Articles de revues sur le sujet « Statistical fractography »
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Ganesan, L., Pritimoy Bhattacharyya et Anil K. Bhowmick. « Quantitative Fractography of Rubber by Image Processing Technique ». Rubber Chemistry and Technology 68, no 1 (1 mars 1995) : 132–45. http://dx.doi.org/10.5254/1.3538724.
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Abstract In this paper, an image processing technique to quantitatively analyze abraded, torn and fatigue failed surfaces is described. The image surfaces were represented in terms of a closed set of orthogonal polynomials. The significant orthogonal effects were measured and combined to represent the local texture, called pronum. The frequency of occurrence of the pronums is the prospectrum, a global descriptor. Various statistical parameters were calculated from the prospectrum and correlated to the ridge spacings on abraded surfaces. The statistical closeness between various textured surfaces was also quantified. Using the image processing technique, the laborious procedure involved for quantification especially of irregular microfeatures has been shown to be overcome. Author to whom correspondence should be addressed.
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Tomaszewski, Tomasz. « Statistical Size Effect in Fatigue Properties for Mini-Specimens ». Materials 13, no 10 (22 mai 2020) : 2384. http://dx.doi.org/10.3390/ma13102384.
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The study verifies the sensitivity of selected construction materials (S235JR structural steel and 1.4301 stainless steel) to the statistical size effect. The P–S–N curves were determined experimentally under high-cycle fatigue conditions for two specimen sizes (mini-specimen and standard specimen). The results were analyzed using a probabilistic model of the three-parameter Weibull cumulative distribution function. The analysis included the evaluation of the technological process effects on the results based on the material microstructure near the surface layer and the macro-fractography. The differences in the susceptibility to the size effect validated the applicability of the test method to mini-specimen and showed different populations of the distribution of critical material defects.
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Chen, An, Jun Yang, Xian Min Chen et Deng Ke Dong. « Fatigue Property of Friction Stir Welded Butt Joints for 6156-T6 Aluminum Alloy ». Materials Science Forum 960 (juin 2019) : 45–50. http://dx.doi.org/10.4028/www.scientific.net/msf.960.45.
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This study was conducted to investigate fatigue behavior of friction stir welding (FSW) butt joints for 6156-T6 aluminum alloy. The detail fatigue rating (DFR) values of 6156-T6 FSW joints is obtained based on statistical analysis of fatigue tests. The micrographs of weld structure were observed by optical microscope (OM), Fatigue fractography was researched under scanning electron microscope (SEM). The results indicate that DFR value of 6156-T6 FSW joints is 153.31MPa. Fatigue property of FSW butt joints is sensitive to the microstructural features, such as nugget zone (NZ), thermo mechanically affected zone (TMAZ) and heat affected zone (HAZ). The hardness distributions of the FSW joints reveal W-shaped profiles. Fractography shows that fatigue cracking is initiated at weak-bonding defects, which are located at the root site of the butt joint. The weak-bonding defects have obvious influence on the fatigue properties of friction stir welding.
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Bona, A. Della, K. J. Anusavice et J. J. Mecholsky. « Apparent Interfacial Fracture Toughness of Resin/Ceramic Systems ». Journal of Dental Research 85, no 11 (novembre 2006) : 1037–41. http://dx.doi.org/10.1177/154405910608501112.
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We suggest that the apparent interfacial fracture toughness (KA) may be estimated by fracture mechanics and fractography. This study tested the hypothesis that the KA of the adhesion zone of resin/ceramic systems is affected by the ceramic microstructure. Lithia disilicate-based (Empress2-E2) and leucite-based (Empress-E1) ceramics were surface-treated with hydrofluoric acid (HF) and/or silane (S), followed by an adhesive resin. Microtensile test specimens (n = 30; area of 1 ± 0.01 mm2) were indented (9.8 N) at the interface and loaded to failure in tension. We used tensile strength (σ) and the critical crack size (c) to calculate KA (KA = Yσc1/2) (Y = 1.65). ANOVA and Weibull analyses were used for statistical analyses. Mean KA (MPa·m1/2) values were: (E1HF) 0.26 ± 0.06; (E1S) 0.23 ± 0.06; (E1HFS) 0.30 ± 0.06; (E2HF) 0.31 ± 0.06; (E2S) 0.13 ± 0.05; and (E2HFS) 0.41 ± 0.07. All fractures originated from indentation sites. Estimation of interfacial toughness was feasible by fracture mechanics and fractography. The KA for the systems tested was affected by the ceramic microstructure and surface treatment.
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Ramprasath, R., S. Jayabal, S. Satiyamurthy et R. Prithivirajan. « Statistical Analysis and Fractography Study of Tensile Behavior in Bio Particulated Coir-Vinyl Ester Composites ». Advanced Materials Research 984-985 (juillet 2014) : 214–20. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.214.
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The natural fiber reinforced polymer composites are recognized as an alternative to wood and plastics in recent years. The natural plant fibers are extracted from various parts of the tree and are used in polymer composites.The present investigation is focused on the improvement of tensile strength of coir-vinyl ester composites by impregnation of bio particulates such as alumina, red mud and rice husk. The fracture method of composite specimens are analyzed with the help of scanning electron micrographs.The observed range of tensile strength values are studied using statistical procedure and non linear regression models are developed.
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Malgaj, Tine, Roman Papšík, Anže Abram, Andraž Kocjan et Peter Jevnikar. « Bonding Performance of Surface-Treated Zirconia Cantilevered Resin-Bonded Fixed Dental Prostheses : In Vitro Evaluation and Finite Element Analysis ». Materials 16, no 7 (27 mars 2023) : 2646. http://dx.doi.org/10.3390/ma16072646.
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Debonding of zirconia cantilevered resin-bonded fixed dental prostheses (RBFDPs) remains the main treatment complication, therefore, the present in vitro study aimed to evaluate the effect of different surface pretreatments on the bonding of zirconia RBFDPs. Eighty milled zirconia maxillary central incisors, with complementary zirconia cantilevered RBFDPs, were randomly subjected to four different surface pretreatments (n = 20): as-machined (AM); airborne-particle abraded (APA); coated with nanostructured alumina coating (NAC); incisor air-abraded and RBFDP coated (NAC_APA). After bonding, half of each group (n = 10) was stored in deionized water (150 days/37 °C), thermocycled (37,500 cycles, 5–55 °C), and cyclically loaded (50 N/1.2 × 106). Load-bearing capacity (LBC) was determined using a quasi-static test. Additionally, finite element analysis (FEA) and fractography were performed. t-test and one-way ANOVA were used for statistical-analysis. Before aging, the NAC group provided superior LBC to other groups (p < 0.05). After aging, the AM specimens debonded spontaneously, while other groups exhibited comparable LBC (p ˃ 0.05). The FEA results correlated with the in vitro experiment and fractography, showing highly stressed areas in the bonding interface, cement layer, and in RBFDP’s retainer wing and connector. The NAC RBFDPs exhibited comparable long-term bonding performance to APA and should be regarded as a zirconia pretreatment alternative to APA.
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YAMADA, HIROYUKI, KEITARO HORIKAWA et HIDETOSHI KOBAYASHI. « IMPACT TENSILE PROPERTIES IN AL-MG-SI BASE ALLOYS FOR AUTOMOTIVE USE ». International Journal of Modern Physics B 22, no 09n11 (30 avril 2008) : 1123–28. http://dx.doi.org/10.1142/s0217979208046414.
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Effect of alloy composition on impact tensile properties [Formula: see text] in Al - Mg - Si base alloys was investigated by means of the split Hopkinson pressure bar method. As a result of the impact test, it was proved that the nominal stress for 5% plastic strain was not changed by changing the strain rate regardless of the alloy composition. In the impact test, the elongation was decreased with increasing the amount of excess Si , while that was increased by the addition of Cu . Fractography revealed that the reduction of the elongation in the excess Si alloy was caused by the change of the fracture mode from the mixture of transgranular and intergranular fracture to the intergranular fracture.
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BASSIM, M. N., A. G. ODESHI et M. BOLDUC. « HIGH STRAIN RATE STUDY OF CERAMICS USING HOPKINSON BAR SYSTEM ». International Journal of Modern Physics B 22, no 09n11 (30 avril 2008) : 1147–52. http://dx.doi.org/10.1142/s0217979208046451.
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There are at present several applications where high strength ceramics have replaced metals that are subjected to high speed impact from projectiles. This requires an evaluation of behavior of ceramics under impact at high strain rates. This current study provides information on high strain-rate behavior of alumina tested in shear using torsional Hopkinson bar. Dynamic stress-strain curves were generated to investigate deformation behavior prior to fracture while fractography of the broken specimens was carried out to establish the mode of failure. The results of this investigation are similar to what is obtainable in metallic materials in which mechanism of damage is controlled by strain localization and formation of adiabatic shear bands.
