Improving grading methods for structural timber by non-destructive techniques

Información del proyecto

Identificador del acuerdo de subvención: CR184091-BRE21567

Proyecto cerrado

Fecha de inicio 1 Diciembre 1994

Fecha de finalización 30 Noviembre 1996

Financiado con arreglo a

• Specific programme of research and technological development in the field of industrial and materials technologies - CRAFT -, 1990-1994

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

Centre Technique du Bois et de l'Ameublement (CTBA)
France

Objetivo

Conclusions on sampling:

The sampling, in the forest and/or in the industry, has covered a wide range of species and sizes. A minimum of 900 pieces is required for the derivation of settings for a new machine with the full range of sizes and grades. The sampling of TIMGRAD (1600 pieces for FRANCE; 900 pieces for UK; 450 pieces for SW) is within this limit. In fact, a sampling method in order to decrease the amount of testing needed has been investigated (SW). The number of specimens was decreased by 80-90% without affecting the relations between the mechanical properties of the material and the tested non-destructive properties.

Conclusions on NDT:

A lot of techniques applicable to timber strength grading have been studied: Some already existed (ScanWood, Metriguard, Cook Bolinder, Computermatic) and other ones have been set up during the project as follows

The SNTRI camera is based on a smart sensor technique together with line-lasers. With this system it was possible to detect knots on Norway spruce timber with a sawn surface, which is generally very difficult with normal camera systems.

By analysing the frequency response of the timber the modulus of elasticity can be determined. This technique available in Sweden enables cross transportation of the timber, which is the normal way of transporting timber at sawmills. The technique works as good as the bending type machines, although it does not measures the local timber characteristics, but rather the global behaviour of each piece of timber.

CTBA introduce X rays device in the project to measure local density. The previous work (Rouger 1994) has shown good correlations between the non destructive parameters and the mechanical properties. The results obtained in TIMGRAD show that the X rays device is quite the best machine.

BRE would recommend further development of the Metriguard ELDECO device, for the devices tested in the UK. There are several reasons for this;
a). It appears to provide the most reliability in operation
b). The operating algorithms are less complicated.
c). The calibration procedures for the device are the simplest and the most straight forward.
d) despite a considerable amount during its development (software), it stills shows problems in use.
e) the calibration of the device will be difficult to prove.

BRE strongly recommends further investigation and development of the electronic noise filtration technology on strength machine. Indications explain that this technology offers the quickest and most cost effective way to produce significant cost benefits for the Sawmillers, although there is still a need for more experimental work to define the magnitude of the benefits. Two particular methods offer the greatest potential;

i)improving the prediction of strength by improving the correlation coeffiecient.
ii)By filtering out frequencies there is a component of the grading machine speed, thereby allowing the grading machines to be run faster.

The smart camera system is not a method with enough accuracy by itself for timber strength grading, but coupled with other techniques, such as the bending machines, grading accuracy can be increased. The camera system studied has the advantage that it can detect knots on sawn surfaces of species such as Norway spruce, which is normally very difficult with camera techniques. Furthermore, using the camera system an appearance grading can be performed, which is of great importance for certain products such as gluelam lamellas. The Maritime Pine is "Red Wood" species. During the measurements of nodosity, it has created difficulties (difference of contrast with Spruce species).

Ámbito científico (EuroSciVoc)

• ciencias naturales › informática y ciencias de la información › software
• ingeniería y tecnología › ingeniería eléctrica, ingeniería electrónica, ingeniería de la información › ingeniería electrónica › sensores › sensores ópticos
• ingeniería y tecnología › ingeniería eléctrica, ingeniería electrónica, ingeniería de la información › ingeniería electrónica › sensores › sensores inteligentes
• ciencias agrícolas › agricultura, silvicultura y pesca › silvicultura

Programa(s)

• FP3-CRAFT - Specific programme of research and technological development in the field of industrial and materials technologies - CRAFT -, 1990-1994

Tema(s)

Datos no disponibles

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

Centre Technique du Bois et de l'Ameublement (CTBA)

• Aportación de la UE: Sin datos
• Dirección: 10 avenue de Saint-Mandé ; 75012 Paris ; Francia
• Coste total: Sin datos

Participantes (1)

Établissements Robert Weisrock

Francia

• Aportación de la UE: Sin datos
• Dirección: 7 rue Jean Jaurès ; 88580 Saulay-sur-Meurthe
• Coste total: Sin datos