Strength Reliability Analysis Research Articles

Prediction and reliability analysis of shear strength of RC deep beams

This study explores machine learning (ML) capabilities for predicting the shear strength of reinforced concrete deep beams (RCDBs). For this purpose, eight typical machine-learning models, i.e., symbolic regression (SR), XGBoost (XGB), CatBoost (CATB), random forest (RF), LightGBM, support vector regression (SVR), artificial neural networks (ANN), and Gaussian process regression (GPR) models, are selected and compared based on a database of 840 samples with 14 input features. The hyperparameter tuning of the introduced ML models is performed using the Bayesian optimization (BO) technique. The comparison results show that the CatBoost model is the most reliable and accurate ML model (R2 = 0.997 and 0.947 in the training and testing sets, respectively). In addition, simple and practical design expressions for RCDBs have been proposed based on the SR model with a physical meaning and acceptable accuracy (an average prediction-to-test ratio of 0.935 and a standard deviation of 0.198). Meanwhile, the shear strength predicted by ML models was then compared with classical mechanics-driven shear models, including two prominent practice codes (i.e., ACI318, EC2) and two previous mechanical models, which indicated that the ML approach is highly reliable and accurate over conventional methods. In addition, a reliability-based design was conducted on two ML models, and their reliability results were compared with those of two code standards. The findings revealed that the ML models demonstrate higher reliability compared to code standards.

Study on the bearing characteristics of overrun hydraulic support under impact loading

In order to study the effects of stress change and adaptability of the overrun hydraulic stent under impact load, the rigid–flexible coupling numerical model of the stent is established using multi-body dynamics simulation software ADAMS. In the model, the stent is flexibilized using the HyperMesh module, and the column and jack are equivalently replaced with a spring damping system. By applying impact loads to different positions above the front roof beam of the stent, the dynamic response characteristics of the column and the articulation point are obtained at different positions with different strengths. The results show that when the impact load is applied to different positions of the front roof beam, the steady-state response force of the column shows an overall “M" distribution, and along the length direction of the roof beam, the steady-state response force of the column shows an upward trend, and the maximum steady-state response force of the column is 547 kN at point (1, 6); when the impact load is applied to both sides of the front roof beam, the response at the articulation point is greater, resulting in a higher maximum simple harmonic response at that articulation point. When the impact load acts on both sides of the front roof beam, the response of the articulation point is greater, with a maximum simple harmonic response coefficient of 0.75 and a maximum excitation response coefficient of 0.28; when the impact loads of different strengths act on the whole front roof beam, the force acting on the column and pin shaft at the articulation point will produce a large impact, reducing its adaptability. To address this, we can consider changing the top plate stress conditions using methods like high-pressure injection of water and control the gradual and slow release of the top plate stresses. The results of the study provide a reference for the structural strength design and reliability analysis of the hydraulic support, which is of practical significance and value for improving the safe mining of the coal mining face.

Stress–Strength Reliability Analysis for Different Distributions Using Progressive Type-II Censoring with Binomial Removal

In the statistical literature, one of the most important subjects that is commonly used is stress–strength reliability, which is defined as δ=PW<V, where V and W are the strength and stress random variables, respectively, and δ is reliability parameter. Type-II progressive censoring with binomial removal is used in this study to examine the inference of δ=PW<V for a component with strength V and being subjected to stress W. We suppose that V and W are independent random variables taken from the Burr XII distribution and the Burr III distribution, respectively, with a common shape parameter. The maximum likelihood estimator of δ is derived. The Bayes estimator of δ under the assumption of independent gamma priors is derived. To determine the Bayes estimates for squared error and linear exponential loss functions in the lack of explicit forms, the Metropolis–Hastings method was provided. Utilizing comprehensive simulations and two metrics (average of estimates and root mean squared errors), we compare these estimators. Further, an analysis is performed on two actual data sets based on breakdown times for insulating fluid between electrodes recorded under varying voltages.

