Tensile Test Samples Research Articles

Fused Deposition Modelling of Natural Fibre/Polylactic Acid Composites

Fused deposition modelling is a simple additive manufacturing technology utilising fine filament extrusion of predominantly thermoplastic materials to build 3D objects layer by layer. This research explores the feasibility and the factors involved in using fused deposition modelling to produce natural fibre reinforced composite components. Uniform 3-mm filaments of both hemp and harakeke (Phormium tenax) in varying weight percentages within polylactic acid (PLA) polymer were successfully produced and used to print tensile test samples. Tensile test results supported harakeke to be a useful fibre in terms of mechanical properties achieved which surpassed the Young’s modulus and tensile strength of plain PLA samples by 42.3% and 5.4%, respectively.

Mechanical Tests of the ITER's PF-1 Coil Electrical Insulation Qualification Samples at 77 K

The PF1 coil is one of six poloidal field coils of the ITER magnet system. In accordance with the PF-1 coil procurement arrangement, JSC NIIEFA have manufactured and tested qualification samples of the PF-1 coil electrical turn insulation. Insulation qualification samples should withstand static and cyclic mechanical tests at 77 K in accordance with specified parameters[1]. In 2015, JSC NIIEFA carried out mechanical tests of the PF-1 coil insulation qualification samples. These tests demonstrated that mechanical properties of the turn insulation of PF-1 coil meet the ITER requirements. The successful test results prove that developed technologies could be used for manufacturing of the electrical insulation of the PF-1 coil. The following tests at 77 K have been carried out in 2015: tensile, interlaminar shear, shear-compression, and push-out tests in the specimens cut from 3 × 3 mock-up sample. Samples for tensile and interlaminar shear tests were cut from plates, which simulate multilayer turn insulation of PF-1 coil. Shear-compression samples were cut from the sandwich plates, which simulate bonding of the insulation to the stainless steel jacket of PF1 conductor. All types of qualification samples successfully passed mechanical tests at 77 K. This paper describes: preparation of insulation qualification samples; VPI process of the insulation qualification samples; and mechanical tests of the qualification insulation samples at 77 K.

Mechanical property effects of symmetrical hour glass shapes formed during double-sided TIG keyhole arc welding of AISI1040 joints

Abstract In this study, AISI1040 steel sheets of 10 mm thickness were welded in butt position without pretreatment by double-sided TIG keyhole arc welding process. Weld joints were produced by using three different welding currents (410, 430 and 450 A), electrode diameter (Φ: 3.2 mm), a constant shielding gas flow rate (8 l × min−1) and welding speed (0.01 m × min−1). Microstructural changes occurred in the fusion line of the weld samples were examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and microhardness analysis. V-notch Charpy and tensile tests were carried out to determine the bond strength of the weld samples. In addition, fracture types of the tensile test samples were determined by the help of fractographic examinations using SEM and EDS. Consequently, the weld samples produced by double-sided TIG keyhole technique are approximately symmetrical and hour glass shaped. Also, it was found that penetration depth increased with current density.

Niobium coating applied by HVOF as protection against hydrogen embrittlement of API 5CT P110 steel

Thermal spraying applications have been growing because of the advantages of these coatings. However, the use of thermal spray coatings to protect components against hydrogen embrittlement has not yet been the subject of studies. In this work, the deposition of niobium coating by high velocity oxygen fuel (HVOF) thermal spraying is performed to obtain a protective barrier against hydrogen intake by the API 5CT P110 steel. The coatings were characterized by scanning electron microscopy, optical microscopy, X-ray diffraction, roughness, porosity, hardness and by monitoring mechanical behaviour of samples in tensile test submitted to previous and simultaneous hydrogen charging. To evaluate the hydrogen absorption capacity, the mass quantities of hydrogen in the API 5CT P110 steel and niobium coating were obtained. The results showed that the niobium coating acted as a barrier to hydrogen intake, minimizing the effect of hydrogen on the mechanical properties of API 5CT P110 steel. Hydrogen measurements showed that the coating had a high hydrogen trapping capacity, 7.5 times higher than that of steel.

