CA2231435A1 - Thermal shock testing of crystalline materials - Google Patents
Thermal shock testing of crystalline materials Download PDFInfo
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- CA2231435A1 CA2231435A1 CA 2231435 CA2231435A CA2231435A1 CA 2231435 A1 CA2231435 A1 CA 2231435A1 CA 2231435 CA2231435 CA 2231435 CA 2231435 A CA2231435 A CA 2231435A CA 2231435 A1 CA2231435 A1 CA 2231435A1
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- crystalline material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M99/00—Subject matter not provided for in other groups of this subclass
- G01M99/002—Thermal testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/60—Investigating resistance of materials, e.g. refractory materials, to rapid heat changes
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- Pathology (AREA)
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
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Abstract
A testing apparatus (10) and method (20) that uses a controlled thermal gradient to develop high surface stresses in sapphire or other crystalline material (11) from which a window or dome (11) may be made. The thermal gradient is developed by preheating the crystalline material (11) to a predetermined temperature and then showering a side with water. By controlling the flow rate, temperature and spray pattern of the water and initial preheat temperature of the crystalline material (11), a controlled and predictable stress is imposed in the material.
Description
W 09~05939 PCTn~S97/13886 THERMAL SHOCK Tl :STING OF CRYSTALLINE MATERIALS
BACKGROUND
The present invention relates ~enr.r~lly to therrnal shock scle~ illg tests, andmore particularly, to an ~ ,.".~..c and a method of pelf~,llllillg thermal shock tests on crystalline m~tf~ ic such as sapphire.
Sapphire is an extremely strong material that unfolLul~lely is brittie and S whose strength can be rir~ctic~lly reduced by i.llp~,.r~ ions. Sapphire used to -- m~m-f~rtl-re infrared Ll".. ~ l;ng domes used in micciif~c and the like is crystal --grown in a process that oc~cion~lly forms il~ u-iLies and other flaws that can weaken the m~tf-ri~l Also, during m~r~ining and polishing processes. surface andsub-surface damage that weakens the m~trri~l are produced. There are three 10 procedures that may be used to assure that the integrity of a particular dome is adequate for missile flight conditions. These procedures include inspection, process controls. or acce~ ce testing. The small size of critical flaws and scratches and the Ll~s~uenl~lup~,~Lies of sapphire are such that visual incpectif n and other optical tests cannot economicallv be used to detect their presence. The state of the art in W O~&'U5~39 PCT~US97/13886 --process controls is also not believed to be economically feasible at this time, so acceptance testing is the most viable solution.
The closest known prior art relating to the present invention is a process currently used at Hughes Elcan Optical Technologies in which an infrared dome to be S tested is immer.eecl in liquid nitrogen, and following a cold soak therein. is inserted convex side first, into boiling water. An analysis of this procedure and test results has lead to the conclusion that stresses imposed by this process are minim~l and do not co.l~liLuLe a rigorous scrce~ g test. The reasons are that at low tf ~ e~ s, the thermal conductivity of sapphire is very high and heat ~ ~, to the boiling water is 10 impeded by the formation of ice orl the side of the dome ~ nt the water.
~mmersion processes have been used in the industry for flaw detection to test infrared domes as noted above and in a sirnilar manner for radome testing by the use of molten salts. Ev~ tion of the i i "., .~ ion method, however, indicates that it is also too benign of a test cl~vilu~ lcnt for domes that are int~n~ i for ~l.c-lle high speed 15 missile applications.
Accordingly, it is an objective of the present invention to provide for an ap~u~dLus and metnod for therrnal shock testing s~phirc and other crystalline materials. It is a further objective of the present invention to provide for an ap~aldL~ls and method for thermal shock testing ~aL)~hirc and other crystalline materials used as 20 infrared domes or windows in mi~:~i1es, and the like.
~- SUMMARY OF THE INVENTION
To meet the above and other objectives, the present invention provides for testing apparatus and a method that uses a controlled therrnal gradient to deveiop high 25 surface stresses in sapphire or other crystalline material from which an infrared window or dome may be made. The thermal gradient is developed by prçhe~tin~ the crystalline material to a preltr~ ;..ed tell~ dlule and then spraying one side with water from a fixture developed for this purpose. By controlling the flow rate, temperature and spray pattern of the water and initial preheat temy~dL~le of the -W O9~h3,~9 PCT~US97113886 crystalline material, predictable stress is imposed in the material. Tensile stresses are in~ ce~l on the sprayed surface.
