JP4218007B2 - Projection coverage confirmation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection coverage confirmation method for confirming / evaluating the projection coverage (the progress of peening, the processing rate) in the surface processing of shot peening and shot blasting to improve fatigue life.
[0002]
[Prior art]
Parts used under high stress conditions, such as gas turbine disks and shafts, are subject to low cycle fatigue due to repeated engine start / stop cycles. Therefore, data for determining the lifetime is required in the design of the component, but it is known that the lifetime is different from the actual lifetime when the lifetime is determined based on data based on a material having no stress or a deteriorated layer.
[0003]
This is because in an actual part, a tensile stress or a thin deteriorated layer is generated on the surface during processing, which shortens the fatigue life.
In order to improve such a fatigue life, it is only necessary to reduce the tensile stress remaining in the component or to generate a compressive stress. For this purpose, surface processing (peening processing) such as shot peening is performed.
[0004]
Shot peening (hereinafter simply referred to as “peening”) is a cold working method in which many particles of steel, glass, ceramic, etc., called shots, are projected onto the surface of an object (actual part) with air or a rotating impeller. By this processing, the object surface is dented, stretched and plastically deformed, and compressive stress remains on the object surface.
[0005]
Here, peening specifies the peening strength (peening strength) and the degree of peening (projection coverage (COVERAGE), progress) according to the peening object in order to generate the desired residual stress on the object surface. Done.
[0006]
The peening intensity is determined by conditions such as shot size and projection speed. As a method for measuring the peening intensity, the method disclosed in US Pat. No. 2,350,440 is generally used. Yes.
[0007]
As shown in FIGS. 3A to 3C, this peening strength measuring method is performed on a strip-shaped test piece 2 (standardized test piece called “almen piece”) fixed to the upper surface of the holder 8. The shot 16 is directly projected from the peening nozzle 11 under the same predetermined projection conditions as when peening an actual object on the entire surface, and then subjected to peening. As shown in FIGS. By measuring the amount (arc height) h, that is, the magnitude of deformation (warpage) generated in the test piece using the dial gauge 13, the peening strength under this condition and the corresponding residual stress (compressive stress) ) Is measured indirectly.
Therefore, the correlation between the peening strength and the residual stress can be obtained by repeating the measurement while changing the predetermined projection condition in various ways.
[0008]
On the other hand, the projection coverage of peening is proportional to the number of shot balls that collided with a predetermined area of the object surface, and is determined by the degree of progress (projection coverage (%)) defined by the area of the peened portion relative to the area of the projection surface. As shown, as a method of confirming this projection coverage,
(1) A method for estimating projection coverage by directly observing the peening surface (2) A method for estimating projection coverage by applying paint to the peening surface and inspecting the degree of peeling after projection (US Pat. No. 3,950,642) )
(3) A method of inspecting the peening surface surface shape (surface roughness) of an entity that has been peened for a time shorter than the actual time and estimating the projection coverage from the shot projection time based on this (US Pat. No. 5,581,483) No., US Pat. No. 5,003,805)
(4) After fixing a standardized test piece called an almen piece to a holder, it is attached to a jig simulating the substance (actual part) and a shot is projected onto it to inspect the surface roughness of the surface. The method to do is used.
[0009]
For reference, a micrograph after peening of the projection surface is shown in FIG. In this photo, the black part is the part where the shot collided (peening area: the part where the projection has changed), (a) the projection coverage is about 45%, and (b) the projection coverage is about 65%. , (C) is for a projection coverage of about 95%.
[0010]
[Problems to be solved by the invention]
However, in the projection coverage confirmation method according to (1) above, (1) it is difficult to visually inspect the narrow part depending on the shape of the part. (2) When confirming the projection projection coverage using actual parts. Is expensive for multiple tests to determine the conditions for peening. (3) Use of a discarded product or a jig simulating a solid shape can reduce the cost of the test, but obtaining a discarded product Is difficult, and there is a problem in economy with jigs that cannot be used repeatedly. (4) If the surface of parts is not allowed to be polished before peening, the measurement accuracy will be reduced. (5) Surface polishing of complex shapes is troublesome. There was a problem that it took.
[0011]
Also, in the projection coverage confirmation method according to (2) above, although there is no need to polish the surface of the object, (1) there are restrictions on the number of tests (1), and (2) it is difficult to obtain discarded products, (3) There is a problem with economic efficiency, and (4) it is necessary to know in advance the relationship between paint peeling and projection coverage, and (5) projection projection is only estimated. As a result, there is a problem that a final confirmation inspection is always necessary.
[0012]
Furthermore, in the method (3), (1) it is difficult to visually inspect the narrow part, (2) there are restrictions on the number of tests, (3) it is difficult to obtain discarded products, and (4) polishing before peening. The measurement accuracy depends on the presence or absence of (5), and (5) the projection coverage is estimated in the same manner as in (2) above, so that there is a need for a confirmation check on the substance.
