CN114563282B - Performance test method for small-size simply supported beam - Google Patents

Performance test method for small-size simply supported beam Download PDF

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CN114563282B
CN114563282B CN202210268857.6A CN202210268857A CN114563282B CN 114563282 B CN114563282 B CN 114563282B CN 202210268857 A CN202210268857 A CN 202210268857A CN 114563282 B CN114563282 B CN 114563282B
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simply supported
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supported beam
strain
load
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CN114563282A (en
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张志杰
郑鹏飞
谌继明
张明
赵婳
徐莉莎
陈宇
李佳霖
张启航
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Southwestern Institute of Physics
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    • 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
    • G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
    • 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
    • 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
    • G01N2203/0014—Type of force applied
    • G01N2203/0023—Bending
    • 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
    • G01N2203/0075—Strain-stress relations or elastic constants
    • 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
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Abstract

In order to solve the problem that the junction can be obtained only by a large amount of finite element calculation in the existing test method of the small-size simply supported beamThe embodiment of the invention provides a performance test method of a small-size simply supported beam, which comprises the following steps: carrying out a three-point bending loading test by using a small-size simply supported beam to obtain a test load-deflection curve of the small-size simply supported beam; predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain yield strength R p0.2 The method comprises the steps of carrying out a first treatment on the surface of the According to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m . The embodiment of the invention solves the problem of sample size limitation, has reliable basic theoretical support, can acquire continuous and complete stress-strain curves without complicated iterative solution, and has great engineering application value.

Description

Performance test method for small-size simply supported beam
Technical Field
The invention relates to a performance test method for a small-size simply supported beam.
Background
In the field of research and development of novel nuclear fusion reactor materials, obtaining the mechanical properties of the fusion reactor material after neutron irradiation has important significance for advanced material research and development, fusion reactor structural design and safety evaluation. However, due to the small neutron irradiation space, irradiation tests are difficult to perform with conventional large-size standard samples (ASTM E8-16a.Standard Test Methods for Tension Testing of Metallic Materials.Annual Book of ASTM Standards.West Conshohocken,PA:American Society for Testing and Materials;2016). Meanwhile, the problems that the utilization rate of the irradiation space is low, the larger the volume of a single sample is, the longer the cooling time after irradiation is and the like are considered in the standard sample. Therefore, small-sized sample testing techniques are the best way to solve the above-mentioned problems.
The three-point bending test of the small-size simply supported beam sample is used as a conventional mechanical property test method and is mainly used for obtaining parameters such as bending strength, bending strain and the like of a material. If the above properties are obtained by a single bending test, more mechanical properties, such as tensile properties of the material, can be obtained. This can certainly improve the utilization rate of irradiation resources and reduce irradiation cost.
Uniaxial stress-strain relationship and yield strength R of material p0.2 Tensile strength R m Belongs to the important mechanical properties of metal materials, and is a key parameter for carrying out optimal design, simulation and integrity evaluation on engineering structures. Therefore, the testing method for obtaining the tensile property of the material through the small-size simply supported beams is widely studied.
In 1988, weihs (Weihs T P, hong S, bravman J C, et al mechanical deflection of cantilever microbeams: A new technique for testing the mechanical properties of thin films [ J ]. Journal of Materials Research,1988,3 (5): 931-942.) and the like firstly obtained the mechanical properties of gold films by using micro-cantilever beam bending test technique, and calculated the elastic modulus of materials by the elastic bending theory of rectangular section cantilever beams. According to the cantilever beam bending theory, the maximum tensile stress of the cantilever beam is generated on the upper surface of the cantilever beam fixed end, and when a bent load-deflection curve is obviously turned from linearity, the cantilever beam fixed end material is considered to yield, so that the material yield strength is calculated; there are also some scholars who indirectly acquire the modulus of elasticity and strength of WC-Co materials based on a combination of multiple finite element calculations and in-situ micro-beam bending tests. The general process can be described as: and (3) performing a quasi-static bending test on the in-service WC-Co micro-beam by adopting a spherical pressure head until the micro-beam breaks, and recording a continuous load-deflection curve in the process. And adjusting the performance parameters of the input materials by using ABAQUS finite element software to enable the result to be close to the test, and finally outputting the material parameters when convergence is achieved, namely the test value.
