Some Observations in Fracture Toughness and Fatigue Testing with Chevron-Notched Specimens

2009 ◽  
pp. 9-9-17 ◽  
Author(s):  
JA Salem ◽  
JL Shannon ◽  
MG Jenkins
Keyword(s):  
Fracture Toughness ◽  
Fatigue Testing ◽  
Notched Specimens

Fracture Toughness and Cracking Behaviour of SCC Compared to VC

2013 ◽  
Vol 577-578 ◽  
pp. 205-208
Author(s):  
Sara Korte ◽  
Veerle Boel ◽  
Wouter de Corte ◽  
Geert de Schutter
Keyword(s):  
Fracture Toughness ◽  
Fracture Process ◽  
Critical Value ◽  
Fracture Parameter ◽  
Self Compacting Concrete ◽  
Bending Tests ◽  
Three Point Bending ◽  
Notched Specimens ◽  
Subsequent Determination

Vibrated concrete (VC) and self-compacting concrete (SCC) have a substantially different composition, resulting in dissimilar mechanical properties regarding cracking behaviour. The critical value of the mode I stress-intensity factor KICis an appropriate fracture parameter for evaluating fracture toughness and can be obtained from three-point bending tests (3PBT) on small, notched specimens. Subsequent determination of the energy release rate thus allows to examine the crack propagation and fracture process of both concrete types. This paper describes the results of such 3PBTs on samples, made from VC and SCC. Evaluation of the cracking behaviour, derived from these results, reveals remarkable differences.

Fracture Toughness Characterization of Carbon Bonded Alumina Using Chevron Notched Specimens

2017 ◽  
Vol 754 ◽  
pp. 71-74 ◽  
Author(s):  
H. Zielke ◽  
Martin Abendroth ◽  
Meinhard Kuna
Keyword(s):  
Fracture Toughness ◽  
Ceramic Material ◽  
Bending Test ◽  
Parameter Study ◽  
Zone Model ◽  
Displacement Curve ◽  
Notched Specimens ◽  
Load Displacement ◽  
Set Up

A new generation of multifunctional filters is made of carbon bonded alumina and is investigated within the collaborative research center 920 (CRC920). These filters are used during a casting process with the aim of reducing non-metallic inclusions in the cast product. The high thermal and mechanical loading of the filter requires a fracture mechanical characterization of the investigated ceramic material. In order to determine the fracture toughness of the ceramic material, a chevron-notched beam method (CNB) is applied. A 4-point-bending test set-up was constructed and brought into service, at which the load-displacement curve of small chevron-notched specimens (5 x 6 x 25 mm3) can be measured. The set-up offers the possibility of testing specimens at temperatures up to 1000oC. Preceding numerically work using the finite element method was performed to identify a suitable notch geometry. For this purpose a cohesive zone model was used. A parameter study is presented, which shows the influence of the notch parameter on the load-displacement curve.

On Material Qualification and Strength Design for Hydrogen Service

2015 ◽  
Author(s):  
Junichiro Yamabe ◽  
Hisao Matsunaga ◽  
Yoshiyuki Furuya ◽  
Saburo Matsuoka
Keyword(s):  
High Pressure ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Safety Factor ◽  
Fatigue Testing ◽  
Hydrogen Gas ◽  
Multiplier Method ◽  
Notched Specimens ◽  
Pressure Hydrogen

To clarify the usefulness of the safety factor multiplier method for hydrogen components given in the CHMC1-2014 standard, we performed slow-strain-rate tensile and fatigue testing by using smooth and notched specimens in air and in high-pressure hydrogen gas. We also conducted fatigue-crack growth tests by using compact tension specimens in air and in hydrogen gas. Testing of notched specimens sampled from a Cr–Mo steel gave a safety factor multiplier of 3.0. This value agreed well with that predicted by crack growth analysis taking into account hydrogen-enhanced fatigue-crack growth. The safety factor multipliers of types 304, 316, and 316L austenitic stainless steels were predicted to be 2.0, 1.6, and 1.3, respectively, from their fatigue-crack growth behaviors. The safety factor based on the safety factor multiplier method seems to be overly conservative for the various steels in high-pressure hydrogen gas service. We therefore propose a new and promising design method for specific component applications that is based on design by rule and design by analysis. The importance of operational histories of components for hydrogen service is introduced to permit the precise prediction of their fatigue lives.

