M. Ibbotson - Professional english in use engineering (794233), страница 15
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.............................. , the workpiece does notneed to be put through (7) .............................. .................................. in order to smooth its edges.Answer the questions below, about non-mechanical machining techniques. Look at B and Copposite to help you.1 In machining, what does EDM stand for?2 What alternative term can be used instead of EDM?3 What type of tool is used in both flame-cutting and plasma cutting?4 What source of heat is used in both EDM and plasma cutting?5 What needs to happen to a gas in order to turn it into plasma?6 What term refers to concentrated light that can be hot enough to cut material?7 What term refers to an area of material that has been changed by high temperature?Ove,r ..f-o tjotc~Give examples of different components, made of different materials, that could be cutusing some of the techniques described opposite.
Say why the cutting technique would beespecially suitable for the component and for the material.Professional English in Use Engineering55InterconnectionAttaching and supportingThe individual components that make up assemblies and structures can be connected (orconnected together) in different ways. The pictures below show an example: a connection (orjoint) between a steel column and a concrete foundation.The foundation supports the column, preventing downward movement. As well as providingsupport, it anchors the column, holding it in position to stop it sliding or lifting. To providea connection, bolts are attached to a plate at the bottom of the column- called a base plate.The bottoms of the bolts are embedded in the concrete of the foundation - that is, they aresurrounded and held by the concrete.attached.connected.joined.A and BareA isattachedconnectedfastenedfixedjoinedattachedconnectedfastenedfixedheldjoinedtogether.to B.Fitting togetherWhen foundations for steel columns are poured, cone-shaped holes are formed in theconcrete to accommodate bolts to hold down the base plate.
The holes allow the tops of thebolts to have a certain amount of play - that is, they are free to move slightly. This means thebolts can be adjusted (moved as required)to allow the bolts to slot through theholes in the base plate, so that the plateand bolts can fit together.As the column is lowered into position,steel wedges are placed below the baseplate. These act as packers (also calledspacers or shims), and leave a gap(narrow space) between the plate andthe concrete. The wedges also enableadjustments to be made.
By hammeringa wedge horizontally, the side of the baseplate can be lifted, allowing the columnto be plumbed (made exactly vertical).wedges enablecolumn to beplumbedA type of cement, called grout, is thenplaced beneath the base plate. This fillsthe gap between the base plate and thefoundation, and the holes around the bolts.It also seals the joint against rainwater,protecting the bolts from corrosion.ped holes-concrete foundationSection at column base56Professional English in Use Engineering25.1Complete the description of parts of a suspension bridge using the correct forms of wordsfrom A opposite. Sometimes there is more than one possible answer.Photo 2Photo 1Photo 1 shows a suspension bridge. The bridge's two main cables are (1) ................................
bytowers. The cables are (2) ................................ at each end by huge blocks of concrete, which aredeeply (3) ................................ in the ground.Photo 2 shows a (4) ................................ between one of the bridge's main cables, and twosmaller suspender cables. The suspender cables are (5) ................................ to the main cableby a component called a saddle.
The saddle is made up of two parts that are fixed(6) ................................ by bolts. The many wires which make up the main cable are covered bya protective layer of very thin wire that is wrapped around the main cable in the form of ahelix (the shape of a spring).25.2Match the two parts of the sentences about possible technical issues during the installation ofcable saddles on a new suspension bridge. Look at B opposite to help you.1 These bolts are slightly too thick, so2 Some of the saddles don't fit tightly enough- there's a slight gap between the saddle andthe cable, so3 The holes in the top of this saddle don't line up exactly with the holes in the bottom part, so4 The wire that's wrapped around the outside of the main cable isn't sealed against the edgeof some of the saddles, so5 The saddles are all different - they're manufactured to correspond with the angle of themain cable at the point where they're fixed, soabcdethey won't fit together properly.the joints aren't properly protected against rainwater.they're not designed for adjustment.they won't slot through the holes in the saddles.even when they're fully tightened there's too much play.Ove,r ..f-o 1:fou~Think of a device or structure you're familiar with.
Describe how it fits together, and howdifferent components are fixed and/or supported.Professional English in Use Engineering57P.I!J Mechanical fasteners 1-BoltsThe photo below shows a common fastener (or fixing): a bolt, with a nut. Bolts have threads-grooves on the outside of the bolt's shaft (or shank), which run around the shaft in a helicalpattern. The threaded shaft allows a nut, which has a thread inside it, to be screwed ontothe bolt (by a turning motion). Nuts usually have a right-hand thread - they are screwed onby turning them clockwise (in the direction of clock hands) and unscrewed by turning themanticlockwise.
