CN115329570A - Method for improving and predicting room temperature bending fatigue life of ceramic part containing microcracks - Google Patents
Method for improving and predicting room temperature bending fatigue life of ceramic part containing microcracks Download PDFInfo
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Abstract
The invention discloses a room temperature bending fatigue life improving and predicting method for a ceramic part containing microcracks, belonging to the technical field of mechanical structure strength, and the method comprises the following steps: collecting the space information of microcracks on the original ceramic piece, and testing the power index and the critical fatigue life of the original ceramic piece; processing the microcracks into circular holes according to the spatial information of the microcracks, and performing a polishing and cleaning procedure on the circular holes to obtain a processed ceramic piece, thereby finishing the improvement of the room-temperature bending fatigue life; measuring the size of the round hole to obtain the radius and the sectional area of the round hole, and calculating the stress limit of the processed ceramic part under the action of the static load by using the radius and the sectional area; drawing an S-N curve of the processed ceramic part by using the stress limit, the power index and the critical fatigue life; and testing the maximum bending stress of the processed ceramic part, and taking the abscissa corresponding to the maximum bending stress on the S-N curve as the prediction result of the room-temperature bending fatigue life.
Description
Technical Field
The invention relates to a method for improving and predicting room-temperature bending fatigue life of a ceramic part containing microcracks, belonging to the technical field of mechanical structure strength.
Background
The ceramic is well known due to the characteristics of light weight, high strength, high hardness, high wear resistance and the like, can replace metal to be used for manufacturing bearings, connecting rods, valves, sealing rings, cutting tools and the like, but the cracking of the ceramic is easily caused by microcracks due to the intrinsic brittleness and low damage tolerance of the ceramic, and particularly in the use scenes of the bearings, the connecting rods, the tools and the like under cyclic bending load, the random fatigue failure of the ceramic parts caused by the microcracks is very serious, so that the ceramic parts are easy to break under a low stress level on one hand, and the fatigue life of the ceramic parts is greatly reduced on the other hand.
At present, the improvement method and the prediction method of the room-temperature bending fatigue life of the ceramic part are not researched too much, the improvement effect is poor, and the prediction accuracy is low.
Disclosure of Invention
The invention aims to provide a method for improving and predicting the room-temperature bending fatigue life of a ceramic part containing microcracks, which solves the problems of poor room-temperature bending fatigue life improving effect, low prediction accuracy and the like in the prior art.
In order to realize the purpose, the invention adopts the following technical scheme:
the invention provides a method for improving and predicting the room-temperature bending fatigue life of a ceramic part containing microcracks, which comprises the following steps:
collecting the space information of microcracks on the original ceramic piece, and testing the power index and the critical fatigue life of the original ceramic piece;
processing the microcracks into circular holes according to the spatial information of the microcracks, and performing a polishing and cleaning procedure on the circular holes to obtain a processed ceramic piece, thereby finishing the improvement of the room-temperature bending fatigue life;
measuring the size of the round hole to obtain the radius and the sectional area of the round hole, and calculating the stress limit of the processed ceramic part under the action of the static load by using the radius and the sectional area;
drawing an S-N curve of the processed ceramic part by using the stress limit, the power index and the critical fatigue life;
and testing the maximum bending stress of the processed ceramic part, and taking the abscissa corresponding to the maximum bending stress on the S-N curve as the prediction result of the room-temperature bending fatigue life.
Furthermore, the spatial information comprises length, depth and position coordinate parameters, and is acquired through a nondestructive testing process.
Further, the processing the microcracks into circular holes according to the spatial information of the microcracks comprises:
finding the microcrack according to the position coordinate parameters, processing the microcrack into a circular hole by using a femtosecond laser processing procedure, wherein the parameters of the femtosecond laser processing procedure are set according to the depth of the microcrack, so that the depth of the circular hole is ensured to be 80-110% of the depth of the microcrack, and the diameter of the circular hole is 100-120% of the length of the microcrack.
Further, the size measurement of the circular hole to obtain the radius and the sectional area thereof includes:
measuring the diameter of the circular hole by using an optical microscope to obtain the radius of the circular hole;
and measuring the sectional area of the round hole by using a roughness analyzer, and ensuring that the measured section is parallel to the bending loading direction during measurement.
