Calibration method for loading shaft of planar biaxial mechanical property testing machine

Abstract

The invention belongs to the field of measurement and testing, and relates to a method for calibrating a loading shaft of a planar biaxial mechanical property testing machine, which comprises the following steps of: arranging strain gauges on the upper and lower bottom surfaces of all loading arms of a calibration standard sample in areas near the axes of the loading arms; fixing all the loading arms by using four loading shafts, recording strain information of strain gauges on the upper and lower bottom surfaces of all the loading arms before the tensile load is applied, and calibrating inclination angles of all the loading shafts relative to the loading shaft coplane; the relative coplanar inclination angle of the loading shafts is calibrated based on the strain information of the strain gauges when the tensile load is applied, so that the flatness of all the loading shafts is calibrated when the load is applied. The strain gauges are arranged on the upper bottom surface and the lower bottom surface of all the loading arms of the calibration standard sample, so that the strain of the loading arms can be simultaneously measured on the upper surfaces and the lower surfaces of the loading arms, the relatively ideal coplanar inclination angle of the loading shafts is adjusted and calibrated, the flatness of the loading shafts is calibrated, and the defect of calibrating the flatness of the loading shafts is overcome.

Description

Technical Field

[0001] The present invention relates to the field of measurement and testing technology, and in particular to a calibration method for a loading axis of a planar biaxial mechanical property testing machine. Background Art

[0002] Planar biaxial mechanical properties test can conduct more realistic mechanical properties tests on structural components under different temperatures, test frequencies, load ratios and load phase differences. The planar biaxial mechanical properties testing machine not only needs to adjust the coaxiality of the two mutually orthogonal axes, but also must detect whether the four loading axes are perpendicular and coplanar to each other.

[0003] The existing planar biaxial mechanical properties testing device uses the coaxiality calibration method of the uniaxial testing machine to calibrate the two sets of loading axes separately, and it is impossible to calibrate whether the four loading axes are perpendicular to each other and coplanar; if there is an angle and flatness deviation in the loading axes during the planar biaxial mechanical properties test, it will cause additional bending moment and torque during the test, such as Figure 1 Comparing the coaxial line with medium deviation (pink) with the standard coaxial line (red) shows that the deviated coaxial line deviates from the ideal coplanarity of the planar biaxial axis. The two test axes are not actually coplanar, seriously affecting the accuracy of the test data. Existing planar biaxial mechanical properties testing equipment cannot meet the requirements of angle and flatness, and it is difficult to avoid the presence of additional bending and torque during the test, which seriously affects the accuracy of the test data. Summary of the Invention

[0004] In view of the above analysis and in response to the shortcomings in the prior art, the present invention aims to provide a calibration method for the loading axis of a planar biaxial mechanical properties testing machine to solve at least one of the problems existing in the prior art of biaxial mechanical properties testing, namely, the inability to meet the requirements of angles and flatness within the planes of the four loading axes, the presence of additional bending moments and torques during the test, and poor accuracy of test data.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention discloses a calibration method for a loading axis of a planar biaxial mechanical properties testing machine, comprising:

[0007] S1: Strain gauges are installed on the upper and lower bottom surfaces of all loading arms of the calibration standard near the axis of the loading arm;

[0008] S2: Using four loading axes to fix all loading arms, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms before applying the tensile load. Based on the strain information of the strain gauges before applying the tensile load, calibrate the inclination angles of all loading axes relative to the coplanar loading axis to achieve the flatness calibration of all loading axes when no load is applied.

[0009] S3: Select one of the loading axes to apply a tensile load, obtain strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the coplane based on the strain information of the strain gauges when the tensile load is applied;

[0010] S4: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane using the same method as step S3 to achieve calibration of the flatness of all loading axes when load is applied.

[0011] Preferably, the strain gauge arrangement satisfies: 2M strain gauges are provided symmetrically with respect to the axis of the loading arm, where M is a positive integer, so as to facilitate more accurate measurement of areas where the upper and lower bottom surfaces are at the same distance from the calibration standard.

[0012] Preferably, in step S2 and step S3, whether or not the tensile load is applied, the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm can be expressed as ε i-j Indicates, where i represents whether the tensile load is applied or not, which can be 0 or 1, i = 0 means no tensile load is applied, i = 1 means tensile load is applied; j represents the serial number of the strain gauge corresponding to the strain information;

[0013] In step S2, the inclination angles of all loading axes coplanar with respect to the loading axis are calibrated based on the strain information of the strain gauges before the tensile load is applied, including:

[0014] S201: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm before applying the tensile load to obtain ∑ε 0-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm before applying the tensile load is summed to obtain ∑ε 0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0015] S202: Based on ∑ε 0-m ,∑ε 0-n The difference is calibrated for the inclination angle of the loading axis relative to the coplanar loading axis when no load is applied;

[0016] S203: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane according to steps S201 and S202, thereby achieving flatness calibration.

