Analysis of Static and Dynamic Behavior of Thick-Walled PALEO Elements

2019 ◽  
Author(s):  
Yves Klett ◽  
Fabian Muhs ◽  
Peter Middendorf
Keyword(s):  
Dynamic Behavior ◽  
Elastic Deformation ◽  
Large Range ◽  
Fatigue Behavior ◽  
Dynamic Test ◽  
Fe Analysis ◽  
Flat Sheet ◽  
Unit Cells ◽  
And Behavior ◽  
External Stimuli

Abstract Plastically annealed lamina emergent mechanisms have been recently introduced as origami-based structures that can be designed with a tendency to return into arbitrary folding states without additional actuators or external stimuli. The inherent elasticity of the surrogate hinges can realize a large range of elastic deformation. This paper describes the implementation of the PALEO principle for structures made from 2mm thick polycarbonate. The flat sheet is machined to generate the hinge elements and is afterwards folded and thermally annealed in a non-flat state. A FE analysis of the initial folding and behavior after annealing is carried out in parallel, with the goal to determine strains and stresses for different hinge configurations. Finally, a dynamic test is carried out on PALEO unit cells to determine the fatigue behavior of the manufactured samples.

scholarly journals Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
S. Talebi ◽  
R. Hedayati ◽  
M. Sadighi
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Energy Absorption ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Lattice Structures ◽  
Energy Absorption Capacity ◽  
Closed Cell ◽  
Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

FE Analysis, Dynamic Test and Correlation of Vehicle Structures

1996 ◽  
Author(s):  
Ananda Rao ◽  
B. Srinivasulu ◽  
Alex Bidanov ◽  
Andrew Currie
Keyword(s):  
Dynamic Test ◽  
Fe Analysis

scholarly journals Operational Study of Drone Spraying Application for the Disinfection of Surfaces against the COVID-19 Pandemic

Drones ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 18
Author(s):  
Higinio González Jorge ◽  
Luis Miguel González de Santos ◽  
Noelia Fariñas Álvarez ◽  
Joaquin Martínez Sánchez ◽  
Fermin Navarro Medina
Keyword(s):  
Dynamic Behavior ◽  
Public Services ◽  
Dynamic Test ◽  
Virus Transmission ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Flying Height ◽  
Aircraft Systems ◽  
Human Operators ◽  
Lower Height

The COVID-19 pandemic has shown the need to maximize the cleanliness of outside public services and the need to disinfect these areas to reduce the virus transmission. This work evaluates the possibilities of using unmanned aircraft systems for disinfection tasks in these aeras. The operational study focuses on evaluating the static and dynamic behavior, as well as the influence of the flying height, mission speed and flow of spraying. The most recommended height for correct spraying with the drone system under study is 3.0 m. The dynamic test shows that the lower height, 3.0 m, also provides the most adequate spraying footprint, achieving 2.2 m for a speed of 0.5 m/s. The operational behavior is evaluated on three different scenarios, a skatepark with an area around 882.7 m2, an outdoor gym with an area around 545.0 m2 and a multisport court with an area around 2025.7 m2. The cleaning time evaluates the flying duration, battery change and tank refill and results in 41 min for the skatepark (5 tank refills and 2 battery changes), 28.6 min for the outdoor gym (3 tank refills and 2 battery changes) and 96.4 min for the multisport court (11 tank refills and 5 battery changes). Each battery change and each tank refill are estimated to take 4 min each, with a drone autonomy of 7 min. The technology appears competitive compared to other forms of cleaning based, for example, on human operators.

PALEO: Plastically Annealed Lamina Emergent Origami

2018 ◽  
Author(s):  
Yves Klett
Keyword(s):  
Plastic Deformation ◽  
Elastic Deformation ◽  
Deformation Potential ◽  
Flat Sheet

Origami is usually folded from a flat sheet of material. Folding mostly works by introduction of plastic deformation into that sheet, resulting in a permanently altered region, viz., the crease. Lamina emergent mechanisms also start by definition from the flat state, but make use of compliant elements to provide mobility by elastic deformation. We introduce a combination of origami tessellations with LEM elements that are annealed in a (partially) collapsed state and retain this shape afterwards, while still offering the elastic deformation potential in the annealed shape. A number of such Plastically Annealed Lamina Emergent Origami structures or PALEOs have been successfully designed and tested.