More specifi~lly, the present apparatus that provides for therrnal shock testing of crystalline m~teri~l co~ ;ses a therrnal conditioning ch~mtter for S ~1~ he~ g the crystalline m~t.ori~l, and a test fixture for holding the ~lel1cdL~:d crystalline m~t~ri~l during testing. A water jet spray head is ~tt~.h.o~l to the fixture for spraying water onto a surface of the crystalline material. A water supply 12 is provided and a flow control valve is coupled between the water supply and the water jet spray head. A ~ supply gauge is provided for mollilo~ g the l)lc;~ ; of 10 the water supp}y, and a fixture prC~ulG gauge is provided for monitoring the ~ iUIc;
of the water at the water jet spray head.
The method in~ ies the steps of providing a water supply and providing a - test fixture for secnring the crystalline m~ri~l during testing. The crystalline ms-t~ri~l that is to be tested is disposed in a thermal conditioning chamber. The 15 crystalline is then preheated to a pred~ f~ elevated t~lnl~e~a~ The preheatedcrystalline mz~teriz~l is disposed on the test fixture. A selecte~l surface of the ~ eaLed crystalline mztt-orizll is sprayed with water from the water supply to thPrrn~lly shock it.
The present aL~dldlus and method may be used to verify the structural y of sapphire or other crystalline material domes and windows used on 20 mi~ os, for exarnple. The present testing method screens out infrared ~pl~
domes that are intrinsically weak due to impurities and flaws or that have been mz3ge~1 during m~f~.hining and polishing. The present testing method is an effe-ctive tool for evaluating the strength of damaged domes, and may be used to correlate surface damage to strength of each dome. Ultimately the test may be used to assess 25 the suitability of a flawed dome for safe and sn~ceccful missile operation.
The test method described herein accomplishes this goa} by subJecting the ~hhe material to stress levels that are expected to occur during missile flight.Stresses intlnt~e~ by the present testing method are tensile in nature and are aat the cooled surface of the dome where the highest stresses occur during 30 use. ~requently, it is the surface of the dome that is weakest as a result of an imperfect fini~hing operation or due to surface damage sn~t~in-ori during captive flight W O ~J'~ g ~ PCT~US97/13886 ~- =
operations. Currently there is no other test or process known that ~ tely assures the structural integrity of highly stressed crystalline domes.
BRIEF DESCRIPTION OF THE DRAW1NGS ,~
The various features and advantages of the present invention may be more readily understood with reference to the following ~l~t~ile~ description taken in conjunction with the ~-co~ yillg drawings, wlle~clll like le~,~"lCe ~ci~,n~tç like ~LIur. Iu~al elements, and ;n which: .
Fig. 1 i11~1str~t~e a sch~m~tic of testing d~JaldLLls in acco.,~}ance with the l 0 present invention;
Fig. 2 illustrates a flow ~ r~m of a test method or procedure in accordance with the present invention; and Fig. 3 illustrates a flow diagram of a development and calibration test method used with the present invention.
DETA~LED DESCRIPTION
g to the drawing figures, Fig. l illu~LI~le~ a s< ~lem~t;c~ of testing a~l dlalus 10 in accordance with the present invention. The specific embodiment of the test apparatus l0 shown in Fig. l is used to test inner surfaces of crystalline m~t~ri~1 11. However, it is to be understood that the present invention may be used to test other snrfiqe~ in~lt1-lin~; interior and exterior curved surfaces or flat s-1rf~ce~, and __ the like. Consequently, the embodiment of the present invention shown in Fig. l -should not be taken as limitin~
The testing a~-d-dL.Is 10 comprises a thermal conditioning chamber 18 used to preheat the crysta}line material 1 l that is to be tested. The crystalline material l l may colll~.ise a missile dome l 1, for example. A test fixture l 9 is provided for holding the crystalline m~tPri~ during testing. The crystalline material l l or dome l l that is to be tested is disposed in the thermal conditionin~ chatnber l 8 so that it may be preheated to a pre~let~rrninecl elevated Le,llpc,dL-Ire. A water supply 12 is coupled by way of a ball valve 14 and a flow control valve l 5 to a water jet spray head l 6 qch~cl to the fixture l 9 A pressure supply gauge 13 is provided to monitor the CA 0223143~ 1998-03-09 W O 98/OS939 - PCT~US97/13886 pressure of the water supply l 2 and a fixture ~ ul~ gauge 17 is provided to monitor the pressure of the water at the water jet spray head 16.
