Advances and the future of grading structural timber Prof. - PDF document

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Advances and the future of grading structural timber Prof. Charlotte Bengtsson SP Trätek Linnaeus University WG 3 Strength, Stiffness and Appearance in Quality Control and Processing • More advanced non-destructive methods and combination of methods • More accurate machines at reasonable cost • Grading early in the production process • ”Visual strength grading” by means of surface scanning techniques http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 During this COST action…. • More countries with large interest in grading • More companies (sawmills and machine producers) • EN14081 • Gradewood • A lot of presentations during COST E53 activities Production of machine graded timber in Sweden 1600000 1400000 1200000 Production m3 1000000 800000 Total 600000 Export 400000 Sweden 200000 0 1989 1994 1999 2004 2009 Year http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Gradewood, results are now coming New physically Experimental New statistically based models for research and data based models for strength: WP1 base: WP2&3 grading: WP4&5 Numerical analysis and simulation Novel procedures for More accurate grading grading: WP5 techniques: WP5 Support to New business standardisation and models for wood CE-marking:WP5&6 industries: WP5&6 EN- standards for grading • EN 14081 Timber Structures – Strength graded structural timber with rectangular cross section, allowing CE-marking of graded structural timber, becomes mandatory September 1, 2012 • This standard replaces EN 519 • Four parts – Part 1: General Requirements – Part 2: Machine Grading; additional requirements for initial type testing – Part 3: Machine Grading; additional requirements for factory production control – Part 4: Machine Grading; Grading machine settings for machine controlled systems http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 EN- standards for grading • ”New” procedure for derivation of machine settings • Settings applicable for one country or some countries • Two principles – Machine control – Output control • The standard covers both visual and machine strength grading • Visual override requirements as previously Example from 14081 - 4 Dynagrade Source Source Species Permitted Grade or Settings Comments and additional requirements mark a) country or timber sizes grade IP b) countries combination (machine units) (mm) Finland FI Spruce , 31 ≤ t n ≤ 110 C24 4 300 000 Actual setting, IP is given in machine units and it is not effected 63 ≤ b n ≤ 264 by the timber dimensions. Norway NO TR26 6 150 000 Picea abies Sweden SE C16 4 300 000 Requirements for grading: Estonia ES Fir TR26 6 150 000 − Air temperature 10°C – 50 °C Latvia LV Abies alba C18 4 300 000 − Relative humidity in the air < 85 % Russia d) RU C27 6 150 000 − Timber temperature > -10 °C Poland PL − C18 4 420 000 Timber mean moisture content between 10% and 16% Dynagrade Germany DE C30 6 900 000 − Conveyor speed ≤ 1 m/sec Austria AT C18 4 300 000 − Spacing between pieces ≥ 200mm Czech CZ C30 6 900 000 − Grading speed ≤ 100 pieces/min Republic C24 5 770 000 Dynagrade HC C18 4 650 000 − Conveyor speed ≤ 1,3 m/sec − Spacing between pieces ≥ 225mm − Grading speed for widths ≤ 250mm: ≤ 150 pieces/min Dynagrade XHC − Conveyor speed ≤ 1,3 m/sec − Spacing between pieces ≥ 225mm − Grading speed for width (w) ≤ 100mm: ≤ 240 pieces/min where 100 < w ≤ 250 grading speed = 78000/(w+225) pieces/min Where timber has a mean moisture content between 16% and 20% with a minimum value of 14% and a maximum value of 22% then the settings shall be calculated according to equation (1) and rounded to 3 significant digits. = − 0 , 0738 (1) IP IP IP 18 a) See clause 7.3 in EN14081-1 b) Timber sizes shall be to EN 336. c) Grades prefixed by C are strength classes given in EN 338 d) Settings apply only to timber grown west of the Ural mountain range in Russia