Life Prediction Analysis Research Articles

Fatigue life prediction of hypervapotron for CFETR divertor

The engineering design of China Fusion Engineering Testing Reactor (CFETR) will be finished in the end of this year. Compared with Experimental Advanced Superconducting Tokamak (EAST), this is a large development which means closer to commercial fusion reactors. The design objective of CFETR divertor requires a steady-state thermal load of 10–20MW/m2 exhaust. There are several design options for the CFETR divertor. Hypervapotron with its superior performance has been researched for several decades as one important candidate for future fusion device divertor. In this paper, a new design of hypervapotron plasma facing unit (PFU) was developed. Horizontal and longitudinal ribs were adopted to generate more vaporized cores to enhance heat transfer. Some optimizations were performed based on the allowable max heat flux (MAHF) to get the final design. Rensselaer Polytechnic Institute (RPI) boiling model of Eulerian Multiphase fluid and k-epsilon model of Viscous were chosen to deal with sub-cooled boiling. 3Sm rule and Bree-diagram was used to confirm the rationality of the structure after thermal-mechanical analysis. Numerical simulation results suggested that CuCrZr alloy will experience cyclic plastic strain. Based on this, fatigue life prediction of the hypervapotron PFU at a steady-state heat flux of 10MW/m2 were carried out through local stress-strain method, neuber curve and design fatigue life curve. Eventually, a fatigue life of approximately 1.2489 year was verified for CFETR divertor. This paper provides a systematic method for fatigue life prediction and reliability analysis of hypervapotron.

Research on Creep Behavior of Three-Point Bending Specimen With Fixed Constraints at the Large Deformation Stage

Abstract Three-point bending specimen with fixed constraints is a novel small specimen test technique, which can simultaneously obtain creep deformation and creep fracture data. However, the current research only focused on the small deformation theoretical analysis, which is contrary to the actual experiment results. In this study, the general deformation theory was introduced to analyze creep deformation behavior of three-point bending specimen with fixed constraints at the large deformation stage. Based on this theory, the equivalent stress and strain were analyzed. Then, the feasibility and accuracy were verified by comparing with the experimental data of A7N01 aluminum alloy at 380 °C. The results show that the regressed creep parameters agree well with those from the uni-axial ones. It can be found that the equivalent stress obtained by the general deformation theory can be well used to life prediction analysis of A7N01 aluminum alloy.

A continuum damage model for fatigue life prediction of 2.5D woven composites

Abstract A new model based on continuum damage mechanics is proposed to predict the fatigue life of 2.5D woven composites. First, a full-cell model reflecting the real microstructure of 2.5D woven composites is established in ANSYS. Subsequently, three independent damage variables are defined in the framework of the composite micromechanics to establish the component constitutive relations associated with damage. The strain energy density release rate and damage evolution equations for the matrix, fiber in yarns, and matrix in yarns are derived. Finally, the proposed model is implemented for fatigue life prediction and damage evolution analysis of 2.5D woven composites at 20 and 180°C. The results show that the numerical results are in good agreement with the relevant experimental results.

Service Life Prediction and Lateral Bearing Capacity Analysis of Piles Considering Coupled Corrosion-Temperature Deterioration Processes

High temperatures can enhance the chloride diffusion coefficient and this poses a threat to reinforced concrete (RC) piles. This study intends to propose predictive models that can evaluate the service life and lateral bearing behaviour of reinforced concrete piles subjected to marine environments and varying temperatures. The models show that temperature can accelerate the diffusion rate of chloride and increase the concentration of free chloride in concrete. The distribution law of chloride concentration is obtained by considering the ageing effect as well. Deterministic and probabilistic models are proposed to assess the time to corrosion initiation and propagation. The stiffness degradation coefficient is introduced in the analysis of the lateral bearing capacity of RC piles. The results show that high temperature can decrease the service life of piles and the life spans obtained from deterministic and probabilistic methods are similar; however, the predictions of the latter are more conservative. Temperature can enhance the current density and boost corrosion products, which leads to pile cracking. The rust appearing on the steel surface would make the stiffness degradation coefficient drop sharply. The lateral bearing capacity analysis is conducted from the perspectives of shear force, displacement and bearing moment of the piles.

Fatigue life prediction analysis of high-intensity marine diesel engine cylinder head based on fast thermal fluid solid coupling method

Fatigue life prediction analysis of high-intensity marine diesel engine cylinder head based on fast thermal fluid solid coupling method

Dynamic Behaviour of Bridge Girders with Trapezoidal Profiled Webs Subjected to Moving Loads.

