CN106679852A - Surface layer internal stress measurement method based on microhardness indentation distance change - Google Patents
Surface layer internal stress measurement method based on microhardness indentation distance change Download PDFInfo
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- CN106679852A CN106679852A CN201510757205.9A CN201510757205A CN106679852A CN 106679852 A CN106679852 A CN 106679852A CN 201510757205 A CN201510757205 A CN 201510757205A CN 106679852 A CN106679852 A CN 106679852A
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Abstract
The invention discloses a surface layer internal stress measurement method based on microhardness indentation distance change. The method is characterized by leaving paired microhardness indentations on the surface of a part through a microhardness tester; measuring initial distance between the microhardness indentations through a travelling microscope; carrying out distressing annealing operation on the part in a vacuum furnace to enable the inner stress of in the part to be released; and after cooling, measuring the distance between the microhardness indentations and calculating change of the distance. It can be deemed that the change is fully caused by release of the inner stress, so that the surface layer internal stress can be calculated finally according to the change of the distance between the microhardness indentations. The disclosed measurement method is simple to operate; the needed equipment is low in cost; and precision is reliable.
Description
Technical field
The invention discloses a kind of top layer internal stress measuring method based on microhardness impression distance change, in being related to mechanical engineering
Method for measuring stress technical field.
Background technology
Nowadays existing internal stress measuring technology is broadly divided into disruptive method, non-destructive method and micro- disruptive method.Respectively
Planting mensuration respectively has the pluses and minuses of itself, and its depth bounds that can be measured differs, and needs according to specific need in different occasions
Select correct measuring method.According to the property of internal stress itself, microcosmic internal stress and macroscopical internal stress can be divided into.
The internal stress that microcosmic internal stress mainly exists in the intra-die of material, its measurement depends on nondestructive measurement method, i.e. non-demolition
Property method, and can be determined to a certain extent in the stress on the direction of piece surface.The measurement of microcosmic internal stress
Process is a more complicated process, and it needs the instrument of costliness and can just be completed operation by the technical staff of professional training.
At present X-ray diffraction method is the method for using a kind of more measurement microcosmic internal stress, and in automobile and aviation field, it has had
Semicentennial usage history, the method measures the intra-die institute caused by internal stress on the basis of the linear elasticity based on material
The distortion of generation.X-ray diffraction method is a kind of pure non-destructive method, but it is using having some limitations, the party
Method requires that measured material must have relatively regular crystal grain, and the measurement result of the method can be subject to measured workpiece surface roughness and crystalline substance
The impact of particle size, this is a problem having to take into account that in the measurement of husky die casting.
Due to X-ray it is very shallow for the penetration power of industrial common metal, usual only a few micrometers, therefore to measurement in part depth
Internal stress on direction, it is necessary to delamination is carried out to part and removes material, this nondestructive advantage for allowing for x-ray method is broken.
Another kind is neutron diffraction method based on material grains dislocation displacement internal stress measuring technology, and the equipment required for the method is very
Costliness, only few laboratory and research institution possesses, and due to the method obtain be tested region internal stress it is flat
Average, thus its respectively rate be not very high, for measurement the method for microcosmic internal stress can seem more difficult.
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, and it is according to zero
The part feature that its magnetic can occur certain change under stress is measured, and the method can be used to measure biaxial stress.
Another kind of method of magnetic utilizes barkhausen, by measuring the change of the electromotive force proportional to magnetic so that it is determined that inner-stress value.
The limitation of method of magnetic can only measure magnetic material for it, and magnetic is very sensitive for the change of micro-structural, therefore measure every time
All its magnetic must be calibrated before.
Supercritical ultrasonics technology is mainly using material this feature that ultrasonic wave can change in its internal propagation rate under stress
Determine inner-stress value, the shortcoming of the method is that its measurement result has certain scrambling relative to the micro-structural of measured material.
