bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Chip Back-Flow Angle in Machining With Restricted Contact Grooved Tools
Authors: Fang N. , Jawahir I. S.
Published: November 2021

This paper presents a new predictive model for chip back-flow angle in machining with restricted contact grooved tools. This model is derived from the recently established universal slip-line model for machining with restricted contact cut-away tools. A comprehensive definition of the chip back-flow angle is first developed, and based on this, a quantitative analysis of the effect of chip back-flow is presented for the given set of cutting conditions, tool geometry and variable tool-chip interfacial stress state. This model also predicts cutting forces, chip thickness ratio and chip up-curl radius. A full experimental validation of the predictive model involving the use of high speed filming techniques is then presented for chip back-flow angle and this validation provides a range of feasible/prevalent tool-chip interfacial frictional conditions for a given set of input conditions.
Generic Simulation Approach for Multi-Axis Machining: Part I—Modeling Methodology
Authors: Bailey T. , Elbestawi M. A. , El-Wardany T. I. , Fitzpatrick P.
Published: November 2021

This paper presents a new methodology for analytically simulating multi axis machining of complex sculptured surfaces. A generalized approach is developed for representing an arbitrary cutting edge design, and the local surface topology of a complex sculptured surface. A NURBS curve is used to represent the cutting edge profile. This approach offers the advantages of representing an arbitrary cutting edge design in a generic way, as well as providing standardized techniques for manipulating the location and orientation of the cutting edge. The local surface topology of the part is defined as those surfaces generated by previous tool paths in the vicinity of the current tool position. The local surface topology of the part is represented without using a computationally expensive CAD system. A systematic prediction technique is then developed to determine the instantaneous tool/part interaction during machining. The methodology employed here determines cutting edge in-cut segments by determining the intersection between the NURBS curve representation of the cutting edge and the defined local surface topology. These in-cut segments are then utilized for predicting instantaneous chip load, static and dynamic cutting forces, and tool deflection. Part I of this paper details the modeling methodology and demonstrates the capabilites of the simulation for machining a complex surface. Part II details both the model calibration procedure and discusses a case study of process optimization through feed rate scheduling.
Avoiding Tool Exit in Planar Milling by Adjusting Width of Cut
Authors: Rangarajan Arvind , Chu Chih-Hsing , Dornfeld David
Published: November 2021

Tool failure and milling exit burr formation usually occur when the tool cutting edges move out of the workpiece. One of the most effective methods for minimizing these problems is to prevent the tool from exiting the workpiece while removing material. This can be achieved by special tool path planning. In this paper we presents a set of geometric algorithms that avoid tool exits in planar milling of 2D polygonal and curved contours. Tool paths are generated by offsetting the workpiece edges with appropriate widths of cut, depending on the edge types (straight or circular). A tool path planner is successfully implemented with those algorithms. Tool exits are thus completely eliminated in an automatic manner.
Evaluation of Plastic Bead Blasted Ti-6Al-4V Fatigue Specimens
Authors: Brady Brian G.
Published: November 2021

As part of an evaluation of plastic bead blasting as a means of removing paint from aircraft, fatigue testing was performed on bead blasted material. Typical military aircraft finishes were removed from 0.063 inch (1.6 mm) thick clad aluminum, corrosion resistant steel, and Ti-6Al-4V. Constant amplitude fatigue specimens were then machined from these samples and tested. Results were compared to control samples which had not been bead blasted. Fatigue life of corrosion resistant steel and clad aluminum were unaffected by bead blasting. The bead blasted Ti-6Al-4V samples, however, exhibited a significant decrease in fatigue life when compared to the control samples.

Laboratory evaluation of the bead blasted Ti-6Al-4V samples included binocular and scanning electron microscopic evaluation, energy dispersive x-ray spectrometry (EDX), metallography, and mechanical evaluation of surface roughness. It was determined that the decrease in fatigue life exhibited by the bead blasted samples was caused by improper machining not bead blasting.
Phenomenological and Structural Aspects of the Mechanical Response of Arteries
Authors: Ogden Ray W. , Schulze-Bauer Christian A. J.
Published: November 2021

In this paper we present some new data from extension-inflation tests on a human iliac artery and then, on the basis of the nonlinear theory of elasticity, we examine a possible model to represent this data. The model considers the artery initially as a thick-walled circular cylindrical tube which may consist of two or more concentric layers. In order to take some account of the architecture (morphological structure), each layer of the material is regarded as consisting of two families of mechanically equivalent helical fibers symmetrically disposed with respect to the cylinder axis. The resulting material properties are then orthotropic in each layer. General formulas for the pressure and the axial load in the symmetric inflation of an extended tube are obtained. The starting point is the unloaded circular cylindrical configuration, but (in general unknown) residual stresses are included in the formulation. The model is illustrated by specializing firstly to the case of a single layer so that the consequences of the hypothesis of uniform circumferential stress in the physiological state can be examined theoretically. This enables the required residual stresses to be calculated explicitly. Secondly, the equations are specialized for the membrane approximation in order to show how certain important characteristics of the experimental data can be replicated using a relatively simple anisotropic membrane model.
Time-Dependent Response of Polymer Systems Under Cyclic Loading Conditions
Authors: Schumacher Shane , Vinogradov Aleksandra M. , Liu Zhiyu , Jenkins Christopher H. , Kitahara Isamu , Winter Robb M.
Published: November 2021

