CN106679852B - A kind of surface layer internal stress measuring method based on microhardness impression distance change - Google Patents
A kind of surface layer internal stress measuring method based on microhardness impression distance change Download PDFInfo
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- CN106679852B CN106679852B CN201510757205.9A CN201510757205A CN106679852B CN 106679852 B CN106679852 B CN 106679852B CN 201510757205 A CN201510757205 A CN 201510757205A CN 106679852 B CN106679852 B CN 106679852B
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Abstract
The invention discloses a kind of surface layer internal stress measuring methods based on microhardness impression distance change, pairs of microhardness impression is left on the surface of part by microhardness testers, the initial distance between it is measured with traveling microscope, stress relief annealing operation is carried out to part in a vacuum furnace, so that the internal stress in part is released, the distance between microhardness impression is measured again after its cooling and calculates the variation of its distance, it is considered that the variation be entirely due to the release of internal stress and cause, therefore surface layer internal stress can finally be calculated to obtain according to the variation of the distance between measured impression.Measurement method disclosed in this invention is easy to operate, and required equipment price is cheap, and precision is reliable.
Description
Technical field
The invention discloses a kind of surface layer internal stress measuring methods based on microhardness impression distance change, are related to machinery
Method for measuring stress technical field in engineering.
Background technique
Nowadays existing internal stress measuring technology is broadly divided into disruptive method, non-destructive method and micro- destructiveness side
Method.Various mensurations respectively have the advantage and disadvantage of itself, and the depth bounds being capable of measuring are different, need in different occasions according to tool
The needs of body select correct measurement method.According to the property of internal stress itself, microcosmic internal stress and macro can be divided into
See internal stress.Microcosmic internal stress is mainly the internal stress existing for the intra-die of material, and measurement depends on lossless survey
Amount method, i.e. non-destructive method, and the stress on the direction perpendicular to piece surface can be determined to a certain extent.It is micro-
The measurement process for seeing internal stress is a more complicated process, needs the instrument of valuableness and the technology people by professional training
Member could complete operation.
X-ray diffraction method is using a kind of more method for measuring microcosmic internal stress, in automobile and aviation field at present
It has had semicentennial usage history, and this method is measured as caused by internal stress on the basis of the linear elasticity based on material
The distortion that intra-die is occurred.X-ray diffraction method is a kind of pure non-destructive method, but it uses and exists centainly
Limitation, this method requires measured material that must have relatively regular crystal grain, and the measurement result of this method will receive measured workpiece
The influence of surface roughness and crystallite dimension, this is a problem having to take into account that in the measurement of husky die casting.
Since penetration power of the X-ray for industrial common metal is very shallow, usually only a few micrometers, therefore to measure zero
Internal stress on part depth direction, it is necessary to delamination be carried out to part and remove material, this allows for the nondestructive excellent of x-ray method
Point is broken.
Another kind is neutron diffraction method based on material grains dislocation displacement internal stress measuring technology, is set required for this method
Standby very expensive, only few laboratory and research institution possesses, and what is obtained due to this method is in tested region
The average value of stress, thus its respectively rate be not it is very high, can seem more difficult for measurement this method of microcosmic internal stress.
Other lossless detection methods include method of magnetic and supercritical ultrasonics technology, and method of magnetic is a kind of simple method answered of comparison,
It is measured according to the part feature that certain variation can occur for its magnetism under stress, this method can be used to measure double
Axial stress.Another method of magnetic utilizes barkhausen, by measuring to the variation of magnetic proportional electromotive force to really
Determine inner-stress value.The limitation of method of magnetic is that it can only measure magnetic material, and magnetism is very sensitive for the variation of micro-structure, because
This must all calibrate its magnetism before every measurement.
Supercritical ultrasonics technology mainly utilizes material, and the propagation rate of ultrasonic wave inside it can be changed under stress
This feature determines that inner-stress value, the disadvantages of this method are that its measurement result has centainly relative to the micro-structure of measured material
Scrambling.
