FOURTH PROGRESS REPORT TO MATERIALS LABORATORY WRIGHT AIR DEVELOPMENT CENTER ON EFFECT OF PRIOR CREEP ON MECHANICAL PROPERTIES OF AIRCRAFT STRUCTURAL METALS by J. V. GJuck H. R.' oorhees J. W. Freeman Project 2498 Air Force Contract No. AF33(616)-3368 Task No. 73605 October 20,- 19 56

SUMMARY This report covers progress under Contract AF33(616)-3368 for the period from August 21, 1956 to October 20, 1956 on a study of the effects of prior creep on the short-time mechanical properties of three aircraft sheet metals. The materials under study are: 2024-T86 aluminum alloy; C1 O1M titanium alloy; and 17-7PH precipitation hardening stainless steel. Delivery of all experimental materials has now been completed with the receipt of the C-11OM titanium alloy. Tests of room temperature tensile properties of 17-7PH after exposure to two percent total deformation in 100 hours in the range between 600~ and 900~F indicate that the tensile and yield strengths are increased over the increase previously reported for unstressed exposure. The maximum effect occurs at 800-850~F. At temperatures from 600 to 750~F, stressed exposure resulted in a loss of ductility not commensurate with the effect on tensile strength, The determination of the total deformation properties of the 2024-T86 alloy has been completed and the stressed exposure tests of this material are in progress, The data indicate that increasing time, temperature and total deformation result in a decrease in tensile and yield strength. Tensile tests of the unexposed material are complete at 350~ and 400~F. The effects of unstressed exposure on the room temperature hardness and tensile-impact properties show a decrease in strength with time and temperature of exposure.

2 In this investigation it was decided to fix the timee temperature, and stress of testing. Thus, deformation obtained must be accepted realizing that it might vary somewhat from the nominally specified value, Test stresses are determined from curves of stress versus time for a given total deformation, established for each material at each testing temperature. The generality of the results was ensured by running replicate tests on two random samples for each exposure condition and by establishing the value of the normal properties of the material from 9 or 10 samples chosen randomly from the various sheets of material. All the materials were procured as approximately 0. 064-inch thick sheet, The aluminum and stainless steel alloys were specified to be tested in the direction crosswise to the sheet rolling direction, while the titanium alloy is to be tested parallel to the rolling direction, The aluminum and titanium alloys are to be tested in the conditions as received from the manufacturers. The titanium alloy was furnished as hot rolled and annealed, while the 2024-T86 aluminum alloy was cold worked and artificially aged by the manufacturer. The stainless steel, 17-7PH is being tested in the TH 1050 condition, a double aging treatment at 1400'F and then 1050OF, which is performed at the University. The current contract places emphasis of testing effort on evaluation of the aluminum alloy. In the case of the stainless steel, a survey is being made of the effects of prior creep to 2 percent total deformation in 100 hours on the room-temperature tensile properties. These exposures are being carried out at 50~F temperature intervals between 600~ and 900F,.

3 TEST MATERIALS During the period covered by this report the C-110M titanium alloy was receivedy completing the delivery of all test.materials ordered on this contract, The specifications followC- 11M Titanium Alloy Eleven sheets of annealed C-1lOM titanium alloy were received from the Rem-Cru Titanium Corporations The sheet dimensions were 0, 064 inches thick by 30/36 inches wide by 60/90 inches long. The material was all from heat number A1172600. The chemical analysis furnished by the producer follows: Element Percent (by weight) Manganese 7e 9 Carbon 1, 0 Nitrogen 02 Hydrogen 009.3 Titanium b alanc e SPECIMEN PREPAR. A TION The sampling procedure used for the preparation of specemens for this investigation was designed to, ra:Mndomnixze the test reJsul.ts w.ith respect to, but:h sheettosheet variations and the variatlioans withtin an indi-vidua sheet, Since the as-received sheet sizes of the mnaterials diffllered, the physical details olf the sampling schemes differed, although the principle of selection was the sa.me,, For each material three sheets were arbitrarily selected, Each sheet was divided into panels about 5 inches wide, and the panels themselves subdivided into l-inch wide specimen blanks, Within the panelt the specirmen blanks were so arranged that material was sampled from different locati ons across the panel

4 width. Thus, the sampling pattern with respect to the width of the sheet repeated itself every 5 inches over the length of the sheet. Each specimen was labeled with a code number indicating sheet number, panel numbers and specimen position within the panel, Reference to Figure 1 in the case of the 2024-T86 aluminum alloy and to Figures 2 and 3 in the case of the 17-7PH alloy makes it possible to establish the location of any of the test specimens cited in the section of Results. The dimensions of the various test specimens used are indicated in Figure 4, The specimens for mechanical tests were designed so that they could be cut from creep specimens following the desired exposure. For the exposure itself, the width of the gage section of the creep specimen was machined 0. 030 inches oversize in order that after subsequent remachining the tests would measure the properties of the sheet material itself and not include the particular edge effectss if any, associated with the exposure of the specimen. In the period covered by this report, evaluation of a notched tension-impact specimen was initiated. The dimensions of the proposed specimen are indicated in Figure 5. The specimen was designed to be machined from a creep-exposure specimen. The notched tension-impact specimen was prepared to the major dimensions using standard procedures. Following this, a flat-bottomed V-groove was ground into each edge of the specimen. During this operation the specimen was held in a special fixture so that the location of the notches could be accurately controlled, Next, the center of each flat was nicked with a sharp grinding wheel. Finally, the nicked flat was lapped to the final width and root radius using a lapping compound and a phosphor bronze wire whose radius was slightly under the final radius desired for the notch. For the notch prepared to the dimensions indicated in Figure 5 the theoretical stress concentration factor9 Kt, is equal to 1. 65.

