Cabaran pembelajaran era pandemik : simptom stres di kalangan pelajar program Kejuruteraan Mekanikal UKM

Keadaan pandemik yang melanda dunia sejak penghujung 2019 telah mengubah landskap pembelajaran di universiti. Dengan perubahan pembelajaran secara dalam talian, masa yang perlu diluangkan oleh pelajar di depan komputer adalah lama. Tuntutan menghadiri kuliah secara dalam talian adalah hampir sepanjang hari. Manakala komponen pentaksiran seperti kuiz, tugasan, projek dan makmal telah diubah mengikut kesesuaian era pandemik bagi menepati kaedah pembelajaran baru ini. Walau bagaimanapun, perubahan pembelajaran dan beban pentaksiran ketika musim pandemik dilihat memberi impak kepada kesihatan mental pelajar. Oleh demikian, kajian ini dijalankan untuk mengenalpasti simptom stres yang dihadapi oleh pelajar ketika musim pandemik. Satu kaji selidik secara atas talian telah dijalankan yang melibatkan 173 pelajar Tahun 1 hingga 4 program Kejuruteraan Mekanikal di Jabatan Kejuruteraan Mekanikal dan Pembuatan (JKMP), UKM. Kajian ini bertujuan untuk melihat hubungkait antara simptom stres dengan tahap beban pentaksiran atau beban pembelajaran yang dialami oleh pelajar semasa pembelajaran dalam era pandemik ini. Kajian ini juga telah mengaitkan dan mengembangkan model kegagalan bahan menurut bidang kejuruteraan khususnya sifat mekanik dan tingkah laku bahan. Kefahaman terhadap 4 keadaan di mana stres yang dikenakan boleh dikategorikan sebagai keadaan kompleks yang mampu memberi implikasi kepada kegagalan bahan kejuruteraan, telah dikembangkan untuk mengenalpasti stres terhadap pelajar. Kajian menunjukkan 78% pelajar berpandangan bahawa bebanan aktiviti pembelajaran adalah antara faktor penyebab stres mereka. Namun, hanya 6.9% pelajar merasakan akviti pentaksiran yang diberikan adalah sangat membebankan. Simptom stres yang dihadapi oleh pelajar telah ditunjukkan pada pemikiran, emosi dan fizikal pelajar. Hasil kajian ini memberi implikasi terhadap keperluan kepada program untuk mewujudkan kalendar pentaksiran yang lebih bersifat holistik, melaksanakan program perkongsian mentalsihat dan program jom senaman yang boleh membantu mengurangkan stres dan meningkatkan motivasi pelajar. Kajian ini diharapkan mampu memberi maklumbalas yang lebih tepat terhadap isu stres dari persepektif pelajar dengan lebih jelas

Comparison of design and technology electric buses between Malaysia and Thailand

Pada masa kini, operasi pengangkutan merupakan sumber utama pelepasan gas rumah hijau(GHG). Ia juga menyumbang kepada pencemaran udara di bandar utama serta seluruh dunia dalam bentuk zarah (PM), karbon monoksida (CO), dan karbon dioksida (CO2). Bas elektrik adalah penyelesaian yang menjanjikan untuk mengurangkan pelepasan karbon dan pencemaran udara dalam sektor pengangkutan. Malaysia dan Thailand adalah dua negara Asia Tenggara yang telah menunjukkan minat yang semakin meningkat untuk menggunakan bas elektrik untuk menangani kebimbangan alam sekitar. Oleh itu, kajian ini bertujuan untuk membandingkan reka bentuk dan teknologi bas elektrik di Malaysia dan Thailand. Berdasarkan reka bentuk, bas elektrik Malaysia mempunyai rupa yang lebih moden dan anggun dengan badan yang diperkemas dan cermin depan berpanorama yang besar. Sebaliknya, bas elektrik Thailand cenderung mempunyai penampilan seperti bas yang lebih tradisional dengan bentuk kotak dan cermin depan rata. Berdasarkan teknologi, kedua-dua Malaysia dan Thailand telah giat melaksanakan bas elektrik dengan ciri canggih seperti brek regeneratif, keupayaan pengecasan pantas dan sistem pengangkutan pintar. Bagaimanapun, Malaysia baru-baru ini memperkenalkan teknologi pengecasan tanpa wayar untuk bas elektrik, yang membolehkan bas mengecas semasa menunggu di perhentian bas tanpa memerlukan sambungan fizikal kepada pengecas. Teknologi ini masih belum dilaksanakan secara meluas di Thailand. Secara keseluruhan, kedua-dua Malaysia dan Thailand mengorak langkah dalam menggunakan bas elektrik untuk mengurangkan pelepasan karbon dan meningkatkan kualiti udara. Walaupun terdapat perbezaan dalam reka bentuk dan teknologi, kedua-dua negara sedang berusaha ke arah matlamat bersama pengangkutan mampan