[0017] Preferably, step S202 includes:

[0018] Based on ∑ε 0-m ,∑ε 0-n The absolute value of the difference determines whether the inclination angle of the loading axis relative to the coplane meets the requirements;

[0019] Based on ∑ε 0-m ,∑ε 0-nThe positive or negative value of the difference determines the direction of the inclination adjustment of the loading axis relative to the coplane.

[0020] Preferably, step S202 includes:

[0021] S2021: To|∑ε 0-m -∑ε 0-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0022] When |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0023] When |∑ε 0-m -∑ε 0-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment;

[0024] S2022:|∑ε 0-m -∑ε 0-n | / N>ε P When ∑ε 0-m -∑ε 0-n Positive and negative further judgement;

[0025] When ∑ε 0-m -∑ε 0-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located;

[0026] When ∑ε 0-m -∑ε 0-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located;

[0027] S2023: Obtain ∑ε again according to step S201 for the loading axis after the offset adjustment in step S2022 0-m ,∑ε 0-n , repeat step S2021, step S2022 judgment and adjustment until |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0028] ε P Not 0.

[0029] Preferably, in step S3, calibrating the inclination angle of the loading axis relative to the coplane based on the strain information of the strain gauge when the tensile load is applied includes:

[0030] S301: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm when the tensile load is applied to obtain ∑ε 1-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm when the tensile load is applied is summed to obtain ∑ε 1-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0031] S302: Based on ∑ε 1-m ,∑ε 1-n The difference is calibrated for the inclination of the loading axis relative to the coplanar plane when the load is applied.

[0032] Preferably, step S302 includes:

[0033] S3021: Right |∑ε 1-m -∑ε 1-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0034] When |∑ε 1-m -∑ε 1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0035] When |∑ε 1-m -∑ε 1-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment;

[0036] S3022:|∑ε 1-m -∑ε 1-n | / N>ε P When ∑ε 1-m -∑ε 1-n Positive and negative further judgement;

[0037] When ∑ε 1-m -∑ε 1-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located;

[0038] When ∑ε 1-m -∑ε 1-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located;

[0039] S3023: Obtain ∑ε again according to step S301 for the loading axis after the offset adjustment in step S3022 1-m ,∑ε 1-n , repeat step S3021, step S3022 judgment and adjustment until |∑ε 1-m -∑ε1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0040] ε P Not 0.

[0041] Preferably, step S4 is followed by step S5:

[0042] Based on the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm, the loading axis that has completed flatness calibration is sequentially calibrated for the inclination angle of the loading axis plane when no load is applied and the inclination angle of the loading axis plane when load is applied, thereby achieving the calibration of the verticality of all loading axes.

[0043] Preferably, step S5 includes:

[0044] S501: For the loading axis that has completed flatness calibration, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms when no tensile load is applied. Based on the strain information of the strain gauges before the tensile load is applied, calibrate the inclination angles of all loading axes relative to the vertical direction perpendicular to each other in the plane, thereby achieving calibration of the verticality of all loading axes when no load is applied.

[0045] S502: Obtain the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the vertical direction perpendicular to the loading axes in the plane based on the strain information of the strain gauges when the tensile load is applied, so as to achieve calibration of the verticality of all loading axes when the load is applied.

[0046] Preferably, in step S5, whether or not a tensile load is applied, the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm can be expressed as ε 左-i-j or ε 右-i-j Indicates, where i represents whether a tensile load is applied or not, and can be 0 or 1. i = 0 indicates no tensile load is applied, and i = 1 indicates a tensile load is applied. j represents the serial number of the strain gauge corresponding to the strain information. Left and right are the classifications based on the position of the strain gauge relative to the axis of the loading arm when viewed from the top of the bottom surface of the calibration standard. The strain gauge located to the left of the loading arm axis is classified as left, and the strain gauge located to the right of the loading arm axis is classified as right.

[0047] In step S501, based on the strain information of the strain gauge before applying the tensile load, the inclination calibration of all loading axes relative to the vertical direction perpendicular to each other in the plane includes:

[0048] S5011: Sum the strain information of all strain gauges on the same side of the axis of the same loading arm before applying the tensile load to obtain ∑ε 左-0-m, m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; before applying the tensile load, the strain information of all strain gauges on the other side of the axis of the same loading arm is summed to obtain ∑ε 右-0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0049] S5012: Based on ∑ε 左-0-m ,∑ε 右-0-n The difference is calibrated for the inclination angle in the plane of the loading axis when no load is applied;

[0050] S5013: Calibrate the inclination angles of the remaining three loading axis planes according to steps S5011 and S5012, thereby achieving the verticality calibration of the loading axis.

[0051] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0052] (1) The present invention arranges strain gauges on the upper and lower bottom surfaces of all loading arms of the calibration standard in the vicinity of the loading arm axis, thereby achieving simultaneous measurement of the strain of the loading arm on the upper and lower surfaces, and adjusting and calibrating the inclination angles of all loading axes relative to the ideal coplane based on the difference in strain information of the strain gauges on the upper and lower bottom surfaces, thereby achieving calibration of the flatness of all loading axes, overcoming the defect of the prior art that the loading axis flatness cannot be calibrated.

