Weibull Statistical Analysis Research Articles

Effect of heat‐treatment on the microstructure and room‐temperature mechanical properties of alumina–silica fiber

AbstractEffect of heat‐treatment (900°C∼1600°C) on the microstructure and mechanical properties of alumina–silica fiber was well investigated. The results indicated that the recommended temperature threshold for the use of the alumina–silica fiber was not more than 1100°C to maintain its mechanical integrity. Above this temperature, the elastic modulus of the fibers increased, and the tensile strength significantly decreased, mainly because of the transformation of the structure from γ‐Al2O3 and amorphous SiO2 to mullite. The tensile strength of the fiber was 0.87 GPa at 1200°C. Compared to the as‐received fibers, the strength retention was only 63.50%. Moreover, as revealed by Weibull statistical analysis, the formation of more defects due to mullite phase transformation resulted in higher dispersion of the fiber tensile strength. However, at this temperature, the Young's modulus of the fiber increased from the initial value 146.24 ± 5.19 GPa to 183.06 ± 5.83 GPa. Finally, the rate of mullite reaction was seen to be strongly temperature dependent. The higher the heat‐treated temperature, the shorter the time required for γ‐Al2O3 and amorphous SiO2 to completely transform into mullite grains.

A new proposal to reduce microplastics from cigarette butts: Production of eco-friendly fired clay bricks

It is estimated that approximately 1.2 million tons of cigarette butts (CBs) are introduced into the environment annually. The aim of this work is to analyze the incorporation of shredded CBs into bricks making by extrusion, for recycling and waste recovery purposes. Samples were prepared in compositions of 0 %, 1 %, 2.5 % and 5 % w/w CBs and fired at 700 ºC, 900 ºC and 1000 ºC. Density, water absorption, apparent porosity, linear firing shrinkage, flexural strength, compressive strength, thermal conductivity, diffusivity and sound transmission loss (TL) were determined. A total of 180 samples were taken, and a Weibull statistical analysis was performed for compressive strength. The results showed a decrease in density and an increase in water absorption and apparent porosity of the clay bricks produced by mixing 1–5 % CBs compared to the control bricks. Firing shrinkage decreased with 1 % CBs and up to 2.5 %, its was lower than standard samples. Samples with CBs showed fewer cracks than standard samples. Compressive strength increased with 1 % CBs incorporation for firing temperatures of 900ºC and 1000ºC compared to standard samples. It gradually decreased with larger amounts of waste. For flexural strength, up to 2.5 % CBs, the strength increased in most cases. In addition, there was an improvement in the thermal conductivity of bricks prepared with 5 % CBs and fired at 700ºC and 900ºC (0.46–0.58 W/mK) compared to the reference samples (0.51–0.76 W/mK). All waste samples showed higher TL than the reference pieces. Above 2.5 % CBs, TL decreased, but remained larger than the reference. Thus, the results showed that the use of CBs in fired clay bricks in amounts of up to 5 % w/w is capable of forming porosity in the samples, making the part lighter, in addition to possibly reducing thermal conductivity and sound transmission, being an economical and sustainable alternative for the final disposal of CBs.

Effect of Different Skew Angle on Tensile Fracture Behavior of SiC Fiber Monofilament

Abstract In fiber reinforced composites (FRP), silicon carbide fiber is indispensable. Its mechanical properties determine the performance of ceramic matrix composites. Therefore, the tensile and fracture behavior of silicon carbide fiber monofilaments should be studied in depth. In order to make the test results of fiber properties more accurate, this paper takes SiC fiber monofilament as the research object, carries out tensile tests at different deflection angles, and carries out WEIBULL statistical analysis and comparison of the data. The microscopic morphology of the tensile fracture of each single fiber was observed by SEM, and the change rule of the mechanical properties and fracture behavior of the fiber with the deflection angle was summarized, and whether the slight deflection affected the test results was explored. The results showed that: (1) The mechanical properties of SiC fiber monofilament decreased gradually with the increase of deflection angle, and the extent of decline gradually increased. (2) With the increase of deflection angle, the proportion of stepped fracture gradually increases, and that of flat fracture gradually decreases.

