Needham Method Section Crippling

In the course of writing a section for the textbook, I found a version of the Needham method in the US Airforce Stress Manual, there was one small error in the source material which is corrected in both the textbook and the spreadsheet file.

Section crippling can be a stand alone check, or can be used as an upper boundary strength for a column check – especially for thin walled columns.

 

 

New Spreadsheets

AA-SM-007-002The launch of our new website triggers the staged release of our new – expanded, updated and improved – free analysis spreadsheets. The first tranche of released spreadsheets (about 50) can be found at this link

http://www.abbottaerospace.com/?s=Spreadsheets

The spreadsheets are updated to match the documentation we are going to provide in our free text book to be released later in the year and now have live links to the source reference material in the Technical Library. In some cases they have been reformulated to give an improved and more accurate solution.

Where reading values off graphs is required all of the graphs are now fully digitized and the graphical solution is found without using the old Excel 4.0 Macro code or visual basic.

If you like our free material please share with your colleagues and friends.

Let us know what you think!

 

 


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Welcome to the new Website!

Six months in the making and relying on the talents of our web supremo Mike Sharpe the new website has been launched. The new site back-end architecture and front end will allow us to build our public domain technical library and start to create an interlinked set of references and tools that will be unique and free.

We have been waiting for the new site to be live until we start to post the wealth of new reference data we have discovered and as we do that we will post on a regular basis once again to highlight the data we are making available.

We would love to hear what you think, please feel free to leave us a comment using the comment buttons on the website.


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To try our Add-in for Microsoft Excel for Windows click below

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Merry Christmas and A Free Sample

All of us at Abbott Aerospace SEZC Ltd hope all of you have had a productive and enjoyable 2015.  We wish you a very Merry Christmas and success and happiness for 2016.  In the spirit of the season we have released a sample chapter of the free reference book that we will release in 2016, you can down load the sample here.

In the final version all of the cited texts will be linked to the relevant pdf in our on line library and the spreadsheet boxes will link to the on line spreadsheets.

We would love to hear from you to find out what you think.

Merry Christmas!

 

Richard Abbott


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Website Reference Data – Important Announcement

We have been very busy with a major project that we are planning to launch early next year. Over the last 18 months the interest in the reference material we make available through our website has grown to the point where we have up to one thousand downloads per day. The reference data library is referenced directly from several university libraries and we have regular users from all the major aircraft OEMs. The way the data is kept and the presentation does not serve this demand well and we have been working to create a better website to present more reference data in a much more useful way.

We also have thousands more reference documents and analysis tools that we have accumulated through out work and want to make available to our users. We will be launching the Abbott Aerospace Technical Library to bring all of these documents and tools together stored in a better data storage system with better search methods and a much improved content and still keeping everything completely free.

The analysis spreadsheets have been expanded and updated and we will be moving the analysis spreadsheets back home from the XL-Viking project. They will be curated under the Abbott Aerospace Technical Library. The spreadsheets will be live hyperlinked to the relevant reference material in the library. We have been working on standardizing the spreadsheet methods and presentation. We will also be standardizing the spreadsheets to operate in the Imperial/British unit system of lb/in, this reflects the majority of the public domain material that we now reference. We also have many more spreadsheet methods that we have been developing and will be releasing as they are checked.

We also have been working on a single reference text book that will bring together the public domain references, the spreadsheets and other software tools. This will give the analyst a reference that can be cited and provides fully referenced methods hyper-linked to the source texts and spreadsheet methods to allow the reader to create fully defined and referenced analyses and reports with confidence and ease. This free e-book will be unique in its scope and utility

The reference text book is the end result of the discovery and knowledge of the massive amount of public domain methods and data. We realized that almost all of the methods and data available in commercial and proprietary OEM references originate in the public domain or can be derived from first principles. 50 years ago Bruhn created his excellent book referencing NACA papers and wartime reports, taking those references and giving coherent overviews of the methods and the best compromise analysis method from the multiple sources. We are humbly trying to emulate that example using the best of the public domain data referenced from Bruhn and the best of the public domain information produced in the last 50 years since Bruhn was written.

By making the textbook a free E-book we can update the document on a regular basis as new and improved methods become available. We can incorporate reader suggestions and be reactive to the users.

The library will be searchable using a tag cloud as the primary means of locating material. All the classes of material will be tagged with the type of material, the source of the material and tags relating to the subject material. All of these classes of entries in the Technical Library – the reference data, the spreadsheets, the software tools and the text book will be made available for free for anyone to download, adapt and use.

