CN104759954B - A kind of revolving body workpieces pre-stressed grinding method - Google Patents
A kind of revolving body workpieces pre-stressed grinding method Download PDFInfo
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- CN104759954B CN104759954B CN201510226694.5A CN201510226694A CN104759954B CN 104759954 B CN104759954 B CN 104759954B CN 201510226694 A CN201510226694 A CN 201510226694A CN 104759954 B CN104759954 B CN 104759954B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
Abstract
The invention discloses a kind of revolving body workpieces pre-stressed grinding method, comprises the following steps：(1) the clamping workpiece to be processed on grinding machine；(2) aim at tool operation is carried out, first allows emery wheel and workpiece in lower-speed state, progressively adjust emery wheel position, after surface of the work just spark occurs, grinding speed is adjusted to into ultrahigh speed state vsWorkpiece rotational frequency is adjusted to ultracentrifugation state by >=150m/s；(3) grinding is carried out by certain radial feeds；After completion of processing, first emery wheel is separated with workpiece, then be each decelerated to zero.The revolving body workpieces pre-stressed grinding method of the present invention makes surface of the work obtain residual compressive stress after completion of processing by applying prestressing force, the rotating speed that only need to control workpiece in process to workpiece without using special force application mechanism；As the rotating speed of workpiece with flexible, therefore can obtain different size of residual compressive stress by way of controlling workpiece rotational frequency, to meet the use requirement of different parts.
Description
Technical field
The present invention relates to a kind of machining process, and in particular to a kind of pre-stressed grinding method.
Background technology
Grinding is a kind of conventional machinery processing method that polish is carried out to workpiece, including flat surface grinding and peripheral milling
Cut.In grinding, grinding speed is increased substantially, working (machining) efficiency can be improved, and make workpiece obtain higher processing
Precision.For example, Germany grinding expert Carl.J.Salomom proposes " superhigh speed grinding " on the basis of " heat channel " theory, its
Emery wheel refers to that linear velocity, more than 150m/s, is capable of achieving the high efficiency Precision Machining to workpiece.In " superhigh speed grinding " theory, to work
The rotating speed of part there is no particular requirement that, usually require that workpiece rotational frequency vw≥500r/min.In order to further improve working (machining) efficiency,
" high efficiency deep grinding " theory is proposed in prior art basis, for example, at the end of the seventies, German professor's P.G.Werner prophesy is " high
Effect is deep to grind " there is reasonability, and First high efficiency deep grinding grinding machine in the world is developed in nineteen eighty-three, keeping the rotation of emery wheel ultrahigh speed
On the basis of (being more than 150m/s), workpiece rotational frequency (v is properly increasedw=1kr/min, and grinding depth is bigger, value is less) and
Increase grinding depth.
In many application scenarios, for the behaviour of precision component and heavily loaded part is heavily dependent on theirs
Apparent condition, this is to directly affect its fatigue strength, corrosion resistance, wearability and dimensionally stable due to part finished surface state
Property etc..Research and practice have shown that, by adjustment and control make machined surface that there is suitable residual compressive stress, part can be improved
Fatigue resistance, extend its service life.In prior art, generally using annealing, rolling, shot-peening, ironing and laser
The processing methods such as impact cause surface of the work to produce residual compressive stress, but these methods have apparatus expensive, can make workpiece table
Face was also easy to produce flow harden, reduced the defects such as its impact flexibility.In order to solve the problem, " the remnants of Pre-stress hard cutting
Stress and configuration of surface "【South China Science ＆ Engineering University's journal (natural science edition), the 4th phase of volume 36, the version of in April, 2008；The 6-9 page】
One is disclosed herein the method for carrying out hard turning acquisition residual stress in pre-stressed state, and its ultimate principle is：It is pre- before cutting
First apply the prestressing force in an elastic range to workpiece, workpiece machining surface can produce plastic deformation in working angles, cutting
After discharge the prestressing force, due to the elastic return of matrix, machined surface can produce residual compressive stress.The advantage of prestressing force cutting
It is only surface of the work just need to be made to produce residual compressive stress by machining, and extra Surface hardened layer will not be caused.For
Acquisition prestressing force, applies active force by force application mechanism in prior art generally before carry out machining to workpiece, and
The force state is remained in the course of processing；For example, above-mentioned " residual stress and configuration of surface of Pre-stress hard cutting "
In text so that the inner ring raceway of bearing and outer ring outer round surface carry out Pre-stress hard cutting as an example, using in advance to bearing ring
Endoporus swelling support is big, then makes circumferential pre-tensile stress is produced in bearing ring by way of radial loaded.However, in prior art
Obtain prestressed method to have the following disadvantages：
1st, need to exert a force workpiece using special force application apparatus so that work piece holder structure is more complicated, operate
More bother；And in machining, workpiece needs the occasion of rotation, such as when carrying out cylindricalo grinding, in order to ensure obtaining
The prestressing force that must continue, force application mechanism must be rotated together with workpiece, so as to increased overall inertia, reduce stability,
Affect machining accuracy.
2nd, for specific processing part, it usually needs the specific force application apparatus of design, high cost.
3rd, prestressed size is not easy to control, and especially in process, the prestressing force on workpiece cannot be according to need
Want real-time regulation.
The content of the invention
It is an object of the invention to overcome the deficiencies in the prior art, there is provided a kind of revolving body workpieces pre-stressed grinding method,
The method need not can allow workpiece that prestressing force is obtained in Grinding Process using force application mechanism, and in process should
Prestressed big I flexible.
The present invention solves the technical scheme of above-mentioned technical problem：
A kind of revolving body workpieces pre-stressed grinding method, comprises the following steps：
(1) the clamping workpiece to be processed on grinding machine；
(2) aim at tool operation is carried out, first allows emery wheel and workpiece in lower-speed state, progressively adjust emery wheel position, until workpiece
After surface just spark occurs, grinding speed is adjusted to into ultrahigh speed state vs>=150m/s, by workpiece rotational frequency be adjusted to ultrahigh speed from
Heart shaped state so that workpiece produces centrifugation bulking effect, obtains prestressing force；
(3) grinding is carried out by certain radial feeds；After completion of processing, first emery wheel is separated with workpiece, then each
It is decelerated to zero.
Preferably, in step (2), the workpiece rotational frequency vw≥8kr/min。
Preferably, in step (2), the workpiece rotational frequency 8kr/min≤vw≤10kr/min。
Preferably, in step (3), radial feeds ap=10～100 μm/kr.
By workpiece maximum speed is controlled, in the range of less than 10kr/min, to prevent from rotating because of workpiece ultrahigh speed
And grinding machine spindle stability is impacted, while the shadow produced because workpiece ultrahigh speed is rotated and to wheel life can also be slowed down
Ring.With the development of technology, stability of the grinding machine spindle under ultrahigh speed state can be become better and better, therefore the master when grinding machine works
On the premise of axle stability is good enough, workpiece rotational frequency can also be more than 10kr/min.
