CN111121638B - Method for calibrating displacement of material testing machine - Google Patents
Method for calibrating displacement of material testing machine Download PDFInfo
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- CN111121638B CN111121638B CN201911283610.6A CN201911283610A CN111121638B CN 111121638 B CN111121638 B CN 111121638B CN 201911283610 A CN201911283610 A CN 201911283610A CN 111121638 B CN111121638 B CN 111121638B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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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
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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
- G01N3/02—Details
- G01N3/04—Chucks
Abstract
The invention discloses a method for detecting displacement of a material testing machine. The method comprises the steps of utilizing laser tracker equipment to obtain a piston and structural geometric elements of a material testing machine through measurement, establishing a measurement coordinate system with the appointed coordinate axis of the laser tracker consistent with the direction of a piston line, taking the coordinate value of a preset observation point on the material testing machine as a standard quantity under the measurement coordinate system measured by the laser tracker, taking displacement provided by a material testing machine control system as an indication value, and resolving the detection results of geometric errors such as relative displacement indication value errors, geometric coaxiality, displacement linearity, displacement repeatability, displacement return error and the like of the material testing machine according to multiple cycle measurement values. The embodiment of the invention comprises: the method has the technical effects of simplicity, high digitization degree, accurate and reliable data and strong universality.
Description
Technical Field
The invention relates to the technical field of geometric quantity testing, in particular to a method for detecting displacement of a material testing machine.
Background
In the development of aviation equipment, a large number of material performance tests are required, and various tensile and compressive testing machines and material testing machines are used. With the development of modern technology, a large number of sensors including linear displacement sensors are used in a testing machine, and the sensors are solidified on the testing machine and cannot be detached for independent calibration, so that a field comprehensive detection method is required to complete displacement item detection.
Because the accuracy of the displacement of the material testing machine has certain influence on the test result, the newly issued verification rules of the JJG139-2014 tensile, pressure and material testing machine in China newly increase the requirement of displacement verification on the basis of the old version. However, the measurement method in the new rule is old, the detection apparatus still adopts a height gauge, a steel plate gauge, an indicator and the like, the measurement level is in the analog quantity measurement level, the measurement accuracy is low, the method is not suitable for the scientific research requirement and the development of the current digital detection technology, and the detection method is necessary to be innovated.
The laser tracker is a portable digital three-coordinate measuring device, is widely applied in the field of aviation scientific research, and can be used as a measuring standard device for field detection. At present, there is no public report of using a laser tracker to detect or calibrate the amount of displacement of a testing machine, and the present invention is derived from the engineering practice of the inventors.
Compared with the prior art and obtained by searching:
the prior method comprises the following steps: the manufacturer adopts the measurement methods of a hanging weight, a digital display caliper, a height gauge, a dial indicator and the like according to the relevant national calibration standard. The method has low measurement accuracy, small displacement range, incapability of automatically acquiring data, consideration of evaluation of a local measurement range only and no establishment of an integral unique reference and consciousness of integral evaluation; the labor intensity of repeated measurement and cyclic measurement is high; and the danger is high when the loading is carried out by manual contact measurement.
The prior method II comprises the following steps: and part of calibrators adopt special calibrating devices such as photoelectric encoders, grating rulers and the like. The special calibrating device is complex to fix, needs periodic calibration, has no corresponding regulation/standard in the country, and has unreliability in value tracing.
The existing method is three: shanghai measurement test 2012, the author: a portable three-coordinate measuring arm with a measuring range of 1200mm and a maximum allowable error of (5+8L/1000) mu m (L unit: m) is adopted in a method for realizing the displacement error detection of a beam of an electronic material testing machine by using the portable three-coordinate measuring arm in a Nakayak and Shenqi paper. Because the measuring head is used for contact measurement, the technical requirement on personnel is high, and the measuring danger is high during loading. Limited by the length of the measuring arm, and high implementation difficulty when the beam is lifted and lowered. In the paper, "two planes are generated, and the distance value between the two generated planes is used as a standard value", it should be noted that the problem 1 of this method lies in: the articulated arm has limited measuring range and poor universality, and the problem 2 is as follows: the two planes generated are not absolutely parallel, and no distance can be said between the two non-parallel planes.