The paper concerns the time dependent response of polymer systems subjected to superimposed static and cyclic loads. An experimental study of two materials, Nylon 6/6 and a piezoelectric polyvinylidene fluoride (PVDF)-based composite, has been conducted with the objective to determine the degree of cyclic creep effects depending on the mean stress, cyclic stress amplitude and frequency. Creep acceleration due to cyclic loading effects has been observed in both materials even in the range of stresses well below their respective viscoelastic linearity limits. It is clear that these effects are essentially nonlinear, as the response of the materials to cyclic loading conditions does not represent a simple superposition of the responses to static and fully reversed cyclic loads applied separately. An increase of creep rates in both polymers has been observed consistently as frequencies and amplitudes of vibration tended to increase. However, the relation between cyclic creep effects and the mean stress appears to vary depending on the polymer type and loading conditions. Nylon 6/6 has demonstrated material hardening as a result of cycling. Considerable crack development in Nylon 6/6 has been detected only in the range of stresses approaching yield conditions.
Subsonic and Intersonic Failure of Composites: High-Speed Optical and Thermographic Measurements and Numerical Simulations
Authors: Rosakis A. J. , Coker D. , Yu C. , Ortiz M.
Published: November 2021

In this paper dynamic fracture behavior of unidirectional graphite-epoxy composite plates is investigated experimentally and numerically. Crack propagation experiments are conducted on thick unidirectional graphite-epoxy composite plates subjected to in-plane, symmetric and asymmetric, impact loading. The coherent gradient sensing technique (CGS) is used in conjunction with high-speed photography to visualize the crack growth events. Cracks are found to propagate at subsonic speeds in the Mode-I case, whereas in both mixed mode and Mode-II the crack tip speed clearly exceeds the shear wave speed of the laminate. In the case of symmetric loading (Mode-I), the crack tip speeds approach the Rayleigh wave speed of the composite (1500 m/s), however it never exceeds it as predicted by asymptotic analysis. The situation is found to be entirely different for growing shear (Mode-II) cracks. A shock wave emanating from the crack tip is observed in the optical patterns. This provides direct evidence that the crack propagates faster than the shear wave speed of the composite. The crack tip speed is then observed to jump to a level close to the axial longitudinal wave speed along the fibers (7500 m/s) and then to stabilize to a lower level of approximately 6500 m/s. This speed corresponds to the speed at which the energy release rate required for shear crack growth is non-zero as determined from asymptotic analysis. The CGS interferograms also reveal the existence of large-scale frictional contact of the crack faces behind the moving shear cracks. In addition high speed thermographic measurements are conducted that show concentrated hot spots behind the crack tip indicating crack face frictional contact. Finally, these experiments are modeled by a detailed dynamic finite element calculation involving cohesive elements, newly developed adaptive remeshing using subdivision and edge collapse, composites element, and penalty contact. The numerical calculations are calibrated on the basis of fundamental material properties measured in the laboratory. The numerical methodology is subsequently validated by direct comparison to optical experimental measurements (crack speed record and near tip deformation field structure). For shear crack growth the numerics also reveal the experimentally observed shock wave structure and confirm the optical observation of large-scale crack face contact.
Modeling Damage Accumulation in Laminated Composites Subjected to Impact
Authors: Allen David H. , Searcy Chad R.
Published: November 2021

Because of their high strength-to-weight ratio, laminated composites continue to be an attractive alternative to conventional monolithic media in the design of impact resistant structures. Unfortunately, the high cost of production has been a major limiting factor in the usage of laminated composites in design applications. Contributing to this cost is the complexity of the design process, which calls for an increased number of parameters necessary for the optimal design of impact resistant laminated composite structures. One way to address this complexity is through the use of damage models. Properly constructed damage models have the potential to reduce the cost of design and promote the increased usage of laminated composites in design applications.