We hope to become the engineers best source for reference data, analysis methods and software tools.

Please be patient with us as we move towards this ambitious goal. Updates to the current set of references on the Abbott Aerospace web site will occur less often but the wait will be well worth it.


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AFWAL-TR-85-3069 Buckling Of Composite Plates

AFWAL-TR-85-3069Yet another reference dealing with the buckling of non isotropic plates, in this instance “BUCKLING OF LAMINATED COMPOSITE PLATES AND SHELL PANELS“. This is a long document with over 450 pages and starts with a rather dry, dense theoretical treatment of the subject. The later sections that examine the sensitivity and accuracy of the analysis methods with respect to laminate parameters are well worth a look though.

 

 

 

 


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NASA-N92-32588 A New Approach To Fibrous Composite Laminate Strength Prediction

NASA-N92-32588I first found this paper as part of a set of NASA conference notes from 1990 and it is the earliest, and probably best, explanation of the biaxial strain failure envelope approach for laminated fiber composites. It is authored by the peerless L. J. Hart-Smith, for those of use who have spent any time in the field of composites he is the most consistent and credible developer of robust analysis methods.

This is one paper that is really worth reading through a couple of times and not just keeping in your reference data set for when you might need it in the future.

 

 


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DOT-FAA-AR-95-29 Vol 1

DOT-FAA-AR-95-29 Vol 1This an attempt by the FAA to provide an overview of composite theory and application in the context of the regulations. DOT/FAA/AR/95-29 represents the state of the art in 1997. While the development of reliable and robust laminate failure modes has developed beyond what is presented here much of this is still current and all of it is useful.

 

 

 

 


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To try our Add-in for Microsoft Excel for Windows click below

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Moving you, your family and your business to Cayman – part 2

In the previous post on this subject I went through the preliminary steps of getting incorporated and establishing a business presence on Grand Cayman.  Once you have your business you can offer yourself a job.

As a director of your own business you have to write yourself a formal job offer and go through the work visa process. This can seem overwhelming, and involves a more complex process than both of the work visas our family have traveled under before. But all it takes is patience and a fondness for using UPS to send documents to the island.

You have to make personal statements, take a medical, provide a criminal background check provide notarized copies of many things, set up your health and legally mandated company pension scheme and prove you have a place to live – but the small outlay and inconvenience is worth it. If you use Cayman enterprise city they will give you a good written guide and they have people who will help you through the process. It is advertised that this can be done in a few weeks – it is safer to leave yourself 2-3 months. The time lag of sending documents back and forth, to and from the island and tricky compliance issues can catch you out if you don’t leave yourself enough time margin.

Medical – good family medical and dental cover will cost between $1200 to $1600 per month and the CEC gets a group rate through one of the largest insurers on the island who provide cover under the Aetna PPO which covers treatment on the island in the US.

Pension – is is the law that after 9 months working on the island you pay 3% and your employer pays 3% of your wage (up to a wage level of $60,0000) into a pension scheme. They are quite flexible with the pension funds and if you leave the island to live elsewhere you can transfer the funds off the island.

Accommodation – For first timers it is recommended to rent for the first year to get a feel for the different areas of the island and where you want to live for the long term. The rents run from low to high (I have seen places offered for $12,000 per month) but rents are generally high because you are competing with the holiday short term rental market and that is a lucrative option for local landlords. Property is reasonably priced to purchase and if you are willing to settle for something away from the beach the property prices are very reasonable. Realtors will help you find rental properties, we used Krista at Williams2 and she was very helpful even though we did not rent any of the properties she showed us. Most rental properties are posted on ecaytrade which is the Cayman ‘Ebay’ – you can also find cars, furniture, scuba and other sports equipment on ecaytrade as well.

For getting things done on the island we have found that email is not the best way to get a response, picking up the phone and talking to people is good. While setting up accommodation, pensions and schooling we found that making a trip or two to the island really helps move things along and everyone responds with excellent service when you are dealing with them face to face. It also gives you a chance to explore the island a little more and enjoy the weather and the ocean – always time well spent.

In the next post (and hopefully the final one on this subject) I will cover schools, cars, pets, bank accounts, settling in, iguanas, land crabs and anything else I have forgotten.


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To try our Add-in for Microsoft Excel for Windows click below

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