Linear Damage Research Articles

Method for Evaluating Bolt Competitive Failure Life Under Composite Excitation

In this study, the competitive failure mechanism of bolt loosening and fatigue is elucidated via competitive failure tests on bolts under composite excitation. Based on the competitive failure mechanism, the mode prediction model and “load ratio—life prediction curve” (ξ–N curve) of the bolt competitive failure are established. Given the poor correlation of the ξ–N curve, an evaluation model of the bolt competitive failure life is proposed based on Miner’s linear damage accumulation theory. Based on the force analysis of the thread surface and simulation of the bolt connection under composite excitation, a theoretical equation of the bolt competitive failure life is established to validate the model for evaluating the bolt competitive failure life. The results reveal that the proposed model can accurately predict the competitive failure life of bolts under composite excitation, and thereby, it can provide guidance to engineering applications.

Structural behavior of stainless steel anchor channels embedded in concrete under perpendicular and longitudinal shear

Stainless steel anchor channels with channel bolts (SSAC-CBs) have been chosen as alternatives to conventional carbon steel anchor channels to enhance corrosion resistance, ductility, and load-bearing capacity. This study evaluated the shear performance of SSAC-CBs embedded in concrete members under perpendicular and longitudinal shear loads using static monotonic tests. The failure modes and shear capacities of the specimens were compared with those obtained by finite element analysis (FEA) models established using ABAQUS. Concrete edge breakout failure accompanying the channel flexural yielding and channel bolt fracture dominated in the SSAC-CBs under perpendicular shear. The load–displacement curves for perpendicular shear exhibited four salient stages: initial linear elasticity, slippage, strain hardening, and damage and failure. Under longitudinal shear, the SSAC-CB specimens exhibited a failure of the serrations in the contact area between the serrated channel bolt head and channel lips and slip failure between the hook-type channel bolt and channel lips. In addition, the numerical analysis results indicated that the load-bearing capacities, initial elastic stiffnesses, and failure modes obtained through the FEA models were consistent with the test results. Furthermore, theoretical formulas were proposed for the shear capacity for SSAC-CBs under perpendicular and longitudinal shear. The research outcomes provide valuable guidance for the design and application of SSAC-CBs in engineering.

Fatigue life prediction of stay cables under vehicle load considering corrosion variability

The combined effect of environmental corrosion and fatigue loads can accelerate the failure of stay cables. To ensure the safe operation of stay cables, this paper proposed a method for evaluating the fatigue life of stay cables, considering the variability of steel wire corrosion within the cable. Firstly, the relationship between the mean value and the standard deviation of uniform corrosion depth was established based on the experimental data of the corroded steel wires under the artificial accelerated corrosion environment. Then, the model of cable time-vary corrosion under the actual service environment was substituted, and the distributions of the weight loss rate of steel wires were obtained. Subsequently, a method for calculating the fatigue life of stay cables considering the corrosion variability of steel wires in the cable was proposed based on the parallel system theory and the Miner linear cumulative damage criterion. Finally, the North Channel Bridge (NCB) of Hangzhou Bay Bridge was used as an example, and the fatigue life distribution of stay cable under the combined action of corrosion and vehicle load was predicted. The results indicate that considering the corrosion variation of steel wires in the cable leads to a reduction in the fatigue life of stay cables, and neglecting this variability in fatigue life prediction methods is unsafe and non-conservative.

Machinery Value Estimation Method Based on IIoT System Utilizing 1D-CNN Model for Low Sampling Rate Vibration Signals From MEMS

Accurately estimating the value of an equipment is a significant challenge in the industrial environment. Conventional methods mainly considered discounting the value over time, but they are limited in that they do not consider the status of individual equipment. Recent developments in Industrial Internet of Things (IIoT) and AI technologies have opened up the possibility of real-time remote monitoring on the status of machinery, thus providing an opportunity to more accurately estimate the value of machine equipments. In this study, we designed a sensor that can acquire the vibration and magnetic field data of an equipment, with which we proposed a one-dimensional convolutional neural network that can classify the status of machinery based on the data obtained by the designed sensor. In addition, based on the results of the classification model, the cumulative fatigue of equipment was predicted using the Pålmgren-Miner’s linear damage rule, with which we proposed a model for estimating the value of movable property based on the cumulative fatigue.