Preferably, in step (3), emery wheel is fed by setting radial feeds and is started after grinding, workpiece or/and emery wheel
Grinding is carried out with speed change state；After emery wheel stops radial feed entering the tarry matter stage, workpiece or emery wheel are with speed change state
Tarry matter is carried out, emery wheel is separated with workpiece after finishing and is each decelerated to zero by tarry matter.
The purpose that speed change is carried out in Grinding Process be effectively suppress grinding machine spindle tremor, reduce forced vibration and
Change the rotating ratio of emery wheel and workpiece；For the grinding stage, surface of the work integrity can be improved and extend emery wheel using
In the life-span, for the tarry matter stage, the effect for alleviating that surface of the work produces " corner angle " phenomenon can be reached.In existing tarry matter skill
It is in art, general during tarry matter to keep emery wheel and workpiece rotational frequency constant, so as to form constant velocity ratio, now at the vibration of grinding machine
In a kind of regular state, a kind of regular dynamic relative position relation is maintained between workpiece and emery wheel, so as in workpiece
Surface forms regular non-equivalent grinding, affects workpiece surface quality, " corner angle " phenomenon occurs；And in grinding and tarry matter process
After middle employing method for changing speed, emery wheel and the velocity ratio of workpiece is constantly changed, be not only able to effect and suppress grinding machine spindle tremor, subtract
Little forced vibration, and cause the vibration of grinding machine to be in a kind of irregular state, a kind of nothing is also maintained between workpiece and emery wheel
The dynamic relative position relation of rule, each position of such surface of the work are obtained in that uniform grinding, improve workpiece table
Face integrity, and alleviate the problem that surface of the work produces " corner angle " phenomenon.In speed-change process, if emery wheel is without the need for axially entering
Give, then emery wheel keeps that axial location is constant carries out speed change；If emery wheel needs axial feed, emery wheel to carry out axially entering
Give, carry out speed change.
In speed change, either grinding stage or tarry matter stage, the object of speed change can be workpiece or emery wheel, or
Both persons are while speed change, the form of speed change can accelerate slow down, and the mode of speed change can be continuous change, also may be used
Being staged speed change.
As a kind of preferred version, in the grinding stage, the speed change state of the workpiece or/and emery wheel is：Keep
Workpiece rotational frequency is constant, improves grinding speed；In the tarry matter stage, the speed change state of the workpiece or/and emery wheel is：Keep sand
Wheel linear velocity is constant, reduces workpiece rotational frequency.Using this preferred version except in order to realize suppress main shaft tremor, reduce forced vibration
Outer with workpiece rotational frequency ratio with emery wheel is changed, its reason is：In the grinding stage, by improving grinding speed, a side
Face can be such that the heat of incoming workpiece further reduces, and grinding temperature is reduced, on the other hand due to acting on the mill of same grinding area
Grain number amount increases, and can alleviate makes the problem of its surface roughness increase because improving workpiece rotational frequency；In the tarry matter stage, due to sand
Wheel stops radial feed, and emery wheel is only contacted in " corner angle " of surface of the work, and the formation on surface of the work residual stress has been affected not
Greatly, by reducing workpiece rotational frequency, the not deformed grinding thichness of single abrasive particle reduces (reduces grinding speed relative to the tarry matter stage
For), be conducive to improving the surface roughness of workpiece.
Used as a kind of preferred version, when using continuous change mode, in the grinding stage, emery wheel is with 2m/s2~
5m/s2Linear acceleration accelerated；In the tarry matter stage, workpiece is with 800 π rad/s2～1200 π rad/s2Angular acceleration enter
Row slows down.
When using staged gear shift mode, in the grinding stage, emery wheel is with 6m/s2～8m/s2Linear acceleration add
This process is considered as an acceleration ladder, is circulated 3～5 times by the uniform velocity 1～2s after fast 6m/s～10m/s；In the tarry matter stage, work
Part is with 1200 π rad/s2～1600 π rad/s2Angular acceleration deceleration 500r/min after at the uniform velocity 1～2s, this process is considered as into one
Deceleration ladder, circulates 2 times.
Used as an example, the workpiece is the bearing inner race by made by GCr15 materials, carries out ultracentrifugation grinding and adds
Man-hour workpiece initial speed is 8kr/min；In the grinding stage, emery wheel is with 2m/s2～5m/s2Linear acceleration is carried out continuously
Accelerate；In the tarry matter stage, workpiece is with 800 π rad/s2～1200 π rad/s2Angular acceleration is continuously slowed down, and works as workpiece rotational frequency
When dropping to 7kr/min, emery wheel is separated with workpiece and zero is each decelerated to.In the tarry matter stage, workpiece speed change lower limit determines
For 7kr/min, its reason is：After tarry matter about 2s, the surface integrity of workpiece is unrelated with light time consuming, determines workpiece speed change
Lower limit, it is ensured that working (machining) efficiency.
In process, concrete linear acceleration during concrete angular acceleration and emery wheel speed change during workpiece speed change can basis
Following two conditions are determining：
(1) rotation speed change amplitude should be in the range of speeds that electro spindle justifies bounce control.Electro spindle at this stage can pass through
Dynamic balancing technique by the circle bounce control in the main shaft range of speeds in an accurate scope, jump by the circle of remaining range of speeds
It is dynamic relatively large.Assume that the electro spindle normal revolution for driving workpiece to rotate is 8kr/min, by dynamic balancing technique, can be by the electricity
Main shaft is controlled between 0.5um～1um in the circle bounce of the rotating speed in the range of 6kr/min～10kr/min, remaining section of rotating speed
Circle bounce is more than 1um, therefore the change of rotating speed should be in the range of speeds of setting.
(2) time of speed-change process determine that by process time and the process time is then by total grinding depth and radial feed
Amount apIt is determined that.
Two conditions of summary, when it is determined that after speed change amplitude and shifting time, just can calculate and choose rational angle
Acceleration and linear acceleration, make workpiece and emery wheel justify the range of speeds internal speed-changing of bounce control in respective electro spindle.
The present invention operation principle be：Ultracentrifugation state is lifted to by the rotating speed by workpiece so that workpiece is produced
Centrifugation bulking effect, so as to obtain prestressing force；Grinding is carried out to workpiece under pre-stressed state so that after completion of processing
Surface of the work can obtain the residual compressive stress for needing.
The present invention has following beneficial effect compared with prior art：
1st, apply prestressing force to workpiece without using special force application mechanism, only need to control turning for workpiece in process
Speed can make surface of the work obtain residual compressive stress after completion of processing, simplify clamp structure, reduce cost, operation letter
Just；And stability will not be affected because prestressing force force application mechanism is rotated together with workpiece.
2nd, as the rotating speed of workpiece can be with flexible, and workpiece rotational frequency is higher, and the final residual compressive stress that obtains is bigger,
Therefore different size of residual compressive stress can be obtained by the rotating speed of control workpiece, will with the use for meeting different parts
Ask, this regulative mode is flexible, convenient, and can be with real-time regulation.
3rd, in grinding process, workpiece rotational frequency is improved, the time that single abrasive particle acts on same grinding area in emery wheel shortens,
The heat of incoming workpiece reduces (grinding burn is always on grinding field the difficult problem for being difficult to overcome with crackle), grinding temperature drop
It is low, so that the harmful residual tension of workpiece surface reduces.
