Tensile Tests Research Articles

Comparative Analysis of Mechanical and Thermal Characteristics of 3D‐Printed Polyamide using Material Extrusion and Powder Bed Fusion Process with Industrial and Desktop Printers

AbstractPolyamide (PA) has excellent mechanical properties, making it versatile in various applications, including 3D printing. This paper comprehensively investigates and compares the mechanical, structural, thermal, and geometric properties of 3D‐printed PA12 samples produced with desktop and industrial printers using material extrusion (MEX) and powder bed fusion (PBF) processes. The mechanical tests included tensile, flexural, Charpy impact, Shore hardness, torsion, and water absorption tests. Additionally, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and melt volume rate (MVR) measurements are conducted. To verify printing accuracy from a biomedical perspective, 3D‐printed prosthetic fingers are subjected to geometric assessments. Industrial PBF samples show significantly higher values for most mechanical properties, including a tensile Young's modulus of 1776 ± 19.42 MPa, while the second highest value is 1419 ± 58.77 MPa (MEX desktop). Furthermore, the MVR of the PBF industrial samples is the highest (18.34 cm3/10 min ± 2.32 cm3/10 min) and this printer exhibits superior performance in printing accuracy than the other printers. The balanced print quality and mechanics make the PBF industrial printer the most recommended for medical device production, but lower‐priced desktop FFF printers can be a good alternative for simple, fast solutions that do not require high precision.

The Anti-Flyaway/Frizz Effect by Inducing the α-Helical Structure Transition of Hair

In order to reduce chronic hair flyaways/frizz, both reducing and oxidizing agents have to be used, leaving aside the hair damage issues. This study presents changes in hair morphology caused by treatment with a shampoo containing only reducing agents, excluding oxidizing agents that affect critical hair damages. As a result of flyaway/frizz improvement rates calculated through monitoring of the area of light transmittance in the hair tresses, reducing agents, such as ammonium thioglycolate (ATG), L-cysteine, and sodium sulfite were found to be effective in decreasing hair flyaway/frizz. Additionally, the methods to maintain homeostasis and control damage caused by oxidation during washing were also used to see flyaway/frizz improvement rates. Measurements using electrostatic force microscopy (EFM) showed that the surface charge of hair tresses treated with shampoo containing reducing agents was lowered. Using Raman spectroscopic analysis, it has been suggested that these treatments with reducing agents induced a 3D structural transition of the hair from an α-helix to a random coil. In addition, this structural release was confirmed, identifying the reduction in the enthalpy of the α-helix using differential scanning calorimetry (DSC). Furthermore, we verified that this change causes no hair damage through a tensile strength test. Therefore, the formulation of shampoo with reducing agents can be used as an effective strategy to care for hair flyaway/frizz without hair damage issues.

Processing of Reduced Graphene Oxide Reinforced Ultra High Molecular Weight Polyethylene for Orthopedic Implants

Ultra-high molecular weight polyethylene (UHMWPE) has been used as a bearing material in total joint replacements due to its excellent mechanical properties and biocompatibility. The acetabular cup in total hip replacement and the tibial component in total knee replacement is widely fabricated from UHMWPE. The use of UHMWPE in total joint replacements is well established, and the goal is to improve its mechanical properties, wear resistance, and oxidation resistance. The quality and life span of the artificial joints can be further increased by enhancing the relevant mechanical properties of UHMWPE. The addition of filler material to UHMWPE is an effective way to enhance its relevant properties. In this study, relevant properties of UHMWPE were enhanced by incorporating an appropriate filler. Reduced Graphene Oxide (rGO) was selected as a filler material as it improves mechanical properties, wear resistance, toughness, and thermal stability. Graphene oxide (GO) was synthesized by Modified Hummer’s Method (MHM), and it was thermally reduced to obtain rGO. The synthesized GO was characterized by Fourier Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD) which confirmed the accurate synthesis. The reduction of GO was validated by the disappearance of (OH) broad peak in the FTIR analysis. The rGO/UHMWPE nanocomposite was prepared by adding 0.7 wt.% of rGO employing the solvent mixing method. The morphology of the composite was validated by Scanning Electron Microscopy (SEM). Tensile and Izod Impact tests were performed on the samples which showed an increase in tensile strength of 33.2% and the impact strength increased by 140.5%. The rGO/UHMWPE nanocomposite with greater tensile and impact strength is an excellent candidate to produce orthopedic implants with superior properties.