scholarly journals Non-Auxetic Mechanical Metamaterials

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 635 ◽  
Author(s):  
Christa de Jonge ◽  
Helena Kolken ◽  
Amir Zadpoor
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Fatigue Behavior ◽  
Analytical Data ◽  
Three Dimensional ◽  
Mechanical Metamaterials ◽  
Macro Scale ◽  
Unit Cells ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

The concept of “mechanical metamaterials” has become increasingly popular, since their macro-scale characteristics can be designed to exhibit unusual combinations of mechanical properties on the micro-scale. The advances in additive manufacturing (AM, three-dimensional printing) techniques have boosted the fabrication of these mechanical metamaterials by facilitating a precise control over their micro-architecture. Although mechanical metamaterials with negative Poisson’s ratios (i.e., auxetic metamaterials) have received much attention before and have been reviewed multiple times, no comparable review exists for architected materials with positive Poisson’s ratios. Therefore, this review will focus on the topology-property relationships of non-auxetic mechanical metamaterials in general and five topological designs in particular. These include the designs based on the diamond, cube, truncated cube, rhombic dodecahedron, and the truncated cuboctahedron unit cells. We reviewed the mechanical properties and fatigue behavior of these architected materials, while considering the effects of other factors such as those of the AM process. In addition, we systematically analyzed the experimental, computational, and analytical data and solutions available in the literature for the titanium alloy Ti-6Al-4V. Compression dominated lattices, such as the (truncated) cube, showed the highest mechanical properties. All of the proposed unit cells showed a normalized fatigue strength below that of solid titanium (i.e., 40% of the yield stress), in the range of 12–36% of their yield stress. The unit cells discussed in this review could potentially be applied in bone-mimicking porous structures.

Moxifloxacin-Induced Visual Hallucinations, Alterations in Mood and Behavior, and Hyperglycemia

2019 ◽  
Vol 33 (3) ◽  
pp. 368-371 ◽  
Author(s):  
Burak Uz
Keyword(s):  
Blood Glucose ◽  
Illicit Drug ◽  
Sudden Increase ◽  
Visual Hallucinations ◽  
Drug Reactions ◽  
Behavioral Alterations ◽  
Illicit Drug Abuse ◽  
And Behavior ◽  
Neuropsychiatric Adverse Effects ◽  
External Stimuli

Visual hallucinations are sensory perceptions that occur without external stimuli. Moxifloxacin-induced visual hallucinations are very rarely reported (<0.1%). We describe a 66-year-old woman, without any known neuropsychiatric disorder or illicit drug abuse, who experienced complex visual hallucinations, mood, and behavioral alterations secondary to peroral 1 dose of moxifloxacin treatment that persisted for approximately 36 hours. In addition, a sudden increase in her blood glucose level was noted which also improved a few days after discontinuation of moxifloxacin treatment. Although very rare, it should be kept in mind that moxifloxacin may coincidentally induce neuropsychiatric adverse effects and hyperglycemia. Clinicians should be alert to recognize such uncommon offending adverse drug reactions.

scholarly journals Electrically Reconfigurable Microwave Metasurfaces With Active Lumped Elements: A Mini Review

2021 ◽  
Vol 8 ◽  
Author(s):  
Linda Shao ◽  
Weiren Zhu
Keyword(s):  
Electromagnetic Waves ◽  
Recent Progress ◽  
Two Dimensional ◽  
Microwave Frequencies ◽  
Electromagnetic Responses ◽  
Development Direction ◽  
Engineered Surfaces ◽  
Unit Cells ◽  
Lumped Elements ◽  
External Stimuli

Metasurfaces, a kind of two-dimensional artificially engineered surfaces consist of subwavelength unit cells, have recently attracted tremendous attention, owing to their exotic abilities for tailoring electromagnetic responses. With active lump elements incorporated into the design of metasurfaces, dynamic reconfigurabilities enabled by external stimuli could be realized, offering opportunities for the dynamic manipulation of electromagnetic waves. In this mini review, we present a brief review on the recent progress of electrically reconfigurable metasurfaces at microwave frequencies. A brief discussion will also be given with our outlook on future development direction and possible challenges in this interesting field.

scholarly journals Fixing Efficiency Values by Unfixing Compressor Speed: Dynamic Test Method for Heat Pumps

2019 ◽  
Author(s):  
Carsten Palkowski ◽  
Andreas Zottl ◽  
Ivan Malenkovic ◽  
Anne Simo
Keyword(s):  
Dynamic Behavior ◽  
Heat Pump ◽  
Performance Test ◽  
Dynamic Testing ◽  
Dynamic Test ◽  
Electricity Consumption ◽  
Heat Pumps ◽  
Test Method ◽  
Temperature Changes ◽  
Seasonal Performance

