Frontiers in Materials Science and Technology

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Authors: Xiao Ming Zhang, Zheng Yi Jiang, Hei Jie Li, Z. Fan, Xiang Hua Liu, Guo Dong Wang
Abstract: In twin-roll strip casting process, the temperature variation of casting roll can result in roll thermal stress and fatigue. It not only affects the thermal deformation of casting roll and the generation of the roll surface cracks significantly, but also influences the surface quality, shape and profile of the produced strip, and the service life of the casting roll. In this paper, a 3D coupling thermal-flow finite element modelling has been conducted. For twin-roll casting of stainless steel, the influences of the casting speed and liquid level in molten pool on the temperature field of casting roll have been simulated and discussed. The developed model is very helpful in optimising the processing parameters and the design of casting roll during twin-roll thin strip casting.
169
Authors: Zhong Xiao Peng, Steven Tomovich
Abstract: Quantitative surface measurement is an important field in many applications including materials science and engineering quality control. A non-destructive and versatile technique for quantifying surface roughness in 3D is Confocal Laser Scanning Microscopy (CLSM). However, this technique has not been widely accepted to use for quantitative surface measurements due to limited work on it. The project has researched the suitability of using the system for surface characterization and appropriate settings for image acquisition for quantitative surface analysis. Based on the above fundamental work, this study has developed and presented a comprehensive approach of using the system for quantitative surface characterization through image processing, 3D image construction, image stitching and numerical image analysis. The surface characterization results presented in the paper have demonstrated that the system can be used to accurately measure surface roughness of engineering surfaces.
173
Authors: Header Haddad, Syed H. Masood, Abul B.M. Saifullah
Abstract: Design of gate location is a crucial factor in achieving product quality in injection moulding. It Influences the manner of plastic flow into the cavity. The optimum gate location improves quality and avoids products defects. This paper presents an investigation for the effects of gate location on product quality in injection moulding. Plastic advisor, simulation software embedded in Pro/Engineer package has been used for flow analysis of plastic product for selected gate locations. It has been shown that optimum gate location improves cooling quality resulting in a better product quality. The previous conventional experiences by individual credited engineers have been considered.
181
Authors: Dong Bin Wei, Zheng Yi Jiang, Cheng Lu, Ying De Tang, A. Kiet Tieu
Abstract: It was impossible to obtain the transverse friction along the strip width in most previous studies of cold strip rolling because the surface roughness lays were assumed to be vertical to the rolling direction. In this study, several types of oblique roughness textures were manufactured on aluminum samples and compression tests were carried out to obtain the effect of different textures on the deformation behavior of surface asperity. Different surface textures resulted in very different peak value of stress. It was found that stress was high and changed dramatically at the initial compression stage but tended to be stable when the total reduction increased. The asperity of which the top angle is 160° showed relatively high resistance to deformation.
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Authors: Chaiy Rungsiyakull, Qing Li, Wei Li, Richard Appleyard, Michael Swain
Abstract: This paper provides a preliminary understanding in biomechanics with respect to a fullyporous- coated (FPC) dental implant. A 2D multiscale finite element model is created for a typical dental implantation setting. Under a certain mastication force (<200N), a global response is first obtained from a macro-scale model (without coated surface morphology details), and then it is transferred to a micro-scale model (with coated surface morphology details), which allows determining a local biomechanical field. To facilitate the study in bone remodelling, strain energy density and equivalent strain are analysed respectively. Different porosities of coating are taken into account in this study to investigate the effect of FPC materials on these typical remodelling stimuli. The results evidently reflect the osseointegrative benefits generated from surface coating. The result reveals that increasing in particle sizes has significant effect on biomechanical response.
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Authors: Manoj Khanal, Ying Zheng, Zeng Tao Chen
Abstract: Effects of cement properties on stress distributions at the dentin-cement-post interfaces have been studied using 3D explicit finite element simulations. The mastication and horizontal loadings are simulated with titanium and glass fiber posts. Different type of cements (moduli 2,8,18 and 22 GPa) is considered to study the interface stresses. The interface stresses are evaluated at dentin-cement-post interfaces and along the surface of the post and cement. The element deletion technique from finite element analysis has been used to predict the cement failure. The simulation results suggest that the cement with similar modulus as dentin is preferable to avoid the stress concentration at the dentin-cement interface. The types of cement do not affect the failure initiation location on the cement. Under the simulated conditions, the failure initiation is located at 1.7 to 2.2 mm from the post apex.
