Effect of Room Temperature Creep on Hydrostatic Leak Test

2018 ◽  
Author(s):  
Benjamin B. Zand ◽  
Adam Steiner
Keyword(s):  
Room Temperature ◽  
Leak Test ◽  
Line Pipe ◽  
Hold Period ◽  
Temperature Creep ◽  
Test Pressure ◽  
Pipe Joints ◽  
Room Temperature Creep ◽  
Actual Yield ◽  
Conceptual Study

Because of the stochastic nature of line pipe characteristics a small percentage of the pipe joints in a given pipeline may possess actual yield strengths below the specified minimum yield strength. During a hydrostatic test these segments may experience some plastic deformation as the hoop stress approaches the yield point. It is well known that the effect of room temperature creep near the yield becomes notable and therefore can affect pressure trending during the hold period (leak test). In this work a numerical model is developed for the analysis of creep deformation. A conceptual study is carried out to demonstrate potential effects of creep on hydrostatic test pressure trending during a leak test. This analysis can help operators understand the potential effects of creep and distinguish it from other factors such as temperature changes or leakage and can help identify, or rule out, the occurrence of pipe yielding during hydrostatic tests.

scholarly journals Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1683 ◽  
Author(s):  
Yi Ma ◽  
Xianwei Huang ◽  
Yuxuan Song ◽  
Wei Hang ◽  
Taihua Zhang
Keyword(s):  
Creep Deformation ◽  
Room Temperature ◽  
Activation Volume ◽  
Rate Sensitivity ◽  
Dislocation Nucleation ◽  
Orientation Effect ◽  
Plastic Behavior ◽  
Mechanical Heterogeneity ◽  
Temperature Creep ◽  
Room Temperature Creep

The crystal orientation effect on mechanical heterogeneity of LiTaO3 single crystals is well known, whilst the time-dependent plastic behavior, i.e., creep is still short of understanding. Relying on nanoindentation technology, we systematically studied room-temperature creep flows at various holding depths (100 nm to 1100 nm) in three typical orientations namely the X-112°, Y-36° and Y-42° planes. Creep resistance was much stronger in the X-112° plane than the others. In the meanwhile, creep features were similar in the Y-36° and Y-42° planes. The orientation effect on creep deformation was consistent with that on hardness. The nanoindentation length scale played an important role in creep deformation that creep strains were gradually decreased with the holding depth in all the planes. Based on strain rate sensitivity and yield stress, the activation volumes of dislocation nucleation were computed at various nanoindentation depths. The activation volumes ranged from 5 Å3 to 23 Å3 for the Y-36° and Y-42° planes, indicating that a point-like defect could be the source of plastic initiation. In the X-112° plane, the activation volume was between 6 Å3 and 83 Å3. Cooperative migration of several atoms could also be the mechanism of dislocation activation at deep nanoindentation.

Room Temperature Creep Behaviour of Ramming Paste Baked at Different Temperatures

2014 ◽  
pp. 1221-1226 ◽  
Author(s):  
Pierre-Olivier St-Arnaud ◽  
Donald Picard ◽  
Houshang Alamdari ◽  
Donald Ziegler ◽  
Mario Fafard
Keyword(s):  
Room Temperature ◽  
Creep Behaviour ◽  
Temperature Creep ◽  
Different Temperatures ◽  
Room Temperature Creep

A thermally activated model for room temperature creep in nanocrystalline Au films at intermediate stresses

2013 ◽  
Vol 68 (8) ◽  
pp. 551-554 ◽  
Author(s):  
Nikhil Karanjgaokar ◽  
Fernando Stump ◽  
Philippe Geubelle ◽  
Ioannis Chasiotis
Keyword(s):  
Room Temperature ◽  
Thermally Activated ◽  
Temperature Creep ◽  
Room Temperature Creep
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