CN101487748B - Shearing force measurement bridge circuit in bending-twisting combined test apparatus - Google Patents
Shearing force measurement bridge circuit in bending-twisting combined test apparatus Download PDFInfo
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- CN101487748B CN101487748B CN2009100082890A CN200910008289A CN101487748B CN 101487748 B CN101487748 B CN 101487748B CN 2009100082890 A CN2009100082890 A CN 2009100082890A CN 200910008289 A CN200910008289 A CN 200910008289A CN 101487748 B CN101487748 B CN 101487748B
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Abstract
The invention relates to a shearing force measuring bridge circuit in a crankle combined test device. The device consists of an aluminum alloy cylinder cantilever and a crank which is in an angle of 90 degrees with the cylinder cantilever; the outer circumference of the measured cross section of the aluminum alloy cylindrical cantilever is provided with four 45-degree 3-right angle strain rosettes at an interval of a 90-degree interval according to an order of a strain rosette A, a strain rosette B, a strain rosette C and a strain rosette D; and the device is characterized in that the orientations of the strain rosette B, the strain rosette C and the strain rosette D are the same along the axis direction of the cylinder cantilever, the orientation of the strain rosette A is opposite to the orientations of the other strain rosettes, and a circumference position where a measuring point is located is taken as the symmetric center. The shearing force measuring bridge circuit can obtain higher measuring precision on flexural moment and torque, can effectively measure shearing force, so as to add new teaching experiment content, and can provide a model for internal force measurement of similar components in engineering structures.
Description
The application is that application number is to divide an application for " bending-twisting combined test apparatus and the application in the plain measurement of internal force thereof " for " on June 30th, 2006 ", denomination of invention " 200610088185.1 ", the applying date.
Technical field
The present invention relates to bending-twisting combined test apparatus, the shearing force measurement bridge circuit in the bending-twisting combined test apparatus of more specifically saying so.
Background technology
The resistance strain measurement technology is one of main means of engineering structure Stress analysis from test result, and is widely used in each field of engineering technology such as machinery, building, Aero-Space.Study resistance strain measurement principle is grasped its measuring method and technology, and can skillfully be applied, and is the students of engineering and polytechnic universities, particularly a basic experiment technical ability must grasping of engineering student.Thereby the electrical measurement stress test is one of requisite important content in the experimental teaching, and wherein " cylinder bending combination experiment " is the basic experiment content of electrical measurement stress test.The experiment content of this experiment is to measure internal force elements such as moment of flexure, moment of torsion, shearing on bending and twisting combined action principle stress and the specified cross-section down.The foil gauge arrangement of existing experimental provision, precision is higher when principle stress, moment of flexure and torque measurement, and the error when still measuring shearing is very big, surpasses 50%, has lost the experiment meaning.
Experiment method:
Fig. 1, Fig. 2 and shown in Figure 3; Experimental provision is to be 90 jiaos 2 of crank throws to constitute by aluminum alloy drum cantilever 1 with it; Can be known that by the bending and twisting combined action loading characteristic A, 2 of C are the pure shear stress state, the 45 ° of line strains with-45 ° of directions in 2 edges are respectively:
τ in the formula
TAnd τ
QExpression is reversed and crooked shearing stress respectively.During measurement, 45 ° of directions and-45 ° of orientation-sensitive grid in A, 2 strain rosettes of C are connected into full-bridge bridge circuit as shown in Figure 4, then the measured value of crooked shearing stress does
ε in the formula
Q surveys=(ε
-45 °)
A-(ε
45 °)
A+ (ε
45 °)
C-(ε
-45 °)
CBe the bridge circuit real output value.The substitution following formula
Can obtain the shearing on the I-I cross section, α=d/D wherein, d, D are respectively the inside and outside footpath of cylinder 1.
When acting on the load F=100N of crank throw end, the theoretical value of shearing is F on the I-I cross section
Q=100N.During experiment, adopt equivalent Loading Method step by step, table 1 is one group of measured data.According to table 1 measured data, the shearing that records on the I-I cross section is 157.61N, reaches 57.6% with the relative error of theoretical value.
