CN108021770A - Leaf longevity evaluation method based on CT scan - Google Patents

Leaf longevity evaluation method based on CT scan Download PDF

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Publication number
CN108021770A
CN108021770A CN201711420453.XA CN201711420453A CN108021770A CN 108021770 A CN108021770 A CN 108021770A CN 201711420453 A CN201711420453 A CN 201711420453A CN 108021770 A CN108021770 A CN 108021770A
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China
Prior art keywords
blade
load
military service
scan
carried out
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Pending
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CN201711420453.XA
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Chinese (zh)
Inventor
王潘丁
朱晓磊
陈浩森
方岱宁
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Beijing Institute of Technology BIT
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Beijing Institute of Technology BIT
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Publication of CN108021770A publication Critical patent/CN108021770A/en
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
    • G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/50—Depth or shape recovery
    • G06T7/55—Depth or shape recovery from multiple images
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10072—Tomographic images
    • G06T2207/10081—Computed x-ray tomography [CT]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/30—Subject of image; Context of image processing
    • G06T2207/30108—Industrial image inspection

Abstract

The present invention relates to a kind of leaf longevity evaluation method based on CT scan, belong to computer aided design and manufacture technical field.Blade or other things to be evaluated for internal structure complexity, using the method for CT scan, realize lossless scanning；According to the faultage image of scanning, using the three-dimensional structure and tetrahedral model of the method extraction blade of image procossing；By being alignd to front and rear tringle coal of being on active service by pre-align and local best fit, obtain inside and outside 3-D displacement field and the strain field that blade produces under military service load, by being contrasted with tetrahedral model result of finite element under different loads, determine blade military service load, and and then remaining life of the blade under the load or the ultimate strength that can bear are obtained according to the military service load and the FEM calculation of tetrahedral model.The method of the present invention has taken into full account real structure of the blade in the case where actually using scene, drastically increases the reliability of leaf longevity evaluation.

