Universal Tensile Testing Machine Research Articles

Effect of cooling rates after annealing on the microstructure and properties of 1000 MPa grade automobile steel for cold forming

The effects of different cooling rates (0.05 °C s−1, 0.1 °C s−1, and 0.2 °C s−1) on the microstructure and mechanical properties of 1000 MPa grade automobile steel for cold forming after two-phase annealing were studied. The microstructure of the experimental steel was observed by SEM and TEM, and its mechanical properties were tested by a universal tensile testing machine. The results showed that by increasing the cooling rate of two-phase annealing, more massive retained austenite, more uniform and fine ferrite, better elongation and higher ultimate tensile strength of steel can be obtained, so as to obtain better production of tensile strength and total elongation (product of tensile strength and elongation, PSE). The final result shows that after the test steel is quenched at 800 °C + 10 min and annealed in the two-phase region at 690 °C + 10 min, the faster the cooling rate, the better the mechanical properties. The mechanical properties of the steel plate are the best when the cooling rate reaches 0.2 °C s−1, and PSE can reach 27.44 GPa·%.

Effect of Doped Glass Fibers on Tensile and Shear Strengths and Microstructure of the Modified Shotcrete Material: An Experimental Study and a Simplified 2D Model

Shotcrete material has found extensive applications as a reinforcing material in the engineering sector. This study examined the effect of doped glass fibers on the mechanical performance of the modified shotcrete material composed of aeolian sand, fly ash, cement, quicklime, and doped glass fibers. Its tensile and shear strengths values were experimentally determined via a WAW-1000D computerized hydraulic universal tensile testing machine. Its microstructure was analyzed via a size analyzer, scanning electron microscope (SEM), and X-ray diffractometer (XRD). A 2D simplified mechanical model was elaborated to reflect the influence mechanism of the doped glass fibers on the mechanical performance of the modified shotcrete material. The experimental and mechanical analysis results indicated that, at the macroscopic scale, the experimental tensile and shear strengths of the shotcrete material doped with glass fibers were significantly higher than those of the undoped shotcrete material (by up to 310% and 596%, respectively). These results were in concert with the proposed model predictions, where the compound stresses in the shotcrete material were derived as the sum of the stress borne by the shotcrete material itself and the bridging stress exerted by the glass fibers. At the microscopic scale, SEM observations also revealed that the glass fibers were intertwined with each other and tightly enveloped by the shotcrete material particles within the modified shotcrete specimens, connecting the particles of different components into a whole and improving the overall mechanical strength. In addition, the relationships of the compound stress of the shotcrete material vs. embedment length, embedment angle, and cross-sectional area of the glass fibers were established. The research findings are considered instrumental in clarifying the mechanism by which the glass fibers influence the mechanical performance of shotcrete materials and optimize their solid waste (fly ash and quicklime) utilization.

Influence of Injection Rate on Mechanical Properties of the Molding Composition Based on Polyamide 6 and Carbon Nanotubes

This paper is devoted to obtaining and investigating polymer composites based on polyamide-6 and carbon nanotubes. Polyamide 6, type 210/310, was used as a polymer matrix, and carbon nanotubes manufactured by OcSiAl were used as a modifier. The components were compounded in a co-rotating twin-screw extruder HAAKE Rheomex OS PTW 16 to obtain granulate. The granulate was processed by injection molding on a Babyplast 6/10V machine to obtain test samples as double-sided blades (ISO-527-2, type 5A). Elastic strength tests were carried out on a Gotech UAI-7000M universal tensile-testing machine. It has been shown that introduction of 0.15% CNT promotes an increase in the yield point and the initial modulus of elasticity with a significant decrease in the ultimate strength. The maximum value of the tensile strength (161 MPa) has been obtained for the specified composition at an injection rate of 12.9 ml/s.

