Papers by Keyword: Mechanical Properties

Abstract: The present study evaluated the mechanical behavior of adobe when incorporating crushed barley straw as a natural stabilizer. Specimens were prepared with three different stabilizer proportions: 0, 1, and 2%. These were used to compare their compressive and flexural strength. The results showed an average 10% increase in compressive strength and a 43% increase in flexural strength in adobes incorporating 2% stabilizer compared to the control units. This increase demonstrates the potential of crushed barley straw to improve the load-bearing capacity and ductility of adobe, thus contributing to the creation of sustainable material for construction in rural areas.

Abstract: The mechanical properties and electrical conductivity of the Al–0.15Fe–0.5Si–0.5Mg–0.2Mn alloy with a Mg/Si ratio of 1 were investigated using optical microscopy, scanning and transmission electron microscopy, tensile testing, Vickers hardness measurements, and specific electrical resistivity measurements. To analyze the electrical conductivity data, the unit % IACS was used, calculated as a percentage relative to the conductivity of annealed copper. The alloy was studied in the as-cast condition, in the deformed condition (following extrusion and drawing), and after heat treatments: HT1 — solution treatment at 530°C and aging at 140°C for 8 hours, and HT2 - solution treatment at 560°C and aging at 175°C for 6 hours. The microstructure of the investigated alloy varied depending on the condition and heat treatment parameters, consisting of an aluminum matrix and strengthening particles with different morphologies and chemical compositions. For rods in the as-cast state, the conductivity was 55% IACS, ultimate tensile strength (UTS) — 150 MPa, and elongation — 14%. After HT1: 51% IACS, UTS — 140 MPa, elongation — 19%. After HT2: 51% IACS, UTS — 195 MPa, elongation — 19%.

Abstract: In this paper, the effects of seawater exposure on the bending and damping properties of fibre-reinforced sandwich structures were investigated experimentally and analytically using the residual property model (RPM). Glass fiber reinforced plastics facesheets with PVC foam core, exposed to seawater exposure until saturation was subjected to flexural and dynamic mechanical analysis tests. Key mechanical properties were used to develop an analytical residual property model. Results indicated that after exposure, while the flexural strength and modulus reduced by 20% and 19% respectively, the storage, loss moduli and tan delta increased by 7%, 20% and 12% respectively. Furthermore, the accuracy of property degradation was demonstrated for the predicted properties, thereby establishing the suitability of RPM as a cost-effective means for material property determination.

Abstract: Cissampelos pareira, locally known as Krueo Ma Noy or Monoi, is a traditional Thai medicinal plant whose leaf mucilage has long been used as an edible gel and dessert ingredient. The mucilage, a natural hydrophilic polymer produced by plant metabolism, possesses film-forming potential that could be useful in pharmaceutical applications. This study aimed to develop and evaluate the mechanical properties of films prepared from dried C. pareira leaf mucilage, with the incorporation of various plasticizers—glycerin (Gly), propylene glycol (PG), polyethylene glycol-400 (PEG-400), and low-protein natural rubber latex (LPNRL)—to enhance film flexibility and usability. The unplasticized mucilage film exhibited a high tensile strength of 15.81 ± 0.58 MPa but was brittle, with low elongation at break recorded at 1.62 ± 0.24 percent. The addition of plasticizers significantly improved film elasticity, increasing elongation to a range of 21.41 to 29.93 percent, while reducing tensile strength to between 6.10 and 10.73 MPa. Among the plasticizers tested, LPNRL showed the most favorable mechanical profile, providing a flexible yet sufficiently strong film structure. These results indicate that C. pareira mucilage, when properly modified, can serve as a sustainable and biodegradable alternative for use in pharmaceutical film formulations, including wound dressings, transdermal systems, or oral thin films.

Abstract: Actuality. The accumulation of damage due to fatigue, plastic deformation, and wear significantly reduces the service life of railway rolled metal products. The development of a fatigue crack to its critical length (main cracks) leads to failure at stress levels much lower than the material's strength limit. In industrial-grade steels, there may be chemical micro-inhomogeneity of the main element—carbon. Objective of the study: To determine the effect of chemical micro-inhomogeneity (carbon content variation of 0.02%) on fatigue failure characteristics (crack growth rate, threshold stress intensity factor, fatigue life, and critical defect size) of railway wheel steels of grades ER7 and ER8 according to EN 13262. Results. Segments of the fatigue crack growth rate (FCGR) diagram were constructed to characterize the development of fatigue cracks. The crack growth rate on the second linear section of the diagram and the critical value of the stress intensity factor at which failure occurs were determined. It was found that on the linear portion, which describes the crack growth process, the indicator values vary slightly (up to 10%), indicating that the crack growth rate differs minimally between these steels. Fatigue life—the number of loading cycles until failure—was also determined, and the critical size of the fatigue crack was calculated. A carbon content fluctuation within 0.02% by mass leads to a reduction in fatigue life by approximately 10% for ER7 steel and about 20% for ER8 steel, and a reduction in the critical crack size by around 8% for ER7 and 18% for ER8. Conclusion. Chemical micro-inhomogeneity with carbon content variation in the range of 0.02% in ER7 and ER8 railway wheel steels leads to a decrease in fatigue life (as determined from specimens with cracks) and in the critical size of the fatigue crack (up to 20%). However, it has only a minor effect (about 10%) on the stable fatigue crack growth rate.