A study on the wetting behaviour of Al-Si-Zn brazing filler on AA7075 and AR500 surface

This paper presents the results of an experimental study on wetting and spreading of Al-Si-Zn filler metal on AR500 steel and AA7075 aluminium alloy surface. Wetting and spreading conditions of filler metal onto the surface of the metal were analysed by contact angle and spread ratio with different surface conditions. The contact angle is the measured angle between the tangent to the liquid-vapour interface and the surface of the solid. While, spread ratio measured according to the change in diameter of spread shape geometry of filler metal. The use of the low melting temperature of filler metal is increasingly popular since they are able to reduce the effect of heat on metals. However, the low spreading and de-wetting condition have limited the application of filler metal due to the adverse effect of these conditions on the joint ability. However, overall, this study with different surface conditions of these metals is to identify the wetting and spreading behaviour of filler metal. In this work, Al-Si-Zn filler metal heated by torch brazing was applied to AR500 steel and AA7075 aluminium alloy surface with the different type of surface conditions. Experimental results showed that the higher spreading area of filler metal occurred on a smooth surface compared to the rough surface of metals

Influence of Bi Layer Structure and Sub Layer Distance on the Hardness of Multilayer Thin Film TiAlN and CrN / Siti Fatimah Hassan...[et al.]

Mechanical properties are important in identifying the suitability of a material for a particular usage. One of the important properties is the hardness of the material, which can be defined as the resistance to the material to abrasion, deformation, scratching or to indentation by another hard body. Among others, this property is important for wear resistant applications. In order to obtain the mechanical characterization of thin films, apart from physical nanoindentation testing, researchers have also been using the finite-element modelling (FEM) method to simulate the nanoindentation test. In this study, a nanoindentation model of thin film CrN and TiAlN were developed and simulated to investigate the influence on the number of layers and thin film structure on the overall hardness of multilayer thin film CrN and TiAlN. A total of 10 sets of simulation was conducted with varying structural arrangement (i.e. CrN/TiAlN and TiAlN/CrN), bi-layer thickness (i.e. from 0.2 μm to 2 μm) and number of layers (i.e. 1, 2, 4, 8 and 10 layers). Based on the study, it was found that the optimum distance of sub base for multilayer TiAlN/CrN was 0.8 μm, while the optimum distance of sub-layer for CrN/TiAlN was 0 μm. It can be concluded that the type of material and the distance of sub base thin film layer to the maximum indenter depth will have significant influence on the overall hardness of the thin film system

