CN117131729B - Method for evaluating integrity of composite crack-containing structure under action of ballast load - Google Patents
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Abstract
The invention discloses a method for evaluating the integrity of a pressed load composite crack structure, which comprises the following steps: characterizing the geometric dimension and the defect dimension of the composite crack-containing structure; calculating limit loadP L Buckling loadP B Calculating line elasticity under different ballast loadsJIntegration ofJ e ElastoplasticityJIntegration ofJ ep And calculating the fracture load ratioL r And buckling load ratioB r The method comprises the steps of carrying out a first treatment on the surface of the By calculating cut-off lines of two failure assessment curvesL r max AndB r max establishing a fracture failure evaluation curve and a buckling failure evaluation curve; establishing a three-dimensional failure evaluation curve combining fracture failure and buckling failure; and calculating and evaluating the coordinates of the evaluation points. The invention combines fracture failure and buckling failure, is suitable for defect evaluation of a composite crack structure under pressure load, and expands the existing failure evaluationAnd (5) determining a method.
Description
Technical Field
The invention belongs to fault diagnosis and health maintenance technologies, and particularly relates to an integrity assessment method of a composite crack structure under the action of ballast.
Background
The high-end equipment manufacturing industry is taken as a ridge beam of a modern industrial system, is a strategically emerging industry which takes high and new technology as a guide and determines the comprehensive competitiveness of the whole industrial chain. The fault diagnosis and health maintenance technology is an indispensable ring in nine types of key intelligent basic commonality technologies, and plays a vital role in predicting faults of equipment and structures and providing maintenance suggestions. The integrity assessment of the defect-containing structure belongs to a health maintenance technology, and aims to provide a health management strategy for equipment and engineering structures, optimize use and maintenance and reduce maintenance cost. Under extreme conditions, various engineering structures and equipment such as pressure vessels, pressure pipelines and the like inevitably generate defects in the manufacturing and service processes, so that the integrity assessment of the structure containing the defects plays an important role in ensuring the safe operation of the equipment. For the integrity evaluation of defect-containing structures, a plurality of methods are provided for guarantee, including a COD curve method, a stress intensity factor method, a J criterion method and a most commonly used failure evaluation graph method. The failure evaluation graph method is also called a double-criterion method because brittle fracture failure and ultimate load failure are characterized by the same two-dimensional coordinate system based on fracture mechanics principle and structural strength theory. Therefore, the traditional failure assessment graph method only considers the fracture failure mode, and does not consider the influence of buckling failure on the structural integrity evaluation containing defects.
Patent CN115169115A (method, equipment and storage medium for evaluating the failure of the circumferential weld of the pipeline based on strain) introduces a failure evaluation chart of the circumferential weld of the pipeline based on strain, and accurately characterizes the influence of the strength matching of the weld on the fracture of the structure; the patent CN112287577A (method for evaluating structural integrity by unified restraint in-plane and out-of-plane) proposes a failure evaluation chart based on unified restraint parameters, and improves the evaluation accuracy of the failure evaluation chart. The above patents all relate to improvements in failure assessment graphs, but none consider the impact of buckling failure of composite crack containing structures under compressive loading on defect assessment. Not only does a defect-containing structure fail at break, but it also fails at buckling, depending on the geometry of the structure, the size of the defect, the material properties, and the loading, among other things. Conventional failure-to-fracture assessment graphs are not applicable when buckling failure occurs in a defect-containing structure.
Disclosure of Invention
Compared with the traditional failure evaluation method based on fracture failure, the method comprehensively considers the possible failure modes of the composite crack structure under the ballast load, solves the problem that the traditional fracture failure evaluation graph is not applicable when the structure containing the defects is subjected to buckling failure, and can improve the accuracy of the structural integrity evaluation of the surface crack under the ballast load.
The technical scheme for realizing the invention is as follows: the method for evaluating the integrity of the crack-containing structure under the action of the ballast load comprises the following steps:
step S1: and (2) characterizing the geometric dimension and the defect dimension of the structure containing the composite cracks to be evaluated, determining the material properties of the structure containing the composite cracks, and turning to step S2.
Step S2: according to the geometric dimension, the defect dimension and the material property, the load form is set as the compressive load, a finite element model containing the composite crack structure is established, and the limit load P containing the composite crack structure is determined by a finite element method L And buckling load P B And determining a set L of breaking load ratios at different load ratios r Buckling load ratio set B r Fracture ratio set K r The process proceeds to step S3.
