Bolt, High strength bolts, Screw
The experimental load is an axial loading load. Under this load, the nut must not show any signs of thread peeling or fracture. For testing, the experimental load is a value; For applications in design, the experimental load is maximized.
During the testing process, the experimental load is loaded onto the nut to be tested through axially loaded test bolts or machine tool spindles. When the load is removed, the nut must be able to be freely removed from the bolt or spindle. The latter requirement is very interesting as it proves that the degree of twisting of the threads is not sufficient to bond the engaged threads together. Tests have shown that thread bonding occurs when the external load reaches 95% of the load causing thread peeling. In most nut strength grade standards, the experimental load of the nut is expressed in pounds per square inch using the term "stress". When calculating the actual experimental load in pounds, the experimental stress (psi) should be multiplied by the force area. The last point is important: except for ordinary stress areas, the experimental load is independent of the designated external Threaded fastener. Cone test load The taper test load is the axial outward load that the nut must bear. During the process of bearing the load, the nut must not have thread peeling or inner wall rupture. During the testing process, the nut was installed on a hardened 120 piece conical gasket. The purpose of placing conical washers is to have a strong impact on the expansion of the inner wall of the nut when subjected to axial force. If the nut fails the test, it is usually due to a broken inner wall rather than peeling off the nut. Nuts used in high-temperature environments, including those in ASTMA194, should undergo conical experimental load testing. In addition, the standard for the bearing capacity limit of discontinuous surfaces of nuts defines the conical experimental load test of nuts. Passing the test means that the joints on the nut have not reached the level that affects the working function of the nut. The calculation of the experimental load on the nut cone can also be done by multiplying the specified axial experimental load by a coefficient (0.3-1D). Where D is the nominal diameter of the nut, in inches. Cone experimental load testing is currently the best testing method for identifying different lattice nuts, and it will be considered a feasible requirement until better identification techniques are available. hardness Hardness is an important mechanical property of nuts. This is not only the convenience of hardness testing, but also the only criterion for measuring the acceptability of nuts with experimental loads exceeding the ability of ordinary tensile strength testing. Unlike external Threaded fastener, there is no definable relationship between the hardness and strength of steel nuts or nuts made of other metal materials. The reason is the influence of nut geometry size on the controllability of nut strength. Generally speaking, experimental load testing can be conducted on nuts with a specified experimental load less than 12000 psi. For nuts with higher strength, testing must be conducted based on the minimum hardness value. In addition, the strength level of nuts requires hardness testing of all sizes and grades of nuts to ensure that their hardness does not exceed the specified minimum value. These are particularly important for nuts that have undergone heat treatment. They can prove that the nuts have been properly treated to eliminate any possible embrittlement.
