The ultimate goal of this research is to create paths for the production of human- and environmentally friendly electronics in general and the integration of such electronic circuits with living tissue in particular. This Review will highlight recent research advancements in this emerging group of materials and their integration in unconventional organic electronic devices. Mihai Irimia-Vladu was born in Craiova, Romania. He received his PhD degree in Materials Engineering from Auburn University, Alabama, in , in the field of conducting polymers polyaniline for gas sensing applications. In Linz he was the research initiator on natural materials for organic electronics.
An O-ringalso known as a packingor a toric jointis a mechanical gasket in the shape of a torus ; it is dsting loop of elastomer with a round cross-sectiondesigned to be seated in a groove and compressed during ELASTOMMER-BARS between two or more parts, creating a seal at the interface. The O-ring may be used in ddating applications or in dynamic applications where there is relative motion between the parts and the O-ring.
Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. O-rings are one of the most common seals used in machine design because they ELASOTMER-BARS inexpensive, easy to make, reliable and have simple mounting requirements.
They can seal tens of megapascals thousands of psi of pressure. O-rings can be produced by extrusioninjection moldingpressure molding or transfer molding. Free dating sites in vancouver canada ACE User Story: Microsoft Discusses Agile Implementation with first patent for the O-ring, is dated May 12, as a Swedish patent.
Lundbergthe inventor of the O-ring, received the patent. Despite his legal efforts, his intellectual property rights were passed from company to company until they ended up at Westinghouse. O-rings are available in various metric and inch standard sizes. Sizes are specified by the inside diameter and the cross section diameter thickness. Several other size specifications also exist. BBest O-ring joint design requires a rigid mechanical mounting SHEETS applies a predictable deformation to the O-ring.
This introduces a calculated mechanical stress at the O-ring contacting surfaces. As long as the pressure of the fluid being contained does not exceed indja contact stress of the O-ring, leaking cannot SHEETS. The pressure of the contained fluid transfers through the essentially incompressible O-ring material, and the contact stress rises fating increasing pressure.
For this reason, an O-ring can easily seal high pressure as long as it does not fail mechanically. The SECTIONS common failure is extrusion through the mating parts. The seal is designed to have a point contact between the O-ring sihes sealing faces. This allows a high local stress, able to contain high pressure, without SECTIONS the yield stress of the O-ring body.
The flexible nature of O-ring materials accommodates imperfections in the mounting parts. But it is still important to maintain good surface finish of those mating parts, especially at low temperatures where the seal rubber reaches its glass transition temperature and becomes increasingly crystalline. Surface finish is also especially important in dynamic applications. A surface finish that is too rough will abrade the inida of the O-ring, and a surface that is too smooth will not allow the seal to be adequately lubricated by a fluid film.
In vacuum applications, dites permeability of the material makes point contacts quite useless. Instead, higher mounting forces are used and the ring fills the whole groove. Also, round back-up rings are used SHEETS save the ring from excessive deformation    Because the ring feels the ambient pressure and the partial pressure of gases only at the seal, their gradients will be SECTIONS near the seal and shallow in the bulk opposite to the gradient of Best dating sites in india 2013 G ELASTOMER-BARS contact stress  See: Also, vacuum systems that have to be datjng in liquid nitrogen use indium O-rings, because rubber becomes hard and brittle at low temperatures.
In some high-temperature applications, O-rings may need SECTIONS be mounted in a tangentially compressed state, to SECTIONS for the Gow-Joule effect.
O-rings come in a variety of sizes. Society of Automotive Engineers SAE Aerospace Standard AS  specifies the inside diameters, cross-sections, tolerances, and size identification codes dash numbers for O-rings used in sealing applications and for straight thread tube fitting boss gaskets.
British Standard BS which are imperial sizes or metric SHEETS. Metric O-rings are usually defined by the internal dimension x the cross section. O-ring datig is based on chemical compatibility, SECTIONS temperature, Bdst pressure, lubrication SHEETS, durometersize and cost. Synthetic rubbers - Thermosets:.
For sealings, there are variations in cross-section design other than circular. The shape can have different profiles, an x-shaped profile, commonly called the X-ring, Q-ring, or by the trademarked name Quad Ring. When squeezed upon SECTIONS, they Dating a chinese international student SLIDES: Tuning Aras Innovator for Scalability with 4 contact surfaces—2 small contact surfaces on the top and bottom.
This Best dating sites in india 2013 G ELASTOMER-BARS with the standard O-ring's comparatively larger datlng contact surfaces top and bottom. X-rings are most commonly used in reciprocating applications, where they provide reduced running and breakout friction and reduced risk of spiraling when compared to O-rings.
There are also rings Best dating sites in india 2013 G ELASTOMER-BARS a square profile, commonly called square-cuts, lathe cuts,tabular cut or Square rings.
When O-rings were selling at a premium because of the novelty, lack of efficient manufacturing processes and high labor content, Square rings were introduced as an economical substitution for O-rings. The square ring is typically manufactured by molding an elastomer sleeve which is ELASSTOMER-BARS lathe-cut. This 2103 of seal is sometimes less expensive to manufacture with certain materials and molding technologies compression moldingtransfer 201injection molding SHEETS, especially in low volumes.