Further, the stress limit of the machined ceramic part under the action of the static load is calculated by using the radius and the sectional area, and the stress limit is calculated by the following formula:
wherein R is 0 Is a mechanical constant solved based on the Poisson's ratio, the fracture toughness and the original strength, v is the Poisson's ratio, K Ic For fracture toughness, σ 0 As the original intensity, σ f Is the stress limit under pure I-type failure mode, n is a constant solved based on Poisson's ratio, area is the sectional area of the circular hole, r is the radius of the circular hole, H is a constant solved based on Poisson's ratio, mechanical constant and radius of the circular hole, and sigma is fm The stress limit in the mixed failure mode is obtained, L is the bending moment arm of the ceramic part, B is the half width of the ceramic part, and x and y are the offset of the center of the circular hole in the length direction and the width direction of the ceramic part, which are observed by an optical microscope;
the stress limit in the hybrid failure mode is taken as the stress limit under the static load.
Further, the constant n is solved based on the poisson ratio by the following method:
the constants n are 0.629 and 0.650 when the poisson's ratio is 0 and 0.3, respectively;
when the poisson's ratio is other, the constant n is obtained by interpolation.
Further, the constant H is solved based on the Poisson's ratio, the mechanical constant and the radius of the circular hole by the following method:
when the Poisson's ratio is 0.1, 0.15, 0.2, 0.25 and 0.3, respectively, when R is 0 The constant H is 0.6294, 0.6215, 0.6104, 0.596 and 0.5785 respectively if/R is 0.0005, if R is 0 The constants H are 0.6286, 0.6207, 0.6095, 0.5952 and 0.5777, respectively, if R is 0.001 0 The constant H is 0.6225, 0.6145, 0.6033, 0.5889 and 0.5714 respectively if/R is 0.005 0 The constants H are 0.6149, 0.6068, 0.5956, 0.5813 and 0.5638 respectively if/R is 0.01, if R is 0 The constants H are 0.5599, 0.5515, 0.5401, 0.5258 and 0.5086 respectively if/R is 0.05 0 A constant H is 0.1 for rRespectively 0.5028, 0.4942, 0.4828, 0.4687 and 0.4518, if R 0 The constant H is 0.3528, 0.3445, 0.3341, 0.3216 and 0.3069 if/R is 0.3, respectively 0 The constants H are 0.2672, 0.2599, 0.2508, 0.2401 and 0.2276 if/R is 0.5, respectively 0 The constants H are 0.159, 0.1537, 0.1473, 0.1399 and 0.1314 when/r is 1;
when poisson's ratio and R 0 When/r is other values, the constant H is obtained by interpolation.
Further, the power index k and the critical fatigue life N of the original ceramic piece are tested fc The method comprises the following steps:
the method comprises the steps of testing S-N curves of an original ceramic piece with at least 6 stress levels by using a room temperature bending fatigue testing method, testing odd samples with more than 3 stress levels at each stress level, drawing a testing result into an S-N curve of a log-log coordinate system, obtaining a power index of the S-N curve of the original ceramic piece by taking a median value and performing linear fitting, and obtaining the critical fatigue life at a fatigue limit according to the fitting result of the S-N curve.
Further, the drawing of the S-N curve of the processed ceramic part by using the stress limit, the power index and the critical fatigue life includes:
in a log-log coordinate system, a coordinate point (1, σ) fm ) As a starting point, drawing a slope line by taking the power exponent k of the original ceramic piece as the slope, and taking the critical fatigue life N of the original ceramic piece fc Drawing an S-N curve of the processed ceramic piece for the end point of the oblique line and then for the horizontal transverse line;
wherein σ fm Is the stress limit of the machined ceramic part under a static load.
Further, the maximum bending stress is obtained by testing the processing ceramic piece through a bending stress sensor.
Compared with the prior art, the invention has the following beneficial effects:
according to the method for improving and predicting the room-temperature bending fatigue life of the ceramic part containing the microcracks, provided by the invention, the microcracks with high sensitivity to stress are processed into the round holes with low sensitivity to the stress to obtain the processed ceramic part, so that the fatigue failure probability of the ceramic part containing the microcracks can be effectively reduced, and the fatigue life of the ceramic part containing the microcracks is greatly prolonged; by calculating the stress limit of the processed ceramic part under the action of a static load, combining the power index and the critical fatigue life test of the original ceramic part, combining the stress state analysis of the combined force in the prediction process of the room-temperature bending fatigue life, improving the prediction accuracy of the room-temperature bending fatigue life of the ceramic part, and providing technical support for the reliable application of bending-resistant parts such as ceramic bearings, connecting rods and the like.