5 TEST EQUIPMENT AND PROCEDURES Equipment used for creep-exposures, tensile tests and tension-impact tests was discussed in the first two progress reports. In the period covered by this report the compression test fixture which was described in the third report was modified slightly and the extensometer system for tension and compression tests was rebuilt. In addition, the furnace for elevated-temperature tests was operated successfully. Compression Test Equipment The original design of the compression test fixture, adapted from that of Flanigan et al (1)i consisted of a base, a pair of adjustable guide blocks and a loading ram. The original guide blocks were smooth surfaced. During the initial tests of this unit it was found to be an art to obtain reproducible stressstrain curves with respect to both slope and proportional limit. A report on compression testing techniques from the Titanium Metallurgical Laboratory at Batelle Memorial Institute (2) led to modification of the compression guide blocks. The results of Kotchanik et al were cited to show that values of compressive modulus (slope of the stress strain curve) were independent of supporting force when the guide blocks contained off-set grooves. Accordingly, a set of grooves off-set from each other were machined into the surface of the guide blocks. These are shown in Figure 6. The second modification of the equipment was essentially procedural. According to Kotchanik et al the compressive yield strength was found to have a critical relationship to the supporting force. Consequently, the use of a torque wrench was introduced in tightening the guide blocks preparatory to running the tests, In this way, a moderate and consistent supporting force of from 2 to 4inch pounds could be easily used for all tests.

6 These modifications of the compression test equipment, together with the use of the redesigned extensometer system, simplified the task of obtaining compression test stress-strain data. Extensometer System / The original design of the extensometer system for compression tests and elevated-temperature tensile tests was a rod and tube assembly fastened to the edges of the specimen gage section by tungsten carbide-tipped screws. In this design (3) the extension was transmitted from one side of the specimen only and was sensitive to whether or not the sides of the specimen were parallel and to the axiality of the load application. The relative motion of the rod and tube was picked up by a microformer-type strain gage and recorded automatically. After initial experience with this equipment the desirability of an averagingtype extensometer was recognized and the system accordingly modified. The modified system retains the rod and tube principle but transmits the deformation of the specimen through an averaging linkage. The system as set up for a compression test is shown in Figure 7. The motion of the two gage screw assemblies is transmitted by sets of flat extensometer bars. At the lower ends of these bars are two cross pieces —one attached to a rod and the other containing a tube. The ends of the cross pieces are grooved to fit a pin brazed to the lower end of the extensometer bar, This acts in much the same manner as a knife edge. A spring maintains the seat of the pin in the cross piece. Finally, the microformer pickup is attached to the rod and tube. The details of the lower end assembly are shown in Figure 8. Also essential to this system is the open frame that forms the base for the compression test set-up and which is drilled and tapped at each end so that it can be included in the specimen gripping assembly for tensile tests. The purpose of

7 this frame is to permit the attachment of the microformer to the rod and tube on the center line of the compression or tension axis. This system had been successfully used for obtaining stress-strain curves at room temperature in both tension and compression and at elevated temperature in tension. The extensometer was checked by comparing stress-strain curves obtained with it at room temperature against those in which the microformer was attached directly to the specimen. The results showed excellent agreement. Elevated-Temperature Tensile Tests The elevated-temperature tensile tests have been run in a wire-wound resistance furnace with a 5-inch diametef core having sufficient clearance for the extensometer assembly. Difficulties in obtaining temperature distribution over the specimen gage length are minimized through the use of a slotted transite shield placed over the top opening after the specimen holding assembly is inserted. In addition, the furnace windings were designed to provide a closer spacing at the bottom of the furnace than at the top to compensate for differences in heat loss. With reasonable care a temperature distribution of 2 - 3~F over the 2-inch gage section was found possible at temperatures of 350~ to 500~F. At higher temperatures, preliminary tests indicate that it may be necessary to shunt a portion of the winding. However, the establishment of proper temperature distribution should not prove unduly difficult,

8 RESULTS AND DISCUSSION Stressed Exposure Tests -— 17-7PH Alloy By mutual agreement between the University and WADC the first phase of the evaluation of the 17-7PH alloy was a survey of the effects on the room-temperature tensile properties of elevated temperature stressed exposure to two percent total deformation in 100 hours. The exposure temperatures were fixed at 50~F increments between 600~ and 900~F. The results of this study are summarized in Table 1 together with comparative data for samples given unstressed exposure for the same time period. A plot of tensile strength, yield strength, elongation, and hardness (all taken at room temperature) versus exposure temperature for stressed or unstressed exposure is presented in Figure 9. At least two tests were run for each condition. The effects of both stressed or unstressed exposure were to raise the tensile and yield strengths over the as-treated value. The stressed exposure raised the strength to a greater extent than did the unstressed exposure, with the maximum effect for both occurring at about 850~F. The strengthening effect of stressed exposure over unstressed exposure appears to be greater in the case of the yield strength than for tensile strength. The effects of the exposures on the hardness and elongation were contrary to the trends indicated by the tensile and yield strengths. At the lower end of the range of exposure temperature the elongation was greatly reduced by stressed exposure. At 800~F the elongation of the unstressed samples also showed some reduction, and the elongations for both types of exposures tended to converge thereafter. The final hardness for samples given stressed exposure tended to be slightly lower than the hardnesses of the unstressed samples with the exception

