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Appl. Mech., Volume 4, Issue 2 (June 2023) – 20 articles

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13 pages, 4779 KiB  
Article
Determining the Deformation Characteristics of Railway Ballast by Mathematical Modeling of Elastic Wave Propagation
by Dmytro Kurhan, Mykola Kurhan, Balázs Horváth and Szabolcs Fischer
Appl. Mech. 2023, 4(2), 803-815; https://doi.org/10.3390/applmech4020041 - 19 Jun 2023
Viewed by 1409
Abstract
The article solves the problem of theoretically determining the deformable characteristics of railway ballast, considering its condition through mathematical modeling. Different tasks require mathematical models with different levels of detail of certain elements. After a certain limit, excessive detailing only worsens the quality [...] Read more.
The article solves the problem of theoretically determining the deformable characteristics of railway ballast, considering its condition through mathematical modeling. Different tasks require mathematical models with different levels of detail of certain elements. After a certain limit, excessive detailing only worsens the quality of the model. Therefore, for many problems of the interaction between the track and the rolling stock, it is sufficient to describe the ballast as a homogeneous isotropic layer with a vertical elastic deformation. The elastic deformation of the ballast is formed by the deviation of individual elements; the ballast may have pollutants, the ballast may have places with different levels of compaction, etc. To be able to determine the general characteristics of the layer, a dynamic model of the stress–strain state of the system based on the dynamic problem of the theory of elasticity is applied. The reaction of the ballast to the dynamic load is modeled through the passage of elastic deformation waves. The given results can be applied in the models of the railway track in the other direction as initial data regarding the ballast layer. Full article
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24 pages, 19227 KiB  
Article
Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach
by Izabela Wardach-Święcicka, Sylwia Polesek-Karczewska and Dariusz Kardaś
Appl. Mech. 2023, 4(2), 779-802; https://doi.org/10.3390/applmech4020040 - 17 Jun 2023
Viewed by 1051
Abstract
In the face of threats related to energy supply and climate change, the use of biomass is gaining importance, particularly in distributed energy systems. Combustion of biomass, including residue biomass, is considered one of the routes to increase the share of renewables in [...] Read more.
In the face of threats related to energy supply and climate change, the use of biomass is gaining importance, particularly in distributed energy systems. Combustion of biomass, including residue biomass, is considered one of the routes to increase the share of renewables in energy generation. The modeling of gaseous phase reactions remains crucial in predicting the combustion behavior of biomass and pollutant emissions. However, their simulation becomes a challenging task due to the computational cost. This paper presents a numerical analysis of the combustion process of a gas mixture released during biomass decomposition in a domestic 25 kW coil-type boiler. Three types of biogenic fuels were taken into consideration. The work aimed at examining the available tools for modeling gas burning, thus the geometry of the system was limited only to the 2D case. The thermodynamic equilibrium composition of pyrolysis gas was determined and implemented in Ansys to simulate the process. The computational results showed the potential of detailed, but reduced, combustion mechanisms of CH4/CO/H2 mixtures in predicting the main process features. The mechanism involving 85 reactions appeared to be more reliable compared to that comprising 77 reactions, particularly for volatiles with higher H2 content, whilst offering an acceptable calculation time. The burning characteristics obtained for volatiles with less CH4 and more H2 are in good agreement with the real operation conditions reported for the boiler. Full article
(This article belongs to the Special Issue Applied Thermodynamics: Modern Developments (2nd Volume))
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16 pages, 5444 KiB  
Article
Effects of Hybridization on Tensile, Flexural, and Damage Behaviors of Flax/Carbon Epoxy Composites
by Mohamed Habibi and Luc Laperrière
Appl. Mech. 2023, 4(2), 763-778; https://doi.org/10.3390/applmech4020039 - 13 Jun 2023
Viewed by 1086
Abstract
In recent years, the hybridization of natural fibers with synthetic fibers has received much attention. This paper conducted an experimental study on the tensile and flexural behavior of unidirectional carbon/flax fiber reinforced epoxy composites and single flax fibers. Four hybridization rates were considered [...] Read more.
