A containment of a nuclear power plant is a final barrier against the release of radioactive materials and withstands internal pressure due to an accident. Buckling is a critical failure mode of an ellipsoidal head of steel containment vessel under internal pressure. First, a vessel was designed to measure buckling pressure and shape of the ellipsoidal head. Second, an experiment was successfully performed on an ellipsoidal head which has a diameter of 4797 mm, a radius-to-height ratio of 1.728, and a thickness of 5.5 mm. The initial shape and deformations of the ellipsoidal head were measured by using three-dimensional (3D) laser scanners. The detailed buckling characteristics including shapes, deformations, strains of buckles, and buckling pressures were obtained. Finally, initial buckling pressures were predicted by nonlinear finite element analysis considering the initial measured and the initial perfect shapes of the ellipsoidal head, respectively. The agreement between the initial experimental buckling pressure and that predicted by the analysis considering the initial measured shape is good.

Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII and EN13445-3, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate shape deviation between the two types of heads. Then we compare elastic–plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse (bursting). It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling of ellipsoidal heads based on the geometric equivalency approaches result in uneconomical design. In addition, experimental and numerical results show that such heads experience geometric strengthening. The finite element (FE) method considering the effect of geometric strengthening provides a good prediction of plastic collapse pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design. Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for bursting of ellipsoidal and torispherical heads.

Background: Isolated complete dislocation of the hamate bone is a rare wrist injury. Only 22 cases have been reported in the literature. Four of them were associated with nerve injury, but it is a pity that the causes of ulnar nerve injury had never been deeply analyzed. In the case report, it was stated that the ulnar nerve injury was caused by both displacement of uncinate bone and change of position of transverse carpal ligament. The complete dislocation of the hamate bone is mostly caused by direct force, often accompanied by tears of the surrounding ligaments. Case Description: A 30-year-old woman was treated because her left hand was crushed by a machine roller. Plain film X-ray showed isolated dislocation of the volar hamate and rotation of the hamate bone to the volar side. Clinical manifestations and computed tomography (CT) signs suggest ulnar nerve injury. The patient was quickly transported to the operating room for open reduction and internal fixation of the hamate bone and repair of the dorsal carpal ligament. The patient fully recovered after 12 months. Conclusions: Isolated complete dislocation of the hamate bone is a rare injury. The most common cause is direct compression force to the wrist. Diagnosis can be made through review of the patient’s medical history, physical examination and X-ray, however, CT can accurately evaluate the displacement and rotation of the hamate bone, hamate bone fracture and other concomitant wrist fractures, suggesting compression changes of the median nerve and ulnar nerve to provide a reliable basis for the formulation of a clinical care plan. The case report added the evidence-based practice, and discussed the anatomical mechanism and imaging manifestation of ulnar nerve injury associated with complete dislocation of hamate bone.