scholarly journals Uniaxial compressive strength and failure characteristics of arkosic sandstone after thermal treatment

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2991-3000
Author(s):  
Yuan Zhang ◽  
Yangsheng Ma ◽  
Bin Gu ◽  
Xupeng Ta ◽  
Qun Wang
Keyword(s):  
Mechanical Properties ◽  
Mutual Influence ◽  
Deformation Modulus ◽  
Dominant Factor ◽  
Peak Strain ◽  
Thermal Fracture ◽  
Mechanical Behaviors ◽  
Variation Trend ◽  
Mineral Particles ◽  
Temperature Ranges

Experiments were conducted to study the mechanical characteristics of arkosic sandstones sampled from Pingyi, China. Rock samples were all thermally treated under the temperature ranging from room temperature to 800?C. Results show that as the treatment temperature rises, the arkosic mineral composition does not change obviously, but the mechanical behaviors change regularly. Variation trend changes dramatically at 200?C, 400?C, and 500?C. With thermal expan?sion of mineral particles being the dominant factor, mechanical behaviors barely change below 200?C. When temperature ranges from 200-400?C, it has an important effect on the mechanical properties because of the thermal fracture. From 400-500?C, mechanical properties change dramatically as a result of the mutual influence of thermal fracture, fusion and re-crystallization, but the thermal fracture is the leading factor. Because of the fusion and re-crystallization, fractures are partly filled, which results in partial recovering of the mechanical strength. With the combined action of thermal fracture, fusion and re-crystallization after 600?C, mechanical performance of arkosic sandstones degrades rapidly. Generally, the porosity and peak strain of arkosic sandstones increase with the temperature rising. However, the peak stress, elastic modulus and deformation modulus decrease simultaneously. Influenced by mineral particles? thermal expansion, thermal fracture, fusion, and re-crystallization and so on, the variation trend and amplitude are not the same at different temperature ranges, and the damage mechanism of sandstones also makes a difference.

scholarly journals Influence of water saturation on the strength characteristics and deformation behavior of hardened cement paste backfill

2021 ◽  
Author(s):  
Jie Wang ◽  
Jianxin Fu
Keyword(s):  
Mechanical Properties ◽  
Plastic Strain ◽  
Water Saturation ◽  
Deformation Modulus ◽  
Hardened Cement ◽  
Peak Strain ◽  
Secant Modulus ◽  
Plastic Strain Ratio ◽  
Minimal Impact ◽  
Paste Backfill

Abstract In this study, a uniaxial compression experimental was conducted to examine the mechanical properties of hardened cemented paste backfill (CPB) with different water saturations (0.18%, 4.98%, 9.30%, 21.6%, 32.8%, and 100%). The experimental results demonstrated that water saturation loosened the overall structure of the CPB, which led to the deterioration of its mechanical properties. As the water saturation increased, the uniaxial compressive strength (UCS), residual strength, strength difference, deformation modulus, secant modulus, E50 (the secant modulus at 50% of the UCS), peak strain, and elastic strain decreased, while the plastic strain ratio increased. The UCS, E50, and peak strain demonstrated exponential function relationships with the water saturation. After the peak point, when the water saturation was less than 20%, the strength of the CPB decreased rapidly, and when the water saturation was greater than 30%, the strength decreased slowly. Lastly, the plastic strain, the strain at 50% of the UCS, and the strain at the maximum secant modulus conformed to the normal distribution, and the water saturation had a minimal impact on these three strains. The fractal dimension, D, of the cracks in the CPB increased exponentially with increasing water saturation and demonstrated a negative linear correlation with the UCS.

scholarly journals Mechanical Behavior of Brick Masonry in an Acidic Atmospheric Environment

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2694 ◽  
Author(s):  
Shansuo Zheng ◽  
Lihua Niu ◽  
Pei Pei ◽  
Jinqi Dong
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Acid Rain ◽  
Cement Mortar ◽  
Brick Masonry ◽  
Atmospheric Environment ◽  
Peak Strain ◽  
Lime Mortar ◽  
Attenuation Model

