CN104792440B - Method of testing three-dimensional residual stress inside laser material increase manufacturing part - Google Patents
Method of testing three-dimensional residual stress inside laser material increase manufacturing part Download PDFInfo
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- CN104792440B CN104792440B CN201410024021.7A CN201410024021A CN104792440B CN 104792440 B CN104792440 B CN 104792440B CN 201410024021 A CN201410024021 A CN 201410024021A CN 104792440 B CN104792440 B CN 104792440B
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Abstract
The invention discloses a method of testing three-dimensional residual stress inside a laser material increase manufacturing part, which belongs to the technical field of residual stress testing. The method comprises steps: on the basis of a layer-by-layer hole drilling method, through building a compensation coefficient formula, a compensation coefficient is calculated for compensating a measurement result, and the measurement precision of the layer-by-layer hole drilling method is improved; the three-dimensional residual stress inside a part is measured, a laser material increase manufacturing method is adopted for printing two sample pieces with the same size in the same technology condition, the layer-by-layer hole drilling method is adopted in two directions for residual stress measurement, the measurement results are finally combined, and the three-dimensional residual stress inside the laser material increase manufacturing part is obtained. By adopting the three-dimensional residual stress testing method, the distribution state and the variation trend of the three-dimensional residual stress inside the laser material increase manufacturing part can be accurately detected, and a method and basis are provided for inner stress control of the laser material increase manufacturing part and part deformation and cracking prevention.
Description
Technical field
The present invention relates to residual stress test technical field, specially a kind of laser gain material manufacture inside parts three-dimensional remnants
The method of testing of stress.
Background technology
Increases material manufacturing technology is that deisgn product is passed through into CAD（Computer-aided design）Software is converted into 3D data, afterwards
By specific former（That is increasing material manufacturing machine）, successively " manufactured " and produced with the solid material of liquefaction, powdered, silk
Product.Increases material manufacturing technology is also referred to as " 3D printing " or " quick shaping ".According to the main molding of the different increases material manufacturing technologies of technique
Method includes：Optical soliton interaction（SLA）, layer separated growth（LOM）, laser select domain to sinter（SLS）, fusion sediment shaping
（FDM）And metal near-net-shape etc..Be different from traditional " removal type " manufacture, increases material manufacturing technology without the need for proembryo and mould,
Just directly the object of any shape can be generated by increasing the method for material according to computer graphics data, therefore product can be simplified
The fabrication schedule of product, shortens product development cycle, improves efficiency and reduces cost.
But in metal parts laser gain material manufacture process, the part Jing of manufacture often ask by the quality such as the deformation of appearance and cracking
Topic, these problems are the restriction difficult problems for hindering increases material manufacturing technology development and expanding application.Cause that these problems occur because
It is plain a lot, but most the underlying cause is still that thermo parameters method is uneven caused by laser beam local heating institute, causes zero
Part residual stress concentrations, and then the problems such as cause " strain cracking ".Therefore, laser gain material manufacture part residual stress is surveyed
Examination, analyzes its Evolution, proposes residual stress control method and criterion, is to solve laser gain material manufacture part " strain cracking "
The preferable approach of problem.
At present, the measuring technology of residual stress is developed so far relevant test method up to tens of kinds, but these methods are main
Based on the two dimension residual stress of test part top layer, the method for being capable of test part interior three-dimensional residual stress is few.At present, only
There are shortwave X-ray diffraction method and neutron diffraction method to measure to inside parts three-dimension parameter design.Both approaches
Testing cost is higher, and is not suitable for the measurement of heavy parts scene residual stress.
The content of the invention
For the problem that inside parts triaxiality is measured, the purpose of the present invention cannot be manufactured to laser gain material at present
The method of testing that a kind of laser gain material manufactures inside parts three-dimension parameter design is to provide, the method can accurately detect that laser increases
The interior three-dimensional residual stress distribution state and variation tendency of material manufacture part, is laser gain material manufacture part internal stress control,
Prevent part deformation cracking from providing method and foundation.
