Information and insight from fracture mechanics experts

New Features/Capabilities in AFGROW Release 5.3

AFGROW, Release 5.3 includes a number of new capabilities that have resulted from User requests and input at our Workshops. While we haven’t been able to include all requests, we are happy to announce the following list of improvements and additions. 64 Bit Executable Code Converting AFGROW to 64 bit solves some compatibility issues with other 64 bit Windows software when using COM automation. It also provides a path forward for future Windows OS upgrades. Advanced Bearing Solution for Through Cracked Holes This solution has been long requested because it allows Advanced Models under combined loading conditions to retain the bearing portion of the loading after transition to single or double through cracks. Since this capability will be added, we are also including an out-of-plane bending option that can be used for Advanced through crack models. Out-of-Plane Bending Option In all previous AFGROW releases, out-of-plane bending solution for Classic through crack models have been approximated as 2/3 of the applied tension classic solution. This was done to allow bending effects to be conservatively approximated after transition where the crack was assumed to be straight through crack (single crack length through-the-thickness). Many Users attending our Workshops felt that this approximation was far too conservative, and a factor of 0.4 was more realistic. After comparing analytical results to our oblique crack solution, it looked like the factor varied between 0.4 and 0.5 as a function of thickness. Since the factor, 2/3, has been used to date, we think it makes sense to add a new user-defined preference with a default value of 2/3, but allow users to make a choice from 0.4 to 2/3. As noted above, this will also be applied for Advanced Models where a bending fraction is used for crack(s) at holes. However, it should also be noted that the correction in these cases will be applied to the corresponding Advanced Model Axial solution. Advanced, Axial Load Solution for a Corner Crack at a C/S Knuckle This solution is based on the excellent work done by Jody Cronenberger at SWRI. Jody’s solution set is for a centered hole. We hope to expand this capability in the future to include hole offset and the bearing load case. User-Defined Beta for Interdependent Through Cracks This was another Workshop request to allow user-defined betas to be input for two crack growth directions where the width and thickness of the model may be different for each crack length. The term, interdependent, is used because for many applications the beta solutions will be dependent on the length of the other crack. This means that the user will have to make an assumption regarding the crack lengths expected during the analysis. Examples where this capability may be helpful are: cracks growing through two legs of a stiffener, or a part-through crack where a user has some expectation of the natural crack shape. The ability to use different thickness values for each length is needed for the former example where stress state will be a function of thickness for each crack length and if the NASGRO growth rate model is used, thickness is required as a parameter. New Weight Function Solution for Part-Through Cracks The new solution was provided by Prof. Glinka for use in cases where the stress distribution is changing in the c-direction. In all earlier releases, part-through weight function solutions were limited to stress fields changing in the a-direction. None of these solutions will allow stress fields to change in both directions simultaneously, but the new solution is far more practical. New Weight Function Solutions for Through Crack in Finite Plates We are adding two new weight function solutions from Prof. Glinka for edge through cracks in finite plates. One solution where in-plane rotation is constrained along the cracked edge, and the other has in-plane rotational constraints imposed on the far edge. Using Different Tabular Material Data for Orthogonal Crack Growth Directions This allows users to input different tabular crack growth rate data for the a-direction and c-direction. Normally, crack growth data for the L-T orientation is used for both crack directions. However, as we try to expand our capabilities to predict actual crack shapes seen in the field (or in laboratory tests), it is helpful to have the option to use different data when they may be available. New Spectrum Format An option for XML format is included to allow spectrum levels to be “tagged” to identify temperature (altitude/humidity) or for use in later releases to track damage for different spectrum stress levels. Using Different Tabular Material Data as a Function of the Loading Spectrum This release will allow the use of different tabular crack growth rate data as a function of temperature tags in an xml-based loading spectra. We anticipate that this capability may be expanded in the future to include other tags. Tabular Crack Growth Rate Data Curve Fits Tabular fits for over 60 materials in our Fracture Mechanics Database will be available for download through our AFMAT database on the AFGROW Web Page. We will continue to expand this database as we add more material data to the database.
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