bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage Detection Using Experimental Data Based Methods
Authors: Lestari W. , Hanagud S.
Published: November 2021

The objective of this work is to develop a damage detection algorithm, which is based on experimentally identified data and a mathematical relation between the damage information and the changes in structural dynamic characteristics. The relation is derived in the form of a differential equation, which relate the damage information, natural frequency changes, and the modes of the undamaged and damaged structure. The curvature mode is chosen in this method due to its sensitivity to the presence of the damage and its localized information. The detection algorithm enables one to locate the damages and to obtain the corresponding magnitudes simultaneously. For illustration of the methods numerical simulation on damaged beams were conducted. The damages were considered as point damages. Numerical simulation results are presented.
Semi-Active Damping of Ground Resonance in Helicopters Using Magnetorheological Dampers
Authors: Wereley Norman M. , Costes Nicolas
Published: November 2021

We will assess the capabilities of physically motivated MR dampers to mitigate ground resonance instability and control the damping level of rotor lag modes. The objectives of this research are threefold: (1) develop a methodology for the integration of the MR damper into a classic linear ground resonance analysis assuming an isotropic rotor hub (all dampers and blades similar) and an anisotropic rotor hub (due to lag damper dissimilarity due to damage, for example), (2) assess whether MR dampers can stabilize a rotor system that exhibits unstable ground resonance, (3) assess whether MR dampers can stabilize a rotor which exhibits unstable ground resonance behavior due to lag damper degradation or damage. The analyses developed in this study show that MR dampers are feasible for achieving these goals.
Vibration Control of Laminated Composite Plates Using Magnetostrictive Layers
Authors: Reddy J. N. , Krishnan S.
Published: November 2021

In the present study, a theoretical formulation of laminated composite plates with integrated smart material layers, used as sensors and actuators for the vibration suppression of laminated composite plates, is presented. The third-order shear deformation theory of Reddy and a simple negative velocity feed back control are used to actively control the dynamic response of the plate. The Navier (analytical) solutions are derived for simply supported boundary conditions and a displacement finite element model is developed for a general plate. The effects of material properties, lamination scheme, and placement of the smart material layer on vibration suppression are investigated.
Active Control of Nonlinear Dynamics of Crane Loads
Authors: Li Y.-Y. , Balachandran B. , Krishna K. V.
Published: November 2021

In order to suppress crane-load oscillations on ship vessels, a novel mechanism called a mechanical filter was introduced recently. This system is further numerically studied in the present effort. With the aid of active control, it is illustrated as to how the suppression bandwidth can be tailored and bifurcations in the response of the crane load can be eliminated from the considered range of disturbance parameters. Suppression of crane-load oscillations in the presence of aperiodic ship-roll motions is also addressed.
Performance Enhancement of an Autoparametric Vibration Absorber Using Multiple Pendulums
Authors: Vyas Ashwin , Bajaj Anil K. , Raman Arvind
Published: November 2021

This paper analyzes the dynamics of a resonantly excited single degree-of-freedom linear system coupled to an array of nonlinear autoparametric vibration absorbers (pendulums). The case of a 1:1:…:2 internal resonance between pendulums and the primary oscillator is studied. The method of averaging is used to obtain first-order approximations to the nonlinear response of the system. The stability and bifurcations of the equilibria of the averaged equations are computed. It is shown that the frequency interval of the unstable single-mode response, or the absorber bandwidth, can be enlarged substantially compared to that of a single pendulum absorber by adjusting individually the internal mistunings of the pendulums. Use of multiple pendulums is also shown to engender degenerate bifurcations as the coupled-mode response “switches” from one pendulum to the other with changing external excitation frequency. This results in a significant enhancement of the performance of autoparametric vibration absorbers.
Input Preshaping With Robust Internal–Loop Compensator for Residual Vibration Suppression of a Beam–Mass–Cart System
Authors: Park S. , Kim B. K. , Chung W. K. , Youm Y.
Published: November 2021

In this paper, vibration suppression of an elastic beam fixed on a moving cart and carrying a concentrated or moving mass is considered. An input preshaping method with RIC (Robust Internal–loop Compensator) is proposed to suppress single mode residual vibration and to get accurate positioning of the beam–mass–cart system. The performance of the proposed input preshaping method is compared with that by previous ones by both numerical simulations and experiments.

