Merken

# Mechanical properties of steel 8: formability

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Erkannte Entitäten

Sprachtranskript

00:03

so far we were wrong discussing them some aspects of former ability benefits and so on you were wrong going into this because for mobility is very much about strains whereas us as we have seen in plasticity we were looking that's princess would yield criterion stresses dressed states that corrupt and it wasn't very clear how you made the connection and plasticity With persisted in practice because if you remember well the fastest theory basically tells us something that's not very directly practically usable that is that relates to stresses to strain increments so that's why I'm so we're looking into former ability from a practical point of view here until until we have arrived at this this idea for instance where she'd forming that 1 of the reasons why we concentrate on sheet forming because their demands 4 In form of village of very high we have seen that it was possible to map all possible strains and strain has been a very simple two-dimensional diagram with minor strain on the excesses and the major strains on the Y axis and that we could this experimentally 2 of its value way compare materials in terms of their former ability obtain a fracture limit curves which house basically us that the strains past but remained below this line will not give rise to material fracture and I had to have gone into this explanation that he didn't really have to you go into park making to actually get this curve or you could use this Nakashima approach where you basically have specimens that you form with around punch list of the material is kept this cannot move has kept fixed in this circle by means of a drawl beat Robert has basically I think this is the tool has this change and this is the blind colder air has the shape the the rest of the tool here you basically thanks the fix the the sheet in 2 places by just having this dropping just to prevent the sheet from moving in work there and then you make specimens that are narrower and narrower and as you go make samples of the narrower and narrower you go from about actual stretching to deep drawing nests and then you basically scan the entire time the surface of possible the major strains in -minus stressed that of course but you need to make measurements and I had told you that well only seek materials you just put circle would recall simple graphics little circles of about a millimeter inside you action on the surface and after the deformation or during the defamation you Are you see what's happened to these circles and I told you that automatically be circles will always the :colon ellipses yes and so you can always see what is the major and minor strains Clark professor and an end but put them on your draft so what I had already shown you want somebody after class the last time I pointed this out to me so what would which is basically shown in Zagreb on that 1 string of strange and on the the X axis but for some reason I put the major and minor stringy but it's active position of course has so which basically due the form this material and then you look at the the difference what circles have become yes and then you basically measure for instance in this case this line here so called L 1 course used to be L 0 at the start so natural logarithm of L 1 over 12 0 but gives me 1 of the major straight it's that simple compare and I cost the Matt these values over the sample France's the drawing samples to a narrow sample here yet but we know that when we have a narrow sample we will have specimen that you elongate basically and it gets narrower rights that have a a positive major strength I have a negative -minus training and I have a thickness straight yes and the amount of fitness training depends on our value but you can see here is that this is an example here you have to be the major strains the minor strain and the thickness stress included and its negative In so we would now a sample is a little bit wider U.S. then we have a plane strange situation in this case the minor strain is 0 then there is narrowing of the sample so everything by the increase in line the strain in the line toward the direction be equal to the thickness trend of status and then in by Axel stretching stretch into directions the same amount the true minor straining to meet string of the same and of course I get I think strain that's the sum of but that's not these particular measurements you can see they're not flat nose at all have the same the and the reason is because he's a measurements that are made when the sample broke in as new conceded where where it's breaking I have a very high increase I have an increase in the in the amount of defamation right because of the the breakage right visit these points yes the strain values at this maximum here are put on the a diagram like