Drawings
FIG. 1 is a flow chart of a method for improving and predicting room temperature bending fatigue life of a microcracked ceramic article according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a femtosecond laser processing position of a circular hole provided by an embodiment of the invention;
fig. 3 is an S-N curve of a 3Y-TZP ceramic part for different situations provided by an embodiment of the present invention.
Detailed Description
The present invention is further described with reference to the accompanying drawings, and the following examples are only for clearly illustrating the technical solutions of the present invention, and should not be taken as limiting the scope of the present invention.
Example 1
As shown in fig. 1, a method for improving and predicting room temperature bending fatigue life of a ceramic part with microcracks, provided by an embodiment of the present invention, includes:
s1, collecting space information of microcracks on an original ceramic piece, and testing the power index and the critical fatigue life of the original ceramic piece.
And finding the microcrack on the surface of the original ceramic piece by utilizing a nondestructive testing process, and extracting the spatial information of the microcrack, wherein the spatial information comprises the length, the width and the position coordinate parameters of the microcrack.
And S2, processing the microcracks into circular holes according to the spatial information of the microcracks, and performing a polishing and cleaning procedure on the circular holes to obtain a processed ceramic piece, thereby finishing the improvement of the room-temperature bending fatigue life.
Finding the microcrack according to the position coordinate parameters, processing the microcrack into a circular hole by using a femtosecond laser processing procedure, wherein the parameters of the femtosecond laser processing procedure are set according to the depth of the microcrack, so that the depth of the circular hole is ensured to be 80-110% of the depth of the microcrack, and the diameter of the circular hole is 100-120% of the length of the microcrack.
And (3) polishing and cleaning the round hole, and removing trace burrs and remelting and recrystallizing residues remained in a femtosecond laser processing area so as to ensure the accuracy of subsequent round hole size measurement.
According to the processed ceramic part obtained by the step, the microcracks with high sensitivity to the stress are processed into the round holes with low sensitivity to the stress, so that the fatigue failure probability of the ceramic part containing the microcracks can be effectively reduced, the fatigue life of the ceramic part is greatly prolonged, and the improvement of the room-temperature bending fatigue life is completed.
And S3, measuring the size of the round hole to obtain the radius and the sectional area of the round hole, and calculating the stress limit of the processed ceramic part under the action of the static load by using the radius and the sectional area.
The diameter 2r of the circular hole was measured by an optical microscope to obtain the radius r thereof.
And measuring the sectional area of the round hole by using a roughness analyzer, and ensuring that the measured section is parallel to the bending loading direction during measurement.
Respectively measuring the original intensity sigma of the ceramic according to national standards GB/T37781-2019, GB/T23806-2009 and GB/T38897-2020 0 Fracture toughness K Ic And a Poisson's ratio v, according to v, a value of n is obtained by interpolation, where v is 0 and 0.3, n is 0.629 and 0.650, and where v is other values, n is obtained by interpolation.
Using a formula
Calculation of R 0 ，R 0 Is a mechanical constant solved based on Poisson's ratio, fracture toughness and initial strength.
By means of R 0 The values of/r and v give the constant H:
when the Poisson's ratios are 0.1, 0.15, 0.2, 0.25 and 0.3, respectively, when R is 0 The constant H is 0.6294, 0.6215, 0.6104, 0.596 and 0.5785 respectively if/r is 0.0005R 0 The constants H are 0.6286, 0.6207, 0.6095, 0.5952 and 0.5777 respectively if/R is 0.001 0 The constants H are 0.6225, 0.6145, 0.6033, 0.5889 and 0.5714 respectively if/R is 0.005 0 The constants H are 0.6149, 0.6068, 0.5956, 0.5813 and 0.5638 respectively if/R is 0.01, if R is 0 The constants H are 0.5599, 0.5515, 0.5401, 0.5258 and 0.5086 respectively if/R is 0.05 0 The constants H are 0.5028, 0.4942, 0.4828, 0.4687 and 0.4518 respectively if/R is 0.1, if R is 0 The constants H are 0.3528, 0.3445, 0.3341, 0.3216 and 0.3069 if/R is 0.3, respectively 0 The constants H are 0.2672, 0.2599, 0.2508, 0.2401 and 0.2276 if/R is 0.5, respectively 0 The constants H are 0.159, 0.1537, 0.1473, 0.1399 and 0.1314 when/r is 1; when poisson's ratio and R 0 When/r is other values, the constant H is obtained by interpolation.