Using the proposed method, accurate PTP positioning of the moving mass without residual vibration is obtained experimentally by modifying the proposed input preshaping method. It is also able to suppress initial vibration of the beam–mass–cart system carrying a concentrated mass. Finally, the proposed input preshaping method is applied to the system to follow square trajectories of the moving mass without residual vibration.
Control of Higher-Order Modes in Ducts Using Arrays of Herschel-Quincke Waveguides
Authors: Hallez Raphaël F. , Smith Jerome P. , Burdisso Ricardo A.
Published: November 2021

The Herschel-Quincke (HQ) tube concept is well known for attenuation of plane-wave noise in ducts. However the HQ-tubes system can also be effectively applied to more complex duct sound fields due to higher-order modes. In this paper, an analytical technique is developed to model and predict the effects of HQ waveguides in three-dimensional ducts in which higher-order modes exist. The analytical technique involves modeling the waveguide-duct interfaces as finite piston sources that couple the acoustic field inside the main duct with the acoustic field within the HQ waveguides. The analytical model is used to provide insight into the attenuation mechanisms of the HQ waveguide arrays. The effects of the configuration and number of the HQ waveguides on the performance of the system are investigated. The analytical results are also validated on the inlet of a turbofan engine experimentally. The results demonstrate the potential of the HQ tube concept to reduce noise in ducts in many industrial applications where higher-order modes exist.
Design of LQ and LC Optimal Controllers for Plate Vibration
Authors: Fariborzi Bora
Published: November 2021

The energy based control strategy “Linear Coupling Control (LCC)” (1) is used for controlling free and forced vibrations in a simply supported plate. The control strategy is implemented by coupling a virtual second order linear system (controller) to an oscillatory plant and creating an energy exchange between the two systems (2). The energy transfer phenomena from the plant to the controller is maximized by coupling the appropriate states. Once the transfer of energy has taken place it is dissipated via linear damping. To provide a basis for comparing the results of the proposed control algorithm and the conventional control methods, the linear quadratic optimal control method also was implemented. To investigate the performance of the control method, a laminated simply supported plate and the controller are numerically simulated. This paper focuses on design issues and numerical simulation.
A Comparison of Two Actuators for a Semi-Active Helmholtz Resonator
Authors: Birdsong Charles B. , Radcliffe Clark J.
Published: November 2021

Two electro-mechanical actuators are examined for a semi-active Helmholtz resonator acoustic device. The device is used to reflect narrow band noise back to the source in an acoustic duct. The controller and actuator are used to tune the system on-line allowing optimum performance over a range of operating conditions. Actuator dynamics play an important role in the controller design and the operation of the device. Two variations of an electro-mechanical actuator are considered here. The first uses a dual voice coil speaker with local feedback compensation and the second uses the same speaker without the compensation. It is shown that both arrangements are effective but with competing advantages. The compensated actuator provides more control authority but adds considerable background noise while the uncompensated actuator provides less control authority but adds no background noise. The choice of actuator depends on the noise control objectives of the particular application.
Simulation of Geometric Imperfections of Deformable Assemblies in CAD/CAM
Authors: Sellakh Réda , Riviere Alain , Sellem Eric
Published: November 2021

The dimensioning and tolerancing model presented in this paper allows the functional tolerancing of a class of mechanical parts to be performed. This model is based on the use of the TTRS concept and relative positioning constraints. In addition, the paper presents some improvements in the modelling of the assembly process and describes a sensitivity analysis approach to identify the key characteristics of the assembly.
Fixture Reusability and Reconfigurability Analysis Using Similarity Index
Authors: Smithson Arlene G. , Kong Zhenyu , Ceglarek Dariusz
Published: November 2021

Currently there is a lack of a formal method to utilize previous fixture information into the design of future product and production lines. The utilization of knowledge gained in the design of prior fixtures and the capability assessment of existing reconfigurable fixtures on the design of new product lines allow manufacturing system design for time and cost reductions. This paper presents the evaluation of a fixture design similarity index developed to assess the relevance of current fixtures design information for multi-model production (reconfigurability) or for future production lines design (reusability). The index developed decomposes N-2-1 fixture information into X, Y, and Z data with applicable constrains and part deflection requirements in the X, Y, and Z directions. This allows the evaluation and comparison of physical and performance attributes of any given fixture. An example demonstrating the methodology implementation to single fixture case analysis and conclusions are provided as part of the presentation.
On-Line Chatter Detection Using Wavelet-Based Parameter Estimation
Authors: Choi Taejun , Shin Yung C.
Published: November 2021

A new method for on-line chatter detection is presented. The proposed method characterizes the significant transition from high dimensional to low dimensional dynamics in the cutting process at the onset of chatter. Based on the likeness of the cutting process to the nearly-1/f process, this wavelet-based maximum likelihood (ML) estimation algorithm is applied for on-line chatter detection. The presented chatter detection index γ is independent of the cutting conditions and gives excellent detection accuracy and permissible computational efficiency, which makes it suitable for on-line implementation. The validity of the proposed method is demonstrated through the tests with extensive actual data obtained from turning and milling processes.
Smart Giant Magnetostriction Actuator With Self-Sensing and Thermal Compensation Capability
Authors: Yamamoto Yoshio , Makino Takaaki , Matsui Hiro
Published: November 2021