Basic needs in online learning during covid-19 : a Malaysian students’ survey

The COVID-19 pandemic has ravaged many nations economically and socially. This survey study involved Malaysian students in the tertiary level on their perspectives of online learning - their only possible method of learning throughout almost two-year of the lockdown. The online survey involved 1410 students in science, technology and engineering programmes throughout public and private universities in Malaysia. This study involves perceptions such as an increase in the level of difficulties in technical courses and compared with humanities course and students’ thoughts had they been in different scenarios. Some statistical tests on correlations of important parameters are performed. Despite a well-perceived success in online education, in a contrasting student perspective, there were many challenges faced by students from access to decent device and internet connection to a more mental-related issue such as their study environments. It is possible that the basic expectations in Maslow's hierarchy of needs model in online education are not met. More than 80% of students reported that technical-based courses such as computer programming or material science were harderin online learning. Again, more than 80% of students reported that it would be easier to understand the subject if they had a peer around. To stay current, universities will need to find ways to offer online education with a local blend to their current and prospective students

Investigation of low-velocity impact and flexural loading on AR500 steel/AA7075 aluminum alloy brazed joint

This paper presents the results of an experimental study to evaluate the damage and failure mode of AR500 steel/AA7075 aluminum alloy brazed joint panels caused by an impact load. Drop weight tests were conducted on AR500 steel/AA7075 aluminum alloy brazing joint panels to study their response and performance under impact loading. The use of steel and aluminum joints is becoming increasingly popular since they are well known for excellent weight, strength, and stiffness properties and this condition makes them the material of choice for lightweight applications in the automotive industry. In this work, AR500 steel/AA7075 aluminum alloy plates were fabricated by the torch brazing method with Al-Si-Zn base as the filler metal and evaluated for their impact performance and flexural strength by conducting drop weight tests under low velocity impacts and a three point bend test. Experimental results showed that the AR500 steel/AA7075 aluminum alloy brazed joint panel flexural strength was 615 N and the low velocity impact strength was 1569 N. The experiment caused delamination of the joint at the aluminum and filler metal region. The Al-Si-Zn filler bonding capability on the AA7075 aluminum was low compared to the AR500 steel. However, it is capable of joining these dissimilar metals. The data obtained from this study should assist researchers and designers to better understand damage and failure behaviour of panels made of dissimilar metals which will result in components with a better design. This is particularly so in the aspect of the crashworthiness properties of structural components, especially in static, quasi-static, and dynamic loadings

Ballistic Limit of Laminated Panels with Different Joining Materials Subjected to Steel-Hardened Core Projectile

This paper presents the computational-based ballistic limit of laminated metal panels comprised of high-strength steel and aluminium alloy Al7075-T6 plates to necessitate a weight reduction of 25% in the existing armour steel plate using three different joining materials. Numerical models of the triple-layered panels were developed using the commercial Explicit Finite Element code and were impacted by a 7.62-mm armour-piercing projectile at velocities ranging from 400 m/s to 1000 m/s. The ballistic performance of each configuration plate in terms of the ballistic limit velocity, depth of penetration and end of penetration, was quantified and considered. It was found that the panels with joining materials exhibited a better ballistic limit on an average of 1.5% than that of the panel without a joining material. The penetration depth of the panel joined by polyurethane possessed the lowest depth of 22 mm with a higher contact duration compared to the panel without a joining material. This happened because the polyurethane adhesive was better able to absorb energy at a high strain rate impact than the other joining materials. Thus, based on the investigation that was carried out, polyurethane seems to be the most interesting option for joining different metals of Ar500 and Al7075-T6 as a laminated panel for armoured vehicle applications

A study of the mechanical properties and wear behaviour of the oxide layer formed on high speed steel work rolls