The prior method comprises the following steps: those skilled in the art of geometric testing will typically appreciate the use of laser interferometers to measure displacements. The inventor proves that the method is basically infeasible through experiments. A driving piston of the material testing machine moves up and down while horizontal torsion exists, a laser beam emitted by a laser interferometer is separated from a reflecting mirror along with the deviation of an observation point, and the measurement cannot be carried out unless the reflecting mirror exists in the absolute center of a piston workbench or the piston workbench absolutely does not have torsion.
The invention adopts portable digital geometric measuring equipment, namely a laser tracker. The laser tracker has the advantages that: the measurement range is large; the accuracy is high; the comprehensive precision is as follows: + (15 μm/m +6 μm/m); meanwhile, the device has the tracking and measuring capacity, and the transverse tracking speed is more than 4 m/s; the radial tracking speed is more than 6 m/s; the transverse acceleration is more than 2 g; the longitudinal acceleration is infinite, the real-time tracking measurement of the target can be realized, and the defect of light loss when a laser interferometer is used is overcome; the laser tracker can establish a rectangular coordinate system, so that the measurement accuracy and the intuitiveness of the deviation in the three-coordinate direction are improved; the laser tracker is adopted for measurement, and the same coordinate system is provided, so that the detection method of the material testing machine has the overall evaluation consciousness of the same reference; the diameter of a target ball of the laser tracker is only 0.5 inch, the target ball is conveniently fixed on a piston or an inspection sample, manual close-distance measurement reading is not needed, and safety measurement in a loading state can be realized.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for detecting the displacement of the material testing machine, which is simple, high in digitization degree, accurate and reliable in data and strong in universality.
The invention aims to provide a method for detecting the displacement of a material testing machine, which is used for solving at least one problem in the prior art.
The technical scheme of the invention is as follows: a method for detecting the displacement of a material testing machine is provided. As shown in fig. 1 and 2, the method for detecting the displacement of the material testing machine is as follows:
step S10 is obtained according to an embodiment: clamping and positioning a target seat for measuring a laser tracker at the center of a lower chuck of a tensile test clamping device of a material testing machine to serve as an observation point 1; fixing a second target seat on the upper surface of a moving workbench of the material testing machine or on the test sample as an observation point 2; when a movable cross beam exists, a third target seat is fixed on the movable part and serves as an observation point 3; the method of fixation is not limited to adhesion, magnetic attraction, clamping, etc.;
step S20 is obtained according to an embodiment:
the first aspect is a direct measurement: directly measuring an observation point by using a laser tracker to obtain a point element coordinate;
the second aspect is an indirect construction method: measuring the surface of the piston by using a laser tracker, or measuring horizontal and vertical edges of a V-shaped block auxiliary checking fixture, and constructing a piston line, an axis parallel line and an axis perpendicular line by using measurement software to obtain line elements; when a movable beam exists, necessary line elements are constructed;
step S30 is obtained according to an embodiment: using laser tracker measurement software, defining a piston line or a parallel line of the piston line as a main shaft (such as a Z axis) of a measurement coordinate system, defining an axis vertical line as a second shaft (such as an X axis), defining an observation point 1 as an origin O, and automatically generating a third shaft (such as a Y axis); the measurement coordinate system achieves an ideal position through horizontal rotation and translation;
step S40 is obtained according to an embodiment:
in a first aspect, a method of measuring under no-load conditions includes: clamping and positioning a standard ball auxiliary detection tool on a stress center of a tensile test clamping device of a material testing machine, and measuring more than 5 point coordinates on the surface of a ball by using a laser tracker under an established measurement coordinate system; constructing and obtaining a sphere center coordinate P by using measurement softwareh(xh,yh,zh) (ii) a The auxiliary checking tool is not limited to a standard ball, a standard rod, a target seat capable of centering and the like; under the measurement coordinate system, measuring observation point 1 by using a laser tracker, and recording coordinate value P of piston displacement starting point0(x0,y0,z0) The control system drives the piston in every 10% displacement range, and the piston is measured and recorded to the upper limit of the displacement range in sequence to obtain a positive stroke coordinate value Pi(xi,yi,zi) Reverse stroke coordinate value Pi′(xi′,yi′,zi'), the positive and negative strokes are one measuring cycle, and three measuring cycles are carried out in total;
