scholarly journals A Constitutive Relation Based on the Johnson–Cook Model for Ti-22Al-23Nb-2(Mo, Zr) Alloy at Elevated Temperature

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 754
Author(s):  
Yanju Wang ◽  
Duo Zhou ◽  
Yi Zhou ◽  
Aixue Sha ◽  
Huaxing Cheng ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Constitutive Relation ◽  
Deformation Behavior ◽  
Elevated Temperatures ◽  
Peak Stress ◽  
Testing Temperature ◽  
Effect Of Temperature ◽  
Different Temperatures ◽  
Zr Alloy

Although several schemes have been proposed to modify the classical Johnson–Cook (J-C) model, the effect of temperature on the flow stress of materials at different temperatures has not been clarified. In the current study, to investigate the deformation behavior of Ti-22Al-23Nb-2(Mo, Zr) alloy at different temperatures, uniaxial tension experiments were performed at both room (RT, 28 °C) and elevated temperatures, and a modified J-C model was developed to describe the temperature-dependent plastic flow. In tensile experiments, Ti2AlNb-based alloy showed a continuous work hardening until reaching the ultimate strength at RT, while an apparent drop appeared in the flow stress after the peak stress at elevated temperature. Moreover, the experimental peak stress significantly depends on the testing temperature. To correctly describe the different variations of flow stresses at different temperatures, a parameter, S, which represents the softening behavior of flow stress, is integrated into the classical J-C model. In addition, the applicability and validity of the proposed J-C model were verified by calibration with experimental curves of different temperatures. On the other hand, the fractography of post-test specimens was examined to interrupt the increased fracture brittleness of Ti2AlNb-based alloy at elevated temperatures. The proposed constitutive relation based on the J-C model is applicable to predict the deformation behavior of other Ti2AlNb-based alloys at different temperatures.

Temperature Dependent Plastic Deformation Behavior of AZ31 Magnesium Alloy in Uniaxial and Biaxial Compressions

2016 ◽  
Vol 725 ◽  
pp. 421-426 ◽  
Author(s):  
Ichiro Shimizu
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Temperature Dependency ◽  
Stress Strain ◽  
Stress Strain Relation

Metal forming of magnesium alloys often performed at elevated temperature, because magnesium alloys exhibit peculiar stress-strain relation and inferior ductility compared to conventional metals at room temperature. In the present study, deformation behavior and formability of cast and extruded AZ31 magnesium alloys under uniaxial and biaxial compressions at room temperature and at elevated temperatures were investigated. The results revealed that the compressive stress-strain relation of AZ31 magnesium alloy changed not only with the initial texture but also with the deformation temperature. The temperature dependency of flow stress of the cast alloy was smaller than that of the extruded alloy probably because of less influence of pre-deformation. In addition, the influence of compressive deformation pattern upon flow stress of the extruded alloy remained even at elevated temperature to 523 K. The temperature dependency of compressive fracture was also discussed and it was found that the equi-biaxial condition improved the compressive formability at elevated temperatures.

Tensile Properties of Low Nickel Austenitic Stainless Steel at Elevated Temperatures

2012 ◽  
Vol 159 ◽  
pp. 346-350
Author(s):  
Shu Min Liu ◽  
Jian Bin Zhang
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Elevated Temperatures ◽  
Peak Stress ◽  
Temperature Curve ◽  
Delta Ferrite ◽  
Cross Sectional ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Reduction Percentage

The elevated temperature short-time tensile test with the sample of casting low nickel stainless steel was conducted on SHIMADZU AG-10 at ten temperatures 300, 500, 600, 700, 800, 950, 1000, 1050, 1100, and 1250°C, respectively. The stress-strain curves with the thermal deformation at the different temperatures, the peak stress intensity-temperature curve, and the reduction percentage of cross sectional area-temperature curve were obtained. Metallographic test samples were prepared and the morphology of deforming zone was observed by optical microscopy. The experimental results show that the tensile strength of the test samples decreases with increasing temperature. From 300 to 800°C, the work harding occurred and the tensile strength increases with increasing strain. The work softening occurred and the tensile strength decreases with increasing strain at temperatures of 800 to 1250°C. The minimum value of reduction percentage was measured at 800 °C. The austenite and delta-ferrite are the main phase in the tested samples. When the tensile temperatures are increased to 1200°C, the delta-ferrite became thinner and broke down to be spheroidized.