Using formulas
Calculating the stress limit sigma of the ceramic part processed under the pure I-type failure mode f 。
Measuring the bending moment arm L of the processed ceramic part and the half width B of the processed ceramic part by using a distance measuring instrument such as a vernier caliper or a laser distance measuring instrument; the offset x of the center of the circular hole in the length direction of the ceramic part and the offset y of the center of the circular hole in the width direction of the ceramic part are measured by using an optical microscope, and particularly, the measurement precision is required to be lower than the size of the ceramic part by one order of magnitude.
Using a formula
Calculating the stress limit sigma of the ceramic part processed in the mixed failure mode fm 。
And S4, drawing an S-N curve of the processed ceramic part by utilizing the stress limit, the power index and the critical fatigue life.
Testing S-N curves (stress-life curves) of the original ceramic piece with at least 6 stress levels by using a room temperature bending fatigue testing method, testing odd number of samples with more than 3 stress levels, and drawing a testing result into an S-N curve of a dual logarithmic coordinate systemObtaining the power exponent k of an S-N curve of the original ceramic piece by taking the median value and fitting linearly, and obtaining the critical fatigue life N at the fatigue limit according to the fitting result of the S-N curve fc 。
Sigma by calculation and testing fm K and N fc In a log-log coordinate system, a coordinate point (1, σ) fm ) As a starting point, drawing a slope with the power exponent k as the slope, and using N as the slope fc And drawing an S-N curve of the processed ceramic piece for the end point of the oblique line and the horizontal transverse line.
And S5, testing the maximum bending stress of the processed ceramic part, and taking the abscissa corresponding to the maximum bending stress on the S-N curve as the prediction result of the room-temperature bending fatigue life.
Obtaining the actual maximum bending stress sigma of the processed ceramic part by using a sensor test max At σ of max Substituting the ordinate into an S-N curve of the ceramic part to be processed to obtain a corresponding abscissa numerical value, namely the room-temperature cyclic fatigue life of the ceramic part to be processed under corresponding conditions.
According to the method, the high-precision femtosecond laser processing technology is utilized to process the microcracks with high sensitivity to stress into the round holes with low sensitivity to stress, the method can effectively reduce the fatigue failure probability of the ceramic part containing the microcracks, and the fatigue life of the ceramic part is greatly prolonged; in addition, the invention can effectively reduce the dispersity of the fatigue failure life of the ceramic part, and greatly reduces the traditional dispersity of 5-6 orders of magnitude to 1-2 orders of magnitude; by combining with the stress state analysis, the invention can accurately predict the bending fatigue life of the ceramic part and can provide technical support for the reliable application of bending-resistant parts such as ceramic bearings, connecting rods and the like.
Example 2
The embodiment of the invention provides a room temperature bending fatigue life improving and predicting method for a ceramic part containing microcracks, which is implemented by the following steps:
the nondestructive testing procedure is utilized to find the microcracks on the surface of the 3Y-TZP ceramic piece (the original ceramic piece described in the embodiment 1), the length and the depth of the extracted microcracks are respectively 40 μm and 30 μm, and for the convenience of subsequent comparison, the sections of the microcracks are measured at the same timeVolume size of 715 μm 2 And a position coordinate parameter.
And processing the microcrack region into a circular hole by using a femtosecond laser processing procedure, wherein the central wavelength, the pulse width, the repetition frequency, the power, the ocular magnification factor and the scanning speed of the femtosecond laser ocular are 780nm, 120fs, 80MHz, 20mW, 20 times and 5 mu m/s respectively.
Grinding and polishing the round hole by using 2000-mesh sand paper, ultrasonically cleaning, removing trace burrs and re-melting and re-crystallizing residues remained in a femtosecond laser processing area to obtain a processed ceramic part, measuring the diameter 2r of the round hole by using an optical microscope to be 40 mu m, wherein the radius r is 20 mu m, and measuring the cross section area of the round hole with the cross section parallel to the bending loading direction by using a roughness analyzer to be 1120 mu m 2 。
According to national standards GB/T37781-2019, GB/T23806-2009 and GB/T38897-2020, respectively measuring original intensity sigma 0 Fracture toughness K Ic And a Poisson's ratio v of 1100MPa, 5.26MPa · m 1/2 And 0.3, according to the solution rule in example 1, then n is 0.650.
