A finite element model for asymmetric creep behavior of ceramics

The design of fibre reinforced refractory castable structures for high temperature applications requires the characterisation of the material creep behaviour. As many other heterogeneous ceramics, these materials creep faster under tensile stresses than under compressive ones because of the motion of hard particles in a soft matrix. Bending tests have been performed to characterise the creep behaviour of the considered material, and 3D digital image correlation is used to obtain strain fields after interrupted tests. The position of the neutral axis, defined here from the residual inelastic strain field, allows to highlight the asymmetry of creep and to evaluate the asymmetry ratio.

Section: Introductionmentioning

confidence: 99%

Applicability of image correlation techniques to characterise asymmetric refractory creep during bending tests

Dusserre

Nazaret

Robert

et al. 2013

“…The asymmetric response is governed by the sign of the largest principal stress in magnitude. Lim et al 24 have pointed out that this model does not seem plausible when the difference in magnitude of tensile and compressive principal stresses is very small. Consequently, they propose that the viscoplastic strain rate is the sum of three viscoplastic strain rates developed, respectively, by the three principal stresses, each strain rate depending on the sign of the corresponding principal stress.…”

Section: Introductionmentioning

confidence: 99%

Modelling of high temperature asymmetric creep behavior of ceramics

Blond

Schmitt

Hild

et al. 2005

An extension of the Bingham-Norton's rheological model accounting for high asymmetric tensile-compressive creep behavior is proposed for ceramics subjected to high temperature loadings. Such behavior is observed in heterogeneous ceramics made of grains having a high creep resistance embedded in a softer glassy phase. Two mechanisms of deformation are introduced: namely, under compressive stresses, grain facets are in contact and transmit the load, whereas under tensile stresses the grains are separated and the glassy matrix transmits the load. It leads to a difference in elastic stiffness and strain rate under tensile and compressive stresses. A new three-dimensional constitutive model is developed considering an additive decomposition of the stress tensor into a positive and negative part. Each stress tensor is the driving force of one mechanism of deformation that is characterized in a classical manner. A simplified identification of the model is performed at high temperature on a bauxite-based refractory, which is used in steel ladle linings. It is shown that for this ceramic few material parameters are sufficient to account for major differences of behavior observed in compression tests and three-point bend tests.

“…In this framework, accounting for the well-known asymmetry of ceramics creep behaviour is a key feature, from all points of view: experimental characterization, modelling and parameter identification. The tension/compression asymmetric creep of ceramics at high temperature is generally attributed to preferential damage [1] or cavitation [2,3] in tension, or to the motion of solid particles in a glassy phase during creep deformation [4].…”

Section: Introductionmentioning

confidence: 99%

“…Many uniaxial creep laws exist that relate the strain rate to the applied stress. Some authors propose to explicitly account for the asymmetry by combining two different behaviours depending on the sign of the stress [2,6]. More generally, tri-axial stress fields usually consider that the strain rate tensor derives from pseudo-potential, function of the stress field, and is proportional to a scalar function that describes the uniaxial creep law.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigation of the asymmetric primary creep of a fibre reinforced refractory concrete at 1200 °C

Dusserre

Valentin

Nazaret

et al. 2016

Tension/compression asymmetry is a key feature of the creep behaviour of ceramics at high temperature. This paper investigates the capability of Drucker-Prager creep model, based on a sensitivity of the equivalent creep stress to the pressure, to account for the creep behaviour of a refractory concrete subjected to compression and bending. A relevant calibration procedure is proposed. The analysis mainly focuses on the associativity of the creep flow. A profile analysis of a compressed sample allows concluding that the creep flow is dilatant and thus associated. A discussion on the neutral axis shift during bending creep is carried out with the model calibrated on the experiments.