in a second aspect, a method of measuring under load conditions comprises: clamping a test sample on a material testing machine A1, applying a load, measuring an observation point 2 by using a laser tracker A0 under a measurement coordinate system, setting different measurement modes through measurement software, performing static measurement in equal step length or performing dynamic tracking measurement at equal step length and equal time intervals, recording the space point coordinates or track point coordinates of the observation point 2, and recording the space point coordinates or track point coordinates as a positive stroke coordinate value Pi(xi,yi,zi) Reverse stroke coordinate value Pi′(xi′,yi′,zi'), the positive and negative stroke is a measuring cycle, and the measurement is not less than three cycles; when a cross beam exists, measuring an observation point 3 by the same method;
step S50 is obtained according to an embodiment:
according to the results of the multiple rounds of cyclic measurement, calculating geometric errors by a calculation method or a mapping method, wherein the geometric errors comprise displacement indication relative errors, geometric coaxiality, displacement linearity, displacement repeatability and displacement return errors:
in a first aspect, the displacement indication value relative error calculation method comprises the following steps: under the condition of no load, the difference value of the displacement indication value of the material testing machine control system and the displacement standard quantity measured by the laser tracker on the appointed coordinate axis is measured in percentage of the standard displacement range of the appointed axis.
zi-displacement indication of material testing machine;
z0-displacement standard measured by the laser tracker;
ZFS-a standard displacement range;
in a second aspect, the geometric coaxiality calculating method comprises the following steps: under the no-load condition and the measurement coordinate system, the standard displacement range is taken as the evaluation length, the horizontal offset of the centers of the upper chuck and the lower chuck of the tensile test clamping device is used for representing, and the offset is the diameter of the cylindrical tolerance zone.
xhMeasuring the x coordinate of the center of the upper chuck in a coordinate system;
yhmeasuring the y coordinate of the center of the upper chuck in a coordinate system;
x0measuring the coordinate of the coordinate origin x under a coordinate system;
y0measuring the coordinate origin y coordinate under a coordinate system;
in a third aspect, the displacement linearity and the calculation method are as follows: the displacement linearity of the piston is obtained by a least square method or a drawing method through multiple times of cycle measurement values, and the displacement linearity is calculated according to the percentage of the standard displacement range of the designated shaft.
In a fourth aspect, the displacement repeatability and the calculation method are as follows: and (3) calculating the maximum difference value of the measured values at the same measuring point of the equidirectional travel by using the cycle measured values of multiple times through a Bessel method, a pole difference method or a mapping method, and calculating the maximum difference value according to the percentage of the standard displacement range of the specified shaft.
In a fifth aspect, the displacement return error is calculated by the following method: the maximum difference value of the measured values at the same measuring point of the positive and negative strokes is obtained by a calculation method or a drawing method through multiple rounds of cycle measured values, and the maximum difference value is calculated according to the percentage of the standard displacement range of the designated shaft.
The invention has the beneficial effects that: the method is simple, high in digitization degree, accurate and reliable in data and strong in universality.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of an embodiment of a method for detecting displacement of a material testing machine;
fig. 2 is a schematic flow chart of a method of detecting the amount of displacement of a material testing machine.
Wherein: piston 1, workstation 2, tensile test clamping device 3, target seat 4, target 5, standard ball 6, V type piece are supplementary to be examined utensil 7 and base 8.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Features and illustrative embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific arrangement and method set forth below, but rather covers any improvements, substitutions and modifications in structure, method, and apparatus without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown to avoid unnecessarily obscuring the present invention.