Recently giant magnetostriction materials have drawn a lot of attention because of their unique features which other materials, such as PZT, cannot provide. The features include outstanding magnetostriction, high energy density, high Curie temperature, and quick response. This paper presents two kinds of novel applications of giant magnetostriction materials: a compact fine positioner and a wire clamper. The former is able to achieve highly accurate positioning due to a novel structure design which substantially reduces the influence of Joule heat generated by the solenoid coil. The latter application is motivated by a great demand towards a wire-clamping device for semiconductor manufacturing, which is capable of maintaining a sufficient clamping force without fatigue.
Estimation of Crater Temperatures Using Infrared Camera
Authors: Kwon Patrick
Published: November 2021

A new technique is developed to estimate the average steady state chip-tool interface temperature during turning. An infrared (IR) video camera attached on the carriage of the lathe measures the transient cooling behavior on the rake surface of an insert after the feed motion is halted. This allows the zero heat flux boundary condition, where the transient Laplace heat conduction problem can be solved numerically to obtain the temporal and spatial temperature distribution. With the experimentally determined transient temperature distribution, the 1-D ellipsoidal model is used to estimate the average steady-state chip-tool interface temperature during machining. The results on turning Gray Cast Iron (GCI) and AISI 1045 steels with various coated and uncoated carbide inserts are presented.
Forming of Steels in Mushy States
Authors: Horský J. , Raudenský M. , Kotrbácek P. , Tseng Ampere A.
Published: November 2021

Semisolid or mushy-state processing permits a material to partially solidify before shape making operations. The understanding of material behavior in the mushy state is critical for better control of various semisolid processes. The aim of the present study is to experimentally quantify the deformation behaviours of steel in mushy states. Semisolid specimens under indentation and upsetting deformation were evaluated at various forming speeds and mushy states. The temperature of specimens was carefully controlled to correlate the solid phase content. It has been found that the deformation resistance of steel in a mushy state was dependent on the deformation rate and the solid phase percentage. The relaxation of steel and stress reduction at mushy states were also observed and discussed.
Superplasticity and Microstructural Evolution of a Large-Grained Mg Alloy
Authors: Liu Yi , Shue Kelly , Wu Xin , Li Zhicheng , Xu Yongbo
Published: November 2021

Commercial Mg-3Al-Zn alloys (AZ31) with initial large grains (∼250μm) has been found superplastic at a strain rate of 0.5×10−2s−1 and at 350–500 C. The maximum elongation to failure of 170% at 500°C was obtained. Scanning electron microscope observations with electron back-scattering diffraction technique (SEM-EBSD) indicate that during deformation significant grain size reduction occurred, the average grain size reduced from about 250μm before deformation to about 50μm after deformation at temperatures from 300 C to 400°C, it reduced to about 100μm if deformed at above 400°C. The observed grain refinement at lower temperature and grain growth at higher temperature during the superplastic deformation is believed to be the result of the competing processes between dynamic recrystallization and dynamic grain growth, which are temperature and strain rate dependent. Transmission electron microscope (TEM) observations indicates that most of the grain boundaries are large-angle grain boundaries, though small amount of small-angle grain boundaries are also observed. The density of dislocations in the grains is very low in these superplasticlly deformed samples. It is evident that grain boundary played a role as the source and sink of the dislocation, being responsible for combined dislocation creep and diffusional creel. Therefore, the very large elongation obtained at the very high strain rates and high temperatures is attributed to dynamic dislocation hardening, recovery and recrystallization.
Computer-Aided Design and Simulation of Direct Cold Extrusion Processes
Authors: Wang Karen L. , Argyropoulos Vasilis
Published: November 2021

This paper presents an approach on the design and simulation of direct cold extrusion processes for rapid tooling with the aid of process simulation technologies. The advantage of this approach is to find problems before a metal die prototype is made, and therefore reduces the time from die design to manufacturing. A direct cold drawing die has been designed using a design approach involving the results of analytical calculations from simplified mathematical models. This design is analyzed and modified using commercial process simulation software on digital computers in this paper. This paper presents the modeling techniques involved, the analysis procedure, presentation and evaluation of these results.
Integrated Quality System Oriented Product Life Cycle in CIMS Environment
Authors: Yuan Qing Ke , Chen Xin
Published: November 2021

Since the quality activities is through out the product whole life-cycle, the quality management should be a integrated quality system, facing the product life-cycle. In CIMS (Computer Integrated Manufacturing System), with the assistance of computer and its relative technologies, IQS (Integrated Quality System) can integrate the quality management technique cells into an organic whole, then the quality management will be more coherent and efficient. In this paper the concept, features, components and functions of IQS are been discussed and the key technologies are pointed out.
CAM Software Development for Laminated Tooling: Lamination Cutting Trajectory Algorithms
Authors: Im Yong-Tai , Walczyk Daniel F.
Published: November 2021