Much larger than the crystallite dimension of material, macroscopical internal stress is often main in design and failure analysis for the distribution of macroscopical internal stress
Consideration object.When the method effective and convenient, cheap of pre-test macroscopic view internal stress is boring method, by drilling
Removing material causes internal stress to obtain part release, by measure this process mesopore periphery strain change so as to calculate in material
The value in portion.The existing shortcoming of boring method itself has a series of uncertainty for its own, and the measurement of such as strain value is bored
The proper alignment in hole, the size of bore diameter and the depth of drilling etc., drilling can cause a certain degree of destruction, and zero to part
The surface of part has to carry out a certain degree of process and foil gauge is more successfully affixed on thereon, and this is understood to surface stress
Certain impact is produced, is isotropic and with linear elasticity despite the micro most basic material that is assumed to be of boring method that affects,
Simultaneously it assumes that in the depth direction internal stress is not changed significantly, if therefore the depth that drilled more than hole diameter, its
It is not that highly significant, therefore boring method is often described as half damage detection method under many actual conditions.
If desired deeper part of internal stress is measured, in the another form of boring method that the 20 actual seventies occurred, referred to as deep hole
Method, the method needs to bore a reference bore first on measured workpiece, and measures the change of its diameter in the depth direction, so
Afterwards the periphery in reference bore is drilled again, and reference bore and periphery hole are remeasured, according to the change meter of distance between sky
Calculate the change that must be strained, the method can measure the distribution situation of the internal stress that depth is 10 centimetres, but the knot that the method is obtained
Compared with the result of finite element analysis, it does not have any correlation to fruit substantially, therefore the accuracy of result that the method is obtained also has
Wait to discuss.
The content of the invention
The technical problem to be solved is：For the defect of prior art, there is provided one kind is based on microhardness impression distance
The top layer internal stress measuring method of change, the measuring apparatus needed for it are cheap, do not have strict requirements, and its essence to operating personnel
Degree can meet the industrial requirement of the overwhelming majority.
The present invention is employed the following technical solutions to solve above-mentioned technical problem：
A kind of top layer internal stress measuring method based on microhardness impression distance change, comprises the steps：
Step (1), lay paired microhardness impression on part to be processed surface；
Initial distance between step (2), measurement microhardness impression；
Step (3), part is removed internal stress process；
The change of distance in the direction indicated between step (4), measurement microhardness impression；
The change of distance is right between step (5), the elastic modelling quantity according to material, Poisson's ratio and measured microhardness impression
Inner-stress value is calculated.
Used as present invention further optimization scheme, the computational methods of the step (5) are as follows：
Top layer internal stress σ of X and Y-direction1、σ2Computing formula be respectively:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2)；
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2)；
Wherein, E and μ are respectively the elastic modelling quantity and Poisson's ratio of material, d1And d2Respectively impression is in X and Y-direction
Initial distance, Δ d1With Δ d2Respectively change of the impression in X and the distance of Y-direction.
As present invention further optimization scheme, in the step (1) the distance between paired microhardness impression be more than or
Equal to 50mm.
As present invention further optimization scheme, in the step (2), when needing to measure in direction of feed and cutting direction
During stress, line and the direction of feed angle at 45 ° of two microhardness impressions is set.
It is annealing as the method that internal stress is removed in present invention further optimization scheme, the step (3), in vacuum
Heating anneal is carried out in stove, keeps along with the furnace cooling after the time specified, the temperature and time of annealing to be entered according to different materials
Row is selected.
Used as present invention further optimization scheme, in the step (2), step (4), the distance of microhardness impression is by moving
Survey microscope to measure.In the step (1), microhardness impression is laid to part to be processed using microhardness impression instrument.
The present invention adopts above technical scheme compared with prior art, with following technique effect：Measurement side disclosed in this invention
Method is simple to operate, and required equipment price is cheap, and precision reliability.