08:44

that that's when you do this for different samples this new citizens scattering practice but you can very clearly we tested to materials 1 is a low-carbon steel which has rather good form ability has and this and the other 1 is at the peace deal which is also relatively good well form of all but it's a harder material and then you can see the former ability is less that so this allows us to see the use of what you have is the diagram you can actually use this in practice to solve the press forming problems for instance by applying grade on an actual blank in French the forming this blank yes and measuring where the problem of Kurds you bite by having by measuring the strains and say OK this critical spot and it's breaking their because in that particular spot the deformation is playing strain for instance In a very complex part you cannot see you know is simple part like a cop or a a square part it's easy to see where the plane strange situation as the complex work you contact rights to complex because material flows in probably all the way so you can tell but in this part I'm very close to plane strain and that's why it's we get problems there so we have to change the geometry of and we have to change the geometry or the way we knew applied these these things are the effect is to change the flow of the material so you don't get plane strain in critical spots the time used as of course you can imagine there you will need to find this problem spots you will need to measure the strain but across sheets of materials that may be very large credit and on this so you have to imagine a sheet of material could square meter right and these things are mm sigh so very quickly you understand that there will be thousands and thousands of little squares to measure right so that's all a lot of work and In the past I use the actually used to do this manually the actually used to actually measure you know that this is the 1 . 2 5 mm so and then calculate the strength in and out nowadays we are we can use

11:46

computers to help us yes any computers do 2 things 1st of all they need to recognize the pattern destiny to recognize the circles or another pattern and then analyze this pattern was listed as an example here this is a cop has looking on the side of the cup in you and this is the pattern the pattern is not a a circle pattern the reason why we don't use circle patterns in our in Computer Aided strain analysis is because they digital image analysis is more difficult it's easier too record for the computer to recognize intersections rather than circles right but if you need a new conceded the computer recognizes all these intersections very nice and then it basically plots all the points that had and so it measures here and and many plots old appointed calculates the strains locals when the plot points and took on this side I know Hi the deformations are here and I can tell for instance that well above here on top of the cup this year the 2 points a and B there this strange there are here so and so they're here aren't so what's interesting for instance is this line here and that's the line I the where the strain in this direction and the narrowing US equal the strange indeed are equal and and opposite right so that there is no I can remember that's the line the line of no thickening at any point below here means that this is the thickness has increased right and I already told you that when you make a cop the outer edges part that the thicker than the original material effect and and you can see that the on the program of the new system extend up nicely and that the edge the upper edge of the sample is sector that should indeed be here and of course because it's the form in the indeed drawing interest coming out of the Blanche yes it's on this side on the deep drawings because the the material it is but the B because you know these Major strains the Justice thickness during the wet strain underlying strength and and and these are the principal strains it's also very easy to compute the equivalent strength that's and you can see for instance that in this direction the equivalent if you want to have the equivalent strain the same the amount of strain if you want this indeed drawing against you get you go out much further than in the diagram then in by Axel the restraining but obviously because in this case we have this to positive thickness and went straight it's a very useful to do this in practice and of course most of companies steel companies will nowadays certainly that the bigger ones that are developed the steals for automotive applications for instance I will have the SLD diagrams for steals so press shops can evaluate you know how much the material is easier to deform or not for instance here but you have the IRS feels very formidable reference steals years and then you have other steels but for instance feared put still you may have heard of or trips to and you can see that France is this the trip Steel here which is a very odd uh used a strong stealing a high-strength but has despite its higher Hassan limit forming a curve that's higher than a very formidable stealing and the reason is because it has a very good string hot properties no but of course there's this little cup test these Nakashima tests FLD Tessa all find tests but that that's not only press forming their press forming had all the aspects of the the forming process that they tend to emphasize on the forming behavior there and so is 1 of the just this week condition of forming is this what we call sp foot stretch flanges and basically means it's a defamation that's similar to that of the whole expansion but in an era some application where you actually have a a whole expansions and that and the material behavior there can be very poor that even though the material is very good in general form of Billy and that's the reason is related to the the tickler forming process to this view the deformations that you the material undergoes when you were doing this whole expansion so there are different ways in which you you tests in the laboratory of new flat bottom the test you can do ,comma called the opening of the trial of this whole thing is basically start with that little piece of sheet material where you apply to drill or you will you make a hole in the center and then you expand this whole has basically by trying to make a cup as at work or by pushing a conical tool in and you can see the deformation here used in this case you have you see the grades that the markings on the on the material so that allows me to study the the forming of this Of the mural around this around this

