CN111811991A - Near infrared spectrum analysis method for non-contact testing density of composite solid propellant - Google Patents
Near infrared spectrum analysis method for non-contact testing density of composite solid propellant Download PDFInfo
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- 239000004449 solid propellant Substances 0.000 title claims abstract description 240
- 239000002131 composite material Substances 0.000 title claims abstract description 221
- 238000002329 infrared spectrum Methods 0.000 title claims abstract description 162
- 238000012360 testing method Methods 0.000 title claims abstract description 68
- 238000004458 analytical method Methods 0.000 title claims abstract description 15
- 238000005259 measurement Methods 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 62
- 238000001228 spectrum Methods 0.000 claims description 59
- 239000007787 solid Substances 0.000 claims description 37
- 239000000853 adhesive Substances 0.000 claims description 20
- 230000001070 adhesive effect Effects 0.000 claims description 20
- 239000007800 oxidant agent Substances 0.000 claims description 20
- 230000001590 oxidative effect Effects 0.000 claims description 20
- 239000004014 plasticizer Substances 0.000 claims description 20
- 238000010183 spectrum analysis Methods 0.000 claims description 20
- 239000000126 substance Substances 0.000 claims description 10
- 230000002452 interceptive effect Effects 0.000 claims description 9
- 238000012795 verification Methods 0.000 claims description 9
- 238000004497 NIR spectroscopy Methods 0.000 claims description 6
- 238000007796 conventional method Methods 0.000 claims description 6
- 238000010561 standard procedure Methods 0.000 claims description 6
- 230000003595 spectral effect Effects 0.000 claims description 5
- 238000002203 pretreatment Methods 0.000 claims description 4
- 238000012935 Averaging Methods 0.000 claims description 3
- 238000012569 chemometric method Methods 0.000 claims description 3
- 238000002474 experimental method Methods 0.000 claims description 3
- 238000009472 formulation Methods 0.000 claims description 3
- 239000011810 insulating material Substances 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000010998 test method Methods 0.000 claims description 3
- 239000000523 sample Substances 0.000 abstract description 38
- 238000001514 detection method Methods 0.000 abstract description 6
- 239000013307 optical fiber Substances 0.000 abstract description 5
- 230000007547 defect Effects 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 238000013461 design Methods 0.000 abstract description 2
- 239000002002 slurry Substances 0.000 description 9
- 238000001723 curing Methods 0.000 description 6
- 229940079593 drug Drugs 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000010200 validation analysis Methods 0.000 description 2
- 239000004322 Butylated hydroxytoluene Substances 0.000 description 1
- NLZUEZXRPGMBCV-UHFFFAOYSA-N Butylhydroxytoluene Chemical compound CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 NLZUEZXRPGMBCV-UHFFFAOYSA-N 0.000 description 1
- 229940095259 butylated hydroxytoluene Drugs 0.000 description 1
- 235000010354 butylated hydroxytoluene Nutrition 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011416 infrared curing Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
- 238000003333 near-infrared imaging Methods 0.000 description 1
- 239000003380 propellant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/24—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing the transmission of wave or particle radiation through the material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/36—Analysing materials by measuring the density or specific gravity, e.g. determining quantity of moisture
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Abstract
A near infrared spectrum analysis method for non-contact testing of density of a composite solid propellant is characterized in that a sample is prepared according to a certain composite solid propellant formula and a design formula, one part of an obtained composite solid propellant standard product is used for testing near infrared spectrum, and the other part of the obtained composite solid propellant standard product is cured and formed to test the density of the composite solid propellant standard product. And establishing a relation model between the near infrared spectrum of the composite solid propellant standard product and the density of the composite solid propellant standard product, and detecting the density of the composite solid propellant sample. The near-infrared accessory used in the invention is a diffuse reflection optical fiber, and non-contact sample measurement is adopted, so that the problem that the composite solid propellant is enriched on the surface of the optical fiber probe is solved. The invention achieves the specified detection precision, is efficient and nondestructive in the density detection of the composite solid propellant, overcomes the defect that the traditional detection requires long time for curing and forming, and provides a convenient and rapid detection method for the production quality and safe manufacture of the composite solid propellant.
Description
Technical Field
The invention relates to the field of composite solid propellants, in particular to a near infrared spectrum analysis method for non-contact testing of the density of a composite solid propellant.
Background
Density is a physical parameter which is defined as the mass per unit volume of the substance, i.e. the density of the composite solid propellant is the mass per unit volume of the composite solid propellant. The density of the composite solid propellant is an index for measuring the energy of the composite solid propellant. The density test is based on the Archimedes principle as theory. The density test of the composite solid propellant is also based on the principle. The method for testing the density of the composite solid propellant based on the principle is that after the composite solid propellant slurry is cured for 7 days at 50 ℃, the composite solid propellant slurry is made into a drug strip under corresponding conditions according to a corresponding testing method, and then the density of the composite solid propellant is tested by a corresponding tester. The method has the defects that the curing process is long, and the density of the composite solid propellant cannot be judged by means of the composite solid propellant slurry.