Dielectric, electrical and thermal properties of Sodium Molybdate-hexagonal Boron Nitride composites enabled by cold sintering

Advances in 5G and 6G communication technologies and their applications are in part limited by the capabilities of current electronic packaging materials, as expanded bandwidth is a pressing need for novel dielectric substrates capable of co-firing into packages and devices, characterized by low dielectric loss and enhanced thermal conductivity. This investigation provides further characterization in the dielectric, electrical and thermal conductivity properties over previously reported cold sintered composite of Sodium Molybdate Na2Mo2O7 (NMO) with hexagonal Boron Nitride (hBN), such as relative permittivity (εr) and dielectric loss (tan δ) values at high frequencies of 75–110 GHz, electrical resistivity (ρ) fitting to percolation theory, Weibull statistical analysis of electrical breakdown strength (Eb) and its anisotropic thermal conductivity (κ) influenced by the filler's crystal structure. The cold sintered composites were systematically characterized with respect to filler volume fraction, temperature, and frequency. The findings in this analysis position engineered composites as a promising alternative for microwave substrate materials, with using a densification method that limits interactions and maximizes densification, hence the demonstration with cold sintering.

Evaluation of bond strength between zirconia milled ceramic material and veneered dental porcelain.

This study aimed at examining the bond strength between zirconia and ceramic veneer, following the ISO 9693 guidelines. A total of fifty specimens of zirconia/ceramic-veneer system were produced using two commercial zirconias (VITA YZ-HTWhite and Zolid HT+ White, referred to as Group A and Group B, respectively) and a ceramic-veneering material (Zirkonia 750). The microstructure (via x-ray diffraction analysis, XRD and Secondary Electron mode, SEM) and the mechanical properties (via 3-point bending tests) of the two groups were assessed. Then, experiments were conducted according to the ISO 9693 and conventional protocols applied for producing zirconia/ceramic-veneer restorations. Bond strength values, measured by 3-point bending tests, were 34.42±7.60MPa for Group A and 31.92±6.95MPa for Group B. SEM observations of the cohesively fractured surfaces (on the porcelain side) and the examination for normality using the Shapiro-Wilk test suggested the use of Weibull statistical analysis. Median strength (σ50%) for Group A and Group B was 34.76 and 32.22MPa, while the characteristic strength (σ63.2%) was 35.78 and 33.14MPa, respectively. The Weibull modulus disparity between groups (12.69 and 13.07) was not significant. Bond strength exceeded the ISO 9693 minimum of 20MPa, suggesting satisfactory strength for clinical use.

Fabrication of glass to PLA joints with an intermediate aluminum layer by using low-cost industrial nanosecond IR fiber lasers

We present an adhesive free, low-cost and effective solution for joining of thermoplastic additive manufactured parts to glass using an industrial nanosecond IR pulsed fiber laser. We demonstrate the potential of the method by means of laser joints of glass to Polylactic Acid (PLA). The glass to PLA joints are realized via Laser Transmission Welding (LTW) and Laser Direct Welding (LDW) using an intermediate sacrificial thin layer of aluminum. The laser joints are compared with adhesive glass to PLA joints. The mechanical testing involves a thorough strength evaluation by using block shear test method, demonstrating the superior performance of laser-welded joints over conventional adhesive alternatives. The results of these shear tests reveal a remarkable 565 % improvement in shear strength in comparison to the adhesive joints (maximum shear strength of laser bonds: 9.57 MPa). Furthermore, a Weibull statistical analysis is applied to assess the reliability of the joints, disclosing a very high survival probability of the samples under a loading of 4.5 MPa as well as a σ0 (stress for which the 1/e (37 %) of the samples survive) of 8.15 MPa.