Description

Leaf longevity evaluation method based on CT scan
Technical field
The present invention proposes one kind and is based on computer tomography (Computed Tomography- abbreviation CT) system pair Blade of aviation engine carries out hypostazation reconstruct, and then the method for carrying out life assessment, and the invention belongs to CAD With manufacturing technology field.
Background technology
Blade of aviation engine is the critical component that gas thermal energy is converted to rotating mechanical energy, in In-Flight Performance Ensure and lifting aspect plays the effect that can not be substituted, be known as aircraft " heart in heart ".Blade counts within the engine Measure it is numerous, it is also higher and higher therewith to the performance requirement of aero-engine with the rapid development of aeronautical technology.But turbine Indoor fuel gas temperature is very high, turbo blade high speed rotational operation under the impact of high pressure corrosivity combustion gas, except to bear frequency Outside rate, changes in amplitude huge alternation tension and distorting stress, to be also subject to heat erosion, high-temperature oxydation effect and mechanical friction Effect, along with the frequent start-stop and navigation for a long time of aircraft, makes blade work for a long time under the states such as overload, adverse circumstances, Therefore, it is easier to break down, seriously affected reliability and durability that blade uses.Turbo blade failure is sent out as aviation The most important failure mode of motivation.Therefore stringent Non-Destructive Testing is detected to blade of aviation engine and life assessment seems It is most important.
CT, that is, chromatography imaging technique, optimal nondestructiving detecting means are described as by international Non-Destructive Testing circle.From multiple directions with Certain tomography of transmission of radiation tested part, and the information after recording ray attenuation with flat panel detector, with industrial computer root Information carries out image reconstruction accordingly, and is shown with gray level image.By intuitively faultage image, can clearly see by Detect layer of structure, the defect situation of part.For the part of the internal structures such as blade of aviation engine complexity, CT disclosure satisfy that The requirement of detection.
Find the hypostazation modeling of blade generally using the method for optical scanner or laser scanning, opinion by literature search (blade of aviation engine measuring three-dimensional morphology technical research [D] Nanchang of the Liao Jun based on line-structured light, Nanchang aviation are big for text Learn, 2017) employ line-structured light and carry out three-dimensional measurement to blade surface, but both approaches can only be real to blade surface Existing hypostazation modeling, can not observe the internal structure of blade.And high-precision CT can be directed to leaf characteristic and provide in detail Geometry information, the solid modelling of blade interior structure provide data basis.China is lossless for aeroturbine blade Detection is general in two kinds of situation, the detection method that forge piece is combined using ultrasonic wave and magnetic spy wound；Cast blade is due to structure Complexity, the method being combined using fluoroscopic examination and ray method.Defects detection, damage development and life assessment integration are nothings The new direction of damage detection technique development, and the method that traditional leaf longevity evaluation method is based primarily upon finite element modelling, are established Preferable leaf model containing hole or crackle, have ignored blade and defect in itself due to manufacturing and military service process bears complexity Geometry imperfection caused by environmental load.
The content of the invention
The present invention is to consider that blade is true as a result, lacking to solve current industry for blade of aviation engine Non-Destructive Testing A kind of method of geometry life assessment, it is proposed that leaf longevity evaluation method based on CT scan.
The principle of present aspect is the acquisition deformable blade information by being contrasted to front and rear blade reconstruction model of being on active service, Evaluate the military service load suffered by blade.FEM calculation is carried out by the true tetrahedral model reconstructed under military service load, Predict leaf longevity.
The purpose of the present invention is what is be achieved through the following technical solutions：
A kind of method that life assessment is carried out using CT scan, including procedure below：
Step 1：By the lossless detection method of CT scan, the tomography picture of thing to be evaluated before and after acquisition is on active service；
Step 2：Image procossing is carried out to faultage image before and after military service, image is obtained using image smoothing and partitioning algorithm Inside and outside characteristic boundary and inside and outside point cloud；
Step 3：Internal external point cloud reconstructs the leaf model of tri patch using the method for three-dimensionalreconstruction；
Step 4:Internal external point cloud carries out mesh generation, generates tetrahedral blade finite element model, i.e. tetrahedron mould Type；
Step 5：To being on active service, front and rear blade tringle coal contrasts, the displacement and strain that analysis blade occurs, It is considered as result 1；
Step 6：Predict military service load, prediction result is load 1, is had to tetrahedral model before military service under load 1 Limit is first to be calculated, and carries out contrast with result in step 51 until the two unanimously, obtains true military service load, be denoted as load 2；
Step 7：Under true military service load 2, FEM calculation, prediction are carried out to the tetrahedral model reconstructed after military service The remaining life of blade.
Beneficial effect
The prior art is contrasted, the invention has the characteristics that：
1st, based on high-resolution CT non-destructive testing technologies, the real three-dimensional structure of blade is obtained, realizes complex leaf Three-dimensional geometry reconstructs；
2nd, the defects of considering blade interior and geometry, by contrasting blade three-dimensional structure pattern under different loads, Study the deformation that blade occurs.Blade is generally taken turns using the foreign aid on its surface of three-dimensional optical or the technique study of laser scanning Exterior feature, does not account for the real internal structure of blade.Its novelty is：The geometry that compared for blade inside and outside under different loads becomes Shape.
3rd, based on blade hypostazation reconstruct and Delaunay Meshing Methods, the blade finite element mould of hypostazation is established Type, the model taken into full account blade and wherein the defects of true three-dimension geometry.Based on three-dimensional geometry reconstructed number Modeling technique realizes key member damage development qualitative assessment life time of the level assessment technique.Its novelty is：FEM calculation is examined Consider blade because formed during casting or military service it is true the defects of and blade whole geometry pattern, and then to service life of blade into Row assessment, more approaches engineer application.
