CN104655564B - Detection method for hole defect of double-shaft-shoulder friction stir welding seam - Google Patents
Detection method for hole defect of double-shaft-shoulder friction stir welding seam Download PDFInfo
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- CN104655564B CN104655564B CN201510024502.2A CN201510024502A CN104655564B CN 104655564 B CN104655564 B CN 104655564B CN 201510024502 A CN201510024502 A CN 201510024502A CN 104655564 B CN104655564 B CN 104655564B
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Abstract
The invention discloses a detection method for a hole defect of a double-shaft-shoulder friction stir welding seam. The detection method comprises the steps that a torque low-frequency signal TL and a rectilinear oscillation signal To are extracted from an original welding torque signal T according to the original welding torque signal T, and an hour at which the hole defect possibly exists is judged according to change situations of minimum values of an amplitude value AL of the low-frequency signal TL and an amplitude value Ao of the rectilinear oscillation signal To. Based on a frequency spectrum of a double-shaft-shoulder friction stir welding torque, according to the change situations of the amplitude values of the low-frequency signal and the rectilinear oscillation signal, the hole defect of the welding seam is judged, so that the detection method for the hole defect of the double-shaft-shoulder friction stir welding seam is simple; huge investment on methods and equipment of X-ray detection and the like is not required, so that the cost is low; and the welding seam is not damaged, so that the method is suitable for occasions with low requirements on the joint strength and without damaging the welding seam for detection.
Description
Technical field
The present invention relates to stirring friction welding seam defects detection field, and in particular to a kind of double-shaft shoulder stirring friction welding seam hole
Defect inspection method.
Background technology
A kind of solid-state bonding process that agitating friction weldering (FSW) is proposed in 1991 by Britain's institute of welding (TWI).With
Traditional melt welding method compares, and agitating friction weldering has crystal grain tiny, and fatigue behaviour, tensile property and bending property are good
It is good, without the cloud of dust, pore-free, without splashings, energy-conservation, without the need for welding wire, welding when do not require the use of protective gas, weld after residual stress and
The advantages of deforming little.Agitating friction weldering is used primarily for aluminium alloy, and with going deep into for research, agitating friction weldering can be not only used for aluminum
The welding of alloy.Can be additionally used in the welding between other metals such as copper, titanium and different metal.
But stirring friction welding seam is not perfect in every way, various defects can be also produced, such as common hole defect, tunnel lack
Sunken, surface overlap etc..Hole defect to being present in surface, can be with range estimation inspection；To the hole that is present in inside weld seam or tunnel
Road defect, using nondestructiving detecting means such as x-ray detection, ultrasonic inspections, or weld seam can directly be blocked inspection at present.Using
Though nondestructiving detecting means can realize testing goal, operation is relatively complicated, such as using inspection is blocked, such as blocks inspection, then more
It is loaded down with trivial details, and weld seam is thoroughly destroyed.
Therefore, new lossless detection method how is improved or is proposed, is Welder author's pursuit always.
The content of the invention
Goal of the invention：In order to overcome the deficiencies in the prior art, the present invention to provide a kind of double-shaft shoulder agitating friction weldering
Slot apertures hole defect detection method, it is scarce to judge weld seam hole according to the amplitude situation of change of low frequency signal and rectilinear oscillation signal
Fall into, method is simple.
Technical scheme：To solve above-mentioned technical problem, a kind of double-shaft shoulder stirring friction welding seam hole defect inspection of the present invention
Survey method, for the moment of torsion born by stirring-head in stir friction welding process, extracts the low frequency signal in torque signal respectively
With rectilinear oscillation signal, the amplitude situation of change of low frequency signal amplitude and rectilinear oscillation signal is then detected, when low frequency signal
When amplitude flex point and minimum and rectilinear oscillation signal amplitude occurs and exceedes threshold value, can determine whether now to weld and occur in that Weak link,
Thus judge inside weld seam, there is hole defect.