Mechanical strength analysis of bio composite made by using micro powder made of Prosopis cineraria wood

The Present study examines the mechanical strength of bio-composites fabricated from wood powder of Prosopis cineraria (Khejri) and jute fiber as reinforcement inside an epoxy resin matrix. The mechanical performance of these bio-composites was assessed by altering filler content percentages (0%, 4%, 8%, 12%, 16%, and 20%) and filler particle sizes (250 microns and 500 microns) under standard and carbonate conditions. Tensile strength and impact energy assessments were performed to evaluate the effects of filler content, particle size, and filler type on the mechanical characteristics of the composites. The tensile strength tests reveal that composites with 12% filler and a particle size of 250 microns had the maximum tensile strength, measuring 33.4 MPa under normal settings and 34.8 MPa under carbonate conditions. An increase in filler content over 12% resulted in a reduction in mechanical strength due to filler agglomeration, which decreased stress transfer efficiency. The composites with 250-micron particles consistently demonstrated superior tensile and impact strengths compared to those with 500-micron particles, due to the increased surface area of the smaller particles. Comparative analysis of normal and carbonate conditions demonstrated that carbonate fillers offered superior reinforcement owing to their increased density and enhanced matrix-filler interaction, leading to augmented tensile and impact strength. These findings provide significant insights into the development of bio-composites for structural applications, namely in improving their mechanical strength and durability.

Damage characterization of FRP embedded with different optical fibers under tensile load using acoustic emission and micrographic real-time inspection

Embedding optical fibers into fiber-reinforced plastics (FRPs) for composite health monitoring has attracted the interests of academia and industry recently though the impact of embedded optical fiber on FRP damage has not been clarified. In this study, the damage to the FRP structure caused by the embedded optical fibers was investigated. Five FRP samples incorporated with different types of optical fibers were subjected to tensile testing, and the crack initiation and propagation were in situ monitored using acoustic emission (AE) and micrographic inspection. After the AE signals were classified in terms of peak amplitude and peak frequency using K-means++ clustering, the damage progression from matrix cracking, fiber/matrix debonding, delamination, and fiber break were characterized. In-situ micrographic inspection clearly revealed the damage evolution around the embedded optical fiber. By correlating the stress-strain curves with the AE clustering and micrographic inspection results, it was verified that larger-diameter optical fibers reduce the modulus and ultimate strength of the FRP, while a good optical fiber/matrix interface mitigates these negative effects. The embedded optical fiber accelerated the crack propagation around it, leading to changes in the damage pattern. This phenomenon is the primary cause of FRP failure. Notably, polyimide-coated optical fibers with an outside diameter of 50 μm are ideal for embedded sensing as their incorporation into the matrix reduces the ultimate strength of FRP by only 1.8% with minimal impact on crack propagation.

Heat‐Treatment and Water Immersion Effect on the Mechanical Properties and Joint Strength of 3D‐Printed Polylactic Acid Parts

ABSTRACTThis paper investigates the effect of short‐time water immersion (WI) and heat‐treatment (HT) post‐processes on the mechanical properties and joint strength of printed polylactic acid (PLA) parts with various raster angles. Using these post‐processing methods to enhance the joint strength of printed PLA parts could be deemed as the novelty and the contribution of the current study. The WI and HT of the tensile test specimens and the adherends of the bonded joints were carried out at 21°C and 90°C, respectively. Depending on the raster angle, the tensile strength of the heat‐treated specimens was about 11%–43% higher than that of the untreated specimens. Interestingly, it was found that WI had a more significant effect on the strength of printed parts than HT. In the case of WI, the tensile strength was increased by about 27%–57% as compared to the untreated specimens. Joint tests revealed that HT and WI exerted a similar positive effect on the strength of the joints. The findings highlighted that short‐time WI is at least as effective as HT in increasing the tensile and joint strengths of 3D‐printed PLA parts.