[0013]
In the method (4), (1) since the projection coverage is inspected by using an alumen material different from the actual material, the relationship of the projection coverage between the material of the almen piece and the material of the actual part is grasped in advance. (2) In the same way as above, confirmation inspection with substance is finally necessary, and (3) In the case of parts with complicated shapes, there may be a part that cannot be inspected because the holder cannot be created. Yes, and (4) there were problems such as the need for a final confirmation test.
[0014]
The present invention has been made in view of the above problems, and enables visual inspection of projection coverage of a narrow portion of an object, can reduce the cost of performing a projection coverage confirmation test, and can improve measurement accuracy. An object of the present invention is to provide a projection coverage confirmation method that solves the problems of the conventional method.
[0015]
[Means for Solving the Problems]
In order to solve the above problem, the present invention is a projection coverage confirmation method for obtaining a correlation between the progress of a peening process on a processed surface of a target object and a shot projection time before performing the peening process on the target object. The surface of the simulation tool created in the same surface shape as the target object is made of the same material as the target object , has a mirror-like polished surface, and has a size that can be applied to the narrow part of the simulation tool. A first step of attaching a thin plate-shaped test piece with the polishing surface as a front surface, a second step of peening the surface of the simulated tool for a predetermined time under a predetermined projection condition, and taking out the test piece and polishing it viewed including a third step of measuring the progress of peening by observing the surface, the projection coverage by repeating the third step from the first step and obtaining the 100% consisting time Projection To provide a storage confirmation method.
[0016]
As described above, the peening is performed after a test piece made of the same material as the object is pasted on the surface of the actual object (part) using a simulation tool that simulates the object before the peening process. A projection coverage confirmation method that can solve all the problems, is easy to implement, and is highly accurate and economical is provided.
In other words, according to the present invention, (1) it is possible to perform a test under the same environment as the actual object by using a simulation tool, and (2) the plasticity is obtained by using a test piece made of the same material as the object. The deformation state can be faithfully reproduced. (3) By attaching a test piece and using it in a peening performed on a narrow part, it is possible to take out this and visually check the projection coverage, and (4) Since the test piece is sufficiently small, it can be affixed even if the projection surface of the object has a complicated shape. (5) The test cost can be reduced by using a test piece that can be manufactured at low cost. (6) The surface of the test piece is easy to polish, and (7) The simulation tool itself can be used repeatedly only by replacing the test piece even when performing multiple tests. (8) Projection coverage Confirmatory test is not required in the final entity because it is not intended to estimate, excellent projection coverage confirmation method which has the effect of like are provided.
[0017]
Here, the degree of progress of the peening process can be measured by visually observing the polished surface using a magnifying glass, or by measuring the area ratio of the portion of the polished surface that has undergone projection alteration.
[0018]
Since a test piece can be taken out after peening, projection coverage can be easily confirmed by evaluating this visually or by using a general surface roughness measuring machine.
[0019]
In a preferred embodiment, the test piece is affixed using an adhesive or a double-sided adhesive tape.
[0020]
By attaching a test piece to the surface of the simulation tool using an adhesive or a double-sided pressure-sensitive adhesive tape, the attachment and removal are simplified, and the test is facilitated. In addition, it has been confirmed by the effect verification test of the present invention that the test piece does not come off the simulated tool even by peening.
[0021]
Moreover, it is preferable that the said simulation tool uses the same kind of discarded parts as a target object.
[0022]
As described above, in the present invention, the simulation tool itself can be used repeatedly, so as long as only one disposal part is obtained, it is possible to perform a plurality of tests by simply replacing the test piece. The cost of performing the test can be reduced. In the test, no special pretreatment (mirror polishing, etc.) is required for the discarded parts.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a projection coverage confirmation test using the projection coverage confirmation method according to the present invention will be described.
[0024]
As described above, peening is performed by applying a shot of fine particles of steel, glass, ceramic, etc. to the surface of an object, that is, an actual part (especially a rotating part such as a blade, a turbine disk, or a shaft). In order to improve the fatigue life of the part by projecting a large number of projections, making the part surface concave and plastically deforming, erasing the tensile stress and altered layer generated on the part surface when processing the part, and leaving the compressive stress remaining It is a surface processing treatment.
[0025]
Actual part peening is often performed with a projection coverage in the range of 100 to 200%. However, when the projection coverage exceeds 100%, the measurement cannot be easily performed, so that the projection coverage is 100%. Time is obtained, and a shot is projected for a projection time predicted to be a desired projection coverage based on this time. Therefore, it is important to accurately obtain the projection time at which the projection coverage is 100%.
[0026]
The projection coverage confirmation test is a projection condition determined by a certain shot size and projection speed, etc., using a simulation tool created on the same surface shape as that part before peening the actual part, that is, Under a certain peening intensity, the shot projection time is changed variously, the progress of the peening process on the projection surface (projection coverage) is measured, and the relationship between the projection time and the projection coverage is obtained from the results, and By intensively testing before and after the projection time when the projection coverage is expected to be 100%, the time when the projection coverage is 100% is accurately obtained by an actual test.