Using formulas
Calculating to obtain R 0 The value of/r is 0.3, and the constant H is 0.3069 according to the solution rule in example 1.
Using formulas
Calculating the stress limit sigma of the ceramic part processed under the pure I-type failure mode f 777MPa, while the above measured sectional area size of the microcracks is 715 μm 2 Substituting the radius r =0 of the crack tip into a formula, and calculating to obtain the stress limit sigma of the ceramic piece under the action of the micro-crack before machining crack 689MPa.
The bending moment arm L of the ceramic workpiece and the half width B of the ceramic workpiece were measured by a vernier caliper to be 30mm and 5mm, respectively, and the offset x of the center of the circular hole in the length direction and the offset y of the center of the circular hole in the width direction were measured by an optical microscope to be 0.87mm and 0.42mm, respectively, as shown in FIG. 2.
Using a formula
Calculating the stress limit sigma of the ceramic piece processed in the mixed failure mode fm 874MPa.
Testing an S-N curve of an original ceramic part by utilizing room temperature bending fatigue, testing 6 stress levels, testing odd samples with more than 3 stress levels, drawing a test result into an S-N curve of a log-log coordinate system, obtaining a power index k of the original ceramic S-N curve as-0.01277 by taking a median value and performing linear fitting, and obtaining the critical fatigue life N at a fatigue limit according to a fitting result of the S-N curve (Line 1 in figure 3) fc Is approximately 10 5 。
Sigma by calculation and testing fm =874MPa, k = -0.01277 and N fc ＝10 5 The S-N curve (Line 3 in FIG. 3) of a ceramic part with circular holes is plotted according to σ for comparison crack =689MPa, k = -0.01277 and N fc ＝10 5 The S-N curve (Line 2 in FIG. 3) of the ceramic part under the action of the microcracks before machining is plotted.
Obtaining the actual maximum bending stress sigma of the ceramic part with the round hole by using the sensor test max The fatigue life of the ceramic part is 591MPa, 591MPa is used as a vertical coordinate to be substituted into an S-N curve of the processed ceramic part, a corresponding horizontal coordinate numerical value (namely the fatigue life) is obtained to be 35451 times, the life value of the ceramic part is obtained to be 156937 times through actual tests (as shown by a five-pointed star point in figure 3), the prediction error is 1 order of magnitude, the fatigue life of the ceramic part containing the microcracks before processing is only 64 times, the fatigue life value of the improved ceramic part is improved by more than 2400 times, and the fatigue life of the ceramic part is greatly improved.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for improving and predicting room temperature bending fatigue life of a microcracked ceramic part, comprising:
collecting the space information of microcracks on the original ceramic piece, and testing the power index and the critical fatigue life of the original ceramic piece;
processing the microcracks into circular holes according to the spatial information of the microcracks, and performing a polishing and cleaning procedure on the circular holes to obtain a processed ceramic part, thereby finishing the improvement of the room-temperature bending fatigue life;
measuring the size of the round hole to obtain the radius and the sectional area of the round hole, and calculating the stress limit of the processed ceramic part under the action of the static load by using the radius and the sectional area;
drawing an S-N curve of the processed ceramic part by using the stress limit, the power index and the critical fatigue life;
and testing the maximum bending stress of the processed ceramic part, and taking the abscissa corresponding to the maximum bending stress on the S-N curve as the prediction result of the room-temperature bending fatigue life.
2. The method as claimed in claim 1, wherein the spatial information includes length, depth and position coordinates, and is collected by a non-destructive testing process.
3. The method for improving and predicting the room temperature bending fatigue life of the ceramic part with the microcracks according to claim 2, wherein the processing of the microcracks into circular holes according to the spatial information of the microcracks comprises:
finding the microcrack according to the position coordinate parameters, processing the microcrack into a circular hole by using a femtosecond laser processing procedure, wherein the parameters of the femtosecond laser processing procedure are set according to the depth of the microcrack, so that the depth of the circular hole is ensured to be 80-110% of the depth of the microcrack, and the diameter of the circular hole is 100-120% of the length of the microcrack.
