Showing papers on "Stress–strain curve published in 2018"
TL;DR: In this article, the effect of adding steel fibers with different lengths and diameters on the mechanical properties of concrete for three values of concrete strength was investigated, and the results indicated that the addition of different content and lengths of steel fiber with increasing water-to-cement ratios caused significant change in concrete, with an increase of about 10-25% in compressive strength and about 31-47% in direct tensile strength.
223 citations
TL;DR: In this article, the variability of peak stress, peak strain, elastic modulus and ultimate strain was found to follow a normal distribution, based on the collected experimental data, a modified RAC stress-strain model was proposed.
112 citations
TL;DR: In this paper, the authors presented the stress-strain behavior of CRC with rubber replacement percentages of 6, 12, and 18% with a constitutive model under uniaxial compression.
99 citations
TL;DR: In this paper, three kinds of polyethylene fibers with different fiber aspect ratios were used as the reinforced fiber in the UHP-ECC. The fiber aspect ratio significantly influenced the tensile properties and failure modes.
Abstract: The direct tensile properties of ultra-high performance engineered cementitious composites (UHP-ECC) were investigated under a range of strain rates from 0.0001 to 0.05 s−1 in this study. Three kinds of polyethylene fibers with different fiber aspect ratios were used as the reinforced fiber in the UHP-ECC. The rate sensitivity of the UHP-ECC in tension was evaluated in terms of initial cracking stress, peak stress, strain capacity, energy absorption capacity and elastic modulus at different strain rates. The cracking patterns, including crack number, crack width and crack spacing, of the UHP-ECC specimens were also monitored. The test results showed a significant rate effect on the initial cracking stress and a moderate effect on the peak stress and strain capacity. The fiber aspect ratio significantly influenced the tensile properties and failure modes of the UHP-ECC. The matrix strength, single fiber tensile and pull-out tests were conducted at corresponding strain rates to further explain the test results. Finally, the micro-structure of the tensile specimens was observed using a scanning electron microscope.
75 citations
TL;DR: In this paper, the authors employed a state-of-the-art crystal plasticity spectral method in conjunction with comparable high-fidelity microstructures to study the coupling effect of micro-mechanical (intrinsic) heterogeneities introduced by grain size, morphology, orientation, and intergranular interaction.
71 citations
TL;DR: In this paper, the formation of stress hotspots in polycrystalline materials under uniaxial tensile deformation was investigated by integrating full field crystal plasticity based deformation models and machine learning techniques to gain data driven insights about microstructural properties.
66 citations
TL;DR: In this article, the axial stress-axial strain behaviors of partially reinforced polymer (FRP) confined concrete with either strain-hardening or strain-softening responses were investigated under axial compression.
65 citations
TL;DR: In this article, the effect of addition of Graded Glass Fibers with different fiber length and volume fraction in Glass Fiber Reinforced Concrete has been made, and the experimental work was carried out under uni-axial tension for M30 grade of concrete with the 0.3% fiber volume, different fiber volume combination of Glass fibers in Short Graded form (3.5mm, 6mm, 12mm and 20mm length fiber) were studied.
60 citations
TL;DR: In this article, the authors proposed a method to directly determine the true stress-strain curve over a large strain range via a special multi-camera digital image correlation (DIC) system.
59 citations
TL;DR: Based on the "elastic modulus method" derived from the hypothesis of strain equivalence and test data of complete stress-strain curves of marble, granite, and sandstone under uniaxial compression, the authors showed that the elastic modulus of sandstone and marble can be computed using the test data.
Abstract: Based on the “elastic modulus method” derived from the hypothesis of strain equivalence and test data of complete stress–strain curves of marble, granite, and sandstone under uniaxial compression, ...
56 citations
TL;DR: In this article, the authors investigated the effect of high loading rate on the behavior and mechanical properties of coal-rock combined body, and the results showed that the dynamic stress-strain curves have a double-peak feature under high loading rates.
