Derivation of Mechanical Properties by Pushing of a Pin into Wood Jan Tippner 1 , Michal Kloiber 2 , Jaroslav Hrivnák 3 Abstract During the structural/technical surveys of built-in wood in historical structures, the priority is to maintain the maximum proportion of the original material. This requires a reliable determination of the extent of damage while also determining the mechanical properties of wood which serves as the basis for the static calculation of the whole of the structure. The paper presents a new diagnostic tool for “in-situ” assessment of timber based on the principle of mechanical resistance against tool (pin) penetration into wood. To verify the proper function of the tool, measuring was conducted using three basic species of softwood. With the aim to discern the variability of properties caused by their distribution along the diameter and the length of trunk, always one complete trunk of spruce, fir and pine was used. The results show a very good correlation of the average force necessary for pin pushing into wood with the wood density and strength ascertained using standard specimens in compression parallel to the grain. Keywords pushing, pin, resistance, mean force, density 1. INTRODUCTION A number of current diagnostic tools and methods use the measurement of resistance against tool penetration into wood mass to describe behavior and properties of wood (Pellerin and Ross 2002). The most widespread resistance method is measuring the depth of pin penetration in which the pin is shot into the material by a constant energy of a spring (indentor) – this can be considered a semi- destructive method (Drdácký et al. 2006). However, the maximum depth of pin indentation is limited due to the construction of the device and thus only superficial properties are measured (Görlacher 1987; Kasal and Anthony 2004). Another alternative of measuring the mechanical resistance of wood is a penetration test based on repeated pin hammering into wood by means of a hammer with a constant energy (Ronca and Gubana 1997). Moreover, there are other resistance methods for wood diagnostics, e.g. resistance microdrilling (Kasal and Antony, 2004) or the screw-withdrawal resistance method (Divós et al. 2011). Instrumented microdrilling differs from the dynamic penetration mainly by the fact that thanks to the gradual penetration through the material we gain an overview of its internal structure. The output is a profile of energy consumption, or a relative resistance, including the elimination of energy consumption caused 1 Jan Tippner, Faculty of Forestry and Wood Technology, Mendel University in Brno, Department of Wood Science, Brno, Czech Republic, tippner@mendelu.cz 2 Michal Kloiber, Institute of Theoretical and Applied Mechanics, Academy of Sciences of Czech Republic, v. v. i., Centre of Excellence ARCchip Telč, Czech Republic, kloiber@itam.cas.cz 3 Jaroslav Hrivnák, Faculty of Wood Sciences and Technology, Technical University in Zvolen, Department of Mechanical Wood Technology, Zvolen, Slovak Republic, xhrivnak@ is.tuzvo.sk