Hasil untuk "Mechanics of engineering. Applied mechanics"

Takács Richárd, Vacula Jirí, Prinsier Johan

Low-pressure exhaust gas recirculation (LP-EGR) is promising strategy for reducing NOx emissions in internal combustion engines, but it presents challenges due to water vapor condensation that can lead to compressor impeller erosion. This study presents a comprehensive thermodynamic analysis to quantify condensate formation and determine dew point temperatures across varying fuels and engine operating conditions. Novel mathematical models are developed to estimate specific humidity and condensation using only standard engine parameters, making them applicable without additional sensors. Results show that both fuel composition - particularly the hydrogen-to-carbon ratio - and LP-EGR rates strongly influence condensation. The study also highlights the impact of alternative fuels and ambient conditions on condensation risk. The developed methodology supports real-time evaluation of condensation potential and offers critical input for erosion risk assessment, component design, and emission control strategy optimization in modern powertrain.

Stephen A. Ajah, Lateef Akanji, Jefferson Gomes

Nuclear power station disasters like those at Chernobyl, Three Mile Island, and Fukushima Daiichi have highlighted how urgently improved nuclear safety is needed. This usually happened due to impeded cooling systems, resulting in heat accumulation, coolant boiling, and phase transformation leading to critical heat flux (CHF) events. Understanding bubble nucleation and dynamics during boiling heat transfer is crucial for ensuring the safety and reliability of pressurized water reactors (PWRs), particularly during postulated severe accident scenarios. Existing numerical models often struggle to accurately capture the complex multifluid interfaces and non-isothermal flow conditions inherent in these events, leading to potential inaccuracies in accident progression predictions. To address this gap, this study presents a novel numerical approach combining a high-order discontinuous Galerkin method (CVFEM), a conservative adaptive interface capturing method (CAICM), and a machine learning (ML) model (CVFEM+CAICM+ML/EoS). The ML component significantly enhances the accuracy of multifluid interface capturing in non-isothermal flows through precise fluid density evaluation, a key improvement over traditional methods. An adaptive mesh algorithm was implemented to optimize computational resource allocation, focusing on critical material interfaces. The model was validated against experimental data on single rising bubble dynamics, demonstrating its reliability. Analysis of dimensionless parameters, specifically the Galileo and Eötvös numbers, revealed the transition from laminar liquid flow to mixed vapor regimes, indicative of severe accident progression. This research provides a robust and validated tool for understanding complex boiling heat transfer mechanisms and bubble nucleation dynamics in PWRs, contributing to enhanced reactor safety.

Suniljit Singh Gill, Lam Rui Qi, Cheong De Yao et al.

Aviation is a highly energy-intensive sector, making it the second-biggest source of greenhouse gas emissions in the transportation sector, with road transport leading the way. Emissions continue to rise despite advancements in aircraft efficiency over the past six decades due to the increasing demand for air travel. Reviewing the reduction of carbon emissions in aviation is essential to protect the environment, drive innovation and secure a sustainable future in aviation. Stakeholders responsible for reducing carbon emissions are primarily found in the industrial sector. The challenges and opportunities related to reducing carbon emissions in aviation are investigated with a focus on Sustainable Aviation Fuels (SAF), advancements in fuel-efficient aircraft, and improvements in air traffic management. Studies have shown that using SAF, derived from renewable resources such as waste oils, algae, and municipal waste, can reduce lifecycle carbon emissions by up to 80% compared to conventional jet fuel. The use of SAF is limited due to cost and the difficulty in producing it. In addition, the use of electric and hydrogen-powered aircraft is highlighted, as it can revolutionise the industry by offering zero-emission alternatives for both short- and long-haul flights. Recommendations are provided to achieve net-zero emissions by 2050, aligning with the Sustainable Development Goals (SDGs) set by the United Nations, specifically SDG 11 (Sustainable Cities and Communities) and SDG 13 (Climate Action).

