Journal of Applied Engineering Science

CALCULATION OF NONLINEAR VIBRATION ISOLATION SYSTEMS UNDER HARMONIC ACTION

Zhetpisbay Bakirov — 2026-04-17

The aim of the study is to develop a methodology for calculating the dynamic characteristics of nonlinear vibration isolators and to evaluate the influence of the type of dissipative forces on the vibration protection efficiency. The paper addresses the calculation of vibration isolators with nonlinear elastic and dissipative properties under harmonic force and kinematic excitations. Using the harmonic linearization method, general expressions were derived for the amplitude-frequency response and the vibration isolation efficiency coefficient. The analysis of these expressions determined the conditions for suppressing large-amplitude vibrations.

Specific analytical relationships were obtained for vibration isolators possessing the most common nonlinear elastic characteristics. These include isolators with odd cubic stiffness characteristics, preloaded systems, systems with symmetric linear elastic stops, and systems with a nonlinear elastic element and symmetric rigid stops.

It was established that the efficiency of vibration protection systems depends significantly on the type of dissipative forces present in the isolator. Analytical relationships were derived, and the performance of vibration isolators with viscous, dry, and internal friction was analyzed. A comparison of the performance efficiency of vibration isolators with different dissipative characteristics was conducted. The possibility of achieving vibration protection goals by combining different forms of damping is highlighted.

MECHANICAL DAMAGE ASSESSMENT IN CONCRETE BEAMS REINFORCED WITH STEEL AND POLYPROPYLENE FIBERS USING ULTRASONIC PULSE VELOCITY TESTING

Andrés G. Sanchez Alvarado — 2026-05-30

Concrete beams are structural elements primarily subjected to vertical loads, including self-weight (dead load) and externally applied actions (live load). The sustained interaction of these loads induces bending deformations. As with all structural materials, concrete beams experience mechanical damage when the applied stresses exceed their ultimate capacity, typically manifested through cracking, which occurs on the tensile face opposite the load application. For several decades, fiber reinforcement has been employed worldwide to enhance the physical and mechanical properties of concrete, particularly its residual strength and crack control. In this study, concrete specimens were reinforced with two types of fibers—steel and polypropylene—and evaluated using ultrasonic pulse velocity (UPV) testing to characterize mechanical damage. After curing time, UPV measurements were taken to assess internal damage development under flexural loading. Based on the experimental data, predictive equations are proposed to estimate mechanical damage as a function of pulse velocity, allowing for improved evaluation of reinforced concrete behavior under stress.

VALIDATION OF THE PERFORMANCE OF HDPE-CONCRETE AS AN ALTERNATIVE FOR SUSTAINABLE CONSTRUCTION

Manuel Gutiérrez — 2026-05-31

Concrete is the most widely used material in global construction, which generates high demand for natural resources and a significant carbon footprint. In response to these challenges, incorporating plastic waste, such as high-density polyethylene (HDPE), has been proposed as a sustainable alternative to reduce dependence on natural aggregates and mitigate plastic pollution. This study evaluates the mechanical performance of concrete with partial replacements of HDPE at 2.5%, 5%, 7.5%, 10%, 15%, 20%, and 30% in sand to produce HDPE-concrete, which is compared against a control mix with 0% replacement. Optimal replacement percentages have been identified in the literature, and 64 specimens were prepared and tested to determine the concrete's behavior, including its strength and flexural performance, to validate the advantages and disadvantages of each replacement in the search for the optimal configuration of sustainable concrete. Results showed that 5% and 7.5% replacement levels achieved optimal compressive (409 kg/cm²) and flexural (49 kg/cm²) strengths, respectively. Although these mixes exhibit slower strength gain reaching peak values at 28 days, lower replacement rates showed superior 7-day strength. Conversely, higher replacement levels increased recycling volume, reduced unit weight and slump, and raised air content without compromising the paste-aggregate bond. The findings suggest that HDPE-concrete is a promising solution for the construction industry, as it not only promotes the circular economy of plastic waste but also offers adequate mechanical performance, making it a viable and eco-friendly alternative for building material production.