Engineering Properties and Performance of Dental Crowns

2005 ◽  
Vol 219 (4) ◽  
pp. 245-255 ◽  
Author(s):  
C A Mitchell ◽  
J F Orr
Keyword(s):  
Fracture Toughness ◽  
Fatigue Testing ◽  
Thin Layers ◽  
Engineering Properties ◽  
Luting Cements ◽  
Tooth Structure ◽  
Chevron Notch ◽  
Dental Crowns ◽  
Luting Cement

Dental crowns are used to replace damaged natural crowns of teeth and are fixed to prepared teeth with luting cements, which should provide an adhesive bond to the tooth structure giving reliable retention and minimal microleakage. Mechanical testing of crowns in vitro gives failure load distributions that are well described by Weibull models, comparing probabilities of survival and reliability. Fatigue testing of crowns is time consuming, but regression analysis to interpolate functions through data points quoting probability limits or applying Weibull analysis is achievable. A complementary approach is to conduct materials tests with appropriate interfacial geometries. Luting cements are used in thin layers of 40–150 um. Contraction during polymerization is restrained by adhesion to substrates, allowing little relaxation of stresses. Conventional and resin-modified glass ionomer cements create thin zones of interaction with dentine and fail cohesively. The chevron notch short rod technique has been used to measure fracture toughness and rank cements. A development of this method, using chevron notch short bar specimens, permitted fracture toughness to be determined for luting cement-dentine substrate interfaces. Representative fracture experiments need to be developed to apply mixed mode conditions. The basic challenge to predict long-term performance from short-term laboratory tests remains.

Notch Effects on Room Temperature Tensile and Bend Properties of Ni3Al and Ni3Al+B

1988 ◽  
Vol 133 ◽  
Author(s):  
P. S. Khadkikar ◽  
J. D. Rigney ◽  
J. J. Lewandowski ◽  
K. Vedula
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Fracture Stress ◽  
Room Temperature ◽  
Tensile Tests ◽  
Boron Addition ◽  
Notched Specimens ◽  
Grain Boundary Fracture ◽  
Bend Tests ◽  
Boundary Fracture

ABSTRACTThe notched mechanical properties of Ni3AI and Ni3Al+B prepared by powder metallurgy techniques have been determined in both tension and bending at room temperature. Ten- sile tests performed using double notched specimens containing relatively blunt notches produced intergranular fracture in both Ni3Al and Ni3AI+B, with evidence of fracture initiating in an intergranular manner ahead of the blunt notch in both cases. Estimates of notched fracture toughness from bend tests and of local grain boundary fracture stress from the notched tensile tests suggest an increase in these values with boron addition.

Effect of Crystallographic Orientation on The Fracture Toughness of NiAl Single Crystals

1994 ◽  
Vol 364 ◽  
Author(s):  
S. Shrivastava ◽  
F. Ebrahimi
Keyword(s):  
Fracture Toughness ◽  
Single Crystals ◽  
Heat Treating ◽  
Sem Analysis ◽  
Internal Stresses ◽  
Electric Discharge Machine ◽  
Notched Specimens ◽  
Heat Treated ◽  
Before And After ◽  
Discharge Machine

AbstractIn the present study, single-edge notched bend specimens of NiAl single crystals were tested in {100}<010>, {101}<101=, and {101}<010} orientations before and after heat-treating the notched specimens at 1000°C for one hour. The fracture toughness data for the non heat-treated specimens were found to be consistent with the previous results. An increase in the fracture toughness of NiAl was observed in all orientations studied upon heat-treating the notched specimens. The toughness ratio for the two orientations obtained from the heat-treated notched specimens was found to be 1.2. This ratio is in agreement with the reported stress analysis considering the crack kinking in {100} oriented specimens. A detailed SEM analysis revealed that the electric discharge machine (EDM) cutting of the notch caused the formation of sharp microcracks at the notch front and also created internal stresses in the vicinity of the notch. The increase in toughness upon heat treatment is attributed to the modification of EDM damage.

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