Characterization of hot deformation behavior of Al-Zn-Mg-Mn-Zr alloy during compression at elevated temperature

2017 ◽  
Vol 24 (3) ◽  
pp. 515-520 ◽  
Author(s):  
Jie Yan ◽  
Qing-lin Pan ◽  
Xiang-kai Zhang ◽  
Xue Sun ◽  
An-de Li ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Hot Deformation Behavior ◽  
Zr Alloy

scholarly journals Acidovorax citrulli is sensitive to elevated temperatures during early stages of watermelon seed germination

2020 ◽  
Vol 48 (1) ◽  
pp. 11-20
Author(s):  
Mei Zhao ◽  
Ron Walcott
Keyword(s):  
Elevated Temperature ◽  
Seed Germination ◽  
Elevated Temperatures ◽  
Transmitted Disease ◽  
Effect Of Temperature ◽  
Crop Species ◽  
Inoculum Concentration ◽  
Bacterial Fruit Blotch ◽  
Acidovorax Citrulli ◽  
Germinating Seeds

Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, is a seed-transmitted disease of cucurbit crop species. During seed-to-seedling transmission of BFB, A. citrulli initially grows as a saprophyte on germinating seeds and subsequently switches to a pathogenic mode. We investigated the effect of temperature on A. citrulli colonisation of germinating watermelon seeds. Seeds were vacuum-infiltrated with 106 CFU/ml A. citrulli, germinated at 28°C and 100% relative humidity, and transferred to 40°C at different times. Mean BFB incidence was significantly lower for seeds that were sown at 28°C and transferred to 40°C three days after sowing (DAS), compared with seeds incubated constantly at 28°C. Seeds showed reduced mean BFB transmission percentages when transferred from 28 to 40°C at 3 DAS, regardless of initial A. citrulli concentration. The effect of increased temperature on BFB seedling transmission was reversible regardless of the initial A. citrulli inoculum concentration. Furthermore, the A. citrulli population on germinating watermelon seedlings that were transferred from 28 to 40°C at 3 DAS was significantly lower than seedlings maintained at 28°C. We conclude that A. citrulli cells associated with germinating watermelon seeds are more sensitive to elevated temperature during the first 3 DAS relative to the later days.

Effect of temperature on the heart in the alligator

1960 ◽  
Vol 198 (4) ◽  
pp. 861-863 ◽  
Author(s):  
Charles G. Wilber
Keyword(s):  
Heart Rate ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Well Being ◽  
Effect Of Temperature ◽  
Optimal Temperature ◽  
General Behavior ◽  
Colonic Temperature

Electrocardiograms were taken on 12 alligators, 18–30 inches in length. Some were exposed to elevated temperatures; the resulting ECG's were compared with controls obtained at 22°C, which were as follows: rate, 40/min.; P-R, 0.4 seconds; Q-T, 0.6 seconds; T, 0.24 second, 0.05 mv; QRS, 0.04 second. Heart rate increased with increased colonic temperature. At 34°C there was marked increase in variability of rate. Above 40°C the heart became irregular and was damaged irreversibly. Duration of T decreased with elevated temperature to about 33°C above which T was prolonged. Optimal temperature for the alligator in terms of tolerance and general behavior is between 32°C and 35°C, with a critical maximum of 38°C. Slightly above that temperature the heart became disorganized. The present results suggest that the alligator's temperature preferendum is sound with respect to cardiac well being.

MEASUREMENT OF STRAINS IN CARBON-REINFORCED POLYMER COMPOSITE PRODUCTS AT ELEVATED TEMPERATURES USING FIBER-OPTIC SENSORS

2019 ◽  
pp. 14-19
Author(s):  
O. N. Budadin ◽  
W. Yu. Kutyurin ◽  
A. N. Rykov ◽  
P. I. Gnusin
Keyword(s):  
Elevated Temperatures ◽  
Fiber Optic ◽  
Fiber Bragg Gratings ◽  
Bragg Gratings ◽  
Fiber Optic Sensors ◽  
Effect Of Temperature ◽  
Main Task ◽  
Reinforced Polymer ◽  
Different Temperatures ◽  
Quantitative Results

The main task of the contribution was the estimation of the possibility of using Fiber Bragg Gratings as a mean of measuring the deformation in standard carbon fiber samples at elevated temperatures. The article presents the results of experiments on the measurement of deformations in a carbon sample using Fiber Bragg Gratings on an optical fiber. Deformations were measured in the process of stretching the sample at different temperatures (range from 20 to 140 °C). It is shown that FBGs integrated into the sample material give more stable, reproducible readings, unlike to inlay on the outer surface. It has been established that the use of several FBGs with different sensitivity to temperature or deformation (created by mechanically decoupling the sensor from the sample) makes it possible to compensate the effect of temperature when measuring deformations. The quantitative results of measurements are provided.

