Tạp chí Khoa học - Công nghệ Thủy Sản, Trường Đại học Nha Trang

Modeling and simulating axial vibrations on the crarkshaft of the large two-stroke marine diesel engine

Ngo D.Vuong, Lai H.Thien, Luu M.Hai, Hoang Q.Dong, Vu V.Tuyen, Do D.Luu — Thu, 28 Mar 2024 00:00:00 +0000

The axial vibration is the strong vibrated phenomenon occurring on the main propulsion using a large two-stroke marine diesel engine. This article researches to build a mathematical model of the axial stiffness coefficient and force generated by the geometric configuration of the crank pin-crank web assemblies and the combustion gas force. The numerical simulation is performed by finite element method, using ANSYS software, applied to the main engine MAN B&W 6G70ME.

Keywords: Axial stiffness; crank pin–crank web set; axial force; diesel crankshaft; large two-stroke marine diesel engine; Axial vibration simulation.

Multi-layer material combination for manufaturing stab-proof life jackets

Duong Tu Tien — Thu, 28 Mar 2024 00:00:00 +0000

In modern times, individuals working in aquatic environments such as fishermen, fishery inspectors, customs officers, and others require a device that offers protection against punctures and drowning. As a result, a multi-layer composite material consisting of para-aramid 200de woven fabric, Dyneema® SB31 coated plates, and foam was evaluated for the creation of a life jacket that combines stab-proof capabilities with anti-drowning features (stab-proof life jacket). The objective of the research was to determine the optimal number of layers and arrangement of the multi-layer composite materials that would meet the NIJ standard level 1 protection against punctures. The study findings demonstrated that utilizing both types of woven fabric and coated plates yielded the most desirable puncture resistance, considering the thickness and weight of the composite materials. The effectiveness of using only woven fabric ranked second, while relying solely on coated plates produced less satisfactory results. Placing the puncture-resistant material above the foam layer proved to be more effective than placing it beneath the foam layer in all three scenarios. These findings lay the groundwork for the design and development of stab-proof life jackets tailored to the needs of professionals in specific aquatic industries.

Keywords: Puncture-resistant life vest, puncture-resistant, multi-layer composite, aramid, UHMWPE

Exploring the impact of industry 4.0 on marine mechanical engineering in the Philippines: Opportunities and challenges in the 21st century

Robert Michael B. Corpus, Meldanette S. Bayani — Thu, 28 Mar 2024 00:00:00 +0000

Industry 4.0 is revolutionizing the way we do business and operate our industries today. The marine mechanical engineering industry in the Philippines is not exempt from this digital transformation. The advancement of technology has paved the way for the development of smart ships and the implementation of automated systems in the maritime industry. This review paper explores the impact of Industry 4.0 on marine mechanical engineering in the Philippines, the opportunities it presents, and the challenges it brings. The paper starts with a brief introduction to Industry 4.0 and its various components that are relevant to the marine mechanical engineering industry. It then delves into the current state of the industry in the Philippines, including its strengths and weaknesses. The review paper discusses the opportunities that Industry 4.0 presents in terms of improving efficiency, reducing costs, and increasing safety in the maritime industry. It also highlights the challenges that come with implementing new technologies, such as cybersecurity threats and the need for upskilling the workforce. The paper concludes by emphasizing the need for the marine mechanical engineering industry in the Philippines to embrace Industry 4.0 to stay competitive and relevant in the 21st century. The authors suggest that stakeholders must work together to develop a clear roadmap for the adoption of new technologies and address any barriers to implementation. The review paper provides valuable insights for policymakers, industry players, and researchers in the field of marine mechanical engineering in the Philippines.

