Fracture Simulation newsletter
BEASY staff attended the 2015 AA&S Conference in Baltimore in April and met with many customers to discuss their applications and update them about projects underway at BEASY.
We had a lot of new interest at our booth this year in the areas of fatigue crack growth in residual stress fields, fracture behaviour of composite plates as well as the modelling of corrosion related damage. There was also considerable interest in the BEASY Corrosion Manager software which is used to predict and simulate galvanic corrosion in structures such as aircraft.
Of particular interest was the impact of residual stresses on the crack path and the rate of growth of cracks. The effect on the crack path can be clearly seen in the above figure where the lines show the predicted crack fronts as the crack grows from a hole with, and without, cold working. The red lines show the predicted crack fronts without cold working and the green dotted lines show the predicted crack fronts with cold working. The study clearly indicates the need to include residual stresses in crack growth calculations as otherwise unexpected failure modes can occur, and excessively conservative designs can result.
Please contact us for background papers on some of the topics presented at AA&S 2015, quoting the name(s) of the papers below:
- Analysis of Fatigue Crack Growth for CFRP-Strengthened Steel Plates with Longitudinal Weld Attachments
- Analysis of CFRP reinforced steel plates
- Analysis of fatigue crack growth for welded connections under bending
- Calculation of bending fatigue life of thin-rim spur gears
- Analysis of fretting fatigue life of dovetail assemblies based on fracture mechanics method
Another area of considerable interest at the AA&S conference was the use of computer simulation to assess the risks associated with corrosion. During the product development process, various design configurations are often exposed to actual environmental conditions for an extended period of time to evaluate corrosion damage in the structural assembly. However, these testing methods require anywhere from several months to several years of exposure time in order to complete. Computer modelling has the potential to significantly shorten, and reduce, the cost of testing by providing a corrosion simulation option that can be used to supplement these long term experimental tests.
In the model shown a computer simulation is used to predict the risk and extent of corrosion damage on a test structure.
Dr Sharon Mellings from BEASY recently attended the ICAF conference in Helsinki and presented a paper describing some recent work on the simulation of corrosion and fracture damage.
Airframe structures regularly operate in environments that can create conditions which allow high levels of corrosion damage, and this damage can lead to stress concentrations within the structure and potential development of cracks. The generation of electrical fields that are necessary for corrosion can occur even when only a thin film of electrolyte is present on the surface of the structure.
Computation of this electrical field can be used to identify areas in the airframe structure that are most susceptible to corrosion damage and which, after possible fatigue crack initiation, may lead to structural failure. Corrosion simulation, by taking account of the properties of the electrolyte and the structural materials, can determine the rate of material loss from the structure.
In this conceptual development, material is removed from the modelled surface (corresponding to corrosion occurring over a given exposure time) the stress concentrations can be evaluated and, if required, cracks can be introduced into the identified problem areas, to identify vulnerability to fatigue failure.
The geometry change caused by corrosion mass loss can be used to perform stress analysis of the structure, to determine the stress concentration in the component at the corresponding time in the life of the aircraft. If it is then assumed that cracks initiate at the peak stress locations, the subsequent crack growth can be simulated. This crack growth takes into account the corrosion damage and will inherently include local stress concentration due to the damaged surface. In the crack growth simulation, the full crack path and direction can be determined together with the fatigue life.
For a copy of the paper, or for more information about corrosion and fracture simulation, please contact us
BEASY will be attending the Aircraft Airworthiness & Sustainability Conference where we will be presenting our corrosion and fracture mechanics simulation solutions for aerospace structures. The conference, will take place between March 30th and April 2nd in Baltimore, Maryland.
We welcome you to come and visit us on booth 206 to find out more about the capabilities of BEASY simulation products, or how BEASY fracture modelling can provide the solutions you need. Alternatively to make an appointment to meet Tom Curtin at the conference, or to obtain further information, please contact us
BEASY Fracture & Crack Growth 10.0r16 provides a great number of new and advanced features that enable engineers to improve fracture analysis and crack growth simulation and provide deeper design insight.
The new release incorporates improvements and enhancements to the core BEASY Fracture & Crack Growth software, allowing more crack growth simulations to be run automatically (such as analyses where only part of the crack is growing) and reducing the need for user intervention.
Partial crack growth
one of the significant new features is that the crack growth algorithms have been enhanced to enable crack growth simulations to be performed automatically for a much wider range of applications.
The new capability is of particular value where residual stresses exist within the structure. The residual stresses can prevent the crack opening thus reducing the Stress Intensity Factors thereby resulting in slower crack growth. As the residual stresses can vary locally within the structure (particularly if they have been applied as some form of surface treatment) this can result in parts of the crack front growing at very different rates or in some cases not growing at all along part of the crack front.
This development also benefits models where crack growth on part of a crack front slows as it approaches a compressive load region but there is significantly faster growth at other parts of the crack front. This is typically the case when looking at crack growth through a gear tooth for example.
The new capability can also be used when simulating multiple cracks where one crack is growing slowly or not growing at all.
For further Highlights about the new release, please click here, and if you would like to find out more about the new features and capabilities in this latest of the BEASY Fracture & Crack Growth Software, please contact us
BEASY will be exhibiting at the 2014 Aircraft Airworthiness & Sustainability Conference in Baltimore this April, presenting the latest developments in our Software and Services for Crack Growth Simulation and Corrosion Management in Aircraft Structures.
We welcome you to come and visit us at booth 404 to find out more about the capabilities of BEASY products, or how BEASY can help with your particular application. Alternatively to make an appointment to meet Tom Curtin at the conference, or to obtain further information, please contact us
BEASY Fatigue & Crack Growth
The BEASY Fatigue and Crack Growth software can be used to perform 3D crack growth simulations to support structural life extension decisions. Sophisticated analysis algorithms have been developed to investigate crack growth behavior in complex loading environments. For example load cases can include residual stresses, fretting fatigue, contact loading and thermal stresses.
Interfaces are also available to enable BEASY to integrate with MSC PATRAN, NASTRAN, ABAQUS, and ANSYS.
BEASY Corrosion Manager
BEASY Corrosion Manager Software enables engineers to quickly assess the risk to components and structures of corrosion and the effectiveness of surface protection systems.
BEASY Corrosion Manager simulations enable engineers to replace the "find it and fix it" approach and replace it with a more fundamental approach based on an understanding of the corrosion process and the ability to predict its behavior.
A focus of interest was BEASY's Fatigue and Crack Growth software used to perform 3D crack growth simulations to support structural life extension decisions and in particular its integration with Finite Element systems such as ABAQUS, ANSYS, NASTRAN and MSC PATRAN. This was demonstrated in a failure investigation where an ABAQUS stress analysis model was available and BEASY was used to perform the crack growth study to gain an understanding of the failure mode.