The growing market penetration of heat pumps indicates the need for a performance test method which better reflects the dynamic behavior of heat pumps. In this contribution, we developed and implemented a dynamic test method for the evaluation of the seasonal performance of heat&nbsp;pumps by means of laboratory testing. Current standards force the heat pump control inactive by&nbsp;fixing the compressor speed. In contrast, during dynamic testing, the compressor runs unfixed while&nbsp;the heat pump is subjected to a temperature profile. The profile consists of the different outdoor&nbsp;temperatures of a typical heating season based on the average European climate and also includes&nbsp;temperature changes to reflect the dynamic behavior of the heat pump. The seasonal performance&nbsp;can be directly obtained from the measured heating energy and electricity consumption making&nbsp;subsequent data interpolation and recalculation with correction factors obsolete. The method delivers&nbsp;results with high precision and high reproducibility and could be an appropriate method for a fair&nbsp;rating of heat pumps.

scholarly journals Effect of external lighting on biopotential of maize leaves caused by pulsed temperature stimulation

2017 ◽  
Vol 8 (2) ◽  
pp. 179-184
Author(s):  
M. P. Motsnyj ◽  
N. P. Botsva ◽  
О. V. Elina ◽  
D. V. Chernetchenko ◽  
L. Y. Sadovskaya ◽  
...  
Keyword(s):  
Computer Software ◽  
Plant Cells ◽  
Cold Stimulation ◽  
Time Period ◽  
The Stability ◽  
Adaptive Ability ◽  
And Behavior ◽  
External Stimuli ◽  
Temperature Stimulation ◽  
Refractory Phase

Study of electrophysiological indicators of the condition and behavior of plants has become more important in the development of farming activities and the search for effective ways to improve the productivity of crops. The influence of external light on the adaptive ability of corn leaf cells to rhythmic cold stimulation was determined experimentally. The method of rhythmic cold stimulation is not adequate for the studied plants, but its application allows us to evaluate the stability of plant cells to external stimuli. The method consists in repeating irritation during the time period of less duration than the relative refractory phase, which causes a response of less than the previous amplitude. Because of this in the system there is a negative feedback that leads to stabilization of the amplitude of biopotentials that are registered. Rhythmic cold stimulation was applied to the leaf with the help of a quick-response thermostimulator. Rhythmic cold stimuli and settings of pulses were set by computer software. Cooling temperature was controlled using miniature differential thermocouple. Potentials of the leaf surface were diverted by an unpolarized macroelectrode and after a preamplifier fed to the input of the USB oscilloscope connected to the computer. Analysis of the results of experiments was performed using automated developed software. As a result, we experimentally established that rhythmic stimulation of leaves by cold leads to stabilization of responding potential. The level of stabilization depends on the frequency of cold stimuli and describes the adaptive properties of the system causing the biopotential. We found that the absence of photosynthesis when there is a deficit outdoor lighting leads to a significant increase in the average level of stabilized responses, indicating increased stability of the system to external influences. The maximum of this increase fell on the fourth day. This increase is likely to be due to the restructuring of functional ion transport through cell membranes, generating potentials registered. In the interval 4–9th days there was a significant decrease in stabilization, probably due to adaptation of plant cells to a lack of light, or depletion of ATP, which provides the active transport of ions across the cell membrane. 

scholarly journals Structure and dynamics of human disease-complication network

2021 ◽  
Author(s):  
Xiongfei Jiang ◽  
Long Xiong ◽  
Ling Bai ◽  
Jie Lin ◽  
Jing-Feng Zhang ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Dynamic Behavior ◽  
Human Disease ◽  
Medical Data ◽  
Structure And Dynamics ◽  
External Stimuli

A complication is an unanticipated disease arisen following, induced by a disease, a treatment or a procedure. We compile the Human Disease-Complication Network from the medical data and investigate the characteristics of the network. It is observed that the modules of the network are dominated by the classes of diseases. The relations between modules are unveiled in detail. Three nontrivial motifs are identified from the network. We further simulate the dynamics of motifs with the Boolean dynamic model. Each motif represents a specific dynamic behavior, which is potentially functional in the disease system, such as generating temporal progressions and governing the responses to fluctuating external stimuli.

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