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The results are intended to help improve control and we had five test specimens with density variability included
optimisation of HF heating during the preheating phase of the in Table 1.
oak wood bending process.
Table 1. Thickness of oak lamellas grouped by relative humidity
(RH = 10–100%) used for dielectric property tests.
Materials Used in the Study Relative Sample Measurement Density(kg/ Moisture
Humidity Thickness Temperatures m3) Content
Radially oriented oak lamellas (R × T × L = 80 × 3 × 500 mm) (%) (mm) (deg C) (%)
were conditioned at 20 deg C above saturated salt solutions 100 3.05–3.14 20 and 90 646–711 16.65–18.34
87 3.07–3.14 20 and 90 557–721 11.43–12.53
and above distilled water at relative air humidity (RH) ranging
75 3.05–3.15 20 and 90 575–715 8.91–9.73
from 10 percent to 100 percent. 65 2.75–3.14 20 and 90 613–742 8.16–8.68
The reason for choosing this RH range is that during 33 3.03–3.16 20 and 90 661–739 6.70–7.10
10 3.04–3.15 20 and 90 652–730 4.73–4.96
industrial bending processing, depending on the working
Steaming 3.19–3.35 90 646–711 10.12–11.15
conditions, there are fluctuations in the RH in the room, which
can lead to changes of moisture contents of the elements To ensure equilibrium moisture content (EMC), all lamellas
meant for bending. were weighed daily until the mass variation was less than
There was also a group of samples steamed for 90 min 0.1 percent over 24 h. The conditioning procedure at 20 deg
before measurement at 90 deg C. For each humidity level, C followed standard static equilibration above saturated salt