LITTLE P.ENG. FOR ENGINEERS TRAINING / Engineering Consultant

Markl's investigation of the fatigue problem, following the earlier recognition of the maximum stress theory of failure, led to identification of the basic problem in the design of piping systems. Not one, but two different criteria must be satisfied, one for primary l...

The Welding Research Council's Bulletin 330, "Accuracy of Code Stress Intensification Factors for Branch Connections" documented a major attempt to re-assess the existing code requirements for the intensification of stresses at tees and other branch connections. The di...

As noted previously, Markl's fatigue tests generated endurance curves for various fitting configurations, such as straight pipe, butt welded pipe, elbows, miters, welding tees, unreinforced and reinforced fabricated tees, mostly using 4" nominal diameter, size-on-size...

In almost all cases the material fatigue curves are generated using a completely alternating stress; i.e., the average stress component is zero. Research has shown that the magnitude of the mean stress can have an effect on the endurance strength of a material, the tre...

At some point, in the vicinity of 7,000 cycles, the (Syc + Syh) limitation intersects the fatigue curve for carbon and low alloy steel. The allowable stress range must therefore be reduced to fit the fatigue curve for cyclic applications with 7,000 cycles or more:

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