CN110823146A - Method for ultrasonic nondestructive measurement of plate thickness - Google Patents
Method for ultrasonic nondestructive measurement of plate thickness Download PDFInfo
- Publication number
- CN110823146A CN110823146A CN201911041578.0A CN201911041578A CN110823146A CN 110823146 A CN110823146 A CN 110823146A CN 201911041578 A CN201911041578 A CN 201911041578A CN 110823146 A CN110823146 A CN 110823146A
- Authority
- CN
- China
- Prior art keywords
- thickness
- probe
- plate
- water
- water tank
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/02—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/011—Velocity or travel time
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02854—Length, thickness
Abstract
The invention belongs to the field of nondestructive testing, and relates to a method for measuring the thickness of a plate in an ultrasonic nondestructive manner. The invention overcomes the defect that the traditional ultrasonic plate thickness measuring method is only suitable for the plate with uniform sound velocity, realizes the measurement and thickness imaging of the plate with the non-uniform sound velocity, is particularly suitable for the thickness nondestructive measurement of resin matrix composite plates, metal matrix composite plates, ceramic matrix composite plates and other plates with non-uniform sound velocity, and is also suitable for the thickness measurement of the plate with the uniform sound velocity.
Description
Technical Field
The invention relates to a method for measuring the thickness of a plate in an ultrasonic nondestructive way, which is suitable for the plate with uneven sound velocity and can also be used for measuring the thickness of the plate with even sound velocity, and belongs to the field of nondestructive testing.
Background
The traditional method for measuring the thickness of the plate by ultrasonic measures the time difference between the ultrasonic echoes of the upper surface and the lower surface of the plate and then multiplies a fixed sound velocity to measure the thickness of the plate. However, for the plate with uneven sound velocity at each position, the traditional method has larger measurement error, and particularly, the traditional method has larger error in thickness measurement of materials with larger uneven sound velocity, such as resin matrix composite materials, metal matrix composite materials, ceramic matrix composite materials and the like.
Disclosure of Invention
Aiming at the problems, the invention designs a method suitable for non-destructive measurement of the thickness of uneven plates, and the purpose of the invention is realized by the following technical scheme:
the method comprises the following steps:
1. a method for ultrasonic nondestructive measurement of plate thickness comprises the following steps:
1.1 sample requirement and Placement
Placing a plate with the thickness of h at the thickest part in a water tank, after the placement is finished, keeping the distance between the water surface in the water tank and the upper surface of a sample to be detected as j, wherein j is larger than h, and cushioning the sample by using a cushion block with the thickness of t to ensure that the distance between the cushion block and the bottom of the water tank is t, and t is smaller than h/4;
1.2 connecting device
The output interface and the synchronous interface of the pulse signal generator are respectively connected with the input interface and the synchronous interface of the multi-channel digital oscilloscope through coaxial cables; a longitudinal wave water immersion direct probe with the frequency of 0.5-25MHz is connected to a transmitting/receiving interface of a pulse signal generator through a coaxial cable; controlling the position of the probe to enable the probe to enter water and keeping the distance between the probe and the upper surface of the plate to be g, wherein g is larger than h/2;
1.3 measuring the velocity of sound in Water
The distance between the probe and the bottom of the water tank is a by utilizing a scanning frame, the time difference b of a primary echo and a secondary echo at the bottom of the water tank is measured, and the sound velocity in water is v, and water is 2 a/b;
1.4 scanning
The probe performs horizontal plane scanning, a multi-channel digital oscilloscope is used for recording the time difference t1i between the nth bottom wave and the first interface wave received by the probe at each detection position in the scanning process and the echo time t2i of the reflected wave at the bottom of the water tank, the plates and the cushion blocks are taken out, horizontal plane scanning is performed again, and the multi-channel digital oscilloscope is used for recording the time t3i of the reflected echo at the bottom of the water tank received by the probe at each detection position in the scanning process;
1.5 imaging
The thickness si of each position of the sheet material is Vwater x (t3i-t2i + t1i)/2n, and coordinates of each detection position form a two-dimensional position matrix.
Preferably, the plate is placed in the step 1.1, and the thickness direction of the plate is ensured to be vertical to the horizontal plane.
Preferably, the bottom surface of the water tank on which the plate is placed in step 1.1 is a plane.
