Experimental investigation of the dynamics of a slider-crank mechanism with local linear force input

Conventional implementation of slider-crank mechanisms result in high loads transmitted through the mechanical structure, inhibiting the design of compact and oil-free machines. Therefore, this research proposes to step away from the conventional, i.e. rotative, actuation and to investigate local linear actuation on the slider-component directly, while maintaining the kinematic link of the slider-crank configuration. In this work the local linear actuating principle is evaluated experimentally where the goal is to obtain a continuous movement of the slider mechanism where Top Dead Centre & Bottom Dead Centre are reached and to minimise the loads transmitted through the mechanical structure. The non-isochronous transient behaviour of a slider-crank mechanism loaded with a spring-damper element is detailed as well as the optimal working conditions at steady state to achieve a reduced loading of the kinematic structure. By matching the operating frequency and resonance frequency of the system, a reduction of the loads transmitted through the system by 63% of the nominal spring load can be achieved. Further experimental (and multibody mechanical) investigation on the influence of flywheel exposes a clear trade-off between the sensitivity of the system and the transmission of the actuation force through the kinematic link.

Tailored Sheared Blanks Produced by Incremental ECAP

Incremental equal channel angular pressing (I-ECAP) is a process used for production of continuous ultrafine grained bars, plates and sheets. Normally the thickness of the processed billet is kept unchanged in consecutive passes to enable repetitive insertion into the same die. This is achieved by controlling the bottom dead centre of the reciprocating punch. However, if a final product requires being thinner and therefore longer, the bottom position of the punch can be lowered before the last pass. Going further, the bottom position of the punch can be changed during the process, which opens up a possibility to vary billet thickness along its length. Such a product, especially sheet, can serve as a preform for further metal forming operations and is known as tailored blank. This paper will show examples of varying thickness sheets produced by different configurations of I-ECAP. Experimental and finite element results will be presented.

Piston Crown Temperatures in a Compression-ignition Engine with “Comet” Head

The paper describes tests on a high-speed compression-ignition engine of 120 mm. bore fitted with a Ricardo “Comet” head in which the piston was of “Y” alloy. The temperatures were measured by thermocouples in the crown, the connexions to the temperature-measuring apparatus being intermittent, and made only when the piston approached bottom dead centre. Thermocouple voltages were measured on a potentiometer, using the “null deflexion” method. Piston crown temperatures were measured for various loads, speeds, and cylinder liner temperatures, and were found to be higher than those obtained in previous investigations because of the very high turbulence induced by the “Comet” type antechamber. Confirmatory tests were made by using temperature-indicating paints, but these were not as satisfactory as had been expected. The results are discussed in the light of knowledge gained in former work on this subject; and, in particular, comparison is made with temperatures obtained in tests on a Mirrlees-Ricardo sleeve valve engine of similar speed and using a piston of the same design and material.