Described double-shaft shoulder stirring friction welding seam hole defect detection method, specifically includes following steps：
The first step：Correction factor k is determined according to rotary speed ω (unit is rpm) of stirring-head, k=0.00274 ω-
0.0689；
Second step：Determine the scope of frequency f of rectilinear oscillation signal,
3rd step：Low frequency signal T in original welding torque signal T is extracted by wave filterLWith rectilinear oscillation signal To,
To TL、ToThe overall length of sequence be modified, make that overall length is L whole 10 times, L is to 60*fs/ ω's rounds, fsIt is original welding
The sample frequency of torque signal T, from TL、ToRow first open the beginning, take respectively a segment length be 10L signal composition sL、so, make
For initial ranging data source；
4th step：Search sLFlex point AG, to low frequency signal sLDiscrete signal ask for first derivative and second dervative, when
Both are zero and correspond to point of the first derivative by corresponding to the negative change positive moment into flex point AG, if any then turning next step, such as not having
Have, proceed to the 7th step；
5th step：Search minimum AMIN, flex point AGAfter appearance, continue detection and AGAdjacent minimum point, when single order is led
It is minimum point A that number is point of the zero, second dervative more than zeroMIN, judge AMINWhether the threshold value A of low frequency signal is less than or equal toF1,
If AMINLess than or equal to AF1, then carry out the 6th step；If greater than AF1, then to the 7th step；
6th step：To rectilinear oscillation signal soCarry out solving first derivative and second dervative, when first derivative is zero, second order
Point of the derivative more than zero is minimum point, searches for soThe minimum of middle appearance, takes the absolute value A of arithmetic averageM, judge AMWhether
More than or equal to rectilinear oscillation signal soThreshold value AF2, in this way, then judge may occur a little as defect herein, and record, be used for
Subsequent review；Such as AMLess than AF2, then it is considered as normal point；
7th step：Judge TLWhether read and finished, if read finished, proceeded to the 9th step；If do not read
Finish, proceed to next step；
8th step：Keep search source sL、soSegment length 10L is constant, and nematic tail direction is sequentially moved, and movable length is L, composition
New search data source, proceeds to the 4th step；
9th step：Detection terminates.
Preferably, the 3rd step median filter includes low pass filter and band filter, low pass filter cuts
Only frequency is 3Hz, and original welding torque signal T extracts low frequency signal T by the low pass filterL, band filter
Upper cut off frequency isLower limiting frequency isK is correction factor, and original welding torque signal T passes through the band
Bandpass filter extracts rectilinear oscillation signal To。
In the present invention, to sLDiscrete signal ask for first derivative and second dervative, when both be zero and correspondence one
Point of the order derivative by corresponding to the negative change positive moment is into flex point AG；Flex point AGAfter appearance, continue detection and AGAdjacent minimum
Point, when the point that first derivative is zero, second dervative more than zero is minimum point AMIN, in the present invention, low frequency signal sLMore than zero.
In the present invention, to soDiscrete signal ask for first derivative and second dervative, when first derivative is that zero, second order is led
Point of the number more than zero is just minimum point；Due to soIt is for rectilinear oscillation signal and with regard to time axial symmetry, very big or minimizing
Absolute value is exactly the amplitude of signal, therefore detectable soThe minimum of appearance, takes the absolute value of these minimizing arithmetic averages,
As amplitude meansigma methodss, are designated as AM。
The method of the present invention, it is adaptable to normally at the uniform velocity weld the stage, is the double-shaft shoulder agitating friction welding incipient stage, stirs
Mix head and part metals can be extruded weld seam, cause torque signal unstable, the detection method is invalid；Double-shaft shoulder agitating friction weldering
When connecing finishing phase, i.e. weld seam formation U-shaped opening, torque signal is equally unstable, and the detection method is invalid.
Beneficial effect：The double-shaft shoulder stirring friction welding seam hole defect detection method of the present invention, with advantages below：
(1) frequency spectrum of moment of torsion is welded based on double-shaft shoulder agitating friction, according to low frequency signal and the amplitude of rectilinear oscillation signal
Judging weld seam hole defect, method is simple for situation of change；
(2) the method is with low cost, without the need for a large amount of inputs of the method equipment such as x-ray detection；
(3) the method is not destroyed to weld seam, is suitable for low bonding strength requirement, need not be destroyed the field of weld seam detection
Close.
