Common case studies of marine structural failures intechopen. Nasgro fatigue crack growth analysis software utmis. An evaluation of the fatigue crack growth and fracture toughness properties of berylliumcopper alloy cda172 royce g. Fatigue crack growth nasaflagro computer program developed as aid in predicting growth of preexisting flaws and cracks in structural components of. Nasaflagro was originally developed at the nasa johnson space center in the.
Probabilistic structural durability prediction college of engineering. K is the controlling parameter in fatigue crack growth assuming conditions are such that lefm applies fatigue crack growth ratefcgr given by rate of. Fatigue crack growth was transgranular with sem fracture surface morphology dependent upon both. The development of this fcgd will begin the process of developing a consistent set of. For each fcl, stress gradients were extracted ahead of the weld toe. In the current version, the software was enhanced to suit the needs of the aircraft industry. Behavior of surface and corner cracks subjected to tensile and bending loads in a ti6al4v alloy. A comprehensive user manual in pdf form describes nasgro features. Flagro4 developed by rockwell international for fracture control analysis of the space shuttle 4. The growth of these flaws and cracks may occur at load levels well below the ultimate load bearing capability of the structure.
The fatigue crack growth computer program, nasa flagro, was developed as an aid in predicting the growth of preexisting flaws and cracks in structural components of space systems. Customizable to your needs the fatigue and fracture modules offer customization capabilities to meet your requirements. Crack growth analysis main cargo door msd cracks 1. The applicable fatigue crack growth rate expression. A fracture mechanics analysis of fatigue crack growth in a complex cross section a fracture mechanics analysis of fatigue crack growth in a complex cross section rifani, a. At high stress intensities, crack growth rates are extremely high and little fatigue life is involved. In order to facilitate accurate and consistent calculations, nasa has developed and distributed a computer code called flagro forman et al. The nasa controller alertness and fatigue monitoring studycafms was sponsored and monitored by the frmt, which partnered with natca to assist with the design, planning and execution of this comprehensive atc research. Nasa flagro fatigue crack growth computer program that provides an automated procedure for calculating the fatigue life of cyclically loaded structures with initial crack like defects 31. Development of the nasaflagro computer program for analysis.
Mmj13 fatigue and fracture mechanics sample test qustion. The nasgro software has been publicly available since the mid80s known as nasa flagro. The fatigue crack growth rate equation incorporated in the data base system and in nasaflagro is a modified. The fracture toughness data require only a directory file, and a specimen information file. Nasgro is a suite of computer programs used to analyze fracture and fatigue crack growth fcg in structures and mechanical components.
To make life estimations for fatigue crack growth and damage tolerant design, the following information are often needed. Applications of the three dimensional finite element. The fatigue loading used in the crack growth testing was of constantamplitude sinusoidal type. Fatigue crack growth tests constant load amplitude fatigue crack growth fcg tests were conducted according to the. Nasfla the main module calculates fatigue crack growth lifetimes. Gangloff university of virginia, charlottesville, virginia nasa cr194982rew computer modeling the fatigue crack growth rate behavior of metals in corrosive environments final report. Fatigue crack growth of ti62222 titanium alloy under. Fatigue crack growth nasaflagro computer program developed as aid in predicting growth of preexisting flaws and cracks in structural components of space. Structure and applications of the nasa fracture mechanics. The crack growth rate accelerates as the maximum stress intensity factor approaches the fracture toughness of the material. Little known and under used crack growth tools embedded in msc fatigue which provide sophisticated crack growth. The modeling of fatigue crack growth of a corner crack located at the weep hole in.
The fatigue crack growth computer program nasaflagro 2. Nasa technical memorandum 109044 fatigue life and crack growth prediction methodology j. Fea model of the tank car was created with mesh refinements at the identified fatigue critical locations fcl. The safelife approach, using standard fatigue analyses, is also used. The faa human factors division provided funding and management for. The current nasa accepted practice in fracture mechanics analysis uses the computer program nasa flagro, which includes interaction effects. Flight spectra life calculations using nasa flagro based upon constant amplitude fatigue crack growth data, were primarily conservative but in good agreement with experimental data. Nasaflagro development to provide fracture control analysis. A preliminary version of a new computer program has been developed for calculating crack propagation in cyclically loaded structures. The software is developed jointly by southwest research institute swri and the national aeronautics and space administration nasa under a space act agreement, with additional support from the nasgro. The fatigue crack growth computer program, nasa flagro, was developed as an aid in predicting the growth of preexisting flaws and cracks in. The fatigue crack growth rates for al and ti are much more rapid than steel for a given. A fracture mechanics analysis of fatigue crack growth in a. The frequency effect on the fatigue crack growth rate of 304 stainless steel.
The fatigue crack growth computer program nasa flagro 2. A crack opening stress equation for fatigue crack growth, international journal of fracture, vol. Msc fatigue strain gauge virtual strain gauges pasted on an fe model for fatigue testanalysis correlation. A pdf flyer describing the current version can be downloaded here. The quantitative statements of the griffith theory 1 are based on elasticity theory and are applicable only to those materials that obey hookes law up to the instant of fracture. Fatigue crack growth experiments and analyses from small.