This research is part of a larger study conducted to understand the wear of hot rolling rolls. A significant cost of hot rolling is associated with the consumption of rolls; hence a comprehensive understanding of how the roll material wears is important. As the surfaces of rolls are covered by an oxide layer it is important that the mechanical and tribological properties of these oxides be known. The mechanical properties of the oxide layer are an important aspect that leads to a better prediction of its behaviour during hot rolling operations. Due to the complex nature of the phenomena that occur in, and the practical difficulty of accessing the hot strip and work roll interface, computer based simulations coupled with experimental study are needed to understand and predict the wear of the oxide layers. A combined FE simulation and nanoindentation experiments approach was developed and used to characterise the mechanical properties of the oxide scale formed on the HSS sample. The main procedure consisted of two approaches: first, a nanoindentation experiment was carried out to determine the load-displacement curve, and second, the load-displacement curve was validated against the simulation based curve. In this thesis, nanoindentations were performed on the cross section of the oxide layers. The experiments clearly revealed the variation of mechanical properties in the inner and outer sub-layer. The XRD pattern and SEM-EDS analysis of the oxide layer sample indicated that these layers consist of two sub-layers, namely Fe2O3 and (Fe, Cr)3O4 in the outer and inner sub-layers respectively. The result of the load-displacement curves indicated that the outer sub-layer of Fe2O3 is generally harder, as demonstrated by the smaller penetration depths on the outer sub-layer compared to the inner sub-layer. It was hypothesized that the mechanical properties of the outer sub-layer were significantly influenced by the hard grains and small pores. From the FE simulations, the output load-displacement curves were obtained. The simulated load-displacement curves were then analysed in terms of the unloading slope (dP/dh) and the maximum load (Pmax) and compared with the experimental curves. Each simulation was refined iteratively until the values of the mechanical properties used in the simulation yielded an average unloading slope and maximum load difference with the experiments of less than 1 percent. FE simulations were carried out to simulate the load-displacement curves of the nanoindentation experiments to give the properties of the oxide layer. In this application the use of a nanoindentation experiment alone to measure the properties was hindered by the unknown value of the Poisson’s ratio and porosity effect of the sample. In a porous media, the load displacement relationship depends on the porosity and grain sizes, which are largely heterogeneous. To account for the porosity effect, the finite element model adopted Gurson’s model of plasticity for porous material. The mechanical properties of the oxide sub-layers were determined from the FE simulations input parameters e.g. elastic modulus, E, yield strength, σy, Poisson’s ratio, υ and pore fraction, ƒ, which could not be measured directly from the nanoindentation experiments. It was found that the outer sub-layer has a higher E of around 200-240 GPa compared to the inner sub-layer’s E of 90-220 GPa. The large variation of E in the inner sub-layer was probably due to the influence of voids and a non-uniform porosity of the sub-layer. The smaller size grains of the inner sub-layer increased the sensitivity of the indentations to variations in porosity. The E and H for the 20 mN load tests are lower than for the 5 mN load. This phenomenon was probably caused by the hardening which arises from the interaction between geometrically necessary dislocations (GNDs) and grain boundaries. To understand how the oxide layer deforms when scratched by asperity, a three-dimensional (3D) finite element (FE) simulation was carried out to investigate an indenter scratching on the oxide layers/high speed steel substrate system. Both ductile and brittle failure models were used to study the deformation and failure modes of the oxide layer. The coefficient of friction increased in an approximately linear function with the depth of the scratch. The oxide layer formed on HSS can be considered as ductile rather than brittle material based on the better agreement between the FE simulations and the scratch experiments when the ductile model was used. In fact the nanoindentation results on the oxide scales showing cracking free deformation, which further corroborated a ductile behaviour of the oxide layers. An investigation on the deformation of the oxide layers and indenter-carbide particle interactions during a scratch test was also carried out using a threedimensional finite element method. The interaction between the indenter and the carbide particle reinforcements were investigated after three different possible scenarios: particle on an oxide free surface, particle on an oxide-substrate interface, and particle in the substrate. The results showed that the magnitude and distribution of stresses/strains in the oxide layer and interaction of the particle with the tip are the main reason for the particle de-bonding during scratching. The von Mises stress at room temperature was significantly higher than at high temperature. This situation was probably due to the difference between the mechanical properties such as elastic modulus and yield strength of the oxide layer in both cases. In summary, this thesis has presented 6 major contributions to the study of oxide layers formed on high speed steel hot rolling material, namely:(i) the development of combined FE simulations and nanoindentation experiments to study the mechanical properties of the oxide layer, (ii) finding the variation in the oxide layer morphology, (iii) finding the significant relationship between the mechanical properties of the oxide layer and the nanoindentation parameters, (iv) development of FE simulation to predict the oxide layer wear, (v) suggestion on how and when to treat the oxide layer as brittle and as ductile material, and (vi) development of an FE model of oxide layer deformation and wear with carbide inclusion

