Carbon fiber reinforced polymer (CFRP) is an anisotropic material with outstanding tensile strength in the axial direction but low compressive strength in the radial direction. In the process of line construction, such as wire crimping and conductor clamping, radial pressure failure and slip failure easily occur. This paper applies finite element analysis (FEA) to the parameters influencing the radial stress and displacement in a CFRP core to research the failure modes of the CFRP core. The selected parameters are the interference of the CFRP core, the friction coefficient between the core and inner wedge, and the angle of the inner wedge. The finite element method is applied to analyze a CFRP core with a self-tightening clamp to find the optimum condition parameters so that the CFRP core experiences neither slip failure nor radial pressure failure. From the study, lower interference and larger friction coefficient and angle lead to lower radial stress. The interference has the largest effect on the mitigation of radial pressure failure. For larger interference, a larger friction coefficient and angle mitigate slip failure. According to the analytic results, an interference between 0.02 mm and 0.025 mm and an angle larger than 3°, coupled with a friction coefficient larger than 0.3, best stop slip failure and radial pressure failure. INDEX TERMS CFRP core; finite element analysis; radial pressure failure; slip failure; self-tightening clamp.

<abstract><p>This paper aims to construct a two-grid mixed finite element scheme for distributed optimal control governed by semilinear elliptic equations. The state and co-state are approximated by the $ P_0^2 $-$ P_1 $ pair and the control variable is approximated by the piecewise constant functions. First, a superclose result for the control variable and a priori error estimates for all variables are obtained. Second, a two-grid $ P_0^2 $-$ P_1 $ mixed finite element algorithm is presented and the corresponding error is analyzed. In the two-grid scheme, the solution of the semilinear elliptic optimal control problem on a fine grid is reduced to the solution of the semilinear elliptic optimal control problem on a much coarser grid and the solution of a linear decoupled algebraic system on the fine grid and the resulting solution still maintains an asymptotically optimal accuracy. We find that the two-grid method achieves the same convergence property as the $ P_0^2 $-$ P_1 $ mixed finite element method if the two mesh sizes satisfy $ h = H^2 $. Finally, a numerical example demonstrating our theoretical results is presented.</p></abstract>

The failure cause of the worm drive in the NMRV reducer of the grounding knife-switch mechanism of State Grid was analyzed in this paper. The macroscopic analysis, chemical composition inspection, microscopic metallographic observation, hardness test, SEM analysis were carried out to evaluate the worm gear failure mechanism. The stress distributions of the tooth flank using dynamic contact finite element simulation were obtained based on ANSYS Workbench software. The results showed that an initial crack at the root position of softer worm gear was caused by excessively high impact at the initial stage of meshing in the worm drive, whose value was 308MPa higher than the allowable contact stress of 220MPa. The main reason for the hardness of the worm gear decreasing was that the amount of (α+δ) eutectoids fell and distributed unevenly.