The aim of this study is to find out the degradation of dynamic behaviour of bridge girders with trapezoidal profiled webs when subjected to different vehicle moving loads. Finite element modelling based parametric analysis is demonstrated to be desirable in capturing the dynamic deflection and stress state of critical structural details of girders. The model is validated in the modal analysis through a comparison with theoretical eigenfrequencies. The vibration characteristics are shown to be significantly affected by the corrugation details. The structural service life results of analysed bridge girders are in close agreement with experimental data. It is shown that the dynamic nodal velocity and deflection of analysed bridge girders are greatly affected by the magnitude of the load corresponding to the overload of the vehicle in contrast to the vehicle travel speed. Similar observations can be made for the fatigue life prediction analysis related to the crack initiation when unfavourable effects of the overload vehicle are concerned. Presented analytical results using a fracture mechanics approach could be taken as a good basis for the service life assessment of related bridges with the desired level of performance or functionality.

Impact Characteristics and Fatigue Life Analysis of Multi-Wire Recoil Spring for Guns

Recoil spring is a key part in automatic or semi-automatic weapons re-entry mechanism. Because the stranded wire helical spring (SWHS) has longer fatigue life than an ordinary single-wire cylindrically helical spring, it is often used as a recoil spring in various weapons. Due to the lack of in-depth research on the dynamic characteristics of the current multi-wire recoil spring in recoil and re-entry processes, the fatigue life analysis of the current multi-wire recoil spring usually only considers uniform loading and does not consider dynamic impact loads, which cannot meet modern design requirements. Therefore, this paper proposes a research method for fatigue life prediction analysis of multi-wire recoil spring. Firstly, based on the secondary development of UG, a three-wire recoil spring parameterized model for a gun is established. Secondly, ABAQUS is used to carry out a finite element analysis of its dynamic response characteristics under impact, and experimental verification is performed. Then, based on the stress-time history curve of the dangerous position obtained by finite element analysis, the rain flow counting method is used to obtain the fatigue stress spectrum of recoil spring. Finally, according to the Miner fatigue cumulative damage theory, the fatigue life prediction of the recoil spring based on the S-N curve of the material is compared with experimental results. The research results show that the recoil spring has obvious transient characteristics during the impact of the bolt carrier. The impact velocity is far greater than the propagation speed of the stress wave in the recoil spring, which easily causes the spring coils to squeeze each other. The maximum stress occurs at the fixed end of the spring. And the mean fatigue curve (50% survival rate) is used to predict the life of the recoil spring. The calculation result is 8.6% different from the experiment value, which proves that the method has certain reliability.

Reliability analysis of rolling bearings considering internal clearance

The internal clearance is a decisive parameter for life prediction and reliability analysis of rolling bearings. In this paper, a comprehensive reliability analysis model of rolling bearings is proposed by considering the internal clearance of rolling bearings. The model of bearings’ working clearance was established after investigating the effect mechanisms of effective interference, temperature, and centrifugal force on the clearance. The validation of the results is carried out by the reliability analysis of a real rolling bearing through the modeling of working clearance probability distribution and the research of life factor. The results indicate that the proposed methodology provides an additional reference way for the reliability analysis of rolling bearings.

Fatigue life prediction of laser and mechanically formed commercially pure grade 2 titanium alloy plates

This paper discusses fatigue life prediction of laser and mechanically formed commercially pure grade 2 titanium alloy plates. It should be noted that predicting fatigue damage for structural components is a complex issue that needs various factors involved in fatigue analysis to be taken into account. This paper looked at available fatigue life prediction theories as a start which then helped formulate and develop the fatigue life prediction analysis used in this study. The predicted fatigue life was not off the mark as it also incorporated the effects of residual stresses which are usually disregarded in studies of this nature. The validity of the fatigue life prediction concept is shown with the aid of calculations versus actual fatigue data results. The results show fatigue life prediction that is stable and less erratic on certain irradiation parameters, while other formed components behaved in a predictable manner. Fatigue life prediction analysis is a challenging undertaking and the behavior of benchmarking components is explained and possible reasons for this elucidated.

Life prediction analysis on underwater acoustic sensors and its experimental validation

An equivalent circuit analysis is presented to predict the acoustic characteristics of resonant hydrophones and the factors leading to their degradation. The circuit parameters of a Tonpilz transducer, operated as a resonant hydrophone in the receiving mode, are determined from the measured complex electrical admittance in water at frequencies in the vicinity of resonance. The parameters are refined by non-linear regression method and used to calculate the receiving sensitivity in the same band. External components such as insulation resistance, cable capacitance and input impedance of the preamplifier are included in the model and their loading effects on the receiving sensitivity are determined. The detrimental effect of drop in insulation resistance on the performance of the resonant hydrophone is studied quantitatively. The cut-off values of insulation resistance at various frequencies and capacitances are prescribed that would mark the end-of-life of the hydrophone. In the present case, the acceptable lower limit of Ri is found to be 1 MΩ at 100 Hz and 10 kΩ at 30 kHz. The model results are validated by experiments and are found to agree well with the measured data. The equivalent circuit model of hydrophones will be useful to optimize the hydrophone- preamplifier combination of underwater acoustic systems by minimizing the receiver noise and enhancing the signal to noise ratio.