Probabilistic-based burst failure mechanism analysis and risk assessment of pipelines with random non-uniform corrosion defects, considering the interacting effects

Corrosion defects were primary causes for pipeline burst failures. Traditional methodologies simplified the realistic irregular-shaped defects as uniform ones, ignoring the effects of random morphologies on failure behaviours, which caused deviations in remaining strength pb estimation and reliability analysis. Addressing this issue, through coupling random field, non-linear finite element analysis and Monte-Carlo Simulation, an integrated methodology was developed to describe failure behaviours of pipelines with random defects. The failure mechanism and reliability analysis were performed. The pbs for random defects exhibited significant variabilities, of which the probability distribution patterns altered with different corrosion depths attributed to multiple failure modes. The main value of pb for random defects was lower than that of uniform defects, especially for deeper corrosion and interacting defects. At maximum, this reduction attained over 28%; The spatial variation gradient of remaining wall thickness dominated failure developments, based on which three failure modes were revealed; The wall thickness, corrosion degree and interacting effects were influential on failure probabilities Pfs. An average failure risk of Pf over 0.6 would be suffered for employing traditional methodologies. Polynomial chaos expansion models were fitted to estimate pb from corrosion morphologies, showing reasonable accuracies. Besides, the performance variations with different cases were discussed.

Residual Strength Modeling and Reliability Analysis of Wind Turbine Gear under Different Random Loadings

A novel method is proposed to investigate the pattern of variation in the residual strength and reliability of wind turbine gear. First, the interaction between loads and the effect of the loading sequence is considered based on the fatigue damage accumulation theory, and a residual strength degradation model with few parameters is established. Experimental data from two materials are used to verify the predictive performance of the proposed model. Secondly, the modeling and simulation of the wind turbine gear is conducted to analyze the types of fatigue failures and obtain their fatigue life curves. Due to the randomness of the load on the gear, the rain flow counting method and the Goodman method are employed. Thirdly, considering the seasonal variation of load, the decreasing trend of gear fatigue strength under multistage random load is calculated. Finally, the dynamic failure rate and reliability of gear fatigue failure under multistage random loads are analyzed. The results demonstrate that the randomness of residual strength increases with increasing service time. The seasonality of load causes fluctuations in the reliability of gear, providing a new idea for evaluating the reliability of the wind turbine gear.

Time-varying Reliability Analysis of Contact Fatigue Strength for Nutation Face Gear Transmission

Background: Nutation face gear transmission is a patent about a new type of transmission based on meshing between two face gears. It replaces spur gear with internal face gear to form a “faceface” meshing gear pair and actualizes its deceleration function by combining the nutation principle, which has the advantages of both face gear and nutation drive. Objective: The purpose of this paper is to establish the time-varying reliability calculation model of contact fatigue strength based on fractal contact theory, so as to improve the reliability, safe service and further optimization design of the nutation face gear transmission. Methods: The time-varying uncertainties of the contact stress and the allowable contact stress of the face gear teeth are analyzed respectively, and then the time-varying reliability model of the contact fatigue strength is established. Finally, the drift rate and fluctuation rate of each random variable are simulated using the Monte Carlo simulation method to obtain the time-varying reliability of the contact fatigue strength for the nutation face gear drive. Results: The results show that the general trend of geometric Brownian motion locus of each random variable is consistent with the actual situation. Conclusion: For the given example of the nutation face gear transmission device, the reliability of the contact fatigue strength of the planetary face gear meshing with the fixed face gear and the rotating face gear within one year is calculated to be 0.9912 and 0.9856 respectively, and the maximum vibration noise is about 68dB, which meets the expected value.

Reliability Analysis of Structure Strength based on Spacer Installation Robot

During the construction of high-altitude 10kV power lines, manual installation for spacers has considerably numerous limitations and problems, for example, safety issues, efficiency etc. A new-type spacer installation robot has been introduced to assist the worker to install spacer in air. Prior to put it into usage or production, the reliability of structure strength needs to be tested and verified. This paper verifies the reliability through mathematical calculation and Solidworks/Simulation in which generates stress and displacement plots to determine whether the stresses and elongations in the structure are in a reasonably safe range for both under working conditions and without load.

