Experimental Study on Ultimate Strength of a Ellipsoidal Dished Head Plate Under Pressure on Convex Surface

2016 ◽  
Author(s):  
Hiroki Yada ◽  
Masanori Ando ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Evaluation Method ◽  
Convex Surface ◽  
Safety Margin ◽  
Fem Analysis ◽  
External Pressure ◽  
Containment Vessel ◽  
Side Pressure ◽  
Safety Margins ◽  
Intermediate Heat Exchanger ◽  
Radioactive Release

Containment vessel is an important structure to prevent a significant and sudden radioactive release, however, the safety margin of the containment vessel against the internal or external pressure are not numerically clarified. Namely, the safety margins due to the relationship of the ultimate toughness of containment vessel structures and maximum design pressure is not clear. Indeed, to clarify the progress of events under the beyond design basis events (BDBE) and to design the BDBE countermeasure equipment, it is necessary to evaluate the pressure toughness of containment vessel adequately. The containment vessel of fast reactor is composed of the various structures. The head plate that forms the boundary between primary and secondary coolant in intermediate heat exchanger has an important role when the progress of the BDBE is considered. In this study, in order to develop the evaluation method of the pressure toughness of the head plate under the BDBE, the ultimate pressure test of the head plate test specimen subjected to convex side pressure was performed, and also FEM analysis was performed for discussion.

Experimental Study on Ultimate Strength of Single and Double Type Bellows Under Internal Pressure

2016 ◽  
Author(s):  
Masanori Ando ◽  
Hiroki Yada ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Internal Pressure ◽  
Fast Reactor ◽  
Evaluation Method ◽  
Safety Margin ◽  
External Pressure ◽  
Element Analysis ◽  
Primary Coolant ◽  
Containment Vessel ◽  
Safety Margins ◽  
Intermediate Heat Exchanger

Containment vessel is an important structure to prevent a significant and sudden radioactive release, however, the safety margin of the containment vessel against the internal or external pressure are not numerically clarified. Namely, the safety margins due to the relationship of the ultimate toughness of containment vessel structures and maximum design pressure is not clear. Indeed, to clarify the progress of the events under the beyond design basis events (BDBE) and to design the BDBE countermeasure equipment, it is necessary to evaluate the pressure toughness of containment vessel adequately. The containment vessel of fast reactor is composed of the various structures, and one of the thinnest boundary structures is bellows structure to absorb the thermal expansion of the coolant piping penetrating the containment vessel. In addition to the containment vessel boundary, evaluating the pressure toughness of reactor coolant and gas boundary is also important because of same reason of that in the containment vessel boundary. In the primary coolant and gas boundary, the cover gas bellows of the intermediate heat exchanger in fast reactor is one of the thinnest structures and has important role when the progress of the BDBE is considered. Therefore, in order to develop the evaluation method of the pressure toughness of bellows structure under the BDBE, the pressure failure tests and finite element analysis of the bellows structure subjected to internal pressure were performed in this study.

Effect of 3-D Initial Imperfections on the Deformation Behaviors of Head Plates Subjected to Convex Side Pressure

2018 ◽  
Author(s):  
Hiroki Yada ◽  
Masanori Ando ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Finite Element ◽  
Power Plants ◽  
Evaluation Method ◽  
Safety Margin ◽  
External Pressure ◽  
Convex Side ◽  
Element Analysis ◽  
Containment Vessel ◽  
Side Pressure ◽  
Post Buckling

Containment vessel (CV) of nuclear power plants is an important structure to prevent a significant and sudden radioactive release, however, the safety margin of the containment vessel against the internal or external pressure are not numerically clarified. The head plate is one of the components which constitute the CV boundary. In order to develop the evaluation method of the pressure toughness of the head plate at beyond design basis events, the pressure failure tests and finite element analysis of the head plates subjected to convex side pressure were performed. In the tests, non-axisymmetric deformations with local deformation concentration were observed in post buckling behavior in the case of the thin thickness head plate. In this study, to evaluate these non-axisymmetric deformations in the test, finite element analyses using detailed 3-D solid model constructed by precise dimensions of the head plates measured by 3-D scanner were performed. Moreover, FEA using simplified model with uniform or non-uniform thickness model were performed. Through a series of FEA, it was clarified the effect of each thickness pattern on post buckling non-axisymmetric deformation.

