Tensile Tests Research Articles

Joint formation mechanism and mechanical properties of laser brazed Zn coated steel under different defocusing conditions

Laser brazing, producing a class-A joint surface in automotive, relies on the defocus control to manage laser heating mode and braze performance. This work demonstrates that the laser interaction mechanism transitioned from keyhole welding to conduction brazing as defocus distances increased from −20 to ≥18 mm while keeping other parameters consistent. Uniform brazed joints were achieved at defocuses of +22, +25 and + 30 mm. Increased defocus distance resulted in a wider bead, with a larger laser irradiation area and expanded heat affected zone (HAZ), leading to increased steel melting and more Fe-rich precipitates within the Cu braze. The interfacial reaction layers remained Fe(Si) with increasing thickness as defocus changed from +22 to +30 mm, and two distinct Fe(Si) phases were initially identified. The steel Zn coating evaporated upon direct laser irradiation at upper two regions while participated in interfacial reactions at the weld root. At the weld root, a dramatic phase transition from Zn–Cu to Cu was observed, with liquid Zn(Cu) phases particularly forming in joints with a +30 mm defocus, led to solidification cracks that acted as failure initiation sites during tensile testing. Cracks propagated along the interfacial reaction layer/bead interface, or along large Fe-rich precipitates within the bead. A +30 mm defocus produced a lower hardness HAZ than with a +22 mm defocus, due to the higher content of bainite and tempered martensite resulting from a slower cooling rate. This work provides insights into optimizing laser brazing parameters for Zn-coated steel.

Influence of heat treatment temperature on grain structures and properties of a Ni-based superalloy fabricated via selective laser melting

This paper investigated the grain structures and mechanical properties of GH3625 alloy fabricated by Selective Laser Melting （SLM）technology at different heat treatment temperatures. GH3625 alloy samples were fabricated using SLM and subjected to heat treatment at different temperatures. Microstructural characterization was conducted using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Electron Backscatter Diffraction (EBSD). Tensile tests were also performed to evaluate the mechanical properties. It was found that the heat treatment temperature significantly affects the microstructure of SLM-fabricated GH3625 alloy. As the temperature increases from 950°C to 1100°C, the grains gradually become uniform equiaxed morphologies with weakened grain preferred orientation, increased grain size, reduced average misorientation, and increased proportion of high-angle grain boundaries. The transformation of microstructure leads to a decrease in tensile strength and an increase in plasticity of the alloy. Samples treated at 950°C have higher tensile strength,while at 1100°C exhibits higher plasticity. The study shows that by controlling the heat treatment temperature, the grain size, grain boundary characteristics, and dislocation density of SLM GH3625 alloy can be adjusted, thereby affecting the mechanical properties of the alloy, providing important technical support for its application in high-performance fields.

Study on the structure and property of metallocene ethylene/1-heptene and ethylene/1-octene copolymers

Polyolefin elastomers are typically copolymers of ethylene with 1-butene, 1-hexene, or 1-octene. Other types of comonomers have not been widely applied industrially. The cost of 1-heptene obtained from Fischer-Tropsch synthesis is only half that of 1-octene, making it a viable economical substitute. This work utilized 1-heptene from Fischer-Tropsch synthesis and 1-octene from ethylene oligomerization as research subjects. Eight metallocene POEs based on 1-heptene and 1-octene were synthesized using Me2Si(C5Me4)(N t Bu)]TiCl2 (Ti-CGC) catalyst. The copolymers’ molecular structures and physical properties were characterized using HT-GPC, Temperature Rising Elution Fractionation (TREF),13C-NMR, DSC, Melt Index (MI), and Tensile tests. Compared to 1-heptene, 1-octene more effectively reduces the melting point and crystallinity, while 1-heptene’s stronger comonomer insertion capability facilitates the production of copolymers with higher comonomer content. Similar ternary sequence distributions and molecular dynamics indicate that ethylene/1-heptene and ethylene/1-octene copolymers possess comparable chain microstructures. Both ethylene/1-heptene copolymers and ethylene/1-octene copolymers exhibit excellent toughness and mechanical properties. Although the activity and insertion capacity of ethylene and 1-heptene decrease at low comonomer concentrations, they significantly improve at higher comonomer concentrations. Thus, Fischer-Tropsch synthesis of metallocene ethylene/1-heptene copolymers can effectively reduce raw material costs and be a cost-effective alternative to ethylene/1-octene copolymers.