In recent years, the hybridization of natural fibers with synthetic fibers has received much attention. This paper conducted an experimental study on the tensile and flexural behavior of unidirectional carbon/flax fiber reinforced epoxy composites and single flax fibers. Four hybridization rates were considered for 16 reinforced layers in a symmetric staking sequence, with the carbon ply at the surface. The damage evolution under load increase was monitored using the acoustic emission (AE) technique. The Davies–Bouldin index and the K-means clustering algorithm were used to correlate the hybridization rates to the contribution of each damage mechanism to overall failure. AE monitoring of tensile and flexural behaviors showed that delamination and fiber breakage mechanisms dominate the composite failure, regardless of the hybridization rate. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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11 pages, 1642 KiB  
Article
Machine Learning-Assisted Tensile Modulus Prediction for Flax Fiber/Shape Memory Epoxy Hygromorph Composites
by Tarik Sadat
Appl. Mech. 2023, 4(2), 752-762; https://doi.org/10.3390/applmech4020038 - 09 Jun 2023
Cited by 1 | Viewed by 1738
Abstract
Flax fiber/shape memory epoxy hygromorph composites are a promising area of research in the field of biocomposites. This paper focuses on the tensile modulus of these composites and investigates how it is affected by factors such as fiber orientation (0° and 90°), temperature [...] Read more.
Flax fiber/shape memory epoxy hygromorph composites are a promising area of research in the field of biocomposites. This paper focuses on the tensile modulus of these composites and investigates how it is affected by factors such as fiber orientation (0° and 90°), temperature (20 °C, 40 °C, 60 °C, 80 °C, and 100 °C), and humidity (50% and fully immersed) conditions. Machine learning algorithms were utilized to predict the tensile modulus based on non-linearly dependent initial variables. Both decision tree (DT) and random forest (RF) algorithms were employed to analyze the data, and the results showed high coefficient of determination R2 values of 0.94 and 0.95, respectively. These findings demonstrate the effectiveness of machine learning in analyzing large datasets of mechanical properties in biocomposites. Moreover, the study revealed that the orientation of the flax fibers had the greatest impact on the tensile modulus value (with feature importance of 0.598 and 0.605 for the DT and RF models, respectively), indicating that it is a crucial factor to consider when designing these materials. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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23 pages, 1669 KiB  
Article
Applying the Action Principle of Classical Mechanics to the Thermodynamics of the Troposphere
by Ivan R. Kennedy and Migdat Hodzic
Appl. Mech. 2023, 4(2), 729-751; https://doi.org/10.3390/applmech4020037 - 05 Jun 2023
Viewed by 1421
Abstract
Advances in applied mechanics have facilitated a better understanding of the recycling of heat and work in the troposphere. This goal is important to meet practical needs for better management of climate science. Achieving this objective may require the application of quantum principles [...] Read more.
Advances in applied mechanics have facilitated a better understanding of the recycling of heat and work in the troposphere. This goal is important to meet practical needs for better management of climate science. Achieving this objective may require the application of quantum principles in action mechanics, recently employed to analyze the reversible thermodynamics of Carnot’s heat engine cycle. The testable proposals suggested here seek to solve several problems including (i) the phenomena of decreasing temperature and molecular entropy but increasing Gibbs energy with altitude in the troposphere; (ii) a reversible system storing thermal energy to drive vortical wind flow in anticyclones while frictionally warming the Earth’s surface by heat release from turbulence; (iii) vortical generation of electrical power from translational momentum in airflow in wind farms; and (iv) vortical energy in the destructive power of tropical cyclones. The scalar property of molecular action (@t mvds, J-sec) is used to show how equilibrium temperatures are achieved from statistical equality of mechanical torques (mv2 or mr2ω2); these are exerted by Gibbs field quanta for each kind of gas phase molecule as rates of translational action (d@t/dt ≡mr2ω/dt ≡ mv2). These torques result from the impulsive density of resonant quantum or Gibbs fields with molecules, configuring the trajectories of gas molecules while balancing molecular pressure against the density of field energy (J/m3). Gibbs energy fields contain no resonant quanta at zero Kelvin, with this chemical potential diminishing in magnitude as the translational action of vapor molecules and quantum field energy content increases with temperature. These cases distinguish symmetrically between causal fields of impulsive quanta (Σhν) that energize the action of matter and the resultant kinetic torques of molecular mechanics (mv2). The quanta of these different fields display mean wavelengths from 10−4 m to 1012 m, with radial mechanical advantages many orders of magnitude greater than the corresponding translational actions, though with mean quantum frequencies (v) similar to those of radial Brownian movement for independent particles (ω). Widespread neglect of the Gibbs field energy component of natural systems may be preventing advances in tropospheric mechanics. A better understanding of these vortical Gibbs energy fields as thermodynamically reversible reservoirs for heat can help optimize work processes on Earth, delaying the achievement of maximum entropy production from short-wave solar radiation being converted to outgoing long-wave radiation to space. This understanding may improve strategies for management of global changes in climate. Full article