Near infrared spectroscopy is an analysis method of secondary measurement, namely an indirect measurement technology, and a correction model is established by correlating near infrared spectrum data of a sample with quality parameters of the sample. The relevant quality parameters of the test sample are quickly given by means of the model. In recent years, the application of near infrared spectroscopy in the field of composite solid propellants mainly aims at component research of the butylated hydroxytoluene propellant, and no report is found for non-contact testing of the degree of the composite solid propellant.
Disclosure of Invention
In order to overcome the defect of long curing time in the density test process of the composite solid propellant in the prior art, the invention provides a near infrared spectrum analysis method for testing the density of the composite solid propellant in a non-contact manner.
The specific process of the invention is as follows:
the samples required by the relation model comprise 50 parts of near infrared spectrum test samples and 50 parts of solid composite solid propellant standard;
the near infrared spectrum test sample and the solid composite solid propellant standard are both prepared by changing the mass percentage of the components influencing the initial modulus of uniaxial tension in the composite solid propellant formula;
the components influencing the density comprise an adhesive, a plasticizer and an oxidant. The density-influencing component is changed by fluctuating the content of the adhesive within +/-10% of the formula, fluctuating the content of the plasticizer within +/-20% of the formula and fluctuating the content of the oxidant within +/-3% of the formula. According to the changed content, 50 standard formulations of the composite solid propellant are obtained through orthogonal experiments.
Step 2, determining the optimal acquisition parameters of the near infrared spectrum of the composite solid propellant
The acquisition parameters comprise scanning times, spectral range and resolution.
And adjusting the spectrum acquisition parameters of the near-infrared spectrometer by the near-infrared spectrometer. Taking any one part of the near infrared spectrum test sample obtained in the step 1 as a test sample; and carrying out near infrared spectrum test on the infrared spectrum test sample by using a near infrared spectrometer.
Determining the near infrared spectrum acquisition parameters of the composite solid propellant as follows:
wave number range: 4000-120000cm-1；
The scanning times are as follows: 120 times;
resolution ratio: 4cm-1。
The process of determining the optimal scanning times is to adjust the scanning times of the near-infrared spectrometer to be 50 times, 100 times, 120 times, 160 times and 200 times respectively, and to perform near-infrared spectrum acquisition on the samples used by the acquisition parameters according to the determined scanning times respectively; obtaining a near infrared spectrum after each near infrared spectrum acquisition; five near infrared spectra were obtained in this example. And sequentially arranging the five pieces of near infrared spectrum noise according to the obtained five pieces of near infrared spectrum noise values from large to small. And selecting a near infrared spectrum with the minimum scanning frequency from the near infrared spectra with similar noise values, and taking the scanning frequency of the near infrared spectrum as the optimal scanning frequency.
The process of determining the optimal resolution is to adjust the resolution of the near infrared spectrometer to be 2cm respectively-1、4cm-1、8cm-1Sequentially carrying out near infrared spectrum collection on the samples used by the collection parameters, and obtaining a near infrared spectrum after each near infrared spectrum collection; three near infrared spectra were obtained in this example. And sequentially arranging the three pieces of near infrared spectrum noise according to the obtained three pieces of near infrared spectrum noise values from large to small. And selecting one near infrared spectrum with the minimum noise value from the three near infrared spectrums, and taking the scanning times of the near infrared spectrum as the optimal resolution.
Step 3, acquiring near infrared spectrum of 50 composite solid propellant standard products
And (3) respectively acquiring the near infrared spectrums of 50 standard products of the composite solid propellant according to the near infrared spectrum acquisition parameters of the composite solid propellant determined in the step (2). The method comprises the following steps:
the near infrared spectrometer is started up and preheated for one hour.
Collecting a near infrared spectrum of a first composite solid propellant standard; three spectra were collected for the first composite solid propellant standard. And averaging the three spectra of the sample by using test software carried by a near infrared spectrometer to obtain the average spectrum of the composite solid propellant standard.
And repeating the process of collecting the near infrared spectrum of the first composite solid propellant standard until the near infrared spectrum collection of the 50 composite solid propellant standards is completed, so as to obtain the average spectrum of the 50 composite solid propellant standards.
Thus, the acquisition of near infrared spectra of 50 composite solid propellant standards is completed.
In the near infrared spectrum collection, the room temperature of the collection environment is 25 +/-2 ℃, and the relative humidity is less than or equal to 65%.
And taking the obtained average spectrum of 50 composite solid propellant standards as the near infrared spectrum of the composite solid propellant standard in the relational model.