[0053] (2) The present invention calibrates the loading axis twice, when no load is applied and when a load is applied, thereby avoiding the accumulation of loading axis deviation during the load application process and further improving the calibration accuracy.

[0054] (3) The present invention improves the accuracy and precision of subsequent calibration by applying a tensile load to each loading arm individually; at the same time, it realizes the individual detection and individual adjustment of the inclination angle of the loading arm relative to the ideal coplane, has better adjustment directionality, and improves the adjustment and calibration efficiency.

[0055] (4) The present invention arranges strain gauges on the upper and lower bottom surfaces of all loading arms of the calibration standard in the area near the axis of the loading arm, thereby realizing simultaneous measurement of the strain of the loading arm on the upper and lower surfaces, and adjusting and calibrating the inclination angles in the plane of all loading axes based on the difference in strain information of the strain gauges on the left and right sides of the loading arm, thereby realizing calibration of the verticality of all loading axes, overcoming the defect of the prior art that the verticality of the loading axis cannot be calibrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0057] Figure 1 Schematic diagram of flatness deviation.

[0058] Figure 2 Flowchart of the calibration method of the present invention.

[0059] Figure 3 Schematic diagram of the arrangement of the strain gauge on the bottom surface of the calibration standard in an embodiment of the present invention (top view of the bottom surface).

[0060] Figure 4 Schematic diagram of the arrangement of the strain gauge on the bottom surface of the calibration standard in an embodiment of the present invention (bottom surface bottom view).

[0061] Reference numerals:

[0062] Strain gauge 1, strain gauge 2, strain gauge 3, strain gauge 4, strain gauge 17, strain gauge 18, strain gauge 19, strain gauge 20. DETAILED DESCRIPTION

[0063] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0064] Definition of terms:

[0065] In-plane inclination angle: refers to the angle between the loading axis axis and its own axis when the projections of all loading axes in the ideal coplane are perpendicular to the loading axes.

[0066] Inclination angle relative to the coplanarity of the loading axis: refers to the inclination angle between the loading axis axis and the ideal coplanarity of all loading axes.

[0067] In one aspect, the present invention discloses a calibration standard for a loading axis of a planar biaxial mechanical properties testing machine, comprising: four loading arms;

[0068] The four loading arms are identical in shape, are opposite to each other in two in the same plane, and are arranged symmetrically relative to the center of the calibration standard.

[0069] Specifically, the calibration standard can be a rigid cross-shaped thin plate structure of equal thickness, and no plastic deformation should occur during the calibration process of the loading axis.

[0070] Specifically, the length of the loading arm must be greater than or equal to twice the width of the loading arm to ensure stable clamping while the strain gauge measures the strain as stably as possible with good repeatability and will not be affected by changes in the clamping position of the loading arm by the testing machine.

[0071] Preferably, a transition arc is provided at the fixed connection between the loading arm and the calibration standard to reduce stress concentration.

[0072] It should be noted that, ideally, the four loading axes of a planar biaxial mechanical properties testing machine should be perpendicular and coplanar to each other. It can be understood that the calibration of the loading axes should satisfy the calibration of the ideal coplanar inclination angle relative to the loading axes and the calibration of the in-plane inclination angle.

[0073] In another aspect, the present invention discloses a method for calibrating a loading axis of a planar biaxial mechanical properties testing machine, comprising:

[0074] S1: Strain gauges are installed on the upper and lower bottom surfaces of all loading arms of the calibration standard near the axis of the loading arm;

[0075] S2: Using four loading axes to fix all loading arms, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms before applying the tensile load. Based on the strain information of the strain gauges before applying the tensile load, calibrate the inclination angles of all loading axes relative to the coplanar loading axis to achieve the flatness calibration of all loading axes when no load is applied.

[0076] S3: Select one of the loading axes to apply a tensile load, obtain strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the coplane based on the strain information of the strain gauges when the tensile load is applied;

[0077] S4: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane using the same method as step S3 to achieve calibration of the flatness of all loading axes when load is applied.

[0078] During implementation, after the load is applied, the strain gauge can collect the strain information of the loading arm relative to zero load; based on the difference in strain information of the strain gauges on the upper and lower bottom surfaces, the inclination angle of the loading axis relative to the ideal coplane is adjusted.

[0079] Compared with the prior art, the present invention realizes simultaneous measurement of the strain of the loading arm on the upper and lower surfaces of the loading arms of the calibration standard by arranging strain gauges in the area near the axis of the loading arm, and adjusts and calibrates the inclination angle of all loading axes relative to the ideal coplane based on the difference in strain information of the strain gauges on the upper and lower bottom surfaces, thereby realizing calibration of the flatness of all loading axes, overcoming the defect of the prior art that the flatness of the loading axis cannot be calibrated.

