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Τopology Optimization under a Single Displacement Constraint Using a Strain Energy Criterion Τopology基于应变能准则的单位移约束优化
1区 工程技术 Q1 MECHANICS Pub Date : 2023-05-05 DOI: 10.3390/applmech4020031
Christopher G. Provatidis
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.
本文基于先前已成功应用于桁架和框架结构尺寸优化的概念,扩展和改进了单一位移约束下二维连续体结构拓扑优化中的应变能准则。为了使所提出的方法对其他研究人员透明并同时具有意义,在相同的边界条件和相同的外力下,将位移约束的数值设为等于通过著名的固体各向同性材料惩罚(SIMP)方法得到的数值。该方法比SIMP方法更有效,同时得到的拓扑结构与SIMP方法非常接近。
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引用次数: 0
A Numerically Efficient Method to Assess the Elastic–Plastic Strain Energy Density of Notched and Imperfective Cast Steel Components 一种评估缺口和缺陷铸钢构件弹塑性应变能密度的有效数值方法
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-27 DOI: 10.3390/applmech4020030
M. Horvath, M. Oberreiter, M. Stoschka
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.
铸钢构件的疲劳强度受到制造工艺的体积和表面缺陷的严重影响。由于这些缺陷结构具有任意的空间形状,因此鼓励采用局部评估方法进行使用强度设计。本文应用弹塑性应变能密度概念研究了高强度铸钢合金G12MnMo7-4+QT的疲劳强度特性。基于非线性有限元分析,将三种不同应力比下无缺口和有缺口小尺寸试样的高周疲劳试验结果合并为一个独特的窄散射带,其散射指数为1:TΔW¯(t)=2.43,导出了疲劳设计极限曲线。与先前研究中进行的线弹性评估的比较表明,由于考虑了材料的弹塑性行为,预测精度有了显着提高。为了减少计算量,提出了一种新的基于线弹性有限元结果和Neuber概念的弹塑性应变能密度近似方法。评估框架的验证显示了与非线性模拟结果的令人满意的一致性,在总应变能密度方面显示平均均方根偏差仅约为8%。为了研究体缺陷和表面缺陷对铸钢构件疲劳强度的影响,采用本文提出的弹塑性框架对大型铸钢构件进行了疲劳强度评估,得到的疲劳强度结果与导出的设计极限曲线的散射带合并。由于所进行的疲劳评估仅基于线弹性二维模拟,因此大大减少了计算量。在本研究中,计算时间减少了大约400倍。因此,所建立的评估框架为基于快速总应变能密度计算的不完善铸钢构件疲劳寿命评估提供了一种工程可行的方法。
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引用次数: 0
Delamination Behavior of Highly Stretchable Soft Islands Multi-Layer Materials 高拉伸软岛多层材料的分层行为
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-26 DOI: 10.3390/applmech4020029
Philipp Kowol, S. Bargmann, P. Görrn, J. Wilmers
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.
可拉伸电子产品依靠复杂的结构设计,使脆性金属导体适应弯曲或移动的基板。层状银- pdms复合材料中的软岛和稳定裂纹模式通过裂纹打开和岛应变的应变局部化提供了卓越的拉伸性。为了研究可靠性和潜在的失效模式,我们研究了脱层的发生和扩展与金属-聚合物键合的结构几何形状和质量的关系。我们的数值实验表明,结合良好的金属膜没有分层的危险。即使是弱键合的金属薄膜,在软岛结构中发生分层之前,也能承受远高于经典电子材料极限的适度应变。如果发生分层,它会以可预测的模式发生,在故障发生之前,在一个显着的两位数的应变范围内保持功能,因此,在应用中提供安全边界。
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引用次数: 1
Effect of Control Parameters on Hybrid Electric Propulsion UAV Performance for Various Flight Conditions: Parametric Study 控制参数对混合动力推进无人机不同飞行条件下性能影响的参数化研究
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-25 DOI: 10.3390/applmech4020028
A. Benmoussa, P. Gamboa
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.
