Difference of Strength Evaluation Approach Between for DBE and for BDBE

2017 ◽  
Author(s):  
Naoto Kasahara ◽  
Takuya Sato
Keyword(s):  
Failure Modes ◽  
New Technologies ◽  
Lessons Learned ◽  
Failure Behavior ◽  
Design Factor ◽  
Strength Evaluation ◽  
Evaluation Approach ◽  
Design Basis ◽  
Probabilistic Evaluation ◽  
Actual Strength

Preparation for beyond design basis events (BDBE) becomes important as the lessons learned from the Fukushima Daiichi nuclear accident. The objective of strength evaluation for design basis events (DBE) is a confirmation to prevent structural failure for assumed events. For BDBE, main objectives are weak point survey, deterministic and probabilistic risk assessment, and planning of countermeasures including potable equipment and accident management. According to the above objectives, strength evaluation approach have to be different between for DBE and for BDBE. (1) DBE Conservative approach to prevent of failure. Design by analysis concept is basically adopted Assumption of hypothetical failure modes to prevent actual failure modes Stress criteria to bond actual strength Elastic analyses for conservative loading assumption Design factor to bound uncertainties (2) BDBE Best estimation of failure behavior with uncertainties to plan mitigations Identification of realistic failure modes to identify failure consequences Criteria by dominant parameters of failure phenomena Inelastic analyses for realistic loading prediction Probabilistic evaluation to quantify uncertainties. Strength evaluation concept has not yet been established for BDBE. It is necessary to discuss from basic philosophy to make sharable concepts. Adequate criteria is required to meet above concepts. Instead of stress, strain is one of candidate. New evaluation technics are desired to satisfy above criteria. This paper indicates the direction of strength evaluation for BDBE with same examples proposals. Its aims is to promote international discussions and to implement new technologies to actual countermeasures against BDBE.

Application of Fracture Control to Mitigate Failure Consequence Under BDBE

2020 ◽  
Author(s):  
Naoto Kasahara ◽  
Takashi Wakai ◽  
Izumi Nakamura ◽  
Takuya Sato ◽  
Masakazu Ichimiya
Keyword(s):  
Failure Modes ◽  
Natural Frequencies ◽  
Reactor Vessel ◽  
The Other ◽  
Severe Accident ◽  
Seismic Loads ◽  
Strength Evaluation ◽  
Modes Of Failure ◽  
Design Basis ◽  
Fracture Control

Abstract As a lesson learned from the Fukushima nuclear power plant accident, the industry recognized the imporatance of mitigating accident consequences after Beyond Design Basis Events (BDBE). We propose the concept of applying fracture control to mitigate failure consequences of nuclear components under BDBE. Requirements are different between Design Basis Events (DBE) and BDBE. In the case of DBE, it requires preventing occurrence of failures, and thus, its structural approach is strengthening. On the other hand, BDBE requires mitigating failure consequences. The simple strengthening approach with DBE is inappropriate for this BDBE requirement. As the structural strengthening approach for mitigating failure consequences, we propose applying the concept of fracture control. The fundamental idea is to control the sequence of failure locations and modes. Preceding failures release loadings and prevent further catastrophic consequent failures. At the end, locations and modes of failure are limited. Absolute strength evaluation for each failure mode is not easy especially for BDBE. Fracture control, however, requires only relative strength evaluation among different locations and failure modes. Our paper discusses two sample applications of our proposed method. One is a fast reactor vessel under severe accident conditions. Our method controls the upper part of a vessel above the liquid coolant surface weaker than the lower part. This strength control maintains enough coolant even after a high pressure and high temperature condition causes failure of the reactor vessel because structural failure in the upper part releases internal pressure to protect the lower part. The other example is the piping under a large earthquake. Our proposal controls strength of supports weaker than the piping itself. When the supports fail first, natural frequencies of piping systems drop. When the natural frequencies of dominant modes are lower than the peak frequency of seismic loads, seismic loads hardly transfer to the piping and catastrophic failures such as collapse or break are avoided.

