scholarly journals Prediction of Stress–Strain Curves Based on Hydric Non-Destructive Tests on Sandstones

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3366 ◽  
Author(s):  
Marco Ludovico-Marques ◽  
Carlos Chastre
Keyword(s):  
Physical Properties ◽  
Mechanical Behavior ◽  
Water Absorption ◽  
Analytical Model ◽  
Strain Curve ◽  
Low Pressure ◽  
Design Parameters ◽  
Compression Tests ◽  
Stress Strain ◽  
Non Destructive

The study of the mechanical behavior of building stones is traditionally supported by destructive compression tests carried out on representative specimens. However, in order to respect the monuments’ integrity, the study of the mechanical behavior of stones can be based mostly on physical properties obtained from non-destructive tests (NDT). For this study, a simple and cheap NDT—water absorption under low pressure—was used to carry out fast surveys and to predict the most important design parameters of loadbearing masonry, among which are the compressive strength, strain at failure, and even elastic modulus on monument blocks. The paper presents the results of the experimental work conducted to obtain the physical properties and stress–strain curves of the sandstones tested. Supported by these results, it was possible to correlate the various parameters and develop an analytical model that predicts the stress–strain curve of the sandstones based on water absorption under low pressure tests. A good agreement is observed between the analytical model and the experimental tests.

scholarly journals Comparison of Mechanical Behavior and Acoustic Emission Characteristics of Three Thermally-Damaged Rocks

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2350 ◽  
Author(s):  
Jun Peng ◽  
Sheng-Qi Yang
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Mechanical Behavior ◽  
Thermal Damage ◽  
Strain Curve ◽  
Treatment Temperature ◽  
P Wave ◽  
High Temperature Treatment ◽  
High Porosity ◽  
Compression Tests

High temperature treatment has a significant influence on the mechanical behavior and the associated microcracking characteristic of rocks. A good understanding of the thermal damage effects on rock behavior is helpful for design and stability evaluation of engineering structures in the geothermal field. This paper studies the mechanical behavior and the acoustic emission (AE) characteristic of three typical rocks (i.e., sedimentary, metamorphic, and igneous), with an emphasis on how the difference in rock type (i.e., porosity and mineralogical composition) affects the rock behavior in response to thermal damage. Compression tests are carried out on rock specimens which are thermally damaged and AE monitoring is conducted during the compression tests. The mechanical properties including P-wave velocity, compressive strength, and Young’s modulus for the three rocks are found to generally show a decreasing trend as the temperature applied to the rock increases. However, these mechanical properties for quartz sandstone first increase to a certain extent and then decrease as the treatment temperature increases, which is mainly attributed to the high porosity of quartz sandstone. The results obtained from stress–strain curve, failure mode, and AE characteristic also show that the failure of quartz-rich rock (i.e., quartz sandstone and granite) is more brittle when compared with that of calcite-rich rock (i.e., marble). However, the ductility is enhanced to some extent as the treatment temperature increases for all the three examined rocks. Due to high brittleness of quartz sandstone and granite, more AE activities can be detected during loading and the recorded AE activities mostly accumulate when the stress approaches the peak strength, which is quite different from the results of marble.

scholarly journals Constant Strain-Rate Tensile Testing of Natural Snow

1980 ◽  
Vol 26 (94) ◽  
pp. 519 ◽  
Author(s):  
H. Singh ◽  
F.W. Smith
Keyword(s):  
Strain Rate ◽  
Strain Gage ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Rates ◽  
Strain Gages ◽  
Compression Tests ◽  
Snow Sample ◽  
Stress Strain ◽  
Natural Snow

Abstract In conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates. A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample. A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free. The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit. Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied. “Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.