The actual measurement output valve of table 1 electric bridge
| Load F/N | 50 | 150 | 250 | 350 | 450 |
| Strain-ga(u)ge reading ε Real/με | 34 | 102 | 171 | 239 | 307 |
Error analysis
According to the strain gage testing principle, foil gauge records the mean strain that strain is a sensitive grid, is approximately equal to the strain of sensitive grid center position.When adopting 45 °-3 rectangular rosettes to measure, owing to the sensitive grid center does not overlap with measurement point, when adopting full bridge measurement bending shearing stress; Can only offset shearing stress in torsion power; And additional bending normal stresses can't be eliminated, thereby causes measuring error very big, also can be found out by Fig. 5; Except the influence in transversal effect and stickup orientation, the main error of shearing force measurement is because the stress state and inconsistent the causing of measured point pure shear stress state of strain rosette sensitive grid center.
Summary of the invention
The present invention is for avoiding above-mentioned existing in prior technology weak point; Shearing force measurement bridge circuit in a kind of bending-twisting combined test apparatus is provided; As experimental provision, can not only aspect moment of flexure, moment of torsion, obtain higher measuring accuracy on the one hand, can effectively measure shearing simultaneously; Thereby increase new experiment content, transform the experiment of raising type as; Offer reference for the internal force measurement of similar component in the engineering structure on the other hand.
The technical scheme that technical solution problem of the present invention is adopted is:
The shearing force measurement bridge circuit that bending-twisting combined test apparatus of the present invention constitutes; Said bending-twisting combined test apparatus is to adopt aluminum alloy drum cantilever crank throw structure; The crank throw that is 90 jiaos by the aluminum alloy drum cantilever with it constitutes; On the tested xsect excircle of said aluminum alloy drum cantilever,, be 90 angular spacings successively and arrange four 45 °-3 rectangular rosettes according to the order of strain rosette A, strain rosette B, strain rosette C and strain rosette D; Be characterized in that said bending-twisting combined test apparatus is on the axis direction of said cylinder cantilever; Strain rosette B, strain rosette C and strain rosette D towards identical; Strain rosette A and other three strain rosettes are towards on the contrary, and are symcenter with measurement point place circumferential position; Said shearing force measurement bridge circuit is: in the access measurement bridge circuit is 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette A and strain rosette C;-45 ° of orientation-sensitive grid of said strain rosette A insert input end A and the output terminal B that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette A insert input end C and the output terminal B that measures bridge circuit;-45 ° of orientation-sensitive grid of strain rosette C insert input end A and the output terminal D that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette C insert input end C and the output terminal D that measures bridge circuit, constitute the full bridge measurement bridge circuit.
The present invention with the strain rosette Rotate 180 ° stickup at A point place, then can eliminate shearing stress in torsion power and additional bending normal stresses according to the strain rosette arrangement in the prior art simultaneously, thereby improves the measuring accuracy of shearing.Compared with present technology, beneficial effect of the present invention is embodied in:
1, the shearing and the moment of torsion of 45 ° of directions and-45 ° of orientation-sensitive grid central point place cross-section are all constant in apparatus of the present invention, and moment of flexure changes and is no more than 2%, thereby can be similar to and think that its stress state remains unchanged.
2, apparatus of the present invention can not only obtain higher measuring accuracy aspect moment of flexure, moment of torsion; Can also effectively measure shearing simultaneously; Enriched experimental teaching content on the one hand; Increased the thinking property and the interest of experiment, deepened the understanding of student's counter stress state notion with group bridge principle and method, the internal force measurement for similar component in the engineering structure provides reference on the other hand.
Description of drawings
Fig. 1 is the experimental provision structural representation.
Fig. 2 is the point position synoptic diagram on the I-I xsect.
Strain rosette arrangement synoptic diagram in Fig. 3 prior art.
Fig. 4 is the shearing force measurement bridge circuit synoptic diagram in the prior art.
Fig. 5 is the strain rosette structural representation.
Fig. 6 is a strain rosette arrangement synoptic diagram of the present invention.
