Ferenc Divos

The effect of gamma irradiation on the MOE of various species

Gamma irradiation is a simple and effective method to sterilize wood and stop fungal decay. Unfortunately, little is known of the effect of this method on other properties of wood. The purpose of the present study was to establish the relationship between irradiation dosage and the elastic characteristics of wood. The longitudinal and transverse dynamic MOE of five wood species were measured periodically between subsequent irradiation phases. There was a steady decrease in MOE as gamma dosage increased, for all species included. The extent of this decrease was different between the examined species. The experimental data suggests that the MOE of lower density species decreases more sharply than that of higher density ones. Interpolation between the experimental data points shows that the necessary dose for fungal sterilization does not significantly reduce the MOE of the species involved in this study.

Delamination Evaluation of in-Service Glulam Beams and other Structural Members Via Ultrasonics

The importance of nondestructive techniques for assessing the internal conditions of structural members is generally accepted for old or more recent buildings (Ross and Pellerin 1994; Pellerin and Ross 2002, Tanaka et al. 1998; Brashaw et al. 2005; Wacker et al. 2007). Efforts to preserve buildings that have nationally significant importance have been based on the development of nondestructive techniques able to assess their mechanical performances (Wang X and Wacker 2006; Sandoz and Benoit 2007; Lee et al. 2007; Divos et al. 2007). The overall goal of these efforts is to preserve to the maximum possible extent of the historical materials used for the monuments. On the other hand, in recent years, the stability of existing glulam structures became an important issue after the collapse of some of the early structures. For example, in Germany on Jan.2, 2006, 15 people, most of them children on a school holiday, died when the roof of a skating rink fell in the Bavarian town of Bad Reichenhall, after heavy wet snow falls (Associated Press 2006).

Utilization of Fourier transform of the absolute amplitude spectrum in wood anatomy

In this study we present the Fourier transform (FT) of the absolute amplitude spectrum for direct application to wood anatomy. In spite of its simplicity, to our knowledge there is no reference in the literature regarding the use of repeated FT of an arbitrary vibration.

Characterization of inhomogeneity perpendicular to the surface of composite boards

To characterize the vertical inhomogeneity of composite materials, the ratio of the bending and longitudinal Modulus of Elasticity of the material is proposed. Veneer coated MDF board was used for the experiments. Very good correlation was found between the veneer and MDF layers modulus elasticity ratio and the proposed inhomogeneity parameter.