scholarly journals An Experimental Study of the Tension-Compression Asymmetry of Extruded Ti-6.5Al-2Zr-1Mo-1V under Quasi-Static Conditions at High Temperature

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1299
Author(s):  
Chen Zhang ◽  
Dongsheng Li ◽  
Xiaoqiang Li ◽  
Yong Li
Keyword(s):  
High Temperature ◽  
Strain Hardening ◽  
Yield Stress ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Uniaxial Tensile ◽  
Tensile Direction ◽  
Stress Asymmetry ◽  
Static Conditions ◽  
Tension Compression Asymmetry

The tension-compression asymmetry (TCA) behavior of an extruded titanium alloy at high temperatures has been investigated experimentally in this study. Uniaxial tensile and compressive tests were conducted from 923 to 1023 K with various strain rates under quasi-static conditions. The corresponding yield stress and asymmetric strain hardening behavior were obtained and analyzed. In addition, the microstructure at different temperatures and stress states indicates that the extruded TA15 profile exhibits a significant yield stress asymmetry at different testing temperatures. The flow stress and yield stress during tension are greater than compression. The yield stress asymmetry decreases with the increase in temperature. The alloy also exhibits TCA behavior on the strain hardening rate. Its mechanical response during compression is more sensitive than tension. A dynamic recrystallization phenomenon is observed instead of twin generated in tension and compression under high-temperature quasi-static conditions. The grains are elongated along the tensile direction and deformed by about 45° along the compressive load axis. Finally, the TCA of Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy is due to slip displacement. The tensile deformation activates basal <a>, prismatic <a> and pyramidal <c + a> slip modes, while the compressive deformation activates only prismatic <a> and pyramidal <c + a> slip modes.

Effect of network structure from different processing conditions on the mechanical property of semi-crystalline polymers

2014 ◽  
Vol 1619 ◽  
Author(s):  
Xin Dong ◽  
David McDowell ◽  
Karl Jacob
Keyword(s):  
Mechanical Property ◽  
Strain Hardening ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Processing Condition ◽  
Constant Stress ◽  
Uniaxial Tensile ◽  
Initial Structure ◽  
Stress Strain ◽  
Strain Hardening Behavior

ABSTRACTSemi-crystalline structures were prepared from different processing condition. Biaxial oriented melt were crystallized at 375 K and atmospheric pressure for 10 nanoseconds (ns), to generate a lamellar semi-crystalline structure. Similar structures were also prepared from deformation of a cubic amorphous initial structure isothermally at 375 K. For comparison, two different thermostats, the constant stress (NPT) and constant volume (NVT) conditions were applied to the system during 10 ns of crystallization. The semi-crystalline samples shared common morphological features such as in the crystallinity, crystal orientation, lamellae thickness and density distribution, etc. However, during the subsequent uniaxial tensile deformation test of the samples to strain of 0.5, different stress-strain behaviors were demonstrated. By combining the observations of morphologies during deformation tests and analysis of the stress-strain curves, conclusions were made that the effectiveness of the network had a strong influence on the mechanical property and strain hardening behavior. The oriented network from the constant stress crystallization, owing to the taut chains, gave rise to optimal mechanical response with substantial strain-hardening.

scholarly journals Creep Rupture Analysis of Candidate Steels for the Traveling Wave Reactor

2018 ◽  
Author(s):  
Cheng Xu
Keyword(s):  
High Temperature ◽  
Yield Stress ◽  
Traveling Wave ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Thermal Creep ◽  
Uniaxial Tensile ◽  
Advantages And Disadvantages ◽  
Analysis Methods ◽  
Best Estimate

TerraPower has developed sophisticated computational analysis tools to support the design and fabrication of high temperature components to be used in the Traveling Wave Reactor (TWR). One of the key material properties required to predict material damage and remaining lifetime of key in-reactor components is the thermal creep rupture time. Although TerraPower optimized ferritic-martensitic (FM) HT9 steel has shown consistent improvement in yield stress and creep rupture strength through uniaxial tensile tests, extrapolations of existing test data are still needed to fully support the complex analysis used in the TWR design. Traditional Larson-Miller analysis for creep rupture was used to compare the TerraPower optimized HT9 steel to the existing historical database. The results of the Larson-Miller analysis were compared to the results from the Wilshire analysis to explore the relative advantages and disadvantages of each method. The best estimate values for fitting constants and activation energies were determined for both methods, taking into account the effects of the higher yield stress observed in TerraPower optimized HT9 compared to historic HT9. Likewise, the best estimate creep rupture stresses for TerraPower optimized HT9 at various times and temperatures were determined by extrapolations using both the Larson-Miller and Wilshire analysis. The allowable stresses of historical and TerraPower optimized HT9 steels were compared to those of existing materials (9Cr-1Mo-V) in the ASME high temperature code. The comparison of analysis methods and rupture stresses demonstrate that TerraPower FM steel thermal creep performance and analysis methods are comparable to existing ASME qualified materials for high temperature applications.