(This article belongs to the Special Issue Applied Thermodynamics: Modern Developments (2nd Volume))
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14 pages, 2491 KiB  
Technical Note
Analytical Modeling for Mechanical Straightening Process of Case-Hardened Circular Shaft
by Shizhu Xing
Appl. Mech. 2023, 4(2), 715-728; https://doi.org/10.3390/applmech4020036 - 05 Jun 2023
Viewed by 1198
Abstract
Straightening has to be carried out in order to ensure the straightness of a shaft, as distortions exceed the tolerance limit. Since the straightening load is typically large enough to produce plastic and residual deformation, repeated straightening loading cycles are very likely to [...] Read more.
Straightening has to be carried out in order to ensure the straightness of a shaft, as distortions exceed the tolerance limit. Since the straightening load is typically large enough to produce plastic and residual deformation, repeated straightening loading cycles are very likely to induce cracks or fractures on the case-hardened shaft surface. In this study, in order to minimize repeated straightening cycles, an analytical straightening model is developed which calculates optimum stroke displacements corresponding to measured straightness errors so as to achieve the desired residual deflections and eliminate straightness errors. First, the hardness variation in the shaft radial direction is considered in the analytical model. Then, the proposed theoretical model is validated by numerical simulations. The results suggest that the analytically predicted stroke displacements and residual deflections agree very well with the numerical results when using induction-hardened SAE 4140 steel, and this signifies that the analytical straightening model developed in this study is capable of providing predictions of straightening stokes. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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16 pages, 2680 KiB  
Article
Free Vibration of Single-Walled Carbon Nanotubes Using Nonlocal Truncated Timoshenko-Ehrenfest Beam Theory
by Maria Anna De Rosa, Maria Lippiello, Antonella Onorato and Isaac Elishakoff
Appl. Mech. 2023, 4(2), 699-714; https://doi.org/10.3390/applmech4020035 - 12 May 2023
Cited by 1 | Viewed by 1371
Abstract
Carbon nanotubes with their outstanding mechanical, physical and electrical properties have stimulated a significant amount of scientific and technological research due to their uniqueness compared to conventional materials. As a result, an extensive study on their mechanical properties has been conducted, and the [...] Read more.
Carbon nanotubes with their outstanding mechanical, physical and electrical properties have stimulated a significant amount of scientific and technological research due to their uniqueness compared to conventional materials. As a result, an extensive study on their mechanical properties has been conducted, and the static and dynamic behavior of single- walled and multi-walled carbon nanotubes has been examined using Euler-Bernoulli and Timoshenko beam models. The main objective of this paper is to study the free vibration behaviour of single-walled carbon nanotubes (SWCNT) using the nonlocal truncated Timoshenko beam theory. According to the Hamilton principle, the equation of motion of Timoshenko single-walled carbon nanotubes is calculated taking into account the truncated theory; and the general corresponding boundary conditions are derived. Finally, some numerical examples are performed to evaluate the effects of the nonlocal coefficient and the length of the nanotube. The obtained results are validated by comparing them with those found in the literature, and they show the accuracy and efficiency of the developed model. Particularly, the results demonstrate that the present formulation is highly efficient and capable of satisfactorily describing the behavior of nanobeams. Full article
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31 pages, 8231 KiB  
Article
Explainable Artificial Intelligence (XAI) and Supervised Machine Learning-based Algorithms for Prediction of Surface Roughness of Additively Manufactured Polylactic Acid (PLA) Specimens
by Akshansh Mishra, Vijaykumar S. Jatti, Eyob Messele Sefene and Shivangi Paliwal
Appl. Mech. 2023, 4(2), 668-698; https://doi.org/10.3390/applmech4020034 - 12 May 2023
Cited by 4 | Viewed by 2178
Abstract
Structural integrity is a crucial aspect of engineering components, particularly in the field of additive manufacturing (AM). Surface roughness is a vital parameter that significantly influences the structural integrity of additively manufactured parts. This research work focuses on the prediction of the surface [...] Read more.
