scholarly journals Effect of Loading Rate on Creep Properties of HgCdTe Epitaxial Films

2020 ◽  
Vol 70 (5) ◽  
pp. 493-497
Author(s):  
Hemant Kumar Sharma ◽  
Rajesh Prasad ◽  
Raghvendra Sahai Saxena ◽  
Aditya Gokhale ◽  
Rajesh Kumar Sharma
Keyword(s):  
Elastic Modulus ◽  
Stress Exponent ◽  
Loading Rate ◽  
Creep Behaviour ◽  
Strong Dependence ◽  
Hold Time ◽  
Peak Load ◽  
Epitaxial Films ◽  
Creep Properties ◽  
Loading Rates

Nanoindentation creep studies were performed on Hg1-xCdxTe (x~0.29) epitaxial films using different loading rates of 0.5 mN.s-1, 1 mN.s-1, 2 mN.s-1 and 4 mN.s-1, keeping a constant peak load of 10 mN. A constant hold time of 20 sec at peak load was maintained for all experiments. The effect of loading rate on creep behaviour of material has been investigated. Creep displacement had shown increasing trend with increase of loading rates. Stress exponents were extracted using creep curve fitting with an empirical equation. A strong dependence of loading rate on stress exponent was observed. The value of stress exponent was found varying in the range 0.60-1.76, 0.96-2.23, 0.98-2,87 and 0.90-2.81 for loading rates 0.5 mN.s-1, 1 mN.s-1, 2 mN.s-1 and 4 mN.s-1, respectively. The change of stress exponent was attributed to change of creep mechanism. Hardness and elastic modulus were extracted from load-displacement curves and it was found that with the increase of the loading rate hardness increases, while elastic modulus remains constant. A correlation between variation of hardness and creep displacement has also been presented.

scholarly journals Experimental Research on the Mechanical Behavior of Lime-Treated Soil under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Yue Qiang ◽  
Yulong Chen
Keyword(s):  
Shear Strength ◽  
Elastic Modulus ◽  
Internal Friction ◽  
Mechanical Behavior ◽  
Loading Rate ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Treated Soil ◽  
Loading Rates ◽  
Lime Content

In order to study the mechanical behavior of lime-treated soil under different loading rates, a series of monotonous three-axial compression tests are carried out under different lime contents, different loading rates, and different curing periods. The test results indicate that the lime content can significantly improve the mechanical behaviors of soil, such as shear strength and elastic modulus. On the other hand, three-axial compression test of soil is carried out under the loading rate ranging from 0.1%/min to 8%/min. Experimental results indicate that the mechanical behavior of lime-treated soil is sensitive to loading rate. Besides, the corresponding relationship between internal friction angle, cohesion, lime content, and loading rate is discussed. The results indicate that the loading rate almost has no influence on internal friction angle but significant influence on lime content. Cohesion is affected by lime content and loading rate. Shear strength, elastic modulus, and cohesion all increase with the increase of loading rate. Longer curing period is associated with greater parameter value. Shear strength, elastic modulus, and internal friction angle all firstly increase and then decrease when lime content increases, which all reach the maximum at 6%.

Nano-Indentation for Measurement on Mechanical Property of Building Integrated Amorphous Silicon Thin-Film PV Cell

2014 ◽  
Vol 638-640 ◽  
pp. 1365-1368
Author(s):  
Shun Mei Li ◽  
Jun Mei ◽  
Yu Liu ◽  
Yong Yao ◽  
Lin Gang Lan ◽  
...  
Keyword(s):  
Thin Film ◽  
Elastic Modulus ◽  
Amorphous Silicon ◽  
Loading Rate ◽  
Silicon Film ◽  
Peak Load ◽  
Silicon Layer ◽  
Silicon Thin Film ◽  
Testing Method ◽  
Pv Cell

