Prediction of Flow Path Pressure Drops in Curved Galleries for Additively Manufactured Hydraulic Manifolds

Hydraulic manifolds are traditionally manufactured using externally drilled intersecting galleries. This results in undesirable artefacts in the flow path such as sharp corners, and dead oil volumes, and requires additional plugs to blank redundant holes. These artefacts affect flow separation, aggravate pressure-drop and reduce hydraulic stiffness. Recent advancements in additive manufacturing (AM) technology have enabled the development of additively manufactured components which provide greater freedom in channel design and routing. Galleries can provide flow paths which are smoothly curved in 3 dimensions. AM manifold geometry can be optimized to reduce size and weight. In this research, analytical expressions are sought to approximate pressure drops in complex curved flow paths, which can subsequently be used for manifold optimization. The curved flow paths are defined by polynomial splines which are then fragmented into a series of segments each defined by a bend angle and bend radius. This paper uses approximations to Computational Fluid Dynamics (CFD) results to form pressure-drop models over a range of segment bend radii and angles. These models are then used to predict the pressure drops for curved galleries used in AM manifolds. The method is applied to four example curved galleries, and provides a reasonably accurate pressure-drop prediction in each case.

A Resonant Pressure Microsensor with a Wide Pressure Measurement Range

This paper presents a resonant pressure microsensor with a wide range of pressure measurements. The developed microsensor is mainly composed of a silicon-on-insulator (SOI) wafer to form pressure-sensing elements, and a silicon-on-glass (SOG) cap to form vacuum encapsulation. To realize a wide range of pressure measurements, silicon islands were deployed on the device layer of the SOI wafer to enhance equivalent stiffness and structural stability of the pressure-sensitive diaphragm. Moreover, a cylindrical vacuum cavity was deployed on the SOG cap with the purpose to decrease the stresses generated during the silicon-to-glass contact during pressure measurements. The fabrication processes mainly contained photolithography, deep reactive ion etching (DRIE), chemical mechanical planarization (CMP) and anodic bonding. According to the characterization experiments, the quality factors of the resonators were higher than 15,000 with pressure sensitivities of 0.51 Hz/kPa (resonator I), −1.75 Hz/kPa (resonator II) and temperature coefficients of frequency of 1.92 Hz/°C (resonator I), 1.98 Hz/°C (resonator II). Following temperature compensation, the fitting error of the microsensor was within the range of 0.006% FS and the measurement accuracy was as high as 0.017% FS in the pressure range of 200 ~ 7000 kPa and the temperature range of −40 °C to 80 °C.

Design of a Compliant Hinge Based on Closed Form Pressure Balancing

Compliant mechanisms consist of a monolithic body and obtain motion through elastic deformation. Multiple compliant flexure designs are known but their translational to rotation stiffness ratio is often limited. This work introduces a novel compliant hinge design with increased stiffness ratio compared to the state of the art compliant hinges. The hinge functions by having an encapsulated fluid medium that contributes to high normal stiffness, but doesn’t influence the rotational stiffness. A 2D design model is presented that shows the effect of the geometry on the stiffness ratio performance. Subsequently, a computational 3D analysis is performed and the resulting design is realized as a demonstrator. The performance is compared to conventional compliant hinges based on the stiffness ratio. This shows an increase of at least a factor 30 on the stiffness ratio.

Bridge Substructure Repairs with Self-Consolidating Concrete and Galvanic Anodes

Historically, the Virginia Department of Transportation (VDOT) has repaired chloride-contaminated reinforced concrete bridge substructure elements that contain vertical and overhead sections with either shotcrete or a conventional A3 (3,000 psi) or A4 (4,000 psi) concrete. This study investigated using self-consolidating concrete (SCC), which has a high flow rate, bonds well, has low permeability, and provides smooth surfaces, as another option. The study also explored the use of galvanic anodes to control corrosion activity in SCC repairs. In VDOT’s Lynchburg and Staunton Districts, SCC repairs were made with and without the use of galvanic anodes. This provided a means for determining the benefit of using the anodes. The needed repair areas were determined by visual observation and sounding. After 7 years of service, SCC repair areas with and without anodes did not exhibit corrosion activity; small vertical cracks were evident in the SCC but did not affect performance. The anodes can provide protection to the steel immediately adjacent to the repair areas. However, unrepaired concrete areas away from the patched area with anodes now require additional repairs. SCC can be successfully placed; however, attention should be paid to form pressure and slump loss. Selection of repair areas should be based on corrosion-related measurements such as half-cell or chloride content, rather than sounding. Progression of corrosion demonstrates the necessity of removing all chloride-contaminated concrete not just adjacent to, but also away from the reinforcement, as anodes in the repair area will provide protection only in a narrow area around the patch.