High-Temperature Mechanical Behavior of B2 Type IrAl Doped With Ni

ABSTRACTConstant-velocity and constant-load compression tests have been conducted to examine the mechanical behavior of polycrystalline IrAl and Ir1-xNixAl at ambient and elevated temperatures. Although IrAl exhibits brittle fracture before or immediately after yielding below 1073K, steady-state deformation takes place at temperatures higher than 1273K. Ductility of Ir1-xNixAl is improved with increasing x. On the contrary, strength decreases with increasing x. IrAl exhibits the 0.2% flow stress of 1200MPa at 1073K and 350MPa at 1473K, about an order of magnitude higher than NiAl. Secondary creep of IrAl and Ir0.2Ni0.8Al(i.e., modified NiAl) exhibits class II and class I behavior respectively. Creep strength of binary IrAl and modified NiAl with Ir is about a magnitude of 4 higher than that of single-phase and multi-phase NiAl at a given applied stress.

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Mechanical Behavior of Molybdenum Disilicide-Based Alloys

MRS Proceedings ◽

10.1557/proc-646-n4.7.1 ◽

2000 ◽

Vol 646 ◽

Cited By ~ 2

Author(s):

A. Misra ◽

A.A. Sharif ◽

J. J. Petrovic ◽

T. E. Mitchell

Keyword(s):

Mechanical Behavior ◽

Single Phase ◽

Elevated Temperatures ◽

Molybdenum Disilicide ◽

Solution Hardening ◽

Ambient Temperatures ◽

Polycrystalline Alloys ◽

Order Of Magnitude ◽

Body Center ◽

Magnitude Increase

ABSTRACTWe have investigated the mechanical behavior of the following single-phase polycrystalline alloys with the MoSi2 body-center tetragonal structure: MoSi2 alloyed with ∼2.5 at.% Re, MoSi2 alloyed with 2 at.% Al, MoSi2 alloyed with 1 at.% Nb, and MoSi2 alloyed with 1 at.% Re and 2 at.% Al. Several anomalies in the mechanical behavior of alloyed materials were observed. For example, (i) addition of only ∼2.5 at. % Re results in an order of magnitude increase in compressive strength at 1600 °C, (ii) additions of Nb and Al cause solution softening at near-ambient temperatures, and (iii) quaternary MoSi2-Re-Al alloys show strengthening at elevated temperatures and reduction in flow stress with enhanced plasticity at near-ambient temperatures in compression. The mechanisms of anomalous solution hardening and softening are discussed.

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Analysis of a proposed connection for the two-winding single-phase self-excited induction generator operating at constant voltage and frequency

Journal of Electrical Systems and Information Technology ◽

10.1186/s43067-019-0002-3 ◽

2019 ◽

Vol 6 (1) ◽

Author(s):

H. H. Hanafy ◽

Heba. M. Soufi ◽

Amr A. Saleh ◽

Magdy B. Eteiba

Keyword(s):

Steady State ◽

Single Phase ◽

Constant Load ◽

Impedance Method ◽

Induction Generator ◽

Variable Load ◽

Prime Mover ◽

Load Impedance ◽

Load Voltage ◽

Load Conditions

AbstractThis paper introduces the steady-state and dynamic behaviors of a proposed connection for the two-winding single-phase self-excited induction generator (TWSPSEIG) equipped with an excitation capacitor and a compensation capacitor for operation at constant load voltage and frequency irrespective of the no-load or different load conditions. The performance equations at steady-state conditions are attained by applying loop impedance method via the exact equivalent circuit models of the TWSPSEIG based on the double revolving field theory. Keeping the values of the excitation capacitor and the compensation capacitor as unknowns, two second-order equations, for given values of generator parameters, prime mover speed, frequency and load impedance, are derived. These equations are solved using simple iterative method to calculate the optimum values of the two capacitors under the constraints that the load voltage and frequency are constant. The range of capacitor variations for variable load at variable prime mover speed is also calculated. The steady-state results are verified by developing the dynamic model of the proposed connection incorporating its nonlinearity behavior and various no-load and load conditions. The dynamic behavior of the proposed connection proves the capabilities of the proposed configuration and calculation method to maintain both the load voltage and frequency constants. A comparative study between the performances of the proposed connection and the traditional connection of the TWSPSEIG is presented to illustrate the merits of the proposed connection.

