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The electric fatigue load has a significant effect on the crack propagation behavior and failure life of piezoelectric materials and devices. In this paper, an electrical mixed-mode fatigue crack propagation model for piezoelectric materials is proposed based on the piezoelectric Jk-integral theory. The crack initiation, propagation, and life prediction criteria of piezoelectric materials under electric fatigue loading are given by this model, and the finite element simulation model is established to study the electrical mixed-mode crack propagation behavior of piezoelectric structures. Meanwhile, the electrical mixed-mode fatigue crack propagation model is applied to the fatigue crack propagation behavior of a piezoelectric typical defective structure, the crack–hole interference model. The mixed-mode crack propagation, fatigue life, and the interference behavior between the crack and hole at various hole locations of the crack–hole interference model are well recognized by this model. The crack propagation behavior under different electrical load intensities is also considered. The results show that the hole in front of the crack tip inhibits crack propagation to a certain extent, and the strength of electrical load affects the fatigue life of piezoelectric materials and structures. Therefore, the proposed electrical mixed-mode fatigue crack propagation model provides a reference for predicting the mixed-mode fatigue crack propagation behavior and fatigue life of piezoelectric structures under electric fatigue loading. [ABSTRACT FROM AUTHOR]

In advanced nuclear power systems, structure materials have compatibility problems with lead-bismuth eutectic coolants such as liquid metal corrosion, and the corrosion failure behavior of the circulation pump is one of the main causes of nuclear safety accidents. Specifically, this paper reviews the failure behavior of the main pump in a flowing lead-bismuth environment for a prolonged period, alongside the prediction of the impeller blade's fatigue life. The development process and main structure of the nuclear reactor are introduced, and the failure behavior and influencing factors of the impeller blade of the main pump are discussed in detail. This paper also provides an in-depth analysis of material composition, oxygen content, temperature, corrosion time, relative velocity, and coating, to identify the failure reason and mechanism of the structural components featuring austenitic stainless steel as the main material. Finally, the fatigue life of the impeller and its prediction model are described from the perspective of fatigue failure, and the reliability analysis of fatigue life prediction is analyzed. [ABSTRACT FROM AUTHOR]

The study aims to determine how cyclic loading affects the structural integrity and lifespan of composite repair systems used to restore corroded steel pipelines. As specified in Annexure C of the ISO 24817 repair code, pipe specimens are machined to produce flaws with 80 % wall loss. Testing under static and cyclic pressure loading is done as per ASTM D2992 and ASTM D2143. Static pressure loading is accomplished by continually pressurizing the pipe specimen, and burst pressure is assessed. Various Rc-ratios or levels of cyclic loading severity are used in cyclic pressure loading tests. Each case’s number of cycles before failure is determined experimentally, and the service de-rating factor is assessed in accordance with ISO 24817. The 235 bar pressure was sustained by the static-loaded repaired pipe specimens with 80 % wall loss, and the failure was catastrophic. At around 7000 cycles, the cyclically loaded repaired samples with 80 % wall loss failed, and the failure manifests as debonding or a leak. [ABSTRACT FROM AUTHOR]

In this study, a new model is developed for fretting fatigue crack initiation life prediction based on the slip amplitude as a macroscopic feature of the contact interfaces. The main difference between the presented model and many other fretting fatigue life prediction models is the focus on the fretting specific characteristics. In this model, a damage parameter is combined with a damage severity factor to obtain a new fretting fatigue crack initiation life prediction parameter. To investigate the accuracy of this new parameter, a series of fretting fatigue tests were conducted. Also, crack initiation life data from the literature were added to enhance parameter accuracy investigation. It was shown that the effective slip amplitude was an unbiased geometric-independent parameter in fretting fatigue crack initiation life prediction. Also, comparison of the prediction results from the effective slip amplitude with those of Smith-Watson-Topper and Ruiz parameters illustrated that the new parameter could outperform available fretting fatigue life prediction parameters. [ABSTRACT FROM AUTHOR]

The wind turbine blades are key components of wind turbines. During the working process, the blades are subjected to fatigue loading, resulting in the failure of wind turbine blades. The surface temperature of blade materials will change when subjected to fatigue loading and the temperature rise rate of blade surface under fatigue loading can be used as an index to predict fatigue life. However, the frequency of fatigue loading on the wind turbine blades is low, the non-adiabatic response under low frequency fatigue loading would lead to temperature dissipation. In this paper, fatigue life prediction under low frequency fatigue loading was studied. Based on the law of energy conservation and the laws of heat conduction, heat convection, heat radiation, the temperature evolution of materials under low frequency fatigue loading was theoretically analyzed. Epoxy resin was selected as testing material and fatigue tests were conducted on epoxy resin specimens. During the fatigue test, the infrared thermal imager was used to monitor the samples surface temperature in real-time. The results show that the predicted life considering temperature dissipation effect is closer to the real life. Meanwhile, the general application of life prediction model is further verified by metal material. This work can be used for predicting the fatigue life of wind turbine blades under low frequency. [ABSTRACT FROM AUTHOR]