Failure Mode of ED and AD Type Head Plates Subject to Convex Side Pressure

2017 ◽  
Author(s):  
Hiroki Yada ◽  
Masanori Ando ◽  
Kazuyuki Tsukimori ◽  
Masakazu Ichimiya ◽  
Yoshinari Anoda
Keyword(s):  
Failure Mode ◽  
Convex Side ◽  
Bending Deformation ◽  
Containment Vessel ◽  
Side Pressure ◽  
Safety Margins ◽  
Bending Radius ◽  
Pressure Failure ◽  
The Relationship ◽  
Inside Out

Containment vessel is an important structure to prevent a significant and sudden radioactive release, however, the safety margin of the containment vessel against the internal or external pressure are not numerically clarified. Namely, the safety margins due to the relationship of the ultimate toughness of containment vessel structures and maximum design pressure is not clear. Indeed, to clarify the progress of events under the beyond design basis events (BDBE) and to design the BDBE countermeasure equipment, it is necessary to evaluate the pressure toughness of containment vessel adequately. The containment vessel of fast reactor is composed of the various structures. The head plate that composes the boundary between primary and secondary coolant in intermediate heat exchanger has an important role when the progress of the BDBE is considered. Therefore, in order to develop the evaluation method of the pressure toughness of the head plate under the BDBE, the pressure failure tests and finite element analysis of head plate structure subjected to convex side pressure was performed in this study. Two types of head plates were applied for pressure failure tests. ED type and AD type head plates were chosen as a representative to clarify the effect of shape. These head plates have 250mm diameter and 3mm thickness. The head plates were subjected to pressure on convex side by water in the pressure failure tests. In tests, almost completely inside-out of each head plate was caused after buckling. Then after that, leakage was observed near the rim. Two types of head plates had similar failure mode in spite of difference original shapes. The circumferential through-wall crack was observed near the rim of each head plates. According to the results of pressure failure tests, it is seemed that the circumferential crack was caused by straightening following bending associated with large deformation as inside-out. To clarify the relationship between bending radius and crack initiation, straightening following the bending deformation (bending-straightening) tests were performed. As a result, the crack was initiated in the test case of the bending radius smaller than 3 mm. 3 mm of bending radius generate 33 % strain. The bending radius at the time of leakage observed of head plates was estimated almost similar value at which crack initiated. Therefore, it can be concluded that a failure mode of a head plate subjected convex side pressure is circumferential through-wall crack caused by straightening following bending deformation near the rim.

Comparison of Web Stress Concentration Factors and Safety Margins for a Thin Webbed Spur Gear Subjected to Static and Cyclic Loading Conditions

1992 ◽  
Author(s):  
Paolo Clerici ◽  
Ambrogio Girotti ◽  
Alessandro Perazzolo
Keyword(s):  
Safety Margin ◽  
Fem Analysis ◽  
Spur Gear ◽  
Safety Margins ◽  
Transmission Geometry ◽  
Circular Holes ◽  
Stress Concentration Factors ◽  
Static And Cyclic Loading ◽  
Stress Variations ◽  
The Web

Abstract The stress distribution in the holed web of a gear was studied in order to evaluate the effects of overstress caused by a reduction in weight in comparison with a gear without lightening holes. The analysed gear is a component of a helicopter principal transmission: geometry and dimensions (web with eight circular holes) are usually employed. A 3-D mesh of the gears was made using PATRAN and a FEM analysis was carried out using NASTRAN 65a2. Moreover the principal stress history in one revolution of the gear was reconstructed at the critical points of the web. Thus it was possible to evaluate the actual fatigue cycle and the consequent safety margin for the different load conditions under which helicopter transmissions are generally checked. It was found that the stress variations in one revolution of the gear are significant even in constant power conditions and that the stresses at each point on the border of the holes always have the same sign in a complete revolution. Safety margins in the web were evaluated and compared using different formulas.

scholarly journals Bootstrap and Order Statistics for Quantifying Thermal-Hydraulic Code Uncertainties in the Estimation of Safety Margins

