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 The Choice of Vascular Implants in Accordance with Age-Related Vessel Changes

2020 ◽  
Vol 9 (2) ◽  
pp. 195-200
Author(s):  
V. A. Lipatov ◽  
N. N. Grigoryev ◽  
D. A. Severinov ◽  
A. R. Sahakyan
Keyword(s):  
Mechanical Properties ◽  
Plastic Strain ◽  
Thoracic Aorta ◽  
Finite Length ◽  
Abdominal Aorta ◽  
Tensile Load ◽  
Study Groups ◽  
Plastic Strain Ratio ◽  
Group 2 ◽  
Group 1

Background Today, one of the problems of modern society in the health are the high rates of mortality from cardiovascular disease.Aim of study Study of physico-mechanical properties of the vascular implants and aortic wall to support an adequate choice of the plastic material when performing reconstructive surgeries in patients of various age groups.Material and methods As an object of study, sections of the anterior wall of the thoracic and abdominal aorta were taken from 30 corpses. Study groups: Group 1 - from 33 to 60 years, Group 2 - from 60 to 92 years. We also evaluated the physical and mechanical properties (finite length, plastic strain ratio, tensileuniaxial load (longitudinal)) of the three vascular implants made of polyethylene terephthalate and polytetrafluoroethylene. Kruskal–Wallis H test was used to determine the significance of differences.Results The finite length of the aortic wall varies slightly in the study groups, while plastic strain rate of the abdominal aorta in Group 1 was 1.3 times higher than that in the chest. When assessing physical and mechanical properties of thoracic and abdominal aorta, values of “finite length” (1.4 times) and “plastic strain ratio” (1.5 times) were higher in Group 1, and the value of the tensile load indicator is higher in Group 2 compared to Group 1 (1.47 times). The tensile load of the thoracic aorta in Group 1 is 14 H and 27 H lower than the samples of Groups 1 and 3, respectively, but 1.6 times higher than the sample of Group 2. The tensile  load of the abdominal aorta of Group 1 is 13 H higher compared to the sample of Group 1 and twice higher compared to the sample of Group 2. The study Group 2 values of tensile load for thoracic aorta are 1.3 times, 2.4 times and 1.16 times higher than respective implant values (sample 1, 2 and 3, respectively).Conclusion We used samples of Group 3 vascular implants for replacement of abdominal aorta and Group 1 implants for thoracic aorta. In study Group 2 vascular implants of Group 3 may be used for abdominal and thoracic aorta replacement due to the proximity of the values of the evaluated characteristics.

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 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.

Effects of Cold-Rolling Reduction on Microstructure and Mechanical Properties of Ti50Zr30Nb10Ta10 Alloy

2016 ◽  
Vol 849 ◽  
pp. 376-381
Author(s):  
Ming Long Li ◽  
Yu Jie Geng ◽  
Chen Chen ◽  
Shu Jie Pang ◽  
Tao Zhang
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Plastic Strain ◽  
Cold Rolling ◽  
Reduction Ratio ◽  
High Fracture ◽  
Dendrite Structure ◽  
Microstructure And Mechanical Properties ◽  
Cold Rolling Reduction ◽  
Cold Rolled

The effects of cold-rolling with different reduction ratios of 70%-90% on the microstructure and mechanical properties of Ti50Zr30Nb10Ta10 alloy were investigated. It was found that the β-Ti phase in this alloy was stable under cold-rolling. With the increase in reduction ratio from 70% to 90%, the microstructure of the alloys evolved from deformed dendrite structure to fiber-like structure. The alloy cold-rolled with the reduction ratio of 70% exhibited optimum mechanical properties of combined high fracture strength of 1012 MPa and plastic strain of 10.1%, which are closely correlated with the dendrite structure of the alloy. It is indicated that the proper cold-rolling is an effective way to improve the mechanical properties of the titanium alloy.

Influence of the Composition of Cement Mortars Modified by Lime or Polymers on the Mechanical Properties and Microstructure of Mortars

2013 ◽  
Vol 592-593 ◽  
pp. 647-650 ◽  
Author(s):  
Małgorzata Lenart
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Reinforced Concrete ◽  
Flexural Strength ◽  
Polyvinyl Alcohol ◽  
Polymer Composites ◽  
Adhesion Strength ◽  
Hardened Cement ◽  
Cement Mortars ◽  
Styrene Butadiene

Cement – polymer composites are nowadays widely used in repair systems not only in case of concrete or reinforced concrete constructions but also in masonry. Polymers addition for example already at 5% m.c. modifies the structure of the cement – polymer composite in a way that many of the mechanical properties such as flexural strength, tensile strength or adhesion to substrates are improved. The paper presents the results of tests such as flexural, compressive or adhesion strength to ceramic substrate of hardened cement mortars with different composition, as well as selected cement mortars modified by two polymers: polyvinyl alcohol and styrene – butadiene polymer dosed at 5 % m.c. Four types of cement mortars modified by lime (component used in historical constructions as well as in contemporary masonry mortars) are also examined for comparison.

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.

Effect of Cu Content on the Formability and Portevin-Le Chatelier Effect of Al-Mg Alloys

2015 ◽  
Vol 817 ◽  
pp. 150-157
Author(s):  
Peng Cheng Ma ◽  
Di Zhang ◽  
Lin Zhong Zhuang ◽  
Ji Shan Zhang
Keyword(s):  
Plastic Strain ◽  
Stress Drop ◽  
Strain Ratio ◽  
Mg Alloys ◽  
Dynamic Strain ◽  
Strain Hardening Exponent ◽  
Drawing Ratio ◽  
Plastic Strain Ratio ◽  
Cu Content ◽  
Al Mg Alloys

Al-Mg alloys developed for auto body sheets with different Cu contents were fabricated in the laboratory scale. The effects of Cu content on the microstructures, formability and Portevin–Le Chatelier(PLC) effect of the alloys were investigated by polarizied optical microscopy and room temperature tensile testing. It has been found that with increasing Cu content, there was little change of the strain hardening exponent, but the plastic strain ratio and limiting drawing ratio increased firstly and then decreased. A quantitative statistical analysis of the characteristics of the PLC effect was made, including the stress drop and the reloading time, which follow a common linear relationship with plastic strain, and the increase rate of stress drop and reloading time was bigger with more Cu content. A detailed discussion of the corresponding mechanism of Cu and Cu-containing precipitates on the dynamic strain aging(DSA) was made.

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