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In this study, a new method of replaceable supporting member within orthotropic steel box girder is proposed in order to reduce stress amplitude and improve fatigue life of orthotropic steel box girder. The component model was established by ABAQUS, and the experiment was conducted to analyze stress amplitude of easily fatigue cracking areas of orthotropic steel box girder with and without the supporting member. In addition, the fatigue life was analyzed and predicted. The comparison results show that the finite element analytical results are in good agreement with the experimental results. The reduced proportion of stress amplitude of U rib, T rib grooves and mid-span of top plate of orthotropic steel box girder range from 40% to 60% and 20% to 40%, respectively. The analytical results show that the stress amplitude of orthotropic steel box girder can be reduced by the similar extent with the addition of the same supporting member under different loading pressure; The supporting member can improve the fatigue life of orthotropic steel box girder pertinently, which is simple in construction and low in cost, and can provide suggestions for solving fatigue problem of orthotropic steel box girder in engineering practice.

In this contribution, it was suggested an extension of Gurson model for cyclic application, regarding the prediction of fretting fatigue life and the study of the influence of the plastic strain field on fretting fatigue for an aluminum alloy 7050-T7451. In this setting, a modification in the defects growth mechanism was done, including a variable that distinguishes the evolution rate of Gurson damage in tension-compressive loads and, the coupling of the Xue shear mechanism to the extension of the model to low range of stress triaxiality. Initial simulations were performed for traditional fatigue tests and the suggested model has worked in good agreement with experimental data. After that, experimental fretting fatigue tests were proposed and carried out in order to observe the influence of the contact pressure of the fretting pad on the fretting specimen and in the system life. Numerical simulations were performed, considering now the modeling of the fretting fatigue problem by Finite Elements Method and life predictions were calculated, applying the suggested Gurson-based continuum damage formulation, by an analysis in a Gauss point. The calculated and observed life diagram has shown a robustness performance of formulation, predicting lives within a band factor of 2. It was also verified that the plastic strain field introduced, due to the increase in contact pressure on the fretting pad, benefits the specimen life, since the plastic strain was induced by the appearance of dislocations, which causes a hardening and an increase of the macroscopic material properties, as well as a negative mean stress into the specimen.

Fatigue cracking of rib-to-deck welded joints is the major fatigue problem of the orthotropic steel deck (OSD). It is important to evaluate the fatigue performance improvement of rib-to-deck double-side welded joints in an OSD when compared with single-side welded joints. In this study, the software ABAQUS and FRANC3D were used to set up a multiscale finite element model for segments of an OSD. Under vehicle load, the mode I stress intensity factor (SIF) of a fatigue crack at the rib-to-deck single-side and double-side welded details without or with the effect of welding residual stress was computed. The relationship between the mode I SIF of the fatigue crack and the key parameters was analyzed, including welded penetration, thickness of deck plate and the initial crack surface length and depth. The results showed that the welding residual stress can significantly influence the SIF values of the rib-to-deck welded joints in the OSD. The maximum SIF of the crack in the rib-to-deck double-side welded joints was 29.6% less than that of the single-side welded joints, which can effectively improve the fatigue performance of the rib-to-deck welded joints. The effect of the welded penetration rate on the fatigue performance of rib-to-deck double-side welded joints was only slight. By increasing the thickness of the deck, reducing the initial crack surface length and depth, the SIF of cracks in the rib-to-deck double-side welded joints can be significantly decreased, and this approach improves fatigue performance.

The objective of this study is to develop a Driving Fatigue Strain Index using fuzzy logic to analyze the risk levels of driving activity among road users. Driving fatigue is always related to the driving activity and has been identified as one of the vital contributors to the road accidents and fatalities in Malaysia. Therefore, the present paper introduces the use of fuzzy logic for the development of strain index to provide the systematic analysis and propose an appropriate solution in minimizing the number of road accidents and fatalities. The development of strain index is based on the six risk factors associated with driving fatigue; muscle activity, heart rate, hand grip pressure force, seat pressure distribution, whole-body vibration, and driving duration. The data is collected for all the risk factors and consequently, the three conditions or risk levels are defined as “safe”, “slightly unsafe”, and “unsafe”. A membership function is defined for each fuzzy conditions. IF-THEN rules were used to define the input and output variables which correspond to physical measures. This index is a reliable advisory tool for providing analysis and solutions to driving fatigue problem, which constitutes the first effort toward the minimization of road accidents and fatalities.