193
Authors: Hung Kha, Sigrid Tuble, Shankar Kalyanasundaram, Richard E. Williamson
Abstract: Illuminating fundamental aspects of plant cell wall mechanics will lead to novel biological and engineering inspired strategies for application in the cotton and wood fiber industries and in developing novel plant-derived materials that are increasingly seen as environmentally friendly alternatives. The stiffness properties of cell wall polymers such as cellulose microfibrils and xyloglucans are known but the relationship between the composite structure of the wall and its effective stiffness remains poorly understood. Understanding this relationship is important to engineers using and designing plant-derived materials and to biologists studying plant growth. We have developed a software system to generate microfibril-xyloglucan networks resembling those found in cell walls. Finite element analysis was implemented to predict the effective Young’s modulus of varying sizes of the microfibril-xyloglucan network. Results from the finite element models show that the network’s effective moduli of the cell walls having microfibrils parallel to applied loadings are relatively high (~90-215MPa) compared with those of the walls having randomly oriented microfibrils (~20-47MPa). The walls having microfibrils parallel to each other but perpendicular to applied loadings have lowest stiffness (~17-118kPa). The Young’s moduli are significantly lower than those of its constituent polymers and generally in agreement with experimentally measured values.
197
Authors: Xiao Fei Song, Ling Yin
Abstract: Failure rate is noticeably high in dental bioceramics for restorations even though progress has been made in reinforcement of the materials. One of the major causes of failures is due to surface and subsurface damage induced in intraoral adjustments. This process is a routine clinical procedure for marginal and occlusal fit using high-speed dental handpieces and diamond burs. Material removal using the diamond burs easily produce surface and subsurface damage in ceramic prostheses. Therefore, it is essential to minimize the surface damage in clinical dentistry. In this paper, we investigated the effect of diamond burs with coarse, medium and fine grit sizes on the degrees of subsurface damage in in vitro dental adjustments via numerical modeling. Finite element analysis was applied to model the dental adjusting processes and to predict the degrees of subsurface damage using different grit sizes of diamond burs.
203
Authors: H. Wang, Zhi Ming Shi, K. Yang
Abstract: Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium alloys have been highly considered as Mg has a high biocorrosion potential and is essential to bodies. In this study, corrosion behaviour of pure magnesium and magnesium alloy AZ31 in both static and dynamic physiological conditions (Hank’s solution) has been investigated. It is found that the materials degrade fast at beginning, then stabilize after 5 days of immersion. High purity in the materials reduces the corrosion rate while the dynamic condition accelerates the degradation process. In order to slow down the degradation process to meet the requirement for their bio-applications, an anodized coating is applied and is proved as effective in controlling the biodegradation rate.
207
Authors: X. Miao
Abstract: Porous biomaterials including porous bioceramics play important roles for hard tissue replacement and regeneration. I this paper, porous alumina (with and without zirconia addition) ceramics were produced via coating polyurethane (PU) foams with Al2O3 (ZrO2) slurries, followed by drying at room temperature and sintering at 1300 oC. The advantage of the PU foam method was the achieved high pore interconnectivity, but the mechanical properties of the porous ceramics were rather poor due to the high macroporosity and the high microporosity. To remove the microporosity and strengthen the porous alumina ceramics, a lanthanum-modified aluminosilicate (LAS) glass was used to infiltrate the alumina struts. Nevertheless, the resulting LAS-modified macroporous alumina ceramics would have no ability to bond to bone tissues. To impart a bioactivity (i.e. the ability of bone bonding) to the bioinert porous ceramics, a bioactive glass layer was applied by dipping with the bioactive glass slurry and sintering at 1200 oC. The twice coated porous alumina ceramics would exhibit high compressive strengths, allow bone tissue ingrowth, and form strong bonematerial integration. A biodegradable filler – calcium phosphate cement was also incorporated. A possible application of the porous bioceramics would be for the maxillofacial reconstruction.
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