Journal of Applied Science and Technology

THE EFFECT OF INDENTER SIZE ON THE DEFORMATION MECHANISM AND DISLOCATION MOTION IN CoCrFeNiCu HEA COATING ON Cu SUBSTRATE USING MOLECULAR DYNAMICS SIMULATION

Anh-Tuan Nguyen — 2025-07-15

In this study, we used molecular dynamics (MD) simulations to analyze the deformation behavior of CoCrFeNiCu HEA coatings on Cu substrates, with the radius of the indenter as a simulation variable. Employing dislocation extraction analysis (DXA) and common neighbor analysis (CNA), we evaluated the change in the deformation morphology of atoms subjected to stress shear strain > 0.1. At the same time, the study also predicted the direction of dislocation motion, determined the orientation and shape of the Burgers vector, and the evolution of the dislocation length during the nanoindentation process. The results demonstrate the protective performance of the HEA coating on the Cu substrate and serve as a theoretical basis for applying HEA coatings in manufacturing industries.

GREY-BASED MULTI-OBJECTIVE OPTIMIZATION OF MACHINING FACTORS AFFECTING SURFACE ROUGHNESS AND MATERIAL REMOVAL RATE IN STAINLESS STEEL

Thi –Hoa Pham — 2025-09-20

Currently, surface roughness and material removal rate (MRR) are two key indicators that directly impact both the service life of machine components and overall machining productivity. Achieving an optimal balance between surface quality and material removal efficiency through the selection of appropriate cutting parameters has become a crucial objective for manufacturers. This study investigates the effects of cutting parameters, including cutting speed (V), feed rate (S), and depth of cut (t), on surface roughness and material removal rate (MRR) using the Taguchi design of experiments method in the machining of 304 stainless steel. The analytical results show that among the three parameters, feed rate (S) exerts the greatest influence on surface roughness, followed by depth of cut (t), while cutting speed (V) contributes the least. The optimal cutting parameter set for achieving the lowest surface roughness is V = 100 m/min, S = 0.1 mm/rev, and t = 0.5 mm. In contrast, for maximizing the material removal rate (MRR), cutting speed (V) has the strongest effect, followed by feed rate (S) and depth of cut (t). The optimal conditions for achieving the highest MRR are V = 100 m/min, S = 0.3 mm/rev, and t = 1.3 mm. Additionally, Grey Relational Analysis (GRA) is applied as a multi-objective optimization method to simultaneously minimize surface roughness and maximize MRR. The results indicate that the optimal cutting parameter combination is V = 100 m/min, S = 0.1 mm/rev, and t = 0.5 mm.

INFLUENCE OF SUBSTRATE TEMPERATURE ON THE GROWTH OF Ti₄₅Ni₅₅ FILMS ON Ni SURFACES

Anh-Vu Pham — 2025-09-08

Molecular dynamics simulations were employed to examine the influence of substrate temperature on the growth behavior of Ti₄₅Ni₅₅ thin films on stepped Ni(001) surfaces. Deposition cases were performed over a temperature range from 300 K to 1100 K under constant deposition energy and incident angle conditions. The results reveal that elevated temperatures facilitate interfacial intermixing, induce structural disorder, and lead to film amorphization. Furthermore, the presence of stepped surfaces significantly enhances atomic diffusion and mixing at the interface. These atomic-scale insights highlight the critical role of temperature in driving film evolution and support the potential formation of amorphous TiNi coatings.

STUDY ON THE EFFECT OF TEMPERATURE-DEPENDENT MATERIAL PROPERTIES ON 2D THERMAL SIMULATION OF PLASTIC INJECTION MOLDS

Van-The Than — 2025-09-25

Accurate prediction of mold temperature distribution is crucial for optimizing cooling design and ensuring product quality in injection molding. Numerous studies simplify simulations by assuming constant thermophysical properties of mold materials, overlooking their temperature-dependent nature and thus compromising accuracy. This work develops a 2D numerical heat transfer model in COMSOL Multiphysics that incorporates temperature-dependent thermal conductivity, specific heat capacity, and density for P20 steel. The model is validated against previous ANSYS Workbench results and subjected to mesh sensitivity analysis to balance accuracy and computation time. Results show that accounting for temperature dependence increases the predicted maximum mold temperature by 4.3 °C (7.12%) compared with the constant-property model. Effects of mesh size on temperature results were investigated. By enhancing thermal simulation accuracy, the proposed modeling approach enables reliable prediction of cooling performance and supports the optimization of injection mold cooling systems. This contributes to reduced cycle time, minimized residual stresses, and improved dimensional stability of molded parts.

