Welding time as an important factor of beech welding/Vrijeme trajanja zavarivanja kao vazan cimbenik zavarivanja bukovine

Bonding of wood by virtue of wedge, without any adhesives and welding, has been done for centuries. If such wedge (in this research wood dowels) are rotated during the bonding with the surface (in controlled conditions) at certain parameters, a firm joint is formed. Welding of wood is a process where chemical and physical reactions take place, heat is formed during the friction that melts and softens the structure of wood, and a firm joint is formed by cooling of the melt. The paper shows world findings so far, as well as the results of our own research of the influence of welding process on the dowel embedded force between the beech wood dowel and the beech surface. The joints with the best results concerning the dowel embedded force (4994 N) were the joints where the process of impressing wood dowels lasted from 0.56 to 0.9 s (with each turn of the wood dowel, the movement was 1.41 to 0.88 mm) and the lowest dowel embedded force (2869 N) was recorded when the duration of the impressing lasted from 1.81 to 2.61 s. The average embedded force of glued spirally grooved dowels amounts to 5028 N. Key words: welding of beech, welding time, strength of the welded joint, dowels, embedded force Spajanje drva klinovima bez ikakva lijepljenja i zavarivanja bilo je koristeno stoljecima. Ako ti klinovi (u ovom istrazivanju mozdanici) rotiraju prilikom spajanja s podlogom (u kontroliranim uvjetima), uz odredene parametre nastaje cvrsti spoj znatne cvrstoce. Zavarivanje drva je proces u kojemu se zbivaju kemijsko-fizikalne reakcije, zbog trenja nastaje toplina koja tali i omeksava strukturu drva, a hladenjem tako nastale taline dobiva se cvrsti spoj. U radu su prikazane dosadasnje svjetske spoznaje, ali i rezultati vlastitih istrazivanja utjecaja trajanja procesa zavarivanja na izvlacnu silu izmedu bukova mozdanika ipodloge. Najbolje rezultate izvlacne sile (4 994 N) imali su spojevi kod kojih je proces zavarivanja mozdanika trajao od 0,56 do 0,9 s (po svakom okretaju mozdanika pomak je bio 1,41 do 0,88 mm), a najmanja izvlacna silu (2 869 N) zabiljezena jepri trajanju zavarivanja od 1,81 od 2,61 s. Prosjecna izvlacna sila spoja lijepljenih spiralno nazlijebljenih mozdanika iznosila je 5 028 N. Kljucne rijeci: zavarivanje masivnog drva, vrijeme zavarivanja, cvrstoca zavarenog spoja, mozdanici, izvlacna sila