In order to evaluate the deterioration regularity for the mechanical properties of brick masonry due to acid rain corrosion, a series of mechanical property tests for mortars, bricks, shear prisms, and compressive prisms after acid rain corrosion were conducted. The apparent morphology and the compressive strength of the masonry materials (cement mortar, cement-lime mortar, cement-fly ash mortar, and brick), the shear behavior of the masonry, and the compression behavior of the masonry were analyzed. The resistance of acid rain corrosion for the cement-lime mortar prisms was the worst, and the incorporation of fly ash into the cement mortar did not improve the acid rain corrosion resistance. The effect of the acid rain corrosion damage on the mechanical properties for the brick was significant. With an increasing number of acid rain corrosion cycles, the compressive strength of the mortar prisms, and the shear and compressive strengths of the brick masonry first increased and then decreased. The peak stress first increased and then decreased whereas the peak strain gradually increased. The slope of the stress-strain curve for the compression prisms gradually decreased. Furthermore, a mathematical degradation model for the compressive strength of the masonry material (cement mortar, cement-lime mortar, cement-fly ash mortar, and brick), as well as the shear strength attenuation model and the compressive strength attenuation model of brick masonry after acid rain corrosion were proposed.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

scholarly journals Mechanical Properties of Grains Sorghum Subjected to Compression at Different Moisture Contents

2019 ◽  
Vol 11 (4) ◽  
pp. 279
Author(s):  
Gabrielly B. Rodrigues ◽  
Osvaldo Resende ◽  
Daniel E. C. de Oliveira ◽  
Lígia C. de M. Silva ◽  
Weder N. Ferreira Junior
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Uniaxial Compression ◽  
Deformation Modulus ◽  
Grain Sorghum ◽  
Parallel Plates ◽  
Compression Force ◽  
Moisture Contents ◽  
Rest Position ◽  
Different Temperatures

This study aimed to evaluate the influence of drying at different temperatures on the mechanical properties of grains of grain sorghum subjected to compression at the natural rest position. Grains dried at temperatures of 60, 80 and 100 °C with different moisture contents (0.515; 0.408; 0.315; 0.234; 0.162 and 0.099 (d.b.)) were subjected to uniaxial compression between two parallel plates, applied at their natural rest position, at a rate of 0.001 m s-1. The force required to rupture in grains of grain sorghum increased as their moisture contents decreased, with values of 47.17 to 78.44 N, 61.81 to 69.66 N and 52.07 to 70.89 N for the temperatures of 60, 80 and 100 °C, respectively. The compression force required to deform grain sorghum decreased with the increment in moisture content, and the proportional deformation modulus increases with moisture content reduction. Within the studied range of moisture content, the values were 87 × 10-7 to 354.99 × 10-7 Pa, 132.63 × 10-7 to 465.98 × 10-7 Pa and 80.18 × 10-7 to 429.85 × 10-7 Pa for the temperatures of 60, 80 and 100 °C, respectively.

scholarly journals Experimental Research on the Influence of Temperature on the Static Properties of Skarn

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lei Liu ◽  
Xiang Meng ◽  
Hao Qin ◽  
Zhaozhao Chang
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Testing Machine ◽  
Strain Curve ◽  
Physical Parameters ◽  
Peak Strain ◽  
Static Properties ◽  
Static Tests ◽  
High Temperature Mechanical Properties ◽  
Cooling Methods

Studying the high-temperature mechanical properties of rocks is of great significance to engineering disasters caused by deep rock mining and underground protection projects. In view of insufficient research on the high-temperature mechanical properties of deep rocks in southwestern China, we used high-temperature heating devices and statics equipment to conduct static tests on Skarn. XW7L-12 box-type resistance furnace was adopted to heat Skarn (25°C, 200°C, 400°C, 600°C, and 800°C), and the temperature effect of its basic physical parameters (density and wave velocity) was measured and analyzed. Uniaxial compression experiments were performed on two cooling methods of Skarn (natural cooling and water cooling) by a constant stress pressure testing machine to obtain a stress-strain curve and analyze its statics index (peak strength, tensile strength, elastic modulus, and peak strain) and the change rule of failure mode with temperature rise and different cooling methods. With the temperature increasing, various static mechanical indexes of Skarn will be greatly affected. Meanwhile, the different cooling methods are not related to the change trend of the mechanical properties of Skarn under high temperature.

Experimental Study on Mechanical Properties of Larch Glulam Columns under Axial Compression

2016 ◽  
Vol 847 ◽  
pp. 38-45
Author(s):  
Xian Yan Zhou ◽  
Dan Zeng ◽  
Zhi Feng Wang
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Bearing Capacity ◽  
Axial Strain ◽  
Slenderness Ratio ◽  
Axial Loading ◽  
Ultimate Bearing Capacity ◽  
Reduction Factor ◽  
Peak Strain ◽  
Short Columns

At present, the relevant researches of Glulam columns in China are mainly restricted to short columns. In order to study the mechanical properties of long columns under axial loading, an experimental study on five different slenderness ratios of Larch Glulam columns was carried out. With slenderness ratio changing, the variations of experimental data such as axial strain, lateral deflection at mid-height, ultimate bearing capacity, and peak strain were comparatively analyzed. The failure pattern and failure mechanism of long columns were discussed. The results indicate that the ultimate bearing capacity of Larch Glulam columns gradually decreases as the slenderness radio increases and the failure mode is gradually converted from strength failure to instability failure. The ultimate load reduction factor is obtained by regression analysis based on the experiment results of Larch Glulam short columns. The basis for design and application of Larch Glulam columns are provided.

