Service Life Prediction Models Research Articles

Multi-factor corrosion model of TP110TS steel in H2S/CO2 coexistence and life prediction of petroleum casings

The failure of petroleum casings due to the combined effects of CO2/H2S corrosion and internal pressure has become a main concern during the exploitation of high-temperature, high-pressure, and high-corrosion gas fields. Therefore, establishing a corrosion evolution model is crucial for accurately predicting the service life of casings. In this study, an analytical model describing the corrosion rate of casing steel TP110TS under different CO2/H2S partial pressures and applied stresses was established, combined with the mechanical-chemical effect. The weightlessness method was used to determine the model parameters from the experimental results using a multiple regression. Based on the elasticity, a service life prediction model considering mechanical property attenuation and casing stress fluctuation was established from the assumption of uniform thickness thinning. The effects of internal pressure and CO2/H2S partial pressures on the service life were analyzed. The corrosion rate initially decreased with time. However, the stress increased as the wall thickness decreases from corrosion. The stress-promoting corrosion effect gradually manifested, and the corrosion rate rapidly increased. The higher the internal pressure and H2S/CO2 partial pressure, the shorter was the service life of the casing. In the H2S/CO2 coexistence environment, the influence of H2S partial pressure was more significant than that of CO2.

Research on performance degradation patterns of metal rubber components under the coupling of static compression and full immersion corrosive environment

Metal rubber component (MRC) is commonly used in special work conditions such as high temperature/corrosive environments primarily due to its excellent vibration damping/insulation properties. But in special work conditions for a long time, the performance of MRC will deteriorate to a failure to meet the work requirements. Therefore, it is imperative to enhance the performance of MRC and study its performance degradation in special work conditions. In this paper, pickling, silanization and pickle-silanization surface treatments for metal rubber components (MRCs) were carried out. The properties of MRCs after surface treatment under static compression and full immersion corrosive test were studied, and a remaining service life prediction model of MRCs under corrosion condition was established. Compared with MRC without surface treatment (U-MRC), the performance degradation degree of several MRCs was evaluated based on four physical and mechanical parameters - the amplitude of variation in height, average stiffness, energy dissipation, and loss factor. The results indicated that MRCs exhibited different degrees of performance degradation. Among them, pickling-silanized MRC (PS-MRC) has the best corrosion resistance. The stiffness variation amplitude must be nearly 8% smaller than that of U-MRC, and the energy consumption variation amplitude is about 12% smaller than that of U-MRC.

A lifetime prediction model based on two-path convolution with attention mechanism and bidirectional long short-term memory network

With the continuous advancement of technology, modern industrial equipment is becoming increasingly complex, integrated, and automated. The complexity of industrial processes often involves multiple variables, strong coupling, nonlinearity, variable operating conditions, and significant noise, making the establishment of accurate remaining useful life (RUL) prediction models a challenging research direction. This paper proposes a lifetime prediction model based on two-path convolution with attention mechanisms and a bidirectional long short-term memory (BiLSTM) network. The model’s front end employs two-path convolution scales and attention modules to extract key fault information from bearings, enhancing the model’s noise resistance. It utilizes adaptive batch normalization and Meta-Aconc activation functions to adaptively adjust the neurons of the model, thereby enhancing its generalization capabilities. The model’s back end uses a BiLSTM network to remember and process the degradation information of bearings, achieving the prediction of bearing RUL. Furthermore, the model’s accuracy is evaluated using root mean square error and a scoring function assessment system. Comparative experiments demonstrate the model’s higher predictive accuracy. Finally, robustness and generalization experiments have proven the model to adapt well in scenarios with noise interference and working condition transitions. This model provides a reference for the prediction of the life of rotating machinery in practical scenarios with strong noise and variable operating conditions.

Combined high and low cycle fatigue analysis of FGH96 alloy under high temperature conditions

The FGH96 alloy as a common material for preparing turbine discs, can withstand high- and low-cycle combined loading during service, which significantly affects its fatigue performance. In this work, the combined high and low cycle fatigue (CCF) behavior of the FGH96 alloy was explored at various low cycle stress amplitudes (600, 630, 650, 680, and 700 MPa) using a self-improved experimental platform at a high temperature of 650 °C. The results indicate that increasing the amplitude of the low-cycle stress decreases the service endurance of the FGH96 alloy at CCF condition. Under the same low cycle stress amplitude, its CCF life of alloy is lower than the pure low cycle fatigue life. A fatigue service life prediction model, grounded in the theory of crystal plasticity, has been developed to assess the combined fatigue service life across different low-cycle stress amplitudes. A comparison between the predicted and actual lifespan showed that the predicted lifetime fell within a range three times the scattering band.

