Accepted Manuscripts

Harish Kumar Arya, Kulwant Singh and R. K. Saxena
J. Pressure Vessel Technol   doi: 10.1115/1.4038018
Most of the microstructural changes in weldment takes place during weld cooling from 800 to 500 ° C (t8/5) specially in heat affected zone. Weld strength and cracking tendency can also relate to t8/5. A generalized model using dimensional analysis has been proposed for estimation of weld cooling time (t8/5) for variable plate thicknesses. The proposed model is based on rotatable central composite designed submerged arc welding experiments. Model considers material properties, weld parameters and environmental conditions for submerged arc welding. Model is validated with experimental data and cooling time observed by other researchers. The adequacy of model found 97% and able to predict cooling time for a plate thickness ranging from 8 to 41.5 mm thickness.
TOPICS: Cooling, Steel, Dimensional analysis, Pressure vessels, Arc welding, Composite materials, Cracking (Materials), Materials properties, Fracture (Process), Heat
Naoya Tada, Takeshi Uemori and Toshiya Nakata
J. Pressure Vessel Technol   doi: 10.1115/1.4038012
Commercial pure titanium has been widely used in the aerospace, chemical, and biomedical industries because of its light weight, high corrosion resistance, high strength, high heat resistance, and good biocompatibility. Pure titanium takes the form of a hexagonal closed-pack structure with anisotropic elasticity and plasticity, with most of its components being polycrystalline aggregates having different crystal orientations. Small mechanical loading under elastic conditions therefore always induces inhomogeneous microscopic deformation, and the resulting inhomogeneity brings about various defects such as inhomogeneous plastic deformation, microcracking, and necking. It is therefore important to investigate the microscopic inhomogeneous deformation under elastic and plastic conditions. In this study, a plate specimen of commercial pure titanium was subjected to a tensile test on the stage of a digital holographic microscope, and the microscopic deformation of grains in the specimen under elastic and plastic conditions were observed and measured. During the test, the grains' height distribution was measured in a fixed area on the specimen's surface at each tensile loading step, and the correlation between height distributions at different loads were examined. We found from the measurements that each grain shows a different height change even under elastic conditions with a small load. This inhomogeneous height change was enhanced as the load was increased to plastic conditions. A strong correlation between the height changes under elastic and plastic conditions was also found. This result suggests that the microscopic deformation experienced under plastic conditions is predictable from that observed under elastic conditions.
TOPICS: Tension, Titanium, Deformation, Stress, Anisotropy, Aerospace industry, Corrosion resistance, Necking, Heat, Crystals, Weight (Mass), Elasticity, Plasticity, Microscopes, Biocompatibility, Biomedicine
Keming Li, Jinyang Zheng, Zekun Zhang, Chaohua Gu, Xiaoping Zhang, Shenghua Liu, Honghui Ge, Caisheng Gu and Guanghua Lin
J. Pressure Vessel Technol   doi: 10.1115/1.4038013
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 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.
TOPICS: Steel, Buckling, Containment, Shapes, Pressure, Deformation, Lasers, Nuclear power stations, Radioactive substances, Accidents, Failure mechanisms, Finite element analysis, Vessels, Containment vessels
Technology Review  
Kyle Gough and Daniel Peters
J. Pressure Vessel Technol   doi: 10.1115/1.4037197
Layered vessels have been in-service for many years which use layered construction. This construction technique has been employed since the 1930's. This generally involved either concentric plates or spirally wrapped plates to manufacture vessels with thick walls that otherwise would require very thick and heavy forgings. Long term asset management of these vessels, including non-destructive evaluation of the vessels welds and life assessment of the vessels due to operational cycling the vessels experience can be challenging. This paper is meant to address some of the challenges in managing these critical assets and provide a discussion on the application of state of the art techniques which are being applied today.
TOPICS: Design, Vessels, Fitness-for-service, Plates (structures), Construction, Nondestructive evaluation, Forgings (Products), Welded joints

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