Long-term strength of polymethylmethacrylate under the influence of liquid media and elevated temperatures

1972 ◽  
Vol 5 (4) ◽  
pp. 377-380
Author(s):  
A. N. Tynnyi ◽  
N. A. Ol'khovich-Novosadyuk ◽  
A. I. Soshko ◽  
N. G. Kalinin ◽  
O. A. Mikityuk
Keyword(s):  
Elevated Temperatures ◽  
Term Strength ◽  
Liquid Media

Machine for investigating creep and long-term strength of polymer. Materials in liquid media at elevated temperatures

1972 ◽  
Vol 6 (1) ◽  
pp. 86-87
Author(s):  
Yu. V. Kolevatov ◽  
A. I. Soshko ◽  
N. G. Kalinin ◽  
T. Yu. Stefyuk ◽  
A. N. Tynnyi
Keyword(s):  
Elevated Temperatures ◽  
Polymer Materials ◽  
Term Strength ◽  
Liquid Media

Long-Term Strength and Design of Polyethylene Compounds for Pressure Pipe Applications

2009 ◽  
Author(s):  
Stephen J. Boros
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Hydrostatic Stress ◽  
Stress Rupture ◽  
Term Strength ◽  
Viscoelastic Creep ◽  
Pressure Pipe ◽  
Code Language

The interest in using polyethylene pipe in Class 3 safety water systems in nuclear power plants has grown tremendously in the last few years. PE pipe brings a host of benefits to the application in the form of long-term performance and reliability due to not being prone to corrosion and tuberculation. As the work continues through various ASME committees to develop the appropriate code language for the design and use of PE pipe, it is clear that plastics are not evaluated the same way metallic components would be in similar applications. However, the nature of the failure (i.e. ductile or brittle) is important for both. This paper will give an overview of the methodology used to establish the long-term hydrostatic strength of polyethylene compounds, and how that strength is used for engineering design in a safe a reliable manner. The strength of a polyethylene compound, being a thermoplastic, cannot be determined from a short-term tensile strength test, as with most metals. As such, testing and evaluation methodologies have been developed which take into account the viscoelastic creep response of thermoplastics, as well as potential changes in failure mode, in order to forecast the long-term hydrostatic strength of these materials so they can be safely used in a pressure pipe application. Since PE was first used in a piping application in the late 1950s, PE has continued to evolve as have the methodologies used to evaluate its strength against stresses induced by hydrostatic pressure. The common method for evaluation relies on putting specimens under multiple continuous, steady-state stress levels until failure. These data points are then used in a log-log linear regression evaluation. This regression equation is then extrapolated to a point sufficiently further out in time to where a long-term strength can be established. It has been clearly established that over a temperature range that the stress rupture behavior of PE follows an Arrhenius, or rate process, relationship between temperature and strength. By testing at elevated temperatures it can be “validated” that the extrapolation remains linear and ductile beyond the actual test data. This and other criteria established by ASTM D 2837 and the Plastics Pipe Institute’s Hydrostatic Stress Board allow for establishing an appropriate maximum working stress that will assure a very long design life.

Devices for the long-term-strength (creep) testing of metals in liquid media

1974 ◽  
Vol 8 (5) ◽  
pp. 603-605
Author(s):  
M. G. Khitarishvili ◽  
I. I. Vasilenko ◽  
N. N. Zhagalyak ◽  
R. K. Melekhov ◽  
M. I. Filevich
Keyword(s):  
Creep Testing ◽  
Term Strength ◽  
Liquid Media

Subcritical Crack Growth and Long-Term Strength in Rock and High-Strength and Ultra Low-Permeability Concrete

2009 ◽  
Vol 58 (6) ◽  
pp. 525-532 ◽  
Author(s):  
Yoshitaka NARA ◽  
Masafumi TAKADA ◽  
Daisuke MORI ◽  
Hitoshi OWADA ◽  
Tetsuro YONEDA ◽  
...  
Keyword(s):  
Crack Growth ◽  
Subcritical Crack Growth ◽  
High Strength ◽  
Low Permeability ◽  
Term Strength
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