However, the existing test method of the small-size simply supported beam needs a large amount of finite element calculation after each test to obtain a result, and the process is complicated.
Disclosure of Invention
In order to solve the technical problem that the conventional test method of the small-size simply supported beam can acquire a result through a large number of finite element calculations, the process is complicated, and the embodiment of the invention provides a performance test method of the small-size simply supported beam.
The embodiment of the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a performance test method for a small-sized simply supported beam, including:
carrying out a three-point bending loading test by using a small-size simply supported beam to obtain a test load-deflection curve of the small-size simply supported beam;
predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship;
converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain yield strength R p0.2 ；
According to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m 。
Furthermore, the small-size simply supported beam is of a rectangular structure with the surface subjected to polishing treatment; the length L of the small-sized simply supported beams is greater than or equal to 1.2 times the clear span.
Further, according to the test load-deflection curve of the small-size simply supported beam, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to the load-deflection relationship; comprising the following steps:
linear fitting is carried out on the initial line elastic segment of the load-deflection curve to obtain a slope C e The modulus of elasticity E of the material is calculated by equation (1):
Figure BDA0003553655530000021
wherein P is the test load, W is the deflection, E is the elastic modulus of the material, S is the clear span of the simply supported beam, B is the sample width, and W is the sample height.
Further, according to the test load-deflection curve of the small-size simply supported beam, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to the load-deflection relationship; further comprises:
performing power law fitting on an elastoplastic segment of a load-deflection curve to obtain a formula (2), and obtaining a loading coefficient C and a loading index m according to the formula (2):
P＝Cw m (2)
the loading coefficient C and the loading index m are substituted into formula (3):
Figure BDA0003553655530000031
wherein n is a strain hardening exponent, K is a strain hardening coefficient, K 1 、k 2 、k 3 、k 4 Taking the clear span S of the simply supported beam as the characteristic length h, A * ＝BW 3 /S 2 Is the feature area.
Further, according to the test load-deflection curve of the small-size simply supported beam, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to the load-deflection relationship; further comprises:
e, K and n are substituted into the Hollomon model to obtain the uniaxial true stress-strain relationship of the material as shown in formula (4):
Figure BDA0003553655530000032
in sigma T Is true stress, epsilon T Is true strain, sigma y Is the nominal yield strength。
Further, converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain a yield strength Rp 0 2; comprising the following steps:
the resulting true stress-strain relationship is converted into an engineering stress-strain curve according to equation (5):
Figure BDA0003553655530000033
wherein e is a natural constant, ε E For engineering strain, sigma E Is engineering stress;
determining the yield strength R through the intersection point of the bias line and the engineering stress-strain curve P0.2 。
Further, the yield strength R is obtained by determining the intersection point of the bias line and the engineering stress-strain curve P0.2 Comprising:
the yield strength R is determined by the intersection point of the 0.2% offset line and the engineering stress-strain curve P0.2 。
Further, according to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m The method comprises the steps of carrying out a first treatment on the surface of the Comprising the following steps:
predicting and obtaining the tensile strength R of the material according to the formula (6) m ：
Figure BDA0003553655530000034
Further, the size range of the small-size simply supported beam is as follows: sample width b=3 mm, sample height w=3 mm, simply supported beam clear span s=4w=12 mm; the surface of the small-size simply supported beam is manually and finely polished by using sand paper with more than 800 meshes.
