CN116660026A - Device and method for measuring fatigue crack growth rate of metal sheet - Google Patents

Device and method for measuring fatigue crack growth rate of metal sheet Download PDF

Info

Publication number
CN116660026A
CN116660026A CN202310552508.1A CN202310552508A CN116660026A CN 116660026 A CN116660026 A CN 116660026A CN 202310552508 A CN202310552508 A CN 202310552508A CN 116660026 A CN116660026 A CN 116660026A
Authority
CN
China
Prior art keywords
crack
clamping
knife edge
test piece
chuck
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
Application number
CN202310552508.1A
Other languages
Chinese (zh)
Inventor
郭瑾
刘天奇
陈程
李晨
秦晓陈
葛爽
陈晨忻
徐吉峰
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commercial Aircraft Corp of China Ltd
Beijing Aeronautic Science and Technology Research Institute of COMAC
Original Assignee
Commercial Aircraft Corp of China Ltd
Beijing Aeronautic Science and Technology Research Institute of COMAC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Commercial Aircraft Corp of China Ltd, Beijing Aeronautic Science and Technology Research Institute of COMAC filed Critical Commercial Aircraft Corp of China Ltd
Priority to CN202310552508.1A priority Critical patent/CN116660026A/en
Publication of CN116660026A publication Critical patent/CN116660026A/en
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
    • G01B5/02—Measuring arrangements characterised by the use of mechanical techniques for measuring length, width or thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/04—Chucks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0073—Fatigue
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

The invention discloses a device and a method for measuring the fatigue crack growth rate of a metal sheet, which belong to the field of metal material fatigue and damage tolerance test, and comprise the following steps: the metal sheet fatigue crack propagation test piece is characterized in that one end of the metal sheet fatigue crack propagation test piece is a clamping end, the other end of the metal sheet fatigue crack propagation test piece is a loading end, and a pre-fabricated crack is arranged on the surface of the test piece; the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the test piece and positioned at two sides of the prefabricated crack, and a knife edge protruding part is arranged on each of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge; the COD gauge comprises a first chuck and a second chuck, wherein a chuck clamping groove is formed in each of the first chuck and the second chuck, and the knife edge protruding part is clamped in the chuck clamping groove. The invention provides a device and a method for measuring the fatigue crack growth rate of a thin-wall metal wallboard, which solve the problem of poor measurement precision caused by installing a COD gauge in bolt connection.