Mohammadreza Sheakholeslami, Mahdi Bayat Kazazi, Abbas Amoochi et al.

According to the properties of the pine tree trunk and its wide range of applications, finding its defects can play a vital role in reducing costs. Since the ultrasonic test is a non-destructive method, this method is an appropriate alternative to find defects in the pine tree trunks. Optimizing the ultrasonic non-destructive test is necessary because the correct choice of the ultrasonic test affecting factors increases the reliability of the test results. In this paper, at first, a simulation method for non-destructive ultrasonic tests in wooden parts using COMSOL Multiphysics software is presented. Both size and location of the defects have a considerable impact on the signal in the simulation. The defect size has a higher effect on signal amplitude and signal-to-noise ratio changes. So, the location of the defects is detected according to the amplitude of signals received in three points according to the method described in the paper. In the following, using the method of design of experiments, the effect of input factors containing frequency and signal amplitude on responses such as signal-to-noise ratio and loss of signal amplitude has been investigated. Results showed that these have an important effect on the output signal. Finally, the optimal simulation settings have been determined. According to the analysis, if the test frequency is 50 kHz and the amplitude of the input signal is 0.08 mm, the desirability value is equal to 100%, which indicates the high desirability of the ultrasonic test of wooden parts under the mentioned settings.

M. Akbar, A. Khan, Saima Rafi

Quantum computing systems harness the power of quantum mechanics to execute computationally demanding tasks more effectively than their classical counterparts. This has led to the emergence of Quantum Software Engineering (QSE), which focuses on unlocking the full potential of quantum computing systems. As QSE gains prominence, it seeks to address the evolving challenges of quantum software development by offering comprehensive concepts, principles, and guidelines. This paper aims to identify, prioritize, and develop a systematic decision-making framework of the challenging factors associated with QSE process execution. We conducted a literature survey to identify the challenging factors associated with QSE process and mapped them into 7 core categories. Additionally, we used a questionnaire survey to collect insights from practitioners regarding these challenges. To examine the relationships between core categories of challenging factors, we applied Interpretive Structure Modeling (ISM). Lastly, we applied fuzzy TOPSIS to rank the identified challenging factors concerning to their criticality for QSE process. We have identified 22 challenging factors of QSE process and mapped them to 7 core categories. The ISM results indicate that the ‘resources’ category has the most decisive influence on the other six core categories of the identified challenging factors. Moreover, the fuzzy TOPSIS indicates that ‘complex programming’, ‘limited software libraries’, ‘maintenance complexity’, ‘lack of training and workshops’, and ‘data encoding issues’ are the highest priority challenging factor for QSE process execution. Organizations using QSE could consider the identified challenging factors and their prioritization to improve their QSE process.

James Walker

Material is in motion all around us. Sometimes the relative motion leads to collisions, either accidental or intentional. The purpose of this book is to describe the mechanics of these collisions and the impact or penetration that follows, and to provide tools for determining the forces and deformation involved. Representative speeds of interest are shown in Table 1.1. This book is an applied mechanics text, meaning it develops the mathematical tools in physics and engineering that are required to solve impact and penetration problems. Our primary interest is in solid materials. Since impacts can lead to large forces, there will be large deformations, and so our mathematical tools and our material models will address large deformation. A big step is understanding the stress tensor – the relationship of the stress tensor to the strain tensor contains information about the stiffness and strength (resistance to shear) of solids. We will explore how metals deform, flow, and break. We will explore how yarns and fabrics undergo large deflections. Modern armors are made from metals, ceramics, fabrics, explosives, and space. Armors are interesting in that they are designed to be as light weight as possible, and during an impact event the armor material is utilized through large deflection and deformation all the way to material failure (material separation). The general framework we use is continuum mechanics. Continuum mechanics is the study of materials that can be viewed as a continuous material. This means that there is a smallest scale that it can reasonably address – on the order of tens of nanometers; otherwise atoms must be modeled. Our interest is typically in much larger scales, in macroscopic objects that are usually on the order of millimeters to meters. The basic equations of continuum mechanics will be developed – equations of conservation of mass, momentum, and energy. Then they will be applied. We will study waves in detail. All information in dynamic mechanical systems is conveyed through mechanical waves. In metals, the low pressure acoustical waves have a typical speed of 5 to 6 km/s, which is 15 to 18 times the speed of sound in air. High pressure shocks can travel faster than these acoustical waves. In modern mechanics we have a threefold approach to understanding, namely experiments, analytical modeling, and large-scale numerical simulations. As a preliminary step, basic material tests are performed and the response of materials is either fit to analytic forms or stored in tables. The material response is typically referred to as equation of state and constitutive models. These material models are then used in analytical modeling and large-scale numerical simulations. When it comes to applications to mechanics problems in impact and penetration, the analytical modeling approach makes assumptions about the geometry of the system response that reduce the problem to a handful of ordinary differential equations that are solved either explicitly or numerically. Large-scale numerical

