M. Ibbotson - Professional english in use engineering (794233), страница 5
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It deforms. Before deformation,this part of the tyre forms an arc of the circle,between points A and B. So, as you can seein this diagram, it's not a straight line - it's acurved line. But after deformation, it's no longera curve. The tyre becomes deformed betweenpoints A and B.
It becomes a chord of the samecircle, forming a straight line between A and B.However, the length of a chord and the lengthof an arc, between the same two points on acircle, are different. So the design of the tyrehas to allow for this change in shape- from arounded edge to a straight edge.'Note: See Appendix II on page 99 for more on shapes.-circumference of outside of tyreLdiameter of wheeldiameter of tyreroad------~~~~~~~--surtacechordl- -----!- - 'AcrownSpecific terms are used to describe the circulardimensions of pipes. The width of the inside of apipe is called the inside diameter (ID).
It can alsobe called the bore. The outside width is calledthe outside diameter (OD). When pipes are laidhorizontally, the top of the outside of the pipe iscalled the crown, and the bottom of the inside ofthe pipe is called the invert.inside diameter(ID) or boreoutside diameter(OD)Professional English in Use Engineering:'''. ----· :~Pipe dimensions181Barc6.1Complete the notes, made by a salesperson attending the engineer's talk, using the words inthe box.
Look at A opposite to help you.arcchordcircularcircumferenceconstantcurveddeformeddiameterradiusE>e.tore. tyrH A.re. .fftte.d to ve.hicle.~:- ~hA.!>e. i~ rolAI\d - olAt~ide. e.d1e. i~ l'>e.r.fe.ctly C I) ............................... .- di~tA.I\Ce.
.froM ce.l\tre. ot whe.e.l to e.d1e. ot tyre. = C2') ................................- totA-l di~tMce. A.cro~S" tyre. = 2 x rA.di~ = C3') ................................ ot tyre.- A.ll Me.MLAre.Me.l\t~ .froM ce."tre. to F>Oi"t~ A.rolAI\d tyre. '~ C4') ................................ A.re.e.'lMI - tyre. hM (~') ................................ rA.di~- bottoM ot tyre. i~ C6 ') ................................
ot A. circle.Whe." .fftte.d to ve.hicle., bottoM ot tyre. i~ COM!>re.He.d A.l\d C7') ................................ chM1e.~ .froM C8') ................................ li...e. to ~trA.i1ht li...e.. ~trA.i1ht lil\e. i~C9') ................................ ot A. circle..6.2 Find words and expressions in B opposite with the following meanings. One question hastwo possible answers.the highest point of a horizontal pipe2 the lowest point of the inside of a horizontal pipe3 the maximum overall external width of a pipe4 the maximum internal width between the pipe walls6.3Change one word in each of the sentences below to correct them. Look at A and B oppositeto help you.1 The distance travelled by the vehicle each time its wheels turncompletely is equal to the radius of one of its tyres.2 The diameter of the tyre is measured from the centre of thewheel to the outside edge of the tyre.3 The radius of the curve in the motorway is constant,so the edges of the road follow chords of a circle.4 The curve in the motorway has a constant radius, sothe inside and outside edges of the road are arcs of twodeformed circles that have the same centre.5 The invert is on the circumference of the external face of thepipe, and therefore cannot be in contact with the liquid flowinginside the pipe.6 The thickness of the wall at the bottom of the pipe, plus thedistance between the invert and the crown of the pipe, is equalto the inside diameter of the pipe.Over 1-o tjotc·~•Choose an object which has circular and/or curved shapes.
Describe it using languagefrom A opposite. (You could also give approximate measurements.)•Imagine you arc designing the object. What measurements and lines will be needed todefine its circular/curved features?Professional English in Use Engineering19Dimensional accuracy-Precision and toleranceIt is impossible to produce components with dimensions that are absolutely precise, withsizes exactly the same as those specified in a design. This is because all production processesare imprecise to a certain extent. Therefore, the sizes of several components produced fromthe same design will vary (differ). Although the variation may only be a few hundredths of amillimetre, sizes will not be 100% accurate (exact) compared with the design.Because engineers know that accuracy cannot be perfect, in designs they often specifytolerances -that is, acceptable variations in precision.
