Experimental Tensile Tests Research Articles

Calculation methodology of additive manufacturing processed parts

Additive manufacturing technologies allow us the creation of 3D objects through layer overlay. This process is faster than other traditional manufacturing processes and it enables the customization of parts. Nowadays Fused Deposition Modelling (FDM) is the most used techonology. However, due to the nature of the process, resulting parts have complex mechanical behaviour, due to the fact that their properties vary according to the direction or the type of effort, which limits their applications in functional parts. To predict the behavior of a component Finite Element Analysis (FEA) are made. Although, the material models used by these analysis tools are not able to simulate the mechanical behavior of FDM products. Thus, a model supported by a finite element analysis tool, able to predict the behaviour of these materials has been developed. It works in the elastic and plastic region, for any geometry and load case. The model, feed by theoretical behavior models and experimental tensile, compression and shear tests, and implemented in FEA software, allows us to simulate the anisotropy of these materials in an easy and versatile way. The calculation methodology has also been experimentally validated.

Effect of grain refiner, modifier and graphene on the mechanical properties of hyper eutectic Al-Si alloys by experimental and numerical investigation

The present work focuses on the study of mechanical properties of die cast hypereutectic Al-16Si alloys that are subjected to grain refinement and modification. It further deals with the study of the influence of the reinforcement of graphene to the sample that is simultaneously grain refined and modified. Hyper eutectic Al-16Si alloys are die casted with five different compositions. The Vickers hardness test and tensile strength test are performed on the all the casted samples. The Optical microstructure examination of the specimens is performed. The numerical simulation data derived from finite element analysis of the tensile test is validated against experimental tensile test results and both were found to coincide. Using experimental data, two alternative constitutive models, namely the modified Johnson Cook (m-JC) model and the integrated JC-ZA model, were formulated on the investigated materials for precise flow stress behaviour prediction. The JC-ZA model's integration is expected to improve prediction power in relevant consideration conditions.

Optimisation of numerical models of welded joints with multiple defect combinations

This paper presents the continued efforts in investigating behaviour of low-alloyed low-carbon steel welded joints in the presence of different combinations of multiple welding defects, (undercuts, incomplete root penetration, misalignments). Since these defect combinations can greatly affect the integrity of welded joints, due to significant changes in geometry which are induced by their presence. For this reason, a total of 8 numerical models were made, including four different defect combinations (2 models for each group). This number of models was equal to the number of actual test specimens that were used for tensile test experiments, which also provided the necessary input data (mechanical properties) for each model. The goal was to determine if the two models from each group were sufficiently similar to each other, so that in the future research, they could be replaced by a single, unified model for each defect combination. Comparison was made in terms of stress and strain distribution, and it was determined that three out of four models have nearly identical values, whereas the first group specimens had shown slightly bigger differences, which were still acceptable. Thus, it was concluded that a single representative model could be made for each defect combination group.

The tensile properties of 2219 aluminum alloy plate butt joint welded by novel laser mirror welding

For thicker weldments, penetration requires higher welding heat input. The significant difference in temperature between the front and back of the weldment will inevitably produce more significant welding distortion. The symmetrical double laser heat sources act on the flat plate butt joint structure during the laser mirror welding process, which can realize the deformation-free and high-efficiency welding of thick plates. Due to the particular welding method of laser mirror welding, there are complex interactions of double keyholes and double-sided joint pools during the welding process. However, there is no relevant research on laser mirror welding of aluminum alloys. Therefore, experimental analysis on laser mirror welding of the 2219 aluminum alloy is performed in this paper. The relationship between welding process parameters and weld bead formation is explored by quantitative research about the macro morphology of the weld seam. Then, the typical microstructure distribution is studied by the microstructure of laser mirror welded joints. Finally, the tensile test experiment is performed to observe the microscopic morphology of the tensile fracture to analyze the fracture mode of the joint. This article discussed the intrinsic relationship between the stability of the molten pool and the tensile properties. The study found that when the molten pool is formed, the stability of the keyhole is the worst, and the tensile performance is poor.