This paper addresses the research and development of a Computer-Aided Manufacturing (CAM) software package used for fabricating Profiled-Edge Lamination (PEL) tooling. Background research in PEL tooling is reviewed and possible applications for PEL tooling in seven different manufacturing processes are examined. The general PEL tooling process is outlined and the fundamental role that the CAM software plays in this process are discussed. The CAM software is used to create and simulate appropriate line-of-sight cutting trajectories for an Abrasive Water Jet (AWJ) cutting machine. Using this CAM software, PEL cutting trajectories and the resulting PEL tool shape can be compared with the original CAD tool shape. After the tool shape is evaluated, the CAM software exports CNC G-code to an AWJ cutting machine for cutting individual laminations. Four algorithms have been developed to create suitable cutting trajectories for PELs. Each algorithm is evaluated through simulation using the benchmark tool shape. As a result of this evaluation, one particular algorithm was found to be the most promising because it 1) successfully produces sharp edges with no loss of original shape, 2) allows unlimited tool orientation, and 3) better handles complicated tooling geometries. Finally, future work to validate the cutting trajectory algorithms is outlined.
Low Temperature Polymer Infiltration for Rapid Tooling
Authors: Kokkengada Monnappa , Zhou Jack G. , He Zongyan
Published: November 2021

The research presented in this paper is an effort toward developing a technique to produce injection mold inserts to handle small batch production of around a few thousand parts. Common infiltration methods used in rapid tooling have certain limitations viz., cracks, distortion and shrinkage caused by high temperature infiltration. Poor surface quality is also a limitation of conventional infiltration techniques. The high temperatures involved in conventional infiltration techniques make the process more expensive, complex and difficult to control. To overcome these difficulties, as well as to generate tooling for a small batch production, a low temperature polymer infiltration method is proposed in conjunction with existing rapid tooling techniques. Based on the curing principles of polymer materials, several infiltration materials were selected and their mechanical and chemical characteristics were investigated. To determine the necessary amount of polymer materials in the sintered mold an infiltration model is derived and results compared with experimental data. Testing results have shown significant improvements in the thermal resistance and mechanical properties of the rapid tool as a result of the resin infiltration.
Stamping Blank Optimal Layout and Coil Slitting Widths for Single and Dual Blanks
Authors: Nye T. J.
Published: November 2021

In stamping, operating costs are dominated by raw material costs, which can typically reach 75% of total costs in a stamping facility. In this paper, material utilization efficiency is modeled by considering two primary sources of scrap: material cut away from the exterior of each blank on the strip and off-cuts of unusable narrow strips generated when wide master coils are slit into strips for subsequent stamping. Based on these, layout optimization techniques for minimizing raw material usage are described that predict the optimal blank orientation on the strip and the optimum slitting width for the strip. In addition, methods are given for determining optimal common strip widths for multiple parts, both for dependent and independent demand. These algorithms are ideally suited for incorporation into die design CAE systems.
Failure Analysis of Tubular Hydroforming
Authors: Xia Z. C.
Published: November 2021

A mathematical analysis of failure developments for tubular hydroforming under combined internal pressure and end feeding is presented in this paper. Under considerations are two distinct failure modes, namely the bursting and the wrinkling. Bursting is an instability phenomenon where the tube can’t sustain any more tensile loading. Splitting usually follows due to extreme deformations in the bursting area. Wrinkling is due to high compression load, which deteriates the qulity of the final product. The deformation theory of plasticity is utilized in this study that takes into account of material anisotropy. The governing equations for the onset of both failure modes are established. The results are presented as Hydroforming Failure Diagram in the End Feed – Internal Pressure space. A parametric study of the failure criteria for a variety of materials and process parameters is performed. It is shown that the material anisotropy plays a significant role. The results provide guidelines for product designers and process engineers for the avoidance of failure during hydroforming. The validity and applicability of current study are also discussed.
Development of a Mini-LDH Test for Sheet Metal
Authors: Gerdeen James C.
Published: November 2021

The literature on formability and LDH (Limited Dome Height) testing is reviewed. The LDH tooling uses a 4.0 inch (100 mm) diameter punch, and various widths of specimens are used to give various strain ratios. The strains are then plotted on forming limit curves (FLD’s).

In this paper, the development of a new mini-LDH test for thin sheet metal is described. The test involves a new geometry of specimens and a fixture which can be mounted in any universal testing machine with a low enough force range. The size effect is studied by conducting LDH tests with smaller diameter punches: 2.0 inch (50.8 mm), 0.50 inch (12.7 mm), and 0.25 inch (6.35 mm) diameters. Experimental results are presented for 0.010 inch (0.254 mm) thick 1100-H19 aluminum, and 5182-H19 aluminum.

