Effect of easement geometry on rail end fillet stress at bolted rail joints for transit track

Continuously welded rail (CWR) has become more popular than bolted joints because of the advantages of continuous geometry and stiffness and the resulting maintenance savings. Due to a variety of reasons, a considerable number of bolted joints are still in service in rail transit systems. With the high frequency of impact loads, rail at bolted joints are vulnerable to defects, such as cracking and head-web separation that could lead to more drastic failures and consequences (i.e. derailments, etc.). To prolong the service life of joint bars and rails, rail-end easements in the center of the bar were proposed and became standard in some freight rail companies. However, the effectiveness of a joint bar easement largely depends on the geometry of the easement. Therefore, the easement designed for freight track may not be effective for rail transit infrastructure. Further, the effect of easement geometry has not been thoroughly investigated and documented. Therefore, this study investigates the stress distribution at the rail end bolt-hole and upper fillet areas for joint bars with different easement geometries through a parametric analysis performed with Finite Element (FE) modeling. The FE model used in this study was developed specifically to study rail joints and was validated through full-scale laboratory testing. Results from this study show that a deeper easement yields lower contact stresses, while a longer easement does not necessarily reduce the contact stresses with the studied combination of rails and bolted joints for transit track. An easement may reduce the service life of the joint if the geometry of the easement is not properly engineered.

The #-Filter Anti-Aliasing Based on Sub-Pixel Continuous Edges

Anti-aliasing plays a decisive role in enhancing immersion experience in games and 3D visualization fields. In general, hardware anti-aliasing is not directly compatible with deferred shading. It is challenging to detect geometry edges accurately from sub-pixel to alleviate artifacts. In this paper, we propose an anti-aliasing algorithm of the #-filter anti-aliasing based on sub-pixel continuous edges. It can solve the geometry edges aliasing and the flicker problem in deferred shading. First, the geometry scene with multi-sampling anti-aliasing (MSAA) is rendered to a G-Buffer designed elaborately. Second, the geometry edges are detected on the sub-pixel-level. We mainly take advantage of the Chebyshev inequality to adaptively determine the edges from the probability statistic and the view frustum location. Third, the continuous geometry edges are reconstructed by a #-filter method. Finally, the edge pixels are shaded adaptively. The implementation demonstrates that our algorithm is efficient and scalable for generating high-quality anti-aliasing geometry and reducing shading calculation overhead.

Fatigue assessment in welded joints based on geometrical variations measured by laser scanning

In the current study a method to determine the location of fracture initiation for non-load carrying fillet welds based on continuous geometry measurements is proposed. Measurements and weld quality evaluation were carried out on welded specimens using the Winteria® software qWeld. One hundred nineteen specimens were produced, scanned, and fatigue tested until failure. The fracture surfaces have been investigated in order to find the location(s) for most probable point(s) of initiation. These data were then used to fit the proposed model parameters used to predict the point of initiation. Local weld geometry measurements were extracted from the predicted fracture initiation location(s) to analyse the correlation between local weld geometry and fatigue life. It was observed that fatigue life and leg length were positively correlated and that strong correlations exist between the individual geometrical parameters with regard to location of the fatigue crack initiation.

Fermions, loop quantum gravity and geometry

We discuss here the geometry associated with the loop quantum gravity when it is considered to be generated from fermionic degrees of freedom. It is pointed out that a closed loop having the holonomy associated with the [Formula: see text] gauge group is realized from the rotation of the direction vector associated with the quantization of a fermion depicting the spin degrees of freedom. During the formation of a loop a noncyclic path with open ends can be mapped onto a closed loop when the holonomy involves [Formula: see text]-deformed gauge group [Formula: see text]. In this case, the spinorial variable attached to a node of a link is a quasispinor equipped with quasispin associated with the [Formula: see text] group. The quasispinors essentially correspond to the fermions attached to the end points of an open path in loop space. We can consider adiabatic iteration such that the quasispin associated with the [Formula: see text] group gradually evolves as the time dependent deformation parameter [Formula: see text] changes and we have the holonomy associated with the [Formula: see text] group in the limit [Formula: see text]. In this way we can have a continuous geometry developed through a sequence of [Formula: see text]-deformed holonomy-flux phase space variables which leads to a continuous gravitational field. Also it is pointed out that for a truncated general relativity given by loop quantum gravity on a fixed graph we can achieve twisted geometry and Regge geometry.

Time Varying Approaches to Dynamic Analysis of a Planetary Gear System Using a Discrete and a Continuous Models

Two time varying approaches are executed in analyzing dynamics for an involute planetary gear system, which respectively use a conventional discrete model of the equivalent mass-damping-spring elements and a continuous geometry model by the finite element method. In the discrete approach, the tooth number, position, and phasing difference of the meshing tooth pairs are described by time varying and nonlinear meshing stiffnesses. Natural frequencies, deformations, meshing forces, fillet stresses, and dynamic factors can be calculated by using the Jacobi transformation and the Runge-Kutta integration. In the continuum approach, dynamics of the planetary gear system is analyzed using the software, LS-DYNA. The approach of the continuous geometry model can incorporate the time varying properties intrinsically. In this continuum study, not CAD models, high quality mesh elements of the planetary gear system are automatically generated directly using the derived tooth profile equations. After assigning initial and boundary conditions, dynamic responses for the planetary gear system are solved. Natural frequencies and fillet stresses of the both approaches are verified by each other comparison. Potentially, the continuum approach can extensively and sophistically analyze dynamics problems of the planetary gear systems.