Applied Mechanics and Materials Vols. 465-466

Abstract: This paper explains the measurement of anthropometricdimensions ofprimary school children and investigation ofrisk factors associated with musculoskeletal disorders (MSDs) among primary school children. A total of 266 students within three different schools were participated in anthropometric data measurements and questionnaire survey of the MSDs prevelance complain among them. Ten anthropometric measurements (Stature, Sitting height, Sitting shoulder height, Popliteal height, Hip breadth, Elbow seat height, Buttock-popliteal length, Buttock-knee length, Thigh clearance and Weight) were used. Martin type anthropometer set, height scale and weighing scale were used as a direct measurement method for the data collection on this study. Musculoskeletal symptoms were recorded using Modified Nordic Body Map Questionnaires. In addition Rapid Upper Limb Assessment (RULA) was used to assess the awkward posture of the school children for both designs. The results of the proposed furniture shows a better RULA final score for each group of muscles which give a score ranging from only 1 to 2 (Acceptable Posture) compared to the existing furniture that need further investigation. This anthropometrics data is very useful to the furniture manufacturer in designing school furniture in order to reduce the mismatch between furniture designed and Malaysian primary school children.

Abstract: Work environment factors such as air quality in the industry have become a public concern recently especially due to issues related to respirable dust. Most of industrial workers are exposed to dust during their daily work activities. A preliminary study was conducted at a paper based mill, palm oil mill and automotive plant in Malaysia to monitor the personal exposure of respirable dust. Personal sampling and questionnaires were administrated in purposed to determine the respiratory health symptoms and supported by a pulmonary lung function test. The result of the study showed most of the workers in paper based mill were exposed to respirable dust when the Time Weightage Average (TWA) result was above the permissible exposure limit which is 5 mg/m³ and 3 mg/m³ from Occupational Safety and Health Administration (OSHA) and American Conference of Governmental Industrial Hygienists (ACGIH) standard respectively. From the survey feedbacks, out of 30 symptoms, there are only five symptoms that are significant with the year of exposure. For pulmonary lung function test, there were 81.81% workers are in normal of spiro status for paper based mill. Meanwhile, for palm oil mill and automotive plant, there were almost 53.33% and 65.63% workers in normal spiro status respectively. However, there was no significant relation with the variables noted. Therefore, for a better future for industrial workers, some engineering control and approach have been suggested to the safety and health team to control machines that are fully operated and consider looking into the dust concentration.

Abstract: The most common body parts that sustain injuries at the workplace are the hands and fingers. In association to this, researchers have conducted various studies on grip span, forces, postures, contact area and strength. However, it appears that limited studies have been done on the design of screw knobs of ergonomic shapes and sizes for pinch grip activities. Thus, the aim of this study is to design, develop and assess screw knobs of ergonomic shapes and sizes for pinching activities. Several designs of screw knobs were designed and fabricated. The assessment of the knobs involved workers from a manufacturing firm. The ratings on the efforts to pinch and turn the knobs were collected using surveys and analyzed with reliability and descriptive and analyses. The results show that the workers mostly preferred using the small 5-lobes knob. However, the large ball knob was the least preferred knob to be used. The findings of this study can be used to create design guidelines on knob shapes and sizes to develop safer, more ergonomic and efficient knobs.

Abstract: Austenitic stainless steels have gathered wide acceptance in the fabrication of components, which require high temperature resistance and corrosion resistance, such as metal bellows used in expansion joints in aircraft, aerospace and petroleum industry. In case of single pass welding of thinner sections of this alloy, pulsed current micro plasma arc welding was found beneficial due to its advantages over the conventional continuous current process. The paper focuses on studying the effect of continuous current and pulsed current in welding AISI 304 L sheets using Micro Plasma Arc Welding (MPAW) process. Welding was carried out on 0.25 mm thick AISI 304 L sheets using continuous current mode and pulsed current mode separately keeping all other welding parameters constant. Weld quality characteristics like micro structure, hardness and tensile properties are investigated and it is found that the usage of pulsed current leads to better weld quality characteristics when compared to continuous current mode.

Abstract: The machining ability of electrical discharge machining (EDM) die-sinking on aluminium LM6 (Al-Sil2) as a new material is investigated.The objective of this paper is to determine the relationship between the machining parameters which are pulse-on time, pulse-off time and peak current on the material characteristics such as material removal rate (MRR), electrode wear rate (EWR) and surface roughness (Ra). Tungsten copper tool of diameter 10mm was chosen as an electrode. Design of experiment using Taguchi method was used to develop experimental matrix and optimize the MRR, EWR and Ra. The analysis was done using the Minitab software. It is found that the current and pulse on time are significantly affected the MRR, EWR and Ra while pulse off time and voltage are less significant factor that affected the responses. From the Taguchi method, the best setting of optimum value was obtained. Thus, it shows that Taguchi method is the best quality tools that can be applied for production.