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Hong, Myung-Sik, Yu-Sung Choi, Hae-Hyoung Lee, Jung-Hwan Lee et Junyong Ahn. « Comparison of Mechanical Properties of Chairside CAD/CAM Restorations Fabricated Using a Standardization Method ». Materials 14, no 11 (6 juin 2021) : 3115. http://dx.doi.org/10.3390/ma14113115.
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The aim of this in vitro study was to investigate the fracture resistance, fracture failure pattern, and fractography of four types of chairside computer-aided design/computer-aided manufacturing (CAD/CAM) restoration materials in teeth and titanium abutments fabricated using a standardization method. An artificial mandibular left first premolar prepared for all-ceramic crown restoration was scanned. Forty extracted mandibular molars and cylindrical titanium specimens were milled into a standardized shape. A total of eighty CAD/CAM restoration blocks were milled into a crown and twenty pieces of each lithium disilicate (LS), polymer-infiltrated-ceramic-network (PICN), resin nano ceramic (RNC), and zirconia-reinforced lithium silicate (ZLS) materials were used. Crowns were bonded to abutments, and all specimens underwent thermal cycling treatment for 10,000 cycles. Fracture resistance was measured using a universal testing machine and fracture failure patterns were analyzed using optical microscopy and scanning electron microscopy. Statistical differences were analyzed using appropriate ANOVA, Tukey HSD post hoc tests, and independent sample t-tests (α = 0.05). The results indicated that, in both teeth abutments and titanium abutments, the fracture resistances showed significantly the highest values in LS and the second highest in ZLS (p < 0.05). The fracture resistances based on teeth abutments and titanium abutments were significantly different in all the CAD/CAM restoration materials (p < 0.05). There are statistically significant correlations between the types of materials and the types of abutments (p < 0.05). Each of the different materials showed different fracture failure patterns, and there was no noticeable difference in fractographic analysis. Lithium disilicates and zirconia-reinforced lithium silicates exhibited statistically high fracture resistance, indicating their suitability as restoration materials for natural teeth or implant abutments. There were no distinct differences in the fracture pattern based on the restoration and abutment materials showed that the fracture initiated at the groove where the ball indenter was toughed and propagated toward the axial wall.
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Hwang, Young Jin, Ki Kyung Kang, Jong-Bum Kim et Seok Soon Lee. « A Study on the Crack Propagation Behavior of Aluminum Alloy Plates with a Single Edge Crack under Random Loading Spectrum ». International Journal of Modern Physics B 17, no 08n09 (10 avril 2003) : 1891–97. http://dx.doi.org/10.1142/s0217979203019836.
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Modern aircraft are designed using the damage tolerance concept. Fatigue cracks will be occurred at the initial flaw such as micro flaws in the material and scratches during the material manufacturing process. And stress concentration on notches, fillets and rivet holes under random loads caused to initiate the crack. This crack will propagate by repeated loads and finally failure. Therefore aircraft parts must be performed the damage tolerance test to prove the safety of the design life under the loads during operation. In this study, we have tested and analyzed the crack propagation behavior of aluminum alloy 2024-T3 plate under random loads. The crack lengths measured by the fractography analysis were compared to the analysis results with the retardation effect.
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James, M. Neil. « Learning from History : The Reliability of Experts and Expert Systems ». Advanced Materials Research 44-46 (juin 2008) : 15–23. http://dx.doi.org/10.4028/www.scientific.net/amr.44-46.15.
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Engineering design must be cost-effective over its complete life cycle and this necessitates a statistical approach to product and service reliability. A particular design therefore has a finite probability of failure during its lifetime and this has implications in terms of ensuring that design procedures, management of design, and operation and inspection are appropriate, effective and sufficient. Sophisticated expert system software packages have enabled wide access to rapid development to prototype and production stages. The expert knowledge encapsulated in such systems may be inadvertently used outside its intended application envelope, leading to unexpected and unwelcome failures. This paper highlights the role of failure analysis and fractography in the context of product reliability. It will present case studies illustrating typical structural reliability problems that highlight issues connected with the ‘reliability’ of experts in assessing the reasons for failure.
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Ganesh, K., K. Hemachandra Reddy, S. Sudhakar Babu et R. Suresh. « Investigation on Microstructure, Hardness, Wear behavior and Fracture Surface Analysis of Strontium (Sr) and Calcium (Ca) Content A357 Modified Alloy by Statistical Technique ». Frattura ed Integrità Strutturale 17, no 65 (22 juin 2023) : 32–46. http://dx.doi.org/10.3221/igf-esis.65.03.
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The aluminum alloy are extensively used in several industrial applications. Stir casting is one of the most frequently accepted methods. In the present investigation, how the microstructure, mechanical and wear mechanics of A357 alloy were impacted by the presence of Sr/Ca was investigated. The outcomes revealed that addition of elements (Sr/Ca) enhance the microstructural features. Uniform dispersal of particulates (Sr/ Ca) in Al357 alloy and also the modified structure of silicon (Si) were observed. Hardness of modified alloy was evaluated by using hardness tester. A result reveals that hardness of modified alloy was improved by increasing in the Sr/Ca content. The wear rate of modified alloy was evaluated by using Pin and Disc wear test rig. Test trials were conducted according to Taguchi technique. L27 array was implemented for evaluation of data. The effect of varying parameters (factors) on wear loss and COF were analyzed using ANOVA (Analysis of Variance) method. ANOVA outcomes shown that, the Sr/Ca content has a better significant impact on wear behavior and COF of the modified alloy. A wear fractography result shows the internal fracture structure of a wornout surface which was studied by SEM analysis.
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Watson, Robert, Tayeb Zeguer, Mike Buckley, Nick R. Green, Simon Ruffle et William D. Griffiths. « The Response of Entrainment Defect Distribution to Varied Fluid Flow Parameters in the High Pressure Die Casting of Al Alloys ». Materials Science Forum 765 (juillet 2013) : 326–30. http://dx.doi.org/10.4028/www.scientific.net/msf.765.326.
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High Pressure Die Casting is an economical means of manufacturing complex thin walled parts in high volumes. However, the process is prone to high levels of surface turbulence and fluid break-up, which results in the entrainment of bifilm defects. A study was carried out on a commercial casting to identify how changes in melt velocity and mould geometry affected the distribution of damaging bifilm defects, and the distribution of fracture stress. The statistical analysis of tensile test data indicated that two distinct defect populations existed; one of which caused relatively few failures, but often accounted for a large reduction in fracture stress when present. Where this defect population was not significant, Weibull moduli of 20 to 30 were achieved, comparable to sand castings with well-designed running systems. SEM fractography was also performed on a selection of samples to determine the probable cause of failure. A comparison of the SEM analysis to the statistical results indicated that bi-film defects initiated the fracture of those samples that failed at significantly lower stresses. Additionally, it was demonstrated that the geometric distribution of these cases was strongly correlated to changes in fluid flow conditions, suggesting that targeted modifications to mould geometry could increase the in-service reliability of High Pressure Die Castings.
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CAO, XIAOJIAN, RI-ICHI MURAKAMI et QINGYUAN WANG. « FATIGUE PROPERTIES OF TI-6AL-4V SUBJECTED TO 0.9% PHYSIOLOGICAL SALINE SOLUTION ». International Journal of Modern Physics B 24, no 15n16 (30 juin 2010) : 2518–23. http://dx.doi.org/10.1142/s0217979210065192.
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Fatigue properties of Ti -6 Al -4 V (TC4) subjected to 0.9% physiological saline solutions were presented in this paper. The ultrasonic fatigue test method has been used to investigate the very high cycle fatigue properties of commercial titanium alloy TC4 with the microstructure of tramsformed lamellar dipped into 0.9% physiological saline solution prior to testing. Three estimated times have been decided for subjecting at 37 °C, such as 24 hours, 2 weeks and 4 weeks. The results show that physiological saline solution treatment makes a little influence on the ultrasonic fatigue life of TC4. The slope of S-N curve decreases as the dipping time increases. Dipping tests for three estimated times also have been performed. When TC4 has been dipped into physiological saline solution for 4 weeks, homogeneous white points have been observed on specular facet specimen. And in the fracture surface of which has been dipped for 4 weeks, new inclusion sized 5-10 µm in the crack initiation has been observed. The fractography pictures show the fracture to be transcrystalline plastic. Cracks are initiated because of the subsurface inclusion and the facet slip of α-phase.
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Choudhary, Ankush, Munish Kumar Gupta et Manoj Kumar. « Investigating the effect of electrode preheating in novel water-cooled advanced submerged arc welding process ». Proceedings of the Institution of Mechanical Engineers, Part L : Journal of Materials : Design and Applications 233, no 10 (7 novembre 2018) : 2015–29. http://dx.doi.org/10.1177/1464420718810962.