A. Mohamadi, M. Behnia, Mahmoud Alneasan

Angela Minichiello, David Armijo, Sarbajit Mukherjee et al.

A robust and intuitive understanding of fluid mechanics—the applied science of fluid motion—is foundational within many engineering disciplines, including aerospace, chemical, civil, mechanical, naval, and ocean engineering. In‐depth knowledge of fluid mechanics is critical to safe and economical design of engineering applications employed globally everyday, such as automobiles, aircraft, and sea craft, and to meeting global 21st century engineering challenges, such as developing renewable energy sources, providing access to clean water, managing the environmental nitrogen cycle, and improving urban infrastructure. Despite the fundamental nature of fluid mechanics within the broader undergraduate engineering curriculum, students often characterize courses in fluid mechanics as mathematically onerous, conceptually difficult, and aesthetically uninteresting; anecdotally, undergraduates may choose to opt‐out of fluids engineering‐related careers based on their early experiences in fluids courses. Therefore, the continued development of new frameworks for engineering instruction in fluid mechanics is needed. Toward that end, this paper introduces mobile instructional particle image velocimetry (mI‐PIV), a low‐cost, open‐source, mobile application‐based educational tool under development for smartphones and tablets running Android. The mobile application provides learners with both technological capability and guided instruction that enables them to visualize and experiment with authentic flow fields in real time. The mI‐PIV tool is designed to generate interest in and intuition about fluid flow and to improve understanding of mathematical concepts as they relate to fluid mechanics by providing opportunities for fluids‐related active engagement and discovery in both formal and informal learning contexts.

G. Ren, R. Younis

Abstract Integrated models for fluid-driven fracture propagation and general multiphase flow in porous media are valuable to the study and engineering of several systems, including hydraulic fracturing, underground disposal of waste, and geohazard mitigation across such applications. This work extends the coupled model multiphase flow and poromechanical model of Ren et al. (2018) to admit fracture propagation (FP). The coupled XFEM-EDFM scheme utilizes a separate fracture mesh that is embedded on a static background mesh. The onset and dynamics of fracture propagation are governed by the equivalent stress intensity factor (SIF) criterion. A domain-integral method (J integral) is applied to compute this information. An adaptive time-marching scheme is proposed to rapidly restrict and grow temporal resolution to match the underlying time-scales. The proposed model is verified with analytical solutions, and shows the capability to accurately and adaptively co-simulate fluid transport and deformation as well as the propagation of multiple fractures.

