Optimising slew torque on a mining dragline via a four degree of freedom dynamic model

A dynamic model of a dragline is developed in the form of a fundamental nonlinear rotating multibody system with energy dissipation. Its dynamic behaviour is investigated using measured field data. Model predictions of dynamic behaviour and stresses during operation are investigated and a comparison with measured data presented. Preliminary results from an investigation into reducing fatigue duty via improved slew torque control are also presented. The dynamics of the dragline bucket swing motion during house slewing (rotation) are of particular importance for both structural loading and efficient operation

A Smorgasbord of Railway Dynamic and Acoustic Phenomena

Railway technology continues to provide challenges in the dynamical and acoustical analysis of engineering systems that typically involve understanding and controlling undesirable behaviour. This seminar will outline some of the new (and old!) research being undertaken in this area by the Rail Mechanics Group at The University of Queensland, Australia. In particular, results for prediction, measurement and control of rail corrugation, prediction and field investigation of railway noise and wheel squeal will be presented.\ua0\ua0The paper will provide an overview of major results in these areas and then focus on the prediction of vibration amplitude and sound pressure level of wheel squeal noise. The predicted squeal sound level trend is shown to compare well with testrig results at various crabbing velocities (or angles of attack) and rolling speeds. The results concur with experimental and field observations but also provide important theoretical insight into the useful mechanisms of controlling railway dynamic and acoustic phenomena based on underlying mechanics modelling

Review of Contact and Dynamic Phenomena in Cold Roll Forming

This review reflects the state of the art in study of contact and dynamic phenomena occurring in cold roll forming. The importance of taking these phenomena into account is determined by significant machine time and tooling costs spent on worn out forming rolls replacement and equipment adjustment in cold roll forming. Predictive modelling of the tool wear caused by contact and dynamic phenomena can reduce the production losses in this technological process

Investigation of the effect of crabbing velocity on squeal noise based on a rolling contact two disc test rig

The effect of crabbing velocity, namely lateral sliding velocity, on the sound pressure level of squeal noise is investigated using a rolling contact two disk test rig. The sound is recorded at various crabbing velocities when the test rig is running at different rolling speeds. The results show that the sound pressure level of squeal noise increases with crabbing velocity even though the rolling speeds are different when the sound was recorded. The vibration velocity of the test rig's lower wheel is simulated using a mathematical model in the time domain. The results show that the vibration velocity increases steadily until its amplitude approximates to the crabbing velocity. Furthermore, the lateral force and power input at different instants are simulated to illustrate the reason for this phenomenon. The research presented in this paper provides a theoretical foundation for mitigating squeal noise by controlling crabbing

Wear simulation for boundary lubricated, radially loaded, spherical roller bearings

The wear of railway axle bearings is an important phenomenon. Rail companies must keep their rolling stock in a serviceable condition as excessively worn bearings can contribute to safety issues such as vibrations, excessive clearances and possibly even derailments. At present, maintenance scheduling is typically performed at predetermined time intervals. Predicting the wear and degradation of the bearings, would enable operators and bearing manufacturers to 1) optimise the design and maintenance of the bearings, and 2) quantitatively determine the best time to replace the bearings. This paper presents a model developed for predicting the wear in radially loaded spherical roller railway axle bearings. It uses a slice method to calculate the roller load, traction and creep distribution along the roller for the contact mechanics, and predicts wear using a frictional power model. The model is first validated with the wear in a thrust bearing in the literature and then used to predict wear in the radial bearing. The wear contribution from each roller in the loading zone due to the radial loading is calculated and combined for an overall wear profile.\ua0\ua

A novel cellular pathway of antigen presentation and CD4 T cell activation in vivo

Dendritic cell activation of CD4 T cells in the lymph node draining a site of infection or vaccination is widely considered the central event in initiating adaptive immunity. The accepted dogma is that this occurs by stimulating local activation and antigen acquisition by dendritic cells, with subsequent lymph node migration, however the generalizability of this mechanism is unclear. Here we show that in some circumstances antigen can bypass the injection site inflammatory response, draining freely and rapidly to the lymph nodes where it interacts with subcapsular sinus (SCS) macrophages resulting in their death. Debris from these dying SCS macrophages is internalized by monocytes recruited from the circulation. This coordinated response leads to antigen presentation by monocytes and interactions with naïve CD4 T cells that can drive the initiation of T cell and B cell responses. These studies demonstrate an entirely novel pathway leading to initiation of adaptive immune responses in vivo

Frictional contact analysis in a spherical roller bearing

Numerical analyses of the roller–raceway contact have been carried out in a spherical roller bearing using frictional contact models of different complexity. The models used in the study include an implementation of Kalker’s exact contact theory named CECT (Conformal Exact Contact Theory) and detailed Finite Element models. The adequacy of the more simplified contact solutions is assessed by contrasting them with the solutions obtained with the more comprehensive models. Additionally, the use of the exact contact theory, well known in the wheel–rail application, is demonstrated in contact mechanics analyses in rolling bearings, describing relevant details of its implementation for this application. Situations with different normal loads and friction levels have been analysed, and two distinct steady equilibrium configurations of the roller have been identified.J.B.-L., J.S., and E.G.V. gratefully acknowledge financial support from the European Horizon 2020 Joint Technology Initiative Shift2Rail through contracts 826255 and 101012456 (IN2TRACK2 and IN2TRACK3), from the Spanish Research Ministry MICINN/Economy and Competitiveness Ministry MINECO and MCI/AEI through contract PID2019-109483RB-I00, including funding by the FEDER-ERDF European Regional Development Fund, and from the Basque Government through IT1764-22