Characteristics of Al-Si-Mg Reinforced SiC Composites Produced by Stir Casting Route

Al-Si-Mg alloy that is strengthened by silicon carbide particles has the potential to have excellent mechanical properties with light weight. In this study, metal matrix composites reinforced silicon carbide from 2 vf-% to 15 vf-% and magnesium amounted to 10 wt-% as an external dopant were fabricated by stir casting route. The magnesium was added to promote the wetting between Al matrix and reinforced SiC. The process involved SiC blended inside the molten Al by a stirrer with a rotational speed of 500 rpm at 800 °C for 2 minutes and degassed with Ar gas for 4 minutes to remove all of the gas content in the molten Al. The molten composite was then cast into the plate and tensile test sample molds. The effect of SiC addition on the mechanical properties and microstructure of the composites was investigated. The result showed that the optimum tensile strength was reached at 8 vf-% SiC with the value of 175 MPa, while the elongation was 9.1%. The maximum hardness and wear rate were achieved at 10 vf-% SiC with the values of 57 HRB and 0.0022 mm3/m, respectively. Such increase was related to the microstructures dominated by the presence of Chinese script, primary and eutectic Mg2Si which were contributed to the mechanical properties of the composites.

Processing and Evaluation of Mechanical Properties of Sugarcane Fiber Reinforced Natural Composites

In the present work, the natural composites based on sugarcane bagasse fiber and/or coconut shell powder were processed using hand lay-up technique. The matrix selected was polyester. Three different types of composites were considered: polyester matrix + sugarcane fiber, polyester matrix + sugarcane fiber + metal mesh and polyester matrix + sugarcane fiber + coconut shell filler. The sugarcane fibers were used in three forms: (1) chemically treated by NaOH, (2) chemically treated by HCl, and (3) untreated condition. In total, 9 types of composites were developed and studied for tensile, flexural and impact properties. The fracture surface of the tensile and flexural test samples was examined with the aid of scanning electron microscope to understand the bonding characteristics and the mode of failure. The key-findings from the present work are: (1) the composites reinforced with the NaOH treated sugarcane fiber and the metal mesh show superior tensile and impact properties whereas the composites reinforced with the NaOH treated sugarcane fiber show the best flexural properties, (2) NaOH treatment of sugarcane fibres has a significant effect in improving the mechanical properties by surface modification of fibres through OH− functional groups. In contrast, HCl treatment of sugarcane deteriorates the surface of the sugarcane by absorbing the electrons. The damaged surface results in weak bonding causing poor mechanical properties, (3) From the SEM analysis of the surface of the sugarcane fiber, it may be concluded that the surface condition of the sugarcane fibres decide the bonding with the matrix. The fiber pull-outs and porosities are less in the NaOH treated sugarcane reinforced composites. The fiber failure is the main mechanism of failure in the tensile test whereas the fiber debonding from the matrix is the main source of failure in the flexural test.

Diffusible Hydrogen Level in Deposited Metal and Their Effect on Tensile Properties and Flexural Strength of P91 Steel

In a “very high-temperature reactor” (VHTR), the Nb–V-modified 9Cr–1Mo creep strength enhance the ferritic (CSEF) steel which is the chosen material for fabrication of reactor pressure vessels and piping because of its excellent high temperature thermal and mechanical properties. In such CSEF steel weldments, the hydrogen-induced cracking (HIC) is a critical issue. In the present work, the different levels of hydrogen have been induced in P91 CSEF weld metal to study their effect on HIC. The HIC susceptibility of P91 steel welds has been studied by carrying out the tensile test and flexural test for the different level of diffusible hydrogen. The hydrogen levels in deposited metals have been measured by using the mercury method. The fracture tensile and flexural test samples have been characterized based on the field-emission scanning electron microscope (FE-SEM). It is concluded that higher the level of diffusible hydrogen in deposited metal, more is the susceptibility of P91 steel to HIC. The minimum flexural and tensile strength are 507.45 MPa and 282 MPa, respectively, for 12.54 ml volume of diffusible hydrogen in 100 g of deposited weld metal.

