CN1900670A - Bending and twisting combined test device and its use in measuring internal force - Google Patents
Bending and twisting combined test device and its use in measuring internal force Download PDFInfo
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- CN1900670A CN1900670A CN 200610088185 CN200610088185A CN1900670A CN 1900670 A CN1900670 A CN 1900670A CN 200610088185 CN200610088185 CN 200610088185 CN 200610088185 A CN200610088185 A CN 200610088185A CN 1900670 A CN1900670 A CN 1900670A
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- strain rosette
- bridge circuit
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- sensitive grid
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Abstract
The test unit includes cantilever of cylinder in aluminum alloy, and bell crank in 90 degrees to the cantilever. According to strain rosette A, strain rosette B, strain rosette C, and strain rosette D sequence, four pieces of 45 degrees -3 right angle strain rosette are arranged with 90 degrees angular interval in sequence on excircle of cross section to be measured of the cantilever of cylinder in aluminum alloy. Characters are that in axial direction of the cantilever, strain rosette B, strain rosette C, and strain rosette D are in same direction, and strain rosette A is in opposite direction by using circle the measuring point located being as center of symmetry. The invention obtains high precision of measuring bending moment and torsional moment, and can measure shearing force effectively. The invention adds new content of teaching experiment, and provides reference for measurement of internal force of similar component in engineering structure.
Description
Technical field:
The present invention relates to the plain measuring method of bending-twisting combined test apparatus and internal force.
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 principle stress under the bending and twisting combined action and the specified cross-section.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 crank throw 2 to be constituted by aluminum alloy drum cantilever 1 with it, by the bending and twisting combined action loading characteristic as can be known, 2 of A, C are the pure shear stress state, and the line strains along 45 ° and-45 ° of directions in 2 o'clock are respectively:
τ in the formula
TAnd τ
QExpression is reversed and crooked shearing stress respectively.During measurement, 45 ° of directions in 2 strain rosettes of A, C and-45 ° of orientation-sensitive grid are connected into as shown in Figure 4 full-bridge bridge circuit, then the measured value of crooked shearing stress is
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, because 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, by Fig. 5 also as can be seen, 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, a kind of bending-twisting combined test apparatus and the application in the plain measurement of internal force thereof are provided, on the one hand as experimental provision, can not only aspect moment of flexure, moment of torsion, obtain higher measuring accuracy, 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:
Bending-twisting combined test apparatus of the present invention 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 described 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.
The design feature of apparatus of the present invention is, along on the axis direction of described cylinder cantilever 1, strain rosette B, strain rosette C and strain rosette D towards identical, three strain rosettes of strain rosette A and other are towards opposite, and are symcenter with measurement point place circumferential position.
The feature that constitutes shearing force measurement bridge circuit with apparatus of the present invention is:
Shearing force measurement bridge circuit is set, 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 described 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 feature that constitutes the torque measurement bridge circuit with apparatus of the present invention is:
The torque measurement bridge circuit is set, in the access measurement bridge circuit is 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette B and strain rosette D,-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 feature that constitutes the addition bend normal stress measurement bridge circuit with apparatus of the present invention is:
The addition bend normal stress measurement bridge circuit is set, 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 described 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, 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 the prior art, 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 to be 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, the thinking and the interest of experiment have been increased, deepened the understanding of student's counter stress state notion and group bridge principle and method, the internal force measurement for similar component in the engineering structure provides reference on the other hand.
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.
Number in the figure: 1 aluminum alloy drum cantilever, 2 crank throws.
Below by 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, three strain rosettes of strain rosette A and other are towards opposite, 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 2 of A, C locate 45 ° of directions in the strain rosette and-45 ° of orientation-sensitive grid central points 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 2 of A, 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.
Shu Chu measurement strain stress then
Q surveysFor
The shearing that records is
As can be seen, adopt new paster mode, eliminated 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, D to locate strain rosette at 2 are measured.The crooked shearing stress of these sensitive grid central points is very little, is approximately zero, and shearing stress in torsion power is identical with A, C point.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 2 strain rosettes of B, 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
Shu Chu measurement strain stress then
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, constitute the full bridge measurement bridge circuit
According to the characteristics of Wheatstone bridge series connection bridge circuit, and, can export the measurement strain stress in conjunction with (4) and (5) formula
M surveysFor
The addition bend normal stress that records is
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 (4)
1, bending-twisting combined test apparatus, 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 described 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; It is characterized in that along on the axis direction of described cylinder cantilever (1), strain rosette B, strain rosette C and strain rosette D towards identical, three strain rosettes of strain rosette A and other are towards opposite, and are symcenter with measurement point place circumferential position.
2, the shearing force measurement bridge circuit that the described device of a kind of claim 1 constitutes, it is characterized in that inserting that to measure in the bridge circuit be 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette A and strain rosette C,-45 ° of orientation-sensitive grid of described 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.
3, the torque measurement bridge circuit that the described device of a kind of claim 1 constitutes, it is characterized in that inserting that to measure in the bridge circuit be 45 ° of directions and-45 ° of orientation-sensitive grid of strain rosette B and strain rosette D,-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.
4, the addition bend normal stress measurement bridge circuit of the described device formation of a kind of claim 1, it is characterized in that inserting that to measure in the bridge circuit be 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 described 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, constitute the full bridge measurement bridge circuit.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2006100881851A 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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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2006100881851A 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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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009100049939A Division CN101482436B (en) | 2006-06-30 | 2006-06-30 | Additional bending normal stress measurement bridge circuit in bending combination test apparatus |
| CN2009100082890A Division CN101487748B (en) | 2006-06-30 | 2006-06-30 | Shearing force measurement bridge circuit in bending-twisting combined test apparatus |
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| CN1900670A true CN1900670A (en) | 2007-01-24 |
| CN100494934C CN100494934C (en) | 2009-06-03 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103439036A (en) * | 2013-09-05 | 2013-12-11 | 北京航空航天大学 | Oil pumping rod underground stress measuring device |
| US20160052583A1 (en) * | 2014-08-22 | 2016-02-25 | Shimano Inc. | Bicycle pedal |
| CN113108686A (en) * | 2021-04-13 | 2021-07-13 | 上海卫星工程研究所 | Strain measuring device for spacecraft and measuring method thereof |
-
2006
- 2006-06-30 CN CNB2006100881851A patent/CN100494934C/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103439036A (en) * | 2013-09-05 | 2013-12-11 | 北京航空航天大学 | Oil pumping rod underground stress measuring device |
| CN103439036B (en) * | 2013-09-05 | 2015-06-10 | 北京航空航天大学 | Oil pumping rod underground stress measuring device |
| US20160052583A1 (en) * | 2014-08-22 | 2016-02-25 | Shimano Inc. | Bicycle pedal |
| US10000249B2 (en) * | 2014-08-22 | 2018-06-19 | Shimano Inc. | Bicycle pedal |
| CN113108686A (en) * | 2021-04-13 | 2021-07-13 | 上海卫星工程研究所 | Strain measuring device for spacecraft and measuring method thereof |
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| Publication number | Publication date |
|---|---|
| CN100494934C (en) | 2009-06-03 |
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Granted publication date: 20090603 Termination date: 20120630 |