Rupture Curves Research Articles

Time-dependent plastic behavior of bacteria leading to rupture

A study of the mechanical response of bacteria is essential in designing an antibacterial surface for implants and food packaging applications. This research evaluated the mechanical response of Escherichia coli under different loading conditions. Indentation and prolonged creep tests were performed to understand their viscoelastic-plastic response. The results indicate that varying loading rates from 1 μm/s to 5 μm/s show an increase in modulus of 182% and 90%, calculated in the loading and unloading cycles, respectively, and a decrease in adhesion force by 42%. However, on varying loads from 5 nN to 25 nN, nominal change is observed in both modulus and adhesion force. The rupture curve at 100 nN load shows elastic and a small plastic deformation accompanied by a sharp peak indicating the cell wall rupture. The rupture force at the peak was found to be 34.38 ± 5.15 nN, irrespective of the loading rate, making it a failure criterion for bacteria rupture. The creep response of bacteria increases (for 6 s) and then remains constant (for 15 s) with time, indicating that a standard linear solid (SLS) model applies to this behavior. This work attempts to evaluate the mechanical properties of E. coli bacteria focusing on its rupture by contact killing mechanism.

Thermal aging of Gr. 91 steel in supercritical thermal plant and its effect on structural integrity at elevated temperature

In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 °C for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

Remaining Creep Life Prediction Method for In-Service Boiler Pipe Weldment Using Small Scale Specimen

Abstract The author proposes a remaining creep life prediction method for weldment of Grade 91 steel using a small specimen taken not from the weldment but from the base metal. Analysis of creep data obtained from long-term used steels indicates that the shape of the master rupture curve given by the Larson-Miller parameter remains almost the same regardless of the heat-to-heat variation of the creep life of the steels, and the life of each steel can be expressed by the parallel displacement of the master rupture curves along the abscissa direction. Therefore, we can estimate the life of used steels with only one datum even if it is obtained with a short-time creep test. This approach of extrapolation is effective for the proposed method because the number of test specimens taken from the pipe is at most two or three in power plants in Japan. The results of investigation of the relationships among creep strength, deformation, and ductility suggest that the creep deformation property primarily determines the creep life of the materials used in this study. Finally, the proposed method is applied to the in-service boiler pipe weldment of Grade 91 steel, and its features are described in comparison with the conventional life assessment method.

Adsorption study of non-ionic ethoxylated nonylphenol surfactant for sandstone reservoirs: Batch and continuous flow systems

The use of surfactants in Enhanced Oil Recovery (EOR) projects has been extensively studied. The process of adsorption of these substances in the reservoir rocks is strictly important, since it provides a change in their wettability, allowing an increase in the oil recovery factor. However, the understanding of how the adsorption of surfactants occurs and the main phenomena involved in this process is still widely discussed. Thus, the objective of this work is to investigate and elucidate the adsorption behavior of surfactants of the Nonylphenol ethoxylated family (10EO, 40EO and 100EO) in sandstone rocks. It was possible to verify that the higher the degree of ethoxylation of the surfactant solutions used, the lower the adsorption capacity. The batch adsorption presented the Redlich-Peterson model as the answer that best determines the adsorption isotherm, where the adsorption occurs in monolayer and multilayers. As for the study of adsorption flow, the Chu logistic model is recommended, to determine the necessary parameters of the rupture curves and apply the other models to calculate the adsorption capacity. The Thomas and Yoon-Nelson models showed adsorption capacity values with a mean relative error of 10.38 % and 10.75 %, respectively.

Creep rupture prediction using constrained neural networks with error estimates

ABSTRACT Creep rupture prediction for materials serving in fossil-fired power plants has been a critical issue for many decades. There are many empirical methods with several fitting or adjustable parameters that have been proposed for creep rupture strength prediction. Fundamental models based on the microstructure mechanism have been developed but are not widely used due to their complicated nature. Neural Network (NN) is a powerful tool for handling complicated mechanical behaviour; However, unexpected results and excessive errors can be generated. To avoid this, constraints on the first and second derivatives of the creep rupture curves have been introduced and combined with the NN. With the constrained NN models, extrapolated results with controlled errors can be obtained, which is verified by methods for error analysis. Furthermore, ECCC Post Assessment Tests (PATs) 1.1 to 2.2 are satisfied. The methods are illustrated for two creep-resistant austenitic steels Sanicro 25 and Super304H.