Hydrothermal aging of glass fiber epoxy‐carbon nanocomposites and its service life predictions based on tensile strength

AbstractThis paper investigates the hydrothermal aging of pultruded glass‐fiber reinforced epoxy nanocomposite rods with carbon nanofillers. The nanocomposites developed in this study are proposed for the core of high‐tension low‐sag conductors in power transmission. Nanocomposites were fabricated with a nanomodified matrix containing 0.2 wt.% of multi‐walled carbon nanotubes and 0.6 wt.% of graphene nanoplatelets. The epoxy nanocomposites tensile strength and life predictions were determined under different water aging conditions. Objective of the study is to evaluate the water absorption kinetics and its impact on tensile strength, microstructure and to compute the service life under hydrothermal aging by predictive techniques. Nanocomposites were aged in water at 30, 50, and 80°C for a duration of 3000 h, and the microstructure and chemical composition were investigated. Based on Arrhenius's theory, a service life prediction model based on the tensile‐strength of the nanocomposite is established for hydrothermal aging. The results have shown that the addition of carbon nanofillers to the epoxy matrix improves the hydrophobicity and reduces the water diffusion coefficient. Water absorptions of the nanocomposites are observed to follow Fick's law, and its influence on the mechanical properties of the nanocomposite is evident and is more significant in epoxy composites without carbon nanofillers. After 3000 h of immersion at 50 and 80°C, the tensile strength retention is above 85%. The hydrothermal environment accelerates the development of micro‐voids and cracks, which are initially formed and observed to be the primary reason for the degradation in mechanical strength under service conditions, in addition to debonding of the fibers.Highlights Carbon nanocomposites were aged at different temperatures and durations. Service life prediction model established based on Arrhenius's theory. Addition of carbon nanofillers enhances hydrophobicity and reduces water diffusion. Tensile strength retention above 85% after 3000 h of aging. Hydrothermal aging accelerates aging contributing to strength degradation.

In-ground and above-ground service life prediction for timber reusability - Progressing towards circular construction

The increasing demand for and consumption of wood requires special attention in order to keep the wood industry sustainable. Therefore, timber reuse is presented as a solution to control the demand side. Unfortunately, the perception of timber decay poses a major barrier for reuse practices. Therefore, this article presents a factorised service life prediction model for wooden components that aims to promote their reuse. The model is based on the Australian service life prediction model, Timberlife, and the European CLICKdesign model's dose-response model. It predicts the potential for reuse of timber components based on their expected and remaining service life. To determine the service life, the model includes factors that differentiate between wood species, soil characteristics, regional climate and how the investigated components are connected to other components. The presented model focuses on in-ground and above-ground fungal decay and is limited to northwestern Europe. Opportunities for further research include, e.g., a further investigation of the soil characteristics' influence on decay, and evaluating the lag time for regions outside northwestern Europe. The presented service life prediction model can increase awareness and support a circular construction industry.

Service life prediction model for chloride-induced corrosion of concrete-steel tubular columns

Service life prediction model for chloride-induced corrosion of concrete-steel tubular columns

To what extent does decreasing the proportion of clinker in cement production effectively decrease its carbon footprint?

The current context of global warming requires urgent action to reduce carbon emissions from all industries, including the concrete production. To meet this challenge, the European cement standard, EN 197–5, has been implemented to introduce CEM II/C-M low-carbon Portland cements incorporating a higher percentage of mineral additions (up to 50%), and a new family CEM VI cements with a very low clinker content, ranging from 35 to 49%. This work focuses on these new cements, mainly ternary mixtures based on clinker, slag and limestone filler for high clinker replacement rates. This choice is based on the exploitation of the synergy between limestone and mineral additions containing aluminates which has been established in the literature. This study is focused on concretes based on these new ternary clinker-slag-limestone cements, to compare them with existing binary cements in terms of durability with respect to corrosion induced by carbonation. Two main tests were performed: accelerated carbonation that reveals corrosion initiation time, and electrical resistivity that provides insights into corrosion propagation time. Additional microstructural characterization was also carried out to understand the link between the macroscopic durability properties and the microstructure. A service life prediction model was used to quantify the service life of the concrete cover from material properties. Concretes were then compared on the basis of two carbon efficiency indicators corresponding respectively to the carbon cost of 1 MPa and one year of service life. Opposite trends are observed on the carbonation resistance and electrical resistivity. Good durability can be expected for low carbon cements, as they have high electrical resistivity and therefore a long corrosion propagation time, despite their relatively low carbonation resistance,. The carbon footprint indicator related to service life is more relevant than the one related to mechanical performance since it takes into account an important function of concrete which is durability.

