Papers by Author: Han Huang

Abstract: Precision grinding of a multilayered thin film solar panel is recognized as the bottleneck in its manufacturing process. A primary challenge is the significantly high stress induced at the thin film interfaces during grinding. Such stress concentration can result in interfacial delamination between two dissimilar materials and thus device malfunction. This study used a finite element modelling analysis to understand the stress evolution of the multilayer thin film structure during a single grit scratching that simulates the individual interaction between abrasive grits and work materials in grinding. The results demonstrated that significant tensile and shear stresses were formed at interfaces during scratching, which could be traced back to the experimental evidence obtained from the nanoscratching process. The maximum stresses undertaken by the interfaces were simulated.

Abstract: Current packaging robots cannot achieve the required speed due to the use of heavy parts. Magnesium alloys with appropriate surface treatment may be used to replace the traditional steel or aluminum parts and therefore to reduce robot arm weight. In this work, different prototype designs were made to examine the feasibility of the application of light alloys for robot arm, in comparison to conventional materials. Finite element modelling (FEM) studies were performed for structural analysis. The results demonstrated that magnesium alloys has advantages over steel or aluminum alloys in terms of the ratio of modulus over density, and the stress and elastic deformation experienced during operation due to arm weight.

Abstract: Application of polycrystalline diamond compact (PDC) based cutting tools for hard rock excavation in mining and construction industries has increased significantly in recent years due to their super hardness, superb thermal conductivity and long life durability. Super Material Abrasive Resistant Tool (SMART*CUT) technology has been developed by CSIRO (Commonwealth Scientific and Industrial Research Organisation) in the last 15 years, which includes the replacement of tungsten carbide (WC) tips of the conventional picks with thermally stable diamond composite (TSDC) tips, attachment of the TSDC tips to steel tool bodies with CSIRO’s worldwide patented bonding technology. The wear characteristics of TSDC cutting elements have been investigated previously. In this paper, the preliminary results of cutter forces and resultant angle of SMART*CUT picks were compared with that of traditional WC picks. A tri-axial force dynamometer and a data acquisition system were used to measure the cutter forces. Besides, the cutting area temperature during cutting process was continuously measured by a FLIR SC7600M thermal infrared camera and the recorded data were processed by Altair Software.

Abstract: This study aimed to investigate the effect of grinding conditions, including depth of cut and grinding direction, on the material removal and surface finish of multilayered thin film structures. It was found that the increase in depth of cut improved the material removal rate, but worsened the ground surface finish. The grinding perpendicular to the thin films caused less damage and produced better surface than that parallel to the films. The characteristics of wheel wear were also studied. Grit pull-out and micro-fracture should be attributed to the wheel wear.

Abstract: The deformation and removal mechanism of a multilayered thin film structure involved in nanoscratching and diamond lapping processes were investigated. The results obtained from the two processes were compared, in terms of deformation characteristics and surface finish. It was found that both nanoscratching and lapping demonstrated similar characteristics. This work provides insight into the deformation and removal of a thin film multilayered structure under mechanical loading, and thus the outcome is of value for developing the efficient machining process for such structures.

Abstract: Three-dimensional molecular dynamics (3D MD) simulation was carried out to investigate the deformation of single crystal gallium arsenide (GaAs) during nanoindentation. Tersoff potential was used to simulate the atomistic interaction under an extremely low load of indentation. The coordination number and atomic displacement were studied and the cross-sectional profiles of the simulated indent were examined. The simulation results revealed that the lattice deformation of GaAs was influenced by polarity, showing distinct patterns on different crystalline planes. Slip band and dislocation were found to be the dominant deformation phenomena.

Abstract: The short life due to heavy wear is a bottleneck that limits the usage of mechanical excavators for hard rock cutting. Thermally stable diamond composite (TSDC) tipped cutting tools have the main advantages of good thermal stability, high wear resistance and ability to mine harder deposit compared to the conventional tungsten carbide (WC) tipped cutting tools. Super Material Abrasive Resistant Tool (SMART*CUT) based on TSDC tip has been developed by CSIRO to improve the effectiveness of cutting tools when dealing with hard deposit in mining and civil industries. In this study, the effects of attack angle and depth of cut on the cutting performance of SMART*CUT picks in different cutting orientations were investigated. A tri-axial dynamometer and a data acquisition system were used to measure the cutter forces. Normal force, cutting force and resultant angle were correlated with depth of cut and attack angle. Cutting performances were compared in different cutting orientations. The results would be beneficial to the selection of mechanical excavator motor and the optimization of cutting drum design to some extent.

Abstract: Tungsten based products are extensively used in engineering practices. However, there exist some controversies in deformation behaviour between polycrystalline tungsten and its bulk counterpart. In this work, elastic modulus, hardness and removal characteristics of polycrystalline tungsten (poly-W) were investigated by use of nanoindentation and nanoscratch. Atomic Force microscopy (AFM) and Scanning Electron Microscopy (SEM) were employed to characterize the surfaces prior to and after indenting/scratching. The elastic modulus and hardness of the poly-W obtained were 323.6 and 7.1 GPa, respectively. Elastic recovery was barely observed in poly-W after indenting and scratching, indicating that the material was dominantly deformed in plastic regime. The plastic deformation of the poly-W was found to be somehow different from the bulk W, but similar to that of single crystal W nanowhiskers. In multi-scratch test, the pitch distance and scratching speed demonstrated to affect the roughness of the scratched surfaces.

Abstract: t is challenging to achieve good surface quality and high efficiency simultaneously when machining thin film solar panels. In this study the machining characteristics of a multilayered thin film structure were investigated using diamond wire sawing and grinding. It was found that the efficiency in sawing was significantly greater than that of the employed grinding process, but the machined surface quality was much worse. The results indicated that grinding could still be the solution for such processing and sawing must be improved before this technology could be further progressed for machining thin film multilayered structures.

Abstract: The failure characteristics of silicon nitride thin film deposited on GaAs substrate were investigated by use of nanoscratch. It was found that the film started to failvia delamination or buckling, which should beattributed to interfacial shear stress. The cracks were then formed and propagated around the edge of the delaminated film before it was chipped away by the moving tip. A normal load of 6.5 mN, corresponding to a depth of 150 nm, was found to be the critical threshold for theinterfacial failure. The fracture energy release rateof the film/substrate interface, or the work of adhesion, was calculated as 2.90 J/m2.