- 材料 (ISSN:05145163)
- vol.23, no.250, pp.588-592, 1974-07-15
The effects of dimensions and supporting conditions on the compressive strength and deformation of polyvinylchloride pipes under external pressure were discussed. The following four kinds of pipe supporting conditions were used; (A) compression between two steel plates, (B) compression between a steel plate and a concave wooden block, (C) compression between two concave wooden blocks, and (D) compression between two concave hard rubber supporters. The main results obtained are as follows. (1) The relation between the compressive strength P and the dimensions of PVC pipe is given by the following formula, similar to the mid load bending for a both end flxed straight beam with a rectangular section; P=(4σ_b・l・t^2)/(3・Dm)・c_1 (a) where, l, t and D_m are the length, thickness and diameter of pipe, respectively, c_1 the correction coefficient according to pipe supporting conditions, and σ_b the bending stress in kg/mm^2. The value of correction coefficient c_1 was 0.81〜1.35 for A-method, 1.35 for B-method, 8.0 for C-method and 2.3 for D-method, respectively. (2) The deflection δ under elastic deformation is given by the following formula; δ=(P・D_m^3)/(8E・l・t^3)c_2 (b) where, E is Young's modulus in kg/mm^2 of pipe material, and c_2 the correction coefficient similar to c_1. The value of c_2 was 2.22 for A-method. (3) It seems reasonable, therefore, that the theory of straight beam may be applied to the compressive strength and deflection of plastics-pipe under external pressure by using the correction coefficient c_1 or c_2.