Failure assessment diagram

FIG. VI. 1. Failure assessment diagrams for elastic-plastic fracture mechanics treatments [VI.16]. (a) Level 2 assessment diagram, (b) Level 3 assessment diagram. 

In reality, the transition between plastic collapse and crack propagation is not abrupt, but gradual. If we draw both failure limits into a diagram with the stress a and the stress intensity factor Kj as axes, we obtain a failure-assessment diagram fad, figure 5.10). The dashed lines depict the idealised behaviour with an abrupt transition between crack propagation and plastic collapse the solid line shows a more realistic behaviour. 

Fig. 5.10. Failure-assessment diagram (after [21]) in standardised form for Y = const. The arrows show how the state of the loaded component changes when the corresponding parameter is raised. Thus, increasing the limiting stress criimit or the initial crack length a increases the tendency for failure by crack propagation, whereas increasing the fracture toughness Kic decreases it. Within the region marked with EPFM, elastic-plastic fracture mechanics has to be used because the plastic zone near the crack tip is not small. This theory is the topic of section 5.3...

A failure assessment diagram for the R6 method. A point on the graph can be plotted corresponding to a known defect and loading conditions. The points are experimental results from validation tests where failure occurred - the key requirement to validate the R6 method is that no failure should occur on the side of the line labeled safe". 

Table 4.4 R6 method of fracture assessment The failure assessment diagram for the R6 method (courtesy of CEGB, UK).

Assessment of brittle-ductile failure using failure assessment diagrams... 

System failure, probability of, 13 167 System flow diagram, in life cycle assessment, 14 811-813 Systemic infections, sulfonamides for, 23 498-499... 

The Process Hazards Analysis team takes a systematic approach to identify potential process hazards and to document them [51]. The Hazardous-Operation Analysis (Haz-Op) is a method by which the process procedures, process and instrument diagrams, and process flow diagrams are evaluated for operability and safety. Fault-Tree Analysis (FTA) is also a method, which investigates the assessment of what-if scenarios and failure conditions. The outcomes of this analysis are recommendations for the col-... 

An analytic RAM model has been developed for the availability assessments and decision situations described above. The model adapts both single-state and multi-state consequences of component/system failures. The FPSO system is modeUed by rehabhity block diagrams where each block represents a single component or a sub-system. Production availability figures of the sub-systems are estimated based on the system configuration. Finally, the total system availability is estimated. The component availabihties are calculated based on the component-failure rates and... 

Functional safety assessment checklists, truth tables, failure analysis, common-cause (or common-mode) failure analysis, reliability block diagrams... 

This involves assessing the design, by means of reliability analysis techniques, to determine whether the targets can be met. Techniques include fault tree and logic block diagram and FMEA analysis, redundancy modeling, assessments of common cause failure, human error modeling, and the choice of appropriate component failure rate data. Reliability assessment may also be used to evaluate potential financial loss. The process is described in Work Instruc-tion/001 (Random hardware failures). 

Presently safety of DP operations assessed by dynamic positioning operator (DPO) on the basis of Company Safety Management System (SMS) requirements, Failure Modes Effects Analyses (FMEA) and using capability plot diagrams. 

Although studies have been published on safety analysis approaches, controlled experiments are rarely reported. St lhane and colleagues published a set of controlled experiments with students comparing different approaches in the area of security and safety with respect to the subjects performance, i.e., the number of identified hazards. They compared misuse cases (MUC) with FMEA [10], MUC with textual use cases (TUC) [11], and system sequence diagrams (SSD) with TUC [12]. Like FT, FMEA can be used for failure propagation analyses, but it is used here for hazard identification. Learning from those experiments, the assessment of participants perception is an appropriate complement to objective metrics such as number of correct solutions. 

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