Method for judging whether main bearing hole area of engine body fatigue test sample piece fails or not

Abstract

The invention provides a method for judging whether a main bearing hole area of an engine body fatigue test sample piece fails or not. The method comprises the following steps that S1, an ultrasonic probe is installed at the head of a main bearing bolt bearing a test load; s2, measuring and recording the initial length of the bolt in an unloaded state; s3, measuring the dynamic change of the total length of the bolt in real time in the fatigue test process; and S4, judging whether crack failure occurs or not by comparing the deviation between the real-time length and the reference length. According to the method, only the ultrasonic probe needs to be arranged at the head of the main bearing bolt, and the length of the main bearing bolt is measured in the test process, so that the flexibility change of a connected structure is judged, whether cracks appear near the main bearing hole of a machine body or not can be found in time, and the method is simple to operate, sensitive in detection and accurate in result.

Description

Technical Field

[0001] The present invention belongs to the field of fatigue testing, and particularly relates to a method for judging whether the main bearing hole area of a fatigue test specimen of an engine block fails. Background Art

[0002] The fatigue test of an engine block is an important means for checking the strength of the block, and the test results will be used for the evaluation of the engine reliability. At present, the fatigue test of an engine block generally uses a hydraulic fatigue test device; it is very important to judge when the block fails during the test. The currently commonly used failure diagnosis methods are as follows: (1) Visual inspection During the test, regularly check whether there are cracks on the block. It is very difficult to detect the initiation of cracks in a timely and accurate manner by this method. Generally, when cracks are found, they have already propagated or broken. The disadvantage of this method is very low accuracy.

[0003] (2) Video detection Currently, a camera can replace manual visual inspection, but there are still the following problems: a) The space is limited, and it is sometimes very difficult to arrange a camera; b) The failure position is not fixed, and the crack failure part cannot be accurately detected every time; c) There are situations such as oil stains, vibrations, and light changes in the test environment, and it is easy for video monitoring to miss detecting cracks or make misjudgments; (3) Detection through equipment parameters Currently, hydraulic test equipment can perform some detections of equipment parameters. The changes in equipment parameters can assist in diagnosing whether there is a failure. However, due to too many influencing factors during the test, there is also a probability of abnormal changes in various parameters of the test equipment. It is very difficult to accurately diagnose in the actual process. In a large number of cases, it is found that it has already broken when detected.

[0004] (4) Detection through strain or vibration sensors Strain gauges or vibration sensors are arranged on the block, and the diagnosis is carried out by detecting the signal changes. However, if the measuring point position is far from the failure position, the detection accuracy is also relatively low, and accurate judgment cannot be made. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for judging whether the main bearing hole area of a fatigue test specimen of an engine block fails. Only by arranging an ultrasonic probe at the head of the main bearing bolt and measuring the length of the main bearing bolt during the test, the judgment of the change in the flexibility of the connected structure can be realized, and whether there are cracks near the main bearing hole of the block can be detected in a timely manner. This method is simple to operate, sensitive in detection, and accurate in results.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows: A method for judging whether the main bearing hole area of an engine block fatigue test specimen fails, comprising the following steps: S1. Install an ultrasonic probe on the head of the main bearing bolt under the test load; S2. Measure and record the initial length of the bolt in the unloaded state; S3. During the fatigue test, measure the dynamic change of the total length of the bolt in real time; S4. Judge whether crack failure occurs by comparing the deviation between the real-time length and the reference length.

[0007] Further, in step S2, record the initial length of the bolt in the unloaded state as .

[0008] Further, in step S3, start the engine block fatigue test according to the specified load. After the test is stable, record the dynamic change waveform of the total length of the bolt through an ultrasonic measuring instrument, extract a section of the waveform, and take the average value of the peak value of the total length of the bolt as the reference length .

[0009] Further, in step S4, record the total length of the bolt in real time. If the total length of the bolt deviates significantly from the reference length, an alarm is given to prompt inspection and record relevant information, which can also be used to control the shutdown of the test system.

[0010] Further: After the bolt is installed, the bolt pre-tightening force and the compression force of the connected parts are equal; : bolt flexibility, ; : flexibility of the connected parts, ; After the bolt bears the load, the working load is borne by the bolt and the connected parts, ; The bolt elongation and the compression amount of the connected parts are equal. After bearing the load, the total length of the bolt is: ; When a crack appears in the engine block, it will cause the flexibility of the connected parts to increase. When bearing the same load will increase, and then the total length of the bolt will also increase. According to whether the total length of the bolt changes significantly, it can be used to assist in judging whether a crack appears in the engine block.

