Results Of Tension Tests Research Articles

Wedge tension test of a high-strength bolt of fully pearlitic high-carbon steel

Using a wedge tension test for service and safety reasons, this study determines the fracture location of a previously developed high-strength M8 bolt with a tensile strength of 1600MPa. The strength distributions of the manufactured bolt are examined in compression and microhardness tests to ensure a better understanding of the experimental results of the wedge tension test. The strength variations of the manufactured bolt were confirmed through scanning electron microscope measurements of the interlamellar spacing of the pearlite. Because of the strength condition in the neck of the bolt and the geometry-induced stress concentration, the head of the manufactured bolt can be separated from the neck during the wedge tension test. In this study, stress analyses were therefore conduced to prevent the head separation. That is, the stress concentration on the neck of the bolt was checked by varying the fillet radius for a given pitch size of the bolt. The numerical findings were subsequently validated by the wedge tension test. The findings are the basis of practical industrial design guidelines on the fillet radius to prevent the head of the manufactured bolt from being separated.

Effect of Yield Phenomenon on Fatigue Damage in Commercially Pure Iron Thin Wires

The effect of the specimen size on tensile and fatigue properties was studied by using thin wires with the grain size of 22μm and the diameter, Dmin, of 800μm, 700μm and 500μm (these are named Specimen-800, 700 and 500, respectivly). For tension test results, the yield strength (proof stress) strongly depended on the specimen diameter. All Specimen-800 and Specimen-700 and a part of Specimen-500 show the clear yield phenomena. However, most of Specimen-500 did not show yielding. For all specimens fractured under cyclic loading, the necking was occurred at the final stage of the fatigue process, and the initiation and the propagation of fatigue cracks were not observed. Two kinds of failure processes were observed. One was ratcheting failure and the other was delayed yielding failure. After the delayed yielding, specimens showed the process similar to ratcheting failure. It was concluded that these size effect are caused by the difference in the number of grains at the minimum cross section. Regardless of diameters of specimens, the scatter in fatigue life was very large compared with that of bulk specimen. It was concluded that the main cause of the large scatter in fatigue life was attributed to the scatter in the number of cycles to start ratcheting deformation (delayed yielding).

A model to describe the high rate performance of self-piercing riveted joints in sheet aluminium

This paper investigates the performance of self-piercing riveted joints in aluminium sheet (A5754) at typical automotive crash speeds. Tension, shear and peel joint specimens have been tested over the speed range from low rate (10−3m/s) to high rate (5m/s), using a high rate servo-hydraulic machine. A heat treatment was applied to some of the material and joint specimens to simulate the paint bake conditioning applied to a car body in industry.The aluminium sheet material used to form the substrates was tested over the strain rate range from quasi-static (∼10−3s−1) to near 500s−1, and strain rate dependency on strength was not observed. Although the sheet material tested showed no strain rate dependency, this paper reports a measurable reduction in performance for the tension and shear joint test results at higher rate, which has not been previously reported. Common to all joint types tested in this paper is interlock failure and this is a tension failure mode. A rate dependent empirical model which relates energy to the negative exponential of test speed is shown to be a good fit to the joint tension test results. The same model holds for the relationship between maximum displacement and test speed. After calibration, the model shows a transition in which performance decreases rapidly at higher rate for the joint interlock failure mode. An explanation of the cause is discussed.Critical to the findings reported in this paper is the design of the fixture and force transducer to test U shaped tension specimens over the speed range of interest. A finite element model of the fixture and test measurement system was developed to ensure a near optimal design. Sufficient details of these are given to reproduce the test results.

Hot deformation behavior and microstructure evolution of TC4 titanium alloy

The hot deformation behavior of Ti-6Al-4V (TC4) titanium alloy was investigated in the temperature range from 650 °C to 950 °C with the strain rate ranging from 7.7×10 −4 s −1 to 7.7×10 −2 s −1. The hot tension test results indicate that the flow stress decreases with increasing the deformation temperature and increases with increasing the strain rate. XRD analysis result reveals that only deformation temperature affects the phase constitution. The microstructure evolution under different deformation conditions was characterized by TEM observation. For the deformation of TC4 alloy, the work-hardening is dominant at low temperature, while the dynamic recovery and dynamic re-crystallization assisted softening is dominant at high temperature.

Mechanical Characteristics of Typical Plant Leaves

Plant leaf is a natural composite biomaterial, and its strength is closely related to the microstructure. In this paper, the mechanical characteristics of eight species of plant leaves were investigated and analyzed. The ultimate strength of leaves and the hardness of leaf surfaces were measured by using universal testing machine and nanoindenter tester, respectively. The tensile strength of the parallel microstructure was investigated based on its cross-sectional mechanical model. The results of tension tests indicate that the ultimate strength of a leaf is related to the material composition and structure. The coriaceous leaves usually exhibit higher tensile strength. For example, the Phyllostachys pubescens leaf can achieve the maximum ultimate strength of 5.9091 N·mm −2. It is concluded from the results of hardness tests that material components of leaf surface can influence the surface hardness evidently. The leaf surface composed of more lignin and cellulose materials shows a higher surface hardness than that composed of more carbohydrates materials.

