Materials Science Forum Vol. 1173

Abstract: This research focuses on formability analysis of the complex S-rail drawing parts made out of the 1-mm thick DP590 and DP780 advanced high-strength steel sheets. Developing formability evaluation tools across an extensive breadth of deformation states begins with the acquirement of principal fracture strains at varying strain ratios. Two simple tensile tests on two different sophisticatedly designed butterfly specimens are carried out to obtain fracture strains on the pure-shear state and the state in between the pure shear and uniaxial tension. Meanwhile, for the strain states from the uniaxial to the balanced biaxial tension, the stretching test with a hemispherical punch are conducted on Nakajima samples with five varying widths. Based on those strain data, a fracture forming limit curve (FFLC), a fracture forming limit stress curve (FFLSC) and two fracture loci (FLs) based on the Lou-Huh (LH) and Hosford-Coulomb (HC) ductile fracture criteria (DFCs) are settled for both steels. All fracture criteria are experimentally and simulatively verified against strain or stress paths extracted from the fracture area of the deep-drawn DP590 and DP780 S-rail parts. Both strain-based FFLCs unfortunately do not sense part failure. In contrast, the FFLSCs, LH-FLs and HC-FLs, counting on the anisotropic Hill’48 yield criterion and hybrid Swift-Voce strain hardening law, well capture the fracture moment of both deep-drawn DP590 and DP780 S-rail parts. By the way, the DP780 LH-FL debatably has the edge over the DP780 HC-FL. This study confirms the need for inclusion of such deformation behaviors as anisotropy and strain hardening into sheet formability investigation of complex parts.

Abstract: Selective Laser Melting (SLM) is a promising technique for fabricating intricate metal components. The scanning strategy is a critical parameter that can be optimized to improve the quality of the final parts, as different strategies produce temperature distribution variations. It can impact on the melt pool dynamics and the mechanical properties of the fabricated components. In this study, four scanning strategies were investigated: uni-directional scanning, altered-sequence uni-directional scanning, bi-directional scanning, and altered-sequence bi-directional scanning. Their effects on localized temperature distribution, melt pool morphology, and surface roughness (Ra) during the SLM process of Ti-6Al-4V across five tracks were evaluated using numerical simulation. The simulations were performed using FLOW-3D AM. This simulation integrates the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) model. The simulation results demonstrated that the scanning sequence and scanning direction directly effects on the localized temperature distribution. Heat accumulation is more diffusely distributed over the last three scanned tracks in bi-directional scanning and altered sequences of bi-directional scanning. The scanning sequence significantly affects melt pool depth. A symmetric depth profiles of the five tracks were formed at altered sequences of uni-directional scanning and altered sequences of bi-directional scanning cases. Conversely, the left-skewed profiles, where melt pool depth gradually increases with each additional track, peaking at the last one, were generated at uni-directional scanning and bi-directional scanning cases. This trend is primarily attributed to heat accumulation from preceding solidified tracks. In addition, both scanning direction and scanning sequence are significantly impact on the surface roughness by changing from uni-directional scanning to bi-directional scanning showed 27.38% of Ra reduction and changing from uni-directional scanning to altered sequences of uni-directional showed 14.29% of Ra reduction.

Abstract: The current research aimed to study microstructure evolution and wear resistance properties of coating layers on R900A rail steel. Powdery type laser cladding was carried out employing a three-jet coaxial laser nozzle by using the 3650 (Chromium-Nickel steel) powder. The key laser cladding parameters included a laser power of 1 - 1.5 kW, a scanning speed of 5 - 15 mm/s, and a powder feed rate of 10 – 20 g/min. After laser cladding completion, the coated specimens were carried out into the pin-on-disc tribometer for abrasive wear resistance evaluation compared to the reference rail material. The specimens were weighed before and after the wear test by an electronic balance with 0.0001g resolution. The hardness test and microstructure evolution were performed on the cross-sectional area of the specimen. After the wear test, the worn surface profile and wear morphology of the tested specimen were evaluated to determine the wear mechanism and severity. The hardness test shows that the 3650 had a higher hardness than the conventional rail steel. The microstructure of coating surfaces was composed of various carbide compounds such as Cr₂₃C₆ and Cr₇C₃, which are distributed in the austenite matrix. Moreover, the 3650 cladding surface provided greater wear resistance than rail steel and not much difference in hardness, which is suitable for rail maintenance in a realistic situation.

Abstract: Die deformation has long been suspected to cause bad damages that are challenging to recover and have a straight impact on the quality of the final product. The forming industry would greatly be benefited if this mystery is faithfully uncovered. This study tries to investigate the effect of die deformation on the geometrical quality of the workpiece in terms of springback through finite element simulation. The forming process of a 1-m-long car chassis component made out of the HR420LA hot-rolled high-strength low alloy steel sheet with a thickness of 3 mm is particularly picked out to be examined. Therein, the mechanical properties of the steel sheet are neatly characterized through a group of uniaxial tensile tests. The two similar r-based Hill48 criteria are used to model the yield behavior of the steel sheet. The hybrid Ludwig-Voce strain hardening law is applied to account for the hardening during plastic deformation. The simulation results show that die deformation has a very limited effect on part springback as the evaluated dies are fairly rigid and hence deform very little by less than 0.25 mm. The effect of yield model variation is even negligible on part springback as the two chosen models are closely connected. Taking die deformation into consideration when designing new dies is unnecessary if the anticipated degree of deformation is not large enough.

