Service Life Distribution Research Articles

Digital image correlation approach for low-cycle fatigue life monitoring of 13HMF power engineering steel

In this paper, strain evolution of 13HMF power engineering steel was analysed during force-controlled low cycle fatigue (LCF). The material performance under cyclic loading was monitored by using Digital Image Correlation (DIC) technique for different values of stress amplitude exceeding the yield strength of the material significantly. Data collected from DIC was compared to the extensometer ones to confirm the effectiveness of the proposed approach. Finally, the cloud data reflecting the fatigue performance of 13HMF was generated in the form of strain-stress amplitude - service life distribution map.

Probabilistic Service Life Model of Pavement Marking by Degradation Data

Pavement markings are important features for improving road safety. As these markings must possess adequate retroreflectivity, road agencies are concerned about retroreflectivity maintenance. Consequently there is an increased focus on modeling the durability of pavement markings. Such models use time-to-failure data from life test experiments. The current study proposes a new method that consists of three steps: (i) designing an accelerated experiment for data collection; (ii) fitting a pavement marking retroreflectivity model using a generalized linear mixed model and the degradation data from the planned experiment, confirming the goodness of fit of the fitted model through the residual analysis; and (iii) conducting Monte Carlo simulation (with at least 10,000 runs of simulated vectors of the fitted model’s coefficients) to obtain the pavement marking service life distribution for a failure retroreflectivity threshold level. The simulation of service life of pavement marking provides relevant information, such as service life expectation and empirical quantities of interest (as median). The proposed method is applied to data on retroreflectivity degradation obtained from an experimental test site, a Brazilian highway with a high traffic volume, with two fixed factors (waterborne paints and glass bead application rates, both with three levels). The model indicates that retroreflectivity decreases at an average rate of 2% per day, and how materials differ from each other. The proposed model is easily implementable and can help management teams to adequately plan the maintenance time for pavement markings.

The Effect of Lightweight Functional Aggregates on the Mitigation of Anode Degradation of Impressed Current Cathodic Protection for Reinforced Concrete.

The local acidification of secondary anode mortar was regarded as the primary reason for the degradation of the anode system, leading to a decreased service life and uneven distribution of the protection current within the impressed current cathodic protection system for reinforced concrete structures. In related previous studies, a novel type of lightweight functional aggregate was designed and prepared for the secondary anode mortar system, aiming to improve anode performance via acidification mitigation. However, the relationship between optimization effects and this functional component has not been fully clarified. In this study, two sets of experiments were carried out to investigate the effects of lightweight functional aggregates on acidification mitigation and the protection of current distribution. Research results proved that the presence of this functional aggregate was beneficial for mitigated acidification propagation and a more uniform distributed protection current, which demonstrated the importance and effectiveness of acidification inhibition on the optimization of anode performance.

A modified quality loss model of service life prediction for products via wear regularity

It is very important to consider the life change regularity of products during full life-cycle based on product geometric quality characteristics. The relationship between product quality loss and service life distribution is analyzed to estimate the average life of products during service time, and the range of concentrated distribution of product service life is determined. To estimate the quality loss of products more accurately, the viewpoint is put forward that the main quality characteristic values should obey the nonlinear change during service time. Then, the service quality loss function (QLF) is modified based on the wear regularity. The effect of different parameters on the average service life of products is discussed with practical case, such as design, production and service parameters. A new research method is proposed on the full life-cycle variation rule of mechanical products.