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In this paper, a novel developed water-cooled advanced submerged arc welding (WASAW) process has been designed and established. The developed WASAW process can be utilized for higher preheating currents at 100% duty cycle. Subsequently, a multi-pass welding investigation has been carried out on AISI 1023 steel plates as per the L8 Taguchi orthogonal array by varying WASAW input factors namely voltage (V), wire feed rate (WFR), welding speed (WS), nozzle to plate distance (NPD), and preheat current (I), respectively. The relationships between selected WASAW process parameters and responses namely tensile strength (TS), yield strength (YS), percentage elongation (E), and weld metal hardness (H) has been established with statistical regression analysis and ANOVA method. Then, the effect of each input factor and their interactions on selected responses was analyzed using single effect and 3D surface plots. Lately, the fractography analysis of tensile fractured surfaces has been carried out to study the failure in all weld metals. Finally, Jaya and genetic algorithms have been applied to optimize the WASAW performance. Overall, the outcomes reveal that developed WASAW process yields a substantial enhancement in the mechanical behavior of all weld metals.
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Guilardi, LF, GKR Pereira, AS Vallau, IA Silva, JC Giordani, LF Valandro et MP Rippe. « Fatigue Failure Load of a Bonded Simplified Monolithic Feldspathic Ceramic : Influence of Hydrofluoric Acid Etching and Thermocycling ». Operative Dentistry 45, no 1 (1 janvier 2020) : E21—E31. http://dx.doi.org/10.2341/19-069-l.
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SUMMARY Objective: To evaluate the effect of hydrofluoric acid (HF) etching and thermocycling (Tc) on fatigue failure load of feldspathic ceramic restorations cemented with two resin cements. Methods: Disc-shaped feldspathic ceramic (Vitablocs Mark II; Ø=10 mm, 1.0-mm thick) and G10 epoxy resin (Ø=10 mm, 2.5-mm thick) specimens were made and randomly allocated considering three factors: ceramic etching (ie, with vs without 10% HF plus silane application), resin cement (ie, self-adhesive [RelyX U200; U200] or conventional [Multilink Automix; MA]), and Tc (ie, with vs without 5-55°C/12,000 cycles). Adhesive cementation followed each manufacturer's instructions. The fatigue test (n=20) was based on the staircase approach (250,000 cycles; 20 Hz). Contact angle, surface topography, and fractography analysis were also executed. Specific statistical tests were employed for each outcome (α=0.05). Results: The interaction of HF and Tc factors decreased the fatigue resistance for both cements (U200 542.63>U200/HF-Tc 495.00; MA 544.47>MA/HF-Tc 506.84). Comparing the cements associated with HF or Tc, there was statistical superiority for MA (U200-Tc 537.37<MA-Tc 561.32; U200/HF 535.79<MA/HF 557.11), and no statistical difference was detected when only cement type or its association with HF-Tc was compared (U200 542.63=MA 544.47; U200/HF-Tc 495.00=MA/HF-Tc 506.84). The fracture always originated from defects at the ceramic-intaglio surface as radial cracks. Conclusion: HF etching plus silane agent increased the ceramic surface free energy and its wettability, but it did not provide better results in terms of fatigue resistance compared with silane agent application only. The association of HF etching and aging significantly reduced the fatigue resistance of the material, regardless of the resin cement used.
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Chee, Siew Sand, Mohammad Jawaid, Othman Y. Alothman et Hassan Fouad. « Effects of Nanoclay on Mechanical and Dynamic Mechanical Properties of Bamboo/Kenaf Reinforced Epoxy Hybrid Composites ». Polymers 13, no 3 (27 janvier 2021) : 395. http://dx.doi.org/10.3390/polym13030395.
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Current work aims to study the mechanical and dynamical mechanical properties of non-woven bamboo (B)/woven kenaf (K)/epoxy (E) hybrid composites filled with nanoclay. The nanoclay-filled BK/E hybrid composites were prepared by dispersing 1 wt.% nanoclay (organically-modified montmorillonite (MMT; OMMT), montmorillonite (MMT), and halloysite nanotube (HNT)) with high shear speed homogenizer followed by hand lay-up fabrication technique. The effect of adding nanoclay on the tensile, flexural, and impact properties of the hybrid nanocomposites were studied. Fractography of tensile-fractured sample of hybrid composites was studied by field emission scanning electron microscope. The dynamic mechanical analyzer was used to study the viscoelastic properties of the hybrid nanocomposites. BK/E-OMMT exhibit enhanced mechanical properties compared to the other hybrid nanocomposites, with tensile, flexural, and impact strength values of 55.82 MPa, 105 MPa, and 65.68 J/m, respectively. Statistical analysis and grouping information were performed by one-way ANOVA (analysis of variance) and Tukey method, and it corroborates that the mechanical properties of the nanoclay-filled hybrid nanocomposites are statistically significant. The storage modulus of the hybrid nanocomposites was improved by 98.4%, 41.5%, and 21.7% with the addition of OMMT, MMT, and HNT, respectively. Morphology of the tensile fracture BK/E-OMMT composites shows that lesser voids, microcracks and fibers pull out due to strong fiber–matrix adhesion compared to other hybrid composites. Hence, the OMMT-filled BK/E hybrid nanocomposites can be utilized for load-bearing structure applications, such as floor panels and seatbacks, whereby lightweight and high strength are the main requirements.
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Lamon, Jacques, et Adrien Laforêt. « Static Fatigue of SiC/SiC Minicomposites at High Temperatures Up to 1200 °C in Air : Multiscale Approach ». Journal of Composites Science 5, no 3 (28 février 2021) : 67. http://dx.doi.org/10.3390/jcs5030067.
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The present paper investigates the static fatigue behavior of Hi-Nicalon fiber-reinforced SiC–SiC minicomposites at high temperatures in the 900–1200 °C range, and under tensile stresses above the proportional limit. The stress–rupture time relation was analyzed with respect to subcritical crack growth in filaments and fiber tow fracture. Slow crack growth from flaws located at the surface of filaments is driven by the oxidation of free carbon at the grain boundaries. Lifetime of the reinforcing tows depends on the statistical distribution of filament strength and on structural factors, which are enhanced by temperature increase. The rupture time data were plotted in terms of initial stresses on reinforcing filaments. The effect of temperature and load on the stress–rupture time relation for minicomposites was investigated using results of fractography and predictions of minicomposite lifetime using a model of subcritical growth for critical filaments. The critical filament is the one whose failure by slow crack-growth triggers unstable fracture of the minicomposite. This is identified by the strength–probability relation provided by the cumulative distribution function for filament strength at room temperature. The results were compared to the fatigue behavior of dry tows. The influence of various factors related to oxidation, including multiple failures, load sharing, and variability, was analyzed.
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Nečas, Alois, Lucie Urbanová, Tomáš Fürst, Pavel Ženčák et Pavel Tuček. « Mathematical Modelling of Crack Fractography after Implant Failure of Titanium 4.5 LCP Used for Flexible Bridging Osteosynthesis in a Miniature Pig ». Acta Veterinaria Brno 79, no 4 (2010) : 621–26. http://dx.doi.org/10.2754/avb201079040621.
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Biomechanics of fracture fixation and testing of mechanical properties of bone/implant construct from the viewpoint of checking the strength and resistance ability to acting forces are of current interest. Computer modelling known as mathematical modelling is regarded as an alternative to mechanical testing of properties on a testing machine. As a result, we get a 3D model of a real object (i.e., implant for fracture fixation in our case), which can be exposed to deformation processes in the environment of the mathematical software in order to characterize forces acting on the implant and subsequently analyze the forces causing the implant failure (broken plate). The goal of this study was to employ mathematical-statistical modelling for determination of forces that caused failure (broken implant) of a five-hole titanium 4.5 mm Locking Compression Plate. This plate has been used for flexible bridging osteosynthesis of segmental femoral diaphyseal defect in a miniature pig to investigate bone healing after transplantation of mesenchymal stem cells in combination with biocompatible scaffolds. Mathematical modelling has been performed with COMSOL Multiphysics software. Numerical study that describes deformation processes taking place in implant failure demonstrates the possibilities of deformation of five-hole titanium 4.5 mm LCP in the case of exceeding the elastic limits of a material. Knowledge of the forces acting on implants used for fracture fixation acquired from mathematical modelling might be used in clinical practice in order to prevent undesirable implant failure.
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Viljoen, David, Matthieu Fischer, Ines Kühnert et Johan Labuschagné. « The Tensile Behaviour of Highly Filled High-Density Polyethylene Quaternary Composites : Weld-Line Effects, DIC Curiosities and Shifted Deformation Mechanisms ». Polymers 13, no 4 (10 février 2021) : 527. http://dx.doi.org/10.3390/polym13040527.
