the test on the preceding sample. The known system therefore had the disadvantage that these being based on usage of single test rig, the determination of LCS is time consuming.
In the available Implant test systems, discrete weights are used which are unsuitable for getting an accurate LCS value, as few intermediate stress levels may often get missed inadvertently and so the intermediate stress levels cannot be ascertained with this system. Also the initiation of hydrogen cracks is a temperature dependent process between -1000C to + 100'C. Hence, the application of load in the proper temperature range is very crucial in obtaining not only an accurate LCS value but also in producing the repeatability of the test results.
These available Implant test systems have further drawback that there is no provision in the system for automatic triggering of a pre-set load when the preset load when the pre-set temperature of the weld is reached. Due to this, it is not possible to obtain accurate values and repeatability of results.
Object of the present invention
The primary object of the present invention is to propose an improved implant testing system which enables quantitative determination of HICC susceptibility of high strength steel weldments in a reasonably shorter time.
Another object of the present invention is to propose an improved implant system which enables quantitative determination of HICC suspectibi1ity with higher accuracy as compared with known implant test systems.
Still another object of the present invention is to propose an improved implant test system with four independent test rigs each with its own loading mechanisms which enable simultaneous testing of four samples under different load conditions.
Further object of the present invention is to propose an improved implant test system which incorporates an improved servo controlled load positioner which enables automatic application of pre-set load in the continuous range upto 50KN in place of manual application of discrete weights in the known system.
Still further object of the present invention is to propose an improved implant test system which incorporates a thermocouple which enables automatic triggering of the loading mechanisms at a pre-set load level as soon as present
: temperature of the weld is sensed by the thermocouple.
Yet further object of the present invention is to propose an improved implant test system which incorporates double lever cant lever loading mechanism which enables a 100 fold load multiplication.
Still further object of the present invention is to propose an improved implant test system when incorporates a data acquisition system which collects real time load and weld-temperature data and feeds to the main controller.
Yet further object of the present invention is to propose an improved implant test system when incorporates LVDT to measure the strain in the welded sample to order to few hundred microns.
STATEMENT OF INVENTION
According to this invention there is provided an improved implant test apparatus for quantitative assessment of hydrogen induced cold cracking (HICC) susceptibility of high strength steel weldments characterised in that
the system has a plurality of independent test rigs, each with its own loading mechanism which enable simultaneous testing of several samples under different load conditions and wherein each test rig comprises:
(a) loading structure for holding a test sample,
(b) load cell disposed below of loading structure,
(c) double cantilever mechanism held to said load cell,
(d) servo controlled load positioner held to said cantilever
mechanism,
(e) weld temperature sensors as herein described,
(f) data acquisition system to record the temperature changes,
(g) Linearly Variable Displacement Transducer (LVDT) for strain
measurement.
The proposed system considerably reduces the total time of testing by providing four independent test rigs, each with its own loading mechanism. This make is possible to test four different samples simultaneously by loading each test rig with different sample to desired
load levels. A servo controlled load positioner is provided which enables automatic application of pre-set load. This servo controlled load positioner moves on a rotary to line converter in the horizontal direction and enables use * of continuous range of load upto 50KN in place of manual application of discrete weights in the earlier test systems. This enable precision in determination of lower critical stress (LCS) value. Double lever cantilever mechanism has been provided which enables 100 fold load multiplication. A thermocouple has been provided in the apparatus which enables automatic triggering of the loading mechanism at a pre-set load level as soon as the pre-set temperature of the cooling weld is sensed by thermocouple. This adds to the accuracy and enables repeatability of results. The •precision strain gauge based load cells, measure the effective loading on each specimen throughout the entire testing period. "The system also makes it possible to measure the magnitude of strain due to hydrogen cracking in the test system during the entire test range by suitable Linearly Variable Displacement Transducer (LVDT).
Using this test system, a lower critical stress (LCS) is obtained, below which a given weldment will not fail, at a constant diffusible hydrogen level. A comparison of the
LCS values of various steels welded under identical conditions, gives a relative ranking of these steels with
-respect of their "susceptibility to- HICC. Susceptibility to HICC of various high strength structural steels like HY-80, HSLA-80 have been carried out. When welded at a heat input of 2Kj/mm, HY-80 steel was observed to have LCS values varied from 565 N/mm2 to 309 N/mm2 at diffusible hydrogen levels of 3ml/lOO gm to 16ml/100 gm respectively.
Description of figures
The preferred embodiment of present invention will now be illustrated with the following figures which are intended to illustrate an embodiment of the proposed apparatus, without intending to limit in any way, the scope of the present invention, wherein:-
Fig.l - Shows the complete apparatus for Implant Test System
Fig.2 - Shows front-view and top-view of the implant test system for four samples
Fig.3 - Shows Servo controlled load positioner Description with respect to drawings
Referring to fig(l), the specimen (3) whose HICC susceptibility is to be determined, is placed between the specimen holder (4) and the backing plate(1). The specimen (3) is held in position by passing it through a hole at the middle of both bearing plate (2) and backing plate(1). The spring (5) provides the support to the specimen holder(4) The specimen holder (4) and the spring (5) are housed in a holder(6). The specimen (3) is held in position with the help of spring(5) till the actual load is transmitted-to the specimen(3) after being welded to the backing plate(1). The
load cell (7) measures the actual load being transmitted to
for example the specimen (3) . The load cell has a capacity of/ 50 KN. As
the load is applied over a period of 24 hours or more. The load cell has a very high degree of accuracy over the entire time frame in the measurement of load being applied to the sample. The primary fixed load(14) is multiplied twice by the primary lever(18) and secondary lever (17) arms through cantilever mechanism. The arms X1 and X2 of. secondary lever (17) are preferably in the ratio 1:10 and the arms L1 and L2 of the primary lever (18) are preferably in the ratio 10:1. Knife edge bearings(9) are provided to minimise the loss of load when being transferred from one member to another and also at the lever fulcrums. The actuator servo motor(10) controls the movement of the load positioner (15) so that the effective arm length of the primary lever is changed accordingly and the desired load is actually applied to the test sample (3). The hydraulic dampers (11) make the movement of the primary lever smooth during loading/unloading. Provisions for Linearly Variable Displacement Transducer(16) are kept to measure the actual strain occuring in the test sample prior to failures, if any. The strain measured is of
the order of few hundred microns.
The poise 8 (a) is positioned at the lower end of
primary lever arm(18) and poise 8 (b) is positioned at the
lower end of secondary arm (17) makes .sure that the lever
arms are free from any stress before a new experiment is
carried out. The load cell guides (12) maintain proper
alignment of the load cell(7) during up and down movement of
the load cell(7) during-loading and unloading. The lifting
cylinder(13) keeps the primary lever arm(18) in position so
that the load applied on- the primary lever (18) is not
transmitted to the test sample in the beginning.
Immediately after welding, when the load is required to be
transmitted to the test sample, the lifting cylinder comes
down .and - gets detached from the primary lever. At this
condition, the test sample is. fully under the applied load.
If sample fails during experimentation, the primary
lever (18) arm comes down and rests on the lifting
cylinder(13) . - .
The weld temperature sensors used are preferably -K type chromel- (+)-Alumel(-) thermocouple having ;high sensitivity (10 to 55 nv/°C), high accuracy (ii2.2°C) within a range of -18 to 12.00°C. The one end of thermocouple is properly placed ' in the vicinity of weld being made to measure ti.e temperature of the cooling weld. The other end is fed into the central controller having a data acquisition system which records the temperature changes as experienced by the tip of the thermocouple.
The fig 2 shows the front view and top-view of the apparatus for four, test samples.
The figure (3) gives -the details of .Servo Controlled load positioner. the servo controlled load positioner basically consists of a load mover, (15) (fig 1) , a helically threaded power screw(19) (fig 3) and a arctuator servo motor(lO) (fig 1). The motor rotates the screw to which the load positioner is held and brings the load positioner to the desired place on the primary lever(: 8) arm. Subsequently the load positioner is separated from the screw and the load positioner rests only on the primary lever (18) arm.
It is to be understood that the above description of the present invention is susceptible to considerable modifications, change and adapations by those skilled in the art, such modifications and adaptations are intended to be considered to be within the scope of the present invention, which is set forth by the following claims:-

