Observation and discussion on bolt breakage
Under the macroscopic view, the crankshaft bolts are broken, the fractures are flush, there is no plastic deformation nearby, the section is clean, there is no corrosion product, there are radioactive patterns, the origin of the fracture is point source, and the microscopic topography at the origin of the fracture is rock candy block. Separated along the crystal, the crystal plane of the fracture is flat, there is no deposit, and there is a secondary crack. The morphology of the extension zone is along the crystal along with the dimple, and the final fracture zone is a complete dimple feature.
The composition analysis and microscopic analysis results of the materials meet the bolt technical standards. The hardness test results are higher than the technical standards, which will increase the material brittleness and increase the hydrogen embrittlement sensitivity. From the fracture analysis, the fracture has hydrogen embrittlement characteristics, and the fracture is brittle fracture along the grain boundary, that is, hydrogen brittle fracture. The so-called hydrogen embrittlement, that is, the damage caused by hydrogen infiltration, causes the metal member to fail at a lower angle than the yield limit of the material. Metal materials are attacked by hydrogen during processing and manufacturing or in the environment of use. Since hydrogen atoms have a minimum atomic radius (0. 05 nm), they are easy to enter the metal lattice. Subsequent to the static stress (including the applied, residual and interaction forces), the diffusion is concentrated to the high stress, and the atom is changed into a molecule. In combination with the production process of the bolts, the surface of the parts is finally galvanized. During electroplating, the part acts as a cathode. At this time, hydrogen can be released on the macrocathode or microscopic cathode. The hydrogen produced by the reaction escapes in the form of molecular hydrogen, and some hydrogen ion infiltrates into the interior of the metal. Therefore, in practice, the electroplating solution with less hydrogen embrittlement is used as much as possible, or the method of dehydrogenation after plating is used to minimize the infiltration of hydrogen. If the dehydrogenation treatment is not timely or the process control is improper, it will cause excessive hydrogen infiltration, resulting in hydrogen embrittlement, and eventually the part fracture failure.
It is recommended (1) to strictly control the dehydrogenation process after galvanizing parts. (2) The hardness of the part is controlled near the middle limit of the technical requirements.
Why choose to use the trunking?
The trunking will be pre-laid with wires before leaving factory, and there is no need to lay other wires during installation, It can save labor costs. Linear Trunking Light can realize seamless splicing, and various shapes can be spliced through L/T/X connectors, as shown below
The length of the trunking is generally 1 meter, 1.5 meters and 2 meters. 3 Wire trunking linear lights can only achieve basic lighting. If you need to add emergency, sensor or dimming functions, you can choose 5 wires/7 wires/8 wires/11 wires.
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