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Dynamic instability is an interesting topic in the mechanics of elastic structures. Though the subject has been formed by many analytical, numerical, and experimental investigations, it has many issues, as evidenced from the critical overview of Elishakoff. Furthermore, the controversial articles of Koiter and Sugiyama on unrealistic and realistic follower forces demand experimental verification. Mullagulov has proposed a device for creating the follower forces and tested steel rods under compression. This paper highlights the experimentation of Mullagulov and his observations briefly to examine the influence of material properties on the stability load estimations and to confirm the practical realization of follower forces.

Tuning of the PID controller is a time consuming and laborious task and several researchers are working on providing better solutions. In this research article, the authors implemented an optimal PID controller for the 4-DOF planar robotic manipulator which will aid in smooth control of joint motions. The dynamics of the manipulator are calculated following the Lagrange-Euler formulation. After the controller is designed, the controller gains have been tuned utilizing manual tuning procedure reported earlier. As the manual procedure does not guarantee optimal parameters, the authors used a population-based optimization algorithm, that is, a Genetic algorithm for achieving better results. The procedure of tuning controller gains using genetic algorithms is presented and further, the performance of the developed algorithm is verified and compared with that obtained using manual procedure using computer simulations.

The dynamic stability of a uniform cantilever column under a tip-concentrated subtangential follower force is examined. The governing two-point boundary value problem is converted to an initial value problem. A simple numerical iterative scheme is followed to generate a load versus frequency curve (eigencurve) in order to study the critical and post-critical behavior of the columns subjected to a tip-concentrated follower force. For the load rotation parameter greater than [Formula: see text], the coalesce frequency and the corresponding critical load are obtained. The deformed configurations of cantilever columns are generated for different load rotation parameters. The details of the critical load parameter, tip angle and tip coordinates of the columns for the specified load rotation parameter are presented. The critical load parameter increases with the load rotation parameter.

This paper presents briefly on the boiler efficiency evaluation procedures by direct and indirect methods useful in thermal power plants. In the direct method consideration is given to the amount of heat utilized while evaluating the efficiency of the boiler, whereas, indirect method accounts for various heat losses. The boiler efficiency evaluated by direct method is found to be lower than that evaluated by indirect method as per the ASME PTC-4.1 standards. However, the direct method helps the plant personnel to evaluate quickly the boiler efficiency with few parameters and less instrumentation.

This paper presents optimum drilling parameters of coir fiber reinforced polyester composites following the Taguchi design of experiment. A simple multi-objective optimization approach is suggested and presented an efficient prediction methodology to estimate thrust force, torque and tool wear for the identified optimum process parameters.