Dynamic Simulation Analysis of Track Tension and the Influencing Factors of Deep-Sea Tracked Mining Vehicle

The deep-sea mining miner requires good passability to operate in complex and changeable terrain environment of the seabed. Among them, the track tension is an important factor to ensure the normal running of the vehicle. Aiming at the complex track tension problem on track link, the forces on each component of the tracked system were analyzed, and the theoretical formulas of track tension were established. The theoretical estimation and dynamic simulation of track tension in uniform speed were carried out by using the multibody dynamics model of the tracked vehicle, and the rationality of the theoretical estimation formula was verified. The influencing factors of track tension also were analyzed, and the significance of each factor on track was discussed by dynamic simulation. The results provided a theoretical basis for design of tracked vehicles.

A New Approach for Modeling Mixed Lubricated Piston-Cylinder Pairs of Variable Lengths in Swash-Plate Axial Piston Pumps

The swash-plate axial piston pump is one of the most widely used pumps due to its simplicity and compactness in structure. In such a pump, the piston-cylinder system plays a crucial role, with its lubrication characteristics greatly affecting the overall pumping performance. A new numerical approach is proposed in this study for modeling mixed lubricated piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps in the framework of multibody dynamics. The approach couples the hydrodynamic mixed lubrication model of the piston-cylinder interface with the multibody dynamics model of the piston pump. The lubrication model is established with a transient average Reynolds equation considering asperity contacts and is solved with the finite element method to derive the hydrodynamic forces of the lubricated pair, while the multibody dynamics model is established with Lagrangian formalism by considering hydrodynamic forces as external forces. Results for piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps are presented, and the impacts of cylinder length and the tilt angle of the swash plate on the tribological performances of the interface are discussed. The results indicate that increasing the cylinder length can improve the stability and wear resistance of the piston, but it can exacerbate the frictional power loss. Moreover, although enlarging the tilt angle of the swash plate can effectively increase pump displacement, it can easily lead to serious friction, wear, and leakage problems. Consequently, the tilt angle of the swash plate should be carefully selected in practical applications.

Validation and Analysis on Numerical Response of Super-High-Speed Railway Pantograph-Catenary Interaction Based on Experimental Test

The numerical tools can be used to facilitate the design of the railway pantograph-catenary system. The validation of the current numerical results is mostly performed at a speed slower than 350 km/h. This paper aims at the validation and analysis of the numerical results at a super-high-speed. The catenary model is constructed based on a nonlinear finite element approach employing the absolute nodal coordinate formulation. A multibody dynamics model is adopted to represent the pantograph. The measurement data are collected by an inspection vehicle equipped with an instrumented pantograph operating at 378 km/h in Chengdu-Chongqing high-speed line. Comparing the numerical simulation and the field test shows that the present pantograph-catenary model can provide reliable numerical results at 378 km/h. The numerical analysis of pantograph-catenary interaction at super-high-speed shows that the trailing pantograph performance does not comply with the assessment standard at 378 km/h. The adjustment of double-pantograph interval and messenger wire tension can effectively improve the trailing pantograph performance.

Discrete element model for general polyhedra

We present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

Developing a Custom Anthropometric Test Device for Experimental Evaluation of Blast Mitigation Seats

The use of improvised explosive devices against moving vehicles has been on the rise recently. Their explosions induce devastating effects on vehicle occupants. Blast mitigation seats are used as a counter measure to reduce such harmful effects. This paper presents the scientific work for evaluating the efficacy of blast mitigation seats. The work involves designing and building a custom anthropometric test device (ATD) and a drop tower test facility that is used to simulate the drop of a vehicle from heights up to 10 m. The ATD was equipped with two accelerometers; at the neck and at the pelvis. For validation, a multibody dynamics model was developed to simulate the drop test and the results were compared with ones from experiments. An overall root mean square error of 1.28 g was achieved. The test facility was then used to measure the performance of a blast mitigation seat. The results showed that blast mitigation seats reduced peak accelerations on the pelvis and neck areas by 92% and 87% respectively and this translates into moving predicted injuries from fatal to moderate.

Behaviour of Metro Coach on Newly Built Track in Kolkata

This paper presents the behaviour of a new metro coach on a newly built track in Kolkata, India. Oscillation trials were conducted using LVDT sensors at different locations to monitor primary and secondary springs compression. Multibody dynamics model is built with actual parameters of coach and track in SIMPACK. The behaviour of the vehicle for given track with elevation and curvature changes has been studied. Vehicle performance has been evaluated based on safety, running behaviour and track fatigue mentioned in UIC 518. Results of primary and secondary spring compressions obtained from field trials and multibody dynamics model have been compared. Coach lateral and vertical acceleration, bogie lateral acceleration, static load at rail wheel contact and derailment coefficient obtained from the multibody dynamics model are discussed. Obtained results were within permission values. Scope of this paper lies in studying the vehicle performance in connection to safety and running behaviour of newly introduced metro in Kolkata.

Mobility Enhancement of Heavy-Duty Tracked Vehicles Under Load Using Real-Time Terrain Characterization, Traction Control, and a Towing Winch

This paper presents a generalized, multibody dynamics model for a tracked vehicle equipped with a towing winch and control strategies that enhance vehicle mobility by regulating track slip based on real-time terrain characterization and automating winch use. The vehicle model is validated under conditions where no action is taken by the winch. Thereafter, two mobility enhancing control strategies are outlined. The first strategy regulates track slip to a real-time estimated value that generates maximum net traction. This is done by computing state-force estimates from a Kalman filter that are compared to terrain traction models using a Bayesian hypothesis selection approach. If the vehicle is traction limited and the first strategy fails, a second strategy that automates winch use is activated. Simulation results are shown for both scenarios.