When the correlation between the projection time and the projection coverage is obtained, it is possible to perform peening with a desired projection coverage when peening an actual part.
[0027]
This projection coverage confirmation test can be used to confirm the projection coverage for any part of the part to be peened. In particular, the surface of the narrow part as shown in FIG. This is very useful when confirming the projection coverage of the projection surface 5 having a complicated shape such as the inner peripheral surface of the attachment portion of the blade (not shown).
[0028]
The confirmation test is performed according to the following procedure.
First, the simulation tool 2 having the same surface shape as the projection surface 5 of the component 7 that is the peening object is manufactured (FIG. 2). In addition, if the used disposal part which is the same kind parts can be obtained, this can be used as a simulation tool, and the manufacture of the simulation tool for the test becomes unnecessary.
Separately from this, the test piece 4 is manufactured using the same material as the actual part. As shown in FIG. 2A, the test piece has a thin plate-like rectangular parallelepiped shape, and one surface thereof is a polished surface 4a polished in a mirror shape. The size of the test piece 4 is “3 × 2 × 1 mm” in the “vertical (l) × horizontal (w) × thickness (t)” in this test. In addition, the magnitude | size of a test piece is not limited to this, It can also change suitably as needed.
A test piece is affixed with a double-sided adhesive tape (not shown) with the polished surface 4a as a table at a location where the progress of the projection coverage of the simulation tool 2 from which dirt on the surface has been removed is to be measured.
In this state, the shot 16 is projected from the shot nozzle 11 for a predetermined time under the same projection conditions as when peening is performed on an actual part, and peening is performed (FIG. 2B).
Finally, the test piece is taken out and the polished surface is visually observed using a microscope to measure the area of the peened portion. The progress of peening (projection coverage (%)) is calculated from the area of the peened portion relative to the mirror surface area (6 mm ² ) of the test piece.
In this case, the polished surface 4a of the test piece 4 is in a state of being lifted from the simulation tool 2 by the thickness t, but it has been demonstrated that a thickness of about 1 mm hardly affects the calculated value of the projection coverage. Has been. However, the test may be performed by forming a recess in the simulation tool 2 so that the polished surface 4a of the test piece 4 is flush with the surface of the simulation tool.
[0029]
In the confirmation test according to the above procedure, the shot projection time is changed in various ways, the correlation between each projection time and the progress of the peening process (projection coverage) is obtained, and the projection time at which the projection coverage is 100% is estimated. Instead, by accurately obtaining the projection time by an actual test, it is possible to accurately perform peening with a desired projection coverage when machining an actual part on the basis of this.
[0030]
In this verification test, the state of plastic deformation that occurs in a part can be easily and faithfully faithfully measured by using a simulation tool that has the same surface shape as the actual part and a test piece made of the same material as the actual part. As a result, a large number of tests can be easily performed, and the projection time at which the projection coverage is 100% can be accurately obtained.
[0031]
Note that the present invention is not limited to the above-described embodiments and examples, and can be variously modified without departing from the gist of the present invention.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to easily perform visual inspection of the projection coverage of the narrow part of the object, reduce the cost of performing the projection coverage confirmation test, and confirm the projection coverage with high measurement accuracy. A method is provided, and the relationship between the projection time and the projection coverage is accurately obtained from the result of the projection coverage measurement test by the method, and when peening is performed on an actual part, peening can be performed with a desired projection coverage.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a projected surface of an actual part that is an object.
FIG. 2 is a conceptual diagram showing an embodiment of the present invention.
FIG. 3 is a diagram showing a peening intensity measuring method.
FIG. 4 is a photomicrograph after peening of the projection surface.
[Explanation of symbols]
2 Simulating tool 4 Test piece 4a Polished surface 5 Projected surface 7 Parts 8 Holder 11 Peening nozzle 13 Dial gauge 16 Shot

Claims (5)

A projection coverage confirmation method for obtaining a correlation between the progress of peening on the machined surface of the object and the shot projection time before subjecting the object to peening , the same surface shape as the object On the surface of the simulated tool prepared in the above, a thin plate-shaped test piece made of the same material as the object and having a mirror-like polished surface and capable of being attached to a narrow part of the simulated tool is applied to the polished surface. Progression of peening process by taking out the test piece and observing its polished surface, the first stage for pasting as a table, the second stage for peening the simulated tool surface for a predetermined time under a certain projection condition third step and, only including, the projection coverage by repeating the third stage from the first stage to seek 100% becomes time, projected coverage confirmation method characterized by measuring the degree. The projection coverage confirmation method according to claim 1, wherein the progress of the peening process is measured by visually observing the polished surface using a magnifying glass. The projection coverage confirmation method according to claim 1, wherein the progress of peening is measured by measuring an area ratio of a projection-deformed portion of the polished surface . The projection coverage confirmation method according to claim 1, wherein the test piece is affixed using an adhesive or a double-sided adhesive tape. 5. The projection coverage confirmation method according to claim 1, wherein the simulation tool uses a disposal component of the same type as the object.

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