Rubber tube has been used to a flexible coupling of life lines for water, gas and electricity, embedded deeply in the earth. Crushing of the rubber coupling due to earthquake motion may often destroy the life lines, causing disastrous accidents to human life.
In this paper, the bending buckling of rubber coupling with finite length is studied analytically and experimentally.
Urethan rubber tube having uniform cross section is provided for the four-point bending test, where both ends of a specimen are closed by a pair of rigid circular cylinders inserted in the spesimen.
Non-linear differential equations for the flattening parameter and the bending curvature are derived by using the energy method.
Finite Difference Method and reiteration method are applied for solving these equations numerically. It is shown that the critical bending moment becomes larger for relatively short rubber tube in length, however, steeply decreases as the length increases, approaching the classical value derived previously by Brazier for an infinitely long tube.
This relationship between the critical moment and the tube length are verified by the experimental rerults.
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