Ultimate strength analysis of longitudinal bending of hull girder based on image analysis

In the traditional code, the allowable stress method is used to check the total longitudinal strength of hull girder, which has the characteristics of simple and quick calculation. However, this method is based on the assumption of elastic materials, and can not truly reflect the actual bearing capacity of the structure. Based on image analysis, a practical method for calculating the ultimate longitudinal strength of ship hull is studied. The average stress-strain relationship of the elements constituting the cross section of the hull girder under axial pressure is given, and the progressive collapse behavior of the hull girder in longitudinal bending is analyzed. Finally, the reliability analysis method for the ultimate strength of the hull girder in longitudinal bending is put forward, and a real ship example is given. The research results show that the proposed method is not only suitable for the safety assessment of ship structures in the conceptual design stage, but also meets the requirements of rapid prediction of real ship wave loads and structural strength reliability analysis.

Fracture Mechanical Analysis of Thin-Walled Cylindrical Shells with Cracks

The fracture mechanical behaviour of thin-walled structures with cracks is highly significant for structural strength design, safety and reliability analysis, and defect evaluation. In this study, the effects of various factors on the fracture parameters, crack initiation angles and plastic zones of thin-walled cylindrical shells with cracks are investigated. First, based on the J-integral and displacement extrapolation methods, the stress intensity factors of thin-walled cylindrical shells with circumferential cracks and compound cracks are studied using linear elastic fracture mechanics, respectively. Second, based on the theory of maximum circumferential tensile stress of compound cracks, the number of singular elements at a crack tip is varied to determine the node of the element corresponding to the maximum circumferential tensile stress, and the initiation angle for a compound crack is predicted. Third, based on the J-integral theory, the size of the plastic zone and J-integral of a thin-walled cylindrical shell with a circumferential crack are analysed, using elastic-plastic fracture mechanics. The results show that the stress in front of a crack tip does not increase after reaching the yield strength and enters the stage of plastic development, and the predicted initiation angle of an oblique crack mainly depends on its original inclination angle. The conclusions have theoretical and engineering significance for the selection of the fracture criteria and determination of the failure modes of thin-walled structures with cracks.

Optimal design and strength reliability analysis of pressure shell with grid sandwich structure

This study focuses on lightweight optimum design of head pressure shell of an autonomous underwater vehicle (AUV) with reliability requirements. The grid sandwich structure is applied to the pressure shell for lightweight. An optimal mathematical model is established, which takes weight and the maximum von-Mises stress as objective and strength requirement as a constraint condition. This optimization model is solved by genetic algorithm (GA) based on back propagation (BP) neural network surrogate model, which is optimized by particle swarm optimization (PSO) for improving accuracy. Additionally, the randomness of geometry sizes, material properties and loads are considered to ensure reliability. A stress-strength interference model is established for obtaining failure probability and reliability according to statistical regularity of yield strength and the maximum von-Mises stress. The result shows that the weight of grid sandwich structure pressure shell is reduced by 38.26% compared with the solid pressure shell. The width of transverse grid has more influence on the maximum von-Mises stress than longitudinal grid. The critical load factor is 21.611 and buckling deformation will not occur under given conditions. The pressure shell with grid sandwich structure meets three sigma level with random variables, which can ensure enough reliability of AUV. The above analysis shows that application of grid sandwich structure to the pressure shell of AUV head is feasible.

Reliability Analysis of Wheel fatigue strength based on active learning Kriging Model

The reliability analysis of fatigue strength of rail vehicle wheels is studied in this paper. On the basis of deterministic analysis, a basic model for reliability analysis of wheel fatigue strength is established by comprehensively considering many uncertain factors. A reliability analysis method based on active learning Kriging (ALK) model is introduced to solve the fatigue strength failure probability of wheels. The results of reliability analysis are verified, and the results show that the reliability analysis based on ALK model can significantly improve the efficiency on condition the accuracy is guaranteed.