Description of the drawings
Fig. 1 is the flow chart of the present invention.
Specific embodiment
Below in conjunction with the accompanying drawings the present invention is further described.
The collection of welding moment of torsion primary signal according to the present invention, existing correlation technique are disclosed, directly can be adopted.
With the rotary speed of stirring-head as 600rpm, thickness be the aluminium alloy of 6mm models 6061, raw torque signal
Sample frequency fsAs a example by 50Hz, testing process refers to Fig. 1：
Step1：According to rotary speed ω=600rpm, k=0.00274 ω -0.0689, correction factor k=is determined
1.5751；
Step2：According to formulaThe frequency f scope for determining rectilinear oscillation signal is
[18.54Hz, 20Hz]；
Step3：Design low pass filter, cut-off frequency is 3Hz；
Step4：Design band filter, upper cut off frequency is 20Hz, and lower limiting frequency is 18.54Hz；
Step5：With original welding torque signal T as low pass filter, the input of band filter, then record respectively corresponding
Output low frequency signal TL, rectilinear oscillation signal To；
Step6：To TL、ToThe overall length of sequence be modified, make that overall length is L (L=5) whole 10 times；Respectively from TL、To
Row first open the beginning, take the s of a segment lengthL、soSignal as initial ranging data source, signal length is 10L；
Step7：Search search source sLFlex point AG, if any then turning next step, if it has not, proceeding to Step10；
Step8：Search minimum AMIN, judge AMINWhether the threshold value A of low frequency signal is less than or equal toF1A is now set (F1
=15), if AMINLess than or equal to AF1, then carry out Step9；If greater than AF1, then to Step10；
Step9：Search search source soAppeared in minimizing arithmetic average, and the A that takes absolute valueM, judge AMIt is whether big
In or equal to the threshold value A of rectilinear oscillation signalF2A is now set (F2=5), in this way, then judge may occur a little as defect herein,
And record；Such as AMLess than AF2, then it is considered as normal point.
Step10：Judge TLWhether read and finished, if read finished, proceeded to Step12；If do not read
Finish, proceed to next step.
Step11：Keep search source sL、soSegment length 10L is constant, and nematic tail direction is sequentially moved, and movable length is L, composition
New search data source, proceeds to Step7.
Step12：Detection terminates.
In the 11st step, original search source is moved to the row tail of original signal, and movable length is L, used as new
Search source sL、so, new search source sLIt is used in the 7th step, the 9th step；When proceeding to seven steps, s is searched forLNew flex point AG；The
In nine steps, new rectilinear oscillation signal s is calculatedoAll of minimum, and all minimum arithmetic mean of instantaneous values are calculated, and be averaged
The absolute value of value.
After the above step is finished, you can complete the detection of double-shaft shoulder stir friction welding process mesopore hole defect；It is this
Detection method, is especially extracted the information of low frequency and radio-frequency component in torque signal, is more truly comprehensively reflected defect characteristic,
Detection mode is simple simultaneously.
The above is only the preferred embodiment of the present invention, it should be pointed out that：For the ordinary skill people of the art
For member, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications also should
It is considered as protection scope of the present invention.
Claims (5)
1. a kind of double-shaft shoulder stirring friction welding seam hole defect detection method, it is characterised in that：For stir friction welding process
The moment of torsion born by middle stirring-head, extracts the low frequency signal and rectilinear oscillation signal in torque signal respectively, then detects low frequency
The amplitude situation of change of signal amplitude and rectilinear oscillation signal, when possessing three below condition, judges that now welding is occurred in that weak
Connection, thus judges there is hole defect inside weld seam：First, there is flex point in the amplitude of low frequency signal；Second, in low frequency signal
There is minimum, and the minimum less than or equal to the threshold value of low frequency signal；3rd, there is minimum in rectilinear oscillation signal,
And the absolute value of its arithmetic average is more than or equal to the threshold value of rectilinear oscillation signal.
