Puteri Sri Melor Binti Megat Yusoff

Investigation of Rheological Behavior of Low Pressure Injection Molded Stainless Steel Feedstocks

The purpose of this research is to investigate the influence of different powder loadings of 316L stainless steel (SS) powders on rheological behavior of feedstocks required for low pressure powder injection molding (L-PIM) process. The main idea consists in development of various formulations by varying 316L SS powder contents in feedstocks and evaluating the temperature sensitivity of feedstock via flow behavior index and activation energy. For this purpose, the irregular shape, spherical shape, and combination of both shapes and sizes (bimodal approach) of 316L SS powders are compounded with wax based composite binder. Moreover, the influence of elemental nanosized boron (B) addition (up to 1.5 wt.%) on rheological properties of irregular shape 316L SS powders is also evaluated using capillary rheometer method. It is observed that rheological parameters for solid powder loading of powder gas atomized (PGA) and bimodal powder P25/75 316L SS underwent sudden change from PGA-69 vol.% to PGA-72 vol.% and P25/75-67 vol.% to P25/75 316L SS 70 vol.%, respectively. Thus it is concluded that PGA-69 vol.% and P25/75-67 vol.% are optimal powder solid loadings corresponding to the lowest values of activation energies.

Effect of Environmental Degradation on Mechanical Properties of Kenaf/Polyethylene Terephthalate Fiber Reinforced Polyoxymethylene Hybrid Composite

The main objective of this research is to investigate the effect of environmental degradation on the mechanical properties of kenaf/PET fiber reinforced POM hybrid composite. Kenaf and PET fibers were selected as reinforcements because of their good mechanical properties and resistance to photodegradation. The test samples were produced by compression molding. The samples were exposed to moisture, water spray, and ultraviolet penetration in an accelerated weathering chamber for 672 hours. The tensile strength of the long fiber POM/kenaf (80/20) composite dropped by 50% from 127.8 to 64.8 MPa while that of the hybrid composite dropped by only 2% from 73.8 to 72.5 MPa. This suggests that the hybrid composite had higher resistance to tensile strength than the POM/kenaf composite. Similarly, the results of flexural and impact strengths also revealed that the hybrid composite showed less degradation compared to the kenaf fiber composite. The results of the investigation revealed that the hybrid composite had better retention of mechanical properties than that of the kenaf fiber composites and may be suitable for outdoor application in the automotive industry.

Meshless local B-spline-FD method and its application for 2D heat conduction problems with spatially varying thermal conductivity

Abstract In this paper, a new class of meshless methods based on local collocation and B-spline basis functions is presented for solving elliptic problems. The proposed approach is called as meshless local B-spline basis functions based finite difference (local B-FD) method. The method was straightforward to develop and program as it was truly meshless. Only scattered nodal distribution was required hence avoiding at all mesh connectivity for field variable approximation and integration. In the method, any governing equations were discretized by B-spline approximation in the spirit of FD technique using local B-spline collocation i.e. any derivative at a point or node was stated as neighboring nodal values based on the B-spline interpolants. In addition, as B-spline basis functions pose favorable properties such as (i) easy to construct to any arbitrary order/degree, (ii) have partition of unity property, and (iii) can be easily designed to pose the Kronecker delta property, the shape function construction as well as the imposition of boundary conditions can be incorporated efficiently in the present method. The applicability and capability of the present local B-FD method were demonstrated through several heat conduction problems with heat generation and spatially varying conductivity.

Neural networks with NARX structure for material lifetime assessment application

In the present paper, neural networks (NN) with non-linear auto-regressive exogenous inputs (NARX) structure is developed and further applied for material lifetime assessment application. Rational of the use of the NARX structure in the application was emphasized and linked to the concept of constant life diagram (CLD), the well known concept in fatigue of material analysis and design. Fatigue life assessment was then performed and realized as one-step ahead prediction with respect to each stress level corresponding to stress ratio values arranged in such a way that transition took place from a fatigue region to another one in the CLD. As a result, material lifetime assessment can be fashioned for a wide spectrum of loading in an efficient manner. The simulation results for different materials and loading situations are presented and discussed.

Influence of Recycling Frequency on Mechanical and Physical Properties of Kenaf Fiber Reinforced Polyoxymethylene Composite

ABSTRACT The main objective of this research is to investigate the effect of compression cycles and hybridization on mechanical and physical properties of kenaf fiber reinforced POM composite. In this study, kenaf, and polyethylene terephthalate (PET) fiber were used as reinforcements due to their excellent mechanical properties and resistance to thermal degradation during recycling process. The matrix used was polyoxymethylene (POM) copolymer due to its hydrophobic characteristics and good mechanical properties. In this investigation, two formulations namely POM/kenaf, and POM/kenaf/PET hybrid composite were carefully studied. The results of the investigation revealed that the tensile strength of both POM/kenaf, and POM/kenaf/PET after first recycling process dropped by approximately 83% and 67%, respectively. The tensile strength remained consistent after second and third compression cycle. The flexural strength of both composites also dropped by nearly 50% and 53%, but remained consistent after second and third compression cycle. However, the composite resistance to water absorption significantly increased due to less voids and micro-cracks observed after recycling process. The results obtained have shown that the recycled composites retained their mechanical properties after the last two compression cycles.

Synergistic Effects of Titanium Dioxide and Zinc Borate on Thermal Degradation and Water Resistance of Epoxy Based Intumescent Fire Retardant Coatings

Abstract. This studies discuss the synergistic effects of titanium dioxide (TiO2) and zinc borate on thermal stability and water resistance of intumescent fire retardant coatings. TiO2 in association with a traditional intumescent flame retardant system which contains ammonium polyphosphate/expandable graphite/melamine/ zinc borate (APP–EG–MEL-ZB) was introduced to epoxy based coatings to improve the fire resistance. The influences of TiO2 on the properties of the coatings were investigated in detail by using Bunsen burner fire test, thermogravimetric analysis (TGA), scanning electron microscope (SEM) and water immersion test. Bunsen burner test revealed that incorporation of titanium dioxide in intumescent formulation reduced the steel substrate temperature from 240 °C to 116 °C. The TGA results proved that addition of TiO2 could enhance the anti-oxidation of the char layers and increase the residue weights of the coatings. The FESEM images demonstrated that addition of TiO2 could improve the foam structure of the char residue. Sea water resistance test demonstrated that the optimum mass % age of TiO2 (6%) exhibited great synergism with natural anti-corrosion agent, zinc borate, and improved corrosion resistance performance of intumescent coating formulations.

Meshless Local B-Spline Basis Functions-FD Method and its Application for Heat Conduction Problem with Spatially Varying Heat Generation

In this paper, a new meshless local B-spline basis functions-finite difference (FD) method is presented for two-dimensional heat conduction problem with spatially varying heat generation. In the method, governing equations are discretized by B-spline approximation in the spirit of FD technique using local B-spline collocation. The key aspect of the method is that any derivative at a point or node is stated as neighbouring nodal values based on the B-spline interpolants. Compared with mesh-based method such as FEM the method is simple and efficient to program. In addition, as the method poses the Kronecker delta property, the imposition of boundary conditions is also easy and straightforward. Moreover, it poses no difficulties in dealing with arbitrary complex domains. Heat conduction problem in complex geometry is presented to demonstrate the accuracy and efficiency of the present method.