NOPR Collection:

Analytical investigation of wave slamming loads on horizontal circular cylinders

Sun, 01 Aug 1999 00:00:00 GMT

Title: Analytical investigation of wave slamming loads on horizontal circular cylinders Authors: Khalil, Gazi Md. Abstract: Horizontal cylinders are subjected to impact loads when suddenly submerged in water. Analysis of the wave forces acting on a fixed , slender, horizontal circular cylinder in the vicinity of the free surface is described here by taking into account the intermittency of submergence and wave slamming by a new analytical approach for deriving an expression for the slamming coefficient. A computer programme is developed on the basis of the aforesaid analysis. The programme is written in FORTRAN 77 and executed on the IBM 4331 L02 computer. The computational results are plotted and interpreted to explain the salient features of wave slamming. These results are expected to be useful in the assessment of hydrodynamic loads on offshore structures like the braces between legs or hulls for jacket structures and semi-submersibles. Page(s): 188-197

Computation of stress intensity factors using a special finite element technique

Sun, 01 Aug 1999 00:00:00 GMT

Title: Computation of stress intensity factors using a special finite element technique Authors: Khalil, Gazi Md. Abstract: The use of a special finite element technique for the computation of stress intensity factors in cracked plates, subjected to in-plane tensile loads, is described here. Seven plates of unit thickness (each 40x40 cm²) are numerically analyzed. Each of the plates contains an edge-crack of varying length (4-28 cm). Firstly, the plates are conceptually divided into two zones, a circular singular zone around the crack-tip and a conventional zone outside the circular boundary. The plates are then discretized into a system of triangular finite elements. The elements near the crack-tip are made much smaller than the remote ones. Appropriate displacement functions are proposed for handling, the inverse square root singularity of stresses at the crack-tip. Also, the conventional elements are used outside the singular zone. Based on the proposed displacement functions, a new stiffness matrix is derived. A suitable computer program is developed for the analysis of stresses in the cracked plates. The stress intensity factors are computed for each of the seven plates and plotted against the ratio of cracklength to plate- length. The results obtained by using the proposed displacement functions are found to be more satisfactory than those obtained by the conventional elements using linear displacement functions. Page(s): 182-187

Stability behaviour of angle ply plates subjected to various types of inplane loadings

Sun, 01 Aug 1999 00:00:00 GMT

Title: Stability behaviour of angle ply plates subjected to various types of inplane loadings Authors: Sarma, M Adinarayana; Singh, Gajbir; Rao, G Venkateswara Abstract: Investigations on the stability characteristics of rectangular angle ply plates subjected to various types of inplane loading are reported here. Variationally consistent governing equations and boundary conditions are derived for this purpose. The possibility of bifurcation instability in angle ply plates subjected to various types of inplane loading is examined. Employing a four node rectangular finite element having ten degrees of freedom per node solves the governing equations. The prediction accuracy of the element is demonstrated through series of numerical examples. The effect of layup, aspect ratio, type of loading (uniaxial/biaxial/positive and negative shear/tension-compression/compressiontension/inplane edge moment) and boundary conditions are studied in detail. Some interesting observations on the stability behaviour of angle ply plates are made. Page(s): 173-181

Tribological evaluation of N-phenylformamidino-N`-alkylthiocarbamides and their Mo-S complexes as EP lubricant additives

Fri, 18 Oct 2013 13:00:14 GMT

Title: Tribological evaluation of N-phenylformamidino-N`-alkylthiocarbamides and their Mo-S complexes as EP lubricant additives Authors: Tripathi, A K; Bhattacharya, A; Singh, R; Prasad, N; Verma, V K Abstract: The tribological properties of 0.5% solutions of N-phenylformamidino-N'-alkylthio-carbamides and their Mo-S complexes, i.e., μ-hydroxo-μ-(N-phenylformamidino-N'-alkylthiocarbamido)-bis-(dioxohydroxo molybdenum VI) in paraffin oil were evaluated in a four-ball test. In particular, μ-hydroxo-μ- (N-phenylformamidino-N'-ethylthiocarbamido)bis-[dioxohydroxo molybdenum VI] was found to exhibit an appreciable increase in the load carrying capacity and values of flash temperature parameter, load wear index and pressure wear index and a decrease in the values of coefficient of friction. However, the Mo-S additives did not markedly improve anti-wear characteristics in the wear tests. A comparative EP evaluation of μ - hydroxo -μ-(N-phenylformamidino-N'- ethylthiocarbamido)-bis- (dioxohydroxo molybdenum VI) using steel balls of different compositions, indicated its suitability of replacing alloy steel balls with cheaper carbon steel balls. The topography of the wear scars on the used steel ball specimen was studied by SEM. Page(s): 206-212