Damage accumulation and cyclic fatigue in Mg-PSZ at Hertzian contacts

1995 ◽  
Vol 10 (10) ◽  
pp. 2613-2625 ◽  
Author(s):  
Antonia Pajares ◽  
Lanhua Wei ◽  
Brian R. Lawn ◽  
David B. Marshall
Keyword(s):  
Monoclinic Phase ◽  
Analytical Techniques ◽  
Cyclic Fatigue ◽  
Hertzian Contact ◽  
Test Duration ◽  
Wave Imaging ◽  
Multiple Cycle ◽  
Cycle Loading ◽  
Peak Aged ◽  
Number Of Cycles

Hertzian contact damage in as-fired, peak-aged, and over-aged Mg-PSZ is studied, in single-cycle and multiple-cycle loading. Indentation stress-strain curves reveal a monotonically increasing quasi-plasticity component in the contact deformation with increasing aging time. A bonded-interface technique is used to obtain surface and subsurface views of the damage zones beneath the spherical indenter. Analytical techniques, including optical and scanning electron microscopy, acoustic emission, Raman spectroscopy, and thermal wave imaging, are used to characterize the damage. The damage patterns are fundamentally different in the three aging states: microfracture dominated in as-fired; tetragonal-monoclinic phase-transformation-dominated in peak-aged; monoclinic-phase twinning-dominated in over-aged. The damage accumulates with increasing number of cycles, most strongly in the as-fired state. It also increases with increasing test duration in the as-fired and over-aged states, but not perceptibly in the peak-aged. The results imply predominantly mechanical fatigue effects, augmented by a chemical component in the as-fired and over-aged states. Broader implications in relation to the susceptibilities of zirconia ceramics to fatigue degradation in concentrated stress configurations, with special relevance to the evolution of flaws at the microstructural level, are considered.

scholarly journals Shaping and Centering Ability, Cyclic Fatigue Resistance and Fractographic Analysis of Three Thermally Treated NiTi Endodontic Instrument Systems

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5823
Author(s):  
Saulius Drukteinis ◽  
Vytaute Peciuliene ◽  
Ruta Bendinskaite ◽  
Vilma Brukiene ◽  
Rasmute Maneliene ◽  
...  
Keyword(s):  
Fatigue Resistance ◽  
Cyclic Fatigue ◽  
Fractographic Analysis ◽  
Significance Level ◽  
Root Canals ◽  
Topographic Features ◽  
New Instrument ◽  
Before And After ◽  
Number Of Cycles ◽  
Thermally Treated

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.

scholarly journals Cyclic fatigue resistance of 2Shape, Twisted File and EndoSequence Xpress nickel-titanium rotary files at intracanal temperature

2018 ◽  
Vol 12 (4) ◽  
pp. 283-287 ◽  
Author(s):  
Gülşah Uslu ◽  
Taha Özyürek ◽  
Mustafa Gündoğar ◽  
Koray Yılmaz
Keyword(s):  
Fatigue Resistance ◽  
Statistical Significance ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Bonferroni Correction ◽  
Significant Difference ◽  
Inner Diameter ◽  
The Difference ◽  
Number Of Cycles ◽  
Analyze Data

Background. The aim of this study was to compare the cyclic fatigue resistance of 2Shape, Twisted File (TF) and EndoSequence Xpress (ESX) nickel-titanium rotary files at intracanal temperature (35°C). Methods. Twenty 2Shape TS1 (25/.04), 20 TF (25/.04) and 20 ESX (25/.04) files were tested for cyclic fatigue at intracanal temperature (35°C). All the instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 60° angle of curvature and a radius curvature of 5 mm until fracture occurred; the time to fracture was recorded in seconds using a digital chronometer and the number of cycles to fracture (NCF) for each file was calculated. Kruskal-Wallis test with Bonferroni correction was performed to statistically analyze data using SPSS 21.0. Statistical significance was set at P<0.05. Results. NCF values revealed that the 2Shape had significantly the highest cyclic fatigue resistance, followed by TF and ESX at intracanal temperature (P<0.05). The difference was significant between the TF and ESX groups (P<0.05). There was no significant difference among the 2Shape, TF and ESX files with respect to the lengths of the fractured file fragments (P>.05). Conclusion. Within the limitations of present study, it was concluded that the cyclic fatigue resistance of 2Shape files at the intracanal temperature is higher than that of TF and ESX files.