Mechanical Properties and Strain Transfer Behavior of Molybdenum Ditelluride (MoTe2) Thin Films

2021 ◽  
pp. 1-31
Author(s):  
Shoieb Ahmed Chowdhury ◽  
Katherine Inzani ◽  
Tara Pena ◽  
Aditya Dey ◽  
Stephen M. Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Change ◽  
Density Functional ◽  
Mechanical Response ◽  
Interatomic Potential ◽  
Tensile Deformation ◽  
Random Search ◽  
Mechanical Strain ◽  
Uniaxial Tensile ◽  
Strain Transfer

Abstract Transition metal dichalcogenides (TMDs) offer superior properties over conventional materials in many areas such as in electronic devices. In recent years, TMDs have been shown to display a phase switching mechanism under the application of external mechanical strain, making them exciting candidates for phase change transistors. Molybdenum ditelluride (MoTe2) is one such material that has been engineered as a strain-based phase change transistor. In this work, we explore various aspects of the mechanical properties of this material by a suite of computational and experimental approaches. Firstly, we present parameterization of an interatomic potential for modeling monolayer as well as multilayered MoTe2 films. For generating the empirical potential parameter set, we fit results from Density Functional Theory calculations using a random search algorithm called particle swarm optimization. The potential closely predicts structural properties, elastic constants, and vibrational frequencies of MoTe2 indicating a reliable fit. Our simulated mechanical response matches earlier larger scale experimental nanoindentation results with excellent prediction of fracture points. Simulation of uniaxial tensile deformation by Molecular Dynamics shows the complete non-linear stress-strain response up to failure. Mechanical behavior, including failure properties, exhibits directional anisotropy due to the variation of bond alignments with crystal orientation. Furthermore, we show the deterioration of mechanical properties with increasing temperature. Finally, we present computational and experimental evidence of an extended c-axis strain transfer length in MoTe2 compared to TMDs with smaller chalcogen atoms.

Finite element simulations to evaluate deformation of polyester tubular braided structures

2016 ◽  
Vol 87 (10) ◽  
pp. 1275-1283 ◽  
Author(s):  
Jerry Ochola ◽  
Benny Malengier ◽  
Lode Daelemans ◽  
Lieva Van Langenhove
Keyword(s):  
Structural Changes ◽  
Large Deformations ◽  
Tensile Deformation ◽  
Deformation Mode ◽  
Experimental Investigations ◽  
Uniaxial Tensile ◽  
Mechanical Modeling ◽  
Geometrical Structures ◽  
Braided Structure ◽  
Static Conditions

The use of narrow tubular braided structures for biological tissue support has made it possible to produce highly flexible and robust soft tissue reinforcement structures. These attributes make the braids ideal in supporting ruptured and broken tissues during healing and regeneration. There have been continued efforts to improve the design in order to reinforce tissues while still maintaining their flexibility; this has been undertaken by exploring the deformation behavior of these structures. Mechanical modeling, which provides an in-depth understanding of the deformation mechanism of structures, plays an important role in designing structural changes in tubular braids. This paper reports the results of numerical and experimental investigations into the radial contraction and deformation mode of two types of tubular braided fabrics—single and double braided—subjected to uniaxial tensile loading under quasi-static conditions. Realistic geometrical structures were developed for mechanical modeling of tubular braids in terms of tensile loads, elongation, radial contraction and braid angle. The results indicated that there was a good match between experimental and simulated tensile behavior of the braided structures. It was established that the amount of braided yarns within the structure had the likelihood of influencing the radial contraction and braid angle in the braided structure under uniaxial tensile deformation. The results portrayed that braided structures would undergo large deformations at low loads. It was also established that there would be more structural stability as the yarns increased, evidenced by more loads in the double-braided structure as compared to the single-braided tubular structure.

scholarly journals Transition in Deformation Mechanism of AZ31 Magnesium Alloy during High-Temperature Tensile Deformation

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Masafumi Noda ◽  
Hisashi Mori ◽  
Kunio Funami
Keyword(s):  
High Temperature ◽  
Deformation Mechanism ◽  
Tensile Deformation ◽  
Initial Strain Rate ◽  
Grain Boundary Sliding ◽  
Mg Alloy ◽  
Uniaxial Tensile ◽  
Specific Strength ◽  
Az31 Mg Alloy ◽  
High Temperature Tensile