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The interactive effects between additives and weld lines, which are frequent injection-moulding defects, were studied in high-density polyethylene (HDPE) and compared to weld-line-free reference samples. These materials were formulated around a D- and I-optimal experimental design, based on a quadratic Scheffé polynomial model, with up to 60 wt% calcium carbonate, masterbatched carbon black and a stabiliser package. Where reasonable and appropriate, the behaviours of the systems were modelled using statistical techniques, for a better understanding of the underlying trends. The characterisations were performed through the use of conventional tensile testing, digital image correlation (DIC) and scanning electron microscopy (SEM). A range of complex interactive effects were found during conventional tensile testing, with DIC used to better understand and explain these effects. SEM is used to better understand the failure mechanics of some of these systems through fractography, particularly regarding particle effects. A measure is introduced to quantify the deviation of the pre-yield deformation curve from the ideal elastic case. Novel analysis of DIC results is proposed, through the use of combined time-series plots and measures quantifying the extent and localisation of peak deformation. Through this, it could be found that strong shifts in the deformation mechanisms occur as a function of formulation and the presence/absence of weld lines. Primarily, changes are noted in the onset of continuous inter- and intralamellar slip and cavitation/fibrillation, seen through the onset of localised deformation and stress-whitening.
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KAMOCHI, Nobuaki, Hiroaki KATSUKI et Takanori WATARI. « Rim impact testing of alumina reinforced porcelain tableware : statistical and fractographic analysis ». Journal of the Ceramic Society of Japan 117, no 1366 (2009) : 724–28. http://dx.doi.org/10.2109/jcersj2.117.724.
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Candido, LM, LN Miotto, LMG Fais, PF Cesar et LAP Pinelli. « Mechanical and Surface Properties of Monolithic Zirconia ». Operative Dentistry 43, no 3 (1 mai 2018) : E119—E128. http://dx.doi.org/10.2341/17-019-l.
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SUMMARY Purpose: This study compared monolithic zirconia with conventional ones based on mean roughness (Ra), Vickers hardness (VHN), topography, transmittance, grain size, flexural strength (FS), Weibull modulus, and fractographic behavior. Methods and Materials: One monolithic (Prettau Zircon [PR group]) and two conventional (ICE Zirkon Transluzent [IZ group] and BloomZir [BL group]) zirconias were used. Specimens were tested using a profilometer, a microhardness tester, a scanning electron microscope, a spectrophotometer, and a Universal Testing Machine (EMIC DL 2000). Ra, VHN, grain size, and transmittance were analyzed using the Kruskal-Wallis test associated with Dunn test (α=0.05). FS was analyzed using one-way analysis of variance with the Tukey honestly significant difference test (α=0.05). Results: Means and standard deviations of roughness, after sintering (Ra, in μm) and VHN, were, respectively, 0.11 ± 0.01, 1452.16 ± 79.49, for the PR group; 0.12 ± 0.02, 1466.72 ± 91.76, for the IZ group; and 0.21 ± 0.08, 1516.06 ± 104.02, for the BL group. BL was statistically rougher (p<0.01) than PR and IZ. Hardness was statistically similar (p=0.30) for all groups. Means and standard deviations of FS (in MPa) were 846.65 ± 81.97 for the PR group, 808.88 ± 117.99 for the IZ group, and 771.81 ± 114.43 for the BL group, with no statistical difference (p>0.05). Weibull moduli were 12.47 for the PR group, 7.24 for the IZ group, and 6.31 for the BL group, with no statistical differences. The PR and BL groups had higher transmittance values and grain sizes than the IZ group (p<0.05). Although the BL group had some fractures that originated in the center of the tensile surface, fractographic analyses showed the same fracture pattern. Conclusions: All tested zirconia showed similar VHN, and the monolithic zirconia had similar roughness compared to one of the conventional zirconias. In addition, the monolithic zirconia showed similar flexural strength and Weibull modulus compared to the others even though its mean grain size was larger. The total transmittance of monolithic zirconia was higher than only one of the conventional zirconias tested.
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Ocelík, Václav, et Pei Ying Liu. « Strain Rate Dependence of Statistical Fractographic Characteristics of Shear Failure on Ni-Si-B Amorphous Ribbons ». Key Engineering Materials 81-83 (janvier 1993) : 613–18. http://dx.doi.org/10.4028/www.scientific.net/kem.81-83.613.
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Ma, Lingyue, Dragan Djurdjanovic et Roberto Dugnani. « Statistical accuracy of fractographic estimation in silicate glasses with design of experiments and pairwise T-tests ». Engineering Failure Analysis 116 (octobre 2020) : 104699. http://dx.doi.org/10.1016/j.engfailanal.2020.104699.
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Traini, Tonino, Roberto Sorrentino, Enrico Gherlone, Federico Perfetti, Patrizio Bollero et Ferdinando Zarone. « Fracture Strength of Zirconia and Alumina Ceramic Crowns Supported by Implants ». Journal of Oral Implantology 41, S1 (1 juillet 2015) : 352–59. http://dx.doi.org/10.1563/aaid-joi-d-13-00142.
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Due to the brittleness and limited tensile strength of the veneering glass-ceramic materials, the methods that combine strong core material (as zirconia or alumina) are still under debate. The present study aims to evaluate the fracture strength and the mechanism of failure through fractographic analysis of single all-ceramic crowns supported by implants. Forty premolar cores were fabricated with CAD/CAM technology using alumina (n = 20) and zirconia (n = 20). The specimens were veneered with glass-ceramic, cemented on titanium abutments, and subjected to loading test until fracture. SEM fractographic analysis was also performed. The fracture load was 1165 (±509) N for alumina and 1638 (±662) N for zirconia with a statistically significant difference between the two groups (P = 0.026). Fractographic analysis of alumina-glass-ceramic crowns, showed the presence of catastrophic cracks through the entire thickness of the alumina core; for the zirconia-glass-ceramic crowns, the cracks involved mainly the thickness of the ceramic veneering layer. The sandblast procedure of the zirconia core influenced crack path deflection. Few samples (n = 3) showed limited microcracks of the zirconia core. Zirconia showed a significantly higher fracture strength value in implant-supported restorations, indicating the role played by the high resistant cores for premolar crowns.
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Schneider, M., D. Bettge, M. Binder, K. Dollmeier, M. Dreyer, K. Hilgenberg, B. Klöden, T. Schlingmann et J. Schmidt. « Reproducibility and Scattering in Additive Manufacturing : Results from a Round Robin on PBF-LB/M AlSi10Mg Alloy ». Practical Metallography 59, no 10 (24 septembre 2022) : 580–614. http://dx.doi.org/10.1515/pm-2022-1018.
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Abstract The round robin test investigated the reliability users can expect for AlSi10Mg additive manufactured specimens by laser powder bed fusion through examining powder quality, process parameter, microstructure defects, strength and fatigue. Besides for one outlier, expected static material properties could be found. Optical microstructure inspection was beneficial to determine true porosity and porosity types to explain the occurring scatter in properties. Fractographic analyses reveal that the fatigue crack propagation starts at the rough as-built surface for all specimens. Statistical analysis of the scatter in fatigue using statistical derived safety factors concludes that at a stress of 36.87 MPa the fatigue limit of 107 cycles could be reached for all specimen with a survival probability of 99.999 %.
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Wan, Di, Antonio Alvaro, Vigdis Olden et Afrooz Barnoush. « Hydrogen-assisted fatigue crack growth in ferritic steels – a fractographic study ». MATEC Web of Conferences 165 (2018) : 03004. http://dx.doi.org/10.1051/matecconf/201816503004.
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Fatigue crack growth (FCG) behavior of a Fe-3wt.%Si ferritic alloy under different environmental conditions using in-situ electrochemical (cathodic) hydrogen (H) charging has been investigated. Three frequencies have been applied. Results clearly show that the FCG rate increased by a factor spanning from 20 to 1000 times, depending on the loading frequencies, when compared to the reference test in air. Lower frequency leads to higher FCG rate. A comprehensive fractographic analysis was carried out: the area fraction of different fracture surface features was measured and taken into statistical analysis. Based on these investigations, the possible mechanisms of H-enhanced FCG are discussed. Similar tests in high-pressure H gas from other studies were also compared and discussed. These results give a preliminary understanding of H effect in fatigue crack propagation procedure in ferritic alloys.
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Zhang, Yuan Bin, Cheng Xin Teng et Tong Guang Zhai. « Porosities and Fatigue Property of Two A356 Cast Aluminum Alloy ». Applied Mechanics and Materials 423-426 (septembre 2013) : 263–66. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.263.