Based on elastoplastic and damage mechanics theory, a new theoretical model of damage cracking on the cover of reinforced concrete structures caused by nonuniform rust expansion is established. The parameter sensitivity analysis indicates that the critical corrosion rate of the structure increases sharply with the increase of the thickness of the concrete cover. The critical corrosion rate decreases when the non-uniform coefficient of the corrosion expansion becomes larger, indicating that the uneven corrosion expansion is disadvantageous for durability. When the rust expands more unevenly, the allowable corrosion amount of the reinforcement becomes smaller. While the concrete grade changes from C15 to C60(concrete design standard in China), the critical corrosion rate modifies between 3.05°C and 4.1°C. To further verify the rationality of the new theoretical model, the model was conducted to predict the standard corrosion tests. Results show that the scatter points predicted by the new model are small-amplitude oscillation near the test line. Thus, it has been proved the new theoretical model proposed in this paper can be used to predict the critical corrosion rate of RC structures. [ABSTRACT FROM AUTHOR]

The underground drainage operation in the coal mine is the key to the mine safety production. The centrifugal pump is generally used for the drainage operation. Therefore, the fault judgment and life prediction of centrifugal pump have become the key problems. In this research, the fault tree method and the fuzzy theory method were used to diagnose the fault of drainage device. Taking the drainage system of the pump room in the fourth panel of Busan Industrial Park of Changping Mine as an example, the life prediction index of the residual life evaluation of centrifugal pump was proposed, and the life evaluation model of centrifugal pump based on support vector machine regression was established. The reliability of residual life evaluation of centrifugal pump was verified by the simulation analysis. The test results showed that the host computer could accurately monitor the system fault, and the service life of the system could be predicted. The automatic control and intelligent load management of the mine drainage system finally was realized. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fatigue fracture is one of the most common failure modes of engineering components, and the combined action of geometric discontinuity and multiaxial loading is more likely to cause severe fatigue damage of components. This work focuses on the fatigue behavior of U-notched Q345 steel specimens with different notch sizes under proportional cyclic tension–torsion. Firstly, based on the concept of strain energy, the calculation method of critical plane is given and the equivalent stress of the specified path on the critical plane is extracted to characterize the equivalent stress distribution state and the stress gradient effect. Then, based on the high stress volume method and theory of critical distance, a simple method for determining the critical distance is given considering the contribution of stress at the dangerous point and the critical point. In addition, based on the idea of stress–distance normalization, a new stress gradient impact factor is defined and a new method for predicting the multiaxial fatigue life of notched specimens is given. The prediction results of the proposed model, the local stress–strain method and the point method of theory of critical distance are compared with the experimental results. The comparisons show that the prediction results of the proposed model are closer to experimental life, and the calculation accuracy is higher. [ABSTRACT FROM AUTHOR]

The service life of proton exchange membrane fuel cell (PEMFC) is an important breakthrough direction in the field of vehicle fuel cell, but the current life prediction method has the problem of low accuracy and efficiency. To solve this problem, this paper proposes an improved CNN network model based residual life prediction method for vehicle high-power proton exchange membrane fuel cells. In this method, the improved dropout and shortcut units are used to improve the convolutional neural network (CNN) network to solve the over fitting problem of prediction network training and improve the overall performance of PEMFC life prediction network model. At the same time, in order to realize the realtime adaptability of the prediction network, Adam optimization algorithm is used to minimize the loss function to support the fast tracking performance of PEMFC life prediction network. Finally, the prediction experiment is carried out based on the general data set. The experimental results show that the prediction error of the proposed method is guaranteed to be 1.5 h, and the maximum relative error is 0.473%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nowadays, LED (Light Emitting Diode) luminaires are beginning to dominate the lighting market with the increasing importance of features such as cost, product life and efficiency. This cause to increase competition in the production of LED drivers and enforce manufacturers to offer the highest quality product to the market at the lowest cost. Designs with low cost targets can cause some problems such as system instability and working in unsafe areas due to restrictions. In this respect, it is great importance to complete "Electronic Design Verification Tests" before the product come onto the market. In this study, it was aimed to design and implement "The Worst Case Situation Tests" for LED driver. In addition, "Electronic Design Verification Tests" for LED drivers are mentioned in detail. [ABSTRACT FROM AUTHOR]

