Alexander David Shaw

Alexander David Shaw
Swansea University | SWAN · College of Engineering

MEng, PhD

About

70
Publications
19,502
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
855
Citations
Additional affiliations
August 2016 - present
Swansea University
Position
  • Lecturer
October 2009 - October 2013
University of Bristol
Position
  • PhD Student

Publications

Publications (70)
Article
The idea of morphing a helicopter blade by using compliant structures promises augmented capabilities in terms of manoeuvrability and fuel efficiency. To achieve morphing, compliant structures work by elastically deforming to achieve the desired response, and therefore actuation must work against the inherent structural stiffness in addition to ext...
Article
Full-text available
The present study performs a set of static tests to demonstrate a novel passive morphing concept. The concept introduces a bend-twist coupled composite spar to rotor blades, allowing for twist morphing to be achieved by imposing a lagwise bending moment using centrifugal forces produced by a movable mass at the blade tip. First, three composite spa...
Article
A translational Lanchester damper is a device that adds damping to a structure at a point using a series combination of a viscous damper and a mass. The problem in the practical realisation of such a device is that a stiffness is required to support the mass, which changes the dynamic behaviour of the device, introducing a resonance frequency due t...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-0172.vid A common issue with morphing structures is that the actuators must work against significant structural and aerodynamic stiffness. The concept of Passive Energy Balancing (PEB) aims to ameliorate this, and thereby reduce system mass, by connecting negative stiffness elements to the act...
Article
Full-text available
Testing nonlinear structures to characterise their internal nonlinear forces is challenging. Often nonlinear structures are excited by harmonic forces and yield a multi-harmonic response. In many systems, particularly ones with strong nonlinearities, the effect of higher harmonics in the force and responses cannot be ignored. Even if the intended e...
Article
Full-text available
With increasing demand for rotor blades in engineering applications, improving the performance of such structures using morphing blades has received considerable attention. Resonant passive energy balancing (RPEB) is a relatively new concept introduced to minimize the required actuation energy. This study investigates RPEB in morphing helicopter bl...
Article
Full-text available
Rotating machines are intrinsically susceptible to expensive and high-risk faults such as rotor–stator rub. During a rub event normal and tangential forces are generated by the contact and friction that cause wear at the contacting interfaces. In the present work, such forces are computed by assuming linear elastic contact and Coulomb friction at m...
Preprint
Full-text available
With increasing demand for rotor blades in applications such as wind turbines, helicopters, and unmanned aircrafts , improving the performance of such structures using morphing blades has received considerable attention. Resonant passive energy balancing is a relatively new concept introduced to minimize the required actuation energy. This study in...
Article
Full-text available
Nonlinearities in rotating systems have been seen to cause a wide variety of rich phenomena; however, the understanding of these phenomena has been limited because numerical approaches typically rely on “brute force” time simulation, which is slow due to issues of step size and settling time, cannot locate unstable solution families, and may miss k...
Article
Full-text available
A novel passive twist morphing concept is examined for helicopter blades. The concept is demonstrated using a thin-walled rectangular composite beam created with symmetric layup to obtain bend-twist property. The twist of a rotor blade is proposed to be actuated though a movable mass at the blade tip which is able to provide a range of lagwise bend...
Article
A rotor can contact a stator thereby inducing some very strong non-linearities that can result in a plethora of vibration phenomena. Synchronous motions, chaotic motion, backward whirl, forward whirl are some of the reported phenomena in the literature. This article presents an experimental approach based on a very flexible rotor rig designed with...
Article
Full-text available
Morphing aircraft structures usually introduce greater compliance into aerodynamic sections, and therefore will affect the aeroelasticity with the potential risk of increased flutter. A low-fidelity model of an active camber morphing wing and its aeroelastic model are developed in order to investigate the potential critical speed by exploiting its...
Article
In some applications, such as ground vibration testing in the aerospace industry, it is of interest to observe the modal behaviour of a slender structure while it is statically loaded. One way of statically loading such a structure is to suspend masses using very soft springs. If the springs are linear, then this results in an extremely large stati...