Comparison of subcritical growth parameters of a Y-TZP obtained via cyclic or dynamic fatigue tests

ObjectiveThe objective of this study was to 1) compare the stress corrosion coefficient (n) of a Y-TZP obtained by two fatigue tests: cyclic and dynamic and 2) evaluate the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and slow crack growth. MethodsA total of 145 Y-TZP specimens were produced in accordance with the manufacturer's instructions. These specimens, measuring 4.0 × 3.0 × 25.0 mm, were used for dynamic (n = 70) and cyclic fatigue tests (n = 75). The specimens were obtained from CAD/CAM blocks, sectioned, and sintered in a furnace at 1530 °C with a heating rate of 25 °C/min. They were tested in their "as-sintered" form without any additional surface treatment. The fatigue tests were conducted using a four-point bending to obtain the slow crack growth parameters (n). The cyclic fatigue test was also conducted in two frequencies (2 and 10 Hz), using stress levels between 350 and 600 MPa. Data from these tests were analyzed using ASTM C 1368–00 formulas and Weibull statistics. Scanning electron microscope (SEM) was used for fracture surface analysis to identify the origin of the fracture. Critical defect size was measured and used, along with flexural strength values, to estimate fracture toughness. Dynamic fatigue test data were used to obtain subcritical crack growth (SCG) parameters and perform Weibull statistical analysis. The cyclic fatigue data were used in the General Log-linear Model equation using the ALTA PRO software. Data were analyzed using one-way ANOVA followed by Tukey post-hoc tests and Student's t-test at a significance level of p ≤ 0.05. ResultsIn the dynamic fatigue test, the values obtained for σfo and n were 667 and 54, respectively. This parameter indicates how the strength of the material diminishes over time due to internal cracks. The Weibull parameters obtained from the same test results were m = 7.9, σ0 = 968, 9 and σ5% = 767, which indicates the reliability of the material. The Weibull parameters obtained by cyclic fatigue were statistically similar for the two frequencies used, the m* was 0.17 (2 Hz) and 0.21 (10 Hz); characteristic lifetimes (η) were 1.93 × 106 and 40,768, respectively. The n values obtained by cyclic fatigue were 48 and 40 at frequencies of 2 and 10 Hz, respectively. There was no effect of the frequency, the stress level or the interaction of the two in the Y-TZP lifetime, when analysed by General Log Linear Model. Significancethe n values obtained by cyclic and dynamic fatigue tests showed no statistically significant difference and the effect of frequency in the characteristic lifetime and the existence of interaction between the cyclic fatigue and subcritical growth were not observed in the tested specimens.

Effect of (0°/90°) and (+45°/–45°) plies position on the failure modes and acoustic signals in carbon fiber reinforced polymer laminates under quasi-static tensile loading

This experimental work investigates the effect of (0°/90°) and (+45°/–45°) plies position on failure modes and acoustic signals in carbon fiber reinforced polymer (CFRP) laminates under quasi-static tensile loading. Five stacking sequences, namely [(0°/90°)2/(±45°)2]S, [(0°/90°)/(±45°)/(0°/90°)/(±45°)]S, [(0°/90°)/(±45°)2/(0°/90°)]S, [(±45°)/(0°/90°)/(±45°)/(0°/90°)]S, and [(±45°)2/(0°/90°)2]S are fabricated by vacuum bagging process. Digital image correlation technique is used to establish strain and displacement fields in CFRP laminates during the tensile loading. Additionally, in situ acoustic sounds produced during specimen failure under tensile testing are correlated to crack formation. Finally, the two-parameter Weibull statistical analysis is employed to assess the reliability and repeatability of the experimental data.

Electrochemical Metallic Ion Migration Property of Multi-Layer Ceramic Capacitor for Car Electronics

As the use of electrical components in automobiles increases, the occurrence of electorchemical metallic ion migration (ECM), which is one of the causes of various failures in electrical components, is also increasing. Therefore, in this study, 1608 MLCC chip components were used for temperature-humidity-bias (THB) tests at 65℃/85%R.H., 65℃/95%R.H., and 85℃/85%R.H. Three types of THB tests were conducted for 2,934 h. For the THB test, voltages of 3.3, 12 and 24 V were applied, and real-time resistance of MLCCs were measured at every 40 mms intervals. During the ECM test, the ECM occurrence time was measured by monitoring the insulation resistance of between the electrode of MLCC under each THB test conditions. The failure criteria for ECM occurrence were 106 Ω or less, and the time when it occurred more than twice was judged as the ECM failure criteria. Based on the ECM occurrence time, the mean life time of ECM occurrence according to temperature, humidity and applied voltage conditions was derived through Weibull statistical analysis. Finally, we compared and analyzed the sensitivity of MLCC components to ECM generation under use environment of automotive electronics.