Step 4, testing the density of the composite solid propellant standard product:
and (3) testing the density of the 50 solid composite solid propellant standard products obtained in the step (1). The method comprises the following steps:
and respectively testing the densities of 50 solid composite solid propellant standard products by using a density tester by adopting a conventional method to respectively obtain the densities of 50 solid composite solid propellant standard products. The test method executes the aerospace industry standard of China general aerospace industry, and the standard number is as follows: QJ917A-97, standard name: composite solid propellant, lining and heat insulating material density measuring method.
The obtained 50 densities of the solid composite solid propellant standard products are used as density data which are related to the near infrared spectrum of the composite solid propellant standard products in a relational model.
Step 5, collecting the near infrared spectrum of the density-influencing component
The density influencing components are respectively an adhesive, a plasticizer and an oxidant.
And (3) acquiring the near infrared spectrum of the density-influencing component according to the optimal acquisition parameters of the near infrared spectrum of the composite solid propellant determined in the step (2), and respectively obtaining near infrared spectrograms of the adhesive, the plasticizer and the oxidant.
Step 6, selecting parameters of the optimal model and establishing a relation model:
and inputting the obtained average spectra of 50 composite solid propellant standard products and the densities of 50 solid composite solid propellant standard products into near infrared spectrum analysis software in a one-to-one correspondence manner, and selecting the optimal modeling parameters through the near infrared spectrum analysis software. The modeling parameters comprise standard substance spectral analysis interval selection, spectrum pretreatment, chemometric method selection and optimal main factor number selection.
The final determined optimal relational model parameters are as follows:
spectral analysis interval: 4000cm-1～9000cm-1；
Spectrum pretreatment: none;
the stoichiometric method comprises the following steps: partial least squares;
number of optimal factors: 8.
and inputting the optimal relation model parameters into chemometrics software to obtain a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant. The relation model is a relation model between the near infrared spectrum of the composite solid propellant standard product and the density of the composite solid propellant standard product. The correlation coefficient of the relational model was 0.99611, and the standard deviation was 0.001.
The concrete process for establishing the optimal model parameter selection and relation model is as follows:
i50 spectrum analysis intervals of the composite solid propellant are selected:
obtaining near infrared spectrograms of the adhesive, the plasticizer and the oxidant through the step 5, and determining a spectral analysis interval of the composite solid propellant standard product, wherein the spectral analysis interval of the composite solid propellant standard product is specifically determined by taking the peak position of the near infrared spectrum of the adhesive, the peak position of the near infrared spectrum of the plasticizer and the peak position of the near infrared spectrum of the oxidant and the peak position of the near infrared spectrum of any one composite solid propellant standard product obtained in the step 3 as ranges in which the peak position of the near infrared spectrum of the composite solid propellant standard product, the peak position of the near infrared spectrum of the adhesive, the peak position of the near infrared spectrum of the plasticizer and the peak position of the near infrared spectrum of the oxidant exist at the same time; the spectral analysis interval of the composite solid propellant standard product is 4000cm-1～9000cm-1。
II, spectrum pretreatment of a composite solid propellant standard product:
and establishing a relation model of the spectra of the 50 composite solid propellant standard products through near infrared processing software. And performing derivative and smooth pretreatment on the spectra of 50 composite solid propellant standard products according to a conventional method, and establishing a relation model of the spectra of the pretreated composite solid propellant standard products.
And comparing the relation model of the spectra of the 50 composite solid propellant standard products with the relation model of the spectra of the pretreated composite solid propellant standard products, and selecting a pretreatment mode with a correlation coefficient closer to 1 and a small standard deviation as a pretreatment method of the relation model.
III selection of the stoichiometric method:
and a partial least square method is adopted as a chemometrics method established by a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant.
IV, selecting the optimal main factor number:
the main factor number is the square of the prediction residual obtained by the interactive verification method, and the optimal factor number is the main factor number with the minimum sum of the squares of the prediction residual obtained by the interactive verification method. The number of main factors selected for establishing the model is too small, so that insufficient fitting can occur, more useful information of an original spectrum can be lost, but too many main factors are selected, so that overfitting can be caused, measurement noise is introduced, the prediction error of the established model can be obviously increased, and the quality of the model is reduced. And calculating the square sum of the prediction residuals obtained by the interactive verification method to obtain the minimum optimal main factor number of the square sum of the residuals.
Step 7, verifying the relation model
And the relational model is a relational model between the spectrum of the standard solid propellant and the density of the standard solid propellant obtained in the sixth step.
10 samples of composite solid propellant with a weight of 2 kg each were taken for the validation of the relational model.
The density of the solid composite solid propellant sample was tested by standard methods: 1/5 of the mass of each composite solid propellant sample is taken as a sample for collecting near infrared spectrum data; 4/5 of the total mass of the 10 samples was cured at 50 ℃ for 7 days to yield 10 solid composite solid propellant samples. The density test was carried out by the method of QJ917A-97 to obtain the density of 10 solid composite solid propellant samples.