This paper demonstrates the effective use of cohesive zone modeling to determine the optimal laminate configurations for impact resistant composites. A nonlinear finite element algorithm equipped with a micromechanically-based viscoelastic cohesive zone model is used to predict the cumulative damage in composite laminates subjected to impact. Several composite layups have been studied to determine an optimal design configuration. Some analytical predictions have been provided for a comparison with the numerical results.
The Micromechanics of Inelastic Processes in Superplastic Materials
Authors: Chandra N.
Published: November 2021

Superplasticity is an intriguing inelastic process in solid materials with deformation upto several thousand percent. Forming sheet and bulk materials using superplastic forming has become an established manufacturing method in aerospace and lately in other industries. Developing the right constitutive behavior is important not only for modeling the process for manufacturing by engineering mechanicians but for choosing the right composition and processing for material scientists. Such an ideal constitutive equation has been eluding the analysis so far. This paper examines some of the fundamental misgivings about the origin of inelastic process in superplasticity compared to other well known deformation processes. Also an attempt is made to understand the basic characteristics of superplastic inelastic deformation at macroscopic, mesoscopic and atomic levels.
The Mechanics of the Secondary Flows of Viscoelastic Fluids in Non-Circular Straight Tubes and the Mean Transversal Field in Pulsating Flows
Authors: Siginer Dennis A. , Letelier Mario F.
Published: November 2021

A survey of secondary flows of viscoelastic liquids in straight tubes is given including recent work pointing at striking analogies with transversal deformations associated with the simple shearing of solid materials. The importance and implications of secondary flows of viscoelastic fluids in heat transfer enhancement are explored together with the difficulties in detecting weak secondary flows (dilute, weakly viscoelastic solutions) in a laboratory setting. Recent new work by the author and colleagues which explores for the first time the structure of the secondary flow field in the pulsating flow of a constitutively nonlinear simple fluid, whose structure is defined by a series of nested integrals over semi-infinite time domains, in straight tubes of arbitrary cross-sections is summarized. The transversal field arises at the second order of the perturbation of the nonlinear constitutive structure, and is driven by first order terms which define the linearly viscoelastic longitudinal flow in the hierarchy of superposed linear flows stemming from the perturbation of the constitutive structure. Arbitrary conduit contours are obtained through a novel approach to the concept of domain perturbation. Time averaged, mean secondary flow streamline contours are presented for the first time for triangular, square and hexagonal pipes.
On the Flow of Mixtures Between Parallel Plates
Authors: Rajagopal K. R.
Published: November 2021

Here, we discuss the flow of a mixture of two fluids between two parallel plates, within the framework of the theory of interacting continua. In the case of a flow due to a pressure gradient along the plates, in marked contrast to the classical Poiseuille flow, we find a variety of solutions, from those that are close to parabolic to those solutions that are spatially periodic across the plates, depending on the values for the viscosities of the fluid.
Fluid Flow Around a Vibrating Beam and Associated Nonlinear Damping
Authors: Chakraborty G. , Mote C. D.
Published: November 2021

Steady flow of a viscous fluid around a transversely oscillating, simply-supported beam is driven by forces represented in the nonlinear terms of the Navier-Stokes’ equation. This flow occurs inside and outside the viscous boundary layer. The flow-velocity amplitude is proportional to the square of the amplitude of the beam transverse velocity and thus it is essentially only observable during high velocity beam vibration. This flow, known as ‘edge streaming’, does not occur in an ideal fluid. In the flow the fluid is ‘drawn in’ at the edges of the beam near the vibrational antinodal points and ‘expelled’ at the nodal points. When a rigid plate is placed parallel to the long axis of the vibrating beam and normal to the vibration velocity, vortices of different orientation are generated depending on the separation of the plate and beam surfaces. When the separation is an order of magnitude greater than the boundary layer thickness, the vortices have the rolling characteristic discussed by Rayleigh [1]. But for small separation of the order of the boundary layer thickness, the vortical axes are perpendicular to that of the former, parallel to the vibration velocity. They have been experimentally observed [6]. Owing to the streaming motion, damping, as measured by the ratio of the dissipation of energy and the total vibration energy over a time period, has a nonlinear hard representation with respect to the vibration amplitude.
Locus of the Axis of Vibration for a Vibrating System With Variable Location of a Mass Center
Authors: Dan Byung Ju , Choi Yong Je
Published: November 2021

A typical approach to a linear vibration analysis of an elastically supported single rigid body is to rearrange a dynamic model into a corresponding eigenvalue problem. From the geometrical point of view, the eigenvectors in the planar vibration analysis can be interpreted as pure rotations about the vibration center or pure translations. In a three dimensional space, they represent repetitive twisting motions about the axes of vibrations. By taking a geometrical approach to the vibration analysis, the vibration mode shapes may be better understood. In this paper, the influence of variable location of a mass center on the locations of the axes of vibrations and the natural frequencies are investigated by means of the locus of the axis of vibration expressed in analytical form, which represents the geometrical locus of the eigenvector. A numerical example is used to clearly illustrate the vibration phenomena of an optical pick-up used in an information storage device.
Sandwich Structures for Naval Ships: Design and Experience
Authors: Olsson Karl-Axel
Published: November 2021