This perspective paper describes the building elements for realizing a precise patient monitoring algorithm to fundamentally address the alarm fatigue problem. Alarm fatigue is well recognized but no solution has been widely successful. Physiologic patient monitors are responsible for the lion’s share of alarms at the bedside, most of which are either false or non-actionable. Algorithms on patient monitors lack precision because they fail to leverage multivariate relationship among variables monitored, to integrate rich patient clinical information from electronic health record system, and to utilize temporal patterns in data streams. Therefore, a solution to patient monitor alarm fatigue is to open the black-box of patient monitors to integrate physiologic data with clinical data from EHR under a four-element algorithm strategy to be described in this paper. This strategy will be presented in this paper in the context of its current status as described in our prior publications.

For warships with long superstructure and complex cabin structure, the obvious stress concentration at the superstructure end had generally led to serious fatigue problem.

Size effects on crack growth are of paramount importance on the fatigue problem. Paris’ and Wohler’s fatigue curves exhibit scale effects, which can be explained in the framework of incomplete self-similarity and fractal geometry concepts. In particular, scaling laws are found for the main fatigue parameters, that is, the fatigue threshold ΔKth and the fatigue limit Δσfl. The fatigue threshold increases with the crack length, whereas the fatigue limit decreases with the specimen size. Eventually, the proposed models are positively compared to experimental data available in the literature.

This article explores the evolution of the nonlinear reduced-order modeling concept and its application to the acoustic fatigue problem as guided by a course of experiments. Since the advent of the jet engine, military aircraft have been plagued by acoustic fatigue. For decades, the resulting cracking has been a nuisance affecting mostly secondary structure, which can be routinely replaced. These thin aircraft panels are excited by ever increasing acoustic energy, causing the vibration to become nonlinear. The nonlinear response had been attributed to nonlinear damping but has been shown to be caused by geometric nonlinearity which results in nonlinear stiffness. Regardless of the cause of the nonlinearity, acoustic fatigue in conventional military aircraft can be controlled via damping treatments. However for high speed vehicles, the availability of high temperature damping treatments is practically non-existent. Furthermore, fatigue cracking in any part of the outer mold line can have catastrophic effects on the aerodynamic heating of these vehicles. Research into the prediction of the nonlinear vibration with reduced-order models has become popular in the past decade to address these concerns. This paper will document some experiences with these concepts through experimental investigations.

The fatigue problem of concrete is still a challenging topic in the researches and applications of concrete engineering. This paper aims to develop a fatigue damage evolution law based model for concrete motivated by the analysis of physical mechanism. In this model, the fatigue energy dissipation process at microscale is investigated with rate process theory. The concept of self-similarity is employed to bridge the scale gap between microscale cracking and mesoscale dissipative element. With the stochastic fracture model, the crack avalanches and macro-crack nucleation processes from mesoscale to macroscale are simulated to obtain the behaviors of macroscope damage evolution of concrete. In conjunction with continuum damage mechanics framework, the fatigue damage constitutive model for concrete is then proposed. Numerical simulations are carried out to verify the model, revealing that the proposed model accommodates well with physical mechanism of fatigue damage evolution of concrete whereby the fatigue life of concrete structures under different stress ranges can be predicted.

The fatigue problem induced by wave loads and floater movements of dynamic umbilicals in deepwater is studied. The prediction method of the fatigue life is investigated by considering no-linear local stress due to contact and friction between components of the umbilical. A case study of a dynamic umbilical for 1500 meters depth in South China Sea was presented. The results showed that the more accurate result of the fatigue life was calculated by considering non-linear local stress. The fatigue life by considering local stress with the no-slip assumption was conservative. An obviously longer fatigue life was obtained by considering local stress with the full-slip assumption.

