scholarly journals Experimentation of the Bilinear Elastic Behavior of Plain-Woven GFRP Composite with Embedded SMA Wires

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 405 ◽  
Author(s):  
Zhiwei Sun ◽  
Yingjie Xu ◽  
Wenzhi Wang
Keyword(s):  
Tensile Strain ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Strain Behavior ◽  
Reinforced Polymer ◽  
Resin Injection ◽  
Stress Threshold ◽  
Gfrp Composite

In this paper, a plain-woven glass-fabric-reinforced polymer (GFRP) composite with embedded shape memory alloy (SMA) wires is investigated by means of experiments. The vacuum-assisted resin injection (VARI) method is utilized to fabricate the composite specimens. Quasi-static uniaxial tensile tests are then carried out to evaluate the influence of SMA reinforcement on the stress–strain behavior of the composite. Only the elastic behavior of the composite is considered in the present study. The tensile strain in all the experiments is kept below 2.5% to avoid debonding of the SMA-resin interface, which would lead to failure of the composite. Stress–strain curves are obtained and shown to present a bilinear behavior due to phase transformation taking place in the SMA wires beyond a certain stress threshold.

Studies on the Stress-Strain Relationship Bovine Cortical Bone Based on Ramberg–Osgood Equation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
N. K. Sharma ◽  
M. D. Sarker ◽  
Saman Naghieh ◽  
Daniel X. B. Chen
Keyword(s):  
Cortical Bone ◽  
Linear Regression Analysis ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Strain Relationship ◽  
Relationship Of

Bone is a complex material that exhibits an amount of plasticity before bone fracture takes place, where the nonlinear relationship between stress and strain is of importance to understand the mechanism behind the fracture. This brief presents our study on the examination of the stress–strain relationship of bovine femoral cortical bone and the relationship representation by employing the Ramberg–Osgood (R–O) equation. Samples were taken and prepared from different locations (upper, middle, and lower) of bone diaphysis and were then subjected to the uniaxial tensile tests under longitudinal and transverse loading conditions, respectively. The stress–strain curves obtained from tests were analyzed via linear regression analysis based on the R–O equation. Our results illustrated that the R–O equation is appropriate to describe the nonlinear stress–strain behavior of cortical bone, while the values of equation parameters vary with the sample locations (upper, middle, and lower) and loading conditions (longitudinal and transverse).

Theoretical Model for the Elastic Behavior of Filler-Reinforced Vulcanized Rubbers

1957 ◽  
Vol 30 (2) ◽  
pp. 555-571 ◽  
Author(s):  
L. Mullins ◽  
N. R. Tobin
Keyword(s):  
Elastic Properties ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Simple Extension ◽  
Stress Strain ◽  
Empirical Relationships ◽  
Equilibrium Stress ◽  
Strain Behavior ◽  
Strain Data ◽  
Limited Applicability

Abstract One of the more important advances in rubber science during the past twenty years has been the development of quantitative theories describing the elastic properties of pure-gum vulcanized rubbers. As a result it is now possible to account for their equilibrium stress-strain behavior with considerable success. There is, however, no adequate theory to describe the elastic properties of filler-reinforced rubber vulcanizates and the work described herein is an attempt to provide a basis for such a theory. When a reinforcing filler is added to rubber it produces a large increase in the stiffness of the vulcanizate. This increase is reduced and may be substantially destroyed by deformation. Numerous attempts have been made to describe the increase of stiffness resulting from the introduction of fillers and relationships describing the dependence of the modulus on the concentration and particle shape of the filler have been developed. However, these do not take into account the softening which results from previous deformation and thus have limited applicability. Recently Blanchard and Parkinson have attempted to develop empirical relationships to describe the elastic properties in simple extension of reinforced rubber vulcanizates after they have been previously deformed. They started with the appropriate stress-strain relationships from the classical kinetic theory and introduced two curve-fitting parameters to describe stress-strain data obtained in conventional tensile tests on a Goodbrand machine. In this way they were able to fit the course of the stress-strain data obtained after previous extension at extensions less than those previously applied and to describe the dependence of the parameters on previous deformation. Unfortunately, the significance of the parameters is obscure.

Stress-Strain Equations for Some Near-Eutectic Tin-Lead Solders

1991 ◽  
Vol 113 (4) ◽  
pp. 475-484 ◽  
Author(s):  
K. P. Jen ◽  
J. N. Majerus
Keyword(s):  
Strain Rate ◽  
Printed Circuit Boards ◽  
Volume Fraction ◽  
Total Error ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Strain Rates ◽  
Stress Strain ◽  
Engineering Strain