Fatigue damage development in new fibre metal laminates made by the VARTM process

This paper investigates the tensile and fatigue properties of a newly developed fibre metal laminate (FML) manufactured using the vacuum assisted resin transfer moulding (VARTM) method. This manufacturing method allows the glass fibre reinforced epoxy and 2024-T3 aluminium FML to be prepared at lower cost than conventionally manufactured FMLs. However, in order for the resin to infiltrate the FML, the metal sheets need to be perforated. These perforation holes act as crack initiators and reduce the FML's performance. Tension and fatigue test results of three different designs are reported and compared to mechanical property predictions. Additionally, single sheet Al alloy specimens were tested in order to analyse the influence of the drilling method.

Microstructure and mechanical properties of friction stir welded Al/Mg 2Si metal matrix cast composite

In this research, friction stir weldability of 15 wt.% Mg 2Si particulate aluminum matrix cast composite and effects of tool rotation speed and number of welding passes on microstructure and mechanical properties of the joints were investigated. Microstructural observations were carried out by employing optical and scanning electron microscopy of the cross sections perpendicular to the tool traverse direction. Mechanical properties including microhardness and tensile strength were evaluated in detail. The results showed fragmentation of Mg 2Si particles and Mg 2Si needles existing in eutectic structure in stir zone. Also, homogeneous distribution of Mg 2Si particles was observed in the stir zone as a result of stirring with high plastic strains. Tension test results indicated that tensile strength of the joint had an optimum at 1120 rpm tool rotation speed and decreased with increasing of the number of welding passes. Hardness of the joint increased due to modification of solidification microstructure of the base composite. This research indicates that friction stir welding is a good candidate for joining of 15 wt.% Mg 2Si aluminum matrix composite castings.

The Indentation Behaviour of Carbon Fibre Composite Tubes-Experiments & Modelling

Metallic tubes have been extensively studied for their crashworthiness as they closely resemble automotive crash rails. Recently, the demand to produce lighter weight, yet safer vehicles has led to the need to understand the crash behaviour of novel materials, such as fibre reinforced polymer composites, metallic foams and sandwich structures. This paper discusses the static indentation response of Carbon Fibre Reinforced Polymer (CFRP) tubes. The side impact on a CFRP tube involves various failure mechanisms. This paper highlights these mechanisms and compares the energy absorption of CFRP tubes with similar Aluminium tubes. The response of the CFRP tubes during bending was modelled using ABAQUS finite element software with a composite fabric material model. The material inputs were given based on standard tension and compression test results and the in-plane damage was defined based on cyclic shear tests. The failure modes and energy absorption observed during the tests were well represented by the finite element model.

Ellipsoidal defect identification in an elastic body from the results of a uniaxial tension (compression) test

We consider the problem of identification of an ellipsoidal cavity or ellipsoidal inclusion (rigid or elastic) in an isotropic linearly elastic body. We solve the problem by a method based on the use of a reciprocity functional. We propose a constructive procedure which allows us to express the defect geometric parameters in terms of the values of the reciprocity functional. These values can be calculated by measuring the displacements on the external surface of the body in a static uniaxial tension (compression) test. The proposed procedure permits exact identification of the parameters of the ellipsoidal defect if it is located in an infinite space. In the case of a bounded elastic body, it can be considered as an approximate procedure.

Modelling the side impact of carbon fibre tubes

Metallic tubes have been extensively studied for their crashworthiness as they closely resemble automotive crash rails. Recently, the demand to improve fuel economy and reduce vehicle emissions has led automobile manufacturers to explore the crash properties of light weight materials such as fibre reinforced polymer composites, metallic foams and sandwich structures in order to use them as crash barriers. This paper discusses the response of carbon fibre reinforced polymer (CFRP) tubes and their failure mechanisms during side impact. The energy absorption of CFRP tubes is compared to similar Aluminium tubes. The response of the CFRP tubes during impact was modelled using Abaqus finite element software with a composite fabric material model. The material inputs were given based on standard tension and compression test results and the in-plane damage was defined based on cyclic shear tests. The failure modes and energy absorption observed during the tests were well represented by the finite element model.

