scispace - formally typeset
Search or ask a question
Book ChapterDOI

Ultrasonic Interrogation of Polycrystalline Materials

TL;DR: In this paper, it was shown that grain scattering depends on size, shape, orientation and anisotropy of the grains, and the structure, thickness and chemistry of their boundaries.
Abstract: It is accepted that the same features of microstructure that dominate α, attenuation of ultrasonic waves also determine mechanical properties of industrial materials. For example, in polycrystalline metals the grain size greatly influences both ultrasonic attenuation [1–4] and material strength, ductility, toughness and formability [5]. Since ultrasonic inspection is less expensive than the destructive tests required to assess mechanical properties many analytical and experimental studies have been directed at establishing whether and how features of microstructure may be inferred from ultrasonic inspection data. One significant contribution to attenuation in polycrystalline materials is scattering by the grains [1,2] and precipitates [6]. This results from interaction with material defects comparable to one wavelength λ in size, such as grain boundaries. Scattering depends on size, shape, orientation and anisotropy of the grains, and the structure, thickness and chemistry of their boundaries. The standard assumptions used when modeling grain scattering are that the discontinuity of the grain boundary is of elastic nature; an individual grain scatterer has a simple shape with the mean grain size D; the grains are randomly located and randomly oriented; the number of grains is large; and the scatter from individual grains is not coherent.
References
More filters
Book
01 Jan 1942
TL;DR: In this article, the Laplace's functions of T, F, V are simultaneously reducible to sums of squares, where T is the length of a string, F is the degree of freedom of the string, and V is the size of the chord.
Abstract: Volume 1: Preface 1. Sound due to vibrations 2. Composition of harmonic motions of like period 3. Systems with one degree of freedom 4. Generalized co-ordinates 5. Cases in which the three functions, T, F, V are simultaneously reducible to sums of squares 6. Law of extension of a string 7. Classification of the vibrations of bars 8. Potential energy of bending 9. Tension of a membrane 10. Vibrations of plates. Volume 2: 11. Aerial vibrations 12. Vibrations in tubes 13. Aerial vibrations in a rectangular chamber 14. Arbitrary initial disturbance in an unlimited atmosphere 15. Secondary waves due to a variation in the medium 16. Theory of resonators 17. Applications of Laplace's functions to acoustical problems 18. Problem of a spherical layer of air 19. Fluid friction Appendix.

1,471 citations

Journal ArticleDOI
TL;DR: In this paper, a spherical obstacle of a plane longitudinal wave propagating in an isotropically elastic solid is computed, and the total scattered energy is derived for three special types of obstacle: a rigid sphere, a spherical cavity, and a spherical rigid sphere.
Abstract: Scattering by a spherical obstacle of a plane longitudinal wave propagating in an isotropically elastic solid is computed. Expressions for the scattered wave and the total scattered energy are given. Three special types of obstacle—an isotropically elastic sphere, a spherical cavity, and a rigid sphere—are discussed in detail, especially for Rayleigh scattering. The result for the isotropically elastic sphere is compared with the well‐known result of scattering of a plane wave propagating in an ideal fluid by a sphere of another ideal fluid.

555 citations

Book
01 Oct 1970
TL;DR: Theory of yield point phenomena and their theoretical background can be found in this paper, where the effects of tensile machine and specimen stiffness on yield point effects are discussed.
Abstract: 1 Yield Point Phenomena and their Theoretical Background.- The effects of tensile machine and specimen stiffness.- Types of yield point effects.- The upper yield point-experimental.- The upper yield point-theoretical.- The lower yield point.- Strain ageing.- Pseudo yield points.- 2 Iron and its Alloys.- Effects of carbon, nitrogen and other elements.- Quench ageing.- Yielding behaviour.- Strainageing kinetics.- Effects of radiation damage-Single crystals.- Steels.- 3 The Group Va and VIa Metals.- Vanadium.- Chromium.- Niobium.- Molybdenum.- Tantalum.- Tungsten-Alloys of these metals.- Discussion.- 4 Hydrogen in Metals.- Hydrogen embrittlement.- Solubility of hydrogen in metals.- Mild steel.- Group Va and VIa metals.- Nickel.- Palladium.- Titanium and zirconium.- 5 Aluminium and its Alloys.- The unloading yield point effect.- 'Commercially pure' aluminium.- Aluminium-copper alloys - Aluminium-magnesium alloys.- Other aluminium alloys.- Theories of yield points in aluminium alloys.- 6 Other Face-Centred Cubic Metals and Alloys.- Copper and its dilute alloys.- Brass.- Silver and its alloys.- Nickel and its alloys.- Thorium.- Ordered alloys.- 7 Miscellaneous Materials.- Whiskers.- Ionic crystals.- Semiconducting materials.- Hexagonal metals and alloys.- 8 Discussion.