Description

Device and method for measuring fatigue crack growth rate of metal sheet
Technical Field
The invention belongs to the field of metal material fatigue and damage tolerance test, and particularly relates to a device and a method for measuring the fatigue crack growth rate of a metal sheet.
Background
At present, a large amount of metal materials exist in the body structure of the advanced civil aircraft, and under the action of fatigue load, cracks in the metal structure are initiated and expanded, so that the structure is finally invalid. In fatigue experiments, it is necessary to measure the relationship between the opening displacement amount of a crack and the load in order to calculate the fracture energy, fracture parameters, etc. of a material.
The crack monitoring method for fatigue fracture test of metal material includes visual inspection method, potentiometric method and crack opening displacement method (COD method). The COD method is also called as a flexibility method and is a common method for testing the opening displacement of fatigue cracks. The crack opening displacement extensometer (COD gauge) is an accurate length change value measuring instrument, is used for testing the displacement change quantity of the crack mouth position of a sample in a test, is widely applied to a material fracture mechanical test, and the accuracy of performance indexes of the crack opening displacement extensometer directly influences the measurement and result judgment of the fracture toughness of the tested metal material.
For the thin-wall metal fatigue crack propagation test piece, the COD gauge clamping knife edge is installed by punching, as shown in figure 1. But in reality, this kind ofMeasurement range L of installation mode 0 As shown in fig. 1, the measured fatigue crack opening displacement amount includes the deformation amount of the thin-wall metal material between the two connecting bolts, and cannot reflect the actual fatigue crack opening displacement.
Therefore, it is desirable to provide a solution that can react to the true fatigue crack opening displacement.
Disclosure of Invention
In order to achieve the above purpose and to improve the measurement precision of the fatigue crack growth rate of the thin-wall structure, the invention provides a device and a method for measuring the fatigue crack growth rate of a thin-wall metal wallboard, and solves the problem of poor measurement precision caused by installing a COD gauge in a bolt connection way.
According to a first aspect of the present invention, there is provided an apparatus for measuring a fatigue crack growth rate of a metal sheet, the apparatus comprising:
the metal sheet fatigue crack propagation test piece is characterized in that one end of the metal sheet fatigue crack propagation test piece is a clamping end, the other end of the metal sheet fatigue crack propagation test piece is a loading end, and a pre-fabricated crack is arranged on the surface of the test piece;
the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the test piece and positioned at two sides of the prefabricated crack, and a knife edge protruding part is arranged on each of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge;
the COD gauge comprises a first chuck and a second chuck, wherein a chuck clamping groove is formed in each of the first chuck and the second chuck, and the knife edge protruding part is clamped in the chuck clamping groove.
Further, the knife edge protruding part is positioned at the inner vertex angle of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge facing the prefabricated crack.
Further, right-angle invagination grooves are formed in the inner vertex angles of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge, which face the prefabricated cracks, and the right-angle edges of the right-angle invagination grooves and the included angle protrusions on the upper surfaces of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge form the knife edge protruding parts.
Further, the right-angle invagination groove is an inclined groove, so that the angle of the included angle protrusion is 45 degrees or 60 degrees. Here, the included angle between the clamping groove of the clamping head and the side edges of the first clamping head and the second clamping head is 110 degrees, and the included angle between the clamping groove of the clamping head and the bottom edges of the first clamping head and the second clamping head is 70 degrees.
Further, the clamping grooves of the clamping heads are positioned on the outer sides of the bottoms of the first clamping heads and the second clamping heads of the COD gauge.
Further, the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the test piece through an adhesive.
Further, the adhesive is a metal-to-metal adhesive, such as an epoxy adhesive.
According to a second aspect of the present invention there is provided a method of measuring crack growth rate of a sheet, the method being operated based on an apparatus according to any one of the above aspects, the method comprising the steps of:
s1: clamping the clamping end and the loading end of the metal sheet fatigue crack propagation test piece through a clamp respectively;
s2: prefabricating cracks on the surface of the sheet metal fatigue crack propagation test piece;