In Sweden we have a long experience with different types of vehicles and ships in sandwich construction, especially Navy ships such as minesweepers, mine-counter-measure-vessels and corvettes. GRP (Glass fibre Reinforced Plastic) and FRP (Fibre Reinforced Plastics) have been the most common face materials, but metallic materials such as Al-alloys, coated carbon steel and stainless steel have also been used. Core materials have usually been cellular plastic foams of cross-linked PVC (Polyvinyl-chloride), but also extruded PS (Poly-styrene), PUR (Poly-urethane), PEI (Poly-ether-imide) and PMI (Poly-methacryl-imide). Different continuous and discontinuous manufacturing processes have been used. Vacuum assisted infusion has been introduced recently, because it is a closed process, gives high fibre content and a good quality of the laminates. Sandwich design has mainly been used in the transportation area, where lightweight design is needed to give higher performance and load bearing capacity. The use of sandwich construction will give high stiffness- and strength-to weight ratio. This is usually not enough from an economic point of view to justify the introduction of sandwich construction, but other integrated functions must be considered, i.e. insulation, energy consumption, damping, fewer components, lower manufacturing costs, low maintenance, signature effects (military) etc.
Lagrangian Simulation of Gas-Solid Flows in Homogeneous Isotropic Turbulence
Authors: Huilier Daniel
Published: November 2021

A Lagrangian approach is developed to describe particle’s dispersion in a stationary, homogeneous and isotropic turbulent flow. Obviously, the particles’ dispersion is influenced by the fluid velocity fluctuations, which are classically simulated by a Monte Carlo process or Markov chains. However, some studies have shown the restrictions of these methods generating the fluid turbulent velocity and have suggested improvements to ensure that the Lagrangian model accounts for the three main effects governing the dispersion in gas-particle flows, namely the inertia, crossing trajectories and continuity effects. The first aim of this paper is to present an improved Lagrangian model which integrates the spatio-temporal characteristics of the fluid turbulence experienced by the particle. The agreement between the numerical results obtained and the analytical expressions derived by Wang and Stock (1993) will be very satisfying. Another interest is to investigate the role of the traditionally-neglected and troublesome added mass and history terms in numerical studies when long time dispersion of inertial particles is the primary concern. Indeed, we will observe that for a large range of values of the ratio of particle to fluid density, these non-stationary forces have statistically no influence on the characteristics of the turbulent particle dispersion and can be safely omitted.
Computational Analysis of Transient 3D-Melt-Water Interactions
Authors: Kolev Nikolay Ivanov
Published: November 2021

This work is part of the Siemens effort to estimate the damage potential of melt water interaction in future nuclear power plants with pressurized water reactors. After creating a modeling technology, the IVA5 computer code, verifying it by comparison with numerous separated effect tests, system tests and analytical benchmarks, performing many 2D computational analysis we present in this work complete 3D analysis of melt water interactions. Interesting conclusions for the systems analyzed are drown. Some of the limitations of the technology are also demonstrated.
The Implementation of the Level Set Method Within the Finite Element Formulation
Authors: Shepel Sergey V. , Paolucci Samuel
Published: November 2021

We apply the Streamline Upwind Petrov Galerkin (SUPG) finite element formulation of the Level Set method to 2D redistancing and advection problems on unstructured triangulated grids. The purpose is to test the Level Set method for mass conservation properties, where the mass is understood as the amount of fluid enclosed by the interface. For the redistancing procedure we implement the idea of mass correction suggested by Sussman and Fatemi (1999) and confirm its high accuracy within the finite element formulation. However, we find that the use of the first order SUPG formulation of the Level Set method for coupled redistancing-advection problems can result in significant loss of mass caused by distortion of the interface due to numerical diffusion. This neccesitates the use of higher order upwind finite element schemes for the advection equation.
Influence of CFD Analysis on the Design of Cooling Channels for the CCL Cavity for the Spallation Neutron Source
Authors: Konecni Snezana , Bultman Nathan K.
Published: November 2021

Water flow in cooling channels was simulated using the computational fluid dynamics (CFD) code CFX4. Pressure drop in the cooling channels of the coupled-cavity linac (CCL) cavity was calculated. The effects of the manifold on the pressure drop were studied also. Reducing the pressure drop was a primary goal of this exercise that led to changing the cooling channel entrance regions. Results of this analysis were used in sizing pumps required for the cooling system.

For the validation of the simplified numerical model, an experiment was performed to measure the pressure drop in the cooling channels for variable flow rate, using a flow loop. Deionized water was circulated through the test section with a pump and its flow rate was monitored with a turbine flow meter. Pressure was monitored with pressure transducers at five locations including a differential pressure transducer across the test section, and water temperature was taken at the exit of the pump.