Structural integrity is a crucial aspect of engineering components, particularly in the field of additive manufacturing (AM). Surface roughness is a vital parameter that significantly influences the structural integrity of additively manufactured parts. This research work focuses on the prediction of the surface roughness of additive-manufactured polylactic acid (PLA) specimens using eight different supervised machine learning regression-based algorithms. For the first time, explainable AI techniques are employed to enhance the interpretability of the machine learning models. The nine algorithms used in this study are Support Vector Regression, Random Forest, XGBoost, AdaBoost, CatBoost, Decision Tree, the Extra Tree Regressor, the Explainable Boosting Model (EBM), and the Gradient Boosting Regressor. This study analyzes the performance of these algorithms to predict the surface roughness of PLA specimens, while also investigating the impacts of individual input parameters through explainable AI methods. The experimental results indicate that the XGBoost algorithm outperforms the other algorithms with the highest coefficient of determination value of 0.9634. This value demonstrates that the XGBoost algorithm provides the most accurate predictions for surface roughness compared with other algorithms. This study also provides a comparative analysis of the performance of all the algorithms used in this study, along with insights derived from explainable AI techniques. Full article
(This article belongs to the Special Issue Early Career Scientists’ (ECS) Contributions to Applied Mechanics)
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24 pages, 991 KiB  
Review
Management of Intracranial Hemorrhage in the Setting of Mechanical Heart Valve Replacement Therapy
by Sahar Khan, Faiz Syed and Milan Toma
Appl. Mech. 2023, 4(2), 644-667; https://doi.org/10.3390/applmech4020033 - 11 May 2023
Cited by 2 | Viewed by 3734
Abstract
The management of an intracranial hemorrhage in patients receiving anticoagulant therapy presents a significant challenge for medical professionals. Anticoagulant treatment is intended to prevent blood clotting, but it can worsen active brain bleeds. Despite this risk, avoiding the prothrombotic state caused by mechanical [...] Read more.
The management of an intracranial hemorrhage in patients receiving anticoagulant therapy presents a significant challenge for medical professionals. Anticoagulant treatment is intended to prevent blood clotting, but it can worsen active brain bleeds. Despite this risk, avoiding the prothrombotic state caused by mechanical heart valves remains crucial. Guidelines on managing this issue are currently lacking, prompting a review that delves into embryonic development and anatomical functions of heart valves, valve replacement therapy for diseased valves, and the need for anticoagulants. Ultimately, recent literature and cases inform discussion regarding how best to manage intracranial hemorrhages in patients with mechanical heart valves. The expectation is that this examination will offer valuable perspectives on the handling of intracranial bleeding among individuals with mechanical heart valves and stimulate additional investigations in this intricate domain, particularly through the lens of applied mechanics. Full article
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59 pages, 5841 KiB  
Article
Employment of Fracture Mechanics Criteria for Accurate Assessment of the Full Set of Elastic Constants of Orthorhombic/Tetragonal Mono-Crystalline YBCO
by Reaz A. Chaudhuri
Appl. Mech. 2023, 4(2), 585-643; https://doi.org/10.3390/applmech4020032 - 08 May 2023
Viewed by 1365
Abstract
The effect of elastic constants, cij, on the nature (easy or difficult) of a cleavage system in mono-crystalline YBa2Cu3O7−δ is investigated by employing a novel three-dimensional eigenfunction expansion technique, based in part on the separation of [...] Read more.
