The reduction or elimination of leakage of hydraulic fluid from fluid power systems is considered a fundamental prerequisite for the expanded use of fluid power. There is also a need to reduce seal friction to both reduce energy dissipation and eliminate control problems. These seals are developed through empirical means at the present time, since the fundamental physics of seal operation has been unclear. This research develops numerical models for analyzing reciprocating hydraulic rod seals with various rod surfaces. These models consist of coupled fluid mechanics, contact mechanics and deformation analyses. Both flooded and starved lubrication boundary conditions are applied. For seals with a smooth rod and a plunge-ground rod, the model combines a 1-D finite volume Reynolds equation solver with a 2-D axisymmetric finite element deformation and static contact mechanics analyses, and a Greenwood-Williamson contact mechanics analysis with rod motion. Leakage and friction, along with sealing zone details with the plunge-ground rod are compared with those with the smooth rod. The influence of rod surface finish on seal performance is investigated and explained, under both flooded and starved conditions For seals with a micro-patterned rod, the model consists of finite volume Reynolds equation solver, finite element deformation and static contact mechanics analyses and a Greenwood-Williamson dynamic contact mechanics analysis. This model is able to handle rod surface pattern with 3-dimensional geometrics. Simulations with different micro-pattern geometries are performed to analyze the fundamental mechanism of surface pattern effects on seal operation. Again, both flooded and starved conditions are applied and the results for both cases are compared and analyzed.

No description available.

No description available.

The drill-strings used in drilling operate under extreme condi-tions, therefore, an accurate understanding of their dynamics is necessary and has attracted much interest. Although a bottom hole assembly (BHA) is to a great ex- tent responsible for the dynamics of the system, the in uence of the drill-pipes has been increasingly neglected by current models. Their dynamics and geometrical behaviour should be better analysed for a deeper understanding of underlying phe- nomena. For example, under stick-slip oscillations, the torque on the drill-string may cause torsional buckling of the drill-pipes, incurring in helical con guration, in which the apparent length is reduced, a ecting the forces at the bit{rock interface. With such behaviour and interactions in mind, this work focuses on elaborating a comprehensive mathematical model to investigate the dynamics of drill-strings, with attention to the drill-pipes section. Firstly, lower dimensional models are used to analyse the stick-slip limit cycle and its limits of existence. Then, a model developed for MEMS is used as a base for a comprehensive model using the formu- lation of Cosserat rods. Relevant boundary conditions are applied and a numerical simulation procedure is established. Simulations are performed for a range of sce- narios under stick-slip occurrence, and the behaviour of the drill-pipes is analysed. Focus is then given to axial vibrations with bit-bounce and the in uence on stick- slip, later to lateral vibrations with whirling motion of the drill-pipes, and nally to helical con gurations, taken by the drill-string under combined torsional, axial and lateral loads, showing the consequent shortening of the drill-string.

Final Project (M.A.)--John F. Kennedy University, 2004. / "August 30, 2004"--T.p. Includes bibliographical references (p. 124-127).

Hot-wire measurements of mean velocity and turbulence parameters were collected at the mid-point of a rod-wall gap and in the centre of a triangular subchannel in accelerating and decelerating flows through a large-scale (12.9:1) model of a 60\degree ~section of a CANadian Deuterium Uranium (CANDU) nuclear reactor 37-rod bundle. A method was developed to correct the axial velocity fluctuations for the effects of cycle-to-cycle variations, which were particularly significant during deceleration. Compared to values in stationary flows, the gap vortex street Strouhal number was slightly larger during accelerating flow and smaller during decelerating flow. The integral length scales of the axial velocity at both locations during both acceleration and deceleration were larger than the corresponding values in stationary flow. The Taylor microscale during transients was slightly larger than the stationary values. The turbulent kinetic energy dissipation rate was larger for accelerating flow and smaller for decelerating flow. The opposite was found to be true for the Kolmogorov microscale.

