SU1225934A1 - Method of fatique testing of sheet materials with holes to receive fasteners - Google Patents

Description

I

The invention relates to mechanical engineering and can be used with reference to the conditions of operation of mechanical point connections to determine the degree of influence of the magnitude of the tensions created when the fastener is set (rivet, bolt, etc.) into the hole of the mixed bag.

out of the structural materials forming the package, including their fibrous composite materials.

The purpose of the invention is to increase the reliability of the test results.

FIG. 1 shows a sample with a hole made of a material under study, for example carbon fiber, and a sleeve made of plastic material placed in this hole, the initial position; Fig. 2 shows the stage of ending the process of precipitation of a sleeve from a plastic material with the creation of a symmetric field of compressive radial stresses; in fig. 3 - experimental dependences of the number of cycles N to failure of the samples at a given cyclically varying relative deformation of the bend on the magnitude of the radial static deformation during the settlement of the sleeve; in fig. 4 - the initial position of the package and equipment before setting the bolt; in fig. 5 — force point with optimal tensions in each of the package elements; in fig. 6 is an installation diagram for carrying out the proposed method; general view.

The method is carried out as follows.

ten

the symmetric field, the characteristics and extent of which determine rto the radial strain subscale (ci, -J predetermined) / with the tension value i d, - rrrdv. The configuration of asymmetric stress across the perimeter of the hole in the test material is created using a sleeve with a non-planar (for example, stepped) working end (from the side of the punch 4).

Then, the sample 5 is fixed on a device containing a pneumatic exciter 6 and a string device 7, and a high-frequency alternating load of the latter is implemented (Fig. 6). For a given degree of flexural deformation of the BC (Fig. 6), the number of loading cycles N image 20 Ca before its destruction is obtained. Experimental dependences N i (i) or N (() for the materials of the elements constituting the package are obtained by setting the values of the tensions 1

 , -do,

redb

or

25 values of radial deformations

8 1 / j,

redb

Then, using the known basic number of cycles of construction materials, the conditions for the operation of a mechanical 3Q rammer find the values of optimal tensions i, and I g or deformations f, and fj for each element of the package (Fig. 3).

Technologically ensuring optimal tension i and 1, in the elements

 - -z package reach as described above

The scheme with the presence in each of them its deformed sleeve (figure 4). The package is fixed with a clamp 2 with a given force Rppil In the hole of the clamp

made of fiber composite material - 40 core with holes in the elements

la type carbon fiber having a through

pre-bore diameter

A sample in the form of a plate, for example.

package (use guide pins), install the sleeve 3, having

 Lredv is placed on the matrix 1 and fikpaket (use guide pins), install the sleeve 3, having

rod diameter equal to d

anticipate

With

squeeze with a clamp 2. In the hole of the image of the impactor of a 4-pulse pulse, install sleeves 3 made of plastic 45

material, such as technically pure aluminum (ADO). In the coaxial orifices of the die 1, the presser 2 and the bushings 3, a stepped die 4 is placed.

extrusion of package elements and setting at the place of connection,. After that the closing head of the rivet is formed without distributing the rod. The height of the sleeve 3 exceeds the thickness of the thickness of the package. Get a power difference. A force P is applied to the stepped plunger 4, plastic bushing is produced and, accordingly, an increase in diameter J of pre-diameter cJ ,, is made (internal 55 d1. The diameter of sleeve J is unchanged). Zoom point, such as a bolted connection (Fig. 5) in each element of the package, having a field of compressive stresses along the perimeter with optimal parameters.

the diameter of the hole in the sample

fAB

 nnpiB till forms perimet

the symmetric field, the characteristics and extent of which determine rto the radial strain subscale (ci, -J predetermined) / with the tension value i d, - rrrdv. The configuration of asymmetric stress across the perimeter of the hole in the test material is created using a sleeve with a non-planar (for example, stepped) working end (from the side of the punch 4).

Then the sample 5 is fixed on the installation containing the pneumatic exciter 6 oscillations and string device 7, the high-frequency alternating load of the latter is realized (Fig. 6). For a given degree of flexural deformation of the BC (Fig. 6), the number of loading cycles N image0 Ca before its destruction is obtained. Experimental dependences N i (i) or N (() for the materials of the elements constituting the package are obtained by setting the values of the tensions 1

 , -do,

redb

or

5 values of radial deformations

8 1 / j,

redb

Then, using the known basic number of cycles of construction materials, with regard to the working conditions of the mechanical Q-point joint, the values of the optimal tensions i, and I g or deformations f, and fj for each element of the package are found (Fig. 3).

