Spring assembly limiting hydraulic spring type direct-stretching sample fixing device

A spring assembly limiting hydraulic spring type direct-stretching sample fixing device is composed of a lower-position clamp and an upper-position clamp, wherein the lower-position clamp comprises a lower connector connected with a loading base at the bottom of a testing machine, a lower end cap for fixing samples, a lower chain for connecting the lower connector and the lower end cap, a first spiral spring, a first center limiting mechanism, a second center limiting mechanism and a first hydraulic mechanism; the upper-position clamp comprises an upper connector connected with a loading base at the top of the testing machine, an upper end cap for fixing the samples, an upper chain for connecting the upper connector and the upper end cap, a second spiral spring, a third center limiting mechanism, a fourth center limiting mechanism and a second hydraulic mechanism; the first center limiting mechanism, the second center limiting mechanism, the third center limiting mechanism and the fourth center limiting mechanism are each composed of a spring limiting assembly, a supporting piece and an adapter plate; the first hydraulic mechanism and the second hydraulic mechanism each comprise an annular piston and an annular oil cylinder combined with the annular piston.