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.

MECHANICAL CHARACTERIZATION OF NOTCHED HOT ROLLED MULTI-PHASE STEEL

This paper presents a series of experimental and numerical studies on Hot Rolled Stretch Flanging steels. This study focuses on four prototyped Hot-Rolled Stretch Flanging steels (HR780SF). Circular- notched sheet steel samples are used to induce different stress triaxiality levels in the rolling direction of sheet materials. Digital image correlation technique measures the local true strain during the deformation process of the notched samples in uniaxial tensile test. The microstructure of the notched samples is examined to evaluate the effect of geometrical features of circular notches on the microstructural evolution during the plastic deformation. Finally, the numerical results obtained via a finite element simulation are validated by the collected experimental data. Our experimental studies reveal the possibility of crack formation along the width of HR780SF steels during the mechanical load. The crack formation, which deteriorates the structural performance of hot rolled steels, can be avoided by the heat treatment of samples prior to the mechanical tests. In addition, it is found that the effect of notch geometry on the stress state is much more considerable at the notch edge than the notch center.

Effects of superimposed hydrostatic pressure on necking and fracture of tube under hydroforming

The finite element method is used to numerically simulate necking and fracture in hydroforming tubes under internal pressure through using the GTN model. The effect of superimposed hydrostatic pressure on necking (both uniform stain and localized necking), fracture initiation and fracture surface formation are studied. It is found that the superimposed hydrostatic pressure has a great impact on the onset of fracture with the increase of superimposed hydrostatic pressure, but insignificant influence on the uniform strain. As the superimposed hydrostatic pressure increases, the fracture surface of the hydroformed tube is also shifted from the P-type mode to C-type mode, a typical transition found experimentally for sheet tensile test samples deformed under superimposed hydrostatic pressure.

Proof of Concept of Integrated Load Measurement in 3D Printed Structures.

Currently, research on structural health monitoring systems is focused on direct integration of the system into a component or structure. The latter results in a so-called smart structure. One example of a smart structure is a component with integrated strain sensing for continuous load monitoring. Additive manufacturing, or 3D printing, now also enables such integration of functions inside components. As a proof-of-concept, the Fused Deposition Modeling (FDM) technique was used to integrate a strain sensing element inside polymer (ABS) tensile test samples. The strain sensing element consisted of a closed capillary filled with a fluid and connected to an externally mounted pressure sensor. The volumetric deformation of the integrated capillary resulted in pressure changes in the fluid. The obtained pressure measurements during tensile testing are reported in this paper and compared to state-of-the-art extensometer measurements. The sensitivity of the 3D printed pressure-based strain sensor is primarily a function of the compressibility of the capillary fluid. Air- and watertightness are of critical importance for the proper functioning of the 3D printed pressure-based strain sensor. Therefore, the best after-treatment procedure was selected on basis of a comparative analysis. The obtained pressure measurements are linear with respect to the extensometer readings, and the uncertainty on the strain measurement of a capillary filled with water (incompressible fluid) is ±3.1 µstrain, which is approximately three times less sensitive than conventional strain gauges (±1 µstrain), but 32 times more sensitive than the same sensor based on air (compressible fluid) (±101 µstrain).

