Accurate determination of interference in pin joints Pin-to-plate interference in experimental models of interference-fit joints is significantly overestimated by direct physical measurements, but it can be accurately determined by a simple photoelastic method

Suitable pin-to-hole interference can significantly increase the fatigue life of a pin joint. In practical design, the initial stresses due to interference are high and they are proportional to the effective interference. In experimental studies on such joints, difficulties have been experienced in estimating the interference accurately from physical measurements of pin and hole diameters. A simple photoelastic method has been developed to determine the effective interference to a high degree of accuracy. This paper presents the method and reports illustrative data from a successful application thereof.

Determination of the orthotropic plate parameters of stiffened plates and grillages in free vibration

It is well known that the analysis of vibration of orthogonally stiffened rectangular plates and grillages may be simplified by replacing the actual structure by an orthotropic plate. This needs a suitable determination of the four elastic rigidity constants Dx, Dy, Dxy, D1 and the mass {Mathematical expression} of the orthotropic plate. A method is developed here for determining these parameters in terms of the sectional properties of the original plate-stiffener combination or the system of interconnected beams. Results of experimental work conducted on aluminium plates agree well with the results of the theory developed here.

On compressible boundary layer on a flat plate with uniform suction

A quartic profile in terms of the normal distance from the wall has been taken and coefficients are evaluated by satisfying one more boundary condition on the wall than the usual one. By doing so, the limitations about the Reynolds number of the quartic profile adopted by Lew (1949) has been removed. The Kármán (1921) Momentum Integral Equation has been used to evaluate the various characteristics of the flow. A comparative study of Lew's quartic profile and exponential profile together with the quartic profile of the present paper has been undertaken and the graphs for the various characteristics of the flow for a number of Mach numbers and suction coefficients have been drawn. At the end, certain conclusions of general nature about the velocity profiles have been recorded.

Boundary layer on a flat plate with suction

In this paper we have discussed the boundary layer on a plate with suction. The problem is solved near the leading edge as well as far downstream. A linear suction law is assumed near the leading edge for simplicity, whereas no restriction is placed on the suction law in the region downstream. An explict expression for boundary layer thickness in terms of suction speed and distance from leading edge is derived. It is found that the thickness of the boundary layer depends on the derivative of the suction speed. The skin friction also has been evaluated. Though near the leading edge a linear law of suction is assumed, the method used in the paper can be easily generalised for any other power law, for example, we may use a power series expansion for the function defining the suction velocity.

Analysis of the performance characteristics of a two-inertia power transmission system with a plate clutch

The performance of a plate clutch in a two-inertia power transmission system is analysed assuming negligible compliance and using a piecewise linear function to represent the clutch torque characteristic. Expressions defining, for all linear segments of the clutch torque characteristic, dimensionless input and output velocities of the clutch and dimensionless slip period are presented. The use of these expressions in preparing design charts to aid analysis and design of the plate clutch is outlined.

A new ELISA plate based microtiter well assay for mycobacterial topoisomerase I for the direct screening of enzyme inhibitory monoclonal antibody supernatants

Antigen specific monoclonal antibodies present in crude hybridoma supernatants are normally screened by ELISA on plates coated with the relevant antigen. Screening for inhibitory monoclonals to enzymes would require the evaluation of purified antibodies or antibody containing supernatants for their inhibition of enzyme activity in a separate assay. However, screening for inhibitory antibodies against DNA transacting enzymes such as topoisomerase I (topo I) cannot be done using hybridoma supernatants due to the presence of nucleases in tissue culture media containing foetal calf serum which degrade the DNA substrates upon addition. We have developed a simple and rapid screening procedure for the identification of clones that secrete inhibitory antibodies against mycobacterial topo I using 96 well ELISA microtiter plates. The principle of the method is the selective capture of monoclonal antibodies from crude hybridoma supernatants by topo I that is tethered to the plate through the use of plate-bound polyclonal anti-topo I antibodies. This step allows the nucleases present in the medium to be washed off leaving the inhibitor bound to the tethered enzyme. The inhibitory activity of the captured antibody is assessed by performing an in situ DNA relaxation assay by the addition of supercoiled DNA substrate directly to the microtiter well followed by the analysis of the reaction products by agarose gel electrophoresis. The validity of this method was confirmed by purification of the identified inhibitory antibody and its evaluation in a DNA relaxation assay. Elimination of all enzyme-inhibitory constituents of the culture medium from the well in which the inhibitory antibody is bound to the tethered enzyme may make this method broadly applicable to enzymes such as DNA gyrases, restriction enzymes and other DNA transaction enzymes. Further, the method is simple and avoids the need of prior antibody purification for testing its inhibitory activity. (C) 2010 Elsevier B.V. All rights reserved.

Robust prediction of residual velocities and ballistic limits of projectiles for impact on thin aluminium plates

This paper deals with the simulation-driven study of the impact of hardened steel projectiles on thin aluminium target plates using explicit finite element analysis as implemented in LS-DYNA. The evaluation of finite element modelling includes a comprehensive mesh convergence study using shell elements for representing target plates and the solid element-based representation of ogivalnosed projectiles. A user-friendly automatic contact detection algorithm is used for capturing interaction between the projectile and the target plate. It is shown that the proper choice of mesh density and strain rate-dependent material properties is crucial as these parameters significantly affect the computed residual velocity. The efficacy of correlation with experimental data is adjudged in terms of a 'correlation index' defined in the present study for which values close to unity are desirable.By simulating laboratory impact tests on thin aluminium plates carried out by earlier investigators, extremely good prediction of experimental ballistic limits has been observed with correlation indices approaching unity. Additional simulation-based parametric studies have been carried out and results consistent with test data have been obtained. The simulation procedures followed in the present study can be applied with confidence in designing thin aluminium armour plates for protection against low calibre projectiles.