Mechanical Properties and Fracture Study of Alumina Dispersion Hardened Copper-Based Nano-Composite at Elevated Temperatures

2013 ◽  
Vol 829 ◽  
pp. 583-588 ◽  
Author(s):  
Ali Dalirbod ◽  
Yahya A. Sorkhe ◽  
Hossein Aghajani
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Fracture Surface ◽  
Yield Strength ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Optical Microscope ◽  
Tensile Fracture ◽  
Different Temperatures

Alumina dispersion hardened copper-base composite was fabricated by internal oxidation method. The high temperature tensile fracture of Cu-Al2O3 composite was studied and tensile strengths were determined at different temperatures of 600, 680 and 780 °C. Microstructure was investigated by means of optical microscope and field emission scanning electron microscope (FESEM) with energy dispersive spectroscopy (EDS). Results show that, ultimate tensile strength and yield strength of copper alumina nanocomposite decrease slowly with increasing temperature. The yield strength reaches 119 MPa and ultimate tensile strength reaches 132 MPa at 780 °C. Surface fractography shows a dimple-type fracture on the fracture surface of the tensile tests where dimple size increases with increasing testing temperature and in some regions brittle fracture characteristics could be observed in the fracture surface.

Investigation of Deformation Behavior of SS304 and Pure Copper Subjected to Electrically Assisted Forming Process

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Tianhao Jiang ◽  
Linfa Peng ◽  
Peiyun Yi ◽  
Xinmin Lai
Keyword(s):  
Elevated Temperature ◽  
Flow Stress ◽  
Constitutive Model ◽  
Electric Current ◽  
Deformation Behavior ◽  
Pure Copper ◽  
Annihilation Process ◽  
Forming Process ◽  
Electrically Assisted ◽  
Dislocation Movement

Both electrically assisted tension (EAT) and thermally assisted tension (TAT) tests were performed on SS304 and pure copper to decouple the influence of elevated temperature from electric current on flow stress and ductility. It is found that the reduction on flow stress and ductility of SS304 are more dependent on the elevated temperature than electric current, but electric current has a stronger effect by 10% on reducing flow stress and ductility of pure copper than the elevated temperature does. As the flow stress and ductility of two metals are related to the dislocation evolution, a constitutive model considering both storage and annihilation process of dislocation was established to describe the effect of electric current and temperature on dislocation movement. It is found that electric current accelerated the annihilation process of dislocation in pure copper up to 20% in EAT compared with that in TAT, but such phenomenon was rarely observed in SS304. Furthermore, attempts have also been made to distinguish the influence of elevated temperature with that of electric current on microstructure evolution and it is also found that the formation of [111] crystals in pure copper is nearly 10% less in EAT than that in TAT.

scholarly journals Effects of Temperature on the Evolution of Yield Surface and Stress Asymmetry in A356–T7 Cast Aluminium Alloy

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7898
Author(s):  
Elanghovan Natesan ◽  
Johan Ahlström ◽  
Stefan Eriksson ◽  
Christer Persson
Keyword(s):  
Flow Stress ◽  
Aluminium Alloy ◽  
Internal Combustion Engines ◽  
Elevated Temperatures ◽  
Internal Combustion ◽  
Effect Of Temperature ◽  
Mean Stress ◽  
Cast Aluminium ◽  
Stress Asymmetry ◽  
Mean Strain

As the electrification of vehicle powertrains takes prominence to meet stringent emission norms, parts of internal combustion engines like cylinder heads are subjected to an increased number of thermal load cycles. The cost-effective design of such structures subjected to cyclic thermo-mechanical loads relies on the development of accurate material models capable of describing the continuum deformation behaviour of the material. This study investigates the effect of temperature on the evolution of flow stress under cyclic loading in A356-T7 + 0.5% Cu cast aluminium alloy commonly used in modern internal combustion engine cylinder heads. The material exhibits peak stress and flow stress asymmetry with the stress response and flow stress of the material under compressive loading higher than under tension. This peak and flow stress asymmetry decrease with an increase in temperature. To compare this stress asymmetry against conventional steel, cyclic strain-controlled fatigue tests are run on fully pearlitic R260 railway steel material. To study the effect of mean strain on the cyclic mean stress evolution and fatigue behaviour of the alloy, tests with tensile and compressive mean strains of +0.2% and −0.2% are compared against fully reversed (Rε = −1) strain-controlled tests. The material exhibits greater stress asymmetry between the peak tensile and peak compressive stresses for the strain-controlled tests with a compressive mean strain than the tests with an identical magnitude tensile mean strain. The material exhibits mean stress relaxation at all temperatures. Reduced durability of the material is observed for the tests with tensile mean strains at lower test temperatures of up to 150 °C. The tensile mean strains at elevated temperatures do not exhibit such a detrimental effect on the endurance limit of the material.

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