Stress and shock wave diagnosis fused LIBS optimization system and method
The present disclosure discloses a stress and shock wave diagnosis fused LIBS optimization system and method, including: collecting a shock wave signal, a stress wave signal and a spectral signal of a detected object subjected to pulsed laser ablation under the current parameter; pre-processing the spectral signal to obtain a spectral intensity of the detected object under the current parameter; processing the shock wave signal and the stress wave signal to obtain a shock wave intensity and a stress wave intensity under the current parameter; adjusting optimization variables until optimization measurement and diagnosis of a spectral enhancement measure or system parameter are completed. Information on other two dimensions is added for an optimization process; and proportions of shock wave propagation in incident laser energy and mechanical stress propagation in a target can be intuitively recognized, so that the scientificity and persuasiveness of an optimization result are improved.
1. A stress and shock wave diagnosis fused LIBS optimization method, comprising the steps of:
collecting a shock wave signal, a stress wave signal and a spectral signal of a detected object subjected to pulsed laser ablation under a current parameter, wherein the step of collecting the shock wave signal, the stress wave signal and the spectral signal of the detected object subjected to pulsed laser ablation under the current parameter comprises:
fixing a first piezoelectric ultrasonic transducer A 1 on a position, away from an ablation point for a distance x, over a target surface of the detected object, and laterally collecting a shock wave signal Φ 1 ; fixing a second piezoelectric ultrasonic transducer A 2 on a position, away from the ablation point for a distance y, on the target surface, and measuring a stress wave signal Φ 2 propagating along the target surface; then, connecting the first piezoelectric ultrasonic transducer A 1 and the second piezoelectric ultrasonic transducer A 2 to an oscilloscope, wherein x is a mounting distance of the first piezoelectric ultrasonic transducer A 1 , and y is a mounting distance of the second piezoelectric ultrasonic transducer A 2 ; recording, by the oscilloscope, waveforms of the shock wave signal Φ 1 and the stress wave signal Φ 2 obtained after continuous N-pulse ablation under each parameter; and measuring a spectral signal Φ 3 of a target element by a spectrometer;
pre-processing the spectral signal to obtain a spectral intensity of the detected object under the current parameter;
processing the shock wave signal and the stress wave signal to obtain a shock wave intensity and a stress wave intensity under the current parameter; and
adjusting optimization variables until optimization measurement and diagnosis of a spectral enhancement measure or system parameter are completed, wherein the step of adjusting optimization variables until optimization measurement and diagnosis of the spectral enhancement measure or system parameter are completed comprises:
selecting an initial optimization interval [a, b] of an optimization variable A, wherein a is the minimum value of the optimization variable A, and b is the maximum value of the optimization variable A; uniformly setting a total of n groups of optimization values, then, setting a shock wave intensity measured in an i th test as (E 1 ) i , setting a stress wave intensity measured in the i th test as (E 2 ) i , setting a spectral intensity measured in the i th test as (E 3 ) i , and setting a value S i of the optimization variable A in the i th test as:
S i =a +( b−a )×( i −1)/( n −1),
wherein i=1,2, . . . n; and
starting a test from i=1, when (E 3 ) 2 measured in a second test is greater than or equal to (E 3 ) 1 measured in a first test, (E 1 ) 2 ≥(E 1 ) 1 , and at the same time, (E 2 ) 2 ≥(E 2 ) 1 , further increasing i with a step length of 1; or else, downwards or upwards replacing an optimization interval with [c, a] or [b, d], wherein c<a, and b<d; starting comparison again from i=1 until (E 3 ) i+1 measured in an (i+1) th test is smaller than (E 3 ) i measured in the i th test, (E 1 ) j+1 <(E 1 ) i , and at the same time, (E 2 ) i+1 < (E 2 ) i , and then, determining S i set during the i th test as an optimal value of the optimization variable A.
2. The stress and shock wave diagnosis fused LIBS optimization method according to claim 1 , wherein the mounting distance x of the first piezoelectric ultrasonic transducer A 1 and the mounting distance y of the second piezoelectric ultrasonic transducer A 2 satisfy the following conditions:
the mounting distance x of the first piezoelectric ultrasonic transducer A 1 makes an actual measurement value thereof satisfy L 1 ∈(0.5ML 1 , ML 1 );
the mounting distance y of the second piezoelectric ultrasonic transducer A 2 makes an actual measurement value thereof satisfy L 2 ∈(0.5ML 2 , ML 2 );
wherein ML 1 is an upper limit of an available range of the first piezoelectric ultrasonic transducer A 1 , and ML 2 is an upper limit of an available range of the second piezoelectric ultrasonic transducer A 2 .
3. The stress and shock wave diagnosis fused LIBS optimization method according to claim 1 , wherein the step of pre-processing the spectral signal to obtain the spectral intensity of the detected object under the current parameter comprises:
calculating a total peak intensity E 31,j , a net peak intensity E 32,j and a net area intensity E 33,j of the spectral signal Φ 3 ; and calculating an average value of the total peak intensity E 31,j , the net peak intensity E 32,j or the net area intensity E 33,j as a spectral intensity index E 3 under the current parameter value:
E
3
=
(
∑
j
=
1
N
E
3
,
j
)
/
N
,
where E 3,j is a spectral line intensity, measured under a j th pulse, of the target element.
