CMC-Vol. 39, No. 2, 2014

Open Access

ARTICLE

A Stochastic Multi-Scale Model for Prediction of the Autogenous Shrinkage Deformations of Early-age Concrete
S. Liu¹, X. Liu^2,3, Y. Yuan², P. F. He¹, H. A. Mang^2,4
CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 85-112, 2014, DOI:10.3970/cmc.2014.039.085
Abstract Autogenous shrinkage is defined as the bulk deformation of a closed, isothermal, cement-based material system, which is not subjected to external forces. It is associated with the hydration process of the cement paste. From the viewpoint of engineering practice, autogenous shrinkage deformations result in an increase of tensile stresses, which may lead to cracking of early-age concrete. Since concrete is a multi-phase composite with different material compositions and microscopic configurations at different scales, autogenous shrinkage does not only depend on the hydration of the cement paste, but also on the mechanical properties of the constituents… More >

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ARTICLE

Rupture and Instability of Soft Films due to Moisture Vaporization in Microelectronic Devices
Linsen Zhu¹, Jiang Zhou², Xuejun Fan²
CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 113-134, 2014, DOI:10.3970/cmc.2014.039.113
Abstract In this paper, a damage mechanics-based continuum theory is developed for the coupled analysis of moisture vaporization, moisture absorption and desorption, heat conduction, and mechanical stress for a reflow process in microelectronic devices. The extremely compliant film has been used in wafer level lamination process. Such a soft film experiences cohesive rupture subjected to moisture absorption during reflow. The numerical simulation results have demonstrated that vapor pressure due to moisture vaporization is the dominant driving force for the failures. The correlation between the vapor pressure evolution and the film rupture observed from the experiments have… More >

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ARTICLE

A Plastic Damage Model with Stress Triaxiality-Dependent Hardening for Concrete
X.P. Shen^1,2, X.C. Wang¹
CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 135-152, 2014, DOI:10.3970/cmc.2014.039.135
Abstract Emphases of this study were placed on the modelling of plastic damage behaviour of prestressed structural concrete, with special attention being paid to the stress-triaxiality dependent plastic hardening law and the corresponding damage evolution law. A definition of stress triaxiality was proposed and introduced in the model presented here. Drucker-Prager -type plasticity was adopted in the formulation of the plastic damage constitutive equations. Numerical validations were performed for the proposed plasticity-based damage model with a driver subroutine developed in this study. The predicted stress-strain behaviour seems reasonably accurate for the uniaxial tension and uniaxial compression More >

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ARTICLE

A Sliding Mode Control Algorithm for Solving an Ill-posed Positive Linear System
Chein-Shan Liu¹
CMC-Computers, Materials & Continua, Vol.39, No.2, pp. 153-178, 2014, DOI:10.3970/cmc.2014.039.153
Abstract For the numerical solution of an ill-posed positive linear system we combine the methods from invariant manifold theory and sliding mode control theory, developing an affine nonlinear dynamical system with a positive control force and with the residual vector as being a gain vector. This system is proven asymptotically stable to the zero residual vector by using an argument from the Lyapunov stability theory. We find that the system fast tends to the sliding surface and then moves with a sliding mode, such that the resultant sliding mode control algorithm (SMCA) is robust against large More >

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