It should be noted that, in the case of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other, and the respective embodiments may be mutually referred to and cited. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
FIG. 1 is a schematic diagram of an embodiment of the present invention.
As shown in fig. 1, a method for detecting the displacement of a material testing machine includes: laser tracker A0, material testing machine A1, piston 1, workstation 2, tensile test clamping device 3, target seat 4, target 5, standard ball 6, "V" type piece auxiliary detection utensil 7.
The device is structurally characterized in that a piston 1 which moves up and down is mounted on a material testing machine A1, a workbench 2 is mounted on the upper end face of the piston 1, a tensile test clamping device 3 is mounted on the workbench 2, a target seat 4 is clamped and positioned in the center of the tensile test clamping device 3, and a target 5 is placed in the target seat 4 during measurement; in addition, a standard ball 6 with a tail handle is fixedly clamped at the stress center on the corresponding fixed end of the tensile test clamping device 3, and a laser tracker A0 is erected near the material testing machine A1, so that the laser beam can reach all observation points.
Fig. 2 is a schematic flow chart of a method of detecting the amount of displacement of a material testing machine.
Step S10 is obtained according to an embodiment: a target holder 4 for measurement of a laser tracker A0 is fixed at the center of a chuck below a tensile test clamping device 3 of a material testing machine A1 and serves as an observation point 1; fixing a second target holder 4 on the upper surface of the workbench 2 or the test sample of the material testing machine A1 as an observation point 2; when a movable beam is available, a third target seat 4 is fixed on the movable part and serves as an observation point 3; the method of fixation is not limited to adhesion, magnetic attraction, clamping, etc.;
step S20 is obtained according to an embodiment:
the first aspect is a direct measurement: directly measuring an observation point by using a laser tracker A0 to obtain a point element coordinate;
the second aspect is an indirect construction method: measuring horizontal and vertical edges of a V-shaped block auxiliary detection tool 7 which is tightly adhered and fixed on the cylindrical surface of the piston 1 by using a laser tracker A0, measuring more than 2 coordinate points on each edge, and constructing a parallel line m of the axis of the piston 1 and a vertical line n of the axis by using measurement software to obtain line elements; when the movable beam is available, necessary line elements are constructed through measurement;
step S30 is obtained according to an embodiment: using the measurement software of the laser tracker A0, determining the parallel line m of the piston axis as the main axis (such as Z axis) of the measurement coordinate system, determining the perpendicular line n of the axis as the second axis (such as X axis), determining the observation point 1 as the origin O of the coordinate system, and automatically generating the third axis (such as Y axis); the measurement coordinate system achieves an ideal position through horizontal rotation and translation;
step S40 is obtained according to an embodiment:
in a first aspect, a method of measuring under no-load conditions includes: clamping and positioning a standard ball 6 auxiliary detection tool on a stress center of a tensile test clamping device 3 of a material testing machine A1, and measuring more than 5 point coordinates on the surface of a ball by using a laser tracker A0 under a measurement coordinate system; constructing and obtaining a sphere center coordinate P by using measurement softwareh(xh,yh,zh) (ii) a The auxiliary checking tool is not limited to a standard ball, a standard rod, a target seat capable of centering and the like; under the measurement coordinate system, the observation point 1 is measured by using a laser tracker A0, and the coordinate value P of the displacement starting point of the piston 1 is recorded0(x0,y0,z0) The control system drives the piston 1 in each 10% displacement range, and the displacement range is measured and recorded to the upper limit of the displacement range in sequence to obtain a positive stroke coordinate value Pi(xi,yi,zi) Reverse stroke coordinate value Pi′(xi′,yi′,zi'), the positive and negative strokes are one measuring cycle, and three measuring cycles are carried out in total;
in a second aspect, a method of measuring under load conditions comprises: clamping a test sample on a material testing machine A1, applying a load, measuring an observation point 2 by using a laser tracker A0 under a measurement coordinate system, setting different measurement modes through measurement software, performing static measurement in equal step length or performing dynamic tracking measurement at equal step length and equal time intervals, recording the space point coordinates or track point coordinates of the observation point 2, and recording the space point coordinates or track point coordinates as a positive stroke coordinate value Pi(xi,yi,zi) Reverse stroke coordinate value Pi′(xi′,yi′,zi'), the positive and negative stroke is a measuring cycle, and the measurement is not less than three cycles; when a cross beam exists, measuring an observation point 3 by the same method;
step S50 is obtained according to an embodiment:
according to the results of the multiple rounds of cyclic measurement, calculating geometric errors by a calculation method or a mapping method, wherein the geometric errors comprise displacement indication relative errors, geometric coaxiality, displacement linearity, displacement repeatability and displacement return errors:
in a first aspect, the displacement indication value relative error calculation method comprises the following steps: under the condition of no load, under the measurement coordinate system, the difference value of the displacement indication value of the control system of the material testing machine A1 and the displacement standard quantity measured by the laser tracker A0 on the designated coordinate axis is calculated as the percentage of the standard displacement range of the designated axis.
