Development And Implementation Of The Damage Constitutive Model Of Refractory Based On Micro Mechanics

The improvement of the life of lining is an important approach to reduce the consumptionof the refractory. Meanwhile, the numerical simulation is an effective method to study how toimprove its life. However, the traditional methods and strength evaluation can not apply anymore because of the complex macro non-linear mechanical behavior and the damage of therefractory material reflected from the micro-heterogeneity, which becomes the major bottleneckto restrict the application of this technology. Therefore, it is essential in the research of how toimprove the life of the lining to study the damage mechanism, predict the damage of the liningmaterials and settle the difficulties of lack of constitutive equation and failure criterion in theanalysis of strength.The mechanical behavior of the magnesia-carbon refractory has been investigated using anAcoustic Emission (AE) unsupervised pattern recognition procedure and a frequency-energycoupled analysis from three aspects of micro mechanical modeling, experimentalcharacterization and the embedment into the construction of the damage constitutive equations.Main works and achievements of the thesis are as follows:1. Based on the micro mechanics, the mechanical performance of the matrix is first studiedAiming to the apparent influence of the matrix to the performance of refractory, the matrixis predicted and the reason for the discrepancy of it is then investigated from the microconstruction and constitution. It is discovered that the performance of the matrix makes a hugeinfluence on that of the refractory, which provides a new method in the evaluation of themechanical performance of the refractory.2. An innovative method on simulating the asymmetry nonlinear damage mechanism of therefractory is put forwardBased on the assumption of uniform temperature, the two kinds of load of compression andtension are endowed with two different kinds of damage models. In the tension state, the matrixis gradually amalgamated with stomata, at the same time, the aggregate is “swallowed” by theamalgamated matrix; On the other hand, in the compression state, only the matrix isamalgamated with stomata and the aggregate remains unchanged. According to the hypothesisproposed, the damage is simulated by the improved Generalized Self-Consistent Scheme (GSCS).Contrast to the experimental data, the numerical results indicate that the introduction of thedamage hypothesis is feasible, which avoids the complicated damage discriminant and providesa new method on the simulation of the damage mechanism of the refractory.3. A micro damage interfacial model is put forward to depict the extent of the damageThe damage mechanism is further investigated from the interface aspect combined with thecomposite sphere assemblage (CSA) and the depiction of the damage evolution as well as the temperature in virtue of characteristic parameter is put forward and inbedded into the damageconstitutive model in form of the subroutine. In virtue of the model, the influence of the damageof the interface to the behavior of the refractory could be directly descried and the interactionbetween the interface and the macro behavior is built, which provides a new method in theevaluation of the mechanical performance of the refractory.4. The damage pattern recognition and feature extraction of the refractory is put forwardThe mechanical behavior is tested with the signal processing method in order to characterthe damage of the material. The method of coefficient analysis of the wavelet energy spectrum iscarried to divide the damage into three periods and the power spectrum analysis is used to extractthe damage characteristics. The centroid energy is put forward as the characteristic parameter,which will be as the input of the damage function and embedded into the construction of themicro damage constitutive model. Avoiding the restrict of the traditional AE data processing, thismethod gives an overall depiction of the damage from the damage pattern recognition andfeature extraction.5. The micro damage model is establishedIn virtue of the conclusions of the theoretical part and the depiction of the experiment, themicro damage model is established. The same damage periods are used in the damage model, thedamage function d is defined and embedded into the construction of the damage constitutiveequations through the UMAT tool in the software ABAQUS to investigate the nonlinearmechanical behavior. At the same time, the interfacial damage model based on the temperature isappended on the damage constitutive model in the form of field variable. The numerical resultsindicate that the compressive result agrees well with the experiment, whereas the M.O.R.strength is larger than the experiment because the tensile constitutive equation is not consideredhere. Combining the theoretics with the experimental processing, the study of the damage of therefractory presents system and consistency, which sets a good foundation for the research of thedamage behavior of the material.