Service life prediction model for marine concrete structures considering structural shape and time-dependent behaviour

A new service life prediction model for marine concrete structures considering the structural shape and time-dependent behaviour of model parameters was proposed in this study. First, a lumped concentration matrix for both triangular elements of two-dimensional diffusion and linear elements of one-dimensional diffusion was developed based on the Galerkin's method of weighted residual and approximate interpolation function, respectively. Then, a dual time-dependent numerical model for chloride diffusion in marine concrete structures was established by considering the time-dependent behaviour of both chloride diffusion coefficient (D) and surface chloride concentration (Cs). Meanwhile, a new service life prediction model for marine concrete structures that considers the influences of structural shape and time-dependent behaviour of model parameters was proposed. Finally, the influences of the structural shape and the time-dependency of D and Cs on service life were investigated. Analysis results show that the service life would be underestimated if the time-dependent behaviour of D or Cs were ignored, while the service life would be overestimated when the influence of structural shape was neglected. Compared with Cs, the time-dependent behaviour of D has more significant effects on service life of marine concrete structures.

6-month evaluation of concrete aging factor using chloride migration test: Effects of binder type and w/b ratio

Service life modeling is a relevant tool in the design of durable concrete structures. Among the service life prediction models, many introduce the so-called concrete aging factor, which aims to express the reduction of concrete diffusivity over time. This paper presents an experimental assessment of the concrete aging factor up to the age of 6 months based on the chloride migration coefficient. Several concretes produced with different binder types, mineral additions, and water/binder ratios were evaluated. Concrete compressive strength and surface electrical resistivity are also addressed. The results indicate a strong influence of the type of binder and the use of mineral additions on the aging factor of the concrete – especially in concretes with water/binder ratio = 0.45. The inclusion of the aging factor in service life prediction models and the extrapolation of data obtained at the first ages of concrete for long-term analysis are discussed.

Service life prediction of reinforced concrete structures subjected to corrosion: a comparative study

PurposeReliable estimations of the extent of corrosion and time required to reach specific safety limits are crucial for assessing the reliability of aging reinforced concrete (RC) bridges. Engineers and decision-makers can use these figures to plan suitable inspection and maintenance operations.Design/methodology/approachAnalytical, empirical and numerical approaches for estimating the service life of corroded RC structures were presented and compared. The concrete cover cracking times, which were predicted by the previously proposed analytical models, were compared with the experimentally obtained cracking times to identify the model/s for RC bridges. The shortcomings and limitations of the existing models are discussed.FindingsThe empirical models typically depend on the rate of corrosion, diameter of steel reinforcement and concrete cover depth and based on basic mathematical formula. In contrast, the analytical and numerical models contain the strength and stiffness properties of concrete as well as type of corrosion products and incorporate more complex mechanical factors. Four existing analytical models were analyzed and their performance was evaluated against existing experimental data in literature. All the considered analytical models were assumed thick-walled cylinder models. The maximum difference between observed cracking time from different test data and calculated cracking time using the developed models is 36.5%. The cracking times extend with increase in concrete cover and decrease with corrosion current density. The development of service life prediction models that considers factors such as heterogeneity of concrete, non-uniform corrosion along rebar, rust production rate and a more accurate representation of the corrosion accommodating region are some of the areas for further research.Research limitations/implicationsOutcome of this paper partially bridge the gap between theory and practice, as it is the basis to estimate the serviceability of corrosion-affected RC structures and to propose maintenance and repair strategies for the structures. For structural design and evaluation, the crack-width criterion is the greatest practical importance, and structural engineers, operators and asset managers should pay close attention to it. Additionally, repair costs for corrosion-induced serviceability failures, particularly concrete cracking and spalling, are significantly higher than those for strength failures. Therefore, to optimize the maintenance cost of RC structures, it is essential to precisely forecast the serviceability of corrosion-affected concrete structures. The lifespan of RC structures may be extended by timely repairs. This helps stake holders to manage the resources.Practical implicationsIn order to improve modeling of corrosion-induced cracking, important areas for future research were identified. Heterogeneity properties of concrete, concept of porous zone (accommodation effect of pores should be quantified), actual corrosion morphology (non-uniform corrosion along the length of rebar), interaction between sustain load and corrosions were not considered in existing models. Therefore, this work suggested for further researches should consider them as input and develop models which have best prediction capacity.Social implicationsThis work has positive impact on society and will not affect the quality of life. Predicting service life of structures is necessary for maintenance and repair strategy plans. Optimizing maintenance strategy is used to extend asset life, reduce asset failures, minimize repair cost, and improve health and safety for society.Originality/valueThe degree of accuracy and applicability of the existing service life prediction models used for RC were assessed by comparing the predicted cracking times with the experimentally obtained times reported in the literature. The shortcomings of the models were identified and areas where further research is required are recommended.

