Application of Acoustic Emission for Measuring Crack Initiation Toughness in Instrumented Charpy Impact Testing

2003 ◽  
Vol 31 (3) ◽  
pp. 11082
Author(s):  
DR Petersen ◽  
RE Link ◽  
JP Tronskar ◽  
MA Mannan ◽  
MO Lai
Keyword(s):  
Acoustic Emission ◽  
Crack Initiation ◽  
Charpy Impact ◽  
Impact Testing ◽  
Initiation Toughness ◽  
Charpy Impact Testing

Crack Arrest Testing of High Strength Steels

2012 ◽  
Author(s):  
Andre Hasenhütl ◽  
Marion Erdelen-Peppler ◽  
Christoph Kalwa ◽  
Martin Pant ◽  
Andreas Liessem
Keyword(s):  
Crack Initiation ◽  
Ductile Fracture ◽  
Impact Energy ◽  
Fracture Propagation ◽  
Charpy Impact ◽  
Impact Testing ◽  
Charpy Impact Energy ◽  
Line Pipe ◽  
Test Standards ◽  
Charpy Impact Testing

Fracture propagation is a major concern for the safe operation of gas transmission pipelines. Ductile fracture resistance, which is required according to line pipe standards, is commonly assessed by Charpy impact testing. If fracture occurs during pipe operation, fracture propagation is required to appear in ductile manner. The prerequisite for this is the demonstration of sufficient shear fracture in the BDWT test and minimum required Charpy impact energy. A combination of both requirements ensures avoidance of brittle fracture as well as control of ductile fracture propagation. The experimental chain of evidence and the Battelle-Two-Curve (BTC) model which is the most widely applied model to predict resistance against fracture propagation have been developed on basis of welded pipes of grade ≤ X70. The model has been calibrated against test data obtained from pipes with Charpy impact energy values below 100 J. In recent years, new material concepts were developed to increase material strength and material toughness. On the one hand, increase in material toughness, which is evaluated by Charpy impact testing, is often achieved by an increase in crack initiation resistance. On the other hand, crack propagation resistance, which is determined by BDWT testing with an instrumented striker, can remain on the same level. Increased material toughness and crack initiation resistance can be manifested by incomplete fracture of Charpy impact specimens in the upper shelf (ductile fracture). Actual Charpy impact test standards for metallic materials do not coincide with each other regarding the validity of Charpy energy of unbroken specimens. Increased crack initiation resistance also affects fracture initiation mechanism in BDWT tests, leading to invalid test results according test standards. Invalidity can be expressed by inverse fracture appearance. To avoid inverse fracture, crack initiation energy can be reduced by changing notch type and therefore changing the constraint in the root of the notch. BDWT test standards also do not agree with each other concerning allowable notch types. While the pressed notch type is the preferred one for low toughness steels and the Chevron notch type for higher toughness steels according some test standards, other test standards allow only for a pressed notch type. Being semi-empirical by nature, the BTC concept strongly depends on the input parameters derived from different material tests. Changing test conditions can have a direct impact on the assessment results.

Alfa fibers for Cereplast bio-composites reinforcement: Effects of chemical and biological treatments on the mechanical properties

2021 ◽  
pp. 096739112110060
Author(s):  
Mouna Werchefani ◽  
Catherine Lacoste ◽  
Hafedh Belguith ◽  
Chedly Bradai
Keyword(s):  
Charpy Impact ◽  
Impact Testing ◽  
Hot Water ◽  
Cellulose Content ◽  
Twin Screw ◽  
Electron Microscopy Analysis ◽  
Alfa Fibers ◽  
Charpy Impact Testing ◽  
Water Treatments ◽  
The Impact

The present work is a comparative study of the impact of Alfa fiber modifications on the Cereplast composites mechanical behavior. Various treatments have been employed, including mechanical, soda, saltwater-retting, hot-water treatments and enzymatic treatment using xylanase. Chemical and morphological analyses were carried out in order to determine the changes of the biochemical composition and the dimensions of fibers. Cereplast composites reinforced with Alfa fibers were fabricated using a twin-screw extrusion followed by an injection molding technique with a fiber load of 20 wt. %. Resulting materials were assessed by means of tensile, flexural and Charpy impact testing. Scanning Electron Microscopy analysis was carried out to investigate the interfacial properties of the composites. The results have shown a significant enhancement of mechanical strengths and rigidities for the xylanase-treated fiber composites, owing to the increase of cellulose content, the enhancement of defibrillation level and the improvement of matrix-fiber adhesion. The data proved that the technology of enzymes can be used as a powerful and eco-friendly approach to modify fiber surfaces and to increase their potential of reinforcement.

Charpy Impact Testing at 20°K

1965 ◽  
pp. 56-62 ◽  
Author(s):  
T. F. Kiefer ◽  
R. D. Keys ◽  
F. R. Schwartzberg
Keyword(s):  
Charpy Impact ◽  
Impact Testing ◽  
Charpy Impact Testing
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