The present invention also comprises a test method 20 by which an hl~ dled or other dome 11 or window 11 used in a missile, for example, may be tested to verify 5 material strength and to assure that no significant material or surface flaws exist that could con.l,.ulllise the integrity of the dome 11 or window I 1. Fig. 2 illustrates a flûw diagram ûf the test method 20 in accordance with the present invention.
In accordance with the present test method 20, a water supply is provided, illustrated by step 21. A test fixture for securing crystalline material 1 1 during testing 10 is provided, illustrated by step 22. Crystalline m~tt~ri~l 11, such as an infrared dome 11, that to be tested is disposed in the therrnal conditioning chamber 18, illustrated by step 23. The crystalline material 11 or dome 11 is preheated to a pre~PtPrrninPcl elevated le---~e.~lu-e, illustrated by step 24. For domes 11 used on ASRAAM-typemissiles, for exarnple, Lclllp~-lalur~s range from 150 to 240 degrees Celsius, and these 15 t~~l~ d~ ,S are used herein for ii~ tr~tive purposes. Once the crystalline mz-tc i~l 11 or dome 11 is elevated to the desired precletPrmin~cl preheat te~ ldLule, it is moved from the conditioning charnber 18 and affixed to or otherwise disposed on the test fixture 19, illustrated by step 25. lmmediately after seCl~ring the crystalline material 11 or dome 11 in place on the fixture 19, the water supply flow control valve 20 15 is turned on to shower a select~cl surface, such as the inside surface of the dome 11, for example, with water, illustrated by step 26 to tht~rrn~lly shock the crystalline - ~ material 11 or dome 11.
The present testing alJpdldllls 10 and method 20 uses a controlled thermal gradient produced by the shower of water to develop high surface stresses in sapphire 25 or other crystalline materials 11 from which a window or dome 11 may be made. The thermal gradient is developed by prPh~ting the crystalline material 11 to the predetermined temperature and then spraying one side of it with water. By controlling the flow rate, temperature and spray pattern of the water and preheated t~ y~d~Lre of the crystalline material 11, a very controlled and predictable stress is 30 imposed in the material. The stresses developed in the crystalline material 11 are primarily tensile in nature on the surface that is exposed to the shower of water.
W O~ 5,39 PCT~US97/13886 --6 ~ _ The present test method 20 has been verified as delineated in method 30, with a combination of empirical test data and analytical predictions. Thermocouple test data using an ~umimlm calorimeter dome 1 la was used to derive heat flux Psctr~ctc~ from the hot al--min--m calorimeter dome 1 la by the cold water during the test.
5After obL~il~ing the heat flux as a function of l~my~laLu~, ofthe al.... ,.~ .".
calorimet~r dome 1 la, a finite difference therrnal model of a sa~ e dome 11 is employed to sim~ t~ the thermal response of an actual s~hile dome 11 to tne ther!mal test. This is achieved by applying the heat flux derived from the test data to the model of the ~ hir~; dome 11. The time-te~ ue-~lure history of the sapphire 10 dome 1 1 is ~ ~ed onto a structural model of the sapphire dome 1 1, from which predicted stresses are obtained. This method 30 is illustrated .sehl-m~tically in Fig. 3.