Technical scheme is as follows：
A kind of laser gain material manufactures the method for testing of inside parts triaxiality, and the method is surveyed initially with incremental hole drilling method
The internal residual stress of the demarcation sample block through destressing heat treatment is measured, and penalty coefficient formula is fitted according to measurement result,
Measurement result is compensated by；Then two block sizes are produced under the conditions of same process using laser gain material manufacturing technology identical
Part, and from both direction residual stress is measured using incremental hole drilling method；Finally using penalty coefficient formula to zero
The residual stress measurement result of part is compensated, and the residual-stress value after compensation is combined again, show that inside parts three-dimensional is residual
Residue stress.Specifically include following steps：
（1）One piece is chosen with part identical material to be measured as sample block is demarcated, destressing heat treatment is carried out to it, made
Its internal stress is uniform；
（2）5 measurement points are taken sample block surface is demarcated, it is measured using incremental hole drilling method, demarcate the residual of sample block
Residue stress value measured value is successively decayed, and needs to compensate；Using the meansigma methodss of 5 measurement point ground floor measured values as whole mark
The standard residual-stress value of random sample block, then should with sample block standard remnants by the 2nd layer of residual-stress value to last layer of measurement
Force value is contrasted, and obtains the penalty coefficient of each layer；The relation of the final foundation number of plies and penalty coefficient, using polynomial regression
Method, fit x to y to residual stress penalty coefficient empirical equation be：
yαx=0.0188x3-0.3174x2+1.9333x-3.3181 （1）
yαy=0.0223x3-0.3607x2+2.0799x-3.5101 （2）
In formula：X be drilling the number of plies, yαxFor the residual stress penalty coefficient in x directions, yαyResidual stress for y directions is mended
Repay coefficient；
（3）Two block-shaped equivalently-sized parts are produced under the conditions of same process using laser gain material manufacturing technology,
The stress distribution of the two parts is identical；Respectively should using the remnants that incremental hole drilling method measures two parts from both direction
Force value, i.e.,：One of part is measured in different depth（Z-direction）In the case of x, y direction residual-stress value, measure another
Part different depth（X-direction）In the case of y, z direction residual-stress value；
（4）Applying step（2）Gained penalty coefficient empirical equation, to step（3）Each residual-stress value of measurement is carried out
Compensation, then each residual-stress value after compensation is combined, finally give inside parts three-dimension parameter design.
Above-mentioned steps（1）Described in destressing Technology for Heating Processing be warming up to 750 DEG C be incubated 4 hours, then stove is cooled to room
Temperature.
The present invention has the advantage that compared with prior art：
（1）Certainty of measurement is high
There is a key in incremental hole drilling method, because the method uses top layer foil gauge answering for each layer is gathered
Become release value, with the increase of hole depth, the certainty of measurement of top layer foil gauge can be affected.Therefore the certainty of measurement of incremental hole drilling method
It is not high, and the measuring method of the proposition of the present invention, penalty coefficient formula is proposed according to big measurements, calculate using formula
Penalty coefficient is compensated by the measurement result of incremental hole drilling method, and certainty of measurement is higher.
（2）Measurement cost is low, is suitable to commercial Application
The test of inside parts three-dimension parameter design is manufactured to laser gain material, both at home and abroad maximally effective measurement means are adopted mostly
With shortwave X-ray diffraction method and neutron diffraction method, and the nucleus equipment cost of both approaches application is very high, the country possess this two
The research institution of the equipment of kind cans be counted on one's fingers.Therefore, the measurement cost of both approaches is of a relatively high, and measurement proposed by the present invention
Method, is only that based on common strain measurement equipment, selected foil gauge is also the strain measurement consumptive material compared with based on, because
This cost and cost are relatively low.And measuring method proposed by the present invention, device therefor portability very well, is particularly suitable for actual work
Industry application.