Fatigue Analysis of FRP Strengthened Masonry by Acoustic Emission Monitoring

2019 ◽  
Vol 817 ◽  
pp. 594-601 ◽  
Author(s):  
Alessandro Grazzini ◽  
Giuseppe Lacidogna
Keyword(s):  
Acoustic Emission ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Fiber Reinforced Polymers ◽  
Test Duration ◽  
Time Behavior ◽  
Damage Growth ◽  
Reinforced Polymers ◽  
Safety Work ◽  
Long Time

The safety work of historical and monumental building heritage requires the use of innovative materials compatible with the high architectural value. The Fiber Reinforced Polymers (FRP) represent a valid alternative to traditional ones, and the carbon fiber sheets are very light and easy to glue to the masonry structures. However, the durability of the application of FRP sheets is still uncertain in the long time behavior, especially with regard to cyclic fatigue loads such as seismic ones. In this work an experimental analysis on a set of strengthened masonry walls under fatigue tests (loading and freezing-thawing test) has been carried out in order to evaluate creep effects. During cyclic tests in the laboratory it was possible to monitor the damage pattern through the acoustic emission (AE) technique. The AE monitoring is useful to estimate the amount of energy released from fracture propagation in the adherence surface between masonry and FRP sheet. The different phases of damage evolution are recognized through the analysis of AE data over time. In particular, the time dependence of AE counting number is useful to indicate the beginning of the unstable damage growth and predicts the possible failure of the specimens at the 80% of the test duration. Furthermore, a sudden decay in the AE frequency is detected during the last phase of the fatigue tests. These results illustrate the applicability and the advantages of AE technique for the monitoring of long-term damage growth in strengthened masonry.

scholarly journals Cyclical fatigue of annealed and of thermally tempered soda-lime-silica glass

2018 ◽  
Vol 165 ◽  
pp. 18003
Author(s):  
Jens Schneider ◽  
Jonas Hilcken
Keyword(s):  
Crack Growth ◽  
Silica Glass ◽  
Subcritical Crack Growth ◽  
Soda Lime ◽  
Cyclic Fatigue ◽  
Growth Exponent ◽  
Static Fatigue ◽  
Strength Increase ◽  
Soda Lime Silica Glass ◽  
Number Of Cycles

We present experimental and theoretical investigations on the cyclic fatigue of annealed and of thermally tempered soda-lime-silica glass. Static fatigue due to subcritical crack growth at micro cracks significantly decreases the macroscopic strength of soda-lime-silica glass and causes a time-dependent strength reduction. A subsequent thermal tempering process is typically used to induce residual surface compression stresses, which inhibit the crack growth of surface cracks, and corresponding bulk tension stresses. From the experimental results we show that the existing models for static fatigue used in linear elastic fracture mechanics can be used for the lifetime prediction of cyclically loaded annealed glass and thermally tempered glass, although the (static) crack growth exponent slightly decreases in cyclic loading. The equivalent duration of tensile stress at the crack tip of a micro crack governs the crack growths and not the number of cycles. The threshold for subcritical crack growth determined from the cyclic experiments was found to be in good agreement with data from literature. But unlike in strength tests with singular and quasi-static re-loading, it could be found that periodic loading with load free intervals does not lead to a strength increase by crack healing effects. Based on the results, an engineering design concept for cyclically loaded glass is presented.

scholarly journals Resistance to Cyclic Fatigue of Nickel-Titanium Files Immersed in Sodium Hypochlorite at Body Temperature