Abstract: Al₂₅Ni₂₅W₂₅Cr₂₀V₅ refractory high entropy alloy (RHEAs) was synthesised by mechanical alloying (MA) and its characterization study and mechanical behaviour of this prepared refractory high entropy alloy was investigated in this research work. After 18 hr of mechanical alloying, fine grained microstructure was obtained and homogeneous distribution of all metal elements was achieved. Crystallite size, lattice strain and phase analysis of prepared RHEAs powders were calculated through X-ray diffraction (XRD) techniques. Morphological study of prepared RHEAs powders was investigated through scanning electron microscopy (SEM). Aluminium, Nickel, Tungsten, Chromium and vanadium elements presented in the prepared RHEAs were identified through Energy dispersive spectrum analysis (EDAX). After milling, powders were compacted and sintered at two temperatures such as 600°C and 800°C. Density, porosity and Vickers micro hardness measurements were taken after sintered at 600°C and 800°C. The results indicate that the sintering environment and conditions will affect the mechanical properties of developed Al₂₅Ni₂₅W₂₅Cr₂₀V₅ refractory high entropy alloy.

Abstract: Preliminary mechanical loading at a temperature close to the ductile-brittle transition temperature leads to stress relaxation near cracks in brittle materials due to local plastic deformation at microcrack tips. As a result, such preloading increases the physical and mechanical properties of ceramic materials when tested at room temperature. In the present work, this phenomenon is investigated for silicon and silicon-based ceramics. A thermomechanical treatment (TMT) method of the mentioned materials has been developed to increase their strength and fracture toughness.

Abstract: The study presents the mechanical performance, particularly energy absorption ability, under uniaxial quasi-static compression of aluminium foams fabricated by melt processing with CaCO₃ blowing agent and B₄C+TiB₂ powder with content varied from 30 to 70%. High-strength Al6Zn2.3Mg alloy comprising brittle eutectic domains was employed for manufacture of the foam. The optimal amount of B₄C + TiB₂ powder was determined to be 50% at which it results in the highest energy absorption. The key role of identity sizes for B₄C + TiB₂ and CaCO₃ powders for the efficiency of the foaming process with the formation of certain particle configurations in the melt was examined and discussed. The results of the present study could be helpful for selecting the aluminium alloy and additives for the foaming process and providing a certain level of the mechanical properties, particularly, energy absorption ability.

Abstract: Phase components of experimental low cost titanium alloys, their substructure and parameters, dislocation structure, features of phase formation in the metal, which differ in alloying systems, were studied using complex research methods. The stoichiometric composition of dispersed phases in the internal volumes of alloy grains was determined by diffraction patterns using transmission electron microscopy. It is shown that in the structure of titanium alloy Ti-2,8Al-5,1Mo-4,9Fe there are dispersed nanoparticles of intermetallic phases of different morphology and stoichiometric composition. These are the phases: Ti₃Al and Fe₂Ti with a size of 10…40 nm; Mo₉Ti₄ - 20…120 nm. Studies of titanium alloy Ti-1,5Fe-O showed the presence in the structure of mainly nanoparticles of oxides: Ti₃O₅ size 10…30 nm and Ti₄Fe₂O, FeTiO₅ (10…90 nm), as well as intermetallics Fe₂Ti (10…40 nm). It is established that the formation of nanoparticles of intermetallic and oxide phases in the thin plate structure of the investigated experimental low cost titanium alloys promotes the formation of the substructure with uniform distribution of dislocation density. This provides a high level of mechanical properties of alloys.

Abstract: Food-grade piping and water transportation systems extensively use dissimilar welding between stainless steel and carbon steel, where cost-effectiveness and corrosion resistance are essential consideration. However, the fusion zone of dissimilar welds often observed microstructural inhomogeneities and hardness changes, thus compromising mechanical qualities and corrosion resistance. This study was seperated in two phases to investigate and optimize dissimilar welding between carbon steel and stainless steel in both plate and pipe applications. Phase 1 studied welding A36 carbon steel plate and A304 stainless steel using gas tungsten arc welding (GTAW) with ER308L filler metal, the effect of post-weld heat treatment (PWHT) holding time on the mechanical and microstructural propertie. PWHT was performed at 650 °C for 20 and 60 minutes. The 20-minute condition yielded an optimal combination of mechanical strength and microstructural refinement, while the 60-minute condition led to grain coarsening and reduced strength. Phase 2 extended the findings to pipe welding applications, adopting the 20-minute PWHT condition. Welding was performed on dissimilar joints between A106-B carbon steel pipe and A312 TP304L stainless steel pipe (2-inch OD) using ER308L and ER309L filler metals under 99.99% argon shielding. Tensile and hardness testing indicated that welds with ER309L offered superior mechanical performance. Microstructural analysis revealed delta-ferrite and stabilized austenite in the fusion zone, with enhanced Cr and Ni concentrations contributing to improved corrosion resistance, as confirmed by electrochemical testing.