Recommendations for the selection of parameters for shunting locomotives

Shunting is an integral part of the partial process. In 1520 mm gauge countries, shunting operations are performed by outdated locomotives, which are being replaced by modern models; the technical parameters best match the conditions of the shunting work performed. The article analyzes recommendations for the selection of parameters of shunting locomotives and the actual indicators of their work. On the basis of this analysis, a requirement was made on the necessity of compulsory consideration of the operating conditions of the locomotive when determining its technical characteristics. As the main technical parameters of shunting locomotives, the tractive power and starting tractive force are taken and their influence on the duration of an elementary shunting movement of the "acceleration-deceleration" type is investigated. This approach advises the regulatory documentation for the organization of shunting work. Tha developed mathematical model allows to carry out research on the influence of tractive power and starting tractive force on the time of acceleration and deceleration. Calculations of the time of the train's acceleration are carried out with varying their mass and the slope of the track at different values of the tractive power starting tractive force. The calculations were carried out for the mass of compositions 1000...5000 Mg for the profile slopes equal to 0 and 1.5 ‰. The speed of the finish of acceleration was taken equal to 15 and 25 km/h. The thrust starting tractive force varied in the range of 150...300 kN, the tractive power - 200 ... 1100 kW. According to the results of calculations, it was found that the reduction in the duration of the elementary shunting movement is more significantly affected by the power of the locomotive than by the starting traction force. The “saturation” effect was noted, in which a significant increase in power or traction force during starting does not cause a significant reduction in the acceleration time. In this regard, for shunting locomotives with AC traction drive, it is recommended to take a pulling force of an equal continuous traction force.

Phase-inherent linear visco-elasticity model for infinitesimal deformations in the multiphase-field context

A linear visco-elasticity ansatz for the multiphase-field method is introduced in the form of a Maxwell-Wiechert model. The implementation follows the idea of solving the mechanical jump conditions in the diffuse interface regions, hence the continuous traction condition and Hadamard’s compatibility condition, respectively. This makes strains and stresses available in their phase-inherent form (e.g. $$\varepsilon ^{\alpha }_{ij}$$ ε ij α , $$\varepsilon ^{\beta }_{ij}$$ ε ij β ), which conveniently allows to model material behaviour for each phase separately on the basis of these quantities. In the case of the Maxwell-Wiechert model this means the introduction of phase-inherent viscous strains. After giving details about the implementation, the results of the model presented are compared to a conventional Voigt/Taylor approach for the linear visco-elasticity model and both are evaluated against analytical and sharp-interface solutions in different simulation setups.

Enhanced Digital Image Correlation Analysis of Ruptures with Enforced Traction Continuity Conditions Across Interfaces

Accurate measurements of displacements around opening or interfacial shear cracks (shear ruptures) are challenging when digital image correlation (DIC) is used to quantify strain and stress fields around such cracks. This study presents an algorithm to locally adjust the displacements computed by DIC near frictional interfaces of shear ruptures, in order for the local stress fields to satisfy the continuity of tractions across the interface. In the algorithm, the stresses near the interface are extrapolated by local polynomials that are constructed using a constrained inversion. This inversion is such that the traction continuity (TC) conditions are satisfied at the interface while simultaneously matching the displacements produced by the DIC solution at the pixels closest to the center of the subset, where the DIC fields are more accurate. We apply the algorithm to displacement fields of experimental shear ruptures obtained using a local DIC approach and show that the algorithm produces the desired continuous traction field across the interface. The experimental data are also used to examine the sensitivity of the algorithm against different geometrical parameters related to construction of the polynomials in order to avoid artifacts in the stress field.

Fracture Shaft of Femur in Children with Newly Designed Femoral Brace

Introduction: With the initial traction and secondary hip spica conservative treatment of fracture shaft of femur in children is an established technique of management all over the world. Three-six weeks of traction followed by another 6-8weeks of immobilization in spica cast at home takes away precious school going time of the children and professional earning time of the parents in our part of the world. The situation compelled us to think and design an Orthosis that not only splints the fractured femur but also maintains the continuous traction and acceptable alignment right from the beginning and allows early mobilization thereby avoiding need of long hospital stay, immobilization on spica cast and abstinence from school. Methods: This Orthosis has been used successfully in 9 children with fractured shaft of femur, age ranged from 3 to 9 years with average age of 5 years. Initially the patients were put on skin traction. In the meantime, measurement of body parts was taken by an orthotist for fabrication of the brace, which was made available on second week. In presence of the orthotist the brace was applied and its fitting and pressure points were properly evaluated. The patients were discharged the next day and asked to follow up at 2,4,6,9 and 12 weeks with a roentgenogram at every visit. Patients were encouraged to bear weight with the affected limb with the brace on after achieving clinical union. Brace was removed after achieving radiological union. Results: One patient did not turn up for follow up after application of brace. So, out of the ten patients, nine were included in this study as they had follow up of at least 12 weeks. Seven cases were male and two female. The average age of the patients was 5 years (range 3 to 9 years). The follow up period ranged from 12 weeks to 3 years with average period of 9.3 months. Radiological union was seen to occur at 12th week in 7 patients and 9th week in 2 patients and the brace was discarded at that time. Fracture united in all patients without any obvious angular, rotational deformities and limb length discrepancy. Conclusion: Preliminary findings of this study showed the use of this Orthosis in the treatment of fracture shaft of femur in children has proved to be as good as the traditional method with distinct advantages of treating at home and early mobilization with the brace on. DOI: http://dx.doi.org/10.2126/joim.v35i1.8892 Journal of Institute of Medicine, April, 2013; 35:18-22