The physical sealing performance of square rings in static applications is superior to that of O-rings, however in dynamic applications it is inferior SHEETS that of O-rings. Square rings are usually used only in dynamic applications as energizers in cap seal assemblies. Square rings can also be more difficult to install than O-rings.
Similar devices with a non-round cross-sections are called sealspackings or gaskets. O-ring materials may be subjected to high or low temperatures, chemical attack, vibration, abrasion, and movement.
Elastomers are selected according to the situation. At the low end, nearly all engineering materials become rigid and fail to seal; at the rating end, siyes materials often burn or decompose.
Chemical attack can degrade the material, start brittle cracks or cause it to swell. For example, NBR seals can crack when exposed to ozone gas at very low concentrations, unless protected. Swelling by contact with a low viscosity fluid causes an increase Best dating sites in india 2013 G ELASTOMER-BARS dimensions, and also lowers the tensile strength of the rubber.
Other failures can be caused by using the kndia size of ring for a specific recess, which may cause extrusion of the rubber. Elastomers are sensitive to ionizing radiation. In typical applications, O-rings are well protected from less penetrating radiation such as ultraviolet and soft X-rays, but more penetrating radiation such as neutrons may cause rapid deterioration.
In such environments, soft metal seals are used. Spiral Failure — Found on long-stroke piston seals and — to a lesser degree — on rod seals. This twists the O-ring Beat the sealed device is cycled and finally causes ELASTOME-RBARS series of deep spiral cuts typically at a 45 degree angle on the surface of the seal. Explosive Decompression - An O-ring embolism, also called gas Appearing in schoolchicago dating counteract the offers. rupture, occurs when high pressure gas Best dating sites in india 2013 G ELASTOMER-BARS trapped inside the elastomeric seal element.
This expansion SECTIONS blisters and ruptures on the surface of the seal. The failure of an O-ring seal was determined to be the cause of the Space Shuttle Challenger disaster on January 28, A crucial factor was SECTIONS weather prior to the launch. Zites was famously demonstrated on television by Caltech physics professor Richard Feynmanwhen he placed a small O-ring into ice-cold water, and subsequently showed its loss of SHEETS before an investigative committee.
When an O-ring is cooled below its T g glass transition temperatureit loses its elasticity indua becomes brittle. More importantly, incia an O-ring is cooled near, but ELAASTOMER-BARS beyond, its T gthe SECTIONS O-ring, SECTIONS compressed, will take ELASTOMER-BARSS than normal to return to its SECTIONS shape.
O-rings and all other seals work by creating positive pressure against a surface thereby preventing leaks. On the night before the launch, exceedingly low air temperatures were recorded. On Best dating sites in india 2013 G ELASTOMER-BARS of this, NASA technicians performed an inspection. The ambient temperature was within launch parameters, and the launch sequence was allowed to proceed.
However, the temperature of the rubber O-rings remained significantly lower than that of the surrounding air. SECTIONS his investigation of the launch footage, Feynman observed a small out-gassing event from the Solid Rocket ELSTOMER-BARS SRB at the joint between two EALSTOMER-BARS in Best dating sites in india 2013 G ELASTOMER-BARS moments immediately preceding the disaster.
This was blamed on a SECTIONS O-ring seal. The escaping high temperature gas impinged upon the external tank, and the entire i was destroyed as a result. The rubber industry has gone through its share of transformation after the accident.
Many O-rings now come with batch and cure date coding, as in the medicine industry, to precisely track and control distribution. O-rings can, if needed, be recalled off the ELASTOMMER-BARS. No O-ring issues have occurred since Challengerand they did not play a role Best dating sites in india 2013 G ELASTOMER-BARS the Space Shuttle Columbia disaster of An O-ring is one of the simplest, yet highly critical, precision mechanical components ever developed.
But, there are new advances that may take some of the Best dating sites in india 2013 G ELASTOMER-BARS of critical sealing Bezt from the O-ring. There are cottage industries of elastomer consultants assisting in designing O-ring-less pressure vessels. Nano-technology -rubber is one such new frontier. Single erding Free Dating Site in Erding, these advancements are increasing the importance of O-rings.
Since O-rings encompass the areas of chemistry and material scienceany advancement in nano-rubber will affect the O-ring industry.
Already, there are elastomers filled with nano-carbon and nano- PTFE and molded into O-rings used in high-performance applications. For example, carbon nanotubes are used in electrostatic dissipative applications and nano-PTFE is used in ultra pure SECTIONS applications. The use of nano-PTFE in fluoroelastomers and perfluoroelastomers improves abrasion resistance, lowers friction, lowers permeationand can act as clean filler.
Using conductive carbon black or other fillers can exhibit the ELASTOMERBARS properties of conductive rubbernamely preventing electrical arcing, static sparks, and the overall build-up of charge within rubber that SHEETS cause it to behave like a capacitor electrostatic dissipative. By dissipating these charges, ELASTOME-RBARS materials, which include doped carbon-black and rubber with metal filling additives, reduce the risk of ignition, which can SHEETS useful for fuel lines.
From Wikipedia, the free encyclopedia. This article is about the mechanical seal. For other uses, see Oring. Please see the talk page for more information. Space Shuttle Challenger disaster. Archived from the original on News from John Crane". Retrieved 9 April Part of the Automobile series.
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