bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavior of Aluminum and Plastic Bumpers Under Low and High Speed Vehicle Impacts
Authors: Alavandi Bhimaraddi , Saha Nripen
Published: January 2022

The most efficient crashworthiness design of a vehicle is achieved by maximizing the energy absorption and minimizing the weight of its structural components. In addition, fuel economy and environmental feasibility are best achieved by reducing the vehicle weight. In this pursuit, automotive engineers have been looking for low density materials to replace the traditional steel. Aluminum and plastic materials offer an excellent opportunity towards this goal. It is well known that material behavior of aluminum and plastic is much different than steel. They are less ductile and have limited plastic flow during deformation. Thus, their failure modes are different. Also, during crash, structures exhibit material and geometric nonlinear behavior. To simulate a high or a low speed impact, one needs to have a good understanding of the material behavior. This requires the mathematical characterization of the materials under consideration. There are several material models available in commercial finite element codes such as RADIOSS, DYNA3D and PAMCRASH (normally used in crash simulation). In this paper various material laws available in RADIOSS are used and compared in the context of aluminum and plastic bumpers. Full vehicle rear impact and the low speed bumper impact cases will be examined to illustrate the differences in various material models. Also, the influence of these models on the failure mode, energy absorption characteristics, and contact interface forces will be discussed.
An Innovative Approach to Improve Energy Absorption in Polymeric Composite Tubes
Authors: Abdel-Haq Mahmoud M. , Newaz Golam M.
Published: January 2022

Results are discussed on the methods to improve the crushing performance and energy absorption of unidirectional polymeric circular composite tubes. The proposed methods included using external constraints to provide hoop constraints and initiator with appropriate radii. The approaches were applied to control the crushing process by controlling the major failure modes in such a way that leads to better crushing performance of polymeric composite tubes. The major failure modes of interest were the axial cracks, delamination and the major transverse cracks. The experimental results for polyester glassfiber reinforced tubes showed that it is possible to reduce significantly the initial peak load, improve the sustained load and eliminate the transverse cracks by using an external constraint. In addition, by using initiators instead of flat platens, it was possible to ensure the splaying failure mode for the crushing process.
A 3D Nonplanar Fracture Model for Life Prediction
Authors: Forth Scott C. , Keat William D.
Published: January 2022

A new fracture analysis tool for simulation of 3D nonplanar growth has been developed by combining a surface integral representation of an arbitrarily shaped nonplanar crack with a finite element model of the uncracked domain. The formulations are coupled through the need to satisfy boundary conditions at the interface of the two models where numerical strategies have been adopted which have effectively decoupled the meshing requirements. As a result, a surface integral model of a crack can be superimposed onto a localized region of a complicated finite element mesh, without impacting design requirements. The crack is then grown automatically through the fixed finite element mesh, using a crack mesher that can sense changing contours and interfaces. This paper focuses on the utilization of this technology to predict fatigue life of real parts.
Life Extension of an X-Ray Tube Target
Authors: Minas Constantinos , Vermilyea Mark E.
Published: January 2022

A methodology for the life extension of an X-Ray target was developed. X-Ray tube targets are rotating axisymmetric multi-component components used in X-Ray tubes of medical equipment. An X-Ray target is subjected to extreme cyclic thermal loading conditions based on the imaging system requirements. A very complex, time dependent stress state is present in such targets because of the combination of processing and utilization. Residual stresses are present following initial target assembly and heat treatment required to establish and maintain the high vacuum required in the X-Ray tube. In addition, cyclic stresses arise from the imaging protocols. The factors controlling these stresses include the thermal expansion coefficients of the various materials, the temperature distributions and the geometry of the components. The proposed methodology for the life extension of an X-Ray target included the development of an integrated thermal and structural axisymmetric finite element model. The combined thermal structural model was initially used to evaluate the severity of the various thermal protocols a target is subjected to. The structural analysis was carried out in the plastic regime, since typical stresses exceeded the yield stress of the materials used. Design of experiment (DOE) studies were carried out in order to evaluate the influence of geometric quantities on the resultant temperature distribution and thermal stresses. Tolerances of geometric quantities were applied to reflect manufacturing inaccuracies. An optimal design was selected for which the equivalent plastic strains were minimized. The effect of the manufacturing tolerances on the optimal solution was also examined.
On the Role of Damage Mechanics in Life Prediction of Composite Structures
Authors: Talreja Ramesh
Published: January 2022

Life prediction of composite structures is still heavy in empiricism. In order to reduce the burden of extensive data generation and proof testing, and to thereby reduce cost, resort must be made to predictive, physically based models. A field with this as a central objective, and with the capability to merge elements of materials science and mechanics, is damage mechanics. This paper will address how specifically damage mechanics may be able to render life prediction methodologies a scientific basis.

