An approach exploiting the relevant conservation laws associated with the wear due to sliding between deformable heat conducting bodies is presented in this work. The proposed methodology considers a pair of wearing objects in contact where their wear behaviors are encapsulated by semantically reduced one-dimensional, time-dependent ordinary differential equations (ODEs) as a replacement to the full mass conservation PDEs governing mass loss due to the various mechanisms present at the interface. At the same time, the conservation of energy and momentum are still expressed by the full form of the PDEs representing them. To assess the feasibility of this approach a reciprocating sliding contact pair of dissimilar materials is considered. The high dimensional thermo-mechanical problem is solved simultaneously and tightly coupled with the two ODE wear models for each of the wear pair bodies, thus enabling predictions of wear for both of them. Furthermore, an Arbitrary-Lagrangian-Eulerian (ALE) approach has been used to produce the evolution of the wear fronts on both elements of the sliding contact pair through physics-informed mesh deformation consistent with the results computed in the previous step. The main advantage of this approach enables the usage of any low dimensional wear model (i.e, mechanical failure, phase transformation-based, etc.) in a computationally detailed and efficient manner.

Flapping insect wings deform under aerodynamic and inertial-elastic loads. Existing aeroelastic wing models are computationally expensive, and consequently, the physics governing flexible wing deformation are not well understood. This paper develops a low-order, one-way coupled aeroelastic model of an arbitrary geometry wing undergoing three-dimensional rotation. The model is developed using the Lagrangian formulation and generalized aerodynamic loads are determined through a blade-element-momentum approach. The in-air and in-vacuum responses of a simulated Hawkmoth wing are compared for various conditions. During normal flight, simulation results show aerodynamic loading causes a 25% increase in maximum wingtip deflection versus a wing flapping in vacuum. This suggests aerodynamics plays a moderate role in structural deformation. Further parametric studies indicate (1) deviations in flap frequency excite torsional resonance and (2) the relative phase between pitch and roll rotations dramatically affects in-air wing response. Both the aeroelastic model and simulation results can guide optimal wing design for small-scale flapping wing micro air vehicles.

Wind turbines can provide energy in developing countries. However, there are limitations to the skilled labor and manufacturing equipment required to manufacture these systems in these regions. Accordingly, the manufacturing process needs to be adapted to the potential of the developing world. In this work, a simplified wind turbine blade design is investigated. The turbine efficiency is analyzed by the blade element momentum (BEM) theory. Two different scenarios are considered to simplify the design of the wind turbine blade. The shape of the blade is simulated by a rectangular root connected to several trapezoidal segments. This results in a simple chord length distribution. The design of the twist angle is also considered. The area under the power curve is used to compare the performance of the simplified blades with that of the original design. Results show that the twist angle can be completely omitted as a tradeoff between efficiency and manufacturability. Depending on the number of simplified design segments, the area under the power curve is reduced between 13% and 25 % with respect to the original blade. The model also demonstrates how the loss in efficiency increases as the simplicity of blade design increases. Still, the design simplification enables a manufacturing process which may facilitate the use of wind energy in the developing world.

When designing a wind turbine blade, the goal is to attain the highest possible power output under specified atmospheric conditions.In this paper,the maximum likelihood estimation method was used to compute the hub height wind speed at 65m mathematical model based on the observation data of He xi Corridor wind at 10m height, taking He xi region of a certain type of 40m blade as an example, based on the Blade Element Momentum Theoty and tip loss, established the blade aerodynamic mathematic model, using the genetic algorithm on the blades. Each section of the chord, twist angle of wind energy utilization coefficient, girder cap layer thickness parameters were optimized, The aerodynamic performance and stress distribution are given out, the results showed that the optimized blade wind energy utilization coefficient is greatly improved and the quality of the blade is significantly reduced. It is suitable for wind the characteristics of the blade design condition performance supper than that of general blade.It provides a theoretical basis for the blade design.

