Papers by Keyword: Mechanical Property

Abstract: Percutaneous coronary intervention (PCI) is a minimally invasive treatment for ischemic heart disease, commonly supported by balloon-expandable stents to prevent arterial restenosis. Stent materials must combine high ultimate tensile strength, high ductility, low 0.2% proof strength, high corrosion resistance, high X-ray visibility, and magnetic susceptibility close to that of human soft tissues. The Co-20Cr-15W-10Ni (mass%) alloy, standardized as ASTM F90 and commonly referred to as L605 is widely employed for this purpose. Recently, the demand for stents with smaller diameters and thinner struts has grown, as these significantly lower restenosis risk. Alloys for thin-strut stents therefore require exceptional mechanical and physical performance. This paper reviews the microstructures and mechanical and physical properties of the carbon- and Pt-modified Co-Cr-W-Ni alloys developed by our group. The Co-20Cr-15W-10Ni-0.2C (mass%) alloy achieved an excellent strength–ductility balance and a low 0.2% proof strength owing to the γ-stabilizing effect of carbon. First-principles calculations further revealed that carbon addition increases stacking fault energies (SFEs) in Co-Cr alloys. Pt-modified Co-Cr alloys exhibited higher X-ray visibility than L605 and greater strength than Pt-Cr steel while maintaining comparable ductility. Collectively, these results indicate that carbon- and Pt-modified Co-Cr alloys are promising candidates for next-generation balloon-expandable stents, particularly thin-strut designs.

Abstract: The incorporation of natural fillers like eggshells in polymers has gain attention due to their potential capability to enhance some properties while providing possible cost savings. In this paper, quail eggshells were used as bio-based filler in silicone rubber and their effects on the mechanical properties were investigated. For the composite manufacturing, samples containing 4.8 wt.% (5 phr), 9.1 wt.% (10 phr) and 13 wt.% (15 phr) of crushed quail eggshells were manually prepared. The mechanical characterization tests considered are compression, tensile and hardness. Based from the results, the sample with 4.8 wt.% filler achieved the highest compressive strength of 2.79 MPa and hardness of 53.3 which correspond to improvements of about 11 % and 6 % as compared to the plain rubber, respectively. These enhancements can be associated with the good dispersion of the filler at lower loading. However, higher filler contents resulted to a decrease in mechanical properties which could be linked to the possible agglomeration of crushed eggshells and weak filler to matrix interaction caused by lack of surface treatment. Nevertheless, the improvements attained by adding quail eggshells at lower percentage in rubber can still make it an alternative filler to consider.

Abstract: This study investigates the mechanical performance of hybrid epoxy composites reinforced with natural (jute) and synthetic (carbon and glass) fibers. Two hybrid laminates were fabricated: unidirectional carbon–woven glass (2UCF–2WGF/EPOXY) and unidirectional carbon–woven jute (2UCF–2WJF/EPOXY). Flexural tests revealed that the carbon–jute composite exhibited higher stiffness with a modulus of 69.12 GPa compared to 19.74 GPa for the carbon–glass system. Conversely, the carbon–glass composite demonstrated greater tensile modulus (5.07 GPa vs. 2.23 GPa) and hardness (37.55 HV vs. 20.37 HV), indicating better load transfer and surface resistance. These differences arise from fiber–matrix adhesion, fracture morphology, and energy absorption mechanisms observed in SEM analyses. The results emphasize that selecting suitable fiber combinations allows control over stiffness and strength balance. Such natural–synthetic hybrid composites present an environmentally sustainable approach for advanced structural and biomedical applications requiring optimized mechanical and functional performance.

Abstract: This study investigates the mechanical properties and microstructure of sintered tungsten under varying sintering conditions. Bending strength tests revealed that sintering at 1400 °C resulted in low flexural strength due to inadequate temperature, whereas sintered tungsten at 1500 °C exhibited improved strength attributed to grain growth. However, temperatures exceeding 1600 °C led to excessive grain growth and a subsequent decline in strength, indicative of grain coarsening and potential localized bonding. Additionally, analysis of holding times at 1500 °C demonstrated that extended durations promoted neck bonding between grains, contributing to the formation of interconnected grains and enhanced mechanical properties. This study underscores the importance of optimizing sintering parameters to control grain growth and achieve desired mechanical properties in sintered tungsten materials.

Abstract: The promotion of green and low-carbon initiatives has spurred the application of lightweight materials in steel/Al car bodies. The development and utilization of large Al alloy die-casting (DCAA) materials and thermo-formed steel plates (TFSS) impose higher demands on joining technologies of the steel/Al dissimilar material. Taking the innovative body with DCAA and TFSP as a case, this paper systematically investigates the principles, characteristics and forming progress of force-self-piercing riveting(FSPR) joining technology for two-layer and three-layer plates with DCAA and TFSP. The types of test samples, the combination of plates and the test methods of mechanical properties are designed. Using the TL4225/C611/CR5 plate combination, the riveting and forming processing, the microstructures and morphologies were studied. Based on it, the methods to achieve high-quality joints were obtained. For the joining of two-layer plates containing DACC and TFSP, better joint forming and higher joint strength can be obtained for the ideal arc gap filling. For the joining of three-layer plates, TFSP will affect the filling effect for the elastic-plastic deformation of the middle layer during the forming. Although the joint can meet the product design, but the strength index is significantly lower than that of the two-layer plates. Based on the relevant data in the course of this experiment, general rules of product design for FSPR joining, such as joining space, flange edge size, plate strength and plate thickness, were analyzed and summarized combining plate characteristics, plate combination, die structure, joining method, joint strength and weld accessibility. The study will provide the technical support for the application of DCAA parts and TFSP in car bodies.

