CN1053740C - 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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- CN1053740C CN1053740C CN 94112642 CN94112642A CN1053740C CN 1053740 C CN1053740 C CN 1053740C CN 94112642 CN94112642 CN 94112642 CN 94112642 A CN94112642 A CN 94112642A CN 1053740 C CN1053740 C CN 1053740C
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- 239000003110 molding sand Substances 0.000 title claims abstract description 41
- 238000000034 method Methods 0.000 title claims abstract description 28
- 239000004576 sand Substances 0.000 claims abstract description 79
- 238000012360 testing method Methods 0.000 claims abstract description 37
- 230000007423 decrease Effects 0.000 claims abstract 2
- 238000007906 compression Methods 0.000 claims description 11
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- 238000001514 detection method Methods 0.000 claims description 6
- 230000004044 response Effects 0.000 claims description 4
- 238000012544 monitoring process Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 238000005266 casting Methods 0.000 abstract description 8
- 238000005516 engineering process Methods 0.000 abstract description 4
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- 239000000440 bentonite Substances 0.000 description 1
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
本发明涉及一项运用现代测试技术检测铸造型砂机械性能的测试方法及实施该方法的系统。其特征在于：将制好的标准砂样装夹于铸造型砂多项机性能测试系统中进行抗压加载测试，先测型砂的抗压强度σm，再用相同标准砂样进行加载测试，当砂样所受应力值临近σm值之前任一位置，停止加载，保持压力传感器的位置不变，砂样在定应变下产生松弛，随着松弛时间的延长，应力逐渐减少，趋于一定值σs，此值即为该型砂的塑性变形临界值。
The invention relates to a test method for detecting the mechanical properties of foundry sand by using modern test technology and a system for implementing the method. It is characterized in that: the prepared standard sand sample is clamped in the casting sand multi-machine performance testing system to carry out the compressive loading test, the compressive strength σ m of the molding sand is measured first, and then the same standard sand sample is used for the loading test, when When the stress value of the sand sample is close to any position before the value of σm , stop loading and keep the position of the pressure sensor unchanged. The sand sample will relax under a constant strain. With the extension of the relaxation time, the stress will gradually decrease and tend to a certain value σ s , this value is the critical value of plastic deformation of the molding sand.
Description
The present invention relates to the method for testing of a casting sand mechanical property and implement the system of this method.
Molding sand is a kind of medium of complexity, has sticking, bullet, plasticity concurrently, external force to its consolidation process in, not only relevant, also relevant with the time factor of consolidation process with the consolidation energy level; 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 degree of packing consolidation method, except sand bond was required to some extent, more viscoelasticity, the plasticity and toughness to molding sand had proposed to require and control.Molding sand is moulded, toughness is to weigh the important indicator of moulding-sand property, impulsive force and the deformability that can bear before the cracking destruction takes place in its reaction molding sand under external force, once used the index of shatter index as molding sand toughness, adopting measurement mechanism 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 shot down by steel ball, as seen this indirect measuring method is no matter on test philosophy and process, still, all make us doubting accurately and on the sensitivity level in data.
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, start vibrating motor and make 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; 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.
Boenisch utilizes PSV type molding sand dial gauge, and the shear displacemant limit (ShearingDeformation 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 the upset plug, the proving installation of being furnished with compactor, have the device of measuring sand sample physical property compact rate of molding, the pick-up unit of the sensor of the sensor of measurement sand humidity and measurement 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 and equipment all exist 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 system that can determine the method for testing of a new molding sand mechanical performance index-plastic deformation threshold convenient, accurately and implement this method.In this system, also can measure the stress-strain curves of molding sand in resistance to compression, relaxation and conventional mechanical performance one sand bond of molding sand, be beneficial to evaluate better and control the combination property of molding sand.
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 multiple measuring mechanical property of the casting sand system of a specialized designs, assembling, 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 again, the input computing machine, just can draw sand sample stress--strain curve by the corresponding software system, stress--the pairing compressive stress (σ of peak value of deformation behaviour curve σ-ε
m) promptly represented the maximum crushing stress that the sand sample pressurized can bear when breaking, according to the relevant notion of mechanics and foundry technology, this normal stress value is the compressive strength of this molding sand.Then, produce the same standard sand sample and carry out similar resistance to compression loading test, in the sand sample loading procedure, control by surveillance, cutting off the electricity supply in arbitrary position before stress value closes on compressive strength, stops to load, the invariant position of sensor keep-ups pressure, it is lax that sand sample is produced under certain strain, obtains stress in showing print system--the relaxation curve of time, along with the prolongation of slack time, stress reduces gradually, and (the σ that tends to certain value 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 made up of slow-speed of revolution low-power machine (1), worm screw (2), the spiral shell wheel (3) that has internal thread and be equipped with spiral handspike (4), 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, worm gear (3) rotates a week, and spiral handspike (4) moves forward a pitch; The sand sample clamping device divides left chuck (8), right chuck (10); Input computing machine disposal plant is made up of standard signal pressure transducer (7), standard signal displacement transducer (6), A/D transition card, main frame, printer.The shelves heads (5) of pressure transducer (7) and displacement transducer (6) are installed on the spiral handspike (4), and 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 characteristic index--the plastic deformation threshold of the tested sand mold essence of a reflection mechanical property rapidly 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 plasticity in any point B ' shutdown between the AM on the test curve σ-t of correspondence and become row critical value (σ
s).The lax equation of being set up from the sand mold rheological model:
σ＝ {σ
o-σ
s}e
-nl+σ
s
Can see that along with the prolongation of slack time, the stress of sand sample trends towards plastic deformation threshold (σ
s), this value is irrelevant with the aircraft gate of testing process.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 molding sand 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 mould dimension precision.
