Walter Gerstle¹, Stewart Silling², David Read³, Vinod Tewary⁴, Richard Lehoucq⁵

CMC-Computers, Materials & Continua, Vol.8, No.2, pp. 75-92, 2008, DOI:10.3970/cmc.2008.008.075

Abstract A theoretical framework, based upon the peridynamic model, is presented for analytical and computational simulation of electromigration. The framework allows four coupled physical processes to be modeled simultaneously: mechanical deformation, heat transfer, electrical potential distribution, and vacancy diffusion. The dynamics of void and crack formation, and hillock and whisker growth can potentially be modeled. The framework can potentially be applied at several modeling scales: atomistic, crystallite, multiple crystallite, and macro. The conceptual simplicity of the model promises to permit many phenomena observed in microchips, including electromigration, thermo-mechanical crack formation, and fatigue crack formation, to be More >

Chein-Shan Liu¹

CMC-Computers, Materials & Continua, Vol.8, No.2, pp. 53-66, 2008, DOI:10.3970/cmc.2008.008.053

Abstract Proposed is a time-marching algorithm to solve a nonlinear system of complementarity equations: P_i(x_j) ≥ 0, Q_i(x_j) ≥ 0 , P_i(x_j)Q_i(x_j) = 0, i, j = 1,...,n, resulting from a discretization of nonlinear obstacle problem. We transform the above nonlinear complementarity problem (NCP) into a nonlinear algebraic equations (NAEs) system: F_i(x_j) = 0 with the aid of the Fischer-Burmeister NCP-function. Such NAEs are semi-smooth, highly nonlinear and usually implicit, being hard to handle by the Newton-like method. Instead of, a first-order system of ODEs is derived through a fictitious time equation. The time-stepping equations are obtained by applying More >

Amiya K. Samanta¹, Somnath Ghosh²

CMC-Computers, Materials & Continua, Vol.8, No.1, pp. 43-52, 2008, DOI:10.3970/cmc.2008.008.043

Abstract A procedure has been described to carry out three-dimensional elastic analysis of reinforced concrete beam employing finite element technique, which uses lower order elements. The proposed procedure utilizes 8-noded isometric solid /hexahedral elements HCiS18 with enhanced assumed strain (EAS) formulation, recently developed in the literature, to predict load-deformation and internal stresses produced in case of a simply supported RC beams in the elastic regime. It models the composite behaviour of concrete and reinforcements in rigid /perfect bond situation and their mutual interaction in bond-slip condition considering continuous interface elements at the material level. Although, bond-slip More >

Huanchun Chen¹, Kunigal Shivakumar¹

CMC-Computers, Materials & Continua, Vol.8, No.1, pp. 33-42, 2008, DOI:10.3970/cmc.2008.008.033

Abstract Thermal cycling degradation effect on tensile and flexural properties of Cytec T650 carbon/Lonza Primaset PT-30 cyanate ester composite rods used for gas turbine engine brush seals was evaluated. The composite rods were thermal cycled in air from room temperature to 315°C for 100, 200, 400, 600 and 800 cycles. Each thermal cycle is a one hour period with 28 minutes hold at peak temperature and a high heating/cooling rate of 73°C/min. The composite withstood the first 100 thermal cycles with less than 10% property change. After that, tensile strength and fracture strain as well as More >

B. Yang², V. K. Tewary³

CMC-Computers, Materials & Continua, Vol.8, No.1, pp. 23-32, 2008, DOI:10.3970/cmc.2008.008.023

Abstract A three-dimensional Green's function for a material system consisting of anisotropic and linearly elastic planar multilayers with interfacial membrane and flexural rigidities has been derived. The Stroh formalism and two-dimensional Fourier transforms are applied to derive the general solution for each homogeneous layer. The Green's function for the multilayers is then solved by imposing the surface boundary condition, the interfacial displacement continuity condition, and the interfacial traction discontinuity condition. The last condition is given by the membrane and bending equilibrium equations of the interphases modeled as Kirchhoff plates. Numerical results that demonstrate the validity and More >