The method 30 illn~tr~tf~ in ~ig. 3 is as ~ollows. First, an al-)-.lil....,. dome I la is instrnment~d with thermocou,ples, il~ tr~t~l by step 31. Data is then acquired for the ~ Illmimmn dome I 1 a during the above-described water jet test~ tr~te(l by 15 step 32. A heat flux versus dome te~ L~e curve is then obtained from test data, ill~l~tr~t~d by step 33. By applying fimrl~mt?nt~l thermodynamic concepts, the heat flux is derived from the rate of tr "1'~ ., e change of the c~ . ;"~ t~ . dome I la measured during the test and the m~t~ri~l ~ro~ ies for the ~h"..illl."~ dome 1 la from the following formula:
~0 Q = p*L*Cp*dT/dt, where, ~ is heat flux in W/cm2, p is the density of all1,..,..1-,~I calorimeter dome 1 1 in ~ ~ gm/cm3, L is the thickness of the ~I.~.. Iil 11~1~ l calorimeter dome I 1 in cm, Cp is the-heat capacity of the ah-rnin--m calorimeter dome 1 1 in Joules/gm-degrees Celsius, and dT
is the telllpelaLuic change over time interval, dt, in degrees Celsius.
A thermal model of the alnmin--m dome I la is created~ and the heat flux versus dome telllpc.~lLule derived ~rom the test data is imposed on the therrnal model of ~he ~Inminnm dome I la~ illustrated by step 34. ~hen it is verified that model predictions match test data for the al--minl-m dome, illustrated by step 35. A ~d~hilc or other crystalline dome thermal model is generated by chzln~in~ material ~lop~,.Lies in the al--minllm dome model. illustrated by step 36. Temperature versus time da~a for the sapphire dome (position through the thickness) is then determined using the _ ~ 7 ~
model. illustrated by step 37. A structural model of the sawllilG dome 11 is then generated, illuskated by step 38. Water jet test stress levels versus time are then predicted, ill~ ed by step 39. Then it is verified that stress levels of the mo-~ele~
s~ ilG dome 11 meet pretest goals, illustrated bY step 40.
The present invention was developed for use in testing domes used on ASRAAM mi.c.cile~. Without the present testing ~p~3~dlus 10 and method 20, U-.;LU~dlly inferior domes 11 could pass visual and optical tests, but have w~k~ c~s that would only be exposed (perhaps catastrophically) during missile flight. Although developed specifically to evaluate dome integrity for missile flight, other applications of the present invention include mea~ulGlnent of the reduction in dome strength due to surface damage, and measurement of dome strength for different fabrication ~ processes. These ~.c~e~, .. e. 1l~ are useful in evaluating missile seekers that use a crystalline grown ceramic m~tP~l as the dome 11. Other applications include structural verification of m~t~ri~l~ grown in a crystalline process.
Thus, an ~cLlus and method of therrnal shock testing crystalline m~t~ri~
such as s~pllil., used as infrared domes or windows in mi~ s, and the like, has been disclosed. It is to be l~n~l~orstood that the described embo~lim~t.~ are merely illustrative of some of the many specific embo~imt?ntc which represent applications of the principles of the present invention. Clearly, numerous and other arrangements can 20 be readily devised by those skilled in the art without departing from the scope of the invention.
BACKGROUND
The present invention relates ~enr.r~lly to therrnal shock scle~ illg tests, andmore particularly, to an ~ ,.".~..c and a method of pelf~,llllillg thermal shock tests on crystalline m~tf~ ic such as sapphire.
Sapphire is an extremely strong material that unfolLul~lely is brittie and S whose strength can be rir~ctic~lly reduced by i.llp~,.r~ ions. Sapphire used to -- m~m-f~rtl-re infrared Ll".. ~ l;ng domes used in micciif~c and the like is crystal --grown in a process that oc~cion~lly forms il~ u-iLies and other flaws that can weaken the m~tf-ri~l Also, during m~r~ining and polishing processes. surface andsub-surface damage that weakens the m~trri~l are produced. There are three 10 procedures that may be used to assure that the integrity of a particular dome is adequate for missile flight conditions. These procedures include inspection, process controls. or acce~ ce testing. The small size of critical flaws and scratches and the Ll~s~uenl~lup~,~Lies of sapphire are such that visual incpectif n and other optical tests cannot economicallv be used to detect their presence. The state of the art in W O~&'U5~39 PCT~US97/13886 --process controls is also not believed to be economically feasible at this time, so acceptance testing is the most viable solution.