Plastic strain effect on cleavage microcracks propagation in probabalistic statement. Part 2. Research results

The second part of the paper presents the results of uniaxial tension testing of smooth round bars of 2Cr–Ni–Mo–V steel in the thermally-embrittled state and St3 steel in the initial state. SEM examination of the fracture surfaces is carried out. The brittle fracture probability is calculated using the Prometey model presented in the first part of this article. It has been found that the plastic strain effect on the microcrack propagation probability is caused by two reasons: (1) the critical brittle fracture stress increase due to formation of new barriers for microcrack under plastic deformation, and (2) the working volume decrease due to the neck formation in tensile round bar. A unified set of parameters has been proposed to take into account the plastic strain effect on cleavage microcracks propagation probability for WWER-1000 RPV steel and low-alloyed low-strength steel.

Experimental Investigation on the Important Factors on Structural Adhesive Joint Strength of Fiber-Reinforced Epoxy Composites

The static strength of fiber-reinforced epoxy composite structural adhesive lap joints was examined experimentally. Surface roughness and geometrical control parameters (adherent and adhesive kinds) were assessed for their effects. To examine load, elongation, and strength at failure, tensile tests were conducted. Cyanoacrylate glue outperformed SHCP 268 resin, and glass fiber-reinforced epoxy composites outperformed sisal fiber-reinforced epoxy composites. The study offers information on how to maximize adhesive bonding for lightweight multi-material design construction.

Tribological and corrosion characteristics of aluminium–copper alloys reinforced with alumina nickel aluminide cermet powder

Aluminium–Copper (Al-10Cu) alloys are widely used for structural components in the aviation sector. This study focuses on the synthesis and characterisation of Al-10Cu alloy reinforced with Al2O3-30(Ni-20Al) cermet particles to evaluate their microstructural, mechanical, tribological and corrosion properties. The Al-10Cu alloy was cast with varying percentages of cermet (2% and 4%) using a controlled casting process. Comprehensive microstructural analyses, including optical microscopy, SEM and EBSD, were performed to assess the grain structure and cermet distribution. The mechanical properties were evaluated through Vickers microhardness and tensile testing, while tribological performance was assessed using a Pin-on-Disc tribometer. Corrosion resistance was investigated through exfoliation and immersion corrosion tests. The results indicated significant improvements in microhardness and wear resistance with the addition of cermet particles, while the tensile strength showed a complex interplay between ductility and brittleness. Corrosion tests revealed enhanced resistance in cermet-reinforced specimens. This study demonstrates the potential of Al2O3-30(Ni-20Al) cermet as an effective reinforcement for aluminium alloys to achieve superior performance in structural applications.

Evaluation of 3-Point and 4-Point Bending Tests for Tensile Strength Assessment of GFRP Bars.

Glass Fiber Reinforced Polymer (GFRP) bars are used as reinforcement for structural concrete, especially in cases where corrosion of traditional steel reinforcement is a problem. The tensile strength of these reinforcing bars is the primary characteristic on which the design of concrete members reinforced with GFRP bars relies. Determination of the tensile strength of the bars using a direct tensile test is a time and resource-intensive task and therefore is not routinely conducted for quality control. The tensile strength can also be measured from flexure tests, which are much simpler than direct tensile tests, and use appropriate correlation formulations. In this paper, the applicability of flexure testing for the identification of bars' tensile strength is investigated by conducting and analyzing both 3-point and 4-point flexure testing. The correlation formulations are presented that allow the determination of tensile strength from the modulus of rupture. The Weibull weakest link model and the assumption of the same flaw distribution in tensile and flexure tests is adopted. The results of the 3-point and the 4-point bending are presented and compared. Comparisons are also conducted to select direct tensile test results. The work shows that 3-point and 4-point bending tests provide very similar results, with the difference between the results being 2% to 10%, suggesting both tests can be used for tensile strength determination of GFRP bars.

