Plastic compression

A formal theory of inelastic compression is presented in one of the chapters, which rigorously lays out the theoretical foundations and provides a rational mechanics framework for describing the plastic compression prop-... 

Physical Properties Under Elastic-Plastic Compression... 

Chapter 5. Physical Properties Under Elastic-Plastic Compression PIus-a Orientation... 

Chapter 5. Physical Properties Under Elastic-Plastic Compression Table 5.1. Compressibilities of nickel-iron alloys (after Graham et al. [67G01]). 

The TS plastic compression-molded products will have a higher shrinkage when ... 

Figure 2.3 Plastic compression of a cylinder. A—Initial configuration. B—compressed cylinder with no frication (a = 0) at platen interfaces. C—compressed cylinder with full friction (a = 1) at platen interfaces.

Prediction of the restitution coefficient has been a challenging research topic for decades. Unfortunately, no reliable and accurate prediction method has been found so far. However, some useful simplified models with certain limits have been developed. One of them is the elastic-plastic impact model in which the compression process is assumed to be plastic with part of the kinetic energy stored for later elastic rebounding, with the rebound process considered to be completely elastic [Johnson, 1985]. In this model, it is postulated that (1) during the plastic compression process, a — r3/2a (2) during the compression process, the averaged contact pressure pm is constant and is equal to 3 Y and (3) the elastic rebound process starts when maximum deformation is reached. Therefore, the compressional force is... 

The surface properties of this kind of supramolecular systems are really scarce. An interplay between short - range van der Waals forces, ionic binding, chemical bonding, elastic/plastic compression, and long - range electrostatic interactions and capillary forces between macromolecules and surfaces seems to be responsible for the variety of observed interfacial behaviors. 

FIGURE 10.3 Construction of the carbon-zinc cells. The zinc chloride and Leclanche have the same construction except for the seal. The zinc chloride has a plastic-compression seal while the Leclanche has a poured hot bituminous seal instead of the plastic-compression seal shown. (Courtesy of Eveready Battery Co., St Louis, MO. With permission.)... 

Because the zinc chloride electrolyte is more acidic, the cell requires a stronger plastic-compression seal. The ingress of oxygen from the air would otherwise react directly with the zinc anode and shorten cell life. 

ISO 844-78 Cellular Plastics — Compression Test for Rigid Materials, 4PP,... 

When a specimen is stretched plastically a few percent and then unloaded, x-ray measurements show a line shift indicating residual compressive macrostress in the direction of prestrain. The effect is symmetrical after plastic compression, x-rays indicate residual tensile stress. It is not a surface effect, because x-ray measurements made after successive removal of surface layers show that the stress persists throughout the specimen. On the other hand, dissection measurements show that a true macrostress does not exist, and, in fact, none would be expected after uniform deformation. The stress indicated by x-rays is called pseudo-macrostress, pseudo because it is not a true macrostress causing strain on dissection and macro because it causes an x-ray line shift. Pseudo-macrostress is actually an unusual kind of microstress, in which the portions of the material that are in tension and in compression are unequal in volume. It has been discussed in various reviews [16.26-16.28]. 

Figure 8 shows the volume as a function of time for four overdriven single shock wave simulations in the [110] direction of a 25688 atom perfect Lennard-Jones face centered cubic crystal. Elastic compression is characterized by VjV 0.9 and plastic compression occurs for smaller volumes. As the shock speed decreases, the amount of time the molecular dynamics system spends in the elastically compressed state increases. This plot illustrates how the final thermodynamic state in the shock is a function of the simulation duration when slow chemical reactions or phase transitions occur. For example, on the 10-20 ps timescale, the 2.8 km/sec shock has an elastically compressed final state on the 100 ps timescale, this simulation has a plastically compressed final state. 

Table I. Mechanical Properties for Main Classes of Styrene-Based Plastics (Compression Molded Specimens) ...

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