First, we shall discuss the essential, sequential and interactive elements of a life prediction methodology relevant to composite structures, identifying the role of damage mechanics in such a scheme. We shall then outline a philosophy (conceptual structure) of an approach to life prediction. A simple scenario will then be treated to illustrate the ideas involved.

Finally, the multiple ways by which damage mechanics can be implemented will be discussed. The limitations inherent in isolationist (pure) forms of damage mechanics will be discussed, laying bare the need for synergistic approaches. One such approach, and the progress made in achieving it, will then be described. The references cited below report related work by this author and his associates.
Nonlinear Behavior of Sandwich Panels With a Transversely Flexible Core: High-Order Theory Approach
Authors: Sokolinsky V. , Frostig Y.
Published: January 2022

Nonlinear behavior of sandwich panels with a transversely flexible core is presented. The panel construction is general and consists of two face sheets metallic or composite laminated symmetric, and a “soft” core made of foam or a low strength honeycomb. The study is based on a high-order nonlinear formulation that includes the influence of the transverse flexibility and shear resistance of the core on the panel behavior, so allowing for interaction between the faces through the core thickness. The solutions obtained are general and are not based on separation of the nonlinear response on the local and global modes as commonly used in the literature on sandwich structures. The governing equations along with the appropriate boundary and continuity conditions are presented and the solution approach is outlined. The formulation is of a mixed form causing the classical solution methods used in the nonlinear structural analysis to be abandoned in favor of the more general techniques. The path-following algorithm devised is based on the natural parameter as well as the arclength continuation techniques. The quasi-Newton framework with line searches is used to solve both the nonlinear equilibrium equations and the bordered equations arising in the case of applying the arclength method. The capabilities of the formulation are demonstrated for various cases including action of a concentrated load at the mid span of the panel, loading of the panel by end couples, and compression of an unsymmetric sandwich panel by longitudinal forces. It is shown that the transverse flexibility of the core is responsible for the interaction between global and local deformation modes. Comparison with linearized buckling results is presented and conclusions are drawn.
Aerospace Composite Structures: Applications/Design/Analysis
Authors: Chamis Christos C.
Published: January 2022

Fiber composites are an emerging material with tailoring potential to achieve substantially “better-cheaper-faster” and even “greener” products. The lecture provides an overview on the advantages of composites design/analysis methods and applications. The review will synoptically cover analysis methods that span all composites scales from constituents (fiber, matrix) and fabrication process to structural optimization. Several typical composites applications to aerospace structures are presented to demonstrate specific advantages of composites in these structures. Recent application to space station, advanced satellites and X-33 are included as are potential applications of smart composite structural concepts for aerospace applications. Emerging simulation methods to evaluate the reliability and risk of aerospace composite structures are summarized. The presentation provides a broad perspective of what can be done with composites and the state of the composites technology readiness to meet even greater application challenges in aerospace structures.
Building Block Approach for Composite Aircraft Structure Prototypes: Allowables and Building Block Testing for DOD/NASA Vehicles
Authors: Grimes Glenn C.
Published: January 2022

Composite material allowables development required for prototype aircraft is discussed along with the related building block test effort necessary for such structure development. Allowables requirements are included as part of building block structural test requirements that are related to aircraft structure part criticality classifications. Then, each part of the building block is related to the test/evaluation/analysis categories that need to be interrogated to study the risk involved. For allowables, the categories are preliminary and “design-to” values related to physical defect minimum requirements in each classification. For the building block structures development test effort categories, the procedure used is progressive scale up of the size and complexity of the test program parts: from single to multiple load paths to joints and shapes. In summary, the relationship of the quality assurance requirements to those required for design allowables for flat panels to those required for intermediate structural components to those required for full size structure are discussed. Quality assurance requirement categories are discussed for each structural classification, size, and complexity of parts to be built. The building block structures test development effort satisfies the goals of:

1. Preliminary and “design-to” material allowables development,

2. Appropriate conceptual structural development,

3. Structural proof of concept and related analytical methods development,

4. Structural verification testing for analytical methods correlation, and

5. Structural integrity testing and FEM validations.

Once these goals are achieved the user has acceptable risk and cost effective prototype composite aircraft structure that has the necessary integrity and reliability needed for the specific prototype aircraft being developed.
Design Approaches for Optical Structures in Space Communication Systems
Authors: Kedward Keith T.
Published: January 2022

In a wide variety of space communication systems advanced composites applications have favorably impacted the performance of optical surfaces and structures. However, there is presently a thrust to advance the state-of-the-art of primary mirrors assemblies for diffraction-limited, visible systems. Such mirror assemblies typically provide areal densities (the index used to convey weight efficiency) ranging from 25 to 30 kg/m2. But composite reflectors have also established their effectiveness by achieving areal densities as low as a few kg/m2 in recent years. As a consequence, opportunities and incentives that embrace composite technology advancements with concomitant benefits to optical performance (enabled by the proven thermal stability advantages) have drawn the attention of the space optics community.