Keywords: Industry 4.0, Marine Mechanical Engineering, Philippines, Opportunities, Challenges

Design optimization of a marine refrigeration system with waste heat recovery channel

Marcelo April L., Palisoc Arriane A., Marcelo Luvisminda D. — Thu, 28 Mar 2024 00:00:00 +0000

This paper presents the design of an optimized marine refrigeration system to be used as a preservation facility for fishermen on boats. This aims to help preserve and maintain the high quality of the catch during fishing operations. This is to replace the manual ice box method. The system is tested in an actual environment offshore. The lowest temperature reached inside the refrigeration when full load is -1.7°C with a maximum time of 6 hours, while the temperature of the fish inside the refrigeration is 2.5°C. These results show the capability of the enhanced marine refrigeration system to achieve the desired temperature for the catch to maintain its good quality. In addition, the usability and user experience survey results indicated that the target beneficiaries agreed that the following aspects of the marine refrigeration system include usefulness and functionality, ease of use, design capacity, dimension, aesthetics, and kerosene as the resources used are excellent.

Keywords: Absorption, Kerosene, Marine Refrigeration

Innovative approaches for sustainable marine ecosystem conservation and pollution mitigation in the Philippines: A comprehensive analysis of technological and policy innovations

Meldanette S. Bayani, Robert Michael B. Corpus — Thu, 28 Mar 2024 00:00:00 +0000

The marine ecosystem is one of the most important natural resources that provide food, income, and livelihood to millions of people worldwide. In the Philippines, marine resources play a significant role in the economy, with the fishing industry alone providing jobs to more than a million people. However, the exploitation of these resources has led to numerous environmental problems such as pollution, overfishing, and habitat destruction, which have detrimental effects on the ecosystem's health and productivity. This review paper aims to provide an overview of innovative approaches that have been developed in the Philippines to address these environmental issues. These approaches include technological innovations such as ocean monitoring systems, marine robotics, and bioremediation, as well as policy innovations such as the establishment of marine protected areas, the implementation of sustainable fishing practices, and the reduction of plastic waste. The paper highlights the importance of collaboration between stakeholders, including government agencies, non-government organizations, and local communities, in the development and implementation of these approaches. Furthermore, the paper stresses the need for continuous monitoring and evaluation of these innovations to ensure their effectiveness and sustainability. In conclusion, this review paper provides valuable insights into the innovative approaches that have been developed in the Philippines to address environmental issues in the marine ecosystem. These approaches offer potential solutions that could be applied in other regions of the world, where similar environmental problems exist.be present in the body of the article.

Keywords: Marine ecosystem, Pollution, Sustainable conservation, Technological innovations, Policy innovations

Effect of the addition of fish protein isolate on biscuits’ physicochemical and sensory properties

Huynh Nguyen Duy Bao, Nguyen Ngoc Thuy Dung — Thu, 28 Mar 2024 00:00:00 +0000

Biscuits are among the most popular baked goods. However, traditional biscuits are frequently poor in protein and low in the content of the essential amino acids. Meanwhile, fish protein isolate (FPI) is proven to contain all the essential amino acids. The addition of FPI to biscuits can improve their nutritional value but may change their physicochemical and sensory properties. The present study was, therefore, conducted to investigate the effect of the addition of different levels of FPI prepared from trimmings of yellowfin tuna on the physicochemical properties and sensory acceptability of biscuits. The results showed that the moisture and water activity of biscuits with 1.6-5.4% FPI added significantly decreased compared with the control biscuits without FPI. The hardness of the biscuits with FPI added compared to the control biscuits, however, was not significantly different. The results of the sensory evaluation also showed that the appearance, texture, color, aroma, taste, mouthfeel, and overall acceptability of the biscuits with FPI added and the control biscuits did not differ significantly, except for the color and aroma of the biscuits with 3.8-5.4% FPI added. The addition of 2.7% FPI to biscuits was found to have no negative impact on the biscuits’ quality. These findings suggest that FPI prepared from the trimmings of yellowfin tuna is a potential protein source that can be used to improve the nutritional value of biscuits.

