D.K. Anding¹

Structural Durability & Health Monitoring, Vol.1, No.2, pp. 95-106, 2005, DOI:10.3970/sdhm.2005.001.095

Abstract The paper deals with the implementation of constitutive equations for isotropic viscoplastic material behaviour into modern Finite Element codes like ABAQUS. ABAQUS provides an user interface called UMAT (USER MATERIAL) for the definition of quite general material behaviour. The user can take advantage of the complete Finite Element code from ABAQUS and has to focus only on the solution of the constitutive equations. Key problems are accuracy and stability of this local solution procedure, which comes from the numerical stiffness of the governing equations (mostly first order ordinary differential equations). The numerical stiffness does not More >

R. Moskovic¹, P. E. J. Flewitt^1,2

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 83-94, 2005, DOI:10.3970/sdhm.2005.001.083

Abstract Consideration of the structural integrity is one of the inputs when evaluating potential solutions to plant problems. Structural integrity assessments of components forming the pressure boundaries of nuclear plant evaluate safety margins against cleavage fracture. These assessments consider the reserve factors between the applied stress and fracture toughness of the material as well as temperature margins between the operating temperature and the temperature at which the steel is ductile as defined by upper shelf behaviour. To carry out these structural integrity assessments, estimates of cleavage fracture toughness are required. The approach presented in this paper… More >

M. Mashayekhi¹, S. Ziaei-Rad², J. Parvizian³, K. Nikbin¹, H. Hadavinia¹

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 67-82, 2005, DOI:10.3970/sdhm.2005.001.067

Abstract The continuum mechanical simulation of microstructural damage process is important in the study of ductile fracture mechanics. An essential feature in these analyses, is the strong influence of stress triaxiality ratio, i.e. the ratio of mean stress to equivalent stress, on the rate of damage growth. In this paper, finite element simulation of damage evolution and fracture initiation in ductile solids will be investigated. A fully coupled constitutive elastic-plastic-damage model has been implemented. The stress update algorithm for the constitutive model is presented together with the consistent tangent operator, which is needed for implicit FEA. More >

P. Horst¹

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 49-66, 2005, DOI:10.3970/sdhm.2005.001.049

Abstract The paper presents a Monte Carlo Simulation method for the assessment of Multiple Site Damage (MSD) and a subsequent attempt to find a way to interpret intermediate results of the Monte Carlo Simulation with respect to the criticality of scenarios. The basic deterministic part of the model is based on the compounding method, which is used in order to gain an acceptable computational effort. Some examples illustrate features of MSD scenarios and this allows to check an approach for feature detection via Wavelet transforms. This Wavelet transform approach shows some positive results in the interpretation More >

D. Gross¹, T. Rangelov², P. Dineva³

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 35-48, 2005, DOI:10.3970/sdhm.2005.001.035

Abstract Scattering of time harmonic waves by a finite crack in a homogeneous piezoelectric plane under plane strain conditions is studied. Using generalized displacements and tractions, the problem is described by a non-hypersingular traction based boundary integral equation method (BIEM). The fundamental solution is derived in closed form by Radon transforms. As a typical example, the procedure is applied to a straight crack under incident longitudinal waves and under vertically polarized shear waves. The K-factor results are compared with those from the literature for a special case. Furthermore, their dependence on parameters like frequency, angle of More >

G. Dhondt¹

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 21-34, 2005, DOI:10.3970/sdhm.2005.001.021

Abstract An algorithm is described which allows for the automatic calculation of crack propagation due to cyclic loading under mixed-mode conditions. The core of the procedure deals with the insertion of an arbitrarily formed crack into a virgin 20-node brick element mesh, thereby generating new quadratic bricks. One especially difficult aspect is the extension of the triangulation of the crack surface up to the boundary of the crack front elements. In the present article the technique is applied to linear elastic calculations using the stress intensity factor concept and a Paris-type law. However, other crack propagation More >

S. N. Atluri¹

Structural Durability & Health Monitoring, Vol.1, No.1, pp. 1-20, 2005, DOI:10.3970/sdhm.2005.001.001

Abstract The solution of three-dimensional cracks (arbitrary surfaces of discontinuity) in solids and structures is considered. The BEM, developed based on the symmetric Galerkin BIEs, is used for obtaining the fracture solutions at the arbitrary crack-front. The finite element method is used to model the uncracked global (built-up) structure for obtaining the stresses in an otherwise uncracked body. The solution for the cracked structural component is obtained in an iteration procedure, which alternates between FEM solution for the uncracked body, and the SGBEM solution for the crack in the local finite-sized subdomain. In addition, some crack… More >

K.Y. Volokh¹

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 77-86, 2005, DOI:10.3970/mcb.2005.002.077

Abstract Recently Volokh and Lev (2005) argued that residual stresses could appear in growing arteries because of the arterial anisotropy. This conclusion emerged from a continuum mechanics theory of growth of soft biological tissues proposed by the authors. This theory included Lagrangian constitutive equations, which were formulated directly with respect to the reference configuration. Alternatively, it is possible to formulate Eulerian constitutive equations with respect to the current configuration and to 'pull them back' to the reference configuration. Such possibility is examined in the present work. The Eulerian formulation of the constitutive equations is used for… More >

Dimitrije Stamenovic´ ¹

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 69-76, 2005, DOI:10.3970/mcb.2005.002.069

Abstract It is well established that adherent cells change their orientation in response to non-uniform substrate stretching. Most observations indicate that cells orient away from the direction of the maximal substrate strain, whereas in some cases cells also align with the direction of the maximal strain. Previous studies suggest that orientation and steering of the cell may be closely tied to cytoskeletal contractile stress but they could not explain the mechanisms that direct cell reorientation. This led us to develop a simple, mechanistic theoretical model that could predict a direction of cell orientation in response to More >

X. Neil Dong^1,2, Xiaohui Zhang¹, X. Edward Guo¹

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 63-68, 2005, DOI:10.3970/mcb.2005.002.063

Abstract In human cortical bone, cement lines (or reversal lines) separate osteons from the interstitial bone tissue, which consists of remnants of primary lamellar bone or fragments of remodeled osteons. There have been experimental evidences of the cement line involvement in the failure process of bone such as fatigue and damage. However, there are almost no experimental data on interfacial properties of cement lines in human cortical bone. The objective of this study is to design and assemble a precision and computer controlled osteon pushout microtesting system, and to experimentally determine the interfacial strength of cement… More >