Creep-fatigue life and damage evaluation under various strain waveforms for Ni-based Alloy 740H

This paper presents creep-fatigue life evaluation of a nickel-based Alloy 740H, for evaluating its performance as a material of advanced ultra-supercritical power plants. Strain controlled creep-fatigue tests were performed under six strain waveforms using solid bar specimens at 700 °C, and the effect of strain waveform on creep-fatigue life was discussed. Creep-fatigue lives were shorter than pure fatigue life depending on the strain waveform. The failure life in symmetrical waveform was reduced to about half as the strain rate decreased by one order of magnitude. The failure lives in the unsymmetrical waveforms were smaller than that in the symmetrical waveform and tensile slow straining was more detrimental to fatigue life than compressive slow straining. The creep-fatigue life decreased significantly due to strain hold, and tensile peak strain hold had more enhanced effect on fatigue life than compressive strain hold. Applicability of five existing approaches based on linear damage summation rule were discussed. In addition, a new approach based on modified ductility exhaustion model with several modifications was proposed in order to improve the life predictability of the classical approach. Time fraction rule with ASME failure envelope and new approach satisfactorily predicted the creep-fatigue lives almost within a scatter band of 2.

New Numerical Method Based on Linear Damage Evolution Law for Predicting Mechanical Properties of TiB2/6061Al.

In order to study the effect of TiB2 particles on the mechanical properties of TiB2/6061Al composites, a series of 3D TiB2/6061Al representative volume elements (RVEs) were established based on SEM photos. This model took into account the ductile damage of the matrix and the traction separation behavior of the interface, and the linear damage evolution law was introduced to characterize stiffness degradation in the matrix elements. Mixed boundary conditions were used in the RVE tensile experiments, and the accuracy of the predicted result was verified by the agreement of the experimental stress-strain curve. The results showed that the addition of TiB2 particles can effectively promote the load-bearing capacity of the composite, but elongation is reduced. When the weight fraction of TiB2 increased from 2.5% to 12.5%, the elastic modulus, yield strength, and tensile strength increased by 8%, 10.37%, and 11.55%, respectively, while the elongation decreased by 10%. The clustering rate of the TiB2 particles is also an important factor affecting the toughness of the composites. With an increase in the clustering rate of TiB2 particles from 20% to 80%, the load-bearing capacity of the composites did not improve, and the elongation of the composites was reduced by 8%. Moreover, the high-strain region provides a path for rapid crack propagation, and particle spacing is a crucial factor that affects the stress field.

Research on fatigue reliability assessment of engine cylinder head based on neural network

Fatigue reliability (FR) evaluation is crucial for extending the service life and improving the reliability of automotive engines. This study proposed a general framework for assessing high cycle FR based on the back propagation neural network (BPNN). Using a diesel engine cylinder head (CH) as an example, the stochastic finite element analysis was implemented by considering the uncertainties of materials and loads. Subsequently, the stochastic finite element calculation process was replaced with the BPNN model to expedite fatigue life prediction. Ultimately, the reliability assessment of the CH was conducted, taking into account the influence of the load sequence. The research findings indicated that the reliable life t0.95 of the CH considering the load sequence was approximately 75 h, representing a 7.1% increase compared to the linear cumulative damage. During the service life of the CH, the failure probability sensitivity factor for the gas force load exceeded 0.9, offering an important reference for optimizing FR.

On a numerical methodology to assess the fatigue life of connecting rods

Although simulation-based fatigue analysis is a standard tool adopted in every sector including automotive industry, the design of engine components in automotive and motorsport applications mostly relies on simplified design approaches supported by time-consuming testing programs. This manuscript proposes a new methodology based on individual engine speed damage estimation and engine speed time history combined with Palmgren-Miner linear damage rule to predict the fatigue state of the connecting rod. The track data, engine multibody simulation (AVL ExciteTM) and engine combustion simulation (AVL BoostTM) are used to generate the initial variable trace that is processed to obtain the block programs. Stress amplitude estimated with finite element analysis (Abaqus) are used to estimate the damage from S-N curve and the cumulative damage is estimated with Palmgren-Miner cumulative damage model. The method proposed is demonstrated using a connecting rod case study and the duty cycle from the race on Sebring international raceway. This work shows the suitability of the approach and the benefit in terms of accuracy in the prediction of the fatigue life.

Fatigue life prediction of orthotropic steel deck strengthened with UHPC under stochastic traffic load

In recent years, the ultra-high performance concrete (UHPC) has been increasingly used to strengthen orthotropic steel decks (OSD) to solve the cracking problems at fatigue-prone details and pavement damage. In this paper, the fatigue life of a cable-stayed orthotropic steel decks bridge under stochastic traffic loads is calculated before and after the orthotropic steel decks strengthened with the ultra-high performance concrete layer. The traffic data of the real bridge for 1 week is first obtained based on the weigh-in-motion system. Then, a stochastic traffic load on the bridge is simulated for its service life by the Monte Carlo method. A fatigue life analysis framework, which includes the traffic load simulation, a refined finite element model, the S-N curve and Miner linear cumulative damage criterion, is proposed for fatigue life prediction of orthotropic steel decks. For the bridge before reinforcement, the predicting results for the fatigue life of three fatigue-prone details, including the scallop cutout, rib-to-diagram and rib-to-deck joint are basically consistent with that of the actual bridge inspection results. After strengthening by ultra-high performance concrete, the fatigue life of the three structural details are increased from 15.87, 13.89, and 32.26 years to more than 100 years, respectively, as compared with the original orthotropic steel decks structure.

A unified fatigue life evaluation method for different failure modes of the repaired rib-to-deck joints in orthotropic steel decks

The rib-to-deck welded joints in orthotropic steel decks (OSDs) are prone to fatigue damage with different fatigue failure modes. The damage accumulation of the corresponding failure modes should be estimated in repair design. This study proposed a unified fatigue life evaluation method for different failure modes of rib-to-deck welded joints based on the structural stress method and linear damage accumulation theory. The method considers the effect of crack depth and crack propagation on life evaluation, validated by the tests of repaired rib-to-deck joints with interior repair welds. Damage accumulation before and after repairing corresponding to different failure modes was assessed. The dominant failure modes before and after repairing were analyzed. Finally, the damage accumulation law of welded joints after repair under standard traffic load was investigated based on the existing damage status of each failure mode of the rib-to-deck welded joint. The results indicate that the failure mode will transfer from root-deck to exterior toe-deck at the rib-to-deck joint after the interior repair welding. The dominant failure mode of the repaired joint is governed by the existing damage status and the repair method.

Study on fatigue life of gun latch based on orthogonal test method

Aiming at the problem of fatigue damage of gun latch caused by long-term impact load, the fatigue life of gun latch was studied. Firstly, the finite element model of gun latch was established by using finite element method. Secondly, the static strength and fatigue life of the gun latch were calculated based on S-N curve and Miner’s linear damage accumulation theory. On this basis, the structural factors affecting the fatigue life of the bolt were analyzed, and four factors including the radial diameter of the latch, the axial bearing thickness of the latch, the spiral Angle of the latch support surface and the gun tail support surface, and the locking clearance between the bolt and the gun tail were set up, as well as three variation levels of each factor. Then, the fatigue life of nine groups of gun latches was simulated by orthogonal test method. In addition, the range analysis method was used to analyze the simulation results, and then the influence law and degree of each factor on the fatigue life of gun latch were obtained. Moreover, the optimal combination scheme of the structure parameters of the gun latch was determined by the comprehensive balance method, and then the finite element simulation was carried out to verify the structure of the gun latch. The results show that the maximum stress of the bolt decreases 21.5% and the maximum stress of the gun tail decreases 28.2%, and the maximum stress of the gun bolt is lower than the yield limit of the material. At the same time, the research also shows that the minimum fatigue life of the bolt increases greatly, the minimum fatigue life of the bolt body is 20.8 times of that before the test, and the minimum fatigue life of the gun tail is 102.1 times of that before the test. The results provide a reference for fatigue life analysis and structural design of gun latch.

Discussion on Fatigue Life Analysis Methods for Connecting Bolts of the Top Cover of Water Pump Turbines

Under the joint action of dynamic and static loads, the connecting bolts of the top cover of the pump turbine are prone to cumulative damage in local areas such as threads, resulting in cracks or development, and fatigue fracture may occur in severe cases, which will cause serious safety accidents. Therefore, it is necessary to carry out accurate fatigue life estimation analysis for connecting bolts, which has always been a hot spot and difficulty in the industry. This paper introduces several commonly used fatigue life analysis methods of parts, combined with the force characteristics and structural characteristics of the connecting bolts of the top cover, and analyzes and discusses the fatigue life analysis methods suitable for the top cover bolts. Finally, it is believed that the application of stress-strain field strength method can better describe the actual state of the bolt danger area, and the current damage state has an influence on the amount of damage generated by further loading, and the fatigue life analysis of connecting bolts can be combined with the stress-strain field strength method and variable damage linear cumulative damage theory, and the fatigue life and residual fatigue life can be estimated in the design stage or after the phased service of the bolt.

Stochastic approach for remaining fatigue life prediction considering parametric distributions

AbstractIn the present work, a stochastic framework, which combines the well‐recognized linear damage rule (LDR) and the uncertainty of material properties under constant amplitude loading, is proposed to improve the accuracy in prediction of remaining fatigue life. The uncertainty quantification approach based on parametric statistics is employed together with the Monte‐Carlo simulation method for modeling the randomness of remaining fatigue life. The impact of several commonly‐used parametric statistics is investigated, and the pertinent one is identified utilizing the Kullback‐Leibler divergence. The proposed framework is validated through the use of experimental fatigue life data under two‐step loading test.

Fatigue life assessment of fuselage panel modification based on flight measurement

During the modification of the aircraft fuselage panel, the fatigue performance of the structure changes. To ensure the safety and reliability of commercial aircraft, the fatigue life assessment of the modified structure is required. In this paper, the detailed fatigue rating method was used for fatigue assessment. The strain information of the modified structure during the flight was obtained by installing fiber Bragg grating sensors. Through the finite element analysis, the fatigue critical parts were determined and the measured data before modification were converted into the data after modification. The detailed fatigue ratings of the fatigue critical parts were calculated. The fatigue life of the critical parts was evaluated based on the linear fatigue damage cumulative rule. According to the results, the most critical part was determined, which provides a basis for the determination of the modification plan of the fuselage panel.

Influence of Power Cycling Test Methodology on the Applicability of the Linear Damage Accumulation Rule for the Lifetime Estimation in Power Devices

The lifetime of power semiconductor devices, operating under a given mission profile and subjected to power cycling stress, is conventionally estimated under the assumption of linear damage accumulation rule, that is the application of the Miner's rule. To this purpose, lifetime models must be properly defined allowing to take into account for the relevant parameters of power cycling stress. This work shows how to estimate a cumulative distribution function in the case of an arbitrary temperature swing profile, starting from the statistical distribution at constant power cycling conditions. It is found that the accuracy of the linear damage accumulation rule is related to the experimental methodology adopted for power cycling tests. A detailed experimental activity is carried out on packaged IGBT devices, providing useful guidelines for the definition of lifetime models to be adopted in the Miner's rule.

Nanopore discrimination and sensitive plasma detection of multiple natriuretic peptides: The representative biomarker of human heart failure

Natriuretic peptides can relieve cardiovascular stress and closely related to heart failure. Besides, these peptides also have preferable interactions of binding to cellular protein receptors, and subsequently mediate various physiology actions. Hence, detection of these circulating biomarkers could be evaluated as a predictor (“Gold standard”) for rapid, early diagnosis and risk stratification in heart failure. Herein, we proposed a measurement to discriminate multiple natriuretic peptides via the peptide-protein nanopore interaction. The nanopore single-molecular kinetics revealed that the strength of peptide-protein interactions was in the order of ANP > CNP > BNP, which was demonstrated by the simulated peptide structures using SWISS-MODEL. More importantly, the peptide-protein interaction analyzing also allowed us to measure the peptide linear analogs and structure damage in peptide by single-chemical bond breakup. Finally, we presented an ultra-sensitive detection of plasma natriuretic peptide using asymmetric electrolyte assay, obtaining a detection limit of ∼770 fM for BNP. At approximately, it is 1597 times lower than that of using symmetric assay (∼1.23 nM), 8 times lower than normal human level (∼6 pM), and 13 times lower than the diagnostic values (∼10.09 pM) complied in the guideline of European Society of Cardiology. That said, the designed nanopore sensor is benefit for natriuretic peptides measurement at single molecule level and demonstrates its potential for heart failure diagnosis.

A new short-time procedure for fatigue life evaluation based on the linear damage accumulation by Palmgren–Miner

The aim of the presented research is to develop a new short-time-procedure based on the linear damage accumulation according to Palmgren–Miner, which can provide an S-N curve in the HCF regime based on results of only one fatigue test. Load increase tests were carried out to determine the partial damage per load level from the material response by using NDT-methods. By converting the calculated partial damage of each load step into the corresponding number of cycles to failure, an S-N curve can be generated. This research focuses on a quenched-tempered 20MnMoNi5-5 steel. The validation was performed on three further steels.

Open-Access Experiment Dataset for Fatigue Damage Accumulation and Life Prediction Models

This work addresses the lack of focus on verification and comparison of existing fatigue damage accumulation and life prediction models on the basis of large and well-documented experiment datasets. Sixty-four constant amplitude, 54 two-level block loading, and 27 three-level block loading valid experiments were performed in order to generate an open-access, high-quality dataset that can be used as a benchmark for existing models. In the future, more experiments of various specimen geometries and loading conditions will be added. The obtained dataset was used for a study comparing five (non)linear fatigue damage and life prediction models. It is shown how the performance of several (non)linear damage models is strongly dependent on the considered material dataset and loading sequence. Therefore, it is important to verify models with a broad set of independent datasets, as many existing models show significant bias to certain datasets.

Extreme structural response prediction and fatigue damage evaluation for large-scale monopile offshore wind turbines subject to typhoon conditions

Offshore wind is becoming the way forward for green energy harnessing worldwide. However, frequent typhoons are a major constraint for the development of offshore wind power for some regions in Asia and North America. Typhoons may pose a huge challenge to offshore wind farm development in southern China. In this paper, a fully-coupled analysis was carried out for a 10 MW large-scale monopile offshore wind turbine (OWT) using SIMO-Riflex-Aerodyn (SRA) code. The response characteristics of the OWTs in different typhoon regions are investigated based on the measured typhoon conditions in China. The effect of aerodynamic damping on the response and the load effect is analyzed in detail. Two different distribution methods are used to statistically extrapolate the response value and get the short-term extreme response. Cumulative linear fatigue damage is evaluated by the rain-flow counting method to explore the possible failure modes of large wind turbines during typhoons. The results show that aerodynamic loads play an important role in large monopile OWTs during high wind speeds in parked conditions. The extreme response and fatigue analyses from this study indicate that fatigue is a dominant failure mode for the large OWT tower during typhoons, while buckling is unlikely.

The Reliability of the Complex Components under Temperature Cycling, Random Vibration, and Combined Loading for Airborne Applications

The electronic devices suffer great vibration and temperature fluctuation in an airborne environment, which has been always a big challenge for reliability design. In this paper, the reliability of the complex electronic components for airborne applications under a thermal cycling test, random vibration and combined loading has been investigated by experiment tests and finite element simulation. The fatigue life and failure location under different loadings have been compared and discussed, respectively. The results indicated that the combined fatigue life was much shorter than a single-factor experiment. The failed solder joints mostly appeared at the interface between the solder and the copper pad on the component side and the location was at the corner for all three harsh environment tests. Nevertheless, several differences could be observed. For temperature cycling, all the specimens failed due to the increase in daisy chain resistance rather than the open circuit for the combined loading test. That is because the degeneration of the solder caused by temperature variation led to lower stress levels and fatigue life. Moreover, the pins fractured at the welding regions have been observed. The modified Coffin—Manson model, Miner’s linear fatigue damage criterion and Steinberg’s model and rapid life-prediction approach were used to predict the fatigue life under temperature cycling, random vibration and combined loading, respectively. With these methods, the accurate numerical models could be developed and validated by experiment results. Thanks to the simulation, the design time could be effectively shortened and the weak point could be determined.