Further, a small-size simply supported beam is used for carrying out a three-point bending loading test, and a test load-deflection curve of the small-size simply supported beam is obtained; comprising the following steps:
the distance between the two rollers of the lower clamp of the testing machine is adjusted to be consistent with a preset clear span S of the test, and a small-size simply supported beam is placed on the two rollers of the lower clamp of the testing machine, so that the axial direction of the rollers is perpendicular to the length direction of the simply supported beam;
and (3) carrying out three-point bending loading on the sample by using a testing machine, and synchronously collecting real-time load and deflection data between the upper clamp and the lower clamp until the loading displacement reaches 0.5W or the load reaches the highest peak and then descends by 10%.
Compared with the prior art, the embodiment of the invention has the following advantages and beneficial effects:
according to the performance test method for the small-size simply supported beam, disclosed by the embodiment of the invention, a test load-deflection curve of the small-size simply supported beam is obtained by using the small-size simply supported beam to carry out a three-point bending loading test; predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain yield strength R p0.2 The method comprises the steps of carrying out a first treatment on the surface of the According to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m The method avoids the use of a large amount of finite element calculation, thereby simplifying the process of obtaining the performance data of the small-size simply supported beam, and simultaneously, the method can accurately obtain the continuous and complete stress-strain relation curve and strength of the metal material after the undetermined parameters of the calibration prediction formula are calculated by using a small amount of finite element simulation calculation, and is suitable for large-scale ductile metal materials.
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In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are needed in the examples will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and that other related drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a sample configuration of a simply supported beam used in an embodiment of the present invention.
FIG. 2 is a finite element analysis model of a simply supported beam sample in an embodiment of the invention.
FIG. 3 is a graph of the Hollomon constitutive model of the present invention.
FIG. 4 is a load-deflection curve of a three-point bending test specimen of CLF-1 steel in an embodiment of the invention.
FIG. 5 is a stress-strain curve of CLF-1 steel in an example of the present invention.
Fig. 6 is a schematic diagram of a three-point bending system for a small-sized simply supported beam sample.
Fig. 7 is a flow chart of a performance test method of a small-sized simply supported beam.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: no such specific details are necessary to practice the invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail in order not to obscure the invention.
Throughout the specification, references to "one embodiment," "an embodiment," "one example," or "an example" mean: a particular feature, structure, or characteristic described in connection with the embodiment or example is included within at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an example," or "in an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Moreover, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and that the illustrations are not necessarily drawn to scale. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the scope of the present invention.
Examples
In order to solve the technical problem that the conventional test method of the small-size simply supported beam needs to obtain a result through a large number of finite element calculations, and thus the process is complicated, an embodiment of the present invention provides a performance test method of the small-size simply supported beam, which is shown in fig. 7, and includes:
s1, performing a three-point bending loading test by using a small-size simply supported beam to obtain a test load-deflection curve of the small-size simply supported beam;
a schematic diagram of a three-point bending system for a small-sized simply supported beam specimen is shown with reference to fig. 6.
S2, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship;
s3, converting the uniaxial true stress-strain relation into an engineering stress-strain curve to obtain yield strength R p0.2 ；
S4, predicting and obtaining the tensile strength R of the material according to the parameters of the Hollomon constitutive model m 。
Therefore, the embodiment of the invention acquires the test load-deflection curve of the small-size simply-supported beam by using the small-size simply-supported beam to carry out a three-point bending loading test; predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain yield strength R p0.2 The method comprises the steps of carrying out a first treatment on the surface of the According to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m Avoiding the use of finite element computation in large quantities, thereby simplifying the acquisitionAnd simultaneously, a small quantity of finite element simulation calculation is applied to calibrate the undetermined parameters of the prediction formula, so that the continuous and complete stress-strain relation curve and strength of the metal material can be accurately obtained, and the method is suitable for large-range ductile metal materials.
Furthermore, the small-size simply supported beam is of a rectangular structure with the surface subjected to polishing treatment; the length L of the small-sized simply supported beams is greater than or equal to 1.2 times the clear span.