Effect of final cooling temperature on the microstructure and mechanical properties of high-strength anti-seismic rebar

Rebar is an important material in the major structural engineering, and its fine structure has a very important effect on the performance of the rebar. In this work, the Gleeble-3800 thermal simulator was used to simulate and control the final cooling temperature process to explore the effect of the precipitation behavior of the microalloying elements on the microstructure and mechanical properties of the rebar. The electron backscatter diffraction (EBSD), high-resolution transmission electron microscope (TEM), and universal tensile testing machine were used to characterize the microstructural transformation and mechanical properties of high-strength anti-seismic rebar. The results shows that under the conditions of different final cooling temperatures, the microstructure of the rebar were mainly composed of ferrite and pearlite. When the final cooling temperature decreased from 750 °C to 650 °C, the ferrite grain size decreased from 0.01237 mm to 0.00678 mm and the pearlite lamellar spacing decreased from 0.226 μm to 0.114 μm. The EBSD results found that the most of ferrite grains with larger misorientation angle (20° ∼ 60°) formed by the different austenite grains. The TEM results found that the main precipitates were (Nb, Ti, V) C, which precipitated on the ferrite matrix, and the shapes were oval, and the average particle sizes were about 20 ∼ 30 nm. When the final cooling temperature was 650 °C, the tensile strength and yield strength of the rebar reached 712.94 MPa and 562.97 MPa, respectively, and strength yield ratio was 1.27. With the decreases in the final cooling temperature, the tensile strength and yield strength of the rebar gradually increased.

Microstructure and Properties of Two Cr8 Cold Working Die Steel

In this paper, we studied the effect on microstructure and properties during low tempering and high tempering temperature of HNC53 and KD11max Cr8 cold working die steel by means of hardness tester, universal tensile testing machine, pendulum impact tester, metallographic microscope, SEM and EDS. The results showed that the microstructure of the two materials were spheroidized pearlite and large eutectic carbide. After quenching then tempering at high temperature 520°C and low temperature 200°C, the microstructure was martensite, eutectic carbide with large particles and small secondary precipitated carbide which was M7C3 type carbide. When KD11max was tempered at high temperature of 520°C, more nano-level secondary carbonization precipitated, and secondary hardening phenomenon was more obvious. The increase of Si and decrease of C could promote secondary hardening and improve the impact toughness of materials. KD11max impact toughness was better than HNC53.

Cold compression behavior on the evolution of microstructure and texture in Beta C titanium alloy

A single-phase Beta-C titanium alloy was subjected to uniaxial compression (up to 75% height reduction) in a universal tensile testing machine at room temperature. The evolution of microstructure during uniaxial cold compression was studied using optical microscopy, scanning electron microscopy, and electron backscattered diffraction, while, bulk crystallographic texture analysis was measured using X-ray diffraction. Evolution of deformation texture during cold compression was simulated using mean-field Taylor models. The deformed microstructure (after 30% compression) showed pronounced shear bands, particularly in compression direction, CD//< 111 >oriented grains. The dominant crystallographic texture components developed during compression were CD//< 100 >fiber and CD//< 111 >fiber. A gradual change in texture was observed with increasing compression. Full constraint Taylor model showed a reasonably good match between simulated and experimental texture.

Microstructure characteristics and mechanical properties of a novel heavy density Ni–W–Co matrix alloy prepared by VIM/VAR

In present work, a novel heavy density matrix alloy (Ni–W–Co) was produced through vacuum induction melting (VIM) and vacuum arc remelting (VAR). The as-cast microstructure, element segregation, and mechanical properties were characterized by optical microscopy, scanning electron microscopy, electron probe microanalysis, and universal tensile testing machine. Results indicated that the present matrix alloy displays a considerable purity and chemical homogeneity. The microstructure exhibits typical dendritic features, which is composed of austenite single-phase structure entirely. The elements Ni and Co are evenly distributed in the matrix, while W shows a distinct segregation trend in the as-cast ingot. The tensile properties of the as-cast alloy at room temperature show that the maximum ultimate tensile strength and fracture elongation are up to 560Mpa and 55.79%, respectively. Tensile fracture morphologies reveal the presence of complex quasi cleavage and ductile fractures. The true stress-plastic strain curves display distinct linear deviation in the region of uniform plastic deformation and exhibit two groups of positive and negative slopes at the lower and higher strains, respectively. The instantaneous work hardening rate-true strain curves depict typical “three stages” hardening characteristics.