This paper presents the evaluation of the stress-strain behavior, as a function of strain-rate, for three tin-lead solders at room temperature. This behavior is critically needed for reliability analysis of printed circuit boards (PCB) since handbooks list minimal mechanical properties for the eutectic solder used in PCBs. Furthermore, most handbook data are for stable eutectic microstructure whereas PCB solder has a metastable microstructure. All three materials were purchased as “eutectics.” However, chemical analysis, volume fraction determination, and microhardness tests show some major variations between the three materials. Two of the materials have a eutectic composition, and one does not. The true stress-strain equations of one eutectic and the one noneutectic material are determined from compressive tests at engineering strain-rates between 0.0002/s and 0.2/s. The second eutectic material is evaluated using tensile tests with strain-rates between 0.00017/s and 0.042/s. The materials appear to exhibit linear elastic behavior only at extremely small strains, i.e., less than 0.0005. However, this “elastic” behavior showed considerable variation, and depended upon the strain rate. In both tension and compression the eutectic alloy exhibits nonlinear plastic behavior, i.e., strain-softening followed by strain-hardening, which depends upon the strain rate. A quadratic equation σy = σy(ε˚/ε˚0) + A(ε˚/ε˚0)ε + B(ε˚/ε˚0)ε2 fit to the data gives correlation coefficients R2 > 0.91. The coefficients σy(ε˚/ε˚0), A(ε˚/ε˚0), B(ε˚/ε˚0) are fitted functions of the normalized engineering strain rate ε˚/ε˚0. Replicated experiments are used at each strain-rate so that a measure of the statistical variation could be estimated. Measures of error associated with the regression analysis are also obtained so that an estimate of the total error in the stress-strain relations can be made.

Nonlinear Rate-Dependent Stress-Strain Behavior of Light-Weight Textile Conveyor Belt

2011 ◽  
Vol 675-677 ◽  
pp. 453-456
Author(s):  
Ze Xing Wang ◽  
Jin Hua Jiang ◽  
Nan Liang Chen
Keyword(s):  
Loading Rate ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Conveyor Belt ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Strain Behavior ◽  
Rate Dependent ◽  
Dependent Behavior

In order to investigate the effect of loading rate on the tensile performance, the uniaxial tensile experiments were conducted on universal testing machine under different loading rates (5 mm/min, 10mm/min, 50 mm/min, 100 mm/min and 150 mm/min), and a constant gage length equal to 200mm, resulting in loading strain rate of 4.17×10-4, 8.33×10-4/s, 4.17×10-3/s, 8.33×10-3/s,1.25×10-2/s, and the tensile stress-strain curves were obtained. The experimental results show that the tensile properties of the conveyor belt exhibit obvious rate-dependent behavior. In this paper, the rate sensitivity coefficient varied with loading rate, was calculated, and the nonlinear rate-dependent behavior was also investigated.

Methods for the Experimental Evaluation of True Stress-Strain Curves After Necking of Conventional Tensile Specimens: Exploratory Investigation and Proposals

2012 ◽  
Author(s):  
Grace Kelly Q. Ganharul ◽  
Nick de Brangança Azevedo ◽  
Gustavo Henrique B. Donato
Keyword(s):  
Real Time ◽  
Weighted Average ◽  
Tensile Tests ◽  
Plastic Instability ◽  
True Stress ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
High Definition ◽  
Stress Strain

Numerical elastic-plastic simulations have undergone significant expansion during the last decades (e.g. refined fracture mechanics finite element models including ductile tearing). However, one limitation to increase the accuracy of such models is the reliable experimental characterization of true stress-strain curves from conventional uniaxial tensile tests after necking (plastic instability), which complicates the direct assessment of the true stress-strain curves until failure. As a step in this direction, this work presents four key activities: i) first, existing correction methods are presented, including Bridgman, power law, weighted average and others; ii) second, selected metals are tested to experimentally characterize loads and the geometric evolution of necking. High-definition images are used to obtain real-time measurements following a proposed methodology; iii) third, refined non-linear FEM models are developed to reproduce necking and assess stresses as a function of normalized neck geometry; iv) finally, existing correction methods are critically compared to experimental results and FEM predictions in terms of potential and accuracy. The experimental results evaluated using high-definition images presented an excellent geometrical characterization of instability. FEM models were able to describe stress-strain-displacement fields after necking, supporting the exploratory validations and proposals of this work. Classical methodologies could be adapted based on experiments to provide accurate stress-strain curves up to failure with less need for real-time measurements, thus giving further support to the determination of true material properties considering severe plasticity.

Departures of the Elastic Behavior of Rubbers in Simple Extension from the Kinetic Theory

1955 ◽  
Vol 28 (1) ◽  
pp. 24-35 ◽  
Author(s):  
S. M. Gumbrell ◽  
L. Mullins ◽  
R. S. Rivlin
Keyword(s):  
Kinetic Theory ◽  
Volume Fraction ◽  
Single Parameter ◽  
Elastic Behavior ◽  
Simple Extension ◽  
Stress Strain ◽  
Equilibrium Stress ◽  
Strain Behavior

Abstract It is shown that the equilibrium stress-strain behavior of highly swollen rubber vulcanizates in simple extension agrees with the predictions of the kinetic theory. The departures from these predictions which are found in dry or lightly swollen rubbers have been investigated, and it is shown that they can be described in terms of a single parameter C2. The magnitude of this parameter is large in dry rubbers, and decreases to zero at high degrees of swelling ; this decrease occurs linearly with decrease in the volume fraction of rubber. The value of C2 is found to be independent of the nature of the rubber polymer, of the degree of vulcanization, and of the nature of the swelling liquid. The possible significance of this parameter is discussed in light of these observations.