WE CLAIM;
1. An improved implant test apparatus for quantitative assessment of
hydrogen induced cold cracking (HICC) susceptibility of high strength
steel elements characterised in that the system has a plurality of
independent test rigs, each with its own loading mechanism which
enable simultaneous testing of several samples under different load
conditions and wherein each test rig comprises:
(a) loading structure for holding a test sample,
(b) load cell disposed below of loading structure,
(c) double cantilever mechanism held to said load cell,
(d) servo controlled load positioner held to said cantilever
mechanism,
(e) weld temperature sensors as herein described,
(f) data acquisition system to record the temperature changes,
(g) Linearly Variable Displacement Transducer (LVDT) for strain
measurement.
2. An improved implant test apparatus as claimed in claim 1 wherein the
said loading structure comprises of backing plate (1) supported on a
bearing plate (2), sample holder (4) held to said sample, spring (5) disposed
within a holder (6) and between holder (4) and holder (6) (fig. 1).
3. An improved implant test apparatus as claimed in claim 1 wherein the
said load cell (7) is held to holder (6) and measures the actual load being
transmitted to the test sample.
4. An improved implant test apparatus as claimed in claim 1 wherein the
said double-cantilever mechanism has primary lever (18) with arms L1, L2
in the ratio of 10:1 and secondary lever arms (17) with arms X1, X2 ratio of
1:10 which enable multiplication the load twice upto a total of 100 times
and hydraulic damper (11) provides smooth loading/unloading.
5. An improved implant test apparatus as claimed in claim 1 wherein the
said servo controlled load positioner comprises of a load positioner (15), a
helically threaded power screw (19) (fig.3) and actuator servo motor (10).
6. An improved implant test apparatus as claimed in claim 5 wherein the
said servo controlled load positioner 5 enables automatic application of
pre-set load in a continuous range of load upto 50 KN in place of
conventional manual application of discrete weight.
7. An improve implant test, apparatus for quantitative . assessment of
hydrogen induced cold cracking substantially as herein described and
illustrated.

