Assessement of tensile strength of graphites by the Iosipescu coupon test

Autor(es)

Luis Guilherme Borzani Manhani ^[1] ; Luiz Claudio Pardini ^[2] ; Flamínio Levy Neto ^[3]

Afiliação do(s) autor(es)

^[1] Centro Técnico Aeroespacial. Instituto Tecnológico de Aeronáutica. Depto. Eng. Aeronáutica e Mecânica - Brasil

^[2] Centro Técnico Aeroespacial. Instituto Tecnológico de Aeronáutica. Divisão de Materiais - AMR - Brasil

^[3] Universidade de Brasília. FT. Departamento de Engenharia Mecânica - Brasil

• Tipo de documento: Artigo Científico
• Fonte: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 10, n. 3, p. 233-239, 2007-09-00.

Resumo

Polycrystalline graphites are widely used in the metallurgical, nuclear and aerospace industries. Graphites are particulated composites manufactured with a mixture of coke with pitch, and changes in relative proportions of these materials cause modifications in their mechanical properties. Uniaxial tension tests must be avoided for mechanical characterization in this kind of brittle material, due to difficulties in making the relatively long specimens and premature damages caused during testing set-up. On other types of tests, e.g. bending tests, the specimens are submitted to combined stress states (normal and transverse shear stresses). The Iosipescu shear test, is performed in a beam with two 90° opposite notches machined at the mid-length of the specimens, by applying two forces couples, so that a pure and uniform shear stress state is generated at the cross section between the two notches. When a material is isotropic and brittle, a failure at 45° in relation to the beam long axis can take place, i.e., the tensile normal stress acts parallel to the lateral surface of the notches, controls the failure and the result of the shear test is numerically equivalent to the tensile strength. This work has evaluated a graphite of the type used in rocket nozzles by the Iosipescu test and the resulted stress, ~11 MPa, was found to be equal to the tensile strength. Thus, the tensile strength can be evaluated just by a single and simple experiment, thus avoiding complicated machining of specimen and testing set-up. (AU)

• Processo FAPESP: 00/04359-3 - Propriedades estruturais de grafites para aplicação em gargantas de tubeiras de foguetes a propelente sólido
• Beneficiário: Luis Guilherme Borzani Manhani
• Modalidade de apoio: Bolsas no Brasil - Mestrado