CN1108389A - Method for investigating critical value of plastical deformation of molding sand - Google Patents
Method for investigating critical value of plastical deformation of molding sand Download PDFInfo
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- CN1108389A CN1108389A CN94112642A CN94112642A CN1108389A CN 1108389 A CN1108389 A CN 1108389A CN 94112642 A CN94112642 A CN 94112642A CN 94112642 A CN94112642 A CN 94112642A CN 1108389 A CN1108389 A CN 1108389A
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Abstract
The measuring method is characterized as follows: place the sand sample in the fixture of a mechanical performance test system for casting sand and perform loading test, during the loading process, when the sand stress reaches whichever position near and before the critical compression strength signma m, cut off the power t stop loading, keep the position of pressure sensor, let the sand sample relax under a definite strain, the stress will reduce gradually along with the relaxation time, and approach a definite value sigma epsilon, that is the plastic deformation critical value of the mould sand, it has practical meaning for evaluating the performance of the mould sand and controlling the accuracy of the casting piece.
Description
The invention belongs to the method for testing of a casting sand mechanical property.
Molding sand is a kind of medium of complexity, have sticking, bullet, plasticity concurrently, external force to its consolidation process in, not only relevant with the consolidation energy level, also relevant with the time factor of consolidation process, for the detection of molding sand mechanical property, what more generally use is intensity meter, but a sand sample can only record a mechanical property-sand bond, and exists the not high disadvantage of measuring accuracy.
The development of high strength consolidation method, except sand bond is required to some extent, more to sticking, the elasticity of molding sand, mould, toughness has proposed control and requirement.Molding sand is moulded, toughness is to weigh the important indicator of moulding-sand property, it has reflected that impulsive force and the deformability that can bear before the cracking destruction takes place molding sand under external force, once used the index of shatter index as molding sand toughness, the proving installation that adopts is the shatter index instrument (toughness index instrument) of steel ball falling type, its process is to stay the toughness of weighing molding sand on the screen cloth with the ratio that falls into the molding sand weight on chassis by calculating the sand sample that is smashed by steel ball, as seen this indirect measuring method is no matter on test philosophy and process, still on the accurate and sensitivity level of data, all make us doubting.
The American once measured the toughness of molding sand with molding sand jarring toughness test instrument, its process is: sand sample is fixed on the pallet, starting vibrating motor makes pallet produce jarring action to sand sample, destroyed until sand sample, number goes out the jarring number of times and weighs the toughness of molding sand with this, and the problem that this method exists also is apparent in view, because the failure mode of molding sand is come in and gone out very big in this failure mode of sand sample and the actual production, simultaneously, more exist the lower problem of stable testing difference and precision.
Beonisch utilizes PSV type molding sand mircrometer gauge, and the shear displacemant limit (Shearing Deformation Limit) of molding sand is measured and studied.Various factors and the rule that influences this deflection analyzed in discussion, and obtain a result and think that this deflection can represent the plasticity of molding sand, but, owing to multiple reason, more than research is not all tested and is analyzed the change procedure of the stress and strain in the whole shear history, therefore cover some molding sand essential characteristic, and had the problem of aspects such as consolidation method and measuring accuracy.
U.S. Pat 4.930.354 discloses a kind of equipment of testing the casting sand performance, comprise the pressue device that has turn sieve, the proving installation of being furnished with compactor has the sensor of measuring sand sample physical property compact rate of molding and humidity and the pick-up unit of measuring the sensor of sand compressive strength.U.S. Pat 4,442.884 discloses a kind of technology and equipment of automatic continuous coverage molding sand shear resistance.But said apparatus all exists problems such as the molding sand mechanical property object of measurement is single, measurement means is incomplete.
Purpose of the present invention just provides a kind of method of testing, in the test macro of a multinomial mechanical property of casting sand, the plastic deformation threshold that can determine molding sand is easily and accurately come, so that provide an important parameter for the comprehensive mechanical performance of evaluating molding sand all sidedly.
The objective of the invention is to be achieved through the following technical solutions:
The standard sand sample that makes is clamped on the sand sample clamping device in the multinomial measuring mechanical property of the casting sand system, carries out resistance to compression and load test.In loading procedure, control is opposite to the pressing speed of sand sample between chuck, to be loaded effect stably.In the test macro, monitor the stress of tested sand sample with pressure-responsive device, the displacement response device monitors the relative shift of tested sand sample, by the A/D conversion voltage analog signal that obtains is changed the input computing machine again, just can draw sand sample stress-deformation curve by corresponding software system, obtain maximum-compressive strength that sand sample can bear.Then, produce the same standard sand sample and carry out similar resistance to compression loading test, in the sand sample loading procedure, cut off the electricity supply in the arbitrary position before stress value closes on compressive strength, stop to load, the keep-up pressure invariant position of sensor, it is loose that sand sample is produced under certain strain, along with the prolongation of relaxation time, stress reduces gradually, and trends towards certain value σ gradually
s, this value is the plastic deformation threshold of this molding sand.
