Evaluation of the Strain-Softening Law of Concrete from the Fracture Test

2012 ◽  
Vol 535-537 ◽  
pp. 1868-1876
Author(s):  
Wai Ching Tang ◽  
Hong Zhi Cui
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Strain Softening ◽  
Peak Load ◽  
Strain Curve ◽  
Tensile Fracture ◽  
Stress Strain ◽  
Ordinary Concrete

This paper proposes a method for evaluating the linear stress-strain curve and bilinear stress-COD curve, suggested by Petersson, which can describe the tensile fracture behaviour of ordinary concrete satisfactorily. The two curves can be evaluated once modulus of elasticity (E), tensile strength (ft) and fracture energy (GF) are determined. It is proposed that the same fracture energy test suggested in the RILEM Recommendation be used to evaluate E, ftand GF. Firstly, the fracture energy was as usual evaluated from the area under the load-deflection curve. Secondly, the modulus of elasticity was calculated from the initial compliance in the same curve. Finally, the tensile strength was derived from the peak load. The proposed method was verified using some experimental data available in literature. The calculated values of the modulus of elasticity and the tensile strength were in good agreement with the corresponding experimental data. The method seems to provide a simple and practical way of evaluating the stress-strain and strain-softening curves of ordinary concrete, though further assessment is needed.

scholarly journals Measurement of fracture energy of concrete at high strain rates

2018 ◽  
Vol 183 ◽  
pp. 02065
Author(s):  
V. Rey-de-Pedraza ◽  
F. Gálvez ◽  
D. Cendón Franco
Keyword(s):  
Tensile Strength ◽  
Fracture Energy ◽  
Dynamic Fracture ◽  
Dynamic Properties ◽  
Hopkinson Bar ◽  
Experimental Information ◽  
Tensile Fracture ◽  
Strain Rates ◽  
Dynamic Tensile Strength ◽  
Conventional Concrete

The Hopkinson Bar has been widely used by many researchers for the analysis of dynamic properties of different brittle materials and, due to its great interest, for the study of concrete. In concrete structures subjected to high velocity impacts, initial compression pulses travel through the material leading to tensile stresses when they reach a free surface. These tensile efforts are the main cause of concrete fracture due to its low tensile strength compared to the compressive one. This is the reason why dynamic tests in concrete are becoming of great interest and are mostly focused in obtaining tensile fracture properties. Apart form the dynamic tensile strength, which has been widely studied by many authors in the last decades, the dynamic fracture energy presents an increased difficulty and so not too much experimental information can be found in literature. Moreover, up to date there is not a clear methodology proposed in order to obtain this parameter in an accurate way. In this work a new methodology for measuring the dynamic fracture energy is proposed by using the Hopkinson Bar technique. Initial tests for a conventional concrete have been carried out and the results for the dynamic fracture energy of concrete at different strain rates are presented.

Effects of AP and AP-ethyl on the properties of PA6

2017 ◽  
Vol 31 (12) ◽  
pp. 1609-1618
Author(s):  
Long Lijuan ◽  
He Wentao ◽  
Li Juan ◽  
Xiang Yushu ◽  
Qin Shuhao ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fracture Surface ◽  
Thermal Degradation ◽  
Flame Retardant ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cone Calorimeter Test ◽  
Mean Size ◽  
The Mean

In this work, the effects of inorganic phosphinate flame retardant of aluminum hypophosphite (AP) and organic phosphinate flame retardant of ethyl substituted phosphinates (AP-ethyl) on the thermal degradation, flame performance, and mechanical properties of polyamide 6 (PA6) were investigated. Scanning electron micrograph showed AP with the shape of bulk and the mean size of 8 μm while AP-ethyl with irregular shape and the mean size of 30 μm. Thermal analysis indicated that the thermal degradation behavior of flame-retardant PA6 was different from pure PA6. Moreover, the cone calorimeter test results revealed that peak heat release rate (PHRR) of PA6/AP (85/15) and PA6/AP-ethyl (85/15) decreased by 51% and 64%, respectively, compared with pure PA6. Furthermore, pure PA6 showed ductile stress–strain curve with the tensile strength of 54.8 MPa. However, PA6/AP and PA6/AP-ethyl displayed brittle stress–strain curve and their tensile strength decreased to 52.3 and 47.1 MPa, respectively. In addition, pure PA6 showed a glossy and tough fracture surface morphology. The rough fracture surface morphologies for PA6/AP and PA6/AP-ethyl were observed, and the interface of PA6/AP was more obscure than that of PA6/AP-ethyl. Consequently, the small particle size of AP had a more uniform dispersion in PA6 matrix.

