Damage zone analysis and its effect on the elastic constants of beech blocks with different grain orientations under compression

Abstract

The damage zone and its effects on orthotropic deformations and elastic constants of beech blocks when subjected to compressive loading were investigated. The impact of surface treatment (sanded and speckled) on strain contours was examined first, followed by evaluating the effects of grain orientation, damage zone location, and load level on the length of damage zone. Subsequently, the effects of damage zone location on measured elastic moduli of beech blocks in various directions were evaluated. Finally, the factors on the elastic constants of beech blocks were investigated by considering six different strain-measuring methods. Experimental analyses found that sanded and speckled blocks had nearly identical strain contours when subjected to compressive loading in radial (R), tangential (T), and RT45° grain orientations, respectively. The length of the damage zone was significantly affected by grain orientation, load level, and damage zone location. The ratios of the length of the damage zone to the length of the tested block in different grain orientations ranged from 0.041 to 0.074 at proportional limit load and 0.045–0.078 at yield load. The mean ratio of each of the three elastic moduli measured in two ends of a tested beech block to one measured in its middle section ranged from 0.41 to 0.58. The length of the damage zone measured in tested beech blocks tended to show a negative correlation to its measured elastic moduli. These findings could provide a basic understanding of damage zones to analytical and numerical modeling of orthotropic deformations of beech wood.