For the simple friction grip joint consists of two joined parts, one of which is tapped and bolted with the other with a bolt, the load capacity (Here, this is expressed by n described below) of the friction grip joint is analyzed using the strength of materials, and FEM analysis is carried out on 10 cases, which result in the following conclusions. [Here, F:Bolt axial tension, μ_{CS} : Friction coefficient on the contact surfaces between joined parts and also on the bolt bearing surface, W_{SCr} : Critical applied shear force without any slip, n : Equivalent number of contact surface (=W_{SCr} /Fμ_{CS}).] (1) Introducing the shear spring constant of the bolt K_{BS} and that of the joined part K_{CS}, the theoretical equation to calculate the load capacity n, which contains only K_{BS} and K_{CS}, is derived. (2) The load capacity n_{th}, calculated by the theoretical equation substituting K_{BS} and K_{CS} obtained through FEM analysis, coincides very well with n_{FEM} obtained through FEM analysis. Therefore, it is concluded that the theoretical equation to calculate n using K_{BS} and K_{CS} is correct. (3)According to this theoretical equation, to increase the load capacity n, it is necessary to develop the joint structure which gives smaller K_{CS}/K_{BS}. (4) The maximum load capacity n=2 is obtained only under K_{CS}=K_{BS} in the case of the concentrated shear load applied on the upper corner of the joined part. (5) The problem left to predict n is to derive the equation that can accurately calculate K_{CS}. (6) From the results of this analysis, the number “q _{F}”, which is described in VDI 2230 Part 2 and corresponds to n, is judged to be too large from the viewpoint of slip.
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