zi-displacement indication of material testing machine;
z0-displacement standard measured by the laser tracker;
ZFS-a standard displacement range;
in a second aspect, the geometric coaxiality calculating method comprises the following steps: under the no-load condition and the measurement coordinate system, the standard displacement range is taken as the evaluation length, and the horizontal offset of the centers of the upper chuck and the lower chuck of the tensile test clamping device 3 is used for representing, wherein the offset is the diameter of the cylindrical tolerance zone.
xhMeasuring the x coordinate of the center of the upper chuck in a coordinate system;
yhmeasuring the y coordinate of the center of the upper chuck in a coordinate system;
x0measuring the coordinate of the coordinate origin x under a coordinate system;
y0measuring the coordinate origin y coordinate under a coordinate system;
in a third aspect, the displacement linearity and the calculation method are as follows: the linearity of the displacement of the piston 1 is determined from the measurements taken over a number of cycles by means of the least squares method or mapping method, in percent of the standard displacement range of the designated axis.
In a fourth aspect, the displacement repeatability and the calculation method are as follows: and (3) calculating the maximum difference value of the measured values at the same measuring point of the equidirectional travel by using the cycle measured values of multiple times through a Bessel method, a pole difference method or a mapping method, and calculating the maximum difference value according to the percentage of the standard displacement range of the specified shaft.
In a fifth aspect, the displacement return error is calculated by the following method: the maximum difference value of the measured values at the same measuring point of the positive and negative strokes is obtained by a calculation method or a drawing method through multiple rounds of cycle measured values, and the maximum difference value is calculated according to the percentage of the standard displacement range of the designated shaft.
The best embodiment is as follows:
taking a material testing machine with the shape height of about 2m, the displacement stroke of 200mm and an axial hydraulic loading type MTS810 full-digital control system as an example, the method disclosed by the invention is adopted to implement displacement detection, and the method is shown in figure 1.
Fig. 1 includes: laser tracker A0, material testing machine A1, piston 1, workstation 2, tensile test clamping device 3, target seat 4, target 5, standard ball 6, "V" type piece auxiliary detection utensil 7.
