RU2249195C2 - Device for determining dynamical characteristics of polymeric fibers - Google Patents

Abstract

FIELD: investigating strength properties of solid materials.

SUBSTANCE: device comprises two vertical pillars, which are provided with a vertically movable unit for unbalancing the specimen-weight system and synchro transmitter, and two horizontal platforms. The axially aligned top and bottom clamps for the specimen are secured to the top plate. The bottom clamp is made of a vertical rod with the area for mounting the stack weight. The movable horizontal plate is mounted on the vertical pillars for permitting vertical movement and has an opening whose center is in coincidence with the longitudinal axis of the specimen and clamps. The opening receives the vertically movable unit for setting the specimen with the weight out of balance. The unit is made of an electromagnet with the core whose diameter is less than that of the opening. The movable plate is provided with a unit having roller system, which is composed of three pairs of rollers arranged at an angle of 120^o to each other and embraces the bottom clam whose cross-section is a regular hexahedron. The top clamp is made of a cantilever provided with a strain-gauge transducer.

EFFECT: enhanced reliability of determining.

2 dwg

Description

The invention relates to the field of dynamic testing of highly oriented polymers and can be used to determine the dynamic characteristics of polymer filaments of various chain flexibility (for example, CBM, Terlon, Armos, Dacron), mainly to determine the dynamic modulus of elasticity, modulus of mechanical loss, tangent of the angle of mechanical loss and coefficient stiffness.

The closest in coincidence of signs to the claimed is a device published in AC No. 1647353 A1, USSR, IPC G 01 N 3/30, May 7, 1991, bulletin No. 17, "A method for determining the dynamic characteristics of complex threads in the creep process." The method uses a device consisting of two vertical struts, on which, with the possibility of vertical movement, a device is mounted for removing the sample-load system from the equilibrium position, which is a spring striker with a striker, and a selsyn sensor, as well as two horizontal platforms, to the top of which the upper clamp of the specimen, the specimen of the studied complex thread and the lower clamp of the specimen, which is a cylindrical rod with an opening for mounting the shoulder of the synchro sensor, are fixed on one axis platform for installing stacked cargo. A vertically suspended sample is statically loaded with a load, which ensures the occurrence of a creep process in the thread. After holding the sample under load for 1 minute, in order to achieve a given creep strain, longitudinal vibrations of the sample are excited by striking a spring hammer on the platform with the load from the bottom up. The force of shock loading is selected from the condition of excitation of oscillations with an amplitude not exceeding the magnitude of the elastic deformations of the loaded sample. Using a syncron sensor, mounted with the possibility of vertical movement on one of the vertical racks of the device, the frequency of the excited oscillations is recorded, by which the dynamic characteristics of the complex thread are determined.

Having a number of advantages at the time of registration, the described device revealed a number of disadvantages, namely:

- due to the lack of control over the coincidence of the point of application of the impulse from the side of the spring striker on the platform from the bottom up to the longitudinal axis of the thread, in the case of an off-center impact of the spring of the spring striker on the site from the bottom up, undesirable transverse vibrations of the sample with the load can occur, which will lead to distortion of the expected oscillatory process and increase the error in determining the dynamic characteristics of polymer fibers;

- when the sample-load system is removed from the equilibrium position in the prototype, the deformation of the sample does not occur immediately, but after a certain period of time, because upon impact, the sample first moves upward under the influence of the impulse from the side of the striker, then, having reached a maximum deviation from its equilibrium position, moves downward under the influence of gravity and, only after passing through the equilibrium position, is deformed under the action of the quasi-elastic force arising in the sample when shifted from the equilibrium position ;

- the prototype provides only a device for measuring strain, which does not allow experimentally determine the stress.

The technical result of the proposed solution is the simultaneous elimination of all these drawbacks, namely, increasing the reliability of determining the dynamic characteristics of polymer filaments, such as dynamic modulus of elasticity, modulus of mechanical loss, tangent of mechanical loss and stiffness coefficient, by eliminating possible transverse vibrations of the sample with the load, instant application efforts when removing the sample from the equilibrium position and reducing the error in determining the voltage in the sample due to experimentally measuring the voltage via the load cell.

The problem is solved in that in a device for determining the dynamic characteristics of polymeric yarns by the method of free longitudinal vibrations, consisting of two vertical posts, on which, with the possibility of vertical movement, a unit is mounted for removing the sample-load system from the equilibrium position and selsyn-sensor, as well as two horizontal platforms, to the upper of which the upper clamp of the sample and, through the sample, its lower clip, which is a vertical rod with with a guard for installing stacked cargo, on vertical racks, with the possibility of vertical movement, an additional movable horizontal platform is placed, having an opening whose center coincides with the longitudinal axis of the sample and clamps, in which a node is also located with the possibility of vertical movement for removing the sample from the position equilibrium, consisting of an electromagnet with a core, the diameter of which is smaller than the diameter of the hole, and on which another node with a roller system is rigidly fixed vertical conductive rod lower jig whose section is a regular hexagon, in its three side faces disposed at an angle of 120 ° relative to each other, and the upper clamp is formed as a console, which is rigidly fixed to the load cell.