Research on Valve Life Prediction Based on PCA-PSO-LSSVM

The valve is a key control component in the oil and gas transportation system, which, due to the environment, transmission medium, and other factors, is susceptible to internal leakage, resulting in valve failure. Conventional testing methods cannot judge the service life of valves. Therefore, it is important to carry out valve life prediction research for oil and gas transmission safety. In this work, a valve service life prediction method based on the PCA-PSO-LSSVM algorithm is proposed. The main factors affecting valve service life are obtained by principal component analysis (PCA), the least squares support vector machine (LSSVM) is used to predict the valve service life, the parameters are optimized by using particle swarm optimization (PSO), and the valve service life prediction model is established. The results show that the predicted valve service life based on the PCA-PSO-LSSVM algorithm is closer to the actual value, with an average relative error (MRE) of 16.57% and a root mean square error (RMSE) of 1.2636. Valve life prediction accuracy is improved, which provides scientific and technical support for the maintenance and replacement of valves.

A practical carbonation model for service life design of reinforced concrete structures

The “Durability Index” (DI) performance-based approach, developed in South Africa, involves the application of early-age concrete test methods together with service life prediction models, and links material properties directly with the expected service life of reinforced concrete (RC) structures under various environmental conditions. The Oxygen Permeability Index (OPI) DI test is based on permeation and relates to carbonation of concrete. As practised in South Africa (e.g. Committee of Transport Officials (COTO)), this approach requires durability considerations to be introduced in the design of the concrete mixture, and provides a quantification of the expected service life duration. This paper presents a design tool based on existing models for use in practical applications for service life design, assuming application of carbonation models and the OPI test method, and representing a probabilistic approach to performance-based durability design. The design tool can be applied for predicting the long-term performance of new RC structures as well as improving the basis for quality assessment of existing, newly built RC structures. This probabilistic approach to performance-based durability assessment is exemplified using actual data reported in the literature.

Prediction of remaining service life of cement concrete pavement in airfield runway

An improved Remaining Service Life (RSL) prediction model of slab based on strain gauge data was presented in this paper. Numerical simulation models were developed to analyse the responses on airfield pavement slabs for more than 10,935 loading scenarios. Then, the bottom transverse strains of the slab, as well as the slab thickness, elastic modulus of the slab, base thickness and elastic modulus of the base, were used to calculate the Cumulative Damage Factor (CDF) of the slab. The slab was divided into different strips to accurately locate the failure zone. The RSL of the slab calculated by the model developed were compared with result of the FAARFIELD software. The results showed that the RSL prediction method proposed in this paper is within 5% of the results of FAARFIELD. Furthermore, the constructed model for predicting the RSL of slabs can capture the failure regions of airfield runways.

Chloride ion transport and service life prediction of aeolian sand concrete under dry–wet cycles

Abstract In this study, the dry–wet cycle test of chloride salt was carried out on aeolian sand concrete with different contents, and the chloride ion content in aeolian sand concrete was determined by taking powder from different depths on one side of the test block. And then combined with Monte Carlo stochastic statistical simulation and Weibull probability distribution function, the service life prediction model of aeolian sand concrete against chloride ion erosion is established. The results show that the free chloride ion content in aeolian sand concrete decreases with the increase in the depth from the surface of the specimen. At the same depth from the surface of the specimen, the free chloride ion content gradually increases with the increase in the number of dry–wet cycles. Through the analysis of life prediction, it is concluded that with the increase in aeolian sand content, the service life of aeolian sand concrete increases first and then decreases. The service life value of concrete with 75% aeolian sand content is the largest, and the greater the thickness of the protective layer, the more favorable the service life value.