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 the multinomial measuring mechanical property systematic sampling of this a casting sand part front view.
Fig. 2 is the front view of motor, worm gear, worm screw.
Fig. 3 is a stress--the characteristic curve of strain.
Fig. 4 is lax 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
sBefore the stress limit of having represented viscoelastic deformation in the sand sample resistance to compression process, compressive stress were worth less than this, sand sample only produced 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, shown in the granularity specification sees the following form.
| Screen size | ＞2.8 | 4 | 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 → dried mixed 4 minutes → added an amount of water → wet mixing 8 minutes → shake out.
After need sieving, the molding sand that goes out to grind make it even, pack into and enter sealing back property in the special polybag, the returning property time is 24 hours, before the test, be that 0.25 inch sieve carries out sieve series, control to desired compact rate of molding returning molding sand mesh that property crosses, produce the standard sand sample with the hammering sampling machine, 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 of system.
In order to obtain stress state stably, eliminate the error of 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, the relative shift of the tested sand sample of displacement response device monitoring with pressure-responsive device; Signal by pressure transducer and displacement transducer collection, change by A/D, the digital quantity that becomes the analog signal conversion of the voltage that obtains computing machine to receive and to store, the A/D card is inserted in main frame (APPLE-2) the 4# groove, signal wire is connected on any two passages of analog switch, finish control to A/D conversion by assembly language, and the data of the gained of will sample are stored in the internal memory, the deposit back is prepared against and is called; Just can draw stress---time curve, the strain---time curve and stress---strain curve of being surveyed by corresponding software system.
The standard sand sample (5) that makes is clamped on the sand sample clamping device in the multinomial measuring mechanical property of the casting sand system, starts motor, carry out resistance to compression and load test, up to the sand sample compression damage, test macro is with auto stop.Resistance to compression by a standard sand sample loads test result, by data processor shown in Figure 7, can obtain the σ-ε curve and the compressive strength σ of this molding sand on printer paper
m, as shown in 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 by monitoring system control
mArbitrary position B ' before cuts off the electricity supply, and the sensing station that keep-ups pressure is constant, and it is lax that sand sample is produced under certain strain, and along with the prolongation of slack time, pressure reduces gradually, is tending towards certain value σ
s, this value is the plastic deformation threshold of molding sand.In lax testing process, its measured value result obtains corresponding stress by data processor shown in Figure 8--strain curve σ-t (1), strain--time curve ε-t (2) and σ
sValue, as shown in Figure 4.The A point reaches stationary value σ for sand sample stress relaxation among the figure
sThe reverse extending line of the horizontal segment of back σ-t curve and the intersection point of curve OB '.
In steady loading procedure, utilize a revolution to be 70rpm, power is the miniature low-speed motor (1) of 15w, motor positive and inverse is reversible, utilize belt to rotate, power is added on the worm screw (2), worm screw (2) drives worm gear and rotates, worm gear (3) rotates a week, spiral push rod (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), (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-Z), printer is formed, the retaining head (5) 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-2), can print test curve, test parameter and various analysis diagram.
Shown in test result sees the following form.
| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
| σ 2(N) | 100.7 | 93.7 | 99.4 | 101.6 | 99.8 | 98.4 | 97.1 | 97.8 | 98.3 | 100.2 | |
| Error | Mean value | 99.06N | |||||||||
| Mean square deviation | 1.73 | ||||||||||
| Relative error | 1.99％ | ||||||||||
| Maximum deviation | 1.96 | ||||||||||
Claims (2)
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 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1108389A CN1108389A (en) | 1995-09-13 |
| CN1053740C true 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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| Country | Link |
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| 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 |
| US10025889B2 (en) * | 2013-11-06 | 2018-07-17 | Vetco Gray, LLC | Stress amplification factor analysis methodology for assessing fatigue performance of threaded connectors |
| CN107014577B (en) * | 2017-03-31 | 2019-04-19 | 共享装备股份有限公司 | A verification method for vibration compaction platform |
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1994
- 1994-11-28 CN CN 94112642 patent/CN1053740C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CN1108389A (en) | 1995-09-13 |
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