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Orono, ME, United States

Bridge J.W.,Maine Maritime Academy | Bridge J.W.,University of Maine, United States | Bridge J.W.,Racing Surfaces Testing Laboratory | Kiziltas A.,University of Maine, United States | And 4 more authors.
TMS Annual Meeting | Year: 2011

Dynamic mechanical thermal analysis (DMTA) tests were conducted on high-oil content, paraffin-based wax used in wax-coated granular composites. These composites make up the surface of synthetic Thoroughbred horse racetracks used in North America. The modulus and damping response from the DMTA tests were correlated with the dynamic triaxial shear strength response of the bulk track material taken at two different operational temperatures and at four strain rates. The purpose of these tests is to understand the mechanisms of shear strengthening of the bulk track material as the wax is heated through the first crystalline solid to liquid nominal transition temperature. Previous work using differential scanning calorimetry confirmed that under common operational surface temperatures, the wax coatings undergo distinct thermal transitions. The resulting increase in triaxial shear strength values affects the consistency of the racetrack which, in turn, can potentially affect Thoroughbred racing performance and safety of the track surface. Source

Mahaffey C.A.,University of Maine, United States | Mahaffey C.A.,Racing Surfaces Testing Laboratory | Peterson M.,University of Maine, United States | Peterson M.,Racing Surfaces Testing Laboratory | And 2 more authors.
Sports Engineering | Year: 2012

In Thoroughbred dirt racetracks, clay content plays a critical role in moisture management and influences mechanical properties. We hypothesized that different dirt track designs developed in response to the track materials used, particularly the clay content of the material. These designs are in turn a function of the local climate, in particular the amount of rainfall and the evaporation rate. X-ray diffraction makes it possible to determine whole rock and clay mineralogy for 26 tracks that were assigned to one of three track designs: shallow sand (SS), false base (FB), or false base with a pad (FBP). Results demonstrate that SS tracks occur in areas with the highest annual precipitation and have the lowest average clay content, whereas FBP tracks have the lowest annual precipitation and the highest average clay content. FB tracks have intermediate levels of precipitation and clay relative to other track styles. Understanding the effects of clay minerals in dirt and how different racetrack designs have evolved to handle differing levels of clay and moisture can aid in quantifying track maintenance decisions. © 2012 International Sports Engineering Association. Source

Bridge J.W.,Oregon Institute of Technology | Bridge J.W.,University of Maine, United States | Bridge J.W.,Racing Surfaces Testing Laboratory | Peterson M.L.,University of Maine, United States | And 2 more authors.
Experimental Techniques | Year: 2012

A series of tests were conducted to determine the tangent modulus (vertical stiffness) values for a wax-coated granular composite material. This material is commonly used as the surface for Thoroughbred horse racetracks. The tangent modulus is important in the vertical loading of the surface by the hoof for a highly nonlinear material. Test temperatures span a range from 0 to 64°C and include the thermal transition regions of the wax coating obtained from differential scanning calorimetry tests. These temperatures also include the range of temperatures that are encountered during use. Creep tests were conducted to obtain steady-state strain conditions at loads ranging from 0.89 to 4.45 kN, the latter load approximating the weight of a Thoroughbred racehorse. Through-transmission ultrasonic waves were utilized to determine the tangent modulus values. The tangent moduli ranged from 74 to 573 MPa for the conditions tested. For all loads tested, a large decrease in modulus and decrease in material nonlinearity occurred as temperatures increased from 20 to 32°C. This temperature range matches the first thermal transition temperature for the wax coating of the track material. The results of this work provide a basis for racetrack maintenance decisions that can eliminate potentially adverse temperature effects and may reduce equine injuries. © 2012, Society for Experimental Mechanics. Source

Bridge J.W.,University of Maine, United States | Bridge J.W.,Racing Surfaces Testing Laboratory | Peterson M.L.,University of Maine, United States | Peterson M.L.,Racing Surfaces Testing Laboratory | And 2 more authors.
Journal of ASTM International | Year: 2010

Triaxial compression tests at a range of confining pressures and temperatures were conducted for wax-coated granular composite materials. The materials investigated for this work are surfaces that are used for thoroughbred horse racing. The purpose of these tests is to examine how track shear strength and cohesion at a range of loads respond to changes in temperature. A wide range of operational temperatures is experienced by these materials in use, which has been shown to impact performance. Preliminary results show that both shear strength and material cohesion are sensitive to temperature changes with maximum strength and cohesion correlating with the thermal transitions in the wax. For both operational tracks tested, the shear strength peaks at temperatures within or near the end of the first thermal differential scanning calorimetry transition region and is immediately followed by a significant drop in strength. Appropriate wax additions may reduce the effect of temperature on shear strength, which may lead to more consistent track surfaces. These results provide a basis for maintenance decisions that can reduce the effect of temperature on the track performance. Copyright © 2010 by ASTM International. Source

Mahaffey C.A.,University of Maine, United States | Mahaffey C.A.,Racing Surfaces Testing Laboratory | Peterson M.L.,University of Maine, United States | Peterson M.L.,Racing Surfaces Testing Laboratory | Roepstorff L.,Swedish University of Agricultural Sciences
Biosystems Engineering | Year: 2013

Surface consistency is an important factor for the safety of thoroughbred racing surfaces. Factors that influence the consistency in dirt tracks include homogeneity of surface material composition, moisture content, and cushion depth. The influence of cushion depth on the dynamic load and accelerations experienced by the horse at a range of moisture levels typical to operating conditions (14%, 16%, and 18% gravimetric for the material tested in this work), and surface maintenance conditions (sealed and harrowed), is addressed. A biomechanical surface tester, designed to simulate the forelimb impact of a galloping thoroughbred horse, was repeatedly dropped on five different surface conditions, each at two cushion depths (100 mm and 150 mm). The difference of 50 mm, a depth range often found within a single track had a statistically significant effect on the peak load and the secondary phase loading rate experienced by a horse, particularly under the outlying moisture content conditions (relatively dry or moisture saturated). The tested material behaved more similarly at the two cushion depths under moisture conditions at which maximum dry density occurred (16%). Peak loads and loading rates were significantly different between the two depths for harrowed, 14% moisture conditions, and sealed, 18% moisture conditions. These cushion depths and surface material moisture levels are within normal operating conditions for thoroughbred race meetings on shallow sand tracks and therefore may influence the development of musculoskeletal disease and the safety of horses and jockeys. © 2012 IAgrE. Source

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