I am still conducting survey analysis on screws. My basic idea about screws is that when installing parts that require maintenance, Bolt fastening is a reason to use it,
I think that it is due to the ease of installation and the simplicity of removal. Against screw loosening which is the point of failure of the screw.Ｉ assumed that we thought that we should use various countermeasures appropriately. According to the result of analyzing the screw trouble, I speculated that a problem occurred due to an appropriate method being not applied. One of the reasons is that some troubles are not correctly analyzed.
So recently, I asked my Japanese college teacher about my doubts of screws.
The summary of the answer of the teacher: Under the operation of the external force about the screw, if the joint surface doesn't cause a separation and a slip, the looseness doesn't happen.
Therefore, to give enough power with the total so as not for the slip to happen to prevent from the looseness of the screw is an essential measure. According to the result of analyzing the screw trouble, I speculated that a problem occurred due to an appropriate method being not applied. One of the reasons is that some troubles are not correctly analyzed.
Therefore, I could not get the results I expected. In other words, we think that the use of screws acknowledged the necessity of maintenance against loosening. So, as an engineer again I wanted to solve this problem. I believe that for screw fastening, the allowable range of screw loosening is accepted. In the previous time, by increasing the bolt length (the length from the bolt seat surface to the first mountain of the nut), by lowering the reduction rate of the bolt axial force by the minute rotation looseness of the nut , the bolt loosening maintenance period We proposed that if we could set the allowable time (product life, periodic inspection time, etc.), we were able to achieve the target of bolt fastening.
In this time we further propose that the effect of lengthening the bolt length is that the torsion spring constant of the bolt can be kept low to be the first advantage. That is, it was presumed that the restoring torque of the bolt due to the twisting of the bolt generated at the final tightening of the bolt fastening greatly influences the rotation loosening of the bolt.
After the reduction of the restoring torque effect, the screw loosening is statically stabilized on the relationship between the friction angle of the screw and the slope effect.
It is generally understood that maintaining the state. However, when there is external vibration, the above balance is lost and screw loosening it happen. I think that the axial force of the bolt is related to the loosening of the screw at this time.
However, experimental verification and theoretical verification has not been done. I would be pleased if you could give me a professor again. Last time, there was an indication about the number of threads, but I think that the condition added is necessary. Assuming that the bolt length (L), the nominal diameter (d) of the bolt and its ratio (R). One of the design criteria of bolt tightening which I would like to propose,
I'd like to propose that "R = L / d ≧ 1".. This is the bolt fastening which is hard to loosen,
We will seek a structure that easily achieves the goal after recognizing the allowable range of screw loosening. Please tell me who has information.
