Method of determining deformation characteristics of polymeric material

FIELD: light industry.

SUBSTANCE: method comprises recording response of the material to be tested that represents an amplitude-frequency characteristic, calculating deformation characteristics, and determining the value of distributed mass of the vibrating part of the material. The response representing two amplitude-frequency characteristics is recorded for the same part of the material to be tested for various masses of two bodies that cause deformation. The deformation characteristics are calculated from equations of vibration theory for viscoelastic bodies.

EFFECT: enhanced precision and reliability.

 

The invention is related to light industry, in particular to methods allowing to determine the stiffness, the value of the viscous friction, the tangent of mechanical loss polymeric materials in a resonant mode.

Known methods of determining the modulus of rigidity in bending /Meredith R. and J., Vshare. Physical methods of research of textile materials. - M.: Gisleham, 1963, str/.

This work presents methods of excitation of transverse oscillations of the fiber and the relationship definitions of the modules of rigidity E1and loss of E2in the form:

where I is the moment of inertia of the cross-section sample, Δv - width of the resonance curve, ν resonant frequency.

This method causes difficulties when calculating module E1and E2due to the complexity of the calculation of moment of inertia I of the cross section of the sample or the amount distributed mass.

The closest analogue of the claimed invention is a method of determining the mechanical properties of leather for the uppers /A.S. USSR №1000910, CL. G01N 33/44, 1981/. This method involves the application to the studied sample skin sinusoidal changing frequency force pressure load and recording the amplitude of the sample and the half width of the resonance curve of the amplitudes of the on-frequency characteristics and the subsequent evaluation of mechanical properties. Sinusoidal load attached to the front surface of the sample of the skin, placed on the unyielding ground. The calculation of the indices produced by the following dependency:

where σ - breaking the tension, ε strain at break, ν resonance frequency, Δν - width of the resonance curve, 1 - thickness of the specimen.

The disadvantage of this method is the bias of the conducted calculations, since the cut-off voltage in polymer materials is fluctuating in nature and not related to linear elasticity, which represents the amplitude-frequency characteristic. Besides the permanent members of the equalities are empirically selected coefficients.

The aim of the invention is to improve the accuracy and reliability of the method for determining the deformation performance of viscoelastic materials.

This objective is achieved in that the method of determining the deformation performance of polymeric materials is determined by application to the studied material sinusoidally varying force action, the registration response response of the investigated material in the form of amplitude-frequency characteristics, an additional determination is elicina distributed mass oscillating part of the material and the registration response response in the form of two amplitude-frequency characteristics for the same topographical area of the studied material at different the masses of two bodies, causing deformation, and deformation calculation of the indicators according to theory of oscillations of viscoelastic bodies with one degree of freedom in a region of linear viscoelasticity.

This theory considers the oscillatory processes of a small mass under the influence of periodically varying power impacts with the force of friction. The use of theory of oscillations allows to obtain a range of deformation performance of polymeric materials. The complexity of the practical use of the method of resonance testing is difficult to determine the moment of inertia or the amount distributed mass Δm oscillating part of the investigated material.

The author of the present invention developed a method of determining the value of the distributed mass Δm oscillating part of the material under various types of deformation. It is known that any mechanical system with mass m and stiffness k, has its own resonant frequency ω0which is expressed by the relation:

For our particular case this ratio will be:

where m1well - known mass attached to the material studied under various types of deformation, or body weight, environmenta is found on the investigated material. If a large mass m1to replace several smaller mass m2then the self-resonant frequency ωp.1change its value in a big way and will be equal to ωp.2. With the rigidity of the studied material will not change, and the stiffness coefficient in this case is determined by the equation:

Then the right hand sides of equalities (4) and (5) are equal, ie,

Where

Thus, by determining the value of the resonant frequencies ωp.1and ωp.2when the respective masses m1and m2it becomes possible to determine the value of distributed mass Δm oscillating part of the investigated material.

Using theory of oscillations of a viscoelastic body in the linear region of the strain off of the amplitude-frequency characteristic of the investigated object, it is possible to find the following indicators:

the stiffness coefficient k

the total mechanical resistance z, acting from a deformable material

which in the case of resonance becomes equal to the value of the coefficient of viscous friction g, as the elastic component of the k/ω and inertial resistance Δmω the mill is become equal quantities and vzaimodeystviya.

The tangent of mechanical loss tgϕ

where β - attenuation factor equal to

q material Q

where Δω - width of the resonance curve at the level of 0,707, xRSthe amplitude of the deformation at resonance, Xarticle- deformation of the material during the ω=0, i.e. static deformation under the influence of a constant force F0.

The relaxation time of the material τshowing the time interval for which the amplitude of the deformation decreased in e times.

the modulus of elasticity E1and the loss modulus E2the energy expended in overcoming the forces of viscous friction, and other important deformation parameters.

From the above analysis it follows that all of the above deformation indicators can be obtained at the various types of deformation under the condition of imposing an oscillatory process of the same material of the two largest known additional mass and receiving two corresponding and amplitude-frequency characteristics.

The difference of the proposed method from the method, taken as a prototype, is that in the proposed method, removed two amplitude-frequency characteristics for the same topographic teaching the TKA at different body masses, causing oscillatory movement of the investigated material that assures high precision and reliability to detect a range of deformation performance of polymeric materials and the finished structures of products of light industry.

The method of determining the deformation performance of polymeric materials by application to the studied material sinusoidally varying force action, the registration response response of the investigated material in the form of amplitude-frequency characteristics and calculation of the deformation parameters, characterized in that it further determine the magnitude of the distributed mass of the oscillating part of the material, while the registration response response in the form of two amplitude-frequency characteristics of the produce for the same topographic portion of the study material for various masses of two bodies, causing deformation, and the deformation calculation of indicators carried out according to theory of oscillations of viscoelastic bodies with one degree of freedom in a region of linear viscoelasticity.



 

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