[0080] It should be noted that when four loading axes are used to secure all loading arms, when no load is applied, the axes may not be mutually perpendicular and coplanar due to uncalibrated loading axes. In this case, the loading axes actually apply load to the loading arms, not meeting the zero-load requirement. Therefore, strain information on the loading arms must be collected regardless of whether a tensile load is applied. Furthermore, the applicant's research has found that even if the loading axes meet the required deviation range when no load is applied, there is a risk that the deviation will increase when a load is applied, necessitating recalibration when a load is applied.

[0081] Compared with the prior art, the present invention avoids the accumulation of loading axis deviation during the load application process by calibrating the loading axis twice, when no load is applied and when a load is applied, thereby further improving the calibration accuracy.

[0082] The applicant's research found that the strain of the loading arm in the calibration standard is mainly affected by the loading axis fixed to it. The present invention applies a tensile load to each loading arm separately, which helps to expand the influence of the inclination angle of the loading axis of the fixed loading arm relative to the ideal coplane on the loading arm and reduce the influence of the remaining loading axes; at the same time, it realizes the separate detection and adjustment of the inclination angle of the loading arm relative to the ideal coplane, has better adjustment directionality, and improves the adjustment and calibration efficiency.

[0083] Compared with the prior art, the present invention improves the accuracy and precision of subsequent calibration by applying a tensile load to each loading arm individually; at the same time, it realizes the individual detection and individual adjustment of the inclination angle of the loading arm relative to the ideal coplane, has better adjustment directionality, and improves the adjustment and calibration efficiency.

[0084] Preferably, the projections of the strain gauges in the upper and lower bottom surfaces on the bottom surface of the calibration standard are the same, so as to facilitate simultaneous measurement of areas of the upper and lower bottom surfaces at the same distance from the calibration standard.

[0085] Preferably, the strain gauge arrangement satisfies: 2M strain gauges are provided symmetrically with respect to the axis of the loading arm, where M is a positive integer, so as to facilitate more accurate measurement of areas where the upper and lower bottom surfaces are at the same distance from the calibration standard.

[0086] For example, in step S1, strain gauges are set on the upper and lower bottom surfaces of all loading arms of the calibration standard near the axis of the loading arm, such as Figure 3-Figure 4 As shown, four strain gauges can be set on the upper and lower bottom surfaces of the loading arm:

[0087] The upper bottom surface is provided with strain gauges 1, 2, 3 and 4; strain gauges 1 and 2 are symmetrically arranged relative to the axis of the loading arm, and strain gauges 3 and 4 are symmetrically arranged relative to the axis of the loading arm;

[0088] The lower bottom surface is provided with strain gauges 17, 18, 19 and 20; strain gauges 17 and 18 are symmetrically arranged relative to the axis of the loading arm, and strain gauges 19 and 20 are symmetrically arranged relative to the axis of the loading arm;

[0089] The projections of strain gauges 17, 18, 19, and 20 on the bottom surface of the calibration standard are respectively the same as the projections of strain gauges 1, 2, 3, and 4 on the bottom surface of the calibration standard. The strain gauges with the same projections on the upper and lower bottom surfaces are at the same distance from the center of the calibration standard.

[0090] Specifically, whether the tensile load is applied in step S2 or step S3, the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm can be expressed as ε i-j Indicates, where i represents whether the tensile load is applied or not, which can be 0 or 1, i=0 means no tensile load is applied, i=1 means tensile load is applied; j represents the serial number of the strain gauge corresponding to the strain information.

[0091] The strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm before the tensile load is applied in step S2 includes the strain information set {ε 0-j}; The strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied in step S3 includes the strain information set {ε 1-j}.

[0092] For example, when four strain gauges are set on each of the upper and lower bottom surfaces of the loading arm, a total of 32 strain gauges are set. The strain information set before tensile loading {ε 0-j} includes 32 sets of data with j varying from 1 to 32; the strain information set {ε 1-j}Includes 32 sets of data where j varies from 1 to 32.

[0093] Further, taking one of the loading arms as an example, Figure 3-Figure 4 As shown, the strain information before tensile load corresponding to strain gauge 1, strain gauge 2, strain gauge 3, strain gauge 4, strain gauge 17, strain gauge 18, strain gauge 19, and strain gauge 20 are ε 0-1 , ε 0-2 , ε 0-3 , ε 0-4 , ε 0-17 , ε 0-18 , ε 0-19 and ε 0-20 The strain information after tensile load corresponding to strain gauge 1, strain gauge 2, strain gauge 3, strain gauge 4, strain gauge 17, strain gauge 18, strain gauge 19, and strain gauge 20 are ε 1-1 , ε 1-2 , ε 1-3 , ε 1-4 , ε 1-17 , ε 1-18 , ε 1-19 and ε 1-20 .