（3）Measurable inside parts three-dimension parameter design
At present, the method for measurement remnant stress is a lot, and destruction is whether there is to test specimen by method of testing, can be divided into physics without
Damage method of testing and machinery damages the big class of method of testing two.Non-destructive testing method has：X-ray diffraction method, method of magnetic, supercritical ultrasonics technology, neutron
Diffraction approach etc., mechanical testing methodologies have：Split full method for releasing, Mach's method, electrochemical corrosion layer stripping, boring method and with drill
Moiréinterferometry and holographic interferometry based on method etc..At present the above method except relatively costly neutron diffraction method and
Outside shortwave X-ray diffraction method, all inside parts three-dimension parameter design cannot be measured, and neutron diffraction method and shortwave X are penetrated
Fathoming for line diffraction approach is also limited（Within 50mm）.Measuring method proposed by the present invention, can by measuring from both direction,
And the mode of measurement in a closed series result, show that laser gain material manufactures inside parts three-dimension parameter design.
Description of the drawings
Fig. 1 is that exemplar laser gain material manufactures the course of processing.
Fig. 2 is that pretreated laser gain material manufactures exemplar.
Fig. 3 is that foil gauge and terminal paste figure.
Fig. 4 is welding lead figure.
Fig. 5 is successively drill drawing.
Fig. 6 is twocouese incremental hole drilling method schematic diagram；In figure：（a）X is to drilling；（b）Y-direction drills；（c）Drill on part
Position.
Fig. 7 is experiment test scene.
Specific embodiment
The solution of the present invention is described in further detail with reference to the accompanying drawings and examples：
Incremental hole drilling method is to be drilled with the small amount of feeding every time, measures the strain value that every time drilling is produced, by meter
Calculation obtains the stress value of different thickness.There are two deficiencies in this method, first it gathers inside parts using top layer foil gauge
Strain relief value, with the increase of hole depth, the certainty of measurement of top layer foil gauge can be affected, or even when reaching certain depth
Afterwards, top layer foil gauge cannot measure strain value；Secondly, incremental hole drilling method measurement is residual on X and Y-direction under different depth
Residue stress, it is impossible to which inside parts triaxiality is measured.
There is measurement error in the present invention, for incremental hole drilling method by measuring the demarcation through destressing heat treatment
The internal residual stress of sample block, and fit penalty coefficient formula according to measurement result, is compensated by measurement result, improve by
The certainty of measurement of layer boring method, while measuring inside parts three-dimension parameter design, is increased under the conditions of same process using laser
The method of material manufacture prints two block size identical exemplars, and carries out residual stress survey using incremental hole drilling method from both direction
Amount, is finally combined to measurement result, show that laser gain material manufactures inside parts three-dimension parameter design.
Embodiment 1：
（1）The preparation of sample
Experiment is in 5KW CO2Carry out on cross-flow laser, and prepare measurement exemplar under vacuum conditions.Laser gain material is manufactured
It is TA15 titanium alloys that powder and substrate used thereof material are the trade mark, first by substrate sanding and polishing before experiment, to remove surface oxidation
Cortex simultaneously increases its surface smoothness, then further cleaning treatment is done to it with acetone, and TA15 titanium alloy powders are then existed
Process is dried under 120 DEG C of vacuum environments.The specific process parameter that experiment is adopted is as shown in table 1.
The laser gain material of table 1 manufactures main technologic parameters
| Laser power | Scanning speed | Powder feed rate | Scan mode |
| P/W | v/ mm·s-1 | f/ g·min-1 | |
| 3500 | 7 | 0.7 | Interlacing |
Prepared exemplar overall dimensions size be 56mm × 24mm × 30mm, exemplar preparation process and it is pretreated swash
Light increasing material manufacturing exemplar is as shown in Figure 1, Figure 2.
（2）Residual stress measurement
The technology for applying of resistance strain gage is more complicated, and the quality of sticking Quality is very big to the reliability effect of measurement, because
This is a very critical link, is operated in strict accordance with following steps in test.
1）Design pieces of cloth scheme：Foil gauge distribution is consistent with exemplar foil gauge distribution is demarcated in test, and bore diameter is
1.5mm, is spaced 18mm between strain gauge, to avoid the interference between Kong Yukong.