Structure and Properties of Recycled Polyester-cotton Blended Fiber/HDPE Composite Board

Recycled polyester-cotton blended fiber/high density polyethylene (HDPE) composite boards were prepared by internal mixing and compression molding two-step process with maleic anhydride grafted ethylene polyethylene-octene elastomer (POE-g-MAH) as compatibilizer. Two kinds of recycled polyester-cotton blended fiber were used as reinforcing fibers, including polyester-cotton long fiber (F1) and polyester-cotton short fiber (F2). Microstructure and properties of the composite boards reinforced with F1 and F2 were characterized by SEM and electronic universal tensile testing machine. The results showed that the comprehensive mechanical properties of polyester-cotton blended long fiber composite boards (F1HC4) and polyester-cotton blended short fiber composite boards (F2HC4) were optimal with a compatibilizer content of 4%. F1 had a significant effect on the mechanical properties of the composite boards in two kinds of fiber with the same addition of compatibilizer. The tensile strength, flexural strength, impact strength and of F1HC4 were 56.4%, 36.4% and 87.5% higher than that of F2HC4, respectively.

Mechanical and Metallurgical Properties of GTAW, GMAW and FSW Lap Joints on AA6061-T6 Alloy

ABSTRACT Friction stir welding (FSW) is an upgraded version of the friction welding process. It was invented in 1991 at The Welding Institute (TWI). It is considered the latest in development and also the most important one in the metal joining process during the past two decades. The present investigation has the objective of comparing the mechanical and metallurgical properties of welding processes such as GTAW, GMAW, and FSW lap joints on the welded AA6061-T6 alloy. Rolled AA6061-T6 plates of 3 mm thickness were used as the base material for preparing lap welded joints. All the welding processes were carried out using optimum parameter conditions. The failure load, tensile shear strength, and the micro-hardness of the welded joints were analysed using a universal tensile test machine and the Vickers’s hardness testing machine. The microstructures of the welded joints were analysed using an Optical Microscope (OM) and a Scanning Electron Microscopy (SEM). Finally, a comparative analysis was done between the results of the general aspects like power and heat input, mechanical and metallurgical properties of TIG, MIG, and FSW lap joint specimens.

Improving the Properties of Laser-Welded Al-Zn-Mg-Cu Alloy Joints by Aging and Double-Sided Ultrasonic Impact Compound Treatment.

To improve the loose structure and serious porosity of (Al–Zn–Mg–Cu) 7075 aluminum alloy laser-welded joints, aging treatment, double-sided ultrasonic impact treatment (DSUIT), and a combination of aging and DSUIT (A–DSUIT) were used to treat joints. In this experiment, the mechanism of A–DSUIT on the microstructure and properties of welded joints was analyzed. The microstructure of the welded joints was observed using optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD). The hardness and tensile properties of the welded components under the different processes were examined via Vickers hardness test and a universal tensile testing machine. The results showed that, after the aging treatment, the dendritic structure of the welded joints transformed into an equiaxed crystal structure. Moreover, the residual tensile stress generated in the welding process was weakened, and the hardness and tensile strength were significantly improved. After DSUIT, a plastic deformation layer of a certain thickness was generated from the surface downward, and the residual compressive stress was introduced to a certain depth of the joint. However, the weld zone unaffected by DSUIT still exhibited residual tensile stress. The inner microhardness of the joint surface improved; the impact surface hardness was the largest and gradually decreased inward to the weld zone base metal hardness, with a small improvement in the tensile strength. Compared with the single treatment process, the microstructural and mechanical properties of the welded joint after A–DSUIT were comprehensively improved. The microhardness and tensile strength of the welded joint reached 200 HV and 615 MPa, respectively, for an increase of 45.8% and 61.8%, respectively. Observation of the fractures of the tensile specimens under the different treatment processes showed that the fractures before the aging treatment were mainly ductile fractures while those after were mainly brittle fractures. After DSUIT of the welded joints, a clear and dense plastic deformation layer was observed in the fracture of the tensile specimens and effectively improved the tensile properties of the welded joints. Under the EBSD characterization, the larger the residual compressive stress near the ultrasonic impact surface, the smaller the grain diameter and misorientation angle, and the lower the texture strength. Finally, after A–DSUIT, the hardness and tensile properties improved the most.

