Condition monitoring and fault diagnosis of planetary gearboxes: A review

The Royal Society has recently published a report on geoengineering - deliberately manipulating the climate. Their survey of the techniques and possibilities is useful and clear, and explores some of the complexities of policy in this area. The issues of moral hazard - whether researching geoengineering is actually dangerous because it distracts from emissions reduction - of side effects - whether these can be predicted, or calculated, and whether they are likely to be worse under a geoengineering scenario than a non-geoengineering scenario - and governance - the possibility of unilateral climate manipulation and the problems of multilateral climate management - are all touched upon. Geoengineering is potentially frightening, but some techniques, notably the use of sulphur aerosols, offer to return the global temperature to pre-industrial levels for just a few tens of billions of dollars a year. Contrary to the somewhat lukewarm approach of the report's conclusions this is something that deserves considerable attention and priority. It may well founder on the problems of side-effects, or be rendered superflous by successful emissions reduction, but it is still too early to say. On the basis of current evidence, geoengineering techniques such as the sulphur-based one are some of the most important contributions to climate policy and discussion of recent years and any serious policy approach to global warming requires engagement with their potential and risks.

Geoengineering the Climate: Science, Governance and Uncertainty

This article reviews Handbook of Noise and Vibration Control by Malcolm J. Crocker , New Jersey, 2007 1584 pp. Price: $195.00 (hardcover) ISBN: 0471395994

Handbook of Noise and Vibration Control.

This paper is a review of the effect of vehicle characteristics on ground- and track borne-vibrations from railways. It combines traditional theory with modern thinking and uses a range of numerical analysis and experimental results to provide a broad analysis of the subject area. First, the effect of different train types on vibration propagation is investigated. Then, despite not being the focus of this work, numerical approaches to vibration propagation modelling within the track and soil are briefly touched upon. Next an in-depth discussion is presented related to the evolution of numerical models, with analysis of the suitability of various modelling approaches for analysing vehicle effects. The differences between quasi-static and dynamic characteristics are also discussed with insights into defects such as wheel/rail irregularities. Additionally, as an appendix, a modest database of train types are presented along with detailed information related to their physical attributes. It is hoped that this information may provide assistance to future researchers attempting to simulate railway vehicle vibrations. It is concluded that train type and the contact conditions at the wheel/rail interface can be influential in the generation of vibration. Therefore, where possible, when using numerical approach, the vehicle should be modelled in detail. Additionally, it was found that there are a wide variety of modelling approaches capable of simulating train types effects. If non-linear behaviour needs to be included in the model, then time domain simulations are preferable, however if the system can be assumed linear then frequency domain simulations are suitable due to their reduced computational demand.

https://www.tandfonline.com/doi/pdf/10.1080/23248378.2014.897791

Railway-induced ground vibrations – a review of vehicle effects

Benchmarking railway vibrations – Track, vehicle, ground and building effects

Despite use of the best in current design practices, high-speed shaft (HSS) bearings, in a wind-turbine gearbox, continue to exhibit a high rate of premature failure. As HSS bearings operate under low loads and high speeds, these bearings are prone to skidding. However, most of the existing methods for analyzing skidding are quasi-static in nature and cannot be used to study dynamic operating conditions. This paper proposes a dynamic model, which includes gyroscopic and centrifugal effects, to study the skidding characteristics of angular-contact ball-bearings. Traction forces between rolling-elements and raceways are obtained using elastohydrodynamic (EHD) lubrication theory. Underlying gross-sliding mechanisms for pure axial loads, and combined radial and axial loads are also studied. The proposed model will enable engineers to improve bearing reliability at the design stage, by estimating the amount of skidding.

https://iopscience.iop.org/article/10.1088/1742-6596/305/1/012027/pdf

A dynamic model to predict the occurrence of skidding in wind-turbine bearings

In this paper, a method is presented for the calculation of the vibration created in buildings by the operation of underground railways. The method is based on the sub-modelling approach which is used to couple a model of a building on a piled foundation to another model that calculates the vibration generated in the soil in underground railway tunnels. The method couples a building on a piled foundation to the soil at discrete points by satisfying equilibrium and compatibility requirements at those points. The method results in efficient numerical calculations. A two-dimensional frame made of beam elements is used to model the building and its piled foundation. The elements are formulated using a dynamic stiffness matrix which accounts for Euler–Bernoulli bending and axial behaviour. Vibrations created by a train moving in an underground tunnel are calculated using the well-known pipe-in-pipe (PiP) model. The model calculates the power spectral density (PSD) of the displacement in the soil. The excitatio...

The use of sub-modelling technique to calculate vibration in buildings from underground railways

Voids at the tunnel-soil interface for calculation of ground vibration from underground railways

The Royal Society report 'Geoengineering the Climate' identified solar radiation management using albedo-enhancing aerosols injected into the stratosphere as the most affordable and effective option for geoengineering, but did not consider in any detail the options for delivery. This paper provides outline engineering analyses of the options, both for batch-delivery processes, following up on previous work for artillery shells, missiles, aircraft and free-flying balloons, as well as a more lengthy analysis of continuous-delivery systems that require a pipe connected to the ground and supported at a height of 20 km, either by a tower or by a tethered balloon. Towers are shown not to be practical, but a tethered balloon delivery system, with high-pressure pumping, appears to have much lower operating and capital costs than all other delivery options. Instead of transporting sulphuric acid mist precursors, such a system could also be used to transport slurries of high refractive index particles such as coated titanium dioxide. The use of such particles would allow useful experiments on opacity, coagulation and atmospheric chemistry at modest rates so as not to perturb regional or global climatic conditions, thus reducing scale-up risks. Criteria for particle choice are discussed, including the need to minimize or prevent ozone destruction. The paper estimates the time scales and relatively modest costs required if a tethered balloon system were to be introduced in a measured way with testing and development work proceeding over three decades, rather than in an emergency. The manufacture of a tether capable of sustaining the high tensions and internal pressures needed, as well as strong winds, is a significant challenge, as is the development of the necessary pumping and dispersion technologies. The greatest challenge may be the manufacture and launch of very large balloons, but means have been identified to significantly reduce the size of such balloons or aerostats.

/pdf/lifting-options-for-stratospheric-aerosol-geoengineering-29ut3k4plo.pdf

Hugh Hunt

Papers

A dynamic model to predict the occurrence of skidding in wind-turbine bearings

The use of sub-modelling technique to calculate vibration in buildings from underground railways

Voids at the tunnel-soil interface for calculation of ground vibration from underground railways

Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems.

Predicting surface vibration from underground railways through inhomogeneous soil