46 CFR Appendix A to Part 154 - Appendix A to Part 154—Equivalent Stress

I. Equivalent stress (σ c) is calculated by the following formula or another formula specially approved by the Commandant (CG–522) as equivalent to the following:

${\sigma }_c=\sqrt{{\sigma }_x^2+{\sigma }_y^2-{\sigma }_x{\sigma }_y+3{\tau }_{\mathrm{xy}}^2}$

where:

σx = total normal stress in “x” direction.

σy = total normal stress in “y” direction.

τxy = total shear stress in “xy” plane.

II. When the static and dynamic stresses are calculated separately, the total stresses in paragraph I are calculated from the following formulae or another formulae specially approved by the Commandant (CG–522) as equivalent to the following:

${\sigma }_x={\sigma }_x\text{(static)}\pm \sqrt{\sum {\left({\sigma }_x\left(\text{(dynamic)}\right)\right)}^2}$

${\sigma }_y={\sigma }_y\left(\text{static}\right)\pm \sqrt{\sum {\left({\sigma }_y\left(\text{dynamic}\right)\right)}^2}$

${\tau }_{xy}={\tau }_{xy}\left(\text{static}\right)\pm \sqrt{\sum {\left({\tau }_{xy}\left(\text{dynamic}\right)\right)}^2}$

III. Each dynamic and static stress is determined from its acceleration component and its hull strain component from hull deflection and torsion.

[CGD 74–289, 44 FR 26009, May 3, 1979, as amended by CGD 82–063b, 48 FR 4782, Feb. 3, 1983]