The effect of elastic constants, cij, on the nature (easy or difficult) of a cleavage system in mono-crystalline YBa2Cu3O7−δ is investigated by employing a novel three-dimensional eigenfunction expansion technique, based in part on the separation of the thickness variable and partly on a modified Frobenius-type series expansion technique in conjunction with Eshelby–Stroh formalism. Out of the three available, complete sets of elastic constants, only the experimental measurements using resonant ultrasound spectroscopy merit serious attention, despite reported values of c12 and, to a lesser extent, c66 being excessively high. The present investigation considers six through-thickness crack systems weakening orthorhombic mono-crystalline Yttrium barium copper oxide (YBCO) plates. More importantly, the present investigation establishes sufficient conditions for crack path stability/instability, which entail a cleavage system being easy or difficult, i.e., whether a crack would propagate in its original plane/direction or deflect to a different one. This criterion of fracture mechanics is then employed for accurate determination of the full set of elastic constants of superconducting mono-crystalline YBCO. Finally, heretofore unavailable results pertaining to the through-thickness variations of stress intensity factors and energy release rates for a crack corresponding to symmetric and skew-symmetric hyperbolic cosine loads, which also satisfy the boundary conditions on the plate surfaces, bridge a longstanding gap. Full article
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18 pages, 5393 KiB  
Article
Τopology Optimization under a Single Displacement Constraint Using a Strain Energy Criterion
by Christopher G. Provatidis
Appl. Mech. 2023, 4(2), 567-584; https://doi.org/10.3390/applmech4020031 - 05 May 2023
Viewed by 1225
Abstract
Based on a previous concept that has been successfully applied to the sizing optimization of truss and frame structures, this work extends and improves the strain energy criterion in the topology optimization of 2D continuum structures under a single displacement constraint. To make [...] Read more.
Based on a previous concept that has been successfully applied to the sizing optimization of truss and frame structures, this work extends and improves the strain energy criterion in the topology optimization of 2D continuum structures under a single displacement constraint. To make the proposed methodology transparent to other researchers and at the same time meaningful, the numerical value of the displacement constraint was taken to be equal to that obtained through the well-known Solid Isotropic Material with Penalization (SIMP) method under the same boundary conditions and the same external forces. The proposed method is more efficient than the SIMP method while leading to topologies very close to those obtained by the latter. Full article
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39 pages, 68312 KiB  
Article
A Numerically Efficient Method to Assess the Elastic–Plastic Strain Energy Density of Notched and Imperfective Cast Steel Components
by Michael Horvath, Matthias Oberreiter and Michael Stoschka
Appl. Mech. 2023, 4(2), 528-566; https://doi.org/10.3390/applmech4020030 - 27 Apr 2023
Viewed by 2004
Abstract
The fatigue strength of cast steel components is severely affected by manufacturing process-based bulk and surface imperfections. As these defect structures possess an arbitrary spatial shape, the utilization of local assessment methods is encouraged to design for service strength. This work applies the [...] Read more.
The fatigue strength of cast steel components is severely affected by manufacturing process-based bulk and surface imperfections. As these defect structures possess an arbitrary spatial shape, the utilization of local assessment methods is encouraged to design for service strength. This work applies the elastic–plastic strain energy density concept to study the fatigue strength properties of a high-strength cast steel alloy G12MnMo7-4+QT. A fatigue design limit curve is derived based on non-linear finite element analyses which merges experimental high-cycle fatigue results of unnotched and notched small-scale specimens tested at three different stress ratios into a unique narrow scatter band characterized by a scatter index of 1:TΔW¯(t)=2.43. A comparison to the linear–elastic assessment conducted in a preceding study reveals a significant improvement in prediction accuracy which is assigned to the consideration of the elastic–plastic material behaviour. In order to reduce computational effort, a novel approximation is presented which facilitates the calculation of the elastic–plastic strain energy density based on linear–elastic finite element results and Neuber’s concept. Validation of the assessment framework reveals a satisfying agreement to non-linear simulation results, showing an average root mean square deviation of only approximately eight percent in terms of total strain energy density. In order to study the effect of bulk and surface imperfections on the fatigue strength of cast steel components, defect-afflicted large-scale specimens are assessed by the presented elastic–plastic framework, yielding fatigue strength results which merge into the scatter band of the derived design limit curve. As the conducted fatigue assessment is based solely on linear–elastic two-dimensional simulations, the computational effort is substantially decreased. Within the present study, a reduction of approximately 400 times in computation time is observed. Hence, the established assessment framework presents an engineering-feasible method to evaluate the fatigue life of imperfective cast steel components based on rapid total strain energy density calculations. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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14 pages, 2175 KiB  
Article
Delamination Behavior of Highly Stretchable Soft Islands Multi-Layer Materials
by Philipp Kowol, Swantje Bargmann, Patrick Görrn and Jana Wilmers
Appl. Mech. 2023, 4(2), 514-527; https://doi.org/10.3390/applmech4020029 - 26 Apr 2023
Cited by 1 | Viewed by 1230
Abstract
Stretchable electronics rely on sophisticated structural designs to allow brittle metallic conductors to adapt to curved or moving substrates. Patterns of soft islands and stable cracks in layered silver-PDMS composites provide exceptional stretchability by means of strain localization as the cracks open and [...] Read more.