Ply Parameters Optimization and Strength Reliability Analysis of Wind Turbine Blade

As the critical component of capturing wind energy, the performance and reliability of blade are directly related to the safe, stable operation and service life of wind turbines. The performance of the blade is mainly determined by the ply parameters, so it has important valueto study the optimization method of ply parameters and the analysis method of strength reliability of wind turbine blade.In this paper, the load of a 1.5MW wind turbine bladeunder the DLC1.5g-2 working condition is calculated and its finite element model is established. Combined with engineering practice, the investigation range of ply parameters is determined, the test scheme is designed by using the mixed level uniform experiment method, and the blade strength is analyzed. Based on the polynomial regression analysis method and simulation results, the quadratic mathematical model between the ply parameters and the Tsai-Wu failure factors is established, and the range of ply parameters is optimized by mean value analysis method and interaction analysis method. On this basis, the ply parameters are regarded as random variables, and the structural performance function of blade failure is constructed. The reliability of the blade is predicted by the first-order second-moment method. The results show that the blade is reliable in the range of optimized ply parameters. The work provides the method and technical support for the laminate structure design and optimization of wind turbine blade.

Reliable Production in Steel Industry and a Case Study: Reliability Analysis of Yield and Tensile Strength of S355JR (EN 10025-2) Steel

Makine ve imalat sektöründe çelik, dayanım ve maliyet faktörleri göz önüne alındığında vazgeçilmez bir malzemedir. Günümüz koşullarında teknolojinin ve buna bağlı olarak tasarımların geldiği noktada, özellikle vasıflı çelikler büyük önem kazanmış, üstün mekanik dayanım ve yorulma özellikleri makine ve imalat endüstrisinin tamamına yakınında bu çeliklerin kullanımını zorunlu hale getirmiştir. Bu çalışmada çelik üretiminde ülkemizde ihmal edilen bir kavram olan güvenirlik ele alınmış, üretimde ve tasarımlarda yapılacak güvenirlik analizlerinin getireceği katkı tartışılmıştır. Çalışma kapsamında örnek bir uygulama olarak S355JR (EN 10025-2) Çeliğinin çekme testinin güvenirlik analizi gerçekleştirilmiştir.

Probabilistic residual ultimate strength assessment of cracked unstiffened and stiffened plates under uniaxial compression

This paper proposes a reliable approach to evaluate the probabilistic residual ultimate strength of cracked unstiffened/stiffened plates by coupling nonlinear finite element analysis and Kriging-based reliability method. A numerical simulation scheme is established to evaluate the residual ultimate strength of cracked plates under uniaxial compression loading, considering the influence of uncertain initial imperfections, cracking damages and material parameters. To improve the efficiency of assessment, Kriging-based Monte Carlo simulation method combined with an active learning (AK-MCS) strategy is adopted to achieve the reliability analysis of ultimate strength. Firstly, a deterministic analysis is implemented to explore the influence of basic variables on the ultimate strength reduction characteristics of cracked plates. Then, probabilistic reliability analysis is performed to investigate the evolution of failure probability and reliability index of each uncertain parameter and to evaluate reliability index of design objective for ultimate strength. Sensitivity analysis of uncertain parameters on the reliability index and failure probability is studied, and the result reveals that its variation tendency is consistent with deterministic analysis. The reliability index is achieved by AK-MCS with a few of FEM calls, indicating the proposed probabilistic ultimate strength assessment method is accurate and efficient for structural reliability analysis of cracked plates.