19:35

the whole here too for instance the let's let's look at what happens onto this here and the punches moved in a little bit and so this material gets stretched units and as the punch moves up in the whole becomes larger and eventually fractures and in the same happens that eventually when you do that the conical tests and of course the idea is that you want to have fun as this is largest expansion of the whole yes without fracture and so 1 of the things that you you can do of course is

20:14

with these these tools that we have nowadays you can you can look at do the did not only the In the end the situation of the defamation but you can also look at all the intermediate states for instance again this is our diagram liners 3 major strength this line here is the line of None of thickening yes so or non sending us on this side material thickens on this side material fans during deformation here as you know there is no data points I know you can see small defamation well you know all the points around here and the greenish yellow points in our here so what the system also allows you to do is to attract you can track the 1 little bit here 1 little the element and see how it before the game and that is what is called the strain packed the 1st is that this little element during deformation king can good through a string pact does not necessarily always the drawing rights but so so let's see what happens here when we when when we the stretch the this whole here as you can see that something very peculiar happens

22:01

OK back to the last 1 year OK so you can see that all the points but remain on this or parallel along the line knows and that the X the point here there's the moves you can see this is 1 element this move this way then it moves literally along a line yes and at the at the edge of the sample are deformations move along these the Y axis so basically at the edge of the sample we can side all the deformation is indeed drawing an antique at the edge of the hole and at the edge of the sample it's a plane strapped for cash the but what's interesting is that it may come as a surprise but at the edge of the deformation is equivalent to a simple unity actual tensile test if the it's moving along here has no show you what I mean by that at the edge of your whole you have it's the defamation is equivalent to the unity actual himself decibel let's have a look at the union actual consultants for some reason the Brixton Bible kept saying we have minor strength diagram and major Strain diagram exhorted of are the strain surface here -minus strain in the x-axis major white accents but we know that the sum of this principle strengths is 0 because volume is that doesn't change in plastic deformation so the thickness strain can be written as minus the sum of major and minor training and we know that the ratio of the minor strain which is the West straying if you want over the thickness strain is that Spector's called are so we can rewrite you put these 2 equations together and and we can write a R my Mitsui minus over our is minus major strain plus minus right this this is the tea this is consistent substituting this will be the tea into this equation because up to now we have an from using this equation here and I just basically play around with it and I write major strain is equal to topless want are divided by far -minus that's a lot my took this is an equation of us of a straight line In this diagram yes basically tells me however the major strain and the Mac minor strains will change during strained yes for instance during the union actual past yes the but but then you see it's it's basically a function of art so if our is equal to 1 the compressible let's let's say are is equal to infinite that's what that means that there are is equal to infant and that means that there's no thickness straight from that so then it the might major strain is equal to minus the ministry and we moved along we have a defamation that moves along this line gets along the lines of they name or no thicker no change in the wind are increase it exuded decreases for its part equals 2 and he made sure it is the -minus we over to the minor if art is equal to 1 epsilon major is equal to minus 2 epsilon minor and so I moved along a line that steeper and steeper and that's basically this strange path you have in the unity actual test will come spring that you have been the actual test and and why is this now you can see why and history are is also important if you look at far from the point of view Of the SLD if I now put and Flt on this same diagram you can see when you do it defamation what you want to avoid forests strains that will lead you quickly to the slot that took our values which are large allow you to stay clear of the f and the fracture condition but that that's what art is indeed drawing mode yes important Of course as soon as you do by Stewart's you the stretching modes the FAA has no impact from him but now is if I may just go back and to buy the edge here of our whole there's so here you have the measurements of defamation yes along the whole and you can see it's along the straight line in deep drawing so that means basically the edge deforms just like tensile specimen with but but it's so and then you can

28:21

actually calculate that um you know from from this line here what the corresponding are of value the new series pretty low are value of . 5 10 and it's again I'm too this is on the whole expansion is an example of former uniform ability on the issue a another example is the problem of spring back you can you can the forum materials yes and when you take them out of the press before the shape should be stable you don't want the fish-shaped suddenly elastically the bad back or be elastically distorted image and so that happens that is very common if you have a very high-strength materials the very high-strength materials as an example the top 1 just made it to the chandelier shaped a part and you can see there is a little bit of elastic spring back but in the in the in the flat parts here and there but if you have a higher strength material on not only do you have accused spring back here but the Wallace curled and so on the Net it's a big problem because remember this part needs to be attached to something that's right and if it's all I bands and crooked on you know you have a problem because you may not be able to welded yes and that it will also look very ugly but badly built and so on so that's not a big issue for leadership and it's also part of the whole package of what what form ability and we won't go into this and

