Summary of the invention
The purpose of this utility model be the diameter measurement for circular section sample in the material mechanical performance test and other similar object provide a kind of simple in structure, easy to use, precision is high, good reproducibility and be suitable for the resistor strain type apparatus for measuring diameter of digital applications.
The resistor strain type apparatus for measuring diameter that the utility model provides, comprise the U-shaped bearing that constitutes by base plate and two root posts, the double cantilever beam resistance strain type sensor, resistance strain measurement instrument and the cylinder guide rod that has the guide and limit groove, cylinder guide rod level is fastened on two root posts of U-shaped bearing, its guide and limit groove is under the bottom, the double cantilever beam resistance strain type sensor is between two root posts, be installed on the cylinder guide rod by the Kong Yikong axle fit system on its back up pad, one vertical threaded guide and limit pin is arranged at the back up pad bottom of double cantilever beam resistance strain type sensor, the light beam of guide and limit pin partly stretches in the guide and limit groove of cylinder guide rod, and with guide and limit groove clearance fit, make the double cantilever beam resistance strain type sensor do the two-way rotation of low-angle with respect to vertical plane of symmetry of cylinder guide rod around the axis of cylinder guide rod, on the screw thread of guide and limit pin, be combined with set nut, the free end of two vertical cantilever of double cantilever beam resistance strain type sensor is respectively arranged with the edge of a knife, parallel being separated by of a pair of edge of a knife on two semi-girders, the root of each semi-girder is along two pieces of strain ga(u)ges of experiencing the strain of semi-girder sweep of axis direction symmetric arrangement of beam, four pieces of strain ga(u)ges on two semi-girders are connected with the resistance strain measurement instrument with the full-bridge form, the top of every root post or be provided with two pieces of pellets shot from a slingshot or be that V-shaped groove constitutes the sample bearing.
For guaranteeing measuring accuracy, making the edge of a knife usually is the block of triangular-section, and the spacing that a pair of edge of a knife is separated by is less than tested sample minimum diameter 0.1~0.15mm.Two semi-girders of double cantilever beam resistance strain type sensor are the straight-bar of square-section.
The using method of resistor strain type apparatus for measuring diameter comprises and demarcates and measure that step is as follows:
1) with normal diameter rule group calibration measurements device: normal diameter rule group comprises the normal diameter rule that quantity is several different-diameters of odd number, minimum diameter value wherein is than the big 0.1~0.15mm of edge of a knife spacing on the double cantilever beam resistance strain type sensor, and diameter value placed in the middle equals the nominal diameter of sample to be tested; Respectively each normal diameter rule is put into the edge of a knife of double cantilever beam resistance strain type sensor from top to bottom, be positioned on the sample bearing, write down each time reading ε of resistance strain measurement instrument
r, utilize least square method to obtain the reading ε of diameter value d and resistance strain measurement instrument then
rFit equation
ε
r=Ad+B
A and B are the constants that obtains with least square method in the formula;
2) measure specimen finish: sample is put into the edge of a knife of double cantilever beam resistance strain type sensor from top to bottom, be positioned on the sample bearing, write down the reading ε of resistance strain measurement instrument
r, use formula then
Calculate the diameter of sample; Rotate sample with hand, measure the diameter of different azimuth on the same cross section of sample; With hand push double cantilever beam resistance strain type sensor, its axis along the cylinder guide rod is slided, measure the diameter of sample different cross section.
