Evaluation charts of thermal stresses in cylindrical vessels induced by thermal stratification of contained fluid

Furuhashi, Ichiro*; Kawasaki, Nobuchika; Kasahara, Naoto

Nihon Kikai Gakkai Rombunshu, A, 73(730), p.686 - 693, 2007/06

https://doi.org/10.1299/kikaia.73.686

Temperature and thermal stress in cylindrical vessels were analysed for the thermal stratification of contained fluid. Two kinds of temperature analysis results were obtained such as the exact temperature solution of eigen-function series and the simple approximate one by the temperature profile method. Furthermore, thermal stress shell solutions were obtained for the simple approximate temperatures. The simple temperature solution is described by one parameter that is the temperature decay factor. The thermal stress shell solutions are described by two parameters. One is the ratio between the temperature decay factor and the load decay factor. Another is the non-dimensional width of stratification. These solutions are so described by few parameters that those are suitable for the simplified thermal stress evaluation charts. These charts enable quick and accurate thermal stress evaluations of cylindrical vessel of this problem compared with conventional methods.

Extension of applicable area of thermal stress charts; Thermal stress of plate subjected to heat transfer on both surfaces

Furuhashi, Ichiro*; Kasahara, Naoto; Shibamoto, Hiroshi

Nihon Kikai Gakkai Rombunshu, B, 72(721), p.2083 - 2090, 2006/09

https://doi.org/10.1299/kikaib.72.2083

Thermal stresses in plate structures subjected to fluid temperature change on both surfaces were analyzed. Through analyses study, new design charts for temperature and stress were developed. Design charts for plate, where one surface is adiabatic, were conventionally used. By using new ones, applicable area of design charts can be greatly extended. New stress design charts were normalized by steady-state stress at fixed back surface temperature in order to reduce reading errors. Maximum stress design charts for step or ramp change of fluid temperature were made. Stress reduction by transferring step change to ramp change can be read directly from the design charts.

Control mechanisms of stress redistribution locus in structures

Kasahara, Naoto; Furuhashi, Ichiro*

Proceedings of 2006 ASME Pressure Vessels and Piping Division Conference (PVP 2006)/International Council on Pressure Vessel Technology (ICPVT-11) (CD-ROM), 8 Pages, 2006/00

Dependency of results of structural analysis on constitutive equations obstructs the application of inelastic analysis methods to design. To overcome this difficulty, a realistic inelastic analysis approach assisted by the stress redistribution locus (SRL) has been proposed for the purpose of design application. The basis of this approach is the existence of an unique SRL in each structure. The final goal of this study is to assure the uniqueness of SRL. To clarify control mechanisms of SRLs in structures, elastic-plastic and elastic-creep behaviors of fundamental structures are analyzed.

Development of thermal stress screening method; Application of Green function method

Furuhashi, Ichiro*; Shibamoto, Hiroshi; Kasahara, Naoto

JNC TN9400 2004-013, 118 Pages, 2003/11

JNC-TN9400-2004-013.pdf:5.2MB

This work was achieved for the development of the screening method of thermal transient stresses in FBR components. We proposed an approximation method for evaluations of thermal stress under variable heat transfer coefficients (non-linear problems) using the Green functions of thermal stresses with constant heat transfer coefficlents (linear problems). Detailed thermal stress analyses provided Green functions for a skirt structure and a tube-sheet of intermediate Heat Exchanger. The upper bound Green functions were obtained by the analyses using those upper bound heat transfer coefficients. The medium and the lower bound Green functions were got by the analyses of those under medium and the lower bound heat transfer coefficients. Conventional evaluations utilized the upper bound Green functions. On the other hand, we proposed a new evaluation method by using the upper bound, medium and the lower bound Green functions. The comparison of above results gave the results as follows. The conventional evaluations were conservative and appropriate for the cases under one fluid thermal transient structure such as the skirt. The conventional evaluations were generally conservative for the complicated structures under two or more fluids thermal transients such as the tube-sheet. But the danger locations could exists for the complicated structures under two or more fluids transients, namely the conventional evaluations were non-conservative. The proposed evaluations gave good estimations for these complicated structures. Though above results, we have made the basic documents of the screening method of thermal transient stresses using the conventional method and the new method.