Pressure drop across the inlet and outlet of the test section was measured and recorded for different flow rates. Flow rate was also monitored and stored simultaneously. From the recorded data, an empirical correlation was derived to describe the pressure drop, dp, as a function of flow rate through the four cooling channels.
Submerged Jet Flows of Non-Newtonian Fluids: A Computational Study
Authors: Hammad Khaled J.
Published: November 2021

Axisymmetric jets of non-Newtonian fluids discharging into a stagnant, identical, fluid from a wall normal to the jet axis were numerically studied. Mass and fully-elliptic momentum conservation equations governing the steady, laminar, submerged jet flow were solved using a block-implicit finite-difference scheme. The Herschel-Bulkley Theological model was used to elucidate the role of yield stress, pseudoplasticity and dilatancy, in the resulting flow structure. Use of the full equations of motion along with an accurate and efficient numerical solution technique allowed for predictions of the jet velocity profiles that are valid throughout the whole flow field. The obtained results clearly indicate the shortcomings of applying the classical boundary-layer theory to model laminar submerged jets of yield stress or shear-thinning fluids.
A Design Study of a Low-Cost Heterogeneous Parallel Computer
Authors: Barata Jorge M. M. , Silva André R. R. , Garcês Raúl L. M.
Published: November 2021

A design study of a low-cost heterogeneous parallel computer based on already existing hardware is presented.

The UNIX operating system is used together with PVM for message passing control. The parallel machine is constructed using existing Intel PC’s and Alpha workstation platforms.

The new techniques and algorithms are successfully applied to the grid generation problem based on the solution of partial differential equations with control of the boundary point distribution.

Two different programming models were used. One uses decomposition of the domain into as many parts as there are processors, and revealed high reductions on the total turnaround time, although load balancing was a major problem. The other programming model has the possibility of changing the position of the points of the interface between each sub-grid, and allows reductions of the total turnaround time up to 1.6 times for the case of 3 processors, while the quality characteristics of the final grid are maintained.

The communication times were reduced up to 7.5% of the total turnaround times, but the recursive nature of the numerical iterative process of the grid generation method causes a substantial increase in the number of iterations, reducing the parallel machine performance.
Implementing a Large Non-Linear Integer Optimization on a Distributed Collection of Office Computers
Authors: Nickel Ronald H. , Mikolic-Torreira Igor , Tolle Jon W.
Published: November 2021

We describe how we implemented the MIMERBS non-linear integer optimization methodology to run across a virtual super-computer of existing Windows NT computers networked together by an ordinary office LAN. We describe how we configured this virtual computer and how we parallelized MIMERBS to work efficiently in view of the high communications costs of our virtual computer. We also describe how we made MIMERBS highly fault-tolerant and dynamically configurable; in particular we describe techniques for handling the loss of individual computers, for automatic on-the-fly addition of new computers, and for dynamic load-balancing. We also describe the techniques we used to share computer resources gracefully with officer workers using the same computers concurrently for ordinary word and data processing.

We present performance results from specific MIMERBS applications. These examples show that performance of several gigaFLOPS is possible with just a few dozen ordinary computers on an office LAN.
Flow Characteristics of Oscillating Flow in a Channel Obstructed by an Array of Circular Cylinders
Authors: Sawada Ken-ichi , Murata Hiroyuki , Kobayashi Michiyuki
Published: November 2021

Flow visualization experiments on oscillating flow in a channel obstructed by an array of circular cylinders were performed. First of all, steady flow experiments without oscillation were carried out. The Karman vortices began to shed in a range of the Reynolds number: 53<Re<68. The Strouhal number showed a tendency to decrease with an increase of the Reynolds number. Oscillating flow experiments were carried out secondly. When the oscillation amplitude was small, Karman vortices shed periodically and its Strouhal number agreed with that in the steady flow. But, when the oscillation amplitude was large, shedding of Karman vortex was well controlled by the oscillating flow. The vortex shedding frequency became large with an increase of the cross-sectional mean velocity. On the other hand, the amplitude of velocity fluctuation in the wake was small in the accelerating phase and large in the decelerating phase.
A Self-Consistent Transient Paint Simulation
Authors: Miller Ronald H. , Strumolo Gary S. , Braslaw Jake
Published: November 2021

Optimizing the painting process involves understanding the many nonlinear dynamics that effect paint transfer efficiency (PTE) such as bell applicator design (bell cup and shaping air ring), operating conditions (shaping air flow rate, paint flow rate, electric potential, downdraft, and bell rotation speed), target location, and paint type. PTE optimization results in less experimental testing and improved paint quality. We have modified a numerical simulation to include self-consistent momentum coupling between a continuum and discrete mass particles, as well as the inclusion of a self-consistent electrostatic field. These modifications enable the simulation tool to address several seminal questions concerning PTE. Several simulations have been performed and the influence of self-consistent modeling is addressed in this paper.
Progress in Railroad Freight Car Engineering
Authors: Punwani Swamidas K.
Published: November 2021