Measuring principle of the present utility model is: the different sample of diameter can cause that the semi-girder on the double cantilever beam resistance strain type sensor produces the elastic deformation of different sizes, strain ga(u)ge on the semi-girder is converted into electric quantity signal by strain bridge with deformation signal, sends into the resistance strain measurement instrument; Strain bridge and resistance strain measurement instrument are linear system, so the reading value of resistance strain measurement instrument is directly proportional with the diameter of sample; Before measurement, with standard measuring system to be demarcated, when then measuring, the resistance strain measurement instrument provides the change amount of specimen finish with respect to standard, thereby obtains the diameter value of sample.If two semi-girders of double cantilever beam resistance strain type sensor are the straight-bar of square-section, the two is symmetry fully.By mechanics of materials flexure theory and resistance strain type sensor theory, when sample entered the edge of a knife and be positioned on the sample bearing, edge of a knife spacing changed, the reading value change amount of resistance strain measurement instrument

For:
H is the thickness of semi-girder in the formula; L is the edge of a knife and the sample contact point distance to the semi-girder root; X is the distance of strain ga(u)ge central point to the semi-girder root; Δ d is the poor of specimen finish d and the original spacing of the edge of a knife, i.e. length change amount between the edge of a knife and the sample contact point; The sensitivity of η reflected measurement is called sensitivity coefficient.
During measurement, sample is put into the edge of a knife of double cantilever beam resistance strain type sensor from the top of sample bearing and double cantilever beam resistance strain type sensor, the deadweight that sample can utilization itself is positioned on the sample bearing.After sample entered the edge of a knife, it is big that edge of a knife spacing becomes, and semi-girder produces deflection deformation, and the reading of resistance strain measurement instrument is changed thereupon.
The sample that is placed on the sample bearing can be done freely to rotate around self axis, and the double cantilever beam resistance strain type sensor can slide on the cylinder guide rod.Therefore, rotate sample, just can measure the diameter of different azimuth on the same cross section of sample, the double cantilever beam resistance strain type sensor is moved along the axis of cylinder guide rod, then can measure the diameter of sample different cross section with hand.
The beneficial effects of the utility model:
1, utilizes the diameter of double cantilever beam resistance strain type sensor and resistance strain measurement apparatus measures conjunction measuring sample, Measurement Resolution can meet or exceed 0.001mm, improve an order of magnitude (resolution of vernier caliper is 0.02mm, or 0.01mm) than the vernier caliper that generally uses at present.
2, by double cantilever beam resistance strain type sensor that has the pair of parallel edge of a knife and top the U-shaped bearing of locating pellet shot from a slingshot or V-shaped groove is housed and cooperates the location survey of realizing sample, and the two-way rotational freedom of the low-angle that utilizes the double cantilever beam resistance strain type sensor makes the sample automatic synchronization in place, thereby guarantee the sample accurate positioning, the good reproducibility of measurement data.
3, can improve the diameter measurement precision of circular section sample in the material mechanical performance test effectively.
4, measurement mechanism of the present utility model is simple in structure, good reliability, and the sample loading, unloading are easy, show the diameter measurement value with digital form, and record data automatically, therefore can significantly improve the work efficiency of measure batch, reduction labour intensity.
5, owing to adopted the resistance strain measurement instrument, can be easily and computer virtual instrument on-line Application, therefore adapt to the digitized demand for development of measuring technique.
Embodiment
Further specify the utility model below in conjunction with accompanying drawing.