The distribution of macroscopical internal stress is much larger than the crystallite dimension of material, is designing with internal stress macroscopical in failure analysis often
It is main consideration object.The current method the most effectively and conveniently, the most cheaply for measuring macroscopical internal stress is boring method, is led to
Crossing drilling removal material makes internal stress obtain part release, by measuring the variation of the strain on this process mesoporous periphery to calculate
Obtain the value of material internal.The existing disadvantage of boring method itself is its own with a series of uncertainty, such as strain value
Measurement, the proper alignment of drilling, size and the depth of drilling of bore diameter etc., drilling can cause part a degree of
It destroys, and the surface of part has to carry out a degree of processing and foil gauge is more successfully affixed on thereon, this
Certain influence can be generated to surface stress, be isotropism despite the most basic material that is assumed to be of micro influence boring method
And there is linear elasticity, while it assumes that internal stress does not change significantly in the depth direction, if therefore the depth that is drilled
Degree is greater than the diameter in hole, is not meaningful under many actual conditions, therefore boring method is often described as the inspection of half damage
Survey method.
If desired deeper part of internal stress is measured, in the another form of boring method that the 20 practical seventies occurred, is claimed
For deep hole method, this method needs to bore a reference bore first on measured workpiece, and measures its diameter in the depth direction
Variation, then drills on the periphery of reference bore, re-measures to reference bore and periphery hole, again according to distance between sky
Variation calculate strain variation, this method can measure the distribution situation for the internal stress that depth is 10 centimetres, however the party
The result that method obtains is compared with the result of finite element analysis, substantially without what correlation, therefore the result that this method obtains
Accuracy need to be discussed.
Summary of the invention
The technical problems to be solved by the present invention are: in view of the drawbacks of the prior art, providing a kind of based on microhardness pressure
The surface layer internal stress measuring method of trace distance change, needed for measuring device it is cheap, there is no strict requirements to operator,
And its precision is able to satisfy the industrial requirement of the overwhelming majority.
The present invention uses following technical scheme to solve above-mentioned technical problem:
A kind of surface layer internal stress measuring method based on microhardness impression distance change, includes the following steps:
Step (1) lays pairs of microhardness impression on part to be processed surface；
Initial distance between step (2), measurement microhardness impression；
Step (3) is removed internal stress processing to part；
The variation of distance in the direction indicated between step (4), measurement microhardness impression；
Step (5), according to the change of distance between the elasticity modulus of material, Poisson's ratio and measured microhardness impression
Change calculates inner-stress value.
As a further preferred embodiment of the present invention, the calculation method of the step (5) is as follows:
The surface layer internal stress σ of X and Y-direction1、σ2Calculation formula be respectively as follows:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2)；
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2)；
Wherein, E and μ is respectively the elasticity modulus and Poisson's ratio of material, d1And d2Respectively impression is in the initial of X and Y-direction
Distance, Δ d1With Δ d2Respectively variation of the impression in X and the distance of Y-direction.
As a further preferred embodiment of the present invention, the distance between pairs of microhardness impression is big in the step (1)
In or equal to 50mm.
As a further preferred embodiment of the present invention, in the step (2), when needing to measure direction of feed and cutting direction
Internal stress when, be arranged two microhardness impressions line and direction of feed angle at 45 °.
As a further preferred embodiment of the present invention, the method for removal internal stress is annealing in the step (3),
Heating anneal is carried out in vacuum drying oven, keeps furnace cooling after specified time, the temperature and time of annealing will be according to different
Material is selected.
As a further preferred embodiment of the present invention, in the step (2), step (4), the distance of microhardness impression passes through
Traveling microscope measures.In the step (1), microhardness impression is laid to part to be processed using microhardness impression instrument.
The invention adopts the above technical scheme compared with prior art, has following technical effect that disclosed in this invention
Measurement method is easy to operate, and required equipment price is cheap, and precision is reliable.
Detailed description of the invention
Fig. 1 be left with the piece surface of microhardness impression instrument after processing as indentation hardness schematic diagram, and with move survey it is aobvious
Micro mirror measures its initial distance d0。
Fig. 2 is to measure the distance between its d to after part destressing processingtCompared to d before0Become smaller, it can be determined that initial
Internal stress is tensile stress state.
Fig. 3 is to measure the distance between its d to after part destressing processingcCompared to d before0Become larger, it can be determined that initial
Internal stress is compressive stress state.
Fig. 4 is while measuring the variation of the distance in direction of feed and cutting direction, and then can acquire two sides simultaneously
To internal stress.
Specific embodiment
Embodiments of the present invention are described below in detail, the example of the embodiment is shown in the accompanying drawings, wherein from beginning
Same or similar element or element with the same or similar functions are indicated to same or similar label eventually.Below by ginseng
The embodiment for examining attached drawing description is exemplary, and for explaining only the invention, and is not construed as limiting the claims.