POSITION-DEPENDENT MECHANICAL PROPERTIES OF GRAPHENE IN AlCrFeCuNi HIGH-ENTROPY ALLOY DURING NANOINDENTATION

Dang-Luan Nguyen — 2025-08-11

This study investigates the nanoindentation behavior of pure AlCrFeCuNi high-entropy alloy (HEA) and AlCrFeCuNi HEA/graphene composites through molecular dynamics simulations, with an emphasis on the effect of graphene embedding depth. Compared to the pure AlCrFeCuNi HEA, AlCrFeCuNi HEA/ graphene composites exhibit significantly improved mechanical response when graphene is positioned near the surface. Specifically, both the indentation load and contact pressure increase, and the measured hardness values are significantly higher. As the embedding depth increases from 10 Å to 60 Å, the strengthening effect diminishes, and the hardness of the composite approaches that of the pure AlCrFeCuNi HEA. Analysis of shear strain and dislocation evolution reveals that the embedded graphene layer effectively suppresses the propagation of plastic deformation, acting as a mechanical barrier. The total dislocation length decreases with deeper graphene placement, confirming its role in limiting subsurface damage.

EXPERIMENTAL INVESTIGATION OF WELDING PARAMETERS ON MECHANICAL PROPERTIES AND CHEMICAL COMPOSITION OF GMAW BUTT-WELDED PIPE JOINTS

Bui Khac Khanh — 2025-09-24

Gas Metal Arc Welding (GMAW) is widely used in manufacturing due to its high productivity and versatility. However, the quality of butt-welded pipe joints strongly depends on the selection of welding parameters. This study investigates the influence of welding current, voltage, and travel speed on the tensile strength, hardness, and chemical composition of S235JR pipe joints welded with GM-70S filler wire. Experiments were designed using the Taguchi method with an orthogonal array of nine tests. Tensile test results indicated that the welding condition M7 (100A, 20V, 4.6mm/s) achieved the maximum tensile strength of 454 MPa. Hardness measurements indicated the metal zone achieved higher values than other regions. Chemical analysis revealed that changes in Mn and C content correlated with hardness and tensile strength. Overall, the Taguchi method proved effective for optimizing welding parameters, minimizing defects, and improving the reliability of butt-welded pipe joints in industrial applications

RESEARCH ON THE DESIGN AND EXPERIMENTAL TESTING OF A CINNAMON BARK DRYING DEVICE BASED ON THE PRINCIPLE OF REVERSE DRYING OF THE DRYING AGENT

Nguyen Dinh Tung — 2025-09-26

In Vietnam today, cinnamon bark after being harvested from the tree (peeled from the tree) will be dried by naturally drying under the sun. In addition to the natural drying method, no processing corporation has been seen using a dryer. When drying under the sun, it will depend a lot on the weather, moreover, it is easily covered with dust and affected by passing animals, etc. Therefore, the application of forced drying technology using a cinnamon bark dryer is necessary and more proactive in production. The dryer can dry cinnamon bark after being harvested from the growing place and brought to the processing factory with a moisture content of w1 (50.29-53.31%) and dried down to a moisture content of w2 (14.23-15.03%) to prevent the growth of fungi, while the temperature of the drying agent is selected from 40-50oC to maintain the content and quality of aetheric oil. With the drying agent temperature changed from 40-50oC under the condition of maintaining the drying agent velocity v = 0.55m/s, we determined the moisture reduction time for cinnamon bark from 12-15 hours with the environmental temperature of 28oC and the relative humidity of the environment about 63%.

RESEARCH ON THE DEVELOPMENT OF FASHION HANDBAG ACCESSORIES USING CLO 3D SOFTWARE

Le Thuy Hang — 2025-08-11

In the era of rapid digitalization, 3D design plays a vital role in fostering innovation in the fashion industry, especially in accessory design. This paper examines the use of CLO 3D software in designing and simulating fashion handbags. By studying trends in shapes, materials, and colors, the authors created experimental prototypes based on design concepts from fashion students. These models were carefully simulated in CLO 3D, featuring detailed specifications, sewing lines, and materials. The findings show that the software effectively aids idea visualization, offers better design control, reduces production errors, and improves communication between designers and clients. Additionally, the study compares digital simulations with real products to evaluate their accuracy and practical use. The research highlights CLO 3D’s potential to enhance accessory design quality. It also points to new opportunities for sustainable product development and the integration of digital technology into modern fashion design education.

OVERVIEW OF STEGANOGRAPHY IN IMAGE

Nguyen Dinh Chien — 2025-09-19

Steganography is a technique to hide secret data in a digital object such as video, image, audio, databases, DNA sequences, and text,... The main purpose of hiding information is to make it impossible for others to recognize, the robustness, and the amount of information hidden in the digital objects. This paper summarizes the steganographic techniques in digital images as well as some basic concepts in the field of data security and safety through data hiding. Some methods of hiding data in JPEG format are also discussed in this paper. By synthesizing some techniques for hiding information in images, we aim to provide basic knowledge, thereby motivating scientists to research methods to improve the quality andembedded capacity in images and be able to avoid attacks.

