Determining Skid Resistance Needs on Horizontal Curves for Different Levels of Precipitation

Horizontal curves are a major cause of crashes that lead to fatal and serious injuries. Much research has been conducted on the safety implications of geometric and traffic characteristics of curves. Variables describing curve geometry and speed have been incorporated into safety prediction methodologies. However, relatively less research has been conducted on the effects of pavement friction and weather data on safety. The objective of this study is to develop a methodology for determining the pavement friction needs for different levels of precipitation. To accomplish the study objective, rural two-lane, four-lane undivided, and four-lane divided horizontal curve data from Texas were used. Safety prediction models were developed that included traffic and geometric characteristics, skid number, and annual precipitation rate. These models were then used to develop the guidelines for assessing the safety performance of a curve of interest by accounting for curve geometry, pavement skid resistance, and exposure to the wet-weather conditions that are most relevant for considerations of skid resistance. For conducting a planning-level analysis to identify candidate sites for pavement friction treatments, researchers developed thresholds based on the combined effect of skid number and annual precipitation variables. Researchers also provided skid number thresholds for high-priority sites for two example locations that experience significantly different levels of annual precipitation.

Preliminary Studies on Transition Curve Geometry: Reality and Virtual Reality

The topic of transition curves is well known in track and road engineering. Over the years the need for easement between straight and curved sections in railway and road design has grown, with an important reason being increase in vehicle speed. Testing of transitions is often done with graph analysis where the property of lateral change of acceleration is compared between varieties of curves. However, graph analysis does not give a clear understanding of the behaviour of a vehicle in a transition phase the way, for instance, field or laboratory experiments might do. In this paper we present an initial study on the behaviour of a down-scaled vehicle model driving through three distinct transitions from straight to curved sections. In addition we show a comparison of the physical model against a virtual model.

Microstrip Patch Strain Sensor Miniaturization Using Sierpinski Curve Fractal Geometry

In this paper miniaturization of a microstrip patch strain sensor (MPSS) using fractal geometry was proposed and analyzed. For this purpose, the transducer of Sierpinski curve geometry was utilized and compared with the most commonly utilized rectangular resonator-based one. Both sensors were designed for the same resonant frequency value (2.725 GHz). This fact allows analysis of the influence of the patch (resonator) shape and size on the resonant frequency shift. This is very important as the sensors with the same resonator shape but designed on various operating frequencies have various resonant frequency shifts. Simulation and experimental analysis for all sensors were carried out. A good convergence between results of simulation and measurements was achieved. The obtained results proved the possibility of microstrip strain sensor dimensions reduction using Sierpinski curve fractal geometry. Additionally, an influence of microstrip line deformation for proposed sensors was studied.

Study of Squeeze Effect and Worm of Rollers Affecting the Inverse Bending on Straighten Steel Pipes

In the manufacturing process of steel pipes, bending or torsion deformation is most usual happened by the variation of temperature, external extension or compression, inner residual stress. The straighten quality is thus out of standard. Tilt roller straightens machine is thus become required equipment in the straightening process. Rollers can generate vertical and radial bending continuously in order to achieve enough straightness. These two direction bending moments have to good match each other. Quality problems, such as surface wear scar, sink in or shorten the length, can thus be avoided. Curve geometry of rollers, squeezing effect and straighten inverse bending moment calculation were considered in the study. Optimal bending stress cannot be lower than 70 % yielding stress and contacting length between roller and pipe cannot be lower than 65% curve length of the roller. The worm of rollers affect contact situation and the tilt angle of roller have to rearrange.

Noncommutativity of Finite Rotations and Definitions of Curvature and Torsion

The geometry of a space curve, including its curvature and torsion, can be uniquely defined in terms of only one parameter which can be the arc length parameter. Using the differential geometry equations, the Frenet frame of the space curve is completely defined using the curve equation and the arc length parameter only. Therefore, when Euler angles are used to describe the curve geometry, these angles are no longer independent and can be expressed in terms of one parameter as field variables. The relationships between Euler angles used in the definition of the curve geometry are developed in a closed-differential form expressed in terms of the curve curvature and torsion. While the curvature and torsion of a space curve are unique, the Euler-angle representation of the space curve is not unique because of the noncommutative nature of the finite rotations. Depending on the sequence of Euler angles used, different expressions for the curvature and torsion can be obtained in terms of Euler angles, despite the fact that only one Euler angle can be treated as an independent variable, and such an independent angle can be used as the curve parameter instead of its arc length, as discussed in this paper. The curve differential equations developed in this paper demonstrate that the curvature and torsion expressed in terms of Euler angles do not depend on the sequence of rotations only in the case of infinitesimal rotations. This important conclusion is consistent with the definition of Euler angles as generalized coordinates in rigid body dynamics. This paper generalizes this definition by demonstrating that finite rotations cannot be directly associated with physical geometric properties or deformation modes except in the cases when infinitesimal-rotation assumptions are used.

Minimizing Voids With Using an Optimal Raster Orientation and Bead Width for a Material Extrusion Based Process

Additive Manufacturing (AM) is the process of joining materials ‘layer by layer’ to make products from Computer Aided Design (CAD) model data. AM processes support faster product realization for a wide selection in industries. The Material Extrusion (ME) process is an AM process that builds a product from thin layers of extruded filaments from a semi-melted material such as a thermoplastic. In commercial systems, the software automatically generates the tool paths for both the model and any necessary supports, based on the curve geometry and the specified build parameters. The interior fill rotates 90° between each layer. Automatically generating the tool path can be the biggest weakness for this process planning strategy. Voids and discontinuities have been observed after evaluating test specimens developed to explore mechanical characteristics. Choosing an optimal raster orientation and bead width will help minimize voids and discontinuities in each layer. A mathematical model is introduced in this paper to find optimal raster orientation and bead widths based on the geometry of the slice for selected 2D extruded parts. As well, preliminary quality assessment metrics are introduced. Void analysis is performed to evaluate solution approaches, and the results compared. The future work will investigate utilizing multiple bead widths for a layer to minimize voids, and developing more comprehensive quality metrics to highlight problematic regions.