The laser tracker A0 is erected on a stable ground about 3m near a material testing machine A1, so that a laser beam can observe a detected part of a material testing machine A1 without shielding, through measurement, geometric elements of relevant points, lines and surfaces on the material testing machine A1 are obtained, and a measurement coordinate system with the appointed coordinate axis Z of the laser tracker A0 consistent with the linear direction of a piston is established by utilizing the geometric elements. A target seat 4 is fixed on the upper surface of a workbench 2 of a piston 1 of a material testing machine A1 and serves as a displacement observation point 2; the fixation of the target seat 4 is realized in an adhesive mode, the laser tracker A0 can be kept in a non-shielding direct-view mode to the target seat 4, and the target seat 4 plays a role in positioning and supporting the target ball 5. The material testing machine A1 is instructed by an industrial personal computer to control and drive the piston 1 to move up and down along the axial direction, so that a test piece clamped on the tensile test clamping device 3 is subjected to tensile load, the target ball 5 synchronously moves along with the material testing machine A1 in a no-load or loading state, a corresponding relation between a displacement indication value and a displacement standard quantity is established, and the detection of the relative error, the geometric coaxiality, the displacement linearity, the displacement repeatability and the displacement return error of the displacement indication value of the material testing machine A1 is completed through multiple times of measurement, recording and data processing. The detection is realized by the following steps:
1. presetting observation points: clamping and positioning a target seat 4 for measurement of a laser tracker A0 at the center of a chuck under a tensile test clamping device 3 of a material testing machine A1 to serve as an observation point 1; fixing a second target holder 4 near the center on the surface of the worktable 2 of the material testing machine A1 as an observation point 2;
2. acquiring geometric elements: the coordinate value O (x) of the starting point of the observation point 1 is measured and recorded by the laser tracker A00,y0,z0) (ii) a Measuring horizontal and vertical edge coordinate points of the V-shaped block auxiliary detection tool 7 on the piston 1 by using a laser tracker A0, and constructing a piston axis parallel line m and an axis vertical line n by using measurement software;
3. establishing a measurement coordinate system: using the measurement software of the laser tracker A0, the parallel line m of the piston axis was defined as the Z axis of the measurement coordinate system, the perpendicular line n of the piston axis was defined as the X-th axis, and the observation point 1 was defined as the origin O (X)0,y0,z0) Automatically generating a Y axis, and establishing an O-XYZ measurement coordinate system;
4. measuring coordinate values of observation points:
4.1 clamping and positioning a standard ball 6 with a tail handle on the fixed end of a material testing machine A1 by applying a force center, measuring the surface of the ball under a measurement coordinate system, and obtaining three coordinate values P of the center of the ballh(0.2050,0.1983,199.0372)；
4.2. Guiding the target 5 from the 'home' point of the laser tracker A0 to the target seat 4 of the observation point 2, sending a motion command by an industrial personal computer of the material testing machine A1, and enabling the coordinate of the detection starting point to be P coordinate from 10% of the displacement range of the material testing machine A1 through translating a coordinate system0(0,0,0) measuring each corresponding displacement standard quantity of the displacement input quantity under the load set by the material testing machine A1 by using a laser tracker A0; setting the interval of one-way stroke at 10mm as 1 observation point, measuring the upper limit to 150mm, measuring forward and backward stroke point by point as one measurement cycle, measuring 3 cycles in total, detecting the point of positive stroke coordinate value P in the 1 st cyclei(xi,yi,zi) Reverse stroke coordinate value Pi(xi′,yi′,zi') 1 st cycle test under no-load conditionThe measured data is shown in a table 1, and the data of the 2 nd cycle and the 3 rd cycle under other load conditions are omitted;
TABLE 1 test data sheet
5. Solving the geometric error:
5.1 the difference value of the displacement indication value of the material testing machine A0 and the standard displacement measured by the laser tracker A1 on the appointed coordinate axis Z, and the obtained displacement indication value relative error detection result is as follows by the percentage of the appointed Z-axis standard displacement range: + 0.62%;
5.2 according to the coordinates P of the center of the standard sphere under the no-load conditionh(xh,yh,zh) Relative to P in the measurement coordinate systemi(xi,yi,zi) Maximum horizontal offset, yielding geometric coaxiality: phi is 0.66mm/200 mm;
5.3 obtaining the displacement linearity plus 0.20 percent by using a least square method according to the measurement values of multiple cycles.
5.4, calculating the absolute value of the maximum difference value of the Z coordinates at the same measuring point of the same directional travel by using multiple times of cyclic measurement values, and calculating by using a pole difference method to obtain the repeatability of 0.08%;
5.5 the maximum difference of the Z coordinates of the same observation point of the positive and negative strokes is obtained by calculation, and the return error is calculated to be 0.12 percent according to the absolute value of the maximum difference.