440 citations


"Ultrasonic Interrogation of Polycry..." refers background in this paper

  • ...For example, in polycrystalline metals the grain size greatly influences both ultrasonic attenuation [1-4] and material strength, ductility, toughness and formability [5]....

    [...]

Journal ArticleDOI
TL;DR: In this article, attenuation and velocity measurements have been made for aluminum and glass rods in the frequency range from 2 to 15 megacycles by using a pulse method, and the measured losses for aluminum rods show a component proportional to the frequency and another component proportionally to the fourth power of the frequency.
Abstract: By using a pulse method, attenuation and velocity measurements have been made for aluminum and glass rods in the frequency range from 2 to 15 megacycles. The sound pulses are generated by crystals waxed to the surface of the rod. This wax joint limits the band width of the transmitted pulse and measurements are made using long pulses and approach steady state conditions. The reflected pulses show evidence of several normal modes which can be minimized by using specially shaped electrodes. Longitudinal waves show delayed pulses of smaller magnitude that are caused by the longitudinal wave breaking up into reflected longitudinal and shear waves at the boundary. This effect is small if the diameter of the rod is 20 wave‐lengths or more. The measured losses for aluminum rods show a component proportional to the frequency and another component proportional to the fourth power of the frequency. The first component is the hysteresis loss found for most solid materials. The component proportional to the fourth power of the frequency is caused by Rayleigh scattering losses which are due to differences in the elastic constants between adjacent grains due to changes in orientation. Calculated scattering losses agree quite well with the measured values. The fourth‐power scattering law holds quite well until the grain size is equal to one‐third of a wave‐length. For higher frequencies the scattering loss increases more nearly with the square of the frequency. Glasses and fused quartz have a loss directly proportional to the frequency showing that any irregularities must be of very small size.

269 citations

Journal ArticleDOI
TL;DR: In this article, ultrasonic attenuation measurements were made from 2 to 100 Mc/sec in the pearlitic plus-ferritic, bainitic, and martensitic transformation products in SAE 4150 steel, a low alloy, 0.5% carbon variety.
Abstract: Ultrasonic attenuation measurements were made from 2 to 100 Mc/sec in the pearlitic‐plus‐ferritic, bainitic, and martensitic transformation products in SAE 4150 steel, a low‐alloy, 0.5% carbon variety. Measurements were also made in the martensitic specimen after tempering. Ultrasonic velocity measurements were made at 10 Mc/sec in each case. To eliminate the question of grain size and grain size distribution, three specimens were treated identically through the austenitizing operation. Then they were cooled differently to produce the three transformation products. The attenuation can be expressed as Af4+Cf2, where f is frequency. The first term is Rayleigh scattering and the second may be from dislocation damping, atomic relaxations, or magnetic domain boundary effects. Both A and C are strong functions of microstructure. Both coefficients decrease in the order pearlite‐plus‐ferrite, bainite, martensite, tempered martensite. On tempering, A decreased in the ratio 3:2 while C decreased 3:1. In pearlite‐plus‐ferrite, A is larger by a factor of 225 than it is in tempered martensite, and C is larger by a factor of 10. The ratio CT/CL (T = transverse waves, L=longitudinal waves) was a constant independent of microstructure and equal to 2.4. This suggests either dislocation damping, an atomic relaxation, or a magnetic effect. The large change in C on tempering (with CT/CL = constant) indicates that the interstitial carbon is involved. The ultrasonic velocity measurements showed an increase in velocity on tempering the martensite. Pearlite‐plus‐ferrite has the highest velocities and density, while raw martensite has the lowest. The differences in velocities arise primarily from differences in the elastic moduli of the transformation products, not from the density differences.

197 citations