Fig. 7 is used for the bridge arrangement synoptic diagram of shearing force measurement for apparatus of the present invention.
Fig. 8 is used for the bridge arrangement synoptic diagram of torque measurement for apparatus of the present invention.
Fig. 9 is used for the bridge arrangement synoptic diagram of addition bend normal stress measurement for apparatus of the present invention.
Label among the figure: 1 aluminum alloy drum cantilever, 2 crank throws.
Below through embodiment the present invention is further described:
Embodiment
Referring to Fig. 1, Fig. 2 and Fig. 6, present embodiment is according to the strain rosette arrangement in the prior art, with the strain rosette Rotate 180 ° stickup at A point place.Shown in the figure; Identical with prior art is; Adopt aluminum alloy drum cantilever crank throw structure, the crank throw 2 that is 90 jiaos by aluminum alloy drum cantilever 1 with it constitutes, on the tested xsect excircle of aluminum alloy drum cantilever 1; According to the order of strain rosette A, strain rosette B, strain rosette C and strain rosette D, be 90 angular spacings successively and arrange four 45 °-3 rectangular rosettes.Different is along on the axis direction of cylinder cantilever 1 with prior art, strain rosette B, strain rosette C and strain rosette D towards identical, strain rosette A and other three strain rosettes are towards on the contrary, and are symcenter with measurement point place circumferential position.
The application of present embodiment bending-twisting combined test apparatus in the plain measurement of internal force:
One of use: the measurement of shearing
The stress state that A, 2 of C locate 45 ° of directions and-45 ° of orientation-sensitive grid central points in the strain rosette can be regarded the stack of uniaxial stressed state and pure shear stress state as.According to generalized Hooke law, when adopting present embodiment cloth sheet scheme, its line strain along the grid length direction is respectively
τ in the formula
TAnd τ
QExpression is reversed and crooked shearing stress, σ respectively
MBe addition bend normal stress.
45 ° of directions and-45 ° of orientation-sensitive grid that A, 2 of C are located in the strain rosette insert bridge circuit respectively by Fig. 7; That is :-45 of strain rosette A ° of orientation-sensitive grid insert input end A and the output terminal B that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette A insert input end C and the output terminal B that measures bridge circuit;-45 ° of orientation-sensitive grid of strain rosette C insert input end A and the output terminal D that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette C insert input end C and the output terminal D that measures bridge circuit, constitute the full bridge measurement bridge circuit.
The measurement strain stress of then exporting
Q surveysFor
The shearing that records does
Can find out, adopt new paster mode, eliminate shearing stress in torsion power and addition bend normal stress simultaneously, can obtain shearing force measurement value comparatively accurately.
Two of application: torque measurement
Adopt present embodiment paster mode,, can't eliminate the addition bend normal stress of sensitive grid central point if still select the strain rosette of 2 of A, C to measure shearing stress in torsion power.Like this, can increase the measuring error of moment of torsion, measuring accuracy is had a negative impact.In the present embodiment, 45 ° of directions and-45 ° of orientation-sensitive grid of selecting B, 2 of D to locate strain rosette are measured.The crooked shearing stress of these sensitive grid central points is very little, is approximately zero, and shearing stress in torsion power and A, C point are identical.Its line strain along the grid length direction is respectively:
σ is a B point bending normal stresses in the formula.
45 ° of directions and-45 ° of orientation-sensitive grid in B, 2 strain rosettes of D are inserted bridge circuit by Fig. 8, that is:
-45 ° of orientation-sensitive grid of strain rosette B are inserted input end A and the output terminal B that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette B insert input end C and the output terminal B that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette D insert input end A and the output terminal D that measures bridge circuit;-45 ° of orientation-sensitive grid of strain rosette D insert input end C and the output terminal D that measures bridge circuit, constitute the full bridge measurement bridge circuit
The measurement strain stress of then exporting
T surveysFor:
The moment of torsion that records is:
Measurement result is consistent with the original measurement effect of A, 2 strain rosettes of C of selecting.