4th, workpiece rotational frequency is improved under conditions of grinding depth is not changed, on the one hand (weigh grinding efficiency than material removal rate
Parameter) improve, on the other hand as workpiece rotational frequency is increased substantially, strain rate is improved, and the mechanical property of workpiece surface material changes
Become, reduce grinding energy ratio (weighing the parameter of capacity usage ratio).
5th, workpiece rotational frequency is greatly improved, and has good ground effect to high-ductility and difficult grind material, and can be more effectively
Is realized to hard brittle material by ductile regime grinding for ground.
Even if during the 6, the gyroscopic effect that Work piece high-speed rotation is produced makes workpiece rotate under larger normal grinding force effect
The direction of heart axle still keeps constant, be workpiece carry out ultracentrifugation grinding create favorable conditions.
7th, after being increased substantially due to workpiece rotational frequency, possessing to carry out the operation of speed governing in grinding process, by speed change
Operation, can effectively suppress tremor (to excite the periodicity self-excited vibration of feedback generation, referred to as tremor to occur to exist by internal system
Under conditions of certain abrasion of grinding wheel area of plane rate), so as to improving surface of the work integrity degree and extending emery wheel service life.
8th, after being increased substantially due to workpiece rotational frequency, possessing to carry out the operation of speed governing in grinding process, by speed change
Operation, can alleviate because under constant velocity-ratio, system forced vibration (is disturbed what is produced by system outer periodic, such as unbalanced sand
Wheel or axle) and " corner angle " phenomenon of workpiece machining surface generation is made, so as to improve workpiece surface quality.
Description of the drawings
Grinding model figures of the Fig. 1 for abrasive grain cutting sword.
Fig. 2 is superhigh speed grinding conceptual schematic view.
Fig. 3 is the internal stress analysis schematic diagram under workpiece centrifugal effect.
Graph of a relation between the surface compress residual stresses that Fig. 4 is obtained for workpiece rotational frequency and after processing.
Fig. 5 is workpiece rotational frequency and circumferential stress graph of a relation.
Fig. 6 and Fig. 7 is the assembly relationship model figure of main shaft and bearing.
Fig. 8 is bearing and main shaft (rotor) wear surface expanded radially deformation relationship curve chart.
Fig. 9 is bearing axial direction and radial rigidity and speed of mainshaft graph of relation.
Figure 10 is the speed of mainshaft and bearing contact angle graph of relation.
Figure 11 is the speed of mainshaft and bearing touch power graph of relation.
Figure 12 is the experiment of relation and simulation result figure between the speed of mainshaft and axis system natural frequency.
Figure 13 is the formation mechenism figure that workpiece is ground surface layer residual stress.
Figure 14 is stress-strain curve diagram of the different strain rate with a temperature of.
Figure 15 is impact figure of the speed change amplitude to chatter growth rate.
Figure 16 is speed change forward spindle system emery wheel and Workpiece vibration signal graph.
Figure 17 is axis system emery wheel and Workpiece vibration signal graph after speed change.
Specific embodiment
With reference to embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited
In this.
Referring to Fig. 1～Figure 17, by taking the periphery grinding of the bearing inner race by made by GCr15 as an example, the present invention's returns
Rotary Workpiece pre-stressed grinding method is comprised the following steps：
(1) the clamping workpiece to be processed on grinding machine；
(2) aim at tool operation is carried out, first allows emery wheel and workpiece in lower-speed state, progressively adjust emery wheel position, until workpiece
After surface just spark occurs, grinding speed is adjusted to into fast state vsWorkpiece rotational frequency is adjusted to ultracentrifugation by >=150m/s
State 8kr/min；
(3) emery wheel presses ap=10～100 μm/kr setting radial feeds feed and start grinding after, entered with speed change state
Row grinding, specifically in the grinding stage, holding workpiece rotational frequency is constant, and emery wheel is with 2m/s2～5m/s2Linear acceleration
Continuously accelerated；After emery wheel stops radial feed entering the tarry matter stage, tarry matter is carried out with speed change state, sand is specifically to maintain
Wheel linear velocity is constant, and workpiece is with 800 π rad/s2～1200 π rad/s2Angular acceleration continuously slowed down, when under workpiece rotational frequency
When being down to 7kr/min, emery wheel is separated with workpiece and zero is each decelerated to, completion of processing.
Below the operation principle of the revolving body workpieces pre-stressed grinding method of the present invention is explained in detail, to verify this
The technique effect of invention.
ABC first to being ground is described, and is that principle analysis below is provided fundamental basis.
1st, it is ground ultimate principle
(1) the irregular abrasive particle of countless sizes is randomly dispersed in wheel face, and each abrasive particle can regard a little steel knife as,
Compared with conventional cutting, grinding has been equivalent to many pocket knife continuous cutting surface of the work, but not all abrasive particle is being ground
Shi Douneng plays shear action；
(2) abrasive grain cutting experiences three processes：Swiping (elastic deformation), cultivated plough (plastic deformation) and cutting, make surface shape
Into thermal stress and distortional stress, model is as shown in Figure 1；
(3) maximum not deformed grinding thichness hgmax(grinding core formula)
In formula, Ag1- proportionality coefficient with static sharpening number
ks- the coefficient relevant with emery wheel sharpening shape
c1- the coefficient relevant with emery wheel sharpening density
vw- workpiece linear velocity
vs- grinding speed
ap- grinding depth (radial feeds)
de- emery wheel equivalent diameter
From the foregoing, after emery wheel type determines, vw、vsAnd apDirectly affect hgmax。
It is and not deformed thickness of cutting has large effect to grinding process, as follows：
1. grinding force of the influence on abrasive particle, so as to affect the bond strength needed for abrasive particle normal work；
2. affect grinding energy ratio esSize；
3. affect grinding area temperature, so as to affect the property of abrasion of grinding wheel and surface layers residual stress, size and
Distribution situation；
4. affect machined surface roughness.
2nd, plain grinding
Grinding dosage (vw、vsAnd ap) impact to grinding force, grinding temperature and surface roughness.
(1) grinding force
1. speed of grinding wheel vsDuring increase, total abrasive particle number that cutting is participated in the unit interval increases, and makes the unchanged of every abrasive particle
Shape grinding thichness hmaxReduce, thus reduce grinding force；
2. grinding depth apDuring increase, the not deformed grinding thichness h of every abrasive particle is not only madegmaxIncrease, emery wheel and work when also
The Grinding Contact arc length of part is lengthened, while the abrasive particle number worked increases, increases grinding force；
3. workpiece rotational frequency vwDuring increase, the not deformed grinding thichness h of every abrasive particlegmaxIncrease, increases grinding force.