A spalling evolution model for time-varying mesh stiffness evaluation and service life prediction of gears

Spalling is one of the most common contact fatigue failure modes on gear face. Although there are some prediction models for spalling formation, few prediction models have previously addressed the evolution from initial defects to spalling cavities. In this paper, a damage-connectivity spalling model (DCSM) is proposed to describe the formation and evolution of multiple irregular spalling cavities on the tooth face deriving from the initial defects. Subsequently, a type of TVMS-based indicator is established to represent the evolutionary severity of irregular spalling cavities. Finally, a service life prediction method is developed based on the proposed indicators. The correctness of the proposed DCSM model is verified by comparison with the extant gear spalling experiments. The effects of working load, depth ratio and quantify ratio of initial defect groups on the service life are discussed, which contributes to the service life improvements of gear pairs in the design stage.

Correction: Study on Microporosity, Mechanics and Service Life Prediction Model of Aeolian Sand Powder Concrete

Correction: Study on Microporosity, Mechanics and Service Life Prediction Model of Aeolian Sand Powder Concrete

Study on Microporosity, Mechanics and Service Life Prediction Model of Aeolian Sand Powder Concrete

Study on Microporosity, Mechanics and Service Life Prediction Model of Aeolian Sand Powder Concrete

Influence Of Marine Environment Exposure On The Engineering Properties Of Steel-concrete Interface

Aims: A detailed and reformed service life prediction model needs to be developed by considering the non-uniform distribution of the porous zone and the non-uniform distribution of the corrosion products layer. Background: The microstructure of the steel-concrete interface (SCI) plays an important role in corrosion initiation and concrete cover cracking. The porous zone around SCI is one of the vital engineering properties that influence the service life of corroding reinforced concrete structures in service life prediction models. Objective: The SCI properties are sensitive to the sample preparation technique of reinforced concrete (RC) samples for studying with the aid of scanning electron microscopy (SEM). A simple step-wise sample preparation technique of RC samples for SEM analysis is proposed where there is minimal damage to the properties of SCI. The development, distribution, and propagation of corrosion products at SCI are investigated for RC samples exposed to the marine environment for different exposure periods. The service life of RC structures was assessed through experimentally determined porous zone thickness (PZT) values. Assuming a uniform and constant value of PZT and uniform distribution of corrosion products around SCI might lead to variation or misinterpretation of the service life of structures. The same is explored in the present study. Methods: In this research investigation, backscattered electron images were obtained for the analysis of porous zone thickness around SCI. The distribution and propagation of corrosion products around SCI were investigated for different mineral admixed reinforced concrete samples exposed to the marine environment. Also, porous zone thickness values were used experimentally measured, and the time from corrosion initiation to corrosion cracking was estimated using a service life prediction model. Results: Results show that porous zone thickness is not uniform around SCI. Once the corrosion is initiated, the corrosion products accumulate in the SCI's porous region. Further, the non-uniform porous zone thickness directly influenced the non-uniform distribution of corrosion products. Assuming a constant or uniform porous zone thickness and uniform distribution of corrosion products around SCI leads to misinterpretation of the service life of corroding reinforced concrete structures. Conclusion: The porous zone thickness values around the steel-concrete interface and corrosion current density play an important role in predicting the service life of reinforced concrete structures exposed to the marine environment.

Transfer Parameter Analysis of Chloride Ingress into Concrete Based on Long-Term Exposure Tests in China’s Coastal Region

Chloride penetration resistance is one of the most important performance measures for the evaluation of the durability of concrete under a chloride environment. Due to differences in theory and experimental conditions, the durability index (chloride diffusion coefficient) obtained from laboratory accelerated migration tests cannot reflect the real process of chloride ingress into concrete in the natural environment. The difference in test methods must be considered and the transfer parameter kt should be introduced into the service life prediction model when the test results of accelerated methods are used. According to the test data of coastal exposure in South China, the attenuation rule of the chloride diffusion coefficient of different cement-based materials changed with time and was analyzed in this paper. Based on the diffusion coefficient-time curve, the theoretical natural diffusion coefficients of 28 d and 56 d were deduced, which were compared with the chloride diffusion coefficients obtained from the non-steady-state rapid migration method (RCM) at the same age. Therefore, the transfer parameter kt that expounds the relationship between concrete resistance to chloride permeability under a non-stationary electrical accelerated state and natural diffusion in the marine environment can be calculated; thus, the RCM testing index can be used to evaluate the long-term performance of the concrete structure in the marine environment. The results show that the value of kt was related to environmental conditions, test methods, and binder systems.