And comparing the density deviation between the solid composite solid propellant sample obtained by the standard method and the density deviation between the solid composite solid propellant sample obtained by the near infrared spectrum method. The obtained deviation is less than 3%, and the test result of the relation model is proved to be accurate.
Therefore, near infrared spectrum analysis of the density of the composite solid propellant is completed, and the obtained relation model is used for testing the density of the composite solid propellant.
Firstly, designing a certain amount of composite solid propellant formulas with known proportions according to a certain composite solid propellant formula and an even distribution principle; secondly, preparing a sample according to a design formula to obtain a certain amount of composite solid propellant slurry with a known proportion, which is called as a composite solid propellant standard product hereinafter, using a part of the obtained composite solid propellant standard product for testing a near infrared spectrum, curing and forming a part of the obtained composite solid propellant standard product, and testing the density of the composite solid propellant standard product; then establishing a relation model between the near infrared spectrum of the composite solid propellant standard product and the density of the composite solid propellant standard product by means of professional quantitative software; and finally, performing the density of the composite solid propellant sample, wherein the density refers to the density of the composite solid propellant sample after being cured, and is hereinafter referred to as the density of the composite solid propellant sample. In the process of detecting the composite solid propellant sample, the testing conditions are ensured to be the same as those of the standard product.
The near-infrared accessory used in the invention is a diffuse reflection optical fiber, and the sample measurement adopts a non-contact type, namely, the near-infrared optical fiber probe is not contacted with the sample to be measured. The non-contact sampling mode overcomes the problem that the composite solid propellant is enriched on the surface of the optical fiber probe in a contact mode.
The relation model in the invention is to determine the relation between the near infrared spectrum of the standard substance and the density of the composite solid propellant after the near infrared spectrum of the standard substance is tested and processed by a spectrum pretreatment method.
According to the invention, the density of the cured composite solid propellant is directly obtained by testing the composite solid propellant slurry, so that the problem that the conventional test of the composite solid propellant slurry can be carried out only after the composite solid propellant slurry is cured for 7 days at 50 ℃ is solved, and the test time of a sample is greatly saved.
The test conditions of the composite solid propellant sample in the invention are consistent with the test conditions of the composite solid propellant standard.
The invention can use 4000--1The establishment of the relation model by the wave band causes large noise signal, slow operation speed and stability of the relation modelPoor, therefore, the spectrum analysis interval of the composite solid propellant standard needs to be selected.
In the invention, the quality of the model is judged by mainly referring to the correlation coefficient and the standard deviation of the model, the closer the correlation coefficient of the model is to 1, the better, namely, the closer the predicted value and the practical value of the model are, the better, which is shown in fig. 1: the abscissa of 1 represents the density of the solid composite solid propellant measured by the method QJ 917A-97; 2, the ordinate represents the density of a certain type of solid propellant standard substance measured by a relation model; 3, representing points corresponding to the predicted value and the actual value, wherein the closer the numerical values of the predicted value and the actual value are, the better the model is; 4 represents a 45 degree line, the closer the point 3 corresponding to the predicted and actual values is to the 45 degree line 4, the better the model. The smaller the standard deviation, the better. The relation model with the optimal correlation coefficient and standard deviation is the optimal model, and the model parameter corresponding to the optimal relation model is the optimal modeling parameter.
The invention utilizes the near infrared technology to analyze the density of the composite solid propellant, and completely reaches the specified detection precision. The density of the composite solid propellant is detected by using the method, so that the aim of high-efficiency and nondestructive analysis can be fulfilled, the defect that the time consumption for curing and forming is long in the traditional test is thoroughly overcome, and the convenient and fast detection method is provided for the production quality and the safe manufacture of the composite solid propellant.
Drawings
FIG. 1 is a graph of the correlation of density using a near infrared method and using a standard test.
Fig. 2 is a flow chart of the present invention.
In the figure: 1. the abscissa represents the density, i.e. the actual density, of the cured standard product measured by using a QJ917A-97 standard; 2. the density of the standard product after curing, namely the predicted density, is obtained by the model test on the ordinate; 3. circles in the graph represent predicted and actual values for the model samples; 4.45 degree line.
Detailed Description
The embodiment is a method for testing the density of a certain type of composite solid propellant, and the specific process is as follows:
first, preparation of samples required for the relational model:
the composite solid propellant comprises more than ten components, and the invention obtains 50 standard product formulas of the composite solid propellant by changing the mass percentage of the components influencing the density according to the formula of the composite solid propellant.
The samples required by the relation model comprise 50 parts of near infrared spectrum test samples and 50 parts of solid composite solid propellant standard;
the components influencing the density comprise an adhesive, a plasticizer and an oxidant.
