Deformation and fracture

400 nm thick solution-cast film, crystallization at 180°C, yielding a fine sheaf-like morphology (dark) with random crystallite orientation (see electron diffraction pattern in the insert) deformed at room temperature in roughly horizontal direction a single craze is running through semicrystalline sheaves  

Syndiotactic PS (sPS), deformed up to more than 20% at 110°C (above glass transition temperature of the amorphous phase)  

Grellmann, W., Knesl, Z., Hutar, P., Nezbedova, E., Bierogel, C., Joining Plastics (Ftigen von Kunststoffen) (2012) 6, pp. 126-133 

Michler, G.H., Balth-Calleja, .]., Nano- and Micromechanics of Polymers Structure Modification and Improvements of Properties (2012) Hanser, Munich, Section 12.3.1, pp. 514-526 

Scholtysek, S., Michler, G.H., unpublished resuits (2007) University Haiie-Wit-tenberg 

All materials undergo a deformation, either noticeable or unnoticeable, whenever they are subjected to an external force. The deformation can be elastic, plastic, elastomeric, or viscoelastic. When an external force is applied on a body, the displacement of points of the body relative to neighboring points is measured as strain and the strength of the force applied to the local point is measured as stress. Elastic deformation such as rubber band stretch is recovered when the stress, or external force, is removed. Plastic deformation such as a dent on a metal car body is permanent and is not recoverable with the removal of the deforming stresses. 

Deformation is caused by stress from either an external force or an imbalance of internal forces. Quantitatively, a stress a on an area of a specimen is equal to the force applied per unit area. Since a force is a vector with three components, the stress component from the normal component of the force is called normal stress it causes elongation or contraction of the material depending on the direction of the force. The stress components from the two tangential components of the force are called shear stresses they are responsible for the shear deformation. 

A strain e is equal to the ratio of the displacement A I caused by a stress to the total length L. Two common methods for strain calculation are used, depending on the magnitude of the strain. When a strain is small, the reference axes remain virtually unchanged so that I essentially maintains its initial length Lq. Hence the strain, known as the nominal strain, is simply 

In the cases where L changes appreciably from its initial value, the method for so-called true strain should be used instead of the nominal strain method. The true strain is calculated by 

The mathematical relationship between the stress and the strain depends on material properties, temperature, and the rate of deformation. Many materials such as metals, ceramics, crystalline polymers, and wood behave elastically at small stresses. For tensile elastic deformation, the linear relation between the stress, a, and strain, e, is described by Hooke s law as 

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Argon A S 1993 Inelastic deformation and fracture of glassy solids Materials Science and Technology vol 6 (Weinheim VCH) pp 462- 508... 

R. W. Hert2berg, Deformation and fracture Mechanics of Engineering Materials, John Wiley Sons, Inc., New York, 1983. 

Film Adhesion. The adhesion of an inorganic thin film to a surface depends on the deformation and fracture modes associated with the failure (4). The strength of the adhesion depends on the mechanical properties of the substrate surface, fracture toughness of the interfacial material, and the appHed stress. Adhesion failure can occur owiag to mechanical stressing, corrosion, or diffusion of interfacial species away from the interface. The failure can be exacerbated by residual stresses in the film, a low fracture toughness of the interfacial material, or the chemical and thermal environment or species in the substrate, such as gases, that can diffuse to the interface. 

The performance of a tool material in a given appHcation is dictated by its response to conditions at the tool tip. High temperatures and stresses can cause blunting from the plastic deformation of the tool tip, whereas high stresses alone may lead to catastrophic fracture. In addition to plastic deformation and fracture, the service life of cutting tools is deterrnined by a number of wear processes, some of which are shown in Figure 2. 

R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th edition, 1996. B. R. Lawn and T. R. Wilshaw, Fracture of Brittle Solids, Cambridge University Press, 1975, Chap. 3. 

R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, 4th edition, Wiley, 1996. 

The most common conditions of possible failure are elastic deflection, inelastic deformation, and fracture. During elastic deflection a product fails because the loads applied produce too large a deflection. In deformation, if it is too great it may cause other parts of an assembly to become misaligned or overstressed. Dynamic deflection can produce unacceptable vibration and noise. When a stable structure is required, the amount of deflection can set the limit for buckling loads or fractures. 

Several aspects of the deformation and fracture of rubbery materials are reviewed in this chapter. They reveal some important gaps in our present understanding of the behavior of simple mbbery solids. 

Bradley W.L. and Cohen R.N. (1987). Matrix deformation and fracture in graphite-reinforced epoxies. In Toughened Composites, ASTM STP 937 (N.J. Johnston ed.), ASTM, Philadelphia, PA, pp. 389-410. 

Fracto-emission (FE) is the emission of particles (electrons, positive ions, and neutral species) and photons, when a material is stressed to failure. In this paper, we examine various FE signals accompanying the deformation and fracture of fiber-reinforced and alumina-filled epoxy, and relate them to the locus and mode of fracture. The intensities are orders of magnitude greater than those observed from the fracture of neat fibers and resins. This difference is attributed to the intense charge separation that accompanies the separation of dissimilar materials (interfacial failure) when a composite fractures. 

In general, the use of FE signals accompanying the deformation and fracture of composites offer elucidation of failure mechanisms and details of the sequence of events leading upto catastrophic failure. The extent of interfacial failure and fiber pull-out are also potential parameters that can be determined. FE can assist in the interpretation of AE and also provide an independent probe of the micro-events occurring prior to failure. FE has been shown to be sensitive to the locus of fracture and efforts are underway to relate emission intensity to fracture mechanics parameters such as fracture toughness (Gjp). Considerable work still remains to fully utilize FE to study the early stages or fracture and failure modes in composites. 

These individuals have areas of increased bone resorption and other areas of abnormal new bone formation. The abnormal bone formation can result in pain, deformity, and fracture of affected bones. The bisphospho-nates and calcitonin are most commonly used in the treatment of this disease. Long-term continuous use of bisphosphonates can be associated with the induction of osteomalacia through a direct impairment of new bone formation. Therefore, the bisphosphonates are given in a cyclic pattern to treat Paget s disease. 

J. Pearson J.S. Reinhart, "Deformation and Fracturing of Thick-Walled Steel , jApplPhys 23, 434-41 (1952) 3) J-S. Rein-... 

Inst of Research, "Plastic Deformation and Fracture of Metals at High Rates of Strain , Final Rept on Contract DA 36-034-ORD-1456, Proj TB 2-0001 (87), 28 Aug 1953 to 27 Aug 1954, Bethlehem, Pa 4a) R.G. Schreffler W.E. Deal, "Free Surface Properties of Explosive-Driven Metal Plates , JApplPhys 24, 44(1953) 5) S. Singh, "Principles of Armor... 

Deformation and Fracturing of Thick-Called Steel Cylinders under Explosive Attacks. 

Fig. 17. Interaction of a crack with a fiber through fiber deformation and fracture...

Deformation and fracturing of thick-walled steel cylinders under expl attack 3 D40... 

Grellmann W, Seidler S (2001) Deformation and fracture behaviour of polymers. Springer, Berlin Heidelberg New York... 

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