Stretchable electronics rely on sophisticated structural designs to allow brittle metallic conductors to adapt to curved or moving substrates. Patterns of soft islands and stable cracks in layered silver-PDMS composites provide exceptional stretchability by means of strain localization as the cracks open and the islands strain. To investigate the reliability and potential failure modes, we study the initiation and propagation of delamination in dependence of structure geometry and quality of the metal-polymer bonding. Our numerical experiments show a well-bonded metal film to be under no risk of delamination. Even weakly bonded metal films sustain moderate strains well above the limits of classical electronic materials before the onset of delamination in the soft islands structures. If delamination occurs, it does so in predictable patterns that retain functionality over a remarkable strain range in the double-digit percent range before failure, thus, providing safety margins in applications. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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21 pages, 2304 KiB  
Article
Effect of Control Parameters on Hybrid Electric Propulsion UAV Performance for Various Flight Conditions: Parametric Study
by Amine Benmoussa and Pedro Vieira Gamboa
Appl. Mech. 2023, 4(2), 493-513; https://doi.org/10.3390/applmech4020028 - 25 Apr 2023
Cited by 3 | Viewed by 1324
Abstract
Nowadays, great efforts of ongoing research are devoted to hybrid-electric propulsion technology that offers various benefits, such as reduced noise and pollution emissions and enhanced aircraft performance and fuel efficiency. The ability to estimate the performance of an aircraft in any flight situation [...] Read more.
Nowadays, great efforts of ongoing research are devoted to hybrid-electric propulsion technology that offers various benefits, such as reduced noise and pollution emissions and enhanced aircraft performance and fuel efficiency. The ability to estimate the performance of an aircraft in any flight situation in which it may operate is essential for aircraft development. In the current study, a simulation model was developed that allows estimating the flight performance and analyzing the mission of a fixed-wing multi-rotor Unmanned Aerial Vehicle (UAV) with a hybrid electric propulsion system (HEPS), with both conventional and Vertical Takeoff and Landing (VTOL) capabilities. The control is based on the continuous specification of pitch angle, propulsion thrust, and lift thrust to achieve the required conditions of a given flight segment. Six different missions were considered to analyze the effect of control parameters exhibiting the most influence on the UAV mission performance. An appropriate set of control parameters was selected through a multidimensional parametric study. The results show that the control parameters, if not well tuned, affect the mission performance: for example, in the deceleration transition, a longer time to reduce the cruise speed to stand still may be the result because the controller struggles to adjust the pitch angle. In addition, the implemented methodology captures the effects of transient maneuvers, unlike typical quasi-static analysis without the complexity of full simulation models. Full article
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17 pages, 12470 KiB  
Article
Symbolic Parametric Representation of the Area and the Second Moments of Area of Periodic B-Spline Cross-Sections
by Martin Denk, Michael Jäger and Sandro Wartzack
Appl. Mech. 2023, 4(2), 476-492; https://doi.org/10.3390/applmech4020027 - 21 Apr 2023
Viewed by 1361
Abstract
The calculation of moments of area is one of the most fundamental aspects of engineering mechanics for calculating the properties of beams or for the determination of invariants in different kind of geometries. While a variety of shapes, such as circles, rectangles, ellipses, [...] Read more.