S2, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; comprising the following steps:
s21, performing linear fitting on an initial line elastic segment of a load-deflection curve to obtain a slope C e The modulus of elasticity E of the material is calculated by equation (1):
Figure BDA0003553655530000061
wherein P is a test load, W is deflection, E is elastic modulus of a material, S is a clear span of a simply supported beam, B is a sample width, and W is a sample height;
s2, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; further comprises:
s22, performing power law fitting on an elastoplastic segment of a load-deflection curve to obtain a formula (2), and obtaining a loading coefficient C and a loading index m according to the formula (2):
P＝Cw m (2)
the loading coefficient C and the loading index m are substituted into formula (3):
Figure BDA0003553655530000062
wherein n is a strain hardening exponent, K is a strain hardening coefficient, K 1 、k 2 、k 3 、k 4 Taking the clear span S of the simply supported beam as the characteristic length h, A * ＝BW 3 /S 2 Is the feature area.
S2, predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; further comprises:
s23, substituting E, K and n into the Hollomon model to obtain a material uniaxial true stress-strain relationship as shown in formula (4):
Figure BDA0003553655530000063
in sigma T Is true stress, epsilon T Is true strain, sigma y Is the nominal yield strength.
Further, S3, converting the uniaxial true stress-strain relation into an engineering stress-strain curve to obtain yield strength Rp 0.2 The method comprises the steps of carrying out a first treatment on the surface of the Comprising the following steps:
s31, converting the obtained true stress-strain relation into an engineering stress-strain curve according to the formula (5):
Figure BDA0003553655530000071
/>
wherein e is a natural constant, ε E For engineering strain, sigma E Is engineering stress;
s32, determining and obtaining yield strength R through intersection points of bias lines and engineering stress-strain curves P0.2 。
Further, S32, determining the yield strength R through the intersection point of the bias line and the engineering stress-strain curve P0.2 Comprising:
s321, determining the yield strength R through the intersection point of the 0.2% bias line and the engineering stress-strain curve P0.2 。
Further, S4, predicting and obtaining the tensile strength R of the material according to the parameters of the Hollomon constitutive model m The method comprises the steps of carrying out a first treatment on the surface of the Comprising the following steps:
s41, predicting and obtaining the tensile strength R of the material according to the formula (6) m ：
Figure BDA0003553655530000072
Further, the size range of the small-size simply supported beam is as follows: sample width b=3 mm, sample height w=3 mm, simply supported beam clear span s=4w=12 mm; the surface of the small-size simply supported beam is manually and finely polished by using sand paper with more than 800 meshes.
S1, performing a three-point bending loading test by using a small-size simply supported beam to obtain a test load-deflection curve of the small-size simply supported beam; comprising the following steps:
s11, adjusting the distance between two rollers of the lower clamp of the testing machine to be consistent with a preset clear span S of the test, placing a small-size simply supported beam on the two rollers of the lower clamp of the testing machine, and enabling the axial direction of the rollers to be perpendicular to the length direction of the simply supported beam;
s12, carrying out three-point bending loading on the sample through a testing machine, and synchronously collecting real-time load and deflection data between the upper clamp and the lower clamp until the loading displacement reaches 0.5W or the load reaches the highest peak and then descends by 10%.
Example 1
The embodiment provides a performance test method for a small-size simply supported beam, in particular to a stress-strain relation and strength test method for a metal material of a small-size simply supported beam sample, wherein the specific test method is as follows:
step 1, processing a metal material into a simply supported beam sample with a specific size through slow wire running according to test requirements, and manually polishing the sample by using sand paper with more than 800 meshes; the total length L of the simply supported beams is more than or equal to 1.2S, and a sample configuration size diagram is provided as shown in figure 1. Fig. 2 shows a finite element analysis model diagram of a small-sized simply supported beam sample for three-point bending load bearing. After the preliminary machining of the sample is completed, it is preferable to manually fine polish the surface of the sample with sandpaper of 800 mesh or more.
