Innovation and application of the test method of t

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Innovation and application of coating test methods

innovation and application of coating test methods

November 30, 2018


in the past two years, the tasks undertaken by the group company in the production of various military and civilian aircraft have increased sharply, and the types of coatings used have also increased accordingly. Through the testing of coating performance, the author actually felt the differences between the domestic and foreign coating industry. Nowadays, many large foreign companies tend to develop and produce universal coatings, and reduce the cost of Chinese Coatings by expanding production. In contrast, the requirements for detection methods and means are higher. In view of this objective fact, it puts forward higher requirements for a coating inspector to improve his professional level and evaluate the performance of a material more objectively and fairly. In order to further understand the specific differences, we consulted the test methods and material standards of all military and civil aircraft coatings of the company, and made innovations in four aspects

1 design and self-made equipment

1.1 improvement of cylindrical mandrel bending testing machine

the newly purchased mandrel bending testing machine does not have the 3/16 inch mandrel required by the technical documents. If 1/16 inch mandrel is used for testing, the assessment requirements are stricter than the test requirements, which increases unnecessary production process costs. The self-made 3/16 inch mandrel meets the production requirements of the company in time

1.2 research on auxiliary positioning device of impactor and self-made

1.2.1 defect statistics of impact resistance test

when conducting impact resistance test of coating, the test specimen cannot be quickly stabilized on the support surface, and several impact points cannot be quickly and accurately positioned. In the actual work, we can only rely on experience to adjust the position of the test piece and then drop the punch. Sometimes, the punch point will not meet the test standard and lead to the failure of the test

the number of test pieces required by our company for coating performance test and process performance test is 2 ~ 3. When testing the impact resistance, the test piece after impact does not meet the test requirements, which will affect the test results or must be prepared again. Most of the test pieces that meet the test requirements are not beautiful. In order to solve this problem, a large number of tests and follow-up investigations were carried out, and the impact test defects were classified and statistically analyzed, as shown in Table 1

1.2.2 cause analysis of impact test defects

it can be seen from table 1 that the main causes of defects in impact test are that the impact point cannot be accurately located, the test time is long, and the aesthetics is poor. In view of the above three situations, the cause analysis is carried out:

(1) cause 1 - the impact point cannot be accurately located. Cause: there is no positioning device

(2) cause 2 - long test time. Cause: the impact point cannot be accurately located

(3) cause 3 - poor aesthetics. Cause: the transverse and longitudinal impact points cannot be determined

1.2.3 measures to remedy defects

in order to confirm the implementation effect and economic effect, the following measures have been taken in a targeted manner, as shown in Table 2, after taking a step-by-step analysis from the four dimensions of finance, customers, internal operations, learning and growth

according to the analysis results of Table 2, it is decided to use self-made equipment to solve this problem. Therefore, the equipment is measured, and the size of the auxiliary parts is calculated according to the data, and then the CAD drawing is used. Material selection, processing and surface treatment were carried out according to the drawings. After being made, the self-made fasteners were installed on the equipment, and many tests and debugging were carried out. The effect of fixed parts after installation is shown in Figure 1

(2) although the fastener improves the stability and accuracy of impact resistance test, through practice, when the test specimen impacts the second point after the first point, the first point protruding on the test specimen affects the impact tests of the second and third points. Therefore, it is planned to machine another groove on the auxiliary device, as shown in Figure 3

the test efficiency and the stability and accuracy of the test process are ensured by self-made auxiliary positioning parts

1.3 design and manufacture viscosity cup fixings

the viscosity performance test of coating refers to the measurement of the ability of liquid molecules to interact with each other and hinder their relative movement between molecules. In addition to controlling the temperature and sample quantity, the test results in a steady state cannot be ignored. If the viscosity cup cannot be kept stable, the deviation of viscosity test results will occur. In addition, it often happens that the lower deviation between the actual test results of coating viscosity and performance indicators is similar. Higher requirements are put forward for coating testers

in order to solve the problem, we first measured three kinds of viscosity cups, and further promoted the development of key technologies and innovative scientific and technological utilization of lightweight plastic parts of China's own brand cars. The results are shown in Table 4

after analyzing the data in Table 4, it is found that the fixed parts of Ford cup and ISO outflow cup are similar in size, so we can consider using the same fixed parts to stabilize the viscosity cup on the basis of ensuring the stability of the viscosity cup. Zahn cup can use a separate fastener or add auxiliary facilities on the basis of Ford cup and ISO outflow cup fastener to ensure the stability of Zahn cup

according to the measured data in Table 4, the fixings of the viscosity cup are designed and manufactured respectively to ensure the accuracy of the test results

figure 4A shows the fixing parts of Zahn cup, and figure 4B shows the fixing parts of Ford cup and ISO outflow cup

the test results show that the viscosity cup can not only maintain a stable state, but also improve the repeatability and reproducibility of the test data, but also have some shortcomings. The deficiencies are improved, and the results are shown in Figure 5

zahn cup fixings are placed on the fixings of Ford cup and ISO outflow cup, which can not only ensure the stability of viscosity cup, but also reduce the test space, but also facilitate the management and maintenance of self-made parts. Because there is no horizontal placement device for the viscosity cup, two people were required to cooperate in the previous test to complete the work. One person is responsible for holding the viscosity cup and stopwatch, and one person is responsible for pouring the sample into the viscosity cup, which is time-consuming and cannot ensure that the viscosity cup remains stable. The self-made fixing parts of the viscosity cup ensure that the viscosity cup does not shake, thus improving the accuracy of the test results