The motor hour (working time) of an armored vehicle's engine reflects its technical state to a certain extent. However, even the same type of engine with the same motor hour shows very different technical states in different working environments. At the same time, it is difficult to obtain the full life data or physical failure mechanism required by the traditional life prediction method. In view of the above problems, a model of engine life prediction based on degradation data and neural networks is built in this paper. Firstly, the degradation parameters are selected according to certain principles, and the sample data are standardized. Then, the principal component analysis method is used to simplify multiple parameters to a comprehensive parameter, and the interpolation method is applied to get the parameter's time series data as the train data of the neural network. Finally, the life prediction model of the engine based on the neural network is established. The validation results indicate that the model runs accurately. It is also practical and worthy of being used abroad. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the life prediction problem of damaged coating steel bar in magnesium cement concrete, this study tries to establish the marginal distribution function by using the corrosion current density as a single degradation factor. Representing the degree of steel corrosion, the corrosion current density were tested in electrochemical workstation. Then based on the Copula function, the joint distribution function of the damaged coating was established. Therefore, it is indicated that the corrosion current density of the bare steel and coated steel bar can be used as the boundary element to establish the marginal distribution function. By using the Frank-Copula function of Copula Archimedean function family, the joint distribution function of the damaged coating steel bar was successfully established. Finally, the life of the damaged coating steel bar has been lost in 7320d. As a new method for the corrosion of steel bar under the multi-dimensional factors, the two-dimensional Copula function has certain practical significance by putting forward some new ideas. [ABSTRACT FROM AUTHOR]

This study investigated a fatigue life prediction method based on extensive experiment results of cast aluminum alloy Al319-T7 subjected to repeated thermal and mechanical loading. Cyclic tests and fully reversed fatigue test results of the material were obtained from the specimens subjected to three different strain rates (5x10 -5 , 5x10 -4 and 5x10 -3 ) and various temperature conditions. At each strain rate the specimens were subjected to room temperature (25°C), 150°C, 200°C, 250°C and 300°C. Thermo-mechanical fatigue (TMF) tests were also conducted for in-phase and out-of-phase conditions of the temperature and mechanical loading. During the thermo-mechanical fatigue tests, the effect of loading phases and dwell time on fatigue life of the specimens was also observed. This study modified Taira’s fatigue damage model for thermo-mechanical loading condition to include the strain rate effect on the fatigue damage. Taira assumed that fatigue damage per reversal is proportional to the damage factor, λ(T), and plastic strain range powered by n, (Δε p ) n . The relationship between the plastic strain range (Δε p ) and the number of cycles to failure (N f ) is presented as λ(T)•(Δε p ) n •N f = C. Where C is a temperature independent material constant. The temperature effect is included in the damage factor, λ(T) that can be determined from the ratio of λ(T)/λ(T o ) for low cycle fatigue test results at various isothermal conditions. T o is the reference temperature and can be determined by experiment. This study used stress range applied instead of plastic strain range in the original equation. Furthermore, the modified equation includes the effect of strain rate, phase, and dwell time. The new fatigue damage equation was well correlated with the experiment results. [ABSTRACT FROM AUTHOR]

A polycrystalline Voronoi aggregation with a free surface is applied as the representative volume element (RVE) of the nickel-based GH4169 superalloy. Considering the plastic deformation mechanism at the grain level and the Bauschinger effect, a crystal plasticity model reflecting the nonlinear kinematic hardening of crystal slipping system is applied. The microscopic inhomogeneous deformation during cyclic loading is calculated through numerical simulation of crystal plasticity. The deformation inhomogeneity on the free surface of the RVE under cyclic loading is described respectively by using the following parameters: standard deviation of the longitudinal strain in macro tensile direction, statistical average of first principal strains, and standard deviation of longitudinal displacement. The relationship between the fatigue cycle number and the evolution of inhomogeneous deformation of the material's free surface is investigated. This research finds that: (1) The inhomogeneous deformation of the material free surface is significantly higher than that of the RVE inside; (2) the increases of the characterization parameters of inhomogeneous deformation on the free surface with cycles reflect the local maximum deformation of the RVE growing during cyclic loading; (3) these parameters can be used as criteria to assess and predict the low-cycle fatigue life rationally. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Beijing Institute of Technology is the property of Beijing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The basis for high-temperature testing and analysis was established a century ago using test equipment that was available at the time. This fostered a tradition in research and engineering applications that has not changed fundamentally. The limitations of this approach are described, with emphasis on problems associated with predicting the remaining life of operating components. A new testing method and analysis philosophy is proposed based on measurement of current performance, with end of life unambiguously identified with limiting acceptable values of these current performance metrics. Instead of a single test to measure creep strength and fracture resistance, the new approach uses separate tests. For creep strength, the stress vs. creep rate curve determined at nearly constant state and covering five decades in creep rate in a one-day test is obtained from a high-precision stress relaxation test (SRT). The results for many alloys and materials often show a sigmoidal curve. Conventional long-time creep tests of steels have shown a similar effect. However, rather than recognising this as a fundamental rate-dependent phenomenon, it has been typically explained in terms of microstructural coarsening. For fracture resistance, a constant displacement rate test across a notch is used at the temperature of greatest sensitivity to high-temperature fracture. This latter test has been very successful in detecting embrittlement in superalloys. For more ductile alloys, a non-destructive measure of ductility based on the strain rate sensitivity determined from the SRT data is shown to have great potential. This introduces the concept of intrinsic ductility that can be determined without ambiguity over a wide range of stress and temperature for both new and serviced components. [ABSTRACT FROM AUTHOR]