Error estimates in extrapolation of creep rupture data and its application to an austenitic stainless steel

ABSTRACT Although fundamental models have been developed for time extrapolation of creep rupture data, empirical methods are still dominating. One limitation with the empirical methods is that no systematic way of estimating the error in the results has been available. To remove this limitation, formulae for error estimates are developed in the present paper. Error estimates are first established for single creep rupture curves. Then error estimates are formulated for creep data at several test temperatures assessed with Time-Temperature Parameters (TTPs). A new requirement is introduced in the optimization, namely that the first and second derivatives of the rupture curve should be negative, referred to as constrained. The constrained optimization significantly reduces the error in the extrapolated values. The constrained procedure is applied to the austenitic steel Sanicro 25. The procedure gives quite a stable result, and the post-assessment tests developed by ECCC are satisfied automatically for five common TTPs tested.

Creep Deformation Property and Creep Life Evaluation of Super304H

Abstract Creep deformation behavior, creep strength property, and microstructural evolution during creep exposure were investigated on Super 304H steel for boiler tube. In the high stress and lower temperature regime, creep rupture strength of Super 304H steel is higher than that of SUS304H steel. The slope of stress versus time to rupture curve of Super 304H steel, however, becomes steeper with increase in creep exposure time and temperature, and the creep rupture strength of Super 304H steel becomes closer to that of SUS304H steel after the tens of thousands of hours at 700 °C and above. In the short-term, at 600 °C, creep rupture ductility increases with increase in creep rupture life. However, it tends to decrease after showing the maximum value and the creep rupture ductility decreases with increase in temperature. The complex shape of creep rate versus time curves, with two minima in creep rate, was observed at 600 °C. Several type precipitates of niobium carbonitride (Nb(C,N)), Z phase (NbCrN), and copper were observed in Super 304H steel, as well as M23C6 carbide and sigma phase observed in SUS304H steel. The change in slope of stress versus time to rupture curve is caused by disappearance of precipitation strengthening effect during creep exposure. Accuracy of creep rupture life evaluation was improved by stress range splitting method which takes into accounts of the change in slope of stress versus time to rupture curves was demonstrated.

Thermal Analysis and Creep Lifetime Prediction Based on the Effectiveness of Thermal Barrier Coating on a Gas Turbine Combustor Liner Using Coupled CFD and FEM Simulation

Thermal barrier coating (TBC) plays a vital role in the gas turbine combustor liner (CL) to mitigate the internal heat transfer from combustion gas to the CL and enhance the parent material lifetime of the CL. This present study examined the thermal analysis and creep lifetime prediction based on three different TBC thicknesses, 400, 800, and 1200 μm, coated on the inner CL using the coupled computational fluid dynamics/finite element method. The simulation method was divided into three models to minimize the amount of computational work involved. The Eddy Dissipation Model was used in the first model to simulate premixed methane-air combustion, and the wall temperature of the inner CL was obtained. The conjugate heat transfer simulation on the external cooling flows from the rib turbulator, impingement jet, and cross flow, and the wall temperature of the outer CL was obtained in the second model. The thermal analysis was carried out in the third model using three different TBC thicknesses and incorporating the wall data from the first and second model. The effect of increasing TBC thickness shows that the TBC surface temperature was increased. Thereby, the inner CL metal temperature was decreased due to the TBC thickness as well as the material properties of Yttria Stabilized Zirconia, which has low thermal conductivity and a high thermal expansion coefficient. With the increase in TBC thickness, the average temperature difference between the TBC surface and the inner metal surface increased. In contrast, the average temperature difference between the inner and outer metal surfaces remained nearly constant. The von Mises equivalent stress, based on the material property and thermal expansion coefficient, was determined and used to find the creep lifetime of the CL using the Larson–Miller rupture curve for all TBC thickness cases in order to analyze the thermo-structure. Except in the C-channel, the increasing TBC thickness was found to effectively increase the CL lifespan. Furthermore, the case without TBC was compared with the damaged CL with cracks due to thermal stress, which was prevented by increasing TBC thickness shown in this present study.

