Standard Tensile Test Specimens Research Articles

Study the Effect of Adding Malic Anhydride and Carbon Fibers to the Mechanical and Morphology Properties of Polypropylene

Adding reinforcement materials like carbon fibers with maleic anhydride improves the strength of polypropylene. The present work aimed to study the effect of adding maleic anhydride and carbon fibers on the mechanical properties of polypropylene enhanced by presenting carbon fibers. Carbon fibers added at different ratios (0, 2, 4, 6, and 8) % and 1% of maleic anhydride were added to pure polypropylene. Standard tensile and impact test specimens were prepared per ASTM standards using an extruder technique. It was observed that increasing the carbon fiber content enhanced the tensile strength, modulus of elasticity, and hardness of polypropylene while the elongation decreased, but it enhanced after MAH addition. SEM and FTIR indicated good adhesion between fibers and polypropylene after adding maleic anhydride (MAH). UV tests showed that carbon fibers protect the composite material from the UV sunlight.

Optimizing energy modeling in PBF-LB/M metal additive manufacturing: a detailed analysis of resource and energy demand based on standard tensile test specimen

Additive manufacturing is an essential tool in modern production processes. Competitive quality and the increasing importance of local manufacturing have allowed companies to maintain their production despite supply chains disrupted by the pandemic. However, the rising awareness of society towards environmental and climate protection, the increasing demand for resource-efficient products, and recent developments in energy costs are leading to a rethink in manufacturing processes. Additive manufacturing offers great potential for resource saving components. This study uses standard tensile test specimens to analyze AM processes regarding energy and material flows. The results show a high dependence of energy demand on process time and are transformed into a data-based energy model. Compared to previous energy models, the accuracy can be significantly improved using model data in combination with specific and system-oriented approaches. In addition to system-related saving potentials, design-related optimization potentials can be identified. Innovative and highly resource-saving components can be designed with a design methodology adapted to the extended degrees of freedom of AM. Further saving and recycling potentials can be identified along the material flows. A long-term goal is optimizing and predicting of resource demand in additive manufacturing with a view to the entire product lifecycle.

The Effect of Heat Treatment on a 3D-Printed PLA Polymer’s Mechanical Properties

Three-dimensional printing is a useful and common process in additive manufacturing nowadays. The advantage of additive polymer technology is its rapidity and design freedom. Polymer materials' mechanical properties depend on the process parameters and the chemical composition of the polymer used. Mechanical properties are very important in product applicability. The mechanical properties of polymers can be enhanced by heat treatment. Additive-manufactured PLA's mechanical properties and structure can be modified via heat treatment after the 3D printing process. The goal of this research was to test the effect of heat treatment on the mechanical and structural parameters of additive-manufactured PLA. This was achieved via the FDM processing of standard PLA tensile test specimens with longitudinal and vertical printing orientations. After printing, the test specimens were heat-treated at 55 °C, 65 °C and 80 °C for 5 h and after being held at 20 °C for 15 h. The printed and heat-treated specimens were tested using tensile tests and microscopy. Based on the test results, we can conclude that the optimal heat treatment process temperature was 65 °C for 5 h. Under the heat treatment, the test specimens did not show any deformation, the tensile strength increased by 35% and the porosity of the PLA structure decreased.

Design and validation of an innovative 3D printer containing a co-rotating twin screw extrusion unit

This paper presents the design and validation of an innovative 3D printer containing a co-rotating twin screw extrusion unit (Co-TSE). Single screw print heads were developed in the mid-2000s as an alternative to filament-based 3D printers, but they have limited process flexibility and mixing capacity. The new design accepts material in powder or micro-pellet form, and its dispersive and distributive mixing capacity can be fine tuned by setting output and screw rotation speed independently. The design combines a miniaturized modular Co-TSE operated under starve-fed conditions with a benchtop Cartesian platform. Numerical calculations were performed to ascertain whether the appropriate thermomechanical environment for polymer processing could be created by the proposed design. A prototype was built and extrusion tests were performed under different operating conditions, using polypropylene and a 90/10 wt% polypropylene/polystyrene blend. Two screw configurations were used, with and without kneading discs, to assess the response of the extrusion unit in terms of flow characteristics and mixing performance. The restriction to flow created by the mixing elements determines the starting melt position, and the average residence times, while their shearing and extensional action enhances homogenization effectiveness. The screw configuration and rotation speed do not affect the output, which depends only on the feed rate. Preliminary deposition tests were conducted to determine the feasible printing parameters. A standard tensile test specimen, a square scaffold and a multicolored rectangular box were successfully printed, validating the innovative design. The mechanical properties of printed test specimens were within the expected values.