MULTI-OBJECTIVE OPTIMIZATION OF TWO-STAGE HELICAL GEARBOXES USING NSGA-II AND MCDM METHODS: MINIMIZING MASS AND MAXIMIZING EFFICIENCY

Dinh Van Thanh — 2026-05-31

This study presents a multi-criteria design approach for two-stage helical gearboxes using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) in combination with MCDM methods. The optimization problem was formulated with two conflicting objectives: minimizing gearbox mass and maximizing transmission efficiency. NSGA-II was employed to generate a set of Pareto-optimal solutions, while three different MCDM methods—MARCOS (the Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS), TOPSIS (Technique for Order Preference by Similarity to Ideal Solution), and SAW (Simple Additive Weighting)— was applied to identify the most preferred compromise design among them. Regression analysis revealed a strong linear relationship between the stage-one gear ratio (u1) and the overall transmission ratio (uh), ensuring practical feasibility of the optimized gear allocation. Numerical results demonstrated that gearboxes designed with transmission ratios in the range of uh=15–25 achieved the most balanced trade-off between reduced mass and high efficiency. The proposed hybrid NSGA-II–MCDM framework thus provides a powerful decision-support tool for gearbox designers, enabling both lightweight and energy-efficient configurations. In addition, the findings have clear practical implications, as the proposed framework can support the development of more compact and efficient gearboxes in automotive and industrial applications, where reducing mass and improving efficiency are critical design requirements.

ENERGY RETROFIT AND RENEWABLE ENERGY INTEGRATION FOR RESILIENT PUBLIC SCHOOL BUILDINGS: A VALIDATED CASE STUDY USING BUILDING ENERGY SIMULATION

Ahmad Younis — 2026-05-31

Jordan places a high priority on improving energy security by lowering energy costs and CO2 emissions through enhanced energy efficiency, boosting investment in renewable energy sources, and diversifying the energy mix. Upgrading public facilities in the area, such as schools, has recently attracted a lot of interest. This study uses carrier HAP and related computations to examine the energy-retrofitting saving potentials model of a local public school, which is driven by the retrofit framework. Five passive and active solutions were evaluated, including the installation of an 84-kWp photovoltaic system. Investment in a PV system, which has a payback period of less than five years, secured a break-even outcome for the expected energy expenses of the resilient school pilot project along with its associated energy demands when strategically paired with other measurements, such as the use of 5cm XPS and 10cm CMU to existing walls and 5cm XPS and other insulative materials to roofs when adhering to local energy code requirements for building envelope retrofits.

ELASTOHYDRODYNAMIC ANALYSIS OF MULTISTEP TEXTURED JOURNAL BEARINGS WITH GROOVE DEPTH VARIATIONS USING CFD–FSI

M. Muchammad — 2026-04-14

Journal bearings are widely employed in numerous industrial machines such as compressors, pumps, turbines, and generators, primarily to support rotating shafts. Compared with other surface texturing geometries, multistep journal bearing represents a geometric modification of conventional designs and is increasingly adopted because of its simple configuration, low manufacturing cost, and ease of fabrication. The stepped profile also facilitates greater lubricant flow, thereby enhancing the bearing’s operational performance. Extensive research has been devoted to evaluating parameters such as pressure distribution, load-carrying capacity, frictional forces and elastic deformation to improve tribological characteristics of journal bearings. This work investigates the influence of groove geometry—specifically groove height and width on the performance of multistep journal bearings in order to develop an optimized configuration. Three-dimensional computational fluid dynamics (CFD) simulations coupled with fluid-structure interaction (FSI) analysis, including cavitation effects, were performed. The results reveal that increasing the number of steps reduces frictional forces, while the load-carrying capacity decreases slightly. For instance, at a groove width of 35°, the load-carrying capacity was 6.96 % lower than at 15°, yet the frictional performance improved by 14.5 %.

OPTIMIZATION OF UNMANNED AERIAL VEHICLE STRUCTURES USING CARBON PLASTIC MATERIALS

Askar Abdykadyrov — 2026-05-31

This research explores the potential of using carbon plastic composite materials to optimize the structure of unmanned aerial vehicles (UAVs). The main issue addressed is reducing the weight of drones while increasing their strength and aerodynamic stability. The study found that the specific strength of carbon composites is 1500 MPa/g/cm³, which is three times higher than that of conventional materials. Additionally, the structural vibration resistance increased by 25-30%, and the weight was reduced by 25%. These results are explained by the low density of the material (1.55 – 1.65 g/cm³) and optimal distribution of stresses in the structure. A key feature of the research is the use of a method based on actual CAD modeling and numerical simulations, and the assessment of the efficiency of 3D printing and Out-of-Autoclave technologies, which supports its industrial potential. The findings can be applied in the construction of lightweight, reliable, and energy-efficient drones. Practical applications of these materials include military, agricultural, and emergency rescue systems, with usage conditions in environments with moderate temperatures and vibrational loads.