Equibiaxial flexural strength determination of UO2 using a ball-on-ring test

To increase nuclear fuel performance and reliability, their mechanical properties require an accurate and statistically relevant assessment. Biaxial flexural strength tests provide an alternative to bend bar techniques for assessing mechanical behavior; namely, the transverse rupture strength (TRS) of ceramic samples. Biaxial test samples require simple geometries and minimal surface preparation, reducing fabrication costs and handling hazards. This study investigated the TRS of polycrystalline UO2 fuel forms at room temperature using a ball-on-ring test fixture. Pellets were fabricated from UO2 powder using conventional powder processing and sintering techniques. The TRS and Weibull parameters were obtained through Weibull statistics on over 60 UO2 samples tested under equibiaxial flexure. The larger sample size in this study enabled a more robust Weibull statistical analysis than alternative test methods, which may not capture the stochastic failure of typical ceramics. Furthermore, two different loading ball diameters were employed to assess the impact of contact damage on fracture strength. While Hertzian contact damage was observed with the smaller loading ball, the fracture strength remained unaffected. A fracture analysis of the tested UO2 samples indicated a mixture of intergranular and transgranular fracture that transitions to transgranular fracture with increasing distance from the fracture origin. The characteristic strength of the combined data sets was determined to be 148 MPa, and the Weibull modulus was determined to be 9.1. The TRS values and Weibull parameters were close to values found in the literature for alternative testing techniques using samples with similar microstructure and density. The findings in this study validate the ball-on-ring method used to obtain the TRS of UO2 with a sample geometry more representative of nuclear fuels. Additionally, experimental TRS results from this study can be implemented in modeling codes to predict fuel performance, which is critical to fuel burnup extension and advanced nuclear fuel technologies.

Response of treated recycled aggregate concrete against low-velocity impact loading: Experimental and Weibull statistical analysis

Sustainable and ecologically friendly building practices require increased conservation and recycling of renewable resources. Because of the rise in development and demolition worldwide, using recycled construction materials as aggregate in new concrete can be an essential step towards making the material more environmentally friendly. Removing or fortifying the adherent mortar is the main technique to advance the poor standard of recycled concrete aggregate, which the adherent mortar causes. The study examines the impact performance of recycled aggregate concrete (RAC) comprising different replacement levels (10, 20, 30 and 40 %) of recycled aggregate (RA). Three concentrations (10, 15, and 20 %) of MgSO4 solution were used to pre-treat the RA and subjected to three different immersion times of 5, 10, and 15 days. For this, thirty-seven mixtures were prepared with the combination of RA contents, MgSO4 concentrations and immersion periods. The study was divided into three phases. The physical properties of RA, slump, and compressive strength tests were studied in the first phase. The best thirteen mixtures that exhibited expectational results in the first phase are put forward to the second phase. The effect of RA content, MgSO4 concentration and immersion periods on the impact strength was studied in the second phase. Besides, the differences in the impact test results were studied by Weibull distribution and results were displayed with regard to the probability of survival. The final phase studied the impact response of reinforced concrete slabs under a large mass impact. The findings reveal that the five days of immersion in a 10 % MgSO4 solution has been shown to enhance the impact strength of RAC, whereas a replacement ratio of 20 % is recommended.

Translucent multi-layered zirconia: Sandblasting effect on optical and mechanical properties.