Work Hardening of Metallic Sheets under Tension-Compression and Simple Shear Reverse Loading

The hardening models have a significant influence on the accuracy of finite element analysis (FEA). Although, isotropic hardening models are the most widely used, it is known that kinematic hardening models (describing the Bauschinger effect and permanent softening) can significantly improve the accuracy of FEA results. However, when considering sheet metal materials, the parameters of kinematic hardening models are difficult to identify due to the challenges of obtaining experimental results from test with strain path inversions. This work considers an experimental procedure that enables the analysis of the mechanical behaviour of sheet metal materials submitted to reverse loadings. A miniaturized test device was developed to perform tension and compression tests, with reverse loadings, for sheet metal materials. This specimen design has two main advantages: (1) reduces buckling during compression (compared to standard tensile test specimens) and, consequently, (2) enables the characterization of the mechanical behaviour under reverse tension-compression strain paths changes. The small size of the specimens, with 2 x 2 mm gauge area, poses the main challenge of the current methodology, namely the measurement of the strain field distribution using the Digital Image Correlation (DIC) technique. The results obtained from tension-compression tests with mini-specimens are validated by comparison with standard tensile and shear (reverse loading) and tests.

Development mechanical and fatigue properties of AA7001 after combined SP with deep cryogenic treatment and UIP with deep cryogenic treatment

Al alloys have long been of interest to the aerospace community, due to their modest specific strength, ease of manufacture, and low cost. In recent years, with the rapid development of weaponry, 7XXX ultra-high strength aluminum alloys used increasingly in military fields. Chemical analysis of the AA 7001 is supported out at The Company State for Engineering, Rehabilitation and Inspection (SIER) in Iraq. Strengthening the surface (shot penning) is beneficial to delay crack nucleation and extend life. The test samples (tensile and fatigue) are subject to the SP process by using ball steel with the parameters (Pressure=12 bars, Speed=40 mm/min, Distance=150 mm, Shot size=2.25 mm, Coverage=100 %). The ultrasonic impact treatment (UIP) machine is used for enhancing the surface properties. For the Deep Cryogenic Treatment (DCT), the samples have been placed in the cooling chamber. A standard tensile test specimen is prepared in a round section with the dimensions chosen according to ASTM (A370-11). Tensile and fatigue of rotating bending with R=–1 have been conducting, after the effect of deep cryogenic treatment (DCT), combined shot peening (SP+DCT), and ultrasonic impact peening (UIP+DCT) of AA7001 have been examining. The maximum improvement percent in ultimate tensile strength (UTS) due to (DCT), (SP+DCT), and (UIP+DCT) were about 3 %, 8.27 %, and 6.25 %, respectively. The rise in the yield stress due to (DCT), (SP+DCT), and (UIP+DCT) were 9.5 %, 14.6 %, and 13.14 %, respectively. The ductility reduced by constituents of 8.57 %, 12.5 %, and 11.42 % sequentially. The improvement in fatigue strength in a high cycle regime is 16 % for (SP+DCT) due to combined effects, it is an 8 % increase in the endurance limit on fatigue behavior due to inducing compressive residual stress (CRS)

Evaluation of tensile strength and elastic modulus of 7075-T6 aluminum alloy by adding SiC reinforcing particles using vortex casting method

In this study, an experimental analysis for the mechanical properties of 7075-T6 aluminum reinforced with SiC particles with three different sizes of nanometer, submicron and micron scales is performed. The composites are made by vortex casting method. Standard tensile test specimens are fabricated by CNC machining. Finally, according to the standard, the tensile experimental test is performed on the selected samples. To perform the tensile test, first the specimens are fixed in the jaws of the device and then at a velocity of 0.2 mm/min is applied, until the specimens are failed. The base alloy in micro scale is examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) images. Field emission scanning electron microscopy (FESEM) images are also used to show the distribution of nanoparticles in the base and it is found that the size of nanoparticles in the base is less than 100 nanometers. SEM images and X-ray diffraction spectroscopy (EDS) analysis results show the presence of phases (Al-Cu-Fe), (Al-Fe), (Al-Fe-Si) and phases ƞ (MgZn2), S (Al2CuMg) in 7075-T6 aluminum alloy. In general, by adding reinforcing particles to aluminum, the ultimate tensile strength increases, except for micron particles with a 5 wt%. This is while the percentage of elongation of composites compared to 7075 aluminum is decreased. Among the nanoparticle-sized specimens, the specimen with 1 wt% of reinforcing particles improved the ultimate tensile strength, which is equivalent to 21.33%. Submicron and micron particles-reinforced specimens, the 2 wt% specimen, improved the ultimate tensile strength about 16.10% and 11.65%, respectively. Hence, it can be concluded that the particles in nanoscale has more effect on the tensile strength of the composite structure.