Preferably, the axis of the probe in step 1.2 is perpendicular to the horizontal plane.
Preferably, the step 1.2 probe is mounted on a scanning gantry or robot capable of three-axis coordinated motion.
Preferably, in step 1.3, a multi-channel digital oscilloscope is used to measure the time difference b between the primary echo and the secondary echo at the bottom of the water tank.
Preferably, in step 1.4, the probe is scanned horizontally by using a scanning frame or a manipulator, and during scanning, the probe enters the water and keeps the distance g between the probe and the upper surface of the plate.
Preferably, in step 1.5, the maximum value of the sound velocity si is defined as 256, the minimum value is defined as 0, 256 levels are equally divided in the middle, each level corresponds to one gray value or color value, the gray value or color value is filled into the corresponding position matrix, and a two-dimensional gray map or a two-dimensional rainbow map of the thickness distribution is drawn. The working principle of the invention is as follows:
the invention has the advantages and beneficial effects that:
the invention develops a method for measuring the thickness of a plate in an ultrasonic nondestructive way, solves the problem of larger error when the plate measures the sound velocity of a material with uneven thickness in the prior art,
Detailed Description
By the time difference t between the nth bottom wave and the first boundary wave1iTime t of echo of reflected wave at bottom of water tank2iAnd the time t of the echo reflected by the bottom of the water tank after the plate and the cushion block are taken out3iThree of theseIndividual time value and sound velocity v in waterWater (W)The thickness measurement error caused by the uneven sound velocity at each position can be eliminated.
Example 1
The thickness measurement steps of the carbon fiber reinforced resin matrix composite plate with the maximum thickness of 5mm are as follows:
1.1 sample requirement and Placement
Placing a carbon fiber reinforced resin matrix composite plate in a water tank, ensuring that the thickness direction of the plate is vertical to the horizontal plane during placement, after the placement is finished, keeping the distance between the water surface in the water tank and the upper surface of the plate to be 50mm, and cushioning a sample by using a cushion block with the thickness of 1mm to ensure that the sample is 1mm away from the bottom of the water tank, wherein the bottom of the water tank is a plane;
1.2 connecting device
The output interface and the synchronous interface of the pulse signal generator are respectively connected with the input interface and the synchronous interface of the multi-channel digital oscilloscope through coaxial cables; a longitudinal wave water immersion direct probe with the frequency of 25MHz is connected to a transmitting/receiving interface of a pulse signal generator through a coaxial cable; the probe is arranged on a scanning frame capable of performing three-axis coordinated motion, the position of the probe is controlled to enable the probe to enter water, the distance between the probe and the upper surface of the plate is kept to be 10mm, and the probe is vertical to the horizontal plane;
1.3 measuring the velocity of sound in Water
The distance between the probe and the bottom of the water tank is a by using a scanning frame, the time difference b of a primary echo and a secondary echo at the bottom of the water tank is measured by using a multi-channel digital oscilloscope, and the sound velocity in water is vWater (W)＝2a/b；
1.3 scanning
The probe is subjected to plane scanning at a fixed horizontal height by using a scanning frame, and the time difference t between the 3 rd bottom wave and the first interface wave received by the probe at all positions in the scanning process is recorded by using a multi-channel digital oscilloscope1iTime t of echo of reflected wave at bottom of water tank2iTaking out the plate and the cushion block, scanning the plane again, and recording the time t of the water tank bottom reflection echo received by the probe at all positions in the scanning process by using a multi-channel digital oscilloscope3i；
1.4 imaging
Thickness s of each position of the sheeti＝vWater (W)×(t3i-t2i+t1i) 6, forming the coordinates of each position into a two-dimensional position matrix, and converting the sound velocity siThe maximum value of the thickness distribution is defined as 256, the minimum value of the thickness distribution is defined as 0, 256 levels are equally divided in the middle, each level corresponds to one gray value or color value, the gray value or the color value is filled into a corresponding position matrix, and a thickness distribution two-dimensional gray map or a thickness distribution two-dimensional rainbow map is drawn.
