Inverted Honeycomb Cell as a Reinforcement Structure for Building Soft Pneumatic Linear Actuators

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
François Schmitt ◽  
Olivier Piccin ◽  
Bernard Bayle ◽  
Pierre Renaud ◽  
Laurent Barbé
Keyword(s):  
Additive Manufacturing ◽  
Large Deformations ◽  
Low Pressure ◽  
Reinforcement Structure ◽  
Mechanical Joint ◽  
Linear Actuators ◽  
Displacement Force ◽  
Honeycomb Cell ◽  
Auxetic Structure

Abstract In this article, the inverted honeycomb cell, known to exhibit an auxetic behavior, is considered to design two pneumatic linear actuators. The actuators are built using a combination of soft and rigid structures. They present complementary performances in terms of displacement, force, and stiffness. Experimental evaluations are conducted using prototypes produced using multimaterial additive manufacturing to combine soft and rigid materials with freedom of shape. The first actuator is inspired by origami structures. The possibility to obtain large deformations under low pressure is observed. The second actuator is based on a cylindrical auxetic structure based on the inverted honeycomb cell. Smaller deformation is reached but the design favors the off-axis stiffness, so the component can be integrated without any additional mechanical joint for translation. A discussion on the relative performances of these two actuators and their possible uses conclude the paper.

scholarly journals Opportunities and Issues in the Application of Titanium Alloys for Aerospace Components

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 705 ◽  
Author(s):  
James C. Williams ◽  
Rodney R. Boyer
Keyword(s):  
Additive Manufacturing ◽  
Titanium Alloys ◽  
Intermetallic Compounds ◽  
Turbine Blades ◽  
Low Pressure ◽  
Current Status ◽  
Rocket Engines ◽  
Low Pressure Turbine ◽  
Investment Cast ◽  
Ti Alloys

The metal titanium (Ti) and its alloys have many attributes which are attractive as structural materials, but they also have one major disadvantage, high initial cost. Nevertheless, Ti and Ti alloys are used extensively in airframes, gas turbine engines (GTE), and rocket engines (RE). The high cost is a deterrent, particularly in airframe applications, in that the other alloys it competes with are, for the most part, significantly lower cost. This is less of a concern for GTE and RE where the cost of titanium is closer to and sometimes even lower than some of the materials it competes with for these applications. In spacecraft the weight savings are so important that cost is a lesser concern. Ti and its alloys consist of five families of alloys; α-Ti, near α-alloys, α + β alloys, β-alloys, and Ti-based intermetallic compounds. The intermetallic compounds of primary interest today are those based on the compound TiAl which, at this time, are only used for engine applications because of their higher temperature capability. These TiAl-based compounds are used in a relatively low, but growing, amounts. The first production application was for low pressure turbine blades in the GE engine (GEnx) used on the Boeing 787, followed by the GE LEAP engine used on A-320neo and B-737MAX. These air foils are investment cast and machined. The next application is for the GE90X which will power the Boeing B-777X. These air foils will be made by additive manufacturing (AM). Unalloyed titanium and titanium alloys are typically melted by vacuum arc melting and re-melted either once (2X VAR) or twice (3X VAR); however a new and very different melting method (cold hearth melting) has recently become favored, mainly for high performance applications such as rotors in aircraft engines. This process resulted in higher quality ingots with a significant reduction in melt-related defects. Once melted and cast into ingots, the alloys can be processed using all the standard thermomechanical working and casting processes used for making components of other types of structural alloys. Because of their limited ductility, the TiAl-based intermetallic compounds are quite difficult to process using ordinary wrought methods. Consequently, the low-pressure turbine blades currently in service are investment cast and machined to net shape. The AM air foils will require minimal machining, which is an advantage. This paper describes some relatively recent developments as well as some issues and opportunities associated with the production and use of Ti and its alloys in aerospace components. Included are new Ti alloys, new applications of Ti alloys, and the current status of several manufacturing processes including a discussion of the promise and current reality of additive manufacturing as a potentially revolutionary method of producing Ti alloy components.

scholarly journals Auxetic Structures for Tissue Engineering Scaffolds and Biomedical Devices

