27.05.2015. What are shock & vibration absorbers? Summary

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Vibration and shock attenuation components include shock absorbers,

linear dampers, wire rope or spring isolators, elastomeric isolators, air

springs, or structural damping treatments. Photo courtesy of ITT Enidine.

What are shock and vibration absorbers? SummaryPosted by Mary Gannon on Tuesday, May 19, 2015 · Leave a Comment

Motion is present in almost all industrial automation systems. Stopping or changing the direction of thatmotion releases kinetic energy, which can cause shock and vibration to occur. Any sudden shock in asystem can cause immediate damage to the overall machine and the components it may be manufacturingor processing. And consistent vibration inputs can cause damaging fatigue over time.

This is why it’s necessary to decelerate a system smoothly through the use of shock and vibrationabsorbers.

Based on the type of inputs present in the application, vibration and shock attenuation components can becomprised of shock absorbers, linear dampers, wire rope or spring isolators, elastomeric isolators, airsprings, or structural damping treatments. These devices help manufacturers reduce equipment downtimeand costly cycle time limitations.

These products can be used in a broad rangeof applications, from the rate controlmechanisms that slow the motion of theoverhead luggage bin or seat recline oncommercial aircraft, to the isolators which keepGPS systems from losing signal or becomingdamaged on farm and construction equipmentas they harvest crops or pave roadways.

Most shock absorbers achieve their dampingcharacteristics through the use of hydraulicfluids. The fluid is pushed by a piston and rodthrough small orifice holes to create damping,and this action compresses some type of gas.This in turn creates a spring force to return therod back to its starting position when the load isremoved.

Shock absorbers and dampers are generallymade of high­strength steel to handle thepressures from the internal hydraulicforces. Elastomeric seals prevent the fluid fromleaking out of the cylinder, and special platingand coatings keep the units protected fromharsh operating environments.

Recent and ongoing developments in sealing technologies and in the internal designs of shock absorbersand dampers have allowed for longer service life and more compact designs. Ongoing research in the fieldof noise attenuation (high frequency, low amplitude vibration) has led to an increased effectiveness in noisereduction technologies.

A unique application for these types of hydraulic damping devices has come with the increased awarenessfor seismic and environmental protection of our infrastructure (buildings and bridges, for example). Byadding damping to these critical structures, energy is absorbed by the hydraulic devices instead ofdamaging the structure.

Vibration isolation products rely generally on mechanical designs to achieve their isolation characteristics. Aspring function provides support for the mounted equipment, while decoupling it from the vibrationsource. Friction and elastomeric material properties give the isolators their damping characteristics.

Isolators can be made from a variety of materials. Wire rope and spring isolators can be made from carbonsteel, stainless steel or aluminum. Elastomeric isolators generally have metallic components that function asmounting brackets, separated by an elastomeric material that provides the stiffness and dampingdesired. Common elastomeric compounds include natural rubber, neoprene and silicone; however, a vastselection of compounds and compound blends can be used to achieve different characteristics specific tothe application.

Air springs are comprised of metallic end fittings coupled by a composite elastomeric­based bladder thatcontains the compressed air used to provide isolation. These single­acting designs are comprised of apressurized bladder and two end plates. As air is directed into the air bladders, they are expanded linearly.

More after the jump.

All of these reusable designs are self­contained, offering a number of advantages over any other technologythat may require outside componentry. For example, hydraulic systems may require plumbing whileelectrical systems may require wiring and power.

Editorial Director, Miles BudimirMiles Budimir holds a BSEE degree, hasseveral years of engineering experienceincluding designing industrial controlsystems, and has been covering the motioncontrol industry for over 13 years.

Managing Editor, Leslie LangnauLeslie Langnau is the Managing Editor of theDesign World Network. She also has morethan 20 years experience as a technologyeditor, covering such areas as controls,mechanics, mechatronics, couplings,industrial networks, and the field now known

as additive manufacturing (formerly rapid prototyping).

Executive Editor, Lee TeschlerLee Teschler is the Executive Editor of theDesign World network of websites, onlineresources and print publications.

Leland (Lee) Teschler worked at PentonMedia for 37 years, starting in 1977 as a

Staff Editor for Machine Design, and worked his way up toChief Editor of the publication in 2006. Prior to that, he hadbeen a communications engineer for the federalgovernment. Teschler holds a B. S. in Engineering and a B.S. in Electrical Engineering from the University of Michigan,and an MBA from Cleveland State University.

Senior Editor, Lisa EitelLisa (Elisabeth) Eitel is a Senior Editor atDesign World magazine and its network ofsites. She has a B.S. in MechanicalEngineering from Fenn College(now Washkewicz College) at ClevelandState University and 14 years of experience

as a technical writer. Her areas of focus include motors,drives, motion control, power transmission, linear motion,and sensing and feedback technologies. She is a judge forthe FIRST Robotics Buckeye Regional competitions, aninductee of Tau Beta Pi engineering honor society, and amember of the Society of Women Engineers. Follow her onTwitter at @DW_LisaEitel

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CONTROLLERS DRIVES ENCODERS MOTORS MECHANICAL PT HOW-TO SELECTION GUIDES SUPPLIERS MILES’ BLOG MOTION BASICS + FAQS

27.05.2015. What are shock & vibration absorbers? Summary

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Wire rope isolators reduce system vibration, which can cause damaging fatigue over time. Photo courtesy of ITT Enidine.

Energy or power dissipation is key when selecting a damper or shock­absorbing device. The size andcharacteristics of the device are based on these inputs, so it is generally the first consideration to make.

Dynamic spring rate and damping are the two biggest considerations when selecting an isolator. Thesecharacteristics will define the natural frequency (sometimes referred to as resonant frequency) of theisolation system and are important in achieving the desired performance.

Category: Basics and FAQs, Mechanical PT, Shock + Vibration Mitigation · Tags: enidine

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27.05.2015. What are shock & vibration absorbers? Summary

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