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To investigate the fatigue property of A356 cast aluminum alloy, the pore size distribution in two kinds of A356 alloy were statistically tested, and the S-N curves were plotted by conducting four-point bend fatigue test, then the fractography of the fatigue specimens were examined under scan electron microscope (SEM). It was indicated that the fatigue strength of the A356.2 alloy contenting more large pores and rougher crystalline grain was lower than that of A356.1 alloy, though the yield strength of A356.2 alloy was higher. Most of the fatigue cracks initiated from the pores that located on or close to the surface of the specimens, and the fracture of the specimens were induced from the growth of multi-sites initiated fatigue crack.
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Nasrin, S., N. Katsube, R. R. Seghi et S. I. Rokhlin. « Survival Predictions of Ceramic Crowns Using Statistical Fracture Mechanics ». Journal of Dental Research 96, no 5 (20 janvier 2017) : 509–15. http://dx.doi.org/10.1177/0022034516688444.
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This work establishes a survival probability methodology for interface-initiated fatigue failures of monolithic ceramic crowns under simulated masticatory loading. A complete 3-dimensional (3D) finite element analysis model of a minimally reduced molar crown was developed using commercially available hardware and software. Estimates of material surface flaw distributions and fatigue parameters for 3 reinforced glass-ceramics (fluormica [FM], leucite [LR], and lithium disilicate [LD]) and a dense sintered yttrium-stabilized zirconia (YZ) were obtained from the literature and incorporated into the model. Utilizing the proposed fracture mechanics–based model, crown survival probability as a function of loading cycles was obtained from simulations performed on the 4 ceramic materials utilizing identical crown geometries and loading conditions. The weaker ceramic materials (FM and LR) resulted in lower survival rates than the more recently developed higher-strength ceramic materials (LD and YZ). The simulated 10-y survival rate of crowns fabricated from YZ was only slightly better than those fabricated from LD. In addition, 2 of the model crown systems (FM and LD) were expanded to determine regional-dependent failure probabilities. This analysis predicted that the LD-based crowns were more likely to fail from fractures initiating from margin areas, whereas the FM-based crowns showed a slightly higher probability of failure from fractures initiating from the occlusal table below the contact areas. These 2 predicted fracture initiation locations have some agreement with reported fractographic analyses of failed crowns. In this model, we considered the maximum tensile stress tangential to the interfacial surface, as opposed to the more universally reported maximum principal stress, because it more directly impacts crack propagation. While the accuracy of these predictions needs to be experimentally verified, the model can provide a fundamental understanding of the importance that pre-existing flaws at the intaglio surface have on fatigue failures.
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Navaneethakrishnan, Sadayan, et Ayyanar Athijayamani. « Analysis of the tensile properties of natural fiber and particulate reinforced polymer composites using a statistical approach ». Journal of Polymer Engineering 35, no 7 (1 septembre 2015) : 665–74. http://dx.doi.org/10.1515/polyeng-2014-0218.
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Abstract In the present study, the effect of fiber and (5% wt) coconut shell powder (CSP) loading on the tensile properties of randomly oriented roselle fiber reinforced vinyl ester (RV) composites was carried out. Composite specimens were fabricated using the hand lay-up technique. It was observed that tensile properties of vinyl ester composites increase upon reinforcement with roselle fibers and CSP particles. The reinforcement of roselle fibers has significant effects on the tensile strength and modulus of the composite. The fractographic study was carried out on the surface of fractured composite specimens using scanning electron microscopy. A better interfacial adhesion, fiber dispersion and less fiber pull out on the surface of fractured composite specimens were identified. The tensile strength of RV composites has also been statistically analyzed by two-parameter Weibull distribution. Twenty-five tension tests were carried out. The results obtained varied between 37.89 MPa and 45.07 MPa. Furthermore, the inspection of the developed distribution was examined by the Kolmogorov-Smirnov (KS) test. The results show that the gained two-parameter Weibull distribution can be used to express the tensile strength and predict its values accurately.
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Śmielak, Beata, Marcin Gołębiowski, Leszek Klimek et Emilia Wołowiec. « Effect of Surface Treatment of Titanium Elements on the Bond Strength to Zirconium Dioxide ». Solid State Phenomena 225 (décembre 2014) : 151–58. http://dx.doi.org/10.4028/www.scientific.net/ssp.225.151.
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The aim of the study was to examine the effect of surface treatment of titanium elements on the bond strength to zirconium dioxide. Forty cylindrical titanium discs (Tritan CpTi 1) were divided into four groups (n=10) that were subject to: grinding (Group A), grinding and acid-etching with 5% HF (Group B), sandblasting with 60μm alumina particles (Group C) and sandblasting with 60μm alumina particles and acid-etching with 5% HF (Group D). Prepared materials were bonded to cylindrical discs made of zirconium dioxide (Ceramill Zi) by composite cement (Panavia F 2.0). The specimens were tested for the shear bond strength. The load was applied to the moment of the bond failure. Than the debonded specimens were vertically sectioned and the fractographic analysis of interfacial fractures under SEM as well as the analysis of chemical composition of the obtained fractures using radiographic spectrum were performed. The results were subject to the statistical analysis by using the analysis of variance. The highest values of bond strength were obtained for specimens whose surface was sandblasted and abraded. Fractographic investigation and the analysis of chemical composition of the cross-sections of the interfacial fractures revealed that the fracture occurred at the titanium-resin cement interface. Air abrasion treatment considerably improves the titanium and composite cement bonding and should be recommended for cementation of prosthodontic restorations constructed on titanium implants.
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JI, WEI, et YAFU FAN. « THE FAILURE BEHAVIOR OF EXTRUDED Mg-12Gd-3Y-0.4Zr ALLOY SUBJECTED TO IMPACT LOADING ». International Journal of Modern Physics B 24, no 15n16 (30 juin 2010) : 2267–72. http://dx.doi.org/10.1142/s0217979210064770.
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Dynamic failure behaviors of the extruded Mg -12 Gd -3 Y -0.4 Zr alloy were investigated by means of optical microscope and scanning electron microscope (SEM). The dynamic tensile and compressive tests were carried out at 423K~798K and strain rates of 102~103s-1 using a split Hopkinson pressure bar. Additionally, in order to study the failure characteristic of this alloy at higher strain rates, such as 107s-1, a series of ballistic tests were carried out. The results indicate that the failure mechanisms of both tensile and compressive specimens exhibit an obvious dependence on the temperature. As the testing temperatures increased from 423K to 798K, the fractographs of the tensile specimens varied from quasi-cleavage fracture to intergranular rupture, and the failure modes of the compressive specimens changed from shear cracks to dynamic recrystallization zone. Adiabatic shear bands with an average width 10µm were observed in the post-test magnesium targets penetrated by steel balls.
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Guilardi, Luis Felipe, Arie Werner, Niek de Jager, Gabriel Kalil Rocha Pereira, Cornelis Johannes Kleverlaan, Marilia Pivetta Rippe et Luiz Felipe Valandro. « The influence of roughness on the resistance to impact of different CAD/CAM dental ceramics ». Brazilian Dental Journal 32, no 6 (novembre 2021) : 54–65. http://dx.doi.org/10.1590/0103-6440202103951.
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Abstract This study aimed to investigate the effect of surface roughness (polished vs. CAD/CAM milling simulation) on impact strength of five dental ceramics for manufacturing CAD/CAM monolithic restorations. Specimens of five ceramics (FC- feldspathic glass-ceramic; PICN- polymer-infiltrated ceramic-network; ZLS- zirconia-reinforced lithium silicate glass-ceramic; LD- lithium disilicate glass-ceramic; YZ- yttria-stabilized tetragonal zirconia polycrystal ceramic) to be tested under impact (15×10×2mm3; n= 15) were divided into two groups, according to surface treatment: polishing (pol) and grinding (gri) as CAD/CAM milling simulation. Impact strength was tested using the Dynstat method. Roughness, topographic, fractographic and finite element analyses were performed. The impact strength data were analyzed by Weibull, and Pearson correlation was used to correlate roughness and impact strength data. The CAD/CAM milling simulation led to significantly (p<0.05) greater roughness (Ra and Rz) and statistically reduced the impact strength for PICN (polPICN= 4.59 to griPICN= 1.09; ±76% decrease), for LD (polLD= 17.69 to griLD= 10.09; ±43% decrease) and for YZ (polYZ= 74.99 to griYZ= 20.67; ±72% decrease) ceramics; and also promoted a more irregular topography with scratches and grooves. Fractographic and FEA analyses depicted the origin of failure at the higher stress concentration side during the impact test, where the pendulum impacted. The CAD/CAM milling simulation significantly decreased the impact strength of the evaluated ceramic materials.
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Sauro, Salvatore, Irina Makeeva, Vicente Faus-Matoses, Federico Foschi, Massimo Giovarruscio, Paula Maciel Pires, Maria Martins Moura, Aline Almeida Neves et Vicente Faus-Llácer. « Effects of Ions-Releasing Restorative Materials on the Dentine Bonding Longevity of Modern Universal Adhesives after Load-Cycle and Prolonged Artificial Saliva Aging ». Materials 12, no 5 (1 mars 2019) : 722. http://dx.doi.org/10.3390/ma12050722.