In some embodiments, a method for calibrating the displacement of a material testing machine may include the steps of:
s10: presetting a plurality of observation points on a material testing machine A1;
s20: acquiring geometric elements on a material testing machine A1;
s30: establishing a measurement coordinate system with the appointed coordinate axis of the laser tracker A0 consistent with the axial direction of the piston;
s40: measuring three coordinate values of a plurality of observation points under the established measurement coordinate system;
s50: and calculating the geometric error of the displacement of the material testing machine according to the three coordinate values.
Wherein: the material testing machine A1 is a material testing machine with an axial hydraulic loading type MTS810 full digital control system, the profile height of which is 2m, the displacement stroke of which is 200 mm.
The testing machine for detecting materials comprises: piston 1, workstation 2, tensile test clamping device 3, target seat 4, target 5, standard ball 6, V type piece are supplementary to be examined utensil 7 and base 8. Wherein: a piston 1 is arranged on the base 8; the side wall of the piston 1 is provided with a V-shaped block auxiliary detection tool 7; the piston 1 is connected with a workbench 2; the openable tensile test clamping device 3 is arranged on the workbench 2; the tensile test clamping device 3 is used for clamping the target seat 4; the target holder 4 is adapted to support a standard ball 6.
In some embodiments, step S10 includes: fixing a target seat for measuring a laser tracker at the center of a lower chuck of a tensile test clamping device of a material testing machine to be used as an observation point 1; fixing a second target seat near the plane center of the moving workbench of the material testing machine or on the test sample as an observation point 2; when a movable beam is available, a third target holder is fixed on the movable part of the beam and serves as an observation point 3.
In some embodiments, step S20 includes: direct measurement: directly measuring by using a laser tracker A0 to obtain point elements; an indirect construction method: measuring the surface of the piston by using a laser tracker A0, or measuring the horizontal and vertical edges of the V-shaped block auxiliary checking fixture 7, and constructing a piston line, an axis parallel line and an axis vertical line by using measurement software to obtain line elements; when there is a moving beam, a line element is constructed.
In some embodiments, step S30 includes: using laser tracker measurement software to determine a piston line or an axis parallel line as a main shaft of a measurement coordinate system; the vertical line of the axis is set as a second axis, the observation point 1 is set as an original point O, and a third axis is automatically generated; the measuring coordinate system achieves an ideal orientation through horizontal rotation and translation.
In some embodiments, step S40 includes: under no-load condition: an auxiliary checking fixture is positioned on a stress center of a tensile test clamping device of a material testing machine, the auxiliary checking fixture is not limited to a standard ball, a standard shaft and a target seat, and the coordinate of an upper stress central point is obtained through measurement under a measurement coordinate system; under a measurement coordinate system, an observation point 1 is measured by using a laser tracker, a coordinate value of a displacement starting point of the piston is recorded, the piston is driven by a control system in equal step length, the piston is sequentially measured and recorded to the upper limit of a displacement range, a forward stroke coordinate value and a reverse stroke coordinate value are obtained, the forward stroke and the reverse stroke are a measurement cycle, and the measurement is not less than three cycles.
Under the load condition: clamping a test sample, applying a load, measuring an observation point 2 by using a laser tracker under a measurement coordinate system, selecting different measurement modes, and performing static measurement in equal step length or dynamically tracking and measuring and recording the track point coordinates of the observation point 2 at intervals of step length and time, wherein the positive and negative strokes are a measurement cycle, and the measurement is not less than three cycles; when a cross beam exists, the coordinates of the track points of the observation points 3 are measured by the same method.
Step S50 includes:
and based on the three coordinate values, calculating the relative error of the displacement indication value, the geometric coaxiality, the displacement linearity, the displacement repeatability and the displacement return error.
Through practical implementation verification, the method is simple, convenient, reliable and easy to implement; and comparing and analyzing the calibration data with the calibration data of the previous metering technical mechanism, and displaying the result that the detection method is feasible.
It should be noted that the above-mentioned flow operations may be combined and applied in different degrees, and for simplicity, implementation manners of various combinations are not described again, and those skilled in the art may flexibly adjust the sequence of the above-mentioned operation steps according to actual needs, or flexibly combine the above-mentioned steps, and the like.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered within the scope of the present invention.