4. The method of claim 1, wherein the step of measuring the size of the circular hole to obtain the radius and cross-sectional area comprises:
measuring the diameter of the circular hole by using an optical microscope to obtain the radius of the circular hole;
and measuring the sectional area of the round hole by using a roughness analyzer, and ensuring that the measured section is parallel to the bending loading direction during measurement.
5. The method of claim 1, wherein the radius and cross-sectional area are used to calculate the stress limit of the ceramic part under static load, and the method is calculated by the following formula:
wherein R is 0 Is a mechanical constant solved based on the Poisson's ratio, the fracture toughness and the original strength, v is the Poisson's ratio, K Ic For fracture toughness, σ 0 As the original intensity, σ f Is the stress limit under pure I-type failure mode, n is a constant solved based on Poisson's ratio, area is the sectional area of the circular hole, r is the radius of the circular hole, H is a constant solved based on Poisson's ratio, mechanical constant and radius of the circular hole, and sigma is fm Is the stress limit in mixed failure mode, L is the bending force arm of the ceramic part, B is the half width of the ceramic part, x and y are the offset of the center of the circular hole in the length and width directions of the ceramic part, and the stress is measured in optical microscopeObserving by a mirror;
the stress limit in the hybrid failure mode is taken as the stress limit under the dead load.
6. The method of claim 5, wherein the constant n is solved based on Poisson's ratio by:
the constant n is 0.629 and 0.650 when the poisson ratio is 0 and 0.3, respectively;
when the poisson's ratio is other, the constant n is obtained by interpolation.
7. The method for improving and predicting the room temperature bending fatigue life of the ceramic part with the microcracks according to claim 5, wherein the constant H is solved based on the Poisson's ratio, the mechanical constant and the radius of the circular holes by the following method:
when the Poisson's ratio is 0.1, 0.15, 0.2, 0.25 and 0.3, respectively, when R is 0 The constant H is 0.6294, 0.6215, 0.6104, 0.596 and 0.5785 respectively if/R is 0.0005, if R is 0 The constants H are 0.6286, 0.6207, 0.6095, 0.5952 and 0.5777, respectively, if R is 0.001 0 The constants H are 0.6225, 0.6145, 0.6033, 0.5889 and 0.5714 respectively if/R is 0.005 0 The constants H are 0.6149, 0.6068, 0.5956, 0.5813 and 0.5638 respectively if/R is 0.01, if R is 0 The constants H are 0.5599, 0.5515, 0.5401, 0.5258 and 0.5086 respectively if/R is 0.05 0 The constants H are 0.5028, 0.4942, 0.4828, 0.4687 and 0.4518 respectively if/R is 0.1, if R is 0 The constant H is 0.3528, 0.3445, 0.3341, 0.3216 and 0.3069 if/R is 0.3, respectively 0 The constants H are 0.2672, 0.2599, 0.2508, 0.2401 and 0.2276 if/R is 0.5, respectively 0 The constants H are 0.159, 0.1537, 0.1473, 0.1399 and 0.1314 when/r is 1;
when poisson's ratio and R 0 When/r is other values, the constant H is obtained by interpolation.
8. The method of claim 1, wherein the testing of the power index and critical fatigue life of the original ceramic part comprises:
testing S-N curves of an original ceramic part with at least 6 stress levels by using a room temperature bending fatigue testing method, testing odd samples with more than 3 stress levels, drawing a testing result into an S-N curve of a log-log coordinate system, obtaining a power index k of the S-N curve of the original ceramic part by taking a median value and performing linear fitting, and obtaining a critical fatigue life N at a fatigue limit according to the S-N curve fitting result fc 。
9. The method of claim 1, wherein the step of using stress limit, power index and critical fatigue life to plot an S-N curve of the ceramic part comprises:
in a log-log coordinate system, a coordinate point (1, σ) fm ) As a starting point, drawing a slope line by taking the power exponent k of the original ceramic piece as the slope, and taking the critical fatigue life N of the original ceramic piece fc Drawing an S-N curve of the processed ceramic piece for the end point of the oblique line and then for the horizontal transverse line;
wherein σ fm Is the stress limit of the machined ceramic part under a static load.
10. The method of claim 1, wherein the maximum bending stress is obtained by testing the ceramic part with a bending stress sensor.
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