Description of the drawings
Fig. 1 is that the piece surface with microhardness impression instrument after processing is stayed as indentation hardness schematic diagram, and is surveyed with traveling microscope
Obtain its initial distance d0。
Fig. 2 is to measure the distance between its d to after part destressing processtD before comparing0Diminish, it can be determined that initial planted agent
Power is tensile stress state.
Fig. 3 is to measure the distance between its d to after part destressing processcD before comparing0Become big, it can be determined that initial planted agent
Power is compressive stress state.
Fig. 4 is while measuring the change of the distance in direction of feed and cutting direction, and then can simultaneously try to achieve the interior of both direction
Stress.
Specific embodiment
Embodiments of the present invention are described below in detail, the example of the embodiment is shown in the drawings, wherein ad initio extremely
Eventually same or similar label represents same or similar element or the element with same or like function.Below by ginseng
The embodiment for examining Description of Drawings is exemplary, is only used for explaining the present invention, and is not construed as limiting the claims.
Technical scheme is described in further detail below in conjunction with the accompanying drawings：
According to the change that microhardness impression occurs with the change of internal stress, can determine first the internal stress be compression also
It is tension.It is observed that it can be found that when the Elastic stress part of part is released microhardness impression shape meeting
There is certain change, it can produce certain impact to the certainty of measurement of this method.When internal stress reaches the hundred of its elastic limit
The hardness of material can have greatly changed when/tetra- more than ten, and then cause microhardness impression to produce larger deformation, and work as
Its impact to hardness when its value is less than the 40 percent of elastic limit is not very big, therefore in order to overcome the shortcoming in the method,
The present invention realizes the measurement to internal stress by the change of distance between microhardness impression before and after measurement internal stresses release, and it is mainly wrapped
Include following steps：
(1) indentation hardness is laid in measured surface with microhardness impression instrument.After part machinery processing is finished (such as machining),
Lay the distance between paired microhardness impression, paired microhardness impression in the surface to be machined of part appropriate, generally into
To the distance between microhardness impression be no less than 50mm, to ensure that its change can be measured relatively accurately.
Indentation hardness is left with microhardness impression instrument piece surface after processing, and its initial distance is measured with traveling microscope
d0, as shown in Figure 1；The distance between its d is measured after processing to part destressingtD before comparing0Diminish, it can be determined that just
Beginning internal stress is tensile stress state, as shown in Figure 2；The distance between its d is measured after processing to part destressingcBefore comparing
d0Become big, 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 be able to measure the multidirectional internal stress of piece surface, microhardness impression
Arrangement will compare science, and preferably with tested direction angle at 45 °, the internal stress to measure direction of feed and cutting direction is only needed
The continuous and direction of feed angle at 45 ° of two microhardness impressions is set, as shown in figure 4, can measure in feeding side simultaneously
To the change with the distance of cutting direction, and then can simultaneously try to achieve the internal stress of both direction.
(3) internal stress process is removed to part.The Re-stress method being usually taken is annealing, the temperature of annealing and annealing
Time to be selected according to different materials, to avoid impact to experimental result after material surface is oxidized, here can be with
Take and carry out in a vacuum furnace heating anneal, first evacuate furnace air, further according to specified speed by heat parts to specifying
Temperature, and kept for the time specified, then along with the furnace cooling, completes the operation of annealing Re-stress.
(4) change of distance between microhardness impression is measured, it needs the change of the distance according to the orientation measurement specified in this direction
Change.
(5) according to the elastic modulus E of material, Poisson's ratio μ and the measured change for distance between indentation hardness are internal
Stress value is calculated.In Fig. 4 apart from d1Changes delta d1It is considered that have the factor collective effect of two aspects and cause,
First, surface internal stress σ of X-direction1Release and material elastic modelling quantity effect, second, the surface planted agent of Y-direction
Power σ2Release and material Poisson's ratio effect, its relational expression is：
ε1=Δ d1/d1=-(σ1-μσ2)/E (1)
Same reason can obtain relational expression:
ε2=Δ d2/d2=-(σ2-μσ1)/E (2)
May finally obtain calculating top layer internal stress σ in terms of X and Y1、σ2Formula be respectively:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2) (3)
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2) (4)
For relaxing for some stress has the material of time-lag effect, no doubt the lax of stress can cause the hardness of material to occur necessarily
Change, but the change of the elastic modelling quantity of material is but very little so that being negligible, this is the bullet due to material
Property modulus is solely dependent upon interatomic active force, and does not include any plastic deformation.