2 improvement of test methods

2.1 quantification of test methods and improvement of the effectiveness of test results in the application period of coatings

the document does not accurately state whether the time specified in the application period includes the curing period (or induction period) of coatings, and there is no reference test method at home and abroad for the test items in the application period. The description of the test method is not rigorous enough. For example, q/12dt0093-2008 states: "after the two components are prepared according to the specified proportion, dilute them to spray viscosity and seal them, place them under standard conditions for 6 hours, and stir the coating liquid with a paint mixing knife or a stirring rod. It is easy to stir evenly, and the coating can still be used as qualified". However, the "paint can still be used as qualified" does not specify which test items can be met to determine as "still usable"

whether the curing period (or induction period) of the coating is included in the time specified in the application period - in theory, the curing period (or induction period) of the coating should not be included. Most of the time specified for the product application period is 1 ~ 2 hours up and down, while the curing period (or induction period) of the coating is generally about 0.5 hours, so it has no impact on the judgment of the test results. For the coating that requires testing the test items in the applicable period, whether the coating can still be used can be determined by testing other coating test items required by the test item table in the applicable period in the technical document

use the specific test items to determine the coating application period, so as to improve the effectiveness and accuracy of the test results without increasing labor intensity, and the enterprise standard has been completed for the improvement of this method

2.2 improvement of adhesive tape adhesion test method

wet scratch adhesion test is relatively complex because of its many test batches, many surface coatings involved, many types of substrate surface treatment, and many grooves involved in surface treatment. However, the current standard does not mention how to test when three variables are involved. The main waste occurs after the test cycle. It is necessary to confirm which one needs to be crossed and which one does not need to be crossed. If it is necessary to cross under load, what standard should be adopted

in addition, in view of the fact that there is cross cutting adhesion in paint testing, how to develop the test of material testing machine, and the test method requires parallel lines with a distance of 25.4mm (1 in). It takes time and energy to draw a line during each test, and then another line after measuring the spacing. The self-made standard simplifies the test process, simplifies the test process, and shortens the test time

in order to improve the efficiency of placing test pieces, list and count them in advance according to the technical requirements, test items, operation process, and specific test requirements. Stick labels on the beaker as shown in Table 5, and then put them on the beaker one by one. In addition, considering the limited space of the laboratory, scientific methods are used to put in multiple test pieces, so as to save costs and improve work efficiency. Considering the temporary production task, production line review and process test, several test containers are reserved. When using the test solution with high conductivity, there may be electrolytic effect, so the method of immersing a separate test piece into the test solution tank should be adopted. And pay attention to the following two aspects: (1) the test pieces should be of the same nature to ensure that the test solution is not affected by the test pieces; (2) For those with a long test cycle, the propaganda on the test fluid network should be added to compensate for the loss of liquid

automatic target identification technology 3 uses statistical tools

coatings with the same name and the same effect have different test items at home and abroad, and mainly focuses on how to specify the entry material test items and process performance test items to play a good complementary role. In view of this problem, I consulted a large number of documents and conducted a large number of comparative tests. First, the classification of test items in the material technical documents is compared at home and abroad, as shown in Table 6

table 6 shows that the classification of test items in material standards in China is not comprehensive enough to analyze and solve problems. It is convenient to understand the material properties and predict the future development direction of coatings. After referring to a number of material standards and coating materials at home and abroad, it is reorganized and classified. After many times of practice, it is found that not all coatings can use one standard for the classification of test items, and some coatings should also use other classification modes. In order that the test items classified in the material standard of the coating can more accurately reflect the performance of the coating itself, the method shown in Table 7 is adopted

4 formulate and sort out the standards of test methods

through a large number of tests and searching for data, we have accumulated a large amount of data in the process of carrying out production tasks at ordinary times; We communicated with experts of production enterprises, and investigated and studied Tianjin lighthouse coating and Beijing Aviation Materials Institute. Experts affirmed the preparation of the test method for the application period of paint and the innovative paint detection mode. In addition, after communicating with German experts, we learned that the current latest coating specification also includes coating applicability test items, but there is no unified test method, but it is vaguely described in the material specification as "coating can still be used as qualified". Nevertheless, compared with those described in some material standards, the index requirements of the coating applicability test project in China are still stringent. In view of this problem, it plays an important role in appropriately improving the safety and reliability of use and improving the performance of coatings by formulating the standards of the test methods for the applicability of coatings

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