Stochastic modelling fatigue crack evolution and optimum maintenance strategy for composite blades of wind turbines

Hua-Peng Chen,Chi Zhang,Tian-Li Huang 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.6

The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.

Gene Mapping Related to Yellow Green Leaf in a Mutant Line in Rice (Oryza sativa L.)

Peng Du,Ying Hua Ling,Xian Chun Sang,Fang Ming Zhao,Rong Xie,Zheng Lin Yang,Guang Hua He 한국유전학회 2009 Genes & Genomics Vol.31 No.2

A mutant, which derived from the restorer line Jinhui10 treated with EMS, showed completely yellow green leaves, and it had low chlorophyll content and poor agronomic characteristics during the growing stage. The F1 plants from the cross between normal × the mutant showed normal green leaves, and the segregation ratio of normal to yellow green leaves was 3:1 in F2 population. It indicated that the trait was controlled by a single recessive nuclear gene, temporarily designated as ygl3. The gene ygl3 was mapped between RM468 and RM3684 with genetic distances 8.4 cM and 1.8 cM on chromosome 3. This result would be used as genetic information for fine mapping and map-based cloning of ygl3 gene.

A novel charring agent containing caged bicyclic phosphate and its application in intumescent flame retardant polypropylene systems

Hua-Qiao Peng,Qian Zhou,De-Yi Wang,Li Chen,Yu-Zhong Wang 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.5

A novel charring agent, bis(2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-oxo-4-hydroxymethyl) phenylphosphonate (BCPPO), was synthesized and characterized by FT-IR, 1H NMR and 31P NMR spectroscopies. Moreover, the novel charring agent combining with ammonium polyphosphate (APP) as well as melamine (MA) was adopted as intumescent flame retardants (IFR) to impart flame retardance and dripping resistance to polypropylene (PP). Flammability and thermal behaviors of the treated PP were investigated by Limiting Oxygen Index (LOI), Vertical Burning Test (UL-94), Thermogravimetric Analysis (TGA) and Cone Calorimeter test. Results indicate that the intumescent flame retardant with the novel charring agent shows both excellent flame retardance and anti-dripping abilities for PP when the three main components of IFR coexist at appropriate proportions, and the optimum flame retardant formulation is APP:MA:BCPPO = 3:1:1 that gives an LOI of 30.3 and UL- 94 V-0 rating, moreover, both the heat release rate (HRR) and the total heat release (THR) of IFR-PP with the optimum formulation decrease significantly relative to PP from cone calorimeter analysis. The residues from decomposition of the IFR-treated PP was characterized by FT-IR spectroscopy and SEM micrograph, and it was found that the char yield as well as char properties have direct effects on the flame retardance and anti-dripping behaviors of the treated PP.

Transcriptome analyses reveal photosynthesis-related genes involved in chloroplast development of the EMS-induced maize mutant

peng Hua,Gao Jiao,song Xia 한국식물생명공학회 2022 Plant biotechnology reports Vol.16 No.5

Chloroplast development together with chlorophyll biosynthesis plays an important role in plant survival and growth. Here, EMS-induced chlorophyll-deficient mutants (wtg, wts, and wta) were obtained from the progeny of Mt128 (MT), generated from the maize inbred line DP128 (WT). Three types of leaf color were segregated from the self-fertilized progenies of MT, including green, narrow-white striped and albino and named wtg, wts, and wta, respectively. We found that the Chl and carotenoid contents were significantly changed in wtg, wts, and wta, especially wta, compared with WT. In addition, leaf transcriptome sequencing of wtg, wts, wta, and WT were also carried out. The DEGs were identified as being related to chloroplast development and photosynthesis. By performing pairwise comparisons of each group, a total of 3685 (1181 upregulated, 2504 downregulated), 2624 (1028 upregulated, 1596 downregulated) and 6693 (3018 upregulated, 3675 downregulated) genes were found to be differentially regulated in wtg, wts, and wta, respectively, compared with WT. Of those, 75 comodulated DEGs with great alterations were identified among the comparison groups. More interestingly, most of the DEGs were found to be significantly involved in photosynthesis, including PSI, PSII, the cytochrome b6f complex, and F-type ATPase. GO enrichment of DEGs revealed that most of DEGs were involved in chloroplast development, chlorophyll biosynthesis, or photosynthesis. KEGG enrichment analysis indicated that the five significantly enriched pathways for comodulated DEGs in all EMS-induced mutant genotypes were as follows: benzoxazinoid biosynthesis, photosynthesis, starch and sucrose metabolism, phenylpropanoid biosynthesis and the photosynthesis–antenna proteins pathway. The results showed that EMS induction is a valid approach for generating mutants for crop breeding research.

Symptom-based reliability analyses and performance assessment of corroded reinforced concrete structures

Hua-Peng Chen,Nan Xiao 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6

Reinforcement corrosion can cause serious safety deterioration to aging concrete structuresexposed in aggressive environments. This paper presents an approach for reliability analyses of deterioratingreinforced concrete structures affected by reinforcement corrosion on the basis of the representativesymptoms identified during the deterioration process. The concrete cracking growth and rebar bond strengthevolution due to reinforcement corrosion are chosen as key symptoms for the performance deterioration ofconcrete structures. The crack width at concrete cover surface largely depends on the corrosion penetrationof rebar due to the expansive rust layer at the bond interface generated by reinforcement corrosion. The bondstrength of rebar in the concrete correlates well with concrete crack width and decays steadily with crackwidth growth. The estimates of cracking development and bond strength deterioration are examined byexperimental data available from various sources, and then matched with symptom-based lifetime Weibullmodel. The symptom reliability and remaining useful life are predicted from the predictive lifetime Weibullmodel for deteriorating concrete structures. Finally, a numerical example is provided to demonstrate theapplicability of the proposed approach for forecasting the performance of concrete structures subject toreinforcement corrosion. The results show that the corrosion rate has significant impact on the reliabilityassociated with serviceability and load bearing capacity of reinforced concrete structures during their servicelife.

