Abstract

The seeds were quasi-statically loaded to determine rupture force, toughness, yield force, rupture stress, modulus of stiffness and elasticity. Compression tests were carried out on seeds at moisture content of 15.76, 19.81 and 34.43% (wb), seed orientation in both the longitudinal and transverse axis at a loading rate of 25 mm/min. Values of the rupture force, toughness, rupture stress, yield force and modulus of stiffness of the seeds decreased linearly from 362.04 to 168.82 N, 1.783 to 0.623 J, 7.4 to 3.15 N/mm², 213.42 to 89.68 N and 39.6 to 21.97 N in transverse axis and from 276.64 to 195.26 N, 1.355 to 0.641 J, 16.12 to 6.23 N/mm², 211.58 to 124.72 N and 38.74 to 24.77 N in longitudinal axis with increase in moisture content from 15.76 to 34.43 (%wb). Values of modulus of elasticity determined using hertz theory of parallel plate contact increased from 1.529 to 3.52 MPa with increase in moisture content from 15.76 to 19.81 (%wb) but decreased to 1.563 MPa with increase in moisture content. Highest value for rupture force (362.04 N) and toughness (1.783 J) of the seeds were obtained at a moisture content of 15.76% wb. The seeds are more flexible in longitudinal orientation and the rupture force requires less energy under longitudinal loading than transverse loading.

Key words: African oil bean seeds, mechanical properties, compressive tests, moisture content, loading orientation.