The closest known prior art relating to the present invention is a process currently used at Hughes Elcan Optical Technologies in which an infrared dome to be S tested is immer.eecl in liquid nitrogen, and following a cold soak therein. is inserted convex side first, into boiling water. An analysis of this procedure and test results has lead to the conclusion that stresses imposed by this process are minim~l and do not co.l~liLuLe a rigorous scrce~ g test. The reasons are that at low tf ~ e~ s, the thermal conductivity of sapphire is very high and heat ~ ~, to the boiling water is 10 impeded by the formation of ice orl the side of the dome ~ nt the water.
~mmersion processes have been used in the industry for flaw detection to test infrared domes as noted above and in a sirnilar manner for radome testing by the use of molten salts. Ev~ tion of the i i "., .~ ion method, however, indicates that it is also too benign of a test cl~vilu~ lcnt for domes that are int~n~ i for ~l.c-lle high speed 15 missile applications.
Accordingly, it is an objective of the present invention to provide for an ap~u~dLus and metnod for therrnal shock testing s~phirc and other crystalline materials. It is a further objective of the present invention to provide for an ap~aldL~ls and method for thermal shock testing ~aL)~hirc and other crystalline materials used as 20 infrared domes or windows in mi~:~i1es, and the like.
~- SUMMARY OF THE INVENTION
To meet the above and other objectives, the present invention provides for testing apparatus and a method that uses a controlled therrnal gradient to deveiop high 25 surface stresses in sapphire or other crystalline material from which an infrared window or dome may be made. The thermal gradient is developed by prçhe~tin~ the crystalline material to a preltr~ ;..ed tell~ dlule and then spraying one side with water from a fixture developed for this purpose. By controlling the flow rate, temperature and spray pattern of the water and initial preheat temy~dL~le of the -W O9~h3,~9 PCT~US97113886 crystalline material, predictable stress is imposed in the material. Tensile stresses are in~ ce~l on the sprayed surface.
More specifi~lly, the present apparatus that provides for therrnal shock testing of crystalline m~teri~l co~ ;ses a therrnal conditioning ch~mtter for S ~1~ he~ g the crystalline m~t.ori~l, and a test fixture for holding the ~lel1cdL~:d crystalline m~t~ri~l during testing. A water jet spray head is ~tt~.h.o~l to the fixture for spraying water onto a surface of the crystalline material. A water supply 12 is provided and a flow control valve is coupled between the water supply and the water jet spray head. A ~ supply gauge is provided for mollilo~ g the l)lc;~ ; of 10 the water supp}y, and a fixture prC~ulG gauge is provided for monitoring the ~ iUIc;
of the water at the water jet spray head.
The method in~ ies the steps of providing a water supply and providing a - test fixture for secnring the crystalline m~ri~l during testing. The crystalline ms-t~ri~l that is to be tested is disposed in a thermal conditioning chamber. The 15 crystalline is then preheated to a pred~ f~ elevated t~lnl~e~a~ The preheatedcrystalline mz~teriz~l is disposed on the test fixture. A selecte~l surface of the ~ eaLed crystalline mztt-orizll is sprayed with water from the water supply to thPrrn~lly shock it.
The present aL~dldlus and method may be used to verify the structural y of sapphire or other crystalline material domes and windows used on 20 mi~ os, for exarnple. The present testing method screens out infrared ~pl~
domes that are intrinsically weak due to impurities and flaws or that have been mz3ge~1 during m~f~.hining and polishing. The present testing method is an effe-ctive tool for evaluating the strength of damaged domes, and may be used to correlate surface damage to strength of each dome. Ultimately the test may be used to assess 25 the suitability of a flawed dome for safe and sn~ceccful missile operation.
The test method described herein accomplishes this goa} by subJecting the ~hhe material to stress levels that are expected to occur during missile flight.Stresses intlnt~e~ by the present testing method are tensile in nature and are aat the cooled surface of the dome where the highest stresses occur during 30 use. ~requently, it is the surface of the dome that is weakest as a result of an imperfect fini~hing operation or due to surface damage sn~t~in-ori during captive flight W O ~J'~ g ~ PCT~US97/13886 ~- =
operations. Currently there is no other test or process known that ~ tely assures the structural integrity of highly stressed crystalline domes.
BRIEF DESCRIPTION OF THE DRAW1NGS ,~
The various features and advantages of the present invention may be more readily understood with reference to the following ~l~t~ile~ description taken in conjunction with the ~-co~ yillg drawings, wlle~clll like le~,~"lCe ~ci~,n~tç like ~LIur. Iu~al elements, and ;n which: .