Mechanical Properties of Functionally Graded Porous Aluminum Consisting of Pure Aluminum and Al-Mg-Si Aluminum Alloy

2017 ◽  
Vol 741 ◽  
pp. 1-6
Author(s):  
Yoshihiko Hangai ◽  
Tomoaki Morita ◽  
Takao Utsunomiya
Keyword(s):  
Aluminum Alloy ◽  
Pure Aluminum ◽  
Strain Curve ◽  
High Energy ◽  
Functionally Graded ◽  
Compression Tests ◽  
Stress Strain ◽  
Plateau Stress ◽  
Porous Aluminum ◽  
Compression Properties

Porous aluminum can potentially satisfy both the lightweight and high-energy-absorption properties required for automotive components. In this study, functionally graded porous aluminum consisting of pure aluminum and Al-Mg-Si A6061 aluminum alloy was fabricated by a sintering and dissolution process. It was found that functionally graded porous aluminum with the same pore structures but different types of aluminum alloy can be fabricated. By performing compression tests on the fabricated functionally graded porous aluminum, it was found that its stress-strain curve initially exhibited a relatively low plateau stress similar to that of uniform porous pure aluminum. Thereafter, the stress-strain curves exhibited a relatively high plateau stress similar to that of the uniform porous A6061 aluminum alloy. Namely, it was found that the compression properties of porous aluminum can be adjusted and optimized by selecting the appropriate type of aluminum alloy.

scholarly journals Constant Strain-Rate Tensile Testing of Natural Snow

1980 ◽  
Vol 26 (94) ◽  
pp. 519-519
Author(s):  
H. Singh ◽  
F.W. Smith
Keyword(s):  
Strain Rate ◽  
Strain Gage ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Rates ◽  
Strain Gages ◽  
Compression Tests ◽  
Snow Sample ◽  
Stress Strain ◽  
Natural Snow

AbstractIn conducting tension and compression tests on snow samples, strains and strain-rates are usually determined from the displacements of the ends of the samples. In this work, a strain-gage which mounts directly onto the snow sample during testing, was developed and was found to give accurate and direct measurements of strain and strain-rates.A commercially available 0-28 pF variable capacitor was modified to perform the required strain measurements. It is a polished metallic plunger sliding inside a metal-coated glass tube. The plunger and tube were each soldered to the end of a spring-steel wire arm. To the other end of these arms were soldered to 10 mm square pads made of thin brass shim stock. The whole device weighs 2.5 g and the low coefficient of friction in the capacitor resulted in a very low actuation force. To mount the strain gage, the pads are wetted and frozen onto the snow sample.A high degree of sensitivity was achieved through the use of “phase-lock-loop” electronic circuitry. The capacitance change caused by the strain in the sample, changes the frequency of output signal from an oscillator and thus causes the change in output from the system. In the locked state, to which the system is constantly driven by a feed-back loop, the system output is almost ripple free.The strain gages were calibrated in the field in order to take into account the effects of very low field temperatures. The calibration curves were almost linear over the travel of 15 mm, the maximum limit. The sensitivity of the system is 4 mV per strain unit, but this could be increased by an order of magnitude by minor adjustments in the circuit.Constant strain-rate tensile tests were performed on natural snow at Berthoud Pass, Colorado, U.S.A., in the density range of 140-290 kg m-3. Four strain gages were mounted onto the samples to sense any non-uniform deformation which otherwise would have gone unnoticed or caused scatter in the data. The average indication of these gages was used to construct stress—strain curves for various types of snow at different strain-rates. The effect of strain-rate on the behavior of snow was studied.“Ratcheting” in the stress-strain curve in the region where the snow becomes plastic was observed first by Kinosita in his compression tests. A similar phenomenon was observed in these tension tests. It was found that directly measured strain is quite different from that which would be calculated from sample end movement. Strain softening was not observed in these tests up to total strains of 8%. The strain-rate effects found were comparable to the results of other investigators.