(2) grinding temperature
1. with grinding depth apIncrease, workpiece surface temperature raise.This is because increase apAfterwards, every abrasive particle is unchanged
Shape grinding thichness hgmaxIncrease, makes the relation of abrasive dust deformation force and frictional force increase in grinding process；
2. with workpiece rotational frequency vwIncrease, workpiece surface temperature may reduce.This is because workpiece rotational frequency vwIncrease
When, though increasing heat source strength, accelerate thermal source translational speed on the surface of the workpiece, and thermal source is made in surface of the work
The reason that time used time shortens；
3. with speed of grinding wheel vsIncrease, workpiece surface temperature raise.This is because working as vsAfter increase, in the unit interval
Work abrasive particle number increase, grinding thichness (not deformed grinding thichness hgmaxReduce) it is thinning, i.e., abrasive dust is split thinner, and abrasive dust becomes
Shape can increase.The abrasive particle number for producing cultivated plough and swiping effect simultaneously increases, and aggravates friction.
(3) surface roughness
1. speed of grinding wheel vsDuring increase, total abrasive particle number that cutting is participated in the unit interval increases, and makes the unchanged of every abrasive particle
Shape grinding thichness hgmaxReduce, thus make surface roughness RaReduce；
2. grinding depth apDuring increase, the not deformed grinding thichness h of every abrasive particle is not only madegmaxIncrease, also makes emery wheel and work
The Grinding Contact arc length of part is lengthened, while the abrasive particle number worked increases, grinding force increase, and thus make surface roughness RaIncrease
Greatly；
3. workpiece rotational frequency vwDuring increase, the not deformed grinding thichness h of every abrasive particlegmaxIncrease, thus increase surface roughness
Greatly；
4. surface roughness and grinding force have that certain functional relationship, i.e. grinding force are bigger, and surface roughness is bigger, otherwise
It is less.
3rd, superhigh speed grinding
The conclusion with regard to " impact of the grinding dosage to grinding force and surface roughness " of plain grinding is still applied to super
High-speed grinding, but there is the change of essence in impact of the grinding dosage to grinding temperature.
The superhigh speed grinding that Germany cutting physicist Carl Salomon are proposed is theoretical：In conventional cutting velocity interval
Cutting temperature raises difference with the increase of cutting speed, when cutting speed increase to it is relevant with the species of workpiece material a certain
After critical velocity, with the increase of cutting speed, cutting temperature reduces (heat channel is theoretical) on the contrary with cutting force, as shown in Figure 2.
Theoretical application：In superhigh speed grinding, as grinding speed is very high, translational speed of the abrasive particle on grinding area is fast
Several times, the time of single chip formation is extremely short.On the one hand, under the temperature lag of strain rate response, even if heat source strength increase,
But the heat incoming workpiece that is not also able to do in time just is taken away by abrasive dust, so that surface of the work grinding temperature decreases, can cross appearance
Easily there is the region of hot injury；On the other hand, the high strain-rate of the abrasive dust for completing in this very short time (can be approximately equal to mill
Cut speed) forming process, it will make surface of the work elastically deformed layer shoal, be ground groove mark both sides because Plastic Flow get along it is grand
Play height to diminish, make the cultivated plough and swiping distance of chip formation diminish, and subtract workpiece surface hardening and residual stress tendency
It is little.
Additionally, find in the research with regard to high efficiency deep grinding, on the basis of the rotation of emery wheel ultrahigh speed is kept, as workpiece turns
Fast vwIncrease, workpiece surface temperature reduced；With grinding depth apIncrease, workpiece surface temperature raise.
It is described in detail below for the related operation principle of the technique effect of the present invention.
First, workpiece is rotated by ultrahigh speed and obtains prestressed principle
1st, centrifugal effect produces prestressing force
Object can produce centrifugal effect when being rotated, all, and the centrifugal effect can promote object with to outward transport
Dynamic trend, from the microstructure of interior of articles, each the minute cells body for constituting object has that what is outwards escaped to become
Gesture, the trend can promote the tension that radial direction is produced between the cell cube of interior of articles, at the same time, with outside escaping tendency
Cell cube form a kind of swelling state, the swelling state can allow and tangential stress is produced between cell cube.Workpiece is in rotary course
In internal stress analysis as shown in figure 3, tangential stress meetAlong workpiece rotational frequency direction (circumferential stress)
With vertical direction (radial stress σρ) it is tension, and radial stress σρCompare circumferential stressIt is little.As can be seen here, the work of rotation
There is certain prestressing force in part, but in the prior art, the rotating speed of workpiece is generally all relatively low in itself, general ultrahigh speed mill
The workpiece maximum (top) speed cut is 0.3～0.5k r/min, and the rotating speed of the workpiece of high efficiency deep grinding also only reaches 1k r/min；And
The stability of grinding machine spindle can be impacted as workpiece rotational frequency is too high, so will not adopt in prior art more high-revolving
Workpiece carries out grinding.And the workpiece under ordinary rotational speed is in Grinding Process, because of the prestressing force that centrifugal action is produced
It is very limited, therefore effect is not produced substantially to residual compressive stress is formed after completion of processing, it usually needs by follow-up other
Processing method obtains residual compressive stress.
2nd, workpiece produces the rate request of effective prestress
During the pretightning force that fixture applies to workpiece when clamping workpiece is not considered, the internal stress that workpiece is produced because of centrifugal effect
Expression formula is：
In formula, υ-Poisson's ratio
P-density of material
ω-workpiece angular velocity
A-workpiece inner circle radius
B-excircle of workpiece radius
Arbitrary radius in ρ-sagittal plane
σρ- workpiece radial stress
- workpiece circumferential stress
Displacement expression formula (workpiece radial expansion volume) expression formula is：
In formula, E-elastic modelling quantity
uρ- radial expansion volume
According to above-mentioned formula, can calculate under the conditions of pretightning force is not considered, the internal stress that workpiece is produced because of centrifugal effect
And radial expansion volume.Due to the Poisson's ratio υ ＜ 1 of most of materials, makeIf considering further that the pretension that fixture applies to workpiece
Power, can make circumferential stressCan further increase (referenceComputing formula), and radial stress and pre-tight stress direction phase
Instead, negative function (generally pre-tight stress can be more than radial stress) is played, therefore in ultracentrifugation grinding process, work
Part plays a leading role to plastic deformation because of the circumferential stress that centrifugal effect is produced, and formation of the circumferential stress to residual compressive stress
Play mastery reaction.
As can be seen here, the circumferential stress of workpiece and the rotating speed of workpiece square are directly proportional；And the circumferential stress of workpiece is bigger,
Residual compressive stress to obtaining after processing is more favourable；Therefore workpiece rotational frequency is higher in theory, after being more conducive to being processed
Residual compressive stress.Through experiment, for general metal parts, the pass between workpiece rotational frequency and the final residual compressive stress for obtaining
System is as shown in figure 4, from fig. 4, it can be seen that with the raising of workpiece rotational frequency, surface of the work residual compressive stress (uses negative value table in figure
Show) also constantly increase, and when workpiece rotational frequency is increased to more than 8kr/min, the amplitude of variation of surface of the work residual compressive stress becomes
Obtain more gentle, therefore when workpiece rotational frequency reaches more than 8kr/min, the residual compressive stress obtained after grinding is more managed
Think.