In the effort to simulate the biologically inspired continuum robot’s dynamic capabilities, researchers have been faced with the daunting task of simulating—in real-time—the complete three dimensional dynamics of the the “beam-like” structure which includes the three “stiff” degrees-ofreedom transverse and dilational shear. Therefore, researchers have traditionally limited the difficulty of the problem with simplifying assumptions. This study, however, puts forward a solution which makes no simplifying assumptions and trades off only the real-time requirement of the desired solution. The solution is a Finite Difference Time Domain method employing an explicit single step method with cheap right hands sides. The cheap right hand sides are the result of a rather ingenious formulation of the classical beam called the Cosserat rod by, first, the Cosserat brothers and, later, Stuart S. Antman which results in five nonlinear but uncoupled equations that require only multiplication and addition. The method is therefore suitable for hardware implementation thus moving the real-time requirement from a software solution to a hardware solution.

Fractures occur commonly in veterinary medicine and are usually the result of vehicular trauma. Traditionally, comminuted mid-diaphyseal fractures are repaired with an interlocking nail, dynamic compression plate, or combination of a bone plate with an intramedullary pin. In recent years, the locking compression plate has gained popularity in human orthopedics due to its biomechanical characteristics and stability in osteoporotic or periprosthetic bone. In addition, the plate may be applied in a percutaneous manner, thereby allowing for biological osteosynthesis. This study evaluates the combination of a locking compression plate and an intramedullary pin in a Delrin rod gap model. Modalities tested include axial load to failure, torsion, and cyclic loading.

Yes / Purpose To record transient ERGs from the lightadapted human retina using silent substitution stimuli which selectively reflect the activity of rod photoreceptors. We aim to describe the morphology of these waveforms and examine how they are affected by the use of less selective stimuli and by retinal pathology. Methods Rod-isolating stimuli with square-wave temporal profiles (250/250 ms onset/offset) were presented using a 4 primary LED ganzfeld stimulator. Experiment 1: ERGs were recorded using a rodisolating stimulus (63 ph Td, rod contrast, Crod = 0.25) from a group (n = 20) of normal trichromatic observers. Experiment 2: Rod ERGs were recorded from a group (n = 5) using a rodisolating stimulus (Crod = 0.25) which varied in retinal illuminance from 40 to 10,000 ph Td. Experiment 3: ERGs were elicited using 2 kinds of nonisolating stimuli; (1) broadband and (2) rod-isolating stimuli which contained varying degrees of L- and M-cone excitation. Experiment 4: Rod ERGs were recorded from two patient groups with rod monochromacy (n = 3) and CSNB (type 1; n = 2). Results The rod-isolated ERGs elicited from normal subjects had a waveform with a positive onset component followed by a negative offset. Response amplitude was maximal at retinal illuminances\100 ph Td and was virtually abolished at 400 ph Td. The use of non-selective stimuli altered the ERG waveform eliciting more photopic-like ERG responses. Rod ERGs recorded from rod monochromats had similar features to those recorded from normal trichromats, in contrast to those recorded from participants with CSNB which had an electronegative appearance. Conclusions Our results demonstrate that ERGs elicited by silent substitution stimuli can selectively reflect the operation of rod photoreceptors in the normal, light-adapted human retina. / Deutsche Forschungsgemeinschaft (DFG) (KR1317/13-1) and Bundesministerium für Bildung und Forschung (BMBF) (01DN14009) provided financial support for JK.

Current scoliosis corrective surgeries may include the use of multiple instrumentation devices including screws, wires, nuts, and rods. The instrumentation in most cases is implemented in its native form. However, the instrumentation rods must be contoured to a desired shape prior to fixation to the spine. The contouring of the instrumentation rod is currently performed manually and may require significant time for completion. This results in an increase of operation time and reduced accuracy of the instrumentation rod. The feasibility of automating the contouring process was studied to determine if the time required to contour a rod could be reduced and if the accuracy of the rod could be improved. This study built upon a previous effort to construct a prototype that would automate the manufacture of spinal instrumentation rods. The Spinal Instrumentation Bending Prototype (SIBP) focused on ease of use, time of manufacture, and accuracy. In order to complete the manufacturing process, the current SIBP uses a set of three dimensional control points that represent the desired contour of the rod. These control points are translated into manufacturing inputs that control the SIBP. The control application for the SIBP contains local and global feedback routines that correct for any manufacturing errors. A comparative study was made between the SIBP and an experienced orthopedic surgeon to determine the level of bending accuracy improvement. / Master of Science