So, we will have today in our lecture about the concept of stress and strain also the plastic and elastic behavior about the types of stresses and also type of strain. The task of the subject is to provide the students with knowledge, which is necessary for them during finding of inventive and complex engineering solutions. Plastic deformation the deformation is irreversible and it stays even after the removal of the applied forces. Our new crystalgraphics chart and diagram slides for powerpoint is a collection of over impressively designed datadriven chart and editable diagram s guaranteed to impress any audience. After plastic deformation the material is not return back to the original position.
Plastic deformation an overview sciencedirect topics. Geometry or shape of the deformation zone affects the redundant deformation work, and hence the total forming force. Once an element has reached its yield state, further increases in stress must be supported by neighbouring elements, which in turn may. Of the two types of deformation the former elastic is reversible whereas the latter plastic is irreversible see table 1. To prevent plastic deformation at the cutting edge, the tool material should possess a high fracture toughness b high hot hardness c chemical stability d adhesion resistance problems problem 1 during turning a metallic rod at a given condition, the tool life was found to increase from 25 min to 50 min. Deformation and fracture mechanics of engineering materials mechanical. Lecture notes mechanical behavior of materials materials. U ts under some circumstances solid polymersare elasticin their mechanical response, particularly at very low temperatures, and at high temperatures t g if they are crosslinked or. As a result, the material undergoes a time dependent increase in length, which could be dangerous while in service. There are different ways of solving the deformation of elastoplastic solids. This method of design limits the structural usefulness of the material upto a certain allowable. More than 50% deformation of supercooled austenite in the zone of relative stability induces an increase of the. If a material is loaded beyond its yield point it experiences both elastic and plastic strain. Therefore, real materials are a times weaker than they should theoretically be.
In modeling internal fields, questions arise regarding what is the statistical nature of defect distribution, what if any correlations there are between defects, and what length scales are required to take these correlations into consideration. Deformation and fracture mechanics of engineering materials. If the material is now loaded again, the forcedisplacement curve will retrace the unloading path cb until it again reaches the plastic state. Chapter outline dislocations and strengthening mechanisms. Plastics processing plastics can be machined, cast, formed, and joined with relative ease requiring little postprocessing or surfacefinish operations plastics melt or cure at relative low temperatures plastics require less energy to process than metals raw materials most commonly are pellets, powders. Discuss design options to minimize creep deformation. Plastic deformation of alloys with submicrongrained structure. Difference between bulk deformation and sheet metal. The conventional theory of crystal plasticity 6, 16 rests on a kinematical interpretation of plastic deformation according to which the rate of plastic deformation in a single crystal is. The resulting plastic deformation is permanent and cannot be recovered by simply removing the stress that caused the deformation.
Extent of elastic and plastic deformations will primarily depend on the kind of material, rate of. There are two basic mechanisms by which plastic deformation takes place in crystal structures. In engineering, deformation refers to the change in size or shape of an object. The plastic deformation of crystals occurs through the nucleation and motion of lattice defects known as dislocations. Lecture 28 plastic capacity of sections under combined loads i lecture 29 plastic capacity of sections under combined loads ii nptel video lecture topic list created by linuxpert systems, chennaiget digimat digital media access terminal for highspeed video streaming of nptel and educational video courses in lan. The inhibition period of the decomposition of deformed austenite in the pearlite and intermediate regions decreases with increasing degree of deformation.
The finite element method is applied for plastic deformation behavior during the tst process. Nptel mechanical engineering forming joint initiative of iits and iisc funded by mhrd page 3 of 9 plasticity 1. The results demonstrate that the tst process can produce relatively homogeneously deformed materials. Pdf the theory of finite plastic deformation of crystalline. Materials science and engineering, a7 1991 3540 35 plastic deformation of alloys with submicrongrained structure r. Analysis of large plastic deformation of elastoplastic solids friction involves large plastic deformation. The further deformation at the area 34 is accompanied by increasing of conventional stress the effect of metal hardening during the process of deformation. Nptel mechanical engineering forming joint initiative of iits and iisc funded by mhrd page 5 of 10 temperature. Concordia university mse 521 lecture 143 creep and high temperature failure constant load applied at constant high temperature deformation as a function of time vs. Nptel mechanical engineering forming joint initiative of iits and iisc funded by mhrd page 8 of.
Nptel mechanical engineering forming joint initiative of iits and iisc. In the last class we are talking about the plastic deformation and i defined. Plastic modulus, shear factor, plastic moment of resistance, load factor, plastic analysis of continuous beam and simple rectangular portals, application of upper and. In rate form, the condition is tr 0 p ffpp 1, where f is the plastic deformation gradient. Generally occurs at high temperature thermal creep, but can also happen at room temperature in certain materials e. Almost all real materials will undergo some permanent deformation, which remains after removal of load. So, we will get this type of things, so that is why it is called a metal forming process. Java project tutorial make login and register form step by step using netbeans and mysql database duration. The book offers an overview of these methods, introduces ultrafinegrained and nanograined metals and methods for various bulk, sheet, tubular and large size. All plastic models potentially involve some degree of permanent, pathdependent deformations. The two dotted horizontal lines represent the lowest and the highest stresses the material can withstand during plastic deformation. The transverse loads cause internal shear forces and bending moments in the beams as shown in figure 1 below. Plasticdeformation mechanism in complex solids nature.
Difference between bulk deformation and sheet metal forming. Of the total plastic work, v, a small fraction, 5%, goes into formation of vacancies. Chart and diagram slides for powerpoint beautifully designed chart and diagram s for powerpoint with visually stunning graphics and animation effects. Nptel mechanical engineering forming joint initiative of iits and iisc funded by mhrd page 3 of 9 1.