Sustained loads have for some Ni-based superalloys been shown to give rise to increased crack growth rate at elevated temperature. Such loads generate a history dependent fatigue problem due to weakening and cracking of grain boundaries during dwell times, later broken apart during subsequent load cycles. So far most studies have focused on the interaction of load cycles, overloads, and temperature. However, vibrations of different kinds are to some extent always present in engine components, and an investigation of how such loads affect the dwell time cracking, and how to incorporate them in a modelling context, is therefore of importance. In this paper a study of the most frequently used gas turbine material, Inconel 718, has been carried out. Mechanical crack propagation testing has been conducted at 550 °C for surface cracks with and without the interaction of superimposed vibrational loads. Subsequent investigation of the fracture behaviour was performed by scanning electron microscopy and the modelling work has been conducted by incorporating the vibration load description within a history dependent crack growth law. The obtained results show reasonable accuracy with respect to the mechanical test results. Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through the Swedish research programme TURBO POWER

The coupled systems of fatigue crack initiation problem undergoing large range damage is defined. The zero different work principle, coupled potential energy principle, coupled complementary energy principle in the coupled system is established. By using of coupled potential energy principle, Closed form solution about predicting fatigue crack initiation life of three-dimensional component which leads to large range damage is derived. Compared with reference [1], the close form solution derived from this some. It is proved that the method is correct. The method adopted in this paper is definite in mechanical concept,it can be widely used in analysis of predicting fatigue crack initiation life of various component which leads to large range damage.

The study of near-threshold fatigue crack growth has long remained an empirical field due principally to the highly microstructure-sensitive nature thereof. The primary challenges have been to forward physical model(s) informed by the governing micromechanism(s), which would be able to predict the experimental behaviors devoid of empiricism. Today, we have sophisticated experimental techniques (e.g. digital image correlation, electron microscopy) as well as atomistic simulation tools (e.g. molecular dynamics) at our disposal to finally revisit the century old fatigue problem in the light of physical phenomena therein. This paper is geared towards achieving such a feat with a very special type of materials, nano-twinned alloys, as the candidate materials, which are of great recent interest due to their reportedly superior damage properties. Specifically, we investigate how the microstructural features (e.g. slip transfer mechanism at coherent twin boundaries, twin thickness/spacing, frictional stress, pre-existent near-tip slip density) can be modulated to improve the damage resistance. The results suggest that these parameters considerably affect the crack propagation impedance (as quantified in terms of Δ K eff th ). A thorough discussion of the current findings and the most recent literature developments in this regard are provided.

Ultra-high cycle fatigue problem has received more and more attention with the continuous improvement of the reliability and life index of modern equipment, and has become a hot spot in fatigue research. As the non-metallic material with the most application potential in the modern aviation industry, the ultra-high cycle fatigue problem of carbon fiber reinforced plastic (CFRP) is the most prominent. In this paper, the research progress of ultra-high cycle fatigue research of CFRP has been systematically sorted out and summarized from three dimensions of test method, fatigue fracture macro-micro characteristics and fatigue damage model construction, including the adopted technical methods, the mechanism of fatigue crack initiation, the characteristics of S-N curve, Goodman diagram and the influence of humidity and other influence factors. The mechanism, evolution and model of CFRP ultra-high cycle fatigue damage are expounded, and the problems existing in the ultra-high cycle fatigue research of CFRP are presented.

The recommender systems tend to face the problem of lacking clues about the new user, as a result, it is difficult for the system to provide users with the right recommendation results. In this study, the Interactive genetic algorithm is adapted to join with recommender system, and this new system is used to solve the problem of the traditional recommender system. In addition, this study proposes a double-layer encoding structure that involves the global and area encoding, which will help the optimization of interactive genetic algorithm (IGA) to solve the user fatigue problem. The case study testified that this recommended framework was able to rapidly filter vast amounts of data and to offer personalized recommendations for each film viewer. For future research, further studies on IGA that integrates analysis of screen genes to achieve a higher quality of recommendation and to further solve IGA user fatigue issues. Finally, this new recommender system was used to test film viewers in Taiwan and Hollywood films released in the past 12 years, and the experimental results show evidence that the new system is useful.