Penggunaan sistem pengesanan emosi bagi melatih kemahiran komunikasi pembentangan

Ekspresi wajah memainkan peranan utama untuk mengesan emosi seseorang. Penggunaan pengesanan emosi dalam pembelajaran boleh mengesan emosi negatif pelajar terutamanya ketika mereka melaksanakan pembentangan projek. Kelemahan yang dikesan ini mampu diatasi dengan latihan bagi meningkatkan keupayaan keyakinan dan kemahiran komunikasi pembentangan. Justeru, kajian ini dijalankan bertujuan untuk mengenal pasti emosi pelajar semasa proses pembentangan kajian projek. Kajian ini menumpukan kepada dua objektif iaitu mengenalpasti elemen-elemen emosi pelajar dan valensi rangsangan muka ketika pembentangan. Melalui sistem pengesanan emosi ini, penambaikan komunikasi pembentangan telah berjaya dicapai melalui latihan menerusi sistem pengesanan emosi yang dapat mengesan ekspresi wajah pelajar. Ujian pengesanan emosi ini melibatkan 10 pelajar yang mengikuti kurus elektif iaitu Topik Terkini Kejuruteraaan Mekanikal. Walau bagaimanapun, keputusan 2 sampel pelajar lelaki dan perempuan telah dipilih untuk didokumentasi secara komprehensif dalam manuskrip ini. Pelajar lelaki mempunyai skala intensiti yang tinggi berbanding pelajar wanita. Skala intensiti yang tinggi menggambarkan kekuatan emosi yang ditionjolkan pada ekspresi wajah. Hasil keputusan menunjukkan kedua-dua pelajar lelaki dan perempuan menunjukkan kecenderungan mempamerkan emosi negatif ketika pembentangan tetapi dengan valensi berbeza antara satu sama lain. Namun proses latihan intensif telah dijalankan untuk memberi latihan komunikasi pembentangan kepada pelajar agar memberi ekspresi wajah tenang semasa pembentangan. Latihan ini berjaya memberikan impak yang positif. Diharapkan latihan pengesanan emosi yang ditindikkan dalam elemen pembentangan ini mampu memberi nilai inovasi baru yang mampu menyumbang ke arah satu keupayaan pembentangan yang lebih baik di kalangan pelajar

Wear Characteristics of Superalloy and Hardface Coatings in Gas Turbine Applications–A Review

In the gas-turbine research field, superalloys are some of the most widely used materials as they offer excellent strength, particularly at extreme temperatures. Vital components such as combustion liners, transition pieces, blades, and vanes, which are often severely affected by wear, have been identified. These critical components are exposed to very high temperatures (ranging from 570 to 1300 °C) in hot-gas-path systems and are generally subjected to heavy repair processes for maintenance works. Major degradation such as abrasive wear and fretting fatigue wear are predominant mechanisms in combustion liners and transition pieces during start–stop or peaking operation, resulting in high cost if inadequately protected. Another type of wear-like erosion is also prominent in turbine blades and vanes. Nimonic 263, Hastelloy X, and GTD 111 are examples of superalloys used in the gas-turbine industry. This review covers the development of hardface coatings used to protect the surfaces of components from wear and erosion. The application of hardface coatings helps reduce friction and wear, which can increase the lifespan of materials. Moreover, chromium carbide and Stellite 6 hardface coatings are widely used for hot-section components in gas turbines because they offer excellent resistance against wear and erosion. The effectiveness of these coatings to mitigate wear and increase the performance is further investigated. We also discuss in detail the current developments in combining these coating with other hard particles to improve wear resistance. The principles of this coating development can be extended to other high-temperature applications in the power-generation industry