30:32

we will start next

30:35

episode get so and so it's it's clear from what that do .period we've come to expect we have not very nice solid theories of plasticity is in the minds of tactical know-how about performing and performing issues and how to test them but again at the end of the day the dead How do you go about and tackling this Our goal or understanding what's happening From the materials .period if you know how OK you know that your material doesn't have as high strain hardening his on you know what do you do or you material is too soft or too strong what do you do have you tinker with the material itself has to to improve things on or develop new materials here we

31:58

go and so on so it was we need to

32:04

understand what's going on in the MicroStrategy and what are the important points that we need to take into account now and the incident is the 1st thing we need to to know something about this on dislocations because to a certain extent in steals and in the most crystallites materials it's actually the dislocations which are the single most important parameter and in particular on it if may be a little bit more precise dislocation density that's that's important and and the reason is very simple basically on permanent deformation is caused by dislocation movement and strength if if you want to express it in its essence it's just basically putting obstacles in way path of motion of this locations and and thereby creating struck him and that's basically in a nutshell what would we're going to try to understand that In the coming lectures and we're going to move away from the field theories of plasticity etc. and try to see what we can do In the material to address the issue of of of strength and and form of the book and so we have to go up but about this locations

33:42

just to make sure that we're all on the same wavelength has there we just a few words about crystallography here yes so you have in crystallography what we call the crystal structure and the crystal structure is a combination of 2 thinks it's a combination of the Broadway lattice units and basis In the case of a Byron and IRA allies would you already know we're interested we have to read the crystal structures knows that occurred in in steals and that is the the so-called Alford Byron structural BCC structure which we always so-called far-right yes and that is the crystal structure is the brother a lattice simple few big brother that is plus a basis of 2 irony atoms 1 will located at 0 0 0 and 1 located at one-half 1 so when I attach this basis to a point in the lattice to all the points in the letters I generate this of this crystal structure in this is that the unit cell of the crystal structure but gamma IRA units the the the brother lattices again a simple simple cubic lattice but here we have 4 items In the face 1 ensues you 0 1 and one-half 1 has 0 1 have 0 1 half and 0 1 and have so far I attach this basis to all the brother lattice points I generate you hope well-known structure for gamma Byron yes FCC irony and then and in the case of the day the Absalon irony as we also have a hexagonal epsilon Byron Wood and certainly in alloys this and that we have simple hexagonal lattice which is shown here it's it's a brother Latins and an attached to it 1 have 1 have 1 has exuded 0 0 0 1 have won have 1 half so I attach this to every lattice .period and I get this crystal structure can 2 don't makes up brother lattices and crystal structure a brother lattices of mathematical thing and it's a mathematical it's its as you know there are only a very limited way 14 ways in which you can have points in space and whereby each point has the same surrounding and so on and the thing has translational symmetry and hinted that gives you the brother lattices you only have crystal structures once you you attach it the basis to this weekend Our so the I'm with what is important also to know is that I have we because we tend to use unit sells bad display the cemetery Of the crystals very nicely we tend to forget that the unit sells the choice of a unit so it's totally arbitrary yes so for instance if you look at the SEC yes but this is a perfectly good units at the US and it's a perfectly good units and and there's nothing cubicle pubic about it and that's so Trigano units but the nice thing about some alternative unit sales the answer is that In defamation studies in transformation studies very often they show better the relationships between the different crystals for instance began to this treatment all units sell units has the this base playing here is nothing else than 1 1 1 place that's 1 the 1 1 1 plane of the gamma our you OK that you can see yes that this is a very Of course similar to this these little units in the HCP lattice yes and that there is an obvious relation between the 1 1 1 Gamma playing and the 0 0 0 1 epsilon hexagonal play and when you get transformation from 1 to the other and that is their orientation relationship and if you look carefully at there is epsilon crystal here you see these 5 atoms here and if you compare this with 1 1 0 Alford is exactly very not exactly but very close lead related to the atoms in in this plane of the bcc lattice and and so when these hello Tropic forms of irony change from 1 to the other by transformation or by their formation yes the 1 1 1 plane of gamma will very often be well always be parallel to the 1 that is 0 0 0 1 of your hexagonal crystal and 1 1 0 of your far-right area al suppressed I'm just make sure that's you were and refresh your knowledge on directions and the Miller indices for the directions and planes crystallographic planes in cubic crystals because we're going to be talking a lot about these things and it's good if you it's not it's not difficult but it's it's good if you are comfortable with this so I just remind you of the fact that a direction is it's unique use 3 in the suspense square brackets and friends the 1 1 1 direction means that it's a vector 1 times a unit factor In the x-direction 81 times in the BUY direction and 1 times that the unit itself the directions sea front so that basically in the in in the unit-cell BCC unit-cell it's diagonal of this itself there were 2 1 1 direction means that instead of going 1 in the displacement 1 indeed a direction you go to India direction 1 in the What is the direction and 1 in the wider action this would be this factor for the planes it's slightly different you remember there you have to work with intercepts intercepts and then take the reciprocal of these intercepts so the 1 1 0 plane means that the the intercepts are the reciprocal of these values so no 1 is of course 1 over 1 wonders what over 1 and 0 is 1 over infinite and so on so that means it might cut off a piece the length of 8 In the x-direction b in the wider action and I do not cut I do not intersect the C X right so that gives me 1 1 infinity and then taking the reciprocal that gives me my Miller indices 2 1 1 planes to the same weighing only Woodard intercepts there's 1 half 1 1 so so 1 half of a here 1 of the 1 of C and and this is the place Of course when we when we talk about crystal planes we also talk about their at any playing in that family of planes in its antiparallel claims it has the same Miller Anderson and around indices for 4 planes were as the site for directions it's square indices we so but when we