This research focusing on fatigue crack growth experiment and assessments of fatigue crack growth model. Fatigue has been considered as the most important phenomena in the engineering problems. It has been found to occur in every engineering field. Many methods were introduced to overcome fatigue problem. One of it is fatigue crack growth prediction models. Fatigue crack growth model prediction can determine the residual life of the mechanical component. Fatigue crack growth is an important parameter in engineering. It may begin from undamaged area and propagate afterwards. In this case, a mechanical component condition before an unstable crack still can be used until fatigue. With the study of fatigue crack growth, it can predict the crack life of the component and can reduce cost to repair the component. In this thesis, primary objective is to develop, test and provide computational fracture mechanics model that emphasized an uncertainties quantification for surface crack. Fracture and failure study that has been promoted by S-version finite element method is focus on the analysis of the surface-crack problem. In this project, a few limitations of the study have been implemented as to present a specific scope of the investigation. Both fatigue crack growth model is considered; Paris law model and modified Forman model. The specimen in this analysis is aluminium al 2024 T3. The effect of load on the fatigue crack growth rate is investigated on aluminium 2024 T3. It is concluded that modified Forman has a low exponent compared to the Paris law. Further the crack growth prediction based on modified Forman is lower than Paris law. Paris law only can predict the crack in the region II while modified Forman can predict the crack in region II and III. After finish setup the project based on the instruction, the project is proceeded and the data is collected. The result is analysed based on the objective by using data collected from the project. After that, conclusion is made based on the result of the project.

Driving fatigue has been recognized as one of the significant contributory factors to the road accidents and fatalities in Malaysia. The aim of this study was to develop an ergonomic vehicle model (EVM) and decision support system (DSSfDF) model for improving the driving fatigue problem among the road users. The ergonomic vehicle model uses to capture the user information data and acts as the database storage to store all the input data and information. While the decision support system provides a systematic analysis and solution to minimize the risk and the number of accidents associated with driving fatigue. There are 6 main components as the pillars for the development of EVM and DSSfDF model; ergonomics evaluation tools, graphical user interface (GUI), ergonomics database, working memory, inference engine, and knowledge base. Both models are essential system and reliable advisory tool for providing analysis on risk factors that contribute significantly to driving fatigue and providing solutions and recommendation to the problem related to driving fatigue. Further analysis and validation are required in future to get the reliable system before being commercialized.

Crankshaft fatigue problem has long been a headache and frequent phenomenon in combustion engine which attracts various efforts especially including fundamental fatigue experimental data. In this paper, the rational experimental method is employed to study the crankshaft fatigue phenomenon based on a customized experiment platform, mimicking the real-world crankshaft working condition physically. Then, based on the experiment data, the statistical regression analysis of eight commonly used hypothesis distributions is conducted. The degrees of fitting effects of the chosen statistical model are evaluated individually. Results show that the three-parameter Weibull distribution model fits the data best which may be used as the fundamental model in future analysis. This study provides a solid foundation for better understanding the mechanism of crankshaft fatigue phenomenon.

Feature fatigue (FF) analysis is of critical importance for product development. To deal with the FF problem, it is essential to decide what features should be added to make the product attractive enough and not too hard to use at the same time. This paper introduces a novel methodology to search for robust feature combinations under uncertain customer preferences in FF analysis. Non-dominated sorting genetic algorithm II (NSGA-II) is firstly adopted to establish a multi-objective optimisation model. Then a grey forecasting model and a worst-case strategy are used to create different coefficient scenarios based on customer evaluation data. After running NSGA-II under each scenario, several candidate solutions for final selection can be obtained according to robustness analysis. Compared with existing studies in FF, the proposed method can obtain multiple optimal solutions rather than just a single one for designers to choose from, and the robustness degree of each solution is computed considering both pre...

As vibrations from vortex-shedding occur at moderate wind speeds, structures undergo a considerable number of stress variations. So risk of fatigue is to be taken into account at the design stage itself. Even if a fatigue analysis is not demanded in the code to be applied, risk of fatigue is to be considered, especially with regard to slender steel chimneys due to larger volumes of material subjected to high stresses. Thus, risk of fatigue which has not been addressed in the Indian context, has been taken care in the present paper. It is envisaged that this formulation will be appropriate for inclusion in Indian codes and standards. As part of the case study, a chimney from an industry having Diesel Power Plant has been undertaken. Fatigue analysis of this chimney has been done and measures to reduce fatigue problem have been suggested.