2020 ◽  
Vol 2020 ◽  
pp. 1-5
Author(s):  
Hind F. Abuhulaibah ◽  
Ammar AbuMostafa
Keyword(s):  
Stainless Steel ◽  
Body Temperature ◽  
Sodium Hypochlorite ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Control Group ◽  
Significant Drop ◽  
Number Of Cycles ◽  
Post Hoc ◽  
One Way Anova

Background/purpose. To assess the resistance to cyclic fatigue (CF) displayed by two nickel-titanium (NiTi) files, One Curve (OC) and ProTaper Gold (PTG), after their immersion in 2.5% sodium hypochlorite (NaOCl) solution at body temperature. Materials and Methods. Forty-five files from each brand were randomly assigned to three groups (n = 15) and subjected to the following: no immersion (control), 1-minute immersion, and 5-minute immersion in 2.5% NaOCl at 37°C. CF for all the files was tested within a well-lubricated stainless-steel artificial canal in a water bath at 37°C simulating body temperature. The procedure was video recorded, and the number of cycles to fracture (NCF) was calculated by multiplying the time taken to fracture, with the number of rotations per second. The data were analyzed for normality, and thereafter, one-way ANOVA with multiple Bonferroni was used as the post hoc test. Results. The resistance to CF of OC files was significantly higher than PTG files in all groups. In groups immersed in NaOCl for one minute, OC files showed significant drop in the CF resistance; PTG files showed a drop as well but not significantly. Both files demonstrated a significant drop in resistance to CF after immersion in NaOCl for five minutes compared to the control group. Conclusion. OC files were significantly more resistant to CF compared to PTG in all groups. Immersion in 2.5% NaOCl for 5 minutes significantly reduced the resistance to CF for all the files.

STRENGTH DEGRADATIONS FROM HERTZIAN CONTACT DAMAGES IN NITRIDED PRESSURELESS SINTERED SILICON NITRIDE CERAMICS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1819-1826 ◽  
Author(s):  
KIL HO GUAHK ◽  
IN SUB HAN ◽  
KEE SUNG LEE
Keyword(s):  
Silicon Nitride ◽  
Hard Spheres ◽  
Continuous Process ◽  
Theoretical Models ◽  
Strength Loss ◽  
Indentation Load ◽  
Hertzian Contact ◽  
Pressureless Sintering ◽  
Nitride Ceramics ◽  
Number Of Cycles

Strength degradations in silicon nitride ceramics subject to damage from contact with hard spheres are investigated. Strengths against indentation load, number of cycles in contact, or stress-rate parameter are reported and compared with theoretical models. Silicon nitride ceramics are prepared by nitride pressureless sintering (NPS) process, which process is the continuous process of nitridation reaction of Si metal combined with subsequent pressureless sintering. Microstructure characterizations reveal silicon nitride fabricated by NPS process exhibits a quasi-plastic mode, with continuous strength loss beyond a load above the onset of yield, and falloff at high number of cycles, > 105 at contact load, P = 950 N , using WC sphere r = 1.98 mm . The strength degradation is substantially faster by dynamic fatigue. Failures originated from contact damages, quasi-plastic microcrack zones, with developing radial cracks during strength test. The implication is that quasi-plastic damage of NPS silicon nitride itself can preserve benefits from the inherent higher damage tolerance at lower number of cycles of contacts, but fatigue susceptibility at multicycle contacts and lower stressing rate.

Accelerated Testing for Demonstration of Product Lifetime Reliability

2004 ◽  
Vol 47 (2) ◽  
pp. 48-58
Author(s):  
Milena Krasich
Keyword(s):  
Analytical Techniques ◽  
Accelerated Testing ◽  
Accelerated Life Test ◽  
Test Sequence ◽  
Detailed Knowledge ◽  
Test Duration ◽  
Reliability Growth ◽  
Product Reliability ◽  
Lifetime Reliability ◽  
The Individual