Experimental Investigation and Numerical Simulation of C-Shape Thin-Walled Steel Profile Joints

The versatility of steel, its high resistance in relation to its low mass, as well as the easily accessible technology in the context of using recyclable materials and the low negative impact on the environment represent important arguments in using thin-walled steel profiles to make structures for buildings with a low height regime. This paper presents the results of an experimental program that investigated the behavior of three types of joints in a T-shape form made of thin-walled steel profiles to make shear wall panels or truss beam floors. Due to the small dimensions of the C-profiles of 89 × 41 × 12 × 1 mm, and of the technology of their joining, manufacturers prefer the hinged connections of elements with self-drilling screws. The purpose of the research presented in this paper is to assess the maximum capacity of the joints, the elastic and post-elastic behavior until failure, and also the mechanisms failure. The types of joints analyzed are commonly used in the production of structural systems for houses. The experimental program, which consisted of testing 5 specimens for each type of joint in tension (shear on screws), showed different behavior in terms of load-displacement. The experimental, tested models were analyzed by finite element simulations in an ANSYS nonlinear static structure with 3D solid models. The materials were defined by a bilinear true stress–strain curve obtained after some experimental tensile tests of the steel. The results of the experimental tests showed that the main failure mechanism is a yielding of the holes where the screws were mounted and a shearing of the profile walls. Adding an additional screw on each side increases the capacity of the joints, but not until a yield loss is obtained. In conclusion, it is shown that the solution is suitable for a low level of loading in a static manner; however, additional studies are necessary in order to develop and verify other solutions, thus improving the strength of the connection.

Experimental and numerical investigation on the structural performance of a novel type of pultruded composite cross-arm for power transmission towers

In the present paper, a novel type of composite cross-arm for power transmission lines has been introduced. The proposed cross-arm consists of composite pultruded tubes and mechanically bolted joints that form a lattice type of cross-arm structure. Experimental and finite element method (FEM) were used together to obtain the proper design and ensure the ideal performance of the presented cross-arm. Material properties for the composites were experimentally obtained prior to analysis as the input for FEM. Thereafter, non-linear Finite element analysis by using sub-modeling technique and employing progressive damage method was used to predict the failure mode and ultimate failure load for the cross-arm. Verification of the model was carried out by comparison with experimental tensile tests on the mechanically bolted joint of the pultruded tube. Finally, finite element results for the whole cross-arm structure were extracted and the ultimate failure load was predicted. Full-scale tests were also performed on the fabricated cross-arm and the maximum failure load was experimentally achieved. The accuracy of the model was revealed by comparing the results. Good agreement between experimental and FE results were obtained for the failure load. According to the outcomes, the presented composite lattice cross-arm structure is perfectly capable of tolerating applied mechanical loads and can be used as an alternative to conventional steel cross-arms.

Experimental Bi-axial tensile tests of spinal meningeal tissues and constitutive models comparison

Introduction This study aims at identifying mechanical characteristics under bi-axial loading conditions of extracted swine pia mater (PM) and dura and arachnoid complex (DAC). Methods 59 porcine spinal samples have been tested on a bi-axial experimental device with a pre-load of 0.01 N and a displacement rate of 0.05 mm·s−1. Post-processing analysis included an elastic modulus, as well as constitutive model identification for Ogden model, reduced Gasser Ogden Holzapfel (GOH) model, anisotropic GOH model, transverse isotropic and anisotropic Gasser models as well as a Mooney-Rivlin model including fiber strengthening for PM. Additionally, micro-structure of the tissue was investigated using a bi-photon microscopy. Results Linear elastic moduli of 108 ± 40 MPa were found for DAC longitudinal direction, 53 ± 32 MPa for DAC circumferential direction, with a significant difference between directions (p < 0.001). PM presented significantly higher longitudinal than circumferential elastic moduli (26 ± 13 MPa vs 13 ± 9 MPa, p < 0.001). Transversely isotropic and anisotropic Gasser models were the most suited models for DAC (r2 = 0.99 and RMSE:0.4 and 0.3 MPa) and PM (r2 = 1 and RMSE:0.06 and 0.07 MPa) modelling. Conclusion This work provides reference values for further quasi-static bi-axial studies, and is the first for PM. Collagen structures observed by two photon microscopy confirmed the use of anisotropic Gasser model for PM and the existence of fenestration. The results from anisotropic Gasser model analysis depicted the best fit to experimental data as per this protocol. Further investigations are required to allow the use of meningeal tissue mechanical behaviour in finite element modelling with respect to physiological applications. Statement of significanceThis study is the first to present biaxial tensile test of pia mater as well as constitutive model comparisons for dura and arachnoid complex tissue based on such tests. Collagen structures observed by semi-quantitative analysis of two photon microscopy confirmed the use of anisotropic Gasser model for pia mater and existence of fenestration. While clear identification of fibre population was not possible in DAC, results from anisotropic Gasser model depicted better fitting on experimental data as per this protocol. Bi-axial mechanical testing allows quasi-static characterization under conditions closer to the physiological context and the results presented could be used for further simulations of physiology. Indeed, the inclusion of meningeal tissue in finite element models will allow more accurate and reliable numerical simulations.