Fig. 1 i11~1str~t~e a sch~m~tic of testing d~JaldLLls in acco.,~}ance with the l 0 present invention;
Fig. 2 illustrates a flow ~ r~m of a test method or procedure in accordance with the present invention; and Fig. 3 illustrates a flow diagram of a development and calibration test method used with the present invention.
DETA~LED DESCRIPTION
g to the drawing figures, Fig. l illu~LI~le~ a s< ~lem~t;c~ of testing a~l dlalus 10 in accordance with the present invention. The specific embodiment of the test apparatus l0 shown in Fig. l is used to test inner surfaces of crystalline m~t~ri~1 11. However, it is to be understood that the present invention may be used to test other snrfiqe~ in~lt1-lin~; interior and exterior curved surfaces or flat s-1rf~ce~, and __ the like. Consequently, the embodiment of the present invention shown in Fig. l -should not be taken as limitin~
The testing a~-d-dL.Is 10 comprises a thermal conditioning chamber 18 used to preheat the crysta}line material 1 l that is to be tested. The crystalline material l l may colll~.ise a missile dome l 1, for example. A test fixture l 9 is provided for holding the crystalline m~tPri~ during testing. The crystalline material l l or dome l l that is to be tested is disposed in the thermal conditionin~ chatnber l 8 so that it may be preheated to a pre~let~rrninecl elevated Le,llpc,dL-Ire. A water supply 12 is coupled by way of a ball valve 14 and a flow control valve l 5 to a water jet spray head l 6 qch~cl to the fixture l 9 A pressure supply gauge 13 is provided to monitor the CA 0223143~ 1998-03-09 W O 98/OS939 - PCT~US97/13886 pressure of the water supply l 2 and a fixture ~ ul~ gauge 17 is provided to monitor the pressure of the water at the water jet spray head 16.
The present invention also comprises a test method 20 by which an hl~ dled or other dome 11 or window 11 used in a missile, for example, may be tested to verify 5 material strength and to assure that no significant material or surface flaws exist that could con.l,.ulllise the integrity of the dome 11 or window I 1. Fig. 2 illustrates a flûw diagram ûf the test method 20 in accordance with the present invention.
In accordance with the present test method 20, a water supply is provided, illustrated by step 21. A test fixture for securing crystalline material 1 1 during testing 10 is provided, illustrated by step 22. Crystalline m~tt~ri~l 11, such as an infrared dome 11, that to be tested is disposed in the therrnal conditioning chamber 18, illustrated by step 23. The crystalline material 11 or dome 11 is preheated to a pre~PtPrrninPcl elevated le---~e.~lu-e, illustrated by step 24. For domes 11 used on ASRAAM-typemissiles, for exarnple, Lclllp~-lalur~s range from 150 to 240 degrees Celsius, and these 15 t~~l~ d~ ,S are used herein for ii~ tr~tive purposes. Once the crystalline mz-tc i~l 11 or dome 11 is elevated to the desired precletPrmin~cl preheat te~ ldLule, it is moved from the conditioning charnber 18 and affixed to or otherwise disposed on the test fixture 19, illustrated by step 25. lmmediately after seCl~ring the crystalline material 11 or dome 11 in place on the fixture 19, the water supply flow control valve 20 15 is turned on to shower a select~cl surface, such as the inside surface of the dome 11, for example, with water, illustrated by step 26 to tht~rrn~lly shock the crystalline - ~ material 11 or dome 11.
The present testing alJpdldllls 10 and method 20 uses a controlled thermal gradient produced by the shower of water to develop high surface stresses in sapphire 25 or other crystalline materials 11 from which a window or dome 11 may be made. The thermal gradient is developed by prPh~ting the crystalline material 11 to the predetermined temperature and then spraying one side of it with water. By controlling the flow rate, temperature and spray pattern of the water and preheated t~ y~d~Lre of the crystalline material 11, a very controlled and predictable stress is 30 imposed in the material. The stresses developed in the crystalline material 11 are primarily tensile in nature on the surface that is exposed to the shower of water.