Wear Analysis of Spatial Parallel Mechanisms With Multiple Three-Dimensional Spherical Clearance Joints

The goal of this work is to investigate the dynamic responses of the parallel mechanism with irregular clearances caused by wear and to further reveal the influences of multiple clearance interaction on wear. The motion model and the force model of spherical clearance joint based on a continuous contact force model and a static friction model are established. The dynamic equation of the spatial parallel mechanism considering two spherical clearance joints is derived. A general wear analysis strategy to establish spherical clearance joint with sustainable updation of the surface profile is presented, and the dynamic responses of parallel mechanism after wear are studied. The interaction between two wear joints with different initial clearance values is further investigated. The results show that it is necessary to consider the factor of irregular clearances caused by wear in the analysis of dynamics behavior for precision mechanisms. Proper distribution of clearance values can reduce wear of clearance joint and improve the useful life of mechanism to a certain extent. This work provides a foundation for life prediction and reliability analysis of parallel mechanisms.

Fatigue life prediction and modal analysis of carbon fiber reinforced composites

Fiber reinforced composite materials are finding increasing applications in aerospace structures, naval industry, military and automotive industry, because of their high specific stiffness and strength. The fatigue of composite materials is not completely understood which is quite different from metal fatigue. The objective of research is to apply modal testing for the fatigue life prediction of Carbon Fiber Reinforced Plastic laminate in plane bending with different fiber orientations. CFRP laminates with three fiber orientations as 0°, 45° and 90° are applied to fatigue loading in plane bending with R = -1 and S-Nf. curves are plotted and power equations are determined. For modal testing of the laminates the specimens previously undergone fatigue loading are tested at specific intervals to determine the effect of modal characteristics on fatigue life of these laminates. The modal characteristics are determined by using FFT analyzer and the frequency effect on fatigue life is determined. Results are plotted between the fatigue life ratio and the natural frequency and empirical equations are generated for predication of fatigue life prediction. From the results it is concluded that the modal testing is an effective nondestructive testing method that can be applied for estimating the fatigue life of composite laminates

Fatigue life evaluation and failure analysis of light beam direction adjusting mechanism of an automobile headlight exposed to random loading

Failure of the light beam direction adjusting mechanism (LDAM) of an automotive headlight might occur after hundreds of driving hours, though the strength of components conforms to the requirement specified in the random vibration bench test standard. In order to determine the causes of the failure, fatigue life prediction and failure analysis based on numerical method of the LDAM exposed to random loading both in bench test and field experiment were carried out. In the bench test analysis, the Dirlik method was utilized to calculate the lifetime by taking the power spectrum density in the frequency domain. In the fatigue analysis for the field experimental loading, to consider the effect of nonuniform temperature distribution, a numerical process in time domain is developed to calculate the lifetime of the LDAM subjected to the random vibration caused by road surface roughness. As a result, the predicted life and failure locations are in good agreement with real life and actual failure regions, respectively.

A mean plastic strain fatigue–creep life prediction and reliability analysis of AISI H13 based on energy method

Abstract

Life Prediction and Stress Intensity Factor (SIF) analysis for the base straight component and weld straight component (Pipes) used in the nuclear power plant

The present investigation, the fatigue crack growth behaviour of surface cracked piping, pressurized base straightcomponent(PBSC) andpressurized base straight weld component(PBWC)are performed on the basis of the linear elastic fracture mechanics (LEFM) principles. The stress intensity factors available in the open literature are evaluated to predict the crack growth behaviour of the component using the specimen tested material data. It is concluded that the available open literature stress intensity factor (SIF) solution like ASM and Bergman for external surface cracked straight pipe case having the semi-elliptical crack profile predicts the fatigue life of the component when having constant crack depth profile.

Remaining Useful Life Prediction and Reliability Analysis for an Individual Ion Thruster

Ion thrusters play an important role in ensuring the success of future deep-space missions. Based on a ground-life test, a proper failure mechanism analysis was conducted, and the groove depth of the centerline accelerator grid aperture can be considered as the key lifetime metric. A nonstationary independent increment degradation model including both deterministic and stochastic parameters was proposed. The maximum likelihood estimation of the model parameters was derived by incorporating the product-level degradation data and the component-level degradation data. A Bayesian method to update the stochastic parameters describing the individual ion thruster characteristics based on product-level degradation data was developed. Then, the remaining useful life and the mean time-to-failure can be estimated and updated once a new online performance measurement is obtained. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed model.