Microstructure evolution of recycled 7075 aluminum alloy and its mechanical and corrosion properties

This paper takes the recycled 7075 aluminum alloy as the object to study its smelting, extrusion and heat treatment processes. The composition, microstructure, mechanical properties and corrosion properties of recycled 7075 aluminum alloys were characterized by spectrometer, optical metallographic microscope, universal tensile testing machine, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results showed that the composition distribution of recycled 7075 aluminum alloy ingots was more uniform and the microstructure was more optimized. The tensile strength, yield strength and elongation of recycled 7075 aluminum alloy plates were higher than American Society of Testing Materials (ASTM) standard. The recycled 7075-T6 aluminum alloy plates had good corrosion resistance to salt spray. This paper aims to provide guidance for the smelting, extrusion and heat treatment processes of scrap aircraft aluminum alloy regeneration process, and to lay the foundation of the recovery and reutilization of scrap aircraft aluminum alloys.

Tensile Behavior of Geometrically Irregular Bagasse Fiber

In the present work, an investigation on the surface topography and geometry variation of bagasse fibers was correlated with their mechanical properties via image analysis. The fibers were tested under a universal tensile testing machine and the diameter of the fibers was calculated using images obtained in a digital microscope. Furthermore, surface characterization and quantification were also performed using images obtained via SEM. The results showed that the surface roughness of alkali-treated bagasse fiber increased compared to that of the untreated one. Moreover, it was observed that the diameter variation of bagasse fiber along its length and among different fibers is not only variable but also unpredictable. The tensile test results revealed that bagasse fibers showed lower stress at a rupture with considerable scatter. It can be inferred that the synergistic effect of thick bagasse fiber, bagasse fiber diameter variations along its length and among fibers, and the fiber fracture mechanism establishes a local condition for fracture and resulted in such variations in tensile properties. Finally, the results clearly showed that the two-parameter Weibull fit the experimental data fairly well (R2=0.97). The Weibull modulus (m) was found to be 1.7, indicating that the strength distribution is high.

Direct tensile strength measurement of granite by the universal tensile testing machine

The direct tensile strength of a typical hard rock like granite is measured by a novel apparatus known as compression-to-tensile load transfer (CTLT) device. The rock specimen is prepared in form of a slab containing a central hole and placed in the universal testing machine where the direct tensile stress can be applied to this specimen by implementing a special type of load transferring device which converts the applied compressive load to that of the tensile during the test. In the present work, some typical hard rock specimens of granite are specially prepared and tested in the laboratory to measure their direct tensile strengths. Then, a new load converting device implemented in the universal tensile testing machine is used to cause the rock specimen to be subjected to a direct tensile loading during the test. The compressive load was applied to the transferring device at the rate of 0.02 MPa/s. Numerical modeling of the tested specimens were accomplished using the discrete element method (DEM) and the higher order displacement discontinuity method (HODDM). The tensile failure of granite rock mainly occurs along the horizontal axis. The experimental results were in a good accordance with DEM results and HODDM outputs.

Effect of Tensile Load on the Mechanical Properties of AlSiC Composite Materials using ANSYS Design Modeller

Aluminium Silicon Carbide (AlSiC) composite materials are used in the electronics industries and other manufacturing companies hence, manufacturing of AlSiC composite materials with the right properties for different applications are vital to most industries. The challenge of testing the same specimens for different properties remains, because most of the tests carried out are destructive. Hence, the use of ANSYS finite element simulation software for the design and analysis of a flat bar specimen. Loads between 3 kN to 21 kN were applied on the specimen since it is within the operating limit of a Universal Tensile Testing Machine (UTTM), while both ends are fixed. The AlSiC composite materials used in this study have a composition of 63 vol% Al (356.2) and 37 vol% SiC and, the resultsshowed that stress was directly proportional to strain. While the calculated Young’s modulus from the stress versus strain plot was approximately 167 GPa for the different tensile loads applied. In addition, the total deformation of the AlSiC composite material increased as the load was increased. Also, the highest deformation of the material was observed around the centre of the test specimen. This is synonymous with the failure observed in practical testing of specimens.&#x0D; Keywords: AlSiC, tensile load, aluminium MMC, stress analysis, deformation, ANSYS

