WOOD RESEARCH Volume 67, Number 6, 2022
Endre Magoss, Richárd Rozs, and Sándor Tatai

Evaluation of wood surface roughness by confocal microscopy

The main aim of this study is to define the usability of the confocal scanning optical microscope (CSOM) to evaluate the wood surface roughness. Therefore, systematic investigation was carried out to define the influences of CSOM on the acquisition of 2D surface roughness parameters. Mahr Perthometer was applied to get reference data to estimate the applicability of the CSOM. Because wood roughness parameters measured with stylus and optical methods are not always comparable a calibration method was conducted on a metal calibration etalon. After the calibration process, the roughness profiles taken with the optical and stylus units were much closer to each other and only the optical Rpk parameter was definitely higher due to artificial peaks generated by the optical system. In order to eliminate this measuring failure, the morphological filter option of the optical apparatus may be activated. The surface roughness parameters were measured on planed Scotch pine samples. The planed surface plains were produced with 0.2 mm parallel offset to investigate the structural influence of the single cutting plains. The obtained results show that the average values for Ra, Rq, Rz, Rk, and Rvk are close to each other for both measuring systems, only the optically measured Rpk values must be corrected. The standard deviations, however, are systematically slightly higher for optical system. This may be explained by the higher resolution of the optical system giving more fine profile details. The earlier developed and introduced dimensionless quantities, such as Abbott ratio, are also fully comparable for both systems provided that the optically measured Rpk values are also correct.

WOOD RESEARCH Volume 62, Number 6, 2017
Zsolt Molnár, GÁBOR NÉMETH, Sándor Héjja, Endre Magoss, and Sándor Tatai

The effect of the position of 2D roughness measurement on the roughness parameters by natural wood material

There are notable differences between the 2-D standardized surface roughness parameters depending on the position of the profil of the surface roughness eavluation of natural wood.Therefore it is fundamental to determine which parameters are the least dependent on the position of the measured profil. The dependence of the standardized roughness parameters on the different measuring positions varies. We observed the smallest average dependence at the arithmetic average roughness (Pa) parameter of the P-premary profile, and at the Mr1 (threshold as the minimal Asperities’ height distribution AHD )and Mr2 (threshold as the maximal AHD) parameters and “reduced” height peak amplitude (Ppk) was more dependent. The greatest deviation occurs in the mean roughness depth (Pz), maximum height of the profile (Pt), and the maximum roughness depth (Pmax) values. These three parameters whoed the highest differences in function of the measuring positiions.

WOOD RESEARCH Volume 63, Number 6, 2018
Antal Kánnár, Laszlo Tolvaj, and Endre Magoss

Colour change of photodegraded spruce wood by water leaching

Spruce samples (Picea abies Karst.) were irradiated by strong ultraviolet (UV) light emitter mercury lamp and another series of specimens were treated with the combination of UV radiation and water leaching. The total duration of UV radiation for both series of specimens was 50 days. The colour parameters (CIE L*, a*, b*) were measured and evaluated after both UV radiation and water leaching. The increase of redness value was two times greater than the yellowness increase based on the initial value at the end of 50 days treatment. The leaching partly removed the yellow and red chromophore molecules generated by the UV radiation. The samples become slightly lighter after water leaching. The leached samples increased slightly more in yellowness and redness during the first 4-6 days of UV radiation than those of the dry series. The change of surface roughness of the specimens was monitored by diffuse reflectance infrared spectroscopy, because the change of roughness alters the light scattering properties of the surface. The roughness of the samples increased during the UV irradiation, and the tendency of roughness change mirrored that of yellowness change. The leaching reduced the roughness value in all examined cases. Good correlation was found between the hue angle and the lightness in both dry UV treatment and combined UV treatment and water leaching.

WOOD RESEARCH Volume 65, Number 4, 2020
Endre Magoss, Sándor Tatai, Zsolt Molnár, and Ingrid Fuchs

A calibration method of the laser triangular measuring system to evaluate wood surface roughness

Due to the fact that wood roughness measurement results measured with stylus and optical methods are not always comparable a new calibration method was proposed. In order to compare the surface roughness parameters of the stylus tactile 2D roughness parameters and the optical 3D roughness parameters a systematic experiment has been carried out on fourteen wood species. The essence of this calibration method is the use of metal calibration etalons for Rz = 20 μm and Rz = 30 μm and the filter option of the optical measuring apparatus. After the calibration process, the roughness profiles taken with the optical and stylus units were much closer each to other decreasing the difference in the measurement results of the two systems. Our study prove that the laser triangular method is less usable for the planed wood surfaces.

WOOD RESEARCH Volume 64, Number 3, 2019
Endre Magoss, Zsolt Molnár, Veronika Suri, and Ingrid Fuchs

Evaluating of wetting-induced effects on the surface stability of sanded wood

A sanding is a common woodworking operation to smooth the surface prior to apply surface finish or coating materials. All cutting processes damage the upper layer of wood surface and sanding also creates a deformation zone. This deformation zone is sensitive to artificial or environmental actions, especially to wetting. In order to determine the effect of wetting on the surface properties, to get insight into the dynamics of surface movement as a function of time during the wetting, special 3D surface roughness measurements were carried out and evaluated. For sanding of samples the most common grit sizes were selected and P100 and P180 sand papers were used. Measuring the weight of the samples the dynamics of evaporation of the applied water was also determined. The surface modification after wetting is caused by moisture gradients in the upper layer associated with swelling and shrinkage resulting in permanent deformations. For this layer the most characteristic roughness parameters are the average roughness Sa and the Abbott parameters Spk, Sk and Svk. The extent of roughness variation due to wetting is characterised by the ratio of roughness after wetting to the initial roughness value. The measurement results have shown that the simultaneous infiltration and evaporation rate has a definite influence on the surface roughness modification. The most stable wood species with the least modification were the ring-porous species, following by the diffuse-porous and conifers species. The evaporation rate measured followed the same sequence for wood species investigated.