Reliability Prediction of Thyristor using Artificial Intelligence Techniques

Objective: To use temperature and duty cycle as a health assessment tool for implementing prognostics and health management in thyristor and which can be further implemented to various other electronics components. Methods: To predict the reliability of thyristor, statistical approach has been identified and analysed for its life prediction. The military handbook MIL-HDBK-217F N2 and Reliability Information Analysis centre RIAC 217Plus™ failure models are explored. Further in order to verify and validate the effectiveness and reliability of these systems, both MIL-HDBK-217F N2 and RIAC 217Plus™ reliability results have been compared. Findings: The operational parameters and modelling of thyristor have been selected and life prediction analysis is carried out. The analysis has been identified by using statistical methods. The various conditions such as temperature, stress and design parameters have been explored and screening has been done to improve reliability. It has been analysed that input current and temperature are the decisive parameters that affects the health and failure mechanism of thyristor. The study of model parameter with respect to variation in stress parameters have been carried out. Novelty: To validate the effectiveness of developed system, both MIL-HDBK-217F N2 and RIAC 217Plus™ assessment prediction equations are compared.

온도변화 환경에서 칩저항 실장용 유·무연솔더의 수명모델 검증연구

Abstract : Recently, life prediction models for Pb-based and Pb-free solders used in chip resistor assemblies under thermal cycling have been introduced. The models suggest that the field lifetimes of Pb-free solders would be better than those of Pb-based solders when used for chip resistors under thermal cycling conditions, while the lifetime of the chip assemblies under accelerated test conditions show a reverse relationship. In this study, the prediction models were verified by applying the model to another research case. Finite element models were built, thermal cycling conditions were applied, and the energy densities were calculated. Finally, life prediction analysis was conducted for the cases where Pb-based and Pb-free solders were used. The prediction results were then compared with the test data of the case. It was verified that the predictions of the developed life cycle models are on the practical scale. † Corresponding Author, cw_han@keti.re.kr Ⓒ2016 The Korean Society of Mechanical Engineers

PENGGUNAAN KITOSAN UNTUK MEMPERPANJANG UMUR SIMPAN BUAH DUKU (Lansium Domesticum Corr)

Lanzones is a highly perishable fruit because the fruit skin will turn brown within 4 or 5 days after harvest so that the necessary methods of proper post-harvest handling. One alternative that can be used to extend the shelf life lanzones cost is relatively light coating lanzones with chitosan. Chitosan coatings have the ability to delay or slow down the process of extending the maturity and post-harvest storage. Research has been conducted in order to study the effect of chitosan on shelf life, physical and chemical properties of lanzones. The study was conducted in three stages namely stage dilution of chitosan in acetic acid, fruit coating stage lanzones with chitosan solution and analysis phase . The study design used was a completely randomized design, with 2 treatment that chitosan treatment concentration ( 0.5 %, 1.5 % and 2.5 % ) and treatment of immersion time (30 and 60 minutes). The next stage is the lanzones fruit storage at room temperature and shelf life prediction analysis with conventional methods, the analysis of physical ( texture and fruit weight) and chemical analysis (water content and the level of sweetness). The results showed that the use of chitosan coating to prolong the shelf life of lanzones up to 6 days, with the best treatment using 1.5 % chitosan and immersion time of 30 seconds. The higher concentration of chitosan is given, change the texture softening and decreased fruit weight more slowly , with the value of the texture and weight of fruit on the 6th day in a row from 225.83 to 234.59 g / mm and 19.70 to 23.47 g per fruit. Based on the chemical properties of the water content and total dissolved solids , it is known that chitosan coating could inhibit the decrease in water content and total dissolved solids. The immersion time of 30 and 60 seconds is not a real effect. Observations on the 6th day of storage for water content , ranging between 84.44 -87.71 % , while the total dissolved solids ranged from 17.22 to 20.12 % Brix.Keyword : duku, chitosan, shelf life

A Method of Virtual Design of the Fatigue Life of a Dynamic Structure

The fatigue life prediction and reliability analysis of dynamic systems under random excitement are important topics in modern engineering design. However, the stress power spectra density of a component in a dynamic system must be known when one predicts its fatigue life and analyzes its reliability. With the rapid development of computer technology and numerical computation theories, it has been possible to simulate stress power spectra density of dynamic systems. Based on this, a method of simulating computation for the fatigue life prediction of a dynamic structure is presented. It depended on some simulating equations of the stress power spectra density of the structure and the fatigue life prediction which was obtained in this paper. By this way, as an example, the virtual design of the fatigue life and reliability analysis for the CW-200k vehicle truck was developed. The method is suitable not only for the running dynamic structure but also for newly designed structures.