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The strength properties of natural rubber vulcanizates, which are widely used in automobile engine mounts and bushes, are important to evaluate the lives of the automobile rubber parts that can withstand together with those of automobile. The tearing energy and flex fatigue life were investigated, with three diffrent types of vulcanizing system (i.e. ‘conventional’, ‘efficient’, and ‘peroxide’ vulcanizing system) in both ‘initial’ and ‘aged’ state. Each stock was made based on same Rheometer torque difference between Tmax and Tmin. Tearing energies were investigated by ‘trouser’ test method using fabric reinforced test pieces over nine different rates of crack propagation. Flex fatigue life was also examined by means of De Mattia flex test. They show that polysulphide type crosslinking, which is commonly known as the most fatigue resistant natural rubber vulcanizate, was not essential to get a high flex fatigue resistance.

Several software packages have been developed for use with minicomputers to decrease the test schedule and cost of modal surveys. The newer development referred to as “single-point random,” appears to have potential cost and schedule advantages, but evaluations of the adequacy of test results and test experience on complex structures are almost nonexistent. The tests, performed on the Mariner Jupiter/Saturn (MJS) spacecraft, provide an additional comparison of the more traditional multipoint sine dwell and the single-point random modal test methods.