HRP20150737A2 - Apparatus for achieving uniform pretensioning of the sample and apparatus for measuring shear tension of flat textile products with dynamometer - Google Patents

Abstract

The device for achieving uniform prestressing of the material simultaneously on all four sides comprises a frame on which the clamps (2) are located, two lever arms (6) are mounted on the angular parts of the frame by a joint (6), on which the shoots (5) are mounted to secure the chains (7). in achieving simultaneous balance of the material and all four sides and weights (1) located on these levers. The clamps (3) of the shear strain gauge for textile sheet products housed within the device for uniform material prestressing, fasten the material with the achieved tension, release the outer clamps (2), move the shear strain measuring device with the material to the dynamometer (4) to the part of the dynamometer terminals.

Description

The field to which the invention relates

This invention consists of two works related to achieving uniform sample stress and measuring the shear stress of textile flat products on a dynamometer, and according to the International Classification of Patents (IPC) it is classified in area G - Physics, 01 - Measurement, testing.

Technical problem

Textile flat products belong to a group of materials whose properties change greatly in the direction of stress, which characterizes them as extremely anisotropic materials. Shear stress appears when an external force acts tangentially on the surface of the material. Of all the methods for testing the mechanical properties of composites, most of them have been developed for testing the shear properties of materials. The reason for this is the difficulty of achieving a clean and uniform state of shear stress on the sample in order to determine the actual shear properties. Another problem is that some methods give satisfactory results of shear strength, but not of shear modulus, while with other methods the reverse is the case. Furthermore, while there are three shear moduli for orthotropic materials, only two can be tested with most shear testing methods.

"Picture Frame Test" is a non-standardized method of testing material shear stresses that has proven to be one of the more appropriate, but its disadvantage is the non-uniformity of the sample's stress in the phase of placing it on the measuring device, and it is precisely in this area that the method and the device itself have been innovated and improved.

State of the art

The shear strength of a flat textile product is an important parameter that is correlated with the deformation that occurs as a result of the conversion of a two-dimensional product into a three-dimensional one. The more accurate the empirical shear parameter, the more reliable the simulation of fabric behavior will be. Deformations caused by shear stress are particularly common in technical fabrics and knits, so it is important to analyze them at the time of multidirectional stress.

This device will expand the knowledge about the behavior of materials with different characteristics under shear load, and thus lead to extremely important data about the material that will define its qualitative and useful values in the area of smaller and larger surface multiaxial stresses, which were unknown until now. It is known that there are several innovative devices in the world that measure the shear strength of textile materials, but the problem that appears is the impossibility of achieving a certain prestress of the sample during its installation. The consequence of this limitation is insufficient reproducibility of the results, which makes such tests unreliable, and for this reason, an additional frame for setting the selected prestress was designed as an addition to this device. Considering the importance and necessity of observing and connecting the parameters of shear stress, modulus of elasticity and Poisson's ratio in synergy to describe the deformability of a flat textile product for the correct simulation of energy distribution and deformation of a flat and three-dimensional textile product, it is desirable that the shapes and dimensions of the test samples when determining all three parameters are equal, and for this reason the frame is such that it is possible to place a sample with dimensions of 200x200 mm.

Presentation of the essence of the invention

The primary goal of the invention is to measure the shear stress of textile flat products on a dynamometer. The purpose of this procedure is to define shear angles and shear stresses during multiaxial stress based on the obtained measurements.

The secondary goal is to ensure equal prestressing of the sample with a certain force in all directions using a device for achieving uniform prestress when placing it on a device for measuring the shear stress of textile flat products on a dynamometer.

Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be learned through practice of the invention.

The invention consists of two parts - a device for achieving uniform prestressing of the sample and a device for measuring the shear stress of textile flat products on a dynamometer. With regard to the current technical problem of achieving a uniform prestressing of the sample when placing it on a device for measuring the shear stress of textile flat products on a dynamometer, the value of this invention is precisely in the frame, that is, a device that ensures uniform prestressing of the sample with a certain force in all directions. This is achieved by preparing the sample outside the dynamometer, by placing the device for measuring shear stress on the device for achieving uniform prestress, where by simultaneously loading the sample in all directions with equal forces, the uniformity of the prestress of the sample is achieved, which is then fixed with the clamps of the device for measuring shear stress and as such is ready for the further measurement procedure on the dynamometer.

A short list of drawings

The drawings, which are included in the description and form part of the description of the invention, illustrate the best way of carrying out the invention thus far considered and help to explain the basic principles of operation of the invention. The drawings include the invention in plan view (Figs. 1 and 2) and in blueprint view (Fig. 3).