In this paper the feasibility of isogrid concepts being used currently for lightweight, precision membrane reflectors is presented and evaluated with respect to future exploitation in the higher precision, mirror applications. We begin with a review of one form of isogrid concept in which the backup structure is comprised of interlocking continuous ribs in the isogrid configuration. Consideration with respect to fiber, matrix, and laminate configuration are presented in the body of the paper. Further, critical design detail treatment is presented with respect to intersections in the backup structure and the attachment of backup structure to the reflector face sheet.

Results of a thermal distortion analysis also serve to emphasize the importance of attention to detail in composite design due to the high degree of anisotropy in stiffness, strength and thermal expansion properties. Finally, the translation of the surface precision from that of the original mold surface to the as-fabricated reflector surface as well as to environmental influences will be addressed.
A Method for Structural Life Predictions Using Time-Domain Non-Linear Dynamic Load Computations
Authors: Lin Woei-Min , Engle Allen , Hay William , Meinhold Michael J.
Published: January 2022

Current surface ship structural design criteria is based on the use of a standard wave for determining primary stresses. Although this approach has worked well, such methods do not explicitly account for the effects of transient hydrodynamic impacts, fatigue or their effects on longitudinal distribution other than by empirical “rules of thumb”.

With the advent of novel ship design concepts, the naval architect has been forced to move away from a static balance approach to more rigorous methods of analysis. This paper presents a procedure for structural life predictions using the results of recent efforts to develop a practical computational method that predicts non-linear time-domain hydrodynamic loads and whipping responses of ship in waves. The time series wave loads and whipping data are used to develop the database and loads spectrum required for structural analysis. The results of this analysis used in conjunction with the spectral methods developed by Sikora, provides the naval architect with predictions for a lifetime maximum combined wave plus whipping bending moment as well as a load exceedence curve that can be used in fatigue analysis.
An Approach to Flexible Modes Identification and Control
Authors: Becraft Marc D.
Published: January 2022

An approach is given for flexible mode identification and robust control. It was successfully implemented and tested in a lab experiment that consists of a simply supported aluminum plate with four piezo-electric actuators and four piezo-electric sensors. The approach is based on measuring mode shapes and using a frequency weighted LQR controller that permits reduced order plant modeling. Lab tests show the first four modes were reduced significantly. The discussion includes derivation of the equations for the model identification scheme. A detailed description is given of the LQR frequency weighting and plant augmentation technique. A fourth order roll-off of control authority was used to gain-stabilize high frequency unmodeled dynamics. The observer uses only mode shape information but no modal frequency information. This provides the controller with robustness to modal frequency changes. Robustness is shown to changes in modal frequency (+/−10%), as well as modal gain and damping.
Vibration Control of Rotationally Periodic Structures Using Passive Piezoelectric Shunt Networks and Active Tuning
Authors: Tang J. , Wang K. W.
Published: January 2022

This paper is on the development of a novel approach for multi-mode vibration suppression of rotationally periodic structures, using identical active-passive hybrid piezoelectric networks on each of the substructures. Active charge and current feedback is used together with passive piezoelectric shunts to optimize the network performance. A new algorithm is synthesized to analytically derive the control parameters through utilizing the unique characteristics of rotationally periodic structures. It is shown that this hybrid approach can suppress all the spatial harmonics, which cannot be achieved by purely passive piezoelectric shunts. It is also observed that such a configuration requires much less control effort (voltage) when compared to a purely active approach.
Hydraulic Single Axis Vehicle Motion Simulator: Hardware and High Fidelity Control Design
Authors: Kuehn Jeffrey L. , Harris Derrick R. , Epp David S. , Patten William N.
Published: January 2022

This paper describes the design of a single degree-of-freedom hydraulic seat simulator. The hardware design includes various provisions to reduce static friction, backlash, etc. The paper also describes the painstaking task of plant identification and the subsequent effort to conceive a control that has near-perfect tracking characteristics. Experimental results are provided which indicate the simulator has flat amplitude and no more than 15 degrees of phase distortion over the range from 0.5 to 50 Hz.
Feedforward/Feedback Active Control With Automotive Applications
Authors: Shoureshi Rahmat A. , Vance James
Published: January 2022

Desire for increased ride comfort through elimination of fatigue caused by low frequency noise and vibration on one hand, and the market demand for smaller and lighter vehicles with enhanced fuel economy without sacrificing safety and comfort on the other hand have forced automotive manufacturers to search for advanced technology in the noise and vibrations areas. This paper presents results of a unique active vibro-acoustic system that handles both random and repetitive excitations. The combined pseudo-feedforward feedback control technology as well as actuator designs capable of performing at low and high frequencies have provided the key elements for our unique active control system. Experimental results demonstrating successful implementation of the active vibro-acoustic technology on different vehicles are presented.
A Study on Predictive Control Using a Short-Term Prediction Method Based on Chaos Theory: Determination of the Control Force Using Plural Predicted Disturbances
Authors: Masumoto Noriyasu , Yamakawa Hiroshi
Published: January 2022