Bio-inspired space-filling fractal metamaterial

Inspired by mammal cranial sutures with spatiotemporal morphological variation, two-phase space-filling fractal metamaterial was designed. Designs with different levels of complexity are fabricated via multi-material polymer jetting. Mechanical tests and systematic finite element (FE) simulations are conducted to evaluate the mechanical performance of the designs. It is found that the hierarchical number N of two-phase space-filling fractal metamaterial played an important role in their mechanical behaviors. The experimental results show that with increasing the hierarchical number N, these metamaterials show enhanced stiffness, strength, and toughness under tensile tests. From the simulation results, we found by decoupling the strain energy density in two phases, with increasing N, the soft phase has contributed almost the same energy level, however, the hard phase has contributed increasing energy level. Moreover, we found the volume fraction and the stiffness ratio of the hard phase dominate the overall mechanical properties of these two-phase space-filling fractal metamaterial. The bio-inspired mechanical metamaterials have broad applications in engineering materials for dissipating energy dissipation, mitigating impact, and retarding damages.

Effects of deposition strategies on microstructure and mechanical properties of wire arc additive manufactured CoCrFeNiMo0.2 high-entropy alloy

High-entropy alloys (HEAs) have great potential for application in various fields due to their excellent performance. However, there are few reports on wire arc additive manufacturing of HEAs. In this study, CoCrFeNiMo0.2 HEA solid wire was prepared and used for WAAM based on cold metal transfer for the first time. Different deposition strategies (namely single-pass (SP), oscillation (OS), and multi-parallel pass (MPP)) were used to prepare metal wall samples of different thicknesses. The HEA samples' microstructure with different deposition strategies were explored by optical and scanning electron microscopy, as well as the electron backscatter diffraction method. Microhardness and tensile tests were used to evaluate the mechanical properties of different samples. The results prove that SP and MPP samples exhibit rougher surfaces due to heat accumulation. The OS sample has the best molding and an effective deposition ratio of up to 91.5 %. The composition of columnar grain grown along the deposition direction with strong {100}<001> cubic texture in both SP and OS samples. Therefore, these two samples have similar mechanical properties, and the mechanical performance in the vertical direction is better than that in the horizontal direction. Due to the complex internal thermal effects and remelting effects between welds, the internal structure of the MPP sample exhibits no obvious preferred orientation. Therefore, the anisotropy of mechanical properties is significantly alleviated.

Ultrasonic Welding Parameter Optimization for Electric Component Welding

Industrial requirements to establish metallic joints between dissimilar metals in the electric area. The ultrasonic welding process is an optimal process to joint thin sheets or foils. The goal of the research was to optimize the ultrasonic welding parameters to join thin nickel-coated copper sheets and aluminium sheets. It used a 0.5 mm thick high-purity copper (Cu-OF-R200) sheet coated with a 10 μm pure nickel layer and a 0.5 mm thick aluminium (1050A H24) sheet. The ultrasonic welding is made by a Branson Ultraweld L20 ultrasonic welder equipment. The mechanical properties and exacting geometrical tolerance of the joint were required. The welding parameter optimization is made empirically, with several welding tests. The optimal welding parameters were confirmed by non-destructive and destructive tests of the joints. The non-destructive tests were the visual inspection and geometrical measurements of the joint sizes. The destructive tests were tensile tests and macroscopic and microscopic tests. The completed test results confirmed the process applicability and the quality of the joint.

Fabrication and characterization of austenite-ferrite stainless steel bimetals by twin wire arc additive manufacturing

In this work, gas metal arc welding (GMAW) based twin wire arc additive manufacturing (TWAAM) system has been employed to deposit to wire materials simultaneously to fabricate austenite-ferrite stainless steel (AFSS) bimetal of austenite stainless steel (SS304L) and ferrite stainless steel (SS430L). A combination of high voltage and wire feed with low torch speed and gas flow resulted in optimal deposition as determined through response surface analysis based on experimental data of single-track bimetal bead on plate depositions. Mechanical and microstructural characterization of the AFSS bimetal was carried out using tensile test, hardness tests, fractography, SEM with EDS, and phase analysis. Tensile properties of the AFSS bimetal were seen to improved with the yield strength of 343 MPa, ultimate strength of 613 MPa and elongation of 67%, and a hardness value of 225 HV. The interface of the AFSS bimetal was found defects free and microstructures contained both austenite and ferrite phases with higher amounts of Ni-content. The fracture morphology of the fabricated AFSS bimetal was seen to contain dimple sizes lying between that of individual steels and resulted in higher elongation than that of the pure ferrite steel. This study demonstrated defects free fabrication of bimetallic structures with unique microstructural features and enhanced mechanical properties.

