Standard Tensile Tests Research Articles

Experimental investigation on mechanical properties of binary and ternary blended pervious concrete

The purpose of the investigation was to study the effect of binary and ternary blends of cement on the mechanical properties of pervious concrete (PC) specimen through destructive (DT) and non-destructive testing (NDT). Various combinations of fly ash (FA), limestone powder (LP), metakaolin (MK), and silica fume (SF) as mineral admixtures have been investigated to partially replace the cement up to 30% by weight in PC. Standard cube specimens of size 150 mm × 150 mm × 150 mm of binary and ternary blends of mineral admixture of pervious concrete were prepared to conduct standard compressive strength test and split tensile test at 7 and 28 days of curing. The ultrasonic pulse velocity (UPV) test and Rebound Hammer test were used as a non-destructive testing tool to substantiate the robustness of PC and to determine the approximate mechanical properties where other destructive testing tools are not feasible in case of in-place pervious pavements. Overall the pervious concrete made with LP based ternary blends (PLM and PLS) were found to perform better than FA based ternary blends (PFM and PFS) and control mix (PC) in destructive and non-destructive testing.

Materials Characterization of Cranial Simulants for Blast-Induced Traumatic Brain Injury

The mechanical response of brain tissue to high-speed forces in the blast and blunt traumatic brain injury is poorly understood. Object-to-object variation and interspecies differences are current limitations in animal and cadaver studies conducted to study damage mechanisms. Biofidelic and transparent tissue simulants allow the use of high-speed optical diagnostics during a blast event, making it possible to observe deformations and damage patterns for comparison to observed injuries seen post-mortem in traumatic brain injury victims. Material properties of several tissue simulants were quantified using standard mechanical characterization techniques, that is, shear rheometric, tensile, and compressive testing. Polyacrylamide simulants exhibited the best optical and mechanical property matching with the fewest trade-offs in the design of a cranial test object. Polyacrylamide gels yielded densities of ~1.04g/cc and shear moduli ranging 1.3-14.55kPa, allowing gray and white matter simulant tuning to a 30-35% difference in shear for biofidelity. These materials are intended for use as layered cranial phantoms in a shock tube and open field blasts, with focus on observing phenomena occurring at the interfaces of adjacent tissue simulant types or material-fluid boundaries. Mechanistic findings from these studies may be used to inform the design of protective gear to mitigate blast injuries.

Correlation between Shock Wave-induced Indentations and Tensile Strength

Cost-efficient and high-throughput material development processes and process chains are needed to meet the on-going demand for new metallic structural materials. Material development involves not only the processing of new material compositions, but also the material characterization. Hence, novel high-throughput screening methods are a promising approach to identify new beneficial material compositions. These methods do not aim to understand the mechanisms of new material compositions. Instead, these methods offer descriptive values, which are correlated with material properties. Here, an indentation method is presented, which is based on laser-induced shock waves. With a high intensity pulsed transversely excited atmospheric-pressure CO2 laser, a shock wave is induced on top of an indenter. The impulse of the shock wave pushes the indenter inside a test material. The created indentations correlate highly with the material hardness measured by conventional techniques. In this study, different descriptive values are extracted and analyzed with respect to the material’s tensile strength (determined with standard tensile tests). Indentations were created in aluminum samples (alloy EN AW-6082), which were heat-treated in different ways. The strongest correlation has been found between the tensile strength and the sink-in and pile-up height instead of the indentation depth or diameter.

Comparative analysis of printing parameters effect on mechanical properties of natural PLA and advanced PLA-X material

FDM is a commercially widespread 3D printing technology which uses thermoplastic materials for building prototypes and functional parts. Most used materials in this technology are PLA (PolyLactic Acid) and ABS (Acrylonitrile Butadiene Styrene) materials which contain dissimilar mechanical properties and printing abilities. PLA is considered as a good material for prototypes and parts that acquire higher dimensional accuracy, and is considered as a material that is easier to print than ABS. Advantages of ABS material, compared to standard PLA are better mechanical properties, sufficiently higher printing speeds and higher heat resistivity. Deficiency of ABS over PLA is shrinking of ABS material after 3D printing-resulting in poor dimensional accuracy or failure during printing. A newly available material PLA-X (‘’mcPP”, Mitsubishi Chemical, Japan) houses advantages of both mentioned materials and may lead to wider commercial and industrial use. Different printing parameters of the same material may lead to different mechanical properties of the finished part. The aim of this paper is to compare how different printing parameters effect on mechanical properties of standard PLA and PLA-X -which is a material that has similar dimensional accuracy of finished parts as PLA and possesses higher mechanical properties like ABS. Samples of PLA and PLA-X where printed in five different printing regimes, varying layer height, number of outline perimeters, infill density and sample humidity, with five samples each (according to ISO 527-2 international standard) and used for mechanical testing on standard tensile testing machine.