For example, used as object, design parameter is as shown in the table for 6203 bearing inner races using GCr15 materials：
Calculated in the situation for not considering pretightning force, the corresponding workpiece surface of different workpieces rotating speed can be drawn according to formula
The circumferential stress of material (i.e. ρ=b), obtainsWorkpiece rotational frequency is as shown in Figure 5 with the curve of circumferential stress relation.From figure
In as can be seen that when workpiece rotational frequency be more than 6kr/min when, workpiece circumferential stress is just more than 1MPa；When workpiece rotational frequency is more than 8kr/
During min, circumferential stress ascendant trend becomes apparent from, and is close to 2MPa, obtains prestressed effect more preferably, so determining that workpiece rotational frequency is
More than 8kr/min is relatively reasonable.
Yes require emphasis, in the present invention, workpiece rotational frequency reaches 8kr/min with " high efficiency deep grinding " of the prior art theory
In rotating speed 1kr/min there is difference substantially, not only have fundamental difference in high-revolving purpose from carrying, and from rotating speed
See also there is the difference of internal in concrete numerical value, the requirement in the present invention to workpiece rotational frequency is " high efficiency deep grinding " of the prior art
8 times of workpiece rotational frequency or so in theory, on the basis of the workpiece rotational frequency 1kr/min of " high efficiency deep grinding ", turn due to improving workpiece
The purpose of speed is different, and those skilled in the art cannot be also obtained even with the basic general knowledge and the experiment of limited number of time of this area
The workpiece rotational frequency more than 8kr/min limited by the present invention.
3rd, the restriction of workpiece rotational frequency
From the above analysis, the rotating speed of workpiece is higher in theory, more advantageously forms residual compressive stress, but too high
Rotating speed, can with other problemses occur, it is therefore necessary to the maximum speed of workpiece is restricted.Deeply grinding through applicant
Study carefully and explore, it is found that workpiece rotational frequency is too high and can mainly bring problems with.
(1) grinding machine spindle stability is impacted
Produce to above-mentioned workpiece that centrifugation expansion is similar under ultrahigh speed state, grinding machine spindle and bearing thereon are in superelevation
Can all produce centrifugation bulking effect under fast apocarpy, and the centrifugation bulking effect can to bearing rigidity and main shaft and bearing it
Between matching relationship produce impact, so as to affect main shaft work stability.
The speed of mainshaft pair is improved to explore below by " high-speed main spindle centrifugation expansion is affected on bearing dynamic characteristic " experiment
The impact of bearing dynamic characteristic.The assembly relationship model of main shaft and bearing is as shown in Figure 6 and Figure 7.
(1.1) bulking effect is centrifuged and impact is produced on the matching relationship between main shaft and bearing
Under normality, it is interference fit relation between bearing inner race and main shaft, therefore pretightning force need to be considered to main shaft and bearing
The impact of inner ring swell increment, on this basis, with reference to the swell increment computing formula of workpiece under above-mentioned centrifugal effect, can derive master
Axle swell increment us(ρ) with bearing inner race swell increment uB(ρ) computing formula, it is specific as follows：
In formula, F-pretightning force
A-main shaft inner circle radius, i.e. r1
B-main shaft exradius, i.e. r2
In formula, F-pretightning force
A-bearing inner race inner circle radius, i.e. r2
B-bearing inner race exradius, i.e. r3
As ρ=r2When, from above-mentioned formula can fit main shaft and bearing fit face diameter to dilatancy with rotating speed change
Curve (high-speed main spindle of each parameter in 715 model CNC milling machine), as a result as shown in Figure 8：
As shown in Figure 8, with the rising of rotating speed, the swell increment of bearing deforms far faster than main shaft, therefore, the centrifugation of main shaft is swollen
The swollen change for not interfering with Bearing inner radial clearance.The magnitude of interference under high-speed cruising state, between bearing inner race and main shaft
Reduce, contact stress diminishes, and the stress being set with rotating speed corresponding when being changed into 0 is referred to as separate speed, releases when rotating speed reaches
After rotating speed, the interference connection between bearing and main shaft will be failed, and be situation about must avoid.Specifically, when rotating speed is more than 8kr/
During min, bearing expansion amplitude is gradually obvious；When rotating speed is more than 10kr/min, the half of initial interference has been reached；Work as rotating speed
During more than 18kr/min, there is de- pine with bearing in main shaft.
Therefore, from the point of view of the matching relationship safety between main shaft and bearing, the rotating speed of main shaft is with less than 10kr/
Min is advisable.
(1.2) impact of the bulking effect to bearing rigidity is centrifuged
The rigidity of bearing has material impact to the stability of main shaft, explores the pass between the speed of mainshaft and bearing rigidity
System, it can be determined that impact of the rotating speed to main shaft stability.Carry out here by experiment high-speed main spindle is installed in CNC milling machine
Experiment, the relation observed between the speed of mainshaft and bearing rigidity, as a result as shown in Figure 9.It can be seen in figure 9 that bearing axial direction
Rigidity and radial rigidity are reduced with the rising of rotating speed, specifically, when rotating speed be more than 5kr/min when, bearing rigidity start be in
Downward trend, but fall is slow；When rotating speed is more than 8kr/min, fall becomes apparent from；When rotating speed is more than 10kr/min
When, the basic linear downward trend of rigidity.As can be seen here, the speed of mainshaft is limited in into the no more than scope of 10kr/min, can
Guarantee that bearing rigidity meets use requirement.
In order to verify the relation between the above-mentioned speed of mainshaft and bearing rigidity, it is also possible to from the speed of mainshaft and bearing touch
Relation between angle, contact force is explored, and its reason is have pass closely between bearing rigidity and contact angle, contact force
System.Tested again by experiment high-speed main spindle is installed in CNC milling machine, obtained main shaft and bearing contact angle, contact force
Between relation, respectively as shown in Figure 10 and Figure 11.It can be seen that with the raising of the speed of mainshaft, bearing inner race
Contact angle increases, contact force reduces, and the contact angle reduction of bearing outer ring, contact force increase, and its reason is located at, during high-speed cruising,
Ball increases bearing inner race contact angle under the action of the centrifugal force, and contact force reduces；And outer ring contact angle reduces, contact force increases
Greatly, so as to causing the decline of bearing axial rigidity and radial rigidity.So as to demonstrate the pass between the speed of mainshaft and bearing rigidity
System.Additionally, compared with the situation of bearing inner race radial centrifugal force bulking effect is not considered, when the bulking effect is considered, bearing
Inside and outside circle will reduce with the contact angle of ball, and contact force increase.When the rotating speed for testing high-speed main spindle is 1.5kr/min, axle
The centrifugation dilatancy for holding inner ring makes inner ring contact angle reduce 3.6%, and outer ring contact angle reduces 2.9%；Contact inner ring
Power increased 3.5%, and outer ring contact force increased 2.8%, therefore, bearing radial rigidity is not relative to considering inner ring centrifugation expansion
In the case of increase.
