Fatigue crack growth modeling of attachment lugs

The sif calculated from xiga are in reasonable agreement with the available data. A threedimensional 3d symmetric galerkin boundaryelement method sgbem. Fatigue life prediction of cracked attachment lugs using. Solid mechanics fatigue crack propagation anders ekberg 4 20 crack growth in region i for small. Request pdf on jan 31, 2014, slobodanka boljanovic and others published fatigue crack growth modeling of attachment lugs find, read and cite all the. Total fatigue life prediction under constant amplitude loading.

Damage tolerance analysis of a cracked attachment lug. A model for predicting the overload effects on fatigue crack growth behavior. In the present paper, stress intensity factor sif analyses and fatigue crack growth simulations of corner cracks emanating from loaded pinholes of attachment lugs in structural assemblies are carried out for different load cases. We evaluate the unigrow fatigue crack growth model under variable. Lug specimens were fabricated from two heats of 6al4v mill annealed titanium representative of material having low and high fracture toughness levels. Maksimovic s 2014 fatigue crack growth modeling of attachment lugs. The total fatigue life of lug was defined from initial flaw to a final fracture. Fatigue crack growth of a corner crack in an attachment lug. Methods tabulated test attachment lugs, aircraft, damage tolerance, experimental testing, data tabulation, crack initiation, propagation, 3 i. Also, crack growth and fatigue life of single crack in attachment lug are estimated and then compared with the available experimental data for two different load ratios equal to 0. Extended isogeometric analysis xiga of fatigue life in. To make life estimations for fatigue crack growth and damage tolerant design, the following information are often needed.

An experimental evaluation of fatigue crack growth. Fatigue crack growth modeling of attachment lugs sciencedirect. Study on fatigue crack growth model of attachment lug. Nasgro is a suite of programs used to analyze fracture and fatigue crack growth fcg in structures and mechanical components. The novel findings are the effect of the size of the hole lug width, elasticity of the material and the type of load cycles on the fatigue crack initiation and crack growth life. Damage tolerance analysis of a cracked attachment lug using bem. Geometry of the component and material data the attachment lug 7 was made of al 7050t7451 aluminium alloy material. The method has been illustrated by analysing fatigue growth of a planar corner crack in an attachment lug made of al7050t7451 alloy.

Fatigue crack growth analysis can be carried out on the wing fuselage lug attachment bracket in the bottom skin of the wing. Crack growth analyses and correlations for attachment lugs. The fatigue crack growth velocity dadn and the stress intensity factors amplitude. A number of analytical and experimental studies have been performed over last three decades, aiming at investigating the fatigue behaviour of attachment lugs under both. Lugtype joints are often used to connect components in various mechanical systems. Single throughthickness and single quarter elliptical corner cracks are considered as crack configurations in the present work. Crack growth analysis in aircrft wing lug section and fatigue life.

To obtain efficient algorithm in crack growth analysis here is derived analytic model. The fatigue crack growth model of attachment lug subjected to oblique pinload is established, offering an analytical as well as experimental method for assessing and designing damage tolerant. Issuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. In the fatigue crack growth and fracture analysis of lugs, accurate calculation of the stress intensity factor k is essential. The reliability of the proposed procedures is verified using experimental fatigue crack growth. In section 3, the fatigue test of attachment lugs is presented and used for validation. Use the total life method to estimate the fatigue life of the weld. A computational models for the strength estimation of cracked aircraft lug are formulated. The residual life estimation of cracked lugs is analyzed by employing the crack growth law based on a twoparameter driving force model. Analysis of fatigue crack growth in an attachment lug based on the weight function technique and the unigrow fatigue crack growth model. In this example, the crack growth analysis of the attachment. Jin qiang dus 12 research works with 4 citations and 81 reads, including. The elastoplastic corpus model will be used to predict crack growth evolution.

Magliaxo alenia azienda finmeccanica, pomigliano darco, naples, italy abstract a detailed 3d analysis using bem bounday element method was performed to determine the stress distribution and sifs of a corner crack of the fuselage to wing attachment lug of a medium. In this prospect, an improved fracture mechanics based design may significantly prolong the fatigue life of attachment lugs while improving model accuracy and system safety. Fatigue crack growth modeling of attachment lugs request pdf. A computational model for estimating the residual fatigue life of attachment lugs is proposed. Based on mansoncoffin and paris formulas, an approach is developed to predict failure of aircraft lugs under thermal stress and oblique loading angle. Here the meshed model of landing gear lug attachment is shown in fig. A unified twoparameter fatigue crack growth driving force model was developed to account for the residual stress and subsequently the stress ratio effect on fatigue crack growth. Use all three methods of fatigue life estimation to design the lug assembly. To validate the proposed method, the fatigue test of attachment lugs is performed, in which the attachment lug is a kind of important joint component and commonly used in aircraft structures. Design and analysis of landing gear lug attachment in an. Two different relationships for crack growth rate need to be analyzed. The applicable fatigue crack growth rate expression.

As far as the lug configuration with quarterelliptical corner crack is concerned, the crack extension in depth and surface directions must be investigated. The crack growth rate is calculated at each stress cycle, and the crack is grown until failure. The crack growth in the surface crack was monitored by crack propagation gage kv25b. K is calculated by the sifs equations to get the values of the paris constants, offering an analytical method for establishment of the fatigue crack growth model of the typical straight lugs. Xfem based analysis of fatigue crack growth in damaged. The authors estimate the residual fatigue crack growth life of 7075t6 aluminum alloy attachment lugs with single throughthickness crack under various loading conditions. In section 2, the proposed method is introduced at first.