scholarly journals Temperature Effect on the Compressive Behavior and Constitutive Model of Plain Hardened Concrete

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2801 ◽  
Author(s):  
Ayman El-Zohairy ◽  
Hunter Hammontree ◽  
Eddie Oh ◽  
Perry Moler
Keyword(s):  
Experimental Data ◽  
Compressive Strength ◽  
Temperature Effect ◽  
Modulus Of Elasticity ◽  
Constitutive Models ◽  
Ultimate Strain ◽  
Effect Of Temperature ◽  
Hardened Concrete ◽  
Compressive Behavior ◽  
Stress Strain

Concrete is one of the most common and versatile construction materials and has been used under a wide range of environmental conditions. Temperature is one of them, which significantly affects the performance of concrete, and therefore, a careful evaluation of the effect of temperature on concrete cannot be overemphasized. In this study, an overview of the temperature effect on the compressive behavior of plain hardened concrete is experimentally provided. Concrete cylinders were prepared, cured, and stored under different temperature conditions to be tested under compression. The stress–strain curve, mode of failure, compressive strength, ultimate strain, and modulus of elasticity of concrete were evaluated between the ages of 7 and 90 days. The experimental results were used to propose constitutive models to predict the mechanical properties of concrete under the effect of temperature. Moreover, previous constitutive models were examined to capture the stress–strain relationships of concrete under the effect of temperature. Based on the experimental data and the proposed models, concrete lost 10–20% of its original compressive strength when heated to 100 °C and 30–40% at 260 °C. The previous constitutive models for stress–strain relationships of concrete at normal temperatures can be used to capture these relationships under the effect of temperature by using the compressive strength, ultimate strain, and modulus of elasticity affected by temperature. The effect of temperature on the modulus of elasticity of concrete was considered in the ACI 318-14 equation by using the compressive strength affected by temperature and the results showed good agreement with the experimental data.

Elastomer Behavior IV. Loop Structure of Elastomer Networks

1966 ◽  
Vol 39 (5) ◽  
pp. 1489-1495
Author(s):  
L. C. Case ◽  
R. V. Wargin
Keyword(s):  
Experimental Data ◽  
Crosslink Density ◽  
Strain Curve ◽  
Uniaxial Stress ◽  
Polymer Chains ◽  
Theoretical Treatment ◽  
Loop Structure ◽  
Stress Strain ◽  
Strain Behavior ◽  
Selection Of

Abstract A new theoretical treatment strongly indicates that an elastomer network actually consists of a system of fused, closed, interpenetrating loops of polymer chains. This interpenetrating loop structure restricts the movement of the chains and thereby affects the stress-strain behavior of the elastomer. Methods have been developed to enable the calculation of the number of effective crosslinks caused by loop interpenetrations (virtual crosslinks). The uniaxial stress-strain behavior of an elastomer predicted using our methods can be fitted almost perfectly to published experimental data by proper selection of chain parameters. Previous theoretical treatments gave only a qualitative fit to the experimental data for the stress-strain behavior of elastomers and were not capable of predicting the correct shape of the experimental stress-strain curve. The present treatment gives a nearly perfect fit for both stress as a function of strain at constant crosslink density, and stress as a function of crosslink density at constant strain, and thus represents a vast improvement.