The basis for high-temperature testing and analysis was established a century ago using test equipment that was available at the time. This fostered a tradition in research and engineering applications that has not changed fundamentally. The limitations of this approach are described, with emphasis on problems associated with predicting the remaining life of operating components. A new testing method and analysis philosophy is proposed based on measurement of current performance, with end of life unambiguously identified with limiting acceptable values of these current performance metrics. Instead of a single test to measure creep strength and fracture resistance, the new approach uses separate tests. For creep strength, the stress vs. creep rate curve determined at nearly constant state and covering five decades in creep rate in a one-day test is obtained from a high-precision stress relaxation test (SRT). The results for many alloys and materials often show a sigmoidal curve. Conventional long-time creep tests of steels have shown a similar effect. However, rather than recognising this as a fundamental rate-dependent phenomenon, it has been typically explained in terms of microstructural coarsening. For fracture resistance, a constant displacement rate test across a notch is used at the temperature of greatest sensitivity to high-temperature fracture. This latter test has been very successful in detecting embrittlement in superalloys. For more ductile alloys, a non-destructive measure of ductility based on the strain rate sensitivity determined from the SRT data is shown to have great potential. This introduces the concept of intrinsic ductility that can be determined without ambiguity over a wide range of stress and temperature for both new and serviced components. [ABSTRACT FROM AUTHOR]

To consider the anisotropic damage in fatigue, an improved boom-panel model is presented to simulate a representative volume element (RVE) in the framework of continuum damage mechanics. The anisotropic damage state of the RVE is described by the continuity extents of booms and panels, whose damage evolutions are assumed to be isotropic. The numerical implementation is proposed on the basis of damage mechanics and the finite element method. Finally, the approach is applied to the fatigue life prediction of 2A12-T4 aluminium alloy specimen under cyclic loading of tension-torsion. The results indicate a good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The aim of this paper was to identify the high-temperature low-cycle fatigue (HTLCF) performances and optimize model parameters of nickel-based GH4169 superalloy. Microanalysis revealed that fatigue lives of specimens obtained from different regions of inhomogeneous radical forging disc were determined by their microstructures, such as the uniformity ratio of grain size and the distribution of δ phase along the grain boundary. Typical fatigue characteristics of all specimens were investigated after HTLCF tests through the analysis on fracture morphologies and secondary cracks. Then, an evolution and optimization process of model parameters in ɛ-N curves was proposed. [ABSTRACT FROM AUTHOR]

Components like elbows operating at high temperature in power and petro-chemical industry are vulnerable to failure of crack growth or net section rupture due to a change in geometry or in mode of loading. In this paper, a P91 reheat elbow subjected to internal pressure of 4.63 MPa at 569 °C for 62,952 h in service with a part-through-wall crack located at the outer surface is considered. Prediction of whether the elbow can be used for the next ten years is made. First, the procedure provided by Annex U of BS7910-2005 is employed to conduct the high-temperature defect assessment. And in this assessment, the margin against creep damage, margin against fast fracture evaluated by failure assessment diagram (FAD) and the concept of creep crack propagation are employed to estimate its safety in service. Then, a simplified assessment based on the concept of time dependent failure assessment diagram (TDFAD) is conducted. The advantage of TDFAD method is that the risk of creep rupture can be demonstrated directly by the location of assessment point on the diagram avoiding the calculation of C* . Results obtained by using the two methods are compared with each other and have both indicated that the elbow with particular crack defect can be safely operated for another ten years after the crack was discovered. [ABSTRACT FROM AUTHOR]