The main objective of the work is to determine the applications of the short-term prediction method, based on chaos theory, to active vibration control problems for mechanical structural systems. In this paper, disturbance time series of a mechanical system’s near future were predicted by the short-term prediction method and the obtained time series were used effectively to determine the control force. A method to extend the prediction range in the time series has been proposed and two methods to determine the control force, using plural predicted disturbance values of a mechanical system’s near future, have been outlined. A method to determine the number of predicted values which should be used in prediction is also proposed. The effectiveness of the proposed control methods has also been presented from the numerical results of an active suspension model for vehicles with two degrees of freedom.
Electro-Hydrodynamic Pumped Hydraulic Actuation
Authors: Kang S. , Hallinan K. P. , Kashani R.
Published: January 2022

A new type of actuation device has been conceptualized that meets the needs of both large displacement, force and bandwidth within a package more compact than currently available magnetostrictive and stack-type piezo actuators of similar rating. This concept relies on micro-scale electrohydrodynamic (EHD) pumping of a dielectric liquid with a small concentration of free charges. Configured as an actuator, the EHD pump(s) would be used to move fluid between two reservoirs — each having a compliant membrane that interfaces to the world to provide the means to achieve vibration cancellation or micro actuation.

Ordinarily limited to generating flow in macroscale applications, the EHD pump is shown to exhibit an exciting scaling law as its size is reduced. As the pump volume to surface area decreases, the energy going toward increasing pressure in the pump has an increasingly larger effect. Since volume/surface area is proportional to 1/a2, where a is the characteristic width or diameter of the pump, the pressure head generated scales similarly. Analytical and numerical studies have shown the EHD-pumped actuator to be capable of delivering equal force and bandwidth to magnetostrictive and stack-type piezo actuators, but with consdierably greater displacement and roughly 1/10th of the size. Further, this type of actuator offers the possibility for deployment in active vibration control or micro actuation applications at significantly greater temperatures.
Refined Micro Moire System and its Applications to Chip Scale and Flip-Chip Packages
Authors: Zou Daqing , He Xiaoyuan , Lu Minfu , Liu Sheng , Guo Yifan
Published: January 2022

The chip scale package (CSP) and flip-chip (FC) technologies are currently developed by electronic industry for high performance, high density and miniaturized assembly applications. The reliability of these packages continues to be a major concern due to the increase of die size, circuit density, and operating temperature.

Moiré interferometry is a full field optical method, which can be used for the thermal mechanical deformation measurement of electronic packages and packaging materials. By using ordinary moiré interferometry, fringes represent displacement contour of 417 nm. In most cases, in a solder bump of CSP and FC packages, the thermal mechanical deformation is usually only 2 or 3 fringes (with relative displacement of about 1.2 μm), but the local strain of the bump is high because of the small size of the bump. It is difficult to resolve the local strain value for ordinary moiré interferometry, which can only resolve strain values averaged over a relative larger area.

Based on high magnification and phase shifting method, refined micro moiré interferometer is expected to have a localized sensitivity and resolution for localized strain measurements.

By using high precision close-loop controller for phase shifting in the refined moiré system, excellent results were obtained in the thermal mechanical deformation study of CSP samples and in the study of the solder bump mis-registration effect of FC samples. The results also showed that refined micro moiré method is effective in resolving deformation within a small area like a corner of a C4 bump.
Analysis of Electromigration Considering Thomson Effect
Authors: Sasagawa Kazuhiko , Yagi Manabu , Saka Masumi , Abé Hiroyuki
Published: January 2022

A parameter dominating electromigration damage, AFD, has been recently proposed. On the other hand, it has been shown that the Thomson effect which is a kind of thermoelectric effect is not negligible for the temperature distribution in the metal line which is subjected to high current density. The effect of the temperature distribution considering the Thomson effect on the void formation induced by electromigration has not been investigated so far. In this study, the temperature distribution in an angled metal line was analyzed considering the Thomson effect, and the void formation near the corner was predicted by obtaining the value of AFD based on the temperature analysis in order to extract the effect of the Thomson effect on the void formation. The Cu line, which was expected as a next line material in near future, was treated in comparison with the Al line.
Warpage Measurement of Microelectronics Devices by Far Infrared Fizeau Interferometry
Authors: Verma K. , Han B.
Published: January 2022

