GB/T 37208-2018Nonmetallic paper based wet type frictional materials (English PDF)

6.5 Determination of wear

After the test samples are soaked, measure and record the thickness of each test sample. For each test sample, measure at least three points (circumferentially equal-divided), these points are permanently marked AND used in the measurement after the test. Record the thickness of each measurement point of each test sample. Use its arithmetic average as the thickness value of the test sample before the test. After completing all the test stages, take out the test samples. Measure and record the thickness of each test sample, at the same measurement point, in the same way. Use the arithmetic mean as the thickness value of the test sample after the test. The thickness difference, before and after the test, is taken as the wear of the test sample. Take the value with the largest wear in a group of test samples, as the reported value.

Use the micron micrometer, which has an accuracy of 0.001 mm, for measurement. The diameter of the measuring head is not less than 3.2 mm.

6.6 Power increment test

The grade test of low-speed power increment test is carried out, according to GB/T 35472.3. The grade test of the high-speed power increment test is carried out, according to GB/T 35472.4.

6.7 Durability test

The durability test is carried out, according to GB/T 35472.5. For the durability test, it shall carry out 200 running-in first; THEN carry out 10000 test cycles, according to the single condition in the power increment stepwise grade test.

7.3 Judgment of results

7.3.1 Appearance quality, flatness, thickness shall be tested piece by piece; it is judged according to Table 5, respectively.

7.3.2 The friction performance is tested by standard samples. When the measured midpoint coefficient, the breakaway coefficient, the ratio of the endpoint coefficient to the midpoint coefficient, the wear all meet the requirements of 5.4, THEN, the above four items of the batch of products are determined qualified. If any item does not meet the requirements of 5.4, it shall use the two sets of standard samples, that have not been tested or used, for two repeated tests. If the two repeated test results meet the requirements of 5.4, it is still judged that the four items of the friction performance of the batch of products are qualified; it shall use the first repeated test data as the reported result. If any of the two repeated test results does not meet the requirements of 5.4, then this item of this batch of products is unqualified.

7.3.3 For the low-speed power increment test grade, the high-speed power increment test grade, the durability test result, the judgment rules shall be determined, through negotiation, between the supplier and the buyer.

7.3.4 When all inspection items are qualified, then the batch of products is determined to be qualified. If any item is unqualified, the batch of products shall be determined as unqualified.

8.1 Marking

The product's packaging carton (box) shall be marked with the product name, model specification, manufacturer name, address, product quantity, this standard number.

8.2 Packaging

8.2.1 The frictional material shall be packed tightly and neatly in a clean, dry, sturdy, durable carton (box).

8.2.2 Each packing carton (box) shall be accompanied by a product qualification certificate.

8.3 Transportation and storage

8.3.1 During transportation, the frictional material shall not be squeezed, […]