Low cycle fatigue behaviour of Q345B steel and its smooth welded joint were experimentally investigated in fully reversed strain-control at constant strain rate of 0·005 s−1. The cyclic stress response characteristics, strain-life and strain-energy relationships were obtained and analysed in the strain regime 0·3-0·7%. It was found that Q345B showed significant cyclic hardening and softening above and below the 0·4% strain amplitudes, respectively. The welded joints showed cyclic hardening in the entire strain regime because of the mechanical inhomogeneity. The low cycle transition life, fatigue strength and fatigue life of welded joint were found significantly lower with increase in the cyclic hardening. The experimental data were used to extract the Coffin-Manson parameters and the strain-life relationship. In addition, the expressions of plastic strain energy and fatigue life were also obtained using the energy prediction method. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBC) are widely used in turbines for propulsion and power generation. Expanded application to more demanding scenarios requires that their basic thermal fatigue characteristic be understood and quantified. In previous works, the plate and tube specimens with TBC have been studied under thermal cyclic load. The thermal fatigue life of vanes with TBC was seldom investigated. In present work, first the thermal fatigue experiments of tube specimens were carried out under different pre-oxidation time. By means of the WALKER constitutive model implemented in ABAQUS/UMAT, the stress-strain state of the interface between the bond coat and top coat was analysed at the meso-scale. The life prediction for TBC system was verified. Then the 3D finite element method (FEM) of a vane was modelled and analysed, negating the TGO thickness and the interface shape because of cross-scale thickness distribution in TBC system. The strain at critical location of the vane was obtained. Finally, the equivalent coefficient with relevance to the macro- and meso-scale FEM results was proposed. As a result, the thermal fatigue life of turbine vanes with TBC was determined. [ABSTRACT FROM AUTHOR]

Low-cycle fatigue properties of 30Cr1Mo1 V steam turbine rotor steel were studied by RDL05 electronic creep fatigue test machine at 0.1%.s -1 , 0.3%.s -1 , 0.5%.s -1 loading rates applied the total strain controlled method. The results involve that with the loading rate increases at 538 °C, cyclic stress of the rotor steel increases, and low-cycle fatigue life increases too; in the same strain range values, the increasing loading rate leads to the greater stress amplitude; with the increase of the strain range values, the stress increases and the low-cycle fatigue life decreases. The relationship of stress-strain and the loading rate is , the relationship of low-cycle fatigue life and the loading rate is . [ABSTRACT FROM AUTHOR]

Abstract: Fatigue investigation on 7050-T7651 chromic acid anodized aluminium alloy has been realized in order to develop a fatigue life predictive model which includes the different experimental aspects of fatigue cracking. In particular, it has been observed that, for this alloy and the sub-mentioned anodizing process conditions, degreasing process used after machining had no influence on fatigue resistance; the essential of the important fatigue resistance decrease was due to pickling process, leading to production of numerous pits which were found to be crack initiation sites; then anodizing process was responsible for a supplementary increase of fatigue resistance decrease. Failure surfaces observations have shown that these pits were responsible for cracks and numerous crack coalescence phenomena have been pointed out. The fatigue life predictive model presented in this paper is based on Suraratchaï’s model, developed at ICA-Toulouse, which is built on the stress concentration effect of machining surface roughness: here pickling pits are considered as stress concentrators from which cracks could occur if stress intensity factor is high enough; considering the very low size of pickling pits, half size of middle recrystallized grain size, this implies the introduction in the model of short cracks considerations such as short crack stress intensity factor range threshold and short crack growth rate law. Coalescence conditions are also introduced. Calculation are conducted from a 3D finite elements built from experimental topographic measurements which allow the determination of stress concentration coefficients induced by machining surface roughness and the presence of the pits. Anodized surface are rebuilt from pickled surface in order to overturn the lack of accuracy during topographic surface measurements. Predictive results fit very well with experimental results whatever the surface state. [Copyright &y& Elsevier]

To solve the problem of prediction of multi-axial fatigue life, a new thought and method of establishing multi-axial fatigue life model is proposed. The multi-axial fatigue life model is established by fitting and optimizing axial and multi-axial test data both. This method reduces the restrictions of the formation of multi-axial fatigue damage parameters and the type of multi-axial fatigue test data. On this basis, a new multi-axial fatigue damage parameter based on maximum shear strain amplitude and normal strain and stress on the plane of maximum shear strain amplitude is proposed. The establishing method of multi-axial fatigue life model is evaluated by the multi-axial fatigue test data of ZTC4 cast titanium alloy, pure titanium and BT9 titanium alloy. The result shows that the new method is feasible. The prediction ability of the establishing life model is almost within a factor of two scatter band. [ABSTRACT FROM AUTHOR]