Post-Impact Behaviour of Pseudo-Ductile Thin-Ply Angle-Ply Hybrid Composites.

This work experimentally explores the post-impact behaviour of thin-ply angle-ply pseudo-ductile carbon fibre laminates subjected to tensile load. Indentation and low-speed impact tests were performed on standard tensile test specimens. Non-destructive tests were used to investigate the damage propagation. Digital Image Correlation (DIC) was adopted to detect the strain distribution during tensile tests. Post-damage pseudo-ductile behaviour was retained in angle-ply hybrid composites subjected to tensile loading conditions.

Experimental Characterization of CFRP by NOL Ring Test

Abstract Carbon fiber composites are widely used in aerospace applications such as rocket motor casings, electronic packaging etc., to gainfully exploit their higher specific strength properties. Commercial availability of carbon fibers like T 700 with superior strength needs an epoxy matrix with higher ductility. In this paper, elaborate experimental results obtained on composite specimens made with T 700 carbon fibers in a special toughened epoxy matrix are presented. Tests in accordance with the relevant ASTM specifications were conducted on standard unidirectional tensile test specimens as well as National Ordnance laboratories (NOL) ring test. It was observed from the experimental results that the strength measured by NOL-Ring test is more reliable than the results of unidirectional tensile test. It was also found that the maximum frequency of repetition of failure stress is in between 1675-1725 M Pa. These results are very useful as reliable design inputs for aerospace and automobile applications.

Analysis and Numerical Simulation of the Structural Performance of Fused Deposition Modeling Samples With Variable Infill Values

The prediction of the structural performance of additive manufacturing (AM) parts has become one of the main challenges to boost the use of AM in industry. The structural properties of AM are very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. While AM experimental studies are common in the literature, a limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches, such as the finite element method (FEM); however, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper, the analysis and numerical simulation of the structural performance of fused deposition modeling (FDM) samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and polylactic acid (PLA) material. These samples were measured and modeled in a computer-aided design (CAD) system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally, the experimental and numerical results were compared and conclusions drawn.

Mechanical characterization and quality of iron castings using optimized mold design: simulations and experimental validation

This paper presents a new approach to analyze the quality of ductile iron castings through simulations and experiments. Standard tensile test specimens are considered as simple cast products for which a multi-cavity mold is designed, simulated, and optimized to minimize porosity using MAGMASoft. X-ray imaging, hardness measurement, and tensile testing are done for selected specimens produced using optimized mold design. Next, finite element simulation of tensile testing until fracture is done in ABAQUS using elastic-plastic material model and porous metal plasticity model. Simulation results for sound specimen are found to be in good agreement with the experimental results. Since mold design optimization is solely based on porosity minimization, no porosity is observed in the final mold design. However, if multi-criteria optimization of mold is done, the specimens may show some porosity which can be integrated in the developed finite element model of tensile testing. It is concluded that simulation-based mold design optimization can produce nearly defect-free castings and at the same time exhibit the similar mechanical properties as their sound counterparts produced with other manufacturing processes.

High cycle fatigue analysis in the presence of autofrettage compressive residual stress

AbstractAn experimental and numerical investigation of the effect of residual compressive stress on the high cycle fatigue life of notched low carbon steel test specimens is presented. Experimentally determined cyclic stress strain curves for S355 low carbon steel are utilized in a finite element analysis plasticity modelling framework incorporating a new cyclic plasticity material model representative of cyclic hardening and softening, cyclic mean stress relaxation, and ratcheting behaviors. Fatigue test results are presented for standard tensile fatigue test specimens and novel double notch specimens. Double notch specimens are tested with and without compressive residual stress prior‐induced through tensile overload. It is shown that cyclic plasticity phenomena have a significant influence on the induced residual stress distribution and also on material behavior when fatigue tested in the high cycle regime. It is observed that higher initial compressive residual stresses magnitude does not necessarily lead to a longer fatigue life. Finite element analysis using the new cyclic plasticity material model shows this behavior is due to combined residual stress redistribution under fatigue test cyclic loading and cyclic hardening effects. A fatigue life methodology based on the stress‐life approach augmented by a critical distance method is proposed and shown to give good agreement with experimental results for test specimens with no induced residual stress. The results obtained for specimens with induced residual stress are more conservative, but the degree of conservatism is significantly lower than that in the conventional stress life approach. The proposed methodology is therefore suitable for analysis and design assessment of components with pre‐service induced compressive residual stress, such as autofrettaged pressure components.