And impact of the change of bearing rigidity to the stability of main shaft can also be verified by testing, can be high by testing
Reflecting the stability of main shaft, the natural frequency of axis system is higher, and stability is better for the natural frequency of fast axis system.Equally
Tested by experiment high-speed main spindle is installed in CNC milling machine, while being simulated emulation, obtained the speed of mainshaft and master
Between axle system natural frequency, the experiment of relation and simulation result are as shown in figure 12, it can be seen that with the speed of mainshaft
Raising, the natural frequency of axis system is on a declining curve, when the speed of mainshaft is more than 10kr/min, the intrinsic frequency of axis system
The basic linear downward trend of rate.
As can be seen here, from from the point of view of centrifugation impact of the bulking effect to bearing rigidity, the rotating speed of main shaft is being less than
10kr/min is advisable.
(2) impact to wheel life
According to Principle of Grinding and Cutting, when workpiece rotational frequency increases, the not deformed grinding thichness increase of every abrasive particle, thus make mill
Cut power increase.In the case where grinding force significantly rises, abrasive particle heavy wear is easily caused, or even is come off, and abrasive wear
Or come off and can increase further grinding force, the service life of emery wheel so as to form vicious cycle, is not only seriously constrained, can also
Make axis system produce high vibration, directly affect workpiece machining surface integrity.
As can be seen here, consider from impact wheel life angle, it is also desirable to which the maximum speed of workpiece is limited.
Need especially, it is emphasized that either from grinding machine spindle stability (being substantially process safety), emery wheel uses the longevity
From the aspect of life or workpiece machining surface quality control etc., all need to limit the workpiece rotational frequency of ultracentrifugation grinding.
As emery wheel service life and workpiece machining surface quality can be improved by all means, but process safety is to must assure that
, so main shaft stability requirement is used as the principal element for limiting workpiece rotational frequency when running at high speed.
In sum, determine workpiece rotational frequency 8kr/min≤vw≤ 10kr/min is more preferred scheme.
2nd, improve the explanation that workpiece rotational frequency reduces grinding temperature
According to maximum not deformed grinding thichness hmaxComputing formula understands, as workpiece rotational frequency vwIncrease, hmaxIncrease, illustrates mill
Cut thickness increase.Grinding thichness increases, and grinding total amount of heat can also increase, and increase substantially yet with workpiece rotational frequency, be ground shape
Into time shorten, even if total amount of heat increase, but have little time incoming workpiece and just taken away by abrasive dust, so as to cause surface of the work to be ground
Temperature is further reduced.
After grinding temperature is reduced, impact of the grinding temperature to residual stress can be improved.In grinding process (plain grinding and
In superhigh speed grinding, grinding temperature is similar to the affecting laws of residual stress), instantaneously making grinding skin reach very high temperature,
And from the depths of 0.05～0.10mm of surface, room temperature will be in.Therefore, when top layer is heated and cools down, internal stress can be sent out
Changing, process are as follows：
In grinding process, after being heated by mill surface layer, shown in the distribution such as Figure 13 (a) of temperature along depth, θpRepresent metal
Into temperature during perfect plasticity flow regime, when metal reaches and exceeds θpWhen, metal be able to will not be produced interior with free wxpansion
Stress.θsRepresent the temperature of certain layer of metal under metal surface, under this temperature action it is metal heated deformation and produce internal stress
More than yield limit, begin to produce plastic deformation, therefore, θsBe in top layer metallic elastic deformation and plastic deformation area point
Boundary's temperature.θsThe plastically deforming area during above (region 2), θsPure elastic Bian Hang areas when (region 3) below.θhRepresent room temperature, here temperature
Degree layer is not affected by grinding heat.
The temperature of a certain depth in grinding top layer is with the variation relation of time t as shown in Figure 13 (a) upper right corner.When temperature from
0 moment reached maximum temperature θ1When, if most skin temperature has exceeded θp, region 1 is completely Plastic Flow state, does not produce interior
Shown in stress, such as Figure 13 (b).In θp～θhRegion 2 and 3, metal level be in expanded by heating state, generate compressive stress.In θp
～θsRegion 2, due to transition of flowing from elastoplasticity to perfect plasticity, therefore compression stress is gradually reduced；In θs～θhRegion
3, as metal is still in elastic stage, still flexible compression produces compressive stress, but tapers into.θhFollowing metal
Because keeping room temperature constant, elastic deformation will not be produced, but under the influence of outer layer thermal expansion metal, will produce what is balanced therewith
Tension.
When wheel grinding terminates, shown in the moment for beginning to cool down, such as Figure 13 (c), outer surface rate of cooling is more than endosexine,
The stressless plastic flow layer of original surface is cooled down rapidly and is shunk, and due to being hindered by lower floor, thus produces tension, while
The compressive stress scope in region 2,3 is made further to increase.This internal surface temperature is inconsistent and stress distribution that cause is extexine
Tension be continuously increased, the compressive stress of endosexine is gradually reduced, be performed until internal and external temperature it is consistent till.When workpiece it is complete
Cooling, when endosexine temperature reaches unanimity, shown in such as Figure 13 (d), there occurs behind region 1,2 two-layer expanded by heating that plasticity compression becomes
Shape, the physical length after cooling than being heated before raw footage it is short, thus the tension in region 1 is further up, region 2 also with
Cool down and become to carry out tension by compressive stress.Region 3,4 two-layers produce compressive stress due to stress equilibrium.Therefore, Figure 13 (d) is
Thermal stress distribution produced by under grinding temperature effect.
When grinding skin temperature and bigger thermograde, residual tension is bigger.In ultracentrifugation grinding process, work
Part rotating speed is increased substantially, and the grinding time in single abrasive particle unit area reduces, and workpiece temperature is reduced, i.e. maximum temperature θ1Subtract
It is little.Due to being constant by the formation mechenism of mill surface layer residual thermal stress, when workpiece temperature gradient, (different depth correspondence is different
Temperature) reduce, under surface of the work in perfect plasticity flowing depth reduce, even there is no Plastic Flow state, equally
After experience expanded by heating and cooling, the depth that residual tension is formed under surface of the work is not only made to reduce, form residual compressive stress
Depth increase, residual tension can also reduced.
3rd, improve the explanation of the impact of workpiece rotational frequency contrast material removal rate and grinding energy ratio
(1) compare material removal rate
Than material removal rate Z 'wThe material volume abraded on unit interval unit grinding wheel width is referred to, computing formula is as follows：
Z′w=vwap/bs
In formula, bs- grinding wheel width
In ultracentrifugation grinding process, grinding depth apIt is constant, workpiece rotational frequency vwSignificantly lifted, emery wheel and workpiece
Contact arc length increase, than material removal rate improve.In same time, the removing amount of metal increases, and grinding efficiency is improved.
(2) grinding energy ratio
Grinding energy ratio refers to the energy for removing that unit volume workpiece material is consumed, and the importance of the parameter is various mills
What grain and workpiece were interfered must all is fulfilled for principle of conservation of energy, and which depends on grinding condition.
In formula, the grinding power of P-system consumption
VwThe volume of-removal material
Ft- tangential grinding force
fa- axial feeding (during cylindricalo grinding=1)
As workpiece rotational frequency is improved, tangential grinding force FtEqually can also change, so workpiece rotational frequency need to first be analyzed to tangential
The influence degree of grinding force.