An analysis is also presented for the fully biaxial case and the plane strain case in order to model the experimental results.
Degradation of a Synthetic Forging Lubricant
Authors: Olson Walter W. , Natarajan Sreekumar , Abraham Martin A.
Published: November 2021

Synthetic forging fluids are marketed as environmentally friendly alternatives to water graphite emulsions. Since these fluids are generally dialkali metal salts of phthalic acids, a concern was the stability of the fluid under forging conditions. The objectives studied were how long does the fluid take to decompose, what are the products and what are the reactions that occur in the decomposition. The material chosen for study after review of patents of synthetic forging fluids was dipotassium orthophthalate which is stabilized by sodium silicate. The findings of the experimental work are that the fluid is quite stable under forging conditions and that the decomposition products are benzene and acetic acid. A proposed reaction from reactants to products has been proposed. The findings of benzene and acetic acid in the products challenges the claims for environmentally friendliness of this product.
Generic Simulation Approach for Multi-Axis Machining: Part II—Model Calibration and Feed Rate Scheduling
Authors: Bailey T. , Elbestawi M. A. , El-Wardany T. I. , Fitzpatrick P.
Published: November 2021

This is the second part of a two-part paper presenting a new methodology for analytically simulating multi axis machining of complex sculptured surfaces. The first section of this paper offers a detailed explanation of the model calibration procedure. A new methodology is presented for accurately determining the cutting force coefficients for multi-axis machining. The force model presented in Part I of this paper is reformulated so that the cutting force coefficients account for the effects of feed rate, cutting speed, and a complex cutting edge design. Experimental results are presented for the calibration procedure. Model verification tests were conducted with these cutting force coefficients. These tests demonstrate that the predicted forces are within 5% of experimentally measured forces. Simulated results are also shown for predicting dynamic cutting forces and static/dynamic tool deflection. The second section of the paper discusses how the modeling methodology can be applied for feed rate scheduling in an industrial application. A case study for process optimization of machining an airfoil-like surface is used for demonstration. Based on the predicted instantaneous chip load and/or a specified force constraint, feed rate scheduling is utilized to increase metal removal rate. The feed rate scheduling implementation results in a 30% reduction in machining time for the airfoil-like surface.
Hemodynamics, Vascular Biology, and Atherosclerosis
Authors: Nerem Robert M.
Published: November 2021

During the latter half of this century biomechanics has made an enormous impact on medicine and biology. This started with the recognition that many tissues within the human body reside in a mechanical environment, i.e. they are subjected to mechanical stresses. Initially the intent was to apply existing knowledge of mechanics to problems arising from medicine and biology. As with all of bioengineering, what has evolved, however, is a true integration of the biology with the mechanics. With this biomechanics has emerged as an important field of endeavor in our attempt to understand basic biological mechanisms, the physiology of the human body, and disease processes. It also has contributed to the development of new clinical treatment strategies and to improved medical devices and implants.
Controlled Porosity Ceramics for Bone Graft Applications
Authors: Bose S. , Darsell J. , Kintner R. , Feely K. , Hosick H. L. , Bandyopadhyay A.
Published: November 2021

Significant research has already been done for the development of bioceramic materials with controlled microstructures using inert, bioactive and bioresorbable ceramics. Microporous implants with controlled pore size in the range of 100-600 μm have proven to be osteoconductive. A minimum pore size of 100 μm is necessary for tissue in-growth and to provide blood supply to the connective tissues to keep them viable and healthy. Bone in-growth takes place within the inter-connected pore channels near the surface and maintains its vascularity and long term viability, and the implant serves as a structural bridge or scaffold for bone formation.

Controlled porosity ceramic scaffolds were fabricated using indirect fused deposition modeling (FDM), a commercially available rapid prototyping process, with alumina and tricalcium phosphate (TCP) ceramics. Pore size and pore volumes were varied by changing road width, road gap and slice thickness of the polymeric molds. Mechanical tests were conducted to understand the influence of porosity parameters on strength degradation. In vitro tests were carried out with human osteoblast (HOB) cells to understand the effects of porosity parameters on cell growth. The paper describes the effects of porosity on the biocompatibility and bio-mechanical properties of controlled porosity alumina and TCP scaffolds.
Morphology and Mechanical Properties of a Novel Family of Porous Polymer Based on UHMW Polyethylene for Biomedical Applications
Authors: Ananthanarayan Venkatesh T. , Shutov Fyodor
Published: November 2021

The objective of the research was to develop and study the properties of porous Ultra High Molecular Weight (UHMW) Polyethylene for biomedical applications. The process, based on the leaching technique does not require any modification in the processing equipment, is environmentally friendly and use raw materials approved by the FDA for in vivo medical applications. It is possible to produce porous polymers having predetermined pore size, pore shape and porosity using the leaching technique. The pores are interconnected and well distributed throughout the three dimensional volume of the sample. The size, shape and content of the porogen in the molding mixture greatly affect the physical properties of the pores in the final porous sample. Maximum porosity of 60% was obtained. The developed porous UHMW polyethylene, which is permeable for liquids, can be used as a substrate matrix in bone regeneration and in hip and knee joint replacements. The porous implants with adequate lubrication would prevent the formation of polymer debris due to friction and thereby increase the life of the biomedical implants. The new generation of porous polymers developed could be used in a wide range of applications.
Strain Rate Effect on Dynamic Compressive Failures in Off-Axis Glass-Epoxy Composites
Authors: Tsai Jialin , Sun C. T.
Published: November 2021