This test is designed with the assumption that product reliability is a combination of its individual reliabilities under various operational and environmental stresses and of the undetermined interaction among these stresses. A well-designed reliability test accounts for all cumulative operational and environmental exposures to the stresses that the product will encounter in field use. To determine the level and duration of each of the individual stresses to be applied in the test, it is assumed that the stresses are independent, and a separate factor is added to make up for any unknown stress interactions. The synergism or the test sequence is not disregarded, as it might be the factor contributing to lower demonstrated reliability. The individual stresses are accelerated to allow for reasonable and cost-effective test duration. This test design cannot be accomplished without detailed knowledge of the product's usage profile, sequence of operation, and expected use environments. The choice of test data analysis technique will depend on whether there were any test failures and on the type of failures. Where failures occur, acceleration factors are applied to determine the corresponding times to failure in field use. The test may be conducted as a reliability growth or a fixed duration test by applying the appropriate analytical techniques. The reliability growth technique may be preferred, as it normally yields tests of shorter duration. Accelerated reliability testing provides realistic lifetime reliability demonstration or validation and, if performed early enough, allows for design changes to improve product reliability. In designing any accelerated life test, caution should be exercised to avoid exceeding the environmental rating of the tested product, as high test acceleration can also induce failures that would normally not be expected to occur in the field life of the product. Also, acceleration factors must be carefully determined, preferably through accelerated testing to the failure mode of interest. Acceleration factors (their constants) may be different for different components of the tested products, thus care must be taken in their selection.

scholarly journals Impact of Peracetic Acid on the Dynamic Cyclic Fatigue of Heat-Treated Nickel-Titanium Rotary Endodontic Instrument

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Suhad Jabbar Hamed Al-Nasrawi ◽  
Zuha Ayad Jaber ◽  
Nibrass Talib Al-Quraine ◽  
Abtesam Imhemed Aljdaimi ◽  
Sattar Jabbar Abdul-Zahra Al-Hmedat ◽  
...  
Keyword(s):  
Fatigue Resistance ◽  
Peracetic Acid ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Control Group ◽  
Heat Treated ◽  
Respective Control Group ◽  
Before And After ◽  
Number Of Cycles ◽  
The Impact

Peracetic acid (PAA) is widely used as a sterilizing/disinfecting agent, and, in endodontics, it has been introduced as a promising irrigant in root canal treatment. It has been used at different concentrations to achieve various functions. However, endodontic instruments in contact with PAA of a certain concentration may affect their fatigue resistance. Therefore, the aim of this study was to investigate the impact of PAA on the cyclic fatigue resistance of three commercial heat-treated nickel-titanium (NiTi) rotary files. Three types of heat-treated NiTi rotary files were selected: One Curve (OC), ProTaper Gold (PTG), and Wave One Gold (WOG). Each type was divided into three subgroups (n = 6 for each file type): (1) untreated instruments; (2) files immersed in 0.002% PAA; and (3) files immersed in 0.35% PAA. The performance of each file type was tested in a simulated canal. The number of cycles to fracture (NCF) was determined to assess cyclic fatigue resistance of the files. Independent sample t-test was applied to compare each treated file within a subgroup with its respective control group, and one-way ANOVA was used for comparison among the main groups. All types of tested files revealed a significant decline in the cyclic fatigue resistance after exposure to 0.002% PAA except the PTG ( P = 0.209 ). After exposure of the files to a higher concentration (0.35% PAA), a dramatic reduction was demonstrated by all the groups. Before and after exposure of the files to PAA, PTG displayed the highest cyclic fatigue resistance, followed by the WOG, while the OC showed the lowest resistance. Exposure of heated-treated NiTi files to PAA in a relatively high or low concentration adversely affects the cyclic fatigue resistance. The PTG files demonstrated the best performance among the tested types and can be disinfected with 0.002% PAA for clinical purpose.

scholarly journals Comparison of cyclic fatigue resistance of XP-endo Shaper, HyFlex CM, FlexMaster and Race instruments

