CN113740040A - Method for testing grinding burn of shaft - Google Patents

Abstract

The invention relates to a method for checking grinding burns of a shaft, comprising the following steps: a) detecting a plurality of shafts of the same model by using a Barkhausen noise instrument, and selecting a plurality of Barkhausen noise values, wherein the detection is performed at the same axial position of the plurality of shafts, b) determining a corresponding residual stress value for each selected Barkhausen value, c) performing linear regression fitting on all data pairs of the obtained Barkhausen noise values and the corresponding residual stress values, determining the correlation between the Barkhausen noise values and the residual stress values, d) measuring the Barkhausen noise values of the shafts to be detected of the model, and determining the grinding burn of the shafts by combining the determined correlation.

Description

Method for testing grinding burn of shaft

Technical Field

The invention relates to a method for testing grinding burn of a shaft.

Background

Grinding burn generated in the processing process of the shaft part has great influence on the product properties of the shaft part. In particular, grinding burns on the crankshaft can lead to engine failure. Therefore, the method is very important for the inspection of the grinding burn of the shaft parts. To identify such defects, conventional acid and galvanic corrosion tests are commonly used, however such methods are not sensitive to minor grinding burns. In addition, the grinding burn can also be evaluated by detecting the residual stress of the shaft-like part, however, this method causes damage to the shaft-like part and thus cannot be directly applied to the inspection of the grinding burn of the shaft-like part.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for detecting grinding burn of a shaft, which comprises the following steps: a) detecting a plurality of shafts of the same model by using a Barkhausen noise instrument, selecting a plurality of Barkhausen noise values (BHN), wherein the detection is performed at the same axial position of the plurality of shafts, b) determining a corresponding residual stress value (XRD) for each selected Barkhausen value, c) performing linear regression fitting on all data pairs of the obtained Barkhausen noise values and the corresponding residual stress values, determining the correlation between the Barkhausen noise values and the residual stress values, d) measuring the Barkhausen noise values of the shafts to be detected of the model, and determining the grinding burn of the shafts by combining the correlations determined in the steps a) to c).

Advantageously, the targeted adjustment of the grinding parameters produces a burnt shaft which is used in steps a) to c).

Preferably, the grinding parameters include cooling speed during grinding, feeding speed of the grinding wheel, rotating speed of the grinding wheel, and granularity of the grinding wheel.

Advantageously, the plurality of barkhausen noise values comprises a maximum barkhausen noise value.

Advantageously, steps a) to c) are carried out for different axial positions of said plurality of axes, so as to obtain respective correlations.

Advantageously, the detection is performed at different stages of the processing of the shaft.

Advantageously, said all data pairs comprise at least ten data pairs.

Advantageously, the measurement is performed after the shaft has been ground.

Advantageously, the shaft is a crankshaft.

According to the method for inspecting grinding burn of the shaft, the relationship between the residual stress and the Barkhausen noise value is established by combining the Barkhausen noise meter and the residual stress analyzer, so that the residual stress of the shaft to be inspected can be known without damage, and the grinding burn can be inspected. This inspection method enables more accurate determination and more sensitive inspection of grinding burn compared to conventional acid etching and electro-etching.

Drawings

Embodiments according to the present invention are explained in detail below with reference to the accompanying drawings. The figures show:

FIG. 1 illustrates selection of Barkhausen noise values and residual stress values for the crankshaft;

FIG. 2 is a graph relating Barkhausen noise values to residual stress values for a crankshaft.

In the drawings, identical or functionally identical components are provided with the same reference symbols. The embodiments shown in the figures are only schematic representations and do not necessarily show dimensional relationships between the various components. In addition, the examples do not limit the scope of the present invention.

Detailed Description

The invention takes the grinding burn of the crankshaft as an embodiment. According to the present invention, a plurality of crankshafts of the same model are detected by using a barkhausen noise meter, thereby obtaining a large amount of barkhausen noise data. The detection may be performed separately at different stages of the crankshaft machining, for example after the crankshaft has finished grinding or after the crankshaft has finished polishing, etc. Further, different portions of the crankshaft may also be detected. Here, the detection portion may be an outer circle, a fillet, a side wall, or the like of a crankshaft main journal or a connecting rod journal.

Fig. 1 shows a barkhausen noise curve obtained by detecting the side wall of the connecting rod journal 1 at the upper part, in which the horizontal axis represents the angle of rotation of the crankshaft and the vertical axis represents the barkhausen noise value. In the barkhausen noise curve shown in fig. 1, a plurality of points (e.g., BHN1 ═ 341mp, BHN2 ═ 278mp, BHN3 ═ 253mp) are selected, preferably including the point having the greatest noise value (BHN1), and the position on the crankshaft represented by the selected point is determined.