Keywords: Protein-enriched biscuit, Thunnus albacares, fish protein isolate, value-added products, malnutrition

The effect of liquid smoked flavourings and wood smoke on the quality of smoked mackerel fillets during chilled storage

Huong Thi Thu Dang, Magnea G. Karlsdottir, Sigurjon Arason — Thu, 28 Mar 2024 00:00:00 +0000

This study was undertaken to evaluate the effects of liquid smoked flavourings and wood smoke on the sensory, color, texture, and lipid stability of smoked mackerel fillets for four weeks chilled storage. Fish fillets were smoked by two methods: (1) immersed in brine (1:1) containing 100 g/L NaCl at 0-5 °C for 3 hours, allowed to drain at room temperature (~20 °C) for 2 hours and smoked directly with wood smoke in a smoking chamber at 25 °C for 3 hours; (2) immersed in brine (1:1) containing 5 mL/L commercial liquid smoke flavourings and 60 g/L NaCl for 16 hours at 0-5 °C then dried at 25 °C for 2 hours in an oven. Smoked samples were then vacuum packed and stored chilled at -1 °C for one week, followed by 4±1°C for three weeks. The quality changes in sensory, color, texture, and lipid stability were observed after 0, 1, 2, 3 and 4 weeks of storage. The results showed that, smoked mackerel using commercial liquid smoked flavourings was higher in rancid flavour, lightness, redness, and yellowness but had less bitter odour and was softer than the wood smoked mackerel. The lipid oxidation was higher after the wood smoke process but was however rather stable during the chilled storage. In contrast, lipid oxidation in the liquid smoked products increased significantly during chilled storage.

Keywords: Atlantic mackerel (Scomber scombrus), color, liquid smoked flavouring, lipid quality, sensory, texture, wood smoke

The importance of technology and cold chain logistics in Vietnam's preservation of harvested seafood

Minh Huong Tang, Thu Hoa Ho Thi — Thu, 28 Mar 2024 00:00:00 +0000

Vietnam has been experiencing significant economic growth in recent years, making it an attractive destination for foreign investors. With globalization and the expansion of trade relationships, logistics management has become crucial for domestic and multinational companies operating in Vietnam. However, logistics operations in Vietnam are exposed to various risks, such as natural disasters, infrastructure issues, regulatory uncertainty, and human factors. Therefore, it is essential to manage logistics risk effectively to ensure the supply chain's resilience and the business's sustainability. This paper aims to provide a critical review of the risk management literature in logistics by analyzing the key concepts of supply chain risk, the principles of logistic risk management, types of logistics risks, and some ideas on solutions in risk management in the supply chain.

Keywords: Supply chain, risk management, Vietnam

Studying influence of the mathematical model error on the results of calculating freedom torsional vibration for marine diesel propulsion system

Bui Minh Tuan, Do Duc Luu, Lai Huy Thien, Luu Minh Hai — Thu, 28 Mar 2024 00:00:00 +0000

The Freedom Torsional Vibrations (FTV) Calculation (FTVC) for the marine main propulsion plant (MPP) to determine the freedom frequencies and the FTV formations of the mechanical system. Normally, the MPP is dynamically modeled as a finite n concentrated masses with the parameters of: Mass moment of inertia J_k (kgm², k = 1÷ n) and the torsional stiffness C_k,k+1(Nm/rad) between the k and k+1 concentrated masses. This paper studies the influence of the number of concentrated masses n as well as the accuracy of determining J_p (Moment of inertia of the propeller) on the solution of the MPP's FTVC. The research verifies to the MMP on the Korean ship XXX-XXX-XXX, using the MDE 6G70MEC.

Keywords: Freedom Torsional Vibration (FTV); Mathematic model of the FTV; Exactness of the FTV calculation.

Advancing turning performance of C45 steel for marine applications: A comprehensive study on optimizing cutting conditions

Huu That Nguyen, Ngoc Chien Vu — Thu, 28 Mar 2024 00:00:00 +0000

Cutting condition is a pivotal factor affecting cutting performance in the turning process, especially in marine engineering, where materials must withstand the challenges of maritime environments. This study presents an experimental investigation of the impact of cutting process parameters on surface roughness, Vicker hardness, and cutting temperature in the turning of C45 steel, a critical material for marine applications. The experiments are meticulously designed based on input parameters, including cutting speed and various cutting conditions (dry, flood, MQL, and nano-MQL), focusing on their relevance to maritime manufacturing. After collecting and analyzing the experimental data, it becomes evident that increasing the cutting velocity significantly reduces surface roughness and temperature, aligning with the marine industry's need for precision and durability. Additionally, Nano-MQL lubrication is the most effective solution for minimizing cutting temperature and improving surface quality. It is a noteworthy advancement for enhancing cutting performance in marine science and engineering.