Documents:

1980-del1997-abstract.pdf

1980-del1997-claims.pdf

1980-del1997-correspondence-others.pdf

1980-del1997-correspondence-po.pdf

1980-del1997-description (complete).pdf

1980-del1997-drawings.pdf

1980-del1997-form-1.pdf

1980-del1997-form-19.pdf

1980-del1997-form-2.pdf

1980-del1997-form-3.pdf

1980-del1997-gpa.pdf

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Patent Number

222418

Indian Patent Application Number

1980/DEL/1997

PG Journal Number

36/2008

Publication Date

05-Sep-2008

Grant Date

08-Aug-2008

Date of Filing

16-Jul-1997

Name of Patentee

THE CHIEF CONTROLLER, RESEARCH AND DEVELOPMENT.

Applicant Address

TECHNICAL CORDIN.DTE., B-341, SENA BHAWAN, DHQ P.O., NEW DELHI-110 011, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SHRI BISWAJYOTI BASU SCIENTIST 'C'	NAVAL MATERIALS RESEARCH LABORATORY, RESEARCH AND DEVELOPMENT ORGANISATION, MINISTRY OF DEFENCE, BOMBAY, INDIA.
2	SHRI SURYA MANI TRIPATHI JSO	NAVAL MATERIALS RESEARCH LABORATORY, RESEARCH AND DEVELOPMENT ORGANISATION, MINISTRY OF DEFENCE, BOMBAY, INDIA.
3	DR. DIPAK KUMAR BISWAS SCIENTIST F	NAVAL MATERIALS RESEARCH LABORATORY, RESEARCH AND DEVELOPMENT ORGANISATION, MINISTRY OF DEFENCE, BOMBAY, INDIA.

PCT International Classification Number

C22C 38/42

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA