Life Prediction Of Components Research Articles

Fatigue life prediction for AlSi10Mg components produced by selective laser melting

Residual defects in additively manufactured metal parts are known to degrade fatigue performance. In this work, pores and oxide particles in AlSi10Mg parts produced by selective laser melting were characterized and quantified by automated scanning electron microscopy (SEM). The fracture surfaces were examined after fatigue tests to identify the critical role of defects in fatigue failure. A correlation between the crack-initiating pore on the fracture surface and fatigue life was established. The pore size distribution measured on a 2D section by scanning electron microscope was used to predict fatigue life using extreme-value theory; good agreement was achieved.

Wear numerical assessment for partial slip fretting fatigue conditions

Abstract The aim of this work is to evaluate wear effects on life prediction for components subjected to fretting conditions. Therefore, fretting fatigue FE simulations have been carried considering the geometry update due to the material removal and results were compared to both experimental data and FE simulations where wear was neglected. Well known multiaxial fatigue criteria in association with the Theory of Critical Distances (TCD) have been used to estimate life. Results have shown that, for the data assessed, where fretting fatigue tests were conducted on a Ti-6Al-4V alloy under partial slip conditions, considering wear effects might slightly increase the accuracy of life estimates. However, this improvement may not be worth the increase in the computational cost in such analysis.

Fatigue stress analysis of the DV-2 engine turbine disk

Purpose The purpose of this study is to improve life prediction of certain components. Fatigue of the high-stressed structural elements is an essential parameter that affects the lifetime of such components. In particular, aviation engines are devices whose failure due to fatigue failure of one of the important components can lead to fatal consequences. Design/methodology/approach In this study, two analyses in the turbine disk of the jet engine during the simulated operating load were performed: The first one was the analysis of the heat-induced stresses using the finite element method. The goal of the second analysis was to determine the residual fatigue strength of a loaded disk by the software tool using the Palmgren - Miner Linear Damage Theory. Findings The results showed a high degree of similarity with the real tests performed on the aircraft engine and revealed the weak points in the design of the jet engine. Research limitations/implications It should be mentioned that without appropriate experiments, results of this analysis could not be verified. Practical implications These results are helpful in the re-designing of the jet engines to increase their technical feasibility. Originality/value Such analysis has been realized in the DV-2 jet engine research and development program for the first time in the history of jet engine manufacturing process in Slovakia and countries of Eastern Europe region.

Computational Methods for Lifetime Prediction of Metallic Components under High-Temperature Fatigue

The issue of service life prediction of hot metallic components subjected to cyclic loadings is addressed. Two classes of lifetime models are considered, namely, the incremental lifetime rules and the parametric models governed by the fracture mechanics concept. Examples of application to an austenitic cast iron are presented. In addition, computational techniques to accelerate the time integration of the incremental models throughout the fatigue loading history are discussed. They efficiently solve problems where a stabilized response of a component is not observed, for example due to the plastic strain which is no longer completely reversed and accumulates throughout the fatigue history. The performance of such an accelerated integration technique is demonstrated for a finite element simulation of a viscoplastic solid under repeating loading–unloading cycles.

Remaining Useful Life Prediction of Drill String Using Fuzzy Systems and Cumulative Damage Theory

Drill string failure is a prevalent and costly problem to the oil and gas industry. This paper proposes a method for remaining useful life prediction of drill string components subjected to fatigue under combined loadings, namely axial stress, bending moment, and torsion. To accomplish this, fuzzy systems are used to model the dimensionless stress intensity factor, β of different API graded drill pipes. Based on the gathered database of the dimensionless stress intensity factor for various crack types, the parameter is numerically estimated using Adaptive Neuro-Fuzzy Inference System in MATLAB. The fuzzy model is then incorporated into the available crack growth models (Paris Law & Walker’s Law) to quantitatively evaluate the number of cycles as the crack propagates from its initial size to its critical size. The nonlinear crack propagation model is solved by Euler’s Method. Finally, a parametric study is performed in order to identify the influence of load magnitudes, the variation of loadings, crack shape, and geometrical parameters on the fatigue life. The ANFIS model developed has a mean square error (MSE) of 8.3e-4, root mean square error (RMSE) of 0.0288 and R-squared error of 0.9807, thus indicating the model is highly reliable. The increase in the magnitude of stress, mean stress ratio (R) and environmental constants reduces the number of cycles to failure, thus indicating shorter RUL.

Residual Remaining Useful Life Prediction Method for Lithium-Ion Batteries in Satellite With Incomplete Healthy Historical Data

Due to the strict requirements of satellite systems, accurate remaining useful life (RUL) prediction of the key components is very important to the reliability and security of satellite systems. Otherwise, a failure could lead to catastrophic consequences and enormous economic losses. Because of the complex structure of the satellite and its complex space environment, the factors that affect the satellite systems status are numerous. Moreover, as a result of the healthy historical data of key components in satellite are too few, which makes the traditional methods based on analysis model are not suitable for RUL prediction of key components in satellite. In this paper, in order to solve the RUL prediction problem of Lithium-ion batteries (LIBs) in satellite with incomplete healthy historical data, we propose an efficient RUL prediction method for key components of satellite, which is called Residual Remaining Useful Life Prediction Method (RRULPM), based on the study of Multivariate State Estimation Technique (MSET). The RRULPM is make up of degradation model based on MSET state estimation and criteria of failure based on historical degradation value, which is developed by improving MSET and combining the residuals with life cycle damage (LCD) prediction creatively when lacking healthy historical data. Experimental results demonstrate that the RRULPM is excellent to achieve the RUL prediction problems of LIBs through the actual in orbit telemetry data. Unlike previous RUL prediction methods, RRULPM provides good feasibility and effectiveness. This research can serve as guidance for prognostics and health management (PHM) of key components in satellite.

Critical assessment 31: on the modelling of tertiary creep in single-crystal superalloys

ABSTRACTModelling of tertiary creep in single-crystal superalloys – operative over the majority of the temperature/stress regime of relevance – is assessed. Traditional, empirical approaches are useful for the prediction of component life; a modern trend is for more physically faithful models which account for microstructure and alloy composition. Calculations are made using different methods, to identify advantages/disadvantages, in an effort to approach best practice. The predictions are tested against experimental data. The creep resistance can be estimated to within approximately one-half of a Larson–Miller parameter, from an input of alloy composition, deformation conditions, and estimates of microstructural parameters, rate laws (and parameters therein), and physical constants. Different merit indices are considered to identify the most appropriate for compositional optimisation.

Nonlinear fatigue damage accumulation and life prediction of metals: A comparative study

AbstractFatigue damage modelling and life prediction of engineering components under variable amplitude loadings are critical for ensuring their operational reliability and structural integrity. In this paper, five typical nonlinear fatigue damage accumulation models are evaluated and compared by considering the influence of load sequence and interaction on fatigue life of P355NL1 steels. Moreover, a new nonlinear fatigue damage accumulation model is proposed to account for these two effects. Experimental datasets of pressure vessel steel P355NL1 and four other materials under two‐block loadings are used for model comparative study. Results indicate that the proposed model yields more accurate fatigue life predictions for the five materials than the other models.

Modeling the residual strength and fatigue life of carbon fiber composites under constant amplitude loading

Fatigue life and residual strength prediction of various engineering components and structures are of primary importance because of economy and safety point of view. This article presents the fatigue life and residual strength of Carbon Fiber Reinforced Polymer (CFRP) composites at constant amplitude condition. Experiments were conducted on CFRP composites at different strain rates to determine its ultimate tensile strength. The lowest tensile strength resulting from different strain rates has been used as the ultimate tensile strength for carrying out the fatigue life and residual strength tests. A two-parameter wear out model for predicting the residual strength and the fatigue life of CFRP composites is proposed explicitly by accounting the effect of stress amplitude when the structure undergoes continuous loading. A model was also proposed to predict the fatigue life of CFRP composites based on the endurance limit. The proposed models show good agreement with the experimental results and with the available models in the literature.

Gradual Change Reliability Sensitivity Design for Spindle System on Fully Stochastic Process

Gradual change reliability design of mechanical components is considered by semi-stochastic process model of loading with change of time and fully stochastic process model of known degradation function of strength at present, yet it can’t obtain reasonable reliability design by existing information of components for these models. Thus the influence of existing information and time-dependent parameters of components on reliability should be taken into account in order to access reliability correctly. By studying effect of loading action and time-dependent character of strength, strength of components is taken as a process of independent increments and autocorrelation coefficient of strength is also calculated, meanwhile, we present a method for computing time-dependent reliability. Combining the reliability design theory with sensitivity analysis method, a numerical method for time-dependent reliability sensitivity design of components based on fully stochastic process is proposed, the variation rules of reliability sensitivity of parameters are given at any moment and the effects of design parameters on reliability of components are also studied. The method presented in this paper provides the theoretical basis for structural design and life prediction of mechanical components.

Strain energy gradient-based LCF life prediction of turbine discs using critical distance concept

For aeroengine components with geometrical discontinuities like notches, low cycle fatigue (LCF) life prediction is critical for ensuring the engine structural integrity. In this regard, a concept of strain energy gradient is elaborated and a general procedure combining this concept with theory of critical distance is established for LCF life prediction of notch components, which relates its life with the strain energy distributed within the effective damage zone. For GH4169 and TC4 notched specimens as well as a case study of a high pressure turbine disc, the proposed procedure provides better life correlations than models of Fatemi-Socie and Smith-Watson-Topper.

RELIABILITY PREDICTION OF A MECHANICAL COMPONENT THROUGH ACCELERATED LIFE TESTING

The reliability prediction (i.e. life prediction) of components and subsystems is a crucial issue for the efficiency of production systems. This paper presents a reliability assessment method, applied to a mechanical component (i.e. gear unit) of an automated manufacturing system. Study is based on accelerated life test approach (ALT). In the study authors used General log-linear model (GLL) combined with a Weibull distribution for time to failures. Researchers did different experimental tests in the laboratory of the Department of Industrial Engineer – University of Bologna, to estimate model parameters. Expected life of component was then evaluated using the proposed ALT model. Finally, results are compared with actual time-to-failure data coming from field. Time-to-failure was collected during about 10 years, on about 20 production lines using the same gear unit. The accordance between real data and life prediction is satisfying. Results confirm Accelerated Life Testing (ALT) is an efficient and effective assessment method for lifetime prediction based on short time tests.

A simple energy‐based model for nonproportional low‐cycle multiaxial fatigue life prediction under constant‐amplitude loading

AbstractFrom the literature concerning the traditional nonproportional (NP) multiaxial cyclic fatigue prediction, special attentions are usually paid to multiaxial constitutive relations to quantify fatigue damage accumulation. As a result, estimation of NP hardening effect decided by the entire history path is always proposed, which is a challenging and complex task. To simplify the procedure of multiaxial fatigue life prediction of engineering components, in this paper, a novel effective energy parameter based on simple material properties is proposed. The parameter combines uniaxial cyclic plastic work and NP hardening effects. The fatigue life has been assessed based on traditional multiaxial fatigue criterion and the proposed parameter, which has been validated by experimental results of 316 L stainless steel under different low‐cycle loading paths.

Effect of heterogeneities on pitting potential of line pipe steels: An adaptive neuro-fuzzy approach

The variations in microstructure of line pipe steel (Grade X60) lead to significant changes in its corrosion behavior. Use of any particular steel for a given environment needs a robust data bank through which life predictions of components can be made confidently to avoid catastrophic failure. In the present endeavor, an adaptive neuro fuzzy based model is proposed to study the effect of microstructural variation on the performance of the candidate steel. This model has been verified with the experimental findings. The developed model will be a useful tool to justify the acceptance/rejection of the alloy on a commercial scale.

Effect of CT Specimen Thickness on the Mechanical Characteristics at the Crack Tip of Stress Corrosion Cracking in Ni-based Alloys

It’s important to obtain accurate stress corrosion crack(SCC) growth rate for quantitative life prediction of components in nuclear power plants. However, the engineering practice shows that the crack tip constraint effect has a great influence on the mechanical properties and crack growth rate of SCC at crack tip. To study the influence of the specimen thickness on the crack tip mechanical properties of SCC, the stress, strain and C integral at creep crack tip are analyzed under different specimens thickness. Results show that the cracked specimen is less likely to crack due to effect of crack tip constraint. When the thickness ratio B/W is larger than 0.1, the crack tip constraint is almost ineffective. Value of C integral is the largest when B/W is 0.25. Then specimen thickness has little effect on the value of C integral. The effect of specimen thickness on the value of C integral is less significant at higher thickness ratio.

Physics-of-failure-based reliability and life prediction for critical components

Physics-of-failure-based reliability and life prediction for critical components

A generalization of the fatigue Kohout-Věchet model for several fatigue damage parameters

A new proposal of generalization of the fatigue Kohout-Věchet (KV) model for different fatigue damage parameters is proposed. The purpose of this generalized model is to describe all fatigue regimes from very low-cycle fatigue (VLCF) to very high-cycle fatigue (VHCF), and accounting for several fatigue damage parameters, such as, strain parameter, Smith-Watson-Topper (SWT) parameter, Walker-like strain parameter, energy-based parameter in uniaxial loading conditions, among others. The full range of fatigue life responses for all loading regimes of materials and structural components are extremely important in the fatigue design. Engineering structures are subjected to different types of loading that cause fatigue failure. These loadings can range from quasi-static monotonic loading to long term dynamic/cyclic loading. In this paper, a proposal of generalization of the KV model for several fatigue damage parameters was verified and compared with experimental fatigue results under uniaxial loading conditions available in literature. This study validates the importance and applicability of full range fatigue life models for different damage parameters in fatigue life prediction of materials and structural components.

A fracture mechanics approach to characterising the environmental stress cracking behaviour of thermoplastics

Environmental stress cracking (ESC) is known to affect certain thermoplastics and occurs under simultaneous exposure to both applied stress and a hostile environment. The combination of these can cause a crack to form from a flaw in the material; upon reaching a critical size, the crack may accelerate thus causing catastrophic failure in the component. Various tests have been utilised to measure the resistance of different polymers to ESC, but these are often material- and application-specific and overlook the different stages of the failure process. In the present work, a fracture mechanics approach has been developed and applied, with a view to developing a test method that has wide applicability and provides both insight into the failure mechanisms as well as information for engineering design. Experimental results are presented for the following polymer-environment combinations: linear low-density PE in Igepal solution, HIPS in sunflower oil, and PMMA in methanol. It is shown that the representation of the results in the form of G versus crack velocity and G versus time can distinguish between materials of varying ESC resistance, identify the important regions of the failure process, and enable component life prediction.

Above-knee prosthesis design based on fatigue life using finite element method and design of experiment

The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction.

Industrial Big Data in an Industry 4.0 Environment: Challenges, Schemes, and Applications for Predictive Maintenance

Industry 4.0 can make a factory smart by applying intelligent information processing approaches, communication systems, future-oriented techniques, and more. However, the high complexity, automation, and flexibility of an intelligent factory bring new challenges to reliability and safety. Industrial big data generated by multisource sensors, intercommunication within the system and external-related information, and so on, might provide new solutions for predictive maintenance to improve system reliability. This paper puts forth attributes of industrial big data processing and actively explores industrial big data processing-based predictive maintenance. A novel framework is proposed for structuring multisource heterogeneous information, characterizing structured data with consideration of the spatiotemporal property, and modeling invisible factors, which would make the production process transparent and eventually implement predictive maintenance on facilities and energy saving in the industry 4.0 era. The effectiveness of the proposed scheme was verified by analyzing multisource heterogeneous industrial data for the remaining life prediction of key components of machining equipment.