Relative grain size influence on the mechanical behavior in shape memory material in flexion test

An experimental study on a Cu-Al-Be shape memory alloy in cantilever flexion arrangement is presented. The samples tested were thin plate of shape memory material polycristallynes with M_S near to -20^oC and a monocrystallyne sample with M_S near to -40 ^oC. The samples were instrumented with electrical strain gauges on top and they were subject to variable load and strain-load curves were plotted. The curves were employed to obtain the critical stress.

A polycrystalline sample was instrumented and tested and then it was cut in three samples to the wide thing. After, these samples were instrumented and tested also. 

The obtained results shown a hard variation in the critical stress for each sample; the three samples obtained of the pattern sample presented lower critical stress than the pattern. 

A results’ analysis showed that the Ms calculated with the critical stress correspond with good agreement with the Ms Measurement by DSC in the case of monocrystalline sample and it present major deviation in the case of pattern sample mentioned before.  

A relation between sample's wide-grain's size was found but don't correspond with the relation: sample's thickness-grain's size reported in the literature for polycristallyne subject to simple tension test. It is because the last relation was constant in pattern sample and the three samples obtained of him. The effect observed in the present work is due to grains constrain condition and could be the responsible of an effect reported in a previous papers.