The density-influencing component is changed by fluctuating the content of the adhesive within +/-10% of the formula, fluctuating the content of the plasticizer within +/-20% of the formula and fluctuating the content of the oxidant within +/-3% of the formula. According to the changed content, 50 standard formulations of the composite solid propellant are obtained through orthogonal experiments.
And (3) preparing the components one by using a 3-liter vertical mixer according to a mixing process to obtain 50 standard products of the composite solid propellant. The standard substance is composite solid propellant slurry.
Respectively taking drug slurry with the mass of 1/5 standard substances from the prepared 50 standard substances for testing the near infrared spectrum to obtain 50 near infrared spectrum test samples; the remaining 4/5 of each standard was used for curing and forming, resulting in 50 solid composite solid propellant standards for testing the density of the composite solid propellant standards. The curing molding is carried out for 7 days at 50 ℃.
Secondly, determining the optimal acquisition parameters of the near infrared spectrum of the composite solid propellant
The acquisition parameters comprise scanning times, spectral range and resolution.
And adjusting the spectrum acquisition parameters of the near-infrared spectrometer by the near-infrared spectrometer. Taking any one part of the near infrared spectrum test sample obtained in the step 1 as a test sample; and carrying out near infrared spectrum test on the infrared spectrum test sample by using a near infrared spectrometer.
The test process is as follows:
determining the optimal scanning times: adjusting the scanning times of the near-infrared spectrometer to be 50 times, 100 times, 120 times, 160 times and 200 times respectively, and performing near-infrared spectrum acquisition on the samples used by the acquisition parameters according to the determined scanning times respectively; obtaining a near infrared spectrum after each near infrared spectrum acquisition; five near infrared spectra were obtained in this example. And sequentially arranging the five pieces of near infrared spectrum noise according to the obtained five pieces of near infrared spectrum noise values from large to small. And selecting a near infrared spectrum with the minimum scanning frequency from the near infrared spectra with similar noise values, and taking the scanning frequency of the near infrared spectrum as the optimal scanning frequency.
Determining the optimal resolution: the resolution ratios of the near-infrared spectrometers are respectively adjusted to be 2cm-1、4cm-1、8cm-1Sequentially carrying out near infrared spectrum collection on the samples used by the collection parameters, and obtaining a near infrared spectrum after each near infrared spectrum collection; three near infrared spectra were obtained in this example. And sequentially arranging the three pieces of near infrared spectrum noise according to the obtained three pieces of near infrared spectrum noise values from large to small. And selecting one near infrared spectrum with the minimum noise value from the three near infrared spectrums, and taking the scanning times of the near infrared spectrum as the optimal resolution.
Selecting a spectral interval: the selected spectral interval is the near infrared band of the near infrared spectrometer employed. In the embodiment, the near-infrared band is 4000-120000cm-1。
Through the process, the composite solid propellant near infrared spectrum acquisition parameters are determined as follows:
wave number range: 4000-120000cm-1；
The scanning times are as follows: 120 times;
resolution ratio: 4cm-1。
Thirdly, collecting near infrared spectra of 50 composite solid propellant standard products
And respectively collecting the near infrared spectrums of 50 standard products of the composite solid propellant according to the near infrared spectrum collection parameters of the composite solid propellant determined in the second step. The method comprises the following steps:
the near infrared spectrometer is started up and preheated for one hour.
Collecting a near infrared spectrum of a first composite solid propellant standard; three spectra were collected for the first composite solid propellant standard. And averaging the three spectra of the sample by using test software carried by a near infrared spectrometer to obtain the average spectrum of the composite solid propellant standard.
And repeating the process of collecting the near infrared spectrum of the first composite solid propellant standard until the near infrared spectrum collection of the 50 composite solid propellant standards is completed, so as to obtain the average spectrum of the 50 composite solid propellant standards.
Thus, the acquisition of near infrared spectra of 50 composite solid propellant standards is completed.
In the near infrared spectrum collection, the room temperature of the collection environment is 25 +/-2 ℃, and the relative humidity is less than or equal to 65%.
And taking the obtained average spectrum of 50 composite solid propellant standards as the near infrared spectrum of the composite solid propellant standard in the relational model.
And fourthly, testing the density of the composite solid propellant standard product:
the density of 50 solid composite solid propellant standards obtained in the first step was tested. The method comprises the following steps:
and respectively testing the densities of 50 solid composite solid propellant standard products by using a density tester by adopting a conventional method to respectively obtain the densities of 50 solid composite solid propellant standard products. The test method executes the aerospace industry standard of China general aerospace industry, and the standard number is as follows: QJ917A-97, standard name: composite solid propellant, lining and heat insulating material density measuring method.
The obtained 50 densities of the solid composite solid propellant standard products are used as density data which are related to the near infrared spectrum of the composite solid propellant standard products in a relational model.