Instead of giving one precise size, atolerance specifies a range of acceptable sizes- an allowed amount of variation. This is oftengiven as a deviation (difference) from a precise size.The drawing below shows a shaft with a specified diameter of 88 mm, plus or minus (±)0.05 mm. This means the diameter may deviate 0.05 mm either side of this size. Therefore,diameters of 87.95 mm and 88.05 mm, which are slightly inaccurate, are still permissible(allowed), as they are within tolerance. However, diameters of 87.94mm or 88.06mm are notpermissible- they are outside tolerance.0du.fr P aa"""'± o.osWhen the permissible deviation in size is very small, we say it is a tight tolerance (or a closetolerance).
A large permissible deviation is a loose tolerance. For example:•Machining a metal component to a tolerance of ±0.1 mm is relatively easy to do, so thistolerance is loose. But a tolerance of just ±0.01 mm is a tight tolerance in metalworking.•In a concrete structure, ±10mm is a loose tolerance. But ±1mm is tight, because it isdifficult to place wet concrete accurately.-FitWhen one component goes through another, such as a shaft or a bolt going through a hole,the two must fit together- their sizes and shapes must match. The key question is, howtightly (or loosely) should they fit together? There are two main types of fit:20•A clearance fit allows a component to slide or turn freely, by leaving clearance (a gap)between itself and the sides of the hole.
This distance must be quite precise. If there isinsufficient clearance - if the gap is too small - the component will fit too tightly. As aresult, the component will bind - it will not be able to slide or turn freely. In other words,there will not be enough play. However, if there is too much clearance, there will be toomuch play and the component will be able to move too much.•An interference fit is a very tight fit which does not allow a component to move freelyinside a hole. This type of fit can be achieved by forcing the component into the hole.Alternatively, the metal around the hole can be heated so that it expands (increases in sizedue to heat).
After sufficient expansion, the component is placed in the hole. The metalthen cools and contracts (decreases in size due to cooling). The contraction results in atight fit. An example of an interference fit is a train wheel fitted on an axle.Professional English in Use Engineering7.1Find words and expressions in A opposite with similar meanings to the words andexpressions below (1-10). Sometimes there is more than one possible answer. The firstone has been done for you.allowedpermissibleexactdiffer4 exactness5 not exact1237.2Match the related sentences. Look at B opposite1 It'll bind.2 It'll contract.3 It'll expa nd .4 There'll be too much play.5 It needs a clearance fit.6 It needs an interference fit.7.3deviation between maximum and minimuman acceptable deviation8 an unacceptable deviation9 little deviation allowed10 large deviation allowed67abcdefTheTheTheTheTheThetohelp you.bolt will have to turn in the hole.bolt won't be able to turn freely enough in the hole.bolt won 't fit tightly enough in the hole.wheel will have to fit very tightly on the axle.hole will widen with the high temperature.shaft will shorten and narrow slightly as it cools.Complete the article about engine blueprinting using the words in the box.
Look at A and Bopposite to help you.clearancesfitmmuspermissiblepluspreCLserangetolerancesThe advantage of racing in a kart class with astandard engine spec seems obvious - everyonehas the same power, so it's driving talentthat makes the difference. But things aren'tquite that simple. No two standard enginesare identical. There will always be a slight(1) ................................ in the size of engine parts,ov~r ~ovariationwithinsince they are manufactured, not to perfectly(2) ................................ dimensions, but to specified(3) ................................
. Although these differencesmay only be (4) ............................. or (5) ............................ .a few hundredths of a millimetre, they willnevertheless result in a slight performance gapbetween any two engines.One way round this problem (if you have thecash) is to have your engine blueprinted. Theprocess is perfectly legal, as the sizes of all partsremain (6) ................................ the tolerances thatare (7) ................................ for the standard enginespecification.
However, by carefully matching pairsor groups of parts that are all in either the loweror upper half of the tolerance (8) ................................ ,a blueprinted engine is built to (9) ............................... .together very precisely, thanks to almost perfect(10) ................................ between moving parts.t:fou . ,Think of a type of product or structure you're familiar with . Imagine you're designing it, andart· discussing the tolcrant-es required for different components.
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