Research Plan on Failure Modes by Extreme Loadings Under Design Extension Conditions

2014 ◽  
Author(s):  
Naoto Kasahara ◽  
Izumi Nakamura ◽  
Hideo Machida ◽  
Hitoshi Nakamura
Keyword(s):  
High Pressure ◽  
Nuclear Power ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Lessons Learned ◽  
Structural Element ◽  
Evaluation Approach ◽  
Severe Accidents ◽  
Nuclear Plants ◽  
Limit Strength

As the important lessons learned from Fukushima-nuclear power plant accident, preparation based on Probabilistic Risk Assessment (PRA) with adequate scenario is strongly recognized as essential countermeasures against severe accidents, which are possible in nuclear plants. IAEA requires design extension conditions (DEC) for considering severe accidents. From a view point of structural design, the strength evaluation approach for DEC is somewhat different from conventional one for design basis accident (DBA). There are additional failure modes by extreme loadings under DEC. Best estimation with possible scenarios is necessary for PRA and planning of accident management (AM). This paper introduces study plan on failure modes and their mechanisms by extreme loadings under DEC. First step is the list-up of possible failure modes which should be assumed for extreme loadings such as very high temperature, high pressure and great earthquakes. Next is clarification of failure mechanism and relevant limit strength. One of examples is the failure modes of structural discontinuities under high pressure such as ductile fracture and local failure. Another example is ones of pipes under severe earthquake such as collapse and low cycle fatigue. To clarify above questions, such different scale tests were planned and conducted as the fundamental tests with simulated materials, structural element tests and structural tests. Preliminary results of above tests and next plans are explained.

scholarly journals Fatigue Resistance and Failure Behavior of Penetration and Non-Penetration Laser Welded Lap Joints

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangzhong Guo ◽  
Wei Liu ◽  
Xiqing Li ◽  
Haowen Shi ◽  
Zhikun Song
Keyword(s):  
Fatigue Resistance ◽  
Failure Modes ◽  
Plate Thickness ◽  
High Stress ◽  
Lap Joints ◽  
Failure Behavior ◽  
Passenger Cars ◽  
Plate Fracture ◽  
The Difference ◽  
Railway Passenger

AbstractPenetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars, while their fatigue performances and the difference between them are not completely understood. In this study, the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated. The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance, and their hardness was lower than that of the plates. The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes, whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes. The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture, respectively, and the primary cracks were initiated at welding fusion lines on the lap surface. There were long plastic ribs on the penetration plate fracture, but not on the non-penetration plate fracture. The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa, respectively, which can be used as reference stress for the fatigue design of the laser welded structures. The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.

scholarly journals Analytical Investigation of Tension Loaded Deformed Rebar Anchors in Concrete

CivilEng ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 442-458
Author(s):  
Sandip Chhetri ◽  
Rachel A. Chicchi
Keyword(s):  
Test Data ◽  
Parametric Study ◽  
Failure Modes ◽  
Experimental Testing ◽  
Analytical Investigation ◽  
Failure Behavior ◽  
Capacity Design ◽  
Simulation Results

Experimental testing of deformed rebar anchors (DRAs) has not been performed extensively, so there is limited test data to understand their failure behavior. This study aims to expand upon these limited tests and understand the behavior of these anchors, when loaded in tension. Analytical benchmark models were created using available test data and a parametric study of deformed rebar anchors was performed. Anchor diameter, spacing, embedment, and number of anchors were varied for a total of 49 concrete breakout simulations. The different failure modes of anchors were predicted analytically, which showed that concrete breakout failure is prominent in the DRA groups. The predicted concrete breakout values were consistent with mean and 5% fractile concrete capacities determined from the ACI concrete capacity design (CCD) method. The 5% fractile factor determined empirically from the simulation results was kc = 26. This value corresponds closely with kc = 24 specified in ACI 318-19 and ACI 349-13 for cast-in place anchors. The analysis results show that the ACI CCD formula can be conservatively used to design DRAs loaded in tension by applying a kc factor no greater than 26.