Effects of ERNiCr-3 butter layer on the microstructure and mechanical properties of API 5L X65/AISI304 dissimilar joint

This paper investigates the effects of ERNiCr-3 butter layer on the microstructure and mechanical properties of API 5 L X65/AISI 304 dissimilar joint, welded by gas tungsten arc welding (GTAW). The butter layer is applied to minimize carbon diffusion from the base metal to the welding pool and to eliminate the risk of the formation of a hard martensitic layer at the fusion line. The microstructures of buttered and non-buttered specimens were studied using the optical microscope, scanning electron microscope (SEM), electron backscattering diffraction (EBSD), X-Ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). Mechanical properties of the joints were also evaluated using standard and sub-sized tensile and impact tests. Hardness profilometry was also conducted across the weldments. Results showed that the application of the butter layer results in the elimination of a rather large brittle martensitic layer from the base metal at the API side. Also, it appears that the weld zone in the buttered sample hardly has any δ-ferrite, which has to do with a high nickel content of the butter layer. Butter layer overall decreases the tensile strength and increases the elongation/ductility of the joints. More importantly, the butter layer essentially acts as a barrier layer between the ferritic side of the weldment and the weld pool, and this, in turn, eliminates two hardness peaks at both sides of the welding pool. The correlations between microstructure and mechanical properties are comprehensively investigated and discussed.

Mechanical, thermal, and morphological properties of powder coating waste reinforced acetal copolymer

The present study investigates the individual effects of three different thermosetting waste materials, used as fillers, on the mechanical, thermal and flow properties of acetal copolymers (POM). Different amounts ranging from 5% to 30% by weight of hydrolyzed powder coating recyclates were mixed as filler material in POM. The matrix and the fillers were first dry-mixed and then compounds were prepared through melt extrusion. The resulting compounds were cooled, granulated, and then standard tensile test bars were produced through use of an injection-molding machine. We investigated the mechanical and thermal properties of test specimens, and tensile strength, bending strength and impact strength were evaluated as a function of type and amount of filler material in the POM matrix. In addition, the change in melt flow index of POM/filler mixtures was determined, before and after extrusion. Furthermore, the morphology of the specimens was examined via electron microscopy. The results of this investigation are encouraging and present an innovative approach to reutilize hydrolyzed electrostatic powder coating wastes with thermoset structures as fillers in acetal copolymers.

Determination of Direct Tensile Strength Values of Rock Materials by a New Test Method of Drilled Disc Tension

Use of drilled disc specimens was investigated with both numerical and experimental studies to determine direct tensile strengths of rock materials. A new loading apparatus with rods to insert into the drill holes of discs has been designed and manufactured to supply tension by using the compression test presses. In addition to the use of popular compressive presses for direct tension, elimination of the gluing in the standard direct tensile strength test method is a significant advantage to make possible both hard and soft rocks to be tested. The Brazilian test discs with the diameter of NX size and length to diameter ratio of 0.5 were used in tests. Different loading apparatus designs were analyzed and ideal angle of contact between rock and the loading rods was assessed to be 50° within various choices investigated in this study. The drilled discs were determined to fail due to the crack initiation under the condition of uniaxial tensile stress distribution at sidewalls of the hole. In addition to the drilled disc tension test, standard direct tensile strength tests were also carried out to take as reference and compare the results obtained from different methods. According to the results of both numerical and experimental studies, an equation was suggested to determine uniaxial tensile strengths of drilled disc specimens with 20 mm hole diameter and the contact angle of 50°.

Integrated Mechanical Strength Tests of the Main Pipeline for Transporting Crude Oil and Refined Products

The state, problems, and prospects of conventional, unified and special laboratory, bench and full-scale tests to substantiate the systematic assessment of strength, durability, survivability, cold resistance, reliability, and safety of the key elements of pipeline transport of crude oil and refined products are considered. These tests correlate with the stages of the pipeline life cycles and basic and reference computational-experimental methods of determining the criterial characteristics of pipe steels, pipes and main pipelines with regard to domestic and foreign practices. The experimental basic mechanical characteristics obtained in standard static tensile tests (yield and strength limits, elastic moduli) are part of the basic static strength calculations of newly designed and operating pipelines. Standard hardness and impact elasticity tests are used to control the pipe steel quality. The results of standard tensile tests provide additional design information for the assessment of static strength with respect to the ductility and degree of steel hardening during elastoplastic deformation. Unified laboratory tests are meant for refining the pipeline strength with allowance for the stress state 3D effects, absolute sizes of the pipeline cross section, strain rate, anisotropy, cold resistance, corrosion, and the presence of welded joints. The assessment of pipe steel crack resistance and pipes according to the criteria of linear and nonlinear fracture mechanics with allowance for technological and operational defects holds a specific place in laboratory and bench testing. The experience in conducting these tests, accumulated in the Russian oil pipeline system is considered.