9 of the tests at 900~F. This was contrary to the normal expectation that increased hardness would accompany the higher tensile and yield strengths of the stressed samples. The most significant results of this survey appear to be the following: 1. Stressed or unstressed exposures between 6000 and 900'F tend to raise the tensile and yield strengths. 2, The effect of stressed exposure is greater than that for unstressed exposure —particularly in reducing the spread between the tensile and yield strengths. 3. The temperature of maximum effect is about 800=850~F. 4. At the lower end of the temperature range, i.e. 600'~750~F, stressed exposure greatly reduced the room-temperature ductility. Attention is called to the variability of total deformation obtained for substantially identical exposure conditions at 600~F. At the lower temperatures of exposure particularly, much of the total deformation is obtained upon loading or shortly thereafter. Another way of stating this would be to say that the proportion of creep deformation comprising the total deformation increases as the exposure temperature is increased, It would appear valuable eventually to extend the testing to temperatures below 600'F in order to better define any adverse effects of stressed exposure on ductility. In addition, the data should be analyzed in terms of the relative components making up the total deformation, Compression Tests-17-7PH Alloy The results of nine compression tests run at room temperature on samples of 17-7PH alloy (TH 1050 condition) are summarized in Table 2, The data presented are the 0, 2 percent offset yield strength and the compression modulus computed

10 from the slope of the stress-strain curve, Also included in Table 2 are the average values of the tensile yield strength and modulus as previously reported for samples from the same sheets of material. The values of compressive yield strength show fair consistency and the scatter between tests was no greater than the scatter previously encountered in tensile tests of the same material, Both the compression yield and modulus are greater than those obtained in tension, with the compression yield about 12-13 percent higher, This compares favorably with the data of the Armco Steel Corporation (4) which indicate the compressive yield to be about 110 percent of the tensile yield. The increase in modulus was of the order of 4-5 percent. Notched Tension-Impact Tests — 17-7PH Alloy In the period covered by this reports studies were initiated on a notched bar tension-impact test to supplement the srnooth-bar test previously reported (5). As discussed in the section on Specimen Preparation (page 4), notched samples were prepared having a theoretical stress concentration factor, Kt, of 1. 65 The results of tests using these samples are summarized in Table 3 together with the smooth-bar data. It should be noted that the gage section width of the smooth-bar samples was 0. 200 inches, while the root width of the notch was 0.250 inches. Thus9 the cross-sectional area of the specimens did not strictly correspond. The notched bar tests showed a much greater scatter than did the tests run on smooth bars. The comparison of the average values of energy absorbed shows that in both cases Sheet 1 had the lowest value, However, Sheet 2 was

11 intermediate in the case of smooth bars while Sheet 3 was intermediate in the case of notched bars. Based on the averages of all tests, the effect of notching the bars was to reduce significantly the amount of energy absorbed in tension-impact, It is possible that the scatter of the notched bars results may be due to slight (and probably unaccountable) differences in the notches themselves, Elevated-TemperatureTensile Tests - -2024-T86 Alloy The results of tensile tests at 350~, 400~, and 500~F on the 2024-T86 alloy are summarized in Table 4. Nine tests, three from each sheet, have been run at 350~ and 400~, while three have been completed so far at 500~F. The purpose of these tests is to establish the normal scatter in properties of the unexposed material at each temperature, The results appear to be quite consistent and the differences between sheets are no greater than the differences within an in~ dividual sheet. At the elevated temperatures, the strengths were lowered and the spread between the tensile and yield strengths was decreased from that at room temperature. At room temperature the yield strength was about 5, 000 psi lower than the tensile strength, while the spread had decreased to approximately 1,500 psi at the temperatures tested. The elongations and reductions of area showed only a moderate increase over the room temperature values for tests up to 500F,. Effect of Unstressed Exposure on. 2024TT86 The third progress report (6) presented data on the effects of unstressed exposure on the room~temperature tensile properties of 2024-T86 aluminum alloy, These tests run for 10, 50, or 100 hours at 350~, 400", or 500~F showed that increasing time and temperatur e resulted in decreased tensile and yield strengths, although, the effect on ductility was not significant.

12 Hardness test results are now available on these specimens and the data are summarized in Table 5 and plotted in Figure 10. In addition, tension-impact tests at room temperature (with smooth specimens) have been run on specimens given the same exposures to time and temperature in the absence of stress. These data are also summarized in Table 5 and plotted in Figure 10. The effect of the unstressed exposures on the hardness of this alloy followed the same course as did the tensile and yield strengths; that is, a decrease with increasing time and temperature. The tension-impact data on the average appear to be consistent with the other results for 10 and 50 hours exposure at the three temperatures, however, the results of the 100-hour exposures are somewhat confusing. Perhaps some of this can be traced to the scatter between duplicate tests of the same condition. This is particularly evident for the 350~F exposure samples. It would appear that the smooth-bar tension-impact test may not be as sensitive to the effect of exposures as are the other tests employed, Total-Deformation Tests —-2024-T86 Alloy The creep-rupture tests at 350~, 4009, and 500OF have been completed on the 2024-T86 alloy. The purpose of these tests was to establish the curves of stress versus time to reach the total deformations specified for the stressed" exposure tests in this investigation. The test data are summarized in Table 6 and plotted in Figure 11, The curves of stress versus rupture time for this material appear to be consistent with the uniformity of the material as revealed by the short-time tests of mechanical properties, The low values of elongation at rupture suggested that some difficulty might be encountered in obtaining the higher amounts of total deformation desired- 2, 0 and 3. 0 percent in 100 hours, This

13 was indeed the case. The curves for 0, 5 and 1. 0 percent total deformation were established without too much difficulty at all three temperatures, however, 2. 0 percent appears to be a practical limit for deformation at 350' and 400 F, Even this requires stresses to within 1000 psi of the rupture strength and examination of Figure 11 reveals the difficulty of stress selection inherent in trying to reach 2. 0 and 3, 0 percent deformations in 10, 50, or 100 hours. For the time being, the attainment of 3. 0 percent total deformation has been ruled out at 3500 and 400 F. Stressed-Exposure Tests - 2024 T86 Alloy Results of the stressed exposure tests completed to date on the 2024-T86 alloy are presented in Table 7, The data included are the effects of stressed exposure on the room-temperature tensile properties, The data for unstressed exposures are also included for comparative purposese The effects on roomntemperature tensile strength of various amounts of total deformation for the time periods and temperatures considered are presented in Figure 12, As this plot indicates, the effects of exposure become more severe as the time, temperature, and amount of deformation are increased, For times of 10 hours at both 350' and 400' there was a slight decrease in tensile strength for exposures of up to 2 percent total deformation. Fifty and 100 hours at these temperatures appeared to result in a greater effect although the data are as yet incomplete, However, the effects of 10-hours exposure at 5000F are large, and 50 and 100hours exposure to stress result in a severe loss of strength, The effects of these exposures on the yield strength and hardness appear to fall in line with the effects noted on tensile strength, while the effects on ductility are inconclusive, Further detailed discussion of the effects of stressed exposure will be deferred to the next report,.