43:41

have a particular playing Prince is the 1 1 2 plane in Altha yes that's what specific the crystal playing I hope that we can also define a family of planes of similar planes and and we say 1 1 2 Alpha planes with these accolades here and that means for instance in this case 6 times we the F-18 planes it seems like there were many different equivalent planes in a oppressed OK I write and am Crystal graphic directions saying things that we have we can have the UV W. direction for instance the 1 1 1 direction but we have a family of equivalent directions and then we use these this stuff of brackets pointed brackets to describe this family of direction so you have in this case you have 8 is when you do crystallography always don't forget you can have the direction you can have its negative right that's why you have 8 and the same with planes by the way we're going to deal with most of the time in the in our cost with cubic lattices has will we will talk about epsilon it should be but we want to much calculations where the remembered that it we have it's relatively simple relations between the 2 the angles of the plane normals if you have 2 planes like the A 1 1 2 plane and 1 old claims there is a normal to these 2 planes this formula allows you to calculate the angle between the normal things very simple HK each 1 K 1 L 1 Our for instance there the page 1 K 1 L 1 that's in Sorensen's 1 1 0 managed OK to sell to this for instance 2 1 1 2 when we talk about planes in general in crystallography was HK up and and and everybody knows you're talking about a place in Oracle you said you do you VW everybody knows you're talking about the direction and then the distance is also of parameters that we will be using the Inter playing distance so for instance if you look at 1 of the previous figures here I have to 2 1 1 planes in succession against their out there have a certain distance this distance is different for all the the families of planes since if you need to calculate this year's this assistance is given by the very simple formerly a being the lattice parameter divided by the square root of each square case where else but so let's that's so sound and have an example I don't think so you need to know what is the Inter playing the spacing for 1 1 0 planes interface with plugged the 1 1 0 and the value of a into this equation -dash Fitzgerald and the 8th year this point to say it's 6 nanometers I am divided by square with new find . 2 more not only was there in the olden days news you can still find it a lot in the literature people would use thanks transcended of its 10 taxes so . 2 centimeters is To and you want to know the angles between for 1 and 1 1 1 "quotation mark file you just plug in the H 1 K 1 L 1 and H 2 OK to L 2 values in the formula we have strong so with that's all and you find 1 over the square root strawberries and a new computer "quotation mark of 1 or oil Of 3 don't forget that that which you get Is there a newsman radiance yes and that we have no need to multiply 5 180 degrees divided by Pioneer agents and that gives you 50 4 . 7 the drinks so a note of caution here and this is the parameter of for Alpha arrow it's pure you will see this but what we already know that that parameter is it's not a constant right it's the changes In particular the changes with temperature because we get thermal expansion will remove contraction in when we call them and and 2nd it's also function of value if we add few cent of silicon to this variety the letters from very different so be careful when you use these the values of the 2 to know that this is the lattice parameters a function of composition and temperature look at this as an example here in America simple example I would like to have here the lattice parameter of algebra and gamma yes and then as a function of temperature SEC the lattice parameter of Elsa pure outfitted all morning 28 you have to see it increased yes it increases its thermal expansion and then when we go to gamma arid land grammar larger as you can see it but very much b the dependent on the amount of carbon the debt as we add carbon the latter's expects considerably on a little bit concerned I you will ask Well you know why don't show any data for all for Arab because it's not soluble in In them variety to this extent but it's very soluble in please don't get fooled about the lattice parameter of gamma being so large it doesn't mean that the latter's expanse when you go from Alpha to gamma actually the ladders contracts there is a higher density is only means that the latter's parameter is is larger but the difference is that here there are 2 atoms per unit cell where as here you have for 4 happens for you if you recalculate in terms of density of atoms a lot of prime and maybe a lot larger here this is the more dense the denser lattice and yes of course you know that as if you continue the increasing the temperature you will revert back to a BCC structure and due to the fact that the damages only stable at between 100 and aunt about 1400 deg C OK but this is kind of enough for a repeat of the crystallography let's and let's talk about some dislocation so again I assume you hear the same as for crystallography you have some basic knowledge at to introduce dislocated with we have a formal way of reducing dislocations and as of this the pieces are not made by the way there is no way that I will explain that all right but that's it's interesting to look at this In terms of that type of formalism yes so is a perfect crystal the idea that this crystal on throughout the year and served the extra planes between but 2 existing and wouldn't I create that instead