Influence of fused deposition modeling parameters on the mechanical properties of ABS parts

This work aims to determine the influence of fused deposition modeling (FDM) printing parameters on the mechanical properties of parts fabricated on an Ultimaker2 printer with acrylonitrile butadiene styrene (ABS). The effect of several parameters such as interlayer cooling time (ILCT), nozzle diameter, infill density, raster angle and layer thickness on the ultimate tensile strength, yield strength, and elastic modulus of produced parts was evaluated. Two independent studies were conducted: a first study dedicated to the ILCT and a second study where the influence of other parameters was evaluated through a design of experiments (DoE) approach. Both studies were carried out through the execution of standard tensile tests. The statistical analysis of tensile tests results was processed with the ANOVA methodology. The obtained results indicate that a reduced ILCT improves the tensile strength of parts. It is shown that nozzle diameter and infill density are the parameters that most influence the mechanical properties of ABS, with the upper range selected values improving the studied mechanical properties. The raster angle configuration of (−45o/45o) benefits UTS and yield strength of ABS samples. Interactions of nozzle diameter on layer thickness were detected. It was observed that smaller layer thickness promotes a higher elastic modulus and UTS; however, for thinner layers (0.06‐0.10 mm), no significant differences were found on strength of samples due to potential high distortion levels.

Effect of material structure on trimming and sheared edge stretchability of 6xxx aluminum alloys

Wide variety of 6xxx Aluminum alloys is currently being used for manufacturing of lightweight automotive components. Very often each car manufacturer gets its own variation of the 6xxx alloy. Majority of these alloys have very similar yield and tensile strength as well as the stress-strain curve. Therefore, selection of the best alloy for each technical application might be challenging. In this paper, a comparison of performance of three 6xxx alloys in trimming process and sheared edge stretchability for wide variety of cutting clearances is being studied. This performance is compared with postnecking behavior of the same sheets in a standard tensile test. The ability of material to form visible diffuse neck and the cutting tool indentation prior to initiation of fracture shows some correlation for three studied 6xxx Aluminum alloys. The material with more pronounced diffuse neck shows a stronger tendency to form burrs at larger cutting clearances. However, other parameters of the standard tensile, such as yield stress, tensile strength, uniform elongation and even total elongation of these three alloys are very similar. Sheared edge stretchability measured via tensile testing of sheared samples showed that the materials with larger diffuse necking in the tensile test have higher sensitivity of edge stretchability to the cutting clearance. For large cutting clearances, the crack usually propagates almost vertically and leads to a burr formation. It appeared that the grain aspect ratio also influences the trajectory of the crack: for the materials with substantially elongated grains, the crack typically propagates more vertically. For the materials with nearly equiaxial grains, the cracks show stronger tendency to turn towards the lower cutting edge. The reason for such a behaviour is in crack propagation via grain boundaries. The experimental study of nanohardness measured at grains and grain boundaries for one of the studied alloys indicated that the grain boundaries have about 30% lower nanohardness than the material inside the grains.

Stress–strain curves of metallic materials and post‐necking strain hardening characterization: A review

AbstractFor metallic materials, standard uniaxial tensile tests with round bar specimens or flat specimens only provide accurate equivalent stress–strain curve before diffuse necking. However, for numerical modelling of problems where very large strains occur, such as plastic forming and ductile damage and fracture, understanding the post‐necking strain hardening behaviour is necessary. Also, welding is a highly complex metallurgical process, and therefore, weldments are susceptible to material discontinuities, flaws, and residual stresses. It becomes even more important to characterize the equivalent stress–strain curve in large strains of each material zone in weldments properly for structural integrity assessment. The aim of this paper is to provide a state‐of‐the‐art review on quasi‐static standard tensile test for stress–strain curves measurement of metallic materials. Meanwhile, methods available in literature for characterization of the equivalent stress–strain curve in the post‐necking regime are introduced. Novel methods with axisymmetric notched round bar specimens for accurately capturing the equivalent stress–strain curve of each material zone in weldment are presented as well. Advantages and limitations of these methods are briefly discussed.