Experimental and Numerical Examination on Formability and Microstructure of AA3003-H18 Alloy in Single Point Incremental Forming Process

The single-point incremental forming process has witnessed significant advantages in automobiles, aerospace, and medical applications in recent years because of its flexibility in manufacturing complex shapes. In detail, the components are produced only using the toolpath, which is guided by computer-aided manufacturing software. However, during the forming process, the parts might experience fractures, which could heavily impact the formed part's geometric accuracy. The main purpose of this study is to analyze the formability of an AA3003-H18 aluminum alloy material in the SPIF process; for this purpose, the material properties are extracted from the experimental simple tensile test in three directions corresponding to the material rolling direction. At first, a simple tensile test is modeled and estimated the material properties for conducting the numerical simulations. Second, the real-time experiments of the SPIF process in terms of predefined forming conditions are performed, and then the surface roughness was measured to check the surface quality of the formed parts. Then, the formed parts are scanned using a 3D ATOS scanner and compared against the desired computer-aided design (CAD) model. Eventually, the numerical results are discussed in comparison with the experimental outcome and displayed a significant correlation toward the expected results. This results comparison communicates that the introduced finite element (FE) model can be adopted for investigating the appearance of thinning location, thinning reduction, distributions of stress and strain. The overall results show that satisfying material formability in better surface finish and geometric dimensional accuracy can be accomplished when the forming conditions are designed appropriately.

Theoretical determination of elastic and flexural modulus for inter-ply and intra-ply hybrid composite material

In this paper a theoretical analysis for determination of elastic and flexural modulus of natural fibre reinforced hybrid composite is proposed. The proposed analytical model is based on the classical lamination approach to predict the theoretical modulus. Experimental tensile and 3-point bending tests were carried out using standard specimens of inter and intra-ply hybrid composite materials. The elastic and flexural modulus predicted by the new approach showed a better agreement with the experimental results, with a maximum deviation of 11.21% and 11.65 % respectively. From the results it was observed that the theoretical value of elastic and flexural modulus was not accurately predicted by rule of hybrid mixture method. The proposed approach can be adopted as a primary tool to predict the modulus of the composite and it can also be used to optimise the composite parameters such as volume fraction of fibre, ply and fibre orientation, etc. for the maximum performance.

Analytic Study on the Force Transfer of Full Encapsulating Rock Bolts Subjected to Tensile Force

Full encapsulating rock bolts are widely used in mining and civil engineering to keep the stability of underground excavations. Nevertheless, decoupling at the interface between the bolt and grout (first interface) still occurs. To disclose the loading mechanism of the bolting system and preventing decoupling at the first interface, experimental and analytic studies were conducted in this paper. First, a nonlinear shearing-slipping law is used to describe the coupling and decoupling behavior of the first interface. Then, this shearing-slipping law is merged into the anchorage body. Following this, the whole loading process is divided into two components: elastic period and elastic-plastic period. Consequently, the analytic force-deformation relation of bolts is obtained. To confirm the rationality of this solution, experimental tensile tests on bolts were performed. It shows that there was a good match between analytic results and experimental tests. With the confirmed analytic solution, a parameter study is performed to investigate the impact of shearing-slipping parameters on the bolting performance. It indicates that increasing the shearing strength of the first interface and the shearing slipping have a positive impact in improving the bearing capacity of bolts. Inversely, the softening coefficient for the post-failure stage has a negative impact on determining the bearing capacity of bolts. Overall, the shearing strength of the first interface has a major impact in determining the loading performance of bolts.

Effect of loading rate on tensile and fracture behavior of AA2050-T84 alloy at high temperature

AA2050-T84 alloy is commonly used in the fabrication of modern commercial aircraft wing parts. Load and temperature variation during aircraft take-off, flight, and landing at different environmental conditions is substantial. Mechanical properties variation of AA2050-T84 alloy at sub-zero and room temperatures are significant and well documented in the literature. In the present work, at a high temperature of 200°C, the effect of load rate variation on tensile and fracture properties of AA2050-T84 alloy are experimentally and numerically studied. The load rates represented in strain rates were applied at 0.01, 0.1, and 1s−1. Experimental tensile tests exhibited the positive strain rate dependency on the yield and ultimate strength of the alloy. 2D numerical elastic-plastic fracture analysis was carried out using Abaqus 6.14. Similar to tensile results, the fracture parameters dependency on strain rates was witnessed. Overall, higher strain rate causes the increased susceptibility of fracture failure with the increase in yield stress of the material.