Keywords: Cutting condition, Nano-MQL, surface roughness, temperature

Analysis sedan vehicle structure in frontal impact using computer model

Nguyen Phu Thuong Luu, Ly Hung Anh, Pham An Binh — Thu, 28 Mar 2024 00:00:00 +0000

This paper presents an overview of Sedan vehicle structure based on frontal impact. The analysis results include parameters on the degree of deformation, the collision absorption ability of the Sedan vehicle structural model in accidents. The purpose is based on the comparison results to simulate the Sedan vehicle structure model that collides with other car chassis models at different speed levels, based on that, compares the crash analysis simulations to find the textures the frame absorbs the maximum impact energy and minimizes the deformation so as not to affect intrusion into the safe space of the passenger compartment of the vehicle. The results of this paper show that the frame structures such as the A-Pillars and Horizontal brace between the engine compartment and the passenger compartment need to be improved to increase the safety for the passengers inside. The study results are expected to be expanded in to optimize the engineering structures and improve the efficiency in various fields included shipbuilding, offshore structures, marine aquaculture structures, etc.

Keywords: Structural, analysis, Sedan, vehicle structure, fontal impact.

A numerical study on thickness of rear under-ride protection in case pick-up to semi-trailer full rear impact

Nguyen Phu Thuong Luu, Pham Cao Anh, Kim Yonghun — Thu, 28 Mar 2024 00:00:00 +0000

In the global supply chain, large trucks, tractors, and semitrailers are essential as the final step in this complex network. However, they have many potential dangers because the gaps from the semi-trailer's floor to the road surface are high, so small cars easily get underride. To solve this issue, some regulations have required the installation of additional protection devices on the front, sides, and rear where these gaps exist, for example, FMVSS 223, 224 of the US, or UNECE R58 of Europe. Using LS-DYNA software and trailer and pick-up models from proven sources to set up a collision simulation, then proceed to change the thickness of the rear underride protection device to assess the effect. The collision was designed with 55.8 km/h of pick-up and a stationary trailer. The effect of change thickness on axial displacement and energy changes is presented. The study results are expected to be helpful for the structural design and safety assessment of various structures including marine vehicles and cars against collisions.

Keywords: Rear under-ride, protection device, design, truck, semi-trailer

Dynamic balancing of rigid rotors by the influence coefficient method

Tuan Le Dinh, Thanh Bui Trung, Ngoc Anh Vu — Thu, 28 Mar 2024 00:00:00 +0000

Applied to rigid rotors, the influence coefficient method is the most adaptable method for rotor dynamic balancing because it uses only experimental information. The sole requirement for balancing rotors with this method is that there exists proportionality between mass unbalance located at correction planes and vibration measured at measuring planes. Hence, the rotors only need to be described by correction and measuring planes. The sensitivity of the measuring planes compared to the correction planes determines the response of the amount of unbalance for a specified rotation speed. The paper aims to describe in detail the experiment for dynamic balancing of rotors to verify the influence coefficient method. The direct calibration on two-plane rigid rotor using this method showed that a significant reduction of unbalances can be obtained. The results can be helpful for the design and safety assessment of dynamic systems equipped with rotors for marine engineering.

Keywords: Rotor dynamic balancing, influence coefficient method, residual unbalances, Discrete Fourier Transform

Effect of probe length on tensile strength of dissimilar friction stir welded lap-joint between AA6061 and 316 stainless steel using marine structure

Huy Huu Ho, Quan Minh Nguyen, Thuyen Van Phi, Hao Dinh Duong, Tra Hung Tran — Thu, 28 Mar 2024 00:00:00 +0000

Recently, optimizing marine structure have been facing with a lot of challenges to reducing weight, increasing strength, and improving resistance corrosion. Using dissimilar joint may be one of the suitable solutions for manufacturer. In this study, dissimilar lap-joints between aluminum alloys 6061 and 316 stainless steel was produced by friction stir welding technology. The attention was put on the effect of different probe lengths on joint strength. The probe length was arranged from 2.7 mm to 2.9 mm. The experimental results show that the tensile strength of lap-joints increased with long probe length. The highest tensile strength is obtained approximately 6976 at the probe length of 2.9 mm that fracture location was found at aluminum side. The impact of interface properties on the joint strength was investigated and analyzed in this work.

