RESUMO
Stroh formalism provides an elegant method of solution for two-dimensional anisotropic elasticity problems through the generalized eigen relation associated with the dual coordinate system that gives the material eigen values and eigen vectors, and also the fundamental elasticity matrix and its associated Barnett-Lothe tensors. The extended Stroh-like formalism of Hwu and Hsieh has expanded the scope of basic Stroh formalism by addressing the electro-mechanical coupling effects in electro elastic plates. This paper presents an inclusive solution that addresses the two-dimensional problems in infinite electro-elastic, anisotropic, and isotropic plates with an arbitrary hole under remote arbitrary coupled electro-mechanical loading. This is achieved by adopting the Stroh formalism and its subsequent versions to consider the anisotropic and electro-elastic plates, and further, by incorporating the arbitrary biaxial loading condition into the boundary conditions, and the generalized mapping function into the basic formulation to accommodate all types of in plane loading and a variety of hole shapes respectively. Various equations of the solution are derived explicitly for easy understanding and computer implementation. The stress function is derived explicitly to satisfy the condition of traction free hole with remote electro-mechanical loading under generalized plane stress-open circuit condition. The stresses and electric displacements around the hole boundary are obtained by taking the derivative of the stress function with respect to unit normal along the hole boundary. The solution presented can be degenerated to the anisotropic or isotropic case by choosing the corresponding material properties, or appropriate values of complex parameters respectively. This general solution has exactly reproduced the results of other solutions in the literature for piezoelectric plates given by different methods. New results of stresses and electric displacements are obtained for various arbitrary holes in [PZT5H/45/-45/PZT5H]s graphite/epoxy plate and PZT 4 plates. Results for holes in piezoelectric laminates and PZT 4 piezo layer are also presented by FEM.
RESUMO
In the area of globalization any manufacturing industry must be competent in terms of productivity, quality, cost and delivery. A fundamental improvement in production is necessary to succeed in the international markets. Work study is one of the earliest scientific management methods used to determine the best way to perform production tasks in order to reduce idle time and worker fatigue as a result, increase productivity. Kombolcha Steel Products Industry, the member of MIDROC Ethiopia Technology Group, producing a variety of metal and engineering products, such as steel poles, steel structures, structural hot dip galvanization, corrugated sheet metal, etc. The company's main focus was meeting the delivery deadlines, with little attention to implementing standard working method and procedures during the production. The inefficient method of piercing the holes in the u-channels to fabricate the electric pole cross arms is causing a drop in productivity. The primary objective of the current study is to identify the bottlneck in the process of electric power poles cross arms fabrication, to set standard time for the process and reduce the cycle time. Time and method studies were used to identify the flaws in the current fabrication process and layout design. The efficient technique to manufacture the product has been replaced by redesigning and implementing a new layout. This arrangement accelerated the process by reducing the idle time for the three punching machines that undertake the piercing operations. The modified layout raised production from the target daily production of 420 pieces to 720 pieces in 8 h, resulting in a 71 % reduction in the previous work cycle from 65 to 39 s. After a time and method study, a simple change in the layout with no capital investment not only increased the company's productivity and profitability, but it also reduced worker fatigue due to extra material handling operations of raw materials and intermediate products.