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This study aimed at evaluating the microtensile bond strength (MTBS) and fractographic features of dentine-bonded specimens created using universal adhesives applied in etch-and-rinse (ER) or self-etching (SE) mode in combination with modern ion-releasing resin-modified glass-ionomer cement (RMGIC)-based materials after load cycling and artificial saliva aging. Two universal adhesives (FTB: Futurabond M+, VOCO, Germany; SCU: Scotchbond Universal, 3M Oral Care, USA) were used. Composite build-ups were made with conventional nano-filled composite (AURA, SDI, Australia), conventional resin-modified glass ionomer cement (Ionolux VOCO, Germany), or a (RMGIC)-based composite (ACTIVA, Pulpdent, USA). The specimens were divided in three groups and immersed in deionized water for 24 h, load-cycled (350,000 cycles; 3 Hz; 70 N), or load-cycled and cut into matchsticks and finally immersed for 8 months in artificial saliva (AS). The specimens were cut into matchsticks and tested for microtensile bond strength. The results were analyzed statistically using three-way ANOVA and Fisher’s LSD post hoc test (p < 0.05). Fractographic analysis was performed through stereomicroscope and FE-SEM. FTB showed no significant drop in bond strength after aging. Unlike the conventional composite, the two RMGIC-based materials caused no bond strength reduction in SCU after load-cycle aging and after prolonged aging (8 months). The SEM fractographic analysis showed severe degradation, especially with composite applied on dentine bonded with SCU in ER mode; such degradation was less evident with the two GIC-based materials. The dentine-bond longevity may be influenced by the composition rather than the mode of application (ER vs. SE) of the universal adhesives. Moreover, the choice of the restorative material may play an important role on the longevity of the finalrestoration. Indeed, bioactive GIC-based materials may contribute to maintain the bonding performance of simplified universal adhesives over time, especially when these bonding systems are applied in ER mode.
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Ponnusamy, Muruganantham, L. Natrayan, Pravin P. Patil, G. Velmurugan et Yirga Terefe Keno. « Statistical Analysis on Interlaminar Shear Strength of Nanosilica Addition with Woven Dharbai/Epoxy Hybrid Nanocomposites under Cryogenic Environment by Taguchi Technique ». Adsorption Science & ; Technology 2022 (4 août 2022) : 1–9. http://dx.doi.org/10.1155/2022/6571515.
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Biocomposites are becoming more popular due to their capacity to replace artificial materials at a lower cost while enhancing environmental responsibility. In contrast, biocomposites have poor mechanical and interface properties. This research is aimed at determining the interlaminar shear strength of composite materials reinforced with Dharbai fibre and nanosilicon powder. The composites were made using a hand lay-up method with the following conditions: (i) weight % of nanosilica filler, (ii) thickness of fibre mat, and (iii) cryogenic treatment period, each at three different levels, to meet the goals mentioned above. The composites were laminated using a traditional hand lay-up method, and their interlaminar shear strength was determined using the ASTM standard. According to a recent study, nanocomposites containing 4% nanoscale silicon and 300 grammes per square metre of woven Dharbai fibre showed the highest interlaminar shear strength after 15 minutes of cryogenic treatment. Fibre content increased the mechanical properties of pure epoxy in general. As the fibre and filler concentrations grew, more energy was required to break the fibre bundles between the matrix and its resin. According to the ANOVA, the cryogenic treatment was the most significant factor, contributing up to 59.58%, followed by woven Dharbai mate, contributing 22.11%, and nanosilicon at 18.30%. SEM is used to investigate the cracked composites’ fractographic examination.
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JIN, S. U., S. S. KIM, Y. S. LEE, Y. N. KWON et J. H. LEE. « EFFECT OF VARIOUS HEAT TREATMENT PROCESSES ON FATIGUE BEHAVIOR OF TOOL STEEL FOR COLD FORGING DIE ». International Journal of Modern Physics B 22, no 31n32 (30 décembre 2008) : 5495–502. http://dx.doi.org/10.1142/s0217979208050711.
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Effects of various heat treatment processes, including "Q/T (quenching and tempering)", "Q/CT/T (Quenching, cryogenic treatment and tempering)", "Q/T (quenching and tempering) + Ti -nitriding" and "Q/CT/T (Cryogenic treatment and tempering) + Ti -nitriding", on S - N fatigue behavior of AISI D2 tool steel were investigated. The optical micrographs and Vicker's hardness values at near surface and core area were examined for each specimen. Uniaxial fatigue tests were performed by using an electro-magnetic resonance fatigue testing machine at a frequency of 80 Hz and an R ratio of -1. The overall resistance to fatigue tends to decrease significantly with Ti -nitriding treatment compared to those for the general Q/T and Q/CT/T specimens. The reduced resistance to fatigue with Ti -nitriding is discussed based on the microstructural and fractographic analyses.
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Fraga, Sara, Gabriel Kalil Rocha Pereira, Luís Felipe Guilardi, Liliana Gressler May, Luiz Felipe Valandro et Cornelis Johannes Kleverlaan. « Influence of testing environment on static fatigue behavior of a glass and a polycrystalline ceramic ». Brazilian Dental Journal 32, no 3 (juin 2021) : 56–64. http://dx.doi.org/10.1590/0103-6440202103961.
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Abstract It aims on evaluate the effect of the test environment on static fatigue behavior of lithium disilicate-based (LD), and yttrium oxide-stabilized zirconia (YSZ) ceramics. Specimens of LD (IPS e.max CAD, Ivoclar Vivadent) and YSZ (IPS e.max ZirCAD MO, 3 mol% Y2O3, Ivoclar Vivadent) were randomly allocated into three groups: tested in air, inert (paraffin oil, Sigma Aldrich) or distilled water. The static fatigue test (n=15) was performed using a piston-on-three ball assembly, adapted from ISO 6872, as follows: starting load 100 N for LD and 300 N for YSZ; loading application time set to 1 hour for each loading step; step size of 50 N for LD and 100 N for YSZ, applied successively until fracture. Data from static fatigue strength (MPa) and time to fracture (hours) were recorded. Fractographic analysis was executed. Survival analysis corroborates absence of influence of environment on static fatigue outcomes (fatigue strength, time to fracture and survival rates) for YSZ. For LD, specimens tested in air presented statistically superior survival rate and static fatigue strength (p= 0.025). In regards of time to fracture, LD tested in air were superior than when tested in distilled water (p=0.019) or inert (p=0.017) environments. No statistical differences for Weibull modulus were observed. Failures started on the tensile stress surface. Thus, the test environment did not affect slow crack growth (SCG) mechanisms during static fatigue test of YSZ ceramics, but it plays a significant role for the static fatigue behavior of lithium disilicate-based glass ceramics, indicating a high susceptibility to SCG.
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Dlouhý, Ivo, Lukáš Řehořek et Zdeněk Chlup. « Tensile Properties of Open Cell Ceramic Foams ». Key Engineering Materials 409 (mars 2009) : 168–75. http://dx.doi.org/10.4028/www.scientific.net/kem.409.168.
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Full understanding of response of highly porous (cellular) ceramic foams to different mechanical loading conditions is important because of their potential use in industry, medical and other applications. Technique of tensile test of ceramic foam materials has been developed and first knowledge is described in the paper. Tested material was based on alumina ceramic; it was manufactured by slurry coating of polyurethane foam. Two cell sizes were included into the study 10 and 60 PPI. Testing procedure consists from fixation of ceramic foam into aluminium pots by suitable adhesive. Tensile test results generated using two specimen sizes with cross-section 10x10 and 15x15 mm have been statistically analysed. Basic fractographic analysis was applied to get corresponding figure about specimens behaviour during tensile loading.
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Bidulská, J., T. Kvačkaj, I. Pokorný, R. Bidulský et M. Actis Grande. « Identification of the Critical Pore Sizes in Sintered and Ecaped Aluminium 6XXX Alloy ». Archives of Metallurgy and Materials 58, no 2 (1 juin 2013) : 371–75. http://dx.doi.org/10.2478/amm-2013-0002.
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The main aim of this paper is to investigate, by means of comparison of experimental studies and mathematical models, the evolution of porosity as consequence of pressing, sintering and ECAPping an aluminium based powder (6xxx). After applying the compacting pressure, specimens were dewaxed in a ventilated furnace at 400º for 60 min. Sintering was carried out in a vacuum furnace at 610ºC for 30 min. The specimens were then ECAPed for 1 pass. The 2-dimensional quantitative image analysis was carried out by means of SEM and OM for the evaluation of the aforementioned characteristics. Results show the effect of processing parameters on the fracture/microstructure behaviour of the studied aluminium PM alloy. Quantitative image analysis, as well as fractographic interpretation and microstructure identification of weak sites in the studied aluminium PM alloy, provide a reliable and reproducible statistical procedure for the identification of the critical pore sizes.