Key works: Dissimilar joint, FSW, probe length, tensile strength.

The intake port of DI-engine type VIKYNO RV165 desinged using 3D-CAE software

Luong Huynh Giang, Chau Vo Tan — Thu, 28 Mar 2024 00:00:00 +0000

The intake manifold profile in a marine diesel engine profoundly influences engine intake performance, which, in turn, significantly impacts the engine's power characteristics and exhaust emissions which leading to marine polution and challenging the marine sustainable development. Improving the performance of the appropriate geometric design of the intake manifold in order to optimize the study time is a key basis. This research aims to build a parametric model for the 3D profile of the VIKYNO RV165-2 engine intake line. By changing the value of parameter variables in the model through SolidWorks software, it is able to design and change the 3D profile design of the intake manifold. The 3D model of the intake line will be parameterized based on the 2D design drawings of this part provided by VIKYNO. The parameter variables used are upper inclination, lower inclination, curvature, intake valve diameter, input cross-section. Many different 3D models of intakes will be created with respect to the values of parameter variables changed by using SolidWorks software. The results of the study provided a parametric model for the 3D profile of the intake tract, linking the parametric variables of the model with Solidwork software as a basis for speeding up this detailed 3D design process. The 3D design of the intake by the parametric model compared to the 3D design of the intake manifold by direct rendering from the 2D drawing has a difference of no more than 2% in volume. This adaptability and precision are crucial for ensuring air intake efficiency for marine engines operating in diverse and challenging marine conditions.From the platform model, the change of input variables is displayed quickly on new designs, in accordance with the standard, and thereby the model is selected for the stage of researching the efficiency of air intake on the engine.

Keywords: CAE, Diesel engine, intake port geometry, numerical design.

Apply and improve the association rules in predicting national high school admission scores to Nha Trang University

Pham Thi Thu Thuy, Bui Xuan Huy, Truong Minh Hieu, Kim Hwa Soo — Thu, 28 Mar 2024 00:00:00 +0000

The paper discusses how the traditional method of association rule mining based on user-defined minimum support and confidence can result in either too many or too few association rules. This could lead to valuable information being missed or redundant rules being generated, which is not practical and can be costly to implement. The paper proposes an improvement of DARIT algorithm to mine association rules without redundancy and applies it to data from previous years of National High School Exams to Nha Trang University. The goal is to use the results to build an admissions counseling system that can help students increase their chances of being admitted to universities based on their exam results.

Keywords: Data mining, Association rule, Missing value, DARIT, consulting system.

Design and simulation of structural durability of passenger car front in collision

Phuong Vu Hoang, Tung Pham Son, Duong Hoang Ngoc, Nguyen Nguyen Khoi — Thu, 28 Mar 2024 00:00:00 +0000

In this paper, design and calculate a damping system with HYPERMESH software. Research using LS-DYNA software to analyze finite element model and structural strength of passenger car front and violate the safe space on impact. Simulation results with a speed of 50 km/h according to ECE R66 standards show a reduction of 27%. Meet the requirements on the condition of the car head structure. The safe space is not violated according to ECE R66 standards in a head-on collision. Additionally, the numerical analysis techniques employed in this study could be used for future research on collisions between maritime structures including fishing boats and aquaculture engineering.

Keywords: ECE R66 standard, HYPERMESH software, LS-SYNA software, collision, passenger car, damping system.

Researching the force absorption system for the front of the passenger car to secure the driver

Phuong Vu Hoang, Tung Pham Son, Duong Hoang Ngoc, Nguyen Nguyen Khoi — Thu, 28 Mar 2024 00:00:00 +0000

Protecting the safety of drivers in the bus is very important and necessary in front collisions. This research on the system shock absorber and absorption of force bus head in front collisions. This design will protect bus heads not violations in safe spaces and protect drivers in front collisions. The finite element model and safety analysis simulation of the system shock absorber and absorption of force by LS – DYNA and MADYMO software. The study’s results show shock absorber structure ensures durability. The head part index is down 35%. The neck part index is down 28%. Drivers are protected more safely. Injury values of driver satisfy safety ECE R94 standard in bus front collision.