S. Uzuner, LePing Li, S. Kucuk et al.

The menisci play a vital role in the mechanical function of knee joint. Unfortunately, meniscal tears often occur. Meniscectomy is a surgical treatment for meniscal tears, however, mechanical changes in the knee joint after meniscectomy is a risk factor to osteoarthritis. The objective of this study was to investigate the altered cartilage mechanics of different medial meniscectomies using a poromechanical model of the knee joint. The cartilaginous tissues were modeled as nonlinear fibril-reinforced porous materials with full saturation. A compressive creep load of ¾ body weight was applied in full extension of the right knee during 200 seconds standing. Four finite element models were developed to simulate different meniscectomies of the joint using the intact model as the reference for comparison. The modeling results showed a higher load support in the lateral than medial compartment in the intact joint, and the difference in the load share between the compartments was augmented with medial meniscectomy. Similarly, the contact and fluid pressures were higher in the lateral compartment. On the other hand, the medial meniscus in the normal joint experienced more loading than the lateral one. Furthermore, the contact pressure distribution changed with creep, resulting in a load transfer between cartilage and meniscus within each compartment while the total load born by the compartment remained unchanged. The present study has quantified the altered contact mechanics on the type and size of meniscectomies, which may be used to understand meniscal tear or support surgical decisions.

Weijian Wu, H. Kolstein, M. Veljković

Abstract The orthotropic steel decks (OSDs) are widely used in bridge engineering to support traffic loads. A possible crack, initiating from the weld toe of rib-to-deck welded joint and growing into the deck plate, is studied using linear elastic fracture mechanics. A detailed FE model is created and the results are compared with the fatigue tests published. Good agreement is found between beach marks from experiments and calculated crack fronts in FE. An engineering approach with the crack shape simplified as a semi-ellipse is applied. Geometric correction factors for a hand calculation method is proposed based on the parametric analysis. Using the proposed correction factors, Monte Carlo simulation is carried out with failure criteria defined with respect of the crack depth reaching “50%” of the deck thickness, “75%” of the deck thickness, and the failure criterion “2A FAD” according to BS7910. Predicted results using the failure criterion “75%” show good agreement with experimental data, for 5%, 50%, and 95% survival probabilities. Effects of initial crack shapes and sizes are discussed using the improved hand calculation model. Lower fatigue resistance is found when the initial crack is shallow or large. In addition to the standard weld geometry in which the weld profile is represented by a straight line, concave and convex arc shape weld profiles are studied. Fatigue resistance is improved in the case with assumption of concave arc weld profile. The difference of fatigue resistance between the cases with a straight line and convex arc weld profiles is small.

C. Scarth, S. Adhikari, P. H. Cabral et al.

Abstract It is important to account for inherent variability in the material properties in the design and analysis of engineering structures. These properties are typically not homogeneous, but vary across the spatial coordinates within a structure, as well as from specimen to specimen. This form of uncertainty is commonly modelled using random fields within the Stochastic Finite Element Method. Simulation within this framework can be complicated by the dependence of a random field’s correlation function upon the geometry of the domain over which it is defined. In this paper, a new method is proposed for simulating random fields over a general two-dimension curved surface, represented as a finite element mesh. The covariance function is parametrised using the geodesic distance, evaluated using the solution to the ‘discrete geodesic problem,’ and a point discretisation approach is subsequently applied in order to sample the random field at the nodes of the model. The major contribution of the present work is the development of a methodology for simulating random fields over curved surfaces of arbitrary geometry, with a focus upon non-intrusive application to industrial finite element models using ‘off the shelf’ commercial software. In order to demonstrate the potential impact of the proposed approach, the algorithm is applied in an uncertainty quantification case study concerning vibration and buckling of an industrial composite aircraft wing model.

Z. Pan, R. Ma, Dalei Wang et al.

T. Kling, Daniel Vogler, L. Pastewka et al.

Zifeng Li, Chaoyue Zhang, Guangming Song

W. Hucho

Zhan WANG, Chao ZHANG, Wen-jing DU et al.