[0094] Specifically, in step S2, based on the strain information of the strain gauge before applying the tensile load, the inclination angles of all loading axes relative to the coplanar loading axis are calibrated, including:

[0095] S201: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm before applying the tensile load to obtain ∑ε 0-m, m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm before applying the tensile load is summed to obtain ∑ε 0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0096] S202: Based on ∑ε 0-m ,∑ε 0-n The difference is calibrated for the inclination angle of the loading axis relative to the coplanar loading axis when no load is applied;

[0097] S203: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane according to steps S201 and S202, thereby achieving flatness calibration.

[0098] Specifically, step S202 includes:

[0099] Based on ∑ε 0-m ,∑ε 0-n The absolute value of the difference determines whether the inclination angle of the loading axis relative to the coplane meets the requirements;

[0100] Based on ∑ε 0-m ,∑ε 0-n The positive or negative value of the difference determines the direction of the inclination adjustment of the loading axis relative to the coplane.

[0101] Specifically, step S202 includes:

[0102] S2021: To|∑ε 0-m -∑ε 0-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0103] When |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0104] When |∑ε 0-m -∑ε 0-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment;

[0105] S2022:|∑ε 0-m -∑ε 0-n | / N>ε P When ∑ε 0-m -∑ε 0-n Positive and negative further judgement;

[0106] When ∑ε 0-m -∑ε 0-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located;

[0107] When ∑ε 0-m -∑ε 0-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located;

[0108] S2023: Obtain ∑ε again according to step S201 for the loading axis after the offset adjustment in step S2022 0-m ,∑ε 0-n , repeat step S2021, step S2022 judgment and adjustment until |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed.

[0109] Specifically, ε P It can be 1%.

[0110] Specifically, similar to step S2, step S3 calibrates the inclination angle of the loading axis relative to the coplane based on the strain information of the strain gauge when the tensile load is applied, including:

[0111] S301: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm when the tensile load is applied to obtain ∑ε 1-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm when the tensile load is applied is summed to obtain ∑ε 1-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0112] S302: Based on ∑ε 1-m ,∑ε 1-n The difference is calibrated for the inclination of the loading axis relative to the coplanar plane when the load is applied.

[0113] Specifically, step S302 includes:

[0114] S3021: Right |∑ε 1-m -∑ε 1-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0115] When |∑ε 1-m -∑ε 1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed;

[0116] When |∑ε 1-m -∑ε 1-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment;

[0117] S3022:|∑ε 1-m -∑ε 1-n | / N>ε P When ∑ε 1-m -∑ε 1-n Positive and negative further judgement;

[0118] When ∑ε 1-m -∑ε 1-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located;

[0119] When ∑ε 1-m -∑ε 1-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located;

[0120] S3023: Obtain ∑ε again according to step S301 for the loading axis after the offset adjustment in step S3022 1-m ,∑ε 1-n , repeat step S3021, step S3022 judgment and adjustment until |∑ε 1-m -∑ε 1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed.

[0121] Specifically, ε P It can be 1%.

[0122] Preferably, step S4 is followed by step S5:

[0123] Based on the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm, the loading axis that has completed flatness calibration is sequentially calibrated for the inclination angle of the loading axis plane when no load is applied and the inclination angle of the loading axis plane when load is applied, thereby achieving the calibration of the verticality of all loading axes.

[0124] Specifically, step S5 includes:

[0125] S501: For the loading axis that has completed flatness calibration, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms when no tensile load is applied. Based on the strain information of the strain gauges before the tensile load is applied, calibrate the inclination angles of all loading axes relative to the vertical direction perpendicular to each other in the plane, thereby achieving calibration of the verticality of all loading axes when no load is applied.

[0126] S502: Obtain the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the vertical direction perpendicular to the loading axes in the plane based on the strain information of the strain gauges when the tensile load is applied, so as to achieve calibration of the verticality of all loading axes when the load is applied.

[0127] It should be noted that, similar to the loading axis flatness calibration described above, when four loading axes are used to secure all loading arms, when no load is applied, the axes may not be mutually perpendicular and coplanar due to their uncalibrated state. In this case, the loading axes will actually apply load to the loading arms, not meeting the zero-load requirement. Therefore, strain information for the loading arms needs to be collected regardless of whether a tensile load is applied. Furthermore, the applicant's research has found that even if the loading axes meet the required deviation range when no load is applied, there is a risk that the corresponding deviation will increase when a load is applied, necessitating recalibration when a load is applied.

[0128] In order to better illustrate the present invention, whether the tensile load is applied in step S5 or not, the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm can be expressed as ε 左-i-j or ε 右-i-j Indicates, where i represents whether a tensile load is applied or not, which can be 0 or 1. i=0 indicates that no tensile load is applied, and i=1 indicates that a tensile load is applied. j represents the serial number of the strain gauge corresponding to the strain information. Left and right are the classifications based on the position of the strain gauge relative to the axis of the loading arm when viewed from the bottom surface of the calibration standard. The strain gauge located to the left of the loading arm axis is classified as left, and the strain gauge located to the right of the loading arm axis is classified as right.