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6821
Author(s):  
Yujin Kim ◽  
Kukhui Son ◽  
Jinwoo Lee
Keyword(s):  
Tissue Engineering ◽  
Stem Cells ◽  
Additive Manufacturing ◽  
Hard Material ◽  
Target Tissue ◽  
Biomedical Devices ◽  
Cultured Fibroblasts ◽  
Auxetic Structures ◽  
Tissue Reconstruction ◽  
Auxetic Structure

An auxetic structure utilizing a negative Poisson’s ratio, which can expand transversally when axially expanded under tensional force, has not yet been studied in the tissue engineering and biomedical area. However, the recent advent of new technologies, such as additive manufacturing or 3D printing, has showed prospective results aimed at producing three-dimensional structures. Auxetic structures are fabricated by additive manufacturing, soft lithography, machining technology, compressed foaming, and textile fabrication using various biomaterials, including poly(ethylene glycol diacrylate), polyurethane, poly(lactic-glycolic acid), chitosan, hydroxyapatite, and using a hard material such as a silicon wafer. After fabricating the scaffold with an auxetic effect, researchers have cultured fibroblasts, osteoblasts, chondrocytes, myoblasts, and various stem cells, including mesenchymal stem cells, bone marrow stem cells, and embryonic stem cells. Additionally, they have shown new possibilities as scaffolds through tissue engineering by cell proliferation, migration, alignment, differentiation, and target tissue regeneration. In addition, auxetic structures and their unique deformation characteristics have been explored in several biomedical devices, including implants, stents, and surgical screws. Although still in the early stages, the auxetic structure, which can create mechanical properties tailored to natural tissue by changing the internal architecture of the structure, is expected to show an improved tissue reconstruction ability. In addition, continuous research at the cellular level using the auxetic micro and nano-environment could provide a breakthrough for tissue reconstruction.

Minimum-Weight Truss Reinforcement of a Composite Beam to Increase the Free-Vibrations Fundamental Eigenfrequency

2018 ◽  
Vol 760 ◽  
pp. 219-224
Author(s):  
Marek Tyburec ◽  
Jan Zeman ◽  
Matěj Lepš ◽  
Michael Somr ◽  
Tomáš Plachý ◽  
...  
Keyword(s):  
Topology Optimization ◽  
Additive Manufacturing ◽  
Composite Beam ◽  
Experimental Validation ◽  
Minimum Weight ◽  
Free Vibrations ◽  
Fabrication Process ◽  
Reinforcement Structure ◽  
Economical Design ◽  
Thin Walled

In this contribution, we design a minimum-weight truss reinforcement of a thin-walled composite beam, such that the fundamental free-vibrations eigenfrequency of the beam is increased to a specific value. The reinforcement structure is designed using techniques of topology optimization and produced using additive manufacturing, in order to achieve economical design and minimize manual interventions in the fabrication process. Finally, an experimental validation of theoretical outcomes is performed on an additively manufactured prototype.

Effects of Electrical Discharges in Low Pressure Gases on the Morphology of Polyethylene Crystals

1974 ◽  
Vol 32 ◽  
pp. 544-545
Author(s):  
L.H. Bolz ◽  
D.H. Reneker
Keyword(s):  
Power Distribution ◽  
Electrical Discharge ◽  
Dielectric Breakdown ◽  
Ionic Species ◽  
Low Pressure ◽  
Polymer Surfaces ◽  
Electrical Discharges ◽  
Adhesive Bonds ◽  
Power Distribution Lines ◽  
Modification Of The Surface

The attack, on the surface of a polymer, by the atomic, molecular and ionic species that are created in a low pressure electrical discharge in a gas is interesting because: 1) significant interior morphological features may be revealed, 2) dielectric breakdown of polymeric insulation on high voltage power distribution lines involves the attack on the polymer of such species created in a corona discharge, 3) adhesive bonds formed between polymer surfaces subjected to such SDecies are much stronger than bonds between untreated surfaces, 4) the chemical modification of the surface creates a reactive surface to which a thin layer of another polymer may be bonded by glow discharge polymerization.

Field ion microscopy

1988 ◽  
Vol 46 ◽  
pp. 434-435
Author(s):  
Gert Ehrlich
Keyword(s):  
Low Temperature ◽  
Sample Surface ◽  
Low Pressure ◽  
Radius Of Curvature ◽  
Field Ion Microscopy ◽  
Phosphor Screen ◽  
Ion Microscopy ◽  
Field Ion Microscope

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.

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