Abstract: A gas turbine blade rotates at high speed in a high-temperature flame, degradation environment under mechanical loading. It is also exposed to a thermo-mechanical fatigue environment caused by frequent starts and shutdowns. Therefore, the life of the blade material should be evaluated considering such various factors.In this study, the low cycle fatigue(LCF) and thermo-mechanical fatigue(TMF) tests were carried out by using a furnace, which directly transfer heat flux, for the life prediction of a Ni-base superalloy. LCF tests were conducted over a wide range of strain conditions considering the gas turbine operating condition. Also, IP (in-phase) and OP (out of-phase) TMF tests were conducted over a wide range of strain conditions. Finally, a fatigue life prediction model of the Ni-base superalloy was obtained from the LCF and TMF test results. And also, a comparison between the LCF and TMF test results was evaluated with respect to fatigue life. [Copyright &y& Elsevier]

Abstract: Throughout the world, extensive low-cycle fatigue (LCF) data, which is traditionally used for design purposes, has been generated isothermally on various high-temperature materials, and thus, it is tempting to try to predict TMF life based mainly on isothermal LCF data. In this contribution, studies on different metallic structural high-temperature materials, which have been carried out in the author's laboratory, are reviewed addressing the question, in which way and to which extent a reliable, unerring and robust TMF life assessment is possible on the basis of isothermally obtained fatigue life data. It is shown by means of examples that a sound TMF life prediction requires a detailed mechanistic understanding of both the non-isothermal cyclic stress-strain response and the TMF-specific damage evolution. [Copyright &y& Elsevier]

Abstract: The application of prestressed carbon reinforced polymer (prestressed CFRP) in reinforced concrete (RC) members can improve the mechanical properties of strengthened structures and strengthening efficiency. This paper proposed a semi-empirical prediction formula of fatigue lives of the RC beams strengthened with prestressed CFRP under bending loads. The formula is established based on the fatigue life prediction method of RC beams and fatigue experimental data of non-prestressed CFRP reinforced beams done before. Fatigue effect coefficient of the formula was confirmed by the fatigue experiments of the RC beams strengthened with prestressed carbon fiber laminate (prestressed CFL) under cyclic bending loads. Fatigue lives of the strengthened beams predicted using the formula agreed well with the experimental data. [Copyright &y& Elsevier]

A theoretical model using Weibull distribution and maximum likelihood estimation (MLE) was established to statistically analyze the test data, which were obtained by three groups of constant stress accelerated life tests. The life prediction software was applied to simplify the calculation and achieve organic light-emitting device (OLED) life estimation. The results indicate that the Weihull distribution is fit to describe white OLED life, and the precise accelerated parameter β is particularly useful to predict the white OLED life within a shorter time, which provides significant guidelines to help engineers make decisions in design and manufacturing strategy from the aspect of reliability life. [ABSTRACT FROM AUTHOR]

Abstract: According to the corrosion failure characteristics of buried oil and gas pipelines, electrochemical corrosion rates of the local corrosion and pitting corrosion flaws were derived by Faraday''s laws, and the limit size model of corrosion defects was established based upon ASME-B31G criteria. A new method of the residual life prediction for buried pipelines was finally developed based on the corrosion rate model and limit size model of corrosion defects, and the prediction method was validated with an example and the results showed that the method is reliable for pipelines with corroded defects. [Copyright &y& Elsevier]

Abstract: This paper presents a life prediction method to predict Degradation Amount Distribution (DAD) of products using a composite time series modeling procedure based on degradation data. Product DAD data are treated as composite time series and described using composite time series model and utilized to predict long-term trend of degradation. A degradation test is processed for a certain electronic product and degradation data are collected for life prediction. A comparison between the predicted DAD using composite time series analysis and the predicted DAD using regression analysis of the electronic product is processed and the results show that the DAD prediction of the product using composite time series analysis is more effective than regression analysis. [Copyright &y& Elsevier]

Abstract: In large power plants, in order to improve safety and stability of HP heaters(High Pressure) in operation, thicker tubeplates are designed and made, which will lead to more thermal stress between tube-plate and end-cover, furthermore, will reduce the thermal fatigue life of HP heaters sharply. so it is necessary to monitor the thermal fatigue its life. However, at presently a large portion of methods carry on calculating or analyzing beforehand or afterwords, which make effect of analyzing life being less greatly. In this paper, according to the theory of calculation of thermal fatigue life, real-time gathering tube-plate''s temperatures, and computing the life everyday, provide the basis of operating and maintaining in the power plate. [Copyright &y& Elsevier]