The nasaflagro nasgro computer program was developed for fracture control analysis of. Fatigue crack growth computer program nasgro version 4. National aeronautics and space administration nasa under a space act agreement, with additional. Computer modeling the fatigue crack growth rate behavior. Pdf a typical fatigue crack growth curve consists of the threshold region, the paris region linear in a logarithmically scaled diagram and the. A crack growth equation can be used to ensure safety, both in the design phase and during operation, by predicting the size of cracks. The new program, titled nasa flagro, has numerous enhanced features over previous programs used for safe life analysis on space systems. Sleep cannot be banked, but sleep deficits accumulate, davenport said.
Pdf modified nasgro equation for physically short cracks. The fatigue countermeasures group at nasa ames research center studies the relationship between sleep loss, circadian desynchrony, cognitive function, and alertness. Crack growth and residual strength analyses lap joint. The fatigue crack growth rate behavior of an aluminum alloy is shown in figure q4. Using this gradient, crack growth analysis was performed using nasa flagro nasgro software. A crack growth equation is used for calculating the size of a fatigue crack growing from cyclic loads. Computer modeling the fatigue crack growth rate behavior of metals in corrosive environments edward richey iii, allen w. The paper examines the problems associated with applying prooftestbased life prediction to vessels made of hightoughness metals. Ams02 integration hardware fracture ams02 cdr integration hardware fracture analysis. Inspection as per nasajsc prc0014 class a flagro model sco1.
Fatigue crack growth rates for the partthroughcracked specimens are compared with a base curve fitted from the data obtained using standard specimens. Fatigue crack growth nasa flagro computer program developed as aid in predicting growth of preexisting flaws and cracks in structural components of space systems. Nasccs calculates critical crack size at failure, or threshold crack size for no growth. Nasa flagro v2 fatigue crack growth computer program developed as an aid in predicting the growth of preexisting flaws and cracks in structural components using a twodimensional model which predicts growth independently in two directions based on the calculation of stress intensity factors. Johnson space center, houston, tx, august 1986, revised march 1989. Applications of the three dimensional method daniel s. For fatigue crack growth data, the file system is made up of a directory file, a specimen information file, and a numerical data points file. Specific materials data are provided for many of the assessment methods.
Fatigue crack growth analysis software has been available to damage tolerance analysts for many years in either commercial products or via proprietary inhouse codes. This crude approximation may create a large jump in stress intensity values, leading to excessively conservative fatigue crack growth predictions. Countermeasures for these effects improve safety, performance, and aid in the overall success of a missions goal. Better ancillary components eg welds, crack growth, etc a. Is enhanced version of flagro4 and incorporates stateoftheart improvements. This document is intended to provide an overview of solutions to the problem of fatigue in the aviation maintenance environment. Fatigue growth of small corner cracks in aluminum 6061t651. Basically, there are two approaches for probabilistic crackpropagationlife prediction. Fatigue crack growth life calculations using nasa flagro were conservative. Results of an experimental investigation of the fatigue growth of small comer cracks emanating from. The growth of fatigue cracks can result in catastrophic failure, particularly in the case of aircraft.
Crack growth analysis main cargo door primary and continuing damage 3. Starting at an initial detectable crack size 18, the crack. K th roughness induced crack closure k the world leader. Test templates are designed for modification to meet specific lab. Two a106 gr b pipe specimens containing long, throughwall, circumferential flaws were tested. Nassif calculates stress intensity factors from a library of solutions. Several classic fracture mechanics problems are analyzed, and computational efficiency as compared to. Selfsimilarity and crack growth instability in the correlation between. Durability and reliability analysis workspace, cen.
Nasgro is actually a suite of different computer programs for different types of fatigue and fracture mechanics analysis. Dotfaaar0515 fatigue crack growth database for damage. This system is designed to be compatible with nasa flagro which is. The frequency effect on the fatigue crack growth rate of. Fracture mechanics and fatigue crack growth analysis. Paris, threshold for fatigue crack growth propagation and effects of load ratio and frequency, in progress in flaw growth and fracture toughness testing, astm stp536, american society for testing and materials, philadelphia, pp. Thereason is that crack size can be used in tnessforpurpose evaluations of damaged elements. Gangloff university of virginia, charlottesville, virginia nasacr194982rew computer modeling the fatigue crack growth rate behavior of metals in corrosive environments final report. Fatigue crack growth analysis software has been available to damage. A fatigue life prediction method based on strain intensity factor. Nasgro software overview southwest research institute. This program automatically computes the increments of crack growth for the specified loading, and continues the calculations until the. Region iii is characterized by rapid, unstable crack growth. The development of this fcgd will begin the process of developing a consistent set of standard fatigue crack growth material properties.
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