The fifth step, collecting the near infrared spectrum of the density-influencing component
The density influencing components are respectively an adhesive, a plasticizer and an oxidant.
And acquiring the component influencing the density according to the optimal acquisition parameters of the composite solid propellant near infrared spectrum determined in the second step to obtain near infrared spectrograms of the adhesive, the plasticizer and the oxidant respectively.
Sixthly, selecting parameters of the optimal model and establishing a relation model:
and inputting the obtained average spectra of 50 composite solid propellant standard products and the densities of 50 solid composite solid propellant standard products into near infrared spectrum analysis software in a one-to-one correspondence manner, and selecting the optimal modeling parameters through the near infrared spectrum analysis software. The modeling parameters comprise standard substance spectral analysis interval selection, spectrum pretreatment, chemometric method selection and optimal main factor number selection.
The specific process is as follows:
i50 spectrum analysis intervals of the composite solid propellant are selected:
obtaining near infrared spectrograms of the adhesive, the plasticizer and the oxidant through the fifth step, and determining a spectral analysis interval of the composite solid propellant standard product, wherein the spectral analysis interval of the composite solid propellant standard product is determined by taking the range of the near infrared spectrograms of the adhesive, the plasticizer and the oxidant, and the near infrared spectrograms of any one composite solid propellant standard product obtained in the third step as the spectral analysis interval of the composite solid propellant standard product; the spectral analysis interval of the composite solid propellant standard product is 4000cm-1～9000cm-1。
II, spectrum pretreatment of a composite solid propellant standard product:
and establishing a relation model of the spectra of the 50 composite solid propellant standard products through near infrared processing software. And performing derivative and smooth pretreatment on the spectra of 50 composite solid propellant standard products according to a conventional method, and establishing a relation model of the spectra of the pretreated composite solid propellant standard products.
And comparing the relation model of the spectra of the 50 composite solid propellant standard products with the relation model of the spectra of the pretreated composite solid propellant standard products, and selecting a pretreatment mode with a correlation coefficient closer to 1 and a small standard deviation as a pretreatment method of the relation model. The comparison result proves that the relation model without spectrum pretreatment is better.
III selection of the stoichiometric method:
and a partial least square method is adopted as a chemometrics method established by a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant.
IV, selecting the optimal main factor number:
the main factor number is the square of the prediction residual obtained by the interactive verification method, and the optimal factor number is the main factor number with the minimum sum of the squares of the prediction residual obtained by the interactive verification method. The number of main factors selected for establishing the model is too small, so that insufficient fitting can occur, more useful information of an original spectrum can be lost, but too many main factors are selected, so that overfitting can be caused, measurement noise is introduced, the prediction error of the established model can be obviously increased, and the quality of the model is reduced. And calculating the square sum of the prediction residuals obtained by the interactive verification method to obtain the minimum corresponding main factor number of the square sum of the residuals as 9, namely the optimal factor number as 9.
The final determined optimal relational model parameters are as follows:
spectral analysis interval: 4000cm-1～9000cm-1；
Spectrum pretreatment: none;
the stoichiometric method comprises the following steps: partial least squares;
number of optimal factors: 8.
and inputting the optimal relation model parameters by means of chemometrics software to obtain a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant. The relation model is a relation model between the near infrared spectrum of the composite solid propellant standard product and the density of the composite solid propellant standard product, the correlation coefficient of the relation model is 0.99611, and the standard deviation is 0.001.
Step 7, verifying the relation model
And the relational model is a relational model between the spectrum of the standard solid propellant and the density of the standard solid propellant obtained in the sixth step.
10 samples of composite solid propellant with a weight of 2 kg each were taken for the validation of the relational model.
The density of the solid composite solid propellant sample was tested by standard methods: 1/5 of the mass of each composite solid propellant sample is taken as a sample for collecting near infrared spectrum data; 4/5 of the total mass of the 10 samples was cured at 50 ℃ for 7 days to yield 10 solid composite solid propellant samples. The density test was carried out by the method of QJ917A-97 to obtain the density of 10 solid composite solid propellant samples.
And comparing the density deviation between the solid composite solid propellant sample obtained by the standard method and the density deviation between the solid composite solid propellant sample obtained by the near infrared spectrum method. The obtained deviation is less than 3%, and the test result of the relation model is proved to be accurate.
Therefore, near infrared spectrum analysis of the density of the composite solid propellant is completed, and the obtained relation model is used for testing the density of the composite solid propellant.
