EVALUATION AND COMPARISON OF QUALITYEVALUATION AND COMPARISON OF QUALITY OF BEECH WOOD (FAGUS SILVATICA L.) AFTER

VACUUM DRYING AND HF-DRYINGVACUUM DRYING AND HF DRYING.

Daniel Karpinský

Prong test - Casehardening

ENV 14464 - Casehardening

GOST 11603-73 - Internal stress

Drying time

Vacuum drying I (with equalizing) => 92 h Vacuum drying II (without equalizing) => 72 hHF drying (after 160 h pre-drying) => 10,5 h

100,0%

60,0%

70,0%

80,0%

90,0%

MC (%

)

20 0%

30,0%

40,0%

50,0%

Ave

rang

e M

0,0%

10,0%

20,0%

0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0 90,0 100,0

Drying time (h)y g ( )

vacuum I vacuum II HF drying

ResultsFinal MC

Vacuum drying I => 2,9 – 3,2 %V d i II 3 7 4 8 %

Final MC

Vacuum drying II => 3,7 – 4,8 %HF drying => 6,1 – 7,5 %

7%

8%

%)

2%

3%

4%

5%

6%

istu

re c

onte

nt (%

0%

1%

2%

1 2 1 2 1 2 3 4

Vacuum drying I Vacuum drying II HF drying

Moi

acuu d y g acuu d y g d y g

Drying / Sample

ResultsMC gradientMC gradient

Vacuum drying I => gradient max. 0,2 %Vacuum drying II => 1 to 1 7 %Vacuum drying II => 1 to 1,7 %HF drying => -0,6 to -1,2 %

Moisture content gradient

7%

8%

4%

5%

6%

7%

e co

nten

t (%

)

Vacuum drying I

Vacuum drying II

HF drying

0%

1%

2%

3%

Moi

stur

e y g

0%Surface I Middle Surface II

Drying / Sample

ResultsCasehardening prong testCasehardening – prong test

Vacuum drying I => 2,2 – 5,4 %Vacuum drying II => 6 6 7 %Vacuum drying II => 6,6 – 7 %HF drying => 6,8 – 11,5 %

10%

12%

4%

6%

8%

ehar

deni

ng (%

)

0%

2%

4%

1 2 1 2 1 2 3 4

Case

Vacuum drying I Vacuum drying II HF drying

Drying / Sample

ResultsCasehardening ENV 14464Casehardening – ENV 14464

Vacuum drying I => 0,5 – 1,2 mmVacuum drying II => 1 46 1 52 mmVacuum drying II => 1,46 – 1,52 mmHF drying => 0 – - 2,8 mm

0 5

1

1,5

2

-1

-0,5

0

0,5

1 2 1 2 1 2 3 4

Vacuum drying I Vacuum drying II HF drying

hard

enin

g (m

m)

-2,5

-2

-1,5

-1

Cas

eh

-3

,

Drying / Sample

ResultsInternal stress (B N Ugolev method)Internal stress (B. N. Ugolev method)

-4,0

-3,0

-2,0

-1,0

0 0Surface I Middle I Middle II Middle III Middle IV Surface II

(MPa

)

0,0

1,0

2,0

3,0

4,0Inte

rnal

str

ess

Prong testCasehardening -

ENV 14464Prong test

8%

Casehardening - ENV 14464

1 55,0

6,0

Vacuum drying I 1 Vacuum drying I 2Vacuum drying II 1 Vacuum drying II 2

4%5%6%7%8%

1

1,5

4%5%6%7%8%

1

1,5

0%1%2%3%4%

0,5

0%1%2%3%%

0

0,5

1 2

Vacuum drying I

01 2

Vacuum drying I

1 2

Vacuum drying II

1 2

Vacuum drying II

Conclusionli l i d d h h d f iquality results is depend on the method for measuringProng test

only reflects the stress condition in the surface layerhigh stress gradients leads to strong deformation of the prong => indicating a low drying quality

slicing tests (as described in ENV 14464)g ( )is based on the internal stress difference between surface and core layersmore reflects an average stress level => indicating a better drying quality

the vacuum and the HF drying methods and the resulting dryingthe vacuum and the HF drying methods and the resulting drying quality of dried material

the material dried in vacuum has lower moisture content gradient and ll d f h d ismaller degree of casehardening

Thank you for your atentationy y