s3: the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the metal sheet fatigue crack propagation test piece through an adhesive and positioned at two sides of the prefabricated crack, and the bonding surface is the bottom surface far away from the protruding part of the knife edge;
s4: clamping chuck clamping grooves on a first chuck and a second chuck of the COD gauge on the protruding part of the knife edge to clamp the COD gauge;
s5: and applying a certain displacement to the metal sheet fatigue crack growth test piece, and measuring the length of the crack and the load at the moment after the crack growth is stable, thereby determining the crack growth rate of the sheet.
Further, in S1, a center line of the sheet metal fatigue crack growth test piece coincides with a center line of the jig.
Further, in S2, the length of the pre-crack is ∈1.3mm.
Further, in S2, the pre-cracking is completed by adopting a constant load or constant K method.
Further, in the step S5, the crack length measurement may be performed by a direct measurement method and a compliance method.
Further, measuring crack length using direct measurement includes:
a e ＝a p +r y
wherein: a, a e -effective crack length; a, a p -observing crack length; r is (r) y The size of the plastic area of the crack tip,
wherein: p-applied load;-corresponding to the observed crack length a p Is a stress intensity factor of (2); sigma (sigma) YS -the yield strength of the material; b-sample thickness; w-sample width.
Further, measuring crack length using the compliance method includes:
wherein: e (E) eff -effective modulus; b-sample thickness; w-sample width; deltav/DeltaP—test piece compliance; y-half of the distance between crack measurement points; a-the load-displacement curve with increasing load corresponds to the effective crack length a e The method comprises the steps of carrying out a first treatment on the surface of the With unloaded load-displacement curve, corresponding to observed crack length a p The method comprises the steps of carrying out a first treatment on the surface of the v-poisson ratio. The cosh function and sinh function are hyperbolic sine and hyperbolicAnd (3) a cosine function.
The invention has the beneficial effects that:
(1) The left and right chucks of the COD gauge are respectively clamped at the clamping knife edge; meanwhile, the COD gauge clamping knife edge is provided with a groove which is matched with the COD gauge chuck, the groove is a right-angle groove, so that the COD gauge can be clamped more firmly, and meanwhile, the free rotation between the COD gauge and the knife edge contact point is ensured, so that reliable test data are obtained.
(2) The COD gauge clamping knife edge is bonded to the surface of the metal sheet fatigue crack propagation test piece in an adhesive connection mode, and is different from the traditional COD gauge knife edge bolt connection scheme, the method can effectively measure the change of the position between the two clamping knife edges in the test process, effectively reduce the influence of the deformation of the sheet metal structure body on the test result, and obtain more accurate crack opening displacement. Meanwhile, the invention can avoid the change of boundary conditions caused by drilling holes on the surface of the metal sheet, and has influence on the fatigue crack expansion performance of the metal sheet structure.
Drawings
FIG. 1 is a schematic diagram of a COD gauge installation mode in the prior art;
FIG. 2 is a schematic diagram of an apparatus for measuring crack growth rate of a sheet according to an embodiment of the present invention;
FIG. 3 is a schematic illustration of an extension test piece according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a COD gauge according to an embodiment of the invention;
FIG. 5 is a schematic diagram of a left blade of a COD gauge clamp according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a COD gauge clamping knife edge groove according to an embodiment of the invention;
FIG. 7 is a schematic view of an assembly of a fatigue test piece and a clamp according to an embodiment of the present invention;
FIG. 8 is a schematic illustration of determining effective crack length by a cut line method according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of determining physical crack length by compliance in accordance with an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples are not representative of all implementations consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present disclosure as detailed in the accompanying claims.
The terms first, second and the like in the description and in the claims, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the disclosure described herein may be capable of being practiced otherwise than as specifically illustrated and described.
Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
A plurality, including two or more.
And/or, it should be understood that for the term "and/or" used in this disclosure, it is merely one association relationship describing associated objects, meaning that there may be three relationships. For example, a and/or B may represent: a exists alone, A and B exist together, and B exists alone.