Example 2
The fiber particle reinforced aluminum matrix composite plate with the maximum thickness of 30mm comprises the following thickness measurement steps:
1.1 sample requirement and Placement
Placing a fiber particle reinforced aluminum-based composite material plate with the maximum thickness of 30mm in a water tank, ensuring that the thickness direction of the plate is vertical to the horizontal plane during placement, after the placement is finished, keeping the distance between the water surface in the water tank and the upper surface of a sample to be detected to be 100, and cushioning the sample by using a cushion block with the thickness of 5mm to ensure that the sample is 5mm away from the bottom of the water tank, wherein the bottom of the water tank is a plane;
1.2 connecting device
The output interface and the synchronous interface of the pulse signal generator are respectively connected with the input interface and the synchronous interface of the multi-channel digital oscilloscope through coaxial cables; a longitudinal wave water immersion direct probe with the frequency of 5MHz is connected to a transmitting/receiving interface of a pulse signal generator through a coaxial cable; the probe is arranged on a scanning frame capable of performing three-axis coordinated motion, the position of the probe is controlled to enable the probe to enter water, the distance between the probe and the upper surface of the plate is kept to be 50mm, and the probe is vertical to the horizontal plane;
1.3 measuring the velocity of sound in Water
The distance between the probe and the bottom of the water tank is a by using a scanning frame, the time difference b of a primary echo and a secondary echo at the bottom of the water tank is measured by using a multi-channel digital oscilloscope, and the sound velocity in water is vWater (W)＝2a/b；
1.3 scanning
The probe is scanned on a plane at a fixed horizontal height by using a scanning frame, and a multi-channel digital oscilloscope is usedRecording the time difference t between the 2 nd bottom wave and the first boundary wave received by the probe at all positions in the scanning process1iTime t of echo of reflected wave at bottom of water tank2iTaking out the plate and the cushion block, scanning the plane again, and recording the time t of the water tank bottom reflection echo received by the probe at all positions in the scanning process by using a multi-channel digital oscilloscope3i；
1.4 imaging
Thickness s of each position of the sheeti＝vWater (W)×(t3i-t2i+t1i) And/4, forming the coordinates of each position into a two-dimensional position matrix, and converting the sound speed siThe maximum value of the thickness distribution is defined as 256, the minimum value of the thickness distribution is defined as 0, 256 levels are equally divided in the middle, each level corresponds to one gray value or color value, the gray value or the color value is filled into a corresponding position matrix, and a thickness distribution two-dimensional gray map or a thickness distribution two-dimensional rainbow map is drawn.
Claims (10)
1. A method for ultrasonic nondestructive measurement of plate thickness is characterized by comprising the following steps:
1.1 sample requirement and Placement
Placing a plate with the thickness of h at the thickest part in a water tank, after the placement is finished, keeping the distance between the water surface in the water tank and the upper surface of a sample to be detected as j, wherein j is larger than h, and cushioning the sample by using a cushion block with the thickness of t to ensure that the distance between the cushion block and the bottom of the water tank is t, and t is smaller than h/4;
1.2 connecting device
The output interface and the synchronous interface of the pulse signal generator are respectively connected with the input interface and the synchronous interface of the multi-channel digital oscilloscope through coaxial cables; connecting the probe to a transmitting/receiving interface of a pulse signal generator through a coaxial cable; controlling the position of the probe to enable the probe to enter water and keeping the distance between the probe and the upper surface of the plate to be g, wherein g is larger than h/2;
1.3 measuring the velocity of sound in Water
The distance between the probe and the bottom of the water tank is a, the time difference b of the primary echo and the secondary echo at the bottom of the water tank is measured, and the sound velocity in the water is vWater (W)＝2a/b；
1.4 scanning
Scanning the horizontal plane by the probe, and recording the time difference t between the nth bottom wave and the first interface wave received by the probe at each detection position in the scanning process by using a multi-channel digital oscilloscope1iTime t of echo of reflected wave at bottom of water tank2iTaking out the plate and the cushion block, scanning the horizontal plane again, and recording the time t of the water tank bottom reflection echo received by each detection position of the probe in the scanning process by using a multi-channel digital oscilloscope3i；
1.5 imaging
Thickness s of each position of the sheeti＝vWater (W)×(t3i-t2i+t1i) And/2 n, forming the coordinates of each detection position into a two-dimensional position matrix.
2. A method for ultrasonic non-destructive measurement of thickness of a sheet material according to claim 1, wherein the sheet material is laid in step 1.1 such that the thickness of the sheet material is oriented perpendicular to the horizontal.
