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Bolts Factory Introduces The Precautions For The Stress Fracture Test Of Fasteners

May 13,2021 / Industry News, News / Author: ShengKui

Bolts Factory introduces the precautions for the stress fracture test of fasteners:


1. Before the test, install the sample in the pre-prepared test tooling. When the sample is installed, no non-axial stress should be generated. When testing bolts or nut components, at least two complete threads should not be screwed together.


2. Unless otherwise specified, the longest test duration should be 24h. For research work, the test can be carried out until the sample is broken.


3. The temperature fluctuation range of the sample in the heating furnace during the whole test period is generally within the range of 13% when the temperature is not higher than 650℃) or t 49C (the temperature exceeds 65090).


4. After reaching the test temperature and the specified temperature gradient, keep it warm for at least 30 minutes to further stabilize the temperature and load it steadily within 1 minute to protect the sample from impact and overload.


5. The thermal joint of the thermocouple should be close to the sample and firmly fixed. The thermocouple should be close to the sample, and its contact should be tied to the sample with asbestos tape. The temperature indicated by the thermocouple should be the temperature of the sample. Prevent thermal radiation from causing inaccurate temperature indications by thermocouples. It is forbidden to weld thermocouples to the specimen.


6. If the test piece is long enough, a thermocouple should be installed at both ends and the middle. If the length of the polished rod of the fastener is less than 50mm, the thermocouple is allowed to be tied to the chuck near the sample. In this case, the temperature reading range of the thermocouple at both ends is allowed to be equal to the first

7. Two times the range of change specified in the article.


Result judgment

1. Apply a load to the sample (the stress fracture load imposed by the standard). After maintaining the standard for a specified time at the highest operating temperature, the sample does not break, then the sample meets the requirements; otherwise, the sample breaks, it is judged as unqualified.


2. If any temperature change during the test exceeds the specified range of the standard, the test is invalid, and the test shall be re-tested with a sample.


3. The sample installation is skewed or the force is abnormal. The test is invalid, and the test should be repeated.