Comparative Analysis of Thermomechanical Properties and Thermal Damage Constitutive Models of Three Soft Sedimentary Rocks

In order to study the difference in thermomechanical properties of soft sedimentary rocks of different coal measures, three types of soft sedimentary rocks, sandstone, sandy mudstone, and mudstone, which are common in deep mines, are tested using the RMT-150B rock mechanics test system and GD-65/150. Uniaxial compression experiments were conducted on three kinds of soft rock-cement mixed specimens at 25°C～55°C multistage temperature in an environmental chamber. The difference of important parameters such as stress-strain curve, peak stress, and elastic modulus was analyzed and compared. The results show that (i) in the test temperature range, the stress-strain curves of the three types of soft rocks at different temperatures are roughly divided into four stages: compaction, elasticity, yield, and failure. The proportion of deformation in the compaction stage to the total deformation decreases gradually with the increase of temperature. (ii) When the temperature is lower than 40°C, the yield stage is shorter, and the peak stress and elastic modulus of the three types of soft rocks decrease significantly with the increase of temperature. (iii) Above 40°C, the decreasing trend of peak stress and elastic modulus curve decreases, and the yield stage becomes more and more obvious. The decreasing rate of elastic modulus of sandstone is 0.041 GPa/°C; the decreasing rate of peak stress is 0.193 MPa/°C, the decreasing rate of sandy mudstone is 0.022 GPa/°C and 0.124 MPa/°C, and the decreasing rate of mudstone is 0.020 GPa/°C and 0.051 MPa/°C. (iv) The rationality of the established thermal damage constitutive model of sedimentary soft rock was verified.

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Mechanical Properties and Uniaxial Compression Stress—Strain Relation of Recycled Coarse Aggregate Concrete after Carbonation

Materials ◽

10.3390/ma14092215 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2215

Author(s):

Tian-Wen Chen ◽

Jin Wu ◽

Guo-Qing Dong

Keyword(s):

Elastic Modulus ◽

Coarse Aggregate ◽

Concrete Structures ◽

Peak Stress ◽

Peak Strain ◽

Stress Strain ◽

Carbonation Depth ◽

Aggregate Concrete ◽

Recycled Coarse Aggregate ◽

Stress Strain Relation

The application of recycled coarse aggregate (RCA) made from waste concrete to replace natural coarse aggregate (NCA) in concrete structures can essentially reduce the excessive consumption of natural resources and environmental pollution. Similar to normal concrete structures, recycled concrete structures would also suffer from the damage of carbonation, which leads to the deterioration of durability and the reduction of service life. This paper presents the experimental results of the cubic compressive strength, the static elastic modulus and the stress–strain relation of recycled coarse aggregate concrete (RAC) after carbonation. The results show that the cubic compressive strength and the static elastic modulus of carbonated RAC gradually increased with the carbonation depth. The uncarbonated and fully carbonated RAC show smaller static elastic modulus than natural aggregate concrete (NAC). As the carbonation depth increased, the peak stress increased, while the peak strain decreased and the descending part of the curves gradually became steeper. As the content of RCA became larger, the peak stress decreased, while the peak strain increased and the descending part of the curves gradually became steeper. An equation for stress–strain curves of RAC after carbonation was proposed, and it was in good agreement with the test results.

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Stress–Strain Curve and Carbonation Resistance of Recycled Aggregate Concrete after Using Different RCA Treatment Techniques

Applied Sciences ◽

10.3390/app11094283 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4283

Author(s):

Long Li ◽

Dongxing Xuan ◽

Chisun Poon

Keyword(s):

Elastic Modulus ◽

Strain Curve ◽

Peak Stress ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Stress Strain Curve ◽

Stress Strain ◽

Aggregate Concrete ◽

Treatment Techniques ◽

Carbonation Resistance

Five recycled coarse aggregate (RCA) treatment techniques including flow-through carbonation, pressurized carbonation, wet carbonation, nano silica (NS) pre-spraying and combined pressurized carbonation with NS pre-spraying, were utilized to improve the performance of recycled aggregate concrete (RAC). The characteristics of the stress–strain curves of RACs including peak stress, peak strain, elastic modulus, ultimate strain and toughness were evaluated after using the above RCA treatment techniques. A theoretical model for natural aggregate concrete was used to analyse the stress–strain curve of RAC. Additionally, the carbonation resistance of RAC after using different RCA treatment techniques were investigated. The results showed that the calculated stress–strain curve of RAC based on the theoretical model matched well with the experimental results. Among the three types of carbonation techniques, pressurized carbonation caused the highest improvement in peak stress and elastic modulus of RAC, followed by flow-through carbonation, the last was wet carbonation. The NS pre-spraying method contributed to even higher improvement in peak stress and elastic modulus of RAC than the pressurized carbonation method. The combined pressurized carbonation with NS pre-spraying exhibited the highest enhancement of RAC because both the RCA and the new interface transition zone (ITZ) were improved. The carbonation resistance of RAC was improved after using all the studied RCA treatment techniques.