Step S3: according to L r 、B r And K r Referring to the GB/T19624-2019 specification, a failure evaluation curve containing a composite crack structure is established, wherein the failure evaluation curve comprises a failure evaluation curve based on fracture failure and a failure evaluation curve based on buckling failure.
Failure assessment Curve expression f (L) r ) The following are provided:
f(L r )＝K r ，L r ≤L r max
failure assessment Curve expression f (B) based on buckling failure r ) The following are provided:
f(B r )＝K r ，B r ≤B r max
wherein L is r max To evaluate the curve cut-off line value for failure based on fracture failure, B r max Curve cutoff values were assessed for failure based on buckling failure.
The process proceeds to step S4.
Step S4: constructing the three-dimensional failure evaluation curve containing the composite crack structure according to the failure evaluation curve containing the composite crack structure, wherein the three-dimensional failure evaluation curve containing the composite crack structure is specifically as follows:
s41, establishing a three-dimensional failure evaluation curve expression f (L) r ,B r )：
f(L r ,B r )＝K r
S42, drawing a three-dimensional failure evaluation curve:
in the three-dimensional failure evaluation curve containing the composite crack structure, L r 、B r 、K r The three-dimensional failure evaluation curves respectively correspond to the X axis, the Y axis and the Z axis and are in L r -K r The projection line in the plane is the fracture failure evaluation curve, at B r -K r The projection line in the plane is a buckling failure assessment curve. And respectively projecting the breaking failure evaluation curve cut-off line and the buckling failure evaluation curve cut-off line onto the three-dimensional failure evaluation curve to form two cut-off lines of the three-dimensional failure evaluation curve, thereby obtaining the three-dimensional failure evaluation curve.
The process proceeds to step S5.
Step S5: applying a certain compressive load F to the structure containing the composite cracks, wherein the coordinate of the evaluation point under the current working condition is (L r * ,B r * ,K r * ) The method is characterized by comprising the following steps:
wherein L is r * Represents the position of the evaluation point on the X-axis, B r * Represents the position of the evaluation point on the Y-axis, K r * Representing the position of the evaluation point on the Z axis. F is a certain ballast load applied to the composite crack-containing structure. K is the crack tip stress intensity factor. K (K) c Is the fracture toughness of the material.
The process proceeds to step S6.
Step S6: judging that the evaluation point is at L r -K r Positional relationship between projected points in plane and fracture failure evaluation curve, and evaluation point in B r -K r And (3) carrying out safety assessment on the structure containing the composite cracks by the position relation between the projection points in the plane and the buckling failure assessment curve:
when evaluating the point coordinates (L r * ,B r * ,K r * ) When the projection points of the composite crack structure fall in the area surrounded by the failure evaluation curve, the cut-off line and the coordinate axis, the composite crack structure is safe under the action of the ballast load F, and the composite crack structure does not generate fracture failure or buckling failure.
When evaluating the point coordinates (L r * ,B r * ,K r * ) The projection points of the test result are located outside the buckling failure evaluation curve and the cut-off line thereof, and when the projection points are located inside the fracture failure curve and the cut-off line thereof, the buckling failure of the composite crack-containing structure is indicated.
When evaluating the point coordinates (L r * ,B r * ,K r * ) The projection point of the (C) is located outside the fracture failure evaluation curve and the cut-off line thereof, and is simultaneously located in the buckling failure curve and the cut-off line thereof, thereby indicating that the composite crack-containing structure is brokenFailure.
Compared with the prior art, the invention has the remarkable advantages that:
(1) Consider the case of buckling failure of a composite crack-containing structure under a compressive load. Therefore, on the basis of the existing fracture failure evaluation curve, the buckling failure evaluation curve is established by considering the buckling failure mode of the composite crack structure under the pressure load. The overall inclusion of the evaluation structure may be more reasonable and accurate than the failure to fracture evaluation mode.
(2) A buckling failure assessment curve corresponding to the conventional fracture failure assessment curve is established.
(3) The failure evaluation graph is a three-dimensional failure evaluation graph of a fracture failure evaluation curve combined with a buckling failure evaluation curve, and can judge the failure mode of the composite crack structure more intuitively.
