Research On Creep Crack Growth Of Nonlinear Viscoelastic Body

Increasingly widely use of nonlinear viscoelastic materials, use of materials under extreme conditions, along with frequent occurrence of delayed catastrophic accidents, all these make the study a pressing problem of initiation and crack growth of nonlinear viscoelastic fracture. Because of the complexity of nonlinear viscoelastic fracture, experiments are often introduced.The main purpose of this paper is to study crack growth rate of a class of nonlinear viscoelastic materials under the condition of constant load and small-strain.In this paper:The new test program is raised by referencing the existing test programs and by our trial and error; In the new test program, facilities involved in the nonlinear viscoelastic crack tests are relatively few, the test process is relatively simple and the data obtained from the experiments are credible. On this basic, the calculation of J integral of nonlinear viscoelastic double cantilever beams specimens and the parameter of fracture work of corresponding nonlinear viscoelasticity are derived. Finally, prediction and experimental result are compared.In details:1. The advantages of double cantilever beams specimens in nonlinear viscoelastic crack growth test are proved. Using these specimens, the relatively long time of crack growth process is obtained, and calculation of J integral is relatively simple.2. The two useful shapes of modified polypropylene specimens and their dimensions in nonlinear viscoelastic crack growth test are proposed. A simple loading system, which can avoid later instability, was applied for the first time.3. After more than four months continuous test, useful data have been obtained.4. Relation graphs such as between crack length and time, crack growth rate and time, crack growth rate and crack length are plotted.5. J integral of nonlinear elastic double cantilever beam specimens is calculated.6. The relationship between J integral of nonlinear elastic double cantilever beam specimens and crack growth rate of nonlinear viscoelastic double cantilever beam specimens is derived.7. Predictions of theory and results of experiments are compared, and what cause error is discussed.