The resistographic analysis (wood penetrometry) is a survey technique for the qualitative evaluation about the wooden works degradation.
The survey is made through a thin tip measuring 30 cm fitted with combined rotation motion and constant speed advancement, implying the piercing of the surface to be examined. It is considered a non-destructive technique, as the hole it has created is similar in terms of dimensions to those made by the xylophagus insects.
The principle is that the wood opposite resistance to the needle is proportional to the material density in the survey point. It is therefore a punctual survey, namely it provides informations about the state of conservation of the pierced area, but the results cannot be extended to the whole wooden surface.
It is considered that the most aprropriate employment is that one designed to evaluate the level of the beams heads degradation. Just in correspondance to the beams’ heads, considering their small size, it is possible to intersect the inspection profiles in order to obtain informations about the conservation state of the whole element. Thi is not possible on the beam’s span because of the great number of perforation to do.
This technique allows to diagnose the presence of degradation but not to measure it; it doesn’t provide informations about the degradation itself typology and about the causes.
The wood’s biological origin determines a significant difference from the others construction materials which don’t suffer from humidity change. For establishing the wooden structure’s conditions it is useful to proceed with the igrometric analysis: in fact, the presence of humidity within a structure can be a trigger of many forms of degradation. The water percentage contained into a wood object is measured through the hygrometer, functioning according to the principle of the electrical conducivity of the examined material’s surface.
L’origine biologica del legno determina una notevole differenza dagli altri materiali da costruzione che non risentono fortemente dei cambiamento di umidità.
Per determinare le condizioni della struttura lignea è utile ricorrere all’analisi igrometrica, infatti la presenza di umidità all’interno di una struttura può essere un fattore scatenante di numerose forme di degrado.
Il contenuto d’acqua percentuale esistente in un manufatto in legno viene misurato tramite l’igrometro il cui funzionamento è basato sul principio della conducibilità elettrica della superfice del materiale in esame.