Drawings
FIG. 1 is a schematic representation of fracture failure assessment curves and buckling failure assessment curves in the present invention.
FIG. 2 is a graphical representation of a three-dimensional failure assessment of the combination of a fracture failure assessment curve and a buckling failure assessment curve in the present invention.
FIG. 3 is a schematic illustration of the placement of evaluation point coordinates into a three-dimensional failure evaluation chart for evaluation, with buckling failure occurring.
FIG. 4 is a schematic diagram of evaluation point coordinates placed into a three-dimensional failure evaluation chart for evaluation, and fracture failure occurs.
FIG. 5 is a schematic representation of geometric and crack size characterization of a composite-containing surface crack plate under a ballasted load according to one embodiment of the invention.
FIG. 6 is a finite element model and crack front grid pattern of a composite surface crack plate under a ballasted load according to one embodiment of the invention.
FIG. 7 is a three-dimensional failure assessment result graph according to one embodiment of the present invention.
FIG. 8 is a flow chart of a method for evaluating the integrity of a composite crack-containing structure under load.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by one of ordinary skill in the art without creative efforts, are within the scope of the present invention based on the embodiments of the present invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to base that the technical solutions can be implemented by those skilled in the art, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered to be absent, and not included in the scope of protection claimed in the present invention.
The following describes the specific embodiments, technical difficulties and inventions of the present invention in further detail in connection with the present design examples.
Referring to fig. 1 to 8, a method for evaluating the integrity of a composite crack-containing structure under the action of a ballast load comprises the following steps:
step S1: the geometry and defect size of the composite crack-containing structure to be assessed were characterized with reference to GB/T19624-2019 and the material properties of the composite crack-containing structure were determined. The defect size comprises a surface crack depth a, a crack semi-long axis c and a composite surface crack inclination angle beta, and the material properties comprise an elastic modulus E, a crack surface friction coefficient mu, a Poisson ratio upsilon and a yield strength sigma s And tensile strength sigma b 。
The process proceeds to step S2.
Step S2: setting the load form as a compressive load according to the geometric dimension, the defect dimension and the material property, and establishing a finite element model containing a composite crack structureDetermining the limit load P containing the composite crack structure by a finite element method L And buckling load P B And determining a set L of breaking load ratios at different load ratios r Buckling load ratio set B r Fracture ratio set K r ：
Wherein P is different ballast loads applied to the composite crack-containing structure; j (J) e Is the linear elasticity J integral, J ep Is the elastoplastic J integral.
The process proceeds to step S3.
Step S3: under ballast load, buckling failure of the structure may occur, depending on the geometry, defect size, material properties, and loading of the composite crack-containing structure, etc. For example, as the thickness of the composite crack-containing plate structure decreases or the defect size increases, the likelihood of buckling failure of the composite crack-containing plate structure increases. At the moment, the traditional fracture failure evaluation chart is used for evaluation, which lacks reasonable basis, and the buckling failure evaluation chart needs to be established to meet the evaluation requirement. According to L r 、B r And K r Referring to the GB/T19624-2019 specification, a failure evaluation curve in a failure evaluation chart containing a composite crack structure is established, wherein the failure evaluation curve comprises a failure evaluation curve based on fracture failure and a failure evaluation curve based on buckling failure (shown in figure 1).
Failure assessment Curve expression f (L) r ) The following are provided:
f(L r )＝K r ，L r ≤L r max
at the time of establishmentWhen the buckling failure evaluation curve is used, the fracture load ratio L of the traditional failure evaluation curve is determined r Change to buckling load ratio B r And both share a fracture ratio K r 。
Failure assessment Curve expression f (B) based on buckling failure r ) The following are provided:
f(B r )＝K r ，B r ≤B r max
wherein L is r max To evaluate the curve cut-off line value for failure based on fracture failure, B r max Curve cutoff values were assessed for failure based on buckling failure.
Wherein sigma b Is the tensile strength of the material; sigma (sigma) s Is the yield strength of the material.
The process proceeds to step S4.