Aiming at the problem of fatigue crack damage expansion of the thin-wall metal plate, the invention provides an improved device for measuring the crack expansion rate of the thin plate, thereby effectively improving the test accuracy of the fatigue crack expansion rate. In the technical scheme of the invention, an improved device for measuring the crack growth rate of the sheet based on the compliance method mainly comprises the following parts: 1. clamping ends of the metal sheet fatigue crack propagation test pieces; 2. a loading end of the metal sheet fatigue crack propagation test piece; 3. a sheet metal fatigue crack propagation test piece; COD gauge; 5, a left chuck of the COD gauge; 6, a right chuck of the COD gauge; 7, clamping a left knife edge by a COD gauge; 8, clamping a right knife edge by a COD gauge; 9. and (5) prefabricating cracks. The improved means for measuring the crack growth rate of the sheet is shown in FIG. 2. The sheet metal fatigue crack growth test piece 3 is shown in fig. 3. The COD gauge 4 is shown in FIG. 4. The left blade 5 of the COD gauge is shown in figure 5, a groove 10 is arranged on the left blade, and the right blade 6 of the COD gauge is similar to the left blade. Different from the design scheme of the bevel cutting of the clamping knife edge of the traditional COD gauge, as shown in figure 1, the clamping knife edge of the COD gauge is provided with the groove, the right-angle edge of the groove and the included angle bulge on the upper surface of the knife edge form the knife edge protruding part, and the knife edge protruding part is clamped in the clamping groove of the clamping head arranged on the clamping head, so that a better clamping effect of the COD gauge can be obtained.
The left and right chucks 5 and 6 of the COD gauge are respectively clamped at the clamping knife edges 7 and 8; meanwhile, a groove 10 is designed on the COD gauge clamping knife edge and is matched with the COD gauge chuck, the groove is a right-angle groove, the related angle is shown in figure 6, the right-angle edge of the groove and the included angle bulge on the upper surface of the knife edge form a knife edge protruding part, and the knife edge protruding part is clamped in a chuck clamping groove arranged on the chuck, so that the purpose of better clamping the COD gauge is achieved, and meanwhile, the free rotation between the COD gauge and a knife edge contact point is ensured, so that reliable test data are obtained.
Meanwhile, unlike the traditional COD gauge blade bolt connection scheme, the COD gauge clamping blade is adhered to the surface of the thin-wall metal fatigue crack propagation test piece in an adhesive connection mode, so that the displacement change between the two clamping blades in the test process can be effectively measured, and the measuring range L is shown in figure 6. Measuring range L of traditional COD gauge knife edge bolt connection scheme 0 As shown in fig. 1.
When the displacement of crack surface opening of the crack tip is measured by adopting two different modes of the scheme and the traditional measurement scheme, the measurement range L of the scheme is closer to the actual fatigue crack opening, and the measurement range L of the traditional COD gauge clamping knife edge bolting scheme 0 The method not only comprises the actual fatigue crack opening amount, but also comprises the deformation amount of the sheet metal material body between the two connecting bolts. Therefore, by the knife edge design scheme and the adhesive connection scheme, the fatigue crack growth speed of the thin-wall structure can be effectively improvedThe measuring precision of the rate improves the problem of poor measuring precision of the expansion displacement of the fatigue crack caused by installing the COD gauge by the bolt connection. Meanwhile, the invention can avoid the change of boundary conditions caused by drilling holes on the surface of the metal sheet, and has influence on the fatigue crack propagation performance of the metal thin-wall fatigue crack propagation test piece.
When the COD method is used for measuring the fracture toughness of the metal material, the clamping mode of the metal thin-wall fatigue crack extension test piece is shown in figure 7, and an electrohydraulic servo fatigue tester can be used for the test. Meanwhile, prefabricating cracks on the metal thin-wall fatigue crack propagation test piece, wherein the length of the prefabricating cracks is larger than or equal to 1.3mm, and the crack prefabricating can be finished by adopting a constant-load (or constant K) method; if the crack prefabrication process is to be completed through multi-stage loading, the final load of crack prefabrication cannot be reduced by more than 30% of the initial load.
For aluminum alloy materials, the recommended value of the crack prefabrication stress intensity factor is delta K=10-12 MPa.m 0.5 ，K max <16.5MPa·m 0.5 。
The crack initiation stress strength factor recommended by ASTM E561 is: k (K) max /E＝0.00013m 0.5 The final stress intensity factor value satisfies K max /E＝0.0001m 0.5 Wherein E represents the elastic modulus.
Then, installing COD gauge clamping edges at two sides of the prefabricated crack, wherein in the concrete structure, left and right chucks 5 and 6 of the COD gauge are respectively clamped at the clamping edges 7 and 8; meanwhile, a groove 10 is designed on the COD gauge clamping knife edge and matched with the COD gauge chuck. The COD gauge clamping knife edge structures 7 and 8 are bonded to two sides of the surface pre-fabricated crack 9 of the thin-wall metal fatigue crack growth test piece 3 in an adhesive connection mode, and the bonding surface is the bottom surface far away from the groove 10 side, so that the COD gauge 4 is clamped.
