Answer
Ƙarƙashin faɗaɗa zoben riƙewa na karkace yana faruwa lokacin da aka shimfiɗa zoben fiye da iyakar sa na roba yayin shigarwa a kan ramin rami ko cikin rami. Wannan yana haifar da nakasar filastik ta dindindin, ma'ana zoben ba zai dawo zuwa ainihin diamita na 'manne' ba, wanda zai haifar da sako-sako a cikin tsagi. Matsakaicin diamita na shigarwa $D_{max}$ yakamata a ƙididdige shi ta yadda damuwan fiber bai wuce ƙarfin yawan amfanin ƙasa $\sigma_y$. Rigakafin ya ƙunshi yin amfani da madaidaicin madauri ko hannun riga don shigarwa, wanda ke sarrafa faɗaɗa zuwa takamaiman iyaka. Bugu da ƙari, dabarar damuwa yayin faɗaɗa shine $ S = \ frac {E \cdot t \cdot (D_s - D_i)}{(D_m^2)}$, inda $D_s $ shine diamita na shaft kuma $ D_i $ shine diamita na cikin kyauta na zobe. Idan $S > \sigma_y$, zoben ya lalace.