14 FUTURE WORK During the next work period the emphasis of the investigation will be devoted to the completion of the testing program on the 2024-T86 alloy. This will include all categories of tests in the testing program. In addition, the evaluation of the notched tensile-impact test on the 17-7PH alloy will be continued. The draft copy of a summary report is scheduled to be submitted during January.

15 REFERENCES 1. Flanigan, Tedsen, Dorn "Compressive Properties of Aluminum Alloy Sheet At Elevated Temperatures," Proceedings A. S. T, M., Vol. 46, pages 951-967, (1946). 2. Hyler, "An Evaluation of Compression-Testing Technique for Determining Elevated Temperature Properties of Titanium Sheet, " Titanium Metallurgical Laboratory, Battelle Memorial Institute, TML Report No. 43, pages 21, A-13 (June 8, 1956). 3. Gluck, Voorhees, Freeman, "Third Progress Report to Materials Laboratory, WADC on Contract AF33(616)-3368, "Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals," page 7, Figure 6. 4. Armco Steel Corporation, Product Data Bulletin on Armco 17-7PH Steel, March 1, 1954. 5. Gluck, Voorhees, Freeman, "Second Progress Report to Materials Laboratory, WADC on Contract AF33(616)-3368, "Effect of Prior Creep on Mechanical Properties of Aircraft Structural Metals," Table 6. 6. Ref. 3 - pages 11, 12, Figure 9.

Table 1 Effect of Stressed or Unstressed Exposure on Room Temperature Tensile Properties of 17-7PH Alloy (TH 1050 Condition) Room Temperature Tensile Properties Exposure Conditions Ult. Tensile 0.2% offset E Temp Stress Time Total De. Strength Yield Strength Elongation Reduction of Hardness Spec. Loc. (~F) (psi) (hr) (%) (psi) (psi) (%/2 in.) Area () 106 psi R"C" Average Properties - 3 sheets - As treated 203,000 193,050 7.1 18.2 28.6 43. 7 2N-T4 600 none 100 none 192,500 184,200 8.0 18.4 29.4 42. 5 3A-T1 600 none 100 212,000 206,000 7.5 19.4 29.8 45. 8 Average 202,250 195,100 7.8 18.9 29.1 45. 3 2N-T1 600 157,000 100.5 1.89 223,000 (223,000) 1.5 13.7 29.4 45.3 3Q-T7 600 157,000 104.5 3.82 209,000 -- 2.0 8.6 30.3 41.1 1P-T24 600 157,000 99.9 5.30(?) 217,500 (188,500) 2.0 5.8 28.9 42.8 Average 3.67(?) 216,500 (205,750) 1.8 9.7 29.5 43.1 2S-T3 650 137,000 105.0 1.87 215,000 215,000 2.5 12.5 30.4 43.5 3B-T4 650 137,000 100.1 2.71 206,000 206,000 2.5 14.0 31.8 41.7 Average 2.29 210,500 210,500 2.5 13.2 31.1 42.6 2R-T6 700 118,000 100.2 1.82 211,000 210,000 4.0 17.7 29.6 42.8 3G-T3 700 118,000 100.7 1.60 218,500 218,000 3.0 16.0 30.8 44.9 Average 1.71 214,750 214,000 3.5 16.8 30.2 43.8 2R-T2 700 120,000 100.1 2.54 219,000 218,000 2.2 13.7 30.6 44.0 3Q-T6* 700 120,000 100.1 1.95 220,000 219,000 3.5 13.8 29.6 44.2 Average 2.24 219,500 218,500 2.8 13.8 30.1 44.1 2J-T5 750 101,000 100.0 1.94 222,000 220,000 3.0 17.0 29.7 44.2 3B-T3 750 101,000 100.0 1.62 218,000 217,000 4.5 16.7 30.0 46.1 Average 1.78 220,000 218,500 3.7 16.8 29.8 45.2 3G-T6 800 none 100.0 none 222,000 216,000 4.0 17.9 29.8 47.4 2N-T2 800 none 100.0 none 222,500 216,000 5.0 17.3 30.2 48. 2 Average none 222,250 216,000 4.5 17.6 30.0 47.8 3P-T1 800 81,000 102.6 2.12 232,000 229,000 3.5 12.1 29.9 46.7 2S-T6 800 81,000 102.1 1.88 227,000 222,000 4.2 15.8 30.2 46.7 Average 2.00 229,500 225,500 3.8 14.0 30.1 46.7 2R-T5 850 66,000 100.0 1.99 235,000 230,000 5.0 13.4 30.8 46. 4 3H-T3 850 66,000 100.1 2.09 231,000 228,000 4.2 14.3 30.0 47.6 Average 2.04 233,000 229,000 4.6 13.8 30.4 47.0 3P-T6 900 none 100.0 none 222,000 215,000 4.5 8.4 30.4 46.2 2N-T5 900 none 100.0 none 220,000 213,000 6.0 17.1 28.8 47.0 Average none 221,000 214,000 5.2 12.8 29.6 46.6 2R-T1 900 49,000 100.0 1.55 214,000 209,000 6.5 16.7 29.9 45.3 50,000 100.0 2.04 224,000 219,000 4.0 15.2 29.7 46.8 50,000 100.0 2.33 235,000 230,000 4.0 13.1 30.0 48.1 Average 1.97 224,333 219,333 4.8 15.0 29.5 46.7 * gage section not remachined before tensile test