we got a call this an exodus so that's a formal way of introducing an edge dislocation it turns out that actually edge dislocations in In the C C that kind of looks like that's not if you if you want to look at them on the atomic get basically looks like I have inserted extra have played in the crystal structure of the what's important here to realize is that if you go away from this yes From this dislocation the lattice becomes normal again right this the distortions that I created here they will fade out and you know 1 from the dislocation the crystal will be perfectly normal again where so 1 of the things that's always it's frustrating when of people introduced dislocations has to undergraduates is that they forget to make the difference between formalism yes and reality and so on missing these recipes actually occurring in steals but when I talk to you and I want to explain the complicated dislocation process yes I can't I cannot draw all this all the time right this would be really hard but I would have to to do all these things and say and you know and my extra happening so instead of doing this yes we agree yes 2 a way to describe this interest in a simple way press and so on attitude do this we use a um the rule yes it's before before I go on this role and that there is another type of dislocation and structure we find that you can make buying power to call a screw dislocations will cut your crystal and instead of moving it department adding occur as part that extra halfway you you shift the top part on the left here toward you and you lose the right part to the back until you that the lattice Matchis again menu you stick it back again and so on and this particular structure you you call a screw dislocations and it's the same as with the edges of it if you go far away enough from this dislocation where you get the normal lattice again the whole street lattice stretch a dies out and you get a pure like so we need to we need something well it's a so let me just go back to so if I want to describe this dislocation I need to have something simple simple method to communicate to you we're talking about this dislocation and so I will have to tell you well how much How much is the defamation here how many planes that I put inside its homage where did the plane come from yes to that with the plane From the Top like this or didn't bring it from the down side that's it's entirely the same on its own but if you have to dislocations that you really need to know right so so we need to have a convention nears but at the convention is as follows 1 of the concerns that any convention got right you can have your own with the convention lets use lot is called F S R H finnish start right hand that is basically the corkscrew units of the we agree to together rest there indeed you know we need to define the direction Of the dislocation so what we called in the direction of dislocation like the CIA at this line here at the end of this extra half that's what we call the dislocation like that's basically along this line that's where all the distortions will be all the lattices and then we need to have something it tells us but the amount of strain or of defamation or basically how many lattice planes that I put em yes In and we call this Burger Specter said so how do we describe this particular situation of the 1st thing we do this week we define line direction and it's totally up to you how you define yeah but the rule as saying by fighting the like direction in this direction and I I did find a snap right not because I'm a professor Mary intelligence is because I decide what's right you can this you'll see you can decide differently but was just then but it if I have if I have decided that this is my direction and I take my hat in the right hand yes and I make my you know my corkscrew right-handed screw shape of my fingers right yet so and I put my finger along the line direction that I have chosen they're not because I'm intelligent just because children again and now my finger I put my finger my thumb In the direction where I the extra half plane is inserted them then the rule says the burger Specter goes In this direction yeah now in this case I know where the extra half playing comes from and put it there myself as standard in this direction In the Zeitoun and there I chose it myself right OK Soderberg specter is defined not in practice yes for instance you do experiments yes and you do you see this location and you do what we call this location analysis and that allows you to say this is this is how it looks when there's not upside down and it's it looks like that's just an idea my Burgos factor is I use this convention yes To see to describe it its instead of making the drawing yes instead of making drawing will to side but I also have a dislocation life here it will just make it straight ahead of this this look at him I say Well this is my this location line direction but was it that is basically a unit vector that moves along the like this as an enemy and then if I sign this is my burger spectrum then you know yes you know I didn't draw anything and little atoms side and drawn extra have which you know that's because I use this you say will very simple where does it Where is my extra halfway right my fingers along this this finger is along the Burgers factor yes so where does my extra have Maine conference like this so here I didn't draw yawning draw 1 line and 2 factors which you know that it looks like this yeah why is this important if you have won this game doesn't really matter but say I have another dislocation and now I'm telling you this is the line direction I chose this and