Determination of the strength characteristics of a flanged joint with a flat gasket and loose retaining rings using a 3-point bending test

Purpose To evaluate the effectiveness of determining the strength of loose rings made, polymer laminate, using a 3-point bending test of rectangular material specimens differing in form and dimensions from actual structural components. Design/methodology/approach The analysis carried out indicated a method of quantitative evaluation that could be directly related to the operating conditions of the rings. A similarity relation between the critical states of the ring and the specimens subjected to bending tests was presented. The assumed hypothesis of maximum tensile stresses of the rigid outer laminate layers provided the basis for formulating a criterion for the allowable loads on the rings, depending on the assembly tension of the bolts and the operating pressure in the installation. Findings The results of the bending tests, both in the elastic and failure range of the samples, confirmed the validity of the hypothesis about the proportionality of the breaking stresses in the ring and the bending, cuboid sample, made of a similar laminate. Practical implications The area of dimensional optimisation of the joint with regard to its strength and stiffness criterion is indicated. Originality/value The method provides a basis for evaluating the strength and tightness of a flange connection by means of experimental testing of specimens made of a laminate similar to the material of the rings. The results of the 3-point bend tests allow for the substitution of difficult tests of complex assembly components such as rings in a flanged connection, including the operating conditions of the connection in a pressure piping system.