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Nonlinear Dynamic Constitutive Model of Frozen Sandstone Based on Weibull Distribution

Advances in Civil Engineering ◽

10.1155/2020/6439207 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Lei Wang ◽

Hongming Su ◽

Shiguan Chen ◽

Yue Qin

Keyword(s):

Elastic Modulus ◽

Constitutive Model ◽

Strain Rate ◽

Split Hopkinson Pressure Bar ◽

Soft Rock ◽

Strain Curve ◽

Peak Stress ◽

Experimental Results ◽

Compression Tests ◽

Hopkinson Pressure Bar

To obtain the dynamic mechanical properties of frozen sandstone at different temperatures (i.e., 20°C, −10°C, −20°C, and −30°C), dynamic uniaxial compression tests of saturated sandstone are conducted using a split-Hopkinson pressure bar. The experimental results demonstrated that the brittleness of the saturated sandstone increased and its plasticity weakened with a decrease in temperature. The peak strength and dynamic elastic modulus of the sandstone were positively correlated with its strain rate. The peak stress was most sensitive to the strain rate at −10°C, and the elastic modulus was most sensitive to the strain rate at −30°C. According to the evident segmentation characteristics of the obtained stress-strain curve, a viscoelastic dynamic constitutive model considering the strain rate effect and temperature effect is developed; this model combines a nonlinear (or linear) body and a Maxwell body in parallel with a damage body. The applicability of the constitutive model is also verified using experimental data. The fitting results were demonstrated to be in good agreement with the experimental results. Furthermore, the fitting results serve as reference for the study of the constitutive model of weakly cemented soft rock and the construction of roadway freezing methods.

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Experimental Research on Uniaxial Compression Constitutive Model of Hybrid Fiber-Reinforced Cementitious Composites

Materials ◽

10.3390/ma12152370 ◽

2019 ◽

Vol 12 (15) ◽

pp. 2370

Author(s):

Tao Cui ◽

Haoxiang He ◽

Weiming Yan

Keyword(s):

Elastic Modulus ◽

Constitutive Model ◽

Peak Stress ◽

Fiber Reinforced Concrete ◽

Forward Peak ◽

Peak Strain ◽

Fiber Reinforced ◽

Hybrid Fiber ◽

Stress Strain ◽

Element Analysis

In order to establish accurate compressive constitutive model of Hybrid Fiber-Reinforced Concrete (HFRC), 10 groups of HFRC specimens containing polyvinyl alcohol (PVA), polypropylene (PP), and steel fibers are designed and compressive testing is conducted. On the basis of summarizing and comparing the existing research, accuracy of various stress-strain constitutive model is compared and the method of calculating fitting parameters is put forward, peak stress, peak strain, and elastic modulus of specimens with different fiber proportion are analyzed, the calculation expressions of each fitting parameter are given. The results show that, under the condition that the volume of the hybrid fiber is 2% with the proportion of the steel fiber increase, the strength of the specimen increases, the peak strain decreases slightly, and the elastic modulus increases significantly. In specimens mixed with PVA-PP hybrid fiber, with the increase of PVA fiber proportion, the peak stress and elastic modulus of the material are improved, and the peak strain are decreased. The existing stress-strain expressions agree well with the tests. Accuracy of exponential model proposed in this paper is the highest, which can be applied in engineering and nonlinear finite element analysis of components.

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Impact of Mechanical Constraints on the Irradiation Performance of U10Mo Monolithic Mini-Plates

ASME 2015 Nuclear Forum ◽

10.1115/nuclrf2015-49455 ◽

2015 ◽

Author(s):

Walid Mohamed ◽

Hee Seok Roh ◽

Gerard Hofman ◽

Pavel G. Medvedev

Keyword(s):

