The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
R Danzer - One of the best experts on this subject based on the ideXlab platform.
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Polished notch modification of SENB-S Fracture Toughness Testing
Journal of the European Ceramic Society, 1997Co-Authors: R Damani, Ch. Schuster, R DanzerAbstract:Abstract In Fracture Toughness Testing it is common for reasons of simplicity and reproducibility to use notches to approximate sharp cracks. However, a dependence of measured Fracture Toughness (KIc) on notch-root radius is observed. This can be explained as a consequence of the interaction of a distorted stress field with material flaws in front of a notch. A relationship to quantify this effect is presented and examined. It is shown that to measure true Fracture Toughness sharp notches of the size of microstructural features are required. A simple method to make very sharp notches is presented. Fracture Toughness values determined with sharp-notched samples are compared with the results of experiments with conventional sawn-in notches. It is shown that sharp notches deliver considerably lower, more accurate and reproducible values of KIc for materials with fine microstructures. These values are thought to lie at the beginning of any R-curve.
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critical notch root radius effect in senb s Fracture Toughness Testing
Journal of The European Ceramic Society, 1996Co-Authors: R Damani, R Gstrein, R DanzerAbstract:Abstract The brittle behaviour of ceramic materials makes imperative the development of accurate and reproducible methods of measuring their resistance to Fracture. To this end, a European round robin was set up to investigate the relative merits of five different methods of Fracture Toughness Testing. Of these the single edge notch bend — saw cut (SENB-S) method seemed to deliver the most reproducible results, both within and between laboratories. However, it has been observed empirically that if notches are cut too thick, the values of Fracture Toughness determined are systematically too high. An explanation and a theoretically based relationship to describe this behaviour are presented. It is suggested that this effect results from the interaction of the stress field around the notch tip and defects related to the microstructure or machining damage. Measured data from a number of materials seem to correlate well with the theory. It is shown that if correct values of Fracture Toughness are to be determined with the SENB-S method, the notch width must be of the order of the size of the relevant microstructural or machining-induced defects (e.g. large pores and weak grain boundaries).
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critical notch root radius effect in senb s Fracture Toughness Testing
Journal of The European Ceramic Society, 1996Co-Authors: R Damani, R Gstrein, R DanzerAbstract:Abstract The brittle behaviour of ceramic materials makes imperative the development of accurate and reproducible methods of measuring their resistance to Fracture. To this end, a European round robin was set up to investigate the relative merits of five different methods of Fracture Toughness Testing. Of these the single edge notch bend — saw cut (SENB-S) method seemed to deliver the most reproducible results, both within and between laboratories. However, it has been observed empirically that if notches are cut too thick, the values of Fracture Toughness determined are systematically too high. An explanation and a theoretically based relationship to describe this behaviour are presented. It is suggested that this effect results from the interaction of the stress field around the notch tip and defects related to the microstructure or machining damage. Measured data from a number of materials seem to correlate well with the theory. It is shown that if correct values of Fracture Toughness are to be determined with the SENB-S method, the notch width must be of the order of the size of the relevant microstructural or machining-induced defects (e.g. large pores and weak grain boundaries).
Ulrich Lohbauer - One of the best experts on this subject based on the ideXlab platform.
