Mechanical Behavior Of Metals Research Articles

The Effect of Ion Implantation on the Mechanical Behavior of Metals and Alloys

Revue de la litterature concernant l'influence d'une modification de surface par implantation ionique sur les proprietes mecaniques des metaux et alliages notamment la deformation monotone, la fatigue et le fluage a haute temperature. Presentation d'exemples

Mechanical behavior of metals under tension- compression loading at high strain rate

By using a new technique based on a split Hopkinson pressure bar method, a sequenced reverse test (quasi-static tensile prestress, followed by dynamic compression and then followed by dynamic tension) at high strain rate was performed and tension-compression stress-strain relations were derived by using one-dimensional stress wave analysis. Three materials, 2017 aluminium alloy, 0.45% carbon steel, and pure aluminium, were investigated at low and high strain rates, and the strain rate effect on the reverse loading stress-strain curves was compared to that on the loading stress-strain curves. It was found that reduction of yield stress is always associated with load reversals, and the strain rate effect on the reverse loading (tension) is almost the same as that during loading (compression) at higher values of reverse deformation.

Radiation-induced structural changes in alloys

Development of alloys for reliable performance in extreme radiation environments is vital for the viability of advanced nuclear reactor systems. Over the past decade, there has been a considerable growth in our understanding of the basic processes of radiation damage, the nature of the induced defects, their interaction and migration, and the influence of these on the mechanical behaviour of metals. This understanding has however come mainly from studies in pure metals and dilute alloys, and there are difficulties when applying these concepts to concentrated alloys, particularly of technological interest. The present article, which attempts to bridge this gap, discusses recent research developments and some of the emerging new concepts as applicable to alloy systems. Interstitialcy transport; percolation effects in defect migration; short range and long range ordering and restructuring of alloys; defects and damage behaviour of metallic glasses; synergetic processes and phase instabilities; and finally, swelling, irradiation creep and ductility behaviour of alloy systems are the topics discussed.

Effect of hydrogen attack on the strength of high purity copper

Experimental as well as theoretical studies [1-4] in relation to the influence of heat treatment on the structural and mechanical behaviour of metals and alloys in hydrogen atmosphere have been extensively undertaken in recent years. Pishko et al. [1] observed that the ultimate tensile strength of various steels pulled at 77 K was a fmaction of the time of exposure to hydrogen at 723 K, due to the formation of voids on certain grain boundaries. Feltham and Evans [2] found that creep in 5N pure copper single crystals between 773 and 1143 K was also significantly influenced by hydrogen uptake. More recently Butt and Feltham [3] studied the effect of hydrogen on grain growth in 5N pure copper at 1073 K; the grain size was found to decrease rather than increase, with increasing time of isothermal annealing, due to the diffusion of hydrogen to grain boundaries. On the theoretical side, Hirth [411 made an attempt to account for the observations on the basis of the distribution of vacancy chemical potential near a nucleating and growing void when cavitation occurs in either creep [5] or hydrogen attack [1-3] of metallic crystals. The main object of the present work was to investigate the effect of hydrogen uptake on the yield strength of 5N pure copper in the range 77 to 300 K. The polycrystalline copper of 5N purity used was supplied by Metals Research Limited, Royston, England in the form of cylindrical rods of 1 cm diameter. Specimens, 2cm long, were cut from the "as-received" rods by means of a fine saw. They were grouped into four batches, and each batch was sealed into a separate silica tube filled with hydrogen at 100 tore They were then annealed for 120 rain at 523 K to minimize internal stresses, before the subsequent isothermal grain growth extending over periods of 15 to 120 rain at 1073 K. Mean grain diameters, 0.9 and 0.35 mm in Fig. 1 and 0.60, 0.45, 0.35 and 0.33 mm in Fig. 2 were obtained by the line-intercept method. Chemical polishing of some of the sp~.'cimens of different grain sizes for about 4rain at 323 to 528K in a solution containing 25vo1% H3PO4, 25vo1% acetic acid and 50vo1% concentrated nitric acid revealed numerous "craters" on the

Connection between structural changes and mechanical behavior of metal during creep. Creep equations

Connection between structural changes and mechanical behavior of metal during creep. Creep equations

