Acoustic Emission Entropy for Evaluation of Fracture Toughness of HSLA Steel Welded Joint

2017 ◽  
Author(s):  
Mengyu Chai ◽  
Weijie Wu ◽  
Zaoxiao Zhang ◽  
Guangxu Cheng ◽  
Quan Duan
Keyword(s):  
Fracture Toughness ◽  
Acoustic Emission ◽  
Welded Joint ◽  
Hsla Steel ◽  
Amplitude Distribution ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
New Approach ◽  
Astm Standard

In this investigation, fracture toughness behavior of high strength low alloy (HSLA) steel welded joint was studied using acoustic emission (AE) monitoring. For the design of new structures and for the safety and reliability analyses of operating components, fracture toughness (KIC) values of materials play an essential role. Acoustic emission technique (AET) has been used for determination of fracture toughness based on some observable changes of AE evolutions. However, the occurrence of appreciable plasticity in materials, the friction between the crack surfaces and mechanical noise could generate high emission and may result in some difficulties in precise determination of fracture toughness. Thus, the objective of this study is to propose a new approach to evaluate fracture toughness values and to characterize the fracture process based on AE entropy. Specimens were selected from 2.25Cr-1Mo-0.25V steel welded joint which were thermally aged at 978 K for 8 h. The AE signals generated during fracture processes were recorded and the corresponding AE entropy was calculated based on the probability amplitude distribution from each original AE waveform. The point of crack initiation was identified by the occurrence of sudden rise of AE entropy and the corresponding critical load was used to estimate fracture toughness value. The estimated values obtained from the proposed new approach were compared with those determined by the methodology proposed by compact tension specimen testing according to ASTM standard E399. The results showed that the estimated values were in close agreement with those gained from ASTM standard. It was concluded that AE entropy was an effective parameter to estimate fracture characteristics and fracture toughness values.

scholarly journals Fracture Toughness Evaluation of S355 Steel Using Circumferentially Notched Round Bars

2018 ◽  
Vol 47 (2) ◽  
pp. 91-95 ◽  
Author(s):  
Fatih Bozkurt ◽  
Eva Schmidová
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Fracture Load ◽  
Alternative Methods ◽  
Test Procedures ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation

In engineering applications, steels are commonly used in various areas. The mechanical members are exposed to different loading conditions and this subject can be investigated in fracture mechanics. Fracture toughness (KIC) is the important material property for fracture mechanics. Determination of this properties is possible using a compact tension specimen, a single edge notched bend or three-point loaded bend specimen, which are standardized by different institutions. Researchers underline that these standardized methods are complex, the manufacturing process is difficult, they require special fixtures for loading during the experiment and the test procedures are time consuming. Alternative methods are always being sought by researchers. In this work, two different approaches are investigated for S355 steels. In the first method, a circumferentially cracked round bar was loaded in tensile mode and pulled till failure. Using suitable equations, fracture toughness can be calculated. In the second method, a circumferentially notched bar specimen without fatigue pre-cracking was loaded in a tensile machine. By means of fracture load values, fracture toughness was determined by the proposed equations. It can be stated that these two different approaches for calculating fracture toughness are simple, fast and economical.

Influence of Sulfur Content on the Fracture Toughness Properties of 2 1/4 Percent Cr-1 Percent Mo Steel

1976 ◽  
Vol 98 (2) ◽  
pp. 135-142 ◽  
Author(s):  
J. F. Copeland
Keyword(s):  
Fracture Toughness ◽  
Sulfur Content ◽  
Detrimental Effect ◽  
Crack Opening ◽  
Analytical Techniques ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen ◽  
Microvoid Coalescence ◽  
Opening Displacement

The effects of sulfur content on the fracture toughness properties of 2 1/4Cr-1 Mo steel were evaluated at test temperatures above, at, and below the nil ductility transition temperature (NDTT) of −23°C (−10°F). Small, 12.7-mm (0.5-in.) thick compact tension specimen results were combined with J-integral, Equivalent Energy, and Crack Opening Displacement analytical techniques to provide KIc results up to 22°C (72°F). It was found that the sulfur content of this steel has a large detrimental effect on KIc at the NDTT and above, where microvoid coalescence is the fracture mode. Sulfur has no significant effect at −73°C (−100°F) where cleavage occurs. These results also indicate that the higher Charpy V-notch energy at NDTT, shown by lower sulfur steels, is translatable into increased fracture resistance.