Abstract: Thermal property of carbon fiber-reinforced polymer composites (CRFPs) fabricated through vacuum assisted resin transfer molding method (VARTM) is investigated using Thermo Gravimetric Analysis/Differential Scanning Calorimetry tool. These analysis on laminate composites with three different orientations are carried out at room temperature up to 800°C. Also, mechanical and water absorption behavior of polymeric composites are determined. Among the orientation effect, a longitudinal direction sample including 39 vol. % carbon fiber in epoxy resin indicated that the mass loss in percentage was lower while decomposition temperature was higher than those of others due to higher mechanical strength. These composites revealed the most thermally stable among the others. Further, lower amounts of water absorption rates were obtained at 0^o-orientation, followed by 0/90^o-orientation composites, but no significant variations occurred with these orientations while some variations occurred for 30^o-orientation with increasing the soaking times.

Abstract: Oil palm empty fruit bunches (OPEFB) are wastes from oil palm processing. The objective of this work is to study the effect of composition on the physical, mechanical, and thermal properties of OPEFB epoxy resin biocomposite. Particles of OPEFB (100 mesh) were mixed with epoxy resin with the ratio of OPEFB to epoxy resin 60/40, 70/30, 80/20, and 90/10 (vol.%/vol.%). Biocomposites were produced by a press method at room temperature with 9 tons-load. The physical properties (density, porosity, water absorption, thickness swelling) of the biocomposite were evaluated. The mechanical properties (modulus of rupture and modulus of elasticity) of biocomposite were determined by using a universal testing machine. The thermal gravimetric analyzer (TGA) was used to examine the thermal properties of the biocomposite. The results show that the density of biocomposite is 1.18 g/cm³ for 60 vol.% of OPEFB composition. It decreases significantly as the OPEFB composition increases. For 60 vol.% of OPEFB, the porosity, water absorption, and thickness swelling of biocomposite (after soaking in water for 24 hours) are 11.9%, 10.1%, and 6.5%, respectively. All these values increase significantly with the increase of OPEFB composition. For 60 vol.% of OPEFB, the modulus of rupture (MOR) and modulus of elasticity (MOE) of biocomposite are 2.31 kgf/mm² and 267 kgf/mm², respectively. The values of MOR and MOE decrease significantly with the increase in OPEFB composition. TGA results show that degradation of biocomposites occurs significantly at 350°C for 60 vol.% OPEFB. The degradation temperature reduces as the composition of OPEFB increases. In general, the physical, mechanical, and thermal properties of biocomposites decrease with increasing OPEFB composition. This happens because the bond between the matrix and the particles decreases as the OPEFB composition increases. The maximum OPEFB composition that can be used for particleboard applications is 80 vol.%, which meet the ANSI 208.1-2009 requirements for application as grade M-2 particleboard.

Abstract: The prefabricated welding of double-connected X80M pipeline steel pipes was completed with self-developed welding equipment, and the welding process used was GMAW + SAW. The key points of welding operation are summarized, hoping to guide site construction. After welding, the weld and heat-affected zone structure of the welded joint were observed by scanning electron microscopy, and the mechanical properties such as tensile, bending, impact, hardness, and CTOD of the joint were measured. The test results show that the welding equipment can efficiently complete the prefabrication welding of double-connected pipes of X80M pipeline steel. The welding joint has excellent performance, which meets the requirements of current standards and the performance at different welding positions was uniform. The GMAW+SAW welding process is a beneficial exploration for efficient welding of long-distance pipelines. Besides, the study shows that the accumulation of granular bainite in the weld zone and the existence of internal and external submerged arc welding boundaries will lead to a decrease in the toughness of the welded joint.

Abstract: Carbon nanotube (CNT) is an innovative material with significant potential for a wide range of applications, including but not limited to the development of lightweight composite materials or superconductors. A single CNT demonstrates an exceptional degree of tensile strength. CNTs are commonly employed in a structure of yarn, wherein several CNT strands are arranged and aligned together. CNT yarns, on the other hand, have a lower tensile strength than individual CNTs due to the different parameters of the yarn. This study aimed to investigate the effect of different structural parameters on the mechanical properties of CNT yarn. Sixty CNT yarn models with different structures were simulated with the molecular dynamic (MD) simulation. The varied parameters are the chirality of the CNTs, CNTs’ inner diameter, number of walls, crosslink density, and yarn twist angle. Tensile strength results from the simulations were compared concerning the varied parameters, and their influence on the nominal tensile strength of the CNT yarn was studied. It was found that the parameters for the CNT yarn that yields a higher tensile strength are the armchair type CNT with a small diameter, a large number of walls, crosslink density higher than approximately 1%, and a low twist angle.

Abstract: Mn_1.25Fe_0.65-xSn_xP_0.50Si_0.50 (0, 0.02, 0.04, 0.05, 0.06, 0.08, 0.09, 0.10, 0.20) series compounds were prepared by mechanical alloying and solid-phase sintering, and their mechanical and magnetic properties were studied. The XRD measurement results show that all the compounds crystalize in Fe₂P hexagonal structures, with a space group of P-62m. With the increase in Sn content, the compressive strength is significantly improved, the Curie temperature of the compound gradually decreases, and the nature of magnetic transition is tuned from a weak to strong first-order one, which is confirmed by the increase of thermal hysteresis of the compounds. The maximum magnetic entropy change of the compound increases from 9.3 J/kg·K at x = 0 to 17.2 J/kg·K at x = 0.04 under a magnetic field change of 0 - 3 T.