Abstract: This paper presents a new fatigue model to predict life of steel bridges considering the effect of high amplitude loading. It consists of a modified strain-life curve and a new strain based damage index. Modified strain-life curve consists of Coffin-Manson relation in low cycle fatigue region and a new strain-life curve in high cycle fatigue region. The damage variable is based on a modified von Mises equivalent strain to account for the effects of loading nonproportionality and strain path orientation in multiaxial stress state. The proposed model was verified with experimental test results of two materials available on the literature. Then, it was illustrated with an old riveted wrought iron railway bridge. The obtained results verify the effectiveness of the proposed model over commonly used Miner''s rule based life prediction of steel bridges. [Copyright &y& Elsevier]

Abstract: This study is concerned with the creep damage evaluation for fine grained heat affected zone (HAZ) of Mod. 9Cr-lMo steel. Circumferentially notched bar creep rupture tests have been conducted in order to examine the effect of multiaxial stress state on creep rupture and creep damage of the fined grained HAZ. The simulated fine grained HAZ has been used. Finite element predictions based on a continuum damage mechanics model with ductility exhaustion approach has been used to predict the creep rupture and the creep damage in the notched specimens. It is found that a ductility exhaustion approach provides very large creep damage which leads to too conservative prediction of creep life for notched specimens. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 [Copyright &y& Elsevier]

Abstract: Optimal gear design consists of determining its proper size, geometry, material, manufacturing processes and process parameters. One of the major steps within such gear design is high-cost gear testing until failure with the goal to determine performance characteristics of gears and also to enable life expectancy evaluations. With the viewpoint in the low-cost failure analysis, considering crack initiation in tooth root fillet, simulation of material behaviour can be based also on recorded material response from the endurance tests on un-notched test circular samples. In order to account for large number of phenomena that appear in material during loading, complex material model for material behaviour modeling is chosen. Material behaviour in low–cycle fatigue regime is described by material model that combines isotropic and kinematic hardening with mechanics of material damage to simulate elastic-plastic response of the material, as well as damage nucleation and accumulation. Chosen material model is implemented into finite element code to enable numerical modeling of materials response in gears tooth root and life prediction, considering crack initiation period. Calculated life expectancy curves show possible increase of gear''s loading capacity as a result of material softening tendency and residual stresses influence in gears tooth root. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 [Copyright &y& Elsevier]

Abstract: The author and his colleagues have proposed in their recent works the creep-fatigue life prediction method based on the strain range partitioning concept for nonproportionally combined tension and torsion using new inelastic strain range parameters and have been studying their applicability to the materials subjected to nonproportional axial-torsional loading at elevated temperatures. In the present paper are summarized the results of in-phase and 90 deg out-of-phase axial-torsional straining tests conducted on thin-walled tubular specimens of SUS304, 316LC and 2.25Cr-1Mo steels. [Copyright &y& Elsevier]

Abstract: Fatigue life evaluations in low dissolved oxygen conditions have been considered as conservative in predicting fatigue strengths of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions becomes higher. In this paper, authors observed effects of dissolved gas on corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength becomes higher in low dissolved O2NaClaq. at stress ratio R=0.1. However, fatigue strength did not change in low dissolved O2NaClaq.at stress ratio R=0.5 because of the effect of work hardening. Cycles to crack initiations became longer and crack growth rates became lower in low dissolved O2NaClaq..In conclusion, dissolved oxygen has effects of accelerating crack propagation processes. [Copyright &y& Elsevier]

New nondestructive inspection methods with high spatial resolution are expected to support the evaluation and enhancement of the reliability of microjoints on printed circuit hoards. An X-ray microtomography system, the SP-μCT has been developed at the Super Photon ring-8 GeV (SPring-8), the largest synchrotron radiation facility in Japan. In this work, the SP-μCT was first applied to the nondestructive evaluation of thermal fatigue phenomena, namely microstructure evolution (i.e., phase growth) and microcrack propagation, appearing in actual solder microbumps of flip chip interconnects due to thermal cyclic loading. In addition, a refraction-contrast imaging technique was simultaneously applied to visualize the fatigue cracks with an actual opening of less than 100 nm. The observed specimen has a flip chip structure joined by Sn-37wt%Ph eutectic solder humps 150 pm in diameter. Consequently, the process of phase growth and crack propagation was determined via observation of consecutive computed tomography (CT) images obtained in the same plane of the same specimen. As the thermal cycle proceeded, remarkable phase growth was clearly observed, followed by the appearance of fatigue cracks in the corners of the interfaces between the solder bump and Cu pad. Moreover, the CT images also enabled us to evaluate the fatigue lifetime of the humps, as follows. The lifetime to fatigue crack initiation was estimated by quantifying the increase in the phase growth. The crack propagation lifetime to failure was then determined by measuring the average crack propagation rate. Such results have not been obtainable at all by X-ray CT systems for industrial use and demonstrate the possibility of nondestructive inspection by a synchrotron radiation X-ray microtomography system. [ABSTRACT FROM AUTHOR]