It is known to eliminate unwanted transverse vibrations when determining the dynamic characteristics of polymer fibers in the process of vibration (see AC No. 1303885 A1, USSR, IPC G 01 N 3/30, published April 15, 1987, Bulletin No. 14 "Method for determining the viscoelastic properties of complex threads" ) In the method, the sample, previously stretched by the weight of the load fixed at its lower end, is lifted with the load for the upper grip of the sample to a predetermined height h and discarded. Impact loading of the sample is achieved by stopping the upper grip. To determine the viscoelastic characteristics, for example, dynamic stiffness, mechanical loss coefficient, the frequency and damping decrement of the longitudinal vibrations of the sample are recorded.

However, in this design, during the impact of the upper grip on the upper horizontal platform, forced longitudinal vibrations of the sample with the load are excited due to the vibration of the upper platform, which received an impulse from the upper grip of the sample. In addition, the uneven friction when sliding the upper sample grip along the opening of the upper horizontal platform causes undesirable low-frequency transverse and torsional vibrations.

Thus, only the claimed combination of features, the presence of additional features and their implementation allow us to achieve the result set forth in the purpose of the invention section, which allows us to conclude that there is an inventive step criterion.

In figures 1 and 2 presents a diagram of the inventive device for determining the dynamic characteristics of polymer fibers by the method of free longitudinal vibrations, consisting of the following main nodes:

- from the lower 1 and upper 2 horizontal platforms (Fig. 1), to the upper of which 2 on the same axis the upper clamp of the cantilever type 3 with the load cell 4 is sequentially fixed, the power of which is supplied from the strain gauge station (not shown in figure 1), the sample under study polymer thread 5 and the lower clamp 6, made in the form of a hexagonal rod with a platform 7 for installing stacked cargo 8;

- two vertical posts 9 and 10 (Fig. 1), on which a horizontal movable platform 11 with a hole 12 is mounted with the possibility of vertical movement, in which an electromagnet 13 is located, consisting of a metal core with a winding, the voltage to which is supplied from the current source (on figure 1), the diameter of which is smaller than the diameter of the hole 12, and the longitudinal axis coincides with the longitudinal axis of the lower clamp 6 and the longitudinal axis of the sample of the investigated polymer thread 5, as well as selsyn sensor 14, the signal from which goes to the loopback illograf type H-117 (in Figure 1 is not specified) and a shoulder which is fixed on the sample yarns five lower clamp axis 6;

- an additional node 15 (Fig. 1), rigidly mounted on a movable horizontal platform 11 and representing a roller system consisting of three pairs of rollers 16, encircling the hexagonal rod of the lower clamp 6 on three sides located at an angle of 120 ° from three sides ( figure 2, items 6 and 16), which slides between them in the process of its vertical movement near the equilibrium position.

The method for determining the dynamic characteristics of polymer fibers by the method of free longitudinal vibrations includes several stages. At the stage of preparation of the device for tests on the electromagnet 13, a predetermined voltage is supplied, after which the metal core of the electromagnet 13 rises to a predetermined height. The pad 7 of the lower clamp 6 is mounted on the upper base of the metal core of the electromagnet 13, thus ensuring the absence of force in the sample 5 when external force is applied. At the stage of testing, a static stacked load 8 is installed on the platform 7 of the lower clamp 6, which does not cause stress in the sample 5 due to the reaction from the side of the metal core of the electromagnet 13. The power to the electromagnet 13 is turned off, after which the metal core of the electromagnet 13 is lowered into a hole of a larger diameter 12, cut in a movable horizontal platform 11, and the sample 5 with the load 8 is deformed, performing longitudinal vibrations around its equilibrium position. Using a strain gauge 4 located on the upper clamp of the cantilever type 3, the force in the sample is recorded, and with the help of a synchro sensor 14, mounted with the possibility of vertical movement on the vertical strut 10, the frequency and amplitude are simultaneously recorded, according to which the dynamic characteristics of the complex threads are determined, and namely, the dynamic elastic modulus E _dyn. , the stiffness coefficient k _W , the tangent of the angle of mechanical losses tan δ and the dynamic module of mechanical losses E _sweat , in a known manner:

where l is the length of the thread, γ is the density of the thread, T is the linear density of the thread, m is the mass of the suspended load, ω is the cyclic vibration frequency of the thread with the load.

where Δ is the logarithmic attenuation coefficient.

E _POT = E _din · tgδ.

Claims (1)

A device for determining the dynamic characteristics of polymer filaments by the method of free longitudinal vibrations, consisting of two vertical struts, on which a node is mounted with the possibility of vertical movement to bring the sample-load system out of equilibrium and a selsyn-sensor, as well as two horizontal platforms, to the upper of which the upper clamp of the specimen is sequentially fixed on one axis and through the specimen its lower clamp, which is a vertical rod with a platform for setting the stacked load, exl characterized in that the vertical racks with the possibility of vertical movement additionally placed a movable horizontal platform having a hole, the center of which coincides with the longitudinal axis of the sample and clamps, in which also with the possibility of vertical movement is a node for removing the sample with the load from the equilibrium position, consisting of an electromagnet with a core, the diameter of which is smaller than the diameter of the hole, and on which another assembly is rigidly fixed with a roller system consisting of three pairs of rollers, p located at an angle of 120 ° relative to each other and grasping the lower clamp, the cross section of which is a regular hexagon, along its three side faces, and the upper clamp is made in the form of a console on which the strain gauge is rigidly fixed.

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