Computational Simulation of Filters Used in the Removal of Heavy Metals Using Rice Husks

The biofiltration technique is of great importance for the removal of heavy metals. In the present work, a laboratory-scale biofilter was modeled using rice husk as a filter material. The Wolborska model was used to know the dimensions necessary for the biofilter to function. The Langmuir and Freundlich isotherms were performed to quantify the filter adsorption process, showing that the Langmuir isotherms are the ones that present the highest correlation coefficient and best represent the removal process of Cd (II), Cu (II) and Cr (VI). According to the Langmuir isotherms, the maximum operating temperature allowed for this model was chosen, which was 303.15 K, because it presents the maximum removal of heavy metals. Regarding the pH variations for Cd (II) and Cu (II), the maximum removal was presented with a pH = 9.0 and for Cr (VI) with a pH = 3.0 the maximum removal was presented. According to the rupture curves, the blocking times were obtained for each height: for Cd (II) the highest tb for h = 0.55, Cu (II) the highest tb for h = 0.40 and for Cr (VI) the highest tb for h = 0.40.

Microstructural stability of ODS steel after very long-term creep test

Microstructure of 9Cr oxide dispersion strengthened (ODS) tempered martensitic steel (TMS) cladding and 12Cr-ODS ferritic steel cladding after very long-term internal pressurized creep tests was observed. The creep test conditions were 700°C for 46,504 h and 750°C for 45,550 h for 9Cr-ODS TMS and 700°C for 30,116 h for 12Cr-ODS ferritic steel. The stability of martensite and ferrite matrix structure, including carbide distribution, dislocation density, and lath boundary, and that of nano-particle distribution were investigated. It was confirmed that the nano-particles were stably present during the high-temperature and very long-term stress loading environment, contributing to the prevention of matrix structure degradation. The results of observation are consistent with the fact that the 9Cr-ODS TMS and 12Cr-ODS ferritic steel exhibit excellent creep strength and show no reduction in the slope of the stress versus time to rupture curve over a significantly extended period of time in the creep test.

In-vitro fatigue and fracture performance of three different ferrulized implant connections used in fixed prosthesis

Background/purposeThe aim of the present in vitro study was to evaluate fatigue resistance of dental fixtures in three different types of fixture/abutment finishing line.Materials and methodsTransmucosal dental implants, with or without ferrulized neck, underwent fatigue tests (static and dynamic load) using the following standard protocol: UNI EN ISO 14801:2016. Two types of loading devices (screw- or cement-retained restoration) were also tested, and fatigue cycle tests were run to failure. Data of static and dynamic load tests were analyzed by proper statistical methods.ResultsFollowing standard protocol for fatigue testing, the ILC type (Implant Level with ferrulized neck and cement-retained crown) showed a non-significant but higher Ultimate Failure Load (UFL = 445.7 N) compared to AL type (Abutment Level without ferrule effect, 421.6 N) and ILS type (Implant Level with ferrulized neck and Screw-retained crown, 362.8 N). No fracture of the titanium-base was registered in the tested specimens during the static loadings. Permanent deformations of the materials were observed.ConclusionThe number of cycles to either fracture or deformation (higher than 4 mm) occurring during fatigue tests showed that the stress rupture curve of the materials in group ILS appeared to be significantly different from those of the ILC and AL groups (p-values < 0.01): much higher life of one-half order of magnitude.

Biossorção de Azul de Metileno empregando serragem do gênero Apuleia Leiocarpa

A adsorção tem se destacado como técnica promissora para a remoção de corantes de efluentes têxteis. O objetivo deste trabalho foi estudar a utilização do pó de serragem (PS) do gênero de madeira Apuleia Leiocarpa como material adsorvente na biossorção de azul de metileno (AM) de efluentes têxteis. Foram realizados testes experimentais em tanque agitado para determinação da isoterma de equilíbrio e a cinética de adsorção, e ajustados os modelos mais empregados na literatura. Os experimentos em leito fixo foram conduzidos em escala de laboratório, para obtenção das curvas de ruptura. Os resultados mostraram uma isoterma de equilíbrio favorável, com uma cinética de adsorção de 2ª ordem. O processo de adsorção no leito fixo foi representado satisfatoriamente pelo modelo de Yan. A operação em leito fixo é promissora devido ao baixo custo do material e a simplicidade de operação. A capacidade máxima de adsorção do corante foi de 66 mg/g de biomassa, demonstrando o potencial de utilização do PS para remoção de AM de efluentes têxteis.

