scholarly journals Dislocation Breakaway Damping in AA7050 Alloy

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1682
Author(s):  
Andrea Di Schino ◽  
Roberto Montanari ◽  
Claudio Testani ◽  
Alessandra Varone
Keyword(s):  
Room Temperature ◽  
Hot Forging ◽  
Cross Slip ◽  
Test Cycle ◽  
Mechanical Spectroscopy ◽  
Link Length ◽  
Second Stage ◽  
The Mean ◽  
Two Stages

The AA7050 alloy prepared through the standard industrial hot-forging cycle has been investigated by means of isothermal mechanical spectroscopy (MS) from room temperature up to 185 °C. Each MS test consisted of a cycle with two stages, at increasing and decreasing strain. After each cycle the damping value resulted to be higher than the original one indicating the occurrence of an irreversible transformation. Such phenomenon, observed for all the test temperatures, becomes more relevant for T ≥ 150 °C. The irreversible transformation has been discussed and explained by considering the evolution of the mean dislocation link length between pinning points represented by nanometric MgZn2 precipitates. The breakaway of dislocation segments from pinning points occurs in the stage at increasing strain and is not fully recovered during the second stage at decreasing strain thus the mean link length increases in a MS test cycle. The onset of thermal activated dislocation cross-slip at about 150 °C favors the dislocation breakaway and consequently enhances the effect on damping.

The Influence of Heat and Two Stages Precipitation in the Process of Natural Polymer Purification from the Byproduct of Bioethanol Process Base on Empty Palm Fruit Bunch

2015 ◽  
Vol 1123 ◽  
pp. 177-181
Author(s):  
Achmad Hanafi ◽  
Harry Budiman ◽  
Fauzan Aulia
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Room Temperature ◽  
Black Liquor ◽  
Ash Content ◽  
Natural Polymer ◽  
Palm Fruit ◽  
Second Stage ◽  
Direct Precipitation ◽  
Two Stages

The biopolymer material, lignin, was recovered from the black liquor by acidification of the black liquor using sulfuric acid. Several purification techniques were carried out to produce the high purity of lignin such as gradual precipitation of lignin from black liquor (first stage: precipitation at pH 7, second stage: precipitation at pH 2) and the diluting of crude lignin by sodium hydroxide then followed by re-precipitation at different temperature. Subsequently, the impurities of lignin product resulted from each purification techniques was determined as ash content that analyzed using temperature program furnace; and the content of lignin was investigated using spectrophotometer UV-Vis. The result showed that the content of lignin of material produced from gradual precipitation was approximately 77.6%. It was higher than the content of lignin about 3.4% of material produced from direct precipitation to pH 2. In addition, the elevating of temperature from 40 to 60°C was no considerably affect to the content of lignin in precipitate produced from re-precipitation of crude lignin solution in sodium hydroxide. Nonetheless, the content of lignin of precipitate improved 15% when the temperature of re-precipitation of crude lignin solution in sodium hydroxide was raised from room temperature to 40-60°C.

scholarly journals Firn Densification: An Empirical Model

1980 ◽  
Vol 25 (93) ◽  
pp. 373-385 ◽  
Author(s):  
Michael M. Herron ◽  
Chester C. Langway
Keyword(s):  
Empirical Model ◽  
Accumulation Rate ◽  
Rate Equations ◽  
Constant Density ◽  
Square Root ◽  
Accumulation Rates ◽  
Densification Rate ◽  
Second Stage ◽  
The Mean ◽  
Two Stages

AbstractAn empirical model of firn densification from the surface to the zone of pore close-off has been constructed. Fundamental rate equations have been derived for the first two stages of densification. In the first stage, for densities less than 0.55 Mg m−3, the densification rate is proportional to the mean annual accumulation times the term (ρi − ρ), where ρ is the density of the snow and ρi is the density of pure ice. The densification rate in the second stage, where 0.55 Mg m −3 < ρ < 0.8 Mg m−3, is proportional to the square root of the accumulation rate and to (ρi− ρ). Depth–density and depth–age calculations from this model are compared with observation. Model accumulation rates are within about 20% of values obtained by other techniques. It is suggested that depth intervals of constant density in some Antarctic cores may represent a synchronous event in the 1880 ’s when ten times the normal accumulation fell within a year or two.