Abstract: This research explored the synthesis of hydrogels from acrylamide-grafted durian rind cellulose using a microwave-assisted method. The objective of this research was to investigate the effect of cellulose preparation and duration of microwave irradiation on the swelling properties of the obtained bead hydrogel. The mixture of cellulose, acrylamide solution, and potassium peroxydisulfate as the initiator agent was irradiated by microwave at 640 W. FTIR analysis showed that acrylamide was grafted into durian rind cellulose successfully. This study found that bead gels from durian rind cellulose, which underwent delignification and bleaching methods, exhibited a greater swelling capacity (855%) after 180 minutes than bead gels from durian rind cellulose without these methods (807%). The optimum microwave irradiation time was found to be 540 s, resulting in a maximum swelling capacity of 676%.

Abstract: This research prepared a bead gel based on acrylamide grafted sugarcane bagasse cellulose and carrageenan mixture. The effect of the weight ratio of sugarcane bagasse cellulose-acrylamide (SCB-AA) on bead gel swelling degree was studied. Acrylamide-grafted cellulose was prepared by microwave-assisted polymerization with potassium peroxydisulfate (KPS) as an initiator. Successful grafting of acrylamide onto the cellulose backbone of bagasse was confirmed through FTIR analysis. A suitable absorption kinetics model based on the result of swelling was also studied. The highest swelling degree was obtained at an SCB-AA ratio of 1:10 (w/w) in a water medium of 621.17% and a 0.1 M NaCl solution of 652.38%. Based on swelling tests carried out on water media and NaCl solution, the highest degree of swelling was obtained in water with a ratio of 1:5 (w/w), reaching 405.61%, 1:10 (w/w), reaching 621.17%, and 1:15 (w/w), reaching 558.63%. Meanwhile, in the NaCl solution at a ratio of 1:5 (w/w), the concentration reaches 308.22%. At a ratio of 1:10 (w/w), the concentration reaches 652.38%, and at a ratio of 1:15 (w/w), it reaches 453.41%. The second-order kinetic model accurately describes the swelling behavior of SCB-AA hydrogel synthesized using microwave irradiation, as tested in both water and NaCl media.

Abstract: Outdoor activities that are inevitable can harm our facial skin, namely, the signs of premature aging. A gel peel-off mask (GPM) is a popular facial skin care treatment that can alleviate these symptoms. This study investigated the influence of polyvinyl alcohol (PVA) and microcrystalline bacterial cellulose (MCBC) concentrations on the gel peel-off mask's features, including organoleptic properties, pH, viscosity, adhesion power, and drying time. The GPM formula contains carboxymethyl cellulose, glycerol, propylene glycol, PVA, and MCBC. The PVA content ranges from 7 to 15%, and the MCBC concentration ranges from 0 to 15%. Furthermore, a test was conducted to assess the potency of MCBC as a delivery agent for the active substance (vitamin C) from the product to the facial skin during skincare application. The experiment revealed that the best product was obtained at a PVA concentration of 13% and MCBC of 10%. Applying a 10% MCBC component can provide active vitamin C to the facial skin with an 85% efficacy. Additionally, respondents completed a product acceptability test. Based on the findings, the usage of MCBC components in gel peel or mask products has the potential to be a commercially viable product. However, research on GPM formula optimization is required for optimal use.

Abstract: The goal of this study is to employ an optimization algorithm to estimate the unknown electrical parameters of equivalent cell circuit of photovoltaic (PV) modules. To estimate the other parameters of the five-parameter model, the suggested approach combines numerical computations with an iterative adjustment of the shunt resistance (R_sh). Under standard test conditions (STC), a series of equations must be solved using the parameters provided in the manufacturer's data sheet. The goal of the parameter extraction criterion is to minimize the discrepancy between the power supplied by the data sheet at the maximum power point (MPP) and the simulated power.Two different solar module types monocrystalline silicon (Mono-Si) and polycrystalline silicon (Poly-Si) representing different technologies are examined in order to verify the efficacy of the suggested approach. Simulated findings are compared with characteristics taken from manufacturers' data sheets and those obtained from methods already in use in the literature, using the Relative Error as statistical criteria to assess the validity of the proposed method, the finding results are compared with the articles “A new method to extract the equivalent circuit parameters of a photovoltaic panel”[1] and “A simple iterative method to determine the electrical parameters of photovoltaic cell”[2], in addition to manufacturer data. The proposed method presents an optimum compromise between simplicity and efficiency, outperforming conventional techniques described in the literature and offering competitive performance compared with those presented in the articles by Chaibi et al.

Abstract: Thallium-doped sodium iodide NaI(Tl) is one of the major scintillators that have been used for radiation detection. In this study, 2"x1.5" cylindrical NaI(Tl) detector was modelled using Monte Carlo simulation code GEANT4 in order to reproduce experimental results using standard point-like gamma sources (⁶⁰Co, ²²Na, ¹³⁷Cs) emitting mono-energetic gammas in the photon energy range 511-1332.5 keV. The modelled NaI(Tl) detector has been used to calculate the absolute and intrinsic efficiencies, as well as the mass attenuation coefficients for three different absorbers: lead (Pb), aluminum (Al), and copper (Cu) at various energies and thicknesses. The experimental and simulated data showed good agreement with a correlation coefficient (R²) of 0.9522 and a mean absolute error (MAE) of 2.03%, confirming the robustness of the simulation models implemented in the GEANT4 simulation toolkit and validate its use for accurately modeling the performance of NaI(Tl) detectors. The findings provide a reliable framework for extending the application of GEANT4 simulations in nuclear instrumentation, radiation protection, and medical physics.