And 2, adjusting the distance between the two rollers of the lower clamp to be consistent with a preset clear span S, placing the small sample of the simply supported beam finished in the step 1 on the two rollers of the lower clamp, and ensuring that the axial direction of the rollers is vertical to the length direction of the simply supported beam.
Step 3, carrying out three-point bending loading on the sample by a testing machine, wherein the loading rate is moderate (0.1 mm min -1 Left and right), synchronously collecting real-time load and deflection data between the upper clamp and the lower clamp until the load displacement reaches 0.5W or the load is reduced by 10% after reaching the highest peak.
Step 4, extracting a test curve, and predicting a stress-strain relationship according with a load-deflection relationship between the upper clamp and the lower clamp of the sample to be in accordance with a material uniaxial stress-strain relationship of the Hollomon constitutive model; the specific operation is as follows:
step 4-1, performing linear fitting on the initial line elastic segment of the load-deflection curve to obtain a slope C e The elastic modulus E of the material can be directly calculated by the elastic bending theory of the simply supported beam with the rectangular section:
Figure BDA0003553655530000081
in the formula (1), P is a test load, W is deflection, E is elastic modulus of a material, S is a clearance span of a simply supported beam, B is a sample width, and W is a sample height;
step 4-2, performing power law fitting on an elastoplastic segment of the load-deflection curve to obtain a loading coefficient C and a loading index m:
P＝Cw m (2)；
step 4-3, substituting parameters C and m of the formula (2) into the following formula (3):
Figure BDA0003553655530000082
in the formula (3), n is a strain hardening index, K is a strain hardening coefficient, and K 1 、k 2 、k 3 、k 4 Taking the clear span S of the simply supported beam as the characteristic length h, A * ＝BW 3 /S 2 Is a characteristic area;
and 4-4, substituting E, K, n obtained in S21 and S23 into a Hollomon model to obtain a uniaxial true stress-strain relation of the material:
Figure BDA0003553655530000083
in formula (4), σ T Is true stress, epsilon T Is true strain, sigma y Is the nominal yield strength;
the parameters associated with the small-size simply supported beam configuration samples are shown in Table 1:
table 1 list of parameters
Figure BDA0003553655530000084
For other similar configuration dimensions, only k needs to be recalibrated 1 、k 2 、k 3 、k 4 The method can be used, and ANSYS software is used for setting the elastic modulus E=200GPa (can be any certain value of 50 GPa-250 GPa) of the material and the nominal yield strength sigma y The values of the transformation strain hardening index n are sequentially 0.1, 0.15, 0.2, 0.25 and 0.3 which are respectively calculated to obtain 5 load-displacement curves, and the parameter k can be calibrated by combining the formulas (1) and (2) and knowing E, K, n 1 、k 2 、k 3 、k 4 。
Step 5, converting the uniaxial true stress-strain relation obtained in the step 4 to obtain an engineering stress-strain curve, and obtaining yield strength R p0.2 。
Converting the obtained true stress-strain relationship into an engineering stress-strain curve:
Figure BDA0003553655530000091
in the formula (5), e is a natural constant, ε E Is engineering ofStrain, sigma E Is engineering stress.
Further, the yield strength R is determined by the intersection of the 0.2% bias line with the engineering stress-strain curve P0.2 。
Step 6, predicting and obtaining the tensile strength R according to the K and the n obtained in the step 4 m As shown in formula (6):
Figure BDA0003553655530000092
description of the preferred embodiments
This example was tested experimentally using the method provided in example 1, and the test method is summarized as follows:
as shown in fig. 2, a finite element simulation model of a small-sized simply supported beam subjected to three-point bending loading is established. The Hollomon constitutive model (shown in figure 3) is adopted as a simulated material constitutive relation, model parameters comprise elastic modulus E, strain hardening index n and strain hardening coefficient K, working condition calculation of the strain hardening index n (at least 5 different n) is changed, load-displacement curves of different imaginary materials are obtained, and calibration of undetermined parameters in a prediction formula is completed.
