Plastic body

To describe the generalized forces in this geometry, we shall choose a volume element with a right-angled triangular cross-section whose shorter sides are perpendicular to the directions of the principal stress (cti and ug) and whose h5rpotenuse is perpendicular to the x direction 

Chapter 12 Mechanical Properties of Powders arid Suspensions 

The following equations are obtained by considering the equilibrium of the forces  

If a solid body is compressed by a normal force against a flat support and subjected to a tangential force it will start to move if 

FIGURE 12J3S The Mohr stress circle (a) is a representatioii of a two-dimensional state of stress in a powder compact (b). The Coulomb 3neld a-iterion is also plotted as a straight line in the Mohr stress circle. 

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Ceramic fonning typically involves using pressure to compact and mould particles to the desired size and shape. Ceramics can be fonned from slurries, pastes, plastic bodies (i.e. such as a stiff mud), and from wet and dry powders. 

Anzellotti G., Giaquinta M. (1982) On the existence of the fields of stresses and displacements for an elasto-perfectly plastic body in static equilibrium. J. Math. Pure Appl. 61, 219-244. 

Arutunyan N.H., Drozdov A.D., Naumov V.E. (1987) Mechanics of growing visco-elasto-plastic bodies. Nauka, Moscow (in Russian). 

Bingham plastic Bingham plastic body BINSERT... 

Ceramic forming iavolves consoHdation and mol ding of ceramic powders to produce a cohesive body of the desired size and shape. Ceramic forming operations (38,40—66) are conducted with dry powders, plastic bodies, pastes, and slurries. 

Attached anodes provide the particular advantage of proportionately low grounding resistance for the protection current because the actual anode body is set into both sloping sides of the plastic body as long narrow strips. The disadvantage is that the body is exposed on the ship s side and can easily be damaged mechanically. 

Fig. 5. Diagram of load versus load-point displacement for an elastic-plastic body experiencing stable crack extension [48],...

These cements have unusual rheological properties (Wilson, 1975b). They can be mixed to higher powder/liquid ratios (6 1 by mass, or more) than any other dental cements and are very fluid. Whereas pastes of other cements behave as plastic bodies, the EBA cement has the characteristics of a very viscous Newtonian liquid and flows under its own weight, even when mixed very thickly (Wilson Batchelor, 1971). High powder/liquid ratios are required for optimum properties 3-5 g cm for luting and 5 to 6 g cm for linings and bases. 

Consistency, working time, setting time and hardening of an AB cement can be assessed only imperfectly in the laboratory. These properties are important to the clinician but are very difficult to define in terms of laboratory tests. The consistency or workability of a cement paste relates to internal forces of cohesion, represented by the yield stress, rather than to viscosity, since cements behave as plastic bodies and not as Newtonian liquids. The optimum stiffness or consistency required of a cement paste depends upon its application. 

Consistency is tested on a measured volume of freshly mixed cement in the form of a cylinder. This specimen is placed between two horizontal plates using the apparatus illustrated in Figure 10.1 and subjected to a vertically applied load. The cement then flows out rapidly to form a disc. This radial flow ceases almost instantaneously because the applied stress decreases as the disc expands and rapidly reaches the yield stress, at which point outward flow ceases. This is the behaviour expected for a plastic body. 

Many years later in Singapore, we were using a specially formulated thermally conductive glue to fix the overtemperature sensing thermistor smack on to the very plastic body of the TO-220 power transistor. We had empirically ascertained that in this way, the junction temperature and the adjacent temperature as seen by the thermistor were less than 10°C apart, even during an abnormal event. So if, for example, we wanted to have the transistor turned off just before it hit 150°C, we simply needed to set the trip temperature (of the thermistor-based circuit) at about 140°C. In that way, we could also be sure that we wouldn t encounter nuisance tripping on a particularly hot day, when the temperature inside the enclosure would also be much higher. 

In the method of producing a hollow foamed plastic body from polyethylene or polypropylene by means of an extrusion blow-moulding process using a single-screw... 

Based on an analysis of the penetration of a thick, rigid plastic body by a rigid cylinder (whose radius is smaller than the radius of the body), A B arrive at... 

Sone, T. 1961. The rheological behavior and thixotropy of a fatty plastic body.. / Phys. Soc. Japan. 16, 961-971. 

A plastic material is defined as one that does not undergo a permanent deformation until a certain yield stress has been exceeded. A perfectly plastic body showing no elasticity would have the stress-strain behavior depicted in Figure 8-15. Under influence of a small stress, no deformation occurs when the stress is increased, the material will suddenly start to flow at applied stress a(t (the yield stress). The material will then continue to flow at the same stress until this is removed the material retains its total deformation. In reality, few bodies are perfectly plastic rather, they are plasto-elastic or plasto-viscoelastic. The mechanical model used to represent a plastic body, also called a St. Venant body, is a friction element. The... 

Figure 8-15 Stress-Strain Curve of an Ideal Plastic Body...

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