Fatigue hardening

Inspection of frame equipment and pipe - lines for the presence of the fatigue, hardening, and other cracks, corrosion. 

Mesoscopic computer simulations [27] of the 3-D dislocation dynamics of fatigue hardening reveal that dipoles forming in one half-cycle unzip during the next, unless stabilized to form EDLs via annihilation. This... 

Brown s statistical theory [30] of annihilation of screw dislocation dipoles by thermally activated jog migration determines the PSB nanostructure and the saturation stress. The statistical theory is compatible with the nanotheory and the required activation energies are available for both cross-slip and jog motion in copper, as described in 2.2 and 2.3. What remains is to combine and quantify the above theories of thermally activated fatigue hardening, PSB nucleation, cyclic saturation and PSB surface damage to test their quantitative predictions against experimental data. 

High temperature fatigue and fretting fatigue behavior has also been improved by implantation (113,114). This has been achieved by using species that inhibit oxidation or harden the surface. It is generally accepted that fretting behavior is closely coimected to oxidation resistance, perhaps due to third party effects of oxidation products. Oxidation resistance alone has also been improved by ion implantation (118—120). 

Figure 4 shows a typical hardness distribution (7). The case depth is considerably less than that for flame and induction hardening. The case has a high compressive residual stress, which improves the fatigue properties (8). 

Many steels used for gears and bearings are surface-hardened by carburizing, quenching, and tempering. Molybdenum is frequendy used in carburized steels, and carburized Ni—Mo steels have been shown to provide optimum resistance to fatigue and impact effects (28). 

Figure 12-7. Piston rods. Precision-manufactured rolled threads and induction hardening provide high fatigue strength and long life in heavy duty service. Standard rod material is AISI 4142 carbon steel other materials are available as required. Tungsten carbide coatings are also available for maximum surface hardness. Pistons are locked securely onto the rods. For higher pressure, smaller bore cylinders, the piston may be integral with the rod. (Used by permission Bui. 85084, 1992. Dresser-Rand Company.)...

The addition of tellurium has a deoxidizing action and confers on lead useful work and precipitation-hardening properties. It also improves resistance to wear, vibration, and mechanical breakdown. These properties, along with improved corrosion resistance, are utilized in the sheathing of power communication and marine cables, in chemical equipment (especially those exposed to sulfuric acid), or where resistance to fatigue is important. Tellurium has successfully replaced tin (1—3% Sn) in the sheathing. Thinner sheaths can be extruded, and the extrusion pressure for 0.05% Te-beafing lead is about the same as for a 3% Sn alloy. 

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