Preparing a simply supported beam sample by using CLF-1 (Chinese Low activation Ferritic) steel, and completing a three-point bending test under displacement control, wherein the sample width B=3 mm, the sample height W=3 mm, and the clear span S=4W=12 mm of the simply supported beam; three-point bending test was performed on 3 parallel test pieces, a Cheng Zaihe-deflection curve was collected for the test, and a continuous and stable load-deflection test curve was collected in FIG. 4.
Fitting the straight line segment of the curve with a linear function to obtain a slope C e The method comprises the steps of carrying out a first treatment on the surface of the And fitting the elastoplastic curve segment by using a power law function to obtain a loading coefficient C and an index m. Combining a formula to obtain a parameter elastic modulus E, a strain hardening coefficient K and a strain hardening index n of the Hollomon constitutive model, and substituting E, K, n into the Hollomon model to obtain a uniaxial true stress-strain relation prediction result of the material; converting the obtained true stress-strain relationship into engineering stress-strain curve to obtain yield strength R p0.2 The method comprises the steps of carrying out a first treatment on the surface of the By the formula R m ＝K(n/e) n Calculated to obtainTo tensile strength R m . Carrying out a uniaxial tensile test on a CLF-1 steel Standard Round Bar (SRB) sample to obtain a uniaxial true stress-strain relationship of the CLF-1 steel; as shown in fig. 5, the uniaxial true stress-strain curve of 3 simply supported beam samples (referring to 3 small-sized simply supported beam samples of the same configuration and size) substantially coincides with the results of the standard round bar. In actual engineering use, the size of the sample can be adjusted, and the undetermined parameters of the calibration prediction model can be calculated only by carrying out simple finite element calculation again. The results of the CLF-1 steel test are shown in Table 2.
TABLE 2 CLF-1 Steel prediction results List
Figure BDA0003553655530000101
Therefore, the embodiment of the invention designs the small-size simply supported beam sample, performs a three-point bending test on the small-size simply supported beam sample, can predict a uniaxial true stress-strain curve corresponding to the material according to a load-deflection curve between an upper clamp and a lower clamp, and can obtain the yield strength R of a common engineering parameter p0.2 And tensile strength R m The method comprises the steps of carrying out a first treatment on the surface of the The invention solves the problem of sample size limitation, has reliable basic theoretical support, does not need complicated iterative solution, and can acquire continuous and complete stress-strain curves. The method has great engineering application value for obtaining the uniaxial stress-strain relation and the strength of materials in the key fields of membranous, platy and other small-size elements, small-size components, pipeline structures, novel materials and the like existing in engineering.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (8)

1. The performance test method of the small-size simply supported beam is characterized by comprising the following steps of:
carrying out a three-point bending loading test by using a small-size simply supported beam to obtain a test load-deflection curve of the small-size simply supported beam;
predicting a uniaxial true stress-strain relationship conforming to the Hollomon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship;
converting the uniaxial true stress-strain relationship into an engineering stress-strain curve to obtain yield strength R p0.2 ；
According to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m ；
Predicting a uniaxial true stress-strain relationship conforming to the Holloon constitutive model according to a test load-deflection curve of the small-size simply supported beam by using a load-deflection relationship; comprising the following steps:
performing power law fitting on an elastoplastic segment of a load-deflection curve to obtain a formula (2), and obtaining a loading coefficient according to the formula (2)CLoad indexm：
Figure QLYQS_1
Loading coefficientCLoad indexmSubstituting into formula (3):
Figure QLYQS_2
in the method, in the process of the invention,nin order to obtain a strain hardening index, the composition,Kin order to achieve a strain hardening coefficient,k 1 、k 2 、k 3 、k 4 taking the clear span of the simply supported beam as the undetermined constant of the finite element model of the simply supported beam sampleSIs the characteristic lengthh*，A * = BW 3 /S 2 Is a characteristic area;
according to the parameters of the Hollomon constitutive model, predicting and obtaining the tensile strength R of the material m The method comprises the steps of carrying out a first treatment on the surface of the Comprising the following steps:
predicting and obtaining the material resistance according to the formula (6)Tensile strength R m ：
Figure QLYQS_3
。
2. The performance test method of the small-size simply supported beam according to claim 1, wherein the small-size simply supported beam has a rectangular structure with a polished surface; the length L of the small-sized simply supported beams is greater than or equal to 1.2 times the clear span.
