Hardening mechanical

Four separate hardening mechanisms are at work during the ageing process ... 

S02-cured epoxy resin. Modified epoxy/acrylic resins (1.2 to 1.4% of sand weight) are mixed with organic peroxide (26 to 60% of resin weight), the mixture is blown into the core box and a hardening mechanism similar to the S02 process takes place. 

PP bead foams were subjected to oblique impacts (167), in which the material was compressed and sheared. This strain combination could occur when a cycle helmet hit a road surface. The results were compared with simple shear tests at low strain rates and to uniaxial compressive tests at impact strain rates. The observed shear hardening was greatest when there was no imposed density increase and practically zero when the angle of impact was less than 15 degrees. The shear hardening appeared to be a unique function of the main tensile extension ratio and was a polymer contribution, whereas the volumetric hardening was due to the isothermal compression of the cell gas. Eoam material models for FEA needed to be reformulated to consider the physics of the hardening mechanisms, so their... 

Preparation of sodium Urushi/ISFET. A mixture of 5 wt. % of ETH 227, 45 wt. % of di-2-ethylhexylphthalate (DOP Kishida Chemical Co. Ltd.) containing 0.5 wt. % of potassium tetrakis(4-chlorophenyl)borate (Dojin Research Laboratories Co. Ltd.) and 50 wt. % of Urushi (Saito Urushi Co. Ltd.) was coated on the FET devices and then the resulting Na+ Urushi membranes were hardened for 10 days at 30 °C and 90% relative humidity. The thickness of the membrane was approximately 0.1 mm. The surface of the Urushi matrix membrane was lustrous, smooth and adhesive to the gate of the device. The hardening mechanisms were discussed in detail elsewhere (6). 

The zone model proposed by Brissonneau is consistent not only with his own field ion microscopic observations, but also with larger scale and often puzzling phenomena observed. PtCo magnets, for instance, form Bitter patterns on a scale quite easily visible under a light microscope. Bitter patterns do not fit the picture of a fine-particle hardening mechanism unless they also describe a larger scale phenomenon, such as Brissonneau zone boundaries. 

For more details regarding the role of C4AF in the hardening mechanisms of Portland cement, see Meller, N. Hall, C. Jupe, A. C. Colston, S. L. Jacques, S. D. M. Barnes, R Phipps, J. J. Mater. Chem. 2004, 14,428, and references therein. 

Thus far, we have focused primarily on Fe-C alloys, with carbon atoms positioned within vacant interstitial sites within the iron lattice. As you may expect, a variety of other elements may also be present in steel that will alter its overall physical properties. For example, all steels contain manganese that assists in hardening mechanisms, as well as removing sulfur and oxygen atoms from the matrix. This prevents FeS formation and removes bubbles in the molten state of steels, both of which would greatly contribute to brittleness of the final product. 

Figure 5.3. Illustration of a hardening mechanism responsible for epoxy resin curing.

As noted above, our working hypothesis concerning the various hardening mechanisms is that chemical impurities, second-phase particles and even other dislocations serve as obstacles to the motion of a given dislocation. As a result of the presence of these obstacles, the intrinsic lattice resistance tp is supplemented by additional terms related to the various strengthening mechanisms. We further assume that the flow stress can be written as... 

Hardening mechanism in lead-calcium alloys. Lead-calcium alloys harden extremely rapidly 80% of the ultimate strength is reached in one day, and virtually full ageing in seven days. Such rapid hardening enhances grid handling and battery production. The rapid hardening was a benefit to VRLA batteries. 

Hardening Mechanisms. Differences in the viscosity response of various glues during bonding are largely associated with differences in their hardening mechanisms. The major hardening mechanisms are as follows. 

Material problems in a nuclear reactor plant can be grouped into two categories, one concerning the nuclear reactor core and one that will apply to all plant materials. This chapter discusses specific material problems associated with fatigue failure, work hardening, mechanical forces applied to materials, stress, and strain. 

Surface hardening (mechanical or chemical to strengthen the surface)... 

The classification of adhesives by hardening mechanism (Table 1) is probably the most informative, but a classification based on the chemical nature of the main polymer present is often used. Such systems require little explanation and might typically order materials first by the class of polymer, thermoset, thermoplastic or (thermoset) elastomeric, often with a separate class for natural polymers, and then snbdivide these classes according to the chemical structure. Table 2 shows how this might be accomplished. 

Schematic of the hardening mechanisms controlling radiation embrittiement. 

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