[0011] Compared with the prior art, the method for judging whether the main bearing hole area of the fatigue test sample of the engine block fails has the following advantages: For the method for judging whether the main bearing hole area of the fatigue test sample of the engine block fails according to the present invention, the failure of the main bearing hole area is the main mode of the fatigue test failure of the engine block. Since the main bearing bolts directly bear the test load and are relatively sensitive to changes in the test state, the present invention does not need to accurately estimate the failure location of the engine block. Only by arranging the ultrasonic probe at the head of the main bearing bolt and measuring the length of the main bearing bolt during the test, the change in the flexibility of the connected structure can be judged, and whether cracks appear near the main bearing hole of the engine block can be detected in time. This method is simple to operate, sensitive in detection, and accurate in results; The ultrasonic measurement system measures the bolt length by the time difference between the transmitted and received ultrasonic pulse electrical signals, and obtains the length change of the bolt by comparing the acoustic time differences in different states. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 It is a schematic diagram of the coordinated deformation relationship between the bolt and the connected body according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0014] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0015] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0017] A method for judging whether the main bearing hole area of a fatigue test specimen of an engine block fails, comprising the following steps: S1. Install an ultrasonic probe on the head of the main bearing bolt under the test load. S2. Measure and record the initial length of the bolt in the unloaded state. S3. During the fatigue test, measure the dynamic change of the total length of the bolt in real time. S4. Judge whether crack failure occurs by comparing the deviation between the real-time length and the reference length.

[0018] Preferably, in step S2, record the initial length of the bolt in the unloaded state as .

[0019] Preferably, in step S3, start the fatigue test of the engine block according to the specified load. After the test is stable, record the dynamic change waveform of the total length of the bolt through an ultrasonic measuring instrument, extract a section of the waveform, and take the average value of the peak value of the total length of the bolt as the reference length .

[0020] Preferably, in step S4, record the total length of the bolt in real time. If the total length of the bolt deviates significantly from the reference length, an alarm will be given to prompt inspection and record relevant information, which can also be used to control the shutdown of the test system.

[0021] Preferably: After the bolt is installed, the bolt pre-tightening force and the compression force of the connected parts are equal; : bolt flexibility, ; : flexibility of the connected parts, ; After the bolt bears the load, the working load is borne by the bolt and the connected parts, ; The elongation of the bolt and the compression amount of the connected parts Equal. After bearing the load, the total length of the bolt is: ; Cracks in the body will cause the flexibility of the connected parts to increase. When bearing the same load will increase, and the total length of the bolt will also increase. Whether the body has cracks can be judged by whether the total length of the bolt changes significantly.

[0022] When there are cracks in the body, the flexibility of the connected parts increases. When bearing the same load will increase, and the total length of the bolt will also increase, with the total length change ΔL. Whether it fails is determined by the magnitude relationship between ΔL and the preset threshold.

[0023] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for judging whether the main bearing hole area of an engine block fatigue test specimen fails, characterized in that: Including the following steps: S1. Install an ultrasonic probe on the head of the main bearing bolt under the test load; S2. Measure and record the initial length of the bolt in the unloaded state; S3. During the fatigue test, dynamically measure the total length change of the bolt in real time; S4. Determine whether crack failure occurs by comparing the deviation between the real-time length and the reference length.

2. A method for determining whether the main bearing hole area of a fatigue test specimen of an engine block fails according to claim 1, characterized in that: In step S2, record the initial length of the bolt in the unloaded state as .

3. A method for judging whether the main bearing hole area of a fatigue test specimen of an engine block fails according to claim 2, characterized in that: In step S3, start the body fatigue test according to the specified load. After the test stabilizes, record the dynamic change waveform of the total bolt length through an ultrasonic measuring instrument, extract a section of the waveform, and take the average value of the peak value of the total bolt length as the reference length .

4. A method for determining whether the main bearing hole area of a fatigue test specimen of an engine block fails according to claim 3, characterized in that: In step S4, the total length of the bolt is recorded in real time. If the total length of the bolt significantly deviates from the reference length, an alarm is given to prompt inspection and relevant information is recorded, which can also be used to control the shutdown of the test system.

5. A method for judging whether the main bearing hole area of a fatigue test specimen of an engine block fails according to claim 1, characterized in that: After the bolt installation is completed, the bolt pre-tightening force and the compression force of the connected parts are equal; : bolt flexibility, ; : Flexibility of the connected parts, ; After the bolt bears the load, the working load is borne by the bolt and the connected parts, ; Bolt elongation and the compression amount of the connected parts are equal. After bearing the load, the total length of the bolt is: ; Cracks in the body will cause the flexibility of the connected parts to increase. When the same load is applied it will increase, and the total length of the bolt will also increase. Whether there is an obvious change in the total length of the bolt can be used to assist in judging whether there are cracks in the body.

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