ANALYSIS OF THE INFLUENCE OF LOAD ON THE TURNING PERFORMANCE OF SMALL TRUCKS CONSIDERING TIRE ELASTIC PROPERTIES USING NUMERICAL SIMULATION METHOD

Nguyen Van Thinh — 2025-09-25

The maneuverability and safety of small trucks operating under the specific traffic conditions in Vietnam heavily rely on their turning performance. This research aims to develop and apply a singletrack planar dynamic model to quantitatively investigate the influence of cargo load (Q) on the turning characteristics of a small truck. The research methodology includes: (1) Developing and establishing a system of differential equations for motion that incorporates the tire’s elastic properties through loaddependent cornering stiffness coefficients (k1, k2); (2) Using the Runge-Kutta 4 numerical method and the Matlab-Simulink software to solve the system of equations. Four load scenarios (Q=0, 1000, 1500, 2000 kg) were surveyed at a velocity V=20 km/h and a maximum steering angle βmax=27.5o. The simulation results show that as the load increases from 0 kg to 2000 kg: the front axle slip angle δ1) significantly increases from 4.80 to 14.50, while the steady-state turning radius (Rcon) only slightly decreases from 6.7759 m to 6.25 m. This outcome confirms that the load increases tire deformation (slip angle) but fundamentally does not significantly alter the maneuverability (turning radius) under conditions where the vehicle has not yet experienced lateral skidding. This research provides a scientific basis for the safe and efficient operation and utilization of small trucks.

THE EFFECTIVENESS OF USING VISUAL RESOURCES IN IMPROVING STUDENTS’ SPEAKING SKILLS

Do Phuc Huong — 2025-09-23

The speaking proficiency of first-year technical students is often constrained by psychological barriers, a lack of authentic practice environments, and insufficient vocabulary retention strategies. This study evaluates the effectiveness of employing visual resources in enhancing English speaking skills compared to traditional text-based methods. Utilizing a quasi-experimental design, the research involved 74 freshmen at Hung Yen University of Technology and Education (UTEHY), divided equally into a control group and an experimental group. The study was conducted over an eight-week intervention period, utilizing pre-tests, post-tests, delayed post-tests, and a structured questionnaire. The findings reveal that the utilization of visual resources had a statistically significant positive impact on students’ performance across different topic types. Specifically, the experimental group achieved a mean score of 7.27 on familiar topics, surpassing the control group’s mean of 6.85. Furthermore, favourable shifts in learning attitudes were observed, with 81% of participants agreeing that visual aids facilitated the speaking process and 73% reporting reduced anxiety. The study concludes that integrating visual aids into the curriculum is a viable strategy for improving oral competence and motivation in technical education settings.

ASSESSMENT OF THE STRENGTH AND ELONGATION PROPERTIES OF SILK AND NYLON SURGICAL SUTURES ACROSS DIFFERENT SUTURE CALIBERS

Hoang Thanh Thao — 2025-09-22

This paper studies the tensile strength and elongation at break of two common non-absorbable surgical sutures currently used in skin, soft tissue, and surgical wound suturing techniques: Silk surgical suture (natural surgical suture) and Nylon surgical suture (synthetic surgical suture) when changing suture sizes to 5/0; 4/0; 3/0; and 2/0. Tests were conducted under three conditions: before attaching the needle, after attaching the needle, and after knot tying. The results showed that: (i) larger suture sizes exhibited higher tensile strength but lower elongation; (ii) Nylon demonstrated higher tensile strength than Silk at the same suture size, whereas Silk had lower elongation, making it easier to handle and providing better knot security; (iii) The relationship between surgical suture size and mechanical properties follows a linear relationship with a correlation coefficient R² of approximately 0.9 or higher. These findings provide surgeons with scientific evidence for selecting suitable sutures according to tissue type and suturing technique, thereby improving clinical outcomes.

RESEARCH ON THE INFLUENCE OF SOME TECHNOLOGICAL PARAMETERS ON THE QUALITY INDICATORS OF SHIRTS' BUTTONLINESS

Nguyen Chi Cong — 2025-09-23

The shape of the buttonhole pattern, the degree of fabric drift, and the wrinkling around the buttonhole are important indicators reflecting the quality of shirt buttonholes. In actual production, technological parameters such as machine speed and thread tension directly affect these quality indicators; however, the specific extent of their influence on each type of fabric has not been clearly determined. This paper presents the results of an experimental study to evaluate the influence of machine speed and thread tension on a Juki LBH 1790S electronic buttonhole sewing machine on the pattern shape, fabric drift, and wrinkling of shirt buttonholes. The study was designed using an experimental model with 27 buttonhole patterns on three types of commercial fabrics (100% cotton, PE/Co 65/35, and 100% PES). Machine speed and thread tension were determined by setting parameters displayed on the buttonhole sewing machine’s screen, measured in revolutions per minute (rpm) and gf. The research results showed that machine speed and thread tension significantly affected the quality indicators of the buttonhole pattern. Based on the analysis of experimental results, the study identified suitable technological parameters for each fabric type, selecting two cotton fabric samples, three PE/Co fabric samples, and one PES fabric sample with the best buttonhole quality based on three evaluation criteria: shape, yarn drift, and fabric wrinkling.