A variable ratio gearbox (VRG) provides discrete variable rotor speed operation, and thus increases wind capture, for small fixed-speed wind turbines. It is a low-cost, reliable alternative to conventional variable speed operation, which requires special power-conditioning equipment. The authors’ previous work has demonstrated the benefit of using a VRG in a fixed-speed system with passive blades. This work characterizes the performance of the VRG when used with active blades. The main contribution of the study is an integrative design framework that maximizes power production while mitigating stress in the blade root. As part of the procedure, three gear ratios are selected for the VRG. It establishes the control rules by defining the gear ratio and pitch angle used in relation to wind speed and mechanical torque. A 300 kW wind turbine model is used for a case study that demonstrates how the framework is implemented. The model consists of aerodynamic, mechanical, and electrical submodels, which work collaboratively to convert kinetic air to electrical power. Blade element momentum theory is used in the aerodynamic model to compute the blade loads. The resulting torque is passed through a mechanical system and subsequently to the induction machine model to generate power. The BEM method also provides the thrust and bending loads that contribute to blade-root stress. The stress in the root of the blade is also computed in response to these loads, as well as those caused by gravity and centrifugal force. Two case studies are performed using wind data that was obtained from the National Renewable Energy Laboratory (NREL). Each of these represents an installation site with a unique set of wind conditions that are used to customize the wind turbine design. The framework uses dynamic programming to simulate the performance of an exhaustive set of combinations. Each combination is evaluated over each set of recorded wind data. The combinations are evaluated in terms of the total energy and stress that is produced over the simulation period. Weights are applied to a multi-objective cost function that identifies the optimal design configurations with respect to the design objectives. As a final design step, a VRG combination is selected, and a control algorithm is established for each set of wind data. During operation, the cost function can also be used to bias the system towards higher power production or lower stress. The results suggest a VRG can improve wind energy production in Region 2 by roughly 10% in both the low and high wind regions. In both cases, stress is also increased in Region 2, as the power increases. However, the stress in Region 3 may be reduced for some wind speeds through the optimal selection of gear combinations.

Analysis of the dynamics of bilinear systems is critical for a variety of civil, mechanical and aerospace structures that contain gaps or prestress that are caused by cracks, delamination, joints or interfaces amongst components. Recently, a method was developed called bilinear amplitude approximation (BAA) to estimate the response of bilinear systems without gaps or prestress. This method was developed on the idea that the bilinear system can be separated into two time intervals both of which the system behaves as a distinct linear system: (1) the open state and (2) the closed or sliding state. In order to couple the linear vibrational response for each time interval, both geometric and momentum constraints are applied as transition conditions between the states. This paper expands the previous BAA method for the case where there are either gaps or prestress in the system. The new method requires the forcing magnitude to be known so that it can accurately determine when the system transitions between the two states, and the new equilibrium positions for each state for a given forcing magnitude. The new method also finds the bilinear frequency of the system, which cannot be computed using the bilinear frequency approximation (BFA) method previously developed since that method is only accurate for the zero gap and no prestress case. The new BAA and BFA methods are demonstrated on single degree of freedom and three degree of freedom systems for a variety of forcing conditions.

Cyber-physical systems are gaining momentum in the domain of manufacturing. Cloud Manufacturing is also revolutionizing the manufacturing world. However, although there exist numerous physical manufacturing machines which are network-ready, very few of them are operated in a networked environment due to lack of scalability of existing cyber-physical systems. Combining the features offered by cloud manufacturing and cyber-physical systems, we develop a service-oriented architecture of scalable cyber-physical manufacturing cloud with MTConnect. A testbed of cyber-physical manufacturing cloud is being developed based on the above scalable architecture. In this system, manufacturing machines and their capabilities virtualized in a cyber-physical cloud. Manufacturing operations are represented as web services so that they are accessible across the Internet. Performance of the testbed of our cyber-physical manufacturing cloud with MTConnect is evaluated and test results show that our system achieves excellent service performance of manufacturing operations across Internet.

