R Gnanamoorthy

Powder metallurgy gears are becoming popular in the drives in many fields for power transmission. In order to expand the scope of PM gears to commercial applications, their worthiness has to be proved by thorough testing. To test the P/M gears in the laboratory, an absorption type test rig has been designed and fabricated. Various facilities available in the test rig to evaluate the P/M gears and the monitoring techniques incorporated in testing are discussed in the paper.

Reliable performance of through-hardened sintered steel gears can be ensured for any application only after prior testing at the operating speed-load limits. This approach is time consuming and costly though it gives guaranteed results. An analytical approach to predict the performance of sintered gears and to cut short the time of testing is given here. This approach takes into account all possible modes of failure and gives the safe working zone for through-hardened sintered steel gears and widens the scope of application of sintered gears.

Filament wound multilayered vessels are fabricated by continuously winding the filament over a mandrel of the shape and size of the desired vessel. The mandrel may be a removable one, or one that remains as a permanent part of the vessel. During fabrication of this kind of vessels, the filaments made up of reinforcing fibers and resins, are wound with tension over the mandrel. This winding tension in the filament induces compressive stresses in the vessel, which in turn increases the burst pressure of the vessel. This paper presents a method to determine the prestresses induced in the filament wound cylinders due to winding tension both in axial and circumferential directions. When a layer is wound with tension, it induces incremental compressive stresses in the preceding layers, while the present layer itself is in tension. The compressive stresses induced by subsequent addition of new layers reduce this tensile stress. The results of the present analysis show that the prestresses compensate the stresses due to working internal pressure. The prestresses induced depend upon various parameters like winding tension, winding angle of each layer, and the material used.

Static and cyclic fatigue crack growth behaviour of gamma base titanium aluminides with three different microstructures were investigated. Influence of cyclic test frequency on fatigue crack growth behaviour was also studied at room temperature under a controlled humidity condition. The crack growth behaviour both under static and cyclic loading was strongly influenced by the microstructure. The threshold stress intensity and crack growth behaviour under cyclic loading were much inferior than that under static loading indicating the `true-cyclic fatigue' effect exhibited in gamma base titanium aluminides. No significant effect of test frequency on the crack growth behaviour was observed for the equiaxed and duplex microstructure materials.