Search results for "kuidut"

Determination of Fibre Orientation Distribution from Images of Fibre Networks

2003

We recall two categories of algorithms for estimating fibre orientation distribution from an image of a spatial fibre system. In the first algorithm, the estimate is a magnitude-weighted distribution from angles perpendicular to the directions of the gradients in the image. The second algorithm is based on the scaled variogram of grey values scanned along a sampling line and its relation to the fibre orientation distribution. Using lines in several directions and assuming a parametric model for the orientation distribution, the orientation parameters are estimated numerically from a least-squares type procedure. Two versions of variogram-based methods are used in this work. We compare the p…

Puukuitususpension putkivirtauksen virtausprofiilin symmetrisyys ja sen turbulenttisen alueen mallintaminen

2007

Simulations of the structure and rheology of wet webs

2009

In this Thesis we modified a recently introduced model for fiber suspensions to be applicable to wet fiber networks so as to analyze by computer simulations their structural and rheological properties. These properties were compared, under tensile loading in particular, to those of wet and dry paper. The model used operated at the fiber level, where the dynamics of fiber motion were determined by fiber stiffness and fiber-fiber interactions such as friction and adhesive forces. Water surface tension, inter-fiber contact area, and moisture content all contributed to the latter force. The tensile strength of wet fiber networks could be described in terms of a very simple function of adhesion-…

Characterization of three-dimensional microstructure of composite materials by X-ray tomography

2016

Analysis methods for X-ray microtomographic images of short fibre composite materials were developed. The methods enable estimation of microstructural properties of the material, e.g., aspect ratio and orientation of fibres. Being based on X-ray microtomography and image analysis, the methods are nondestructive and do not require user intervention. In particular, a method for determination of the aspect ratio of fibres was first developed. The method contains an assumption about similarity of the shape of the fibres. The assumption was relaxed in an improved method that can estimate cross-sectional properties of fibres, too, e.g., cross-sectional area. Additionally, the effect of finite ima…