scholarly journals Structurally informed design of interlocking block assemblages using limit analysis

2020 ◽  
Vol 7 (4) ◽  
pp. 448-468
Author(s):  
Elham Mousavian ◽  
Claudia Casapulla
Keyword(s):  
Limit Analysis ◽  
Rectangular Cross Section ◽  
Single Layer ◽  
Experimental Tests ◽  
Computational Framework ◽  
Coulomb’S Friction ◽  
The Core ◽  
Contact Points ◽  
Proposed Model ◽  
The Stability

Abstract This paper presents a computational framework to design assemblages of interlocking blocks and to analyze their structural feasibility. The core of this framework is an extension of limit analysis to corrugated interfaces with orthotropic sliding behavior. Such block interfaces are made of a number of locks (i.e. projections on the corrugated faces, locking the blocks together) with rectangular cross section. The sliding resistance at the block interfaces is governed by the shear resistance of the locks and Coulomb’s friction law, normal to and along the locks, respectively. This resistance is assumed as a function of different interface geometric parameters and the stress state on an interface is represented by using a number of contact points distributed over the lock centerlines. The abstraction model has been validated through the comparison of the torsion–shear behavior of an interface obtained by the proposed model and experimental tests reported in the literature. The extended limit analysis has been implemented to model single-layer shells. When the model is infeasible, the geometry of the overall shell, blocks, and interlocking interfaces can be adjusted by the designer to make the model structurally feasible. The performance of the framework is presented through several examples, which demonstrate the relationships between the geometry of the interlocking interfaces and the stability of the assemblages.

scholarly journals Analytical and experimental investigation of the delamination during drilling of composite structures with core drill made of diamond grits: X-ray tomography analysis

2017 ◽  
Vol 52 (10) ◽  
pp. 1281-1294 ◽  
Author(s):  
Jamel Saoudi ◽  
Redouane Zitoune ◽  
Suhasini Gururaja ◽  
Mehdi Salem ◽  
Salah Mezleni
Keyword(s):  
Carbon Fibre ◽  
Analytical Model ◽  
Composite Structures ◽  
Thrust Force ◽  
Experimental Tests ◽  
X Ray ◽  
Reinforced Plastics ◽  
The Core ◽  
Proposed Model ◽  
Critical Thrust Force

Among the various forms of material damage, exit-ply delamination has been identified as one of the most deleterious damage processes associated with drilling fibre-reinforced plastics. The thrust force has been cited as the primary cause for drilling-induced exit-ply delamination. Only one analytical model for the prediction of the critical thrust force responsible for delamination using core drills can be found in the literature. In this study, a realistic model to predict critical thrust force responsible for drilling-induced exit-ply delamination in a multi-directional carbon fibre-reinforced plastic laminate with core drill has been proposed. A comparison between the proposed model, literature model as well as the experimental tests conducted during punching tests is presented. The proposed model is found to correlate well with experimental punching tests. In fact, the maximum relative errors recorded between the experimental values of the critical thrust force and the measured values are around 15%. Micro-tomography experiments have also been conducted that capture the drilling-induced damage in multi-directional carbon fibre-reinforced plastics in great detail. The X-ray images highlight the difficulty in controlling the thickness of the uncut plies located under the core drill during punching tests that can be attributed to some deviations in predictions of critical thrust force. Postmortem examination of the blind holes after punching tests also confirms the presence of a net delamination near the vicinity of the nominal diameter of the core drill, which correlates well to the hypothesis of the analytical model.

Static and dynamic response of sandwich beams with lattice and pantographic cores

2021 ◽  
pp. 109963622110338
Author(s):  
Yury Solyaev ◽  
Arseniy Babaytsev ◽  
Anastasia Ustenko ◽  
Andrey Ripetskiy ◽  
Alexander Volkov
Keyword(s):  
Mechanical Performance ◽  
Lattice Structure ◽  
Unit Length ◽  
Experimental Tests ◽  
Plane Geometry ◽  
Sandwich Beams ◽  
Static Tests ◽  
Three Point Bending ◽  
The Core ◽  
The Impact

Mechanical performance of 3d-printed polyamide sandwich beams with different type of the lattice cores is investigated. Four variants of the beams are considered, which differ in the type of connections between the elements in the lattice structure of the core. We consider the pantographic-type lattices formed by the two families of inclined beams placed with small offset and connected by stiff joints (variant 1), by hinges (variant 2) and made without joints (variant 3). The fourth type of the core has the standard plane geometry formed by the intersected beams lying in the same plane (variant 4). Experimental tests were performed for the localized indentation loading according to the three-point bending scheme with small span-to-thickness ratio. From the experiments we found that the plane geometry of variant 4 has the highest rigidity and the highest load bearing capacity in the static tests. However, other three variants of the pantographic-type cores (1–3) demonstrate the better performance under the impact loading. The impact strength of such structures are in 3.5–5 times higher than those one of variant 4 with almost the same mass per unit length. This result is validated by using numerical simulations and explained by the decrease of the stress concentration and the stress state triaxiality and also by the delocalization effects that arise in the pantographic-type cores.