Effect of the nano-filler content on the compressive strength of continuous carbon fibre/epoxy matrix composites

The axial compressive strength of continuous fibres reinforced composite laminates is a key design parameter. Adding nano-fillers to polymer matrices should increase this property but compressive failure modes may change with increasing the nano-filler content. Significant improvement of the compressive strength is observed with increasing nano-filler content. It is also shown that a single experimental tensile test on ± 4 5 ∘ coupons makes it possible to estimate the compressive strength regardless of the nano-filler content. Indeed, the results of such a test include, on the one hand, a shear failure strain that indicates the type of failure mode in compression, and, on the other hand, a non-linear shear behaviour that is used in a corresponding fibre micro-buckling model.

Finite element modelling and evaluation of mechanical properties of wood-PLA parts manufactured through Fused Filament Fabrication

Fused Filament Fabrication (FFF) is one of the most common additive manufacturing (AM) technologies that has arisen interesting from industry in a wide range of applications. In this paper, the mechanical properties of FFF 3D printed wood-PLA (Timberfill®) parts are investigated both experimentally and computationally to predict the mechanical characteristics of this material. Firstly, experimental tensile test is carried out to achieve the properties of the material. Secondly, the obtained parameters (Young’s modulus, Poisson’s ratio and yielding stress) will be use as input data in the ANSYS software to simulate a 4-point bending test. Finally, in order to validate the obtained model, the simulation results are compared to an experimental flexural test results indicating the correspondence between them. The main result of this work is an appropriate model to predict the behaviour of a 3D-printed piece formed by an internal structure with certain characteristics suitable for the manufacturing process and surrounded by a skin, which is subjected to certain external load.

Influence of Infill Pattern on the Elastic Mechanical Properties of Fused Filament Fabrication (FFF) Parts through Experimental Tests and Numerical Analyses.

Fused Filament Fabrication (FFF) is one of the most extensive additive manufacturing technologies for printing prototypes or final parts in various fields. Some printed parts need to meet structural requirements to be functional parts. Therefore, it is necessary to know the mechanical behavior of the printed samples as a function of the printing parameters in order to optimize the material used during the manufacturing process. It is known that FFF parts can present orthotropic characteristics as a consequence of the manufacturing process, in which the material is deposited layer by layer. Therefore, these characteristics must be considered for a correct evaluation of the printed parts from a structural point of view. In this paper, the influence of the type of filling pattern on the main mechanical properties of the printed parts is analyzed. For this purpose, the first parts are 3D printed using three different infill patterns, namely grid, linear with a raster orientation of 0 and 90°, and linear with a raster orientation of 45°. Then, experimental tensile tests, on the one hand, and numerical analyses using finite elements, on the other hand, are carried out. The elastic constants of the material are obtained from the experimental tests. From the finite element analysis, using a simple approach to create a Representative Volume Model (RVE), the constitutive characteristics of the material are estimated: Young’s Moduli and Poisson’s ratios of the printed FFF parts. These values are successfully compared with those of the experimental tests. The results clearly show differences in the mechanical properties of the FFF printed parts, depending on the internal arrangement of the infill pattern, even if similar 3D printing parameters are used.

A Finite Element Study to Investigate the Mechanical Behaviour of Unidirectional Recycled Carbon Fibre/Glass Fibre-Reinforced Epoxy Composites.