Genetic algorithm-based shape optimization of rubber mount for tractor-cabin mounting system

Tractors are widely used for agricultural activities worldwide by farmers. The cabin mount of a tractor supports the weight of the cabin and isolates vibrations from the chassis. In this study, the cabin mount-shape parameters were optimized considering its design characteristics to reduce vibration and noise inside the cabin. Additionally, vibration and noise tests were conducted to evaluate the improvement in isolation performance owing to the optimization. The nonlinear material constants of the Mooney–Rivlin hyperelastic model were obtained through tensile tests on rubber materials. A finite element model of the cabin mount was developed, and an analysis model was constructed to derive the vertical and lateral stiffness and displacement transmissibility through static and dynamic analyses using the ABAQUS program. The shape parameters influencing vertical and lateral stiffness were determined, and an objective function to minimize displacement transmissibility was defined for optimization. The vertical and lateral displacement transmission rates of the mount were successfully decreased through the optimization. The noise and vibration test results indicate that the cabin noise decreased by approximately 1–2 dB, while vibrations in the frequency range below 100 Hz were reduced by more than 3 dB in all directions. The proposed technique can help engineers and manufacturers improve driver comfort and mitigate the adverse effects of excessive noise and vibrations on their mental and physical health.

Near-surface microstructures convolute mechanical properties in additively manufactured metals

Kovar specimens were additively manufactured with 180 variations in process conditions. Three distinct geometries (two tensile geometries and a Charpy specimen) were evaluated for each set of process conditions. Tensile specimens additively manufactured to net shape had less porosity, more uniform material properties, higher average ductility, and they consistently failed via ductile rupture. Tensile specimens harvested via electric discharge machining from larger additively manufactured blocks often contained lack of fusion voids throughout the cross section - those pre-existing pores drove pre-mature failure. As-printed specimens, on the other hand, were more representative of the outer border properties rather than the interior of large printed parts. The properties of the specimens cut from the larger block of additively manufactured material were more representative of the inner hatch properties but were stochastic, depending on the size and location of present voids. Using a high-throughput methodology, the results from over 800 tensile tests are reported here. This extensive statistical sampling allows the effects of specimen type and location to be clearly distinguished from other intentional variables (process parameter variations) and stochastic material variability.

Laser powder bed fusion of GH4099 Ni-based superalloy under a static magnetic field with tailored microstructure and enhanced mechanical performance

ABSTRACT In the present work, the static magnetic field (SMF) was applied in the L-PBF process of a typical γʹ strengthening Ni-based superalloy of GH4099 concerning the as-built and heat-treated conditions. The SMF during the L-PBF process can effectively refine the cellular str ucture, refine the grain size, promote the columnar to equiaxed transition (CET), and reduce the dislocation density. After the solution-aging procedure, the SMF samples exhibited a refined grain structure, suggesting that the tailored microstructure is inherited after the solution-aging treatment. The tensile test results show that by applying the SMF during the L-PBF process, the ductility can be notably improved on both building planes under the as-built and heat-treatment conditions, and the anisotropy along different directions can be reduced. It reveals that the SMF in L-PBF can be an effective method to modulate the microstructure and improve the comprehensive mechanical properties for γʹ strengthening Ni-based superalloys.

Splitting behavior of polyvinyl alcohol fiber reinforced iron ore tailings concrete

To promote solid waste reutilization and reduce natural river sand consumption, iron ore tailings (IOT) are expected to be used in concrete production as a potential substitute for river sand under the premise of comparable material properties with ordinary concrete. In this study an IOT concrete reinforced by Polyvinyl Alcohol (PVA) fiber has been proposed and the slump and splitting behavior under various IOT substitution rates and PVA fiber contents has been experimentally investigated. Slump tests reveal that the optimal PVA fiber content is 0.1 % and IOT substitution rate is 60 % from the view of workability. Splitting tensile tests show a monotonous strength growth with PVA fiber content increase. The incorporation of IOT has increased concrete splitting tensile strength but the strength is smaller than that of normal concrete as soon as IOT substitution rates exceed 50 %. A regression model and Back Propagation (BP) neural network model have been adopted to establish splitting tensile strength prediction model. Compared to regression model, the BP model has exhibited better accuracy which is suitable to predict the splitting tensile strength of PVA-IOT concrete with PVA content less than 0.3 %.