3. The performance test method of the small-size simply supported beam according to claim 1 or 2, wherein the single-axis true stress-strain relationship conforming to the Holloon constitutive model is predicted according to a test load-deflection curve of the small-size simply supported beam by a load-deflection relationship; comprising the following steps:
linear fitting is carried out on the initial line elastic section of the load-deflection curve to obtain a slopeC e Calculating the elastic modulus of the material by the formula (1)E：
Figure QLYQS_4
In the method, in the process of the invention,Pin order to test the load of the test,win order to be able to deflect the material,Eas a function of the modulus of elasticity of the material,Sfor a simply supported beam net span,Bfor the width of the sample to be measured,Wis the sample height.
4. The method for testing the performance of the small-size simply supported beam according to claim 1, wherein the single-axis true stress-strain relationship conforming to the Holloon constitutive model is predicted according to a test load-deflection curve of the small-size simply supported beam by a load-deflection relationship; further comprises:
will beE、KAndnsubstituting the material into the Hollomon model to obtain the uniaxial true stress-strain relationship of the material as shown in the formula (4):
Figure QLYQS_5
in the method, in the process of the invention,σ T is a true stress, and is a true stress,ε T is the true strain of the steel sheet,σ y is the nominal yield strength.
5. The method for testing the performance of a small-sized simply supported beam according to claim 4, wherein the uniaxial true stress-strain relationship is converted into an engineering stress-strain curve to obtain the yield strength R p0.2 The method comprises the steps of carrying out a first treatment on the surface of the Comprising the following steps:
the resulting true stress-strain relationship is converted into an engineering stress-strain curve according to equation (5):
Figure QLYQS_6
wherein e is a natural constant,ε E for the purpose of engineering strain,σ E is engineering stress;
determining the yield strength R through the intersection point of the bias line and the engineering stress-strain curve P0.2 。
6. The method for testing the performance of the small-size simply-supported beam according to claim 5, wherein the yield strength R is obtained by determining the intersection point of the bias line and the engineering stress-strain curve P0.2 Comprising:
the yield strength R is determined by the intersection point of the 0.2% offset line and the engineering stress-strain curve P0.2 。
7. The method for testing the performance of the small-sized simply supported beam according to claim 2, wherein the small-sized simply supported beam has a size range of: sample width b=3 mm, sample height w=3 mm, simply supported beam clear span s=4w=12 mm; the surface of the small-size simply supported beam is manually and finely polished by using sand paper with more than 800 meshes.
8. The method for testing the performance of the small-size simply supported beam according to claim 7, wherein the small-size simply supported beam is used for performing a three-point bending loading test to obtain a test load-deflection curve of the small-size simply supported beam; comprising the following steps:
the distance between the two rollers of the lower clamp of the testing machine is adjusted to be consistent with a preset clear span S of the test, and a small-size simply supported beam is placed on the two rollers of the lower clamp of the testing machine, so that the axial direction of the rollers is perpendicular to the length direction of the simply supported beam;
three-point bending loading is carried out on the sample through a testing machine, and real-time load and deflection data between the upper clamp and the lower clamp are synchronously acquired until the loading displacement reaches 0.5WOr the load drops by 10% after reaching the peak.
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