Magnesium alloys can be used for reducing the weight of various structural products, because of their high specific strength. They have attracted considerable attention as materials with a reduced environmental load, since they help to save both resources and energy. In order to use Mg alloys for manufacturing vehicles, it is important to investigate the deformation mechanism and transition point for optimizing the material and vehicle design. In this study, we investigated the transition of the deformation mechanism during the high-temperature uniaxial tensile deformation of the AZ31 Mg alloy. At a test temperature of 523 K and an initial strain rate of 3×10−3 s-1, the AZ31 Mg alloy (mean grain size: ~5 μm) exhibited stable deformation behavior and the deformation mechanism changed to one dominated by grain boundary sliding.

scholarly journals Hot Gas Pressure Forming of Ti-55 High Temperature Titanium Alloy Tubular Component

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4636
Author(s):  
Kehuan Wang ◽  
Chenyu Shi ◽  
Shiqiang Zhu ◽  
Yongming Wang ◽  
Jintao Shi ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Tensile Deformation ◽  
Electron Backscatter Diffraction ◽  
Thickness Distribution ◽  
Tensile Tests ◽  
Gas Pressure ◽  
Uniaxial Tensile ◽  
Hot Gas ◽  
Tubular Component

In this paper, hot gas pressure forming (HGPF) of Ti-55 high temperature titanium alloy was studied. The hot deformation behavior was studied by uniaxial tensile tests at temperatures ranging from 750 to 900 °C with strain rates ranging from 0.001 to 0.05 s−1, and the microstructure evolution during tensile tests was characterized by electron backscatter diffraction. Finite element (FE) simulation of HGPF was carried out to study the effect of axial feeding on thickness distribution. Forming tests were performed to validate this process for Ti-55 alloy. Results show that when the temperature was higher than 750 °C, the elongation was large enough for HGPF of Ti-55 alloy. Dynamic recrystallization (DRX) occurred during the tensile deformation, which could refine the microstructure. The thickness uniformity of the formed part could be improved by increasing feeding length. The maximum thinning ratio decreased from 27.7% to 11.5% with the feeding length increasing from 0 to 20 mm. A qualified Ti-55 alloy component was successfully formed at 850 °C, the microstructure was slightly refined after forming, and the average post-form yield strength and peak strength were increased by 8.7% and 6.9%, respectively. Pre-heat treatment at 950 °C before HGPF could obtain Ti-55 alloy tubular component with bimodal microstructure and further improve the post-form strength.

Influence of Ageing on Yield Stress Anisotropy of Extruded 7075 Aluminum Alloy Bar at Ambient Temperature

2012 ◽  
Vol 190-191 ◽  
pp. 500-503
Author(s):  
Zhi Min Zhang ◽  
Yong Biao Yang ◽  
Ke Ren Xu
Keyword(s):  
Aluminum Alloy ◽  
Yield Stress ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Test Machine ◽  
7075 Aluminum Alloy ◽  
Tensile Direction ◽  
Solution Treated ◽  
Grain Structures ◽  
Peak Aged

Uniaxial tensile tests of extruded 7075 aluminum alloy bar were carried out on the universal test machine at strain rate of 0.001 s-1. The tensile direction are aligned at 0°, 45°and 90°to the axis direction of the bar. Microstructure and texture was characterized using Optical Microscopy and x ray diffraction analysis. The results show that the yield stress for 0° orientation specimen, which was solution treated, is the highest, while that of 45° orientation is the lowest. The yield stresses are anisotropic for solution treated 7075 extruded bar, which could be attributed to the elongated grain structures and the texture of the bar. The yield stress anisotropic behavior diminished after peak aged.

Chain Entanglements and Mechanical Behavior of High Density Polyethylene

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Joy J. Cheng ◽  
José A. Alvarado-Contreras ◽  
Maria A. Polak ◽  
Alexander Penlidis
Keyword(s):  
Molecular Weight ◽  
Strain Hardening ◽  
Amorphous Phase ◽  
Tensile Deformation ◽  
Micromechanical Modeling ◽  
Uniaxial Tensile ◽  
Hardening Behavior ◽  
Strain Hardening Behavior ◽  
Chain Entanglements

It has long been suspected that physical chain entanglements in the amorphous phase affect the strain hardening behavior of polyethylene. The precise number of chain entanglements in solid polyethylene cannot be measured using any current techniques. Since entanglements in the melt state are known to be preserved in the polymer upon solidification, determination of the molecular weight between entanglements (Me) is used as a measure of chain entanglements for polyethylene. A decrease in molecular weight between entanglements means an increase in the number of entanglements in the polymer. As the Me value decreases, increasing tensile strain hardening of polyethylene is observed. In addition to experimental work, parallel micromechanical modeling was carried out to study the entanglement effect in uniaxial tensile deformation. The model was able to shed more light over the earlier empirical speculations. By combining experimental observations and modeling results, the presence of physical chain entanglements in the amorphous phase was demonstrated to be the controlling factor in strain hardening behavior of polyethylene.

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