Mechanical Behavior of Metals in Dynamic Compression

A technique for the measurement of force and displacement data in metal processing at high rates of deformation is described briefly. Forces are determined by fast Fourier transformation of the signal from a quartz load cell and correction in the frequency domain for dynamic response of the load cell. Displacement is measured by a high frequency response fiber-optic transducer. The force and displacement signals are processed by an on-line computer which enables stress, strain, strain-rate, and other parameters to be determined and plotted rapidly. Results from continuous dynamic compression tests are presented in the form of computer generated stress-strain and stress-strain rate curves for two steels. In the strain rate range 10−3 s−1 to 102 s−1 an hydraulic testing machine is used. In the range 102 s−1 to 104 s−1 a drop forge is used. A discussion of the effects of specimen geometry in compression testing is included.

金属材料の機械的挙動のシミュレーション

金属材料の機械的挙動のシミュレーション

Dynamic Behavior of Metals Under Tensile Impact—Part 1: Elevated Temperature Tests

The mechanical behavior of metals subjected to uniaxial tensile impact at elevated temperatures is reported. Tests were conducted on annealed 1100 aluminum at 200, 350, 550, and 800 deg F; annealed 2024 aluminum at 200, 450, and 600 deg; and annealed C1010 steel at 430, 700, 1050, and 1400 deg F. The materials exhibit a wide range of dynamic behavior, including some in which the stress required to produce a given level of strain is significantly lowered by dynamic loading. The ratios of the dynamic ultimate stresses to the static are found to range from 0.71–6.0.

Dynamic Behavior of Metals Under Tensile Impact—Part 2: Annealed and Cold-Worked Materials

The mechanical behavior of metals subjected to unaxial tensile impact at room temperature is reported. Tests were conducted on 1100 aluminum subjected to light and to heavy cold working; 2024 aluminum after annealing and after light and heavy cold working; C1010 steel in these same three conditions; and OFHC copper and 70–30 brass in an annealed state. In four of the 10 series, the materials were found to possess dynamic stress-strain curves which fell below the static curves. The yield point of the steel was lowered by impact loading. Ratios of dynamic to static ultimate stress were found to range from 0.59–1.3.

Comments on “the effects of the hydrostatic pressure in a deep ocean on the mechanical behaviour of metals”: by A. A. Johnson, T. Lewenstein and E. A. Imbembo

Comments on “the effects of the hydrostatic pressure in a deep ocean on the mechanical behaviour of metals”: by A. A. Johnson, T. Lewenstein and E. A. Imbembo

The effects of the hydrostatic pressure in a deep ocean on the mechanical behaviour of metals

The nucleation of a microcrack in a metal by dislocation coalescence is governed principally by shear stresses and is therefore, to a first approximation, not influenced by the application of a hydrostatic pressure. Its propagation is, however, made more difficult by a hydrostatic pressure because it is governed principally by the tensile components of stress normal to the plane of the crack. As a result, a metal which is brittle at ambient pressure may become ductile when a hydrostatic pressure is applied, i.e. the ductile-brittle transition temperature may be lowered. A simple calculation shows that this decrease in transition temperature should be approximately proportional to the pressure and should be several tens of degrees for the magnitude of pressure found in a deep ocean. A limited number of experiments carried out in laboratory pressure chambers, and reported in the literature, show that this calculation is at least approximately correct. Some recent work reported in the literature has shown that in some cases the application of a pressure may cause mechanical property changes which persist when the pressure is removed. These have been tentatively attributed to effects such as the irreversible generation of dislocations at inclusion-matrix interfaces. The pressures used in this work were much greater than those encountered even in the deepest ocean. Nevertheless, it is worth examining the possibility that similar, if smaller, effects occur when a metal is exposed to a deep ocean environment. Experiments aimed at detecting such effects have been conducted on eight materials—five steels and three titanium alloys. The steels included AISI 1018, AISI 4130, tempered martensitic steels having nominal yield stresses of 130,000 and 170,000 psi, and a maraging steel with a nominal yield stress of 180,000 psi. The three titanium alloys had α, α/ β, and β structures respectively. Tensile and Charpy V-Notch specimens of all eight materials were exposed to a pressure of 25,000 psi, which corresponds to a depth about 50 per cent greater than the deepest known parts of the oceans, for 30 min. Their properties, and the properties of control specimens, were then studied over a range of temperature. The results show that pressurization caused small property changes in four of the eight materials, the AISI 1018 and AISI 4130 steels, the 170,000 psi martensitic steel, and the α β titanium alloy. Preliminary experiments in which tensile specimens of the AISI 1018 steel and the α/β titanium alloy were subjected to 100 pressure cycles suggest that these property changes are not cumulative on cyclic pressurization.