A Newly Generated Nearly Lamellar Microstructure in Cast Ti-48Al-2Nb-2Cr Alloy for High-Temperature Strengthening

Alloy 4822 (Ti-48Al-2Cr-2Nb at. pct) cast material was given a controlled heat treatment cycle to generate a casting nearly lamellar (CNL) microstructure that enhances the temperature capability over its current engineering casting duplex (CDP) microstructure form. The cycle consisted of three steps: a short α field annealing, an α + γ field annealing, and then aging at a low temperature, with each step being followed by controlled cooling. The resulted microstructure is shown to be a mixture of non-uniformly distributed ~ 250 μm size lamellar colonies containing ~ 0.15 µm spaced laths. Standard tensile testing at 700 °C shows a yield stress of 344 MPa that is ~ 55 MPa greater than that of the current engineering CDP form. The sequential microstructure evolution processes following the three-step thermal cycle are assessed and explained in terms of phase transformations taking place across and below the α transus upon isothermal treatment and subsequent cooling. The resulted increases in high-temperature strengthening are explained by the colony and γ grain size distributions. The strengthening mechanism along with the significance is discussed.

Effect of the quench temperature on the mechanical properties of a medium C Mn high Si steel during Q&P heat treatment process

A steel of composition Fe-0.2C-3Mn-2Si-0.5Al was fully austenized followed by a quench and partitioning heat treatment process (Q&P). The quench temperature was varied, which resulted in different volume fractions of retained austenite (RA) and martensite. Analysis of the phase evolution and the resulting microstructures during the Q&P process were carried out using different techniques namely, - dilatometry, FEG SEM, EBSD, and neutron diffraction. Mechanical properties were evaluated by standard tensile tests on samples quenched to different temperatures. The partitioning process was evaluated by dilatometry. The volume fraction of the RA was determined by neutron diffraction. It was found that the volume fraction of RA increased with an increase in the quench temperature contrary to the Speer model. It was also observed that the presence of bainite, which formed during the quench and partitioning temperature significantly stabilized the RA by carbon partitioning. The tensile test results indicated the optimum quench temperature for the best combination of strength and ductility and contrary to expectation, this did not occur in the specimen with the maximum amount of RA. In other words, the mechanical properties of the steel undergoing a Q&P process is influenced by the quench temperatures and is also affected the phase evolution which occurs during both the quench and partitioning process.

In situ characterization of work hardening and springback in grade 2 α-titanium under tensile load

Plastic effects during sheet metal forming can lead to undesirable distortions in formed components. Here, the three-stage work hardening and plastic strain recovery (“springback”) in a cold-rolled, α-phase commercially pure titanium is examined. Interrupted standard tensile tests with in situ x-ray diffraction and quasi-in situ electron backscatter diffraction show that twinning plays a minor role in both of these phenomena. The experiments give evidence that the observed work hardening plateau is the result of an abrupt activation and multiplication of 〈c+a〉 slip and a subsequent redistribution of load between grain families. The springback can be attributed to inelastic backwards motion and annihilation of dislocations, driven by backstresses from dislocation-based hardening during loading. The peak broadening behavior, observed by x-ray diffraction, suggests that the internal stress state is highest in the rolling direction, resulting in consistently higher springback magnitude along this direction.

Mechanical Characterization of 2219 Aluminum Alloy Welded Joints Under Bi-Axial Loading

The mechanical performances of welded joints under bi-axial loading are significant to the reliability of various engineering structures. However, the protocol for the mechanical characterization of welded joints still needs to be improved to represent the mechanical performances of welded joints under complex loading conditions. In this work, an experimental design is proposed for the mechanical characterization of 2219 aluminum alloy welded joints. The target is to investigate the effects of combined tensile-shear load on the mechanical responses and failure behavior of 2219 aluminum alloy welded joints. The tensile-shear characterization was then conducted using a newly developed U-notch aluminum alloy welded joints specimen. In addition, standard tensile test and standard shear test were conducted to validate of the U-notch specimen design. This newly proposed experimental protocol is suitable to obtain mechanical properties of 2219 aluminum alloy welded joints subjected to tensile-shear load.

Determining Deformation Transition in Polyethylene under Tensile Loading.