Mechanical Behavior of Materials under Tensile Loads

2004 ◽  
pp. 13-31
Keyword(s):  
Tensile Test ◽  
Mechanical Behavior ◽  
Tensile Deformation ◽  
True Strain ◽  
Strain Curve ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mathematical Expressions ◽  
Reduction In Area

Abstract This chapter focuses on mechanical behavior under conditions of uniaxial tension during tensile testing. It begins with a discussion on the parameters that are used to describe the engineering stress-strain curve of a metal, namely, tensile strength, yield strength or yield point, percent elongation, and reduction in area. This is followed by a section describing the parameters determined from the true stress-true strain curve. The chapter then presents the mathematical expressions for the flow curve. Next, it reviews the effect of strain rate and temperature on the stress-strain curve. The chapter then describes the instability in tensile deformation and stress distribution at the neck in the tensile specimen. It discusses the processes involved in ductility measurement and notch tensile test in tensile specimens. The parameter that is commonly used to characterize the anisotropy of sheet metal is covered. Finally, the chapter covers the characterization of fractures in tensile test specimens.

Micromechanical Mean-Field Analysis for Stress-Strain Curve of Lotus-Type Porous Iron

2005 ◽  
Vol 486-487 ◽  
pp. 489-492
Author(s):  
Masakazu Tane ◽  
Soong Keun Hyun ◽  
T. Ichitsubo ◽  
Hideo Nakajima
Keyword(s):  
Mean Field Theory ◽  
Mean Field ◽  
Strain Curve ◽  
Longitudinal Axis ◽  
Field Analysis ◽  
Plastic Behavior ◽  
Porous Iron ◽  
Compression Tests ◽  
Stress Strain ◽  
Helium Atmosphere

We studied the plastic behavior of lotus-type porous iron with unidirectional long cylindrical pores. Lotus-type porous iron with different porosities was fabricated by the continuous zone melting method in a pressurized hydrogen and helium atmosphere. To calculate the stress-strain curves for lotus iron, we applied a modified Qiu-Weng’s micromechanical mean-field theory that has recently been proposed by the present authors [J. Mater. Res., in press], and compared the results with those of compression tests. We experimentally found that the deformation resistance and work hardening rate depend on the sample porosity and loading direction. They decrease with an increase in porosity, and their values in the loading along the direction perpendicular to the longitudinal axis of pores are smaller than those in the parallel-direction loading. Our micromechanical calculations reproduce well the stress-strain curves experimentally obtained and express the experimental trends successfully.

Effect of Sulfate Contaminant on Soil Properties and Infrastructure Safety in Permafrost Regions

2010 ◽  
Vol 113-116 ◽  
pp. 1208-1211
Author(s):  
Xi Zhong Yuan ◽  
Yuan Lin Zhu ◽  
Ning Zhang
Keyword(s):  
Physical Properties ◽  
Mechanical Behavior ◽  
Water Content ◽  
Contaminated Soil ◽  
Freezing Temperature ◽  
Frozen Soil ◽  
Unfrozen Water ◽  
Compression Tests ◽  
Exponential Relationship ◽  
Unfrozen Water Content

Contamination of unfrozen water in frozen soil could have adverse effects on surrounding infrastructure such as foundation instability or deterioration of trafficability. This paper describes the results of the experimental examination of the physical properties and mechanical behavior of Na2SO4 contaminated soil. Initial freezing temperature test, unfrozen water content test and unconfined compression tests were conducted on silts with 3 levels of concentrations (6, 18 and 42 ppt) of Na2SO4 and nonsaline cases at temperatures ranging between 0°C and -20°C. The test results indicate that the presence of salt significantly affect the physical properties and mechanical behavior of the frozen soil. Contamination of soils will cause depression of freezing temperature and degradation of permafrost. The freezing temperature depression ratio of Na2SO4 contaminated soil is 0.028°C/ppt. The unfrozen water content increases with an increase in salinity and temperature. The strength decreases with an increase in salinity, and the strength loss ratio of Na2SO4 contaminated soil is among 0.02-0.04MPa/ppt. Combined the effect of salinity and temperature on the strength, the decrease in strength with increase in unfrozen water content follows an exponential relationship. So estimation of salt concentration in the soil, and predictions of future increases of salt in the soil, is essential for design of buildings and roadways in permafrost.