2018 ◽  
Vol 12 (3) ◽  
pp. 208-212 ◽  
Author(s):  
Mehmet Adiguzel ◽  
Ipek Isken ◽  
Ismail Ilker Pamukcu
Keyword(s):  
Body Temperature ◽  
Fatigue Resistance ◽  
Cyclic Fatigue ◽  
Radius Of Curvature ◽  
Rotary Instruments ◽  
Recorded Data ◽  
The Difference ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
One Way Anova

Background. The aim of this study was to compare the cyclic fatigue resistance of XP-endo Shaper, HyFlex CM, FlexMaster and Race rotary instruments at body temperature (37±1°C). Methods. Twenty XP-endo Shaper (#30/.01), 20 HyFlex CM (#30/.04), 20 FlexMaster (#30/.04) and 20 Race (#30/.04) instruments were tested at body temperature (n=20). The instruments were evaluated in artificial canals with a 3-mm radius of curvature and 60° angle of curvature to the center of the 1.5-mm-wide canal. Each instrument was rotated until fracture occurred and the number of cycles to failure (NCF) recorded. Data were analyzed using one-way ANOVA and Tukey HSD tests (P<0.05). Results. The difference in the NCF of all the instruments was statistically significant (P<0.05). The order of the instruments from the highest to the lowest NCF was as follows: XP-endo Shaper (3064.0±248.1), HyFlex CM (1120.5±106.1), FlexMaster (569.8±48.4) and Race (445.5±53.5). Conclusion. Under the limitations of the present study, XP-endo Shaper instruments were more resistant to cyclic fatigue than the #30/.04 nickel-titanium rotary instruments immersed in water at simulated body temperature.

scholarly journals Comparison of Cyclic Fatigue Resistance of Heat-Treated Nickel-Titanium Reciprocating Instruments at the Intracanal Temperature

2021 ◽  
Vol 25 (2) ◽  
pp. 87-91
Author(s):  
Neslihan Büşra Keskin ◽  
Gürkan Güneç
Keyword(s):  
Fatigue Resistance ◽  
Cyclic Fatigue ◽  
Radius Of Curvature ◽  
Heat Treated ◽  
Significant Difference ◽  
Number Of Cycles ◽  
The Moment ◽  
The One ◽  
Post Hoc ◽  
Different Characteristics

Summary Background/Aim: The aim of the present study was to compare the cyclic fatigue resistance of NiTi files running with reciprocal motion and having different characteristics (RPC Blue, WOG, EndoArt Wise Reciproc Gold, EndoArt Wise Reciproc Blue) at the intracanal temperature (35°C) by using NaOCl irrigation solution. Material and Methods: Totally 60 WaveOne GOLD (Dentsply-Sirona, Ballaigues, Switzerland), Reciproc Blue (VDW, Munich, Germany), EndoArt Wise Reciproc Gold, and EndoArt Wise Blue (Inci Dental Productions Co, Istanbul, Turkey) (n= 15) files were used. Each of the rotary files were tested at the intracanal temperature (35°C) using a dynamic model in a stainless-steel artificial canal with an inner diameter of 1.5 mm, 60° angle of curvature, and 2mm radius of curvature until fracture occurred. The device automatically stopped at the moment of fracture and the number of cycles to the fracture was calculated as per second. The lengths of fractured parts were measured using a digital microcaliper. The One-Way Analysis of Variance (ANOVA) and Tukey’s post-hoc tests were used for intergroup comparisons. Results: In 2 mm Radius of curvature, the EndoArt Wise Reciproc Blue group had a significantly higher time to fracture followed by the EndoArt Wise Reciproc Gold, Resiproc Blue, WaveOne Gold. No significant difference was found between EndoArt Wise Reciproc Gold and Resiproc Blue groups (P>0.05). Among the groups, there was no statistically significant difference in the lengths of fractured parts of the instruments (P> 0.05). Conclusions: EndoArt Wise Reciproc Blue files exhibited significantly higher cyclic fatigue resistance compared with other files tested in a 2-mm radius of curvature and a 60° angle in an artificial canal at the intracanal temperature.

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