摘要:

This Borosilicate Glass is the third Standard Reference Material (SRM) to be certified for thermal expansion measurements by the National Bureau of Standards. Copper (SRM 736) and Fused Silica (SRM 739) are the other two materials. The results of tests on six samples taken from the stock will be reported in this paper. These results indicate the stock to be of consistent quality suitable for certification. Measurements were made in the temperature range from 80 to 680 K using an interferometer apgaratus. At 293 K the expansivity is4.78×10−6 K−1and the standard deviation is0.06×10−6 K−1calculated from a least squares fit to the data over the entire temperature range. A description of the calibration of a fused quartz dilatometer using the three Standard Reference Materials will also be presented.

ISSN:0094-243X    

DOI:10.1063/1.2945941

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The design requirements of the aerospace and high temperature nuclear reactor industries necessitate reliable thermal expansion data for graphite and other carbonaceous materials. Currently there are no accepted standards or reference materials which can be used in carbon‐rich atmospheres at temperatures ranging to 2500°C. The feasibility of an acceptable reference for calibration of expansion measuring systems that operate in such test environments (furnaces utilizing graphite heaters, for example) is the prime subject of this work. Present‐day graphite technology provides acceptable materials for stable, reproducible references, as reflected by some of the candidate materials. The repeatability for a single specimen in a given expansion measuring system was found to be± 1%, while the combined results of several tests made on a number of samples fell withina ± 2.5%band. Data on several grades of candidate graphites are discussed, and results of a broad round robin program presented.

ISSN:0094-243X    

DOI:10.1063/1.2945915

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The thermal expansion behavior of unidirectional and balanced symmetrical unidirectional‐angle ply laminated boron and graphite fiber reinforced epoxy resin matrix composites is studied. The expansion coefficient is determined as a function of fiber orientation for a high modulus graphite/epoxy system, a high strength graphite/epoxy system, and a boron/epoxy system. Results for unidirectional materials, axial and transverse, are compared with strain compatability predictions. Effects of moisture absorption and evolution are discussed.

ISSN:0094-243X    

DOI:10.1063/1.2945916

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A fused quartz differential dilatometer was interfaced with a mini‐computer to automatically measure the thermal expansion of solids from 300 to 1000 K. An electronic micrometer, readable to2.5 × 10−6 cm, was employed for length change measurements accurate to2.5 × 10−5 cm. Calibrated thermocouples were used to measure temperature changes to±0.27 K. The complete experimental procedure was under computer control and involved : (a) Regulating the power to the furnace to achieve thermal equilibrium (2–5 hr); (b) Measuring the specimen temperature and length change (1 min.); (c) Remeasuring the specimen temperature and length change to check thermal equilibrium of specimen (15 min.); (d) Increasing or decreasing the specimen temperature to the next set point (1 hr).The software and hardware necessary to accomplish the measurements are described. Measurements on National Bureau of Standard certified fused silica, copper, and tungsten are presented and demonstrate an uncertainty of about±1 × 10−7 K−1in the determination of the coefficient of thermal expansion. The influence of metallurgical creep above 600 K on measurements on copper are discussed and results on commercially pure copper are presented.

ISSN:0094-243X    

DOI:10.1063/1.2945917

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Differential dilatometry is a valuable technique for measuring both differential and absolute expansion of materials. The particular advantages of this technique are discussed and a calibration scheme is presented. Its usefulness and versatility are illustrated by establishment of new reference materials and by citing typical applications of the method.

ISSN:0094-243X    

DOI:10.1063/1.2945918

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A new dilatometer for rapid measurement of thermal expansion at high temperatures is described. The technique utilizes an image follower and a Michelson interferometer. The sample is in the shape of a thin‐walled tube and is heated by a pulse of electrical current. The sample may be heated to temperatures close to the melting point in times of less than one second.

ISSN:0094-243X    

DOI:10.1063/1.2945919

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The determination of the thermal Gru¨neisen parameter of anisotropic reentry vehicle materials has been limited in part by the accuracy of experimentally determined values of the thermal coefficient of linear expansion. In many cases, the coefficient of thermal expansion of recently developed anisotropic materials is very small and precise determination with commercially available dilatometers is, at best, extremely difficult if at all possible. A description will be given of a completely automated dilatometer developed at the Air Force Weapons Laboratory. The instrument employs samples of the materials of interest as the mirror spacing for a confocal, spherical Fabry‐Perot cavity. Results are presented of measurements made on well‐characterized, low expansion materials demonstrating a less than 1% uncertainty in the coefficient of expansion.

ISSN:0094-243X    

DOI:10.1063/1.2945920

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The Gru¨neisen constant and its first order volume dependence, commonly referred to as the second Gru¨neisen constant, are fundamental to the study of many basic phenomena in solids. Knowledge of these two constants enables one to obtain information on the anharmonicity in a solid and to predict a variety of physical properties such as the coefficient of thermal expansion, the equation of state and thermoelastic properties. In the present paper the second Gru¨neisen constant and the pressure dependence of the coefficient of thermal expansion are calculated forCsCl,CsBrandCsIutilizing a volume dependent modified rigid ion model of lattice dynamics . The model parameters are deduced from the three elastic constants and the long wavelength optical mode frequencies. Using the first and second order pressure dependences of these physical observables, the individual second mode‐Gru¨neisen parameters are obtained as a function of wave vector. The temperature variation of the second Gru¨neisen constant is then deduced in a quasi‐harmonic approximation. The second Gru¨neisen constant is also calculated from available thermodynamic data and is in reasonable agreement with the present theoretical prediction. Finally, the pressure dependence of the coefficient of thermal expansion is obtained as a function of temperature.

ISSN:0094-243X    

DOI:10.1063/1.2945921

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The application of plane stress and plane strain equations leads to exact expressions for the composite expansion of laminated plates and cylinders. Under the assumption of equality of Poisson's ratio of all layers these expressions simplify considerably and provide a conceptually simple relationship between the composite expansion and constituent properties. The error introduced by the assumption of equality of Poisson's ratios is found to be negligible indicating that simple expressions are adequate for all practical purposes.

ISSN:0094-243X    

DOI:10.1063/1.2945922

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A self‐consistent procedure for determining the constants that characterize the interionic forces allowed for in a crystal model is described. The procedure allows one to avoid some of the approximations that are commonly made when determining force constants from the experimental values of the bulk modulus and its pressure derivative. The procedure is used in a calculation of the coefficient of thermal expansion ofCsBr, and the values obtained are in good agreement with the experimental values.

ISSN:0094-243X    

DOI:10.1063/1.2945924

出版商:AIP    

年代:1974

数据来源: AIP