Purpose
The purpose of this paper is to propose a set of constitutive functions for dried bodies for accurate prediction of the entire deformation process of ceramic products during firing and to present relevant methods for determining their coefficients from a series of respective thermo-mechanical analysis (TMA) tests.
Design/methodology/approach
The function forms of the sintering-induced strain rate, viscoplastic multiplier and elastic modulus are formulated in order with reference to empirical data of relative densities. Separate TMA tests are conducted to identify their coefficients, while a stairway thermal cycle test is carried out to identify the parameters in the densification rate. Then, various finite element analyses (FEA) are performed for accuracy confirmation.
Findings
The performances of the present constitutive functions along with the identified material parameters were validated in comparison with the relevant test results. It has then been confirmed that these functions enable us to some extent to accurately estimate the non-mechanical and mechanical deformations of dried bodies during firing. Also, by performing FEA of an actual sanitary ware product, the applicability and capability of the proposed set of constitutive functions could be demonstrated.
Practical implications
The present methodology with the proposed constitutive functions is a simple, but reliable and practical approach for simulating the deformation process of arbitrary ceramic products subjected to firing and applicable for practical applications in various engineering fields.
Originality/value
The constitutive functions of the viscoplastic multiplier and elastic modulus, which enable us to properly characterize the mechanical behavior of dried bodies subjected to firing, are originally formulated in analogy with that of the sintering-induced strain.
The relationship between distribution of antioxidant and degradation of polymer is investigated on EPDM compounded with IPPD that is a typical amine type antioxidant for vulcanized rubber. IPPD in EPDM homogeneously-dispersed by kneading is used. Because of decomposition by heat while molding and volatilization from surface of vulcanized rubber, more IPPD exists inside of rubber than the surface. At the depth of 0 ~ about 50 m, percolation of water contained with residual chlorine and polymer degradation occur at the same time, IPPD disappears because of its dissolution into the water and consumption by trapping radical generated polymer degradation caused by residual chlorine and heat. In this area the rubber degradation occurs easily, so almost on the surface oxidation degradation progress even though antioxidant exists enough in vulcanized rubber.
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