Deposition Effects on the Ultimate Strength of Tungsten Alloy

2014 ◽  
Vol 887-888 ◽  
pp. 857-860
Author(s):  
Ying Ge Xu ◽  
Ze Wei Wu
Keyword(s):  
Mechanical Properties ◽  
Ultimate Strength ◽  
Temperature Effects ◽  
Tensile Tests ◽  
Tungsten Alloy ◽  
Fracture Modes ◽  
Fracture Surfaces ◽  
Temperature Ranges

The temperature effects on the ultimate strength of 93WNiFe alloy have been investigated systematically through tensile tests, fracture surfaces and microstructure. The temperature ranges from 10 to 900 degrees. The results show that the ultimate strength decreases with the increase of temperature, and there is a platform in 300 to 600 degrees .The deposition has been observed in fracture surfaces from 500 to 600 degrees. The fracture modes influence the ultimate strength,deposition can improve mechanical properties of W-W and W-M interfaces, it is the cause of the ultimate strength platform.

The Dominant Factor Analysis of Dynamic Shear Modulus of Poplar LVL Based on Grey Theory

2010 ◽  
Vol 113-116 ◽  
pp. 811-814
Author(s):  
Feng Li ◽  
Ying Cheng Hu
Keyword(s):  
Mechanical Properties ◽  
Production Technology ◽  
Dominant Factor ◽  
Process Conditions ◽  
Dynamic Shear Modulus ◽  
Grey Theory ◽  
Dynamic Shear ◽  
Experimental Conditions ◽  
Laminated Veneer Lumber ◽  
Press Temperature

Wood is one kind of natural renewable eco-material. Laminated veneer lumber (LVL) is an engineered wood product made from veneers glued together with parallelly oriented grains under heat and pressure. This paper designed Poplar LVL production experiments under different process conditions, and measured the mechanical properties of poplar LVL specimens under different experimental conditions. In this study, grey theory was used to analyze the influences of different production processes on the mechanical properties, such as press duration, press temperature, pressure and adhesive spread. The results showed that, it is feasible that grey theory is used to analyze the influence level of production technology of poplar LVL on the mechanical properties. So this paper offered a new method to analyze and design the production technology of LVL.

Differential effects of static and cyclic stretching during elastase digestion on the mechanical properties of extracellular matrices

2007 ◽  
Vol 103 (3) ◽  
pp. 803-811 ◽  
Author(s):  
Rajiv Jesudason ◽  
Lauren Black ◽  
Arnab Majumdar ◽  
Phillip Stone ◽  
Bela Suki
Keyword(s):  
Mechanical Properties ◽  
Enzyme Activity ◽  
Failure Stress ◽  
Cyclic Stretch ◽  
Mechanical Forces ◽  
Peak Strain ◽  
Static Stretch ◽  
Cyclic Stretching ◽  
Rate Dependent ◽  
Physiological Processes

Enzyme activity plays an essential role in many physiological processes and diseases such as pulmonary emphysema. While the lung is constantly exposed to cyclic stretching, the effects of stretch on the mechanical properties of the extracellular matrix (ECM) during digestion have not been determined. We measured the mechanical and failure properties of elastin-rich ECM sheets loaded with static or cyclic uniaxial stretch (40% peak strain) during elastase digestion. Quasistatic stress-strain measurements were taken during 30 min of digestion. The incremental stiffness of the sheets decreased exponentially with time during digestion. However, digestion in the presence of static stretch resulted in an accelerated stiffness decrease, with a time constant that was nearly 3× smaller (7.1 min) than during digestion alone (18.4 min). These results were supported by simulations that used a nonlinear spring network model. The reduction in stiffness was larger during static than cyclic stretch, and the latter also depended on the frequency. Stretching at 20 cycles/min decreased stiffness less than stretching at 5 cycles/min, suggesting a rate-dependent coupling between mechanical forces and enzyme activity. Furthermore, pure digestion reduced the failure stress of the sheets from 88 ± 21 kPa in control to 29 ± 15 kPa ( P < 0.05), while static and cyclic stretch resulted in a failure stress of 7 ± 5 kPa ( P < 0.05). We conclude that not only the presence but the dynamic nature of mechanical forces have a significant impact on enzyme activity, hence the deterioration of the functional properties of the ECM during exposure to enzymes.

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