scholarly journals The Failure of Structural Metals Subjected to Strain-Cycling Conditions

1959 ◽  
Vol 81 (2) ◽  
pp. 203-208 ◽  
Author(s):  
R. W. Swindeman ◽  
D. A. Douglas
Keyword(s):  
Grain Size ◽  
Rupture Life ◽  
Thermal Strain ◽  
Coarse Grained ◽  
Fine Grained ◽  
Long Time ◽  
Structural Metals ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Strain Cycling

Data showing the isothermal strain-cycling capacity of three metals, Inconel, Hastelloy B, and beryllium are presented. It is noted that at frequencies of 0.5 cycle per min the data satisfied an equation of the form Nαϵp = K, where N is the number of cycles to failure, ϵp is the plastic strain per cycle, and α and K are constants whose values depend on the material and test conditions. Data on Inconel are given to establish the effect of grain size, specimen geometry, temperature, and frequency. It is found that, at temperatures above 1300 F, grain size and frequency exert a pronounced effect on the rupture life. Fine-grained metal survives more cycles before failure than coarse-grained material. Long time cycles shorten the number of cycles to failure when the strain per cycle is low. Thermal-strain-cycling data for Inconel are compared to strain-cycling data at the same mean temperature. Good correlation is found to exist between the two types of tests.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

Deformation Size Effects Due to Specimen and Grain Size in Microbending

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Sunal Ahmet Parasiz ◽  
Reid VanBenthysen ◽  
Brad L. Kinsey
Keyword(s):  
Grain Size ◽  
Sheet Thickness ◽  
Specimen Size ◽  
Coarse Grained ◽  
Thick Sheet ◽  
Hardness Profile ◽  
Localized Deformation ◽  
Fine Grained ◽  
Deformation Distribution ◽  
Deformation Area

Sheet metal forming often consists of bending processes in which gradients of deformation exists through the thickness of the workpiece in a localized deformation area. In microscale bending, these deformation gradients become much steeper, as the changes in the deformation occur over short distances (in the order of micrometers). In addition, with miniaturization, the number of grains that are present through the thickness decreases significantly. In this research, the effect of grain size and specimen size on the deformation distribution through the thickness of microbent sheet specimens was investigated via microhardness evaluations. It was found that the deformation distribution, i.e., hardness profile, is not affected significantly by the grain size when the sheet thickness is large (for 1.625 mm specimens) or by miniaturization of the specimen size when the grain size is fine. However, the deformation distribution of the coarse grained specimens deviates from the fine grained ones and from the 1.625 mm thick sheet specimens when the specimen size is miniaturized.

Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

2007 ◽  
Vol 551-552 ◽  
pp. 621-626
Author(s):  
Young Gun Ko ◽  
Yong Nam Kwon ◽  
Jung Hwan Lee ◽  
Dong Hyuk Shin ◽  
Chong Soo Lee
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Cavity Growth ◽  
Rate Sensitivity ◽  
Theoretical Models ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Cavitation Behavior

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation. After imposing an effective strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average size and the area fraction of cavities significantly decreased with decreasing grain size and/or increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior, the cavity growth mechanism in UFG alloys was suggested.

Martensitic Transformations and Functional Stability in Ultra-Fine Grained NiTi Shape Memory Alloys

2008 ◽  
Vol 584-586 ◽  
pp. 852-857 ◽  
Author(s):  
Juri Burow ◽  
Egor Prokofiev ◽  
Christoph Somsen ◽  
Jan Frenzel ◽  
Ruslan Valiev ◽  
...  
Keyword(s):  
Grain Size ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Thermomechanical Processing ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Functional Stability ◽  
Fine Grained ◽  
Niti Shape Memory Alloys

Martensitic transformations in NiTi shape memory alloys (SMAs) strongly depend on the microstructure. In the present work, we investigate how martensitic transformations are affected by various types of ultra-fine grained (UFG) microstructures resulting from various processing routes. NiTi SMAs with UFG microstructures were obtained by equal channel angular pressing, high pressure torsion, wire drawing and subsequent annealing treatments. The resulting material states were characterized by transmission electron microscopy and differential scanning calorimetry (DSC). The three thermomechanical processing routes yield microstructures which significantly differ in terms of grain size and related DSC chart features. While the initial coarse grained material shows a well defined one-step martensitic transformation on cooling, two-step transformations were found for all UFG material states. The functional stability of the various UFG microstructures was evaluated by thermal cycling. It was found that UFG NiTi alloys show a significantly higher stability. In the present work, we also provide preliminary results on the effect of grain size on the undercooling required to transform the material into B19’ and on the related heat of transformation.