Chein-Shan Liu¹

CMC-Computers, Materials & Continua, Vol.8, No.1, pp. 1-16, 2008, DOI:10.3970/cmc.2008.008.001

Abstract In the present work we study numerical computations of inverse thermal stress problems. The unknown boundary conditions of an elastically deformable heat conducting rod are not given a priori and are not allowed to measure directly, because the boundary may be not accessible to measure. However, an internal measurement of temperature is available. We treat this inverse problem by using a semi-discretization technique, of which the time domain is divided into many sub-intervals and the physical quantities are discretized at these node points of discrete times. Then the resulting ordinary differential equations in the discretized More >

Arnab Chakrabarty¹, Tahir Çağin¹

CMC-Computers, Materials & Continua, Vol.7, No.3, pp. 167-190, 2008, DOI:10.3970/cmc.2008.007.167

Abstract The excellent set of properties of carbon nanotube and carbon nanotube-based nanostructures has been established by various studies. However the claimed property values and trends have not been unanimously agreed upon. Using state of the art molecular dynamics and ab initio methods, we have extensively studied the mechanical, thermal and structural properties of carbon nanotubes and carbon nanotube based nanostructures. Additionally this study aims to address the approaches used in various studies to assess the validity and influence of various definitions used for determining the physical properties as reported in earlier experiments and theoretical calculations.… More >

Chih-Wen Chang¹, Jiang-Ren Chang¹, Chein-Shan Liu²

CMC-Computers, Materials & Continua, Vol.7, No.3, pp. 139-154, 2008, DOI:10.3970/cmc.2008.007.139

Abstract In this paper, we propose a Lie-group shooting method to deal with the classical Blasius flat-plate problem and to find unknown initial conditions. The pivotal point is based on the erection of a one-step Lie group element$\mathbf G(T) and the formation of a generalized mid-point Lie group element$\mathbf G(r). Then, by imposing G(T) = G(r) we can derive some algebraic equations to recover the missing initial conditions. It is the first time that we can apply the Lie-group shooting method to solve the classical Blasius flat-plate problem. Numerical examples are worked out to persuade that the novel More >

Xiuqing Qian¹, Yanping Cao², Jianyu Zhang¹, Dierk Raabe², Zhenhan Yao³, Binjun Fei¹

CMC-Computers, Materials & Continua, Vol.7, No.1, pp. 33-42, 2008, DOI:10.3970/cmc.2008.007.033

Abstract In this work, an inverse approach based on depth-sensing instrumented indentation tests is proposed to determine the Young's modulus, yield strength and strain hardening exponent of the materials for which the elastoplastic part of the stress-strain curve can be described using a power function. Numerical verifications performed on typical engineering metals demonstrate the effectiveness of the new method. The sensitivity of the method to data noise and some experimental uncertainties are also discussed, which may provide useful information for the application of the method in practice. More >

Premuzic¹ Z, HE Palmucci¹, J Tamborenea¹, M Nakama²

Phyton-International Journal of Experimental Botany, Vol.76, pp. 103-117, 2007, DOI:10.32604/phyton.2007.76.103

Abstract The addition of chlorine constitutes an economical disinfection method for closed, soil-less systems. Three quantities of sodium hypochlorite (0.55, 5.5 and 11 ppm) were applied to closed, soil-less greenhouse- grown lettuce (Lactuca sativa), to study the effect on its production (fresh weight and dry matter) and some commercial and nutritional quality factors (phytotoxicity, Vitamin C, nitrates). Sodium hypochlorite was weekly added within the nutrient solution, and the chemical properties (pH, EC and chlorides) of the recycled solution were measured. Damage to leaves was evaluated 15 days before harvest. Chlorination produced different effects regarding both production and… More >