Article
Full-text available
Recent theory has predicted the onset of asynchronous bouncing motion at speeds beyond those of internal resonance in multi-degree-of-freedom rotating systems with intermittent contact. This paper provides the first attempt to experimentally validate the theory. Vibrations incorporating rotor-stator contact are recorded from a vertically ounted rot...
Article
In this paper, the dynamics of a tailored composite rotating blade with curved tips are investigated, with a view to improving the dynamic behaviour of the blade in flight. The blade tip is curved either in the out-of-plane or in the in-plane directions. The composite blade is modelled by using the exact beam formulation, and the cross-sectional pr...
Article
Full-text available
A passive energy balancing concept for linear actuation is investigated in the current work by adopting a negative stiffness mechanism. The proposed negative stiffness mechanism uses a pre-tensioned spring to produce a passive torque and therefore to transfer the passive torque through a crankshaft for linear motion. The proposed passive energy ba...
Conference Paper
29th Biennial Conference on Noise and Vibration Engineering, ISMA2020
Article
Full-text available
The experimental characterisation of a nonlinear structure is a challenging process, particularly for multiple degree of freedom and continuous structures. Despite attracting much attention from academia, there is much work needed to create processes that can achieve characterisation in timescales suitable for industry, and a key to this is the des...
Conference Paper
Faraday Predictive Ltd want to understand the relative magnitude of distortions to motor current arising from changes in motor load, eccentricity and rotor condition. --- https://dspace.uevora.pt/rdpc/handle/10174/29180 --- https://conferences.leeds.ac.uk/lesgi/
Article
Full-text available
A novel meta-material has been designed and implemented into a rotor blade to enhance aerodynamic efficiency by achieving a passive twist during rotation. The twist is induced by bend-twist coupling exhibited in the meta-material, which is created to possess anisotropic elastic properties at the bulk level. A concept design of a rectangular blade s...
Article
Lattice materials are characterised by their equivalent elastic moduli for analysing mechanical properties of the microstructures. The values of the elastic moduli under static forcing condition are primarily dependent on the geometric properties of the constituent unit cell and the mechanical properties of the intrinsic material. Under a static fo...
Article
Full-text available
The dynamics associated with bouncing-type partial contact cycles are considered for a 2 degree-of-freedom unbalanced rotor in the rigid-stator limit. Specifically, analytical explanation is provided for a previously proposed criterion for the onset upon increasing the rotor speed Ω of single-bounce-per-period periodic motion, namely internal reson...
Article
Full-text available
Control-based continuation (CBC) is a general and systematic method to probe the dynamics of nonlinear experiments. In this paper, CBC is combined with a novel continuation algorithm that is robust to experimental noise and enables the tracking of geometric features of the response surface such as folds. The method uses Gaussian process regression...
Conference Paper
Full-text available
This paper presents the initial performance analysis of a twist morphing concept based on moving a mass in the chordwise direction in hovering flight. The blade structure is considered to be made of composite materials with bend-twist coupling present in the layup. The chordwise movement of the added mass introduces an additional lag moment along t...
Conference Paper
Full-text available
The actuation system of morphing aircraft plays an important role in any promising morphing design. If the structure of the morphing wing needs to be deformed elastically, the actuation system will be required to provide an adequate actuation force while the weight and cost added to the morphing aircraft should be limited to the extent that the per...
Conference Paper
Full-text available
Traditional ways to achieve the desired motion of mechanisms or deformation of morphing structures require external energy for actuation. Frequently the use of these actuators to drive the system can cost noteworthy energy for each cycle of operation and the spent energy cannot be recovered. This work investigates a passive energy balancing concept...
Article
An overhung rotor model is explored to determine the effect of friction during contact between the rotor and stator. The model has two degrees of freedom with rotor stator contact and the equations of motion are non-dimensionalised. A parametric study of the friction coefficient and eccentricity is conducted and the results displayed on three dimen...
Article
In this paper, the effect of various parameters of a specific rotor blade cross-section on the effectiveness of a twist morphing concept is investigated. Then, by considering different constraints, a cross-section consistent with this morphing concept with high lag-twist coupling and low extension-twist, is developed. This lag bending-torsion coupl...