Far infrared Fizeau interferometry is developed and it is proposed as a tool for warpage measurement of microelectronics devices. The method provides a whole-field map of surface topography. Its basic sensitivity is 5.3 μm per fringe contour and a higher sensitivity is achieved by employing the O/DFM method. The method is implemented by a compact apparatus using a computer controlled environmental chamber for real-time measurement. The method retains the simplicity of classical interferometry while providing a wide applicability to dielectric rough surfaces. Roughness tolerance is achieved by utilizing a far infrared light (λ = 10.6 μm). The detailed optical and mechanical configuration is described and selected applications are presented to demonstrate the applicability. The unique advantages of the method are discussed.
Preliminary in Process Stress Analysis of Flip Chip Assemblies During Thermal Cycling
Authors: Palaniappan Prema , Baldwin Daniel F.
Published: January 2022

Thermal cycling of flip chip assemblies is commonly used to establish the reliability of the package. These tests help identify potential reliability concerns in interconnect designs and processes. The CTE mismatch between the various assembly members of a flip chip assembly produces mechanical stresses, which can lead to package failure. Hence, in this study, piezoresistive stress sensing ICs are utilized for experimental stress analysis of electronic packages. ATC4.1 test chips were assembled to low cost organic substrates. In-situ stress analysis of the test vehicle assemblies was performed to investigate the stress history during thermal cycling. The work performed here provides critical data necessary for validating reliability simulation models. Furthermore, in-situ stress measurements can have an immediate impact on reliability testing costs by potentially reducing current thermal cycle times via experimentally characterized die stress tests during temperature cycle.
Oscillatory Viscoelastic Flow in Rectangular Tubes
Authors: Letelier Mario F. , Siginer Dennis A.
Published: January 2022

The longitudinal flow of a Green-Rivlin fluid in rectangular ducts subject to a small pressure gradient is investigated. An exact solution of the momentum equation is developed. The velocity field is computed for several aspect ratios and for several values of the fluid parameters. The elasticity of the fluid is shown to create complex patterns of flow, as depicted by the instantaneous isovels of the flow. The flow patterns depend mainly on the viscosity index of the fluid, the aspect ratio of the tube and of the selected iinstant of time.

These results are useful for understanding both the intrinsic axial flow behavior, and related phenomena such as mass and heat transfer, and secondary flows in the case of fluids best described by constitutive models of the multiple-integral type.
Natural Convection and Thermocapillary Flow of Non-Newtonian Fluids in Layered Systems Heated From the Side in Reduced Gravity
Authors: Siginer Dennis A.
Published: January 2022

The dynamics of the flow in two layered systems heated from the side is investigated both when the fluids are viscoinelastic and viscoelastic. The system is two dimensional and confined to a box of low aspect ratio in reduced gravity. Interfaces are assumed to be flat. The free top surface is taken to be insulated together with the bottom wall. Results are reported for both high and low values of the interfacial Marangoni number when a low Prandtl number Newtonian fluid in the lower layer is encapsulated by a high Prandtl number viscoinelastic or viscoelastic fluid in the top layer.
Interfacial Velocity in the Core-Annular Flow in a Tube
Authors: Bakhtiyarov Sayavur I. , Siginer Dennis A.
Published: January 2022

The lubrication of a non-Newtonian liquid by a Newtonian fluid in the concentrically stratified laminar flow of two immiscible fluids in a horizontal tube has been investigated experimentally by an opto-mechanical method. Data for the interfacial velocity and the total volume flow rate for two zero shear rate viscosity ratio are presented. The results of this investigation are useful in solving high wax content crude oil transportation problems and in the design of lubricated pipelines.
Dynamic Wetting: Displacement of the Triple Line Induced by Air Pressure Oscillations in its Close Vicinity
Authors: Bourgin Patrick , Woehl Pierre
Published: January 2022

The problem of a liquid sheet issuing from an ejector and being coated on a moving solid substrate is classically considered like a free surface flow problem. The viscosity of ambient air is neglected compared with that of the liquid, which equivalently means that the surrounding air is considered to be steady. However, the free surface is affected by the presence of air flows underneath the sheet and by the increase of pressure, which deforms the interface and tends to separate the liquid sheet from the solid substrate. This is a coupled problem, the two unknown functions being the meniscus shape and the pressure generated in the air wedge.

A simple model is proposed here to investigate the possible influence of slight pressure fluctuations in the air on the displacement of the triple line. This model incorporates the liquid wetting properties as well as parameters characteristic of the process and of air pressure oscillations.
Flow Patterns of Viscoelastic Fluids in a Planar Contraction Obtained With a Finite-Volume Simulation
Authors: Oliveira Paulo J. , Pinho Fernando T.
Published: January 2022

A new general finite-volume method based on an efficient collocated mesh arrangement, with the added advantage of indirect addressing, has been applied to predict the flow of UCM fluids in a 4:1 sudden planar contraction. First and second order differencing schemes were used, and the Deborah number ranged from 0 to 10 for a Reynolds number of 0.01.