Dynamic compressive strength of off-axis S2/8552 glass-epoxy composite in the form of fiber microbuckling was studied. Based on the bifurcation buckling analysis, the microbuckling stress is approximately equal to the composite tangent shear modulus. Using a viscoplastic constitutive model to describe the composite tangent shear modulus, microbuckling stresses at various strain rates were predicted. Small angle off-axis composite specimens were tested to failure at various strain rates. For strain rates below 1/sec, the compression tests were conducted on an MTS machine, while higher strain rate tests were carried out using a Split Hopkinson Pressure Bar (SHPB). Fiber microbuckling was found to be the dominant failure mode for 5°, 10° and 15° specimens within the range of tested strain rates. Comparison of model prediction with experimental data shows that the rate-dependent microbuckling model can be used for predicting compressive strengths at strain rates up to 1100/s.
Dynamic Mechanical Properties and Failure Mechanisms of PVC Foams
Authors: Daniel Isaac M. , Rao Shiguo
Published: November 2021

Two closed-cell PVC foams were characterized at strain rates up to 1000 s−1. Experiments in the strain rate range between 10−4 and 1 s−1 were conducted on a servohydraulic testing machine and those in the range between 1 and 103 s−1 were conducted on a modified Split Hopkinson Pressure Bar (SHPB) apparatus. The striker and input/output pressure bars in the latter were made of polycarbonate (Lexan) instead of metal. The polycarbonate material was tested at different strain rates and found to behave linearly for strain rates up to 1000 s−1. All stress-strain curves show typically five deformation stages, initial elastic deformation, nonlinear deformation up to a peak load, softening after the peak, a plateau and finally strain hardening corresponding to material densification. The initial modulus increases slightly with strain rate and both peak and plateau stresses increase with strain rate. The softening stage becomes longer with increasing strain rate, a fact attributed to heat generation during the adiabatic deformation. Failure mechanisms at different stages of deformation were identified by loading specimens to different strain levels and observing them by scanning electron microscopy. The initial elastic behavior corresponds to bending of the cell walls; nonlinear and softening behavior correspond to buckling of the cell walls; and densification results from collapse of the cells.
Dynamic Stress Intensity Factor Due to Concentrated Loads on Semi-Infinite Cracks in Orthotropic Materials
Authors: Rubio-Gonzalez C. , Wang C.-Y. , Mason J. J.
Published: November 2021

The transient elastodynamic response due to concentrated normal or shear impact loads on the faces of a semi-infinite crack in orthotropic materials is examined. Solution for the stress intensity factor history around the crack tip is found. Laplace and Fourier transforms together with the Wiener-Hopf technique are employed to solve the equations of motion in terms of displacements. An asymptotic expression for the stress near the crack tip is analyzed which leads to the dynamic stress intensity factor in modes I and II. Similar to the isotropic case, it is found that the stress intensity factor has a singularity and discontinuity when the Rayleigh wave emitted from the load arrives at the crack tip. Results are presented for a typical orthotropic material.
Impact Failure Analysis of Glass/Epoxy Textile Composites
Authors: Adanur Sabit , Onal Levent
Published: November 2021

The production parameters of composites are effective on the impact properties of the material. The effects of the number of layers, thickness, manufacturing characteristics such as molding time, molding temperature, molding pressure and the mixing ratio of epoxy resin and curing agent were examined at the same volume fraction ratio. There is an optimum point for most of the variables. Parameters below and above of this point lead an increase in deflection level. Impact velocity is effective on the composite properties as well.
Evaluation of P-Q Controllers for an Injection Moulding Machine
Authors: Guerrier Paul K. , Edge Kevin A.
Published: November 2021

There are a number of problems surrounding traditional velocity and pressure controllers used on injection moulding machines. Injection moulding machines are also very expensive and full scale testing is often not appropriate at the beginning of new controller evaluation. This paper presents results for a half scale ‘hardware-in-the-loop’ load emulation of the filling and packing phases of injection moulding, suitable for controller evaluation. The problems linked to the current industry standard velocity and pressure controller are discussed along with alternative strategies. Schemes including single controller fuzzy logic and neural network solutions are discussed and ruled out in favour of ones containing separate velocity and pressure controllers. Results for a model reference adaptive pressure controller are presented and compared with those obtained using a closed loop PI controller experimentally and in simulation. Experimentally the model reference adaptive controller outperforms the PI controller but does suffer from gain drift.
Fluid Power in Large Downhole Seismic Sensor Arrays
Authors: Cole Jack H.
Published: November 2021