Keywords: ECE R94 standard, MADYMO software, LS - DYNA software, collision, injury.

Mechanical and thermal transport in nanoporous graphene-like BC6N

Thi Bao Tien Tran, Huu Nghia Nguyen, Van Thai Nguyen — Thu, 28 Mar 2024 00:00:00 +0000

This work analyzes the thermal transport (TT) and mechanical properties (MP) of nanoporous graphene-like BC₆N monolayer utilizing non-equilibrium molecular dynamics (NEMD) and molecular dynamic (MD) simulations. Herein, the heat transfer and mechanical of nanoporous graphene-like BC₆N membrane with various circle-pore size defects are systematically reviewed and numerically examined. The results show that the BC₆N sheet has a balance on mechanical properties in two directions under biaxial tension as changing pore size from D = 2.0 to D = 7.0 nm. Young's modulus and ultimate strength of BC₆N monolayer with a circle pore decrease when the pore size increases. The trending laws are also shown to predict the mechanical parameters of the porous BC₆N sheet. Besides, the thermal conductivity (TC) of the monolayer BC₆N with a smaller pore size is much higher than that of the sample with a bigger pore size due to higher energy loss. Changing pore size can adjust the TC and 2D temperature distribution around the circle-pore. Furthermore, the pristine BC₆N TC is more heightened than the defective ones. The study results confirm that 2D-BC₆N has outstanding optical, electronic, thermal transport, and mechanical characteristics. It is particularly inspiring for further experimental and theoretical works that advance different technological applications, such as gas sensors, nanoelectronics, and optoelectronic devices. It helps for real-time monitoring, which is critical to improving safety and efficiency in marine and air transportation infrastructure.

Keywords: 2D-BC₆N, mechanical, thermal transport, energy.

Optimizing SKD-61 steel machining for marine component manufacture: A grey-Taguchi study on nanofluid minimum quantity lubrication

Ngoc Chien Vu, Xuan Phuong Dang, Shyh Chour Huang — Thu, 28 Mar 2024 00:00:00 +0000

SKD-61 steel finds extensive application in various sectors, including the marine industry where materials must withstand harsh aquatic conditions. In this study, we employ the Grey-Taguchi approach to optimize surface roughness (Ra), cutting force (Fc), and material removal rate (MRR) when hard-milling SKD-61 steel in pure minimum quantity lubrication (MQL) and nanofluid MQL environments, aligning with the demands of marine engineering. The orthogonal array method generates a set of experiments based on four input parameters: cutting speed, depth of cut, feed per tooth, and cutting condition, which are essential factors in marine component manufacturing. Our approach combines Grey relational analysis (GRA) with the Taguchi method to enhance multi-objective outcomes in machining. The results of this marine-focused study reveal that the lowest surface roughness, cutting force, and highest material removal rates are attained when the cutting conditions align with the principles of nanofluid MQL at a cutting velocity of 80 m/min, a depth of cut of 0.2 mm, and a feed per tooth of 0.01 mm/tooth.

Keywords: hard milling, nanofluid MQL, optimization machining parameters; Grey relational analysis; Taguchi

Effects of impact location on the dynamic response of repeatedly impacted aluminum alloy plates

Dac Dung Truong, Tan Khoa Dang, Tan Loi Vo, Viet Loi Dau — Thu, 28 Mar 2024 00:00:00 +0000

This paper presents a numerical investigation of the effects of impact location on the dynamic response of aluminum alloy plates to repeated mass impacts. The numerical model was developed and validated against relevant test data. In the simulation, the strain hardening was adopted using existing published equations. A parametric study was performed by considering different impact locations while keeping impact energy (mass and velocity) identically for each impact. The results showed that the plate was deformed progressively, and the resulting impact forces increased, while its duration decreased when the plate was impacted repeatedly. While changing in impact location after each impact remarkably affected the response of impacted plates, i.e., less damage was observed. The study results are expected to be helpful for the design of marine structures including fishing boats subjected to repeated impacts arising from collisions or dropped objects.

