Dynamic hardness of wood – measurements with an automated portable hardness tester

Abstract

A research group on forest products from School of Agriculture – Sao Paulo State University. Brazil developed a portable hardness tester for wood, which is based on a displacement transducer and an embedded electronic processor for dynamic evaluation of hardness. This paper presents the results of calibration tests of the equipment, carried out on seven species of Eucalyptus. A new methodology for dynamic hardness calculation has been introduced, which relays on the reaction force of the indentation, while the measurements of indentation depth are performed under load. A moderate to strong linear correlation to Janka hardness and its variations were found. This new approach avoids the classical problems of Brinell hardness test in terms of “sinking-in” (causing diffuse edges) and elastic recovery of the indentation.

Dynamic Hardness of Charcoal Varies According to the Final Temperature of Carbonization

“…DH of wood and charcoal were determined by an automated portable hardness tester, DPM3 (Figure A), according to a procedure fully described in the study by Assis et al…”

“…The equipment DPM3 was originally developed for testing wood specimens. According to Assis et al the energy of indentation of a mass of 1 kg dropping 20 cm is 1.96 J. However, because charcoal is a brittle material, the use of the DPM3 device was adapted: the dropping component was released from 10 cm height for the analyzes in the charcoal (instead of 20 cm, commonly used for wood tests).…”

“…A Brazilian research group has developed a new device for evaluating dynamic hardness (DH) in wood and wood products . The portable equipment is based on a displacement transducer and an embedded electronic processor and can be applied to charcoal specimens to evaluate their mechanical resistance.…”

Vpliv vlažnosti na mikrotrdoto smrekovine, določeno z vtiskanjem

“…Med mehanskimi lastnostmi ima trdota lesa mnogokrat zelo velik pomen za njegovo uporabo (De Assis et al, 2017). Trdota lesa je tako na primer pomembna na področjih uporabe kot so lesene talne obloge, bolj obremenjene površine pohištva (pulti, mize ipd.…”

“…Ta se lahko izvaja na več načinov obremenjevanja (z razenjem, rezanjem, obrabo ter dinamičnim in statičnim vtiskanjem) in s telesi različnih oblik (okrogla, piramidna, stožčasta, cilindrična, iglična) (Broitman, 2017). Trdota lesa se največkrat ugotavlja bodisi z metodami po Brinellu (CEN, 2020), po Janki ali po Monninu (De Assis et al, 2017;Scharf et al, 2022). Pri navajanju vrednosti trdote različnih materialov je zato vedno potrebno navesti tudi metodo, po kateri je bila trdota izmerjena.…”