Every year the Rail Transportation Division (RTD), American Society of Mechanical Engineers (ASME) conducts a survey to document progress in the design, construction and use of freight cars and components. This paper describes the new developments. Some information was obtained from web sites. The industry continued to focus on the evolution of freight equipment in 2000 by adding flexibility and versatility to designs developed in the recent past.
Prediction of Stiffness and Strength of Plain Weave Composites by Mixed Finite Element Method
Authors: Sihn Sangwook , Roy Ajit K.
Published: November 2021

A numerical model for three-dimensional stress analysis, which was formulated in the form of mixed finite element method based on Reissner’s mixed variational principle, is applied to analyze stiffness and strength of woven fabric composites. The model calculates three-dimensional effective elastic moduli and predicts failure strengths and damage modes. The failure analysis includes residual stress calculation to consider hygrothermal effect. The numerical calculations show a good agreement with existing experimental and numerical results on both flat and woven laminated composites with various yarn-waviness ratios.
Failure Mechanisms of Notched Laminates Under Biaxial Compression at Elevated Temperature
Authors: Ahn Junghyun , Waas Anthony M.
Published: November 2021

A compression test at elevated temperature was performed to investigate the notch sensitivity and failure mechanisms of fibrous laminated composite plates containing a stress raiser, in the form of a circular cutout, under equi-biaxial and uniaxial compressive loading. Strains measured at various locations on the specimen surface and cutout edge were used to monitor the initiation of failure. Unloading the specimen before global failure made it possible to understand the failure mechanism associated with the final failure mode.
A Comparison of Component Mode Synthesis Methods for Cyclic Structures
Authors: Tran Duc-Minh
Published: November 2021

Several component mode synthesis methods with fixed, free and hybrid interface are used to compute the eigen solutions and the frequency response of a cyclic structure in combination with the cyclic symmetry properties. In particular, a procedure based on the use of a truncated basis of interface modes has been developed to reduce the number of interface coordinates in the component mode synthesis methods. Both classical and new methods provide very good results and are more efficient than the use of the cyclic symmetry properties only or the combination of the cyclic symmetry with the modal projection method for computing the forced response. For the eigen solutions, the free interface methods are more accurate than the fixed and the hybrid interface methods.
A Symbolic-Numerical Method for Nonlinear Rotor Dynamics Under Fluid Confinement
Authors: Moreira Miguel , Antunes José , Pina Heitor
Published: November 2021

Recently, a theoretical formulation for the nonlinear planar motion of rotors under fluid confinement—motion X (t) taking place in a single direction— was developed. Using the same assumptions and methods a quite involved analytical model for nonlinear orbital motions—motions X (t) and Y (t) taking place in orthogonal directions— was also experimentally obtained and validated.

In this paper a symbolic-numerical procedure, based on a Galerkin approach, was developed to obtain an approximate nonlinear planar model for the rotor dynamics. The approximate model can be automatically generated on a symbolic computer environment, for increasing levels of accuracy. Numerical simulations showed a quite good agreement between this approximate model and the corresponding analytical exact planar model.

The proposed methodology can be used straightforward to obtain approximate nonlinear orbital rotor dynamics models, as well as for other flow-structure coupled vibratory systems.
A New Lower Extremity Modeling of Human Body With Variable Feet Links
Authors: Arafati Nader , Lazennec Jean Yves , Ohayon Roger
Published: November 2021

Human movement modeling has been the object of much research for the past 30 years. In these models the position of foot link was fixed on the ground.

We propose to model the feet links as variable, since the position of foot pressure center changes from heel to toes. The ground reaction forces could also be analyzed in real time. We examined this model for some static postures.

In standing anatomical position, the maximum articular forces are localized in hip and knee joints. In sagittal plane, the ground reaction force vectors are positioned nearly under ankle joints.

The pathological postures like body with pes cavus or with global spine kyphosis increase the articular and muscular forces. In these cases, the position of ground reaction force vectors is moved toward the toes.
Practical Adaptive Robust Controllers for Active Suspensions
Authors: Chantranuwathana Supavut , Peng Huei
Published: November 2021