Article
Full-text available
The energy balancing concept seeks to reduce actuation requirements for a morphing structure by strategically locating negative stiffness devices to tailor the required deployment forces and moments. One such device is the spiral pulley negative stiffness mechanism. This uses a cable connected with a pre-tension spring to convert decreasing spring...
Article
Full-text available
This paper presents an inverse problem of determination of a space-dependent heat flux in steady-state heat conduction problems. The thermal conductivity of a heat conducting body depends on the temperature distribution over the body. In this study the simulated measured temperature distribution on part of the boundary is related to the variable he...
Article
This paper presents a systematic method for exploring the nonlinear dynamics of multi-degree-of-freedom (MDOF) physical experiments. To illustrate the power of this method, known as control-based continuation (CBC), it is applied to a nonlinear beam structure that exhibits a strong 3:1 modal coupling between its first two bending modes. CBC is able...
Article
In this paper, the aeroelastic stability of a composite hingeless rotor blade with a chordwise movable mass is investigated. The point mass is located near the tip of the blade and its chordwise location is variable with respect to the elastic axis and can be moved during the flight. This movable mass is added to the blade to actuate the blade twis...
Article
This work considers analysis of sustained bouncing responses of rotating shafts with nonlinear lateral vibrations due to rotor stator contact. The insight that this is an internal resonance phenomena makes this an ideal system to be studied with the method of normal forms, which assumes that a system may be modelled primarily in terms of just its r...
Preprint
Control-based continuation (CBC) is a general and systematic method to probe the dynamics of nonlinear experiments. In this paper, CBC is combined with a novel continuation algorithm that is robust to experimental noise and enables the tracking of geometric features of the response surface such as folds. The method uses Gaussian process regression...
Article
In this paper, a new concept for morphing composite blades is proposed, and how this concept changes the twist distribution of the blade is explained. A change in the blade twist is obtained by adding a mass to the blade that produces an extra centrifugal force. This centrifugal force then may produce a moment that can change the blade twist via th...
Article
Full-text available
A new concept of an integrated bidirectional torsional negative stiffness mechanism is introduced which allows for passive energy balancing of mechanical systems by reducing actuation requirements and improving energy efficiency. This novel design is a modular device, is bidirectional and is easily integrated and customised for different applicatio...
Preprint
This work considers analysis of sustained bouncing responses of rotating shafts with nonlinear lateral vibrations due to rotor stator contact. The insight that this is an internal resonance phenomena makes this an ideal system to be studied with the method of normal forms, which assumes that a system may be modelled primarily in terms of just its r...
Conference Paper
Full-text available
In this paper, a systematic and reliable approach is presented to design a composite rotor blade cross-section with high in-plane bending-torsion coupling. The composite blade is designed to allow changing of the twist of the blade in flight, actuated by a moving proof mass near the tip of the blade. By shifting the mass along the chord of the blad...
Conference Paper
Full-text available
Traditional morphing concepts require external energy input to achieve the desired changes to the shape of aircraft structures, often working against the inherent stiffness of these structures. This can lead to a requirement for large actuators, and a significant negative impact on system level performance due to the added mass and energy requireme...
Conference Paper
Full-text available
This paper presents a new concept of morphing by changing the twist of a composite blade through the movement of a mass near the tip of the blade. The mass is moved in the chordwise direction which then modifies the centrifugal force near the tip of the blade. The blade is tailored with composite materials and hence coupling is introduced. By movin...
Conference Paper
Full-text available
The energy balancing concept seeks to reduce actuation requirements for a morphing structure by strategically locating negative stiffness devices to tailor the required deployment forces and moments. One such device is the spiral pulley negative stiffness mechanism. This uses a cable connected with a pre-tension spring to covert decreasing spring f...
Article
Full-text available
In this paper, a finite element model is coupled to an homogenisation theory in order to predict the energy harvesting capabilities of a porous piezoelectric energy harvester. The harvester consists of a porous piezoelectric patch bonded to the root of a cantilever beam. The material properties of the porous piezoelectric material are estimated by...
Preprint
Full-text available
This paper presents a systematic method for exploring the nonlinear dynamics of multi-degree-of-freedom (MDOF) physical experiments. To illustrate the power of this method, known as control-based continuation (CBC), it is applied to a nonlinear beam structure that exhibits a strong 3:1 modal coupling between its first two bending modes. CBC is able...