A Microsample Tensile Test Application: Local Strength of Impact Welds Between Sheet Metals

Microsample tensile testing was conducted to evaluate the quality of impact welds created by vaporizing foil actuator welding. Tensile test samples with a gauge length of 0.6 mm were electro-discharge machined out of welds created between 1-mm-thick aluminum alloy type 6061 (AA6061) sheets and 6-mm-thick copper (Cu110) plates. Aluminum sheets were used as flyers, while copper plates acted as targets. Flyer sheets in T6 as well as T4 temper conditions were utilized to create welds. Some of the welds made with T4 temper flyers were heat treated to a T6 temper. It was found that the welds made with T4 temper flyers were slightly stronger (max. of 270 MPa) than those produced with T6 temper flyers. Generally, failure propagated in a brittle manner across the weld interface; however, elemental mapping reveals material transfer on either member of the welded system. This work proves the feasibility to apply microsample tensile testing to assess impact welding, even when conducted with flyer sheets of 1 mm or less, and provides insight that is complementary to other test methods.

Study on the Effect of Production Parameters and Raw Materials Used on the Mechanical Properties of Leaded Brass (CuZn40Pb2) Alloy

Leaded brass alloys used progressively in many applications such as gas valves production owing to their excellent machinability, corrosion resistance and some other specifications. However, the production processes of these alloys involve some problems appearing in the last activities of production as a result of cumulative defects of previous production processes. Therefore, the current investigation studies the effect of process parameters during casting, hot extrusion and cold drawing production stages of CuZn40Pb2 leaded brass alloy on the mechanical properties. Starting with casting process, two types of charges were used. The first charge consists of 100% recycles while the second contains 30% of pure materials such as Cu, Zn and Pb in addition to the recycles. For each production stage, alloy hardness, micro-hardness, ultimate tensile strength and elongation were examined. The results illustrated that high hardness values are obtained during casting process due to some impurities such as iron and the effect of cooling rate through solidification. The hardness values decrease during extrusion process and then rise again by cold drawing for the charge of 30% pure materials. Micro-hardness values for the fractured tensile test samples appeared higher than others due to work hardening effect. The best mechanical properties as ultimate tensile strength of CuZn40Pb2 alloy products are appeared into cold forming samples with the 30% pure material added.

Microstructure and Mechanical Properties of V-Nb Microalloyed Ultrafine-Grained Dual-Phase Steels Processed Through Severe Cold Rolling and Intercritical Annealing

Ultrafine-grained (UFG) dual-phase (DP) steel was produced by severe cold rolling (true strain of 2.4) and intercritical annealing of a low carbon V-Nb microalloyed steel in a temperature range of 1003 K to 1033 K (730 °C to 760 °C) for 2 minutes, and water quenching. The microstructure of UFG DP steels consisted of polygonal ferrite matrix with homogeneously distributed martensite islands (both of size <1 µm) and a small fraction of the inter lath films of retained austenite. The UFG DP steel produced through intercritical annealing at 1013 K (740 °C) has good combination of strength (1295 MPa) and ductility (uniform elongation, 13 pct). The nanoscale V- and Nb-based carbides/carbonitrides and spheroidized cementite particles have played a crucial role in achieving UFG DP microstructure and in improving the strength and work hardening. Analysis of work hardening behavior of the UFG DP steels through modified Crussard–Jaoul analysis showed a continuously varying work hardening rate response which could be approximated by 2 or 3 linear regimes. The transmission electron microscopy analysis on post tensile-tested samples indicated that these regimes are possibly related to the work hardening of ferrite, lath, and twin martensite, respectively.

Strengthening of Zircaloy-4 using Y2O3 particles by a laser-beam-induced surface treatment process

The mechanical strength of Zircaloy-4 was enhanced by surface treatment consisting of laser beam scanning of an oxide-coated Zircaloy-4 sheet. An yttrium oxide (Y2O3) coating 7–55μm thick was applied to Zircaloy-4 sheets. Then, a laser beam was used to form a dispersed oxide layer on the Zircaloy-4 metal surface. The thickness of the dispersed oxide layer varied from 80 to 200μm depending on the process parameters. Tensile tests of samples having both surfaces treated were conducted at room temperature and 380°C. The tensile strength of Zircaloy-4 at room temperature was increased by up to 20% with the formation of a thin dispersed oxide layer with a thickness<10% of that of the Zircaloy-4 substrate. However, the tensile elongation of the samples decreased drastically. The decreased ductility became insignificant as the testing temperature increased to 380°C. The strengthening of the fabricated samples could be explained by two mechanisms: (i) oxide particles dispersed in the metallic matrix and (ii) the phase transformation in Zircaloy-4.