In the shipbuilding industry, the concern of the fatigue problem has been a very important item for the ship owner, shipbuilder, classification society, etc. The evaluation method for fatigue strength is very complex and a time consuming job, but for maintenance purposes it is a very critical item. However, for the opening and hull outfitting, pipes and control units installed on the main deck, the fatigue problems are not considered/evaluated like the other hull structure members. Those are installed and constructed according to Yard's experience and practice without appropriate direct verification procedure for fatigue strength, and hence the occasional occurrence of cracks on the outfitting and around holes on the main deck. For these reasons, the fatigue strength in way of outfitting and openings installed on the main deck are evaluated and verified with the simplified method developed through a Joint Development Project (JDP) between Daewoo Shipbuilding Marine and Engineering (DSME) and Det Norske Ve...

Hammers are most typical of impact machines and are widely used in the mechanical manufacture industry. It is important to predict the effects of the damage growth on the fatigue process of the hammer foundation especially when subjected to long-term repeated impact loading. Although there have been many articles about damage model of soils, few of them have studied the problem of soil failure under cyclic loading as the fatigue damage of soils failure. In this paper, a damage fatigue problem of a hammer foundation system considered with fatigue damage growth and vibration on the machine foundation due to the impact of hammer blows is discussed by numerical results using the concept of damage mechanics based on the interaction between hammer foundation and soil ground. It has been found that the influence of damage due to hammer blows on the responses of the ground soil near the foundation is significantly increased with damage development both in the hammer foundation and the surrounding soil. Therefore, in order to protect the environment from damage due to the blows of a hammer, the design for actively vibration absorbing control and damage control in the hammer foundation system needs to be taken into account.

As the general features of fretting fatigue, initiation of fretting fatigue crack is in the very early stage of the fretting fatigue life and there are small non-propagating cracks in the test specimen that doesn't fracture at the fretting fatigue limit. In accordance with these experimental facts, fretting fatigue problem can be considered as a propagation problem of small crack. Thus, a pre-cracked specimen was used in the fretting fatigue test in this study. The objective was to consider the determinant factors of fretting fatigue strength. In the fretting fatigue test, the fretting fatigue limit of the pre-cracked specimen was once reduced and after increased with increase of the contact pressure. The reason was understood by the stress intensity factor of the pre-crack obtained by a finite element analysis. In this study, the fretting fatigue limit can be predicted by the comparison of ΔK of the pre-crack and the propagation threshold of the pre-crack ΔKth. The effect of the relative location of the pre-crack to the contact edge on the fretting fatigue strength was also discussed by both fretting fatigue test and FEM analysis.

Jianshe bridge is the first self-anchored cable-stayed suspension bridge in the world, localed in Dalian, China. Cable-stayed suspension was presented in history, however cable-stayed bridge and self-anchored suspension combine to make a new type system, which is economy and fit for large span bridge. This paper presents the design of Jianshe bridge. The static and dynamic character of the system and the fatigue of suspender are presented. The computing model of this new system is also introduced in the paper. The structure internal force nonlinearity and stress of the bridge are analyzed. Then analyse the calculate results and draw the conclusions, which self-anchored cable-stayed suspension bridge is fit for large-span bridge, cross suspender can reduce stress amplitude and overcome fatigue problem, and Wind-resistant stability of self-anchored cable-stayed suspension bridge is better than earth anchored system.

Attention has been focused on the fatigue problem for compacted graphite iron, when detonation pressure and temperature becomes higher and higher in combustion chamber for a long time. The compacted graphite iron plays an important role in the cylinder head of diesel industry for its good combination of thermal and mechanical properties. The damage mechanisms of compacted graphite iron under fatigue loading are observed in this study by scanning electron microscope (SEM) and in situ technique at elevated temperatures. The results show that tensile strength of compacted graphite iron decreases slightly at first, then decreases dramatically with the increasing temperature, which is a common phenomenon, even of various metallic materials. For the compacted graphite iron, these two stages are mainly controlled by different transformation mechanisms: the former mechanism, slip band stage, is affected by the inhibition of dislocation movement including strain strengthening, dynamic strain aging and precipitation hardening; and the latter, boundary sliding stage, is controlled by the vacancy diffusion. The newly proposed mechanisms can provide a new clue for the optimization of cast iron design. These damage mechanisms lay the foundation for the application of the crack technology.