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Compression Behavior of L12 Modified Titanium Trialuminides Alloyed with Chromium and Iron

MRS Proceedings ◽

10.1557/proc-646-n3.10.1 ◽

2000 ◽

Vol 646 ◽

Author(s):

Tohru Takahashi ◽

Tadashi Hasegawa

Keyword(s):

Steady State ◽

Flow Stress ◽

Chemical Composition ◽

Single Phase ◽

Strain Softening ◽

Lattice Parameter ◽

Quasi Steady State ◽

Compression Tests ◽

Steady State Flow ◽

Compression Behavior

ABSTRACTL12 modified titanium trialuminides have been prepared by replacing 9at.% of the aluminum in Al3Ti with chromium and/or iron. The materials were recrystallized into single phase polycrystals after isothermal forging resulting in an average grain diameter of about 40μm. Lattice parameter of the material containing 9 at.% chromium or 9 at.% iron, are 0.3959nm and 0.3939nm, respectively. The lattice parameters varied linearly with composition between these values for additions of both chromium and iron. Uniaxial compression tests were performed at temperatures ranging from 293K to 1300K. The yield strength is not sensitive to chemical composition within the range of compositions tested. Flow stress serrations of a few % were observed at temperatures around 600K, where intermittent drops in flow stress started immediately after yielding and continued to the end. These serrations were observed up to about 800K. At 900K and above the materials became fully deformable. Quasi steady state flow and strain softening were observed at 1200K and 1300K, respectively, due to dynamic recrystallization.

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Mechanical Behavior of Epoxy-Graphene Platelets Nanocomposites

Journal of Engineering Materials and Technology ◽

10.1115/1.4006499 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 20

Author(s):

A. Zandiatashbar ◽

R. C. Picu ◽

N. Koratkar

Keyword(s):

Activation Energy ◽

Fracture Toughness ◽

Mechanical Behavior ◽

Elevated Temperatures ◽

Local Scale ◽

Neat Epoxy ◽

Filling Fraction ◽

Fracture Behaviors ◽

Order Of Magnitude ◽

Graphene Platelets

Various aspects of the mechanical behavior of epoxy-based nanocomposites with graphene platelets (GPL) as additives are discussed in this article. The monotonic loading response indicates that at elevated temperatures, the elastic modulus and the yield stress are significantly improved in the composite as compared to neat epoxy. The activation energy for creep is smaller in neat epoxy, which indicates that the composite creeps less, especially at elevated temperatures and higher stresses. The composites also exhibit larger fracture toughness. When subjected to cyclic loading, fatigue crack growth rate is smaller in the composite relative to neat epoxy. This reduction is important by at least an order of magnitude at all stress intensity factor amplitudes. Optimal property improvements in the monotonic, cyclic, and fracture behaviors are obtained for very low filling fraction of approximately 0.1 wt. %. Similar differences in the mechanical behavior are observed when the composite is probed on the local scale by nanoindentation.

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Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

Promyshlennoe i Grazhdanskoe Stroitel stvo ◽

10.33622/0869-7019.2019.11.09-14 ◽

2019 ◽

pp. 9-14

Keyword(s):

Experimental Data ◽

Elastic Modulus ◽

Elevated Temperatures ◽

Peak Load ◽

Relative Deformation ◽

Deformation Characteristics ◽

Compression Tests ◽

Strain Behavior ◽

Different Temperatures ◽

Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

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Exercise slightly above the maximal lactate steady state reduces self-efficacy and increases negative affect

10.31236/osf.io/ecgkp ◽

2019 ◽

Author(s):

James Graeme Wrightson ◽

Louis Passfield

Keyword(s):

Steady State ◽

Negative Affect ◽

Power Output ◽

Self Efficacy ◽

Repeated Measures ◽

Physiological State ◽

Constant Load ◽

Peak Power Output ◽

Time To Exhaustion ◽

Maximal Lactate Steady State

Objectives: To examine the effect of exercise at and slightly above the maximal lactate steady state (MLSS) on self-efficacy, affect and effort, and their associations with exercise tolerance.Design: Counterbalanced, repeated measures designMethod: Participants performed two 30‐minute constant‐load cycling exercise at a power output equal to that at MLSS and 10 W above MLSS, immediately followed by a time‐to‐exhaustion test at 80% of their peak power output. Self-efficacy, affect and effort were measured before and after 30 minutes of cycling at and above MLSS.Results: Negative affect and effort higher, and self-efficacy and time to exhaustion were reduced, following cycling at MLSS + 10 W compared to cycling at the MLSS. Following exercise at the MLSS self-efficacy, affect and effort were all associated with subsequent time-to exhaustion. However, following exercise at MLSS + 10 W, only affect was associated with time-to exhaustion. Conclusions: Self efficacy, affect and effort are profoundly affected by physiological state, highlighting the influence of somatic states on perceptions and emotions during exercise. The affective response to exercise appears to be associated with exercise tolerance, indicating that the emotional, as well as physiological, responses should be considered when prescribing exercise training.

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