Keywords: Numerical simulation, aluminum alloy plate, repeated impacts, residual deformation.

Mechanical properties of fabric-reinforced geocomposites in accordance with novel size-independent flexure-test technique

Doan Hung Tran, O. Bortnovsky, D. Kroisova, Quang Nguyen Pham — Thu, 28 Mar 2024 00:00:00 +0000

In this paper, two silica-based geopolymer matrix systems reinforced composites were synthesized and fabricated at optimal conditions. The composites contained approximately 40 wt.% of Carbon HTA twill (TohoTenax) and 48 wt.% of advanced S-glass twill (Saint-Gobain, Vetrotex), respectively. The resulting composites exhibited quite high toughness, with the shear stress playing a greater role compared to other ceramic matrix composites. To determine the flexural properties of the composites, a universal testing machine was used under the three-point bending mode. This evaluation was conducted using a novel size-independent technique based on testing specimens at different scales of the sample height (H) to span length (L) ratio. Microstructure analysis of the composites was performed using a scanning electron microscope (SEM). The analysis aimed to assess the effective impregnation and adhesion between the fiber and geopolymer matrix, as well as to identify micro-cracks, which are inborn defects in inorganic matrix composites. The findings presented in this study highlight the potential of the synthesized silica-based geopolymer matrix composites and their applicability in various engineering fields.

Keywords: Geopolymer composite, fabric fiber, Size-independent flexure-test technique, flexural properties and microstructure.

Effect of welding speed on mechanical properties of dissimilar friction stir lap-joint welding between AA6061 and C1100 copper

Thu, 28 Mar 2024 00:00:00 +0000

Nowadays, renewable energy such as wind and solar energy can be employed for marine application to enhance clean and green technology. So, using battery is necessary to apply power for ship activities. To contribute sustainable development, optimizing structure in electric transmission such as bimetal connector Cu-Al is necessary to improve joint quality. This study focused the influence of welding parameters on the quality of the lap-joint between AA6061 aluminum alloy and C1100 copper. Experimental results indicate that the welding interface was sensitive to welding speed. Some welding defect was found in the joint such as tunnel and hook defects. The highest tensile strength produced by the welding speed of 200 mm/min was approximately 1100 N. In all experimental regimes, the weld zone structure, hardness distribution, tensile strength, fracture location, and local deformation were analyzed and discussed in detail.

Keywords: Friction stir welding, microstructure, mechanical properties, hardness

A short review of marine renewable energy: Generation, storage, and applications

V. L. Trinh, C. K. Chung, X. C. Nguyen, T. S. Nguyen — Thu, 28 Mar 2024 00:00:00 +0000

Renewable energy is a sustainable and green energy converted from renewable energy resources in the nature. There is a huge amount of renewable energy resources in the ocean that can be changed into useful energy like electricity, store for long time use, or apply in the daily energy consumption. These marine renewable energies (MRE) include wave energy, ocean thermal energy, tidal energy, ocean current energy, salinity gradient energy, and offshore energy. With a big area, the oceans have been prospected that it brings endless renewable energy sources for social development and human demand. The renewable ocean energy shows many advantages of sustainable energy, clean energy, and non-carbon dioxide emissions by generating from wave and water in the ocean with an enormous amount of natural energy resources. The MRE can service at many areas of off-shore, on-shore, and remote areas where need energy to drive daily living demands. The MRE reveals some disadvantages such as the influence of daily, monthly, season, and period of time. The solutions have been developed to solve the limitations of the MRE such as developing the storage method to store energy for long time use or making the balance of the output performance to improve quality of the renewable energy. The MRE has also received many concerns from countries by promulgating policies, strategies, and plans to develop the renewable ocean energy such as green economy development, blue economy strategy, carbon dioxide emission reduction, and encouragement of using marine renewable energy. This paper reviews current marine renewable energy with its generation, storage, and application. The work also mentioned some advantages, disadvantage, policies, strategies, and solutions to encourage the development of the renewable ocean energy in over the world. The results hope that it will be spread development, exploitation, and application of marine renewable energy in the near future.

Keywords: Marine renewable energy, energy storage, generation, application, sustainable energy