MODIFICATION OF SIZE EFFECT FORMULA FOR CONCRETE BEAMS WITHOUT SHEAR REINFORCEMENT

Irina Kerelezova — 2026-05-26

The current state of engineering science and practice has been concluded that the size effect cannot be overlooked, especially in the calculation of the shear capacity. Models based entirely on fracture mechanics have led to complex formulations inconvenient for practical use. Models based on simple theories, are resulting in a formula for determining the shear capacity of reinforced concrete. They are practically convenient, but multiple empirical parameters without a clear physical meaning are involved in their formulation. In the present study one modification of a size effect formula is presented. The purpose of this modification is to replace an empirical coefficient with a fracture mechanic’s parameter with a clear physical meaning.

CAUSES OF TIME OVERRUN IN ROAD CONSTRUCTION PROJECTS

Mega Waty — 2026-04-14

Time overrun is a situation in which construction project exceeds the specified completion date or the period agreed upon by the parties for handover. The concept is also known as overtime and has become a major problem for most construction projects worldwide due to significant waste and missed opportunities for several relevant stakeholders. Therefore, this study aimed to determine the causes of time overrun and mitigate time overrun in road construction projects. The method used includes interviews and questionnaires, which were subjected to focus group discussions (FGDs) with several experts before distribution to competent parties in construction sector. The data collected were analyzed using exploratory factor analysis to ensure accuracy and for optimization. A total of 132 questionnaires were answered correctly and returned. The results identified 7 factors affecting time overrun, which included (1) politics and government, (2) finance and planning, (3) management, (4) resources, (5) delays and errors, (6) projects, and (7) others. A total of 17 causes were also observed including political situations, political interference, economic determinants, land disputes, and late payments for additional work by the owner, followed by 12 other causes. Moreover, mitigation efforts were recommended to prevent and reduce the causes of project time overrun.

CRITICAL FAILURE MODE ANALYSIS OF PROTON EXCHANGE MEMBRANE FUEL CELL USING FUZZY RISK PRIORITY CALCULATION AND PARETO RANKING

Kais Brik — 2026-05-04

Fuel cell systems experience continuous performance degradation due to harsh operating conditions, which limits their durability and reliability. This paper therefore aims to examine the main causes and mechanisms of degradation affecting fuel cells, and in particular Proton Exchange Membrane Fuel Cells (PEMFCs), by conducting a detailed Failure Mode, Effects, and Criticality Analysis (FMECA). Each failure mode is assessed through the Fuzzy Risk Priority Number (FRPN), enabling the identification of the most critical degradation pathways. A Pareto-based classification is then applied to rank failure causes according to their contribution to system performance loss. The combined FMECA and Pareto approach makes it possible to highlight the dominant defects related to auxiliary components, flow regulation, sensor inaccuracies and the aging of the membrane and electrodes. Based on the critical causes identified, specific recommendations are proposed to improve reliability, including improved energy management and operating strategies, optimized control of pressure and humidity, and improved monitoring of auxiliary subsystems. The results provide a structured methodology for prioritizing degradation sources and guiding preventive maintenance and design improvements in fuel cell systems.

TEMPERATURE-DEPENDENT RELATIONSHIP BETWEEN INDIRECT TENSILE STRENGTH AND STIFFNESS MODULUS OF SBS-MODIFIED ASPHALT MIXTURES

Latif Budi Suparma — 2026-04-27

This study investigated the temperature-dependent relationship between indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) in styrene–butadiene–styrene (SBS) polymer-modified asphalt mixtures using a PG 76-22 binder. Cylindrical specimens were tested at four temperatures (20, 30, 40, and 50°C) to evaluate their tensile resistance and stiffness. The results show that both ITS and ITSM decrease markedly with increasing temperature, reflecting a reduction in binder viscosity and a weakening of aggregate interlock. Statistical analysis confirmed a strong positive correlation (r = 0.914, p < 0.001) between ITS and ITSM, with linear regression (R² = 0.9045) indicating that ITS is a reliable predictor of ITSM. An analysis of variance showed that temperature had significant effects on ITS and ITSM. These findings highlight the coupled mechanical behavior of ITS and ITSM, supporting their integration into mechanistic-empirical pavement design and performance-based mix evaluation. The study reinforces the role of SBS modification in enhancing thermal resilience and provides a practical framework for predicting stiffness modulus from tensile strength under varying thermal conditions.