The test process adopts displacement loading, and the displacement loading speed is controlled to ensure that the acceleration of the stress intensity factor K value is between 0.55 and 2.75 MPa.m 0.5 Between them. And after the test is started, applying a certain displacement to the test piece according to the requirement of the displacement loading rate, and recording the length of the crack and the load at the moment after the crack growth is stabilized. The crack length measurement may be performed using direct measurement and compliance.
The direct measurement method can observe the crack length of the surface of the test piece, and the effective crack length needs to consider the influence of a plastic region, as shown in the formula (1):
a e ＝a p +r y …………………………………………(1)
wherein:
a e -effective crack length;
a p -observing crack length;
r y crack tip plastic zone size.
The size of the plastic area of the crack tip can be calculated by the formulas (2) to (3)
Wherein:
p-applied load;
-corresponding to the observed crack length a p Is a stress intensity factor of (2);
σ YS -yield strength of the material.
The KR value corresponding to each effective crack length (shown in formula (1)) was calculated using formula (3).
The compliance method adopts a compliance equation to determine the length of cracks through Deltav/DeltaP, and the effective modulus E eff Determined by an initial load-displacement curve (corresponding to crack length a at the completion of prefabrication 0 ) The calculation method is shown in the formula (4).
Wherein:
E eff -effective modulus;
b-sample thickness;
w-sample width;
Deltav/DeltaP—test piece compliance;
y-half of the distance between crack measurement points;
a-the load-displacement curve with increasing load corresponds to the effective crack length a e The method comprises the steps of carrying out a first treatment on the surface of the With unloaded load-displacement curve, corresponding to observed crack length a p ；
v-poisson ratio.
When the effective crack length is calculated by the line cutting method, at least 20 different points (v i ，P i ) As shown in fig. 8.
Using equation (5), the slope of the cut line is calculated:
calculating effective crack length a by using the slope of the secant given by formula (5), the effective modulus calculated by formula (4) and the test piece size e . The effective crack length and the load corresponding to each point obtained by calculation in the process are adopted to calculate K under different effective crack lengths according to the formula (3) R 。
Will K R Substituting the value of (2) to calculate the plastic region size r' y y, the physical crack length is calculated according to the following:
at the point of adding a' p Substituting (2) to obtain the size r of the plastic region y "true plastic region size at r y ″～r y ' by taking different values in this interval, the true plastic region size r is obtained y Further, the physical crack length a is obtained according to the formula (1) p 。
Calculating effective crack length using unload compliance, determining slope (Deltav/DeltaP) of unload curve at each test point unload As shown in fig. 9.
By (Deltav/DeltaP) unload ，E eff The test piece size, the physical crack length a is calculated according to the formula (4) p And calculating the plastic region size, effective crack length and K according to the formulas (1) to (3) R 。
The loading is continued at the same displacement rate, and the process is repeated until the test piece is broken. After the test is finished, observing the fracture of the test piece, and measuring the initial crack length a 0 ，a 0 The average value of the crack lengths of the test piece at 1/4B, 1/2B and 3/4B along the thickness direction is taken. To ensure test result K R The reliability of the curve is usually required to be no less than 5 data points, preferably 10-15 data points are needed to increase the reliability, and more data points are needed for materials with better toughness.
Aiming at a metal thin-wall fatigue crack propagation test piece, the invention mainly provides 2 innovations: the COD clamping knife edge structure design and the bonding connection mode of the clamping knife edge structure are designed, wherein the novel structure design has higher preparation maturity of the COD clamping knife edge and aims at a plurality of adhesive products such as metal-metal adhesives (epoxy resin adhesives) on the market of metal materials. Therefore, the technical scheme of the invention has higher technical implementation feasibility.
From the above description of the embodiments, it will be apparent to those skilled in the art that the above implementation may be implemented by means of software plus necessary general purpose hardware platform, or of course by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (e.g. ROM/RAM, magnetic disk, optical disk) comprising instructions for causing a terminal (which may be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to perform the method according to the embodiments of the present invention.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.

