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Nano-level mechanical and tribological behavior of additively manufactured AlSi10Mg plates

Murugesan Periyakaruppan, Satheeshkumar V., Jeyaprakash N., Prabu G., Yang Che-Hua

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e62, 2023

EN

This work focuses on the study of the selective laser melting (SLM) fabrication parameter of AlSi10Mg specimen. SLM parameters such as Power and scanning speed are varied to identify the defect-free samples. In addition, X-ray diffraction (XRD) analysis is carried out on the AM AlSi10Mg specimen to study the presence of phase. The results reveal that the Al matrix possesses (200), (220) and (311) phases whereas the AlSil0Mg powder has (111), (200), (220) and (311) phases. The microstructural characterization based on FESEM, TEM and EBSD analysis is carried out. The cross-section of the molten pool appears as a semi-cylindrical shape in the section that is parallel to the plane of powder deposition. The height, width and depth of the molten pool are measured as 150 ± 10 μm, 450 ± 10 μm and 50 ± 10 μm, respectively. TEM analysis reveals that the Si-precipitate and the eutectic Si element of the AM AlSi10Mg specimen are clearly formed in the AM AlSi10Mg specimen. Si precipitate spread within the grains whereas, the eutectic Si element is present at the grain boundary of the specimen. Then, the nanohardness and nanowear behavior are analyzed. Further, the influence of strain rate on the tensile strength is investigated. These mechanical tests are carried out on the defect-free AM AlSi10Mg specimen to assess its maximum performance. Very rough as well as irregular fracture surfaces are observed in the tensile test AM AlSi10Mg specimen. In addition to it, its magnified image reveals that the specimen fracture in the form of river patterns and contains a lot of micron-sized pores throughout the fracture surfaces.

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Study of influence of periodic defects on the propagation of wedge waves using laser ultrasound technique and finite element analysis

Yang Che-Hua, Jeyaprakash N., Fang Chi-Chong

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e74, 1--19

EN

Wedge wave is a kind of elastic wave propagation along the tip of a wedge. In this study, a brass wedge with an apex angle of 60° was used as the substrate test piece and periodic defects were designed at the wedge tips. Laser ultrasonic technique and finite element analysis were used to investigate the influence of periodic defects at the wedge tip. The influence of different periodic defect parameter changes on the guided wave of the wedge body was studied. After obtaining the time-domain signal of the experiment and numerical analysis, the result was compared with the signal processing of Fast Fourier Transform. Result showed that the frequency domain signals would be effected by periodic defects on wedge tips, basic frequency would be downgraded by increase in defect width or increase in number of defects. But, the results did not reflect on the frequency channel phenomenon of phononic crystals. The wedge guided wave passing through three periodic defects and four periodic defects showed an error percentage of 1.4–2.9, which confirm the convergence of the results. The experimental measurement agreed well with the finite element simulation results. The results of this study can be applied to estimate the defect width and penetration wave.

3

Nondestructive characterization of elastic modulus of APS Ni–5Al/10hBN coating on stainless steel 304 under high temperature

Yeh Cheng‑Hung, Jeyaprakash N., Yang Che-Hua

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

116--130

EN

The failure mechanisms of coatings, under high thermo-mechanical loads, can be examined through finite element simulations. However, mechanical properties such as Young’s modulus and Poisson’s ratio are necessary to achieve an accurate model. In this study, nickel–aluminum with hexagonal boron nitride (NiAl/hBN) is deposited on stainless steel 304 substrate using atmospheric plasma spray technique. The effect of the hydrogen content in the plasma-formed gas on the microstructure, hardness, and porosity of the deposited layers is examined. Also, the mechanical properties of the coating are measured at ambient temperatures using non-contact laser ultrasound technique. Results indicated that the flow rate of hydrogen has a major impact on the coating structure and elastic properties. The inhomogeneity in the coating can be minimized by decreasing the hydrogen flow rate. The coating Young’s modulus was increased at room temperature, which slowly decreased while increase in atmospheric temperature. The behavior of Young’s modulus at high temperature causes decrease in flexural strength. In addition, the back calculations are well agreed with experimental results.

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Comparative study of laser melting and pre‑placed Ni–20% Cr alloying over nodular iron surface

Jeyaprakash N., Yang Che-Hua, Duraiselvam Muthukannan, Sivasankaran S.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 1

282--293

EN

In this study, two techniques such as laser surface melting (LSM) and laser surface alloying (LSA) were performed to protect the surface layers of nodular cast iron as it is used to manufacture different machine parts like cams, beds, camshafts, crankshafts, cylinders and engine blocks. The main objective of this research work is to examine the effects of LSM and LSA processes on phases, microstructure, hardness, wear resistance and surface roughness. The outcomes of both LSM and LSA specimens show a homogeneous structure, effective bonding of alloy powders with the base metal and crack-free surfaces. The hardness was improved 4 times (LSM) and 2.62 times (LSA) when compared with the base material. The tribological test shows improved wear resistance of LSM (8.82 × 10−7 kN) and LSA (1.32 × 10−6 kN) samples compared to the base material (4.36 × 10−6 kN). The examined wear tracks indicate that mild abrasion, adhesion and delamination were the major wear mechanisms. The reason for the enhancement of wear resistance is the refinement of microstructure, the solid solution strengthening effect and good bonding between alloy powders and base material. The LSM technique is a potential method to improve the tribological properties of industrial materials.