Cannot understand the result

Hi,

 

I'm trying a basic analysis using a 1D spring element to study its effects under compression(image:loading conditions) and tension.

K= 0.1

GE= 0.5

S= 1

 

The values are arbitrary as this is just a benchmark test. Could someone please look at the attached images. I would think instead of there being a blue and red line. The 1D elements both should be of the same magnitude and direction. Thus depicted in red. I'm not understanding why there is a negative stress value on one side and positive on the other side.  

 

Thank You 

Shishir

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