4. The stress and shock wave diagnosis fused LIBS optimization method according to claim 3 , wherein the step of processing the shock wave signal and the stress wave signal to obtain the shock wave intensity and the stress wave intensity under the current parameter comprises:
calculating a shock wave intensity E 1 under the current parameter:
E
1
=
(
∑
j
=
1
N
E
1
,
j
)
/
N
,
where E 1,j represents a shock wave intensity under the j th pulse; and
calculating a stress wave intensity E 2 under the current parameter:
E
2
=
(
∑
j
=
1
N
E
2
,
j
)
/
N
,
where E 2,j represents a stress wave intensity under the j th pulse.
5. The stress and shock wave diagnosis fused LIBS optimization method according to claim 4 , wherein the shock wave intensity E 1,j under the j th pulse is obtained according to the method of:
selecting, from a shock wave signal Φ 1,j measured under the j th pulse in continuous N pulses, an area where an appearing first peak is located as a subsequent shock wave analysis area Φ′[t] 1,j , wherein j=1,2, . . . , N; firstly, subtracting a shock wave background baseline value Φ 1B,j from the shock wave analysis area Φ′[t] 1,j , next, squaring the shock wave analysis area Φ′ [t] 1,j , and then, performing an integration on the shock wave analysis area Φ′ [t] 1,j within a time range to obtain the shock wave intensity E 1,j under the j th pulse.
6. The stress and shock wave diagnosis fused LIBS optimization method according to claim 4 , wherein the stress wave intensity E 2,j under the j th pulse is obtained according to the method of:
selecting, from a stress wave signal Φ 2,j measured under the j th pulse in continuous N pulses, an area where an appearing first peak is located as a subsequent stress wave analysis area Φ′ [t] 2,j , wherein j=1,2, . . . , N; firstly, subtracting a stress wave background baseline value Φ 2B,j from the stress wave analysis area Φ′[t] 2,j , next, squaring the stress wave analysis area Φ′[t] 2,j , and then, performing an integration on the stress wave analysis area Φ′ [t] 2,j within a time range to obtain the stress wave intensity E 2,j under the j th pulse.
7. A stress and shock wave diagnosis fused LIBS optimization system, comprising:
a signal collection module configured to collect a shock wave signal, a stress wave signal and a spectral signal of a detected object subjected to pulsed laser ablation under a current parameter, wherein the signal collection module is configured to fix a first piezoelectric ultrasonic transducer A 1 on a position, away from an ablation point for a distance x, over a target surface of the detected object, and laterally collecting a shock wave signal Φ 1 ; fix a second piezoelectric ultrasonic transducer A 2 on a position, away from the ablation point for a distance y, on the target surface, and measure a stress wave signal Φ 2 propagating along the target surface; then, connect the first piezoelectric ultrasonic transducer A 1 and the second piezoelectric ultrasonic transducer A 2 to an oscilloscope, wherein x is a mounting distance of the first piezoelectric ultrasonic transducer A 1 , and y is a mounting distance of the second piezoelectric ultrasonic transducer A 2 ; record, by the oscilloscope, waveforms of the shock wave signal Φ 1 and the stress wave signal Φ 2 obtained after continuous N-pulse ablation under each parameter; and measure a spectral signal Φ 3 of a target element by a spectrometer;
a spectral signal processing module configured to pre-process the spectral signal to obtain a spectral intensity of the detected object under the current parameter;
a shock and stress wave processing module configured to process the shock wave signal and the stress wave signal to obtain a shock wave intensity and a stress wave intensity under the current parameter; and
a parameter adjustment module configured to adjust optimization variables until optimization measurement and diagnosis of a spectral enhancement measure or system parameter are completed, wherein the parameter adjustment module is configured to select an initial optimization interval [a, b] of an optimization variable A, wherein a is the minimum value of the optimization variable A, and b is the maximum value of the optimization variable A; uniformly set a total of n groups of optimization values, then, set a shock wave intensity measured in an i th test as (E 1 ) i , set a stress wave intensity measured in the i th test as (E 2 ) i , set a spectral intensity measured in the i th test as (E 3 ) i , and set a value S i of the optimization variable A in the i th test as:
S i =a +( b−a )×( i −1)/( n −1),
wherein i=1,2, . . . n; and
start a test from i=1, when (E 3 ) 2 measured in a second test is greater than or equal to (E 3 ) 1 measured in a first test, (E 1 ) 2 ≥(E 1 ) 1 , and at the same time, (E 2 ) 2 ≥(E 2 ) 1 , further increase i with a step length of 1; or else, downwards or upwards replace an optimization interval with [c, a] or [b, d], wherein c<a, and b<d; start comparison again from i=1 until (E 3 ) i+1 measured in an (i+1) th test is smaller than (E 3 ) i measured in the i th test, (E 1 ) j+1 <(E 1 ) j , and at the same time, (E 2 ) i+1 <(E 2 ) i , and then, determine S i set during the i th test as an optimal value of the optimization variable A.