如今,人们正在努力研究混合动力推进技术,它提供了各种好处,如降低噪音和污染排放,提高飞机性能和燃油效率。在飞机可能运行的任何飞行情况下评估飞机性能的能力对飞机开发至关重要。在目前的研究中,开发了一个仿真模型,可以估计具有混合动力推进系统(HEPS)的固定翼多旋翼无人机(UAV)的飞行性能和分析任务,具有传统和垂直起降(VTOL)能力。该控制是基于连续规范的俯仰角、推进推力和升力推力,以达到给定飞行段的所需条件。考虑了6种不同的任务,分析了对无人机任务性能影响最大的控制参数的影响。通过多维参数研究选择了一组合适的控制参数。结果表明,控制参数如果调整不好,会影响任务性能:例如,在减速过渡阶段,由于控制器难以调整俯仰角,可能导致降低巡航速度到静止的时间较长。此外,所实现的方法捕获了瞬态机动的影响,不像典型的准静态分析,没有完整仿真模型的复杂性。
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引用次数: 1
Symbolic Parametric Representation of the Area and the Second Moments of Area of Periodic B-Spline Cross-Sections 周期b样条截面面积和二次矩的符号参数表示
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-21 DOI: 10.3390/applmech4020027
M. Denk, Michael Jäger, S. Wartzack
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.
面积矩的计算是工程力学中计算梁的性能或确定不同几何形状的不变量的最基本方面之一。虽然各种形状,如圆形、矩形、椭圆或它们的组合,都可以用符号来描述,但这种符号表达对于自由形状的横截面来说是缺失的。特别是,周期b样条截面适用于替代梁截面,例如,用于拓扑优化结果的表示。因此,在这项工作中,计算了这种b样条的各种参数表示的面积矩的符号描述。然后将找到的表达式与其他计算方法进行比较,并检查其有效性。所得到的方程提供了一种简单的方法,可用于快速计算周期b样条曲线的面积矩。
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引用次数: 0
AFM Indentation on Highly Heterogeneous Materials Using Different Indenter Geometries 使用不同压头几何形状的高度非均匀材料的AFM压痕
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-18 DOI: 10.3390/applmech4020026
S. Kontomaris, A. Stylianou, G. Chliveros, A. Malamou
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.
赫兹力学是软生物样品原子力显微镜(AFM)压痕实验中最常用的数据处理理论,由于它的简单性和先前发表的重要科学结果。例如,利用赫兹模型,已经证明了正常组织和癌组织的力学特性存在显著差异,癌细胞的侵袭特性与其纳米力学特性相关。然而,许多科学家对赫兹理论在生物材料中的适用性持怀疑态度,因为它们是高度异质的。当将力压痕数据拟合到赫兹方程时,要解决的主要关键问题是“我们计算什么”。先前的研究表明,当使用圆柱形、抛物线形或锥形压头时,拟合参数为平均杨氏模量。在本文中,证明了在测试软的、非均匀的压头几何形状的样品时,用赫兹力学推导的方程拟合力压痕数据也是有效的。通过这种方法计算的拟合因子总是代表特定压痕深度的平均杨氏模量。因此,赫兹力学可以扩展到柔软的非均质材料,而不考虑压头的形状。
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引用次数: 3
Variation of Elastic Stiffness Parameters of Granitic Rock during Loading in Uniaxial Compressive Test 花岗岩单轴压缩加载过程中弹性刚度参数的变化
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-13 DOI: 10.3390/applmech4020025
S. Narimani, Seyed Morteza Davarpanah, L. Kovács, B. Vásárhelyi
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.
任何岩石力学设计本质上都涉及确定岩石材料的变形特性。本研究的目的是提供计算试样在整个加载过程中直至破坏的体积模量(K)、弹性模量(E)和刚度模量(G)值的公式。同时,由应力-应变曲线表征的泊松比对材料的刚度和体积模量有显著影响。为此目的收集并检查了Morágy(匈牙利)放射性废物储存库场址花岗岩的单轴压缩(UCS)试验结果。E、G和K的波动已成为新的线性和非线性联系的主题。研究表明,对于杨氏模量和剪切模量,所提出的方程在所有情况下都是抛物线型的。此外,在正割、平均和正切情况下提出的体积模量方程也是非线性的。此外,我们在三种不同的情况下实现了E、G和K的高决定因子的相关性:正切、正切和平均。特别有趣的是,弹性刚度参数在结果中表现出很强的相关性。
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引用次数: 2
Structural Design and Numerical Analysis of Hoisting Device of Test Bed for Aircraft Engine 航空发动机试验台提升装置结构设计与数值分析
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-12 DOI: 10.3390/applmech4020023
Hyunbum Park
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.