now I tell you this is the case has this purpose In the other direction OK so how does this 1 look no problems that you take your fingers there's a new set of he's chosen this direction Nos this thing there has to be in the direction of the "quotation mark it's not going it's in it's in the other direction In this case might some points downwards popped up this with this case .period downward so in this case I'm basically telling you In location is like this is oriented like this now you can directly see that its nontrivial because in in this case I will have at this location like likeness and a dislocation like this very close to each other and most will receive about will talk about this in that applies when you have this situation is this occasional move toward each other and then I like now if I had instead but I had this dislocation and next to it was the same dislocation then I would have In this condition right In this case the dislocations would repel each other very strong look at so very important here right all this is the stuff and then and stuff you've learned about making and you counting the atoms and then make breaking closing back and and deciding lobbyists this forget it your professor never worked in locations if you start doing this this is the way that it again their wages will increase and and that's why you never understand it when you know a Guide never done any dislocation work explains it to you is because it's just the reverse if you you you know where the situation and you need a way to express yes what it is without having to draw it over and over again right but this is this is more convenient tried only 1 life and passed it has the advantage of if you when you look at this location so that the thing which is alive look very much like lines even when you do model that you know be models of dislocations by molecular-dynamics skyline realigned its like a to straight of overlap as the and the other debt and so this allows you to to work it out and you know that hopefully we will have right and so on and young please remember this if if you want know this convention you know you can always go back to that convention and then you also don't have to worry about screw dislocations and you know because which dislocations it's like a challenge me that we were doing was good there's no extra have like but how you define no problems 1 of the things that we know of dislocations yes Is that the murderous is a constant that's because the wood to Burtis circus and nothing else there the amount of slack we're giving the crystal and now however I'm going to instead of cutting the crystal and putting in an extra half blamed I'm I'm going to make a dislocation awaits really make us and where it's really made is basically by slept I raised push shared this crystal nose and eyes introduced dislocations by this she mechanism against so it it means it basically means that this part of the Crystal has moved a certain amount with respect to the bottom part and that's what I call the Burgers vector and that's basically the relation between what I was saying the the size of the the thickness of the extra half playing for that include but so record so what which could also be the nice thing is that when you once you know that you screw dislocations it's no problem to make edge dislocations because dislocation lines cannot stop in the crystal yes they must stop at a surface on interface ours but they cannot stop inside the crystal so I say this dislocation here say it makes a a 90 degree bend 90 degree bend OK so the 2 I have here this spite that my unit vector along the line the line direction now is is is always along the line direction might to it's like this just the moves along the lines direct and my barber Spector never changes surface and be here it's being here so when a maker missed the sharp edge dislocation goes from shape type with this to screw type of dislocation yet and I don't have to worry about yes about where want to direction of B with the direction of it's it's given by what I the way I decided to presented in the edge orientation so let's have a look at this situation and will close "quotation mark so it's a safe and pure edges his in here is so that you see here in this edges with if I turn around yes it can become a screw dislocations so close to that Libby is always the same the right and if you added that this is a factor in this is that the arrow for the vector right not for the it's is this just means abuse of bacteria doesn't mean that that's the the actual be vector right to the edge turns into a screw dislocations right took what will use very often yes is the idea of a dislocation in the inside a crystal yes it's very useful to think about this location of so and so inside the crystal has so the edge dislocation segments so that the user are the sports here will have will necessarily have indeed the extra have thing has to be different as to be in the coming from different directions and that the the stays the same but conceivable the Burgos factor is the same along the dislocation lying has so How can I show that the extra have planes coming from top on this side and coming from the bottom he was very simple the line the line direction points in a different direction In 1 case if I choose this 1 this is my line direction then I have to go along and the line direction points in this direction so I use my right hand the start-finish criterion line direction Burgers vector extra have this up work on this In this side of the wine director yesterday workers factor is now in like extra happening is that OK all right so I will stop here and make you