High-resolution subsurface seismic imaging that places sources and receivers in wellbores is an emerging exploration technology that can help petroleum companies find and recover more oil and gas. Successful commercialization of this enabling technology requires the development of receiver arrays that can couple fifty or more three-component sensor modules to the wellbore in a reliable manner. Although electrical clamping systems have been successfully used in small arrays, hydraulic clamping is required for more than ten modules. Both inflatable-bladder and cylinder-actuated clamp arrays have been designed However, when arrays must operate in 200° C environments, elastomer bladders become unsuitable. Research at the University of Arkansas has produced a failsafe fluid power system design makes feasible the successful development of large seismic sensor arrays that can operate in deep well bores.
The Role of Dissolved and Nascent Air in Oil-Hydraulic Systems
Authors: Stern Hansjoerg
Published: November 2021

In modern, high performance hydraulic systems the transient behavior of dissolving, dissolved and nascent air under changing dynamic conditions of pressure and temperature is emerging as an increasingly important factor, capable of creating undesirable operating conditions. The paper discusses the question of how to predict the performance of pump inlets and valve discharges, where we have known for some time that cavitation and cavitation-like conditions exist and can cause significant damage. The steady state conditions at which nascent air evolves from saturated air-in-oil solutions is normally one or two orders of magnitude above the vapor pressure of the system fluid. To what extent, therefore, is “cavitation” in these systems an air-oil problem? Or is it an oil-vapor problem that is analogous to cavitation in water hydraulic pumps and turbines? Or have we created the combination of the two, a three-phase system of liquid, gas and vapor?
An Investigation Into the Characteristics of a “2D” Flow Control Valve
Authors: Ruan J. , Burton R. , Ukrainetz P.
Published: November 2021

In hydraulic servo systems, a pilot stage is often used to reduce the influence of Bernoulli’s forces and frictional forces when trying to accurately position a spool. A unique pilot controlled valve, (defined as a “2D” flow control valve), which utilizes both rotary and linear motions of a single spool, is presented. The rotary motion uses a spiral groove in the sleeve combined with high and low pressure holes on the spool land to control the pressure in the spool chamber, while the linear motion of the spool is actuated by a hydrostatic force. Both linear theory and numerical simulation are adopted in the investigation of the characteristics of the valve. A criterion for stability is established from a linearized model of the valve. The analysis establishes the effects that certain structural parameters have on the valve’s static and dynamic characteristics. Special experimental procedures were designed to obtain properties such as mechanical stiffness, leakage flow rate, and dynamic response under different structural parameters and system pressure. It was shown that the leakage through the spool-sleeve clearance had a favorable effect on the valve stability. Theoretical and experimental results show that it is necessary to establish a balance between the static and dynamic performance in establishing appropriate structural parameters. It is also shown that the 2D flow control valve can demonstrate a high speed of response, while maintaining the pilot flow rate at a low level.
Flowing Granular Materials and the Maxwell-Boltzmann Velocity Distribution
Authors: Boyle Edward J.
Published: November 2021

The single-granule velocity distribution function is shown to be Maxwell-Boltzmann for hard-sphere granular flows at steady-state exhibiting no gradients and absent a body-force. This is accomplished by approximating the two-granule velocity distribution function as the product of two single-granule velocity distribution functions and a correlating function and by applying to a canonical ensemble a function analogous to Boltzmann’s H-function.
A Semi-Analytic Model for Free Vibration Analysis of Longitudinally Loaded Cantilever Shaft-Disk Systems
Authors: Sheu Hong-Cheng , Chen Lien-Wen
Published: November 2021

A semi-analytic model is proposed to study the critical speeds and critical loads of the cantilever shaft-disk systems subjected to longitudinal loads. In the present work, both the exact and approximate stiffness influence coefficients of the longitudinally loaded cantilever shafts are derived. In order to obtain deeper insight into the dynamic behavior of such a shaft-disk system, the present shaft mathematical model has taken account of shear deformation effect. Because the exact stiffness influence coefficients of the shaft are transcendental and difficult to get their characteristics on longitudinal load intuitively, each stiffness influence coefficient is expanded in a Taylor’s series about the longitudinal load. Based on the present approximate stiffness influence coefficients, the critical speeds and critical loads of the cantilever shaft-disk systems can be easily and quickly obtained. Numerical simulations show that the present results are seen to be quite in agreement with the exact solutions.
Effect of Core Plasticity on the Post-Buckling Behavior of Debonded Sandwich Beams
Authors: Sankar Bhavani V. , Narayanan Manickam , Sharma Abhinav
Published: November 2021