Analyzing the Long-Term Service Life of MEP Using the Probabilistic Approach in Residential Buildings

Establishing an effective long-term maintenance plan is essential to ensure the sustainability of a building. Among the various components of a building, the mechanical, electrical, and plumbing (MEP) components are complexly affected by various parameters, such as quality and user pattern, with respect to the service life. Besides, these components are replaced at different points in time, which becomes one of the main risks when establishing a maintenance plan for the building. Therefore, it is very important to consider the uncertainty in calculating the service lives of MEP components in a systematic and reasonable way. This study aims to systemize the MEP components of residential buildings and analyze their service life patterns using a probabilistic approach for long-term maintenance planning. The analysis was performed on 54,318 maintenance cases from 1998 to 2017 at 65 twenty-five-year-old rental apartment buildings in South Korea. Before performing the analysis, a service life matrix was established by classifying the MEP components into 12 types and setting the service life time at 6–25 years. Then, the service life distribution was derived for each MEP component. The probabilistic approach can provide information for rational maintenance decision-making regarding each MEP component as well as basic service life settings. Since the performance of the MEP components deteriorates due to various reasons, de facto uncertainty exists in the service life of each component; thus, the probabilistic approach can serve as an important decision-making method. If probabilistic methods are developed by acquiring the cost data in addition to the frequency of maintenance activity used in this study, a more effective long-term maintenance plan can be established.

Life cycle analysis for concrete beams designed with cross‐sections of equal durability

AbstractDurability at the corners of the cross‐section is relatively weak in the concrete beams of bridges; the reinforcement at the corners therefore corrodes first. In order to delay durability failure at the corners, measures should be taken such as the application of corner concrete coatings or adjustments to the reinforcement at the corners. In this way, the durability resistance would be adjusted to be equal in the section, which is called the equal durability design method. In this paper, the life cycle analyses of a component designed with equal durability and one designed in the traditional way – both in a carbonation environment – are conducted and compared. A probabilistic model of service life is established based on empirical degradation models. Service life distribution is calculated with the Monte Carlo simulation method. Costs associated with durability failure are estimated based on the service life distribution. Related influencing factors are analysed as well. Finally, life cycle cost analyses of the component designed with equal durability and the one designed in the traditional way are conducted and compared. The results show that the component designed with equal durability is more economic over the life cycle if construction cost is kept within about 1.1 times that of the component designed traditionally.

Optimal tolerance design of product based on service quality loss

Design tolerance has tremendous influence on both manufacturing cost and quality of a product. The purpose of the paper is to propose a new way of the product optimal tolerance design based on service quality, which is more realistic because the service quality loss model describes the present worth model of quality loss based on the service life distribution, and expresses an actual loss that a product imparts on society after the product is put into service by considering the parts processing equipment during product manufacturing process, operating environment, and lubrication condition during product service. However, many scholars consider manufacturing cost and quality loss for the optimal tolerance design of product at present, in which uses Taguchi quality loss model or Teran quality loss model. The former reflects the forecast of a loss that a product may bring to the society on the time node before it leaves the factory. Although the latter involves the changes of the product quality characteristics after the product is put into service, but its essence is to transform the product quality loss in a certain service life into the present worth on the time node before the product is put into service, and it is still the forecast of a loss for the society, and has many shortages that it takes quality loss cost as cash flow and service life as a certain value. So the proposed way can extend the product tolerance design from the manufacturing stage to the service stage, and enriches the theory of the product optimal tolerance design.

Modeling Present Worth of Product Quality Loss of STB Characteristic Based on Service Life Distribution

The product smaller-the-better (STB) quality characteristics are continually changing and out of specification limits because of the constant stress, wear and others after the product is put into use, which will cause loss because of the product rejected and scrapped. On the basis of the quality viewpoint that product quality loss is present worth of a loss caused as a result of its quality characteristics because its quality characteristic is out of specification and lead to product scrap after the product is put into service, the paper establishes the present worth model of quality loss of STB characteristic based on service life distribution, and proposes the calculation method on the probability density function (PDF) of the product service life based on the technical specifications of STB quality characteristic. It takes the concentricity between the inner cylindrical surface and the outer cylindrical surface of the link bushing as an example to analysis the various factors that impact on the present worth of concentricity quality loss in the new model, and contrast with Taguchi quality loss model. The results show that the new model describes an actual loss that a product imparts to society after the product is put into service, and can reflect the quality loss of STB characteristic in the product service process, and is more realistic than Taguchi quality loss model of STB. The new model extends tolerance design of STB characteristic from the manufacturing stage to the service stage.