Usage of compliant micro mechanical oscillators has increased in recent years, due to their reliable performance despite the growing demand for miniaturization. However, ambient vibrations affect the momentum of the oscillator, causing inaccuracy, malfunction or even failure of these devices. herefore, this paper presents a compliant force balanced mechanism comprising at least a prismatic joint, thereby creating the opportunity for usage of prismatic oscillators in translational accelerating environments. The proposed mechanism entails the symmetric displacement of two coplanar prismatic joints along non-collinear axes via a shape optimized linkage system. Rigid-body replacement with shape optimized X-bob, Q-LITF and LITF joints yielded a harmonic (R>0.999), low frequency (f = 27 Hz) single piece force balanced micro mechanical oscillator (∅35 mm). Experimental evaluation of large scale prototypes showed a limited ratio of the center of mass compared to the stroke of the device (≈0.01) and proper decoupling of the mechanism from the base, as the oscillating frequency of the balanced devices during ambient disturbances was unaffected, whereas unbalanced devices had frequency deviations up to 1.6%. Moreover, the balanced device reduced the resultant inertial forces transmitted to the base by 95%.

Some new theoretical and numerical results are presented on the dynamic response of a class of mechanical systems with equality motion constraints. At the beginning, the equations of motion of the corresponding unconstrained system are presented, first in strong and then in a weak form. Next, the formulation is extended to systems with holonomic and/or nonholonomic constraints. The formulation is based on a new set of equations of motion, represented by a system of second order ordinary differential equations (ODEs) in both the coordinates and the Lagrange multipliers associated to the motion constraints. Moreover, the position, velocity and momentum type quantities are assumed to be independent, forming a three field set of equations. The weak formulation developed was first used to cast the equations of motion as a set of first order ODEs in the coordinates and the corresponding momenta. Then, the same formulation was also employed as a basis for producing a suitable time integration scheme for the systems examined. The validity and efficiency of this scheme was tested and illustrated by applying it to a number of characteristic example systems.

A computational methodology is proposed for prediction of power losses due to pocketing (pumping or squeezing) of oil at the mesh interface of spiral bevel gears. The model employs an existing cutting simulation procedure to define surface geometries of the gears through face-milling and face-hobbing processes. A novel hypoidal discretization method is proposed to define pocket volumes between meshing gear teeth along circumferential and face width directions. An existing fluid mechanics formulation, utilizing principles of conservation of mass, momentum and energy, is used to compute the load-independent (spin) power losses due to pocketing of the medium in the gear mesh interface. A simulation of aerospace applications is presented to highlight the effects of lubrication conditions, on pocketing power losses.

This paper presents both experiment and simulation of alumina molten flow in a solid rocket motor (SRM), when the propellant combusts, the aluminum is oxidized into alumina (Al2O3) which, under the right flow conditions, tends to agglomerate into molten droplets, impinge on the chamber walls, and then flow along the nozzle wall. Such agglomerates can cause erosive damage. The goal of the present study is to characterize the agglomerate flow within the nozzle section by studying the breakup process of a liquid film that flows along the wall of a straight channel while a high-speed gas moves over it. We have used an unsteady-flow Reynolds-Averaged Navier-Stokes code (URANS) to investigate the interaction of the liquid film flow with the gas flow, and analyzed the breakup process for different flow conditions. The rate of the wave breakup was characterized by introducing a breakup-length-scale for various flow conditions based on the Volume Fraction (VF) of the liquid, which is an indicator of a two-phase flow liquid breakup level. A smaller breakup-length-scale means that smaller drops have been created during the breakup process. The study covers the breakup and fluid behaviors based on different gas-liquid momentum flux ratios, different surface tension and viscosity settings, different Ohnesorge numbers (Oh), and different Weber numbers. Both water and molten aluminum flows were considered in the simulation studies. The analysis demonstrates an effective method of correlating the liquid breakup with the main flow conditions in the nozzle channel path.