The predicted flow patterns showed all the flow features seen in flow visualisation and in recent numerical simulations of contraction flows, namely the corner Moffat vortex, the lip vortex, the fingering and merging of the two vortex types and single vortex growth with Deborah number. The presence of a lip vortex is detected at a Deborah number of 2 and the observations of those flow features requires very fine meshes in the vicinity of the contraction plane.
Dynamic Effects of Air Entrainment in High Velocity Coating Flows
Authors: Bourgin Patrick , Saintlos Sylvie
Published: January 2022

The problem of a liquid sheet issuing from an ejector and being coated on a moving solid substrate (generally flexible such as for instance paper or plastic film) is considered here. Such a situation resorts of dynamic wetting and the classical free surface boundary conditions at the air/liquid interface are applied. The ambient air viscosity is classically neglected in comparison with that of the liquid, which corresponds to consider the surrounding air as steady.

However, it is well known that one of the limiting factors in high velocity coaling flows is the onset of air entrainment into the wedge between the moving solid substrate and the liquid layer. The mechanics of air entrainment of the dynamic wetting line has been studied.
Dynamics of Free Surface and Pure Elongational Flows of Liquid Crystalline Polymers
Authors: Wang Qi , Forest M. Gregory , Zhou Hong
Published: January 2022

The performance properties of many polymers are dominated by the molecular alignment induced during processing by the elongational flow component, that is, the diagonal component of the velocity gradient tensor. Here we discuss two idealizations of this flow-microstructure interaction. We first summarize our recent studies of biaxial nematic patterns and phase transitions (Forest and Wang, 1998a) of lyotropic liquid crystalline polymers (LCPs) in response to imposed elongational flows. We show axisymmetric biaxial nematic patterns coexist with homogeneous biaxial patterns characterized by Rey (Rey, 1995). All biaxial patterns in unidirectional stretching flows are unstable, whereas planar stretching induces candidate stable biaxial nematic patterns. Non-homogeneous biaxial patterns have potential core defects, and two special director alignments are selected by imposing a finite-pressure condition along the axis of flow symmetry. The role of director dynamics in response to flow perturbations is described, and in particular new, elongation-induced, director instabilities are revealed, extending seminal stability and phase transition results (Khokhlov and Semenov, 1982; See et al., 1992; Bhave et al, 1993; Rey, 1995; Hu and Ryskin, 1992). We then examine two special solution families of the governing equations for free surface, axisymmetric, cylindrical LCP fiber flows, following analogous Newtonian results of Segur et al. (Segur et al., 1997). The cylindrical free surface only accommodates uniaxial orientation, and from these ideal transient solutions we analyze the linearized stability of the coupled flow and microstructure in the LCP thin-filament approximation (Forest et al, 1997).
Rheology of Discontinuous Fiber Arrays in Elongation
Authors: Creasy T. S. , Advani S. G.
Published: January 2022

This paper presents a two-fluid shear cell model that may apply to the long-discontinuous-fiber melt system made from AS4 carbon/poly-ether-ketone-ketone. As a 370°C melt at rest, PEKK forms a thermotropic liquid crystal structure. An LDFMS extended in the direction of the fibers generates a magnified local shearing strain rate through relative fiber motion. The boundary between the LCP and isotropic fluids could be a function of the fiber volume fraction, the generated shear strain rate, and the nucleation strength of the fiber surface. The two-cell model shows some of the consequences of generating a two fluid system within the LDFMS. The experimental data in this paper demonstrate the LCP character of PEKK and the nucleation effects of the AS4 fibers.
A Fully Non-Linear Theory of Electro-Magneto-Hydrodynamics
Authors: Ko Hyung-Jong , Dulikravich George S.
Published: January 2022

A number of analytical models exist for both electro-hydrodynamics (EHD), the study of fluid flows containing electric charges under the influence of an electric field and negligible magnetic field, and magneto-hydrodynamics (MHD), the study of fluid flows containing no free electric charges that are under the influence of a magnetic field and no electric field. At the present, there are no practical yet consistent models for the combined electro-magneto-hydrodynamic (EMHD) effects which most often occur in actual situations. This work represents an attempt to develop such a fully consistent analytical model for multi-dimensional, steady and unsteady, compressible and incompressible flows of electrically conducting fluids under the simultaneous or separate influence of externally applied and internally generated steady or unsteady electric and magnetic fields. The approach is based on the fundamental laws of continuum mechanics and thermodynamics with all assumptions clearly stated and consistently applied. The resulting second order EMHD model allows for non-linear polarization and magnetization of the medium. The new model is therefore superior to the existing EMHD models and represents a tractable set of equations suitable for detailed numerical discretization and integration.
Model Recognition and Simulation of an E/H Steering Controller on Off-Road Equipment
Authors: Wu D. , Zhang Q. , Reid J. F. , Qiu H. , Benson E. R.
Published: January 2022