Combining expert knowledge and local data for improved service life modeling of water supply networks

The presented approach aims to overcome the scarce data problem in service life modeling of water networks by combining subjective expert knowledge and local replacement data. A procedure to elicit imprecise quantile estimates of survival functions from experts, considering common cognitive biases, was developed and applied. The individual expert priors of the parameters of the service life distribution are obtained by regression over the stated distribution quantiles and aggregated into a single prior distribution. Furthermore, a likelihood function for the commonly encountered censored and truncated pipe replacement data is formulated. The suitability of the suggested Bayesian approach based on elicitation data from eight experts and real network data is demonstrated. Robust parameter estimates could be derived in data situations where frequentist maximum likelihood estimation is unsatisfactory, and to show how the consideration of imprecision and in-between-variance of experts improves posterior inference.

Modeling Present Worth of Product Quality Losses Based on Service Life Distribution

Taguchi defines product quality as a loss that a product imparts to society from the time the product is shipped,and describes the loss with a quadratic function,but does not indicate what the loss is specifically.The product quality characteristics are continually changing because of pressure,movement and attrition after the product is put into use,which will cause loss because of the product rejected and scrapped.The paper defines product quality losses as present worth of a loss caused by product obsolescence because its quality characteristics are out of specification after it's put into service.On the basis of this view on quality,it establishes the present worth of quality losses model based on service life distribution with the principle of discounted cash flow,and proposes the calculation method of product service life distribution density function based on the technical requirements for tolerance of quality characteristic.It takes the interior diameter dimension characteristic of the shaft sleeve as an example to analysis the impact of various factors of the new model on the present worth of shaft sleeve quality losses,and contrast with Taguchi quality loss model and Teran present worth of quality loss model.The results show that the new model describes an actual loss that a product imparts to society after the product is put into service,and can reflect quality loss of different products in the different service conditions and environment,and is more realistic than Taguchi quality loss model and Teran quality loss model.The new model extends product quality assurance and tolerance design from the manufacturing stage to the service stage,and provides new perspective for quality variation in the life cycle of product design,processing,operation,et al.

Service life analysis from field data on age distributions

In survey investigations of building stocks for example, data on age distributions of construction details are often collected. What interests the material scientist, though, is not the age distribution but rather the service life distribution. Presented herein will be a renewal process model describing the relationship between such an age distribution found and the corresponding service life distribution being sought. The model comprises a phenomenological parameter to accommodate correlations between objects and the service life’s determining factors. However, it is shown that, because of numerical ambiguity, the correlation parameter cannot be uniquely determined from an age distribution. Therefore, some additional information and data processing are required before the full advantage of this model can be realized. This somewhat difficult part has yet to be completed. Nevertheless, in its present form, the model does point out possible ranges of service life distribution parameters in terms of the correlation strength, thus providing uncertainties in the distribution parameters, which up until now have normally been overlooked when estimating the service lives of building materials. For wide service life distributions, it is shown that the possible parameter ranges will also the rather wide.

Belt Number Factor in Multiple V-Belt Drives

Tolerances on belts and pulleys lead to a nonuniform tension distribution among the belts in a multiple belt drive. Material imperfections lead to a service life distribution. Both phenomena contributes to the life of the drive i.e. the shortest life of any of the belts. To compensate for life reduction a belt number factor is introduced. The combined effect of tension and life distributions is simulated and compared with analyses. It appears that life distribution is the major contributor. Practical values of the belt number factor are presented.