To examine the reliability and validity of the Japanese-language version of the PedsQL™ Multidimensional Fatigue Scale and to investigate the agreement between child self-reported fatigue and parent proxy-reported fatigue. The Japanese-language version of the PedsQL™ Multidimensional Fatigue Scale was administered to 652 preschoolers and schoolchildren aged 5–12 and their parents, and to 91 parents of preschool children aged 1–4. Internal consistency reliability was 0.62–0.87 for children and 0.81–0.93 for parents. Known-group validity was examined between a group of healthy samples (n = 530) and chronic condition sample (n = 102); the chronically ill group reported a significantly higher perceived fatigue problem. Correlations between child self- and parent proxy reports ranged from poor to fair. In subgroups identified by cluster analysis based on child self-reported scores, the greatest agreement between child and parent reports was seen in the good HRQOL group, while the least occurred in the poor HRQOL group. The parents overestimated their child’s fatigue more when the child’s HRQOL was low. The Japanese-language version of the PedsQL™ Multidimensional Fatigue Scale demonstrated good reliability and validity and could be useful in evaluating Japanese children in school and health care settings.

A complicated 3D model was established to solve the problem of the lifetime of an engine support. With the finite element analysis software ANSYS, we analyzed the fatigue problem for an engine support and derived the numerical values of the lifetime of a typical engine support. Our work provides the fundamental guidance to optimize the structure of the engine support.

Many mechanical components are subjected to multiaxial fatigue. These conditions are typically coming from external loads, the geometry of the component and/or residual stresses. However the majority of experimental data available in the literature are focused on the simpler uni-axial fatigue problem. The present work describes a series of experimental tests conducted to characterise in a comprehensive way the multiaxial behaviour of a ST52-3N structural steel. First, the monotonic properties of the steel were obtained experimentally. Then cyclic properties were also measured both in the longitudinal and torsional axes. Finally another series of tests were carried out to study the multiaxial response of the material. Both in-phase (proportional) and out-of-phase (non proportional) loadings were employed, thus providing a complete database for improving current models which describe the multiaxial behaviour of materials.

The present paper aims at studying a high-pressure hydrogen storage vessel, combining a steel liner and a wrapped composite reinforcement. Nowadays, this means of storage is notably used in transport. However, limits appear insofar as fatigue problem happens when the operating pressure is 700 bar. This matter has to be solved. This study tries to arrange a method to build a 700 bar vessel which could resist to cyclic pressure loading, and particularly focuses on the behaviour of the liner which seems to be the critical element to control. In addition, as a large part of this gaseous storage is bound to be on board, the composite optimization and thus weight optimization is considered.

Broad acceptance of Finite-Element-based analysis of structural problems and the increased availability of CAD-systems for structural tasks, which help to generate meshes of non-trivial geometries, have been setting a standard for the evaluation of designs in mechanical engineering in the last few decades. The development of automated or semi-automated optimizers, integrated into the Computer-Aided Engineering (CAE)-packages or working as outer loop machines, requiring the solver to do the analysis of the specific designs, has been accepted by most advanced users of the simulation community as well. The availability and inexpensive processing power of computers is increasing without any limitations foreseen in the coming years. There is little doubt that Virtual Product Development will continue using the tools that have proved to be so successful and so easy to handle.

In the statistics of stress-strain cyclic response involved with cyclic-loading, rain-flow counting method has always been thought the most reasonable way to proceed cycle counting, based on which researchers could conduct fatigue test or calculate the damage extent according to e一N(or S一N) curve. That is the main reason why this method is widely used. This article will minutely discuss the principle, developing status, computer-based realization and application of rain-flow counting method, after which briefly discuss its application in fatigue problem in road and bridge.

As colleges and universities confront greater numbers of non-traditional students, there is a need to offer academic experiences in less traditional packages.