Study of Photoplastic Behaviour of Polycarbonate using Digital Image Correlation

Earlier studies on photoplastic behaviour of polycarbonate are limited to the strain at which the localized yielding (necking) initiates (about 6% strain). In this study, the photoplastic behaviour of polycarbonate is studied using digital image correlation (DIC). Two cases are considered: one in which no localized yielding is observed and the other in which initiation and propagation of the localized yielding is observed. For the first case, a modified dog bone specimen is proposed to evaluate the photoplastic constant. In the second case, a conventional tensile test specimen is used. Both photoplasticity (transmission and reflection) and DIC experiments are performed on the specimens to determine the relation between fringe order and principal strain difference for strains of up to 60%. It is observed that the photoplastic constant is a function of strain. Finally, the behaviour of the tensile test specimen is numerically simulated. The true stress-strain curve of polycarbonate needed for FE simulation is determined using DIC experiments on the standard tensile test specimen. By post-processing the FE results, isochromatic fringes are plotted and compared with experimental results.

Variety of Current Power Welding Using Electrode 6013 on Tensile Force of Lower Carbon Metal

The objective of this study is to determine the outstanding tensile value on welding of little carbonate steel electrode 6013/ Ө 2.5 x 350 mm in tensile test. Specimen in tested is a lower carbon steel found in market or sometimes available on welding workshops of plate form. This plate is made refer to Standard Tensile Test specimen ASTM E-8M in thick 5 mm and made plot V 450 in twelve pieces. In welding specimen, inflow current varieties with 60, 80, 100, 120 Ampere and constant power of 20 volt and welding position tilted ranges 600 – 700. In the test found data the lowest tensile strength is 160.62 Mpa of welding current power 60 Ampere and the greatest tensile force 438.80 Mpa with welding power 120 Ampere whereas welding most adaptable is on 80 Ampere 325.96 Mpa. The power force of welding determined to tensile force due electrode fluid completed and influenced to that lower carbon steel mechanical property.

Effect of creep phenomena on room-temperature tensile properties of cast & forged P91 steel

Abstract In present research work, the as-received cast & forged (C&F) P91 steel was subjected to the creep test at temperature of 620 °C and 650 °C for applied stress of 120 MPa. The room temperature tensile test was conducted after normalizing and tempering (N&T) treatment of the ruptured creep specimen. The standard tensile-test specimen was prepared from the gauge section of creep ruptured specimen. The N&T treatment was performed to restore the microstructure and mechanical properties of virgin P91 steel (N&T P91 steel). The microstructure of creep fractured specimen in ruptured state and N&T condition were characterized by using field-emission scanning electron microscope (FE-SEM) with energy dispersive X-ray spectroscopy (EDS). The fracture surface morphology of crept specimen and the tensile tested specimen was also studied. The effect of prior creep deformation on the mechanical strength was more significant in the sample with longer creep rupture life.

Hardness, tensile and impact behaviour of hot forged aluminium metal matrix composites

Tensile and impact testing and hardness measurements were carried out on hot forged aluminium metal matrix composites to understand the influence of alloying element and forming process on their mechanical properties. Pure aluminium preforms together with its composites such as Al4TiC, Al4Fe3C, Al4Mo2C and Al4WC were prepared using a suitable die-set assembly on a 1MN capacity hydraulic press. Sintering operation was carried out in an electric muffle furnace at the temperature of 1200°C for a holding period of 1h. Immediately after the sintering process the cylindrical preforms were hot deformed in to a square cross-section bar of size 24mm×24mm×60mm for preparing of tensile test and impact test specimens as per the respective ASTM standards. Standard tensile and impact test specimens were machined from the forged square rods. Standard ASTM procedure was followed to conduct the aforementioned mechanical testing. Further, microstructural studies on the hot forged square cross-section bar and hardness measurements were obtained and analysed.