Raman Scattering for Tensile Testing of Polyacrylonitrile-Based and Pitch-Based Single Carbon Fibers

Raman Scattering for Tensile Testing of Polyacrylonitrile-Based and Pitch-Based Single Carbon Fibers

Impact force-damage depth model for ship-bridge collision

The impact force-damage depth model, i.e., P-a model, provides a feasible approach to design and evaluate bridge resistance under ship collisions, which is inadequately addressed in the existing specifications and literature. In the present study, based on an 18500 DWT (deadweight tonnage) bulbous bow bulk carrier and the main tower of cable-stayed bridges, the P-a model for ship-bridge collision is established with consideration of pile cap, bridge pylon and striking ship. Firstly, the refined finite element (FE) model of prototype ship was established with detailed modeling of both the main and stiffening components. The material model parameters and FE analysis approach were validated through the existing tensile tests on marine steel coupons and crush tests on ship bow specimens. It is found that the modeling of stiffening components has rationality in predicting the impact force and asymmetrical folding collapse of ship bow. Then, concerning two collision scenarios with the main tower of cable-stayed bridges, i.e., only bulbous bow-pile cap collision and sequential bulbous bow-pile cap and bow overhang-bridge pylon collisions, the influences of nine critical parameters from pile cap (height, curvature and water level), bridge pylon (width, curvature, angle and bow overhang-bridge pylon distance) and striking ship (mass and velocity) on the impact forces and failure patterns of ship bow were comprehensively discussed. It indicates that: (i) the larger impact forces of bulbous bow and bow overhang appear with increased pile cap height, decreased bridge pylon curvature and inward inclined pylon angle; (ii) the loading paths of P-a relationships are approximately identical with different striking ship masses and velocities. Finally, the P-a model for ship-bridge collision was established by response surface methodology, and the corresponding calculation procedure was further given and validated.

End-of-life carbon fiber/poly(phenylene sulfide) semipreg scraps from the aerospace industry: Towards a sustainable product

End-of-Life (EoL) carbon fiber (CF)/poly(phenylene sulfide) (PPS) semipreg scraps from the aerospace industry were used for the development of new products. The scraps were cut and placed randomly in aluminum molds, with and without continuous layers of semipreg, to obtain five different laminates processed by hot compression molding. The laminates were inspected by ultrasound, followed by cutting standardized test specimens using a CNC machine. Afterward, the laminates were evaluated for thermal (differential scanning calorimetry, DSC) and mechanical properties (tensile test and interlaminar shear strength, ILSS). The morphological characteristics of fracture surfaces were evaluated by scanning electron microscopy, SEM, and optical microscopy, OM. Ultrasound inspection indicated that four laminates showed the presence of voids, flaws, defects, and internal discontinuities, some very pronounced. However, the five laminates processed did not show differences in thermal stability. The size of the scraps and the direction of the CF contributed unintentionally so that two laminates presented tensile strength values 15 % lower than the reference laminate (822 MPa) and ILSS values (64 MPa) very close to the reference. The micrographs showed the ordering and positioning of the CF/PPS semipreg layers. The results were promising and could be considered as resources for developing new products through recycling processes.

Texture evolution induced by extrusion parameters and its effect on strengthening-toughening mechanisms of Al-Mg-Si-Cu-Mn alloys

