Effect of Slope of Grain on Modulus of Rupture and Modulus of Elasticity of Sunt (Acacia nilotica ) Wood Grown in Blue Nile State, Sudan

Abstract

This investigation dealt with the effect of grain angle on modulus of rupture (MOR) and modulus of elasticity (MOE) of sunt wood grown in Blue Nile State. Static bending test was carried out on samples with five different grain angles including zero angle i.e. clear wood with straight grain. From test results MOR and MOE were calculated for each slope of grain. Four grades were selected arbitrarily and suitable strength ratios were assigned to these grades. From the test results and using the strength ratios chosen, the MOR was calculated for each grade. Analysis of variance and Duncan�s Multiple Range test were carried out, looking for the level of significance of the variations in MOR and MOE between the different grain angles. Regression analysis was also carried out for establishing relationships between each of MOR and MOE as dependent variables and grain angles as independent variables for estimating grain angles for different grades.. The values of MOR for each grade (MORg) were substituted in the model relating MOR to slope of grain to find the slope of grain for each grade. Highly significant differences were found between MOR for the different slopes of grain (P < 0.0001). Significant differences were also obtained between MOE for the different slopes of grain (p = 0.0086). Regression analysis resulted in a model for estimating MOR from the slope of grain or vice versa. The model is as follows: MOR = 1986-3697.6�SG .Where: SG = slope of grain, The model for MOE was as follows: MOE = 173580 � 189299 � SG Slopes of grain for first, second, third and forth grades were: 1/10, 1/6, � and 1/3 respectively.