The aim of the present study is to numerically investigate the combustion characteristics of Heavy Fuel Oil (HFO) and NO x emissions inside a Calciner used in cement industry. The combustion model was based on the conserved scalar (mixture fraction) and prescribed Probability Density Function (PDF) approach. The (RNG) k-ε turbulence model has been used. The HFO droplet trajectories were predicted by solving the momentum equations for the droplets using Lagrangian treatment. The radiation heat transfer equation was solved using P1 method. A swirl number greater than 0.6 was found to be optimal for good combustion characteristics and NOx emissions concentration. Meanwhile, it was found that the HFO viscosity value assumption has a significant effect on the injection velocity and must be considered as a function of temperature during the analysis as this will significantly affect the combustion characteristics.

In this work, the out-of-plane equation of motion of a wind turbine blade modeled as a beam is developed using the Lagrange formulation. The modeling of aerodynamic loads is done with the blade element momentum theory. The equation of motion has combined effects of parametric and direct excitations and is reduced to a single mode. Perturbation analysis based on previous work shows how various terms affect the steady-state responses near resonance. Numerical simulations using parameters from a real turbine, reveal that these resonance become critical as the blades increase in size. The out-of-plane vibration model shows resonances that would not be expected by blade designers without analysis and modeling techniques presented in this work. The influence of these superharmonic blade vibration responses on the increased loads on the gearbox components would provide insight into premature failure of wind turbine blades and gearboxes.

Our research examines the feasibility of usign a wearable scissored-pair control moment gyroscope (CMG) for human balance assist. The CMG is a momentum exchange device consisting of a fast spinning flywheel mounted on a gimbal. The gimbal motion changes the direction of the flywheel rotation axis, which generates a reactionless torque. A scissored-pair CMG has the additional advantage of isolating the output torque to a single axis, where off-axis torques are canceled out. A properly designed CMG device worn as a backpack can apply a torque in the sagittal plane of the human trunk. This can help in restoring postural balance and in fall mitigation. This paper describes the complete design process of a scissored-pair CMG device with constraints on size, mass and dynamic properties for human wearability. A prototype of this device is built, utilizing a novel dual-flywheel design; it weighs about 8kg and is able to generate over 20Nm of torque. A custom hardware is built specifically for verifying the torque output of the device. To our knowledge this is the only device that generates the range of reactionless torque given its weight and size.

This work presents the integration of a detailed biomechanical model of the arms of a helicopter pilot and an equivalently detailed aeroservoelastic model of a helicopter, resulting in what has been called a ‘bioaeroservoelastic’ analysis. The purpose is to investigate potential adverse interactions, called rotorcraft-pilot couplings, between the aeroservoelastic system and the controls involuntarily introduced by the pilot into the control system in response to rotorcraft vibrations transmitted to the pilot through the cockpit, the so-called biodynamic feedthrough. The force exerted by the pilot on the controls results from the activation of the muscles of the arms according to specific patterns. The reference muscular activation value as a function of the prescribed action on the controls is computed using an inverse kinetostatics/inverse dynamics approach. A first-order quasi-steady correction is adopted to mimic the reflexive contribution to muscle activation. Muscular activation is further augmented by activation patterns that produce elementary actions on the control inceptors. These muscular activation patterns, inferred using perturbation analysis, are applied to control the aircraft through the pilot’s limbs. The resulting biomechanical pilot model is applied to the aeroservoelastic analysis of a helicopter model expressly developed within the same multibody modeling environment to investigate adverse rotorcraft pilot couplings. The model consists of the detailed aeroelastic model of the main rotor, using nonlinear beams and blade element/momentum theory aerodynamics, a component mode synthesis model of the airframe structural dynamics, and servoactuator dynamics. Results in terms of stability analysis of the coupled system are presented in comparison with analogous results obtained using biodynamic feedthrough transfer functions identified from experimental data.