Fuzzy risk assessment for electro-optical target tracker

2016 ◽  
Vol 33 (6) ◽  
pp. 830-851 ◽  
Author(s):  
Soumen Kumar Roy ◽  
A K Sarkar ◽  
Biswajit Mahanty
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Linear Equations ◽  
Mode Analysis ◽  
Failure Behavior ◽  
Membership Functions ◽  
Design And Development ◽  
Effect Analysis ◽  
Content Type ◽  
Criticality Analysis

Purpose – The purpose of this paper is to evolve a guideline for scientists and development engineers to the failure behavior of electro-optical target tracker system (EOTTS) using fuzzy methodology leading to success of short-range homing guided missile (SRHGM) in which this critical subsystems is exploited. Design/methodology/approach – Technology index (TI) and fuzzy failure mode effect analysis (FMEA) are used to build an integrated framework to facilitate the system technology assessment and failure modes. Failure mode analysis is carried out for the system using data gathered from technical experts involved in design and realization of the EOTTS. In order to circumvent the limitations of the traditional failure mode effects and criticality analysis (FMECA), fuzzy FMCEA is adopted for the prioritization of the risks. FMEA parameters – severity, occurrence and detection are fuzzifed with suitable membership functions. These membership functions are used to define failure modes. Open source linear programming solver is used to solve linear equations. Findings – It is found that EOTTS has the highest TI among the major technologies used in the SRHGM. Fuzzy risk priority numbers (FRPN) for all important failure modes of the EOTTS are calculated and the failure modes are ranked to arrive at important monitoring points during design and development of the weapon system. Originality/value – This paper integrates the use of TI, fuzzy logic and experts’ database with FMEA toward assisting the scientists and engineers while conducting failure mode and effect analysis to prioritize failures toward taking corrective measure during the design and development of EOTTS.

Operating Reliability Assessment of FPGA-Based NPP I&C Systems: Approach, Technique and Implementation

2017 ◽  
Author(s):  
Eugene Babeshko ◽  
Ievgenii Bakhmach ◽  
Vyacheslav Kharchenko ◽  
Eugene Ruchkov ◽  
Oleksandr Siora
Keyword(s):  
Integrated Circuits ◽  
Nuclear Power ◽  
Power Plants ◽  
Failure Modes ◽  
New Technologies ◽  
Systems Approach ◽  
Reliability Assessment ◽  
Design Stage ◽  
Fpga Design ◽  
Operating Reliability

Operating reliability assessment of instrumentation and control systems (I&Cs) is always one of the most important activities, especially for critical domains like nuclear power plants (NPPs). Intensive use of relatively new technologies like field programmable gate arrays (FPGAs) in I&C which appear in upgrades and in newly built NPPs makes task to develop and validate advanced operating reliability assessment methods that consider specific technology features very topical. Increased integration densities make the reliability of integrated circuits the most crucial point in modern NPP I&Cs. Moreover, FPGAs differ in some significant ways from other integrated circuits: they are shipped as blanks and are very dependent on design configured into them. Furthermore, FPGA design could be changed during planned NPP outage for different reasons. Considering all possible failure modes of FPGA-based NPP I&C at design stage is a quite challenging task. Therefore, operating reliability assessment is one of the most preferable ways to perform comprehensive analysis of FPGA-based NPP I&Cs. This paper summarizes our experience on operating reliability analysis of FPGA based NPP I&Cs.

Effects of infill patterns on the strength and stiffness of 3D printed topologically optimized geometries

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nadim S. Hmeidat ◽  
Bailey Brown ◽  
Xiu Jia ◽  
Natasha Vermaak ◽  
Brett Compton
Keyword(s):  
Material Properties ◽  
Failure Modes ◽  
Mechanical Anisotropy ◽  
Failure Behavior ◽  
Fused Filament Fabrication ◽  
Content Type ◽  
Orthotropic Composite ◽  
Material Extrusion ◽  
Specific Material ◽  
Strength And Stiffness

Purpose Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM. Design/methodology/approach A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens. Findings Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures. Originality/value This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.

scholarly journals How to approach a many splendoured thing: Proxy Technology Assessment as a methodological praxis to study virtual experience

2010 ◽  
Vol 3 (1) ◽  
Author(s):  
Lizzy Bleumers ◽  
Kris Naessens ◽  
An Jacobs
Keyword(s):  
Virtual Worlds ◽  
Technology Assessment ◽  
New Technologies ◽  
New Technology ◽  
Methodological Approach ◽  
Lessons Learned ◽  
Practical Implementation ◽  
Natural Setting ◽  
Functional Requirements ◽  
Virtual Experiences

