A method for processing plane strain fracture toughness test data

Abstract

The application relates to a plane strain fracture toughness test data processing method in the technical field of composite material testing, and comprises the following processes: acquiring an original data table; checking parameters and row and column numbers in each table, and storing the corrected data in a specified position; developing a VBA module to configure a data storage module, a calculation module, a force-displacement correction module and a data summary module; designing a software interface and various function controls; calling the VBA module, importing the sorted original data, adjusting the corrected force-displacement data into Origin to obtain fracture energy; and calculating the plane strain fracture toughness K Ic and the critical energy release rate G Ic Parameter and statistics. The application solves the problems that the plane strain fracture toughness test data calculation method in the prior art is complicated, a large amount of repetitive work needs to be manually performed, and the efficiency is low, so that the data processing efficiency is greatly improved, the method is clear and intuitive, convenient to use, the work burden of test personnel is reduced, and the production efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material testing, in particular to a plane strain fracture toughness test data processing method. BACKGROUND

[0002] Fracture toughness characterizes the ability of a material to resist crack propagation, and is an important indicator of material toughness. In recent years, there have been more and more studies on the plane fracture toughness of composite materials. The commonly used fracture toughness methods in China are indentation method (IM) and SENB method. In "Evaluation Method of Fracture Toughness of Ceramic Materials", published in "Aerospace Materials and Technology", No. 4, 1995, the differences between indentation method (IM) and SENB method are listed. Since the fracture toughness data obtained by SENB method is more reliable than that obtained by indentation method, SENB method is recognized as a standard fracture toughness test method. However, the test data obtained by SENB method is large, and needs to be processed manually, and there is no mature test data automatic calculation software for data processing. Manual data processing is tedious, inefficient, and prone to errors. SUMMARY

[0003] In order to solve the technical problem of low efficiency and error-prone caused by manual processing of a large amount of data using SENB method, a plane strain fracture toughness test data processing method is disclosed in the present application.

[0004] The technical scheme of the present application is as follows:

[0005] A plane strain fracture toughness test data processing method, comprising the following steps:

[0006] S1, obtaining an original data table;

[0007] S2, checking the parameters and the number of rows and columns in each table, and storing the original data table in a specified folder after correction;

[0008] S3, establishing a data calling work module in a Visual Basic editor;

[0009] S4, configuring a data storage module, a calculation module, a force-displacement correction module and a data summary module in Excel;

[0010] The data storage module is used to store the initial data in the original data table into the worksheet of Excel;

[0011] The calculation module is used to calculate the required data for plane strain fracture toughness test based on the initial data;

[0012] The required data includes the force value F of 5% stiffness reduction 5％, ratio determination, stiffness S, ligament width B, normalized crack length a, geometric correction factor f, energy correction factor f, characteristic length r, 2.5 times characteristic length 2.5r, critical energy release rate condition value G Q , plane strain fracture toughness condition value K Q , stiffness-related elastic modulus E stiff , fracture-related elastic modulus E fract , critical energy release rate G Ic , and plane strain fracture toughness K Ic ;

[0013] The force-displacement correction module uses the corrected displacement-force data and makes a force-displacement correction chart;

[0014] The data summary module is used for data processing and summary;

[0015] S5, configure the interface in Excel and configure the function controls corresponding to the data storage module, calculation module, force-displacement correction module and data summary module;

[0016] S6, the force-displacement correction module triggers the function control, calls the working module, calculates the critical energy release rate condition value G Q and extracts the corrected displacement-force data;

[0017] S7, the calculation module triggers the function control to obtain the F Q value and calculates the plane strain fracture toughness condition value K Q ;

[0018] S8, the corrected displacement-force data is called into Origin software for integral calculation of fracture energy and is transmitted into Excel through the data storage module;

[0019] S9, the calculation module triggers the function control, calls the working module, calculates the plane strain fracture toughness condition value K Q and the critical energy release rate condition value G Q , and after checking the calculated condition values, the plane strain fracture toughness K Ic and the critical energy release rate G Ic are obtained, and are counted into the data summary module;

[0020] S10, the calculation module triggers the function control, calls the working module, and stores the data obtained by the calculation module in S9 step and the data obtained by the force-displacement correction module in S6 step into a second designated folder.

[0021] Preferably, in the S2 step, the raw data table includes Table 1 - Equipment Raw Data Input - Notch Data, Table 2 - Equipment Raw Data Input - No Notch Data, Table 3 - Equipment Raw Data Input - Compression Yield Strength, and Table 4 - Equipment Raw Data Input - Curve Area.