An Experimental Approach and Constructing a New Non-Linear Regression Model for Prediction the Anisotropy Parameters of Annealing Treated Commercially Pure Aluminum Sheets

Earing is a common phenomenon in deep drawing process that increases the waste of metal. This phenomena is affected by material anisotropy, thus, it is important to study the effects of material parameters on this material behavior. This paper focuses on identify the optimal condition of annealing treatment which result in higher value of normal anisotropy and lower value of planar anisotropy which lead to reduce the waste material in subsequent forming processes. Therefore, in this study, anisotropic behavior and formability of commercially pure aluminum thin sheets was investigated after annealing the samples at different temperatures (350, 400, and 450) °C. Uniaxial tensile tests were carried out at room temperature (25°C) to evaluate formability parameters. For this purpose different tensile test samples in the directions of 0°, 45° and 90° in respect to the rolling direction were prepared. In addition to, metallographic test was carried out to as-received and annealed samples to observe the changes in microstructure. Plastic strain ratio and planar anisotropy of samples were calculated from the tensile test data. Based on the tensile test results of samples, the earing phenomenon due to planar anisotropy in commercially pure aluminum sheet was analyzed. The results indicate that the annealing at 400°C brought the optimum conditions. Moreover, new regressions model for prediction the anisotropy parameters of sheet metal using statistical techniques (SPSS software) were constructed in this work. The experimental data were compared to those predicting values. A comparison clearly indicates that there are good identification between measured and predicted values with multiple correlation coefficients R of 0.932 and accuracy of about 87 %. The results reveal that the proposed model is effective and reliable tool to obtain accurate prediction of the anisotropy behavior of metal sheets.

Relationship between chemical composition, crystallinity, orientation and tensile strength of kenaf fiber

The physical properties of natural growth fibers such as chemical composition content and fiber diameter are highly affected by environmental issues such as environmental changes and fiber extraction methods. These irregularities of the natural fibers seriously affect its utilization in composite as reinforcements. In this study, taking into account the importance of the fiber tensile strength, the correlation degrees between the kenaf fiber tensile strength and the fiber chemical composition, crystallinity, orientation degree were analyzed by the grey relational analysis method. Both the kenaf single fiber and fiber bundle were used as XRD and tensile strength test sample. The chemical composition content and the FTIR were carried out to obtain a correct result of the chemical composition content. It found that for the different XRD and tensile strength test samples, the single fiber showed lower crystallinity, higher orientation degree and tensile strength compared with the fiber bundle. The cellulose content and the orientation degree got the higher correlation degree with single fiber tensile strength, which was 0.674 and 0.640. The highest factor associated with the fiber bundle tensile strength was the orientation degree, the correlation degree was 0.747. The hemicellulose content and the crystallinity also got high correlation degree with the fiber bundle strength, which was 0.687 and 0.640.