An automated E/H steering controller is essential for autonomous off-road equipment. This paper presents a methodology for designing the E/H steering controller through a combination of testing and simulation. The steering kinematic model provides the steering linkage gain between the hydraulic actuator and the front wheel. The model makes it possible to close the steering control loop based on the signal of the hydraulic steering actuator rather than the front wheel. Test results were used to identify the non-linear and dynamic characteristics of the original E/H steering system. A Matlab model of E/H steering controller was developed based on the experimental test results.
Life-Cycle Assessment of Oil ‘Hydraulic’ Systems for Environmentally-Sensitive Applications
Authors: Burrows Clifford R. , Hammond Geoffrey P. , McManus Marcelle C.
Published: January 2022

Life-cycle assessment (LCA) techniques have been used in order to evaluate the environmental impact of conventional oil ‘hydraulic’ systems in an ecologically-sensitive application; that of mobile forestry machinery typical of modem European design. A single-grip ‘harvester’ employed for logging and a ‘forwarder’ that subsequently transports the felled and cut-to-length timber out of the forest are analysed. The results of this indicative LCA provide insights into the relative magnitude of the complex range of environmental impacts arising from fluid power systems and their parent vehicles in the forestry context. It also suggests areas for future research, principally on the impact of diesel fuel and hydraulic oil (including their additives) on the forest ecosystem, on the balance between local, regional and global environmental effects, and on the developing methods of LCA itself.
Investigation of the Effects of Swashplate Angle and Suction Timing on the Noise Generation Potential of an Axial Piston Pump
Authors: Wicke Volker , Edge Kevin A. , Vaughan Nicholas D.
Published: January 2022

The paper presents theoretical work carried out with the simulation program Bathfp. Models simulating the dynamic behaviour of axial piston pumps have been extended to investigate piston forces for different valve plate timings and for different swashplate angles. These forces have then been used to calculate the mean and fluctuating components of the moment functions. Since the forces and moments together are the most important inputs causing structure borne noise, the influence of the swashplate angle on the structure borne noise could be investigated. The influence of the suction port timing on both structure borne and fluid borne noise potential is also discussed.
Nonlinear Adaptive Learning for Electrohydraulic Control Systems
Authors: Zheng Danian , Havlicsek Heather , Alleyne Andrew
Published: January 2022

This investigation presents the application of an existing adaptive learning rule to the position control of a hydraulic cylinder driven by an electrohydraulic proportional valve. The system is representative of many types of Manufacturing applications including Injection Molding, Metal Forming and Industrial Presses which perform the same operation repeatedly for many cycles. The system contains several major nonlinearities that limit the ability of simple controllers in achieving satisfactory performance. These nonlinearities include: valve deadzones, valve flow saturation, and cylinder seal friction. Furthermore there is a significant compliance in the system due to the hose length between the valve and the cylinder. The learning algorithm iteratively determines an appropriate feedforward signal to be used in conjunction with simple feedback in order to track a predetermined reference signal. The algorithm is presented along with simulation and experimental results.
A Study of Pneumatic Pipes Modeling
Authors: Bideaux E. , Scavarda S.
Published: January 2022

In fluid power systems, lines or pipes can have a predominant effect on dynamics. Although many studies have been carried out on hydraulic pipe modeling, there are only a few existing approaches for such problems in pneumatics. This paper proposes a basic work for modeling of pneumatic pipes. After presenting the state of the art situation and the nature of this problem, we have proposed two ways of modeling pneumatic pipes. The first one consists of a discretization scheme based on an upwind finite differencing scheme. This method has advantages but can lead to erroneous results in the case of a predominance of the convection effect when the direction of flow changes rapidly. We propose a method for solving such difficulties. We also propose a second method which is based on a finite volume approach. This type of model represents the convection effect better and we will prove its robustness through several examples. Before concluding, in order to validate our propositions, we compare experimental trails to the results given by the simulation of the two methods.
Stochastic Turbulent Fields for Acoustic Numerical Simulations
Authors: Bailly Christophe , Blanc-Benon Philippe
Published: January 2022

The goal of this paper is to show that stochastic turbulent fields can be used in acoustic numerical simulations when only some statistical properties of turbulence are required. The turbulent field is achieved by synthesizing a collection of Random Fourier Modes (RFM) at each point in space. An extension of the RFM method to include a time evolution and spatial inhomogeneous statistics is suggested. Then two applications of the RFM are given for acoustic numerical simulations. The first deals with the atmospheric sound propagation through turbulence over large distances. The second one concerns generation and radiation of noise for subsonic flow at high Reynolds number.
The Influence of Leading Edge Separation on the Unsteady Response of a Thin Airfoil
Authors: Lynch Denis A. , Minniti Robert J. , Mueller Thomas J.
Published: January 2022