However, in some situations, left-hand threads are used.Most bolts have heads with hexagonal perimeters(hexagonal heads or hex heads). These allow a spanner toturn them. Heads can also have a hexagonal hole in theirtop, called a socket head. This allows a hex key (or Allenkey) to fit into them.shaft orshankA nutA boltA spannerNote: A nut is screwed onto a bo lt;a bolt can be screwed into a threaded hole.-A hex key or Allen keyBrE: anticlockwise; ArnE: counterclockwiseBrE: spanner; ArnE: wrenchPreload in bolted jointsTurning force, called torque, is applied to bolts to tighten them- that is, to make them griptightly. As a bolt is tightened, the tension (stretching force) in its shaft increases, and thecomponents being bolted together are pressed tightly together.
This pressing force is calledpreload (or clamp load) . If enough preload is applied, friction between the components willprevent them sliding in different directions. This is an advantage, as sliding subjects the sides ofbolts to shear force (scissoring force), which can cause them to break. In steel structures, boltsthat apply high preloads to prevent sliding are called high strength friction grip (HSFG) bolts.The amount of torque applied to bolts can be adjusted using a torque wrench, a tool which cantighten and loosen bolts, and which indicates how much torque is applied. This helps to ensurethat bolts are tightened enough, but not over-tightened.
Torque wrenches are also useful forchecking that bolted joints do not work loose - that is, that they do not become loose over time.Note: See Unit 31 for more on torque, tension, shear and other forces.-WashersWashers are metal discs which fit between the head of a boltor a nut and the components being bolted together. Ordinarywashers- called flat washers or plain washers- have a largeroutside diameter than the bolt head or nut. Their wider areais intended to spread the load (distribute pressure) over thesurface of the component as the bolt is tightened.Spring washers are designed to be compressed, to allow theamount of preload to be adjusted as the bolt is tightened.In some situations, spring washers are used to allow a boltto move slightly, in order to absorb shocks.
Common typesof spring washer are helical spring washers and conicalspring washers.58Professional English in Use EngineeringA plain orfla t washerA helica lspring washerA con icalspring washer26.1Change one word in each of the sentences below to make them correct. Look at A oppositeto help you.1 Wrenches are well-known examples of fasteners.2 In most cases, nuts are screwed onto bolts by turning them anticlockwise.3The threaded part of a bolt is the head.4 Threads are cut to form a hexagona l pattern.5 Allen keys are designed to fit around the heads of bolts.26.2 Use the words in the box to complete the text about bolted joints, taken from a boltsupplier's website.
Look at B opposite to help you.loosenpreloadshear forcetensiontightentorqueover-tightenwork looseIn structural applications, it is essential to (1) ................................ bolts correctly - firstly to makesure that joints are held together with the right amount of (2) ................................ , and secondlyto help ensure that the bolts do not (3) ................................ over time. However, that does notmean to say, 'the tighter the better'.If excessive force is used to (4) ................................ a bolt, the bolt will no longer be strongenough to transm it the extra load to the joint.
At this point, various problems can occur.The shank may begin to twist as it is subjected to additional (5) ................................ from thewrench , eventually causing the bolt to fail. Alternatively, as the bolt is stretched due toincreasing (6) ................................ in the shank, this force will be transmitted to the threads inthe form of a scissori ng action , resulting in excessive (7) ................................
acting betweenthe threads of the bolt and nut, potentially causing permanent damage to the threads.This will not only make it impossible to subsequently tighten and (8) ................................ the boltnormally, but also cause tension to be released from the shank as the nut slips, reducingpreload and compromising the strength of the joint.26.3Decide whether the sentences below are true or false, and correct the false sentences. Look atC opposite to help you.1 The purpose of all washers is to spread the load from the bolt across the surfaces of thecomponents being bolted together.2 Plain washers are flat.3 Spring washers change shape as a bolt is tightened.4 Spring washers ensure that, no matter how much a bolt is tightened, the amount of preloadremains the same.5 In situations where components are subjected to shocks, spring washers ensure that nomovement occurs between the bolt and the component.Ove,r .f-o !:fouThink about a type of machine or structure you know about which has bolted joints.
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