Dynamic Characterization of Orthogneiss Rock Subjected to Intermediate and High Strain Rates in Tension

The dynamic characterization of rocks under intermediate and high strain rates is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive laws is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. These data are necessary and require experimental techniques able to induce on the rock materials state of loading reproducing the actual dynamic condition. The dynamic characterization has been carried out by means of two special apparatus: the split Hopkinson tension bar and the hydro-pneumatic machine. These equipments are briefly described with a discussion on the results of dynamic tension tests at three different strain rates (0.1, 10, 100 strain/s) on Onsernone Orthogneiss for loading directions 0°, 45° and 90° with respect to the schistosity. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate, up to about two times with respect to the quasi-static conditions in the case of 0° and 45° orientation and more than three times in the case of 90° at high strain rates. Dynamic increase factors versus strain rate curves for tensile strength were also evaluated and discussed.

Direct Tension Performance of Steel Pipelines with Welded Slip Joints

Full-scale direct tension test results are presented in this paper for two steel pipelines with welded slip joints, using high quality external welds, and an outer diameter and wall thickness of 320 and 6.4 mm, (12.5 and 0.25 in.) respectively. The test pipes were loaded to complete circumferential tensile failure. The results of numerical simulations with a two-dimensional axisymmetric solid finite-element (FE) models using the program ABAQUS compare favorably with the experimental measurements. The FE results show that pipelines in the field with high quality welds can sustain maximum tensile strain of about 0.03 even with internal pressure. Assuming good welds, an allowable tensile strain level of 0.01 to 0.015 is recommended. The test results are discussed with respect to welding and inspection practices, as well as their application in the design and risk assessment of pipelines subject to large ground deformation caused by earthquakes, landslides, and subsidence.

Dislocation subgrain structures and modeling the plastic hardening of metallic single crystals

A single crystal plasticity theory for insertion into finite element simulation is formulated using sequential laminates to model subgrain dislocation structures. It is known that local models do not adequately account for latent hardening, as latent hardening is not only a material property, but a nonlocal property (e.g. grain size and shape). The addition of the nonlocal energy from the formation of subgrain structure dislocation walls and the boundary layer misfits provide both latent and self-hardening of a crystal slip. Latent hardening occurs as the formation of new dislocation walls limits motion of new mobile dislocations, thus hardening future slip systems. Self-hardening is accomplished by an evolution of the subgrain structure length scale. The substructure length scale is computed by minimizing the nonlocal energy. The minimization of the nonlocal energy is a competition between the dislocation wall energy and the boundary layer energies. The nonlocal terms are also directly minimized within the subgrain model as they affect deformation response. The geometrical relationship between the dislocation walls and slip planes affecting the dislocation mean free path is taken into account, giving a first-order approximation to shape effects. A coplanar slip model is developed due to requirements while modeling the subgrain structure. This subgrain structure plasticity model is noteworthy as all material parameters are experimentally determined rather than fit. The model also has an inherit path dependence due to the formation of the subgrain structures. Validation is accomplished by comparison with single crystal tension test results.

Application of the Viscoelastic Continuum Damage Model to the Indirect Tension Test at a Single Temperature

The viscoelastic continuum damage model, developed based on Schapery’s correspondence principle and the continuum damage mechanics, has received a great deal of attention because of its mathematical soundness and effectiveness in describing damage growth in viscoelastic media and has been used to make reliable estimations on the fatigue lives of asphalt mixtures. Its applications to field mixtures, however, have been limited because the model requires performing the uniaxial tension test. As an alternative, this study developed an analytical methodology for applying the model to the indirect tension test, which has been successfully used in testing both laboratory-made and field-cored mixtures. From the results of the indirect tension tests conducted on asphalt mixture at three different crosshead-controlled rates, it was found that the stress-pseudostrain curves could be superimposed onto one equality line in the linear viscoelastic range of the given mixture, and its rate dependency was successfully eli...

Useful Lifetime Prediction of Rubber Components Using Accelerated Testing

Rubber material properties, and useful lifetime prediction and evaluation are very important in the design procedure to assure the safety and reliability of rubber components. We have been interested for many years in predicting the lifetimes of rubber materials in oxygen-containing environments using a combination of accelerated aging tests and extrapolation models. In this paper, we investigate the heat aging effects on the material properties, and useful lifetime prediction of ethylene-propylene diene M-class rubber (EPDM), and acrylonitrile-butadiene rubber (NBR) for refrigerator components. The experimental results sssay that the crosslink density changes are varied with compositions of rubber vulcanization, and characteristics of heat aging behaviors of rubber vulcanizates are described well using the activation energy change with aging time. The stress and strain curves were obtained from the results of the simple tension test for specimens. To predict the useful lifetime of EPDM, and NBR, the mechanical property changes were determined under accelerated aging conditions. Rubber was aged at temperatures ranging from 50°C to 100°C for times ranging from 1 to 180 days. We present a general approach for more confidently correlating accelerated aging results with aging under service conditions using the Arrhenius methodology. By using the compression set test, several useful lifetime prediction equations for rubber material are proposed.