Table 2 Room Temperature Compression Test Data 17-7PH Alloy (TH 1050 Condition) 0.2% offset Compression Compression Yield Strength Moulus Spec. Loc. (psi) 10 psi 1C C44 242,000 29. 5 1C-C4 235,000 30.1 1C-C22 228,000 29.6 1U-C4 226,000 29.6 Average 232,750 29.7 2J-C44 195,000 29.6 2E-C2 206,000 30. 1 Average 200,500 29.8 3L-C6 205,000 29.8 3L-C4 234,000 29.6 3L-C44 216,000 30.3 Average 218,333 29.6 Average 9 tests 220,777 29.8 Average of sheet averages 217,194 29 8 Tension Tension Yield Modulus Average of sheet 1 204, 160 28. 8 Average of sheet 2 179,750 28. 4 Average of sheet 3 195,250 28. 7 Average of 3 sheets 193,050 28.6

Table 3 Notched Bar and Smooth Bar Tension-Impact Data at Room Temperature 17-7PH Alloy (TH 1050 Condition) Notch Bar Smooth Bar Energy Energy Absorbed Absorbed Specimen (ft-lb) (ft-lb) 1G-M5 32 1C M5 35 1G-M2 8 1C-M6 37 1U-M2 16 1CM1 45 1U-M4 12 Average 17 Average 39 2E-M6 36 2JM1 48 2N-M4 45 2J-M2 41 2N-M5 9 2E-M1 62 Average 30 Average 50. 3 3F-M5 36 3L-M2 52 3F-M6 49 3L-M5 52 3L-M1 46 3F-M4 33 Average 47 Average 45. 6 Average 10 tests 28.9 Average 9 tests 45.0 Average sheet averages 31.3 Average sheets 45.0 Note: Notched Specimens 0. 250 inch wide at minimum section. Theoretical stress concentration factor, Kt = 1.65. Smooth Specimens 0. 200 inch wide in gauge section.

Table 4 Elevated Temperature Tensile Data 2024-T86 Alloy Ult. Tensile 0.2% offset Elastic Test Temp Strength Yield Strength Elongation Reduction of Modulus _ F Specimen (psi) (ps i) (%/2 in.) Area (%) 106 psi 350 2B-T55 57, 100 55,700 9, 5 15.9 10.5 2F-T3 58,300 56,400 9. 8 20.6 10 2 2M-T2 59,400 58,500 8.5 17.9 10.5 Average 58,267 56,867 9.3 18 1 10.4 3A-T11 56,900 55,500 9.5 20.3 10.6 3G-T3 58,100 56,900 9 0 19. 1 100 3K-T2 57,500 56,700 10.0 20.0 9.9 Average 57,500 56,367 9 5 19.8 10 2 4C-T11 56,800 55,600 7.0 13.1 10.6 4H-X11 58,500 56,900 9,5 18.2 9.8 4Q-T1 58,100 56,900 9.5 17.4 10.3 Average 57,800 56,467 8.7 16.2 10.2 Average 9 tests 57,854 56,456 9.2 18.0 10.3 400 2D-T11 51,800 50,000 9.5 19.2 9.5 2F-T5 52,100 50,300 8,5 16.6 9,3 2M-T3 54,900 53,000 9.5 21.9 9.8 Average 52,933 51, 100 9,2 19,2 9. 3A-T2 54,600 52,300 10.8 20.4 9.0 3G-T1 51,700 50,000 9.0 19.6 9.4 3K-T1 51,700 49,600 8,0 18.6 9.3 Average 52,667 50,633 9.3 19,5 9.2

Table 4 (continued) Ult. Tensile 0.2% offset Elastic Test Temp Strength Yield Strength Elongation Reduction of Modulus ~F Specimen (psi) (psi) (%/2 in ) Area (%) 10 psi 400 4C-T55 51,400 49, 500 7.0 (9.0)* 9, 3 4N-T2 52, 300 50, 700 10.0 18.3 9 1 4P-T3 549400 539900 8.8 18 8 9.5 Average 529700 519 700 8. 6 18.6 9.3 Average 9 tests 529784 51,033 9.0 19.2 9.4 500 2D-T4 37,600 359200 9.5 23.9 7.3 2H-T3 38,900 38,000 9.5 21.6 7.7 2M-T11 43,200 42,000 9.0 19.3 7.9 Average 39,900 38,400 9.3 21.6 7.6 Room Temp. Average 759690 70,560 7.8 11.9 10.8 * omitted from average = broke at gage point

Effect of Unstressed Exposure on Room Temperature Hardness and Tension-Impact Properties 2024-T86 Alloy Tension-Impact Properties (Smooth Bar) Exposure Exposure Hardness after Exposure E.]nergy Temp Time Hardness Absorbed Elongation Red ion of ~F hr Spec. No. Rockwell B Spec, No, (ft-lb) (%/2 in.) Area (%) Unexposed Average 80.3 Average 18,2 5 8 11.2 350 10 2JT1 79,,3 4A X3 15 3,0 7.9 10 4A-T2 80,7 3E-X22 21 5.0 9.9 Average 80.0 Average 18 4.0 8.9 50 2P-T1 77.8 4M-X4 17 5.0 11.4 50 4G-T3 77.2 2C-X22 19 6.0 9.4 Average 77.5 Average 18 5.5 10.4 100 2P-T3 75.8 3L-X4 10 6.0 8.5 100 4M-T1 75.8 2C=X4 16 6.0 6. 1 Average 75.8 Average 13 6.0 7.3 400 10 2P-T2 75.8 4MX3 18 6.5 8.6 10 4G-T1 74.7 2J-X4 17 6.0 11.6 Average 75.2 Average 17.5 6.2 9. 1 50 3E-T4 72.0 4A-X4 11 8.0 13,0 50 4M-T2 71.3 3E-X33 21 6.5 7.7 Average 71.6 Average 16.0 7.2 10.3 100 2C-T3 68.2 2J-X22 18 9.0 12.7 100 3L-T1 68.7 4M-X33 19 7. 5 92 Average 68.4 Average 18 5 8.2 10,9