The calculation of moments of area is one of the most fundamental aspects of engineering mechanics for calculating the properties of beams or for the determination of invariants in different kind of geometries. While a variety of shapes, such as circles, rectangles, ellipses, or their combinations, can be described symbolically, such symbolic expressions are missing for freeform cross-sections. In particular, periodic B-spline cross-sections are suitable for an alternative beam cross-section, e.g., for the representation of topology optimization results. In this work, therefore, a symbolic description of the moments of area of various parametric representations of such B-splines is computed. The expressions found are then compared with alternative computational methods and checked for validity. The resulting equations show a simple method that can be used for the fast conceptual computation of such moments of area of periodic B-splines. Full article
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16 pages, 2544 KiB  
Article
AFM Indentation on Highly Heterogeneous Materials Using Different Indenter Geometries
by Stylianos Vasileios Kontomaris, Andreas Stylianou, Georgios Chliveros and Anna Malamou
Appl. Mech. 2023, 4(2), 460-475; https://doi.org/10.3390/applmech4020026 - 18 Apr 2023
Cited by 3 | Viewed by 1601
Abstract
Hertzian mechanics is the most frequently used theory for data processing in Atomic Force Microscopy (AFM) indentation experiments on soft biological samples, due to its simplicity and significant scientific results previously published. For instance, using the Hertz model, it has been proven that [...] Read more.
Hertzian mechanics is the most frequently used theory for data processing in Atomic Force Microscopy (AFM) indentation experiments on soft biological samples, due to its simplicity and significant scientific results previously published. For instance, using the Hertz model, it has been proven that there are significant differences in the mechanical properties of normal and cancerous tissues and that cancer cells’ invasive properties are correlated with their nanomechanical properties. However, many scientists are skeptical regarding the applicability of the Hertz theory to biological materials, as they are highly heterogeneous. The main critical question to be addressed is “what do we calculate” when fitting the force-indentation data to Hertz equations. Previous studies have shown that when using cylindrical, parabolic, or conical indenters, the fitting parameter is the average Young’s modulus. In this paper, it is demonstrated that it is also valid to fit equations derived from Hertzian mechanics to force-indentation data when testing soft, heterogeneous samples for any indenter geometry. The fitting factor calculated through this approach always represents the average Young’s modulus for a specific indentation depth. Therefore, Hertzian mechanics can be extended to soft heterogeneous materials, regardless of the indenter’s shape. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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15 pages, 4098 KiB  
Article
Variation of Elastic Stiffness Parameters of Granitic Rock during Loading in Uniaxial Compressive Test
by Samad Narimani, Seyed Morteza Davarpanah, László Kovács and Balázs Vásárhelyi
Appl. Mech. 2023, 4(2), 445-459; https://doi.org/10.3390/applmech4020025 - 13 Apr 2023
Cited by 1 | Viewed by 1647
Abstract
Any rock mechanics’ design inherently involves determining the deformation characteristics of the rock material. The purpose of this study is to offer equations for calculating the values of bulk modulus (K), elasticity modulus (E), and rigidity modulus (G) throughout the loading of the [...] Read more.
Any rock mechanics’ design inherently involves determining the deformation characteristics of the rock material. The purpose of this study is to offer equations for calculating the values of bulk modulus (K), elasticity modulus (E), and rigidity modulus (G) throughout the loading of the sample until failure. Also, the Poisson’s ratio, which is characterized from the stress–strain curve, has a significant effect on the rigidity and bulk moduli. The results of a uniaxial compressive (UCS) test on granitic rocks from the Morágy (Hungary) radioactive waste reservoir site were gathered and examined for this purpose. The fluctuation of E, G, and K has been the subject of new linear and nonlinear connections. The proposed equations are parabolic in all of the scenarios for the Young’s modulus and shear modulus, the study indicates. Furthermore, the suggested equations for the bulk modulus in the secant, average, and tangent instances are also nonlinear. Moreover, we achieved correlations with a high determination factor for E, G, and K in three different scenarios: secant, tangent, and average. It is particularly intriguing to observe that the elastic stiffness parameters exhibit strong correlation in the results. Full article
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24 pages, 1410 KiB  
Review
Impact Testing on the Pristine and Repaired Composite Materials for Aerostructures
by Zoe E. C. Hall, Jun Liu, Richard A. Brooks, Haibao Liu and John P. Dear
Appl. Mech. 2023, 4(2), 421-444; https://doi.org/10.3390/applmech4020024 - 12 Apr 2023
Viewed by 1552
Abstract
Aircraft technologies and materials have been developing and improving drastically over the last hundred years. Over the last three decades, an interest in the use of composites for external structures has become prominent. For this to be possible, thorough research on the performance [...] Read more.