Nonlinear finite element analysis was used to simulate compression tests on sandwich composites containing debonded face sheets. The core was modeled as an elastic-perfectly-plastic material, and the face-sheet as elastic isotropic. The effects of core plasticity, face-sheet and core thickness, and debond length on the maximum load the beam can carry were studied. The results indicate that the core plasticity is an important factor that determines the maximum load.
Short Range Atmospheric Dispersion From Evaporation of Explosively Disseminated Liquid Drops on a Sandy Soil Surface
Authors: Mellsen Stanley B.
Published: November 2021

A series of field trials using a chemical simulant was conducted on sandy soil in the Experimental Proving Ground of the Defence Research Establishment Suffield, located near Medicine Hat, Alberta, Canada. Seven trials were conducted with methyl salicylate thickened to a zero shear viscosity of six poise. Explosive dissemination was used to provide liquid drops. The measured total dosage fifty metres downwind of the contaminated area was predicted by means of a previously developed mathematical model. The results of these trials are compared to those of similar trials conducted on prairie grassland.
A Study of Electrostatic Charges on Pneumatically Conveyed Solids
Authors: Zhang Jianyong , Coulthard John , Cheng R. , Keech R. P.
Published: November 2021

Non-restrictive, electrostatic methods have been used for measuring solids concentration of pneumatically conveyed solids under ‘lean-phase’ conditions. The passive measurement is based on the phenomena that, during pneumatic transportation, the solids particles can become naturally charged due to particle-particle interaction, particle-pipe wall impact, friction between particles and the air stream etc. The charges can be measured and, under certain conditions, can be used as an indication of the level of solids concentration. This method has been observed experimentally [1], [2] [3] [4] [9] and confirmed on full-scale power plant by the authors [5]. Several attempts have been made to derive a theoretical relationship between the solids concentration and the resultant charge, for example Gajewski [3] and Masuda [6].

This paper further develops a relationship between the solids concentration and the charges carried by flowing solids particles after making certain limiting assumptions. The solids generate stochastic signals on the electrodes and this is expressed mathematically and related to the charge level. This theory is shortly to be tested on pneumatically conveyed solids as part of a European funded research project at Nottingham university and at Kingsnorth power station in the U.K. [7]. A method of measuring average particle size is also proposed using a combination of measuring techniques.
Effects of Applied Electric Fields on Interface Dynamics and Microstructure Formation During Directional Solidification of BiMn/Bi Eutectic
Authors: Zheng L. L.
Published: November 2021

This paper is to demonstrate that the presence of an electric field can be used to control materials microstructure formation. Special efforts have been made to identify the foremost process control parameters that affect the interface dynamics, and thermoelectric effects on materials microstructure formation during directional solidification. A computational model that integrates microscopic analysis to macroscopic model has been developed and applied to directional solidification of BiMn/Bi eutectic in the presence of electric fields. Numerical results demonstrated that in addition to process parameters, microstructure formation strongly depends on intensity, polarity and duration of applied current, and it changes spontaneously as an electric field is applied. Predicted patterns of microstructures have qualitatively agreed with the experiments. The results indicate the feasibility of utilizing electric fields to control microstructure formation during eutectic growth.
Simulation of Spray Cooling in a Desublimer
Authors: Andrews Malcolm J. , Zwick David
Published: November 2021

Three-dimensional Computational Fluid Dynamics (CFD) simulations are presented for water spray cooling of a Phthalic Anhydride desublimer. The multiphase CFD modeling includes a fully coupled Eulerian/Lagrangian formulation for the carrier gas and water spray, and a quasi-steady model for the desublimation process. The use of a Lagrangian description for the spray enables a drop size distribution, but also necessitates running the simulation through the transient to obtain a steady operation result. The simulation has been used to study effect of drop size, spray dispersion and spray location/orientation.
High Performance Computing: A Mathematical Aerodynamic Model for Vehicle Driving Simulations
Authors: Kao Ben G. , Miller Ronald H. , Greenberg Jeffry A. , Strumolo Gary S.
Published: November 2021

Aerodynamic lift force can affect automobile handling characteristics and wind gust can affect vehicle directional stability. Experimental measurements of the drag forces are usually made for fuel economy estimation and hence do not cover large wind angles that are important for vehicle stability studies of wind gust or extreme maneuvers. The Virtual Aerodynamic Wind Tunnel (VAWT) which uses PowerFlow is an ideal numerical tool in the early vehicle design stage to provide the aerodynamic forces from a vehicle model. The numerical technique is also advantageous over experimental measurements because it does not need a hardware prototype and the computer model is relatively easier to set up for design iterations. Since the dynamic effects of aerodynamic forces on a vehicle and its driver are best studied with a driving simulator in a real time environment, the VAWT calculated air drag coefficients are reduced to a mathematical function suitable for the real time driving simulations. Available test measurements are used to ensure the practicability of the mathematical function. A vehicle model is then used to test the aerodynamic model and study the effects of the aerodynamics on the vehicle directional stability.