The multi-relaxation (MR) test was developed based on the concept that stress relaxation behavior can be used to reflect the material state of polyethylene (PE) under tension. On the basis of this concept, critical stroke for the onset of plastic deformation in the crystalline phase, named the first critical stroke, was determined using the MR test. Results from wide angle X-ray scattering suggest that phase transformation occurred in the crystalline phase of PE after the specimen was stretched beyond the first critical stroke. In this work, the MR test was applied to six PEs of different mass densities to determine their first critical strokes and the corresponding total and quasi-static (QS) stress values. The results show that the first critical stroke had very similar values among the six PEs. More interestingly, the ratio of the QS stress at the first critical stroke to the yield stress from the standard tensile test showed little dependence on PE density. Therefore, it was possible to use the popular short-term tensile test to characterize the critical QS component of the applied stress to initiate plastic deformation in the crystalline phase, which is expected to play a significant role on the long-term, load-carrying applications of PE.

Development of a combined analytical and experimental approach for the determination of the cohesive strength between material extrusion layers using the true area of contact

Material Extrusion (ME) is a type of Additive Manufacturing (AM) process that creates parts by depositing polymer filaments in successive layers. The strength of ME products depends on both the cohesive strength between layers and between rasters. The raster gap is the most significant process factor affecting the strength of ME built parts. Standard tensile tests with a dog-bone shaped specimens are not suitable to determine the strength between layers of the ME built parts. A new model is introduced to predict the cohesive strength between layers using the true area of contact which can be obtained from the apparent values taken from mini three-point bending tests. The accuracy of the introduced model was verified by comparing its bending test results with different build parameters, the applicability and promise of the introduced model were confirmed.

Effects of heat input on the mechanical properties of butt-welded high and ultra-high strength steels

In this study, the mechanical properties of butt-welded thin plates made of S700, S960 and S1100 steels under various heat inputs (HI) are investigated. The gas metal arc welding (GMAW) process with two different levels of HI, and laser welding (LW) are implemented for this purpose. Fully automated welding process is employed to attain high quality and homogeneous weldments. Standard tensile tests of the butt-welded joints, together with micro-hardness measurements are conducted in this study. The microstructure of the heat affected zones (HAZ) of the weldments are closely examined using scanning electron microscopy (SEM). It was observed that while the fracture was occurred at the base materials of all S700 and S1100 weldments, the S960 suffered from failure at the HAZ which resulted in reduction of the joint’s strength and ductility. For all the studied steels, it was found that the joint’s ductility is highly dependent on HI values over the range of 0.3–1.4 kJ/mm for each welding pass. Though, the S1100 steel showed the best performance under welding HI with a moderate change in its mechanical properties and a stable microstructure after welding compared to S700 and S960.

Deformability criteria of metal at uniaxial tension

This paper is devoted to study of the laws of metals deformation behavior determined by carrying out standardized uniaxial tensile tests. The analysis of deformability of materials was carried out. The metals vary in yield limit from 40 to 1050 MPa and in ultimate strength from 460 to 1240 MPa. The ratio of the deformation work of uniform plastic deformation (from the yield point to the ultimate strength of materials) to the volume of the material was determined to assess the mechanical deformability. An inverse relationship between uniform deformation work and ratio of yield limit to ultimate strength was established. It was also found that the normalized specific work of deformation linearly increases with strength. The deformability criterion can be considered as the universal criterion for ferrous and non-ferrous metals and its magnitude can be estimated from known quantity of the ultimate strength. In practice, the numerical values of compliance criterion can be used to predict the behavior of materials with different strength under mechanical perturbations in the course of operation and machining (metal forming and cutting).

Microstructural evolution, mechanical properties and fracture toughness of near β titanium alloy during different solution plus aging heat treatments

Ti-55531 (Ti-5Al-5Mo-5V-3Cr-1Zr) is near β titanium alloy, which plays a significant role in manufacturing landing gears and flap tracks in the aerospace industry. This study aims to find out an optimal heat treatment to obtain an excellent balance of strength, ductility and fracture toughness. For this purpose, the Ti-55531 alloy was subjected to solution plus aging treatments and mechanical properties tests. Optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) were adopted to observe the microstructural evolution including morphology, distribution and size. Standard tensile and compact tension (CT) tests were carried out to obtain the yielding/tensile strength (YS, TS), elongation (EL) and fracture toughness (KIC) of Ti-55531 alloy. The effects of solution temperature, aging temperature and time on the microstructural evolution and fractography were analyzed. The relationships between the mechanical properties and microstructures were qualitatively described. The influencing mechanism of plastic deformation and crack propagation path on the KIC were discussed. Simultaneously, the values of YS and KIC were predicted based on mechanical property models, the predicted values were compared with tested data. Finally, an optimal heat treatment was proposed for the Ti-55531 alloy, to obtain a good balance of strength, ductility and fracture toughness.