Determination of Full Range Stress-Strain Behavior of Pipeline Steels Using Tensile Characteristics

2010 ◽  
Author(s):  
Stijn Hertele´ ◽  
Wim De Waele ◽  
Rudi Denys
Keyword(s):  
Full Range ◽  
Tensile Tests ◽  
Proof Stress ◽  
Stress Strain ◽  
Pipeline Steels ◽  
Strain Behavior ◽  
Parameter Values ◽  
Near Future ◽  
Strain Model

It is standard practice to approximate the post-yield behavior of pipeline steels by means of the Ramberg-Osgood equation. However, the Ramberg-Osgood equation is often unable to accurately describe the stress-strain behavior of contemporary pipeline steels with a high Y/T ratio. This is due to the occurrence of two distinct, independent stages of strain hardening. To address this problem, the authors recently developed a new ‘UGent’ stress-strain model which provides a better description of those steels. This paper elaborates a methodology to estimate suited parameter values for the UGent model, starting from a set of tensile characteristics. Using the proposed methodology, good approximations have been obtained for a preliminary series of eight investigated stress-strain curves. Next to all common tensile characteristics, the 1% proof stress is needed. The authors therefore encourage the future acquisition of this stress level during tensile tests. Currently, the authors perform a further in-depth validation which will be reported in the near future.

Inelastic Strain Accumulation in Cortical Bone During Rapid Transient Tensile Loading

1999 ◽  
Vol 121 (6) ◽  
pp. 616-621 ◽  
Author(s):  
M. T. Fondrk ◽  
E. H. Bahniuk ◽  
D. T. Davy
Keyword(s):  
Cortical Bone ◽  
Axial Strain ◽  
Human Bone ◽  
Elastic Behavior ◽  
Transverse Strain ◽  
Bovine Bone ◽  
Stress Strain ◽  
Nonlinear Strain ◽  
Strain Behavior ◽  
Nonlinear Stress

An experimental study examined the tensile stress-strain behavior of cortical bone during rapid load cycles to high strain amplitudes. Machined bovine and human cortical bone samples were subjected to loading cycles at a nominal load/unload rate of ±420 MPa/s. Loads were reversed at pre-selected strain levels such that load cycles were typically completed in 0.5-0.7 seconds. Axial strain behavior demonstrated considerable nonlinearity in the first load cycle, while transverse strain behavior was essentially linear. For the human bone 29.1 percent (S.D. = 4.7 percent), and for the bovine bone 35.1 percent (S.D. = 10.8 percent) of the maximum nonlinear strain accumulated after load reversal, where nonlinear strain was defined as the difference between total strain and strain corresponding to linear elastic behavior. Average residual axial strain on unloading was 35.4 percent (S.D. = 1.2 percent) for human bone and 35.1 percent (S.D. = 2.9 percent) of maximum nonlinear strain. Corresponding significant volumetric strains and residual volumetric strains were found. The results support the conclusions that the nonlinear stress-strain behavior observed during creep loading also occurs during transient loading at physiological rates. The volume increases suggest that damage accumulation, i.e., new internal surfaces and voids, plays a major role in this behavior. The residual volume increases and associated disruptions in the internal structure of bone provide a potential stimulus for a biological repair response.

scholarly journals Non-linear elastic behavior of carbon fibres of different structural and mechanical characteristic

2007 ◽  
Vol 72 (5) ◽  
pp. 513-521 ◽  
Author(s):  
Isidor Djordjevic ◽  
Daniela Sekulic ◽  
Momcilo Stevanovic
Keyword(s):  
Tensile Strain ◽  
Axial Stress ◽  
Tensile Modulus ◽  
Compression Modulus ◽  
Interlayer Spacing ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Carbon Fibres ◽  
Single Filament ◽  
Breaking Strain

Five types of polyacrylonitrile, PAN, based carbon fibres, differing in modulus, breaking strain and in crystallite orientation, have been studied. Non-Hookean behavior was investigated by computing the tangent tensile and compression moduli as a function of strain, from the axial stress-strain response obtained in standard tensile, compression, as well as in modified flexural tests of unidirectional carbon/ epoxy composites. The dependences of the tensile modulus on tensile strain of the carbon fibres were extracted from data obtained in single-filament tensile tests. Analytical expressions for the tensile modulus-tensile strain and compression modulus-compression strain dependences in the performed test were deduced. The structural characterization of the carbon fibres was performed by X-ray diffraction on bundle of parallel fibres. The interlayer spacing d 002 and the apparent lateral dimension of the crystallites L c were deduced by processing the 002 diffraction profiles. The established modulus-strain dependences were correlated with the fibre characteristics (breaking strain and mean modulus values), as well as with the characteristic of the 002 difraction profile and the d 002 and L c values.

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