MULTI-OBJECTIVE OPTIMIZATION WITH GENETIC ALGORITHM OF AIR SUSPENSION SYSTEM FOR ENHANCING RIDE COMFORT AND ROAD-HOLDING PERFORMANCES

Do Trong Tu — 2026-05-18

This study presents a systematic investigation of air suspension control strategies for vehicular applications, employing computational optimization techniques to enhance both ride comfort and road holding performances. A comprehensive simulation framework was developed, incorporating a quarter-truck model with nonlinear air spring dynamics subjected to spectrally rich road excitations. The research methodology integrates conventional PID control with multi-objective genetic algorithm optimization to determine Pareto-optimal solutions for conflicting performance criteria. Extensive numerical simulations reveal that the optimized controller achieves significant improvements in vibration attenuation (58.4% reduction in sprung mass displacement) while maintaining superior road contact characteristics (41.5% enhancement in tire-road contact force) compared to a passive system. The analysis provides quantitative insights into the fundamental trade-space between ride comfort-oriented and stability-focused control objectives, demonstrating that intelligent optimization approaches can effectively navigate these design compromises. Furthermore, the results establish practical boundaries for control system performance under realistic operating conditions, offering valuable guidelines for automotive suspension system design. The technical contributions include novel control architectures, advanced performance evaluation metrics, and a rigorous methodology for controller optimization in nonlinear air suspension systems. These findings advance the state-of-the-art in vehicle dynamics control and identify several promising avenues for future research in adaptive control systems and hybrid optimization algorithms.

SHEAR STRESSES OF HOLLOW CYLINDRICAL CONCRETE BEAMS MADE WITH RECYCLED CERAMICS AGGREGATES

Salam Salman Chiad Alharishawi — 2026-05-31

The main focus of the study presented in the work is an experimental investigation into the effects related to recycled ceramic coarse aggregates from the industrial brick waste on reinforced concrete beams (RCBs) shear behavior. For such an aim, a total of twelve concrete beams with 250mm height, 1200mm length, and 140mm width have been employed. A total of six Normal Concrete Beams (NCB) models made up of three Solid Normal Concrete Beams (SNCB) and Hollow Normal Concrete Beams (HNCB). Of the six models of Recycled Ceramic Concrete Beams (RCCB), there are also three Solid Recycled Ceramic Concrete Beams (SRCCB) and three Hollow Recycled Ceramic Concrete Beams (HRCCB). At such percentages of 0% and 30%, the weight related to coarse aggregate in concrete mixes is replaced with crushed ceramic that is acquired from building demolition wastes. A total of four points on the samples were examined for bending. The mid-span of the beam had the most deflection. The test evaluated the behavior related to beam concrete with the waste material by measuring the ultimate shear strength and diagonal cracking load. The experiment was designed to determine the impact of crushed ceramic on mechanical characteristics of RCBs. Additionally, the results show that, when compared to control samples, adding crushed ceramic improved the properties of the samples in shear behavior with reference to crushed ceramic concrete beams. Results have shown that the use of recycled ceramic aggregates caused a reduction in ultimate shear capacity of approximately 10–15% compared with conventional beams, while reducing stirrup spacing significantly enhanced shear resistance and crack control. Results have confirmed that recycled ceramic aggregates can be effectively used in reinforced concrete beams without significantly compromising structural performance. This study is limited to a 30% replacement ratio and monotonic static loading conditions. To the best of the authors’ knowledge, limited studies investigated combined effect of recycled ceramic aggregates and longitudinal hollow sections on shear behavior of reinforced concrete beams. This study provides additional information about the feasibility of utilizing ceramic waste in structural applications, thereby supporting sustainable construction practices and reducing environmental impacts associated with construction waste.