In plain grinding, power multifactorial experiment data are carried out using the regression analyses and variance analyses in probabilistic method
Process, establish the grinding force empirical equation of multiple material.In power function relationship between grinding force and grinding dosage, part formula
It is as follows：
During 45 steel of grinding quenching,
When being ground non-Quenched 45 Steel,
During grinding titanium alloy TC4,
From above-mentioned grinding force empirical formula, vwTo grinding energy ratio esImpact compare FtGreatly (during superhigh speed grinding equally such as
This), thus grinding energy ratio esWith vwIncrease reduce.
Except workpiece rotational frequency increase substantially can make grinding energy ratio reduce in addition to, in ultracentrifugation grinding process, strain rate ε
Can remote-effects grinding energy ratio es。
How raising with regard to strain rate affects the mechanical property of material, as shown in figure 14, using heat-mechanics effect coupling
The fracture model of conjunction is illustrated, i.e., so-called Adiabatic Shear or thermoplastic unstability.Two kinds of complete phases can be produced under high strain-rate
Anti- process is affecting material mechanical performance.One side flow stress is improved with strain and the increase of strain rate and (was hardened
Journey)；Another aspect plastic deformation generally, from the beginning of some weak slips region, concentrates on these local deformations under high strain-rate
The temperature in area is raised rapidly, so as to promote flow stress to decline (softening process).The softening of local promotes deformation more to concentrate (office
Portion deformed area is narrower), further promote local temperature acutely to raise (even more than phase transition temperature) in return.Follow such
Under ring emollescence, once softening the impact affected more than hardening, will there is unstability and rupture rapidly in material.Wherein Adiabatic Shear
In temperature rise △ T when plastic work done change into heat energy caused by, formula is as follows：
In formula, ρ-density of material
Cv- specific heat at constant volume
J-the mechanical equivalent of heat
The percentage ratio (0.9～1) of heat is converted in β-plastic work done
εp- plastic strain
Temperature T is the function T=T (ε) of strain, and stress can regard the function of strain and temperature as：
σ=σ (ε, T)=σ (ε, T (ε))
Then plastic instability conditionIt is rewritable to be
Critical strain or the critical strain rate needed for generation thermoplastic unstability can be analyzed from this condition, as measurement material
Index of the material to Adiabatic Shear sensitivity.
As high strain rate is produced during superhigh speed grinding, (ε is up to 10-4～10-6s-1), abrasive dust is in Adiabatic Shear
Formed under state, material removal mechanism occurs transformation (softening affects more than hardening effect).Therefore, it was ground in ultracentrifugation
Cheng Zhong, in the case that workpiece rotational frequency is increased substantially, strain rate ε is improved, and softens tendency more greatly, and the adiabatic cutting of abrasive dust becomes apparent from,
Make the tangential grinding force needed for cutting unit volume metal on a declining curve, so as to affect grinding energy ratio esSize.
Need it is clear that, according to the Theoretical Calculation during abrasive dust with summary of experience, workpiece rotational frequency rise, grinding force F meetings
Improve.Tangential grinding force needed for cutting unit volume metal mentioned here declines, and not representing total tangential grinding force can subtract
It is little, because the not deformed cutting average thickness of every abrasive particleIncrease, so the power for needing is bigger.
4th, improve the explanation of impact of the workpiece rotational frequency to materials processing performance
In ultracentrifugation grinding process, workpiece rotational frequency is increased substantially, and workpiece surface material strain rate is improved, and is softened
Tendency is bigger, and the adiabatic cutting of abrasive dust becomes apparent from, and makes material be easier to abrade, improves the grinding performance of difficult grind material, and right
Hard brittle material realizes ductile regime grinding, while also increasing toughness material in removed ratio of elastic small deformation stage.
5th, improve the Action Specification of the gyroscopic effect that workpiece rotational frequency is produced
Centrifugal force when gyroscopic effect refers to that object is rotated can make itself to keep balance, that is, the object being rotating to have as top
What spiral shell was the same has two features：Precession and gyroscopic inertia --- when the gyro of high speed rotation runs into external force, the direction of its axle
It is will not to change with the direction of external force, but axle is around the precession of a fixed point.
In ultracentrifugation grinding process, workpiece rotational frequency is increased substantially, even if in the presence of larger grinding force, work
Part can keep the stability of its axis of rotation relative inertness direction in space because of resistance torque (gyroscopic couple) that gyroscopic effect is produced, from
And effectively improve the security performance of axis system.
6th, speed change is to suppressing the explanation that grinding machine spindle tremor is acted on
In ultracentrifugation grinding process, workpiece rotational frequency is increased substantially, grinding force increase, is reaching certain grinding force
When, the abrasive particle partial exfoliation of wheel face, grinding force reduce, and make system be more prone to self-excited vibration, and not only reducing emery wheel makes
With the life-span, surface of the work integrity can be also affected.
In order to surface of the work be made to obtain larger residual compressive stress in grinding, can guarantee that again emery wheel service life and
Processing surface of the work integrity, on the one hand can pass through to study the relation of grinding speed and emery wheel durability, draw the v of optimumw/vs
Value；On the other hand tremor can be suppressed by the method for the continuous speed change in grinding.
With regard to whether tremor can be suppressed by speed change during grinding, experimental verification can be passed through：Choose emery wheel cutting speed
0.25mm/min；Workpiece rotational frequency 100r/min；The mean speed of emery wheel in the range of 1150～1660r/min, every 30r/min
One is taken, altogether in the case of 18 kinds of grinding wheel speeds, rotation constant speed and variable-speed grinding mode are tested.To investigate speed change amplitude pair
The affecting laws of chatter growth rate, under given experiment condition, choose speed change amplitude and are respectively 0, ± 0.1, ± 0.2；Speed change ripple
Shape is sine wave；Speed change frequency is 0.1Hz, and experimental result is as shown in figure 15：
According to vibration average rate of increase formula：
In formula, Ts- emery wheel is every to turn the time
t1、t2- time for freely drafting
A1、A2Vibration amplitude under two times of-correspondence
It should be noted that, in order to calculate the average chatter growth rate under various grinding conditions, continuously cut in emery wheel
In grinding process, record respectively and process and be ground to t1=10s, t2The vibrating signal at two moment of=40s, so that it may obtain t1、t2
The tremor amplitude A at two moment1、A2, so as to calculate average chatter growth rate.
Can be obtained by experimental result, as P=0.0, be the equal of constant speed grinding, its corresponding vibration rate of increase is significantly greater than
The vibration rate of increase of corresponding variable-speed grinding during P=0.1 and P=0.2, that is, demonstrate variable-speed grinding and effectively can suppress to quiver
Shake；Additionally, the rate of increase of tremor reduces with the increase of speed change amplitude, increase speed change amplitude is indicated to suppressing tremor to have
Profit.Under these experimental conditions, average chatter growth rate when speed change amplitude is 0.2 is 40% when constant speed is ground.