Recycled carbon fibre–reinforced epoxy (rCF/EP) composites and recycled glass fibre–reinforced epoxy (rGF/EP) composites were numerically investigated to examine their mechanical properties, such as uniaxial tensile and impact resistance, using finite element (FE) methods. The recycled composites possess unidirectional, long and continuous fibre arrangements. A commercially available Abaqus/CAE software was used to perform an explicit non-linear analysis with a macroscale modelling approach, assuming the recycled composites as both homogenous and isotropic hardening. Five composite types were subjected to a numerical study based on the recycled fibre’s volume fraction (40 and 60%) of rCF/EP and rGF/EP, along with (100%) fibreless cured epoxy samples. The materials were defined as elastoplastic with a continuum ductile damage (DUCTCRT) model. The experimental tensile test results were processed and calibrated as primary input data for the developed FE models. The numerical tensile results, maximum principal stress and logarithmic strain were validated with their respective experimental results. The stress–strain curves of both results possess a high accuracy, supporting the developed FE model. The numerical impact tests examined the von Mises stress distribution and found an exponential decrease in the stiffness of the composite types as their strength decreased, with the 60% rCF/EP sample being the stiffest. The model was sensitive to the mesh size, hammer velocity and simulation time step. Additionally, the total internal energy and plastic dissipation energy were measured, but were higher than the experimentally measured energies, as the FE models eliminated the defects from the recycled process, such as a poor fibre wettability to resin, fibre bundle formation in rCFs and char formation in rGFs. Overall, the developed FE models predicted the results for a defect-free rCF/EP and rGF/EP composite. Hence, the adopted modelling techniques can validate the experimental results of recycled composites with complex mechanical properties and damage behaviours in tensile and impact loading conditions.

Correlation of yarn feeding to the dimensional and elastic parameters of tubular knitted fabric

The yarn feeding for a loop formation is a critical factor in determining the size and elasticity of highly elastic knitted fabrics. Currently, the prevalent production processes rely on experienced machine operators to set up the optimal feed rate by trial and error. To improve production efficiency and reduce the reliance on the operator’s skill, we attempt to create a structure model of tubular knitted fabric that could correlate the size as well as elasticity of fabric with the loop geometry parameters (wale spacing, course spacing) of the yarn feeding. The experimental tensile test of the elastic fabric verified that the model is able to deduce the yarn feeding parameters from the elasticity and dimensional requirements of the fabric to be knitted. It is also illustrated that the yarn feeding is a key factor in controlling the elasticity of knitted fabrics.

Numerical study of the viscoelastic mechanical response of polystyrene in the process of thermoforming through the generalized Maxwell model

Polystyrene is thermoformed in a viscous state at temperatures corresponding to its crystalline melting point (100–140 °C). The mechanical properties of the material change with temperature since these plastics behave viscously when temperature is increased. Findings are presented during numerical simulations, implementing a viscoelastic characterization of laminated polystyrene. A viscoelastic generalized Maxwell model with Prony series is used in the simulation to replicate the thermoforming processes. The results were verified by comparing them through experimental tensile tests at different temperatures. The good agreement between the model and experimentation allows the proper selection of operating parameters such as pressure, time and temperature of the process.

Multiscale technique for the analysis of 3D-printed materials

The mechanical behaviour of structural elements made of 3D-printed materials is numerically investigated. With this aim a multiscale approach that allows to determine the macroscopic response, as depending on the material heterogeneity at the microscale level, is conceived. A non-linear laminate finite element that employs a reduced homogenization technique at each integration Gauss point is developed. In detail, the Piecewise Uniform Transformation Field Analysis is implemented. In order to validate the procedure, some numerical applications are developed. The obtained results are compared with evidence of experimental tensile and bending tests, available in literature. The application of a multiscale strategy, employing a reduced order method at the Gauss point level for the analysis of 3D-printed structural elements, could represent a good compromise in terms of accuracy of the results and computational efficiency.

High-level hierarchical morphology reinforcing covalent adaptable networks

High-level hierarchical morphology reinforcing covalent adaptable networks

Properties Comparison of Open Hole and Non-Hole Carbon UD-Lycal Composite with Vacuum Bagging Manufacturing Method

Carbon fiber reinforce polymer is one of some composite materials that has the high strength with light weight material. To apply this composite to the amphibious airplane structure, it should through the experimental tensile test to know the tensile strength and modulus of elasticity of the composite. In this experiment, we use Carbon UD fiber and Lycal resin as the composite material that manufactured with Vacuum Bagging Method. Specimens and testing process refer to ASTM D3039 for non-hole specimen, and ASTM D5766 for open hole specimen of tensile test standard for composite matrix polymers. The result of the experimental test shows that the tensile modulus of elasticity for non-hole composite is 34.92 ± 0.13 GPa, with the Ultimate Tensile Strength of this composite is 1081± 0.03 MPa, and the modulus of elasticity for open hole composite is 41.87± 0.02 GPa, with the Ultimate Tensile Strength of this composite is 899.04± 0.02 MPa. The simulation yields nearly same stress-strain graph with the result of experiment. The result shows that, the open hole composite has the ultimate tensile strength lower than non-hole composite, it’s due to the open hole composite has a trigger failure that may decreasing the tensile strength value.