http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Machine grading principles • M easurement of bending stiffness • Optical detection of knots and other characteristics • Near-Infrared-Reflection spectroscopy (NIR) • Resonant vibrations • Wave propagation speed • Neural nets • Deconvolution technique • Radiation methods – micro waves – x-ray – γ -radiation • Combination of techniques Machine grading principles Flatwise bending Density •Span ca 900 mm γ -ray •Deflection const. measure load •Load const. measure deflection x-ray Pr e s s r ol l e r Di s pl ac e me nt A r i A i r Detectors T i mbe r L oad r ol l e r Density profile Re f e r e nc e Re f e r e nc e L oadc e l l Comput e r r ol e l r r ol l e r Resonant vibrations = ⋅ ρ ⋅ ⋅ 2 4 2 •Measures f E L − A 1 A •length •frequency •density http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Grading machines on the European market Name Principle Computermatic/Micromatic Flatwise bending, measurement of deflection CookBolinders/Techmach Flatwise bending, measurement of load Grademaster Vibration and scanning GoldenEye 702/EuroGreComat 702 X-ray EuroGreComat 704 X-ray and bending GoldenEye 706/EuroGreComat 706 X-ray and vibrations GoldenEye 80/1 X-ray and laser scanner GoldenEye 80/2 X-ray and laser scanner VM Grader 1.0 Visual grading & gravimetric density Dynagrade Vibrations in longitudinal direction Raute Timgrader Flatwise bending, measurement of load Newnes X-ray Ersson ESG-240 Flatwise bending, measurement of load Metriguard 7200 HCLT Flatwise bending, measurement of load Sylvatest Ultrasonic waves Grading machines on the European market, cont. Name Principle Precigrader Vibration and density Timber Grader MTG Vibration VISCAN Vibration Triomatic Ultrasonic waves E-Scan Vibration JRT MSR Machine Bending, measurement of deflection Noesys Vibration Xyloclass T, Xyloclass F Vibration CRP360 Bending Rosgrade Vibration • Machines with settings according to EN 14081 http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Why strength grading? • Accurate knowledge about timber characteristics – strength, stiffness, appearance • Have a common classification within a market • Obtain an engineering material, gives possibilities to develop the timber building technique • Optimise the yield – Adding value – Use of resources – Optimise the use (use good enough quality) • Timber for structural applications requires grading • Strength, stiffness and density properties need to be known and to be controlled to stay within desirable limits Examples from EN 338 Characteristic property Strength class C18 C24 C30 Strength properties (MPa), 5%-percentile Bending strength f 18 24 30 , m k Tension strength, parallel to the grain f 11 14 18 . 0 . t k Tension strength, perpendicular to the grain 0,3 0,4 0,4 f t . 90 . k Compression strength, parallel to the grain f 18 21 23 . 0 . c k Compression strength, perpendicular to the grain f 4,8 5,3 5,7 , 90 . c k Shear strength f . 2,0 2,5 3,0 ν k Stiffness properties (MPa) E , MoE parallel to the grain, mean value 9 000 11 000 12 000 0 mean MoE parallel to the grain, 5%-percentile E 6 000 7 400 8 000 0 , 05 MoE, perpendicular to the grain, mean value 300 370 400 E 90 , mean Shear modulus, mean value 560 690 750 G mean Density (kg/m³) Density, 5%-percentile ρ 320 350 380 12 , k Density, mean value ρ 12 , mean 380 420 460 • Grades can also be defined elsewhere, ex. LS, L, LD for glulam laminations http://cte.napier.ac.uk/e53

‘The Future of Quality Control for Wood & Wood Products’, 4-7th May 2010, Edinburgh The Final Conference of COST Action E53 Basics • Visual grading –Grading rules, with maximum knot size etc –Trained graders –Scanners • Machine strength grading –Prediction of strength properties –Classification into strength classes, i.e C18, C24 etc Visual grading • Visual strength grading has a long tradition • Formal grading rules were established beginning of 20 th century (US) • 1930 and onwards visual grading rules were introduced in Europe http://cte.napier.ac.uk/e53