Abstract: In order to investigate the high loading rate effect on the behaviour and mechanical properties of coal-rock combined body, the dynamic compressive tests were conducted by using the Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s. The stress-strain curves, dynamic peak stress and strain, elastic modulus, and energy distribution law of coal-rock combined body under different loading rates were analyzed and discussed. The results show that the dynamic stress-strain curves of coal-rock combined body have a double-peak feature under high loading rate range, which can be divided into the initial bearing stage, the bearing decline stage, the bearing enhance stage, and the unstable stage. The first peak stress of the coal-rock combined body is independent of the loading rate, while the dynamic compressive strength (the second peak stress) and dynamic peak strain (the second peak strain) have a strong loading rate effect and will generally increase linearly with the loading rate. The first and second elastic moduli of coal-rock combined body are not sensitive to the loading rate. With the increase of the loading rate, the incident energy and reflective energy of coal-rock combined body increase rapidly, while the change of transmitted energy is very small. The absorption energy ratio of the coal-rock combined body shows a good linear law with the incident energy under different loading rates.
TL;DR: In this article, the stress-strain behavior of ferrite and austenite in a commercial 2205 duplex stainless steel was investigated by using nanoindentation test and microstructure-based finite element method (FEM).
Abstract: The stress-strain behavior of ferrite and austenite in a commercial 2205 duplex stainless steel was investigated by using nanoindentation test and microstructure-based finite element method (FEM). Results showed that the optimum load range for measuring phase properties in nanoindentation test was from 3000 μN to 7000 μN. The ferrite has slightly higher average elastic modulus than austenite, while austenite has higher average nanohardness than ferrite. Representative stress-strain curves of ferrite and austenite were determined by means of the power-law hardening and empirical relationship. Based on FEM, the differences in distribution and portion of stress-strain in local phases were visualized, and the overall flow curve of the sample 2205 was extracted, which was in good agreement with the obtained results from uniaxial tensile experiment.
TL;DR: In this paper, the flow behavior of as-cast AZ91D magnesium alloy was evaluated by isothermal compression tests within the temperatures of 220 °C, 260′°c, 300′c, 340′C, and 380ò°C and the strain rates of 0.001, 0.1, 1 and 10s−1.
TL;DR: In this article, the compressive behavior of circular FRP-confined concrete columns with preload is analyzed with the introduction of a modified analysis-oriented model, and the proposed model is also suitable for the determination of the combined response of unconfined and confined concrete subjected to an established stress/strain state.
Abstract: The compressive behavior of FRP-confined concrete is a current issue in the field of structural retrofitting. The available models well predict the stress–strain behavior under monotonic and cyclic loads. However, in the practical applications, columns that need an increasing of bearing capacity are often strengthened under serviceability load conditions, with a stress and strain state that could change the response of the reinforced systems with respect to the case of the unloaded state. In this paper, the compressive behavior of circular FRP-confined concrete columns with preload is analyzed with the introduction of a modified analysis-oriented model. Differently from the classical formulations in which stress–strain model is aimed to the evaluation of the confinement capacity of non-preloaded elements in monotonic regime, the proposed model is also suitable for the determination of the combined response of unconfined and confined concrete subjected to an established stress/strain state in the unconfined state. The proposed model is also compared with the experimental results available in the literature under different assigned preloading levels.
TL;DR: In this paper, the behavior mechanisms and efficiency of concrete confinement formed with the hybridization of two different types of fiber reinforced polymer (FRP) sheets with the aim of utilizing superior features of these two FRP types.
Abstract: This study investigates the behavior mechanisms and efficiency of concrete confinement formed with the hybridization of two different types of fiber reinforced polymer (FRP) sheets with the aim of utilizing superior features of these two FRP types. The originality of the study is to combine carbon or glass FRP sheets (CFRP or GFRP) with polyethylene terephthalate FRP sheets (PET-FRP), which have different mechanical features, particularly in terms of deformability. While CFRP and GFRP sheets have relatively high tensile strength and low rupture strain capacity, PET-FRP sheets have low tensile strength but remarkably high rupture strain capacity. Hybridization is performed through external wrapping of two different FRP sheets in a successive way. 24 standard cylinder concrete specimens are tested under compression loading. The test variables of the study are the types and number of layers of the inner and outer FRP constituents of hybrid jacket. Test results show that hybrid confinement of FRP sheets with low and high rupture strain capacities offers an enhanced ductility. Furthermore, it is seen that through the hybridization of FRP sheets with different mechanical properties, stress-strain relationship of FRP confined concrete can be tailored. Several available analytical models developed for stress-strain relationship of the concrete confined with a single type of FRP sheet and one model developed for the hybrid FRP confined concrete are used to predict key stress and strain values of the hybrid confined concrete. Considering the behavior mechanisms of the hybrid confined concrete specimens, several assumptions are made during the application of these models. It is shown that key stress and strain values of hybrid confined concrete can be reasonably predicted.