Three of application: addition bend normal stress measurement
Adopt present embodiment paster mode, can increase the new experiment content of measuring A, 2 strain rosette addition bends of C normal stress.45 ° of directions and-45 ° of orientation-sensitive grid in A, B, C, the D four measuring point strain rosette are inserted the measurement bridge circuit respectively according to Fig. 9, that is:
In the access measurement bridge circuit is 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette A, strain rosette B, strain rosette C and strain rosette D; 45 ° of orientation-sensitive grid series connection of-45 ° of orientation-sensitive grid of strain rosette B and strain rosette A insert input end A and the output terminal B that measures bridge circuit again;-45 ° of orientation-sensitive grid series connection of the 45 ° of orientation-sensitive grid of strain rosette B and strain rosette A insert input end C and the output terminal B that measures bridge circuit again; 45 ° of orientation-sensitive grid series connection of-45 ° of orientation-sensitive grid of strain rosette C and strain rosette D insert input end A and the output terminal D that measures bridge circuit again;-45 ° of orientation-sensitive grid series connection of the 45 ° of orientation-sensitive grid of strain rosette C and strain rosette D insert input end C and the output terminal D that measures bridge circuit again, formation full bridge measurement bridge circuit
According to the characteristics of Wheatstone bridge series connection bridge circuit, and combine (4) and (5) formula, can export the measurement strain stress
M surveysFor
The addition bend normal stress that records does
This experiment content not only can be measured the source of error (addition bend normal stress) that produces shearing dexterously, and the Wheatstone bridge bridge circuit of connecting is applied in the experimental teaching, thereby deepens the understanding of student to bridge circuit, widens the vision.
Claims (1)
1. the shearing force measurement bridge circuit that constitutes of a bending-twisting combined test apparatus; Said bending-twisting combined test apparatus is to adopt aluminum alloy drum cantilever crank throw structure; The crank throw (2) that is 90 jiaos by aluminum alloy drum cantilever (1) with it constitutes; On the tested xsect excircle of said aluminum alloy drum cantilever (1),, be 90 angular spacings successively and arrange four 45 °-3 rectangular rosettes according to the order of strain rosette A, strain rosette B, strain rosette C and strain rosette D; It is characterized in that:
Said bending-twisting combined test apparatus is along on the axis direction of said cylinder cantilever (1), strain rosette B, strain rosette C and strain rosette D towards identical, strain rosette A and other three strain rosettes are towards on the contrary, and to belong to circumferential position with measurement point be symcenter;
Said shearing force measurement bridge circuit in the bridge circuit is 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette A and strain rosette C for insert measuring;-45 ° of orientation-sensitive grid of said strain rosette A insert input end A and the output terminal B that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette A insert input end C and the output terminal B that measures bridge circuit;-45 ° of orientation-sensitive grid of strain rosette C insert input end A and the output terminal D that measures bridge circuit; 45 ° of orientation-sensitive grid of strain rosette C insert input end C and the output terminal D that measures bridge circuit, constitute the full bridge measurement bridge circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100082890A CN101487748B (en) | 2006-06-30 | 2006-06-30 | Shearing force measurement bridge circuit in bending-twisting combined test apparatus |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100082890A CN101487748B (en) | 2006-06-30 | 2006-06-30 | Shearing force measurement bridge circuit in bending-twisting combined test apparatus |
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|---|---|---|---|
| CNB2006100881851A Division CN100494934C (en) | 2006-06-30 | 2006-06-30 | Bending and twisting combined test device and its use in measuring internal force |
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|---|---|
| CN101487748A CN101487748A (en) | 2009-07-22 |
| CN101487748B true CN101487748B (en) | 2012-05-09 |
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| CN102519648B (en) * | 2011-12-22 | 2013-11-20 | 北京航空航天大学 | Simple shear connection structure pin load vector measuring method and measuring instrument thereof |
| CN112649130B (en) * | 2020-12-29 | 2022-03-08 | 上海海事大学 | Integrated testing method for interaction mechanical property of medical puncture biopsy needle interface |
| CN113108686B (en) * | 2021-04-13 | 2023-05-05 | 上海卫星工程研究所 | Strain measuring device for spacecraft and measuring method thereof |
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