Claims (6)
1. A near infrared spectrum analysis method for non-contact testing of density of a composite solid propellant is characterized by comprising the following specific processes:
step 1, preparation of a sample required by a relation model:
the samples required by the relation model comprise 50 parts of near infrared spectrum test samples and 50 parts of solid composite solid propellant standard;
the near infrared spectrum test sample and the solid composite solid propellant standard are both prepared by changing the mass percentage of the components influencing the initial modulus of uniaxial tension in the composite solid propellant formula;
step 2, determining the optimal acquisition parameters of the near infrared spectrum of the composite solid propellant:
the acquisition parameters comprise scanning times, spectral range and resolution;
adjusting the spectrum acquisition parameters of the near-infrared spectrometer by the near-infrared spectrometer; taking any one part of the near infrared spectrum test sample obtained in the step 1 as a test sample; performing near infrared spectrum test on the infrared spectrum test sample by using a near infrared spectrometer;
determining the near infrared spectrum acquisition parameters of the composite solid propellant as follows:
wave number range: 4000-120000cm-1；
The scanning times are as follows: 120 times;
resolution ratio: 4cm-1；
And 3, acquiring near infrared spectrums of 50 composite solid propellant standard products:
respectively collecting the near infrared spectrums of 50 standard products of the composite solid propellant according to the near infrared spectrum collection parameters of the composite solid propellant determined in the step 2; the method comprises the following steps:
preheating for one hour by starting the near-infrared spectrometer;
collecting a near infrared spectrum of a first composite solid propellant standard; collecting three spectra of a first composite solid propellant standard; averaging the three spectra of the sample by using test software of a near infrared spectrometer to obtain an average spectrum of the composite solid propellant standard;
repeating the process of acquiring the near infrared spectrum of the first composite solid propellant standard until the near infrared spectrum acquisition of the 50 composite solid propellant standards is completed, so as to obtain the average spectrum of the 50 composite solid propellant standards;
so far, the near infrared spectrum collection of 50 composite solid propellant standards is completed;
in the near infrared spectrum collection, the room temperature of the collection environment is 25 +/-2 ℃, and the relative humidity is less than or equal to 65%;
taking the obtained average spectra of 50 composite solid propellant standards as the near infrared spectrum of the composite solid propellant standard in a relational model;
step 4, testing the density of the composite solid propellant standard product:
testing the density of 50 solid composite solid propellant standard products obtained in the step 1; the method comprises the following steps:
respectively testing the densities of 50 solid composite solid propellant standard products by using a density tester by adopting a conventional method to respectively obtain the densities of 50 solid composite solid propellant standard products; the test method executes the aerospace industry standard of China general aerospace industry, and the standard number is as follows: QJ917A-97, standard name: measuring the density of the composite solid propellant, the lining and the heat-insulating material;
the obtained densities of 50 solid composite solid propellant standard products are used as density data associated with the near infrared spectrum of the composite solid propellant standard products in a relational model;
and 5, collecting a near infrared spectrum of the components influencing the density:
the density influencing components are respectively an adhesive, a plasticizer and an oxidant;
acquiring the near infrared spectrum of the density-influencing component according to the optimal acquisition parameters of the near infrared spectrum of the composite solid propellant determined in the step 2 to respectively obtain near infrared spectrograms of the adhesive, the plasticizer and the oxidant;
step 6, selecting parameters of the optimal model and establishing a relation model:
inputting the obtained average spectra of 50 composite solid propellant standard products and the densities of 50 solid composite solid propellant standard products into near infrared spectrum analysis software in a one-to-one correspondence manner, and selecting the optimal modeling parameters through the near infrared spectrum analysis software; the modeling parameters comprise standard substance spectral analysis interval selection, spectrum pretreatment, selection of a chemometric method and optimal main factor number selection;
the final determined optimal relational model parameters are as follows:
spectral analysis interval: 4000cm-1～9000cm-1；
Spectrum pretreatment: none;
the stoichiometric method comprises the following steps: partial least squares;
number of optimal factors: 8;
inputting the optimal relation model parameters into chemometrics software to obtain a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant; the relation model is a relation model between the near infrared spectrum of the composite solid propellant standard product and the density of the composite solid propellant standard product;
and 7, verifying the relation model:
the relation model is a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant obtained in the sixth step;
taking 10 composite solid propellant samples with the weight of 2 kilograms respectively for verifying a relation model;
the density of the solid composite solid propellant sample was tested by standard methods: 1/5 of the mass of each composite solid propellant sample is taken as a sample for collecting near infrared spectrum data; 4/5 of the total mass of the 10 samples are cured for 7 days at 50 ℃ to obtain 10 solid composite solid propellant samples; the density test is carried out by a method QJ917A-97 to obtain the density of 10 solid composite solid propellant samples;
comparing the density deviation between the solid composite solid propellant sample obtained by the standard method and the density deviation between the solid composite solid propellant sample obtained by the near infrared spectrum method; the obtained deviation is less than 3%, and the test result of the relation model is proved to be accurate;
therefore, near infrared spectrum analysis of the density of the composite solid propellant is completed, and the obtained relation model is used for testing the density of the composite solid propellant.