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Vasiliu, Roxana Diana, Ion-Dragoș Uțu, Lucian Rusu, Adrian Boloș et Liliana Porojan. « Fractographic and Microhardness Evaluation of All-Ceramic Hot-Pressed and CAD/CAM Restorations after Hydrothermal Aging ». Materials 15, no 11 (3 juin 2022) : 3987. http://dx.doi.org/10.3390/ma15113987.
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All-ceramic dental restorations have great advantages, such as highly esthetical properties, a less complex fabrication, and a similar abrasion resistance to enamel. Despite these advantages, ceramic materials are more prone to fracture due to their brittle microstructure. The main aim of this in vitro study was to determine the difference in hot-pressed and milled glass-ceramic mechanical properties such as fracture resistance and microhardness (VHN). Four types of ceramics, two hot-pressed and two milled, feldspathic glass-ceramics and zirconia-reinforced glass-ceramics were selected in this study and tested using the static loading test and Vicker’s testing. Hydrothermal aging, consisting of different baths with temperatures between 5 degrees Celsius and 55 degrees Celsius, was chosen as the in vitro aging method. Statistical analyses are performed using SPSS Statistics software at a significance level of p < 0.05. Micro-hardness values decrease after hydrothermal aging. The static loading test reveals a significant difference between the feldspathic hot-pressed glass-ceramic, which fractures at lower forces, and milled zirconia-reinforced lithium silicate glass-ceramic, which fractures at greater forces (N). Fractographic analysis of the fractured fragments resulted in the static loading test revealing different surface features about the crack origins and propagations under a stereomicroscope.
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SHIN, HYUNG-SEOP, KI-HYUN KIM et SANG-YEOB OH. « FRACTURE BEHAVIOR OF Zr-BASED BULK METALLIC GLASS UNDER IMPACT LOADING ». International Journal of Modern Physics B 20, no 25n27 (30 octobre 2006) : 4359–64. http://dx.doi.org/10.1142/s0217979206041355.
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The fracture behavior of a Zr -based bulk amorphous metal under impact loading using subsize V-shaped Charpy specimens was investigated. Influences of loading rate on the fracture behavior of amorphous Zr - Al - Ni - Cu alloy were examined. As a result, the maximum load and absorbed fracture energy under impact loading were lower than those under quasi-static loading. A large part of the absorbed fracture energy in the Zr -based BMG was consumed in the process for crack initiation and not for crack propagation. In addition, fractographic characteristics of BMGs, especially the initiation and development of shear bands at the notch tip were investigated. Fractured surfaces under impact loading are smoother than those under quasi-static loading. The absorbed fracture energy appeared differently depending on the appearance of the shear bands developed. It can be found that the fracture energy and fracture toughness of Zr -based BMG are closely related with the extent of shear bands developed during fracture.
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Drukteinis, Saulius, Vytaute Peciuliene, Ruta Bendinskaite, Vilma Brukiene, Rasmute Maneliene et Vygandas Rutkunas. « Shaping and Centering Ability, Cyclic Fatigue Resistance and Fractographic Analysis of Three Thermally Treated NiTi Endodontic Instrument Systems ». Materials 13, no 24 (21 décembre 2020) : 5823. http://dx.doi.org/10.3390/ma13245823.
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The better understanding of the clinically important behavioral features of new instrument systems has an important significance for the clinical endodontics. This study aimed to investigate the shaping and centering ability as well as cyclic fatigue resistance of HyFlex CM (CM), HyFlex EDM (EDM) and EdgeFile (EF) thermally treated nickel–titanium (NiTi) endodontic instrument systems. Sixty curved root canals of the mesial roots of mandibular molars were randomly assigned into three groups (n = 20) and shaped using CM, EDM and EF files up to the size 40 and taper 04 of the instruments. µCT scanning of the specimens before and after preparation was performed and the morphometric 2D and 3D parameters were evaluated in the apical, middle and coronal thirds of root canals. In each group, 40.04 instruments (n = 20) were subjected to the cyclic fatigue resistance test in artificial root canals at 37 °C temperature until fractures occurred, and the number of cycles to failure (NCF) was calculated. The fractographic analysis was performed using a scanning electron microscope, evaluating topographic features and surface profiles of the separated instruments. The one-way analysis of variance with post hoc Tuckey’s test was used for statistical analysis of the data; the significance level was set at 5%. All systems prepared the comparable percentage of root canal surface with the similar magnitude of canal transportation in all root thirds (p > 0.05), but demonstrated significantly different resistance to cyclic fatigue (p < 0.05). The most resistant to fracture was EF, followed by EDM and CM. The length of the fractured fragments was not significantly different between the groups, and fractographic analysis by SEM detected the typical topographic features of separated thermally treated NiTi instrument surfaces.
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Piccoli, A. C., et M. Borba. « Influence of the fabrication method on the fracture behavior of all-ceramic prosthesis ». Cerâmica 64, no 370 (juin 2018) : 284–87. http://dx.doi.org/10.1590/0366-69132018643702371.
Texte intégralRésumé :
Abstract Different methods are available to produce all-ceramic dental prosthesis. Each processing step may introduce flaws to the material, which compromises its properties and reliability. The objective of this study was to evaluate the effect of fabrication method on the fracture behavior of prosthetic crowns produced with an alumina-based glass-infiltrated zirconia-reinforced ceramic. Two groups of all-ceramic crowns were produced according to the fabrication method of the infrastructure (IS) (n=30): IZC - IS produced by CAD-CAM; IZS - IS produced by slip-casting. The IS were veneered with porcelain and cemented to fiber-reinforced composite dies with resin cement. Crowns were loaded in compression to failure using a universal testing machine, at 1 mm/min crosshead speed and 37 ºC distilled water. Fractography was performed using stereomicroscope and SEM. Data were statistically analyzed with Student’s t test (α=0.05) and Weibull analysis. There were no significant differences among the experimental groups for fracture load (p=0.481) and Weibull modulus. For both groups, the failure mode was catastrophic failure involving IS and porcelain. It was concluded that the fabrication methods evaluated resulted in all-ceramic crowns with similar fracture behavior and reliability.
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Nourian-Avval, Ahmad, et Ali Fatemi. « Characterization and Analysis of Porosities in High Pressure Die Cast Aluminum by Using Metallography, X-Ray Radiography, and Micro-Computed Tomography ». Materials 13, no 14 (9 juillet 2020) : 3068. http://dx.doi.org/10.3390/ma13143068.
Texte intégralRésumé :
Mechanical performance of cast aluminum alloys is strongly affected by the defects formed during solidification. For example, fractography studies of the fatigue specimens have shown that fatigue failure in aluminum castings containing defects is almost always initiated from defects, among which pores are most detrimental. However, elimination of these pores is neither always economically nor technically possible. This work characterizes defects in high pressure die cast aluminum alloy as an illustrative material, but the methods used can be applicable to other types of castings and defects. The defects were evaluated using metallography as well as micro-computed tomography techniques. The variability of defects between the specimens of two sizes as well as different porosity levels are studied statistically. The distributions of defects based on location within the specimens are also analyzed. Moreover, the maximum defect size within the specimens are estimated using extreme value statistics, which can be used as an input to fatigue life prediction models. Extreme value statistics is applied on both 2D and 3D defect data. The accuracy of each approach is verified by comparing the estimated maximum defect size within the specimens with the maximum observed defects on fracture surfaces of fatigue specimens.
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Perdigão, J., SD Fernandes, AM Pinto et FA Oliveira. « Effect of Artificial Aging and Surface Treatment on Bond Strengths to Dental Zirconia ». Operative Dentistry 38, no 2 (1 mars 2013) : 168–76. http://dx.doi.org/10.2341/11-489-l.