In this study, extrusion experiments were carried out on Al-Mg-Si-Cu-Mn alloys with different extrusion ratios (ERs), extrusion temperatures (ETs), and extrusion speeds (ESs). By using electron backscatter diffraction (EBSD) analysis, tensile testing, and other analytical means, the evolution of microstructure, texture, and properties of the extruded alloys was systematically investigated, and the strengthening-toughening mechanism induced by the extrusion parameters was revealed. It was found that the strength of the extruded alloy shows a tendency to first increase and then decrease with the increase of the ER and ES, and the ‘critical ER' and ‘critical ES' are 29.5 and 2.5 mm/s, respectively; the strength of the extruded alloy gradually increases with the increase of the ET. The alloy achieved excellent strength-toughness matching at the ER of 29.5, ET of 480 °C, and ES of 2.5 mm/s. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the extruded alloy at this condition were ∼169.58 MPa, ∼314.36 MPa, and ∼16.57 %, respectively. This excellent strength-toughness matching is mainly related to the following aspects: 1) grain refinement provides high grain boundary strengthening effect and appropriate work hardening ability; 2) <111>//ED texture has a strong preferential orientation; 3) the variation trend of dislocation density is importantly related to <111>//ED and EXa{011}<111> textures; 4) Cube{001}<100> and Goss{011}<100> textures have a softening effect. The above findings provide new insights into the potential mechanisms of hot extrusion forming of aluminum alloys, which are of important guiding for the design and development of aluminum alloys with excellent strength-toughness combinations.

Temperature dependence of the deformation behavior and mechanical properties of a Fe–Mn–Al–C low-density steel for cryogenic application

The temperature dependence of the deformation behavior and mechanical properties of a Fe–20Mn–6Al-0.6C-0.15Si austenitic low-density steel was studied by tensile test and Charpy impact test at −196 °C, −77 °C and room temperature (RT), followed by microstructure analyses. The results indicate that the decreased tensile temperature, which is corresponding to reduced stacking fault energy (SFE), promotes the planar glide of dislocations. This led to larger fraction of low-angle grain boundaries (LAGBs) at lower tensile temperature. Consequently, both the tensile strength and elongation were improved as temperature decreased. At lower impact test temperature, the load and energy of crack initiation were larger, indicating a higher resistance to crack initiation. However, the transition from stable to unstable crack propagation occurred more rapidly at lower temperature, resulting in lower crack propagation energy and reduced resistance to crack propagation. This is because less region experienced planar glide. Due to the rapid unstable crack propagation, the Charpy absorbed energy at −196 °C was the lowest. The smaller fracture surface area, larger fibrous zone and more obvious ductile fracture characteristics in radial zone suggest that the toughness is better at higher temperature. Additionally, the presence of secondary cracks at RT delayed fracture, therefore benefitting toughness.

Evading intermediate temperature embrittlement of FeCoCrNiMn high entropy alloy via N-doping

High entropy alloys (HEAs) exhibit high strength and excellent ductility at both room and low temperatures. The loss of ductility with increasing the tensile temperature above room temperature has been widely observed in single phase face-centered cubic structured HEAs. In this work, a N and Si doped FeCoCrNiMn-(N,Si) HEA with preexisting nano-sized Cr2N particles was fabricated by laser powder bed fusion (LPBF) and subsequent cold-rolling and annealing treatment. Tensile testing was conducted on the alloy at 298 K, 573 K, 773 K, 873 K, and 973 K, respectively. It has been shown that the FeCoCrNiMn-(N,Si) alloy with preexisting Cr2N phase exhibits a steady ductility with increasing the tensile temperature. The intermediate temperature embrittlement is evaded in the FeCoCrNiMn-(N,Si) alloy via N-doping. The widely reported loss of ductility with increasing deformation temperature was avoided in present FeCoCrNiMn-(N,Si) HEA by shifting fast segregation of element Cr from GBs into preexisting Cr2N phase due to the high affinity between N and Cr elements, leading to the increases in the content and size of Cr2N particles after high temperature deformation.

Valorizing Biopolyester Suberin: Modification of Cellulose Nanocrystals and Performance Assessment in 3D-Printed Biobased Acrylates.

Suberin, a common biomass processing waste, is a complex biopolymer and a promising source for the biorefinery of chemicals. Six different approaches for the extraction of birch outer bark suberin fatty acids (SFAs) were explored, and their application in grafting the surface of cellulose nanocrystals (CNCs) was investigated. Successful CNC functionalization was controlled with FTIR and NMR analyses. In-depth research allowed us to evaluate the interface of the nanocellulose and polymer matrix. Three structurally distinct SFA-grafted CNCs were integrated into a vegetable oil-based acrylate resin in an ultralow concentration of 0.1 wt %. Five biobased acrylic resin formulations were prepared: without reinforcement, with CNC, and with three distinct SFA-grafted CNCs. Vat photopolymerization (VP) 3D printing was utilized for sample preparation. The effects of grafted CNC components on 3D-printed samples' thermal stability, thermomechanical properties, and wettability were evaluated in detail. CNC functionalization enhanced the interface with the polymer matrix, yielding up to a 2-fold increase in elongation and up to a 2.5-fold increase in strength in tensile and flexural tests compared to the polymeric matrix. The CNC-SFA-modified filler demonstrated performance comparable to, or even better than, petroleum-based chemical modification routes found in the existing literature. This study highlights a promising approach for green functionalization of CNCs and verifies its use in interface enhancement using a biobased acrylate matrix.