Introduction and Objectives: The dental prostheses are typical biomechanical structures because they have the objective to restore the mastication functions and are responsible for replacing the original tooth that was damaged. In the last few years, many studies have been done and big achievements have been noticed in this area. However, clinical studies and experimental procedures for these conditions are sometimes impractical, due to the biological nature of these components and the difficult to reproduce and to analyze such conditions. Moreover, it involves complex geometries, loads and mechanical behaviors, which analytical solution is very difficult to achieve. For these reasons, many researchers have applied the Finite Element Method (FEM). This method allows the evaluation of non-linear situations (e.g. biomechanical interactions) with complex geometries where experimental tests are usually difficult to be conducted. Furthermore, the uses of this method allow failure evaluation and it forecast occurrence. Like any mechanical structure, prostheses are sensible to failures. The cyclic nature of the loading that components are exposed means that fatigue failures are the type of failure which needs more attention in these kinds of structures. Therefore, this project aims to develop a tridimensional finite element model of dental prosthesis in order to evaluate the fatigue problem. Methods: A geometric model from a single dental prosthesis compounded by an implant, an abutment screw, an abutment, a fixation’s screw and a crown will be generated from Micro CT and scanning data. Then, the geometry will be exported to finite element software where a finite element model will be created. After these steps, boundaries conditions will be applied and simulations will be done. Finally, the simulation results will be analyzed. Results: The results from fatigue simulations and analysis demonstrated that abutment screw will have a finite life in most of the analyzed cases, and the fixation screw will be an infinite life. Conclusion: The results obtained illustrate the efficiency of Finite Element Method on simulating the biomechanical conditions, mainly in dental prostheses. In this study, the fatigue conditions were explored and analyzed. Finally, the knowledge about this problem could be improved.Copyright © 2015 by ASME

This paper shows the fatigue properties and fracture mechanism of modified 2.25Cr–1Mo steel. In refineries or chemical plants, modified 2.25Cr–1Mo steel is used in hot and high-pressure environments. Recently, a new fatigue problem concerning these facilities has become important, because number of cycles to failure that should be taken into consideration for maintenance has increased to over 107 cycles. For ultra-high-cycle fatigue, interior inclusions in the material are the dominant factor in a fatigue life, but the fracture mechanism for this has not been clearly elucidated. The results of ultra-high-cycle fatigue properties at elevated temperatures are presented. Interior fracture takes place at an ultra-high-cycle region, although many cases show no inclusions in the origins of an interior fracture. Crack growth life is predicted using fracture mechanics, so that life prediction for modified 2.25Cr–1Mo steel is possible.

A new multiaxial fatigue damage model named characteristic plane approach is proposed in this paper, in which the strain components are used to correlate with the fatigue damage. The characteristic plane is defined as a material plane on which the complex three-dimensional (3D) fatigue problem can be approximated using the plane strain components. Compared with most available critical plane-based models for multiaxial fatigue problem, the physical basis of the characteristic plane does not rely on the observations of the fatigue crack in the proposed model. The cracking information is not required for multiaxial fatigue analysis, and the proposed model can automatically adapt for different failure modes, such as shear or tensile-dominated failure. Mean stress effect is also included in the proposed model by a correction factor. The life predictions of the proposed fatigue damage model under constant amplitude loading are compared with a wide range of metal fatigue results in the literature.

The user fatigue problem in interactive evolutionary computation (IEC) is a complex and interesting issue. If the IEC search space is created from the experience or knowledge of domain experts rather than from users values, it causes two potential problems which lead to fatigue problems in IEC: 1) inefficiency and 2) boredom. Therefore. we propose a customer values-based IEC model, solving the fatigue problem by avoiding the potential problems. A case study involving the design of mineral water bottles was used to verify the anti-fatigue capability of the users when using the proposed model. For comparison with the traditional domain knowledge based model. we built two IEC systems, a customer values-based system and a traditional system, and conducted a user burden test and a system efficiency test over a two-week period. The results of both tests show that our proposed system performed better than the traditional system in designing mineral water bottles.