Article
Full-text available
Compliant structures, such as flexible corrugated panels and honeycomb structures, are promising structural solutions for morphing aircraft. The compliant structure can be tailored to carry aerodynamic loads and achieve the geometry change simultaneously, while the reliability of the morphing aircraft can be guaranteed if conventional components an...
Article
Full-text available
This paper proposes a model updating strategy for localised nonlinear structures. It utilises an initial finite-element (FE) model of the structure and primary harmonic response data taken from low and high amplitude excitations. The underlying linear part of the FE model is first updated using low-amplitude test data with established techniques. T...
Article
In this study a mechanical model of an overhung rotor is explored to determine the effect of gravity on the nonlinear dynamics of an aero-engine. The model is an overhung disc with rotor-stator contact. The model has two degrees of freedom with lumped parameters; friction is neglected in the contact and the equations of motion are non-dimensionalis...
Article
This paper presents a procedure to localise nonlinear elements using spatially incomplete measured frequency response data from the structural vibration test. The method does not require measurements of all the responses associated with nonlinear elements and the information about the types of nonlinear elements. In this procedure, the Craig-Bampto...
Article
Full-text available
One of the key problems in the development of morphing aircraft is the morphing structure, which should be able to carry loads and change its geometry simultaneously. This paper investigates a compliant structure, which has the potential to change the dihedral angle of morphing wing-tip devices. The compliant structure is able to induce deformation...
Article
Full-text available
This work considers analysis of sustained impacting cycles of rotating shafts with potentially many disks. The insight that this is an internal resonance phenomena makes this an ideal system to be studied with the method of normal forms. However, the presence of arbitrary non smooth nonlinearities due to impact and rub mean that the method must be...
Article
Full-text available
This paper investigates the use of an electrostatic device to improve the performance of MEMS piezoelectric harvesters in the presence of geometric and structural variabilities due to the manufacturing process. Different types of uncertain parameters including material and geometric uncertainties have been considered. The variability of these param...
Conference Paper
Full-text available
The nonlinear vibrations due to rotor-stator contact show a variety of phenomena that are not well understood, particularly in rotors with higher degrees of freedom. Recent work suggests many responses involving intermittent contact between the rotor and stator are explain by internal resonance when the system is seen in a rotating coordinate frame...
Conference Paper
Compliant structures, such as flexible corrugated panels and honeycomb structures, are promising structural solutions for morphing aircraft. The compliant structure can be tailored to carry aerodynamic loads and achieve the geometry change simultaneously, while the reliability of the morphing aircraft can be guaranteed if conventional components an...
Conference Paper
Full-text available
In this paper, a homogenised finite element model is developed to predict the energy harvesting capabilities of a porous piezoelectric energy harvester. The harvester consists of a porous piezoelectric patch bonded to a cantilever beam. The material properties of the porous piezoelectric material are estimated by the Mori-Tanaka homogenisation meth...
Article
Full-text available
In this paper, modification of an existing equivalent model of the corrugated panel is investigated. The axial and bending coupling of the corrugated panel supplements the previous equivalent properties when the corrugated panel has a fixed boundary condition. The analytical expressions of the coupling vertical deflections are obtained and verified...
Article
Full-text available
Sudden onset of violent chattering or whirling rotor{\textendash}stator contact motion in rotational machines can cause significant damage in many industrial applications. It is shown that internal resonance can lead to the onset of bouncing-type partial contact motion away from primary resonances. These partial contact limit cycles can involve any...
Article
Full-text available
This work presents a conceptually simple experiment consisting of a cantilever beam with a nonlinear spring at the tip. The configuration allows manipulation of the relative spacing between the modal frequencies of the underlying linear structure, and this permits the deliberate introduction of internal resonance. A 3:1 resonance is studied in deta...
Chapter
Engineered structures are becoming increasingly lightweight and flexible, and as such more likely to achieve large amplitude and nonlinear vibratory responses. This leads to a demand for new methods and experimental test structures to see how in practice nonlinearity can be handled. In previous work, the authors studied a continuous modal structure...