00:00

Feinstblech

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08:43

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Fahrzeug

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Schnittmuster

Hobel

VW-Golf GTI

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Förderleistung

Institut für Raumfahrtsysteme

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Druckmaschine

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Körner <Metallbearbeitung>

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Kaltumformen

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19:30

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Locher

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Rungenwagen

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22:01

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Bergmann

Fertigpackung

30:28

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Entwicklung <Photographie>

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Schusswaffe

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Edelsteinindustrie

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31:51

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Vorlesung/Konferenz

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33:41

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VW-Golf GTI

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Satz <Drucktechnik>

Institut für Raumfahrtsysteme

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Hobel

Avro Arrow

Druckmaschine

Holz

ISS <Raumfahrt>

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Schärfen

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Spiel <Technik>

SS-20

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Setztechnik

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Anstellwinkel

### Metadaten

#### Formale Metadaten

Titel | Mechanical properties of steel 8: formability |

Serientitel | Mechanical properties of steel |

Teil | 8 |

Anzahl der Teile | 24 |

Autor | Cooman, Bruno C. de |

Lizenz |
CC-Namensnennung 3.0 Unported: Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen. |

DOI | 10.5446/18314 |

Herausgeber | University of Cambridge |

Erscheinungsjahr | 2013 |

Sprache | Englisch |

#### Technische Metadaten

Dauer | 1:14:53 |

#### Inhaltliche Metadaten

Fachgebiet | Technik |

Abstract | The eighth in a series of lectures given by Professor Bruno de Cooman of the Graduate Institute of Ferrous Technology, POSTECH, South Korea. This particular lecture deals in more detail with the formability of steels, particularly those for automotive applications. |

Schlagwörter | The Graduate Institute of Ferrous Technology (GIFT) |