Materials Science Forum Vol. 975

Abstract: Rebound hammer tests are one of the most popular non-destructive testing methods to examine the concrete compressive strength in the field. Rebound hammer tests are relatively easy to conduct and low cost. More importantly, it will not cause damage to the existing structure and can obtain the results in a short time. However, concrete compressive strength estimations provided by rebound hammer tests have an average of around 20% mean absolute percentage error (MAPE) when comparing to the results from destructive tests. This research proposes an alternative approach to estimate the concrete compressive strengths using the rebound hammer test data. The alternative approach is to adopt the Artificial Neural Fuzzy Inference Systems, ANFIS, to develop an AI-based prediction model for the rebound hammer tests. A total of 100 rebound hammer tests are conducted in a 24-story residential building. Core samples are carefully taken to obtain the actual compressive tests. The data collected are used to train and validate the ANFIS prediction model. The results show that the proposed ANFIS model has successfully reduced the MAPE to 10.01%.

Abstract: Innovations were conducted continuously to create sustainable asphalt modifier. In this research it is focused on the investigation work of the asphalt binder modified properties with different percentages of one different micro material. This material is Parit Nipah Peat. The investigation is about the physical properties of asphalt binders modified with Parit Nipah Peat PNpt.M.A. PNpt leads to make a lot of changes in internal and external of the samples that checked via penetration test, ductility test, and Scanning Electron Microscopic. The Parit Nipah Peat was added to the original binder with a high shear blender then used at 1500 rpm to mix the PNpt with the binder. Three (3) different percentages were mixed by weight of binder to modify the asphalt binder with the binder at 0, 3%, 5% and 7%. This material has a high ability to distribution with asphalt, appears to be plain and homogeneous and different structure after blended with bitumen. The physical property of modified binders enhanced the binder properties, as the results of penetration test, ductility test and distribution inside the binder showed that. Adding a different concentration of PNpt to base binder had significant effects of high resistant changing volume and increased hardness.

Abstract: Constitutive models for soils are usually adopted in numerical method to analyze the behavior of geotechnical structures. This study performs a series of consolidated-undrained triaxial tests to establish the stress-strain curve of clay. A constitutive model that considers continuous strain hardening-softening is proposed based on the results of triaxial tests. Triaxial test results reveal that undrained shear strength linearly increases with an increase in consolidated pressure , the normalized undrained shear strength is about 0.52 not only for this study but also for the other two cases around Taipei Basin. Due to undrained condition, an associated flow rule between plastic strain increment and stress tensor is adopted. As accumulative plastic strain or/and consolidated pressure change, the mobilized undrained shear strength also changes. All parameters needed for the proposed model can be expressed as a function of undrained shear strength S_u, The mobilized undrained shear strength for the proposed model during strain hardening-softening can be in term of accumulative plastic strain. This model can calculate the stress-strain curves of clayed soils accurately.

Abstract: Road condition in term of road surface condition depends on the subgrade soil strength. Therefore, a weak subgrade condition requires improvements in stabilization. Soil stabilization is the alteration of one or more geotechnical properties to create an improved soil material possessing the desired engineering properties. The main purpose of the soil stabilization is to increase the shear strength of an existing ground condition to enhance its load-bearing capacity, achieve a desired improved permeability and enhance the durability of the soil to resistance to the process of weathering, and traffic usage among others. Three method in soil stabilization considered in this study are chemical admixture, mechanical and geosynthetics methods. The difference in soil stabilization methods depends on the different road surface conditions. Road condition with weakness subgrade is more appropriate and economical in used stabilization chemical method. In this paper, discussing the road condition requires the ground improvement through soil stabilization

Abstract: This paper presents a comprehensive method to consider the size effect of the drill bit on the lateral and torsional vibrations of micro-drill tool accurately. Based on the Euler angles, and Lagrange’s equation, the dynamic micro-drilling spindle model including micro-drilling tool is derived. To express more realistic behaviors of the model, the Timoshenko beam model is employed. The dynamic responses of the micro-drill tool are obtained by utilizing the finite element method and Newmark’s method. The influences of the drill bit with high length to diameter are investigated in three cases as 15:1, 18:1, and 20:1 using the same 0.1 mm diameter drill at a rotational speed of 5×10⁴ rpm during air cutting and cutting of the 6-layer FR-4 composite board. The hole-quality is used to discuss the influences of those drill bit aspect ratios.