Amorphous silicon thin-film PV cell(AST) generally consists of a few – micron thick silicon film on a glass substrate, which has difficulty for being accurately measured by using a conventional testing method to obtain its elastic modulus and hardness. In our study, we are applying nanoindentation for the measurement purpose and divide the sample into five regions for studying. Both of peak load - and loading rate - dependences supervise us to more accurately measure the mechanical properties of silicon layer through defining the peak load at 9000μN and loading rate at 1000μN/s. It was also observed that across the whole sample measurements on the elastic modulus have much better consistence than those on the hardness. We therefore propose a method of partitioning the sample into two parts for counting the different hardness measurements.

scholarly journals Cyclic creep behaviour of two-phase Ti-6Al-2Mo-2Cr alloy

2020 ◽  
Vol 321 ◽  
pp. 11079
Author(s):  
Waldemar Ziaja ◽  
Maciej Motyka ◽  
Krzysztof Kubiak ◽  
Jan Sieniawski
Keyword(s):  
Heat Treatment ◽  
Elevated Temperature ◽  
Titanium Alloys ◽  
Creep Behaviour ◽  
Strong Dependence ◽  
Cyclic Creep ◽  
Tensile Creep ◽  
Two Phase ◽  
Creep Properties ◽  
Cyclic Creep Behaviour

One of the important criteria for selection titanium alloys for discs and blades of turbine engine compressor is their fatigue and creep strength at room and elevated temperature. Fatigue and creep properties of two-phase titanium alloys show strong dependence on microstructure, especially morphology of the α and β phases which can be controlled to certain extent by proper selection of hot working and heat treatment conditions. Quantitative description of two-phase titanium alloys behaviour under loading and environmental conditions leading to combined creep and fatigue processes has been always very challenging task due to large number of factors affecting deformation and fracture behaviour of the material. In the course of the research cyclic creep behaviour of Ti-6Al-2Mo-2Cr alloy (VT3-1) was investigated and compared to low-cycle fatigue and static creep properties at the temperature of 450°C. Microstructure of the alloy was varied by means of the heat treatment. Constant load tensile creep tests were carried out. Tension-tension cyclic loading was applied at the constant stress ratio with and without hold time at maximum load. The effect of test parameters on the creep-fatigue life at elevated temperature was estimated. Characteristic features of fracture surfaces were identified by scanning electron microscopy methods.

scholarly journals Study of Nano-Mechanical Performance of Pretreated Natural Fiber in LDPE Composite for Packaging Applications

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4977
Author(s):  
Muhammad Sulaiman ◽  
Tanveer Iqbal ◽  
Saima Yasin ◽  
Hamayoun Mahmood ◽  
Ahmad Shakeel
Keyword(s):  
Elastic Modulus ◽  
Creep Rate ◽  
Mechanical Performance ◽  
Natural Fiber ◽  
Choline Chloride ◽  
Peak Load ◽  
Substantial Effect ◽  
Melt Processing ◽  
Creep Properties ◽  
Composite Samples

In this work, the effects of chemical pretreatment and different fiber loadings on mechanical properties of the composites at the sub-micron scale were studied through nanoindentation. The composites were prepared by incorporating choline chloride (ChCl) pretreated rice husk waste (RHW) in low-density polyethylene (LDPE) using melt processing, followed by a thermal press technique. Nanoindentation experiments with quasi continuous stiffness mode (QCSM) were performed on the surface of produced composites with varying content of pretreated RHW (i.e., 10, 15, and 20 wt.%). Elastic modulus, hardness, and creep properties of fabricated composites were measured as a function of contact depth. The results confirmed the appreciable changes in hardness, elastic modulus, and creep rate of the composites. Compliance curves indicated that the composite having 20 wt.% of pretreated RHW loading was harder compared to that of the pure LDPE and other composite samples. The values of elastic modulus and hardness of the composite containing 20 wt.% pretreated RHW were increased by 4.1% and 24% as compared to that of the pure LDPE, respectively. The creep rate of 42.65 nm/s and change in depth of 650.42 nm were also noted for the composite with RHW loading of 20 wt.%, which showed the substantial effect of holding time at an applied peak load of 100 mN. We believe that the developed composite could be a promising biodegradable packaging material due to its good tribo-mechanical performance.

scholarly journals High Temperature Creep Behaviour of Cast Nickel-Based Superalloys INC 713 LC, B1914 and MAR-M247