Technical solution of the present invention is described in further detail with reference to the accompanying drawing:
According to the variation that microhardness impression occurs with the variation of internal stress, it can determine that the internal stress is pressure first
Stress or tensile stress.It is observed that it can be found that when the Elastic stress part of part is released microhardness impression
Shape certain variation can occur, certain influence can be generated to the measurement accuracy of this method.When internal stress reaches its bullet
Property the limit 40 or more percent when material hardness can have greatly changed, and then cause microhardness impression generate it is larger
Deformation, and when its value is lower than the 40 percent of elastic limit, its influence to hardness is not very big, therefore in order to overcome
Disadvantage in this method, the present invention are internally answered by the variation realization of distance between microhardness impression before and after measurement internal stresses release
The measurement of power, mainly includes the following steps:
(1) indentation hardness is laid in measured surface with microhardness impression instrument.It is complete in part machinery processing (such as machining)
Bi Hou lays pairs of microhardness impression in the surface to be machined of part, and the distance between pairs of microhardness impression is appropriate,
The distance between usually pairs of microhardness impression no less than 50mm, to guarantee that its variation can be measured relatively accurately.
Indentation hardness is left with the piece surface of microhardness impression instrument after processing, and measures it initially with traveling microscope
Distance d0, as shown in Figure 1；The distance between its d is measured after handling to part destressingtCompared to d before0Become smaller, it can be determined that
Initial internal stress is tensile stress state, as shown in Figure 2；The distance between its d is measured after handling to part destressingcCompared to before
D0Become larger, it can be determined that initial internal stress is compressive stress state, as shown in Figure 3.
(2) initial distance between impression is measured.In order to measure the multidirectional internal stress of piece surface, microhardness pressure
The arrangement of trace is more scientific, preferably with tested direction angle at 45 °, to measure direction of feed and cutting direction internal stress,
Only the continuous and direction of feed angle at 45 ° of two microhardness impressions need to be set, as shown in figure 4, can measure simultaneously into
To the variation in direction and the distance of cutting direction, and then the internal stress of both direction can be acquired simultaneously.
(3) internal stress processing is removed to part.The Re-stress method being usually taken be annealing, the temperature of annealing and
The time of annealing will be selected according to different materials, for the influence after avoiding material surface from being oxidized to experimental result, this
In can take and carry out heating anneal in a vacuum furnace, first furnace air is evacuated, further according to specified rate by heat parts
To specified temperature, and kept for the specified time, the operation of annealing Re-stress is completed in then furnace cooling.
(4) variation for measuring distance between microhardness impression, need according to specified orientation measurement in this direction away from
From variation.
(5) according to the elastic modulus E of material, the variation pair of Poisson's ratio μ and the measured distance between indentation hardness
Inner-stress value is calculated.Distance d in Fig. 41Changes delta d1It is considered that drawing there are two the factor collective effect of aspect
It rises, first, the surface internal stress σ of X-direction1Release and material elasticity modulus effect, second, in the surface of Y-direction
Stress σ2Release and material Poisson's ratio effect, relational expression are as follows:
ε1=Δ d1/d1=-(σ1-μσ2)/E (1)
The available relational expression of same reason:
ε2=Δ d2/d2=-(σ2-μσ1)/E (2)
It may finally obtain the surface layer internal stress σ in terms of calculating X and Y1、σ2Formula be respectively as follows:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2) (3)
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2) (4)
There is the material of time-lag effect for the relaxation of some stress, no doubt the relaxation of stress can cause the hardness of material to be sent out
Raw certain variation, but the variation of the elasticity modulus of material is very little, so that can be ignored, this is because material
The elasticity modulus of material is solely dependent upon interatomic active force, and does not include any plastic deformation.
In order to more accurately measure the variation of the distance between microhardness impression, by calculating, microhardness impression
The distance between cannot be less than 50mm, the variation of distance measure with traveling microscope.
Embodiments of the present invention are explained in detail above in conjunction with attached drawing, but the present invention is not limited to above-mentioned implementations
Mode within the knowledge of a person skilled in the art can also be without departing from the purpose of the present invention
It makes a variety of changes.The above described is only a preferred embodiment of the present invention, not making limit in any form to the present invention
System, although the present invention has been disclosed as a preferred embodiment, however, it is not intended to limit the invention, any skill for being familiar with this profession
Art personnel, without departing from the scope of the present invention, be modified when the technology contents using the disclosure above or
It is modified to the equivalent embodiment of equivalent variations, but without departing from the technical solutions of the present invention, technology according to the present invention is real
Matter, within the spirit and principles in the present invention, any simple modifications, equivalent substitutions and improvements to the above embodiments
Deng, fall within the scope of protection of the technical scheme of the present invention within.