Microstructural Evolution of Synthetic Forsterite Aggregates Deformed to High Strain

2004 ◽  
Vol 467-470 ◽  
pp. 579-584 ◽  
Author(s):  
A. Kellermann Slotemaker ◽  
J.H.P. de Bresser ◽  
C.J. Spiers ◽  
M.R. Drury
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Growth ◽  
Microstructural Evolution ◽  
Large Scale ◽  
High Strain ◽  
Confining Pressure ◽  
Size Reduction ◽  
Coarse Grained ◽  
Fine Grained

Microstructures provide the crucial link between solid state flow of rock materials in the laboratory and large-scale tectonic processes in nature. In this context, microstructural evolution of olivine aggregates is of particular importance, since this material controls the flow of the Earth’s upper mantle and affects the dynamics of the outer Earth. From previous work it has become apparent that if olivine rocks are plastically deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that show grain size reduction through dynamic recrystallization. In the present study we focused on fine-grained (~1 µm) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3), Samples were axially compressed to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. We observed syndeformational grain growth rather than grain size reduction, and relate this to strain hardening seen in the stress-strain curves.

scholarly journals Ultrasonic Pulse Velocities And Dynamic Elastic Constants Of Sandstones From The Semanggol Formation, Beris Dam, Kedah Darul Aman

Warta Geologi ◽  
2021 ◽  
Vol 47 (1) ◽  
pp. 1-8
Author(s):  
John K. Raj
Keyword(s):  
Grain Size ◽  
Elastic Constants ◽  
Ultrasonic Pulse ◽  
Coarse Grained ◽  
Unconfined Compression ◽  
Ultrasonic Velocities ◽  
Unconfined Compression Test ◽  
Fine Grained ◽  
Wave Velocities ◽  
Shear Wave Velocities

The main Beris Dam is founded on a sequence of thick bedded conglomerates and pebbly to fine grained sandstones with minor mudstone mapped as the Semanggol Formation of Triassic age. Ultrasonic pulse measurements show velocities of compressional and shear waves through the sandstones to increase with decreasing grain size; the pebbly sandstone with velocities of 2.210, and 5.171, km/s, and the coarse grained sandstone with velocities of 2.477, and 5.612, km/s, respectively. The medium grained sandstones have compressional and shear wave velocities of 2.457, and 5.793, km/s and the fine grained sandstones, velocities of 2.572, and 5.867 km/s, respectively. Dynamic elastic constants computed from the ultrasonic velocities also increase in values with decreasing grain size; Poisson’s ratio varying from 0.36 to 0.39, the modulus of elasticity from 35.076 to 48.210 GPa, the bulk modulus from 52.260 to 67.362 GPa and the modulus of rigidity from 12.637 to 17.468 GPa. Increasing velocities and elastic constants with decreasing grain size are considered to result from a denser arrangement of constituent grains as shown by increasing dry unit weights. Comparison with the results of an unconfined compression test on a fine grained sandstone indicate that the ultrasonic elastic constants are good approximations of static elastic constants.

Studies with the intraruminal selenium pellet. 2. The effect of grain size of selenium on the functional life of pellets in sheep

1981 ◽  
Vol 32 (6) ◽  
pp. 935 ◽  
Author(s):  
DR Hudson ◽  
RA Hunter ◽  
DW Peter
Keyword(s):  
Grain Size ◽  
Progressive Increase ◽  
Coarse Grained ◽  
Elemental Selenium ◽  
Average Composition ◽  
Plasma Selenium ◽  
Iron Selenide ◽  
Fine Grained ◽  
Grain Sizes

Grain size of elemental selenium is a major factor controlling the long-term effectiveness of intraruminal selenium pellets. Microscope studies of polished sections of new and used selenium pellets showed that two commercially manufactured pellets contained selenium with average grain sizes about 4 and 40 �m respectively. Plasma selenium concentrations in sheep treated with pellets containing the coarse-grained selenium were maintained at higher levels over longer periods of time than those measured for sheep treated with pellets with fine-grained selenium. Pellets removed from sheep after 2, 4, 8, 16 and 28 days showed a progressive increase in the degree of alteration of selenium to a compound of average composition (g/100 g) iron, 33.7; selenium, 51.3 ; oxygen, 15.0. After 28 days only a small percentage of elemental selenium remained in pellets with fine-grained selenium, whereas about 50% remained in pellets with coarse-grained selenium. CSIRO prototype pellets, for which long-term effectiveness had been established, also contained coarse-grained selenium, and remnants of selenium were found in pellets that had been in sheep for periods up to 3 years. Selenium, administered in gelatin capsules or as sachets containing glass-selenium mixtures, was stable under the pH-Eh conditions of the rumen, but was rendered unstable in selenium pellets or iron-selenium mixtures by the presence of iron. It is probable that the most rapid release of selenium to the sheep occurs as a result of a chemical reaction involving the oxidation of iron and concomitant alteration of elemental selenium to iron selenide.