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 152
Author(s):  
Marie Kvapilova ◽  
Petr Kral ◽  
Jiri Dvorak ◽  
Vaclav Sklenicka
Keyword(s):  
High Temperature ◽  
Stress Exponent ◽  
Creep Deformation ◽  
Creep Behaviour ◽  
Constant Load ◽  
Strength Properties ◽  
Creep Tests ◽  
Creep Properties ◽  
High Temperature Components ◽  
High Level

Cast nickel-based superalloys INC713 LC, B1914 and MAR-M247 are widely used for high temperature components in the aerospace, automotive and power industries due to their good castability, high level of strength properties at high temperature and hot corrosion resistance. The present study is focused on the mutual comparison of the creep properties of the above-mentioned superalloys, their creep and fracture behaviour and the identification of creep deformation mechanism(s). Standard constant load uniaxial creep tests were carried out up to the rupture at applied stress ranging from 150 to 700 MPa and temperatures of 800–1000 °C. The experimentally determined values of the stress exponent of the minimum creep rate, n, were rationalized by considering the existence of the threshold stress, σ0. The corrected values of the stress exponent correspond to the power-law creep regime and suggest dislocation climb and glide as dominating creep deformation mechanisms. Fractographic observations clearly indicate that the creep fracture is a brittle mostly mixed transgranular and intergranular mode, resulting in relatively low values of fracture strain. Determined main creep parameters show that the superalloy MAR-M247 exhibits the best creep properties, followed by B1914 and then the superalloy INC713 LC. However, that each of the investigated superalloys can be successfully used for high temperature components fulfils the required service loading conditions.

Micromechanical Properties of Polyacrylamide Hydrogels Measured by Spherical Nanoindentation

2014 ◽  
Vol 606 ◽  
pp. 121-124 ◽  
Author(s):  
Jiri Nohava ◽  
Michael Swain ◽  
Philipp Eberwein
Keyword(s):  
Elastic Modulus ◽  
Mechanical Response ◽  
Large Radius ◽  
Instrumented Indentation ◽  
Creep Properties ◽  
Loading Rates ◽  
Hold Period ◽  
Polyacrylamide Hydrogels ◽  
Precise Knowledge ◽  
Cellular Regeneration

Hydrogels are very compliant materials suitable for tissue engineering in various areas of biological and clinical research. Appropriate and effective application of hydrogels for specific cellular regeneration often requires precise knowledge of their mechanical properties. The present work focuses on measurements of mechanical deformation and creep properties of polyacrylamide hydrogels using a novel indentation system. Four concentrations of polyacrylamide gel were tested under four different loading rates to study the mechanical response of the material to various loading rates. A spherical indenter with large radius was used in the experiments and all indentations were done with the sample completely immersed in water. The results show that higher acrylamide concentration in the gel leads to higher elastic modulus and decrease of creep. Similarly, faster loading rates lead to higher elastic modulus and larger creep during the hold period. The data were analyzed using both Hertzian fit to the loading part and Oliver-Pharr approach to the unloading part. The discrepancy between these two approaches and significant creep behavior are related to the viscoelasticity of the tested materials. This work contributes to understanding the results of instrumented indentation of extremely compliant materials with respect to their viscoelastic properties.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

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.

scholarly journals Experimental and Numerical Analysis of the Mechanical Properties of a Pretreated Shape Memory Alloy Wire in a Self-Centering Steel Brace

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 80
Author(s):  
Bo Zhang ◽  
Sizhi Zeng ◽  
Fenghua Tang ◽  
Shujun Hu ◽  
Qiang Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Energy Dissipation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Loading Rate ◽  
Effective Elastic Modulus ◽  
Maximum Energy ◽  
Numerical Results ◽  
Energy Dissipation Capacity

