Downloaded from https://www.everyspec.com PROPERTIFS OF MATERIALS point, specific heat, thermal conductivity and tion with the interpretation of the curves -coefficient of thermal expansion. In this corn- shown in these Pi/ures. The stress-strain pilatijn, only one or two alloys of steel, curves shown P -e obtained at a:constant tern- magnesium, aluminum and titanium are perat.me given by the intersection of the listed, but thi. properties of materials such curve with the temperature axis.
The stress- as copper, tungsten, molybdenum, oxides, strain curves are spread in their correct carbides and borides are presented because posti*;t on the temperature axis (abscipsa) of the attractiveness of one or more of their in order that curves at intermediate tern- properties at elevated tcrmperatures. Mean peratures; m'fy be interpolated. For an.y given values of the thermal properties are given stress-strain curve, the strain at any stress i together with the temperature range within level may ;ie obtained by interpolation be- which they are applicable.
For a number of tween constant strain lines or by using the materials, the, thermal properties are plotted strain smle (shown only in Figure 2-9) and as a function of temperature and a reference measurinr . from the point of zero stress. An to the corresponding figure is given. illustrativ3 example :s given in Figure 2-9 In Figure,, 2-5 and 2-6 the modulus of fo further clarifi-a;. n. elasticity anSi the yield stress are plotted a±angent nio4u ata at various stresses are shown fot" J . _niinum alloy in Figure functions of the temperature for a selected are shoTh valuf . nninum as io F number of typical materials.
As alreAdy men- T e value, ,xe 4,owp s Mos of tioned, the principal purpose is not only to at Moulus , b A Maulus, of at various ternper.'n A tabulation of show the variation of these properties for a mechanical pronerties a room and elevated material, but: also to indicate the relative temperatres fir an aluminum alloy is given magnitudes and the behavior between differ- t-r . Cre ep aalu iue a s e ent materials. It is significant to point out included. that these properties are affected by the rate incle of heating, soaking time at test temperature, Th ree in h F pres by asthe ctrain rate.
Most of the mechanical through 2-17 are in the forms preferred by properties shown are for moderate heating structural designers and analysts. In Figure and strain rate, and are soaked for one-half 2-15, the reader should note that the elastic strain is subtracted from the total strain to hour or more at the test temperature. Short time test results, which are not quite as plen- obtain the curves.
The log-log plot of mini- tiful, indicate an increase in the modulus of mum creep rate as a function of stress in elsticityl, dyiedstress with an increase Figure 2-16 is particularly useful in the elasticity end yield srswihainese formulr'~nn of creep laws for engineering in the heating rate and strain rate and with mtr ina in he aster creerves a decrease in the soaking time. materiai.. Finally, in the master creep curves of Figure 2-17, the parameters are total The weight-strength and cost-strength strain, and a so-called Larson-Miller param- ratios of one alloy each of aluminum, mag- eter which includes both the time and tem- nesium, titanium, steel and nickel are pre- perature effect.
The comments made in con- sented in Figures 2-7 and 2-8. Note how effec- nection with Figures 2-9 and 2-10 also hold tively the curves give an approximate idea for this figure except that temperature is of the maximum useful temperatures of the replaced by the Larson-Miller parameter. various alloys based upon these criteria. Cost Inasmuch as fatigue considerations are data are listed in Table 2-7 and strength data relatively unimportant in missile type struc- are based on the tensile yield strength given tures, only one set of curves is given for an in Figure 2-6. The r eader is cautioned against alloy of aluminum in Figure 2-18.
arriving at any broad generalization based The final set of figures, 2-19 through 2-21, upon criteria of this type. show the thermal properties of a wide va- Stress-strain curves at various tempera- riety of materials as functions of tempera- tures are shown for an aluminum alloy and ture. To enable a comparison between the a steel alloy in Figures 2-9 and 2-10 respec- various materials, each figure shows the tively. A word of caution is made in connec- variation of a particular thermal property. 17 I.