Frequency response function of stress intensity factors to fluid temperature fluctuations

Kasahara, Naoto; Furuhashi, Ichiro*; *; Ando, Masanori; *

JNC TN9400 2002-047, 107 Pages, 2002/08

JNC-TN9400-2002-047.pdf:4.3MB

Temperature fluctuation from incomplete fluid mixing induces fatigue damages on structures of nuclear components, which should be prevented. For rational evaluation of fatigue crack initiation against this phenomenon, the authors have developed a frequency response function of thermal stress to fluid temperature. Since an actual failure mode has crack initiation, propagation and penetration processes, Fracture mechanics approach such as repair based on crack propagation characteristics and crack arrest evaluation are effective to prevent failure. This study proposed a frequency response function of stress intensity factors to fluid temperature fluctuations in order to evaluate thermal fatigue based on crack propagations. Stress intensity factor decreases according to crack propagation under high cycle fluctuation. On the other han, it increases under low cycle one and membrane constraint conditions.

Structural analyses on piping systems of sodium reactors(2); Eigenvalue analyses of hot-leg pipelines of large scale sodium reactors

Furuhashi, Ichiro*; kasahara, Naoto

JNC TN9400 2001-119, 33 Pages, 2002/01

JNC-TN9400-2001-119.pdf:0.94MB

Two types of finite element models analyzed eigenvalues of hot-leg pipelines of a large-scale sodium reactor. One is a beam element model, which is usual for pipe analyses. The other is a shell element model to evaluate particular modes in thin pipes with large diameters. Summary of analysis results: (1)A beam element model and a shell element model evaluated the same mode for the first order natural frequency. A beam element model is available to get the first order vibration mode. (2)The maximum difference ratio of beam mode natural frequencies was 14% between a beam element model with no shear deformations and a shell element model. However, its difference becomes very small, when shear deformations are considered in beam element. Beam analysis Beam analysis Shell analysis Shear ignored Shear considered Shear considered The first order X-directional horizontal mode 13.47Hz 12.03Hz 11.84Hz The first order Y-directional horizontal mode 13.51Hz 12.06Hz 11.82Hz The first order Z-directional vertical mode 46.33Hz 45.33Hz 43.75Hz (3)In the first order horizontal mode, the Y-piece acts like a pendulum, and the elbow acts like the hinge. The natural frequency is strongly affected by the bending and shear rigidities of the outer supporting pipe. (4)In the first order vertical mode, the vertical sections of the outer and inner pipes moves in the axial-directional piston mode, the horizontal section of inner pipe behaves like the cantilever, and the elbow acts Hke the hinge. The natural frequency is strongly affected by the axial rigidity of outer supporting pipe. (5)Both effective masses and participation factors were small for particular shell modes.

Extension of finite element nonlinear structural analysis system 'FINAS'; Modeling of thinning process of structures in temperature analysis

Tsukimori, Kazuyuki; Furuhashi, Ichiro*

JNC TN9400 2001-015, 80 Pages, 2000/11

JNC-TN9400-2001-015.pdf:2.62MB

It is important to consider the thinning process in analyzing the behavior of structures including the change of their strength when thinning of structures is significant due to corrosion etc. The thinning process has already been considered in the integrity analyses of the liner affected corrosion thinning due to leaked sodium. However, in these cases the thinning process was considered only in stress analyses not in both temperature analyses and stress analyses, since the thickness of the liner was thin. In the cases of thick structures or the structures of which temperature gradient in the thickness is expected to be large due to thermal boundary conditions, the thinning process should be considered in the temperature analyses as well as stress analyses. In this study the function of modeling of thinning process in temperature analysis was developed. The concept of the method, the formulation, installation to 'FINAS', guideline of usage and the verification of the function are described. A simplified model of corrosion problem of a tube is pick up as an example. The effecct of thinning process in temperature analysis is discussed.

Structural analysis methods for liner integrity evaluation; Modeling of thinning process of liner due to corrosion

Tsukimori, Kazuyuki; *; Furuhashi, Ichiro*; ;

JNC TN9400 99-056, 62 Pages, 1999/06

JNC-TN9400-99-056.pdf:1.48MB

The lining structure of LMFBR has an important function to prohibit leaked sodium from having contact with floor concrete at sodium leakage accident. Therefore, the integrity of the liner during the sodium leakage accident should be confirmed. The maximum temperature of the liner at the sodium leakage accident rises very quickly. On the other hand, thinning of the liner due to corrosion progresses gradually compared with the rise of temperature even if the thinning rate in case of molten salt type corrosion is assumed. Therefore, there is a possibility to estimate maximum strain of the liner excessively large compared with the actual value. In this study the modeling of thinning process of liner was developed in order to realize reasonable analysis from the point of view of actual phenomena. The concept of the method is to release the stress of the losing region by using artificial creep and reducing Young's modulus. The validity of this method was verified through some example analyses by FINAS equipped with this thinning model as users' subroutines.