Towards a new design with generic modeling and adaptive control of a transformable quadrotor

2021 ◽  
pp. 1-31
Author(s):  
S.H. Derrouaoui ◽  
Y. Bouzid ◽  
M. Guiatni
Keyword(s):  
Adaptive Control ◽  
Control Strategy ◽  
Experimental Tests ◽  
Generic Model ◽  
System Control ◽  
System A ◽  
Viable Solution ◽  
Generic Modeling ◽  
Adaptive Control Strategy ◽  
The Stability

Abstract Recently, transformable Unmanned Aerial Vehicles (UAVs) have become a subject of great interest in the field of flying systems, due to their maneuverability, agility and morphological capacities. They can be used for specific missions and in more congested spaces. Moreover, this novel class of UAVs is considered as a viable solution for providing flying robots with specific and versatile functionalities. In this paper, we propose (i) a new design of a transformable quadrotor with (ii) generic modeling and (iii) adaptive control strategy. The proposed UAV is able to change its flight configuration by rotating its four arms independently around a central body, thanks to its adaptive geometry. To simplify and lighten the prototype, a simple mechanism with a light mechanical structure is proposed. Since the Center of Gravity (CoG) of the UAV moves according to the desired morphology of the system, a variation of the inertia and the allocation matrix occurs instantly. These dynamics parameters play an important role in the system control and its stability, representing a key difference compared with the classic quadrotor. Thus, a new generic model is developed, taking into account all these variations together with aerodynamic effects. To validate this model and ensure the stability of the designed UAV, an adaptive backstepping control strategy based on the change in the flight configuration is applied. MATLAB simulations are provided to evaluate and illustrate the performance and efficiency of the proposed controller. Finally, some experimental tests are presented.

scholarly journals Experimental Tests for Measuring Individual Attentional Characteristics in Songbirds

Animals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2233
Author(s):  
Loïc Pougnault ◽  
Hugo Cousillas ◽  
Christine Heyraud ◽  
Ludwig Huber ◽  
Martine Hausberger ◽  
...  
Keyword(s):  
Cognitive Processes ◽  
Comparative Research ◽  
Visual Stimuli ◽  
Experimental Tests ◽  
European Starling ◽  
Auditory Stimuli ◽  
The Core ◽  
Cognitive Studies ◽  
Individual Variations ◽  
Species Specific

Attention is defined as the ability to process selectively one aspect of the environment over others and is at the core of all cognitive processes such as learning, memorization, and categorization. Thus, evaluating and comparing attentional characteristics between individuals and according to situations is an important aspect of cognitive studies. Recent studies showed the interest of analyzing spontaneous attention in standardized situations, but data are still scarce, especially for songbirds. The present study adapted three tests of attention (towards visual non-social, visual social, and auditory stimuli) as tools for future comparative research in the European starling (Sturnus vulgaris), a species that is well known to present individual variations in social learning or engagement. Our results reveal that attentional characteristics (glances versus gazes) vary according to the stimulus broadcasted: more gazes towards unusual visual stimuli and species-specific auditory stimuli and more glances towards species-specific visual stimuli and hetero-specific auditory stimuli. This study revealing individual variations shows that these tests constitute a very useful and easy-to-use tool for evaluating spontaneous individual attentional characteristics and their modulation by a variety of factors. Our results also indicate that attentional skills are not a uniform concept and depend upon the modality and the stimulus type.

SHELL MATERIAL'S PERFORMANCE OF THE MICROCAPSULE FOR ELECTROLYTIC CO-DEPOSITION

2010 ◽  
Vol 24 (15n16) ◽  
pp. 3124-3130 ◽  
Author(s):  
HUI CONG LIU ◽  
XIU QING XU ◽  
WEI PING LI ◽  
YAN HONG GUO ◽  
LI-QUN ZHU
Keyword(s):  
Composite Coating ◽  
Methyl Cellulose ◽  
Water Vapor Permeability ◽  
Core Material ◽  
Vapor Permeability ◽  
Shell Material ◽  
The Core ◽  
Surface Performance ◽  
The Stability ◽  
Positive Effect