In order to be able to the change for more accurately measuring the distance between microhardness impression, through calculating, between microhardness impression
Distance can not be less than 50mm, and the change of its distance is measured with traveling microscope.
Embodiments of the present invention are explained in detail above in conjunction with accompanying drawing, but the present invention is not limited to above-mentioned embodiment,
In the ken that those of ordinary skill in the art possess, can be making various on the premise of without departing from present inventive concept
Change.The above, is only presently preferred embodiments of the present invention, and any pro forma restriction is not made to the present invention, although
The present invention is disclosed above with preferred embodiment, but is not limited to the present invention, any those skilled in the art,
In the range of without departing from technical solution of the present invention, when making a little change using the technology contents of the disclosure above or be modified to equivalent
The Equivalent embodiments of change, as long as being without departing from technical solution of the present invention content, according to the technical spirit of the present invention, in the present invention
Spirit and principle within, any simple modification that above example is made, equivalent and improve etc., still fall within this
Within the protection domain of inventive technique scheme.
Claims (7)
1. a kind of top layer internal stress measuring method based on microhardness impression distance change, it is characterised in that comprise the steps：
Step (1), lay paired microhardness impression on part to be processed surface；
Initial distance between step (2), measurement microhardness impression；
Step (3), part is removed internal stress process；
The change of distance in the direction indicated between step (4), measurement microhardness impression；
The change of distance is right between step (5), the elastic modelling quantity according to material, Poisson's ratio and measured microhardness impression
Inner-stress value is calculated.
2. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, it is characterised in that
The computational methods of the step (5) are as follows：
Top layer internal stress σ of X and Y-direction1、σ2Computing formula be respectively:
σ1=-E (Δ d1/d1+μΔd2/d2)/(1-μ2)；
σ2=-E (Δ d2/d2+μΔd1/d1)/(1-μ2)；
Wherein, E and μ are respectively the elastic modelling quantity and Poisson's ratio of material, d1And d2Respectively impression is in X and Y-direction
Initial distance, Δ d1With Δ d2Respectively change of the impression in X and the distance of Y-direction.
3. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, it is characterised in that：
The distance between paired microhardness impression is more than or equal to 50mm in the step (1).
4. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, it is characterised in that：
In the step (2), when needing to measure the internal stress of direction of feed and cutting direction, the line of two microhardness impressions is set
With direction of feed angle at 45 °.
5. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, it is characterised in that：
The method that internal stress is removed in the step (3) is annealing, and heating anneal is carried out in a vacuum furnace, is kept for the time specified
Along with the furnace cooling afterwards, the temperature and time of annealing will be selected according to different materials.
6. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, it is characterised in that：
In the step (2), step (4), the distance of microhardness impression is measured by traveling microscope.
7. a kind of top layer internal stress measuring method based on microhardness impression distance change as claimed in claim 1, its feature
It is：In the step (1), microhardness impression is laid to part to be processed using microhardness impression instrument.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111678823A (en) * | 2020-06-22 | 2020-09-18 | 上海交通大学 | Method for measuring microhardness of surface layer of titanium alloy milled |
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| 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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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 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111678823A (en) * | 2020-06-22 | 2020-09-18 | 上海交通大学 | Method for measuring microhardness of surface layer of titanium alloy milled |
| CN111678823B (en) * | 2020-06-22 | 2023-02-21 | 上海交通大学 | Method for measuring microhardness of surface layer of titanium alloy milled |
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