Fracture Mechanical Properties of Rocks and Mortar/Rock Interfaces

1994 ◽  
Vol 370 ◽  
Author(s):  
Manouchehr Hassanzadeh
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Splitting Tensile Strength ◽  
Coarse Grained ◽  
Interfacial Zone ◽  
Test Results

AbstractThis study has determined the fracture mechanical properties of 9 types of rock, namely fine-, medium- and coarse-grained granites, gneiss, quartzite, diabase, gabbro, and fine- and coarse-grained limestones. Test results show among other things that quartzite has the highest compressive strength and fracture energy, while diabase has the highest splitting tensile strength and modulus of elasticity. Furthermore, the strength and fracture energy of the interfacial zone between the rocks and 6 different mortars have been determined. The results showed that, in this investigation, the mortar/rock interfaces are in most cases weaker than both mortars and rocks.

Experimental Study of Stress-Strain Curves of Lightweight Aggregate Concrete

2010 ◽  
Vol 163-167 ◽  
pp. 1762-1767 ◽  
Author(s):  
Xiang Liu ◽  
Jiang Tao Kong
Keyword(s):  
Strain Curve ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Concrete Material ◽  
Aggregate Concrete ◽  
Ordinary Concrete ◽  
Strength Grade ◽  
Strain Relationship

According to the contrast test of LC30, LC40 lightweight aggregate concrete and C30, C40 common concrete , the text researched the mechanical property of lightweight aggregate concrete and ordinary concrete in the same strength grade and obtained the regularity of stress-strain curve of lightweight aggregate concrete in different strength grade. Then we contrasted the experimental results and planning model, analysed the difference, and suggested that the standards should improve the descent stage of the stress-strain curve of lightweight aggregate concrete combined with correlative experiments data, and give the equation of the descent stage of stress-strain curves. Concrete material in axial compression is the basic physical mechanical performance of concrete material, and is the main basis for researching bearing capacity and deformation of concrete construction. The stress-strain relationship is all-around macroscopic reaction of basal compressive property . There have been many experiments work about the stress-strain relationship of lightweight aggregate concrete at home and abroad , and found the peak strain of lightweight aggregate concrete is higher than that of ordinary concrete in the context of same peak stress .In this paper, on the basis of experimental investigations of lightweight aggregate concrete , aim at the stress-strain relationship ,we have take comparison experiment about LC30,LC40 lightweight aggregate concrete and C30,C40 ordinary concrete , and sort out stress-strain curve under the condition of the shaft center being compressed, so get the average tress-strain curve of LC30,LC40 lightweight aggregate concrete , and analyse the curve.

Stress Strain Testing of the Strand of E-Glass Fibers

2008 ◽  
Vol 39-40 ◽  
pp. 165-168
Author(s):  
Mária Chromčíková ◽  
Marek Liška
Keyword(s):  
Experimental Data ◽  
Fiber Strength ◽  
Glass Fibers ◽  
Length Distribution ◽  
Continuous Distribution ◽  
Strain Curve ◽  
Young Modulus ◽  
Strength Distribution ◽  
Stress Strain ◽  
Strain Testing

The mathematical model of the stress-strain curve of the strand of glass fibers was proposed and applied on the experimental data obtained for E glass fibers. The model reflects the lognormal continuous distribution of the unstrained lengths of glass fibers and the Weibull distribution of the fibers strength. The regression treatment of experimental data provided the statistically robust estimates of the parameters of the lognormal length distribution, of the Young modulus, and of the parameters of the Weibull glass fibers strength distribution. It was shown that neglecting of the continuous unstrained length distribution leads to serious errors in estimates of the fiber strength distribution.