Step S4: the three-dimensional failure evaluation curve (shown in fig. 2) containing the composite crack structure is constructed according to the failure evaluation curve containing the composite crack structure, and the three-dimensional failure evaluation curve containing the composite crack structure is specifically as follows:
s41, establishing a three-dimensional failure evaluation curve expression f (L) r ,B r )：
f(L r ,B r )＝K r
S42, drawing a three-dimensional failure evaluation curve:
in the three-dimensional failure evaluation curve containing the composite crack structure, L r 、B r 、K r The three-dimensional failure evaluation curves respectively correspond to the X axis, the Y axis and the Z axis and are in L r -K r The projection line in the plane is the fracture failure evaluation curve, at B r -K r The projection line in the plane is a buckling failure evaluation curve; and respectively projecting the cut-off line of the fracture failure evaluation curve and the cut-off line of the buckling failure evaluation curve onto the three-dimensional failure evaluation curve to form two cut-off lines of the three-dimensional failure evaluation curve, thereby obtaining the three-dimensional failure evaluation curve.
The process proceeds to step S5.
Step S5: applying a certain compressive load F to the structure containing the composite cracks, wherein the coordinate of the evaluation point under the current working condition is (L r * ,B r * ,K r * ) The method is characterized by comprising the following steps:
wherein L is r * Represents the position of the evaluation point on the X-axis, B r * Represents the position of the evaluation point on the Y-axis, K r * Represents the position of the evaluation point on the Z axis, K is the crack tip stress intensity factor obtained by finite element method calculation, K c Is the fracture toughness of the material.
Fracture toughness K of material c The following are provided:
wherein E is the elastic modulus of the material, v is the Poisson's ratio of the material, J IC Is ductile fracture toughness of the material.
For the stress intensity factor K of the crack tip, the stress intensity factor value of the crack front is selected, and the I-type stress intensity factor K is obtained because the composite crack-containing structure is subjected to the action of compressive loading I Is 0. The stress intensity factor takes the II type stress intensity factor K of the crack front II And type III stress intensity factor K III Values. And J is IC Is the ductile fracture toughness of the material, and can be obtained through experiments or standards.
The process proceeds to step S6.
Step S6: judging that the evaluation point is at L r -K r Positional relationship between projected points in plane and fracture failure evaluation curve, and evaluation point in B r -K r And (3) carrying out safety assessment on the structure containing the composite cracks by the position relation between the projection points in the plane and the buckling failure assessment curve:
when evaluating the point coordinates (L r * ,B r * ,K r * ) When the projection points of the composite crack structure fall in the area surrounded by the failure evaluation curve, the cut-off line and the coordinate axis, the composite crack structure is safe under the action of the ballast load F, and the composite crack structure does not generate fracture failure or buckling failure.
When evaluating the point coordinates (L r * ,B r * ,K r * ) When the projection points of the composite crack containing structure fall outside the buckling failure evaluation curve and the cut-off line thereof and fall inside the fracture failure curve and the cut-off line thereof, the buckling failure of the composite crack containing structure is indicated (shown in fig. 3).
When evaluating the point coordinates (L r * ,B r * ,K r * ) When the projection points of the composite crack structure fall outside the fracture failure evaluation curve and the cut-off line thereof and fall inside the buckling failure curve and the cut-off line thereof, the fracture failure of the composite crack structure is indicated (as shown in fig. 4).
Examples
In this embodiment, the composite crack-containing structure to be evaluated is a plate, the material of which is TA2 industrial pure titanium, the elastic modulus e= 113161.41MPa, and the poisson ratio v=0.348. Yield strength sigma s = 418.23MPa, tensile strength σ b = 500.18MPa. The aggregate size of the composite-containing slit plates was t=10 mm, and the width 2 w=200 mm. The composite surface crack size was a=4mm, c=20mm (a/c=0.2, a/t=0.4, the inclination angle β=45°, t is the plate thickness), the crack surface friction coefficient μ was 0.3, and the ballast load f=300 MPa was applied to the upper and lower ends of the crack plate.
Step S1: the geometry (plate thickness t=10 mm and plate width 2w=200 mm), defect size (composite surface crack depth a=4 mm and crack semi-major axis c=20 mm, crack inclination β=45°) (as shown in fig. 5) and material properties (elastic modulus e= 113161.41MPa and poisson ratio v=0.348) of the structure to be assessed are well defined.