In sum, in ultracentrifugation grinding process, main shaft tremor can effectively be suppressed by speed change, with system
The reduction of tremor just can reach protection emery wheel and ensure the purpose of workpiece machining surface quality.
7th, speed change produces the explanation of " corner angle " phenomenon effect to alleviating surface of the work
In ultracentrifugation grinding process, workpiece rotational frequency is increased substantially, grinding force increase, axis system dynamic characteristic
Change, causes which more violent because of the forced vibration that uneven emery wheel or axle cause, the surface of the work under constant velocity-ratio effect
It is possible that the small defect in local or protuberance, that is, generate " corner angle " phenomenon, crudy is difficult to ensure that.
In order to surface of the work be made to obtain larger residual compressive stress in grinding, its surface quality is can guarantee that again, one
Aspect requires that lathe not only to be had the axis system of high rigidity, high intensity, high rotating accuracy and high balance quality, and will have excellent
Good overall dynamics characteristic；On the other hand " corner angle " that surface of the work generation can be alleviated by the method for the speed change in grinding are existing
As.
Crudy is ensured by the speed change in grinding, theory analysis is as shown in the vibration signal time function of Figure 16.
For convenience of explanation, in the case where not considering that system self-excited vibration and natural frequency cause resonance, it is assumed that emery wheel is with workpiece only
Forced vibration is produced, and initial vibration signal is that amplitude and frequency are equal, but phase place sine wave x not etc.s(t)=Asin (ω0And x t)w(t)=A (ω0t+π).In the case where grinding dosage is constant, if xs(t) and xwT the phase between () is 0
When, ground effect is most preferable, but if during phase by pi between them, " corner angle " phenomenon that workpiece machining surface is produced is most
Seriously --- work as t=ToWhen/4, emery wheel offsets up maximum, and workpiece offsets downward maximum, grinding depth apIt is decreased to minima；
Work as t=ToWhen/2, emery wheel to workpiece variation be 0, grinding depth apRecover to setting value；Work as t=3ToWhen/4, emery wheel downward bias
Move maximum, workpiece offsets up maximum, grinding depth apIncrease to maximum；Work as t=ToWhen, emery wheel to workpiece variation be 0,
Grinding depth apRecover to setting value again.With this continuous circulation, until completion of processing, so that surface of the work produces " corner angle " now
As.According to vibration principle, when axis system speed changes, what the vibration signal of output also changed therewith.Such as
Amplitude A, circular frequency shown in the vibration signal time function of Figure 17, when workpiece rotational frequency progressively reduces, in Workpiece vibration signal
ω0And phase placeCorrespondingly will change, wherein amplitude A and circular frequency ω0To reduce.Due to the change of work spindle vibration signal,
Because forced vibration causes the degree of grinding depth change reduce, so as to reach the effect for alleviating that surface of the work produces " corner angle " phenomenon
Really.It should be noted that in real ultracentrifugation grinding process, as emery wheel is at a relatively high with the rotating speed of workpiece, exciting is frequently
Natural frequency of the rate away from " lathe-workpiece-grinding tool " process system, so the vibration that axis system is produced mainly includes self-excitation
Vibrate and forced vibration, and emery wheel is differed with the vibration signal produced by workpiece.Even so, but still can be by becoming
Speed is reducing vibrating impact to axis system.
It is above-mentioned not limited by the above for the present invention preferably embodiment, but embodiments of the present invention, its
He any spirit and the change, modification, replacement made under principle without departing from the present invention, combine, simplification, should be
The substitute mode of effect, is included within protection scope of the present invention.
Claims (9)
1. a kind of revolving body workpieces pre-stressed grinding method, it is characterised in that comprise the following steps：
(1) the clamping workpiece to be processed on grinding machine；
(2) aim at tool operation is carried out, first allows emery wheel and workpiece in lower-speed state, progressively adjust emery wheel position, until surface of the work
After just there is spark, grinding speed is adjusted to into ultrahigh speed state vsWorkpiece rotational frequency is adjusted to ultracentrifugation shape by >=150m/s
State, the workpiece rotational frequency vw>=8kr/min so that workpiece produces centrifugation bulking effect, obtains prestressing force；
(3) grinding is carried out by certain radial feeds；After completion of processing, first emery wheel is separated with workpiece, then each slowed down
To zero.
2. revolving body workpieces pre-stressed grinding method according to claim 1, it is characterised in that：It is in step (2), described
Workpiece rotational frequency 8kr/min≤vw≤10kr/min。
3. revolving body workpieces pre-stressed grinding method according to claim 1, it is characterised in that：It is in step (3), described
Radial feeds ap=10～100 μm/kr.
4. the revolving body workpieces pre-stressed grinding method according to claims 1 to 3 any one, it is characterised in that：In step
Suddenly, in (3), emery wheel is fed by setting radial feeds and is started after grinding, and workpiece or/and emery wheel are ground with speed change state
Processing；After emery wheel stops radial feed entering the tarry matter stage, workpiece or/and emery wheel carry out tarry matter with speed change state, and tarry matter is complete
Emery wheel is separated with workpiece after finishing and be each decelerated to zero.
5. revolving body workpieces pre-stressed grinding method according to claim 4, it is characterised in that in the grinding stage,
The speed change state of the workpiece or/and emery wheel is：Keep workpiece rotational frequency constant, improve grinding speed；It is in the tarry matter stage, described
The speed change state of workpiece or/and emery wheel is：Keep grinding speed constant, reduce workpiece rotational frequency.
6. revolving body workpieces pre-stressed grinding method according to claim 4, it is characterised in that the grinding stage with
And in the tarry matter process segment, the gear shift mode of the workpiece or/and emery wheel is continuous change or staged speed change.
7. revolving body workpieces pre-stressed grinding method according to claim 6, it is characterised in that when using continuous change side
During formula, in the grinding stage, emery wheel is with 2m/s2～5m/s2Linear acceleration accelerated；In the tarry matter stage, workpiece with
800πrad/s2～1200 π rad/s2Angular acceleration slowed down.
8. revolving body workpieces pre-stressed grinding method according to claim 6, it is characterised in that when using staged speed change
During mode, in the grinding stage, emery wheel is with 6m/s2～8m/s2Linear acceleration accelerate 6m/s～10m/s after at the uniform velocity 1～
This process is considered as an acceleration ladder, is circulated 3～5 times by 2s；In the tarry matter stage, workpiece is with 1200 π rad/s2～1600 π
rad/s2Angular acceleration deceleration 500r/min after at the uniform velocity 1～2s, this process is considered as into a deceleration ladder, is circulated 2 times.
9. revolving body workpieces pre-stressed grinding method according to claim 6, it is characterised in that：The workpiece is served as reasons
Bearing inner race made by GCr15 materials, it is 8kr/min to carry out workpiece initial speed during ultracentrifugation grinding；In grinding
In process segment, emery wheel is with 2m/s2～5m/s2Linear acceleration continuously accelerated；In the tarry matter stage, workpiece is with 800 π
rad/s2～1200 π rad/s2Angular acceleration continuously slowed down, when workpiece rotational frequency drops to 7kr/min, by emery wheel and work
Part is separated and is each decelerated to zero.
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