The multinomial measuring mechanical property of casting sand involved in the present invention system comprises: steady charger, sand sample clamping device, input computer processor unit.Steadily charger is by slow-speed of revolution low-power machine (1), worm screw (2), the worm gear (3) that has internal thread and be equipped with spiral handspike (4) is formed, miniature slow-speed of revolution low-power machine (1) passes through belt gear, power is added on the worm screw (2), worm screw (2) drives worm gear (3) and rotates, turbine (3) rotates a week, spiral handspike (4) moves forward a pitch, the chuck of sand sample clamping device divides left chuck (8), right chuck (10), the input computer processor unit is by standard signal pressure transducer (7), standard signal displacement transducer (6), the A/D transition card, main frame, printer is formed, the retaining head of pressure transducer (7) and displacement transducer (6) is installed on the spiral handspike (4), pressure transducer (7) joins with left chuck (8), and detected standard signal enters computing machine through the A/D transition card; Printer is connected with main frame, can print test curve, test parameter and various analysis diagram.
Detecting the data file program mainly is the control sampling period, drives the A/D converse routine, and read test result and deposit also can be carried out some simple calculating.
Detecting sampling A/D converse routine mainly is that the digital quantity that the A/D card is converted to is gathered, and is stored in specific region of memory, calls in order to deposit.
Data processor mainly is that the data after the deposit are carried out analyzing and processing, runs a curve, and draws required parameters calculated, and prints the result.This part is on the basis that theory is analyzed, and the gained data are handled, calculated, and draws desired parameter.
Its advantage of detection method that the present invention adopts is that it has used modern measuring technology and means of testing; by test to the standard sand sample; can provide the characteristic index-plastic deformation threshold of the tested molding sand essence of a reflection mechanical property quickly and accurately; it is the viscoelastic deformation stress limit of tested standard sand sample; aircraft gate in this value and the testing process is irrelevant; promptly, all can obtain identical plastic deformation threshold σ in any point B ' shutdown between the AM on the test curve σ-t of correspondence
SFrom the resulting loose equation of the molding sand rheological model of setting up:
σ＝（σ
o-σ
s）e
-nt+σ
s
Can see, along with the prolongation of relaxation time, the stress of sand sample trend plastic deformation threshold σ
s, the aircraft gate of it and testing process is irrelevant.Thereby all having proved this invention from rheology theory and measured result is new making known to objective law.Plastic deformation threshold has characterized the ability that molding sand is subjected to opposing plastic yield under the external force state, be to prevent moving, the performance index of consolidation distortion again of sand mold type wall shift, also be the characteristic index that direct relation is arranged with the molding sand rebound performance, realistic meaning will be arranged the control of casting dimension accuracy.
The system of method of the present invention and this method of enforcement can describe in detail with reference to the accompanying drawings:
Fig. 1 is this test macro sampling section front view
Fig. 2 is the front view of motor, worm gear, worm screw
Fig. 3 is the characteristic curve of stress-strain
Fig. 4 is loose detection curve
Fig. 5 is for setting up the file routine block diagram
Fig. 6 is an A/D converse routine block diagram
Fig. 7, Fig. 8 are the data processor block diagram
In Fig. 3:
σ
mRepresent the ultimate stress that can bear in the sand sample resistance to compression process, represented the compressive strength of molding sand.
In Fig. 4:
σ
sThe stress limit of having represented viscoelastic deformation in the sand sample resistance to compression process: compressive stress is less than before this value, and sand sample only produces viscoelastic deformation, and after compressive stress surpasses this value, sand sample will produce the visco-plasticity distortion.Therefore, claim σ
sBe plastic deformation threshold.
Embodiment:
Using molding sand, used roughing sand with the mixed system test of simpson mill is the Da Lin normal sand, and label is: NBS55/100, and the granularity specification sees the following form:
| Screen size | >28 | 45 | 55 | 75 | 100 | 150 | 200 | Silt content |
| Residual quantity % | <2 | <13 | 18－23 | 40－46 | 13－17 | <8 | <3 | <0.5 |
Used clay is the Black Hills calcium-base bentonite, and concrete sand mulling craft is as follows:
Roughing sand+cementing agent → do to mix 4 minutes → add 8 minutes → knockability of an amount of water → wet mixing, the returning property time is 24 hours, before the test, carry out sieve series with returning molding sand that property crosses sieve (0.794cm) with 0.25 inch in mesh, control to desired compact rate of molding, the sand sample height is 50 ± 0.2mm, and the sand sample that makes is taken out from the sample tube, is positioned between the chuck in the system.
For the state that is steadily loaded, the error of elimination system, in loading procedure, control the pressing speed that is opposite to the sand sample between chuck, when compression test, monitor the stress of tested sand sample with pressure-responsive device, the relative shift of the tested sand sample of displacement response device monitoring, signal by pressure transducer and displacement transducer collection, change by A/D, digital quantity the analog signal conversion of the voltage that obtains becomes computing machine to receive and to store is inserted in main frame (APPLE-II) 4 with the A/D card
#In the groove, signal wire is connected on any two passages of analog switch, finish the control that A/D is changed by assembly language, and the data of the gained of will sampling are stored in the internal memory, deposit by driver then, in order to calling, just can draw stress time curve, strain-time curve and the stress-strain curve of being surveyed by corresponding software system.