2）Chip select：First check for the outward appearance of foil gauge, reject sensitive grid have in shape defect and piece have bubble, mildew,
The foil gauge of rust spot, then with the resistance value of electric bridge measuring strain piece, and carry out resistance apolegamy.
3）Polishing：Surface of test piece tested point position is polished so as to which surfacing is smooth.
4）Setting-out：In measured point accurately cross wire is finished to position with draw point.
5）Cleaning：Detected part surface is cleaned with the absorbent cotton for being soaked with acetone, grease dust is removed, keeps cleaning clean.
6）Paste：The foil gauge back side chosen is uniformly coated with into a layer binder, bondline thickness is moderate, then should
Become the cross wire of the reticle alignment test specimen detected part of piece, gently orientation, then covers a cellophane, uses handss
Finger rolls in one direction foil gauge, extrudes the glue of bubble and excess, it is ensured that glue-line is as uniform and thin as possible, then with same
Binding agent joined lead terminal（Shown in Fig. 3）.
7）Solidification：Spontaneously dry more than 4 hours after paster.
8）Check：By general-purpose table look-up foil gauge resistance and foil gauge lead wire insulation situation.
9）Fixed wire：Two wire lead-out wires of foil gauge are welded on binding post, then by connecting wire by wiring
Terminal is drawn（Shown in Fig. 4）.
10）Exemplar internal residual stress is measured with incremental hole drilling method.Microscope is passed through to boring using alignment device during drilling
Hole site is aligned, and is then successively at the uniform velocity drilled（Fig. 5）To set depth, drill 5 layers altogether here, be 1mm per thickness degree.
（3）Penalty coefficient fitting formula
Choose the demarcation sample block of one block of material identical with part to be measured（TA15）, destressing heat treatment is carried out to it（750
DEG C insulation 4 hours+stove it is cold）So as to internal stress is uniform.5 points are taken sample block surface is demarcated, it is entered using incremental hole drilling method
Row measurement, discovery ought be successively bored into after the 2nd layer, and residual-stress value measured value is constantly decayed, and needs to compensate.Here with
The meansigma methodss of 5 measurement point ground floor measured values as the whole standard residual-stress value for demarcating sample block, then by the residual of 2-8 layers
Residue stress value is contrasted with sample block standard residual-stress value, obtains the penalty coefficient of each layer.It is final to be according to the number of plies and compensation
Several relations, using polynomial regression, fit x and y to residual stress penalty coefficient empirical equation, specifically such as the He of formula 1
Shown in formula 2.
yαx=0.0188x3-0.3174x2+1.9333x-3.3181 （1）
yαy=0.0223x3-0.3607x2+2.0799x-3.5101 （2）
Wherein x be drilling the number of plies, yαxFor the residual stress penalty coefficient in x directions, yαyResidual stress for y directions is mended
Repay coefficient.
（4）Laser gain material manufacture inside parts three-dimension parameter design measurement
Two samples are manufactured under same process parameter, the stress distribution of the two samples should be essentially identical.Point
The residual-stress value (Fig. 6) of two samples is not measured using incremental hole drilling method from both direction, the different depth of test specimen 1 is measured（Z side
To）In the case of x, y direction residual-stress value, measure the different depth of sample 2（X-direction）In the case of y, z direction residual stress
Value.Penalty coefficient formula is reapplied, it is compensated.Last measurement in a closed series value, obtains exemplar interior three-dimensional residual stress such as
Shown in table 2, test site is as shown in Figure 7.
The three-dimension parameter design measured value of table 2（Unit：MPa）
Note：σxFor the residual-stress value in x directions, σyFor the residual-stress value in y directions, σzFor the residual-stress value in z directions.
Analytical table 2 understands, inside exemplar, σzGenerally compare σxAnd σyIt is much bigger, and for compressive stress, and both ends is residual
Residue stress value is bigger than the residual-stress value of middle part.And the exemplar internal residual stress of laser gain material manufacture manufacture is less than table
Layer residual stress, with the increase of drilling depth, exemplar internal residual stress is gradually reduced.And surface residual stress is with tension
Based on, and go deep into 6 layers of exemplar（6.6mm）Compressive stress is gradually converted into afterwards.