Technologically ensuring optimal tension i and 1, in the elements

 - -z package reach as described above

package (use guide pins), install the sleeve 3, having

rod diameter equal to d

anticipate

With

the impact of the hammer 4 impulse sy- nr the sleeve 3 makes it

extrusion of package elements and setting at the place of connection,. After that, the closing head of the rivet is formed without distribution of the core to the package thickness. Get silo

a specific point, for example, a bolted joint (Fig. 5) in each element of the package, which has a field of compressive stresses along its perimeter with optimal parameters.

The invention can be used in the manufacture of riveted panels.

consisting of aluminum (D16AT) oblikn and string sraz nz boroaluminium (LDO + B) with a volume fraction of strengthened:: yuchshchich fibers (25%). The thickness of the skin and shelves stringers of 2.0 mm. Before staging at the junction of rivets with a diameter of 4.0 mm, alloy B65 and riveting of the bags are made of the above materials, samples with dimensions:

40 mm wide, 150 mm long. At the center of the pulsed installation, the MIU-10, with the energy of the samples, is punched with the aid of tooling, made according to the 7th quality of discharge accuracy of 2 kJ. After that, blind holes (1.5 mm in diameter, 6.0 mm in depth) are drilled on the protruding parts of the rivet rods, and then closing rivet heads are formed in two transitions. The panels (6 pieces) are tested at the stand, imitated by the operating conditions.

holes with diameters of 3, (in samples of boroaluminium) and 3, (in samples of D16AT). Sleeves of technically pure aluminum (ADO) with a wall thickness equal to 1 Ohm are installed without holes in the sample holes. The height of each sleeve is greater than the sample thickness. On the device, which allows to control the movement of the tool, plastic sleeves of the sleeves are produced with ensuring the specified degrees of radial deformation: for samples from D16AT alloy from O to 10%, for samples from boroaluminium from O to 1.0%. To ensure the sustainability of the riveted riveting process, the rivet is calibrated to a diameter of 4.0 mm. After testing the samples using the resonance method, the curves for the number of cycles N are obtained before the sample is destroyed (a decrease in the resonant frequency was recorded by no more than 20%) holes. It was found that with a base number of oscillation cycles of M 500 thousand, the optimal degrees of radial deformation are 0.8% for samples from boroaluminium and 1.32% for samples from D16AT.

Holes in boroaluminium1- (x stringers and alloy casing to ensure the required tensions are made by punching, respectively, with the following diameters 3.97 and 3.95 mm. The rivets are inserted into the holes of the assembled elements by means of a hammer About the impulse installation MIU-10 at

15 ZO 5 about 5

0

The discharge rate is 2 kJ. After that, blind holes (1.5 mm in diameter, 6.0 mm in depth) are drilled on the protruding parts of the rivet rods, and then closing rivet heads are formed in two transitions. The panels (6 pieces) are tested at the stand, imitated by the operating conditions.

The proposed sposs of fatigue tests of sheet materials with holes for fasteners allows increasing, by optimizing the tension of the panels, the life of the panels by 30-40% compared to the resource of similar panels made without taking into account the specificity of riveted joints on packages containing fibrous composite materials, to determine operational characteristics of the future connection by imposing practically any configuration of the field of compressive stresses and predict the strength of the joints under operating conditions oatsii and this sharply reduce the volume of full-scale samples of mockups.

In addition, the proposed method allows reducing the test duration by more than 10 times and significantly reducing the amount of test materials, which is very important for structural elements made of fibrous composite materials, since their cost is many times higher than the cost of traditional materials.

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Editor G.-Volkova

Compiled by M. Prokonnchev

Tehred I. VeresKorrektor M. Sharoshi

2108/22

Circulation 777

State / 1 Vienna Committee for Inventory 1 I11 and Discoveries P3 (3), Moscna, F-35, Raushsk iab., 4/5

Production of polygraphic polygraphic P1i d11 and Tie, Uzhgorod, st. Er (I: ctn 1, A

FIG. 6

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Claims (1)

METHOD OF TIRED TESTS OF SHEET MATERIALS WITH HOLES by creating radial compressive forces around the perimeter of the hole for fasteners. Fig. 1 yuo SL ςο with 4 *