Effects of Humidity on Mycelium-Based Leather.

Leather is a product that has been used for millennia. While it is a natural material, its production raises serious environmental and ethical concerns. To mitigate those, the engineering of sustainable biobased leather substitutes has become a trend over the past few years. Among the biobased materials, mycelium, the fungal "root" of a mushroom, is one of the promising alternatives to animal leather, as a material with tunable physicomechanical properties. Understanding the effect of humidity on mycelium-based leather material properties is essential to the production of durable, competitive, and sustainable leather products. To this end, we measured the water sorption isotherms on several samples of mycelium-based leather materials and investigated the effects of water sorption on their elastic properties. The ultrasonic pulse transmission method was used to measure the wave speed through the materials while measuring their sorption isotherms at different humidity levels. Additionally, the material's properties were mechanically tested by performing uniaxial tensile tests under ambient and immersed conditions. An overall reduction in elastic moduli was observed during both absorption and immersion. The changes in the measured longitudinal modulus during water sorption reveal changes in the elasticity of the test materials. The observed irreversible variation of the longitudinal modulus during the initial water sorption can be related to the material production process and the presence of various additives that affect the mechanical properties of the leather materials. Our results presented here should be of interest to material science experts developing a new generation of sustainable leather products.

Hot extrusion, tensile deformation behavior and deformation mechanism analysis of a wrought superalloy with a high γ′ phase volume fraction of 64 %

A hundred kilograms of GH4975 extrusion bar, featuring fine equiaxed grains, were successfully fabricated using electron beam smelting layer solidification(EBSL) and hot extrusion techniques. Subsequent analysis focused on the microstructure and tensile properties of the extruded bar. The study also delved into the influence of temperature on tensile deformation behavior and mechanisms of the alloy after standard heat treatment(SHT). The results revealed uniformity in precipitated phase size and morphology across the extruded bar, with grain size being the largest at the center and smallest at the edge. Tensile tests conducted at 20 °C and 650 °C show an obvious work hardening phenomenon, and the deformation mechanism is dominated by APB coupled dislocation pairs shearing. With the increase of deformation temperature, the work-hardening phenomenon gradually weakens, and SFs emerge as the primary deformation mechanism at 750 °C. As the deformation temperature further rises, cross slip, Orowan bypass and dislocation climbing gradually dominate. The fracture mode changes from brittle fracture to ductile and brittle mixed fracture, and ultimately to brittle fracture. Compared with the traditional preparation method, the hundred kilograms of GH4975 extrusion bar prepared by this technology still show better mechanical properties.

Benefits of Environmentally Friendly Plaster on Mechanical Properties When Combined with Polyester Resin and Hardener Are Examined under Compression and Tension.

Recently, plaster has gained increasing attention as a mechanical and environmentally friendly option and is an effective alternative to traditional cement products. Additionally, polyester has an effective impact on the mechanical properties of materials, in addition to being one of the most environmentally friendly materials. However, studies are still ongoing to reach the best ratios of polyester resin, polyester hardener, and gypsum plaster that can improve mechanical properties. This research aims to investigate the impact of these components at various ratios (30%, 45%, and 60%) of gypsum plaster weight on the mechanical properties of plaster material. This study is carried out by conducting compression and tensile tests for three ratios, which are considered among the most important mechanical tests according to their applications. In addition, the environmental emissions resulting from the three different ratios of plaster are evaluated to determine their environmental impact. This study found that the largest ratio (30%) was the most effective from an economic and mechanical point of view, while achieving lower carbon emissions compared to the other ratios, which enhances the trend towards achieving the environmental goals of the Kingdom of Saudi Arabia's Vision 2030 to reach zero emissions. This study is highly significant both in terms of scientific research and practical application across a range of industries, since it integrates the enhancement of material performance with the achievement of environmental sustainability requirements.