Recall if a material experiences only elastic deformation, when the stress is removed the elastic strain will be recovered. Deflection is the relative change in external displacements on an object. So that is why at very, at low temperatures at high stresses or even at for that matter even if you go to very high temperatures, dislocation glide is going to be the deformation mechanism. Korber, director of the kaiser wilhelminstitut fur eisenforschung, dusseldorf, delivered the twentysecond annual may lecture of the institute of metals in london on may 11, on the. Experiments show that the critical shear stress for plastic deformation in single crystals is mostly 0. Plasticity of materials, department of materials forming, fmme, vsb tu ostrava. Treatise on materials science and technology, volume 6. The moment the stress is removed, the body comes to initial position. Ppt plastic deformation powerpoint presentation free.
Finite element analysis of the plastic deformation in tandem. Methods, processing and properties examines all severe plastic deformation techniques developed over the past two decades, exploring the appropriate severe plastic deformation method for a particular case. Plastic deformation is defined as permanent, nonrecoverable deformation. Strain hardening as you have seen in the tensile test that when plastic deformation occurs in the material after a certain amount of strain if you want to further. Aug 09, 2019 what is the difference between bulk deformation and sheet metal forming. Plastic modulus, shear factor, plastic moment of resistance, load factor. Maiti,department of metallurgy and material science,iit kharagpur. Concept of stress and strain, elastic and plastic behavior nptel. At any stage beyond ys the total stain has both elastic and plastic components.
Creep and high temperature failure concordia university. In particular, the effects of back pressure and processing order on the plastic deformation behaviors in the tst process are systematically analyzed. Plastic deformation is, as elastic deformation, also characterized by defining the relation between stresses and the corresponding strains. Analysis of large plastic deformation of elastoplastic solids. The rate of decomposition during isothermal heating increases most intensely when the degree of swaging is higher than 75%. Deformation plasticity an overview sciencedirect topics. Such interactions are responsible for defect aggregation. The average of the two is defined as its flow stress. Bulk deformation is the metal forming operation where a significant change in shape occurs via plastic deformation in metallic parts, while sheet metal forming is a metal forming operation in which the geometry of a piece of sheet undergoes modification upon the addition of a force.
Plastic deformation is, as elastic deformation, also. Plastic deformation of structural steel springerlink. Stick ing friction could happen at normal stresses. The volume conservation condition during plastic deformation can be stated as det 1 cp p where c is the plastic right cauchygreen tensor miehe et al. Abstract the peculiarities of a submicrongrained structure formation in a series of aluminium and magnesium. Apart from the overall loss of shape, the lack of homogeneity in plastic deformation can lead to a significant variation in. Agenda define creep and discuss its importance in materials engineering. Plastic deformations of members with a single plane of symmetry plastic deformations of members with a single plane of symmetry fully plastic deformation of a beam with only a.
Engineering fracture mechanics dislocations and plastic deformation explains the. Basic principles of elasticity and plasticity plastic range plastic range. Chapter outline dislocations and plastic deformation 9motion of dislocations in response to stress 9slip systems 9plastic deformation in single crystals polycrystalline materials strengthening mechanisms 9grain size reduction. The slope of the curve 7 is a measure of its strain hardening. Introduction plastic deformation occurs when a material is stressed above its elastic limit, i. In comparison with the plastic deformation of regular crystalline materials, the mechanisms that govern complex solids with hundreds of atoms in a single unit cell are much less understood. The book presents articles on the low temperature of deformation of bcc metals and their solidsolution alloys. Because during deformation this area cross section also changes and we define the engineering stress on to the cylindrical specimen as the force divided by the. It is a time dependent deformation under a certain applied load. Strain is the relative internal change in shape of an infinitesimally small cube of material and can be expressed as a nondimensional change in length or angle of.
This lecture discusses the yielding phenomenon and slip systems in different crystal structures. One is the slipping of one plane of atoms over an adjacent plane called the slip plane under a shear stress. Plastic analysis version ii 35 1 plastic analysis 1. Deformation in this case is permanent plastic deformation. Displacements are the absolute change in position of a point on the object.
Forming web course course outline stress strain relations, stress and strain transformations, elastic and plastic behaviour, yield criteria, elementary principles of metal forming cold, hot and warm working, effect of parameters such as temperature, strain rate, friction. The critical resolved shear stress, is the minimum value of. Plastic deformation is the permanent distortion that occurs when a material is subjected to tensile, compressive, bending, or torsion stresses that exceed its yield strength and cause it to elongate, compress, buckle, bend, or twist. Ppt plastic deformation powerpoint presentation free to. Ghosh, dept of metallurgical and materials engineering keywords.
Volume conservation during finite plastic deformation. The strain which remains upon unloading is the permanent plastic deformation. Plastic processing technique plastic processing can be defined as the process of converting the plastics raw material into semifinished products. Buckets, automobile parts, crates, tanks, pipes, bottles, carry bags, ropes, profiles etc. An elastoplastic model allows and solves for yielding within the model and the resulting displacements that arise. Tsenev institute for metals superplasticity problems, u. Academic resource center illinois institute of technology. Plastic deformation is not linear with applied stress. Plastic deformation along shear plane merchant the fig. Find materials for this course in the pages linked along the left. Elasticity and plasticity in building engineering theoretical basement for the theory of structures important for steel, concret, timber structures design to be able design safe structures to resist mechanical load, temperature load statics. Mechanical properties of metals mechanical properties refers to the behavior of material when external forces are applied.