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Although nondestructive ultrasonic technologies have been applied in laboratory and field tests in the field of heritage conservation, few studies have quantified the relationship among the real microstructures, micromechanical properties, and macroscopic acoustic responses of earthen-site soils. This paper develops a micromechanics-based multiscale model for quantitatively exploring the ultrasonic propagation characteristics of elastic waves in untreated and consolidated earthen-site soils. Scanning electron microscope images and image processing technology are integrated into the finite-element simulation. The effects of microstructure and wave features on the acoustic characteristics of soils are quantitatively investigated under pulsive loading. The simulation results of untreated and consolidated soils are efficiently compared to ultrasonic test data. It is demonstrated that the integration of microstructure image processing and multiscale modeling can predict the ultrasonic pulse velocity well, which improves the accuracy of laboratory testing and field monitoring and better serves the evaluation and implementation of engineering practice in the field of heritage conservation. [ABSTRACT FROM AUTHOR]

The use of numerical modelling allows us to shorten the time for development of new technologies and to optimise the existing ones in view of final material properties. The paper presents the modelling of shape rolling of 5 mm round bars in diamond and oval grooves. Modelling scheme consists of three stages. The first stage is a development of rolling schedule, which is based on finite-element method simulations. The schedule design begins from the last pass. The paper presents the schedule developed for the last six passes. Then, in the second stage, finite-element method simulations were fulfilled in the proper rolling sequence. The aim of this stage is obtaining the thermomechanical parameters of the process. These parameters are transferred to frontal cellular automata model that takes into account the deformation and simulates microstructure evolution. Some results of finite-element method and frontal cellular automata modelling are presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to model the creep behavior of cement paste at early ages. The creep behavior is simulated by applying a time-varying generalized Maxwell model on the individual elements of a finite-element mesh of a simulated three-dimensional microstructure and compared with results in the literature. All mechanical properties of the constituent phases are taken from literature and Maxwell chain parameters are obtained by fitting the intrinsic creep of calcium silicate hydrate (C-S-H). A reasonable agreement between the simulations and the experimental results are obtained by assuming a constant C-S-H density of 2.0 g=cm³. It was found that better agreements could be obtained at low degree of hydrations, by assuming a loosely packed C-S-H growing in the microstructure. It was also found that the short-term creep characteristics of C-S-H from nanoindentation can be used to reproduce macroscopic creep at least over a few days. The results show how numerical models can be used to upscale phase characteristics to macroscopic properties of composites. [ABSTRACT FROM AUTHOR]

Locally averaged random fields can be used to represent composite material properties at an intermediate scale. These types of fields provide the basis for stochastic simulation to generate nominally identical realizations of random composite microstructures to be used in reliability analysis. One challenge in choosing an appropriate local averaging technique and mesoscale length parameter is the difficulty of quantifying the accuracy of the locally averaged model. Although mesoscale models may offer advantages over the use of a representative volume element (RVE), particularly in regions of high stress gradients, mesoscale approximations do not converge to an effective medium, so the accuracy of the mesoscale representation cannot be quantified. In this paper, a matrix norm error is developed to test locally averaged material property approximations where loading is not specified a priori. This norm-based approach illustrates the advantage of local averaging over global averaging when small-scale variation in load may be present. This metric provides a basis for comparing locally averaged material property approximations of a benchmark composite microstructure. [ABSTRACT FROM AUTHOR]