An experimental investigation of the influence of a leading edge separation region on the unsteady aerodynamic problem for thin, symmetric airfoils exposed to periodic gusting was performed in a subsonic indraft wind tunnel. Two leading edge shapes for the airfoil were used to examine the influence of flow separation both in the unsteady velocity and pressure fields. It is shown that flow separation near the leading edge causes a sharp increase in the unsteady RMS velocity and unsteady surface pressure variation associated with the gust frequency. This also causes a departure from the expectation that the gust information is convected downstream by the freestream in the velocity field. In the absence of such a separation region, velocity and surface pressure results closely resemble inviscid theoretical predictions and expectations. Accurate prediction of unsteady pressure is crucial in estimating the acoustic production of the system.
Anechoic Box Method for Measurement of Industrial Sound
Authors: Huang Xiubao , Balligand Hélène
Published: January 2022

A new method is described to measure the free field sound pressure level in a non-anechoic test laboratory for industrial equipment. The method, called anechoic box method, uses a small anechoic box to house the microphone, instead of using a conventional large semi anechoic room to house the large size machinery. A window opening on one wall of the box faces the sound source and all other walls (five sides) are closed. The noise source within the field of view of the microphone gives an equivalent free field sound pressure level in a non-anechoic industrial environment when the noise source is positioned exactly at the window. This method is also capable of isolating unwanted noise sources. Experimental results based on a 2000 Hz noise source demonstrate the effectiveness of isolation by field of view and show consistent results when field of view is changed systematically.
Low Velocity Impact Characterization of Neat Vinyl Ester 411-350 Resin System
Authors: Motuku M. , Janowski G. M. , Vaidya U. K. , Mahfuz H. , Jeelani S.
Published: January 2022

The room temperature impact response of DERAKANE 411-350 vinyl ester neat resin system (unreinforced matrix) has been investigated as a function of sample thickness and impact energy level. Vinyl ester resins are of interest in ballistic applications such as in armored vehicles. The response of neat resin to impact loading was investigated using the impact load histories (load-time and load-deflection traces), impact plots and fractography analysis. The maximum load or peak contact force, energy to maximum load, total energy and deflection at maximum load were found to increase in a nearly parabolic manner with increase in impact energy level, whereas time-to-maximum load or impact duration at the peak load decreased linearly. Total energy-to-impact energy ratio changed in a step-wise manner with impact energy. The slope of the load-deflection (load-time) traces, which is related to the impact modulus or relative stiffness of the material, increased with impact energy level and sample thickness. The change of slope with impact energy level and sample thickness indicated the dependence of impact modulus on the impact energy level and target geometry. The threshold impact energy levels, which were associated with the onset of catastrophic matrix failure and extensive tensile strength losses, were identified from the impact plots. Multiple radial cracking, perforations in the form of a truncated cone at the point of impact and support induced damage were identified as the dominant failure characteristics.
High Frequency Vibration Analysis Performed by a Statistical Energy Analysis Formulation and an Energy Finite Element Formulation
Authors: Vlahopoulos Nickolas , Garza-Rios Luis Octavio , Nelson Richard K.
Published: January 2022

The Energy Finite Element Analysis (EFEA) offers significant advantages in the areas of model generation, interpretation of results, and definition of design variables for parametric analyses, with respect to the established Statistical Energy Analysis (SEA). A theoretical overview and comparison of the two methods is presented first. A published marine application is analyzed, and comparison of the results offers an initial validation of the EFEA. Numerical models for a fishing boat are generated for both methods and utilized for further comparison between the two formulations. The applicability of the EFEA in the marine field is demonstrated and its benefits are discussed.
Parallel Computation of Harmonic Waves Using Domain Decomposition: Part 2 — Numerical Implementation and Applications
Authors: Susan-Resiga Romeo F. , Atassi Hafiz M.
Published: January 2022

A numerical implementation of the Domain Decomposition (DD) method for parallel computation of time-harmonic waves is presented. The Finite Element method on unstructured mesh is employed to discretize the boundary-value problem. A nonover-lapping mesh partitioning is used to build an overlapping domain decomposition. The algorithm also defines the new subdomain boundaries, other than the original boundaries of the global computational domain, on which transmission conditions are introduced. The independent subdomain problems can be solved concurrently, one problem per processor, on a parallel computer. The iterative scheme used to update the subdomain transmission conditions is computationally efficient and only swaps the nodal values in the overlapping region between adjacent subdomains. For exterior problems, the communication required to update the conditions on the outer boundary is substantially reduced by employing a modified Dirichlet-to-Neumann (DtN) map with truncated support. Numerical results are presented for a radiation model problem. It is shown that the DtN nonreflecting conditions eliminate spurious reflections and that the iterative scheme leads to a continuous global solution. The DD algorithm also has a very good convergence rate and significantly reduces memory requirement in comparison with a direct solver.