A STUDY ON YIELD AND FLOW OF ORTHOTROPIC MATERIALS

On the assumption that the yield criterion of orthotropic materials is isomorphic with Huber-Mises criterion of isotropic materials, we put forward a dimensionless stress yield criterion, and obtained the associated plastic flow law. Using experimental stress-strain curves in various simple stress states, generalized effective stress-strain formulae may be derived correspondingly in various forms.

A New Type of Multielements-Doped,Carbon-based Materials Characterized by High-thermoconductiv-ity,Low Chemical Sputtering,Low RES Yield and Exposure to Plasma

Low-Z materials, such as carbon-based materials and Be, are major plasma-facing material (PFM) for current, even in future fusion devices. In this paper, a new type of multielement-doped carbon-based materials developed are presented along with experimental re-sults of their properties. The results indicate a decrease in chemical sputtering yield by one order of magnitude, a decrease in both thermal shock resistance and radiation-enhanced sublimation, an evidently lower temperature desorption spectrum, and combined properties of exposing to plasma.

Impact of Heart Rot of <i>Pericopsis elata</i>(Harms) Van Meeuwen on Yield at Harvest in Production Forests in South-Eastern Cameroon

This study of the impact of heart rot of Pericopsis elata on logging yield was conducted in Libongo, in three logging concessions of the Société d'Exploitation Forestière et Agricole du Cameroun (SEFAC). An inventory of 92 P. elata stumps in four Annual Cutting Areas (AACs) divided among three Forest Management Units (FMUs) distinguished by Minimum Operating Diameter (MOD) revealed that 22 stumps were rotten. Decay was visible on stumps with a diameter of more than 100 cm with a frequency of occurrence of 23.91%, a percentage of abandonment of 55.20% and a yield of 44.79%. The most important economic loss was revealed on 9 abandoned whole logs that cumulated a volume of 145.547 m3. The correlation between the diameter of the stumps and that of the decay gives a coefficient or correlation rate r = 0.31. The MOD for P. elata could be 80 cm and covers the biological risk class. The results indicate that P. elata shows an increasing gradient of decay rate with increasing tree diameter, resulting in a loss of material for larger diameter trees, and consequently a decrease in material yield at processing.

A quadratic yield function with multi-involved-yield surfaces describing anisotropic behaviors of sheet metals under tension/compression

A quadratic yield function which can describe the anisotropic behaviors of sheet metals with tension/compression symmetry and asymmetry is proposed.Five mechanical properties are adopted to determine the coefficients of each part of the yield function.For particular cases,the proposed yield function can be simplified to Mises or Hill’s quadratic yield function.The anisotropic mechanical properties are expressed by defining an angle between the current normalized principal stress space and the reference direction with the assumption of orthotropic anisotropy.The accuracy of the proposed yield function in describing the anisotropy under tension and compression is demonstrated.