Revisions of fracture mechanics parameters analysis code CANIS-J(2D)

Furuhashi, Ichiro*; Wakai, Takashi

PNC TN9410 95-080, 84 Pages, 1995/02

PNC-TN9410-95-080.pdf:2.82MB

Revisions have been done on CANIS-J(2D) that calculates fracture mechanics parameters of 2-dimensional structures containing cracks or notches. (a)Evaluation of △K between arbitrary two steps on the basis of △. (b)Evaluation of △J and △J between arbitrary two steps on the basis of △, △ε and △u. (c)Evaluation of each terms of J (△J)-integral and J (△J)-integral. (d)Execution of following three mode calculations in one job run. Mode- 0 calculation of K, J and J at any step. Mode- 1 calculation of △K, △J and △J between arbitrary two steps. Mode- 2 calculation of J and J between any continuous steps. To verify the validity of the revised code, we performed fracture mechanics analyses and crack growth simulations of thermal fatigue crack growth tests of circumferentially slitted cylinders subjected to cyclic thermal transients. And we got following results. (1)At thermal-elastic and at thermal-elasto-plastic conditions, J (△J) - integral is not path-independent and can not be properly evaluated. The reason is that J - integral is defined at elastic condition. (2)At thermal-elastic and at thermal-elasto-plastic conditions, J (△J) -integral is good enough path-independent and can be properly evaluated. The reason is that J -integral is defined at more generalized stress conditions. (3)△Jhat, thermal-elastic △K △ (or △ε) at near the crack tip, and net-section bending stress range S at crack ligament, these take approximate maximum values between the common two steps. (4)Crack growth simulations based on △J agree well with the behaviors observed at tests. (5)These results assist that, on the fracture mechanics evaluations of flawed structures subjected to complicated thermal-elasto-plastic load cycles, J (△J) -integral will be a possible fracture mechanics parameter which corresponds to ...

Development and revisions of simplified crack analysis code CANIS

Furuhashi, Ichiro*; *

PNC TN9410 94-201, 301 Pages, 1994/04

PNC-TN9410-94-201.pdf:11.35MB

Development and revisions of simplified crack analysis code CANIS-system were done for fracture mechanics evaluation of FBR structures. CANIS-system is composed of CANIS-G, K and -I. Following revisions were done on CANIS-G that evaluate creep fatigue crack growth history. (1.1)0uter crack of cylinder can be treated, addition to inner crack. (1.2)Axial bending load on cylinder can be treated. (1.3)Displacement controlled load such as thermal stresses can be easily treated. (1.4)Libraly of shape functions for net section stress and libraly of stress intensity factor solutions were expanded to support above subjects. (1.5)Material properties such as elasto-plastic stress-strain relation, creep strain relation, creep rupture time and fatigue failure life of 7 kinds of materials those have been gotten in PNC were added on libralies. (1.6)Backward analysis can be done to estimate past time crack shapes. And now CANIS-K that evaluate fracture mechanics parameters and CANIS-I that evaluate crack initiation probability have been developped. CANIS-K can be used in the following subjects. (2.1)Calculate and print details of fracture mechanics parameters such as stress intensity factor K, J-integral and creep J-integral for given crack shapes, and maximum and minimum values and time histories of those parameters. (2.2)Calculate and print crack growth rates, crack opening area and leak rates. CANIS-I can be used in the following subjects. (3.1)Evaluate time dependant fatigue damage and creep damage. (3.2)Evaluate time dependant crack initiation probability with reference of statistical crack initiation data that caused by fatigue damage or by creep damage. Input data format and subroutine programs of these CANIS-G, -K and -I are commonly, so future expansions and revisions will be done easily and commonly. CANIS is very powerful computational tool in the following regions and can be employed in many practical applications. (4.1)Remaining life predictions of cracked ...