| 摘要 |
Residual favorable stresses are induced in a zone of stress concentration in a coupling and connection joint mechanism of a drill collar or drilling tool, for example. The residual favorable stress is created by tensily stressing the material within elastic limits, relieving the stress in the zone by heating the material therein into a nonstressed plastic or liquid state, and releasing the tensile stress maintained in an area adjacent the zone. The residual force of elasticity in the area adjacent the zone applies the favorable residual stress in the zone. Preferably, the favorable residual stress is a compressive stress to resist fatigue failures from tension-induced cracks. The extent and depth of penetration of the favorable residual stress in the zone is controlled and is substantially greater than that available from mechanical cold-working surface-hardening techniques.
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