SU1455253A1 - Bench for fatigue testing of connecting rods - Google Patents

Abstract

The invention makes it possible to increase the reliability of the test results. The device 2 for installing connecting rods, static and dynamic loading mechanisms and a beam 10 with a movable element 11 and a support 12 are placed on frame 1. The dynamic loading mechanism is made in the form of an exciter 9 oscillations. The placement on the frame of the mechanisms is made on the sides of the support 12 of the beam 10 at its ends. The spring mechanism is made in the form of a package of disc springs 14. The stand allows to obtain large dynamic forces on the tested connecting rod with small dynamic loads of the exciter. 2 Il. .o b

Description

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The invention relates to equipment for testing machine parts and can be used to test rods for internal combustion engines for fatigue strength.

The purpose of the invention is to increase the reliability of the test results at a given asymmetry factor of the loading cycle.

Figure 1 shows the proposed stand, a longitudinal section; figure 2 - section aa in figure 1.

The stand contains a vibration-insulated frame I, on which the device 2 is placed for installation at equal angles to the horizontal with the help of hinges 3 and 4 of two connecting rods 5 and 6 with force sensors 7, a spring mechanism 8

The beam allows to increase the amplitude value of the force acting on the connecting rod, all other conditions being equal, since the displacement S of the spring no longer depends on the displacements caused by the deformation of the oscillating beam on the side of the exciter of oscillations.

The placement of the static loading mechanism and the vibrator at the ends of the beam on the sides of the connecting rod is due to the fact that the placement of the static mechanism between the connecting rod and the inertial vibrator during operation of the stand S resonance mode significantly reduces the accuracy of maintaining the cycle asymmetry factor at a given level.

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static loading, the mechanism of di-20 overcoming the elastic deformation of prosta

with and

- rast

In the case of loading, made in the form of an electrodynamic exciter 9 oscillations and beams 10 with a movable element 11 mounted on it, mounted in bearings of the bearing 12. 25 are as follows: The upper heads of the connecting rods 5 and 6 are hinged on the same axis of the suspension g 13, fixed on the beam 10. The static loading mechanism 8 and the P driver 9 oscillations are placed on opposite sides of the support 12 of the beam 10. The spring loading mechanism 8 of static loading is made in the form of a package of disk-shaped springs 14, upirancy- to the beam 10. 35

The stand works in the following way.

Using the mechanism 8 by means of cup springs 14 acting on the beam 10, the rods 5 and 6 are loaded to a predetermined value of the pre-compression force, which is fixed by means of the force sensor 7. Using the driver 9, the beam 10 oscillates in a vertical plane. The cyclic forces of elastic deformation of the beam 10 developed at the same time provide the specified value of aAglugite of variable force, which is superimposed on the constant component of the s-; In order to pre-compress the connecting rods, JQ provides a predetermined cycle asymmetry factor. The reliability of the test results is increased by stabilizing the force of the preliminary compression of the connecting rods 5 and 6 during the operation of the stand.

Static placement mechanism

loading and exciter -12 oscillations with g on opposite sides of the support

gin, providing pre-compression of the connecting rod and the percussies elastic oscillations in the same phase with the beam, the coefficient; cycle asymmetry

P .... I.,., (O Rost e C S - amplitude of force, ea

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spraying on deformation of the spring; compression and tensioning forces, respectively;

spring stiffness; The displacement of springs is determined by the sum of displacements due to clearances in the hinge joints and connecting rod deformation, and the same deformation of the beam itself in the oscillation mode, taking into account the alignment of the shoulders from the beam end to the connecting rod and to the spring defined by the Kg value.

When testing connecting rods for fatigue, in order to obtain reliable results, it is necessary to implement an asymmetric loading cycle with kits of asymmetry equal to t. The value of the coefficient of asymmetry of the cylinder can vary within

five,

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The beam allows to increase the amplitude value of the force acting on the connecting rod, all other conditions being equal, since the displacement S of the spring no longer depends on the displacements caused by the deformation of the oscillating beam on the side of the exciter of oscillations.

The placement of the static loading mechanism and the vibrator at the ends of the beam on the sides of the connecting rod is due to the fact that the placement of the static mechanism between the connecting rod and the inertial vibrator during operation of the stand S resonance mode significantly reduces the accuracy of maintaining the cycle asymmetry factor at a given level. Since the energy of elastic deformation of the beam is spent additionally on

15

overcoming the elastic deformation of prulu by the formula g where P

gin, providing pre-compression of the connecting rod and the percussion elastic oscillations in one phase with the beam, the coefficient; cycle asymmetry

with and

- rast

In the formula according to where r

P .... I.,., (O Rost e C S - amplitude of force, ea

spraying on deformation of the spring; compressive and expandable forces, respectively;

spring stiffness; spring movement determined by the sum of movements due to gaps in the hinged joints and deformation of the connecting rod, as well as deformation of the beam itself in the oscillation mode, taking into account the ratio of the shoulders from the beam support to the connecting rod and to the spring determined by the Kg value.

When testing connecting rods for fatigue, in order to obtain reliable results, it is necessary to implement an asymmetrical loading cycle with Koailr asymmetry equal to. The value of the loop asymmetry factor can vary within

five,

-them

where P and RIC are loads from gas and inertial forces, respectively.

In order to preload the connecting rod with a force of several tons, it is necessary to use, for example, a high stiffness coil spring and to provide a ratio of arms leverage satisfying the condition Kg 1. On the other hand, in the dynamics, even small movements of the spring will lead to significant changes in the cycle asymmetry factor compared to given its value, especially with an increase due to the development of gaps in the hinged joints during prolonged tests of the connecting rod for fatigue. In addition, the introduction of a spring at the same amplitude of the disturbing force leads to a decrease in the load on the rod.

The implementation of the spring of the static loading mechanism in the form of a packet of disc springs reduces the stiffness C of the spring with a large amount of preload compression of the connecting rod and thus (according to (1))

reduce the value of Kg.

The test bench ensures that the rods are tested for fatigue at a given cycle asymmetry coefficient with a high degree of accuracy of its maintenance throughout the entire testing process, which significantly increases the reliability of the experimental results under conditions close to the real loads acting on the rod in the engine from inertia and gas forces. forces on the strokes of compression and stroke, which, basically, determine the destruction

connecting rod At the proposed stand, with a sufficient degree of reliability, it is possible to work out various designs of connecting rods in order to determine their service life. In addition, the test bench allows to obtain on the tested connecting rod large dynamic tensile stress forces with low dynamic loads of the exciter itself, i.e. the circuit gives a large gain factor ng1) narrow, which additionally increases due to the position of the connecting rods at an angle about the horizontal axis at at 30.

Claims (1)

Invention Formula A bench for testing connecting rods for fatigue, comprising a frame, a device for installing rods, a spring-loaded static loading mechanism, a Dynamic loading mechanism, a beam with a moving element and a beam support, in which a movable element is placed, the device for installing connecting rods, static and dynamic loading mechanisms and a beam with a movable element and support are placed on the frame, and the dynamic loading mechanism is made in the form of a vibration exciter, in order to increase the reliability test results for a given coefficient of asymmetry of the loading cycle, the placement on the frame of the mechanisms of static and dynamic loading is performed on the sides of the beam support at its ends, and the spring mechanism The static load measurement is made in the form of a package of Belleville springs. YU 7 ////// 4i /