Softening effect during cyclic stretching of titanium nickelide knitwear | Mekhanika | kompozitsionnykh | materialov i konstruktsii

Softening effect during cyclic stretching of titanium nickelide knitwear

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Abstract:

Samples of knitwear made of TiNi wire with a thickness of 40 microns, 60 microns and 90 microns were studied by the method of soft zero cyclic loading under the action of uniaxial tensile stress and stretching to rupture. It has been found that metal friction, when stretched, behaves like a hyperelastic material. The effect of superelasticity was found in TiNi wire, but it did not manifest itself in knitwear made of it. The effect of softening and lagging of elastic unloading was detected during cyclic stretching of the metal mesh. The calculation of the cyclic stretching of knitted material was carried out using the calculation models of Gent, Neo-Hooke, Mooney-Rivlin, Bergstrom-Boyce, using experimental data on the cyclic stretching of knitted tapes made of titanium nickelide. The discovered similarity of the hyperelastic behavior of metallotricotage and computational models will allow us to develop a method for comparative evaluation of knitted materials made of titanium nickelide wire of different thicknesses and criteria for choosing a knitted material for the plastic of hyperelastic biological tissues. The main criteria for the rheological similarity of metallotricotage and soft tissues can be considered: the value of the tensile strength; elastic modulus and the range of low-modulus and high-modulus elastic deformation under load and unloading; the amount of residual deformation under cyclic tension. It has been found that the metal mesh made of superelastic TiNi wire under soft zero cyclic loading under the action of uniaxial tensile stress exhibits a rubber-like behavior characteristic of hyperelastic materials. At the same time, in the most loaded contact sections of the superelastic TiNi wire, the martensitic phase transition did not affect the stretching diagram of the hyperelastic knitwear. The residual macro-deformation during the first two stretching cycles is caused by the slipping of the loops on the contact sections during loading and friction, which counteracts the restoration of elastic deformation during unloading. The effect of softening and lagging of elastic unloading was detected during the cyclic loading of TiNi metal drainage. This effect is due to the heterogeneity of the elastic load distribution in the knitwear loops and the friction in the contact sections of the loops, which resists the elastic deformation of the loops. It is established that the Bergstrom-Beuys model is closest in the stress-strain diagram to the knitted ribbon diagram.

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