2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
Enrico Zio ◽  
Francesco Di Maio
Keyword(s):  
Confidence Interval ◽  
Order Statistics ◽  
Nuclear Reactor ◽  
Safety Margin ◽  
Fuel Cladding ◽  
Complete Group ◽  
Bootstrap Technique ◽  
Safety Margins ◽  
Group Distribution

In the present work, the uncertainties affecting the safety margins estimated from thermal-hydraulic code calculations are captured quantitatively by resorting to the order statistics and the bootstrap technique. The proposed framework of analysis is applied to the estimation of the safety margin, with its confidence interval, of the maximum fuel cladding temperature reached during a complete group distribution blockage scenario in a RBMK-1500 nuclear reactor.

Evaluated Results of Seismic Design Approach Using Inelastic Dynamic Analysis for Equipment

2019 ◽  
Author(s):  
Ichiro Tamura ◽  
Atsushi Okubo ◽  
Yusuke Minakawa ◽  
Tadashi Iijima ◽  
Yoshio Namita ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Static Analysis ◽  
Seismic Design ◽  
Evaluation Method ◽  
Design Approach ◽  
Model Parameters ◽  
Seismic Safety ◽  
Inelastic Analysis ◽  
Safety Margins ◽  
Core Shroud

Abstract Securing adequate seismic safety margins has been important in safety reviews regarding the seismic design of equipment and piping systems in nuclear power plants, and there exists an increasing need for a more exact method for evaluating these margins. To this end, it is reasonable to take into account the reduction of seismic responses resulting from inelastic deformation. The authors studied this approach utilizing an elastic allowable limit in existing standard. The applicability of the proposed evaluation method was investigated by comparison with the conventional evaluation method. The proposed method consists of an inelastic dynamic analysis and an elastic-static analysis. The elastic-static analysis uses a load obtained from the inelastic dynamic analysis. For the investigation, the result obtained from the proposed method was compared with that obtained from the conventional elastic analysis to quantify the reduction in responses leading to seismic safety margins. For the comparison, the authors constructed three models that simulate a cantilever-type beam, four-legged tank, and core shroud and applied them to the analysis herein, and the applicability of our method was discussed for these models. In this paper, we present three topics. First, we present a scheme for developing the design approach of using inelastic analysis. Second, we report a sensitivity study of model parameters, such as yielding stress and second stiffness, done by analyzing the cantilever-type beam for the proposed method. Finally, we report the application of the method to the four-legged tank and core shroud.

Commentary on the basic philosophy and recent development of safety margins

1976 ◽  
Vol 3 (3) ◽  
pp. 409-416 ◽  
Author(s):  
Franz Knoll
Keyword(s):  
Safety Margin ◽  
Building Code ◽  
Structural Failure ◽  
Design Rules ◽  
Human Errors ◽  
Safety Margins ◽  
Low Levels ◽  
Basic Philosophy

The principal effects influencing safety margins are recapitulated. Human errors are found to be the major source of structural failure. A revised format for safety margins is proposed, using partial factors, one of which should represent the effects of human errors. It should be used as a basic safety margin, reflecting the fact of the importance of human errors.Recent changes in design rules as set forth in the National Building Code of Canada 1975, are discussed and criticized for having reduced effective safety margins to unacceptably low levels. Examples are given to illustrate possible consequences of the use of such low safety margins.

External Cooling: The SWR 1000 Severe Accident Management Strategy

2004 ◽  
Author(s):  
Nikolay Ivanov Kolev
Keyword(s):  
Management Strategy ◽  
External Pressure ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Core Flooding ◽  
External Cooling ◽  
Structural Resistance ◽  
Safety Margins ◽  
Accident Management ◽  
Management Concept

This paper provides the description of the basics behind design features for the severe accident management strategy of the SWR 1000. The hydrogen detonation/deflagration problem is avoided by containment inertization. In-vessel retention of molten core debris via water cooling of the external surface of the reactor vessel is the severe accident management concept of the SWR 1000 passive plant. During postulated bounding severe accidents, the accident management strategy is to flood the reactor cavity with Core Flooding Pool water and to submerge the reactor vessel, thus preventing vessel failure in the SWR 1000. Considerable safety margins have been determined by using state of the art experiment and analysis: regarding (a) strength of the vessel during the melt relocation and its interaction with water; (b) the heat flux at the external vessel wall; (c) the structural resistance of the hot structures during the long term period. Ex-vessel events are prevented by preserving the integrity of the vessel and its penetrations and by assuring positive external pressure at the predominant part of the external vessel in the region of the molten corium pool.