Brief description of the drawings
Fig. 1 is cone-beam CT scan principle schematic；
Fig. 2 is the flow diagram of metal blade hypostazation reconstruct and Mesh Generation Methods For Finite Element Computation；
Fig. 3 is alignment and the hypostazation finite element model contrast schematic diagram of hypostazation model；
Fig. 4 is iso-surface algorithms (Marching Cubes) process schematic；
Fig. 5 throws for Delaunay triangles divides schematic diagram.
Embodiment
Below in conjunction with the accompanying drawings and technical solution, the embodiment that the present invention will be described in detail.
Blade of aviation engine is easily cracked after longtime running in the presence of a harsh environment, hole, corrosion equivalent damage, and It is deformed.Defect and deformation can cause safety problem in military service, and the present invention illustrates this hair by taking blade of aviation engine as an example Bright implementation process, finally realizes the life assessment of blade of aviation engine.The method of the present invention is encoded in Matlab and realized.In detail Step is as follows：
Step 1, the present embodiment carries out tomoscan using cone-beam micro-CT to blade before and after military service, realizes to blade High-precision Non-Destructive Testing, scanning theory is as shown in Figure 1, blade sample is located on precise rotating platform, by 360 ° of rotations of turntable, Realize the Non-Destructive Testing to blade, obtain the tomography picture of blade.
Step 2, as shown in Fig. 2, carrying out image procossing to faultage image before and after military service, image smoothing and partitioning algorithm are utilized Obtain the inside and outside characteristic boundary and inside and outside point cloud of image.
In the present embodiment, image procossing is carried out to the scanning faultage image of blade before and after military service, utilizes medium filtering Smoothing methods such as (Median filter) removes the picture noise produced in CT scan；Utilize maximum entropy, maximum between-cluster variance etc. Method, determines the threshold value of image, carries out image segmentation to image, obtains the inside and outside characteristic boundary and inside and outside point cloud of image.
Certainly, one skilled in the art will appreciate that not limited to this, can use image procossing any existing suitable calculation Method, as long as the inside and outside characteristic boundary of the tested object image of approaching to reality as far as possible and inside and outside point cloud can be obtained.
Step 3, as shown in figure 4, being obtained by contour surface (Marching Cubes) scheduling algorithm processing step two inside and outside Portion border, obtains the geometry mechanism of blade tri patch, exports stl file, is interacted with other software.
Step 4, the blade inside and outside point cloud obtained by step 2, is thrown using the Delaunay shown in Fig. 5 and divides algorithm will Blade is reconstructed into tetrahedral grid, constructs a triangular, comprising all scatterplots, is put into triangle chained list.Concentrated Scatterplot be sequentially inserted into, found out in triangle chained list circumscribed circle include insertion point triangle (be known as the point influence triangle Shape), the common edge for influencing triangle is deleted, insertion point is connected with the whole vertex for influencing triangle, completes a point Insertion in Delaunay triangle chained lists.According to Optimality Criteria to the local Triangles Optimization newly formed.By the three of formation It is angular to be put into Delaunay triangle chained lists.By compiling file, the INP files containing grid node, grid cell, file are exported The FEM calculation that ABAQUS finite element softwares carry out metal blade hypostazation structure can be imported into.
Step 5, the front and rear blade tringle coal that will be on active service is carried out pair by pre-align and local best-fit algorithm Together, as shown in figure 3, contrast draws the front and rear deformation and strain occurred of model, it is considered as result 1, in deformation pattern such as Fig. 3 in dotted line frame It is shown.
Step 6：By step 5 as a result, substantially predicting blade military service load, load is load 1, by four in step 4 Face volume mesh structure is imported in ABAQUS finite element analysis softwares, under 1 time progress finite element explicit algorithm of load, output loads Deformation field and displacement field, contrasted with result 1, whether proof load 1 is military service load, if it is, load 1 is denoted as load 2, output loads 2 are false if not, repeat step 6, until output loads 2.
Step 7：Following 2 kinds of situations are divided to assess the remaining life of blade：
Situation 1, considers the fatigue rupture of blade, by under cyclic loading 2, military service rear blade tetrahedral model it is limited First result of calculation, determines the cycle-index and remaining life of blade.
Situation 2, considers failure damage of the blade under complex environment, proportionally increases the size of load 2, determine load 3, under load 3 to military service after tetrahedral grid structure carry out FEM calculation, determine the ultimate strength and residue of metal blade Service life.
Above-described embodiment is directed to the blade of internal structure complexity, using the method for CT scan, realizes the lossless scanning of blade. According to the faultage image of scanning, using the method for image procossing, the three-dimensional structure of blade is extracted, produces hypostazation structure respectively The cad file of STL forms and the ABAQUS FEM calculation files of INP forms.By being scanned to front and rear blade of being on active service, The CAD model of two groups of blades is alignd by pre-align and local best fit, obtains production of the blade under military service load Raw inside and outside 3-D displacement field and strain field, by with hypostazation model result of finite element pair under different loads Than determining the remaining life of blade military service load and blade under the load.By evaluation procedure, the present invention fully examines Consider real structure of the blade in the case where actually using scene, drastically increase the reliability of leaf longevity evaluation.
In order to illustrate present disclosure and embodiment, this specification gives specific embodiment.Draw in embodiment The purpose for entering details is not the scope for limiting claims, and is to aid in understanding the method for the invention.The technology of this area Personnel should be understood that：Do not departing from the present invention and its spirit and scope of the appended claims, to each of most preferred embodiment step Kind modification, change or replacement are all possible.Therefore, the present invention should not be limited to most preferred embodiment and interior disclosed in attached drawing Hold.