Joint Inclination Effect on Strength, Stress-Strain Curve and Strain Localization of Rock in Plane Strain Compression

2005 ◽  
Vol 495-497 ◽  
pp. 69-76 ◽  
Author(s):  
X.B. Wang
Keyword(s):  
Plane Strain ◽  
Strain Softening ◽  
Strain Curve ◽  
Plane Strain Compression ◽  
Peak Strength ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Softening Behavior ◽  
Ideal Plastic ◽  
Joint Inclination

Peak strength, mechanical behavior, and shear band (SB) of anisotropic jointed rock (JR) were modeled by Fast Lagrangian Analysis of Continua (FLAC). The failure criterion of rock was a composite Mohr-Coulomb criterion with tension cut-off and the post-peak constitutive relation was linear strain-softening. An inclined joint was treated as square elements of ideal plastic material beyond the peak strength. A FISH function was written to find automatically elements in the joint. For the lower or higher joint inclination (JI), the higher peak strength and more apparent strain-softening behavior are observed; the failure of JR is due to the slip along the joint and the new generated SBs initiated at joint’s two ends. For the lower JI, the slope of softening branch of stress-strain curve is not concerned with JI since the new and longer SBs’s inclination is not dependent on JI, as can be qualitatively explained by previous analytical solution of post-peak slope of stress-strain curve for rock specimen subjected to shear failure in uniaxial compression based on gradient-dependent plasticity. For the higher JI, the post-peak stress-strain curve becomes steeper as JI increases since the contribution of the new SBs undergoing strain-softening behavior to axial strain of JR increases with JI. For the moderate JI, the lower strength and ideal plastic behavior beyond the elastic stage are found, reflecting that the inclined joint governs the deformation of JR. The present numerical prediction on anisotropic peak strength in plane strain compression qualitatively agrees with triaxial experimental tests of many kinds of rocks. Comparison of the present numerical prediction on JI corresponding to the minimum peak strength of JR and the oversimplified theoretical result by Jaeger shows that Jaeger’s formula has overestimated the value of JI.

Model for predicting the variation of shear stress in unsaturated soils during strain-softening

2020 ◽  
Author(s):  
Xiuhan Yang ◽  
Sai Vanapalli
Keyword(s):  
Shear Stress ◽  
Large Deformation ◽  
Unsaturated Soils ◽  
Strain Softening ◽  
Strain Curve ◽  
Published Data ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
State Stress

Several of the geotechnical structures constructed with unsaturated soils undergo a large deformation prior to reaching failure conditions (e.g. progressive failure of a soil slope). During this process, the shear stress in soils typically increases initially and then reduces with an increase in the shear strain. The prediction of the stress-strain relationship is critical for reasonable interpretation of the mechanical behavior of those geo-structures that undergo large deformation. This paper introduces a model based on the disturbed state concept (DSC) to predict the variation of shear stress in unsaturated soils during strain-softening process under consolidated drained triaxial compression condition. In this model, the apparent stress-strain relationship is formulated as a weighted average of a hyperbolic hardening response extending the pre-peak state stress-strain curve and a linear response extending the critical state stress-strain curve with an assumed disturbance function as the weight. The prediction procedure is described in detail and the proposed model is validated using several sets of published data on unsaturated soils varying from coarse- to fine-grained soils. Finally, a comprehensive error analysis is undertaken based on an index of agreement approach.

A Three Dimensional Graphical Aid for Fatigue Data Analysis

2011 ◽  
Vol 488-489 ◽  
pp. 755-758 ◽  
Author(s):  
Bruno Atzori ◽  
Giovanni Meneghetti ◽  
Mauro Ricotta
Keyword(s):  
Experimental Data ◽  
Data Analysis ◽  
Three Dimensional ◽  
Strain Curve ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Compatibility Conditions ◽  
Stress Strain ◽  
Fatigue Data ◽  
Best Fitting

The fatigue behaviour of materials is usually synthesised in terms of stress-life (S-N) curve or in terms of strain-life (e-N) curve, the latter being described by the so-called Manson-Coffin equation. It is known that the assumption of equality of the plastic and elastic components between the Manson-Coffin and the stabilised stress-strain curves leads to the so-called compatibility conditions which connect the equations theoretically. The material constants of the Manson-Coffin and of the stabilised stress-strain curve are commonly determined by best fitting separately the experimental data obtained from strain-controlled fatigue tests. As a consequence the compatibility conditions may not be fulfilled. In this paper a method for fatigue data analysis that ensures the compatibility conditions is proposed and validated against experimental data.

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