2. The near infrared spectrum analysis method for non-contact testing of the density of the composite solid propellant according to claim 1 is characterized by comprising the following specific processes: the components influencing the density comprise an adhesive, a plasticizer and an oxidant; the components for changing and influencing the density are that the adhesive fluctuates between plus or minus 10 percent of the content in the formula, the plasticizer fluctuates between plus or minus 20 percent of the content in the formula, and the oxidant fluctuates between plus or minus 3 percent of the content in the formula; according to the changed content, 50 standard formulations of the composite solid propellant are obtained through orthogonal experiments.
3. The method for non-contact near infrared spectroscopy analysis of density of composite solid propellant according to claim 1, wherein the process of determining the optimal number of scans in step 2 is:
determining the optimal scanning times: adjusting the scanning times of the near-infrared spectrometer to be 50 times, 100 times, 120 times, 160 times and 200 times respectively, and performing near-infrared spectrum acquisition on the samples used by the acquisition parameters according to the determined scanning times respectively; obtaining a near infrared spectrum after each near infrared spectrum acquisition; five near infrared spectra were obtained in this example; sequentially arranging the five pieces of near infrared spectrum noise according to the five obtained near infrared spectrum noise values from large to small; and selecting a near infrared spectrum with the minimum scanning frequency from the near infrared spectra with similar noise values, and taking the scanning frequency of the near infrared spectrum as the optimal scanning frequency.
4. The method for non-contact near infrared spectroscopy analysis of density of a composite solid propellant according to claim 1, wherein the step 2 of determining the optimal resolution is:
the resolution ratios of the near-infrared spectrometers are respectively adjusted to be 2cm-1、4cm-1、8cm-1Sequentially carrying out near infrared spectrum collection on the samples used by the collection parameters, and obtaining a near infrared spectrum after each near infrared spectrum collection; three near infrared spectra were obtained in this example; sequentially arranging the three pieces of near infrared spectrum noise according to the obtained three pieces of near infrared spectrum noise values from large to small; and selecting one near infrared spectrum with the minimum noise value from the three near infrared spectrums, and taking the scanning times of the near infrared spectrum as the optimal resolution.
5. The near infrared spectroscopy analysis method for non-contact testing of density of composite solid propellant according to claim 1, wherein the specific process of establishing the optimal model parameter selection and relation model in the step 6 is as follows:
i50 spectrum analysis intervals of the composite solid propellant are selected:
obtaining near infrared spectrograms of the adhesive, the plasticizer and the oxidant through the step 5, and determining a spectral analysis interval of the composite solid propellant standard product, wherein the spectral analysis interval of the composite solid propellant standard product is specifically determined by taking the peak position of the near infrared spectrum of the adhesive, the peak position of the near infrared spectrum of the plasticizer and the peak position of the near infrared spectrum of the oxidant and the peak position of the near infrared spectrum of any one composite solid propellant standard product obtained in the step 3 as ranges in which the peak position of the near infrared spectrum of the composite solid propellant standard product, the peak position of the near infrared spectrum of the adhesive, the peak position of the near infrared spectrum of the plasticizer and the peak position of the near infrared spectrum of the oxidant exist at the same time; the spectral analysis interval of the composite solid propellant standard product is 4000cm-1～9000cm-1；
II, spectrum pretreatment of a composite solid propellant standard product:
establishing a relation model of the spectra of the 50 composite solid propellant standard products through near-infrared processing software; performing derivative and smooth pretreatment on the spectra of 50 composite solid propellant standard products according to a conventional method, and establishing a relation model of the spectra of the pretreated composite solid propellant standard products;
comparing the relation models of the spectra of the 50 composite solid propellant standard products with the relation models of the spectra of the pretreated composite solid propellant standard products, and selecting a pretreatment mode with a correlation coefficient closer to 1 and a small standard deviation as a pretreatment method of the relation models;
III selection of the stoichiometric method:
a chemometrics method established by taking a partial least square method as a relation model between the spectrum of the standard solid propellant and the density of the standard solid propellant;
IV, selecting the optimal main factor number:
the main factor number is the square of the prediction residual obtained by the interactive verification method, and the optimal factor number is the main factor number with the minimum sum of the squares of the prediction residual obtained by the interactive verification method; the number of main factors selected for establishing the model is too small, so that insufficient fitting can occur, more useful information of an original spectrum can be lost, but too many main factors are selected, so that overfitting can be caused, measurement noise is introduced, the prediction error of the established model can be obviously increased, and the quality of the model is reduced; and calculating the square sum of the prediction residuals obtained by the interactive verification method to obtain the minimum optimal main factor number of the square sum of the residuals.
6. The method for near infrared spectroscopy of non-contact testing the density of a composite solid propellant according to claim 1, wherein the correlation coefficient of the relational model is 0.99611 with a standard deviation of 0.001.
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