Abstract: The glove formers are tools used to pick up the coagulants and rubber latex, so the vulcanised rubber takes the form of hands upon drying. As the demands of gloves quality is crucial to serve the purpose of gloves as a bidirectional protective barrier; the gloves are required to be both sturdy and strong as to prevent tearing while also being elastic and comfortable to use. This research is a comparison study on the surface treatment of a ceramic glove former and how it affects the contact angle between the former surface and the coagulant, and the latex being deposited on the former. The study also focuses on the mechanical properties of the gloves and defects produced by the formers. Gloves were made using the two types of formers and the gloves were then tested for their masses, thickness distributions, tensile strengths, elongations and defects. It was found that the talc treated formers was able to adhere coagulant better, a lower contact angle of 22.10 as compared to the untreated former which had a contact angle of 27.60. This enabled the talc treated former to produce natural rubber gloves which had higher mass and more evenly distributed.

Abstract: Produced Profiles by direct recycling of aluminum chips in hot extrusion process were achieved by temperature related parameters using preheating temperature 450 °C, 500 °C, and 550 °C for duration 1 hour, 2 hours, and 3 hours preheating time. By using Design of Experiments (DOE) procedure with full factorial design and three center points analysis, the results showed that the preheating temperature factor is more important to be controlled rather than the preheating duration and increase of temperature conducted to the high tensile strength. The profiles extruded at 550 °C and 3 hours’ duration had obtained the optimum condition to get the maximum tensile strength. The influence of parameters of hot extrusion process on fracture surfaces of the recycled samples was also investigated and discussed.

Abstract: None of the research found in the literature investigates and optimizes the subtractive rapid prototyping process parameters in order to fabricate polycarbonate material. This research is conducted to optimize the subtractive rapid prototyping process parameters of polycarbonate material in order to achieve the maximum material rate removal without exceeding the dimensional error value of 1 mm, similar to the result of additive manufacturing. The response surface methodology is implemented in this research to optimized three process parameters, which are feed rate, step-over, and depth of cut. Two responses investigated in this research are material rate removal and dimensional error. The response optimizer is used to optimize the responses. The result shows that optimum material removal rate and dimensional error that can be achieved is 2.494 mm³/s and 0.97 mm respectively. A confirmation test experiment has been conducted to verify the optimization result.

Abstract: High Pressure Die Casting (HPDC) is a manufacturing process producing complex and precise products by injecting molten material into mold cavity at top speed and pressure. The quality of product is highly related with mold cavity design. Casting defects due to inappropriate mold design will affect mechanical properties, surface quality and product life cycle. Optimization of runner system is essential to manufacture complex and precision product design with minimal defects. The combination of runner and gating system is investigated in this paper. This paper investigated the effect of runner and gating optimization in reducing the gas porosity inside casting by evaluating the fluid and thermal distribution behavior in experimental and Computational Fluid Dynamic (CFD). The gas porosity generated in the molten magnesium alloy is due to the turbulent flow and the inconsistency of the fluid flow to push the gas bubble away from the main casting. This paper includes an X-ray of a sample product that shows correlation between gas porosity and CFD results. Results show that localize porosity gathered at the bottom of the main casting. Based on localized porosity position, runner and gating system is modified and numerical simulation is carried out for analysis. An inspection instrument step-type test piece is taken as an investigation sample to illustrate the technique of design modifications and improvements. Process parameters considered in this paper are injection speed, injection pressure, melt temperature and mold temperature. This paper proposed new runner designs that can generate balanced velocity and temperature distribution inside mold cavity, improving the solidification process aimed for reducing casting defects.