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During single-grain grinding material is removed in three phases, namely the rubbing, ploughing and chip formation phases. The rubbing and ploughing phases are important phases to be considered as they are precursors to chip formation, where material is first removed, and represent process inefficiencies. Investigation of these phases is considerably difficult given the irregular shape of the abrasive grains and as a result these phases are often simulated by scratch tests using spherical indenters. The current work presents a finite element (FE) model of the rubbing and ploughing phases in single-grain grinding. Significant emphasis is placed on the experimental validation of the model, with a view towards its future use as an investigative tool. Single-grain grinding was simulated via a scratch test setup which produced similar surface features and the measured forces were compared against the FE predicted results with good agreement. The model developed here represents an incremental advancement of grinding FE models of the rubbing and ploughing phases by using advanced constitutive models as well as simulating the formation of a scratch.

The results of a study of the three-dimensional vibration of two dry human skulls in response to harmonic excitation are presented. The vibratory response exhibits three distinct types of motion across the range of audible frequencies. At low frequencies below 1000 Hz, whole-head quasi-rigid motion is seen. At the middle frequencies between 1000 and 6000 Hz, the motion exhibits a series of increasingly complex modal patterns. Above 6000 Hz, the response is wavelike and clear wavefronts can be distinguished in the vibration data. In this regime the relationship between wavelength and frequency is calculated and compared to a number of theories of skull vibration that have been proposed.

Tidal turbine developers and researchers use small scale testing (i.e. tow tank and flume testing) as a cost effective and low risk way to conduct proof-of-concept studies and evaluate early stage device performance. This paper presents experimental performance data for a three-bladed 1/20 th scale NREL S814 tidal turbine rotor, produced at the 4.6 x 2.5 m and 76 m long Kelvin Hydrodynamics Laboratory tow tank at Strathclyde University. The rotor performance was characterised from very low tip speed ratios to runaway for four carriage speeds. A maximum C P of 0.285 and a maximum C T of 0.452 were recorded at tip speed ratios of 3.53 and 4.45 for a carriage speed of 1m/s. The uncertainty in the instrument calibration and experimental measurements was quantified, allowing accurate representation of the experiments in numerical models. The methodology behind the uncertainty calculations is described in this paper. The uncertainty in the experimental measurements was found to be less than 5% for over 87% of the tests. Reynolds number scaling effects were found to be influential on the rotor performance in the range of velocities tested.

Polyurethane rubber materials have widespread usage in large-deformation energy absorption and dissipation applications. Accurate design modeling with these materials requires an appropriate constitutive material model that accounts for both static (low strain rate) and dynamic (high strain rate) responses. A common modeling approach is the use of hyperviscoelastic formulations, which couple quasi-static hyperelastic with dynamic viscoelastic responses and describe the material response over a range of deformation rates. In this work the effectiveness of two models, the Modified Quasi-Linear Viscoelastic and Non-Linear Hyper-Viscoelastic, are investigated to describe the high-rate behaviour of two different grades of polyurethane rubber. From quasi-static, uniaxial compression tests, a Rivlin hyperelastic formulation was found to describe the low-rate response well. High-rate, uniaxial compressions test were performed using a Polymeric Split Hopkinson Pressure Bar (PSHPB), supported by high-speed photography. In general, it was found that the Modified QuasiLinear Viscoelastic model did not fit the experimental data well due to its limited non-linear terms, while the Non-Linear Hyper-Viscoelastic provided very good agreement.

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Passively adaptive bend-twist (BT) tidal turbine blades made of non-homogeneous composite materials have the potential to reduce the structural loads on turbines so that smaller more cost effective components can be used. Using BT blades can also moderate the demands on the turbine generator above design conditions. This paper presents experimental towing tank test results for an 828 mm diameter turbine with composite BT blades compared to a turbine with geometrically equivalent rigid aluminum blades. The BT blades were constructed of a graphite-epoxy unidirectional composite material with ply angles of 26.8° to induce BT coupling, and an epoxy foam core. For steady flow conditions the BT blades were found to have up to 11% lower thrust loads compared to rigid blades, with the load reductions varying as a function of flow speed and rotational speed. A coupled finite element model-blade element momentum theory design tool was developed to iterate between the structural (deformation and stresses) and hydrodynamic (power and thrust loads) responses of these adaptive composite blades. When compared to the experimental test results, the design tool predictions were within at least 8% of the experimental results for tip-speed ratios greater than 2.5