This paper presents adaptive robust controllers for force tracking application in a quarter-car active suspension system. In previous publications (Chantranuwathana and Peng 1999a, 1999b), an active suspension architecture was presented. The overall active suspension system was decomposed into two loops. At the main-loop, the desired force signal is calculated while the sub-loop force tracking controller tries to keep the actual force close to this desired force. An Adaptive Robust Control (Yao and Tomizuka 1997) design technique was used to achieve good force tracking performance in a robust manner under plant uncertainties. It was found that force-tracking of up to 5Hz can be reliably achieved. It is, however, found to be unreliable in experiments, especially when high frequency disturbances are present. In this paper, we will show that unmodeled dynamics and especially, the delay (first order lag) in implementing the control signal is a main cause of the problem. With this insight, three controller modifications are proposed to reduce the effect of the unmodeled dynamics, 1) include the actuator dynamics in the ARC design, 2) cancellation of the actuator dynamics and 3) online-adaptation of an ARC parameter. A number of simulation results will be presented to show the effect of these remedies. The last two modifications were found to be promising for actual implementations.
A Knowledge-Based Tuning Method for Injection Molding Machines
Authors: Yang Dongzhe , Danai Kourosh , Kazmer David
Published: November 2021

Complexity of manufacturing processes has hindered methodical specification of machine setpoints for improving productivity. Traditionally in injection molding, the machine setpoints are assigned either by trial and error, based on heuristic knowledge of an experienced operator, or according to an empirical model between the inputs and part quality attributes obtained from statistical design of experiments (DOE). In this paper, a Knowledge-Based Tuning (KBT) Method is presented which takes advantage of the a priori knowledge of the process, in the form of a qualitative model, to reduce the demand for experimentation. The KBT Method is designed to provide an estimate of the process feasible region (process window) as the basis of finding the optimal setpoints, and to update its knowledge-base according to new input-output data that becomes available during tuning. The KBT Method’s utility is demonstrated in production of digital video disks (DVDs).
Adaptive Passivity-Based Nonlinear Control for Strict Feedback Form Systems
Authors: Seiler Peter , Alleyne Andrew
Published: November 2021

This paper presents a tracking algorithm for the adaptive control of nonlinear dynamic systems represented in Strict Feedback Form with parametric uncertainty. The construction of the stabilizing algorithm is given using Passivity-based arguments that result in an Adaptive Passivity-Based Controller (APBC). This paper also shows a comparison with a controller designed via Adaptive Backstepping with tuning functions. The Adaptive Backstepping Controller (ABC) has many additional coupling terms that make its design and implementation more complex and may also result in unwanted transients. On the other hand, the APBC has a convenient decoupling property that provides a diagnostic tool for detection of non-parametric model error.
Robust Steering and Differential Braking Control for Automated Guidance of Tractor-Semitrailer Combination Vehicles
Authors: Wang Jeng-Yu , Tomizuka Masayoshi
Published: November 2021

In this paper, a robust linear steering and differential braking controller is designed for the automated guidance of tractor-semitrailer combination vehicles using the H∞ loop-shaping methodology. Only the articulation angle, the lateral errors at the front and rear axle of the tractor, and the angular velocities of the rear wheels of the trailer or the brake line pressure signals, are assumed to be available for the synthesis of control inputs. The controller is designed to ensure the robustness to model uncertainties due to variations in vehicle longitudinal speed, road adhesion coefficient and trailer cargo load. Closed-loop simulation results show the robustness of the proposed controller and the resulting smaller lateral error at the trailer end when compared to the controller using the steering input only. More damped transient responses of articulation angle when using the steering and braking control also improve the yaw stability of the trailer.
Transient and Steady-State Adaptive Fueling Control of Spark Ignition IC Engines
Authors: Stroh David J. , Franchek Matthew A. , Kerns James M.
Published: November 2021

Presented in this paper is an adaptive, model based, fueling control system for spark ignition-internal combustion engines. Since the fueling control system is model based, the engine maps currently used in engine fueling control are eliminated. This proposed fueling control system is modular and can therefore accommodate changes in the engine sensor set such as replacing the mass-air flow sensor with a manifold air pressure sensor. The fueling algorithm can operate with either a switching type O2 sensor or a linear O2 sensor. The fueling control system is also parceled into steady state fueling compensation and transient fueling compensation. This feature provides the distinction between fueling control adaptation for transient fueling and steady state fueling. The steady state feedforward controller is comprised of two nonlinear models. These models are adapted via a recursive least squares method to accommodate product variability, engine aging, and changes in the operating environment. The transient fueling compensation also utilizes a feedforward controller that captures the essential dynamic characteristics of the transient fueling operation. This controller is measured using a frequency domain system identification approach. This proposed fueling control system is demonstrated on a Ford 4.6L V-8 fuel injected engine.
Discrete-Time LQR and H
2 Damping Control of Flexible Payloads Using a Robot Manipulator With a Wrist-Mounted Force/Torque Sensor
Authors: Lee Chunhao Joseph , Mavroidis Constantinos
Published: November 2021