On the Determination of Material Mechanical Properties of St 37 Steel Pipes Using O-Ring Specimens

This paper presents experimental, analytical and numerical studies of testing O-rings specimens cut from an St 37 steel pipe. These studies are meant to determine the mechanical properties of the St 37 material and to predict the behavior of its pipes when subjected to internal pressure. This was done by applying transversely concentrated force on relatively small rings (outer diameter = 60.3 mm and the wall thickness = 3.9 mm) until the rupture of the ring. A universal tensile testing machine along with specially designed holders were used to measure the load-line displacement of the rings. In addition, formulas to determine the displacement of the loading pin were derived using the straight beam theory and the curved beam theory. Both elastic and plastic deformations were calculated and compared in the results. Furthermore, finite element analyses (FEA) were carried out using strain hardening material model, to obtain the full deformation behavior of the O-ring during testing until rupture. From the experimental results, it was possible to determine the material yield strength and modulus of elasticity. The analytically obtained results predicted the material modulus of elasticity which was in very good agreement with the published values. The FE analyses were able to predict the full behavior of the rings.

Optimization of ultimate tensile strength of welded Inconel 625 and duplex 2205

The ultimate strength is an important property of any material for the manufacturing of components. This paper utilized the laser beam welding (LBW), due to its smaller dimension, which produces lesser distortion and process velocity is higher. Inconel 625 alloy and duplex 2205 stainless steel is having higher strength and corrosive resistance properties. Due to the above-mentioned properties, it could be used in oil and gas storage containers, marine and geothermal applications. This research work presents an investigation of various input variable effects on the output variable (ultimate tensile strength) in LBW for dissimilar materials namely, Inconel 625 alloy and duplex 2205 stainless steel. The input variables for this research are the power of a laser, welding speed, and focal position. The experimental runs are developed with the help of design of experiment (DOE) and utilized statistical design expert software. The ultimate tensile strength on different runs is measured using a universal tensile testing machine. Then from a response surface methodology and ANOVA, the optimum value of ultimate tensile strength was determined to maximize the weld joint and bead geometry. Finally, the confirmation test was carried out, it reveals the maximum error of 0.912% with the predicted value. In addition, the microstructure of the weld beads was examined using optical microscopy.

Influences of Stress State, Temperature, and Strain Rate on Ductility of Pure Iron

In this study, the plastic response of pure iron DT8 at different stress states, temperatures, and strain rates is investigated. Specimens with different structures designed for different stress states are subjected to quasi-static uniaxial tension tests to investigate the effect of stress state on the fracture behavior of pure iron. Standard specimens at temperatures ranging from 100 to 900 °C are tested by a quasi-static uniaxial tension machine. Double-notch shear specimens are subjected to a universal electronic tensile testing machine and an improved split-Hopkinson pressure bar device with strain rates ranging from 0.0033 to 227450/s to investigate the effect of strain rate on the fracture behavior of pure iron. Results show that the flow stress of pure iron DT8 slightly increases with the increase in stress triaxiality before the material breaks. With the increase in stress triaxiality from 0.333 to 0.550, the fracture strain of pure iron DT8 decreases almost linearly from 1.949 to 0.898. With the increase in temperature, the fracture strain increases almost linearly from 1.43 at 100 °C to 3.19 at 900 °C. A blue brittleness effect occurs at about 300 °C, where the yield and tensile strengths of pure iron increase slightly. In the low strain rate range from 0.0033 to 800/s, the fracture strain of pure iron is almost stable at approximately 2.0. Then, the fracture strain increases with the further increase in strain rate. When the strain rate reaches 120850/s, the fracture strain reaches its peak value of 3.64. Thereafter, the fracture strain decreases rapidly as the strain rate increases. The fracture surfaces of the specimens take on different fracture morphologies with the increase in strain rate. The nature of the strain rate’s effect on material ductility is discussed.

