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JNC TN9400 2000-047, 114 Pages, 2000/03
JNC-TN9400-2000-047.pdf:8.25MB
Prediction of weld residual stresses by a general finite element code is beneficial to the improvement of the accuracy of integrity assessment and residual life assessment of FBR plants. This reports develops an evaluation method of weld residual stresses using FINAS. Firstly, we suggested a basic procedure derived from parametric analyses with a simple weld joint model. The procedure can be summarized as follows: (1)For heat conduction analysis, prepare different models corresponding to the number of layers to be modeled. Hand over the analytical results to the following model. (2)Use multi-linear stress-strain curves for modeling the stress-strain response of base metal and weld metal. Use the isotropic hardening rule. (3)When metals are melt, use a user-subroutine to keep stresses from arising. (4)Put the thermal expansion coefficient as zero when heat is being input. Then, using the above procedure and TIG welding, we predicted the weld residual stresses of plate and tube. The results agreed well with the other reports, showing the suggested procedure was reasonable.
Uwaba, Tomoyuki; ;
JNC TN9400 2000-006, 50 Pages, 1999/11
JNC-TN9400-2000-006.pdf:2.17MB
In the fast reactor the swelling of the fuel cladding occur due to the irradiation. Under the irradiation, the temperature gradient of the cladding through the direction of its thickness causes the swelling gradient and this will cause the secondary stress. In this study, we analyzed this secondary stress using the finite element model of the irradiation induced deformation of the cladding by FINAS code. The result of this analysis is summarized as follows. (1)The secondary stress is mainly caused by the gradient of the incubation period of the swelling, The secondary stress becomes very small at the end of irradiation due to the relieving of the stress by the irradiation creep deformation accelerated by the swelling. (2)The calculated maximum stress including the secondary stress under the irradiation is compared with the design value of the ultimate tensile strength for PNC316 for trial. The calculated value are lower than the design value. (3)The effect of the swelling accelerated by the stress is analyzed using the correlation between the swelling and the stress. The result shows that the increasing of the secondary stress due to the acceleration of the swelling is very small because the irradiation creep deformation relieves the stress more effectively by the acceleration of the irradiation creep rate due to the swelling.
PNC TN9410 93-037, 99 Pages, 1992/12
In the frame work of international cooperation between PNC and European AGT9B, benchmark studies were planned on the structural integrity analyses, Among these, a problem on the dynamic buckling of a hemisphere was supplied by the European side. A small annular gap between two concentric hemisphere is filled with water and the whole system is subjected to a vertical harmonic excitation so that the inner thin shell buckles by the dynamic fluid pressure. The problem is to infer the frequency of the excitation and the pressure at which the hemisphere buckles. An intensive series of analyses were performed using a general purpose non-linear finite element code, FINAS. The analyses were a blind test since no information was available on the experimental results. It is inferred as a result of the analyses that; (1)The frequency of the excitation is 27 Hz. (2)The critical buckling pressure is about 0.16 MPa. (3)The fundamental vibration mode and the buckling mode are axi-symmetric, and the buckling occurs in the elastic range. Discussion on the adequacy of the analyses will be made when the experimental result is available.