[0022] Preferably, in the S4 step, the required data calculated by the calculation module includes the force value F 5％ , the ratio determination, the stiffness S, the ligament width B, the normalized crack length a, the geometric correction factor f, the energy correction factor f, the characteristic length r, the 2.5 times characteristic length 2.5r, the critical energy release rate condition value G Q , the plane strain fracture toughness condition value K Q , the stiffness-related elastic modulus E stiff , the fracture-related elastic modulus E fract , the critical energy release rate G Ic , and the plane strain fracture toughness K Ic .

[0023] Preferably, the S9 includes S9.1: ratio determination; S9.2: size evaluation and result verification; S9.3: result recheck.

[0024] Preferably, in the S9.1, the result of the ratio determination satisfies F m / F 5％ <1.1, the data is valid;

[0025] wherein F m is the maximum force value of the SENB sample test.

[0026] Preferably, in the S9.2, the result of the size evaluation satisfies h, B, and a are all greater than 2.5r, then the critical energy release rate G Ic = the critical energy release rate condition value G Q , the plane strain fracture toughness K Ic = the plane strain fracture toughness condition value K Q .

[0027] wherein h is the actual crack thickness of the SENB sample, and a is the actual crack length of the SENB sample.

[0028] Preferably, in the S9.3, the result verification satisfies the difference between the stiffness-related elastic modulus E stiff and the fracture-related elastic modulus E fract is less than 15%, then the obtained G Ic and K Ic results are correct.

[0029] Preferably, the working module is used for switching the work sheet in Excel, and the work sheet has text box, list box, drawing box and command button.

[0030] The present application solves the technical problems of complicated calculation method process, low efficiency caused by a large amount of repetitive work of manual operation in the prior art, and greatly improves the data processing efficiency by using the VBA module in Excel combined with the SENB method, which is clear and intuitive, convenient to use, reduces the work burden of the test personnel, and greatly improves the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0031] The drawings needed in the embodiments or prior art description will be briefly introduced as follows, and obviously, the drawings in the following description are only one embodiment of the present application, and other drawings can be obtained according to the drawings without creative labor for those skilled in the art.

[0032] Figure 1 It is a flow chart for processing the plane strain fracture toughness test data of the SENB sample in the embodiment;

[0033] Figure 2 It is a collation diagram of the original data table (Table 1) of the three-point bending test of the SENB sample in the embodiment;

[0034] Figure 3 It is a collation diagram of the original data table (Table 2) of the three-point bending test of the unnotched sample in the embodiment;

[0035] Figure 4 It is a collation diagram of the original data table (Table 3) of the compression strength test of the B-type sample (see the test standard ISO 604 for details) in the embodiment;

[0036] Figure 5 It is a collation diagram of the data table (Table 4) obtained by integral of Origin in the embodiment;

[0037] Figure 6 It is a calculation diagram of the calculation module for the SENB sample data in the embodiment;

[0038] Figure 7 It is a data display interface diagram of the displacement correction of the calculation module for the SENB sample in the embodiment;

[0039] Figure 8 It is a corrected data diagram of the three-point bending test of the SENB sample in the embodiment;

[0040] Figure 9 It is a part of code diagram of the test data processing in the embodiment;

[0041] Figure 10 Interface diagram of the summary module for the examples;

[0042] Figure 11 Schematic diagram of the three-point bending test for the SENB specimen.

[0043] The symbols in the above figures have the following meanings:

[0044] a, b, h - actual crack length, specimen width and specimen thickness of the SENB specimen, in mm;

[0045] L - span, L = (4.0 ± 0.1) b, in mm;

[0046] S - SENB specimen test curve stiffness, in N / mm;

[0047] F 5％ - force value at which the stiffness of the SENB specimen is reduced by 5%, in N;

[0048] F m - maximum force value of the SENB specimen test, in N;

[0049] F Q - crack propagation initiation force value of the SENB specimen test, in N;

[0050] W - fracture energy, in J;

[0051] B - ligament width, in mm;

[0052] a - normalized crack length;

[0053] f - geometric correction factor;

[0054] f - geometric correction factor;

[0055] G Q - critical energy release rate condition value, in kJ / m 2 ;

[0056] K Q - plane strain fracture toughness condition value, in

[0057] - characteristic length, in mm;

[0058] G Ic - critical energy release rate, in kJ / m 2 ;

[0059] K Ic - plane strain fracture toughness, in

[0060] Esiff - Stiffness related elastic modulus, unit GPa;

[0061] E fract - Fracture related elastic modulus, unit GPa.