Claims (3)
1. a kind of laser gain material manufactures the method for testing of inside parts three-dimension parameter design, it is characterised in that：The method is adopted first
The internal residual stress of the demarcation sample block through destressing heat treatment is measured with incremental hole drilling method, and is fitted according to measurement result
Penalty coefficient formula, is compensated by measurement result；Then manufactured under the conditions of same process using laser gain material manufacturing technology
Go out two block size identical parts, and from both direction residual stress is measured using incremental hole drilling method；Finally using benefit
Repay coefficient formula to compensate the residual stress measurement result of part, the residual-stress value after compensation is combined again, draws
Inside parts three-dimension parameter design；The method comprises the steps：
(1) one piece is chosen with part identical material to be measured as sample block is demarcated, destressing heat treatment is carried out to it so as to interior
Portion's stress is uniform；
(2) 5 measurement points are taken on demarcation sample block surface, it is measured using incremental hole drilling method, the remnants for demarcating sample block should
Force measurement value successively decays, and needs to compensate；Sample is demarcated using the meansigma methodss of 5 measurement point ground floor measured values as whole
The standard residual-stress value of block, then by the 2nd layer of residual-stress value to last layer of measurement and sample block standard residual-stress value
Contrasted, obtained the penalty coefficient of each layer；The relation of the final foundation number of plies and penalty coefficient, using polynomial regression, intends
Close out x to y to residual stress penalty coefficient empirical equation be：
yαx=0.0188x3-0.3174x2+1.9333x-3.3181 (1)
yαy=0.0223x3-0.3607x2+2.0799x-3.5101 (2)
In formula：X be drilling the number of plies, yαxFor the residual stress penalty coefficient in x directions, yαyFor the residual stress compensation system in y directions
Number；
(3) two block-shaped equivalently-sized parts are produced under the conditions of same process using laser gain material manufacturing technology, this two
The stress distribution of individual part is identical；Measure the residual stress of two parts using incremental hole drilling method from both direction respectively
Value；
(4) applying step (2) gained penalty coefficient empirical equation, compensates to each residual-stress value of step (3) measurement,
The each residual-stress value after compensation is combined again, finally gives inside parts three-dimension parameter design.
2. laser gain material according to claim 1 manufactures the method for testing of inside parts three-dimension parameter design, and its feature exists
In：Destressing Technology for Heating Processing described in step (1) is to be warming up to 750 DEG C to be incubated 4 hours, and then stove is cooled to room temperature.
3. laser gain material according to claim 1 manufactures the method for testing of inside parts three-dimension parameter design, and its feature exists
In：Described in step (3) respectively from both direction using incremental hole drilling method measure two parts residual-stress value refer to：Measurement
The residual-stress value in one of part x and y directions in the case of different depth, in the case of measuring another part different depth
The residual-stress value in y and z directions.
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| CN105269269B (en) * | 2015-11-18 | 2017-08-11 | 华中科技大学 | A kind of metal increasing material manufacturing method of super large draw ratio deep-hole type parts |
| CN111044192A (en) * | 2019-11-29 | 2020-04-21 | 安徽高德铝业有限公司 | Residual stress detection method for aluminum product |
| CN111122448A (en) * | 2019-12-20 | 2020-05-08 | 东莞理工学院 | Additive manufacturing map type stress analysis method |
| CN111337174B (en) * | 2020-03-23 | 2021-06-01 | 北京科技大学 | Method for measuring residual stress inside thick-wall circular tube |
| CN111829868B (en) * | 2020-07-13 | 2023-07-14 | 清华大学 | Research method for high-flux metal additive manufacturing process parameters |
| CN112730492A (en) * | 2020-12-16 | 2021-04-30 | 安徽恒利增材制造科技有限公司 | Stress field testing method and system for additive manufacturing high-strength aluminum alloy |
| CN113245585A (en) * | 2021-05-11 | 2021-08-13 | 北京航空航天大学 | Automatic drilling testing arrangement of blind hole method residual stress |
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