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Fracture Toughness Testing of biomedical ceramic based materials using beams plates and discs
Journal of The European Ceramic Society, 2018Co-Authors: Renan Belli, Michael Wendler, Anselm Petschelt, Tanja Lube, Ulrich LohbauerAbstract:Abstract The Testing of Fracture Toughness becomes problematic when only limited amount of material is available that hinders the production of typical beam specimens to be tested in bending. Here we explore Fracture Toughness Testing methodologies that allow for small discs and plates having surface cracks to be tested in biaxial flexure using the Ball-on-3-balls (B3B) set-up, or sawed notches as in the Compact Tension geometry. The B3B-KIc test has shown to be versatile and account for a very small overestimation of the KIc-value in the order of 0.8–1.25% due to in-plane crack mispositioning, and a maximum of 4% if a worst-case scenario of additional out-of-plane mispositioning is assumed. The geometrical factor in the standard SCF method, derived by Newman and Raju, resulted in an overestimation of ∼8% of the KIc-value compared to the new calculation by Strobl et al. for materials with Poisson’s ratio
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Fracture Toughness Testing of Dental Restoratives: a Critical Evaluation
Current Oral Health Reports, 2018Co-Authors: Renan Belli, Jose Zorzin, Ulrich LohbauerAbstract:Purpose of Review We intend by this short critical review to highlight important aspects regarding the mechanical Testing of Fracture Toughness. The final aim is to increase the awareness to the test sensitivity, ultimately increasing the quality and reliability of reported Testing results. Recent Findings In a well-intended attempt to facilitate Testing procedures or provide alternatives for Testing material interfaces, authors are resorting to adaptation of Testing methodologies without proper theoretical and experimental validation. The assumption of validity in such cases endangers the perpetration of Testing strategies that are not safeguarded by sound theoretical bases. The use of improper statistical treatments based on extreme-value distributions further aggravates this scenario. Summary We supply here some directions for authors concerning method selection, interpretation of data scatter, statistical treatment, and possibilities for test validation.
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practical and theoretical considerations on the Fracture Toughness Testing of dental restorative materials
Dental Materials, 2018Co-Authors: Renan Belli, Michael Wendler, Jose Zorzin, Ulrich LohbauerAbstract:Abstract Background An important tool in materials research, development and characterization regarding mechanical performance is the Testing of Fracture Toughness. A high level of accuracy in executing this sort of test is necessary, with strict requirements given in extensive Testing standard documents. Proficiency in quality specimen fabrication and test requires practice and a solid theoretical background, oftentimes overlooked in the dental community. Aims: In this review we go through some fundamentals of the Fracture mechanics concepts that are relevant to the understanding of Fracture Toughness Testing, and draw attention to critical aspects of practical nature that must be fulfilled for validity and accuracy in results. We describe our experience with some Testing methodologies for CAD/CAM materials and discuss advantages and shortcomings of different tests in terms of errors in Testing the applicability of the concept of Fracture Toughness as a single-value material-specific property.
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adm guidance ceramics Fracture Toughness Testing and method selection
Dental Materials, 2017Co-Authors: Paulo Francisco Cesar, Alvaro Della Bona, Susanne S Scherrer, Michael Tholey, Richard Van Noort, Alessandro Vichi, Robert Kelly, Ulrich LohbauerAbstract:Abstract Objectives The objective is within the scope of the Academy of Dental Materials Guidance Project, which is to provide dental materials researchers with a critical analysis of Fracture Toughness (FT) tests such that the assessment of the FT of dental ceramics is conducted in a reliable, repeatable and reproducible way. Methods Fracture mechanics theory and FT methodologies were critically reviewed to introduce basic Fracture principles and determine the main advantages and disadvantages of existing FT methods from the standpoint of the dental researcher. Results The recommended methods for FT determination of dental ceramics were the Single Edge “V” Notch Beam (SEVNB), Single Edge Precracked Beam (SEPB), Chevron Notch Beam (CNB), and Surface Crack in Flexure (SCF). SEVNB’s main advantage is the ease of producing the notch via a cutting disk, SEPB allows for production of an atomically sharp crack generated by a specific precracking device, CNB is technically difficult, but based on solid Fracture mechanics solutions, and SCF involves Fracture from a clinically sized precrack. The IF test should be avoided due to heavy criticism that has arisen in the engineering field regarding the empirical nature of the calculations used for FT determination. Significance Dental researchers interested in FT measurement of dental ceramics should start with a broad review of Fracture mechanics theory to understand the underlying principles involved in fast Fracture of ceramics. The choice of FT methodology should be based on the pros and cons of each test, as described in this literature review.
Rolf Sandström - One of the best experts on this subject based on the ideXlab platform.