Due to the challenges involved with modeling complex molecular systems, it is essential that computationally intelligent schemes be produced that put the computational effort where and when it is needed to capture important phenomena, and maintain needed accuracy at minimum costs. In this work, we investigate and propose some key issues for the adaptive modeling and simulation of the dynamic behavior of highly complex multiscale processes. This is accomplished through the appropriate use of an adaptive hybridization of existing, newly developed, and proposed advanced multibody dynamics algorithms and modeling strategies for forward dynamic simulation. The adaptive multiscale simulation technique discussed here benefits from the highly parallelizable structure of the divide and conquer (DCA) framework for modeling multibody systems. These algorithms include Flexible Divide and Conquer Algorithm (FDCA), Orthogonal Complement Divide-and-Conquer Algorithm (ODCA) and generalized momentum approaches for modeling discontinuous changes in the system. These algorithms permits a large complex molecule (or systems of molecules) to be seamlessly treated using a hierarchy of reduced order models ranging from atomistic to the continuum scale.

A new fluid dynamics model is proposed to predict the power losses due to pocketing of air, oil, or an air-oil mixture in the helical gear meshes. The proposed computational procedure treats a helical gear pair as combination of a number of narrow face width spur gear segments staggered according to the helix angle and forms a discrete, fluid dynamics model of the medium being pocketed in the gear mesh. Continuity and conservation of momentum equations are applied to each coupled control volume filled with a compressible fluid mixture to predict fluid pressure and velocity distributions from, which the instantaneous pocketing power loss is calculated. The proposed model is exercised in order to investigate fluid pressure and velocity distributions in time, as well as pocketing power loss as a function of speed, helix angle and oil-to-air ratio.

Many conventional time integration schemes frequently adopted in flexible multibody dynamics fail to retain the fundamental conservation laws of energy and momentum of the continuous time domain. Lack of conservation, however, in particular of angular momentum, may give rise to unexpected, unphysical results. To avoid such problems, a scheme for the consistent integration of modally reduced multibody systems subjected to holonomic constraints is developed in the present paper. As opposed to the conventional approach, in which the floating frame of reference formulation is combined with component mode synthesis for approximating the flexible deformation, an alternative, recently proposed formulation based on absolute coordinates is adopted in the analysis. Owing to the linear relationship between the generalized coordinates and the absolute displacement, the inertia terms in the equations of motion attain a very simple structure. The mass matrix remains independent of the current state of deformation and the velocity dependent term known from the floating frame approach vanishes due to the absence of relative coordinates. These advantageous properties facilitate the construction of an energy and momentum consistent integration scheme. By the mid-point rule, algorithmic conservation of both linear and angular momentum is achieved. In order to consistently integrate the total energy of the system, the discrete derivative needs to be adopted when evaluating the strain energy gradient and the derivative of the algebraic constraint equations.

This paper considers the energy aspects of fractional elements defined by the equation F t = k λ D t λ 0 x t . In contrast to the typically conservative assumption of classical physics that lead to the potential and kinetic energy expressions, a number of important non-conservative differences are exposed. Firstly, the considerations must be time-based rather than displacement or momentum based variables. Time based equations for energy behavior of fractional elements are presented and example applications are considered. The effect of fractional order on the energy requirements and energy return of these systems is shown. Importantly, it is shown that the history, or initialization, has a strong effect on energy requirements. Finally, compact expressions for the work or energy, are developed.

Mass center of a human body is not a fixed point on the human body because the inertia distribution of the human body changes with body posture. Real-time estimation of the location of human mass center is often required for many biomechanical or biomedical applications. This is not an easy task if the inertia properties of the human’s body segments are unknown. This paper presents a technique for estimating the trajectory of the human mass center based on a recently developed inertia properties identification technology which was derived based on the impulse-momentum principle. The proposed technique assumes a human body as a general treelike multibody system, such that the mass center of the human is predictable with the knowledge of the barycentric parameters of the human. The latter can be identified using inertia identification method. This technique is advantageous because it requires only the 3D motion capture data as its primary input and does not need to know the inertia and geometric parameters of individual body segments of the human. The paper presents a dynamic simulation based study of the proposed estimation technique and also describes an ongoing experimental testing.