scholarly journals A Simple Method for Theoretical Prediction of Fracture Toughness of Multilayered Composites

2003 ◽  
Vol 12 (4) ◽  
pp. 096369350301200 ◽  
Author(s):  
R. Ramesh Kumar ◽  
P.N. Dileep ◽  
S. Renjith ◽  
G. Venkateswara Rao
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Theoretical Prediction ◽  
Test Data ◽  
Fibre Orientation ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Initial Crack ◽  
Simple Method ◽  
Multilayered Composites

Intralaminar fracture toughness of a fibre-reinforced angle ply and cross ply laminates are generally obtained by testing compact tension specimen and theoretically predicted using the well-known MCCI approach. The crack initiation direction, which is treated as a branch direction for the theoretical prediction, is an apriori. A conservative estimation on the toughness value obtained by considering branch crack angle corresponding to each fibre orientation in a laminate shows a gross error with respect to test data. In the present study a new criterion for the prediction of crack initiation angle is arrived at based on Tsai-Hill minimum strain energy density criterion. This shows a very good agreement with test data available in literature on fracture toughness of various multilayered composites with large size cracks with a/w ≥ 0.3. It is interesting to note that in a multilayered composite a simple method of prediction in which crack initiation direction is assumed to be the fibre orientation that is close to the initial crack direction gives a good estimation of the intralaminar fracture toughness.

A new approach for detection of wear mechanisms and determination of tool life in turning using acoustic emission

2015 ◽  
Vol 92 ◽  
pp. 519-532 ◽  
Author(s):  
Luis Henrique Andrade Maia ◽  
Alexandre Mendes Abrao ◽  
Wander Luiz Vasconcelos ◽  
Wisley Falco Sales ◽  
Alisson Rocha Machado
Keyword(s):  
Acoustic Emission ◽  
Tool Life ◽  
Wear Mechanisms ◽  
New Approach

C-Specimen Fracture Toughness Testing: Effect of Side Grooves and η Factor

2003 ◽  
Author(s):  
Y. Kim ◽  
Y. J. Chao ◽  
M. J. Pechersky ◽  
M. J. Morgan
Keyword(s):  
Fracture Toughness ◽  
Plane Strain ◽  
Crack Front ◽  
Testing Effect ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
J Integral ◽  
Η Factor

Elastic-plastic crack front fields in arc-shaped tension specimens (C-specimens) were analyzed by a three-dimensional finite element method. The effect of side grooves on the ductile fracture behavior was investigated by studying the J-integral distribution, plane-strain constraint parameter, and development of plastic zones and comparing to experimental data. The applicability of the η factor (derived for use with compact tension specimens) for the calculation of J-integral values for the C-specimen was also investigated. The results show that side grooves promote and establish near plane strain conditions at the crack front in sub-size specimens. It was also found that a two-dimensional plane-strain analysis in conjunction with the standard American Society for Testing and Materials (ASTM) tests was sufficient to determine the fracture toughness values from side-grooved C-specimen. The results indicate the η factor for compact tension specimen as specified in the ASTM standards appears to produce reliable results for the calculation of J of C-specimens.

Fracture Mechanics of Conventional and Narrow Groove Pulse Current Gas Metal Arc Welds of HSLA Steel

2012 ◽  
Vol 710 ◽  
pp. 451-456
Author(s):  
Ravi Ranjan Kumar ◽  
P. K. Ghosh
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Tensile Properties ◽  
Arc Welding ◽  
Hsla Steel ◽  
Gas Metal Arc Welding ◽  
High Strength ◽  
Compact Tension ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding

Mechanical and fracture properties of 20MnMoNi55 grade high strength low alloy (HSLA) steel welds have been studied. The weld joints were made using Gas Tungsten Arc Welding (GTAW), Shielded Metal Arc Welding (SMAW) and Pulse Gas Metal Arc Welding (P-GMAW) methods on conventional V-groove (V-Groove) and Narrow groove (NG-13). The base metal and weld metal were characterised in terms of their metallurgical, mechanical and fracture toughness properties by following ASTM procedures. The J-Integral fracture test was carried out using compact tension C(T) specimen for base and weld metal. The fracture toughness and tensile properties of welds have been correlated with microstructure. In conventional V-groove welds prepared by P-GMAW shows the improvement in initiation fracture toughness (JIC) as compared to the weld prepared by SMAW. Similar improvements in tensile properties have also been observed. This is attributed to reduction in co-axial dendrite content due to lower heat input during P-GMAW process as compared to SMAW. In the narrow groove P-GMA weld prepared at f value of 0.15 has shown relative improvement of JIC as compared to that of the weld prepared by SMAW process.