[0062] 1- Distance of SENB specimen that displacement sensor can detect;

[0063] 2- Protruding part of SENB specimen that is fixed. DETAILED DESCRIPTION

[0064] The technical solutions of the present application will be described clearly and completely below in combination with the drawings of the embodiments and examples of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0065] EMBODIMENT

[0066] In a specific embodiment, as shown in FIG. 1, a method for processing the test data of the plane strain fracture toughness of a composite material includes the following steps: Figures 1-11

[0067] Importing the original data into Excel and arranging them;

[0068] Renaming the original data tables as Table 1-Device Original Data Input-Notch Data, Table 2-Device Original Data Input-Non-Notch Data, Table 3-Device Original Data Input-Compression Yield Strength and Table 4-Device Original Data Input-Curve Area, checking the parameters in each table and the corresponding row and column numbers, and storing the tables 1, 2, 3 and 4 in a designated folder. In this embodiment, the designated folder is named "00 Input Table".

[0069] In the Visual Basic editor of Excel, a working module associated with the data calling in Microsoft Excel is established, which is used to switch the worksheets in Excel, and the worksheets have text boxes, list boxes, drawing boxes and command buttons.

[0070] In Excel, data storage modules, calculation modules, force-displacement correction modules and data summary modules are configured.

[0071] The data storage module is used to store the initial data in the original data tables (Tables 1, 2, 3 and 4) into the worksheets of Excel.

[0072] The calculation module is provided with a force value F 5％ ​Ratio determination, stiffness S, ligament width B, normalized crack length α, geometric correction factor f, energy correction factor φ, characteristic length 2.5 times the feature length Critical energy release rate condition value G Q plane strain fracture toughness condition value K Q Stiffness-related elastic modulus E stiff Fracture-related elastic modulus E fract Critical energy release rate G Ic plane strain fracture toughness K Ic The calculation formula.

[0073] The force-displacement correction module is used to subtract the original force-displacement data from Tables 1 and 2 to perform displacement correction, plot the corrected force-displacement, and select the crack propagation initiation force value F. Q The data aggregation module is used for summarizing data after processing.

[0074] Configure the interface in Excel and configure the corresponding functional controls for the data storage module, calculation module, force-displacement correction module, and data summary module; the functional controls include the functional areas of each working module and trigger call controls, the calculation area for the calculation module, the correction area for the force-displacement correction module, and the data summary area for the summary module.

[0075] Select the linear segment range in the force-displacement correction module. The force-displacement correction module triggers the function control, calls the working module, imports the processed raw data, and the critical energy release rate condition value G. Q And extract the corrected force-displacement data;

[0076] Selecting the initial linear segment range of the curve in Table 1, the calculation module triggers the function control to calculate the plane strain fracture toughness condition value K based on the original data. Q ;

[0077] The force-displacement data, corrected by the force-displacement correction module, is called into the surface integral calculation software for fitting and integration calculation. The calculated area value is the fracture energy W. The fracture energy is then transferred to the corresponding column position in Table 4 of Excel through the data storage module.

[0078] The surface integral calculation software used in this embodiment is Origin.

[0079] Then, the calculation module triggers the function control again, calls the working module, and calculates the plane strain fracture toughness K. Ic and critical energy release rate parameter G Ic And the statistics are included in the data aggregation module.

[0080] The process data calculated by the above calculation module and the force-displacement correction module are stored in a second designated folder. In this embodiment, the second designated folder is named "01 Process Data".

[0081] According to the test standard ISO 13586, the specific calculation formula is as follows:

[0082] The stiffness S (stiffness = force / displacement) is obtained by fitting the initial linear segment of the force-displacement original data in Table 1.

[0083] The crack propagation starting force value F Q is selected by the force-displacement correction module, and the ratio is determined, and the fracture energy W is calculated by fitting the integral using Origin.