Stochastic modelling and optimum inspection and maintenance strategy for fatigue affected steel bridge members

Hua-Peng Chen,Tian-Li Huang,Hao Zhou,Wei-Xin Ren 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.3

This paper presents a method for stochastic modelling of fatigue crack growth and optimising inspection and maintenance strategy for the structural members of steel bridges. The fatigue crack evolution is considered as a stochastic process with uncertainties, and the Gamma process is adopted to simulate the propagation of fatigue crack in steel bridge members. From the stochastic modelling for fatigue crack growth, the probability of failure caused by fatigue is predicted over the service life of steel bridge members. The remaining fatigue life of steel bridge members is determined by comparing the fatigue crack length with its predetermined threshold. Furthermore, the probability of detection is adopted to consider the uncertainties in detecting fatigue crack by using existing damage detection techniques. A multi-objective optimisation problem is proposed and solved by a genetic algorithm to determine the optimised inspection and maintenance strategy for the fatigue affected steel bridge members. The optimised strategy is achieved by minimizing the life-cycle cost, including the inspection, maintenance and failure costs, and maximizing the service life after necessary intervention. The number of intervention during the service life is also taken into account to investigate the relationship between the service life and the cost for maintenance. The results from numerical examples show that the proposed method can provide a useful approach for cost-effective inspection and maintenance strategy for fatigue affected steel bridges.

Stochastic modelling and lifecycle performance assessment of bond strength of corroded reinforcement in concrete

Hua-Peng Chen,Jaya Nepal 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.2

Life cycle performance of corrosion affected RC structures is an important and challengingissue for effective infrastructure management. The accurate condition assessment of corroded RC structuresmainly depends on the effective evaluation of deterioration occurring in the structures. Structuralperformance deterioration caused by reinforcement corrosion is a complex phenomenon which is generallyuncertain and non-decreasing. Therefore, a stochastic modelling such as the gamma process can be aneffective tool to consider the temporal uncertainty associated with performance deterioration. This paperpresents a time-dependent reliability analysis of corrosion affected RC structures associated bond strengthdegradation. Initially, an analytical model to evaluate cracking in the concrete cover and the associated lossof bond between the corroded steel and the surrounding cracked concrete is developed. The analytical resultsof cover surface cracking and bond strength deterioration are examined by experimental data available. Thenthe verified analytical results are used for the stochastic deterioration modelling, presented here as gammaprocess. The application of the proposed approach is illustrated with a numerical example. The results fromthe illustrative example show that the proposed approach is capable of assessing performance of the bondstrength of concrete structures affected by reinforcement corrosion during their lifecycle.

Mode shape expansion with consideration of analytical modelling errors and modal measurement uncertainty

Hua-Peng Chen,Kong Fah Tee,Yi-Qing Ni 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.5

Mode shape expansion is useful in structural dynamic studies such as vibration based structural health monitoring; however most existing expansion methods can not consider the modelling errors in the finite element model and the measurement uncertainty in the modal properties identified from vibration data. This paper presents a reliable approach for expanding mode shapes with consideration of both the errors in analytical model and noise in measured modal data. The proposed approach takes the perturbed force as an unknown vector that contains the discrepancies in structural parameters between the analytical model and tested structure. A regularisation algorithm based on the Tikhonov solution incorporating the L-curve criterion is adopted to reduce the influence of measurement uncertainties and to produce smooth and optimised expansion estimates in the least squares sense. The Canton Tower benchmark problem established by the Hong Kong Polytechnic University is then utilised to demonstrate the applicability of the proposed expansion approach to the actual structure. The results from the benchmark problem studies show that the proposed approach can provide reliable predictions of mode shape expansion using only limited information on the operational modal data identified from the recorded ambient vibration measurements.

Updating finite element model using dynamic perturbation method and regularization algorithm

Hua-Peng Chen,Tian-Li Huang 국제구조공학회 2012 Smart Structures and Systems, An International Jou Vol.10 No.5

An effective approach for updating finite element model is presented which can provide reliable estimates for structural updating parameters from identified operational modal data. On the basis of the dynamic perturbation method, an exact relationship between the perturbation of structural parameters such as stiffness change and the modal properties of the tested structure is developed. An iterative solution procedure is then provided to solve for the structural updating parameters that characterise the modifications of structural parameters at element level, giving optimised solutions in the least squares sense without requiring an optimisation method. A regularization algorithm based on the Tikhonov solution incorporating the generalised cross-validation method is employed to reduce the influence of measurement errors in vibration modal data and then to produce stable and reasonable solutions for the structural updating parameters. The Canton Tower benchmark problem established by the Hong Kong Polytechnic University is employed to demonstrate the effectiveness and applicability of the proposed model updating technique. The results from the benchmark problem studies show that the proposed technique can successfully adjust the reduced finite element model of the structure using only limited number of frequencies identified from the recorded ambient vibration measurements.

Effect of cover cracking on reliability of corroded reinforced concrete structures

Hua-Peng Chen,Jaya Nepal 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.5

The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.