Delayed failure in tympanoplasty: A 20‐year study of the incidence and reasons for re‐perforation in 359 patients

2020 ◽  
Vol 45 (3) ◽  
pp. 429-431 ◽  
Author(s):  
Fatemeh Hassannia ◽  
Jennifer Lee ◽  
John Alexander Rutka
Keyword(s):  
Delayed Failure

A Pressure Reduction to Prevent a Time-Delayed Failure in a Damaged Pipeline

2020 ◽  
Author(s):  
Andrew Cosham ◽  
Brian N. Leis ◽  
Paul Roovers ◽  
Mures Zarèa ◽  
Valerie Linton
Keyword(s):  
Full Scale ◽  
The Other ◽  
Battelle Memorial Institute ◽  
Pressure Reduction ◽  
Pipe Steels ◽  
Percent Reduction ◽  
Lower Strength ◽  
Line Pipe ◽  
Delayed Failure ◽  
Strength And Toughness

Abstract A time-delayed failure due to stress-activated creep (cold-creep) is a failure that occurs under a constant load and with no growth due corrosion, fatigue or some other environmentally assisted time-dependent degradation mechanism. A time-delayed failure is prevented by reducing the pressure. ASME B31.4 and B31.8 recommend a 20 percent reduction, to 80 percent of the pressure at the time of damage or discovery. T/PM/P/11 Management Procedure for Inspection, assessment and repair of damaged (non-leaking) steel pipelines, an internal procedure used by National Grid, specifies a 15 percent reduction. The guidance in ASME B31.4 and B31.8, and in T/PM/P/11, is directly or indirectly based on the results of tests on the long term stability of defects conducted by the Battelle Memorial Institute and British Gas Corporation in the 1960s and 70s. The line pipe steels were Grades X52 or X60, and the full-size equivalent Charpy V-notch impact energy (where reported) did not exceed 35 J. The tests indicated that the threshold for a time-delayed failure was approximately 85–95% SAPF (straightaway-pressure-to-failure). The strength and toughness of line pipe steels has significantly increased over the decades due to developments in steel-making and processing. The question then is whether an empirical threshold based on tests on lower strength and lower toughness steels is applicable to higher strength and higher toughness steels. In the Tripartite Project, the Australian Pipelines and Gas Association (APGA), the European Pipeline Research Group (EPRG) and the Pipeline Research Council International (PRCI) collaborated in conducting full-scale six step-load-hold tests on higher strength and higher toughness steels. Companion papers present the other aspects of this multi-year project. An empirical threshold for a time-delayed failure is estimated using the results of the six step-load-hold tests. That estimate is also informed by the other published small and full-scale tests (on lower strength and lower toughness steels). The Ductile Flaw Growth Model is used to infer the effect of strength and toughness on the threshold for a time-delayed failure. A 15 percent pressure reduction, to 85 percent of the pressure at the time of damage (or of the maximum pressure that has occurred since the time of damage), is considered to be sufficient to prevent a time-delayed failure due to stress-activated creep in lower and higher toughness, in lower and higher strength, and in older and newer line pipe steels.

scholarly journals Effect of stress wave form on crack initiation in delayed failure under repeated loads.

1984 ◽  
Vol 33 (375) ◽  
pp. 1493-1498 ◽  
Author(s):  
Mitsuo KIDO ◽  
Hisashi ITOH ◽  
Keijiro NAKASA ◽  
Hideo TAKEI
Keyword(s):  
Crack Initiation ◽  
Stress Wave ◽  
Wave Form ◽  
Delayed Failure ◽  
Repeated Loads

Rheological Fracture Analysis of Beam

2011 ◽  
Vol 189-193 ◽  
pp. 328-331 ◽  
Author(s):  
Ling Qiang Yang ◽  
Xu Cong Liu ◽  
Qing Lian Shu
Keyword(s):  
Crack Propagation ◽  
Rheological Model ◽  
Fracture Analysis ◽  
Kelvin Model ◽  
Delayed Failure ◽  
Failure State ◽  
Rheology Model ◽  
Element Method

Based on the normal H-K rheology model, a new rheological model containing fracture elements for concrete or rock cracked body is introduced. The method to ascertain rheology state is put forward. The new rheological model can change to Maxwell or Kelvin model to express the instantaneous failure, delayed failure state and the accelerating segment. The researching failure element method was used to study the crack propagation. Then the cracking elements were studied using rheology mechanics to solve the cracking time. At last a case study was given to validate the method is feasible.

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