GB/T 39814-2021Test method for impact strength of ultrathin glass—Ball drop method (English PDF)

3.1 Impact strength

The ability of ultra-thin glass or its products to resist impact load is expressed by the energy at the time of impact damage.

3.2 Ultrathin glass products

Components or parts made of ultra-thin glass materials.

5.1 Falling ball impact testing machine

The structure diagram of the falling ball impact testing machine is shown in Figure 1.It consists of a vertical support rod, a horizontal support rod, a positioning laser generator, and a falling ball release device.

Component, base and other components. The drop height range of the steel ball of the falling ball impact tester is 0mm~2000mm; the vertical support rod and the horizontal support rod should be It has sufficient rigidity to ensure that no deformation should occur during the test; the height of the vertical support rod is adjustable, and the resolution accuracy is 1.0mm; the falling ball release device The placement should be electromagnetic, and the deviation between the impact point of the falling ball and the preset impact point should not exceed 3.0mm; the base should be 304 grade and the thickness should be (10± 0.5) mm stainless steel plate, and the upper surface should be flat, and there should be no dents, bumps and scratches visible to the naked eye.

The upper and lower surfaces of the cushion should be smooth, and there should be no dents or protrusions visible to the naked eye.

6.1 Sample preparation

6.1.1 Ultra-thin glass sample

Rectangular specimens should be prepared with ultra-thin glass materials of the same material, the same process, and the same thickness. The length and width dimensions of the specimen are recommended (150±1)mm×(75±1)mm. There should be no visible scratches, damage and other defects on the surface of the sample. The edge of the sample should be thrown Light, and there are no defects such as edge bursts and cracks visually.

6.1.2 Ultra-thin glass product samples

Ultra-thin glass products should be directly used as the sample, and the surface of the sample should not have visible scratches, damage and other defects.

6.2 Number of samples

The number of samples is not less than 30 pieces. When doing Weibul statistical analysis, the number of samples is not less than 50 pieces, including the test process The test result is invalid in the sample.

7.1 Test environment

The test should be carried out in an environment with room temperature and relative humidity (50±20)%.

7.2 Sample handling

Before the test, use a soft cloth and cleaning agent to remove the dust, oil and other impurities on the surface of the sample that may affect the test result, and rinse with distilled water Wash it and place it for at least 4h under the environmental conditions specified in 7.1. The surface of the sample should not be damaged when the sample is processed.

7.3 Impact location

Multi-point impact method is adopted. Divide the sample into nine small squares, and the center point of each small square is used as the impact point of the sample.

The distance between the point and the adjacent impact point is not less than 10.0mm, and the distance between all impact points and the edge of the sample is not less than 10.0mm.

The impact point location is shown in Figure 2.The impact point location can be pre-marked on the sample pad.

7.4 Safety protection

During the test, goggles with side protection should be worn, and gloves should be worn when cleaning broken glass.

7.5 Impact resistance test

7.5.1 Test procedure

The test should be carried out according to the following steps.

a) Remove the glass fragments and other debris on the sample pad and the base.

b) Impact height estimation. Select a piece of sample and place it on the sample pad, adjust the height of the horizontal support rod, and make the bottom of the steel ball away from the sample The surface is 50.0mm, release the steel ball, observe whether the impacted part of the sample is damaged, and do the following treatment according to the damage.

---If the sample is not damaged, on this basis, increase the horizontal support rod up to 50.0mm and continue to impact the sample until Impact the sample to damage, take the corresponding impact height when the above sample is damaged by impact and subtract the value of 50.0mm as The estimated impact height of the next sample test.

---If the sample is damaged at the impact height of 50.0mm, on this basis, lower the horizontal support rod by 10.0mm After that, another sample is selected to continue the test until the sample is not damaged by impact. Reduce the impact height corresponding to the undamaged sample Remove the value of 10.0mm as the estimated value of impact height for the next test. For each impact above, the next impact point should be The distance from the impact point is not less than 10.0mm, and the distance from all impact points to the edge of the sample is not less than 10.0mm.

c) According to Figure 2, use a marker to pre-mark the impact point location on the sample pad. Placing the specimen on the specimen block marked impact Point at the corresponding position, and properly fix the sample with flexible tape on the edge. The sample should be in close contact with the sample pad and subject to impact When the sample does not move. When testing ultra-thin glass products, the side that is susceptible to impact from external objects should be selected as the impact surface.

The impact surface of the flat sample should be kept horizontal, and the whole sample should be kept in a horizontal state when testing the curved sample.

d) Adjust the horizontal support rod until the impact height is the estimated impact height value, accurate to 1.0mm, and the impact height should be from the bottom of the ball to the test The vertical distance of the impact surface.

e) Turn on the laser generator, and then move the sample pad so that the laser projection point coincides with the required impact point of the sample. Test impact point For the sequence, you can choose either side of the sample as the direction, from left to right, and from top to bottom.

f) Place the steel ball on the bottom end of the falling ball release device, turn on the falling ball release button, and make the falling ball impact the surface of the specimen in a free fall.

Each impact point only impacts once. During the impact process, if the rebound height of the steel ball exceeds 50mm, it should be connected in time.

Take it back to avoid the secondary impact sample caused by its fall. If there is a secondary impact sample during the test, the sample will be invalid and another sample will be taken. Re-test one piece of sample.

g) After the impact, check the damage condition at the impact point and take a photo for record.

h) If the sample is not damaged at the first impact point, adjust the impact height, and continue to the next point of impact according to the above steps, and the next point of impact height Increase by 10.0mm in turn until the sample is damaged by impact. If the sample is still not damaged after the 9 points of the sample are impacted in sequence, the sample is tested If the test fails and becomes invalid, take another sample and restart the test according to the above method. For example, after 9 consecutive impacts of 3 specimens are completed If there is no damage, it is recommended to select the maximum impact height of the upper specimen as the estimated impact of the specimen when testing the next specimen. Height value, until the sample is damaged by impact.

i) If the sample has been damaged at the first impact point, the test of the sample will fail and become invalid. Take another sample and start the test again according to the above method.

Test. If three consecutive specimens are damaged after the first impact, when testing the next specimen, it is recommended to select the upper specimen corresponding to the impact.

The impact height value minus 10.0mm~50.0mm is the estimated impact height value of the sample, until the first impact of the sample does not appear Damage, proceed to the next test according to 7.5.1h) method.

Note: Record the damage state of the sample after the impact. During each impact, only observe the damage state of the impact point. If the damage point is not at the impact point, then The sample failed the test and became invalid.

7.5.2 Identification of impact damage of specimen

After the sample is impacted, if one of the following occurs, it is judged that the sample has been damaged.

a) Visually visible contact damage spots on the surface of the ultra-thin glass at the impact point;

b) The sample is broken into two or more pieces;

c) Obviously visible cracks appear on the sample visually.

7.5.3 Determination of the maximum impact height

Select the height value corresponding to the effective sample impact damage specified in 7.5.2 as the maximum impact height value of the sample against the impact of a falling ball.

7.5.4 Impact energy calculation

(1) Perform impact energy calculation.

7.5.5 Data processing

Expressed by the arithmetic mean and standard deviation of valid data, with no less than 15 valid data, if Weibul statistics are required When analyzing, there are no less than 30 valid test data. The average intensity E and standard deviation s are calculated according to formula (2) and formula (3).

7.6 Passability test

Use the specified impact energy or impact height to impact the center of the plate of the sample, and only measure each sample once, and visually check the damage of the sample. Injury situation.