Interpretation of mechanical properties gradient in laser-welded joints: Experiments and grain morphology-dependent crystal plasticity modeling

The grain size and morphology of laser welds show a gradient distribution, leading to variations in mechanical properties. This study proposes a microscopic crystal plasticity constitutive (CPC) model to examine the effect of ER4047 welding wire on the mechanical properties of laser-welded aluminum alloy joints. A finite element model updating strategy was used to fully invert the morphological mechanical parameters, marking a significant advancement. This study combines mesoscale electron backscatter diffraction (EBSD) observations with macroscopic uniaxial tensile tests to obtain crystal plasticity finite element analysis and strain field data from digital image correlation. The mechanical property gradient of the welded joints was systematically analyzed from a crystal perspective. The CPC parameters were inverted for different grain sizes and morphologies. The study found that using ER4047 welding wire significantly enhanced the mechanical properties of the welded joints, especially in the welding zone. As grain size increased, the yield strength of the material decreased, while the hardening modulus increased. Additionally, the cast characteristics of columnar crystal morphology reduced both yield strength and hardening modulus.

High‐Throughput Electrospinning of Unmodified and Aminated Poly(Pentafluorostyrene) for Fiber‐Reinforced Proton Exchange Membranes

AbstractThis study demonstrates a high‐throughput fabrication of fiber interlayers for proton exchange membranes based on poly(pentafluorostyrene) (PPFSt) and its aminated derivatives. The fibers are produced by electrospinning, where the parameters are carefully screened. The controlled parameters are solvent composition, weight percentage, voltage, flow rate, and temperature, controlled with a self‐designed heating jacket. The parameters are iterated toward optimized fiber structure and maximum output. The yielded fibers are infiltrated with Nafion and sulfonated polymer from bisphenol AF and decafluorobiphenyl (SFS001) by spray‐coating and doctor blading to obtain the fiber‐reinforced proton exchange membranes. Tensile tests reveal a higher Young's modulus and yield stress than pure Nafion. Here, the basicity of the aminated PPFSt fibers correlates with the Young's modulus due to improved acid‐base interactions between amine groups and sulfonic acid. The acid‐base interactions influence the composite membrane's proton conductivity, varying from 23 mS cm−1 for strongly alkaline fibers to 69 mS cm−1 for non‐basic fibers. These findings can be transferred to fabricating fiber reinforcements beyond routinely used poly(benzimidazoles).

Experimental study on seismic performance of bridge pier with new HRB650E high-strength steel bar

To facilitate the application of high-strength steel in reinforced concrete bridge structures, this study explores the seismic performance of full-scale HRB650E high-strength reinforced concrete bridge piers. Initially, monotonic tensile tests were conducted on HRB400 and HRB650E steel rebars with the same slenderness ratio to analyze the differences in their mechanical properties. Subsequently, quasi-static cyclic tests were carried out on four square full-scale RC bridge piers to examine the influence of new high-strength rebars, stirrup ratios, and axial load ratios on the seismic performance. Based on the experimental results, a hysteresis model suitable for HRB650E reinforced concrete columns was developed. The findings indicate that the HRB650E steel bar exhibited lower uniform elongation and fracture elongation compared to HRB400 steel bar. The displacement at which HRB650E piers reached crack damage was 36 % higher than that of HRB400 piers, and they also showed lower residual displacements at all load levels. The maximum lateral load capacity and the ductility coefficient of HRB650E piers increased significantly compared to HRB400 piers. While the initial secant stiffness of both types was comparable, HRB650E piers exhibited a slower rate of stiffness degradation, resulting in higher secant stiffness at the ultimate state. They also demonstrated 35 % higher cumulative energy dissipation at the ultimate state. When the stirrup ratio of HRB650E piers was increased from 1.1 % to 1.7 %, there was a slight reduction in residual displacement, a small increase of the yield strength, and a minor improvement in the maximum lateral load capacity. Furthermore, a higher stirrup ratio was observed to improve energy dissipation levels at all loading stages. Increasing the axial load ratio of HRB650E piers from 0.1 to 0.2 allowed the piers to withstand greater deformations at the same repairable ultimate state, with significant increases in yield strength, maximum lateral load capacity, initial secant stiffness, and secant stiffness at the ultimate state, but a small increase in the cumulative energy dissipation. The hysteresis model for HRB650E RC columns, based on experimental data, exhibited good computational accuracy.

