Modeling of autoresonant control of a parametrically excited screen machine

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Modelling of nonlinear dynamic response of a screen machine described by the nonlinear coupled differential equations and excited by the system of autoresonant control is presented. The displacement signal of the screen is fed to the screen excitation directly by means of positive feedback. Negative feedback is used to fix the level of screen amplitude response within the expected range. The screen is anticipated to vibrate with a parametric resonance and the excitation, stabilization and control response of the system are studied in the stable mode. Autoresonant control is thoroughly investigated and output tracking is reported. The control developed provides the possibility of self-tuning and self-adaptation mechanisms that allow the screen machine to maintain a parametric resonant mode of oscillation under a wide range of uncertainty of mass and viscosit

Application of smooth-particle hydrodynamics in metal machining

The finite element (FE) method has been extensively used to model complex cutting processes. However, due to large strains in a process zone, leading to increased element distortions, such simulations are confronted with numerical difficulties. Smooth-particle hydrodynamics (SPH) is a mesh-free computational method, which has been used to simulate multi-body problems. In this paper we present a 3D hybrid modelling approach for orthogonal micro-machining of a copper single crystal with the use of SPH and continuum FE. The model is implemented in a commercial FE software ABAQUS/Explicit. The study is used to gain insight into the effects of crystallographic anisotropy on the machining response of f.c.c. cubic metals

Ti alloy with enhanced machinability in UAT turning

Metastable β-titanium alloys such as Ti 15V 3Al 3Cr 3Sn are of great technological interest thanks to their high fatigue strength-to-density ratio. However, their high hardness and poor machinability increase machining costs. Additionally, formation of undesirable long chips increases the machining time. To address those issues, a metastable β-titanium alloy (Ti 15V 3Al 3Cr 2Zr 0.9La) with enhanced machinability was developed to produce short chips even at low cutting speeds. A hybrid ultrasonically assisted machining technique, known to reduce cutting forces, was employed in this study. Cutting force components and surface quality of the finished work-pieces were analyzed for a range of cutting speeds in comparison with those for more traditional Ti 15V 3Al 3Cr 3Sn. The novel alloy demonstrated slightly improved machining characteristics at higher cutting speeds and is now ready for industrial applications

An experimental investigation into resonance dry grinding of hardened steel and nickel alloys with element of MQL

Current policies on environmental issues put extra pressures on manufacturing processes to be resource efficient and eco-friendly. However, in grinding processes, large amounts of cutting fluids are used. These fluids are not environmental friendly thus require proper management before disposal with associated cost. Hence, this work sets to explore low-frequency vibration in grinding in order to improve coolant application in conventional grinding at the first stage with the aim to introduce this into high efficiency deep grinding (HEDG) at latter stage. An attempt is made to grind nickel alloys with minimum quantity lubricant (MQL) as oppose to flood cooling. To achieve this with minimum alterations to the machine tool, a piezo-driven workpiece holder was developed for surface grinding. This simple innovative workpiece holder allowed oscillating during actual grinding process. However, this paper presents the results of low-frequency oscillatory grinding in dry and near-dry conditions. The response of the machine tool spindle unit is presented alongside with the workpiece holder response. In this investigation, hardened steels and nickel alloys were ground with vibration assistance. The grinding forces are illustrated together with the surface finish. The wheel performance is given in terms of grinding ratio

Vibration control of linear split Stirling cryogenic cooler for airborne infrared application

Modern infrared imagers often rely on the split Stirling cryogenic coolers the linear compressors of which are the wellknown sources of harmonic disturbance. The traditional method of their passive isolation fails to meet the restraints on the static and dynamic deflections which are originated by the combined action of the airborne g-loading and harsh random vibration. The vibration protection system, which combines a stiff and heavily damped vibration isolator with tuned dynamic absorber, is studied and optimised for use in the design of an airborne infrared device. Such a design is aimed, primarily, at essential dynamic suppression of the harmonic force which is produced by the linear compressor and, secondarily, at minimisation of environmental vibration loads transmitted through the infrared device to the linear compressor. Experimental testing backed up the theoretical results

Dynamics of an impact oscillator near a degenerate graze

We give a complete analysis of low-velocity dynamics close to grazingfor a generic one degree of freedom impact oscillator. This includes nondegenerate (quadratic) grazing and minimallydegenerate (cubic) grazing, corresponding respectively to nondegenerateand degenerate chatter. We also describe the dynamics associatedwith generic one-parameter bifurcation at a more degenerate (quartic)graze, showing in particular how this gives rise to the often-observedhighly convoluted structure in the stable manifolds of chattering orbits.The approach adopted is geometric, using methods from singularity theory