Claims (10)

1. An apparatus for measuring the fatigue crack growth rate of a sheet metal, the apparatus comprising:
the metal sheet fatigue crack propagation test piece is characterized in that one end of the metal sheet fatigue crack propagation test piece is a clamping end, the other end of the metal sheet fatigue crack propagation test piece is a loading end, and a pre-fabricated crack is arranged on the surface of the test piece;
the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the test piece and positioned at two sides of the prefabricated crack, and a knife edge protruding part is arranged on each of the first COD gauge clamping knife edge and the second COD gauge clamping knife edge;
the COD gauge comprises a first chuck and a second chuck, wherein a chuck clamping groove is formed in each of the first chuck and the second chuck, and the knife edge protruding part is clamped in the chuck clamping groove.
2. The apparatus for measuring the fatigue crack growth rate of a metal sheet according to claim 1, wherein the knife edge protrusion is positioned at an inner top angle of the first and second COD gauge holding knife edges toward the pre-crack.
3. The device for measuring the fatigue crack growth rate of the metal sheet according to claim 2, wherein the first and second COD gauge clamping edges are provided with right-angle invagination grooves at the inner top corners of the first and second COD gauge clamping edges facing the prefabricated crack, and the right-angle edges of the right-angle invagination grooves and the included angle protrusions of the upper surfaces of the first and second COD gauge clamping edges form the edge protruding parts.
4. A device for measuring the fatigue crack growth rate of sheet metal according to claim 3, wherein the right angle invagination groove is an inclined groove such that the angle of the included angle protrusion is 45 degrees or 60 degrees.
5. The apparatus for measuring the fatigue crack growth rate of a metal sheet according to claim 1, wherein the chuck clamping groove is positioned outside the bottoms of the first chuck and the second chuck of the COD gauge.
6. The apparatus for measuring the fatigue crack growth rate of a metal sheet according to claim 1, wherein the first COD gauge gripping edge and the second COD gauge gripping edge are fixed on the surface of the test piece by an adhesive.
7. A method of measuring the crack growth rate of a sheet metal, characterized in that the method is operated on the basis of an apparatus according to any one of claims 1 to 6, the method comprising the steps of:
s1: clamping the clamping end and the loading end of the metal sheet fatigue crack propagation test piece through a clamp respectively;
s2: prefabricating cracks on the surface of the sheet metal fatigue crack propagation test piece;
s3: the first COD gauge clamping knife edge and the second COD gauge clamping knife edge are fixedly arranged on the surface of the metal sheet fatigue crack propagation test piece through an adhesive and positioned at two sides of the prefabricated crack, and the bonding surface is the bottom surface far away from the protruding part of the knife edge;
s4: clamping chuck clamping grooves on a first chuck and a second chuck of the COD gauge on the protruding part of the knife edge to clamp the COD gauge;
s5: and applying a certain displacement to the metal sheet fatigue crack growth test piece, and measuring the length of the crack and the load at the moment after the crack growth is stable, thereby determining the crack growth rate of the sheet.
8. The method of measuring a crack growth rate of a metal sheet as set forth in claim 7, wherein in S1, a center line of the metal sheet fatigue crack growth test piece coincides with a center line of the jig.
9. The method for measuring crack growth rate of a metal sheet according to claim 7, wherein in S2, the pre-crack is completed by adopting a constant load or constant K method, and the length of the pre-crack is equal to or greater than 1.3mm.
10. The method for measuring crack growth rate of a metal sheet as defined in claim 7, wherein in S5, the crack length measurement is performed by a direct measurement method and a compliance method,
the measuring of the crack length using direct measurement includes:
a e ＝a p +r y
wherein: a, a e -effective crack length; a, a p -observing crack length; r is (r) y The size of the plastic area of the crack tip,
wherein: p-applied load;-corresponding to the observed crack length a p Is a stress intensity factor of (2); sigma (sigma) YS -the yield strength of the material; b-sample thickness; w-sample width;
the measurement of crack length using the compliance method includes:
wherein: e (E) eff -effective modulus; b-sample thickness; w-sample width; deltav/DeltaP—test piece compliance; y-half of the distance between crack measurement points; a-the load-displacement curve with increasing load corresponds to the effective crack length a e The method comprises the steps of carrying out a first treatment on the surface of the With unloaded load-displacement curve, corresponding to observed crack length a p The method comprises the steps of carrying out a first treatment on the surface of the v-poisson ratio.
CN202310552508.1A 2023-05-16 2023-05-16 Device and method for measuring fatigue crack growth rate of metal sheet Pending CN116660026A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310552508.1A CN116660026A (en) 2023-05-16 2023-05-16 Device and method for measuring fatigue crack growth rate of metal sheet