Claims (6)
1. a kind of surface layer internal stress measuring method based on microhardness impression distance change, which is characterized in that including walking as follows
It is rapid:
Step (1) lays pairs of microhardness impression on part to be processed surface；
Initial distance between step (2), measurement microhardness impression；
Step (3) is removed internal stress processing to part；
The variation of distance in the direction indicated between step (4), measurement microhardness impression；
Step (5), according to the variation pair of distance between the elasticity modulus of material, Poisson's ratio and measured microhardness impression
Inner-stress value is calculated；
The calculation method of the step (5) is as follows:
The surface layer internal stress σ of X and Y-direction1、σ2Calculation formula be respectively as follows:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2)；
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2)；
Wherein, E and μ is respectively the elasticity modulus and Poisson's ratio of material, d1And d2Respectively impression X and Y-direction it is initial away from
From Δ d1With Δ d2Respectively variation of the impression in X and the distance of Y-direction.
2. a kind of surface layer internal stress measuring method based on microhardness impression distance change as described in claim 1, special
Sign is: the distance between pairs of microhardness impression is more than or equal to 50mm in the step (1).
3. a kind of surface layer internal stress measuring method based on microhardness impression distance change as described in claim 1, special
Sign is: in the step (2), when needing to measure the internal stress of direction of feed and cutting direction, two microhardness pressures are arranged
The line of trace and direction of feed angle at 45 °.
4. a kind of surface layer internal stress measuring method based on microhardness impression distance change as described in claim 1, special
Sign is: the method for removal internal stress is annealing in the step (3), carries out heating anneal in a vacuum furnace, keeps referring to
The temperature and time of furnace cooling after the fixed time, annealing will be selected according to different materials.
5. a kind of surface layer internal stress measuring method based on microhardness impression distance change as described in claim 1, special
Sign is: in the step (2), step (4), the distance of microhardness impression is measured by traveling microscope.
6. a kind of surface layer internal stress measuring method based on microhardness impression distance change as described in claim 1, special
Sign is: in the step (1), laying microhardness impression to part to be processed using microhardness impression instrument.
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| CN1091825A (en) * | 1993-03-03 | 1994-09-07 | 中国科学院金属研究所 | Method of impact indentation assaying residual stress |
| CN102288499A (en) * | 2011-08-31 | 2011-12-21 | 湖南大学 | Detection method for identifying static mechanical performance parameters of materials in different regions of weld joint |
| CN103808575A (en) * | 2012-11-09 | 2014-05-21 | 徐世铭 | Residual stress testing method |
| CN103969108A (en) * | 2014-05-15 | 2014-08-06 | 北京科技大学 | Method for measuring residual stress on surface of metal sample based on micro indentation |
| CN104122205A (en) * | 2014-07-31 | 2014-10-29 | 华中科技大学 | Method for measuring residual stress by using uplift amount of indentation |
| CN204855050U (en) * | 2015-08-26 | 2015-12-09 | 武汉钢铁(集团)公司 | Matrix indentation method distributing of stress testing arrangement |
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- 2015-11-09 CN CN201510757205.9A patent/CN106679852B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1091825A (en) * | 1993-03-03 | 1994-09-07 | 中国科学院金属研究所 | Method of impact indentation assaying residual stress |
| CN102288499A (en) * | 2011-08-31 | 2011-12-21 | 湖南大学 | Detection method for identifying static mechanical performance parameters of materials in different regions of weld joint |
| CN103808575A (en) * | 2012-11-09 | 2014-05-21 | 徐世铭 | Residual stress testing method |
| CN103969108A (en) * | 2014-05-15 | 2014-08-06 | 北京科技大学 | Method for measuring residual stress on surface of metal sample based on micro indentation |
| CN104122205A (en) * | 2014-07-31 | 2014-10-29 | 华中科技大学 | Method for measuring residual stress by using uplift amount of indentation |
| CN204855050U (en) * | 2015-08-26 | 2015-12-09 | 武汉钢铁(集团)公司 | Matrix indentation method distributing of stress testing arrangement |
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