3. The method for ultrasonic non-destructive measurement of thickness of a plate according to claim 1, wherein the bottom surface of the water tank on which the plate is placed in step 1.1 is a flat surface.
4. A method for ultrasonic non-destructive measurement of thickness of sheet material according to claim 2, wherein in step 1.2 the axis of the probe is perpendicular to the horizontal plane.
5. A method for ultrasonic non-destructive measurement of thickness of sheet material according to claim 4, wherein step 1.2 the probe is mounted on a scanning gantry or robot capable of three-axis coordinated motion.
6. The method for ultrasonic non-destructive measurement of thickness of a plate according to claim 1, wherein in step 1.3, the time difference b between the primary echo and the secondary echo at the bottom of the water tank is measured using a multi-channel digital oscilloscope.
7. The method for ultrasonic non-destructive measurement of thickness of a plate material according to claim 1, wherein in step 1.4 the probe is scanned horizontally by a scanning frame or a robot, wherein during scanning the probe is moved into the water and the probe is kept at a distance g from the upper surface of the plate material.
8. The method for ultrasonic non-destructive measurement of thickness of a plate material according to claim 1, wherein in step 1.5, the maximum value of the sound velocity si is defined as 256, the minimum value is defined as 0, 256 levels are equally divided in the middle, each level corresponds to a gray value, the gray value is filled in the corresponding position matrix, and a two-dimensional gray map of the thickness distribution is drawn.
9. The method for ultrasonic non-destructive measurement of thickness of a plate material according to claim 1, wherein in step 1.5, the maximum value of the sound velocity si is defined as 256, the minimum value is defined as 0, 256 levels are equally divided in the middle, each level corresponds to one color value, the color values are filled into the corresponding position matrix, and a two-dimensional rainbow diagram of the thickness distribution is drawn.
10. The method for ultrasonic non-destructive measurement of thickness of a plate material according to claim 1, wherein in step 1.2, the direct probe is immersed in longitudinal wave water having a frequency of 0.5-25MHz by a coaxial cable to a transmitting/receiving interface of a pulse signal generator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911041578.0A CN110823146A (en) | 2019-10-29 | 2019-10-29 | Method for ultrasonic nondestructive measurement of plate thickness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911041578.0A CN110823146A (en) | 2019-10-29 | 2019-10-29 | Method for ultrasonic nondestructive measurement of plate thickness |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN110823146A true CN110823146A (en) | 2020-02-21 |
Family
ID=69551194
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911041578.0A Pending CN110823146A (en) | 2019-10-29 | 2019-10-29 | Method for ultrasonic nondestructive measurement of plate thickness |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110823146A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113639804A (en) * | 2021-10-19 | 2021-11-12 | 中国电力科学研究院有限公司 | Method and system for detecting quality of cable conduit |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0835952A (en) * | 1994-07-25 | 1996-02-06 | Ebara Corp | Method for measuring corrosion depth of tungsten carbide sintered body |
| US5777230A (en) * | 1995-02-23 | 1998-07-07 | Defelsko Corporation | Delay line for an ultrasonic probe and method of using same |
| CN101266228A (en) * | 2008-03-10 | 2008-09-17 | 河北省电力研究院 | Material sonic velocity measurement method |
| CN102183229A (en) * | 2011-02-25 | 2011-09-14 | 武汉大学 | Ultrasonic detection method of scale thickness in pipeline |
| CN105066918A (en) * | 2015-08-10 | 2015-11-18 | 上海应用技术学院 | Ultrasonic underwater target thickness measuring system and thickness measuring method |
| CN105806946A (en) * | 2016-05-03 | 2016-07-27 | 中国航空工业集团公司北京航空材料研究院 | Ultrasonic detection method for different technical stages of composite blade ring |
| CN106017372A (en) * | 2016-05-04 | 2016-10-12 | 大连理工大学 | Ultrasonic non-destructive abrasion-resistant coating thickness and elastic modulus measuring method |
| CN107907079A (en) * | 2017-11-16 | 2018-04-13 | 哈尔滨工程大学 | A kind of ultrasound thin oil film calibration testboard |