Role of severe plastic deformation on mechanical behavior of irradiated materials: A case study with Nb-1Zr alloy

In this investigation, the effect of 5.6 MeV proton irradiation on the microstructure and mechanical properties of coarse grained (CG) and nanocrystalline (NC) Nb-1wt.%Zr (NZ) has been analysed. Bulk nanocrystalline microstructure was obtained by subjecting the alloy to room temperature high pressure torsion under 6 GPa hydrostatic pressure and 5 rotations. The CG and NC samples were irradiated at doses of 1.9 × 1017 p/cm2 and 1.8 × 1017 p/cm2, respectively. Microstructural parameters like crystallite size, dislocation density, and dislocation arrangements were studied in detail using X-ray line profile analysis (XLPA) by Convolutional Multiple Whole Profile (CMWP) fitting. Microscopic observations were made with electron microscopy techniques in the scanning and transmission modes. Differential Scanning Calorimetry (DSC) was performed to estimate the concentration of vacancies after HPT processing and irradiation. Tensile tests of irradiated CG and NC irradiated samples were performed and compared to those in unirradiated conditions. In the NC condition, not only did the irradiated sample show higher ultimate tensile strength but also twice the amount of uniform elongation as compared to the irradiated CG sample. The fracture surface clearly exhibited this higher plasticity post-irradiation in the NC samples. The change in deformation mechanisms due to nano-structuring of the microstructure has been anticipated to be a reason for the increase in ductility in a single-phase alloy has been explained thereafter.

Radiation and thermal embrittlement of RPV steels: the links of embrittlement mechanisms, fracture modes and microcrack nucleation and propagation. Part 2. Strength and plasticity properties

The uniaxial tension test results are represented over wide temperature range for smooth round bars of 2Cr–Ni–Mo–V steel and A533 steel used for RPVs of WWER and PWR types. These steels are studied in the following states: (1) the initial (as-produced) state; (2) the thermally embrittled state modelling hardening mechanism of embrittlement; (3) the thermally embrittled state modelling non-hardening mechanism of embrittlement; (4) the irradiated state. The true stress-strain curves are determined over wide temperature range that is required for calculation of the stress-and-strain fields for various specimens. The true stress-strain curves for the investigated steels in the initial and thermally embrittled states are obtained when using standard mechanical characteristics. For the irradiated steels the true stress-strain curves are obtained when using the data of the digital video recording under continuous in-testing monitoring of the cylindrical parts of tensile bars. For the irradiated materials the procedure based on standard characteristics cannot be used as it is connected with very small strain. The procedure based on the digital video recording data is verified by comparison of the stress-strain curves obtained for the initial and thermally embrittled states on the basis of the digital video recording data and standard characteristics.

Length scale effects of micro- and meso‑scale tensile tests of unirradiated and irradiated Zircaloy-4 cladding

Zircaloy-4 is an essential material for cladding structures within fission-based reactors. To explore the changes in properties measured on differing length scales, FIB-machined micro-scale tensile tests were performed on both irradiated and control groups of Zircaloy-4. This was correlated with tensile testing on femtosecond laser-machined meso‑scale specimens. Pronounced size effects were found when varying specimen geometry. Increases in tensile geometry size were associated with a reduction in measured yield stress for both irradiated and unirradiated samples. Meso-scale testing found strength and strain values similar to that of bulk-scale testing.