Лако-красочные материалы — производство

Test methods such as ASTM D3166, Standard Test Method for Fatigue Properties of Adhesives in Shear by Tension Loading (Metal/Metal) and ISO 9664 Adhesives — Test methods for fatigue properties of structural adhesives in tensile shear, describe ways to assess the durability of adhesive joints under cyclic loading conditions. In both cases a testing machine, capable of applying a sinusoidal cyclic axial load is required. Depending on the experimental parameters (testing frequency load or displacement — controlled tests) the results can vary, and therefore these parameters should be exactly specified beforehand in the material specification. The testing frequency must be carefully chosen so as to avoid significant heating of the specimen due to its viscoelastic energy dissipation. In ASTM D3166 a maximum frequency of 30 Hz is specified, with specimens being tested at five or more different maximum load amplitudes selected such that failures occur with regular spacing over a range varying from at least 10 000 000 cycles to not less than 2000 cycles. (As a guide, the initial maximum load may be 50% of the strength of the adhesive determined by shear tests beforehand). On completion of the test the location of failure (adhesive or joint material), as well as the failure mode (cohesive, adhesive or mixed fracture) are relevant when assessing the fatigue performance of the adhesive joint.

7.4