Compression damage

It has been proposed that chipping could be conducted in two stages to obtain chips with less compression damage. Whatever method of chipping is used uniformity of size is important to the yield and the strength of the pulp produced. Any fines have to be screened out and cooked under different conditions than regular sized chips to decrease loss of cellulose. Any oversize material has to be further processed for use. Blade sharpness, speed of disk rotation, weight of log(s) in the spout, and whether the butt or the top of the log is fed in first, all affect chip consistency and quality. 

Figure 15.2 Compression damage of fiber composites through microhuckling. (a) Undulations of buckled fibers (b) kink band local failure schematic and (c) micrograph of kink hand formation in a T800/924C carbon-fiber composite [6].

ANALYSIS OF COAL ROCK UNIAXIAL COMPRESSION DAMAGE... 

The pressures involved in porosimetry are so high (e.g. 1000 atm = 6-6 ton in" ) that the question as to whether the pore structure is damaged by mercury intrusion naturally arises. This possibility was recognized by Drake, but as a result of several intrusion-extrusion runs at pressures up to 4000 atm on a number of porous catalysts Drake concluded that any deformation caused by compression was elastic and therefore not permanent. 

An expandable anode involves compression of the anode stmcture using cHps during cell assembly so as not to damage the diaphragm already deposited on the cathode (Eig. 3a). When the cathode is in position on the anode base, 3-mm diameter spacers are placed over the cathode and the cHps removed from the anode. The spring-actuated anode surfaces then move outward to bear on the spacers, creating a controlled 3-mm gap between anode and cathode (Eig. 3b). This design has also been appHed to cells for the production of sodium chlorate (22). 

A 2.54-cm Styrofoam plastic foam with thermal conductivity of ca 0.03 W/ (m-K) (0.21 (Btu-in.)/(ft-b°F)) is equivalent to 61 cm of gravel. Any synthetic foam having compressive strength sufficiently high and thermal conductivity sufficiently low is effective. However, the resistance of PS-type foams to water, frost damage, and microorganisms in the sod makes them especially desirable. An interesting and important appHcation of this concept was the use of Styrofoam in the constmction of the Alaska pipeline. In this case, the foam was used to protect the permafrost. 

It is critical that surface treatment conditions be optimized to composite properties since overtreatment as well as undertreatment will degrade composite properties. Typically composite interlaminar shear strength (ILSS), in-plane shear, and transverse tension ate used to assess the effectiveness of surface treatment. More recently damage tolerance properties such as edge delamination strength, open hole compression, and compression after impact have become more important in evaluating the toughness of composite parts. 

Pressure Development Overpressure in a UVCE results from turbulence that promotes a sudden release of energy. Tests in the open without obstacles or confining structures do not produce damaging overpressure. Nevertheless, combustion in a vapor cloud within a partially confined space or around turbulence-producing obstacles may generate damaging overpressure. Also, turbulence in a jet release, such as may occur with compressed natural gas discharged from a ruptured pipehne, may result in blast pressure. 

Resiheut, compressible and strong, but not impermeable. Resists medium-strength mineral acids and dilute mineral solutions if not intermittently dried. Resists oils, greases, waxes, most solvents. Damaged by alkahes. 

Investigations in the field of shoek eompression of solid materials were originally performed for military purposes. Speeimens sueh as armor were subjected to either projectile impact or explosive detonation, and the severity and character of the resulting damage constituted the experimental data (see, e.g., Helie, 1840). Investigations of this type continue today, and although they certainly have their place, they are now considered more as engineering experiments than scientific research, inasmuch as they do little to illuminate the basic physics and material properties which determine the results of shock-compression events. 

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