Sl. 1 is a perspective view of the prestressing frame with the shear stress measuring device installed

Sl. 2 is a perspective view of the prestressing frame

Sl. 3 is a spatial view of the device for measuring shear stress

Sl. 4 is a side view of a section of the prestressing frame with the shear stress measuring device installed.

Detailed description of the drawing of the device for achieving uniform prestress and the device for measuring the shear stress of textile flat products on a dynamometer

Reference will now be made to the details of this proposed embodiment of the invention, one example of which is illustrated in the accompanying drawings.

According to Figure 1, 2 and 3, it can be seen that the invention comprises two devices that complement each other in the preparation of the sample for shear stress testing. The frame for prestressing the material (fig. 2) before fixing it on the device for measuring shear stress enables simultaneous tensioning of the material on all four sides. The material tension is regulated by moving the weights (1) on the arms of the prestressing frame (6). Shifting the weight to a larger lever arm allows for greater tension in the material. Clamps (2) secure the material with screws (8). The balance of forces between the weights and the material is regulated by means of the spur (5) and the chain (6).

Before placing the material on the prestressing frame, place a shear stressing device on it (fig. 1). The upper clamp of the shear stress measuring device (3) is removed by unscrewing the screws (9) so that the material can be placed smoothly in the outer clamps of the prestressing frame (2). Achieving the appropriate tension of the material on all four sides is done by moving the weight (1) on the two-armed levers (6) and fixing the chain (7) on the branch (5), then fixing the upper clamp of the prestressing frame (2). The method of prestressing the material is shown in Fig. 4, where two clamps are shown, one next to the other, a chain, a spur and a weight on the arm of the prestressing device. This places and secures the upper clamps (3) of the device for measuring shear stress. Then the outer clamps (2) of the frame for prestressing the material are released and the material is released from the clamps. The device for shear stress with the material that is uniformly tensioned and fixed in the corresponding clamps (3) is transferred to the dynamometer for the break stretching of textile flat materials. The device for shear stress is fixed by means of the attachment (4) to the clamp part of the dynamometer and the measurement of shear stress is possible. The size of the material sample for measuring the shear stress is 200×200 mm, and the size of the device is adapted to the size of the distance between the clamps of the dynamometer. The device can be adapted to any dynamometer without major interventions on the accessory (4).

Method of application of the invention

The application of the invention, i.e. the device for achieving uniform prestressing of the sample and the device for measuring the shear stress of textile flat products on a dynamometer is useful for wider application and simple because the device is designed as a separate unit (addition device) with the possibility of adaptation to any dynamometer. According to the modernization of the dynamometer, it is possible to obtain results through a computer program (software) and thus enables the storage of data, statistical processing and drawing of diagrams of the forces created during shear stress under different conditions that the dynamometer allows.

List of used call signs

1 - weights for tension regulation

2 - clamps on the material prestressing device (external clamps)

3 - clamps on the device for measuring shear stress (internal clamps)

4 - accessory for fastening the shear stress device to the dynamometer

5 - chain fasteners for tension regulation

6 - double levers

7 - chains for maintaining the balance between the clamp and the weights

8 - screws on the clamps of the device for measuring shear stress

9 - screws on the frame clamps for prestressing the material

Claims (3)

1. The device for achieving uniform prestressing of the material simultaneously on all four sides includes clamps (2) with screws (8) for attaching the upper and lower clamps that are fixed to the frame, on the corner parts of the frame two-armed levers (6) are fixed with hinged design, on which weights (1) are placed with the possibility of movement when regulating the tension of the material, and the chain attachment shoots for maintaining the balance between the weights (1) and the material fixed in the clamps (2), by means of screws (8), indicated by the said weights (1) on the two-armed levers (6), tension the material from all four sides at the same time, in order to balance the force between the weights (1) and the material, then fix the upper clamps for the lower one (2) and fix the tension of the material. 2. Device for measuring the shear stress of textile flat products according to claim 1 characterized by the fact that the said device for achieving uniform prestressing of the material simultaneously on all four sides prepared a sample with the achieved and fixed tension of the material for fastening the clamps (3) with screws (9), which they form part of the device for shear stress, and which are placed inside the device to achieve a uniform prestressing of the material and thus maintain the set tension of the material on all four sides. 3. Device for measuring shear stress of textile flat products according to claim 2 characterized in that said device for measuring shear stress with a material of certain tension is fixed to the dynamometer using the accessory (4) for measuring shear stress.