The aim of this study was to evaluate the influence of the sandblasting treatment on the microstructure, optical and mechanical properties of multi-layered translucent zirconia. Samples of yttria-stabilized zirconia were prepared by stratifying four layers (L1, L2, L3 and L4) of ML-type KATANA multi-layered monolithic discs, whose surfaces were then sandblasted with alumina particles (110µm and 0.2MPa) in order to evaluate its effect on the presence of different crystalline phases as well as on the optical and mechanical properties of each of the four layers. The optical characterization was carried out by measuring the reflectance spectrum and colorimetric parameters by UV-Vis spectrophotometric analysis and the transmittance curves were indirectly obtained using the Kubelka-Munk model (KM). Microstructural, structural, mechanical and roughness characterizations were also performed using SEM, XRD, biaxial flexural strength B3B, and light interferometry, respectively RESULTS: According to the KM model there are different degrees of translucency between the upper and lower layers of the monolithic discs, but there was no influence of the Al2O3-sandblasting treatment on this optical property. The disk pigmentation causes greater absorption of light below 600nm, decreasing the transmittance rate to values below 25% in this region of the spectrum. The yellowing index presented higher values for inner disk layers L3 and L4, in agreement with the highest values of the light absorption coefficient K observed for these layers. The roughness of the samples did not change significantly with the surface treatment performed and the sandblasting did not result in new crystalline phases. SEM analysis showed the presence of different grain sizes in all layers analyzed, being related to the co-occurring presence of cubic (c-ZrO2) and tetragonal (t-ZrO2) phases in similar contents (∼ 50wt%). The Weibull statistical analysis, in turn, showed an increase in the Weibull characteristic stress value (σ0) for most layers subjected to sandblasting, except for the second layer (central region of the disk). It was also verified an increase in the value of the structural reliability of the material (m), referring to the samples of the central region of the disc (L2 and L3 layers) after sandblasting. The pigmentation in the disk causes a decrease of the transmittance rate to values well below 25% in the region of the spectrum 400-600nm and the inner layers (L3 and L4) have even lower transmittance than the outer layers in this spectrum range. Although the CR index indicates variation related to the Al2O3-sandblasting treatment, the transmittance spectra of KM model show that the sandblasting did not cause a significant change in the transmittance rate of the four analyzed layers. Also, there is no significant difference in the light scattering of the different layers of the disc, either before or after Al2O3-sandblasting treatment.

Ballistic Performance, Thermal and Chemical Characterization of Ubim Fiber (Geonoma baculifera) Reinforced Epoxy Matrix Composites.

The search for unexplored natural materials as an alternative to synthetic components has driven the development of novel polymeric composites reinforced with environmentally-friendly materials. Natural lignocellulosic fibers (NLFs) have been highlighted as potential reinforcement in composite materials for engineering applications. In this work, a less known Amazonian fiber, the ubim fiber (Geonoma baculifera), is investigated as a possible reinforcement in epoxy composites and was, for the first time, thermally characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, its chemical structure was elucidated by Fourier transform infrared spectroscopy (FTIR). Ballistic tests were also performed against the threat of a 7.62 mm high-speed lead projectile. The results were statistically analyzed by the Weibull statistical analysis method. FTIR analysis showed the functional groups normally found for NLFs highly rich in cellulose, hemicellulose, and lignin. The TGA/DTG results showed the onset of thermal degradation for the composites (325~335 °C), which represents better thermal stability than isolated ubim fiber (259 °C), but slightly lower than that of pure epoxy (352 °C). The DSC results of the composites indicate endothermic peaks between 54 and 56 °C, and for the ubim fibers, at 71 °C. Ballistic tests revealed higher energy absorption in composites with lower fiber content due to the more intense action of the brittle fracture mechanisms of the epoxy resin, which tended to dissipate more energy. These failure mechanisms revealed the presence of river marks, cracks, and broken fibers with a detachment interface. These results may contribute to the production of ubim fiber-reinforced composites in engineering applications, such as ballistic armors.

The combined impact of voids and thermal aging on the mechanical reliability of epoxy resin evaluated by statistical analysis