scholarly journals Temporary Shelter Simulation Towards Effectiveness Value of OTTV and Thermal Comfort

2019 ◽  
Vol 36 (3) ◽  
Author(s):  
Dyah Puspa Ayu ◽  
Budi Prayitno ◽  
Agus Hariyadi
Keyword(s):  
Thermal Comfort ◽  
Natural Disasters ◽  
Room Temperature ◽  
Human Life ◽  
Air Humidity ◽  
Value Differences ◽  
Second Stage ◽  
Thermal Transfer ◽  
A Value ◽  
Two Stages

Indonesia is prone to a variety of natural disasters, one of which is earthquakes. Earthquakes are detrimental to human life, causing among other things a loss of shelter. As such, victims of earthquakes need basic assistance in the form of shelter, which the Indonesian government provides in the transition phase of emergency responses. Several innovations in the provision of temporary shelter have arisen in terms of packaging and fast unloading. This research aimed to examine the effective value of OTTV energy (overall thermal transfer value), differences in room temperature, and thermal comfort in existing temporary shelters. OTTV values and thermal comfort are adapted to Indonesia's humid tropical climate, which has a temperature ranging 24–30°C and air humidity of 75%. Temporary shelters were simulated with Rhinoceros and Grasshopper softwares. The simulation was carried out in two stages, with the first stage simulating the temporary shelter materials and the second stage simulating according to a predetermined standard. The results concluded that the effective value of OTTV with the use of Styrofoam-based shelter gives a value of 27.63 W/m2 with a decrease of up to 4.70 W/m2 and the temperature drops to 2–3°C.

Firn Densification: An Empirical Model

1980 ◽  
Vol 25 (93) ◽  
pp. 373-385 ◽  
Author(s):  
Michael M. Herron ◽  
Chester C. Langway
Keyword(s):  
Empirical Model ◽  
Accumulation Rate ◽  
Rate Equations ◽  
Constant Density ◽  
Square Root ◽  
Accumulation Rates ◽  
Densification Rate ◽  
Second Stage ◽  
The Mean ◽  
Two Stages

AbstractAn empirical model of firn densification from the surface to the zone of pore close-off has been constructed. Fundamental rate equations have been derived for the first two stages of densification. In the first stage, for densities less than 0.55 Mg m−3, the densification rate is proportional to the mean annual accumulation times the term (ρi−ρ), whereρis the density of the snow andρiis the density of pure ice. The densification rate in the second stage, where 0.55 Mg m−3&lt; ρ &lt; 0.8 Mg m−3, is proportional to the square root of the accumulation rate and to (ρi−ρ). Depth–density and depth–age calculations from this model are compared with observation. Model accumulation rates are within about 20% of values obtained by other techniques. It is suggested that depth intervals of constant density in some Antarctic cores may represent a synchronous event in the 1880 ’s when ten times the normal accumulation fell within a year or two.

scholarly journals Treatment of Mining and Thermoelectric Waste Through the Geopolymerization Process

2021 ◽  
Vol 100 ◽  
pp. 05003
Author(s):  
Morales-Aranibar Carlos ◽  
Linares Nataniel ◽  
Soto Tolomeo ◽  
Morales-Aranibar Luis
Keyword(s):  
Fly Ash ◽  
Mine Tailings ◽  
Room Temperature ◽  
Hydroelectric Plant ◽  
Chemical Characterization ◽  
Second Stage ◽  
Pyrite Content ◽  
Two Stages ◽  
Sem Morphology

Currently, energy and extraction activities generate large amounts of highly polluting waste, so there is a need for sustainable and environmentally friendly technologies. The aim of the study is to treat mining tailings and fly ash through the process of geopolymerization. The samples studied were obtained from the Toquepala mine, Tacna and from the ENGIE-Moquegua hydroelectric plant (Peru). The methodology was based on two stages, the first characterization of Fly Ash (FA) and mine tailings (MT) by EDX chemical characterization, SEM morphology, the second was prepared mixtures of MT and FA in 10 M alkaline solution, cured in 35 days at room temperature and the characterization of the geopolymer by organoleptic analysis, SEM and TCLP. The first stage shows high aluminosilicate content 20.44% Al2O3 and 53.39 % SiO2 for (MT); 22.11% Al2O3 and 51.76% SiO2 for (FA), presents metal and pyrite content. In the second stage, the samples show health and environmental harmlessness, with the formation of tetragonal structures typical of the geopolymer, the samples show a significant reduction of Sr, Ca, Fe, Pb, Ba, Be, and Cu, demonstrating the effectiveness of treatment by means of geopolymerization opening a new field for the environmental passive treatment.