The service life distribution of axles: Cheng, Y. and Nogata, F. Proc. Conf. Mechanical Behaviour of Materials-VI., Kyoto, Japan, 29 July–2 Aug. 1991, Vol. 4, pp. 439–444

It is well-known from the literature that an interaction effect on crack propagation arises when a specimen or a component is subjected to variable amplitude loading. In dependence of the applied load sequence, a certain amount of retardation or acceleration onto fatigue crack growth rate can then be observed if compared to the constant amplitude case. In the case of structural ductile materials, the interaction phenomenon is mainly addressed by the local plasticity at the crack tip and can be explained, from a global point of view, by adopting the crack closure concept. Considering the applicative case of railway axles, a good correlation between crack growth interaction effects under variable amplitude loading and the amount of plasticity-induced crack closure has been previously derived by the authors, relatively to the standardized EA1N steel. The other standardized European steel for railway axles, a 25CrMo4 grade named EA4T, is instead considered in the present research, as well as an high strenght steel grade. An experimental campaign was carried on this material, using SE(T) specimens, in order to understand and quantify the interaction effects arising from relevant load sequences derived from service. Firstly, tests were performed directly applying the acquired load time history. Eventually, the load history was transformed into an equivalent block loading sequence and applied to different specimens varying the number of cycles of each single block. Finally, the experimental outcomes were modeled adopting both a strip yield model and a simple no-interaction approach, in order to quantify the possible interaction effects. The modeling was carried out considering different experimental techniques for deriving the crack growth and threshold behaviors of the material, i.e. the traditional ΔK-decreasing technique and the compression pre-cracking one.

A Sampling Procedure for Estimating the Residual Life of Fossil-Fuelled Plant Boiler Tubing

Abstract A Monte Carlo simulation has been performed to approximate the service life distribution of thermal plant boiler tubes, using temperature, initial tube wall thickness, corrosion rate and metallurgical creep life as normal random variables. The stress sensitivity and activation energy of corrosion were included by using a sensitivity analysis. The approach was based on a recently-developed residual life model [3], which can predict boiler tube life on the basis of in-plant wall-thinning measurements. This model does not depend on knowledge of the tube effective operating temperature, in contrast with other approaches.For reheater tubes, it is shown that an estimate of the mean service life of the given tube population can be obtained to ± 10000 h with 95 % confidence by examining about eight sample tubes. For superheater tubes which have a greater standard deviation, sample size is typically about 22 tubes.

Statistical evaluation of the service life of a complex shaped, large-scale part

1. A method is proposed for calculating the service life of actual parts according to the parameter of failure probability with the use of fatigue resistance characteristics of large-scale models, which is suitable for calculations concerning parts of arbitrary complex shape given representative statistical data about loading. The method is recommended for engineering calculations of service life according to fatigue strength criteria on a probability basis for different unique complex shaped parts for which direct fatigue tests are impossible. 2. The basic stages of the calculation are: statistical evaluation of loading on the part; fatigue tests on large-scale models of the actual part, making possible integral consideration of the effect of stress state on fatigue resistance of the complex shaped gauge section; determination of the fatigue limit distribution function for the actual part; calculation of the service life distribution function of the actual part. 3. Experimental verification was obtained for the high reliability of calculated stress state parameters in complex-shaped parts under torsion by the proposed method based on fatigue test results for large-scale specimens. Application to the wobbler spindle of the Pilger mill at the 220 plant in the CTRW gave a service life distribution function L with a median value L=1.8 years of rolling mill operating time, agreeing with data from VNIImetmash on the service life of this spindle. 4. Numerical evaluation of fatigue failure probability for critical large-scale, complex-shaped parts, carried out by this method in the working design stage, is necessary to provide the specific γ-percent service life of the machine as a whole.

Sequential Models in Probabilistic Depreciation

Abstract : Probabilistic depreciation is a method of determining the proper depreciation charge in each year of an asset's service life, when the service life is a random variable with known distribution. The paper discusses how the service life distribution is modified as more information is obtained about the actual lifetime of the asset. The problem of determining the proper amount to be charged each year to depreciation while at the same time maintaining the proper balance in the accumulated depreciation account is considered. The analysis is done both for a single asset case and for group depreciation. A final section discusses the use of Bayesian analysis for estimating the particular form of the service life distribution while the assets are in service.