Table 5 (continued) TensionsImpact Properties (Smooth Bars) Exposure Exposure Hardness after Exposure nergy Temp Time Hardness Absorbed Elongation Reduction of ~F hr Spec. No, Rockwell B Spec. No. (ft-lb) (%/2 in. ) Area(%) 500 10 2P-T11 65.3 4G-X22 13 5.5 10.2 10 3E-T3 66.8 3EoX4 14 6.0 11.0 Average 66.0 Average 13.5 5.8 10.6 50 2C-T4 68.0 4G-X4 11 4.0 11.5 50 4G-T4 66,1 2P-X33 14 4.5 9.2 Average 67.0 Average 12.5 4.2 10.4 100 3L-T4 54.3 2P-X4 15 6.0 13.8 100 4A-T3 54.7 3L-X22 14 6.0 13.9 Average 54.5 Average 14.5 6.0 13.8

Table 6 Rupture and Total Deformation Data 2024-T86 Aluminum Alloy Time to Reach Indicated Total Deformation Test Temp Stress Rupture Time Elongation Reduction of Loading hrs Spec. Loc. ~F (psi) hrs (%/2 in.) Area (%) Def. % 0. 5% 1. 0% 2.0% 3.0% 2B-T5 350 46, 000 20.4 6.0 8.8.51 -- approx. 7 3L-T11 45,000 24.5 4.2 9.2.47.08 -- -- -- 4A-T4 40,000 82.3 4.5 6.7.42 1.0 40.0 71.0 -- 3E-T5 37,500 171.3 3.0 4.6.38 6.5 76.0 approx 7 2C-TI 35,000 481.Z Z. 8 4. 1.37 19.5 256.0 -- 4M-T4 32,000 460.5 2.0 5.1.32 31.5 310.0 -- 2F-T11 30,000 (742. 5)b -- -- 32 46.0 554.0 2P-T4 400 40,000 6.6 7.0 14.4.46 0.3 -- -- -- 3D-T3 37,500 19.2 5.0 8. 1.41 0.5 8. 1 18 (est) 4M-T11 35,000 28.1 2.0 1.6.41 1. 2 15.0 -- 3E-T11 30,000 (51.5)a 1.5 4.6.32 4.0 32.0 -- 2C-T5 30,000 83.1 4.0 6.6.33 4.0 43.5 76.5 -- 2J-T5 25,000 360.6 3.5 6.2.29 23.0 169.0 354.0 -- 4G-T5 20,000 (1127.8)b -. --.21 160.0 825.0 -- 3L-T2 500 25,000 1.7 7.0 20.4.34.06.51 1.05 1.5 2J-T2 20,000 8.6 + 1 10.5 22.0.26 1.1 4.0 -- _ 4G-TII11 20,000 7.1 + 1.5 11.0 27.4.27 0.6 2.6 -- -- 2J-T11 19,000 22.8 9.2 13.1.22 2.4 7.9 9 __ 2C-T11 15,000 113.1 9.2 16.3.16 11.1.42.4 -- 4A-T1 14, 000 66.6 9.3 19. 1. 18 8.4 26.0 45.8 60 (est) 3D-T5 14,000 104.5 8.8 13.6.17 11.5 40.0 73.5 85 (est) 4A-T11 10,000 461.0 8.7 19.4.13 74.0 184.0 378.0 438.0 (a) failed at collar; collar on gage section in this instance (b) Test discontinued without failure