[0129] The strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm before the tensile load is applied in step S5 includes the strain information set {ε 左-0-j ; ε 右-0-j}; The strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied includes the strain information set {ε 左-1-j ; ε 右-1-j}.

[0130] For example, when four strain gauges are set on each of the upper and lower bottom surfaces of the loading arm, a total of 32 strain gauges are set. The strain information set before tensile loading {ε 左-0-j ; ε 右-0-j} includes 32 sets of data with j varying from 1 to 32; the strain information set {ε 左-1-j ; ε 右-1-j}Includes 32 sets of data where j varies from 1 to 32.

[0131] Further, taking one of the loading arms as an example, Figure 3-Figure 4 As shown, the strain information before tensile load corresponding to strain gauge 1, strain gauge 2, strain gauge 3, strain gauge 4, strain gauge 17, strain gauge 18, strain gauge 19, and strain gauge 20 are ε 左-0-1 , ε 右-0-2 , ε 左-0-3 , ε 右-0-4 , ε 左-0-17 , ε右-0-18 , ε 左-0-19 and ε 右-0-20 The strain information after tensile load corresponding to strain gauge 1, strain gauge 2, strain gauge 3, strain gauge 4, strain gauge 17, strain gauge 18, strain gauge 19, and strain gauge 20 are ε 左-1-1 , ε 右-1-2 , ε 左-1-3 , ε 右-1-4 , ε 左-1-17 , ε 右-1-18 , ε 左-1-19 and ε 右-1-20 .

[0132] Specifically, in step S501, based on the strain information of the strain gauge before applying the tensile load, the inclination calibration of all loading axes relative to the vertical direction perpendicular to each other in the plane includes:

[0133] S5011: Sum the strain information of all strain gauges on the same side of the axis of the same loading arm before applying the tensile load to obtain ∑ε 左-0-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; before applying the tensile load, the strain information of all strain gauges on the other side of the axis of the same loading arm is summed to obtain ∑ε 右-0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0134] S5012: Based on ∑ε 左-0-m ,∑ε 右-0-n The difference is calibrated for the inclination angle in the plane of the loading axis when no load is applied;

[0135] S5013: Calibrate the inclination angles of the remaining three loading axis planes according to steps S5011 and S5012, thereby achieving the verticality calibration of the loading axis.

[0136] Specifically, step S5012 includes:

[0137] Based on ∑ε 左-0-m ,∑ε 右-0-n The absolute value of the difference is used to determine whether the inclination angle in the loading axis plane meets the requirements;

[0138] Based on ∑ε 左-0-m ,∑ε 右-0-n The positive or negative value of the difference determines the adjustment direction of the inclination angle in the loading axis plane.

[0139] Specifically, step S5012 includes:

[0140] S50121: for |∑ε 左-0-m -∑ε 右-0-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0141] When |∑ε左-0-m -∑ε 右-0-n | / N≤ε O , the inclination angle in the loading axis plane is qualified, and the loading axis verticality calibration is completed;

[0142] When |∑ε 左-0-m -∑ε 右-0-n | / N>ε O , the inclination angle in the loading axis plane is too large and needs further adjustment;

[0143] S50122:|∑ε 左-0-m -∑ε 右-0-n | / N>ε O When ∑ε 左-0-m -∑ε 右-0-n Positive and negative further judgement;

[0144] When ∑ε 左-0-m -∑ε 右-0-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge is located on the left;

[0145] When ∑ε 左-0-m -∑ε 右-0-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge is located on the right side;

[0146] S50123: Obtain ∑ε again according to step S5011 for the loading axis after the offset adjustment in step S50122 左-0-m ,∑ε 右-0-n , repeat step S50121, step S50122 judgment and adjustment until |∑ε 左-0-m -∑ε 右-0-n | / N≤ε O , the inclination angle in the loading axis plane is qualified, and the loading axis verticality calibration is completed;

[0147] ε O Set the threshold value for , and it is not 0.

[0148] Specifically, ε O It can be 1%.

[0149] Specifically, step S502 calibrates the inclination of the loading axis relative to the vertical direction perpendicular to the loading axes in the plane based on the strain information of the strain gauge when the tensile load is applied, including:

[0150] S5021: Sum the strain information of all strain gauges on the same side of the axis of the same loading arm when the tensile load is applied to obtain ∑ε 左-1-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; when the tensile load is applied, the strain information of all strain gauges on the other side of the axis of the same loading arm is summed to obtain ∑ε右-1-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces;

[0151] S5022: Based on ∑ε 左-1-m ,∑ε 右-1-n The difference is calibrated for the inclination angle in the plane of the loading axis when no load is applied;

[0152] S5023: Calibrate the inclination angles of the remaining three loading axis planes according to steps S5021 and S5022, thereby achieving the verticality calibration of the loading axis.

