TECHNOLOGICAL OPTIMIZATION OF POSITIONING PRISMATIC-BODY DETAILS IN HOLDING DEVICES

The aim of the present work is to propose and substantiate a scheme of a device for positioning prismatic-body details on two holes with parallel axes and a plane, perpendicular to them. This will help to achieve high accuracy of linear and angular orientation of the workpiece. Thus the requirements for the accuracy of the center-to-center distance of the base holes will be reduced and the process of assembling the workpiece to the grip pawls will be simplified.

Non-Linear Signal Analysis Applied to Surface Wear Condition Monitoring in Reciprocating Sliding Testing Machines

When the surfaces of two elastic bodies present relative motions under certain amount of contact pressure the mechanical system can be unstable. Experiments conducted on elastic bodies in contact shown that the dynamic system is self-excited by the non-linear behavior of the friction forces. The main objective of this paper is to estimate the friction force using the vibrations signals, measured on a reciprocating wear testing machine, by the proposed non-linear signal analysis formulation. In the proposed formulation the system global output is the sum of two outputs produced by a linear path associated in parallel with a non-linear path. This last path is a non-linear model that represents the friction force. Since the linear path can be identified by traditional signal analysis, the non-linear function can be evaluated by the global input/output relationships. Validation tests are conducted in a tribological system composed by a sphere in contact with and a prismatic body, which has an imposed harmonic motion. The global output force is simultaneously measured by a piezoelectric and by a piezoresistive load cells. The sphere and prismatic body vibrations are measured by a laser Doppler vibrometer and by an accelerometer respectively. All signals are digitalized at the same time base and the data is transferred to a microcomputer. The non-linear signal analysis technique uses this data to identify the friction force.

Geophysical interpretation of the Torngat orogen along the North River – Nutak transect, Labrador

A 19.3 mGal (1 Gal = 1 cm/s2) positive Bouguer gravity anomaly and a broad aeromagnetic low coincide with the Tasiuyak domain of the early paleo-Proterozoic Torngat orogen. The domain evolved during the collision of the western margin of the Archean Nain Province with an inferred, eastward-facing, platform-to-rise, sedimentary wedge sited on a proto-continent of Churchill (Rae) Province.A density contrast of +0.065 g∙cm−3 was measured between rocks of the Tasiuyak domain and those of the flanking Lac Lomier complex of the orogen and Nain Province. Using this contrast, a two and one-half dimensional model shows that rocks of Tasiuyak domain constitute a triangular prismatic body with maximum thickness of 13 km adjacent to Nain Province, which thins westward to a feather edge. The model is compatible, qualitatively, with the aeromagnetic anomaly and consonant with geological interpretation of an eastward-facing and thickening continental slope deposit. Deep exhumation of the Torngat orogen may account for the absence of paired gravity anomalies characteristic of many sutures elsewhere in the Canadian Shield.

A Note on Choking Cavitation Flow Past Bluff Bodies

A model is developed to predict the choking cavitation number for sharp edged bluff bodies subject to wall interference effects. The fact that the forebody pressure distribution under cavitating conditions essentially resembles the values obtained in noncavitating flows is made use of in the development of the model. The model is verified using experimental results from present and previous studies for a specific case of choking flow past a two-dimensional prismatic body.