scholarly journals A Time Dependent Process Zone Model for Slow Crack Growth of Polyethylene Pipe Material

2020 ◽  
Vol 1634 ◽  
pp. 012140
Author(s):  
Yijiang Liu ◽  
Yan Li ◽  
Xiu Liu ◽  
Wenbo Luo ◽  
Bo Yang ◽  
...  
Keyword(s):  
Crack Growth ◽  
Process Zone ◽  
Slow Crack Growth ◽  
Time Dependent ◽  
Zone Model ◽  
Pipe Material ◽  
Polyethylene Pipe ◽  
Time Dependent Process ◽  
Dependent Process

Time dependent process-zone growth in polycarbonate

KSME Journal ◽  
1995 ◽  
Vol 9 (4) ◽  
pp. 421-427 ◽  
Author(s):  
Amkee Kim ◽  
Sam-Hong Song
Keyword(s):  
Process Zone ◽  
Time Dependent ◽  
Time Dependent Process ◽  
Dependent Process ◽  
Zone Growth

Slow Crack Growth Resistance of Parent and Joint Materials From PE4710 Piping for Safety-Related Nuclear Power Plant Piping

2011 ◽  
Author(s):  
S. Kalyanam ◽  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
Y. Hioe
Keyword(s):  
Crack Growth ◽  
Nuclear Power ◽  
Power Plants ◽  
Slow Crack Growth ◽  
Nuclear Industry ◽  
Pipe Material ◽  
Service Water ◽  
Hdpe Pipe ◽  
Pipe Materials ◽  
Hdpe Pipes

HDPE pipes are considered by the nuclear industry as a potential replacement option to currently employed metallic piping for service-water applications. The pipes operate under high temperatures and pressures. Hence HDPE pipes are being evaluated from perspective of design, operation, and service life requirements before routine installation in nuclear power plants. Various articles of the ASME Code Case N-755 consider the different aspects related to material performance, design, fabrication, and examination of HDPE materials. Amongst them, the material resistance (part of Article 2000) to the slow crack growth (SCG) from flaws/cracks present in HDPE pipe materials is an important concern. Experimental investigations have revealed that there is a marked difference (almost three orders less) in the time to failure when the notch/flaw is in the butt-fusion joint, as opposed to when the notch/flaw is located in the parent HDPE material. As part of ongoing studies, the material resistance to SCG was investigated earlier for unimodal materials. The current study investigated the SCG in parent and butt-fusion joint materials of bimodal HDPE (PE4710) pipe materials acquired from two different manufacturers. The various stages of the specimen deformation and failure during the creep test are characterized. Detailed photographs of the specimen side-surface were used to monitor the specimen damage accumulation and SCG. The SCG was tested using a large specimen (large creep frame) as well as using a smaller size specimen (PENT frame) and the results were compared. Further, the effect of polymer orientation or microstructure in the bimodal HDPE pipe on the SCG was studied using specimens with axial and circumferential notch orientations in the parent pipe material.

Sleep is for rest, waking consciousness is for learning and memory – of any kind

2005 ◽  
Vol 28 (1) ◽  
pp. 86-87 ◽  
Author(s):  
Robert P. Vertes
Keyword(s):  
Learning And Memory ◽  
Time Dependent ◽  
Slow Time ◽  
Substantial Evidence ◽  
Unique Role ◽  
Memory Processing ◽  
Time Dependent Process ◽  
Dependent Process ◽  
Procedural Tasks ◽  
Task Acquisition

Although considerable attention has been paid to the possible involvement of sleep in memory processing, there is no substantial evidence for it. Walker describes a phenomenon of consolidation-based enhancement (CBE), whereby performance on select procedural tasks improves with overnight sleep; that is, without additional practice on the tasks. CBE, however, appears restricted to a few tasks, and even with these tasks CBE is not confined to sleep but also occurs during wakefulness. Sleep serves no unique role in this process. At best, CBE is a slow, time-dependent process of consolidation that begins with task acquisition in waking and can under some circumstances extend to sleep.

scholarly journals Initiation and growth of microtubules from mitotic centers in lysed mammalian cells.

1975 ◽  
Vol 67 (3) ◽  
pp. 744-760 ◽  
Author(s):  
J A Snyder ◽  
J R McIntosh
Keyword(s):  
Mammalian Cells ◽  
Linear Increase ◽  
Time Dependent ◽  
Microtubule Assembly ◽  
Concentration Increase ◽  
Time Dependent Process ◽  
Dependent Process ◽  
Microtubule Protein ◽  
Microtubule Formation ◽  
The Relationship

Metaphase PtK1 cells, lysed into polymerization-competent microtubule protein, maintain a spindle which will gain or lose birefringence depending on the concentration of disassembled tubulin subunits used in the lysis medium. Concentrations of tubulin subunits greater than the equilibrium monomer value promote a rate and extent of birefringence increase that is proportional to the subunit concentration. Increase in spindle birefringence can be correlated with an increase in tubule number, though the relationship is not strictly linear. Increase in spindle tubule number is due to an vivo-like initiation of tubules at the mitotic centers, as well as tubulin addition onto pre-existing spindle fragments. Colcemid-treated prometaphase cells lysed into polymerization-competent tubulin develop large asters in the region of the centrioles and short tubules at kinetochores, making it unlikely that all microtubule formation in lysed cell preparations is dependent on tubulin addition to short tubule fragments. Asters can also form in colcemid-treated prometaphase cells lysed in tubulin that is incapable of spontaneous tubule initiation, suggesting that the centriolar region serves a tubule-initiator function in our lysed cell preparations. The ability of the centriole to initiate microtubule assembly is a time-dependent process-a ripening effect takes place between prophase and late prometaphase. Ripening is expressed by an increase in the number and length of tubules found associated with the centriolar region.

Viscoelastic and Damage Model of Polyethylene Pipe Material for Slow Crack Growth Analysis

2017 ◽  
Author(s):  
Yue Zhang ◽  
Xiangpeng Luo ◽  
Jianfeng Shi
Keyword(s):  
Crack Growth ◽  
Slow Crack Growth ◽  
Crack Opening ◽  
Failure Process ◽  
Viscoelastic Model ◽  
Material Behavior ◽  
Damage Effect ◽  
Resistance Testing ◽  
Testing Time ◽  
Pipe Material

Polyethylene (PE) pipe is widely used for oil and gas transportation. Slow crack growth (SCG) is the main failure mechanism of PE pipes. Current SCG resistance testing methods for PE pipes have significant drawbacks, including high cost, time-comsuming and uncertain reliability. Alternative method is in need to reduce the testing time and/or cost. In this paper, a numerical model is proposed by taking the viscoelastic and damage effect of PE material into account. The material behavior is described on the basis of linear viscoelastic integral constitutive model, along with damage effect in effective configuraion concept. Three dimensional incremental form of damage viscoelastic model is derived and implemented by ABAQUS UMAT. It is found that the curve of tensile displacement via time, as well as the curve of crack opening displacement via time from numerical results fit well with those from the standard PENT test (ASTM 1473). Based on the proposed model, SCG failure process is analyzed, and the effects of damage parameters on SCG process are furtherly studied and discussed.

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