By the loading compression test result of a standard sand sample,, can obtain the σ-ε curve and the compressive strength σ of this molding sand by data processor shown in Figure 7
m(see figure 3).Then, produce the same standard sand sample again and place and similarly load detection between chuck, close on compressive strength σ when sand sample is loaded on institute's compression chord
m(any point B ' on σ-t curve between the AM of arbitrary position before.Herein, the A point is the terminal point of sand sample viscoelasticity linear deformation), to cut off the electricity supply, the sensing station that keep-ups pressure is constant, and it is loose that sand sample is produced under certain strain, and along with the prolongation of relaxation time, stress reduces gradually, is tending towards certain value σ
s, this value is the plastic deformation threshold of molding sand.In loose testing process, its measured value result obtains corresponding stress time curve σ-t, strain-time curve ε-t and σ by data processor shown in Figure 8
sValue.
In loading procedure stably, utilize a rotating speed to be 70rpm, power is the miniature low-speed motor of 15W, motor positive and inverse is reversible, utilize belt gear, power is added on the worm screw (2), worm screw (2) drives worm gear and rotates, worm gear (3) rotates a week, spiral handspike (4) moves forward a pitch, the chuck of sand sample clamping device divides left chuck (8), right chuck (10), the input computer processor unit is by the standard signal pressure transducer, the standard signal displacement transducer, (this blocks by 8 digit buffer 74LS174 the A/D transition card, 2716EPROM, 6D trigger 74LS174,12 figure place moulds conversion AD7521 and reverser, comparer, 16 tunnels analogy switches, 4067 compositions such as grade), main frame (APPLE-II), printer is formed, the retaining head of pressure transducer and displacement transducer is installed on the spiral handspike (4), pressure transducer (7) joins with left chuck (8), measured signal is sent into main frame through the A/D transition card, printer connects with main frame (APPLE-II), can print test curve, test parameter and various analysis diagram.
Test result is as follows:
Claims (1)
- A kind of method of testing of casting sand plastic deformation threshold, it is characterized in that: the standard sand sample that makes is clamped on the sand sample clamping device in the multinomial measuring mechanical property of the casting sand system, carry out resistance to compression and load test, obtain its maximum crushing stress-compressive strength; Then, the same standard sand sample is placed similarly load test between chuck.In loading procedure, cut off the electricity supply in arbitrary position before the suffered stress value of sand sample closes on compressive strength, stop to load, and the invariant position of the sensor that keep-ups pressure, it is loose that sand sample is produced under certain stress, obtains the plastic deformation threshold of this molding sand thus.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 94112642 CN1053740C (en) | 1994-11-28 | 1994-11-28 | Method for investigating critical value of plastical deformation of molding sand |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 94112642 CN1053740C (en) | 1994-11-28 | 1994-11-28 | Method for investigating critical value of plastical deformation of molding sand |
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| Publication Number | Publication Date |
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| CN1108389A true CN1108389A (en) | 1995-09-13 |
| CN1053740C CN1053740C (en) | 2000-06-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 94112642 Expired - Fee Related CN1053740C (en) | 1994-11-28 | 1994-11-28 | Method for investigating critical value of plastical deformation of molding sand |
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| CN (1) | CN1053740C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102980693A (en) * | 2012-11-21 | 2013-03-20 | 东北大学 | Two-stage calibration conversion method using viscous-elastic piezoresistive material to monitor stress variation after high-speed loading |
| CN105683972A (en) * | 2013-11-06 | 2016-06-15 | 韦特柯格雷公司 | Stress amplification factor analysis methodology for assessing fatigue performance of threaded connectors |
| CN107014577A (en) * | 2017-03-31 | 2017-08-04 | 共享装备股份有限公司 | A kind of method of calibration of vibration ramming platform |
-
1994
- 1994-11-28 CN CN 94112642 patent/CN1053740C/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102980693A (en) * | 2012-11-21 | 2013-03-20 | 东北大学 | Two-stage calibration conversion method using viscous-elastic piezoresistive material to monitor stress variation after high-speed loading |
| CN105683972A (en) * | 2013-11-06 | 2016-06-15 | 韦特柯格雷公司 | Stress amplification factor analysis methodology for assessing fatigue performance of threaded connectors |
| CN105683972B (en) * | 2013-11-06 | 2019-04-30 | 韦特柯格雷公司 | For assessing the Amplification factor analysis method of the fatigue behaviour of screw thread coupling |
| CN107014577A (en) * | 2017-03-31 | 2017-08-04 | 共享装备股份有限公司 | A kind of method of calibration of vibration ramming platform |
| CN107014577B (en) * | 2017-03-31 | 2019-04-19 | 共享装备股份有限公司 | A kind of method of calibration of vibration ramming platform |
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| Publication number | Publication date |
|---|---|
| CN1053740C (en) | 2000-06-21 |
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