A Three-Dimensional Constitutive Model for the Dynamic Response of Rubber

Abstract REFERENCE: Liu, M. and Hoo Fatt, M. S., "A Three-Dimensional Constitutive Model for the Dynamic Response of Rubber," Tire Science and Technology, TSTCA, Vol. 37, No. 4, October - December 2009, pp. 226-253. The development of a constitutive model to describe the dynamic response of a filled rubber compound is presented in this paper. A series of cyclic tension tests were done on the rubber compound with mean strains ranging from 0.2 to 0.5, strain amplitudes ranging from 0.05 to 0.2, and strain rates ranging from 0.1 to 10 s−1. The cyclic strain-controlled test results showed material rate dependence and hysteresis, and this motivated the development of a phenomenological-based, hyper-viscoelastic constitutive model. A Zener model, i.e., a spring in parallel with a Maxwell element, was assumed. The total stress was decomposed into a rate-independent equilibrium stress and a rate-dependent overstress. The springs were modeled as neo-Hookean, while the damper was defined by a nonlinear viscosity function. Material constants for the constitutive model were calculated from the cyclic tension test results. Cyclic tension tests were also performed on a sheet with central hole to check the accuracy of the constitutive model. The constitutive model was implemented into ABAQUS Standard with a user-defined material subroutine. The finite element analysis simulation of the rubber sheet with a central hole demonstrated relatively good agreement with the experimental data.

Microstructural and mechanical behavior of 4.5Cr–2W–0.25V–0.1C steel

In this paper the microstructural and mechanical properties of a hot rolled Cr–W–V steel were studied. The 4.5Cr–2W–0.25V–0.1C steel was austenitized at 1000 °C for 30 min and then tempered at 600 and 700 °C for 1 h. The physical metallurgy of this steel was studied by optical, scanning electron and transmission electron microscopes and X-ray and electron diffraction patterns. The results showed that four types of carbide were precipitated as MC, M 3C, M 7C 3 and M 23C 6 along prior austenite grains and lath boundaries and within martensitic matrix. The average sizes of the M 7C 3 and M 23C 6 carbides in the specimens tempered at 600 °C were about 100 and 180 nm, and in specimens tempered at 700 °C were about 110 and 210 nm, respectively. When the tempering temperature was increased, weight percent of extracted precipitates and the formation rate of the stable carbides such as M 23C 6 and dissolution rate of the metastable carbides such as M 3C and M 7C 3 were also increased. The results of hot tension tests showed the strength and elongation of tempered specimens were decreased when the test temperature was increased. The strength decrease was slow at range of 200–500 °C but sharp at test temperature of 600 °C. The results suggested tempering at 700 °C has better tensile properties at operating temperature (500–600 °C) when compared to tempering at 600 °C.

초미세 결정립 Cu-3%Ag 합금의 기계적/전기적 특성

The present work demonstrates the mechanical and electrical responses of submicrocrystalline Cu-3%Ag alloy as a function of strain imposed by equal channel angular pressing(ECAP). From transmission electron microscope observation, the resulting microstructures of Cu-3%Ag alloy deformed by ECAP for 8-pass or more consist of reasonably fine, equiaxed grains without having a strong preferred orientation, suggesting that microstructure evolution is slower than that of pure-Al and its alloys owing to low stacking fault energy. The results of room temperature tension tests reveal that, as the amount of applied strain increases, the tensile strength of submicrocrystalline Cu-3%Ag alloy increases whereas losing both the ductility and the electrical conductivity. Such phenomenon can be explained based on microstructure featured by the non-equilibrium grain boundaries.

Pulse current treatment effect on the strength of reinforcing steel and its weld joint under impact loading

We present results of static and impact tension tests of as-received reinforcing steel specimens, specimens with weld joints in their test portion, as well as specimens pretreated by high-density pulse current. As test results demonstrate, an increased strain rate enhances strength, and the pulse current treatment greatly influences the strength and plasticity of a defect-containing weld metal under static and impact tension.

490MPa급 고장력강 탄뎀 가스메탈아크 용접부에 대한 기계적 성질과 미세조직 비교

Tandem GMAW is one of the high performance welding process and used in many industries to increase the productivity. An evaluation is presented of the mechanical properties and microstructural characteristics of the Tandem GMAW and conventional Single GMAW welds in 30mm thickness 490MPa grade steel by comparison method. Welding sequence and bead with and hight was kept, avoiding the effect of the bead shape and welding sequence. Tension, bending, hardness and Charpy impact test results of Tandem GMAW met the requirement of specification and showed similar distribution with conventional Single GMAW. Volume fraction of ferrite phase in weld metal showed little difference between Tandem GMAW and Single GMAW