A multiscale model is developed for fatigue life predictions of elastoplastic solids and structures. The fatigue problem is formulated using a variant of the mathematical homogenization theory developed to account for almost periodic fields. Multiple temporal scales are employed to resolve the solution within a load cycle as well as to predict the useful life span of a structural component. The concept of almost-periodicity is introduced to account for irreversible inelastic deformation, which gives rise to nonperiodic fields in time domain. By this approach the original initial boundary value problem is decomposed into coupled microchronological (fast time-scale) and macro-chronological (slow time-scale) problems. The proposed life prediction methodology was implemented in ABAQUS and verified against the direct cycle-by-cycle simulation.

load. Abstract:The mechanical properties of rubber materials are complex, and the strength problem is getting more and more attention. This paper summarizes the research status of mechanics experiment of rubber materials under dynamic and static load, commented recent years domestic and foreign the progress on the field of rubber uniaxial and multiaxial fatigue. Introduced strength problem research under quasi static load of commonly used constitutive model, selection of constitutive model and determination of parameters status, pointed out the exist problems in experimental study of rubber materials strength.

The fatigue problem in ferroelectric thin films is investigated based on the switched charge per unit area versus switching cycles. The temperature, dielectric permittivity, voltage bias, defect valence and frequency dependent switching polarization properties are calculated quantitatively with an extended Dawber-Scott model. The results are compared with recent experiments. Some features of polarization fatigue and in correlation with parameters of ferroelectric thin films are reported.

In this paper, for the mixed mode fatigue problem, the method of determining testing load was proposed. It is based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E 647-00. The application method of maximum tangential stress criterion and the stress intensity factor for the finite width specimen was proposed. In the result of applying the method to mixed mode fat gut test for A5052 H34, it obtained the satisfactory experimental results on the stable crack growth.

Based on linear damage accumulation law, this paper investigates the fatigue problem of drill-strings in time domain. Rainflow algorithms are developed to count the stress cycles. The stress within the drill-string is calculated with finite element models which is developed using Euler-Bernoulli beam theory. Both deterministic and random excitations to the drill-string system are taken into account. With this model, the stress time history in random nature at any location of the drill-string can be obtained by solving the random dynamic model of the drill-string. Then the random time history is analyzed using rainflow counting method. The fatigue life of the drill-string under both deterministic and random excitations can therefore be predicted.Copyright © 2014 by ASME

In this paper, a comprehensive approach is developed to integrate computational reliability methods and nondestructive inspection (NDI) for fatigue reliability evaluation. Uncertainties existing in the performance and outcome of NDI are considered through numerical statistical measures, and the mathematical relationships among these measures are derived. A new method is proposed to estimate the probability of detection (POD) and confidence interval using these relationships. Also, a new method of using the NDI results to update the reliability estimation is presented, which accounts for POD, measurement accuracy, false call probability, and the probability that a very large flaw may not be detected. The application of the proposed methods is illustrated through an example fatigue problem and inspection techniques with different POD characteristics are compared.

This paper is aimed at developing a methodology and strategy for fatigue damage assessment and life prediction of bridge-deck sections of existing bridges with online structural health monitoring data. A fatigue damage model based on the continuum damage mechanics (CDM) is developed for evaluating accumulative fatigue damage of existing bridges. A structural model for the fatigue stress analysis of bridge-deck structures is proposed, in which structures are modeled by elastic members and welded connections with possible accumulative damage. Based on the proposed model, an analytical approach for evaluating the fatigue damage and service life of bridge-deck sections based on strain history data from an online structural health monitoring system and the CDM fatigue model are suggested. The updating of the representative block of cycles of the local stress by online monitoring data in the future is included in the computational approach. In order to compare results of fatigue damage and service life prediction evaluated by the CDM fatigue damage model, a modified Palmgren–Miner rule is developed for the same fatigue problem.

Aircraft structures are susceptible to fatigue and corrosion damage, notably at joints. There may be interactions between fatigue and corrosion, especially as aircraft age. Longitudinal lap splices from several types of transport aircraft pressure cabins were disassembled and investigated for Multiple Site Damage (MSD) fatigue cracking and corrosion. The results are compared with NASA data for a full-scale fatigue test. Broadly speaking, pressure cabin lap splices have either a fatigue problem or a corrosion problem: MSD fatigue cracking is not initiated by corrosion. The results are discussed with respect to lap splice MSD fatigue modelling, testing and analysis.