scholarly journals Assessment of Hand Function Through the Coordination of Contact Forces in Manipulation Tasks

2013 ◽  
Vol 36 (1) ◽  
pp. 5-160 ◽  
Author(s):  
Slobodan Jaric ◽  
Mehmet Uygur
Keyword(s):  
Hand Function ◽  
Safety Margin ◽  
Tangential Component ◽  
Contact Forces ◽  
Load Force ◽  
Dominant Hand ◽  
Factors Affecting ◽  
Relative Safety ◽  
Safety Margins ◽  
Mechanical Factors

Exploration of force coordination has been one of the most often used approaches in studies of hand function. When holding and manipulating a hand-held object healthy individuals are typically able to highly coordinate the perpendicular (grip force; GF) with the tangential component of the contact force (load force; LF). The purpose of this review is to present the findings of our recent studies of GF-LF coordination. Regarding the mechanical factors affecting GF-LF coordination, our data suggest that both different hand segments and their particular skin areas could have markedly different friction properties. It also appears that the absolute, rather than relative safety margin (i.e., how much the actual GF exceeds the minimum value that prevents slipping) should be a variable of choice when assessing the applied magnitude of GF. The safety margin could also be lower in static than in free holding tasks. Regarding the involved neural factors, the data suggest that the increased frequency, rather than an increased range of a cyclic LF could have a prominent detrimental effect on the GF-LF coordination. Finally, it appears that the given instructions (e.g., 'to hold' vs. 'to pull') can prominently alter GF-LF coordination in otherwise identical manipulation tasks. Conversely, the effects of handedness could be relatively week showing only slight lagging of GF in the non-dominant, but not in the dominant hand. The presented findings reveal important aspects of hand function as seen through GF-LF coordination. Specifically, the use of specific hand areas for grasping, calculation of particular safety margins, the role of LF frequency (but not of LF range) and the effects of given instructions should be all taken into account when conducting future studies of manipulation tasks, standardizing their procedures and designing routine clinical tests of hand function.

Effect of Reinforcement on the Strength of Junctions Between Cylindrical and Conical Shells

1995 ◽  
Vol 117 (2) ◽  
pp. 135-141 ◽  
Author(s):  
A. Kalnins ◽  
D. P. Updike
Keyword(s):  
Failure Criterion ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
External Pressure ◽  
Cycle Fatigue ◽  
Conical Shells ◽  
Section Viii ◽  
Cyclic Service ◽  
Reinforcement Distribution

Two failure modes are addressed for cylinder-cone junctions under internal or external pressure: axisymmetric yielding and low-cycle fatigue. If the junction fails to meet the failure criterion of any one of the two modes, then it must be strengthened by reinforcement. It is shown in the paper that the degree to which a junction is strengthened depends on the distribution of the reinforcement. A placement of reinforcement on the cylinder alone, leaving the actual connection between the cylinder and cone unreinforced, adds strength with regard to axisymmetric yielding, but may not strengthen the junction sufficiently with regard to low-cycle fatigue. This means that the junction may appear reinforced, but is not strengthened. It is pointed out that the design rules of Section VIII, Div. 1 of the ASME B & PV Code (1992) set the need for reinforcement according to the failure criterion of low-cycle fatigue, while the distribution of the reinforcement is guided by the criterion of axisymmetric yielding. There is no assurance that the reinforced junction will meet the failure criterion of low-cycle fatigue. This means that the safety margin on the number of allowed cycles is less than that which is expected and that the junction may be unfit for cyclic service. It is also shown in the paper that a reinforcement distribution that requires minimum thicknesses for sections of both the cylinder and cone near the junction can satisfy criteria for both failure modes. This approach is already used in Code Case 2150 of Section VIII, Div. 1, for half-apex cone angles from 30 to 60 deg, and required in Div. 2 for cone angles from 0 to 30 deg. Its extension to angles from 0 to 60 deg for both internal and external pressure is recommended.

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