Decentralized approach for incorporating waste wind turbine blades into 3D printing filaments using mechanical recycling

AbstractThe increasing awareness in environmental safety has led to rapid development in production of electricity using wind energy with wind turbines. The widespread deployment of wind turbines has outpaced the effective recycling of End‐of‐Life wind turbines. This study explores the potential of mechanically recycling decommissioned wind turbine blades (WTB) as reinforcement material in 3D printing processes. Utilizing mechanical grinding, materials were extracted from the waste blades and subsequently analyzed using Fourier transform infrared spectroscopy, Differential scanning calorimetry, and thermogravimetric analysis to determine optimal processing conditions. The reclaimed materials were then blended with recycled polypropylene through single‐screw extrusion to fabricate tensile test samples via Fused Deposition Modeling. The impact of print orientation on mechanical strength was examined at 0°, 45°, and 90° angles. Morphological analysis was conducted on the fractured specimens to assess the failure characteristics. The findings indicate that samples printed at a 90° orientation exhibited superior mechanical properties, suggesting a viable pathway for incorporating wind turbine waste into sustainable manufacturing cycles.Highlights A decentralized‐mechanical recycling technique to the waste WTB. The necessary material parameters for the operations employed in this study. Reinforced 3D printable filaments from waste WTB. Stronger reinforced filaments obtained from proper fiber alignment.

Comparison of the Young’s modulus of the lead free solder alloy Sn-Ag3.8-Cu0.7 determined by hot tensile tests, ultrasonic measurements and [formula omitted]-Sn single crystal calculations

Sn-based solders are known for their tendency to form coarse grained microstructures. In combination with the high elastic anisotropy of β-Sn, the overall elastic properties and their interpretation require a careful discussion of the structure–property-relationship as elastic constants are often important input parameters for creep or fatigue models. This study therefore investigates the influence of microstructure and testing method on the Young’s modulus E for the widespread lead free solder alloy Sn-Ag3.8-Cu0.7 (SAC387) using bulk specimens. Due to its already high homologous temperature at room temperature (Thom≈ 0.6 = T/Tm for Tm being the melting temperature), hot tensile tests generally bear the risk of superimposed creep deformation. Mechanical testing becomes even more challenging, since yield strengths are usually low for these alloys. Consequently, in addition to the hot tensile tests executed for the engineering strain rate ϵ̇e=1⋅10−3 s−1, two supplemental methods are used to determine the Young’s modulus comprising of the dynamic resonance frequency measurement and the calculation of the Young’s modulus based on single crystal compliance data of the majority phase β-Sn.Young’s moduli yielded from dynamic resonance frequency measurement and calculations based on single crystal compliance data showed comparable results of (E35 °C≈ 55 GPa, E80 °C≈ 51 GPa and E125 °C≈ 48 GPa). Hot tensile tests showed similar data with the largest deviation at 80 °C, where E80 °C≈ 53 GPa was determined. These absolute values and their temperature dependence can be attributed to the microstructure of the cast specimens which show a general preferred orientation of β-Sn grains close to <110> after analysis via electron backscattered diffraction (EBSD). A comparison with literature data revealed significant differences in the Young’s moduli which are likely to be attributed to differences in the preferred orientation of β-Sn grains.

Failure evaluation of outdoor polymeric insulators based on statistical condition-assessment methods

Field aging of outdoor polymeric insulators results in unscheduled outages in power systems particularly in harsh climate conditions. In this paper, a strategic maintenance framework is proposed in order to prevent overhead line outages. The presented scheme is based on condition assessment of the real aged polymeric insulators. Data of tensile test, hardness test, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) are used to extract critical features of the aged samples based on classification of fuzzy c-means clustering. Then, a lifetime prediction analysis is done based on Cox hazards analysis to develop further maintenance strategy. The proposed model is validated through numerical analyses on polymeric insulators for various validation evaluations including pollution severity analysis and hydrophobicity class (HC) measurement. Obtained results verify accuracy of the intelligent model to predict lifetime of the aged polymeric insulators. The presented strategic framework can be effectively applied to online monitoring, condition assessment and preventive maintenance programs of the power system utilities.