Determination of the Fracture Toughness Parameters for an MDF Cement Composite

1985 ◽  
Vol 64 ◽  
Author(s):  
M. Arzamendi ◽  
R. L. Sierakowski ◽  
W. E. Wolfe
Keyword(s):  
Fracture Toughness ◽  
Cement Composite ◽  
Compact Tension ◽  
Test Methods ◽  
Standard Test ◽  
Elastic Behavior ◽  
Hardened Cement ◽  
Linear Elastic ◽  
Toughness Testing

ABSTRACTThe experimental results of fracture toughness testing of a Macro Defect (MDF) Free cement are presented. The material, a hydraulic cement with hydrolyzed polyvinyl polymers, behaves much like a hardened ceramic with measured maximum compressive and tensile strengths of 380 MN/m2 and 69 MN/m2 respectively. Fracture toughness tests were performed on compact tension (CT) and single edge notched beam (SENB) specimens cut from test panels which were supplied in 3mm, 5mm and 10mm thicknesses. The results were evaluated with respect to the fracture toughness parameter Kic using a modification of standard test methods as determined by observed natural behavior. The MDF material exhibited an essentially linear elastic behavior with a fracture toughness slightly higher than typical values recorded for hardened cement paste.

C-Specimen Fracture Toughness Testing: Effect of Side Grooves and η Factor

2004 ◽  
Vol 126 (3) ◽  
pp. 293-299 ◽  
Author(s):  
Y. Kim ◽  
Y. J. Chao ◽  
M. J. Pechersky ◽  
M. J. Morgan
Keyword(s):  
Fracture Toughness ◽  
Plane Strain ◽  
Crack Front ◽  
Testing Effect ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
J Integral ◽  
Η Factor

Elastic-plastic crack front fields in arc-shaped tension specimens (C-specimens) were analyzed by a three-dimensional finite element method. The effect of side grooves on the ductile fracture behavior was investigated by studying the J-integral distribution, plane-strain constraint parameter, and development of plastic zones and comparing to experimental data. The applicability of the η factor (derived for use with compact tension specimens) for the calculation of J-integral values for the C-specimen was also investigated. The results show that side grooves promote and establish near plane strain conditions at the crack front in sub-size specimens. It was also found that a two-dimensional plane-strain analysis in conjunction with the standard American Society for Testing and Materials (ASTM) tests was sufficient to determine the fracture toughness values from side-grooved C-specimen. The results indicate the η factor for compact tension specimen as specified in the ASTM standards appears to produce reliable results for the calculation of J of C-specimens.

Numerical Modeling of Fracture Toughness in RPV Steel Containing Segregated Zones

2002 ◽  
Author(s):  
Claire Naudin ◽  
Andre´ Pineau ◽  
Jean Michel Frund
Keyword(s):  
Fracture Toughness ◽  
Compact Tension ◽  
Maximum Tensile Stress ◽  
Compact Tension Specimen ◽  
Critical Distance ◽  
Line Density ◽  
Rpv Steel ◽  
Critical Fracture ◽  
Element Simulation ◽  
Critical Fracture Stress

Segregation zones, called ghost lines, may be present near the inner side of PWR vessel issued from plain ingots of A508 class 3 steel. They are enriched in alloying elements and impurities and may have a significant influence on mechanical properties, in particular on fracture toughness. Toughness values of a compact tension specimen containing segregation zones have been evaluated using a bimaterial model with a 3 D finite element simulation. Two fracture criteria have been tested and the results compared with the French database of RPV steel toughness values. The first model assumes that fracture occurs when the maximum tensile stress ahead of the crack tip reaches a critical value over a critical distance. The second model, which is statistical, is based on Beremin’s theory. The results obtained with both models are compared. It is shown that the critical fracture stress model reproduces with a good accuracy the lower bound of toughness values which were determined in RPV steel. The Beremin model gives an estimate of the scatter in fracture toughness measurements. This model takes also into account a size effect related to the ghost line density present along the crack front.

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