Abstract: Gating system in a casting mold consists of a series of channels and reservoirs designed to feed molten metal to all parts of the mold cavity. The design of the system is the principle means by which the mold designer can control the rate of the metal flow and promote the desirable temperature distribution of cooling that will take place within the filled cavity. This research was conducted to determine the effects of vortex well thickness on the microstructure and mechanical properties of Aluminium LM6 in sand casting process. The experimental results show that increasing the vortex well thickness leads to a significance improvement on the flexural strength of the cast material. In addition, casting defects such as shrinkage porosity and gas porosity would be minimized as the thickness of the vortex well increases.

Abstract: This paper presents an investigation on the accuracy of average roughness (Ra) in three surface areas of specimen. For this study, we used two different probes of Mahr Surf XR20 which was MFW 250 tracing arm 6851804 (4.5mm) and tracing arm 6851806 (9.0mm). Full factorial design was used in the experiment plan. The normal probability graph, main effect and interaction plot had been analyzed by using MINITAB (software). The experiment result showed that the tracing arm 6851804 (4.5mm) consisted of small errors compared to the tracing arm 6851806 (9.0mm) based on the main effect plot and interaction plot analysis.

Abstract: The aim of this paper is to investigate the influence of pressure angle on drive and coast sides in conventional design asymmetric normal contact ratio spur gear, considering the load sharing between the gear teeth pair. The multi pair contact model in finite element analysis is used to find the load sharing ratio and respective stresses. It has been found out that the predictions through multipoint contact model are in good agreement with the available literature. A unique Ansys parametric design language code is developed for this study. It is found that, the maximum fillet stress decreases up to the threshold point for drive side (35^o) and coast side (25^o) pressure angles, beyond this point it increases. The load share based maximum fillet and contact stresses are lower in the high pressure angle side than that of the low pressure angle side, when it is loaded at the critical loading points.

Abstract: The tooth fracture occurs due to high fillet stress developed at the root fillet region along the face width, when the tooth is normally loaded. Hence, an accurate estimation of critical loading position on the tooth along the line of contact for maximum fillet stress and its location along the face width become important to reduce the tooth fracture. In the present work, the maximum fillet stress is evaluated based on load sharing ratio using the finite element method through the multi pair loaded model and using the results, the influence of cutter tip radius and addendum height on the load sharing ratio and respective maximum fillet stress is evaluated. The maximum fillet stress is lesser in the gear drives which is generated by the full round cutter and it increases due to increase the addendum height. The location at which the maximum fillet stress occurs along the face width is determined, when the load is applied at the critical loading position in the helical gear drive.

Abstract: The instability of petroleum prices in the world market has caused the price of fuel in Malaysia to increase, especially in the transportation sector. As an alternative, a research has been conducted from a technical aspect on the profitability of using hydrogen onboard as fuel for internal combustion engine. The process of producing hydrogen through chemical reaction between aluminum and hydrochloric acid (Al+HCl) has been successfully applied. Applications using a mixture of petrol with hydrogen (P+H₂) as an alternative fuel in four-stroke motorcycles have been tested using a chassis dynamometer model ATV Inertial Dyno, 054-500-1K. Hydrogen requirement in the petrol mixing ratio is dependent on the operating system of the engine ignition system which is controlled by hydrogen pressure in the cylinder. Three stages of load test on the engine performance have been conducted on the chassis dynamometer, namely, load test L0 is equal 0 ampere (L0), load test L1 is equal 1 ampere, and load test L2 is equal 2. This results showed 0.7412 mole of hydrogen can be generated through the chemical reaction between 20 grams of aluminium with 250 ml of hydrochloric acid or 1 kg of aluminium can produce 37.06 moles which is equivalent to 108 grams hydrogen. Fuel economy of each load test was 6.5% (L0), 18.5% (L1) and 30% (L2) in grams per kilowatt hour. The rate used in each test load was 100 g/kWh (L0), 80.77 g/kWh (L1), and 112 g/kWh (L2) compared to petrol of 107 g/kWh (L0), 99.23 g/kWh (L1) and 162 g/kWh (L2). Results from the combustion of petrol, air and hydrogen in proportion of 100 g/kWh, 80.77 g/kWh and 112 g/kWh was able to improve the quality of combustion compared to the normal fuel consumption. The total use of sfc achieved 20.3% savings in grams per kilowatt hour for the engine (G + H₂) with an average value of 98 g/kWh compared to the engine (G) with an average value of 123 g/kWh. The successful development of a prototype model with a reduction in fuel consumption in the system's ability to meet the basic needs of the internal combustion engine cycle can be beneficial to the development of the automotive industry, particularly in the transport sector.