In this study, the properties of the flat-plate film-cooling with transverse and arched trenches are investigated. The conjugate temperature field and thermal stress field were both predicted by the multi-field coupling method. In addition, the transverse trench configuration was investigated and compared as the benchmark case. The results show that the blockage effect formed by the arched trench is helpful to improve the coolant lateral coverage and thus the cooling performance. Meanwhile, the thermal stress concentration may be stronger due to the higher temperature gradient for the arched trench configuration. The distance between the downstream trench edges and the holes is of great importance to the cooling performance. The closer this distance, the more conductive to the blockage effect and the lateral coverage, which is helpful to improve the cooling performance. The distance between the upstream trench edges and the holes shows less impact on the cooling performance. Compared with the non-trench film cooling, the trenched models can form higher temperature gradient, so the thermal expansion near the film hole is more different from that in other region, which tend to form stronger stress concentration near the film hole. Compared with the transverse trench, the arched trench can deliver the coolant jet from the center line to the lateral side, which is helpful to form laterally coverage in the downstream region, especially under the higher blowing ratio. So the arched trench can form lower temperature gradient and relative uniform thermal expansion, which is helpful to decrease the stress concentration around the cooling hole.

Sugeng Slamet, Suyitno ., Indraswari Kusumaningtyas

The effect of tin composition and pouring temperature on the length of fluidity, microstructure, density, hardness, tensile strength and bending of Cu-Sn alloy with sand casting method has been investigated. Cu(20-24)wt.%Sn were casted in two different pouring temperatures (1000 ºC  and 1100 ºC)  in strip plate pattern sand mold. The sand mold has a length of 400 mm, width of 10 mm with a thickness of the mold cavity varied from 1.5 to 5 mm. The results show that the increase in composition (20-22) wt.% Sn decreases the length of fluidity while the composition (22-24) wt.% Sn length fluidity increase again. Increase of the pouring temperature and mold cavity thickness can increase the length of fluidity. Increasing tin composition and pouring temperature can increase the phase of α structure, porosity, hardness of the alloy and trigger the growth of dendrite columnar and secondary dendrite (DAS) microstructure.While the density, tensile strength and bending strength of the alloy tend to decrease. Increasing tin composition and pouring temperature in Cu(20-24) wt.% Sn caused the alloy to be more brittle.

Antonelli Dario, Bruno Giulia

Collaborative robots belong to the enabling technologies of Industry 4.0. They allow the set-up of semi-automatic workcells where robots and humans collaborate in the execution of complex tasks, with unprecedented flexibility if compared with standard robotic cells. This paper addresses some of the many issues that arise from introducing in the factory, not only a new workcell, but also a new working paradigm. The study considers the introduction of collaborative robots in a small production workcell. To increase the chances of success of the new cell, it proposes a method for firstly assigning tasks to human and robotics operators, based on the task characteristics and operator abilities, and then dynamically reassigning tasks to overcome disturbances or delays at the shop floor level. The justification of the method is that outages are frequent in small non-standardized productions, therefore offline optimized task assignment could be ineffective. The method is tested against an industrial case study and the results are discussed.

Sergey Fedorovich Podust, Denis Alexandrovich Kuklin

Rails refer to the intensive sources of the acoustic radiation. In rail traffic, rails to a large extent form an acoustic field at the work places of locomotive crews, and in the adjacent residential area nearby the railway track. A considerable extended line source is taken as a noise source model. Analytical dependences of sound pressure are obtained. At determining vibration velocities, the rail ballast layer is represented as a partially open-shell profile. It has different inertia moments in the vertical and horizontal planes (OZ and OY), and it lies on the elastic dissipative foundation. The force impact is considered as the load moving along the rail at the speed of the rake traffic. The obtained analytical dependences of sound pressure permit engineering and dissipative characteristics of the rail and ballast layer, and they are base ones for calculating the noise emitted by the rail. Besides, on the basis of the obtained dependences of sound pressure, it is possible to estimate the vibration levels on the rail, and to use the data to solve the problem of vibration impact on the residential buildings located close to the railway track.