Effect of alloy grain size on oxidation resistance of silica-coated stainless steel

1994 ◽  
Vol 52 ◽  
pp. 676-677
Author(s):  
C. S. McDowell ◽  
S. N. Basu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Stainless Steel ◽  
Oxidation Resistance ◽  
Powder Processing ◽  
Hot Isostatic Pressing ◽  
Silica Coating ◽  
Austenitic Steels ◽  
Coarse Grained ◽  
Fine Grained

Oxidation resistance of stainless steels, which rely on the formation of a Cr2O3 (chromia) scale, can be further improved through minor alloying additions such as Al or Si, or by application of coatings to the exposed surfaces. Although, additions of Si to austenitic steels have demonstrated an improvement in oxidation resistance, high Si contents can be detrimental to the mechanical properties of these alloys. The application of a silica coating on the surface of the stainless steel provides improved oxidation resistance without detrimental effects on the mechanical properties. This study examines the effect of the grain size of the stainless steel on the effectiveness of a silica coating as an oxidation barrier.Fully austenitic stainless steel of composition Fe-18(wt%)Cr-20Ni-1.5Mn was produced in both coarsegrained and fine-grained form. The coarse-grained alloy, with a grain size of approximately 100 μm, was produced by casting and hot rolling. The fine-grained alloy, with a grain size of approximately 5 μm, was produced by rapid solidification powder processing, followed by consolidated by hot isostatic pressing and swaging.

The Impact of Grain Size on Oxidation Behavior of TP304H Austenitic Stainless Steel at High Temperature in Air

2011 ◽  
Vol 117-119 ◽  
pp. 990-994
Author(s):  
Wei Wei ◽  
Zhi Wu Wang ◽  
Mao Lin Liu
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Oxide Scale ◽  
Grain Refinement ◽  
Coarse Grained ◽  
X Ray ◽  
Fine Grained ◽  
Different Grain Size ◽  
The Impact

Exposed to 650°C air, TP304H stainless steel with two different grain size was oxidized at this temperature. At the meantime, comparison of their oxidation was through the oxidation kinetics curves and analysis of the morphology and composition of oxide scale which conducted by SEM and X-ray. The results showed that the oxidation rate of TP304H stainless steel was slowed down by grain refinement and oxide scale of fine-grained TP304H steel was thinner than that of coarse-grained steel. The nucleation and the growth of nuclei of coarse-grained oxide scale were more rapid. In addition, the grain refinement of austenitic stainless steel accelerated the diffusivity of Cr and made for the formation of dense and continuous oxide scale, so that the oxidation of stainless steel can be effectively inhabited.

Texture of Al-Cu Alloys Deformed by ECAP

2005 ◽  
Vol 495-497 ◽  
pp. 851-856 ◽  
Author(s):  
Jan Kuśnierz ◽  
Marie Helene Mathon ◽  
Thierry Baudin ◽  
Zdzislaw Jasieński ◽  
Richard Penelle
Keyword(s):  
Grain Size ◽  
Aluminium Alloys ◽  
Superplastic Forming ◽  
Orientation Distribution ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Cu Alloys ◽  
Super Plastic ◽  
Short Time

Materials of ultra-fine grained microstructure (sub-micrometer grain size) exhibit large strength, hardness and ductility and also the increased toughness in comparison with conventional coarse-grained ones. In these materials also the super-plastic flow at lower temperatures is observed. This behaviour may be interesting when aluminium alloys like AlCuZr, used in superplastic forming, are considered. In the paper, the methods of preparing such materials by equal-channel angular pressing (ECAP) is proposed and the texture analysis, based on neutron diffraction pole figure measurements and calculated orientation distribution function of two alloys AlCu4SiMn and AlCu5AgMgZr is discussed. The influence of short time recrystallization is discussed in relation with TEM and SEM observations.

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