Suspension Testing of 3 Heavy Vehicles - Methodology and Preliminary Frequency Analysis

Three air-sprung heavy vehicles (HVs) were instrumented and tested on typical suburban and highway road sections at typical operational speeds. The vehicles used were a tri-axle semi-trailer towed with a prime mover, an interstate coach with 3 axles and a school bus with 2 axles. The air springs (air bags) of the axle/axle group of interest were configured such that they could be connected using either standard longitudinal air lines or an innovative suspension system comprising larger-than-standard longitudinal air lines. Data for dynamic forces on axles, wheels and chassis were gathered for the purposes of: analysis of the relative performance of the HVs for the two sizes of air lines; informing the QUT/Main Roads project Heavy vehicle suspensions – testing and analysis; and providing a reference source for future projects. This reports sets down the methodology and preliminary results of the testing carried out. Accordingly, Fast-Fourier plots are provided to show indicative frequency spectra for HV axles, wheel forces and air springs during typical use. The results are documented in Appendices 3 to 5. There appears to be little or no correlation between dynamic forces in the air springs and the wheel forces in the HVs tested. Axle-hop at frequencies between 10-15 Hz predominated for unsprung masses in the HV suspensions tested. Air-spring forces are present in the sub-1.0 Hz to approximately 2 Hz frequency range. With the qualification that only one set of data from each test speed is presented herein, in general, the peaks in the frequency spectra of the body-bounce forces and wheel forces were reduced for the tests with the larger longitudinal air lines. More research needs to be done on the load sharing mechanisms between axles on air-sprung HVs. In particular, how and whether improved load sharing can be effected and whether better load sharing between axles will reduce dynamic wheel and chassis forces. This last point, in particular, in relation to the varied dynamic measures used by the HV testing community to compare different suspension types

Procedure for Asphalt Mixture Friction Evaluation for WVDOH

Monitoring asphalt skid resistance in the laboratory could aid in improved friction prediction capabilities and provide insight for developing alternative asphalt mixture designs in the future. The West Virginia Department of Highways (WVDOH) sought the design of a laboratory accelerated asphalt polishing machine to further expand on current skid resistance measurement practices. The design is modeled after the North Carolina State University (NCSU) polishing machine detailed in ASTM E660. The purpose of this research was to develop a testing procedure for the polishing equipment. Friction was monitored with the British Pendulum Tester (BPT) according to ASTM E303. Specimens were prepared using a Superpave Gyratory Compactor (SGC) at two air void contents (4% and 8%) using four asphalt surface course mixtures (JFA 12.5mm Skid-RAP, WVP W1-RAP, Greer W1, WVP 12.5mm Skid-RAP). Specimens were placed in the polishing machine for a minimum of 48,000 wheel passes and conditioned with silicon carbide abrasive powder for accelerated polishing. Tire toe angles were adjusted between low (4° toed in and 2° toed out) and high (8° toed in and 4° toed out) toe angles. Average BPN values were plotted and used for slope calculations to investigate asymptotic behavior. These trend lines were also used as prediction models to determine the number of wheel passes required to reach minimum BPN limits; a larger number of wheel passes indicates more polish resistance. Variables evaluated: specimen air void content (VTM), tire toe angles, tire type, nominal maximum aggregate size (NMAS), and asphalt production company were considered for analysis. Data were compared using t-tests at 95% confidence to determine statistical differences between average BPN measurements. The most polish resistant mixture was the WVP W1-RAP mix; JFA 12.5mm Skid-RAP was the least. T-tests concluded only statistically different results for toe angles and lab/field comparisons. Lower friction values for higher toe angles suggest increased polishing when using higher toe. These results could provide insight on polishing procedure optimization and skid resistant characteristics of asphalt mixtures

Frontiers in Ultra-Precision Machining

Ultra-precision machining is a multi-disciplinary research area that is an important branch of manufacturing technology. It targets achieving ultra-precision form or surface roughness accuracy, forming the backbone and support of today’s innovative technology industries in aerospace, semiconductors, optics, telecommunications, energy, etc. The increasing demand for components with ultra-precision accuracy has stimulated the development of ultra-precision machining technology in recent decades. Accordingly, this Special Issue includes reviews and regular research papers on the frontiers of ultra-precision machining and will serve as a platform for the communication of the latest development and innovations of ultra-precision machining technologies

The design, construction and testing of the optics for a 147-cm-aperture telescope

Geodetic optics research for the Air Force Cambridge Research Laboratories (AFCRL) is described. The work consisted mainly of the fabrication of the optical components for a telescope with a 152-cm-diam (60-in.) primary mirror masked down to 147-cm-diam for use by the AFCRL for a lunar ranging experiment. Among the achievements of this contract were the following: completion of the primary and secondary mirrors for a high-quality 147-cm-diam telescope system in eight months from the start of edging the primary; manufacture and testing of a unique center mount for the primary according to an AFCRL design that allowed for a thin-edged and therefore less-massive mirror; and development of a quantitative analysis of the wire test for calculating the departure of the mirror figure from the design figure quickly and accurately after each polishing step. This analysis method in conjunction with a knowledge of polishing rates for given weights and diameters of tools, mirror, and polishing materials should considerably reduce the polishing time required for future large mirrors