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310552508.1A CN116660026A (en) 2023-05-16 2023-05-16 Device and method for measuring fatigue crack growth rate of metal sheet

Publications (1)

Publication Number Publication Date
CN116660026A true CN116660026A (en) 2023-08-29

Family

ID=87711002

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310552508.1A Pending CN116660026A (en) 2023-05-16 2023-05-16 Device and method for measuring fatigue crack growth rate of metal sheet

Country Status (1)

Country Link
CN (1) CN116660026A (en)

Similar Documents

Publication Publication Date Title
Sancaktar et al. Increasing strength of single lap joints of metal adherends by taper minimization
Boutar et al. Characterization of aluminium one-component polyurethane adhesive joints as a function of bond thickness for the automotive industry: Fracture analysis and behavior
US9513200B1 (en) Determination of a threshold crack length
CN105628610A (en) Integration equipment and detection method for evaluating coating bonding strength based on interface fracture toughness
CN110108864B (en) Nondestructive testing system and method for prestressed concrete beam
CN110108567B (en) Ceramic matrix composite interlaminar tensile test piece, and preparation method and test method thereof
CN112858039A (en) Inverse analysis method for steel fiber concrete stress-crack width constitutive relation
CN101487780A (en) Method and apparatus for detecting non-work directional performance of medium plate
CN112036059B (en) Method for detecting working stress based on blind hole method
CN110987791B (en) Test method for determining normal bonding parameters of steel plate and concrete
Park et al. Fracture toughness measurements using two single-edge notched bend test methods in a single specimen
Yoshihara Shear modulus and shear strength evaluation of solid wood by a modified ISO 15310 square-plate twist method
CN220356828U (en) Device for measuring fatigue crack growth rate of metal sheet
CN116660026A (en) Device and method for measuring fatigue crack growth rate of metal sheet
Van Tooren et al. Experimental verification of a stress singularity model to predict the effect of bondline thickness on joint strength
CN105890994A (en) Method for evaluating interface combination strength of layered metal composite material
Park et al. Low-constraint toughness testing of two SE (T) methods in a single specimen
Inoue et al. Evaluation of interfacial strength of multilayer thin films polymer by nanoindentation technique
Takiguchi et al. Deformation characteristics and delamination strength of adhesively bonded aluminium alloy sheet under plastic bending
CN112525644B (en) Prefabricated crack copper alloy polyurethane bonding structure tensile pull-off test piece and manufacturing method thereof
CN110044965A (en) A kind of aging influence degree calculation method of metal adhesive connector in temperature environment
WO2013030566A1 (en) Method and apparatus for determining interlaminar shear mechanical properties of composite laminates
CN111239040A (en) Asymmetric composite material interface shear mechanical property test device and test method
Ripling et al. Fracture toughness of composite adherend adhesive joints under mixed mode I and III loading
Chataigner et al. Characterization of FRP-to-concrete bonded interface: description of the single lap shear test

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