[0153] Specifically, step S5022 includes:

[0154] Based on ∑ε 左-1-m ,∑ε 右-1-n The absolute value of the difference is used to determine whether the inclination angle in the loading axis plane meets the requirements;

[0155] Based on ∑ε 左-1-m ,∑ε 右-1-n The positive or negative value of the difference determines the direction of the inclination adjustment in the loading axis plane.

[0156] Specifically, step S5022 includes:

[0157] S50221: Right |∑ε 左-1-m -∑ε 右-1-n | / N numerical judgment, N is the number of all strain gauges on the loading axis;

[0158] When |∑ε 左-1-m -∑ε 右-1-n | / N≤ε P , the inclination angle in the loading axis plane is qualified, and the loading axis verticality calibration is completed;

[0159] When |∑ε 左-1-m -∑ε 右-1-n | / N>ε O , the inclination angle in the loading axis plane is too large and needs further adjustment;

[0160] S50222:|∑ε 左-1-m -∑ε 右-1-n | / N>ε O When ∑ε 左-1-m -∑ε 右-1-n Positive and negative further judgement;

[0161] When ∑ε 左-1-m -∑ε 右-1-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge is located on the left;

[0162] When ∑ε 左-1-m -∑ε 右-1-n<0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge is located on the right side;

[0163] S50223: Obtain ∑ε again according to step S5021 for the loading axis after the offset adjustment in step S50222 左-1-m ,∑ε 右-1-n , repeat step S50221, step S50222 judgment and adjustment until |∑ε 左-1-m -∑ε 右-1-n | / N≤ε O , the inclination angle in the loading axis plane is qualified, and the loading axis verticality calibration is completed;

[0164] ε O Set the threshold value for , and it is not 0.

[0165] Specifically, ε O It can be 1%.

[0166] Compared with the prior art, the present invention realizes the simultaneous measurement of the strain of the loading arm on the upper and lower surfaces of all loading arms of the calibration standard in the area near the axis of the loading arm, and adjusts and calibrates the inclination angles in the plane of all loading axes based on the difference in strain information of the strain gauges on the left and right sides of the loading arm, thereby realizing the calibration of the verticality of all loading axes, overcoming the defect of the prior art that the verticality of the loading axis cannot be calibrated.

[0167] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for calibrating a loading axis of a planar biaxial mechanical properties testing machine, characterized in that: include: S1: Strain gauges are installed on the upper and lower bottom surfaces of all loading arms of the calibration standard near the axis of the loading arm; S2: Using four loading axes to fix all loading arms, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms before applying the tensile load. Based on the strain information of the strain gauges before applying the tensile load, calibrate the inclination angles of all loading axes relative to the coplanar loading axis to achieve the flatness calibration of all loading axes when no load is applied. S3: Select one of the loading axes to apply a tensile load, obtain strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the coplane based on the strain information of the strain gauges when the tensile load is applied; S4: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane using the same method as step S3 to achieve calibration of the flatness of all loading axes when load is applied.

2. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 1, wherein: The strain gauge setting satisfies: 2M strain gauges are symmetrically arranged relative to the axis of the loading arm, so as to facilitate more accurate measurement of the area with the same distance between the upper and lower bottom surfaces and the calibration standard, where M is a positive integer.

3. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 2, wherein: The strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm before and after the tensile load is applied in steps S2 and S3 is expressed as ε i-j Indicates, where i represents whether the tensile load is applied or not, and is 0 or 1, i=0 means no tensile load is applied, and i=1 means tensile load is applied; j represents the serial number of the strain gauge corresponding to the strain information; In step S2, the inclination angles of all loading axes coplanar with respect to the loading axis are calibrated based on the strain information of the strain gauges before the tensile load is applied, including: S201: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm before applying the tensile load to obtain ∑ε 0-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm before applying the tensile load is summed to obtain ∑ε 0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces; S202: Based on ∑ε 0-m ,∑ε 0-n The difference is calibrated for the inclination angle of the loading axis relative to the coplanar loading axis when no load is applied; S203: Calibrate the inclination angles of the remaining three loading axes relative to the coplanar plane according to steps S201 and S202, thereby achieving flatness calibration.

4. The method for calibrating a loading axis of a planar biaxial mechanical properties testing machine according to claim 3, wherein: Step S202 includes: Based on ∑ε 0-m ,∑ε 0-n The absolute value of the difference determines whether the inclination angle of the loading axis relative to the coplane meets the requirements; Based on ∑ε 0-m ,∑ε 0-n The positive or negative value of the difference determines the direction of the inclination adjustment of the loading axis relative to the coplane.

5. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 4, wherein: Step S202 includes: S2021: To|∑ε 0-m -∑ε 0-n | / N numerical judgment, N is the number of all strain gauges on the loading axis; When |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed; When |∑ε 0-m -∑ε 0-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment; S2022:|∑ε 0-m -∑ε 0-n | / N>ε P When ∑ε 0-m -∑ε 0-n Positive and negative further judgement; When ∑ε 0-m -∑ε 0-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located; When ∑ε 0-m -∑ε 0-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located; S2023: Obtain ∑ε again according to step S201 for the loading axis after the offset adjustment in step S2022 0-m ,∑ε 0-n , repeat step S2021, step S2022 judgment and adjustment until |∑ε 0-m -∑ε 0-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed; ε P It is the set threshold value and is not 0.

6. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 5, wherein: In step S3, the inclination angle of the loading axis relative to the coplanar surface is calibrated based on the strain information of the strain gauge when the tensile load is applied, including: S301: Sum the strain information of all strain gauges on the upper bottom surface of the same loading arm when the tensile load is applied to obtain ∑ε 1-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; the strain information of all strain gauges on the lower bottom surface of the same loading arm when the tensile load is applied is summed to obtain ∑ε 1-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces; S302: Based on ∑ε 1-m ,∑ε 1-n The difference is calibrated for the inclination of the loading axis relative to the coplanar plane when the load is applied.

7. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 6, wherein: Step S302 includes: S3021: Right |∑ε 1-m -∑ε 1-n | / N numerical judgment, N is the number of all strain gauges on the loading axis; When |∑ε 1-m -∑ε 1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed; When |∑ε 1-m -∑ε 1-n | / N>ε P , the inclination angle of the loading axis relative to the coplane is too large and needs further adjustment; S3022:|∑ε 1-m -∑ε 1-n | / N>ε P When ∑ε 1-m -∑ε 1-n Positive and negative further judgement; When ∑ε 1-m -∑ε 1-n >0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the bottom surface strain gauge is located; When ∑ε 1-m -∑ε 1-n <0, adjust the centering adjustment device of the corresponding loading axis so that the loading axis is offset to the side where the strain gauge on the bottom surface is located; S3023: Obtain ∑ε again according to step S301 for the loading axis after the offset adjustment in step S3022 1-m ,∑ε 1-n , repeat step S3021, step S3022 judgment and adjustment until |∑ε 1-m -∑ε 1-n | / N≤ε P , the inclination angle of the loading axis relative to the coplane is qualified, and the loading axis flatness calibration is completed; ε P It is the set threshold value and is not 0.

8. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 7, wherein: Step S4 is followed by step S5: Based on the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm, the loading axis that has completed flatness calibration is sequentially calibrated for the inclination angle of the loading axis plane when no load is applied and the inclination angle of the loading axis plane when load is applied, thereby achieving the calibration of the verticality of all loading axes.

9. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 8, wherein: Step S5 includes: S501: For the loading axis that has completed flatness calibration, record the strain information of the strain gauges on the upper and lower bottom surfaces of all loading arms when no tensile load is applied. Based on the strain information of the strain gauges before the tensile load is applied, calibrate the inclination angles of all loading axes relative to the vertical direction perpendicular to each other in the plane, thereby achieving calibration of the verticality of all loading axes when no load is applied. S502: Obtain the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm when the tensile load is applied, and calibrate the inclination angle of the loading axis relative to the vertical direction perpendicular to the loading axes in the plane based on the strain information of the strain gauges when the tensile load is applied, so as to achieve calibration of the verticality of all loading axes when the load is applied.

10. The method for calibrating the loading axis of a planar biaxial mechanical properties testing machine according to claim 9, wherein: In step S5, whether or not a tensile load is applied, the strain information of the strain gauges on the upper and lower bottom surfaces of the loading arm is expressed as ε 左-i-j or ε 右-i-j Indicates, where i represents whether a tensile load is applied or not, and is 0 or 1, i=0 indicates no tensile load is applied, and i=1 indicates tensile load is applied; j represents the serial number of the strain gauge corresponding to the strain information; left and right are the classifications based on the position of the strain gauge relative to the axis of the loading arm when viewed from the top of the bottom surface of the calibration standard. The strain gauge located to the left of the loading arm axis is classified as left, and the strain gauge located to the right of the loading arm axis is classified as right; In step S501, based on the strain information of the strain gauge before applying the tensile load, the inclination calibration of all loading axes relative to the vertical direction perpendicular to each other in the plane includes: S5011: Sum the strain information of all strain gauges on the same side of the axis of the same loading arm before applying the tensile load to obtain ∑ε 左-0-m , m∈j, corresponding to the serial number of all strain gauges on the upper bottom surface; before applying the tensile load, the strain information of all strain gauges on the other side of the axis of the same loading arm is summed to obtain ∑ε 右-0-n , n∈j, corresponding to the serial numbers of all strain gauges on the upper and lower bottom surfaces; S5012: Based on ∑ε 左-0-m ,∑ε 右-0-n The difference is calibrated for the inclination angle in the plane of the loading axis when no load is applied; S5013: Calibrate the inclination angles of the remaining three loading axis planes according to steps S5011 and S5012, thereby achieving the verticality calibration of the loading axis.

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