scholarly journals Mechanical Behavior of Red Sandstone under Incremental Uniaxial Cyclical Compressive and Tensile Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Baoyun Zhao ◽  
Dongyan Liu ◽  
Tianzhu Huang ◽  
Wei Huang ◽  
Wei Liu
Keyword(s):  
Energy Dissipation ◽  
Mechanical Behavior ◽  
Strain Curve ◽  
Tensile Loading ◽  
Creep Model ◽  
Short Term ◽  
Stress Strain ◽  
Cycle Number ◽  
Red Sandstone ◽  
Residual Strains

Uniaxial experiments were carried out on red sandstone specimens to investigate their short-term and creep mechanical behavior under incremental cyclic compressive and tensile loading. First, based on the results of short-term uniaxial incremental cyclic compressive and tensile loading experiments, deformation characteristics and energy dissipation were analyzed. The results show that the stress-strain curve of red sandstone has an obvious memory effect in the compressive and tensile loading stages. The strains at peak stresses and residual strains increase with the cycle number. Energy dissipation, defined as the area of the hysteresis loop in the stress-strain curves, increases nearly in a power function with the cycle number. Creep test of the red sandstone was also conducted. Results show that the creep curve under each compressive or tensile stress level can be divided into decay and steady stages, which cannot be described by the conventional Burgers model. Therefore, an improved Burgers creep model of rock material is constructed through viscoplastic mechanics, which agrees very well with the experimental results and can describe the creep behavior of red sandstone better than the Burgers creep model.

Characterization of Silicate Ceramics Using Ultrasonics Test Method

2014 ◽  
Vol 92 ◽  
pp. 194-202 ◽  
Author(s):  
Semra Kurama ◽  
Elif Eren Gültekin
Keyword(s):  
Physical Properties ◽  
Water Absorption ◽  
Bulk Density ◽  
Test Methods ◽  
Ultrasonic Test ◽  
Test Method ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Non Destructive

Non-destructive testing techniques are widely used for testing ceramic materials. In our studies, two different types of ultrasonic test methods (A-scan and C-Scan) were investigated as non-destructive testing methods for characterization of porcelain tiles. Tiles were sintered in different temperatures to change their porosity and density properties. By changing of ultrasonic time and velocity related with samples’ some physical properties (such as bulk density, apparent density, apparent porosity (%), water absorption (%)) inspected via contact A-scan ultrasonic test method. The results show that without necessity of traditional test methods, some physical properties of ceramics can be determined by using obtained ultrasonic velocity-bulk density, apparent density, apparent porosity (%) and water absorption (%) calibration plots. Additionally, various defects were inspected in samples by using water immersion ultrasonic C-scan method. These results supported this study to obtain the information about defects’ size and place in the ceramic tiles. To support this non-destructive method results scanning electron microscope (SEM) characterization was done and images give the information about the place of the defect.

Prediction of the Effective Stress-Strain Curves of Ductile Polymer 1D-Reinforced Composites Filled with Hollow Fibers Using Parameterized Model Based on Bezier Curves

2020 ◽  
Vol 833 ◽  
pp. 93-100
Author(s):  
Alexander Pavlovich Sokolov ◽  
Vitaliy Nikolaevich Schetinin ◽  
Arseniy Sergeevich Sapelkin ◽  
Mikhail Sergeevich Kuts ◽  
Konstantin Valerievich Mikhailovskiy
Keyword(s):  
Effective Stress ◽  
Experimental Studies ◽  
Strain Curve ◽  
Ductile Material ◽  
Compression Tests ◽  
Stress Strain ◽  
Bezier Curves ◽  
Bézier Curves ◽  
Model Based ◽  
Parameterized Model

The article presents the results of numerical and experimental studies of stress-strain curves of 1D-reinforced polymer composite materials based on hollow porous fibers and epoxy matrix. The two-scale nature of the composite under research was taken into account. A surrogate easily parameterized model based on Bezier curves was developed and used to approximate the stress-strain curve of ductile material. The calculations were performed using reversible homogenization and finite element methods, which were implemented in computational subsystem of DCS GCD. Representative volume elements of the investigated materials were created using the geometry generating subsystem of DCS GCD. Test samples were made using three-axis milling machine and compression tests were carried out. Computational results of effective stress-strain curves determination were obtained and compared with experiments.

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