本文设计了某型飞机推力试验的试验台和试验台结构。发动机试验台由推力架、试验台、运输系统和起重装置组成。本文对发动机推力试验台机架和试验台进行了结构设计和分析。机架结构支撑发动机,试验台移动推力试验设备和发动机。通过对工况的分析,确定了结构设计荷载。根据结构设计结果进行结构分析。通过对主要设计荷载——推力的结构安全性分析,认为该结构是足够安全的。最后对目标结构进行了制造,验证了设计结果。
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引用次数: 1
Impact Testing on the Pristine and Repaired Composite Materials for Aerostructures 航空结构原始和修复复合材料的冲击试验
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-04-12 DOI: 10.3390/applmech4020024
Z. Hall, Jun Liu, Richard A. Brooks, Haibao Liu, J. Dear
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.
在过去的一百年里,飞机技术和材料一直在飞速发展和改进。在过去的三十年中,在外部结构中使用复合材料的兴趣已经变得突出。为了实现这一点,对复合材料的性能,特别是冲击性能进行了深入的研究。例如,对原始碳增强环氧复合材料的冲击测试研究将基体裂纹、纤维断裂和分层作为需要监测的失效模式。此外,对粘接修复的复合材料进行了深入的测试,观察了调理对粘接修复的影响。结果表明,在测试条件下,胶粘剂没有发生大的变化。本文通过对航空结构原始和修复复合材料冲击试验的回顾,阐述了研究的主要成果,并对未来的工作进行了展望。
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引用次数: 0
Multi-body Hydrodynamic Interactions in Fish-like Swimming 类鱼游泳中的多体水动力相互作用
IF 14.3 1区 工程技术 Q1 MECHANICS Pub Date : 2023-03-28 DOI: 10.1115/1.4062219
M. Timm, R. Pandhare, Hassan Masoud
Many animals in nature travel in groups either for protection, survival, or endurance. Among these, certain species do so under the burden of aero/hydrodynamic loads, which incites questions as to the significance of the multi-body fluid-mediated interactions that are inherent to collective flying/swimming. Prime examples of such creatures are fish, which are commonly seen traveling in highly organized groups of large numbers. Indeed, over the years, there have been numerous attempts to examine hydrodynamic interactions among self-propelled fish-like swimmers. Though many have studied this phenomenon, their motivations have varied from understanding animal behavior to extracting universal fluid dynamical principles and transplanting them into engineering applications. The approaches utilized to carry out these investigations include theoretical and computational analyses, field observations, and experiments using various abstractions of biological fish. Here, we compile representative investigations focused on the collective hydrodynamics of fish-like swimmers. The selected body of works are reviewed in the context of their methodologies and findings, so as to draw parallels, reveal previously unnoticed associations, contrast differences, and highlight open questions.
自然界中的许多动物成群结队地旅行,要么是为了保护自己,要么是为了生存,要么是为了耐力。其中,某些物种是在空气/水动力载荷的负担下这样做的,这引发了关于集体飞行/游泳所固有的多体流体介导的相互作用的重要性的问题。这种生物的主要例子是鱼,它们通常以高度有组织的大群旅行。事实上,多年来,已经有无数的尝试来研究自我推进的鱼状游泳者之间的流体动力学相互作用。虽然许多人已经研究了这一现象,但他们的动机各不相同,从理解动物行为到提取通用流体动力学原理并将其移植到工程应用中。用于开展这些调查的方法包括理论和计算分析、实地观察和使用各种生物鱼类抽象的实验。在这里,我们汇编了有代表性的研究,集中在鱼状游泳者的集体流体动力学上。选定的作品体在其方法和发现的背景下进行审查,以便绘制相似之处,揭示以前未被注意到的联系,对比差异,并突出开放的问题。
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引用次数: 0
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Applied Mechanics Reviews
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