TL;DR: In this paper, the deformation behavior of pure molybdenum (Mo) was studied in very high temperature range (1400-1700 degrees C) by carrying out uniaxial compression tests at four different strain rates (0.01-10 s(-1)).
Abstract: The deformation behavior of pure molybdenum (Mo) was studied in very high temperature range (1400-1700 degrees C) by carrying out uniaxial compression tests at four different strain rates (0.01-10 s(-1)). Three types of stress-strain curves including work hardening, steady state and softening behavior were observed depending upon the deformation condition. The strain rate sensitivity (m) map generated from the flow stress data revealed two domains of high m values - one at about 1400 degrees C and 10(-1) s(-1) and the second one at similar to 1700 degrees C and strain rate of 10(-2)-1 s(-1). The kinetic analysis of the deformation data yielded the apparent activation energy as 390 kJ mol(-1), the stress exponent as 8.5, and the activation volume about 100-600 b(3) for pure Mo. Microstructures of the deformed samples were investigated using the electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The appearance of smaller strain-free grains along the boundaries of deformed grains indicated the occurrence of dynamic recrystallization (DRX) in the samples deformed at conditions corresponding to the high m values. Grain growth was significant at higher temperature and lower strain rate deformation. Bulk texture measurements of the hot deformed samples indicated strengthening of fiber texture during occurrence of the DRX.
TL;DR: In this paper, a compliant bond at the lap end of a single-lap joint configuration is used to increase the strength and stiffness of a tri-layered assembly in a single lap joint configuration.
Abstract: Multilayered multi-material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi-material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially-tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri-layered assembly in a single-lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance-tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi-material interfaces can be improved substantially via the compliance-tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding.
TL;DR: In this article, the axial compressive behavior of cementitious composites with hybrid steel-polyvinyl alcohol (PVA) fibers was investigated and the failure modes, peak stress, peak strain, elastic modulus, toughness index, as well as stress strain curves were obtained and carefully interpreted.
TL;DR: In this article, a finite element (FE) model for the compressive behavior of fiber-reinforced polymer (FRP)-confined steel fiber reinforced concrete (SFRC) is presented.
TL;DR: In this article, steady state tests have been conducted on steel cables with tensile strength of 60MPa, which consist of a group of 7-wire twisted strands, to study their full range of stress strain relationships at elevated temperature.
TL;DR: The modified JC constitutive model is more suitable to describe the temperature-dependent hardening effect, which provides strong support for accurate finite element simulation of high-speed machining Ti-6Al-4V alloy.
Abstract: The mechanical properties of Ti-6Al-4V alloy are sensitive to strain rate and temperature load. The finite element simulation results of high-speed machining Ti-6Al-4V alloy depend on the accurate description of dynamic deformation. However, it is hard to describe the flow stress behavior in current constitutive models in a complex high-speed machining process for Ti-6Al-4V alloy. In this paper, the stress-strain curves of Ti-6Al-4V alloy under the wide ranges of strain rate and temperature are obtained by high-velocity uniaxial impact tests. The apparent coupling between temperature and strain is observed, which proves that the temperature is dependent on a hardening effect for Ti-6Al-4V alloy. A function describing the coupling between temperature and strain is then introduced into the modification for the original Johnson-Cook (JC) constitutive model. The maximum deviation between the predicted data from using the proposed modified JC constitutive model and experimental data is reduced from 10.43% to 4.19%. It can be concluded that the modified JC constitutive model is more suitable to describe the temperature-dependent hardening effect, which provides strong support for accurate finite element simulation of high-speed machining Ti-6Al-4V alloy.
TL;DR: In this article, a combined experimental and modelling approach was used to study the micro-mechanism of central damage in cross-wedge rolling of steel, and the evolution process of the microvoids initiation, growth and coalescence during cross-wing rolling was observed.
TL;DR: In this article, a rotational viscometer (RV) was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled.