This paper presents robust and optimal control methods to suppress vibrations of flexible payloads carried by robotic systems. A new improved estimator in discrete-time H2 optimal control design based on the Kalman Filter predictor form is developed here. Two control design methods using state-space models, LQR and H2 Optimal Design, in discrete-time domain are applied and compared. The manipulator joint encoders and the wrist-mounted six-degree-of-freedom force/torque sensor provide the control feedback. A complete dynamic model of the robot/payload system is taken into account to synthesize the controllers. Experimental verifications of both methods are performed using a Mitsubishi five-degree-of-freedom robot manipulator that carries a flexible beam. It is shown that both methods damp out the vibrations of the payload very effectively.
General Evaluation Method for Safety Control of Human-Care Robots
Authors: Ikuta Koji , Nokata Makoto , Ishii Hideki
Published: November 2021

In this paper, the first danger-evaluation method for use in various kinds of control strategies for human-care robots is proposed. In the case of a careless collision between a robot and a human, impact force and impact stress are chosen as evaluation values, and a danger index is defined to quantitatively evaluate the effectiveness of each safety strategy used for control. As in the previous paper on safety design, this proposed method allows us to assess the contribution of each safety control strategy to the overall safety performance of a human-care robot. In addition, a new type of robot simulation system for danger-evaluation is constructed on a workstation. The system simplifies the evaluation of danger in both the design and control of human-care robots to quantify the effectiveness of various safety strategies. Here we describe the results obtained, the successful optimization of a safety control strategy for human-care robots.
Development and Testing of a Telemanipulation System With Arm and Hand Motion
Authors: Turner Michael L. , Findley Ryan P. , Griffin Weston B. , Cutkosky Mark R. , Gomez Daniel H.
Published: November 2021

This paper describes the development of a system for dexterous telemanipulation and presents the results of tests involving simple manipulation tasks. The user wears an instrumented glove augmented with an arm-grounded haptic feedback apparatus. A linkage attached to the user’s wrist measures gross motions of the arm. The movements of the user are transferred to a two fingered dexterous robot hand mounted on the end of a 4-DOF industrial robot arm. Forces measured at the robot fingers can be transmitted back to the user via the haptic feedback apparatus. The results obtained in block-stacking and object-rolling experiments indicate that the addition of force feedback to the user did not improve the speed of task execution. In fact, in some cases the presence of incomplete force information is detrimental to performance speed compared to no force information. There are indications that the presence of force feedback did aid in task learning.
Haptic Interaction Within a Planar Environment
Authors: DiMaio S. P. , Salcudean S. E. , Sirouspour M. R.
Published: November 2021

A haptic simulation environment to simulate planar three-degree-of-freedom motion has been developed by the authors. The system consists of a novel parallel manipulandum and associated control, collision detection and dynamic simulation software running on a QNX PC. This paper describes haptic interface control and outlines the control systems that have been designed for the haptic rendering of virtual environments. Virtual environment design and implementation are also discussed. Using the haptic simulation environment that has been developed, a four-channel teleoperation architecture is shown to be an effective means to display a variety of simulated environments and is compared with a popular impedance-based approach.
Modeling Vehicles’ Offset Impacts Using Recurrent Artificial Neural Networks
Authors: Omar Tarek A. , Eskandarian Azim , Bedewi Nabih E.
Published: November 2021

In the last few years, the demand for general-purpose Finite Element (FE) vehicle models with fine mesh and small elements has increased the size of these models dramatically. The FE simulation of these models requires extensive CPU time, which makes the simulation cost an important issue to consider. The main objective of this research is to develop an accurate and computationally inexpensive method to predict a vehicle’s crash performance in the event of a collision. This becomes very important as the demand for performing several impact scenarios for each vehicle becomes excessive. This demand is driven by the desire to investigate different impact scenarios and to study the effect of the impact velocity, the offset-barrier ratio, and the impact angle on the dynamic behavior of the vehicle structure in crash events.

In the last decade, Artificial Neural Networks (ANN) emerged as a reliable tool for solving nonlinear problems in variety of applications. The most important feature in ANNs is its ability to infer the nonlinear characteristics of any complex system, even if the mathematical model of the system does not exist. This is an extremely important feature when dealing with highly nonlinear dynamic problems such as vehicles collision. In a previous research conducted by the authors, advanced ANNs were developed and trained to model vehicles frontal impacts. This paper extends the concept and technique in order to use ANNs in modeling vehicles offset-barrier impacts.

Special ANNs were developed, trained and tested through numerical examples for two different offset impact cases. The first case was 50% offset-barrier impact at five different impact velocities, while the second case was 35 mph frontal impact at five different offset-barrier ratios. Validated FE vehicle model was used to perform FE simulations for many different offset-barrier impacts. The crash profiles obtained from the FE simulations were used to train and test the developed ANNs. The results of these numerical examples indicated the ability of the ANNs to accurately capture the nonlinear dynamic characteristics of the vehicle structure for offset impacts. The trained networks could then be used to predict the crash profiles of any offset impact scenario within the training range.