Abstract: The author and his colleagues have proposed in their recent works the creep-fatigue life prediction method based on the strain range partitioning concept for nonproportionally combined tension and torsion using new inelastic strain range parameters and have been studying their applicability to the materials subjected to nonproportional axial-torsional loading at elevated temperatures. In the present paper are summarized the results of in-phase and 90 deg out-of-phase axial-torsional straining tests conducted on thin-walled tubular specimens of SUS304, 316LC and 2.25Cr-1Mo steels. [Copyright &y& Elsevier]

Abstract: Fatigue life evaluations in low dissolved oxygen conditions have been considered as conservative in predicting fatigue strengths of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions becomes higher. In this paper, authors observed effects of dissolved gas on corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength becomes higher in low dissolved O2NaClaq. at stress ratio R=0.1. However, fatigue strength did not change in low dissolved O2NaClaq.at stress ratio R=0.5 because of the effect of work hardening. Cycles to crack initiations became longer and crack growth rates became lower in low dissolved O2NaClaq..In conclusion, dissolved oxygen has effects of accelerating crack propagation processes. [Copyright &y& Elsevier]

Abstract: Optimal gear design consists of determining its proper size, geometry, material, manufacturing processes and process parameters. One of the major steps within such gear design is high-cost gear testing until failure with the goal to determine performance characteristics of gears and also to enable life expectancy evaluations. With the viewpoint in the low-cost failure analysis, considering crack initiation in tooth root fillet, simulation of material behaviour can be based also on recorded material response from the endurance tests on un-notched test circular samples. In order to account for large number of phenomena that appear in material during loading, complex material model for material behaviour modeling is chosen. Material behaviour in low–cycle fatigue regime is described by material model that combines isotropic and kinematic hardening with mechanics of material damage to simulate elastic-plastic response of the material, as well as damage nucleation and accumulation. Chosen material model is implemented into finite element code to enable numerical modeling of materials response in gears tooth root and life prediction, considering crack initiation period. Calculated life expectancy curves show possible increase of gear''s loading capacity as a result of material softening tendency and residual stresses influence in gears tooth root. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 [Copyright &y& Elsevier]

Abstract: This study is concerned with the creep damage evaluation for fine grained heat affected zone (HAZ) of Mod. 9Cr-lMo steel. Circumferentially notched bar creep rupture tests have been conducted in order to examine the effect of multiaxial stress state on creep rupture and creep damage of the fined grained HAZ. The simulated fine grained HAZ has been used. Finite element predictions based on a continuum damage mechanics model with ductility exhaustion approach has been used to predict the creep rupture and the creep damage in the notched specimens. It is found that a ductility exhaustion approach provides very large creep damage which leads to too conservative prediction of creep life for notched specimens. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11 [Copyright &y& Elsevier]

Abstract: Low cycle fatigue (LCF) and fatigue-creep tests were conducted under different dwell conditions at 650 °C on a P/M nickel base superalloy, which was used widely as aero-engine turbine disc. The specimens, taken from a hot isostatic pressing (HIP) disc , were tested under total fully reversed axial strain control. Compared with continuous cycling tests without dwell, the ones with tensile, compressive or tensile-compressive strain dwells showed some shorter fatigue lives. The difference of fatigue lives under different strain dwells reflects the fatigue-creep interactions at elevated temperature. The cyclic deformation and life distribution features were analysed and a lifing model was proposed to evaluate the fatigue life of the alloy. The prediction agrees well with the experimental results. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a fatigue analysis of a CF-18 aft wing fold shear-tie lug, which involved multiple crack nucleation sites and short crack growth under complex geometry and loading conditions. A three-dimensional (3D) finite element model was developed to simulate the loading applied in the shear-tie lug test and determine the local stress/strain distribution. Short crack data and the subsequent material model, were specifically developed for the lug material (7050-T7452 forging), in which work the Holistic Structural Integrity Process (HOLSIP) approach was used to correlate the short crack model with material microstructural features, such as constituent particles and porosities. After the shear-tie lug fatigue test, quantitative fractography (QF) was carried out to measure the crack growth size. Based on the failure mechanisms, a simplified single crack model was proposed to analyze this multiple crack growth problem, and the life estimation compared well with the test results. [Copyright &y& Elsevier]