W O~ 5,39 PCT~US97/13886 --6 ~ _ The present test method 20 has been verified as delineated in method 30, with a combination of empirical test data and analytical predictions. Thermocouple test data using an ~umimlm calorimeter dome 1 la was used to derive heat flux Psctr~ctc~ from the hot al--min--m calorimeter dome 1 la by the cold water during the test.
5After obL~il~ing the heat flux as a function of l~my~laLu~, ofthe al.... ,.~ .".
calorimet~r dome 1 la, a finite difference therrnal model of a sa~ e dome 11 is employed to sim~ t~ the thermal response of an actual s~hile dome 11 to tne ther!mal test. This is achieved by applying the heat flux derived from the test data to the model of the ~ hir~; dome 11. The time-te~ ue-~lure history of the sapphire 10 dome 1 1 is ~ ~ed onto a structural model of the sapphire dome 1 1, from which predicted stresses are obtained. This method 30 is illustrated .sehl-m~tically in Fig. 3.
The method 30 illn~tr~tf~ in ~ig. 3 is as ~ollows. First, an al-)-.lil....,. dome I la is instrnment~d with thermocou,ples, il~ tr~t~l by step 31. Data is then acquired for the ~ Illmimmn dome I 1 a during the above-described water jet test~ tr~te(l by 15 step 32. A heat flux versus dome te~ L~e curve is then obtained from test data, ill~l~tr~t~d by step 33. By applying fimrl~mt?nt~l thermodynamic concepts, the heat flux is derived from the rate of tr "1'~ ., e change of the c~ . ;"~ t~ . dome I la measured during the test and the m~t~ri~l ~ro~ ies for the ~h"..illl."~ dome 1 la from the following formula:
~0 Q = p*L*Cp*dT/dt, where, ~ is heat flux in W/cm2, p is the density of all1,..,..1-,~I calorimeter dome 1 1 in ~ ~ gm/cm3, L is the thickness of the ~I.~.. Iil 11~1~ l calorimeter dome I 1 in cm, Cp is the-heat capacity of the ah-rnin--m calorimeter dome 1 1 in Joules/gm-degrees Celsius, and dT
is the telllpelaLuic change over time interval, dt, in degrees Celsius.
A thermal model of the alnmin--m dome I la is created~ and the heat flux versus dome telllpc.~lLule derived ~rom the test data is imposed on the therrnal model of ~he ~Inminnm dome I la~ illustrated by step 34. ~hen it is verified that model predictions match test data for the al--minl-m dome, illustrated by step 35. A ~d~hilc or other crystalline dome thermal model is generated by chzln~in~ material ~lop~,.Lies in the al--minllm dome model. illustrated by step 36. Temperature versus time da~a for the sapphire dome (position through the thickness) is then determined using the _ ~ 7 ~
model. illustrated by step 37. A structural model of the sawllilG dome 11 is then generated, illuskated by step 38. Water jet test stress levels versus time are then predicted, ill~ ed by step 39. Then it is verified that stress levels of the mo-~ele~
s~ ilG dome 11 meet pretest goals, illustrated bY step 40.
The present invention was developed for use in testing domes used on ASRAAM mi.c.cile~. Without the present testing ~p~3~dlus 10 and method 20, U-.;LU~dlly inferior domes 11 could pass visual and optical tests, but have w~k~ c~s that would only be exposed (perhaps catastrophically) during missile flight. Although developed specifically to evaluate dome integrity for missile flight, other applications of the present invention include mea~ulGlnent of the reduction in dome strength due to surface damage, and measurement of dome strength for different fabrication ~ processes. These ~.c~e~, .. e. 1l~ are useful in evaluating missile seekers that use a crystalline grown ceramic m~tP~l as the dome 11. Other applications include structural verification of m~t~ri~l~ grown in a crystalline process.
Thus, an ~cLlus and method of therrnal shock testing crystalline m~t~ri~
such as s~pllil., used as infrared domes or windows in mi~ s, and the like, has been disclosed. It is to be l~n~l~orstood that the described embo~lim~t.~ are merely illustrative of some of the many specific embo~imt?ntc which represent applications of the principles of the present invention. Clearly, numerous and other arrangements can 20 be readily devised by those skilled in the art without departing from the scope of the invention.