-
2019
- 2019-10-29 CN CN201911041578.0A patent/CN110823146A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0835952A (en) * | 1994-07-25 | 1996-02-06 | Ebara Corp | Method for measuring corrosion depth of tungsten carbide sintered body |
| US5777230A (en) * | 1995-02-23 | 1998-07-07 | Defelsko Corporation | Delay line for an ultrasonic probe and method of using same |
| CN101266228A (en) * | 2008-03-10 | 2008-09-17 | 河北省电力研究院 | Material sonic velocity measurement method |
| CN102183229A (en) * | 2011-02-25 | 2011-09-14 | 武汉大学 | Ultrasonic detection method of scale thickness in pipeline |
| CN105066918A (en) * | 2015-08-10 | 2015-11-18 | 上海应用技术学院 | Ultrasonic underwater target thickness measuring system and thickness measuring method |
| CN105806946A (en) * | 2016-05-03 | 2016-07-27 | 中国航空工业集团公司北京航空材料研究院 | Ultrasonic detection method for different technical stages of composite blade ring |
| CN106017372A (en) * | 2016-05-04 | 2016-10-12 | 大连理工大学 | Ultrasonic non-destructive abrasion-resistant coating thickness and elastic modulus measuring method |
| CN107907079A (en) * | 2017-11-16 | 2018-04-13 | 哈尔滨工程大学 | A kind of ultrasound thin oil film calibration testboard |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113639804A (en) * | 2021-10-19 | 2021-11-12 | 中国电力科学研究院有限公司 | Method and system for detecting quality of cable conduit |
| CN113639804B (en) * | 2021-10-19 | 2022-02-08 | 中国电力科学研究院有限公司 | Method and system for detecting quality of cable conduit |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN105158342B (en) | A kind of method of ultrasonic water immersion Nondestructive Evaluation residual stress | |
| EP1709418B1 (en) | Method and apparatus for examining the interior material of an object, such as a pipeline or a human body from a surface of the object using ultrasound | |
| CN108169331B (en) | Sheet grid wing structure welding seam phased array ultrasonic detection device and detection method | |
| CN113899816B (en) | Ultrasonic nondestructive testing device and method for T-shaped composite structure and R-region testing method and device | |
| CN107102065A (en) | The ultrasonic wave detecting system of one kind of multiple coupled modes | |
| CN111289627B (en) | Method for improving R-region phased array ultrasonic detection capability of complex-shaped component | |
| CN103033153B (en) | Method for scanning ultrasonic microscope and meanwhile measuring mechanical property parameter of lamina material | |
| US20190004013A1 (en) | Crack measurement device and method | |
| CN110133102B (en) | Water immersion type ultrasonic detection system for aluminum alloy flat cast ingot and use method thereof | |
| CN106353410A (en) | Ultrasonic phased array imaging detection device for aluminum alloy friction stir weldment | |
| CN112525996B (en) | Ultrasonic imaging detection method for isotropic pyrolytic graphite | |
| CN110823146A (en) | Method for ultrasonic nondestructive measurement of plate thickness | |
| US7086285B2 (en) | Nondestructive inspection method and system therefor | |
| CN104931581A (en) | Immersion phased array ultrasonic detection method for pre-stretched aluminum alloy plate | |
| CN106501377A (en) | A kind of method that employing ultrasonic phase array detects R corner structure flaw sizes | |
| Hayashi et al. | Rapid thickness measurements using guided waves from a scanning laser source | |
| CN117388370A (en) | Reinforced concrete structure array ultrasonic high-resolution combined imaging method | |
| CN110824015A (en) | Ultrasonic evaluation method for powder superalloy density distribution imaging | |
| Mineo et al. | Robotic geometric and volumetric inspection of high value and large scale aircraft wings | |
| US20130192374A1 (en) | Retroreflector for ultrasonic inspection | |
| CN107064294B (en) | Data acquisition device of submarine sediment in-situ acoustic measurement system | |
| CN112862971A (en) | Three-dimensional image reconstruction method and device for detecting irregular defects in plate | |
| CN108008007A (en) | Aluminium alloy cast ingot defect-detecting equipment and method of detection | |
| KR20150123607A (en) | Apparatus for adjusting horizontal of ultrasonic immersion testing system | |
| Lethiecq et al. | An ultrasonic array-based system for real-time inspection of carbon-epoxy composite plates |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20200221 |