Aircraft technologies and materials have been developing and improving drastically over the last hundred years. Over the last three decades, an interest in the use of composites for external structures has become prominent. For this to be possible, thorough research on the performance of composite materials, specifically the impact performance, have been carried out. For example, research of impact testing for pristine carbon-reinforced epoxy composites mentions matrix cracks, fibre fracture, and delamination as the failure modes that require monitoring. In addition, thorough testing has been carried out on composites repaired with an adhesive bond to observe the effects of conditioning on the adhesively bonded repair. The results suggest there are no major changes in the adhesive under the testing condition. By reviewing the impact testing on the pristine and repaired composite materials for aerostructures, this paper aims to illustrate the main findings and also explore the potential future work in this research scope. Full article
(This article belongs to the Special Issue Feature Papers in Material Mechanics)
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14 pages, 6156 KiB  
Article
Structural Design and Numerical Analysis of Hoisting Device of Test Bed for Aircraft Engine
by Hyunbum Park
Appl. Mech. 2023, 4(2), 407-420; https://doi.org/10.3390/applmech4020023 - 12 Apr 2023
Cited by 1 | Viewed by 1345
Abstract
In this work, a test bed and stand structure were designed for the thrust test of an aircraft. The engine test rig consists of a thrust stand, test bed, transport system, and hoisting device. In this study, structural design and analysis of the [...] Read more.
In this work, a test bed and stand structure were designed for the thrust test of an aircraft. The engine test rig consists of a thrust stand, test bed, transport system, and hoisting device. In this study, structural design and analysis of the stand and bed for engine thrust test equipment were performed. The stand structure supported the engine, and the test bed moved the thrust test equipment and the engine. Structural design loads were defined by analyzing the operating conditions. Structural analysis was performed based on the structural design results. As a result of analyzing the structural safety against thrust, which is the main design load, it was considered to be sufficiently safe. Finally, the target structure was manufactured to verify the design result. Full article
(This article belongs to the Topic Advances on Structural Engineering, 2nd Volume)
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18 pages, 5916 KiB  
Article
Analysis and Design of Lateral Framing Systems for Multi-Story Steel Buildings
by Husam Al Dughaishi, Jawad Al Lawati, Moad Alosta, Shaker Mahmood, Mohamed Faisal Al-Kazee, Nur Izzi Md Yusoff and Abdalrhman Milad
Appl. Mech. 2023, 4(2), 389-406; https://doi.org/10.3390/applmech4020022 - 27 Mar 2023
Viewed by 4104
Abstract
This study focused on identifying the most appropriate structural system for multi-story buildings and analyzing its response to lateral loads. The study analyzed and compared the different structural systems to determine the most suitable option. The study aims to utilize three lateral framing [...] Read more.
This study focused on identifying the most appropriate structural system for multi-story buildings and analyzing its response to lateral loads. The study analyzed and compared the different structural systems to determine the most suitable option. The study aims to utilize three lateral framing systems (moment, braced, and diagrid) in order to investigate which system needs the least amount of steel to meet the design requirements. Thus, in order to determine the estimated steel savings of this system as compared to the moment and braced frames, the four-story and eight-story buildings that are 96′ × 96′ in the plane and utilize moment frames, braced frame, and diagrid framing structural systems are presented. Based on the American Society of Civil Engineers (ASCE) 7–10, load combinations are considered for the designs, and the RAM structural analysis is used for the modeling and analysis of the structural systems. The findings of this study’s illustrations were the optimum for the analysis of wind of 176 kips and seismic loads of 122 kips, the building’s lateral displacements, which were the lowest at 0.045 inches, the story drift, the story stiffness, and the story shear for each structural system. In addition, the diagrid system also had the least amount of shear for all the stories, suggesting that it is better able to manage the lateral forces. These results indicate that the diagrid system is a more efficient structural system and can be recommended for use in multi-story buildings. Full article
(This article belongs to the Special Issue Feature Papers in Applied Mechanics)
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