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires may not be accurately obtained. In this paper, the cyclic tensile tests of a kind of SMA wire with a 1 mm diameter and special element composition were tested under multi-working conditions, which were pretreated by first tensioning to the 0.06 strain amplitude for 40 cycles, so the mechanical properties of the pretreated SMA wires can be simulated in detail. The accuracy of the numerical results with the improved model of Graesser’s theory was verified by a comparison to the experimental results. The experimental results show that the number of cycles has no significant effect on the mechanical properties of SMA wires after a certain number of cyclic tensile training. With the loading rate increasing, the pinch effect of the hysteresis curves will be enlarged, while the effective elastic modulus and slope of the transformation stresses in the process of loading and unloading are also increased, and the maximum energy dissipation capacity of the SMA wires appears at a loading rate of 0.675 mm/s. Moreover, with the initial strain increasing, the slope of the transformation stresses in the process of loading is increased, while the effective elastic modulus and slope of the transformation stresses in the process of unloading are decreased, and the maximum energy dissipation capacity appears at the initial strain of 0.0075. In addition, a good agreement between the test and numerical results is obtained by comparing with the hysteresis curves and energy dissipation values, so the numerical model is useful to predict the stress–strain relations at different stages. The test and numerical results will also provide a basis for the design of corresponding self-centering steel dampers.

Coarse filters for pond effluent polishing: comparison of loading rates and grain sizes

2007 ◽  
Vol 55 (11) ◽  
pp. 121-126 ◽  
Author(s):  
M. von Sperling ◽  
J.G.B. de Andrada ◽  
W.R. de Melo Júnior
Keyword(s):  
Loading Rate ◽  
Uasb Reactor ◽  
E Coli ◽  
Effluent Quality ◽  
Loading Rates ◽  
Hydraulic Loading ◽  
Grain Sizes ◽  
Belo Horizonte ◽  
The City ◽  
Rock Size

A system comprising a UASB reactor, shallow polishing ponds and shallow coarse filters, treating actual wastewater from the city of Belo Horizonte, Brazil, has been evaluated. The main focus of the research was to compare grain sizes and hydraulic loading rates in the coarse filters. Two filters operating in parallel were investigated, with the following grain sizes: Filter 1: 3 to 10 cm; Filter 2: 8 to 20 cm. Two hydraulic loading rates were tested: 0.5 and 1.0 m3/m3.d. The filter with the lower rock size had a better performance than the filter with the larger rock size in the removal of SS and, as a consequence, BOD and COD. A better performance was obtained with the hydraulic loading rate of 0.5 m3/m3.d, as compared to the rate of 1.0 m3/m3.d. The effluent quality during the period with the lower loading rate was very good for discharge into water bodies or for agricultural reuse (median effluent concentrations from Filter 1: BOD: 20 mg/L; COD: 106 mg/L; SS: 28 mg/L; E. coli: 528 MPN/100 mL).

scholarly journals Development of friction-induced triboluminescent sensor for load monitoring

2017 ◽  
Vol 29 (5) ◽  
pp. 883-895 ◽  
Author(s):  
Md Abu S Shohag ◽  
Zhengqian Jiang ◽  
Emily C Hammel ◽  
Lucas Braga Carani ◽  
David O Olawale ◽  
...  
Keyword(s):  
Applied Load ◽  
Loading Rate ◽  
Turbine Blades ◽  
Wind Turbine Blades ◽  
Loading Rates ◽  
Load Monitoring ◽  
The Coefficient Of Friction ◽  
Dynamic Structures ◽  
Sample Configuration

Real-time load monitoring of critical civil and mechanical structures especially dynamic structures such as wind turbine blades is imperative for longer service life. This article proposed a novel sensor system based on the proprietary in situ triboluminescent optical fiber (ITOF) sensor for dynamic load monitoring. The new ITOF sensor patch consists of an ITOF sensor network with micro-exciters integrated within a polymer matrix. The sensor patch was subjected to repeated flexural loading and produced triboluminescent emissions due to the friction between micro-exciters and ITOF sensors corresponding to each loading cycle. The friction-induced triboluminescent intensity directly depends on the loading rate, the coefficient of friction, and the applied load on patch. In general, the triboluminescent intensity increases exponentially with an increase in load. Additionally, the sensor patches comprising the coarser micro-exciters exhibited better results. Similarly, better results were achieved at higher loading rates although a threshold loading rate is required to excite the triboluminescent crystals for this sample configuration. The proposed new sensor has the ability to monitor dynamic continuous applied loads.

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