Reliability analysis of compact and high efficient heat exchanger for FLNG devices

Objectives So far, the compact and high-efficiency heat exchanger is the best choice for floating liquefied natural gas (FLNG) heat exchangers. Static strength analysis and reliability analysis are required to optimize the structural parameters of a heat exchanger and improve its performance. Methods First, the strength of the heat exchanger core is analyzed using the ANSYS Workbench static analysis module, and a simplified model is established which can represent the stress level of most channels. Next, the reliability analysis of the heat exchanger is conducted using the six sigma analysis of the ANSYS Workbench by choosing the cold channel thickness, cold channel pressure, hot channel pressure and elastic modulus as input random variables, and the effects of these random variables on the reliability of the heat exchanger are studied. Results The reliability analysis results show that the cold channel pressure loading is the greatest factor in structural strength, and the reliability of the heat exchanger is more than 99.9%, so the possibility of failure is very low. Conclusions The results of this study can serve as valuable references for the reliability analysis of heat exchangers based on strength.

Reliability analysis of hull girder ultimate strength for large container ships under whipping loads

The two incident reports for MSC (Mediterranean Shipping Company) Napoli in 2008 and MOL (Mitsui O.S.K. Lines) Comfort in 2015 both pointed out that whipping response was one main reason for inducing the catastrophes. Subsequently, International Association of Classification Societies (IACS) proposed a Unified Requirement (UR) S11A for ultimate strength evaluation of container ships, and main classification societies also updated their guidelines for whipping response. However, there are big differences in these requirements, and the safety level of ultimate strength under whipping loads is still unclear. This article is to find the effect of the whipping loads on hull girder reliability. Two large container ships 14500TEU and 19000TEU designed by China Classification Society (CCS) Rules are selected as case studies. Hull girder ultimate capacity in mid-ship section under hogging conditions is adopted as the dangerous failure mode, which is predicted by the increment-iterative method in IACS Common Structural Rules (CSR). The whipping effect on hull girder reliability is accounted for by a factor attaching on wave-induced moment. Then, a new evaluation criterion is proposed to evaluate hull girder ultimate strength for container ships under whipping loads, and sensitivity analysis of whipping effect is carried out. The conclusions in this article can provide a guidance for revising rule requirements in classification societies and optimising container ship structural design.

Investigation of twist structure contributing to strength improvement of a ramie twisted yarn and strength reliability analysis using Markov process

Investigation of twist structure contributing to strength improvement of a ramie twisted yarn and strength reliability analysis using Markov process

Strength properties and reliability analysis of unidirectional CFRP with a small number of fibers

Strength properties and reliability analysis of unidirectional CFRP with a small number of fibers

Reliability analysis of shear strength of reinforced concrete deep beams using NLFEA

Nonlinear finite element analysis (NLFEA) is an important tool for solving deterministic structural problems and predicting the behavior of concrete structures. Nevertheless, inherent uncertainties in structural engineering cannot be considered using deterministic approaches. For that reason, the inclusion of reliability concepts in NLFEA has been a frequent subject in recent investigations. This work aims to study the safety of the design of reinforced concrete deep beams. This is done by coupling the finite element analysis and reliability theory approaches. The assessment of the shear capacity of deep beams involves different phenomenons such as discontinuity regions and size effect. Therefore, this cannot be designed or analyzed by simple calculations. In this study, a simply supported deep beam designed with the strut-and-tie method (STM) is used as an example of structural reliability assessment. The nonlinear analyses were performed in the software ATENA, based on concrete fracture and plasticity theory. For reducing computational effort, the reliability analysis was performed using two different Response Surface Method (RSM) strategies. Uncertainties from concrete properties and geometrical dimensions were considered using probability density functions. As a result, the safety of the deep beam design was expressed in terms of the reliability index β and the probability of failure Pf. According to the results obtained, the conclusion was that NLFEA combined with the reliability theory concept can allow an advanced safety assessment of deep beam design.

An interval interference reliability evaluation method for structural strength

The structural strength reliability analysis can effectively improve the service life of the structure. Based on the interval method and stress-strength interference method, the structural stress and strength at any time can be converted into the standardized interval. According to the relationship between the critical state function and the standardized interval, the interval interference reliability index η is defined. And then an interval interference evaluation method is proposed for structural strength. The validity of the method is verified through compared with the interval reliability method and the stress-strength interference reliability method. The results show that the proposed method can analysis the structural strength reliability without the parameter distribution form.