[0084] The ligament width B is calculated:

[0085] B = b - a

[0086] The normalized crack length a is calculated:

[0087] a = a / b

[0088] The geometric correction factor f is calculated:

[0089]

[0090] The energy correction factor f is calculated:

[0091]

[0092]

[0093] The critical energy release rate condition value G Q is calculated:

[0094]

[0095] The plane strain fracture toughness condition value K Q is calculated:

[0096]

[0097] The characteristic length and

[0098]

[0099] Size evaluation and result verification are performed, and if the following conditions are met, the critical energy release rate G Ic = G Q , and the plane strain fracture toughness K Ic = K QIf not, bracket mark is made, and is not included in data statistics:

[0100]

[0101]

[0102]

[0103] The difference between the following stiffness-related modulus and fracture-related modulus should be less than 15%, if not, bracket mark is made, and is not included in data statistics.

[0104] Calculate the stiffness-related elastic modulus E siff :

[0105]

[0106] Calculate the fracture-related elastic modulus E fract :

[0107]

[0108] Through the above calculation, the test parameters specified in ISO 13586 have been completed.

[0109] The present application is based on the ISO 13586 test standard, and realizes the automatic processing of the composite material fracture toughness test data by combining the SENB method with the Excel VBA code, effectively avoids the possible errors of manual data processing, reduces the burden of manual test data processing, makes the data processing more convenient and fast, and greatly improves the work efficiency.

Claims

1. A method for processing plane strain fracture toughness test data, characterized in that, It comprises the following steps: S1, obtaining original data table; S2, checking parameters and row and column numbers in each table, and storing the original data table into a specified folder after correction; S3, establishing a data calling work module in Visual Basic editor; S4, configuring a data storage module, a calculation module, a force-displacement correction module and a data summary module in Excel; The data storage module is used for storing initial data in the original data table into a worksheet in Excel; The calculation module is used for calculating data required for plane strain fracture toughness test based on the initial data; The force-displacement correction module is used for correcting displacement-force data and making a force-displacement correction graph; The data summary module is used for summarizing data after processing; S5, configuring an interface in Excel and configuring function controls corresponding to the data storage module, the calculation module, the force-displacement correction module and the data summary module; S6, the force-displacement correction module triggers the function control, calls the working module, and calculates the critical energy release rate condition value based on the original data and extracts the corrected displacement-force data; S7, the computing module triggers the function control to acquire the crack propagation starting force value and calculates the plane strain fracture toughness condition value ; S8, calling the corrected displacement-force data into Origin software for integral calculation of fracture energy and transmitting into Excel through the data storage module; S9, the calculation module triggers the function control, calls the working module, and calculates the plane strain fracture toughness condition value and the critical energy release rate condition value , and after checking the calculated condition value, the plane strain fracture toughness and the critical energy release rate are obtained, and are counted into the data summary module; S10, triggering the function control of the calculation module, calling the work module, and storing the data obtained by the calculation module in S9 and the data obtained by the force-displacement correction module in S6 into a second specified folder.

2. The method of claim 1, wherein, In the S2 step, the original data table comprises Table 1-device original data input-notch data, Table 2-device original data input-no notch data, Table 3-device original data input-compression yield strength and Table 4-device original data input-curve area.

3. The method of claim 2, wherein, The required data calculated by the calculation module in the S4 step includes a force value of a 5% stiffness reduction , stiffness S, ligament width B, normalized crack length geometric correction factor f, energy correction factor , characteristic length , 2.5 times characteristic length 2.5 , critical energy release rate condition value , plane strain fracture toughness condition value , stiffness-dependent elastic modulus , fracture-dependent elastic modulus , critical energy release rate , and plane strain fracture toughness ; is the maximum force value of the SENB specimen test.

4. The method of claim 3, wherein, The S9 comprises S9.1: Ratio decision: if the result of the ratio decision meets F m / F 5% <1.1, the subsequent calculation result is valid, otherwise the test result is invalid; S9.2: Size rating and result verification; the result of the size rating and result verification satisfies h, B and are all greater than 2.5 , the critical energy release rate = critical energy release rate condition value , the plane strain fracture toughness = plane strain fracture toughness condition value ; where h is the SENB specimen thickness, is the actual crack length of the SENB specimen; S9.3: result rechecking.

5. The method of claim 4, wherein, In the S9.3, the result rechecked the result satisfies the difference of the stiffness related elastic modulus and the fracture related elastic modulus is less than 15%, then the result is correct. and ​ 6. The method of processing plane-strain fracture toughness test data according to any one of claims 1-5, wherein, The work module is used for switching the worksheet in Excel, and the worksheet has text boxes, list boxes, drawing boxes and command buttons.

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