Optimization of the Effect of Temperature and Bed Height on Cr (VI) Bioadsorption in Continuous System

In the present paper, the residues of the plantain starch extraction process are proposed as an adsorbent to remove Cr (VI) in a continuous fixed bed-system, varying the temperature in 33, 40, 55, 70 y 76 °C and bed height in the range of 15.5, 30, 65, 100, 114.5 mm. The adsorbent material was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD). The Cr (VI) solution at 100 ppm had contact with the column by gravity, with a flow rate of 0.75 mL/s at the different working conditions. At the end of the process, the residual concentration of the metal was measured by UV-Vis spectroscopy using the standard method for the determination of Cr (VI) in water ASTM D1687-17. From the results, it was established that the bioadsorbent has the presence of hydroxyl, carboxyl and methyl functional groups and that the adsorption process is controlled by electrostatic interactions; the variables evaluated had a significant influence on the process because applying the RSM methodology it was observed that the optimal operating conditions are 81.49 mm of bed height and temperature of 68 ºC. Based on the behavior of the rupture curve, it was found that the bio-material has the potential to be used as a filler in an adsorption column with the purpose of remove Cr (VI).

Type IV failure in weldment of creep resistant ferritic alloys: II. Creep fracture and lifetime prediction

The creep rupture behavior (Type IV failure) for weldments of creep strength enhanced ferritic steel is numerically analyzed, using an integrated microstructure- and micromechanics-based finite element model. To account for the large microstructure gradients across weldments, a two-dimensional digital microstructure is constructed based on the actual observed microstructure of ferritic steel weldment by using the Voronoi-tessellation method. According to the fracture mechanism studies and literature experimental observations, the Type IV failure is identified as an intergranular creep fracture in the fine-grained or intercritical heated affected zone (FGHAZ or ICHAZ). In the present study, the following micromechanics model is employed to determine the micromechanical and microstructural origins for the failure process above, accounting for the underlying physical fracture mechanisms at different length scales, including nucleation of grain boundary cavities, their growth by competition of grain boundary diffusion and grain interior creep, viscous grain boundary sliding, and the emergence of microcracks by coalescence and their evolution to the ultimate failure. The methodology demonstrates the capabilities in modeling the Type IV failure and providing quantitative creep rupture lifetime prediction which shows an excellent agreement with long-term creep experimental data for creep strength enhanced ferritic steels and their weldments. In particular, the drop-off in time to rupture at high temperatures and low stress levels in the creep rupture curves is quantitatively predicted, and the transition of failure mechanisms from creep-controlled to diffusion-controlled creep fracture mechanism is illustrated.

Influence of Oxidation on Estimation of Long-Term Creep Rupture Strength of 2.25Cr–1Mo Steel by Larson–Miller Method

AbstractThe influence of oxidation on the estimation of long-term creep rupture strength is investigated for 2.25% chromium (Cr)–1% molybdenum (Mo) steel specified as JIS STBA 24, JIS SCMV 4 NT, and ASTM A542/A542M by the Larson–Miller method using creep rupture data in the National Institute for Materials Science (NIMS) Creep Data Sheets at 450–650 °C for up to 313,000 h. The creep rupture data exhibit a change in slope of the stress versus time to rupture curves due to oxidation in air during 600 °C creep tests at 15,000–40,000 h and 650 °C tests at 2000–3500 h for different size specimens, which indicates degradation in creep life by the oxidation. The estimated 100,000 h creep rupture strength using regression analysis is increased by the elimination of long-term data degraded by the oxidation. Several metallurgical factors, such as the initial strength represented by the 0.2% proof stress at the creep test temperature and the concentration of aluminum (Al) impurity, also affect the creep life of the tested steel.

