Ship Structure Committee – SR 1460
Kick-off Meeting Minutes - 02/05/2009
Attendees
Pradeep Sensharma –BMT Designers & Planners Inc
Matthew Collette – SAIC
Joey Harrington – BMT Designers & Planners Inc
Kim Tran – NSWCCD
Jeannette Grant – USCG
Chao Lin - MARAD
Phone -
Gopal Magadi – ABS
Natasa Kowarski – Transport Canada
Steve Tarpy – BIW
Jason Smith – SSC
Christina Wang – ABS
Ray Kramer – Raytheon
Rong Huang
Mike Webster – Austal
Steve Billian – Lockheed Martin
Bob Sielski
Minutes
Kim Tran – Brief introduction on intent of committee
Chao Lin – COTR responsibilities are to keep the focus of the panel and make sure that time is not spend chasing tangents. It is important to stick to the SOW. Also, any changes must be approved before official release.
Pradeep Sensharma - Objectives of the project and background of aluminum alloys selected.
Chao Lin – Is 50% reduction in strength for welded aluminum determined by empirical data or equations?
Pradeep Sensharma & Matthew Collette – Both have been used and up to 50% reduction in yield strength being a generally accepted value.
Pradeep Sensharma – Background of traditional approach using (Heat Affected Zone) HAZ. This study would like to use extent of HAZ = 3 x thickness of plate.
Pradeep Sensharma – The first task is the literature survey that will primarily be performed by Matthew Collette.
Ray Kramer – Will fusion welds be the only welds studied? Will friction welds be included?
Pradeep Sensharma – Only fusion weld will be considered.
Chao Lin – How many standards are being considered?
Matthew Collette – ABS, Aluminum Association and Eurocode 9. There hasn’t been a solid standard developed for the type of problem we’re studying.
Question – Will DNV be included?
Matthew Collette – We can include DNV
Rong Huang – Will butt welds be studied?
Pradeep Sensharma – We will look into butt welds and fillet welds (shows slide demonstrating approach)
Christina Wang – Will you be looking at test data currently existing?
Matthew Collette – Yes, there has been research at NTNU and MIT
Christina Wang – Will you compare the FE results to test data?
Telephone – We need to validate the FE to testing.
Gopal Magadi – The microstructure will not be accounted for in the FE. How will you account for this?
Pradeep Sensharma – We cannot examine microstructure with the mesh size we plan to use. We’ll compare FEA results to the experimental data available. If the results follow the trends we can assume that we are accurately modeling the problem.
Christina Wang - What type of software will you be using?
Pradeep Sensharma – NASTRAN with FEMAP for pre/post-processing
Pradeep Sensharma – The second task will be to create models with varying plate thickness, stiffener size and material.
Question – Is 6082 a new alloy?
Matthew Collette – No, it’s a European alloy it is becoming popular because it’s very good for extrusions.
Kim Tran – 6082 is similar to 6061.
Question – How do we know the size of the HAZ?
Pradeep Sensharma – We must make an assumption. For this study HAZ = 3 x thickness of plate.
Pradeep Sensharma – In generating the models, we must decide between using 3 bays and a ½ + 1 + ½ bay model.
Matthew Collette – The ½ + 1 + ½ bay model is more conservative.
Rong Huang – Recommend using 3 bay models.
Pradeep Sensharma – Preference is to use 3 bay model, but we must see the run time for analyzing non-linear FEA. We may be forced to use fewer elements.
Pradeep Sensharma – We must put an initial deflection into the plating. Rigo used a inform pressure to create a maximum of 2mm deflection. The pressure was removed and the deflected shape was used as the initial shape.
Chao Lin – How did Rigo get 2mm deflection? Is this okay for our study?
Matthew Collette – We must do more literature survey to determine if this is okay and if there are other techniques that have been used.
Ray Kramer– A lateral pressure will create a uniform deformation. Actual uniform deflections are non-uniform. Can we create this?
Pradeep Sensharma – This will be a problem with the time limitation.
Question – Do design codes have requirements for initial distortion?
Answer – The rules require a rule determined load to be applied and look for a correlation with the rule prediction.
Matthew Collette – We need to have an initial deformation to get collapse.
Answer – Current HSV loads are based on experimental data. A Q-factor is used to determine the required scantlings.
Gopal Magadi – We should ask Derek Novak to help clarify how the rules currently work.
Gopal Magadi – Why not use 3D elements?
Pradeep Sensharma – 3D elements will require more time to create models and run the analysis.
Question - Will this affect the results?
Pradeep Sensharma & Matthew Collette – Most people have used plate elements and get good correlation with experimental results. We should be okay with plate elements for this study.
Question – How do you account for residual stresses in welds?
Pradeep Sensharma – Residual stresses will not be accounted for in this study. In ALP/HULL uses a ratio of residual stress to yield stress.
Pradeep Sensharma – The official close date is 12/18/2009. We would like to end this study a year after the kick-off meeting, 02/05/2010.
Chao Lin – You must request a no-cost extension with a reason.
Matthew Collette – Review of progress in the literature survey. We would like to concentrate on stronger structures so we can analyze the stresses in the HAZ before yielding begins.
Rong Huang – Do we meet the ABS requirement for stiffener spacing?
Matthew Collette – Yes
Rong Huang – Why did Paik use 300mm stiffener spacing?
Matthew Collette – We’ll check into this.
Mike Webster – Will you check into 6061 alloy and extruded planking?
Matthew Collette – Models 9-12 have the same material for plating and stiffeners and are designed to examine extruded planking. Time may not allow examination of 6061, but the differences with 6082 are small.
Mike Webster – ABS has different requirements for the 2 materials.
Matthew Collette – We’ll look into this.
Matthew Collette – We’ll add DNV to the standards to look at.
Rong Huang – Professor Paik’s SSC-451 and SR-1454have data on butt welds. This should be looked at.
Matthew Collette – No one has tested non-loaded fillet weld coupons as Huang stated.
Bob Sielski – 50mm vs. 250mm samples for tensile properties of welds. Data goes into the rules. Are we trying to address what an appropriate yield stress would be?
Pradeep Sensharma – We need to follow ABS in this case, but they should look into this.
Bob Sielski – There is a question regarding mixing 50mm and 250mm yield strengths. Existing codes may have been developed based on 250mm gauge length specimens, and using this standards with 50mm gauge length experimental data may be conservative.
Answer – We must be consistent with the rules.
Chao Lin – We must stay on focus and this is likely outside the focus of this committee.
Bob Sielski – Paik’s results are for compression failure. Do we have something to compare for tensile and bending failure?
Matthew Collette – We’re looking. We’ve found lateral loading and stiffened beams thus far.
Bob Sielski – How do we address bending?
Pradeep Sensharma – Max strain or max deflection
Bob Sielski – We could use a full model with stiffeners that have a robust flange to examine tensile failure.
Pradeep Sensharma – When do we stop? When has tensile failure occurred?
Matthew Collette – We could designate a strain limit in the HAZ.
Ray Kramer – Does ABS use properties of base material or welded properties?
Answer – ABS uses welded allowable.
Bob Sielski – How should we communicate?
Jeannette Grant – Website. Contact me if you have problems with the site.
Ray Kramer – When are we starting FE models?
Pradeep Sensharma – We have. We should have some results for QPR2.
Actions
-Send Chao Lin application for no cost extension of project to 02/05/2010.
-Send project schedule to Kim Tran
-Send Kim Tran updated slides for today’s presentation