Experimental dataset for the macro-scale compression of Norway Spruce perpendicular to grain direction

This article presents load and displacement data of Norway Spruce quasi-static compression test as well as video recordings of the experiment using the Universal Testing Machine (UTM). The specimens are 4 cm × 4 cm × 8 cm clear-wood cuboids with grain direction perpendicular to and loading direction parallel to the long axis. Due to the radially-arranged annual ring at such scale of the specimens, the plane of interest features significantly-varying orientation of the weak axes, namely the radial (R) and tangential (T) directions. A hemispherical knee joint underneath the specimen were fine-adjusted under preload before each experiment to ensure evenly-distributed load. Additionally, grids of 5 mm spacing were drawn on the plane of interest for better clarity of the deformed shape. Both load and displacement history recorded by the UTM as well as the deformation process recorded as video may provide valuable information for validation of wood material models or simulation methods with wood material implementations.


Specifications
Civil and Structural Engineering Specific subject area Experimental study of wood material behaviour in transverse direction Type of data

Value of the Data
• The data provides insight on the failure mode of symmetrical clear wood specimen with asymmetrical arrangement of material orientation. • Numerical studies with wood material that differentiates transverse direction into radial (R) and tangential (T) (via e.g. macroscopic material or multiscale modelling) may use the data for validation. • The data can be reused in inverse-problem studies to predict radial (R) and tangential (T) wood material behaviour.

"Load-Disp history.xlsx"
The excel file contains load and displacement history recorded by the Universal Testing Machine (UTM) at 50 Hz. The specimens are renamed to match the nomenclature of the supported research article.

"Specimen1.mp4"
Recording of the compression test of specimen 1 (nomenclature matched with "Load-Disp History.xlsx"). Recording started before loading process commenced and ended after reaching the 20 mm displacement target.

"Specimen2.mp4"
Recording of the compression test of specimen 2 (nomenclature matched with "Load-Disp History.xlsx"). Recording started before loading process commenced and ended after reaching the 20 mm displacement target.

"Specimen3.mp4"
Recording of the compression test of specimen 3 (nomenclature matched with "Load-Disp History.xlsx"). Recording started before loading process commenced but unfortunately ended prematurely near the beginning.

"Specimen Weights and Dimensions.xlsx"
The excel file contains weights and dimension measurements of all the three specimens, with specimen nomenclature following that in "Load-Disp History.xlsx".

Specimen
The tested specimens are three 4 cm × 4 cm × 8 cm Norway Spruce clear wood cut from beams in a way so that the centre of the annual ring is situated near one edge of the specimen. Fig. 1 (a) illustrates how we aim to cut the specimens in terms of dimension and position of  Fig. 1 (a).   Fig. 3. Specimens 1 (a), 2 (b), and 3 (c) just before experiment starts [3] .
the centre of the annual ring, while Fig. 1 (b) shows the plane-of-interest in this experiment. An example of a cut sample according to the said specifications is shown in Fig. 2 . For the particular tested specimens, Fig.s 3 (a)-(c) show their state before the experiment. Of all the produced samples, about half were discarded due to the presence of wood imperfections. Defectfree samples are stored in climate room of 20 °C temperature and 65% relative humidity for about 1 month to approach 12% moisture content (see [2] ).  All specimens are weighed before the experiment. Additionally, we measure the specimen's dimensions to ensure good approximation to the aforementioned target sizes. Table 1 shows the weights and dimensions of specimens 1-3. The dimensions are reported by averaging calliper measurements from all 4 edges (see Fig.s 4 (a), (b), and (c) for height (h), width (w), and thickness (t) respectively). Table 2 shows the measurements of those four edges for each dimension. The data presented in both Tables 1 and 2 and Fig. 4 are included in Specimen Weights and Dimensions.xlsx .

Procedure
The compression experiment utilizes the Zwick RK 250/50 Universal Testing Machine (UTM) shown in Fig. 5 , which provides displacement-controlled compression and records the data. The procedure follows the guidelines of SFS EN 408:2010 + A1:2012 [1] for wood compressive strength test perpendicular to grain direction. Before every compression test, the knee joint was fine-adjusted with rubber hammer under preload to ensure even compression throughout the specimen. After locking the knee joint, compression test proceeded with displacement-controlled compression loading up to 20 mm of displacement, which allows plenty of compression for observation of the post-failure behaviour. The loading rate is determined by preliminary tests before the actual experiment.
The European Standard [1] requires compression test to reach maximum load within the range of (300 ± 120) s. Note that the definition of maximum load in said literature does not necessarily mean the highest load achieved throughout the test, but rather determined by the iterative 1%-offset approach (see [1] ). Preliminary tests revealed 0.5 mm/minute to be the ideal Additional floodlights provided even illumination of the video-recorded surface. We chose DC-powered lights to eliminate the possibility of flickering due to AC polarity reversal. Fig. 6 shows the deformed shape of specimen 1 throughout the experiment at various displacements taken from the video frames of Specimen1.mp4 . The resulting load-displacement curves from load and displacement history data in Load-Disp History.xlsx is plotted in Fig. 7 .    7. The load-displacement curves of specimens 1-3 from data presented in Load-Disp History.xlsx [3] .

Ethics Statement
This work involves neither human nor animal subjects.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.