Discussion of “the effects of the hydrostatic pressure in a deep ocean on the mechanical behaviour of metals”: by A. A. Johnson, T. Lewenstein and E. A. Imbembo, with comments by H. L. Wain

Discussion of “the effects of the hydrostatic pressure in a deep ocean on the mechanical behaviour of metals”: by A. A. Johnson, T. Lewenstein and E. A. Imbembo, with comments by H. L. Wain

Automatic flight management of future high- performance aircraft.

liar to Fatigue Deformation, Acta Metallurgica, Vol. 11, No. 7, July 1963, p. 643. 3 Sinclair, G. M., Proceedings of American Society for Test Material, Vol. 52, 1952, p. 743. 4 on the Role of Substructure in the Mechanical Behavior of Metals, ASD-TDR 63-324, April 1963, Air Systems Div., pp. 1-22. 5 Zirinsky, S., Switsky, H., and Kenger, A., Utilization of an Ultrasonic Fatigue Damage Indicator for Inspection and Design, 1966 Symposium for Reliability, Nov. 1966, Los Angeles, Calif. 6 Cory, G. et al., of Latent Fatigue Damage in Metals and Alloys/' Contract NOw 59-1202-C, June 1960, Southwest Research Institute. 7 Kunsenberger, F. et al., of Test Device for Study of Fatigue Damage, Contract NOw 61-0685-C, June 1962, Southwest Research Institute. 8 Kusenberger, F. and Barton, Substantiation of Fatigue Detection Capability, Contract N600 (19)-59307, June 1963, Southwest Research Institute. 9 Kusenberger, F. et al., Non-Destructive Evaluation of Metal Fatigue, AF 49(638)-1352, March 1965, AD61985, Southwest Research Institute. 10 Kusenberger, F. et al., Non-Destructive Evaluation of Metal Fatigue, AF 49(638)-1502, March 1966, Southwest Research Institute. 11 Harting, D. The S/N Fatigue Life Gage: Direct Means for Measuring Cumulative Fatigue Damage, Experimental Mechanics, Feb. 1966. 12 Brosius, H. et al., of Fatigue Damage with Rayleigh Waves, TR 60-307, Aug. 1960, Aeronautical Research Laboratory. 13 Truell, R. et al., The Use of Ultrasonic Methods to Determine Fatigue Effects in Metals, TR59-389, Nov. 1959, Wright Air Development Center. 14 Rasmussen, J. G., Prediction of Fatigue Failure Using Ultrasonic Surface Waves, Reprint 901, Krautkramer Ultrasonics Inc. 15 Hardrath, H. F., A Review of Fatigue Research in the United States, TM-X-56562, NASA.

1554. Effect of vacuum on the mechanical behaviour of metals

1554. Effect of vacuum on the mechanical behaviour of metals

Mechanical Behaviour of Metals in Deep Ocean Environments

THE rapidly developing interest in deep ocean engineering makes it necessary to consider possible effects of deep ocean environments on the properties of engineering materials. The principal difference between a deep ocean environment and an environment just below the surface of an ocean is, of course, that in the former there exists a large hydrostatic pressure. It can easily be shown that if the depth from the surface, h, is measured in fathoms, the hydrostatic pressure, P, is given by: This communication considers the changes in mechanical properties which might be expected to result from this hydrostatic pressure. We shall consider first reversible effects, that is, effects which should be observed only when a metal or alloy is stressed while submerged in a deep ocean, and, secondly, possible irreversible effects, that is, property changes which might be caused by deep submergence and persist after the metal or alloy has been removed from the deep ocean environment.

The influence of a space environment on the mechanical behavior of metals

The effect of low pressures on the fatigue, tensile and creep behavior is discussed. The data are interpreted in terms of the accumulation of dislocations in the surface region. It is suggested that the mechanical behavior is influenced by the rate of escape of dislocations through the surface. Initially, the oxide layer plays an important role; however, as the strain increases, the dislocation layer exerts a large influence.

On the mechanical behaviour of metals in the strain-hardening range

On the mechanical behaviour of metals in the strain-hardening range