High Performance ◽

Peak Stress ◽

Stress Strain ◽

Mechanical Constraints ◽

Uranium Fuel ◽

Operational Variables ◽

The Difference ◽

Irradiation Performance ◽

Fuel Elements ◽

Performance Research

For the conversion of high performance research reactors to low enrichment Uranium fuel, U-Mo alloy based fuels in monolithic form were proposed. These plate-type fuels consist of a high uranium density, low enrichment uranium (LEU) foil contained within a diffusion barrier, and encapsulated within a cladding. To benchmark this new design, effects of various geometrical and operational variables on irradiation performance have been evaluated. In this work, the effects of mechanical constraints on the thermo-mechanical behavior of a plate were studied. To evaluate these effects, a selected plate from RERTR-12 experiments (Plate L1P756) was simulated. Four distinct cases which represent four distinct welding conditions were considered. Evaluation of the stress-strain fields in the fuel elements revealed that mechanical constraints may impact the plate’s performance. These constraints include (a) inlet side, (b) outlet side, (c) both inlet and outlet sides; and finally, (d) entire long edges. Results of these cases were then compared with the ideal case. The peak stress-strain magnitudes, displacement, stress and strain profiles on the fuel elements are evaluated to make a comparative assessment. The results indicated that the cases with constraints on “inlet side only” and “outlet side only” yielded lower cladding strains compared with other cases. The difference on the displacement profiles on the fuel foil was not significant. Peak stresses on the foil did not change considerably. These results imply that the mechanical constraints effects peak cladding strains, while it does not cause significant effects on the fuel behavior.

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Mechanical Properties of Concrete in Compression Exposed to Sulfuric Acid

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.711.302 ◽

2016 ◽

Vol 711 ◽

pp. 302-309 ◽

Cited By ~ 8

Author(s):

Muttaqin Hasan ◽

Saiful Husin ◽

Cut Nursaniah

Keyword(s):

Compressive Strength ◽

Sulfuric Acid ◽

Elastic Modulus ◽

Mathematical Expression ◽

Peak Stress ◽

Pulse Velocity ◽

Dynamic Elastic Modulus ◽

Compression Tests ◽

Initial Stiffness ◽

Stress Strain

This paper presents the degradation of compressive strength and stiffness of concrete after immersed in 2,5 % sulfuric acid solution. The durations of immersion are 0, 3, 7, 14, and 28 days. After the immersion, ultrasonic pulse velocity and compression tests are performed on the specimens. The relative dynamic elastic modulus, compressive strength and its initial stiffness decrease with increasing the duration of immersion, as a result of the increasing microcracks in the concrete. The strain at peak stress increases with increasing the duration of immersion. The degradation of compressive strength, the degradation of initial stiffness and the value of strain at peak stress of damaged concrete are formulated as a function of relative dynamic elastic modulus. A simple mathematical expression for stress-strain relationship of concrete damaged by sulfuric acid is proposed and stress-strain curves at different level of damage are compared.

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Behavior of Weakly Cemented Rock with Different Moisture Contents under Various Tri-Axial Loading States

Energies ◽

10.3390/en12081563 ◽

2019 ◽

Vol 12 (8) ◽

pp. 1563

Author(s):

Honglin Liu ◽

Dongsheng Zhang ◽

Hongchao Zhao ◽

Mingbo Chi ◽

Wei Yu

Keyword(s):

Residual Stress ◽

Moisture Content ◽

Water Conservation ◽

Peak Stress ◽

Confining Pressure ◽

Geological Condition ◽

Stress Strain ◽

Strain Behavior ◽

Moisture Contents ◽

Sandy Mudstone

To better understand the physical and mechanical behavior of weakly cemented rock with different moisture contents for the success of water-preserved mining, this paper presents the systematic tri-axial compression tests on three typical rock samples (i.e., mudstone, sandstone, and sandy mudstone) sampled from Ili mining area, where the environmental requirements for water conservation are significantly strict. Both the influences of moisture content and confining pressure on the failure mode and the stress-strain behavior of weakly cemented rock have been discussed and compared with each other. Test results showed that: (1) compared to sandstone and sandy mudstone, both the peak stress and residual stress of the weakly cemented mudstone are much more sensitive to confining pressure and moisture content. In detail, the peak stress is very relevant to moisture content, whereas, the residual stress is more sensitive to the confining pressure, (2) with the increase of moisture content, both the yield and ductility of weakly cemented mudstone have been significantly enhanced. However, a similar experimental observation has been found for sandstone and sandy mudstone, and (3) the microstructure and the mineral component are believed to be the two main factors leading to the scatter in terms of the stress-strain behavior for different weakly cemented rocks. Experimental results and discussions presented in this paper can provide the guideline for further research on the application of water-preserved mining in other coal mines with a similar geological condition.