Texte intégralRésumé :
SUMMARY The objective of this project was to study the influence of artificial aging and surface treatment on the microtensile bond strengths (μTBS) between zirconia and a phosphate monomer–based self-adhesive cement. Thirty zirconia disks (IPS e.max ZirCAD, Ivoclar Vivadent) were randomly assigned to two aging regimens: AR, used as received, which served as a control, and AG, artificial aging to simulate low-temperature degradation. Subsequently, the disks of each aging regimen were assigned to three surface treatments: NT, no surface treatment; CO, surface silicatization with CoJet sand (3M ESPE); and ZP, zirconia surface treated with Z-Prime Plus (Bisco Inc). Thirty discs were made of Filtek Z250 (3M ESPE) composite resin and luted to the zirconia discs using RelyX Unicem (3M ESPE). The specimens were sectioned with a diamond blade in X and Y directions to obtain bonded beams with a cross-section of 1.0 ± 0.2 mm. The beams were tested in tensile mode in a universal testing machine at a speed of 0.5 mm/min to measure μTBS. Selected beams were selected for fractographic analysis under the SEM. Statistical analysis was carried out with two-way analysis of variance and Dunnett T3 post hoc test at a significance level of 95%. The mean μTBS for the three AR subgroups (AR-NT, AR-CO, and AR-ZP) were significantly higher than those of the corresponding AG groups (p<0.0001). Both AR-CO and AR-ZP resulted in statistically significant higher mean bond strengths than the group AR-NT (p<0.006 and p<0.0001, respectively). Both AG-CO and AG-ZP resulted in statistically significant higher mean bond strengths than the group AG-NT (both at p<0.0001). Overall, AG decreased mean μTBS. Under the SEM, mixed failures showed residual cement attached to the zirconia side of the beams. CO resulted in a characteristic roughness of the zirconia surface. AR-ZP was the only group for which the amount of residual cement occupied at least 50% of the interface in mixed failures.
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Croccolo, Dario, Massimiliano de Agostinis, Stefano Fini, Giorgio Olmi, Luca Paiardini, Francesco Robusto et Antonio Bonomo. « Influence of Heat and Surface Treatments on the Fatigue Response of DMLS Manufactured AlSi10mg ». Materials Science Forum 1016 (janvier 2021) : 1205–10. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1205.
Texte intégralRésumé :
The aim of this study is to analyze how the fatigue behavior of DMLS built AlSi10Mg may be affected by heat and surface treatments. A three-by-three factorial plan has been arranged for this purpose. Particularly, regarding the heat treatment, three levels were considered (as built, age hardening and stress relief), whereas, for the surface treatment, three levels were investigated (micro shot-peening, micro shot-peening plus fine blasting and DMLS production, machining and lapping). Ten specimens per type were built with vertical orientation and with a cylindrical smooth geometry. 90 samples were tested on a four-point rotating bending machine, aiming at the determination of S-N curves in the finite life domain. The experimental results were statistically processed and compared. The outcome was that heat treatment significantly affects the fatigue response and stress relief may have a detrimental impact. Fractographic studies were performed as well, to individuate the crack initiation points. Finally, density measurements were carried out to quantify the porosity level.
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Judawisastra, Hermawan, et Gunawan Refiadi. « Permanganate Treatment Optimization on Tensile Properties and Water Absorption of Kenaf Fiber-Polypropylene Biocomposites ». International Journal of Automotive and Mechanical Engineering 19, no 1 (10 mai 2022) : 9623–33. http://dx.doi.org/10.15282/ijame.19.1.2022.23.0742.
Texte intégralRésumé :
Kenaf fiber has been studied for biocomposites reinforcement due to its renewable and carbon neutrality. Meanwhile, polypropylene sheets are easily processed and considered a prospective thermoplastic matrix source for biocomposites. Hence, the combination of both materials is expected to form an attractive biocomposite. This study aimed to optimize permanganate treatment on tensile properties and water absorption of kenaf-reinforced propylene biocomposites. It thermally tested kenaf fibers and PP using differential scanning calorimetry (DSC) before performing compression molding at 185°C and 70 bars using the film stacking method. The kenaf fiber variables were untreated, alkaline pre-treated, and alkaline-permanganate treated to low concentrations of 0.01 to 0.05 wt% of KMnO4. Furthermore, this study conducted Yarn tensile test and Weibull distribution to find a strength variability statistically. Composite tensile and burn tests were performed to obtain tensile strength, constituent materials, and void volume fractions. Composites fractography was implemented to examine the effect of permanganate on composite water uptake behavior using scanning electron microscopy. This study used low concentration in permanganate treatments than several previous studies. The results showed that biocomposites have a tensile strength of 125 MPa, higher than in previous studies that found a value less than 80 MPa. This study has contributed to the green optimization treatment using lower chemical concentrations but with better results on impregnation, interfacial, water absorption, and mechanical properties of kenaf or polypropylene composites.
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Mills, W. J., et L. D. Blackburn. « Variations in Fracture Toughness for Alloy 718 Given a Modified Heat Treatment ». Journal of Engineering Materials and Technology 112, no 1 (1 janvier 1990) : 116–23. http://dx.doi.org/10.1115/1.2903178.
Texte intégralRésumé :
Heat-to-heat and product-form variations in the JIC fracture toughness for Alloy 718 were characterized at 24, 427, and 538°C using the multiple-specimen JR-curve method. Six different material heats along with three product forms from one of the heats were tested in the modified heat treated condition. This heat treatment was developed at Idaho National Engineering Laboratory to improve the impact toughness for Alloy 718 weldments, but it has also been found to enhance the fracture resistance for the base metal. Statistical analysis of test results revealed four distinguishable JIC levels with mean toughness levels ranging from 87 to 190 kJ/m2 at 24°C. At 538°C, JIC values were 15 to 20 percent lower than room temperature toughness levels. Minimum expected values of JIC (ranging from 72 kJ/m2 at 24°C to 48 kJ/m2 at 538°C) and dJR/da (27 MPa at 24 to 538°C) were established based on tolerance intervals bracketing 90 percent of the lowest JIC and dJR/da populations at a 95 percent confidence level. Metallographic and fractographic examinations were performed to relate key microstructural features and operative fracture mechanisms to macroscopic properties.
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Baruwa, Abayomi Omokeji, Claudia Mazzitelli, Tatjana Maravic, Jorge N. R. Martins, Annalisa Mazzoni et António Ginjeira. « In Situ Zymography Analysis of Matrix Metalloproteinases Activity Following Endodontic Irrigation Protocols and Correlation to Root Dentine Bond Strength ». Polymers 14, no 17 (30 août 2022) : 3567. http://dx.doi.org/10.3390/polym14173567.
Texte intégralRésumé :
The objective was to evaluate the effect of different root canal irrigating solutions on the activity of matrix metalloproteinases (MMPs), and correlation to the push-out bond strength (PBS) and nanoleakage expression (NL) in the root dentin. Seventy-two single-rooted teeth were treated endodontically and distributed into four groups (n = 6 for in-situ zymography, n = 10 for PBS, and n = 2 for NL per group) according to the irrigating solutions used: (I) saline (S); (II) 5.25% sodium hypochlorite (SH); (III) 5.25% SH + 10% citric acid (CA); and (IV) 5.25% SH + 10% CA + 0.2% chlorhexidine (CHX). After root canal obturation, post space was prepared to receive the glass fiber post. Dual-cure resin was used for luting and light polymerization was performed. The root/fiber post assemblies were sectioned and subjected to in situ zymography, and PBS and NL expression analysis tests. The enzymatic activity was quantified and expressed as a percentage of the green fluorescence, while fractographic evaluation was performed after PBS with a stereomicroscope, and data were statistically analyzed at p < 0.05. The zymography analysis shows high expression of MMPs in the middle third of the root in all groups, while the most abundant activity of MMPs following the irrigating solutions is observed in groups I and III, where saline and citric acid are used, respectively. Inversely, group IV, where chlorhexidine is the final rinse, records the lowest MMP activity with the highest PBS, and the statistical analysis of the groups are ranked as: IV > II > III > I (p < 0.05). The combination of SH, CA, and CHX results in lower expression of MMPs and higher push-out bond strength of fiber posts to root dentin, with no difference seen in the nanoleakage expression (p > 0.05); hence, this irrigation regime with chlorhexidine as a final rinse is more favorable than other combinations in ensuring optimal adhesion to root dentine.
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Bertorello, Argüelles, Mollón, Bonhomme, Viña et Viña. « Use of a LHFB Device for Testing Mode III in a Composite Laminate ». Polymers 11, no 8 (26 juillet 2019) : 1243. http://dx.doi.org/10.3390/polym11081243.
Texte intégralRésumé :
The present paper studies the fatigue delamination behaviour of an epoxy/carbon composite material under mode III loading using a longitudinal half fixed beam (LHFB) device initially designed for mode III static tests of composite materials formed by the stacking of plies. For this purpose, a series of tests was carried out at different levels of loading representative of the fatigue behaviour of the material, from the crack onset phase through the delamination phase to final fracture. The experimental results were treated statistically, obtaining the values of the fatigue limit for probabilities of fracture of 5% and 50%. Finally, a fractographic analysis of the fracture surfaces was performed which allowed us to identify the same characteristic patterns of static mode III fracture, namely broken fibres, cusps and saw-teeth, in addition to a new morphology consisting of the formation of agglomerations of resin produced by the friction between the lips of the specimen in the fracture zone that point to dynamic mode III fracture. These agglomerations eventually crack and become detached from the fibres, leaving these free of resin.