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influence of nickel on the Toughness of lean duplex stainless steel welds
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Johan Pilhagen, Rolf SandströmAbstract:Abstract Three weldments with the nickel contents 1.3, 4.9 and 6.0 wt% were made from 30 mm LDX 2101® plates. The weldments were subjected to tensile, impact and Fracture Toughness Testing. The aim was to evaluate the susceptibility for brittle failure in the weld metal at sub-zero temperatures (°C). The amount of ferrite was higher for the 1.3 wt% nickel weldment compared to the other two which had similar phase composition and mean free ferrite distance. The result from the tensile Testing showed that for the weldment with the highest nickel content the ductility remained unchanged with decreasing temperature while the other two weldments became less ductile with decreasing temperature. J-integral based Fracture Toughness Testing showed a significant difference in the susceptibility for brittle failure with higher values for the weldment with 6 wt% nickel than for the others with lower nickel content.
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Loss of constraint during Fracture Toughness Testing of duplex stainless steels
Engineering Fracture Mechanics, 2013Co-Authors: Johan Pilhagen, Rolf SandströmAbstract:Abstract Delamination of the Fracture surfaces, so called splits, is an important phenomenon that occurs at sub-zero temperature for hot-rolled duplex stainless steels during impact and Fracture Toughness Testing. To evaluate how the splits influence the Fracture Toughness, sub-zero temperature Fracture Toughness Testing of 50, 30 and 10 mm thick plates of hot rolled 2205 duplex stainless steel was performed. The results show that the splits cause loss of constraint along the crack front. This can be observed as local difference in crack growth in the specimen. The initiation Fracture Toughness is not influenced by the specimen thickness. Furthermore, due to the delamination the material exhibit s a stable Fracture process despite the presence of cleavage Fracture. This is interfering with the master curve method so for evaluating the Fracture Toughness at sub-zero temperatures an assessment of the Fracture resistance curve is instead suggested. For assessing the brittle crack behaviour at sub-zero temperatures it is proposed to use the split initiation as a “failure” criteria. The splits are also the cause of the pop-in behaviour observed for the duplex stainless steels. The susceptibility for pop-in is influenced by the microstructure.
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Fracture Toughness of a welded duplex stainless steel
Engineering Fracture Mechanics, 2006Co-Authors: Henrik Sieurin, Rolf SandströmAbstract:The present work includes Fracture Toughness Testing on 30 and 50 mm thick duplex stainless steel 2205 (22% Cr, 5.5% Ni, 3% Mo, 0.15% N). Base metal and submerged arc weldments (SAW) at subzero t ...
R Damani - One of the best experts on this subject based on the ideXlab platform.
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Polished notch modification of SENB-S Fracture Toughness Testing
Journal of the European Ceramic Society, 1997Co-Authors: R Damani, Ch. Schuster, R DanzerAbstract:Abstract In Fracture Toughness Testing it is common for reasons of simplicity and reproducibility to use notches to approximate sharp cracks. However, a dependence of measured Fracture Toughness (KIc) on notch-root radius is observed. This can be explained as a consequence of the interaction of a distorted stress field with material flaws in front of a notch. A relationship to quantify this effect is presented and examined. It is shown that to measure true Fracture Toughness sharp notches of the size of microstructural features are required. A simple method to make very sharp notches is presented. Fracture Toughness values determined with sharp-notched samples are compared with the results of experiments with conventional sawn-in notches. It is shown that sharp notches deliver considerably lower, more accurate and reproducible values of KIc for materials with fine microstructures. These values are thought to lie at the beginning of any R-curve.