Epoxy resin is widely used in electrical engineering, and its long-term mechanical performance is directly related to the durability of the equipment. The issue might be aggravated when voids are introduced during manufacturing process and when the material is used under high temperature environment. This study aims to precisely reveal the effects of voids and thermal aging on mechanical strength of epoxy resin. Specimens with low and high void content were prepared and thermally aged at 105 ℃ for various lengths of time. Tensile test, scanning electron microscope (SEM) and the finite element simulation were employed to investigate the failure mechanism. The chemical change due to thermal aging was studied by Fourier Transform Infrared Spectroscopy (FTIR). The results illustrate the crack is initiated at the edge of the void due to stress concentration. With the increased void content, there was a slight decrease in the mean tensile strength but a large (108%) increase in the standard deviation. During thermal aging, the chain scission and oxidation were observed via FTIR, along with the inhomogeneity of chemical compounds. A defect density parameter ρ was proposed and integrated into the Weibull distribution to study the synergistic effect of voids and thermal aging on the mechanical properties. This statistical analysis quantitatively describes the decrease in average tensile strength and the increase in data scattering with ascending defect density ρ, due to higher void content and thermal aging. When 0.0005% failure probability is required, the predicted failure stress is significantly reduced from 49.6 MPa to 1.18 MPa for the specimen with high level of void after the long-term aging. In this work, we demonstrate that Weibull statistical analysis can quantitatively evaluate the impact of void defects and thermal aging and provide strength design for the high-reliability epoxy material.

Extraction and characterization of novel lignocellulosic fibers from Centaurea hyalolepis plant as a potential reinforcement for composite materials

The aim of this investigation is to evaluate the use of new lignocellulosic fiber extracted from Centaurea hyalolepis plant as a potential reinforcement for light-weight composite applications. In this study, anatomical structure and morphological surface of Centaurea hyalolepis fiber were conducted. The physical-chemical, thermal, crystalline,mechanical, characteristics of extracted fibers were also examined using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and tensile test. ATR-FTIR analysis confirmed the existence of the main components of lignocellulosic fiber (lignin, cellulose, and hemicellulose). XRD revealed the presence of cellulose with a crystallinity index of 57.93%.By densimetry, the density of Centaurea hyalolepis was determined as 1.13 g/cm3. The Centaurea hyalolepis was found to be thermally stable up to 271°C. The kinetic activation energy was determined as 115.943 kJ/mol. Tensile tests revealed that the mean tensile strength and Young’s modulus of Centaurea hyalolepis fiber were about 372,5 MPa and 9.036 GPa respectively. Because of the dispersion in the experimental tensile results, the Weibull statistical analysis with two parameters was carried out. Regard these findings, the Centaurea hyalolepis fibers can be a suitable candidate for low density polymeric composites reinforcement.

Material characterization of coconut midrib strip - a sustainable material for ground improvement

The tensile behavior of soil is of utmost importance in civil engineering as tensile failure can cause cracking earthen dam construction and road pavement subgrade. To address this issue, natural fiber reinforced geotextiles are increasingly being utilized in various geotechnical applications. This study aims to investigate the effect of gauge length, strain rate, and Young's modulus of a single coconut midrib taken from a leaf by conducting a series of uni-axial tensile strength tests. Additionally, the characteristic tensile strength is determined using Weibull statistical distribution analysis to evaluate the consistency of test results. Overall, this article contributes to a better understanding of the tensile behavior of natural fiber reinforced geotextiles and can aid in the design and construction of geotechnical structures that are resistant to tensile failure. According to the study's findings, an increase in gauge length and strain rate led to a decrease in the Weibull modulus. Moreover, for larger gauge lengths and strain rates, inconsistent variations in the coefficient of variation were observed. The experiments also showed that midribs immersed in water for seven days exhibited lower tensile strength, and consistent outcomes were obtained when using a gauge length of 150 mm and a strain rate of 0.3%/min. These results contribute to a better understanding of the factors that affect the tensile behavior of coconut midribs, particularly when used in geotechnical applications, and can inform the selection of appropriate testing parameters for future studies.

The Cyclic Fatigue Resistance of Different Lengths of CM Gold Wire and CM Blue Wire NiTi Alloy Endodontic Rotary Files: An In Vitro Study