Claims (6)

  1. A kind of 1. method that life assessment is carried out using CT scan, it is characterised in that：Comprise the following steps：
    Step 1：By the lossless detection method of CT scan, the tomography picture of thing to be evaluated before and after acquisition is on active service；
    Step 2：Image procossing is carried out to faultage image before and after military service, is obtained using image smoothing and partitioning algorithm in image Surface border and inside and outside point cloud；
    Step 3：Internal external point cloud reconstructs the leaf model of tri patch using the method for three-dimensionalreconstruction；
    Step 4:Internal external point cloud carries out mesh generation, generates tetrahedral blade finite element model, i.e. tetrahedral model；
    Step 5：To being on active service, front and rear blade tringle coal contrasts, and the displacement and strain that analysis blade occurs, are considered as As a result 1；
    Step 6：Predict military service load, prediction result is load 1, to tetrahedral model before military service in 1 time progress finite element of load Calculate, carry out contrast with result in step 51 until the two unanimously, obtains true military service load, be denoted as load 2；
    Step 7：Under true military service load 2, FEM calculation is carried out to the tetrahedral model reconstructed after military service, predicts blade Remaining life；Or load 2 is proportionally increased it is after-applied in tetrahedral model carry out FEM calculation, determine metal blade Ultimate strength and remaining life.
  2. A kind of 2. method that life assessment is carried out using CT scan according to claim 1, it is characterised in that：The step One carries out tomoscan using cone-beam micro-CT to blade before and after military service obtains tomography picture.
  3. A kind of 3. method that life assessment is carried out using CT scan according to claim 1, it is characterised in that：Described image Smoothing algorithm is median filtering algorithm.
  4. A kind of 4. method that life assessment is carried out using CT scan according to claim 1, it is characterised in that：The three-dimensional The method of reconstruct is contour surface method.
  5. A kind of 5. method that life assessment is carried out using CT scan according to claim 1, it is characterised in that：Step 4 institute Stating progress mesh generation and being thrown using Delaunay divides algorithm to realize.
  6. 6. according to a kind of any methods that life assessment is carried out using CT scan of claim 1-5, it is characterised in that：Step Rapid five described pairs front and rear blade tringle coals of being on active service carry out contrast and are realized by pre-align and local best-fit algorithm.
CN201711420453.XA 2017-12-04 2017-12-25 Leaf longevity evaluation method based on CT scan Pending CN108021770A (en)

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Application publication date: 20180511