2. double-shaft shoulder stirring friction welding seam hole defect detection method according to claim 1, it is characterised in that include with
Lower step：
The first step：Correction factor k, k=0.00274 ω -0.0689 are determined according to rotary speed ω of stirring-head；
Second step：Determine the scope of frequency f of rectilinear oscillation signal,
3rd step：Low frequency signal T in original welding torque signal T is extracted by wave filterLWith rectilinear oscillation signal To, to TL、
ToThe overall length of sequence be modified, make TL、ToThe overall length of sequence be whole 10 times of L, L is to 60*fs/ ω's rounds, fsIt is
The sample frequency of original welding torque signal T, respectively from TL、ToRow first open the beginning, take respectively a segment length signal composition
sL、so, used as initial ranging data source, signal length is 10L；
4th step：Search sLFlex point AG, to low frequency signal sLDiscrete signal ask for first derivative and second dervative, when both
Be zero and point of the first derivative by corresponding to the negative change positive moment is corresponded to into flex point AG, if any, then turn next step, if it has not,
Proceed to the 7th step；
5th step：Search minimum AMIN, flex point AGAfter appearance, continue detection and AGAdjacent minimum point, when first derivative is
0th, point of the second dervative more than zero is minimum point AMIN, judge AMINWhether the threshold value A of low frequency signal is less than or equal toF1If,
AMINLess than or equal to AF1, then carry out the 6th step；If greater than AF1, then to the 7th step；
6th step：To rectilinear oscillation signal soCarry out solving first derivative and second dervative, when first derivative is zero, second dervative
Point more than zero is minimum point, searches for soThe minimum of middle appearance, takes the absolute value A of arithmetic averageM, judge AMWhether it is more than
Or it is equal to rectilinear oscillation signal soThreshold value AF2, in this way, then judge may occur a little as defect herein, and record, for follow-up
Check；Such as AMLess than AF2, then it is considered as normal point；
7th step：Judge TLWhether read and finished, if read finished, proceeded to the 9th step；If do not read finished,
Proceed to next step；
8th step：Keep search source sL、soSegment length 10L is constant, and nematic tail direction is sequentially moved, and movable length is L, constitutes new
Search data source, proceeds to the 4th step；
9th step：Detection terminates.
3. double-shaft shoulder stirring friction welding seam hole defect detection method according to claim 2, it is characterised in that：Described
Three step median filters include low pass filter, and the cut-off frequency of low pass filter is 3Hz, and original welding torque signal T is by institute
State low pass filter and extract low frequency signal TL。
4. double-shaft shoulder stirring friction welding seam hole defect detection method according to claim 2, it is characterised in that：Described
Three step median filters include band filter, and the upper cut off frequency of band filter isLower limiting frequency is
K is correction factor, and original welding torque signal T extracts rectilinear oscillation signal T by the band filtero。
5. double-shaft shoulder stirring friction welding seam hole defect detection method according to claim 2, it is characterised in that：Described
In one step, when determining correction factor k according to rotary speed ω of stirring-head, it should in normally at the uniform velocity welding the stage；It is double
Shaft shoulder agitating friction welds the incipient stage, and part metals can be extruded weld seam by stirring-head, and detection method is invalid；Double-shaft shoulder stirring rubs
Welding finishing phase is wiped, when weld seam forms U-shaped opening, detection method is invalid.
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| DE102016204577B4 (en) * | 2016-03-18 | 2019-07-11 | Trumpf Laser- Und Systemtechnik Gmbh | Method for determining the quality of a weld and associated methods for optimizing and controlling manufacturing parameters |
| CN105928979B (en) * | 2016-07-05 | 2018-12-18 | 南京中车浦镇城轨车辆有限责任公司 | A kind of agitating friction welding hole hole measurement method and equipment |
| CN109570729B (en) * | 2018-11-28 | 2020-11-13 | 湘潭大学 | Method for dynamically detecting quality of friction stir welding seam based on torque |
| CN109507295A (en) * | 2018-11-30 | 2019-03-22 | 中国兵器工业第五九研究所 | A kind of lossless detection method of radial direction friction welding connector Weak link defect |
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