Abstract: To successfully process concrete, it is necessary to predict and control its flow behavior. However, the workability of concrete is not completely measured or specified by current standard tests. Furthermore, it is only with a clear picture of cement hydration and setting that full prediction and control of concrete performance can be generalized. In order to investigate the rheological properties of blended cement pastes, a rotational viscometer (RV) was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled. Additionally, a dynamic shear rheometer (DSR) was used to characterize both the viscous and elastic components of pastes. Ordinary Portland cement paste and blended pastes (slag, fly ash, and silica fume) were investigated in this study. The stress and strain of the blended specimens were measured by the DSR, which characterizes both viscous and elastic behaviors by measuring the complex shear modulus (the ratio of total shear stress to total shear strain) and phase angle (an indicator of the relative amounts of recoverable and nonrecoverable deformation) of materials. Cement pastes generally exhibit different rheological behaviors with respect to age, mineral admixture type, and cement replacement level.
TL;DR: Experimental results indicated that increase of rubber content linearly decreases compressive strength and elastic modulus, but increases ductility, and an improvement of an existing model was proposed, which provides better agreement with experimental curves.
Abstract: Inclusion of rubber into concrete changes its behavior and the established shape of its stress-strain curve. Existing constitutive stress-strain models for concrete are not valid in case of rubberized concrete, and currently available modified models require additional validation on a larger database of experimental results, with a wider set of influential parameters. By executing uniaxial compressive tests on concrete with rubber substituting 10%, 20%, 30%, and 40% of aggregate, it was possible to study and evaluate the influence of rubber content on its mechanical behavior. The stress-strain curve was investigated in its entirety, including compressive strength, elastic modulus, strains at significant levels of stress, and failure patterns. Experimental results indicated that increase of rubber content linearly decreases compressive strength and elastic modulus, but increases ductility. By comparing experimental stress-strain curves with those plotted using available constitutive stress-strain models it was concluded that they are inadequate for rubberized concrete with high rubber content. Based on determined deviations an improvement of an existing model was proposed, which provides better agreement with experimental curves. Obtained research results enabled important insights into correlations between rubber content and changes of the stress-strain curve required when utilizing nonlinear material properties.
TL;DR: In this paper, a model based on the mechanical threshold Ansatz in combination with a Labusch type solid solution hardening approach and a model for dynamic strain ageing to describe the temperature and strain rate dependence of the yield stress in a thermal activation framework is developed and introduced.
TL;DR: In this paper, the relationship between the leakage magnetic field of at certain point of cold rolled steel specimen and the tensile stress was measured during the process of loading and unloading by repeated.
TL;DR: In this article, the authors demonstrate a procedure to find out the true tensile stress-strain curve of the steel sheet after necking using digital image correlation (DIC) technique.
Abstract: The stress–strain behavior of sheet metal is commonly evaluated by tensile test. However, the true stress–strain curve is restricted up to uniform elongation of the material. Usually, after the uniform elongation of the material the true stress–strain is obtained by extrapolation. The present work demonstrates a procedure to find out the true tensile stress–strain curve of the steel sheet after necking using digital image correlation (DIC) technique. Hill’s normal anisotropic yield criteria and local strains measured by DIC technique are used to correct the local stress and strain states at the diffuse necked area. The proposed procedure is shown to successfully determine the true tensile stress–strain curve of ferritic and dual-phase steel sheets after necking/uniform elongation.
TL;DR: In this article, the fracture mechanics of a stationary crack in a polyvinylalcohol (PVA) hydrogel with a network consisting of chemical and physical crosslinks is studied.
Abstract: The fracture mechanics of a stationary crack in a Poly(vinylalcohol) (PVA) hydrogel with a network consisting of chemical and physical crosslinks is studied here. Prior research by the authors has shown that the time- dependent stress strain behavior of this gel can be captured very accurately with a 3D, large deformation nonlinear viscoelastic model based on breaking kinetics of physical crosslinks. This model is used together with a novel time integration scheme to study the stress and deformation fields near the tip of a stationary crack in single edge cracked specimens. The theoretical and finite element results agree remarkably well with experimentally observed crack opening profiles. For the special case of relaxation tests exact asymptotic crack tip solutions are obtained in specimens loaded under predominantly plane stress conditions.
TL;DR: In this article, a small punch testing-related stress-strain relation (SPT-SR) model is proposed to predict the stressstrain relations of materials on the basis of equivalent energy principle.
TL;DR: In this article, a series of experiments were conducted to determine the fatigue and time-dependent behaviors of 316L stainless steel, including monotonic tensile and stress relaxation with different strain rates, fully reversed cyclic plasticity, creep and relaxation interaction, and cyclic stress relaxation tests.