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## Main Question or Discussion Point

Hello, I am reading a book about finite elements with regards to stress analysis. I'm pretty sure the book is full of mistakes, which makes following and doing the examples fairly difficult.

I have posted a 1D analysis from the book, I'm not even sure how he comes up with some of the numbers in the calculations.

I do understand the method but what hasn't exactly "clicked" is the sign convention or the displacement of each node equating to the change in element length. The author has (u1-u2), then on the last element he switches to (u4-u3), is there a reason for this or is it because u4 is the last node?

Would someone mind having a really quick look at the images I posted to give their oppinion. But definetely his answers do not satisfy the simulataneous equations.

Thanks a lot for your time.

http://img2.imageshack.us/img2/3816/scan0001xo.jpg [Broken]

http://img203.imageshack.us/img203/8407/scan0002r.jpg [Broken]

http://img242.imageshack.us/img242/3311/scan0003e.jpg [Broken]

http://img43.imageshack.us/img43/5510/scan0004al.jpg [Broken]

I'm sorry, I've posted this in the general maths forum too but thinking about it, I think this area is more relevant.

I have posted a 1D analysis from the book, I'm not even sure how he comes up with some of the numbers in the calculations.

I do understand the method but what hasn't exactly "clicked" is the sign convention or the displacement of each node equating to the change in element length. The author has (u1-u2), then on the last element he switches to (u4-u3), is there a reason for this or is it because u4 is the last node?

Would someone mind having a really quick look at the images I posted to give their oppinion. But definetely his answers do not satisfy the simulataneous equations.

Thanks a lot for your time.

http://img2.imageshack.us/img2/3816/scan0001xo.jpg [Broken]

http://img203.imageshack.us/img203/8407/scan0002r.jpg [Broken]

http://img242.imageshack.us/img242/3311/scan0003e.jpg [Broken]

http://img43.imageshack.us/img43/5510/scan0004al.jpg [Broken]

I'm sorry, I've posted this in the general maths forum too but thinking about it, I think this area is more relevant.

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