Step S2: calculating the plastic limit load P of the composite surface crack plate under the ballast load (shown in figure 6) by adopting a finite element method L 370.441MPa and buckling load P B = 297.558MPa; determining a set of breaking load ratios L by applying different loads P r And buckling load ratio B r Is a value of (2); by applying different loads P, the elastic J integral J under different loads is obtained by a finite element method e And elastoplastic J integral J ep Ratio J of (1) e /J ep Further, a fracture ratio set K is determined r Values.
Step S3: according to L r 、B r And K r Establishing a failure evaluation curve containing a composite crack structure according to GB/T19624-2019 specification, wherein the failure evaluation curve comprises a failure evaluation curve based on fracture failure and a failure evaluation curve based on buckling failure; calculating to obtain a cut-off line L r max (B r max )＝1.1。
Step S4: constructing the three-dimensional failure evaluation curve containing the composite crack structure according to the failure evaluation curve containing the composite crack structure, wherein the three-dimensional failure evaluation curve containing the composite crack structure is specifically as follows:
s41, establishing a three-dimensional failure evaluation curve expression f (L) r ,B r )：
f(L r ,B r )＝K r
S42, drawing a three-dimensional failure evaluation curve:
in the three-dimensional failure evaluation curve containing the composite crack structure, L r 、B r 、K r The three-dimensional failure evaluation curves respectively correspond to the X axis, the Y axis and the Z axis and are in L r -K r The projection line in the plane is the fracture failure evaluation curve, at B r -K r The projection line in the plane is a buckling failure evaluation curve; then respectively projecting the fracture failure evaluation curve cut-off line and the buckling failure evaluation curve cut-off line onto the three-dimensional failure evaluation curve to form two cut-off lines of the three-dimensional failure evaluation curve, thereby obtaining threeAnd (5) maintaining a failure assessment curve.
Step S5: applying a certain compressive load F to the structure containing the composite cracks, wherein the coordinate of the evaluation point under the current working condition is (L r * ,B r * ,K r * ) The method is characterized by comprising the following steps:
calculating stress intensity factor value at deepest point of crack front by adopting finite element methodObtaining ductile fracture toughness J of a material by experiment or standard IC ＝182.76KJ·m -2 Calculating the fracture toughness of the material>
Step S6: evaluation Point coordinates (L) r * ,B r * ,K r * ) The projected points of (a) fall within the three-dimensional region enclosed by the respective failure assessment curves, cut-off lines and coordinate axes, indicating that the crack plate is safe under a ballasting load f=300 MPa, and that no strength failure or buckling failure of the crack plate occurs (as shown in fig. 7).
Claims (7)
1. The method for evaluating the integrity of the composite crack-containing structure under the action of the ballast load is characterized by comprising the following steps:
step S1: characterizing the geometric dimension and the defect dimension of the structure containing the composite cracks to be evaluated, determining the material properties of the structure containing the composite cracks, and turning to the step S2;
step S2: according to the geometric dimension, the defect dimension and the material property, the load form is set as the compressive load, a finite element model containing the composite crack structure is established, and the limit load P containing the composite crack structure is determined by a finite element method L And buckling load P B And determining a set L of breaking load ratios at different load ratios r Buckling load ratio set B r Fracture ratio set K r Step S3 is carried out;
step S3: according to L r 、B r And K r Establishing a failure evaluation curve containing a composite crack structure according to GB/T19624-2019 specification, wherein the failure evaluation curve comprises a failure evaluation curve based on fracture failure and a failure evaluation curve based on buckling failure;
failure assessment Curve expression f (L) r ) The following are provided:
f(L r )＝K r ，L r ≤L r max
failure assessment Curve expression f (B) based on buckling failure r ) The following are provided:
f(B r )＝K r ，B r ≤B r max
wherein L is r max To evaluate the curve cut-off line value for failure based on fracture failure, B r max Evaluating a curve cutoff value for a failure based on a buckling failure;
turning to step S4;
step S4: constructing the three-dimensional failure evaluation curve containing the composite crack structure according to the failure evaluation curve containing the composite crack structure, wherein the three-dimensional failure evaluation curve containing the composite crack structure is specifically as follows:
s41, establishing a three-dimensional failure evaluation curve expression f (L) r ,B r )：
f(L r ,B r )＝K r
S42, drawing a three-dimensional failure evaluation curve:
