The Experimental Study On Mechanical Behaviour Of Prestrain A3 Steel

The A3 steel is a kind of plastic material which we commonly used in our daily life and teaching, But there is not much study of mechanical behaviour of the material after pretorsion and pretension intensify at present. It is not yet very known especially of the mechanical behaviour after secondary hardening such as torsion - tension - tension and tension - torsion - tension.The mechanical behaviour of A3 steel specimen under monotonic tension, pure torsion, torsion - tension, tension - torsion, torsion - tension - tension, tension - torsion - tension were studied by standard cylinder specimen in this paper. There were obvious yield point jog both when the A3 steel specimen are under monotonic tension and pure torsion,this illustrates that there are obvious physical yield procedure in these process. When we draw the stress-strain relation of monotonic tension and pure torsion at the same co-ordinate namely equivalent effective stress and equivalent effective strain co-ordinate, It is obviously that the equivalent effective stress- strain curve of monotonic tension and pure torsion are basicly superposition while the equivalent effective strain is smaller.But equivalent effective stress level of monotonic tension was higher a little than that of pure torsion. While the equivalent effective strain was higher,there was significant difference between the two curve gradually . Under macrostrain large strain,the equivalent effective stress of pure torsion was higher. The equivalent effective stress -strain curve of pure torsion was five - six times longer than that of tension experiment.After pretorsion the successor tensile yield limit and strength limit both improved very highly,but the trend of the increase of the strength limit was suspended till the pretorsional capacity reached 17Ï€ ,when the pretorsional capacity was greater than17Ï€( prestrain value was 81.19% of total strain),the successor strength limit rapid failed and approached the yield limit.This illustrate the A3 steel specimen translate from plasticity into friability after pretorsion strengthen.When the specimen was operated by tension - torsion action, the yield limit had very large improved,but the strength limit changed very little.Furthermore,the trend of the increase of the strength limit was suspended till the pretension capacity reached 0.25(prestrain value was 66.93% of total strain).When the A3 steel specimen was operated by tension - torsion - tension action, both the yield limit and strength limit had very large improved compared with that of monotonic tension.The improve scope of the yield limit could be 109.36%,the strength limit could be 56.26%.The yield limit value reached the max. after pretension 0.1 strain and pretorsion to 14Ï€, whereas the strength limit keep on increasing in company with the pretorsional capacity.Comparing with these several strengthen formal, towards strength limit's improvement, the effect of torsion - tension and tension - torsion -tension was close; simply tension - torsion - tension required a little larger prestrain quantity. whereas, towards yield limit 's improvement,the effect of torsion - tension -tension action's strengthen was the best.Consider the total plasticity of these several kinds of prestrain A3 steel specimen.The total plasticity of tension - torsion - tension action was higher than that of torsion - tension and torsion - tension - tension action.But the max.values of their total plasticity were all greater than those of any single destructional form.