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Material yield strain identification using energy absorption

The Journal of Strain Analysis for Engineering Design ◽

10.1177/0309324718774950 ◽

2018 ◽

Vol 53 (6) ◽

pp. 463-469

Author(s):

S Abdul Jalil ◽

A Anwar ◽

SM Chou ◽

K Tai

Keyword(s):

Elastic Modulus ◽

Yield Point ◽

Gold Standard ◽

Strain Curve ◽

Peak Stress ◽

Strain Identification ◽

Stress Strain Curve ◽

Yield Strain ◽

Stress Strain ◽

Mathematical Process

The current gold standard of identifying yield points from stress strain curves involves identifying a significant change in elastic modulus or using an arbitrary strain offset (0.1%, 0.2% or 2%) of the elastic modulus. The development of the offset method was due to the ambiguous definitions of yield point. The result is an arbitrary yield point which is prone to various human-related errors. This article presents a method to identify a unique yield point consistently using energy absorbed by the material up to first peak stress. This mathematical process idealises the stress strain curve for easy identification of the yield point. The method was tested on three possible types of stress strain curves with either a distinct yield point or without a distinct yield point (with peak stress closer to elastic region or closer to fracture). The yield points obtained by the proposed method are shown to be robust, consistent and unaffected by variations of the stress strain curves and data noises.

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Experimental study on stress-strain curves of seawater sea-sand concrete under uniaxial compression with different strain rates

Advances in Structural Engineering ◽

10.1177/1369433220958765 ◽

2020 ◽

pp. 136943322095876

Author(s):

Kaijian Zhang ◽

Jianzhuang Xiao ◽

Qingtian Zhang

Keyword(s):

Compressive Strength ◽

Elastic Modulus ◽

Strain Rate ◽

Uniaxial Compression ◽

Peak Stress ◽

Ultimate Strain ◽

Strain Rates ◽

Peak Strain ◽

Stress Strain ◽

Sea Sand

In order to investigate the mechanical properties of seawater sea-sand concrete (SSC) under uniaxial compression, the SSC prisms with different mix proportions are designed and prepared, and the compressive strength and stress-strain curves under uniaxial compression are tested, in which five loading strain rates 10−5/s, 10−4/s, 10−3/s, 10−2/s, and 10−1/s are selected. The failure patterns of the SSC specimens under different strain rates are discussed, and the peak stress, peak strain (strain at the peak stress), elastic modulus, and ultimate strain are analyzed. The influence of the strain rate and the shell particle content on the stress-strain curves is intensively evaluated. It shows that the peak stress and elastic modulus increase with an increasing strain rate while the peak strain and ultimate strain have no obvious trend. Additionally, the shell particles seem to have contributions to the increase of the compressive strength of SSC base on the test results of cube and prism specimens, but further considerations about this phenomenon are necessary. Finally, the dynamic increase factor (DIF) of characteristic indices of SSC is put forward.

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An Experimental Study on the Compressive Dynamic Performance of Rubber Concrete under Freeze-Thaw Cycles

Advances in Civil Engineering ◽

10.1155/2021/6655799 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Juntao Zhang ◽

Guangli Zhang ◽

Xinjian Sun ◽

Wenguo Pan ◽

Peijie Huang ◽

...

Keyword(s):

Experimental Study ◽

Elastic Modulus ◽

Strain Rate ◽

Compressive Stress ◽

Dynamic Performance ◽

Peak Stress ◽

Engineering Practice ◽

Stress Strain ◽

Freeze Thaw ◽

Rubber Concrete

An experimental study was conducted using a hydraulic servo machine to examine the compressive dynamic performance of rubber concrete under freeze-thaw cycles by considering 4 different numbers of freeze-thaw cycles and 8 different strain rates. The compressive stress-strain curves of rubber concrete under different loading conditions were obtained. By comparatively analyzing the mechanical characteristic parameters of the compressive stress-strain curves (i.e., peak stress, elastic modulus, and peak strain), the following conclusions were drawn: at the same loading strain rate, the compressive peak stress of rubber concrete is gradually decreased while the mass loss rate is gradually increased, as the number of freeze-thaw cycles increases. Compared to ordinary concrete, rubber concrete has a better frost resistance property. At the same number of freeze-thaw cycles, the compressive peak stress and elastic modulus of rubber concrete are gradually increased as the loading strain rate increases. The increase in the number of freeze-thaw cycles enlarges the increasing amplitude of the peak stress and elastic modulus under the action of loading strain rate. The compressive peak stress and elastic modulus dynamic increase factors of rubber concrete exhibit a linear relationship with the dimensionless logarithm of the loading strain rate. Meanwhile, a calculation model was proposed for the compressive peak stress dynamic increase factor of rubber concrete under the coupling effect of freeze-thaw cycles and loading strain rate, and the corresponding stress mechanism was discussed in detail. The research findings are of great significance to the application and development of antifreeze concrete in engineering practice.

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