Many cracks occurring at hatch corners in ships indicate that there is a need for design improvement. Therefore in order to get a better understanding of the stress concentration phenomenon at hatch corners and to prevent the damage and failure of ships, investigations are carried out by finite element method and photoelastic experiment.
Circular, parabolic, elliptic, and recessed circular hatch corner shapes are compared by finite element method under longitudinal uniform tension due to vertical bending of a ship. The finite element program using 6-node triangular and 8-node quadrilateral parabolic isoparametric elements is developed.
Numerical results indicate that, when M denotes longitudinal axis length of a hatch corner and N denotes transverse axis length of a hatch corner, the stress concentration factor becomes smaller with $0.4M\leqqN\leqq 0.6M$ for elliptic hatch corners and with $0.5M\leqq N\leqq 1.0M$ for parabolic hatch corners, and that the elliptic hatch corner is favorable. The stress concentration can also be reduced with a larger recessed circular hatch corner when the cross deck plating is sufficiently wide, and reduced to 50% by lengthening M to 4N for elliptic hatch corner comparing with M=N.
Photoelastic experimental results overestimates the numerical results within about 5%.