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critical notch root radius effect in senb s Fracture Toughness Testing
Journal of The European Ceramic Society, 1996Co-Authors: R Damani, R Gstrein, R DanzerAbstract:Abstract The brittle behaviour of ceramic materials makes imperative the development of accurate and reproducible methods of measuring their resistance to Fracture. To this end, a European round robin was set up to investigate the relative merits of five different methods of Fracture Toughness Testing. Of these the single edge notch bend — saw cut (SENB-S) method seemed to deliver the most reproducible results, both within and between laboratories. However, it has been observed empirically that if notches are cut too thick, the values of Fracture Toughness determined are systematically too high. An explanation and a theoretically based relationship to describe this behaviour are presented. It is suggested that this effect results from the interaction of the stress field around the notch tip and defects related to the microstructure or machining damage. Measured data from a number of materials seem to correlate well with the theory. It is shown that if correct values of Fracture Toughness are to be determined with the SENB-S method, the notch width must be of the order of the size of the relevant microstructural or machining-induced defects (e.g. large pores and weak grain boundaries).
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critical notch root radius effect in senb s Fracture Toughness Testing
Journal of The European Ceramic Society, 1996Co-Authors: R Damani, R Gstrein, R DanzerAbstract:Abstract The brittle behaviour of ceramic materials makes imperative the development of accurate and reproducible methods of measuring their resistance to Fracture. To this end, a European round robin was set up to investigate the relative merits of five different methods of Fracture Toughness Testing. Of these the single edge notch bend — saw cut (SENB-S) method seemed to deliver the most reproducible results, both within and between laboratories. However, it has been observed empirically that if notches are cut too thick, the values of Fracture Toughness determined are systematically too high. An explanation and a theoretically based relationship to describe this behaviour are presented. It is suggested that this effect results from the interaction of the stress field around the notch tip and defects related to the microstructure or machining damage. Measured data from a number of materials seem to correlate well with the theory. It is shown that if correct values of Fracture Toughness are to be determined with the SENB-S method, the notch width must be of the order of the size of the relevant microstructural or machining-induced defects (e.g. large pores and weak grain boundaries).
Johan Pilhagen - One of the best experts on this subject based on the ideXlab platform.
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influence of nickel on the Toughness of lean duplex stainless steel welds
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Johan Pilhagen, Rolf SandströmAbstract:Abstract Three weldments with the nickel contents 1.3, 4.9 and 6.0 wt% were made from 30 mm LDX 2101® plates. The weldments were subjected to tensile, impact and Fracture Toughness Testing. The aim was to evaluate the susceptibility for brittle failure in the weld metal at sub-zero temperatures (°C). The amount of ferrite was higher for the 1.3 wt% nickel weldment compared to the other two which had similar phase composition and mean free ferrite distance. The result from the tensile Testing showed that for the weldment with the highest nickel content the ductility remained unchanged with decreasing temperature while the other two weldments became less ductile with decreasing temperature. J-integral based Fracture Toughness Testing showed a significant difference in the susceptibility for brittle failure with higher values for the weldment with 6 wt% nickel than for the others with lower nickel content.
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Loss of constraint during Fracture Toughness Testing of duplex stainless steels
Engineering Fracture Mechanics, 2013Co-Authors: Johan Pilhagen, Rolf SandströmAbstract:Abstract Delamination of the Fracture surfaces, so called splits, is an important phenomenon that occurs at sub-zero temperature for hot-rolled duplex stainless steels during impact and Fracture Toughness Testing. To evaluate how the splits influence the Fracture Toughness, sub-zero temperature Fracture Toughness Testing of 50, 30 and 10 mm thick plates of hot rolled 2205 duplex stainless steel was performed. The results show that the splits cause loss of constraint along the crack front. This can be observed as local difference in crack growth in the specimen. The initiation Fracture Toughness is not influenced by the specimen thickness. Furthermore, due to the delamination the material exhibit s a stable Fracture process despite the presence of cleavage Fracture. This is interfering with the master curve method so for evaluating the Fracture Toughness at sub-zero temperatures an assessment of the Fracture resistance curve is instead suggested. For assessing the brittle crack behaviour at sub-zero temperatures it is proposed to use the split initiation as a “failure” criteria. The splits are also the cause of the pop-in behaviour observed for the duplex stainless steels. The susceptibility for pop-in is influenced by the microstructure.