With reference to accompanying drawing, resistor strain type apparatus for measuring diameter of the present utility model comprises the U-shaped bearing that is made of base plate 5 and two root posts 6, double cantilever beam resistance strain type sensor 2, resistance strain measurement instrument 3 and the cylinder guide rod 8 that has guide and limit groove 10, cylinder guide rod 8 levels are fastened on two root posts of U-shaped bearing, and its guide and limit groove 10 is under the bottom, here, the two ends of cylinder guide rod 8 are processed with screw thread, by two pieces of nuts 9 cylinder guide rod 8 are tightened up the location.The length of guide and limit groove 10, the moving range of decision double cantilever beam resistance strain type sensor 2 is determined according to the gauge length of tested sample.Double cantilever beam resistance strain type sensor 2 is installed on the cylinder guide rod 8 by the Kong Yikong axle fit system on its back up pad, and can moves axially on cylinder guide rod 8 between two root posts.One vertical threaded guide and limit pin 11 is arranged at the back up pad bottom of double cantilever beam resistance strain type sensor 2, the light beam of guide and limit pin 11 partly stretches in the guide and limit groove 10 of cylinder guide rod 8, and with guide and limit groove 10 clearance fit, make double cantilever beam resistance strain type sensor 2 do the two-way rotation of low-angle with respect to vertical plane of symmetry of cylinder guide rod around the axis of cylinder guide rod 8, on the screw thread of guide and limit pin 11, be screwed with set nut 12, be used for fixing guide and limit pin 11.The free end of two vertical cantilever 13 of double cantilever beam resistance strain type sensor 2 is respectively arranged with the edge of a knife 1, and in the legend, the edge of a knife 1 is selected the block in the good material triangularity cross section of wearing quality, is fixed on the free end inboard of semi-girder 13 with screw 16.Two semi-girders are the straight-bar of square-section.Parallel being separated by of a pair of edge of a knife on two semi-girders 13, the spacing that the edge of a knife is separated by is less than tested sample 4 minimum diameters 0.1~0.15mm.For example, be the sample of 9.90mm for minimum diameter, edge of a knife spacing can be taken as 9.80mm.The root of each semi-girder 13 is used to experience the sweep strain of semi-girder 13 along two pieces of strain ga(u)ges 14 of experiencing the strain of semi-girder sweep of axis direction symmetric arrangement of beam.Four pieces of strain ga(u)ges 14 on two semi-girders are connected with resistance strain measurement instrument 3 with the full-bridge form, and resistance strain measurement instrument 3 can adopt ordinary numbers formula electric wire strain gauge.The top of every root post 6 or be provided with two pieces of pellets shot from a slingshot 7 or for V-shaped groove constitutes the sample bearing, for sample 4 provides the constraint of four point locations.This example is processed with two counterbores 15 at the top of every root post 6, location pellet shot from a slingshot 7 is assemblied in the counterbore 15 in the wringing fit mode, and the degree of depth that falls into counterbore 15 is slightly larger than the radius of location pellet shot from a slingshot 7.Can adopt smooth steel ball, the roller of ball bearing for example is as location pellet shot from a slingshot 7.
The use of resistor strain type apparatus for measuring diameter comprises demarcates and measured for two steps.The effect of demarcating is the reading ε that obtains the resistance strain measurement instrument
rFuntcional relationship with specimen finish d.Demarcate to adopt normal diameter rule group as standard, normal diameter rule group comprises the normal diameter rule of several different-diameters, and the quantity of normal diameter rule is odd number, and for example 5 or 7.The diameter of each normal diameter rule is generally arranged by the equal difference rule, wherein minimum directly through value than the big 0.1~0.15mm of edge of a knife spacing on the double cantilever beam resistance strain type sensor,, and diameter value placed in the middle should equal the nominal diameter of sample to be tested.For example, the nominal diameter of establishing sample to be tested is 10mm, and tolerance is ± 0.05mm, and measuring desired precision is 0.01mm, and the quantity that can get normal diameter rule is 5, and diameter is followed successively by 9.900mm, 9.950mm, 10.000mm, 10.050mm, 10.100mm.Timing signal is advised the sample bearing of putting into measurement mechanism successively with each normal diameter, makes the edge of a knife spacing of double cantilever beam resistance strain type sensor produce the variations of different sizes, and writes down the reading of resistance strain measurement instrument.Utilize least square method to obtain diameter value d and resistance strain measurement instrument readings ε then
rFit equation
ε
r=Ad+B (2),
A and B are the constants that obtains with least square method in the formula.
During measurement, sample 4 is put into the edge of a knife 1 of double cantilever beam resistance strain type sensor 2 from top to bottom, and be positioned on the sample bearing, write down the reading ε of resistance strain measurement instrument
r, use formula then
Calculate the diameter of sample.Resistance strain measurement instrument 3 also can be connected with the computer virtual instrument, utilizes software to finish the computing of formula (3) automatically by the computer virtual instrument, and record also directly shows the diameter of sample.Rotate sample with hand, can measure the diameter of different azimuth on the same cross section of sample.With hand push double cantilever beam resistance strain type sensor, its axis along the cylinder guide rod is slided, can measure the diameter of sample different cross section.