The reliability of the proposed procedures is verified using experimental fatigue crack growth data. In this thesis he has proposed the methodology of fatigue analysis carried out for lug. The fatigue crack growth model of attachment lug subjected to oblique pinload is established, offering an analytical as well as experimental method for assessing and designing damage tolerant attachment lugs. Fatigue crack growth behavior of al7050t7451 attachment. The attachment lug demands careful fatigue life analysis especially in crack growth phase. Prediction of fatigue life by crack growth analysis springerlink. Statespace model for fatigue crack growth the dynamic stochastic process of fatigue crack growth is the process of crack. Use crack initiation and crack growth to estimate the fatigue life of the lug specimen. The approach discussed below is based on the weight function method 4 and the unigrow fatigue crack growth model proposed determine the instantaneous fatigue crack growth rate using the unigrow fatigue model.

The crack growth rates are determined by paris law. Study on fatigue crack growth model of attachment lug subjected to oblique pinload. We estimate sifs for a cornertoedge crack using the weight function method. The research presented in this paper is based on the use of extended finite element method xfem for stress intensity factors sifs determination in the case of fatigue crack presented in the wingfuselage attachment lug used in light aerobatic aircraft. The literature contains noteworthy studies of fatigue crack growth analysis for the fatigue life evaluation of structural components.

This volume also contains the baseline material property data. Fatigue crack growth behavior of al7050t7451 attachment lugs under flight spectrum variation article pdf available in theoretical and applied fracture mechanics 402. The proposed method is verified through fatigue tests of attachment lugs, which are a kind of important joint component in aerospace systems. Moreover, a comparison with the available experimental data is performed. Dynamic fatigue testing machines swiss made duration.

The deterministic resampling pf drpf is proposed to be used in fatigue crack growth prognosis, which can overcome the sample impoverishment problem. Prognostic analysis of fastener joints in straight. An application of the energy release rate concept to crack. Stress intensity factors required for the fatigue crack growth analysis were calculated using the weight function method.

An application of the energy release rate concept to crack growth in attachment lugs, aiaaasmeasceams 22nd structure, structural dynamics and material conference. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. These stress intensity factors and crack growth analyses are used in task iv to predict the residual strenglh and the crack growth behavior for a. Analysis of fatigue crack growth in an attachment lug based. We evaluate the loadshedding effect using the finite element method. Fatigue crack growth prediction of the attachment lug. Thesifsofthecrackfrontare computed during each step of crack increment.

To evaluate fatigue life of aircraft lugs, an accurate calculation of fatigue life is essential. Fatigue strength simulation of aircraft lug semantic. Stress analysis for a lug under various conditions g s. Lamb waveminimum sampling variance particle filterbased. The present paper aims to utilize xfem to model fatigue crack growth of attachment lugs. Analysis of fatigue crack growth in an attachment lug based on the weight function technique and the unigrow fatigue crack growth model 1. But crack growth approach is having challenges in computing energy release rate which is associated with crack and predicting location and path of crack.

K region i, crack propagation is difficult to predict since it depends on microstructure and flow properties of the material here, the growth may even come to an arrest crack growth rate is. K are calculated by the sif equation to get the values of the paris constants. Given other parameters constant, bigger size hole and stiffer pin lead to lesser life. The structural fatigue failure of a common connecting joint used to attach aircraft wingfuselage components was investigated too. Prediction of fatigue life by crack growth analysis. Easily share your publications and get them in front of issuus. Cyclic loading is applied in the form of a stress history. Jin qiang dus research works air force engineering. Abaqus commercial software 26 with xfem capability is chosen for modeling and simulation software. Therefore, thermal stress and loading angle are introduced to establish the numerical model. In the present paper, stress intensity factor sif analyses and fatiguecrackgrowth simulations of corner cracks emanating from loaded pinholes of attachment lugs in structural assemblies are carried out for different load cases.

Online crack prognosis in attachment lug using lamb wave. Spectrum crack growth calculations were made using the resulting stress intensity values and the wheeler retardation crack growth model. The fatigue crack growth calculator allows for fatigue crack growth analysis of a cracked part. In the present paper, the fatigue growth of corner cracks emanating from the pinholes of attachment lugs is studied in detail by employing the 3d sgbemfem alternating method han and atluri2002. The effect of frictional forces on fatigue crack growth in lugs. Conceptual catiav5 assembly to show location of lug in an aircraft is shown in fig.

Highlights we investigate the fatigue behaviour of an attachment lug made of al 7050t7451. Improved pf based fatigue crack growth prediction 2. Nasgro is a suite of computer programs used to analyze fracture and fatigue crack growth fcg in structures and mechanical components. The finite element model of a straight attachment lug subjected to an oblique loading less than 45 degrees is built by using the finite element software ansys, a cosine pinbearing pressure distribution is applied on the hole of lug as a boundary condition. Analysis of fatigue crack growth in an attachment lug. Fatigue tests of simple attachment lug with initial corner crack are conducted at 7 hz and compared with analytical predictions. Residual stresses due to reversed cyclic deformations are included into fcg analysis.

Moreover, the crack growth path for the lug with quarterelliptical crack is simulated. Numerical method for fatigue life of aircraft lugs under. Review on fatigue and damage tolerance evaluation of. Citeseerx threedimensional sgbemfem alternating method. The proposed parameter investigates fatigue crack growth fcg u. Study on fatigue crack growth model of attachment lug subjected. Citeseerx document details isaac councill, lee giles, pradeep teregowda. The lug is used to join the oleostrut and bulkhead of the fuselage. Damage tolerance analysis of a cracked attachment lug using bem a. Study on fatigue crack growth model of 7075t7410 aluminum. Residual stress intensity factors are determined using the weight function through numerical analysis. In strength analysis, the lug with single quarterelliptical corner. Download citation study on fatigue crack growth model of attachment lug subjected to oblique pinload the finite element model of a straight attachment.