Table 7 Effect of Stressed and Unstressed Exposure on Room Temperature Tensile Properties of 2024-T86 Alloy ____________________________Room Temperature Tensile Properties_____ ____________ GUltExposure C onditions, Ult. Tensile -- 0.2% offsetNominal Te-p Stress Actual Time Total Def. Strength Yield Strength Elongation Reduction of E Hardness Time Spec. Loc.'F (psi) hrs (%) (psi) (psi) (%/Z in Ae(%) 106 pj R"B" Avrag, Propertis - Unepoed 75,690 70,560 7.8 11.9 10.8 80.3 3GT5 J 10 0..0 980 69,000 7.5 90.8 10.9 6. 2J-TI 350 none 10none 74,900 69,000 7.5 9.2 10.9 79.3 -IA-T2 350 none 10 none 75,400 69,500 8.Z 13.8 10.1 80.7 Average 350 none 10 7none75,150 69,250 78 11778 1075 80.0 10 hr 3H-T5 350 36,000 10.1 0.52 74,800 68,600 8.5 13.8 10.7 78.2 2F-T4 350 14,500 10.0 1.13 73,600 68,000 7.0 14.2 10.7 80.2 3K-T11 350 17,000 10.1 1.62 71,300 69,200 10. 0 12.6 10.0 79.3 2P-TI 350 none 50 none 73,300 66,100 7.5 9.9 11.0 77.8 4G-T3 350 none 50 none 74,500 65,900 7.5 8.1 10.8 77.2 50 hr Aerage 350 none 50 none73,900 66,000 775 90 10.9 77. 5 3G-T55 350 39,500 50.0 1.10 69,800 62,400 8.5 10.8 10.7 76.8 2P-T3 350 none 100 none 71,600 63,500 7.5 11.1 10.8 75.8 4M-T1 350 none 100 none 71,500 63,200 7.0 11.0 10.8 75.8 Average 350 none 100 none71,550 63,350 72 11.0 10.8 75. 8 100 hr 4P-T4 350 37,500 100 1.13 71,700 62,900 8.5 10.8 10.7 76.8 3K-T5 350 39,000 100.1 1.95 65,100 60,000 5.0 4.7 10,9 na 2P-T2 1400,none 10.one, 71,600 63,900 6.5 15.3 11.0 75.8 4G-TI 400 none 10 none 71,200 63,300 6.5 12.3 11.0 74.7 Average 400 noe 10ne 71,400 63,6 — 00 6E5 - 13.7 18, -0 75,210 hr 2B-TI 400 28,000 10.0.66 68,800 59,300 7.5. 13 0.6 74.3 4C-T3* 400 28,000 12.4.82 70,500 60,900 8.0 14.8 10.5 76.1 3D-Ti1 400 36,000 10.7 1.13 69,000 60,000 8.0 14.2 10.9 75.0 4C-T4* 400 36,000 12.4 1.39 68,600 59,200 8.5 12.3 10.9 74.3 3E-T4 400 none 50 none 67,000 56,900 7.5 12.9 11.0 72.0 4M-T2 400 none 50 none 66,600 56,500 7.5 11.4 11.3 71.3 Average 400 none 50 none 66,800 56,700 7,15 1 1.2 112 71.6 50 hr 4H-T1 400 23,000 50.0.53 65,300 55,100 8.0 9.6 10.8 71.3 3K-T3 400 23,000 50.3.58 66,600 56,000 8.5 10.6 10.7 na Average 400 23,000 50,2.56 65,650 55,550 872 10.1 10.8 3K-T55 400 29,000 50.1.96 65,900 56,000 7.5 8.6 11.3 72.1 2B-T4* 400 30,000 50.1 1.43 64,500 53,800 7.0 10.6 10.7 70.8 2C-T3 400 none 100.0 none 64,500 53,800 7.5 12.1 10.7 68.2 3L-TI 400 none 100.0 none 64,300 53,800 7.5 13.0 11.3 68.7 Average 400 none 100.0 none64,400 53,8000 75 12.6 11.0 68.4 100 hr 3D-T4 400 21,000 100.0.59 64,500 53,100 9.0 14.6 10.9 70.0 4H-T55 400 21,000 100.2.55 64,500 53,900 8.5 11.7 11.0 68.9 Average 400 21,000 100.1.57 64,500 53,500 8.8 13.7 11.0 69.5 4H-T3 400 27,000 100.3 1.07 61,800 50,800 11.0 11.7 10.4 69.0 3A-T5* 400 29,000 100.0 1.53 60,600 50,900 5.5 7.5 10.9 na 2P-T11 500 none 10 none 62,500 50,100 7.0 10.0 10.6 65.3 3E-T3 500 none 10 none 61,500 49,300 7.0 12.6 10.9 66.8 Average 500 none 10 none 62,000 49,700 7.0 11.3 10.5 66.0 10 hr 2B-T3* 500 14,500 21.2 n. 51,300 35,900 9.0 14.1 10.7 54.0 4H-T4 500 18,000 10.0 na 48,900 33,400 8.0 13.9 10.7 50.3 2C-T4 500 none 50 none 62,400 50,300 7.5 11.0 10.8 68.0 4G -T4 500 none 50 none 59,900 48,500 7.0 11.7 10.6 66.1 Average 500 none 50 none 61,150 49,400 7.2 10.8 10.7 67.0 50 hr 4P-T55 500 11,000 53.6 na 42,200 25,000 10.2 18.4 10.7 35.3 3G-T2 500 14,000 50.3 1.59 46,100 29,400 10.0 15.7 10.6 na 3L-T4 500 none 50.0 none 51,500 37,000 7.0 13.0 10.9 54.3 4A-T3 500 none 50.0 none 52,100 38,800 6.5 13.6 10.6 54.7 Average 500 none 507on5ne0,0- 51,800 37,900 6.8 13.3 10.8 54.5 100 hr 3D-T55 500 9,000 100.0.62 44,400 28,200 9.8 17.5 10.7 na data included for comparative purposes; test conditions not otherise applicable na- not yet aailable

SHEET 2 SHEET 3 SHEET 4 PANEL NO. R 0, A R _____________________ B Cl ___R__R C R __________ D ________________Q ______________ E R ___________ F ____________R 0O) G R H O0______ J ___________~R__________ K Q__________________ _______ Q___________ L _R _______ M N _________~ ___ _____~ ~ R P 0 20 SHEET SAMPLING SCHEME 2024-T86 SCA LE........ INCHES T Til I I TI T TENSILE 2| X22 1M22 I X2 I T2 M 2 C COMPRESSION X 33 33 T3,3 X3 M TENSION-IMPACT M44 1 T4 X44 I M4 X4 4 X EXTRA T5 I MS X5 PANEL SAMPLING SCHEME Q Tl |IXI _ TI ALL BLANKS X22 I T2 |X2 I INCH WIDE X33 |T3 I X 3 1X44 T 4 T X4 T55 IX5 I T5 PANEL SAMPLING SCHEME R 0 10 SHEET SIZE 48, 72,.065-INCHES SCALE....,...., PANEL SIZE 48, 5-5- 1/2 INCHES INCHES SAMPLE CODE-(EXAMPLE) 4C-T2,I.E.,SHEET 4- LENGTH ONLY PANEL C -TENSILE SPEC. NO.2 Figure 1. - Sampling Procedure for s-.eets of 2024-T86 aluminum alloy