Experimental study on the influence of bending and straightening cycles for non-destructive and destructive coiled tubing

During each operation in wells, the coiled tubing has to undergo three straightening-bending-straightening plastic deformations, causing different damages on coiled tubing (ellipse, scratches on the surface), which results in low cycle fatigue failure occurring frequently. According to the failure shapes and causes of the coiled tubing, the described damage forms of coiled tubing are: ellipticity, axial scratches, circumferential scratches and square pits. A special fatigue experimental device is designed and built under the electronic universal tensile testing machine CMT5105 in the laboratory, and the commonly used 2–3/8″ coiled tubing is selected. The non-destructive and destructive coiled tubing with ellipse and scratches are carried out cyclic bending-straightening experiments. The experimental results show that: (1) When the internal pressure of the coiled tubing is less than 40 MPa, it does not affect the number of underground operations for the coiled tubing, but the applied internal pressure is equal to or greater than 40 MPa, the number of underground operations is significantly reduced. (2) If the internal pressure and ellipse exist simultaneously on the coiled tubing, the ellipse has little effect on the number of operations. (3) The influence of circumferential scratches on the fatigue life is greater for the coiled tubing, while the axial and square pits have less effect on the cyclic numbers. (4) The formula of fatigue life is established for destructive coiled tubing, which can provide theoretical basis for the failure prediction and control for coiled tubing in engineering.

A nonlinear damage constitutive model of PVC coated fabrics

A simple and effective damage constitutive model for PVC-coated fabrics be developed, which could be used to predict the nonlinear mechanical response of membrane structures under tension more accurately. In this paper, based on continuum damage mechanics theory, a nonlinear damage constitutive model for PVC-coated fabrics was established. Firstly, the off-axis tensile tests were carried out on the membrane material at 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° with an electronic universal tensile testing machine, and the tensile curves of seven specimens were obtained. Then, the Helmholtz free energy function is constructed based on the continuum damage mechanics theory and the existing research foundation, and the constitutive equation of the material is derived. Then, according to the characteristics of the off-axial tensile test curve of the coated fabrics, a damage evolution equation for the materials under tension was established with strain as an independent variable. By compiling a MATLAB program of the constitutive model, the parameters were obtained, and the off-axial tensile test curves of PVC-coated fabrics were predicted. The constitutive model was compiled using the user-defined subroutine UMAT in ABAQUS, and the correctness of the model was verified by simulating a static loading test of the membrane structure under in-plane tension. The model shows a good performance in computation and the obtained results are also in good agreement with experimental data. These features enable the proposed model to be used in numerical calculations for membrane structures.

Effect of Al on characterization and properties of AlxCoCrFeNi high entropy alloy prepared via electro-deoxidization of the metal oxides and vacuum hot pressing sintering process

AlxCoCrFeNi high-entropy alloys with different Al contents (x in molar ratio, x = 0 – 2.0) were prepared by electrochemical process using the mixed metal oxides as the precursor. The effects of Al addition on the crystal structure, microstructure, mechanical property and corrosion behavior were investigated by XRD, XPS, SEM, FE-EPMA, universal tensile testing machine, Vickers hardness tester and electrochemical workstation. With the increase of Al contents, the crystal structure of AlxCoCrFeNi HEAs transformed from FCC to the mixed crystal structures of FCC and BCC, finally, to BCC + B2. The σ-phase was formed in AlxCoCrFeNi (x = 0.8 – 1.5) HEAs during the electrolysis deoxidization. The bulk HEAs could be prepared successfully via vacuum hot pressing sintering process. The bulk HEAs exhibit excellent ultimate tensile strength (UTS) and hardness. The hardness of the Al0 (245.2 HV) HEA and Al0.3 (261.2 HV) HEA was twice high of the sample prepared by arc-melting method. Compared with 304 stainless steel (304SS) and AlxCoCrFeNi HEAs prepared by other method, AlxCoCrFeNi HEAs prepared by the united process shows a comparable corrosion resistance in acid, alkali and salt aqueous solutions.