Crystal plasticity extended models based on thermal mechanism and damage functions: Application to multiscale modeling of aluminum alloy tensile behavior

The mechanical anisotropic properties of aluminum alloy are studied using multi-level approaches for strain-rate and temperature-sensitive large plastic deformation of polycrystalline aggregates. Unlike previous researches, the thermal effect and the damage evolution process are considered simultaneously and integrated in the CPFEM method. In the microscopic constitutive equation of crystal plasticity, the shear strain rate on the slip system is described by an advanced exponential function based on thermal activated mechanism, instead of traditional phenomenological power-law function. To determine the rate-sensitive material parameters in this new model, the strain rate and temperature jump tests are performed. In addition, a simulation of one representative volume element is compared to the results of conventional tensile tests to obtain other thermal parameters. Coupled with the continuum damage evolution formula, this thermal affected crystal plasticity model is then implemented in a single crystal analysis for different orientation, temperature and strain rate conditions. Finally, this extended crystal plasticity model is applied in the finite element method to simulate the mechanical properties of 5052 aluminum alloy at absolute temperature 473 K. Taylor model is also used to compare these simulations as well as the experimental data. The results show that the damage model coupled in the crystal plasticity is able to predict the mechanical response of 5052 aluminum alloy; moreover, this model can simulate the explicit evolution of damage factor and local stress concentration in the deformation of standard tensile test specimen. In the simulation, the specimen is meshed by rectangular elements and each element is given an initial orientation at the first time increment step. This study argues that even in high temperature, the orientation mismatch between adjacent grains could lead to early cavity or crack initiation and the damage development is similar to the void evolution theory. An explanation of the possible fracture angle is given in the thermal tensile test due to polycrystalline anisotropy. At last, the analysis of stress heterogeneity and texture evolution is also shown in this study.

Effects of high-dose gamma irradiation on tensile properties of human cortical bone: Comparison of different radioprotective treatment methods

There are growing interests in the radioprotective methods that can reduce the damaging effects of ionizing radiation on sterilized bone allografts. The aim of this study was to investigate the effects of 50kGy (single dose, and fractionated) gamma irradiation, in presence and absence of l-Cysteine (LC) free radical scavenger, on tensile properties of human femoral cortical bone. A total of 48 standard tensile test specimens was prepared from diaphysis of femurs of three male cadavers (age: 52, 52, and 54 years). The specimens were assigned to six groups (n=8) according to different irradiation schemes, i.e.; Control (Non-irradiated), LC-treated control, a single dose of 50kGy (sole irradiation), a single dose of 50kGy in presence of LC, 10 fractions of 5kGy (sole irradiation), and 10 fractions of 5kGy in presence of LC. Uniaxial tensile tests were carried out to evaluate the variations in tensile properties of the specimens. Fractographic analysis was performed to examine the microstructural features of the fracture surfaces. The results of multivariate analysis showed that fractionation of the radiation dose, as well as the LC treatment of the 50kGy irradiated specimens, significantly reduced the radiation-induced impairment of the tensile properties of the specimens (P<0.05). The fractographic observations were consistent with the mechanical test results. In summary, this study showed that the detrimental effects of gamma sterilization on tensile properties of human cortical bone can be substantially reduced by free radical scavenger treatment, dose fractionation, and the combined treatment of these two methods.

Failure prediction of full-size reactor components from tensile specimen data on NBG-18 nuclear graphite

This paper concerns itself with predicting the failure of a full-size NBG-18 nuclear graphite reactor component based only on test data obtained from standard tensile test specimens. A full-size specimen structural test was developed to simulate the same failure conditions expected during a normal operation of the reactor in order to validate the failure prediction. The full-size specimen designed for this test is almost a hundred times larger than the tensile test specimen, has a completely different geometry and experiences a different loading condition to the standard tensile test specimen. Failure of the full-size component is predicted realistically, but conservatively.

임펠러식 쇼트피닝 머신에 의한 표면 커버리지 시뮬레이션

Shot-peening is frequently used on various mechanical parts because it can improve the fatigue life of components by generating compressive residual stresses on the surface. This can be done by repeatedly hitting the work-piece surface with small balls and making indentations on it. In fact, finding optimal peening time among various peening parameters is the most important. Under-peening can not improve the fatigue life sufficiently while over-peening causes cracks and reduces fatigue life in contrast. In general, optimal peening time is experimentally determined by measuring arc-height using Almen-strip in accordance with SAE J442 standard. To save the time and efforts spent in carrying out experiments to find optimal peening time, this paper presents a computer simulation algorithm for the estimation of surface coverage made by impeller type shot-peening machines (PMI-0608). Surface coverage is defined as the proportion of the work-piece surface that has been indented in a given time of shot-peening. An example (standard tensile test specimen) is presented to validate the proposed method.