POtLSOUTIOFORP normal stress in the r direction is called radial normal stress denoted by o. normal stress in the 0 direction is called tangential normal stress ss denoted by oes shear stress is denoted by I-o, stipulation of sign of each stress component are similar to ones in rectangular coordinates. Body force components of radial and hoop are denoted by k and Ke respectively. Fig 4-1 Considering equilibrium of an unit O叉 element, there have three equilibrium equations fro+.gp dr dr ∑F=0.∑F=0.∑M=0 o+-rdr ar Fig 4-1 99 Considering equilibrium of an unit element,there have three equilibrium equations: r r r r d       r r r r r d              d          d r r     d r r  dr K Kr y x o P A B C Fig.4－1 Fr  0,F  0, M  0 normal stress in the direction is called radial normal stress denoted by ;normal stress in the direction is called tangential normal stress denoted by ;shear stress is denoted by ,stipulation of sign of each stress component are similar to ones in rectangular coordinates.Body force components of radial and hoop are denoted by and ,respectively. Fig.4-1.  r     r Kr K r