This article introduces Proxy Technology Assessment (PTA) as a methodological approach that can widen the scope of virtual world and game research. Studies of how people experience virtual worlds and games often focus on individual in-world or in-game experiences. However, people do not perceive these worlds and games in isolation. They are embedded within a social context that has strongly intertwined online and offline components. Studying virtual experiences while accounting for these interconnections calls for new methodological approaches. PTA answers this call.Combining several methods, PTA can be used to investigate how new technology may impact and settle within people's everyday life (Pierson et al., 2006). It involves introducing related devices or applications, available today, to users in their natural setting and studying the context-embedded practices they alter or evoke. This allows researchers to detect social and functional requirements to improve the design of new technologies. These requirements, like the practices under investigation, do not stop at the outlines of a magic circle (cf. Huizinga, 1955).We will start this article by contextualizing and defining PTA. Next, we will describe the practical implementation of PTA. Each step of the procedure will be illustrated with examples and supplemented with lessons learned from two interdisciplinary scientific projects, Hi-Masquerade and Teleon, concerned with how people perceive and use virtual worlds and games respectively.

Identification of Failure Modes Under Design Extension Conditions

2015 ◽  
Author(s):  
Naoto Kasahara ◽  
Izumi Nakamura ◽  
Hideo Machida ◽  
Hitoshi Nakamura ◽  
Koji Okamoto
Keyword(s):  
High Temperature ◽  
Nuclear Power ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
External Pressure ◽  
Lessons Learned ◽  
Local Failure ◽  
Severe Accident ◽  
Mitigation Measures ◽  
Loading Mode

As the important lessons learned from the Fukushima-nuclear power plant accident, mitigation of failure consequences and prevention of catastrophic failure became essential against severe accident and excessive earthquake conditions. To improve mitigation measures and accident management, clarification of failure behaviors with locations is premise under design extension conditions such as severe accidents and earthquakes. Design extension conditions induce some different failure modes from design conditions. Furthermore, best estimation for these failure modes are required for preparing countermeasures and management. Therefore, this study focused on identification of failure modes under design extension conditions. To observe ultimate failure behaviors of structures under extreme loadings, new experimental techniques were adopted with simulation materials such as lead and lead-antimony alloy, which has very small yield stress. Postulated failure modes of main components under design extension conditions were investigated according three categories of loading modes. The first loading mode is high temperature and internal pressure. Under this mode, ductile fracture and local failure were investigated. At the structural discontinuities, local failure may become dominant. The second is high temperature and external pressure loading mode. Buckling and fracture were investigated. Buckling occurs however hardly break without additional loads or constraints. The last loading is excessive earthquake. Ratchet deformation, collapse, and fatigue were investigated. Among them, low-cycle fatigue is dominant.

scholarly journals Recruitment and Retention Strategies for Community-Based Longitudinal Studies in Urban, Minority Neighborhoods: Lessons Learned from the PARCS Study (Preprint)

2020 ◽  
Author(s):  
Emily B Ferris ◽  
Katarzyna Wyka ◽  
Kelly R. Evenson ◽  
Joan M Dorn ◽  
Lorna Thorpe ◽  
...  
Keyword(s):  
Longitudinal Studies ◽  
Low Income ◽  
Lessons Learned ◽  
Natural Experiments ◽  
Retention Strategies ◽  
Recruitment And Retention ◽  
Four Dimensions ◽  
Evaluation Approach ◽  
Measurement And Evaluation ◽  
The Impact

UNSTRUCTURED Longitudinal, natural experiments provide an ideal evaluation approach to better understand the impact of built environment interventions on community health outcomes, particularly heath disparities. As there are many recruitment and retention challenges inherent to the design of longitudinal, natural experiments, adaptive and iterative recruitment and retention strategies are critical to the success of a study. This paper documents lessons learned from the Physical Activity and Redesigned Community Spaces (PARCS) Study. The PARCS Study, while ongoing, has developed several approaches to improve the recruitment and retention protocols by prioritizing the following four dimensions: 1) building trust with communities; 2) adapting the study protocol to meet participants’ needs and to reflect their capacity for participation; 3) operational flexibility; and 4) measurement and evaluation systems. These strategies may help researchers more successfully recruit and retain participants, particularly in low-income, minority neighborhoods, into longitudinal studies.

Sign in / Sign up

Export Citation Format

Share Document