IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372. Volume 4, Issue 5 (Sep. - Oct. 2013), PP 50-56 www.iosrjournals.org www.iosrjournals.org 50 | Page Relationship between Mechanical Properties of Vitex doniana, a Lesser Known Species and Implications for Utilization K.M. Ogunjobi 1 , A.C. Adetogun 1 , A.O. Omole 2 , S.O Owoeye 3 and J.B. Odebiyi 4 1Department of Forestry and Wildlife Management, Federal University of Agriculture, Abeokuta, Nigeria 2 Department of Forest Resources Management, University of Ibadan, Ibadan, Nigeria 3 Department of Mechanical Engineering, Federal University of Agriculture, Abeokuta, Nigeria 4 Bola- Biyi Agroforestry Consultancy, Nigeria. Abstract: Relationship between the mechanical properties of Vitex doniana, a lesser known wood species was investigated towards determining its potentials for utilization. Four trees obtained from the free area of Olokemeji Forest Reserve, Ogun State, Nigeria were sampled at butt (50cm above the ground) and at 10%, 30%, 50%, 70% and 90% of merchantable height (MH) The samples were also partitioned into corewood, middlewood and outerwood. Impact Bending (IMB), Modulus of Rupture (MOR), Modulus of Elasticity (MOE) and Maximum Compressive Strength Parallel to Grain (MCS//) were determined. Relationship between the mechanical properties was determined using regression equation. Results showed that Mean IMB, MOR, MOE and MCSS// were 0.69m, 85.4 N/mm 2 , 6380N/mm 2 and 40.8N/mm 2 respectively. The best relationship existed between IMB and MCS// (R 2 = 0.75) followed by between MOR and MOE (R 2 =0.71) while the least relationship (R 2 = 0.43) existed between MOR and MCS//. Keywords: Axial variation, Mechanical properties, relationship, radial variation, Vitex doniana. I. Introduction The generic name “Vitex”, is an old Latin name for the genus. Vitex doniana is the most abundant and widespread of the genus occurring in Savannah regions. Vitex doniana (Verbanaceae) commonly known as black plum or “ori-nla” is wide spread in the south western Nigeria as a perennial tree. It is a deciduous forest tree of coastal woodland, riverine and lowland forests and deciduous woodland, extending as high as upland grassland. It is a medium sized deciduous tree which is about 8-18m high. It has a heavy rounded crown and a clear bole up to 5m. The bark is rough, pale brown or greyish white, rather smooth with narrow fissures. The bases of old trees have oblong scales. The mechanical properties of a wood are the behaviour of the wood under an applied force. It refers to the ability of the material to resist eternal loads or forces tending to cause change in its size and alteration in its shape. These changes in size or shape are known as deformation or strain. [1] identified three kinds of primary stresses acting on a body. The force may be acting in compression if it shortens a dimension or reduces the volume of the body in which case it is called compressive stress. The behaviour of wood under an applied force on the other hand depends on the kind of forces applied, cellular alignment and content of wood. The mechanical properties of a wood are the cumulative effect of inherent attributes. The parameters that are often used in determining the mechanical properties of wood include Impact Bending (IMB), Modulus of Rupture (MOR), Modulus of Elasticity (MOE),Maximum Compressive Strength Parallel to Grain (MCS//). Impact bending which is also known as maximum hammer drop shows the ability of wood samples to resist suddenly applied load. It is one of the three criteria used in the laboratory for measuring toughness [1]. The amount of shock resistance of a solid body depends on the ability to absorb energy and dissipate it before deformation [2]. MOR is the ultimate bending strength of a material which describes the load required to cause a wood beam to fail and can be thought of as the ultimate resistance or strength that can be expected. MOR is a parameter for measuring bending strength of wood. It measures the equivalent of stress in the extreme fibres of the specimen at the point of failure. [3] described MOR as the magnitude of load required to cause failure in bending stresses. Modulus of elasticity is the ability of a material to regain its original shape and size after being stressed [3 and 1]. The ability of a wood member to bend freely and regain normal shape is called flexibility and the ability to resist bending is called stiffness. The modulus of elasticity which is a measure of the relationship between stress and strain within the limit of proportionality provides a convenient measure of stiffness or flexibility of a timber. The greater the MOE the stiffer the timber and conversely, the lower the modulus of elasticity MOE, the more flexible is the wood member.MCS // is the ability of a piece of material to withstand loads in compression parallel to the grain