RU2473065C2 - Bench test method of assemblies and units of motor vehicles - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: comparison tests of two assemblies or units with their attachment components to motor vehicle are conducted at the same and maximum possible steady-state loading mode during operation of the vehicle, which is close to resonant one. At that, one of assemblies or units is reference and has prolonged interval both of running, and bench tests, and has no remarks during operation as a part of the vehicle.

EFFECT: reduction of the time and cost of tests; improvement of reproduction accuracy of the most hazardous loads taking place during the operation, during replacement of out-dated assemblies and units.

3 cl

Description

The method of bench testing of components and assemblies of a vehicle and their fastening elements for durability relates to mechanical engineering, in particular to methods of durability testing of new components and assemblies of vehicles.

A known method of testing the durability of the coupling elements (AS USSR No. 1437718, G01M 15/00), used for accelerated testing of threaded joints of internal combustion engines.

The disadvantage of this method is the need for a preliminary calculation of the values of the stresses arising in the tested clamping elements, and determination of the potential energy of elastic deformation in them for the entire resource of their work. Most components and assemblies of vehicles are complex spatial structures for which it is impossible to accurately calculate the stresses arising in them. In addition, information about the load conditions of the nodes and assemblies of vehicles during their operation are scattered and insufficient. To obtain reliable data on the actual loads occurring in operation, costly lengthy field tests are required.

As a prototype, as the one closest to the claimed technical solution, the method of checking the durability of the units and assemblies of the vehicle (1) is selected, in which the loading mode is set by blocks that take into account the actual operational load and oscillatory mode, taking into account the normative distribution of vehicle mileage over different types of roads and realizing a certain mileage of the car. Since the load and vibrational regime in such units varies over a wide range (from the minimum values of the amplitudes of the accelerations of oscillations to the maximum), the total test time is significant, which leads to their cost increase. At the same time, the minimum values of the amplitudes of the acceleration of oscillations included in the load and oscillatory regimes, slightly affect the decrease in the durability of the vehicle units and their fastening elements.

The purpose of the proposed method for bench testing of units and assemblies of vehicles and their fastening elements is to reduce the time and cost of testing, increase the accuracy of the most dangerous loads that occur in operation when replacing obsolete components and assemblies.

This is achieved by the fact that comparative tests are carried out simultaneously of two nodes or assemblies with elements of their fastening to a motor vehicle with the same and maximum possible steady-state loading mode, which is close to resonant, during car operation. At the same time, one of the units or assemblies is a reference one, having a long time of both road and bench tests, and not having comments during operation as part of a car.

The method is as follows.

Experienced and reference units or assemblies with fasteners are installed on the frame of the test bench, which has geometric and stiffness characteristics that are identical to the frame of the car.

To assign the test mode, the amplitude-frequency characteristic (AFC) installed on the frame of the units or assemblies in the frequency range of the real operational oscillatory mode f _min ... f _{max is} determined, but the load mode is set tenfold lower and the same for the installed units is ensured, i.e. . in order to exclude breakdowns of the tested nodes or assemblies when determining the frequency response, the rms values (hereinafter RMS) of the vibration accelerations on the frame side members and _experience and the _standard in the section of the center of mass installed on the frame of the experimental and reference components or assemblies are set from the condition: (and _experience = a _standard ) ≤0.1a _max , where a _max is the maximum possible RMS of vibration acceleration on the frame side members when operating the car.

According to the results of measuring the RMS of vibration accelerations at the control points of the experimental and reference unit or assembly and the elements of their fastening to the frame of the stand, the dependencies are built: Н _standard (f) = а _et.node / а _standard , N _experience (f) = а _op.node / a _experience , where a _et.node and _a.op.node are measured RMS of vibration accelerations at control points of the experimental and reference unit or assembly.

According to the obtained dependences H _i (f), eigenfrequencies of vibrations _{fresi of the} experimental and reference unit or assembly mounted on the frame are detected, the frequency of the exciting effect f _{duty is} determined from the condition:

f _debt ≤ (0.5 ... 0.8) f _rez.gl.i.

In this case, the difference in the magnitude of the amplitudes of vibration acceleration of the units is determined. At frequency f _{debt, the} difference in the magnitude of the amplitudes of the acceleration oscillations of the units mounted on the stand is minimal:

(and _experience ≈a _standard ) ≤a _max ,

(and _{experience is the standard} ) / and the _standard × 100≤10%,

f _rez.gl.i - the first natural frequencies of oscillations of the experimental and reference node or unit.

In the process of durability tests, the ratio of the rms values of vertical accelerations at the experimental and reference units or assemblies, their fasteners, and the stand frame spar is used as a criterion for loss of performance. When their magnitude changes by more than 15%, the tests are stopped, a visual inspection is carried out to detect cracks and fractures of the experimental and reference unit or assembly, their fastening elements or frame spars. When an experimental unit or unit has accumulated a basic number of loading cycles or greater than that of the reference one, the experimental unit or unit is deemed suitable for use in a vehicle.

Given that the claimed technical solution has novelty, the presence of distinctive features and industrial applicability, the applicant believes that it can be protected by a patent for an invention.

Literature

1. VB Tsymbalin and others, "Tests of cars", M., ed. "Engineering", 1978

Claims (3)

1. The method of bench testing of units, assemblies of the car and their fastening elements for durability, which consists in the fact that the tested units and their fastening elements are installed on the frame of the stand, identical in geometric and stiffness characteristics to the frame of the car; to assign a test mode determine the amplitude-frequency characteristic of the units with the elements of their fastening; determine the resonant frequency, characterized in that they establish the frequency of the exciting effect f _debt , at which comparative tests are carried out for a pair of units, one of which is a reference, and their fastening elements; determine the difference in the magnitude of the amplitudes of vibration acceleration of the nodes, units. 2. The method of bench testing of units and their fastening elements for durability according to claim 1, characterized in that for assigning the test mode, the amplitude-frequency characteristic of the units with their fastening elements is determined in the frequency range of the real operational vibrational mode, but the load mode is set for all units tenfold lower relative to the maximum operational vibration acceleration. 3. The method of bench tests of vehicle assemblies and their fastening elements for durability according to claim 1, characterized in that the frequency of the stimulating effect f _debt is determined in the range (0.5 ... 0.8) from the resonance, with the difference in the magnitude of the amplitudes of the vibration accelerations aggregates is not more than 10%.