Room-Temperature Strength of Sintered Silicon Nitride Subjected to High-Temperature Creep Loading

1994 ◽  
Author(s):  
Yoshizumi Nakasuji ◽  
Hiroyuki Iwasaki ◽  
Hiroaki Sakai
Keyword(s):  
Silicon Nitride ◽  
Room Temperature ◽  
Strength Degradation ◽  
Creep Tests ◽  
Second Stage ◽  
Two Stages ◽  
Creep Loading ◽  
Applied Stresses ◽  
Room Temperature Strength ◽  
Sintered Silicon

Room-temperature strength was evaluated using sintered silicon nitride crept specimens. Creep tests were performed using 4-point bending loading at 1400°C in air. The bending creep tests applied stresses from 100 to 400 MPa for 10−1 to 3×103 hours. For applied stress over 200 MPa, the room-temperature strength of the crept specimen had two stages. In the first stage the strength degraded slowly, and in the second stage the strength degraded rapidly. In the first stage, oxidation caused the strength degradation, since the degradation was similar for the different applied stresses. In the second stage, large creep deformation mainly caused the strength degradation. Early in the stage, creep induced matrix and boundary damage under the oxidation layer caused the degradation. At the end of the stage, cracks induced by creep caused the degradation.

MEASUREMENT THE EFFECT OF γ-IRRADIATION DOSES ON AlCu8.5 BY POSITRON ANNIHILATION DOPPLER-BROADENING SPECTROSCOPY

2007 ◽  
Vol 21 (22) ◽  
pp. 3901-3907
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. ABDEL-RAHMAN ◽  
M. ABO-ELSOUD ◽  
M. F. EISSA ◽  
YAHIA A. LOTFY ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Irradiation Dose ◽  
Room Temperature ◽  
Doppler Broadening ◽  
Γ Irradiation ◽  
Second Stage ◽  
S Parameter ◽  
Controlling Mechanism ◽  
Γ Ray ◽  
Two Stages

The effect of irradiation dose (kGy) on a set of AlCu 8.5 samples has been studied. The samples were irradiated to doses of 10, 30, 50, 70, 100, 300, 500, 700 and 1000 kGy of 60 Co γ-source at room temperature. The effect of γ-ray irradiation on the values of the S- and W-parameters reveals two stages. In the first stage, the S-parameter increases, while the W-parameter decreases up to 70 kGy. In the second stage, the S- and W-parameters decrease and increase respectively in the dose region from 100 to 1000 kGy. The dominant controlling mechanism of the S- and W-parameters was observed.

Cold-Rolling and Subsequent Annealing of Ti-Rich Tial Polysynthetically Twinned (PST) Crystals

1990 ◽  
Vol 213 ◽  
Author(s):  
M.H. Oh ◽  
H. Inui ◽  
S.R. Nishitani ◽  
M. Yamaguchi
Keyword(s):  
Dislocation Density ◽  
Cold Rolling ◽  
Shear Deformation ◽  
Lamellar Structure ◽  
Room Temperature ◽  
Subsequent Annealing ◽  
Second Stage ◽  
Cold Rolled ◽  
Two Stages ◽  
Equiaxed Grains

ABSTRACTPolysynthetically twinned (PST) crystals of Ti-rich TiAl have been grown and specimens cut from these crystals have been rolled at room temperature and subsequently annealed at 900°C and 1000°C. When the shear deformation parallel to the lamellar boundaries occurs during rolling, PST crystals of Ti-rich TiAl can be rolled to about 50% reduction in thickness at room temperature.The recovery in microhardness occurs in two stages; the first stage associated with the decrease in dislocation density and the second stage connected with the annealing-out of deformation induced twins. The recrystallization mode depends on the amount of reduction. Up to 20% reduction, the lamellar structure is preserved even after the full recovery in hardness. When the amount of reduction exceeds 40%, a structure composed of equiaxed grains of TiAl is obtained after recrystallization. A mechanism of recrystallization of cold-rolled PST crystals, which may explain the dependence of recrystallization mode on the amount of reduction, is proposed.

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

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