Effect of twin-roll casting parameters on microstructure and mechanical properties of AA5083-H321 sheet

The purpose of the present paper is to study the mechanical properties and microstructure of the twin-roll cast and cold rolled AA5083 aluminum alloy sheet in strain-hardened H321 temper. To reach this goal, first, a sound surface slab of 8.90 mm thick and 1260 mm wide was cast by a 15° tilt back twin roll caster at a casting speed of 490 mm/min. After homogenization at 520 °C, the product was cold rolled to two thicknesses of 6.30 mm and 3.85 mm with an intermediate annealing at 370 °C and final stabilization at 180 °C. Optical microscopy and scanning electron microscopy (SEM) investigations of the as-cast state depicted the segregation of intermetallic particles mainly in grain boundaries which was the cause of grain removal observed in the fracture surface of tensile test samples. In addition, mechanical properties indicated an increase in total elongation after homogenization heat treatment due to the elimination of the grain boundary segregations. Finally, it was observed that the properties of the 3.85 mm thick sheet were consistent with the H321 temper requirements according to ASTM B 290M standard due to applying sufficient cold reduction during cold rolling stage.

Mechanical properties of the samples produced by volume powder cladding of stainless steel using a continuous fiber laser

Samples for tensile tests were manufactured by using one of the additive technologies - direct laser material deposition. Investigations were carried out at the facility Huffman HC-205 equipped with a fiber laser with a power up to 3.5 kW. Various strategies of layering metallic powder of stainless steel 316L were considered to optimize the modes of constructing the samples. We measured the stress-strain state of the produced samples by the method of digital image correlation. It is found that the nominal tensile strength of the samples produced by the direct growing using laser powder of 316L steel is of high level - 767 MPa.

Crack Initiation of Type 316L Stainless Steel Under Cyclic Deformation in Simulated Body Fluid

The inside of body is a complex environment for metallic biomaterials because of the synergetic effects of biological factors such as a body fluid including Cl-, proteins and cells, and mechanical factors such as strain, bending and friction. These complex factors may lead the corrosion fatigue which is the commonly experienced degradation of metallic biomaterials. However, crack initiation on type 316L stainless steel with cyclic loading in a simulated body fluid including proteins and cells has been little examined. In the present study, a cyclic stress was applied to the tensile specimen of type 316L stainless steel in the simulated body fluid with cell culturing in order to investigate the crack initiation on the metallic biomaterials in the body environment. A sheet of type 316L stainless steel was shaped into samples for tensile test with a gauge size of 8×4×1 mm3. The samples were mirror-finished, then immersed in a-MEM (Minimum Essential Medium) for 1 day which is a simulated body fluid commonly used for cell culturing (Immersed sample), or immersed in a-MEM+10 vol.% FBS (Fetal Bovine Serum) with cell culturing for 1 week (Sample with cells). During immersion, a-MEM and a-MEM+10 vol.% FBS were kept at 37 °C under an atmosphere of 5 % CO2-20% O2-75 % N2. Initially, Immersed sample and sample with cells were placed in the electrochemical cell filled with a-MEM kept at same condition in immersion, then attached to a corrosion fatigue test machine. A cyclic stress was applied to the sample until 107 cycles. The stress ratio was 0.1 (R=0.1) and the maximum stress was 300 MPa, not exceeding the elastic limit of type 316L stainless steel. The stress frequency was 10 Hz. For comparison, the sample not immersed was also subjected to the test in the air (Sample in the air). After cyclic deformation, cracks initiated on the sample surface were observed using FE-SEM. In addition, crystalline structure of the sample was analyzed using EBSD (Electron Backscatter Diffraction Analysis). From surface observation and EBSD, the relationship of crack initiation and crystalline structure was studied. Most cracks observed on the sample in the air, immersed sample and sample with cells initiated in the grains with Schmidt factor being from 0.4 to 0.5. This result indicates that the cracks tend to initiate along crystal plane with the largest Schmid factor where slip deformation preferentially occurs. On the other hand, non-negligible amount of cracks were observed on the crystal plane with Schmid factor less than 0.4 for the immersed sample and sample with cells. Such cracks initiated along the slip direction toward inside of the sample. In this case, the newly created surface was exposed to a solution, then corrosion along the slip steps was enhanced. Therefore, in the immersed sample and sample with cells, crack initiation was prompted on the crystal plane with the non-largest Schmid factor.