A i B 1 C DEFK L | M l | P l | 5 | T I U |-PANEL NO. jI' | 1 i r i I I I E Y - w 1 Y yyw SHEET 3 Ij ~IIIW iI I Y_.. SHEET2 i 1 r i!!' I' I' Sheet Dimensions: 36 x 120 x 0. 064 inches Panel Width: 6-1/4 to 6-1/2 inches Sheet Designation: 1, 2, 3, etc. Panel Designation: A, B, C, etc. Panel Location Code: 1A, 3L, etc. (Sheet No. - Panel No.) Specimen Blank Sampling Scheme: W, Y, or Z' (see Figure 3) Figure 2. - Panel sampling scheme for sheets of 17-7PH stainless steel sheet

XI IM I Tl M2 22 T2 C2 X33 T3 X3 -C4| T4 4 X4 i T5 MT | Y5 Y66 |C6 M6 YC T J5 ^1 |T21 X22 XT2 X2 X44 T4 X4 1T5 Y5 XG T2 T26 -'0 10 SCALE:........... INCHES T - TENSILE (LENGTH ONLY) C - COMPRESSION ALL BLANKS I INCH WIDE M - TENSION-IMPACT X - EXTRA Figure 3. - Specimen blank sampling schemes for panels of 17-7PH stainless steel sheet

EXP. SPEC..530:.003 TENSILE SPEC..500.^ 15 Is.j l. I, —. ~- 4.82.I ~'~"' a-' T-T \r an ----— O RADIUS THI CKES, _GRINQ, LAST' EACH __ 5 DIA 2 HOL. ES I3 BA PUNCH EDGE, LONG'rUDINALLY M-ECI - ES a"- HOLES TENSILE OR CREEP-EXPOSURE SPECIMEN from Creep Specimens after Exposure). TENSION- IMPACT SPECIMEN DO NOT SCALE co ALL SPECIMEa5 oo FULL SHEET THICKNESS,_________,n< 0.064 INCHES COMPRESSION SPECIMEN from Creep Specimens after Exposure).

R = 1" -1-1/4 k.0 2,1 1 -/4' _____"-1/4 —f ull s-he-et thickness -.064 inches Figure 5. - Design of notched tension-impact specimen

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250 Tensile Strength 240 I30 4j O\ m ^ Average of m-i 3 sheets E 200 O 190 I0 230 Yield Strength p *3. 2 (0.2% offs et) \ o 0., I 220 4 ~A / ) Vn 2 10 Code H g..0 Average of Elongation uH Average of (>-Zero stress for Figure~ 9. - Effcts of 1100 hrs i k 200z - 3 sheets —-A — — A —2% nominal total 0 u o e t deformation in wo 190 -- 100 hrs.,-4 0 180 10 Average of Elongation o 3 sheets ~r = 50 1 Hardness [ Average of <u 3 sheets 40 0 100 200 300 400 500 600 700 800 900 1000 Exposure temperature - *F Figure 9. - Effects of 100 hours unstressed exposure or 100 hours stressed exposure to 2 percent total deformation at indicated temperatures on room temperature tensile properties of 1I -7Pf alloy (T' 1050 conditio7;)

Hardness 80 - 70~ ~ 350 70 80 0 =, O;400 oI~ I 6I0'60 -- EI I ^"^ 500~ Ud 50 I I I I I I I I I I 20 o Tension-Impact - _ ___ __O Ah ^~ =A 4004~F. — | 05000F u' U 350 I I 10 _ El' Exposure time - hours E, O 350'F OAd 400~F O 0 ~ri F: ~ 500~F r L 0 10 20 30 40 50 60 70 80 90 100 Exposure time - hours Figure 10. - Effect of unstressed exposure on hardness and roomtemperature tension-impact strength of 2024-T86 alloy.

30 0 2, 40 -^ —-- -^I\-TI 40010F - 00.5%)~~~~~~~~~~~~~~~~~~~~~50 00 R uptur e ^ ^^ ^ s,^ ^ ^ ^"^ s^ ^ ^:::S > > (4.5 ) R uptu re ^ ~ A 1.0% Total Deformation (3.-^^ ^ ^:::'5) 40~~~~~~~~~~~~~~~~~~~~~~~~~~30 ^~~20 zoI^'*0.% 10^^ 30 I0 I I 2 0.5 1.0% 30 I I~ I'II II I I I I0" 0(5- 0) 20~~~~~~~~~~~~~~~~~~~~~~~~,0 Co0. 1 1. 0 10 100 1000 ~Rupture (4.)Time - hours 30 ( )Elongation on rupture R ( ~ uptur e Figure 11. - Stress versus matime for rupture and specified total deformations for 2024-T86 aluminum alloy at 350~, 400~, 5O0~. o ~~X 2, 0%/ C) + 3. 0%1 En 0. 516.5~ 3 0 (7. 0) 2 0 2) Ruturee (9. 2) (8. 8) (9. 3) 10 ~~5%'~..0% ijlz% 0. I 1. 0 10 100 10 Time - hours Figure 1 1. Stress versus time for rupture and specified total deformations for 2024-T86 aluminum allo a 3 50 0P 40 0 0 500 OF.

80 350~F unexposed 10 hrs 70 - 50 hrs 100 hrs CO o 60' — 400~F 4 70 Clc)P~~~a,~~~~ O~ ~10 hrs n-~;50 hrs Iu - ^ ------— 0 100 hrs h 60 60 50 I I I I I I 0 0 8 —-- 10 hrs 500~F 60 Exposure Times 60 ----- - unexposed *^.~~~~~ O 10 hrs I 12.4 hrs 50I *I unex e dA 50 hrs 1 100 hrs 50 \ t 50 hrs 100 hrs 40 0(.5 1.0 1.5 2.0 Total Deformation - percent Figure 12. - Effect on room temperature tensile strength of 2024-T86 alloy from exposure to temperature and stress as indicated.