Residual stress measurements are then taken at these locations on the crankshaft, resulting in three residual stress profiles as shown in the middle of FIG. 1. In these graphs, it can be seen that:

for BHN1 at 341mp, the maximum value of residual stress at 0.05mm depth was approximately XRD1 at 290 Mpa;

for BHN2 at 278mp, the maximum value of residual stress at 0.05mm depth was about XRD2 at 254.5 Mpa;

for BHN3 at 253mp, the maximum residual stress at a depth of 0.09mm was approximately XRD3 at 213.2 Mpa.

Three pairs of barkhausen noise values and residual stress values (BHN1, XRD1), (BHN2, XRD2), (BHN3, XRD3) were thus determined.

It should be noted here that more than 3 or less than 3 points may be selected on a certain part of the same crankshaft, for example, on the barkhausen noise curve of the connecting rod journal 1, as long as it is satisfied that the finally selected large number of barkhausen noise values can be as uniform and as dispersed as possible. Preferably, the maximum value is included in the barkhausen noise values.

Furthermore, in order to make the finally determined correlation curve of the barkhausen noise value and the residual stress value reflect the actual characteristics of the crankshaft as much as possible, burned crankshafts can also be manufactured by adjusting the grinding parameters in a targeted manner in the grinding process and the (BHN, XRD) data of the crankshafts can be obtained by carrying out the above detection. Here, the selectable grinding parameters include: cooling speed in the grinding process, feeding speed of the grinding wheel, rotating speed of the grinding wheel, granularity of the grinding wheel and the like. This makes it possible to obtain crankshafts with different grinding burns, so that their barkhausen noise values can cover a different, broader range of values.

Fig. 2 shows all (BHN, XRD) data obtained by testing all connecting rod journal sidewalls of a plurality of crankshafts of the same model and establishing a relationship between a barkhausen noise value and a residual stress value by linear regression. The fitted curve in fig. 2 was obtained from 20 pairs (BHN, XRD) of data and had a linear fit correlation coefficient of 90%. It is also possible to perform a linear regression with more or less data, for example by examining 40 pairs of data, in which case a linear fit correlation coefficient of 80% is also acceptable. However, in order to ensure the reliability of the correlation curve between the barkhausen noise value and the residual stress value, the number of data should be greater than 10 pairs.

According to actual needs, the steps can be carried out on different axial parts of the crankshaft, such as the excircle, fillet or side wall of a main journal or a connecting rod journal of the crankshaft, so as to respectively obtain corresponding relevant curves.

Finally, according to the method according to the invention, after the grinding of the crankshaft is completed, the barkhausen noise values of the crankshaft are conducted without damage to different parts using the barkhausen noise meter, and the determined correlation between the barkhausen noise values and the residual stress values is combined, thereby determining the grinding burn of the crankshaft.

The above embodiments are merely for illustrative purposes to illustrate the present invention, but the present invention is not limited to the embodiments. In particular, the straightness detection card according to the invention is not only used for crankshafts, but also can be used for straightness control of other similar shaft parts. On the basis of the embodiments described, a person skilled in the art will be able to make any modifications, alterations or combinations of the features illustrated in the present description without departing from the scope of protection of the invention.

Claims (9)

1. A method for inspecting a shaft for grinding burn, the method comprising the steps of:

a) detecting a plurality of shafts with the same model by using a Barkhausen noise instrument, selecting a plurality of Barkhausen noise values, wherein the detection is carried out at the same axial position of the shafts,

b) determining a corresponding residual stress value for each of the selected barkhausen values,

c) performing a linear regression fit on all data pairs of the obtained Barkhausen noise values and the corresponding residual stress values, determining a correlation between the Barkhausen noise values and the residual stress values,

d) measuring the Barkhausen noise value for the type of shaft to be inspected and determining the grinding burn of the shaft in combination with the correlation determined by steps a) to c).

2. Method according to claim 1, characterized in that the targeted adjustment of the grinding parameters produces a burnt shaft which is used for steps a) to c).

3. The method of claim 2, wherein the grinding parameters include cooling rate during grinding, feed rate of the grinding wheel, rotational speed of the grinding wheel, and grit size of the grinding wheel.

4. The method of any one of claims 1 to 3, wherein the plurality of Barkhausen noise values comprises a maximum Barkhausen noise value.

5. A method according to any one of claims 1 to 3, wherein steps a) to c) are performed for different axial locations of the plurality of axes, so as to obtain respective correlations.

6. A method according to any one of claims 1 to 3, wherein the detection is performed at different stages of the processing of the shaft.

7. The method of any one of claims 1 to 3, wherein the all data pairs comprise at least ten data pairs.

8. A method according to any one of claims 1 to 3, wherein the measurement is made after the shaft has been ground.

9. The method of any one of claims 1 to 3, wherein the shaft is a crankshaft.

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