Claims (9)
1. Apparatus (10) for thermal shock testing crystalline material (11), said apparatus (10) characterized by:
a thermal conditioning chamber (18) for preheating the crystalline material (11);
a test fixture (19) for holding the preheated crystalline material (11) that is to be tested;
a water jet spray head (16) attached to the fixture (19) for spraying water onto a surface of the crystalline material (11);
a water supply (12);
a flow control valve (15) coupled between the water supply (12) and the water jet spray head (16);
a pressure supply gauge (13) for monitoring the pressure of the water supply (12); and a fixture pressure gauge (17) for monitoring the pressure of the water at the water jet spray head (16).
a thermal conditioning chamber (18) for preheating the crystalline material (11);
a test fixture (19) for holding the preheated crystalline material (11) that is to be tested;
a water jet spray head (16) attached to the fixture (19) for spraying water onto a surface of the crystalline material (11);
a water supply (12);
a flow control valve (15) coupled between the water supply (12) and the water jet spray head (16);
a pressure supply gauge (13) for monitoring the pressure of the water supply (12); and a fixture pressure gauge (17) for monitoring the pressure of the water at the water jet spray head (16).
2. The apparatus (10) of Claim 1 wherein the crystalline material (11) is characterized by a dome (11).
3. The apparatus (10) of Claim 1 wherein the crystalline material (11) is characterized by a sapphire dome (11).
4. The apparatus (10) of Claim 1 further characterized by a plurality of valves (14, 15) serially coupled between the water supply (12) and the water jet spray head (16).
5. A method (20) for thermal shock testing crystalline material (11), said method (20) characterized by the steps of:
providing (21) a controlled water supply;
providing (22) a test fixture (19) for securing the crystalline material (11) during testing;
disposing (23) the crystalline material (11) that to be tested in a thermal conditioning chamber (18);
preheating (24) the crystalline material (11) to a predetermined elevated temperature;
disposing (25) the preheated crystalline material (11) on the test fixture (19);showering (26) a selected surface of the preheated crystalline material (11) with water from the water supply to thermally shock the crystalline material (11).
providing (21) a controlled water supply;
providing (22) a test fixture (19) for securing the crystalline material (11) during testing;
disposing (23) the crystalline material (11) that to be tested in a thermal conditioning chamber (18);
preheating (24) the crystalline material (11) to a predetermined elevated temperature;
disposing (25) the preheated crystalline material (11) on the test fixture (19);showering (26) a selected surface of the preheated crystalline material (11) with water from the water supply to thermally shock the crystalline material (11).
6. The method (20) of Claim 4 wherein the crystalline material (11) is characterized by a dome (11).
7. The method (20) of Claim 4 wherein the predetermined elevated temperature is about (17)0 degrees Celsius.
8. The method (20) of Claim 4 wherein the predetermined elevated temperature is in the range of from 150 to 240 degrees Celsius.
9. The method (20) of Claim 6 wherein a selected surface of the dome (11) is showered with water.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US69120196A | 1996-08-05 | 1996-08-05 | |
| US08/691,201 | 1996-08-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2231435A1 true CA2231435A1 (en) | 1998-02-12 |
Family
ID=24775557
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2231435 Abandoned CA2231435A1 (en) | 1996-08-05 | 1997-08-05 | Thermal shock testing of crystalline materials |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2231435A1 (en) |
| NO (1) | NO981538L (en) |
| WO (1) | WO1998005939A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19845594A1 (en) * | 1998-10-05 | 2000-04-06 | Bosch Gmbh Robert | Device and method for measuring the strength and thermal shock behavior of material samples |
| CN104181066A (en) * | 2013-05-27 | 2014-12-03 | 海洋王（东莞）照明科技有限公司 | Detection device for transparent member of lamp |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4733973A (en) * | 1986-05-12 | 1988-03-29 | American Glass Research, Inc. | Method and apparatus for testing glassware |
-
1997
- 1997-08-05 CA CA 2231435 patent/CA2231435A1/en not_active Abandoned
- 1997-08-05 WO PCT/US1997/013886 patent/WO1998005939A1/en active Application Filing
-
1998
- 1998-04-03 NO NO981538A patent/NO981538L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1998005939A1 (en) | 1998-02-12 |
| NO981538D0 (en) | 1998-04-03 |
| NO981538L (en) | 1998-04-03 |
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