A framework for digitisation of manual manufacturing task knowledge using gaming interface technology

Intense market competition and the global skill supply crunch are hurting the manufacturing industry, which is heavily dependent on skilled labour. Companies must look for innovative ways to acquire manufacturing skills from their experts and transfer them to novices and eventually to machines to remain competitive. There is a lack of systematic processes in the manufacturing industry and research for cost-effective capture and transfer of human skills. Therefore, the aim of this research is to develop a framework for digitisation of manual manufacturing task knowledge, a major constituent of which is human skill. The proposed digitisation framework is based on the theory of human-workpiece interactions that is developed in this research. The unique aspect of the framework is the use of consumer-grade gaming interface technology to capture and record manual manufacturing tasks in digital form to enable the extraction, decoding and transfer of manufacturing knowledge constituents that are associated with the task. The framework is implemented, tested and refined using 5 case studies, including 1 toy assembly task, 2 real-life-like assembly tasks, 1 simulated assembly task and 1 real-life composite layup task. It is successfully validated based on the outcomes of the case studies and a benchmarking exercise that was conducted to evaluate its performance. This research contributes to knowledge in five main areas, namely, (1) the theory of human-workpiece interactions to decipher human behaviour in manual manufacturing tasks, (2) a cohesive and holistic framework to digitise manual manufacturing task knowledge, especially tacit knowledge such as human action and reaction skills, (3) the use of low-cost gaming interface technology to capture human actions and the effect of those actions on workpieces during a manufacturing task, (4) a new way to use hidden Markov modelling to produce digital skill models to represent human ability to perform complex tasks and (5) extraction and decoding of manufacturing knowledge constituents from the digital skill models

The Galaxy Evolution Explorer

The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750Å and 1750-2800Å) will range from an all-sky survey (limit m_(AB)~20-21) to an ultra-deep survey of 4 square degrees (limit m_(AB)~26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (m_(AB)~20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800Å band. The instrument includes a 50 cm modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey

Laser surface texturing of stainless steel 316L cylindrical pins for interference fit applications

This study is focused on the development of a novel method for designing high-end interference fit fasteners. In this work, a new surface laser treatment process was utilized to enable enhanced usability and bond strength control of press-fit connections. Cylindrical 10 mm diameter pins of 316L were textured over a 10 mm length using a pulsed CO2 laser beam focused one millimeter below the surface, with the thermal energy adjusted to bring the surface to just above the melting point of the metal. The pin surface morphology and dimensions were precisely controlled by controlling the laser processing parameters specifically the laser beam power, the pulse repetition frequency, and the overlap between scan tracks. The pin was inserted into a hub hole diameter of 10.05±0.003 mm and pull out joint bond strengths were examined. The results of this study showed that surface thus altered provided improved control of the bond strength which is a particular novelty of this new interference fit joining method. Surface roughness, Ra, from 40 to 160 µm, melt pool depths from 0.4 to 1.7 mm, increases in the pin outer diameter from 0.5 to 1.1 mm, and pull out forces of up to 7.51 kN were achieved. The bond joint was found to re-grip before final failure providing a more secure joint and increased safety. This joining method allows for the possibility of joining different materials. The pulse repetition frequency was measured to be the most significant processing parameter for control of the resulting mechanical properties and the bond strength with a clear inverse relationship

Investigation of Spherical Bearings for Use in the UltraForm Finishing Polishing Process

UltraForm Finishing (UFF) is a production-level optical polishing process consisting of a moving belt that is pressed into an optical surface by a carrier wheel. The current configuration is comprised of a cylindrical carrier wheel attached to cylindrical roller bearings. As the optics market is moving towards aspheric geometry with smaller radii of curvature, geometric limitations associated with roller bearings requires the development of a modified approach to the UFF process. This thesis explores the feasibility of incorporating spherical fluid bearing elements in the UFF process as a replacement for roller bearings. Self-acting (or wedge film) and externally pressurized hydrostatic spherical fluid-film bearings were investigated for the UFF process. The self-acting bearing was modeled and analyzed using a previously developed hydrodynamic finite element computer program. The hydrostatic bearing was modeled using an analytical formulation of the Reynolds equation coupled with empirical data to account for entrance flow effects at the feed hole and to account for pressure drops in the bearing fluid supply system. Both bearing configurations predicted adequate fluid film thickness under steady load and speed. Performance tests on the UFF were completed with both bearing configurations under steady load and speed. Ball to cup seizure was observed with the self-acting configuration nearly immediately after initial load and speed application, with seizure presumably due to inadequate squeeze film resistance during the transient startup period. The hydrostatic bearing operated successfully over a wide range of applied loads and speeds employed in the current UFF process with minimal cup and ball wear. The feasibility of the hydrostatic spherical bearing element in the UFF process was subsequently demonstrated through the generation of repeatable and acceptable removal function maps which were then employed in the polishing of a planar optical surface