A REVIEW OF FAILURE MODES IN DYNAMIC POSITIONING VESSEL OPERATIONS

Hasanudin — 2026-05-31

Dynamic positioning (DP) is a key enabling technology for offshore drilling, subsea construction, and renewable energy operations, yet loss-of-position incidents continue to pose significant safety, environmental, and financial risks. This paper reviews failure modes in DP vessel operations over the 2015–2024 period by integrating a structured literature review, bibliometric co-occurrence analysis, and content analysis of incident and reliability studies. A PRISMA-style screening applied to Scopus and complementary databases identifies 26 relevant publications, of which 10 are selected as core analytical studies addressing DP failure mechanisms and reliability modelling. The synthesis indicates that technical failures in power generation and distribution, thruster and propulsion systems, and sensor and reference subsystems dominate DP incidents in drilling and construction operations. In addition, human and organisational factors are directly involved in approximately 20% of reported incidents based on a dataset of 311 DP cases, with higher proportions (up to 29.5%) observed in drilling and diving operations where human involvement is more direct. The variation across studies reflects differences in operational context, incident classification methodology, and dataset scope. Incident-based risk analyses further show that power generation failures and adverse environmental conditions disproportionately contribute to expected economic losses. Quantitative reliability and RAM studies consistently report lower failure probabilities for DP3 architectures compared with DP2, while identifying components such as busbars and wind sensors as critical risk contributors. Recent advances, including Bayesian networks, Monte Carlo–based RAM modelling, and the Dynamic Positioning Reliability Index (DP-RI), as well as LSTM-based real-time reliability prediction, demonstrate the potential of data-driven methods to combine incident statistics, equipment failure data, and operational conditions into dynamic risk indicators. Building on these insights, this paper proposes a hybrid framework integrating incident analytics, RAM modelling, and AI-enabled condition monitoring to support more resilient DP operations and to inform future research on human reliability, predictive maintenance, and decision-support integration with class and industry guidance.

SURFACE ROUGHNESS ANALYSIS OF SLM-PRODUCED TI-6AL-4V MILLING USING TAGUCHI DOE

Ikhsan Siregar — 2026-05-31

Selective Laser Melting (SLM) is an advanced additive manufacturing technique widely used to produce Ti-6Al-4V components with complex geometries and high material efficiency. However, SLM-produced Ti-6Al-4V commonly exhibits surface irregularities and a hardened microstructure, which necessitate post-processing by machining to achieve the required surface quality. Surface roughness is a critical parameter that influences the functional performance, fatigue life, and reliability of machined components, particularly in high-precision applications such as biomedical and aerospace engineering. This study investigates the surface roughness behaviour during milling of SLM-produced Ti-6Al-4V using a Taguchi-based Design of Experiments (DOE) approach. An L9 orthogonal array was employed to evaluate the effects of three machining parameters—spindle speed, feed rate, and depth of cut—each at three different levels. Surface roughness was assessed using the arithmetic mean roughness (Ra), measured with a contact-type surface profilometer. The experimental data were analysed using signal-to-noise (S/N) ratio analysis, supported by analysis of variance (ANOVA) to determine the contribution of each parameter. The results indicate that spindle speed is the most influential factor affecting surface roughness, contributing approximately 83.66% to the total variation. The optimal machining parameters for minimizing surface roughness were identified as a spindle speed of 7000 rpm, a depth of cut of 0.1 mm, and a feed rate of 1200 mm/min. These findings demonstrate the effectiveness of the Taguchi DOE method and provide practical guidance for optimizing milling parameters in post-processing of SLM-produced Ti-6Al-4V components.

METHODS AND TECHNIQUES FOR ESTIMATING CONCEPTUAL COSTS IN PUBLIC HIGHWAY PROJECTS: A SYSTEMATIC LITERATURE REVIEW

Milan Mirkovic — 2026-05-04

Accurate cost estimation during the conceptual phase of public highway construction is essential for effective transportation planning and budgeting. This paper reviews techniques and methods for initial cost estimation in highway projects, focusing on accuracy, trends, and key cost drivers. The research methodology involved selecting relevant papers by reviewing titles, abstracts, keywords, and full texts during the final stage. This process yielded 87 relevant publications and 33 cost estimation methods and techniques spanning the period from 1980 to 2025. The study found that artificial neural networks, machine learning, and regression analysis are the most used methods for predicting costs early in projects, with machine learning techniques showing the highest accuracy. Among the 184 cost drivers reviewed, 50 were grouped into five categories, providing a basis for selecting critical inputs during the planning phase of cost estimation for highway projects. A thorough review of the research literature highlights gaps and provides recommendations for future studies to focus on the use of advanced technologies to improve cost estimation. Specifically, employing GIS and 3D terrain models, along with geomechanical data, can help accurately calculate the quantities of all items in the bill of quantities. Such advancements are expected to enhance the precision of conceptual cost estimation in highway construction.