On the creep fatigue and creep rupture behaviours of 9–12% Cr steam turbine rotor

This paper presents the study of creep-fatigue interaction damage and creep rupture limit for 9–12% Cr steam turbine rotor under coupled cyclic thermal-mechanical loadings that alter in phase and out of phase. The investigation is implemented using the Linear Matching Method (LMM) and based on the newly developed creep-fatigue and creep rupture evaluation procedures. Latest experimental creep data of FB2 which belongs to 9–12% Cr heat-resistant steel family is employed to calculate creep-related damage and creep rupture bearing capacity of steam turbine rotor. Various factors that affect creep and fatigue damage of steam turbine rotor are analyzed and discussed, including dwell period and rotating speed of rotor. From the parametric studies, the damage locations and cycles to failure induced by creep and fatigue mechanism are presented respectively. Moreover, through creep rupture analyses for varying desired fracture time, the novel creep rupture curves under multi-type double-cyclic-loading conditions are given and further compared with cyclic plasticity failure curve. These surrogate-model analyses offer a deep understanding of structural responses of steam turbine rotor under long-term high temperature operation and provide critical loading conditions to be referenced for smooth running.

Addendum to: Reliable analysis and extrapolation of creep rupture data

This addendum to Reliable analysis and extrapolation of creep rupture data, Int J Press Vessels Pip 2017, covers matters that were insufficiently addressed in the original article. Uncertainties that obscure evaluation of the P-NID procedure by analysis of multi-batch data are addressed by blind testing the procedure for individual batches of an 18%Cr steel, Type 316 SS. Uncertainties that arise in the extrapolation of near-linear rupture curves are addressed by the inclusion of temperature dependence in parametric stress equations. The use of Tensile Strength data as equivalent short-term rupture data is demonstrated and discussed.

Investigation of Moringa oleifera seeds as effective and low-cost adsorbent to remove yellow dye tartrazine in fixed-bed column

ABSTRACTThe aim of the present work was to evaluate the adsorption behaviour of tartrazine yellow dye using Moringa oleifera (moringa) seeds in a fixed bed, through the variation of operational parameters and evaluation of mathematical models. The results showed that the biosorption process showed higher efficiency when the column was operated at 1 mL min−1 flow, with a height of 14 cm and pH 5 of the dye solution, which had a removal percentage of 44.89% and removal capacity of 0.504 mg g −1. When the adsorption models were applied, it was found that the Adams–Bohart model best represents the initial part of the rupture curve, whereas the Dose-Response model best reproduces the entire rupture curve. The regeneration experiments demonstrate that it is possible to regenerate the biosorbent and its removal capacity remains at approximately 33% from the 4th cycle, satisfactory results for the reuse of the moringa seeds in the removal of tartrazine dye.

Parameter optimization for Cr(VI) adsorption breakdown curves onto cocoa shell

The aim of the present investigation was to evaluate the cocoa shell (Theobroma cacao L .) for its use in the adsorption of hexavalent chromium in aqueous solution using packed bed column, applying the surface response method (SRM) in order to determine the optimum values of the variables involved in the process. The adsorption tests were carried out with these values. Was used a central composite experiment design with star points. The biomass was washed, dried, decreased size and sieved; the experiments were carried out at 25°C, at different particle sizes, flow rate and amount of biomass, in columns in continuous system; obtaining a percentage of removal of 39 .16% of C (VI) . Was obtained when performing the experiments in batch system that at a size of 0 .355mm particle favors the adsorption . From the adsorption tests in the column using the optimum parameters obtained by the MSR, was obtained a removal percentage of 62 .65%; finding that the models of Yoon-Nelson and Thomas were those that adjusted the experimental data of the rupture curve, with R2 = 0 .98. It’s concluded that the cocoa shell is a good precursor of bioadsorbents and that the most influential variables in Cr (VI) adsorption in batch and continuous systems are particle size and bed height.

Fixed bed column modeling of lead(II) and cadmium(II) ions biosorption on sugarcane bagasse

In this paper the results of the biosorption of lead(II) and cadmium(II) with sugarcane bagasse in fixed bed columns are presented. Experimental data were fitted to several models describing the rupture curve for single-component and two-component systems. The percentages of removal of lead and cadmium in single-component systems are 91% and 90%, respectively. In lead-cadmium bicomponent systems the percentage of elimination of lead was 90% and cadmium 92%. In single-component systems, Yoon-Nelson and Thomas models successfully reproduce the rupture curves. In two-component system, the Dose-Response model was the best one reproducing the experimental rupture curves in the entire measured range.