Background: The objective of the present study was to measure and compare how the length of CM Gold Wire and CM Blue Wire NiTi alloy endodontic rotary files impacts their resistance to cyclic fatigue. Methods: A total of 40 sterile endodontic rotary files were chosen and allocated to the following study groups: (A) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 31 mm in length (n = 10); (B) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 25 mm in length (n = 10); (C) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 21 mm in length (n = 10); and (D) 25.06 CM Blue wire NiTi alloy endodontic rotary files, 17 mm in length (n = 10). A specialized device was designed using artificial root canal systems made from stainless steel for the dynamic cyclic fatigue tests, with an apical diameter of 250 µm, curvature angle of 60°, radius of curvature of 5 mm, lengths of 31, 25, 21, and 17 mm, and a 6% taper. An individual operator determined failure of the endodontic rotary instrument through direct observation and the tests were filmed so as to precisely measure the exact time to failure. The results were analyzed using ANOVA and Weibull statistical analysis. Results: The results found statistically significant differences across all study groups (p < 0.05). Conclusions: Rotary file length is inversely proportional to the cyclic fatigue resistance of the 25.06 CM Gold wire NiTi alloy at 31 mm, 25 mm, and 21 mm in length and of the 25.06 CM Blue wire NiTi alloy 17 mm length endodontic rotary files, with a greater length contributing to lower resistance to cyclic fatigue.

A Data-Based Reliability Analysis of ESP Failures in Oil Production Wells

Electrical Submersible Pumps (ESPs) are one of the most widely used artificial lift methods in the petroleum industry. However, ESP failures are unanticipated and common occurrences with significant financial impacts for the operators. Analysis of the ESP performance and failures are essential in its design and optimization. This paper presents a statistical approach for diagnosing and evaluating the root causes of ESP failures. The analysis is based on the field data gathered from the surface and downhole ESP monitoring equipment over five years of production of 10 wells. Electrical failures are the most common general cause of ESP failures, accounting for 61% of all failures, followed by motor failure and gas locking. Specifically, power failure, under-voltage, voltage unbalance, and motor underload are the most common occurrences. The data trends are analyzed for the two weeks before each specific failure, and conclusions are made on the warning signs to predict failures. In addition, a Weibull statistical analysis model is constructed to evaluate the reliability features and estimate the ESP failure probability, allowing operators to perform preventive maintenance. The results provide guidelines for ESP operations and contribute to reducing or preventing ESP downtimes and operating costs.

Evaluation of the Wind Power Potential in the Northeast of Chad

Chad has done the study and development of renewable resources a priority in its energy mix. Wind energy is one of the renewable sources that can help Chad to develop rural areas and preserve the environment. This study presents from data obtained from NASA, the wind characteristics in Amdjarass, and Fada over thirty (30) years. The wind distribution density and energy potential at different heights were evaluated using the Weibull statistical analysis method. The aim of this paper is to evaluate the wind energy potential of two important sites in Chad. The study shows that over the 30 years, the mean annual wind speeds vary randomly between 4.7 m/s and 5.4 m/s over an average period of 2 years. Eight months of good average wind speeds were recorded, ranging from 5.01 m/s to 6.31 m/s at Amdjarass and 4.92 m/s to 5.70 m/s at Fada. The 04 months of low velocities observed are in the range of 3.211 m/s - 4.064 m/s at Amdjarass and 3.504 m/s - 4.516 m/s at Fada. The power density varies between 21.53 W/m2 and 111.89 W/m2 in Amdjarass, while in Fada, it varies from 19.85 W/m2 to 86.92 W/m2.

Nanoindentation responses of black anodic coating on additively manufactured Al–10Si–Mg alloy

The present work reveals the variation of nanomechanical properties (nanohardness-H and modulus-E) of black anodic coating on additively manufactured Al–10Si–Mg alloy. The plan-section of the coating has mud-crack-like morphology with various nano/micro-pores, micro-channels, and irregularities. In contrast, the cross-section possesses a compact morphology with minimum surface/sub-surface defects like micro-cracks or irregularities. The H and E are derived from nanoindentation experiments using Berkovich tip at loads 10–50 mN. The nanomechanical properties are higher across the cross-section than the plan section of the coating, attributing to the difference in morphology between the plan- and the cross-sections. Due to characteristic porosities, defects, and nano/micro-cracks in the anodic coating, Weibull statistical analysis has been employed to rationalize the scatter in nanoindentation-based data. For both plan and cross-sections, the H and E values decrease as the indentation load increases from 10 to 50 mN, confirming the indentation size effect (ISE). The well-established Meyer's law, Hays–Kendall approach, elastic recovery model, proportional specimen resistance (PSR) model and the modified PSR model have been used to thoroughly analyze the ISE characteristics.