Claims (5)
1. A method for calibrating displacement of a material testing machine is characterized by comprising the following steps:
s10: presetting a plurality of observation points on a material testing machine (A1), the material testing machine (A1) comprising: piston (1), workstation (2), tensile test clamping device (3), target seat (4), target (5), standard ball (6), supplementary utensil (7) and base (8) of examining of V type piece, wherein: a piston (1) is arranged on the base (8); the side wall of the piston (1) is provided with a V-shaped block auxiliary detection tool (7); the piston (1) is connected with a workbench (2); the openable tensile test clamping device (3) is arranged on the workbench (2); the tensile test clamping device (3) is used for clamping the target seat (4); the target seat (4) is used for supporting a standard ball (6);
a target holder for measurement of a laser tracker (A0) is fixed at the center of a chuck under a tensile test clamping device of a material testing machine (A1) and is used as an observation point 1; fixing a second target seat near the center of the plane of the moving workbench of the material testing machine (A1) or on the test sample as an observation point 2; when a movable cross beam exists, fixing a third target seat on a movable part of the cross beam as an observation point 3;
s20: obtaining geometric elements on a material testing machine (A1);
s30: establishing a measurement coordinate system with the designated coordinate axis of the laser tracker (A0) consistent with the axial direction of the piston;
s40: under the established measurement coordinate system, measuring three coordinate values of a plurality of observation points, wherein the three coordinate values comprise:
under no-load condition:
an auxiliary checking fixture is positioned on a stress center of a tensile test clamping device of a material testing machine, the auxiliary checking fixture is not limited to a standard ball, a standard shaft and a target seat, and the coordinate of an upper stress central point is obtained through measurement under a measurement coordinate system;
under a measurement coordinate system, measuring an observation point 1 by using a laser tracker, recording a coordinate value of a displacement starting point of a piston, driving the piston by a control system in an equal step length, sequentially measuring and recording the piston to the upper limit of a displacement range to obtain a forward stroke coordinate value and a backward stroke coordinate value, wherein the forward stroke and the backward stroke are a measurement cycle, and the measurement is not less than three cycles;
under the load condition:
clamping a test sample, applying a load, measuring an observation point 2 by using a laser tracker under a measurement coordinate system, selecting different measurement modes, and performing static measurement in equal step length or dynamically tracking and measuring and recording the track point coordinates of the observation point 2 at intervals of step length and time, wherein the positive and negative strokes are a measurement cycle, and the measurement is not less than three cycles; when a cross beam exists, measuring the coordinates of the track points of the observation points 3 by the same method;
s50: according to the three coordinate values, the geometric error of the displacement of the material testing machine (A1) is calculated.
2. The method of claim 1, wherein:
the material testing machine (A1) is a material testing machine with an axial hydraulic loading type MTS810 full digital control system, the profile height of which is 2m, the displacement stroke of which is 200 mm.
3. The method according to claim 1, wherein step S20 includes:
direct measurement: directly measuring the point elements by using a laser tracker (A0);
an indirect construction method: measuring the surface of the piston by using a laser tracker (A0), or measuring the horizontal and vertical edges of a V-shaped block auxiliary detection tool (7), and constructing a piston line, an axis parallel line and an axis vertical line by using measurement software to obtain line elements; when there is a moving beam, a line element is constructed.
4. The method according to claim 1, wherein step S30 includes:
using laser tracker measurement software to determine a piston line or an axis parallel line as a main shaft of a measurement coordinate system;
the vertical line of the axis is set as a second axis, the observation point 1 is set as an original point O, and a third axis is automatically generated; the measuring coordinate system achieves an ideal orientation through horizontal rotation and translation.
5. The method according to claim 1, wherein step S50 includes:
and based on the three coordinate values, calculating the relative error of the displacement indication value, the geometric coaxiality, the displacement linearity, the displacement repeatability and the displacement return error.
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