The shell material of microcapsules has an important effect on the electrolytic co-deposition behavior, the release of core material and the surface performance of composite coating. This paper discussed the tensile property and the stability of three shell materials including polyvinyl alcohol (PVA), gelatin and methyl cellulose (MC). It is found that these three shell materials have good mechanical strength and flexibility which are favorable to electrolytic co-deposition and stability of microcapsules in composite coating and that MC has well permeability and porosity which has a positive effect on the release of the core material in composite coating. Moreover, the study of the thermal properties and water vapor permeability of the three shell materials showed that their permeability improved with increase of temperature and humidity. In addition, the composite copper coating containing microcapsules with PVA, gelatin or MC as shell material was prepared respectively.

Light-Induced Metastable Defects in a-Si:H: Towards an Understanding

1985 ◽  
Vol 49 ◽  
Author(s):  
Martin Stutzmann ◽  
Warren B. Jackson ◽  
Chuang Chuang Tsai
Keyword(s):  
Amorphous Silicon ◽  
Mechanical Stress ◽  
Hydrogenated Amorphous Silicon ◽  
Material Parameters ◽  
Kinetic Behaviour ◽  
Proposed Model ◽  
Special Cases ◽  
The Stability ◽  
Hydrogenated Amorphous

AbstractThe dependence of the creation and the annealing of metastable dangling bonds in hydrogenated amorphous silicon on various material parameters will be discussed in the context of a recently proposed model. After a brief review of the kinetic behaviour governing defect creation and annealing in undoped a- Si:H, a number of special cases will be analyzed: the influence of alloying with O, N, C, and Ge, changes introduced by doping and compensation, and the role of mechanical stress. Finally, possibilities to increase the stability of a-Si:H based devices will be examined.

Thermodynamic Studies of the Core Histones:  pH and Ionic Strength Effects on the Stability of the (H3−H4)/(H3−H4)2System†

Biochemistry ◽  
1996 ◽  
Vol 35 (6) ◽  
pp. 2037-2046 ◽  
Author(s):  
Vassiliki Karantza ◽  
Ernesto Freire ◽  
Evangelos N. Moudrianakis
Keyword(s):  
Ionic Strength ◽  
Thermodynamic Studies ◽  
The Core ◽  
Core Histones ◽  
The Stability

Release Profile of a Model Protein Drug Depending on the Stability of Microspheres Based on Polyelectrolyte Complex

2007 ◽  
Vol 342-343 ◽  
pp. 505-508
Author(s):  
Sung Won Kim ◽  
Yun Sik Nam ◽  
Yeon Jin Min ◽  
Jong Ho Kim ◽  
Kwang Meyong Kim ◽  
...  
Keyword(s):  
Polyelectrolyte Complex ◽  
Coating Layer ◽  
Great Influence ◽  
Release Profile ◽  
Core Material ◽  
Glycol Chitosan ◽  
The Core ◽  
Key Factor ◽  
Model Protein ◽  
The Stability

Stability and disintegration of natural polyelectrolyte complex microspheres for protein drugs delivery have been extensively investigated because of their great influence on the drug release patterns. In this study, we tested stability of microspheres with alginate (Alg) core layered by either chitosan (Chi) or glycol chitosan (GChi) by examining release profiles of fluorophorelabeled bovine serum albumin (BSA) and lysozyme (Lys) from the microspheres. While GChi shell was disintegrated quickly, Chi-shell microspheres showed good stability in PBS. Disintegration of the coated layer induced the core material instable. The results indicated that while the charges of the shell material provided additional diffusion barrier against the protein release, the key factor to hold the proteins inside the microspheres was the integrity of the outer coating layer.

Analysis of Acoustic-Structure Interaction Using a High-Order Doubly Asymptotic Approximation

2016 ◽  
Vol 24 (01) ◽  
pp. 1550021 ◽  
Author(s):  
Heekyu Woo ◽  
Young S. Shin
Keyword(s):  
Order Approximation ◽  
Stable Model ◽  
Approximation Model ◽  
Third Order ◽  
Acoustic Structure ◽  
Structure Interaction ◽  
Proposed Model ◽  
The Stability ◽  
Third Order Approximation ◽  
Interaction Problem

In this paper, a new third-order approximation model for an acoustic-structure interaction problem is introduced. The new approximation model is designed to be an accurate and a stable model for predicting the response of a submerged structure. The proposed model is obtained by combining two lower order approximation models instead of using an operator matching method. The stability of this model is checked by a modal analysis. Finally, the approximation model is coupled to the spherical shell structure, and its performance is checked by a shock analysis.

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