in the three-dimensional failure evaluation curve containing the composite crack structure, L r 、B r 、K r Respectively are provided withCorresponding to the X axis, the Y axis and the Z axis, the three-dimensional failure evaluation curve is in L r -K r The projection line in the plane is the fracture failure evaluation curve, at B r -K r The projection line in the plane is a buckling failure evaluation curve; respectively projecting the breaking failure evaluation curve cut-off line and the buckling failure evaluation curve cut-off line onto the three-dimensional failure evaluation curve to form two cut-off lines of the three-dimensional failure evaluation curve, thereby obtaining the three-dimensional failure evaluation curve;
turning to step S5;
step S5: applying a certain compressive load F to the structure containing the composite cracks, wherein the coordinate of the evaluation point under the current working condition is (L r * ,B r * ,K r * ) The method is characterized by comprising the following steps:
wherein L is r * Represents the position of the evaluation point on the X-axis, B r * Represents the position of the evaluation point on the Y-axis, K r * Representing the position of the evaluation point on the Z axis; f is a certain ballast load applied to the structure containing the composite cracks; k is a crack tip stress intensity factor; k (K) c Fracture toughness of the material;
turning to step S6;
step S6: judging that the evaluation point is at L r -K r Positional relationship between projected points in plane and fracture failure evaluation curve, and evaluation point in B r -K r And (3) carrying out safety assessment on the structure containing the composite cracks by the position relation between the projection points in the plane and the buckling failure assessment curve:
when evaluating the point coordinates (L r * ,B r * ,K r * ) When the projection points of the composite crack structure fall in the area surrounded by the failure evaluation curve, the cut-off line and the coordinate axis, the composite crack structure is safe under the action of the ballast load F, and the composite crack structure does not generate fracture failure or buckling failure;
when evaluating the point coordinates (L r * ,B r * ,K r * ) The projection points of the (a) fall outside the buckling failure evaluation curve and the cut-off line thereof, and fall inside the fracture failure curve and the cut-off line thereof, so that the buckling failure of the composite crack-containing structure is indicated;
when evaluating the point coordinates (L r * ,B r * ,K r * ) The projection points of the composite crack structure are located outside the fracture failure evaluation curve and the cut-off line thereof, and the projection points of the composite crack structure are located in the buckling failure curve and the cut-off line thereof at the same time, so that the composite crack structure is indicated to have fracture failure.
2. The method for evaluating the integrity of a composite crack-containing structure under a compressive load according to claim 1, wherein in step S1, the geometric dimensions and the defect dimensions of the composite crack-containing structure to be evaluated are measured and characterized, and the material properties of the composite crack-containing structure are determined, specifically as follows:
performing defect size characterization on the composite crack by referring to GB/T19624-2019;
the defect size comprises a surface crack depth a, a crack semi-long axis c and a composite surface crack inclination angle beta, and the material properties comprise an elastic modulus E, a crack surface friction coefficient mu, a Poisson ratio upsilon and a yield strength sigma s And tensile strength sigma b 。
3. The method for evaluating the structural integrity of a composite crack-containing structure under a compressive load according to claim 1, wherein in step S2,
wherein P is different ballast loads applied to the composite crack-containing structure; j (J) e Is the linear elasticity J integral, J ep Is the elastoplastic J integral.
4. The method for evaluating the structural integrity of a composite crack-containing structure under a compressive load as set forth in claim 1, wherein in step S3, the cutoff value L of the failure evaluation curve based on fracture failure is set r max And a cutoff value B of a failure assessment curve based on buckling failure r max Is defined as
Wherein sigma b Is the tensile strength of the material; sigma (sigma) s Is the yield strength of the material.
5. The method for evaluating the structural integrity of a composite crack under a compressive load according to claim 1, wherein in step S5, the crack tip stress intensity factor K is calculated by a finite element method;
fracture toughness K of material c The following are provided:
wherein E is the elastic modulus of the material, v is the Poisson's ratio of the material, J IC Is ductile fracture toughness of the material.
6. The method of claim 5, wherein the crack tip stress intensity factor K is selected from the group consisting of stress intensity factor values of crack fronts, and I-type stress intensity factor K due to the compressive loading of the composite crack structure I Is 0; the stress intensity factor takes the II type stress intensity factor K of the crack front II And type III stress intensity factor K III Values.
7. The method for evaluating the structural integrity of a composite crack-containing structure under a compressive load as set forth in claim 5, wherein J IC Is the ductile fracture toughness of the material, and can be obtained through experiments or standards.
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