bluuebunny/crossref_metadata_2025 huggingface dataset:
On Line Inspection and Control of Workpiece Dimension Using Ultrasonic Sensors
Authors: Rosenberger T. , Teltz R. , Shawky A. , Elbestawi M.
Published: March 2022

In this paper new approaches to the inspection and control of workpiece dimension in turning are presented. The paper focuses on the novel application of ultrasonic sensors to provide improved part monitoring and feedback to the process controller. The measurement setup is used for both part diameter and wall thickness of hollow shafts. Compensation for sensor misalignment errors are addressed. The dimensional data obtained during cutting is used in a closed feedback control loop to compensate for dimensional errors in real time. The results demonstrate the accuracy, robustness, and capability of the described techniques in operating in wet cutting environment.
NARMAX Modeling and Robust Controller Design for Internal Combustion Engines
Authors: Glass John W. , Franchek Matthew A.
Published: March 2022

Presented in this paper is the conversion of NARMAX models to describing function based models for the purpose of robust feedback controller design. This investigation develops discrete NARMAX models to represent the nonlinear dynamics of a Ford 4.6L V-8 fuel injection engine operating at a preset idle speed. A SISO NARMAX model of the engine is developed between the By-Pass Idle Air Valve (BPAV) and engine speed. From this model, a describing function is obtained for the purpose of controller design. The objective of the controller design is to regulate engine speed within a 100 rpm tolerance about 700 rpm despite external torque disturbances. The design is executed in the frequency domain which incorporates model uncertainty and the transport delay of the engine. A controller is designed and verified using both numerical simulations and experimental verification.
A Finite Volume Colocated-Mesh Method for the Prediction of Non-Newtonian Fluid Flow
Authors: Oliveira Paulo J. , Pinho Fernando T. , Pinto Gilberte A.
Published: March 2022

This paper reports the development of a methodology for calculating the flow of upper convected Maxwell fluids using a finite-volume based method. The algorithm was developed for a general non-orthogonal collocated grid, and the pressure-velocity-stress coupling was addressed by a special interpolation technique inspired by Rhie and Chow’s (1982) method. The differencing schemes are second order accurate and calculations were carried on for a two-dimensional entry channel flow in order to assess the performance of the method. The interpolation technique specially devised for the stresses was found to work well and the results of the simulation compared favourably with those of the literature (Eggleton et al, 1996). Convergence was attained for Deborah and Reynolds numbers identical to those reported in the literature for a similar flow problem using other numerical methods.

Viscoelasticity was responsible for the development of very intense normal stresses, which were tractive in the wall region. As a consequence the viscoelastic fluid was forced to move away from the wall, in a more intense way than with Newtonian fluids, thus reducing locally the shear rates and the role of viscosity in redeveloping the flow.
Static and Dynamic Structures of Polarizable Fluids
Authors: Tao R.
Published: March 2022

In a strong electric field, polarizable fluids have a structural transition at a critical shear stress. When there is no flow, polarizable fluids form a body-centered tetragonal lattice which consists of closely packed chains. When the shear stress is increased from zero up to a critical value, the flow (in x-direction) has a flowing-chain (FC) structure, consisting of tilted or broken chains along the field (z-direction). At the critical shear stress, the FC structure gives way to a flowing-hexagonal-layered (FHL) structure, consisting of several two-dimensional layers which are parallel to the x-z plane. Within one layer, particles form strings in the flow direction. The effective viscosity drops dramatically at the structural change. As the shear stress reduces, the FHL structure persists even under a stress-free state if the thermal fluctuation is very weak.
Mixer-Type Rheometry for Complex Fluids
Authors: Ait-Kadi A. , Marchal P. , Chrissemant A. S. , Bousmina M. , Choplin L.
Published: March 2022

A procedure to quantitatively analyze torque/rotor speed data in order to extract viscosity/shear-rate curves using non conventional geometries is presented. The approach is based on the Couette analogy. It is first validated using a relatively simple geometry for which the equivalent internal radius used in the analogy can be analytically obtained. The results showed that the equivalent internal radius depends only slightly on the nature of the fluid. The experimental results with complex geometries and complex fluids are found to coincide, within experimental errors, with those obtained using standard geometries over a wide range of shear rates. For certain fluids such as tomato ketchup, only a specific mixing device (the helical ribbon impeller in this case) can be used to obtain reproducible viscosity/shear-rate curves.
Elongational Flow of Long Discontinuous Fiber Composites
Authors: Creasy Terry S. , Advani Suresh G.
Published: March 2022

Two fiber/polymer composite systems provided an opportunity to determine the dominant properties that set the behavior of the systems in extensional flow. Industrial users are interested in these systems for the savings of process time and labor they may bring to high strength composite construction. To understand the basic behavior of highly aligned fiber systems, the paper presents a model system designed to provide extensional data at low and moderate fiber aspect ratio and a high aspect ratio system. The model system shows the trend to a shift from neat polymer elongational response to a shear flow dominated response as the aspect ratio increases. The high aspect ratio system demonstrates the effect of extreme filament length on the transient response.
The ER Long-Stroke Damper: Experimental Verification of Mathematical Models
Authors: Peel D. J. , Stanway R. , Bullough W. A.
Published: March 2022

Traditionally, procedures of modelling the performance of electro-rheological (ER) devices have been severely hampered by the absence of robust methods for characterising the behaviour of the ER fluids themselves. Recent publications by the authors have described a non-dimensional characterisation procedure. Not only does this new approach drastically reduce the number of variables but through a generalised analysis enables tire steady flow characteristics of different types and sizes of devices to be related.

In this paper, the authors describe the extension of the characterisation technique to consider the behaviour of a controllable vibration damper which uses ER fluid as the working medium. A critical comparison is made between the model predictions and the observed behaviour of a test facility specially constructed to examine the response of an ER damper to harmonic displacement excitation. Emphasis is placed upon the influence of fluid inertia and compressibility on dynamic response and upon phenomena which are observed at the reversal of fluid motion; suggestions are made for further work.
Shearing Deformation in Partial Areal Arrays: Analytical Results
Authors: Heinrich S. M. , Shakya S. , Lee P. S.
Published: March 2022

Simple, closed-form expressions, based on elasticity theory, are derived for determining the location and magnitude of the maximum shearing displacement in a partial areal array of solder joints. Both uniform and non-uniform thermal loadings are considered, as is the heterogeneity of the component, which often arises due to different values of coefficient of thermal expansion (CTE) and elastic properties among the module’s constituent materials. The model is based on the assumptions that (a) the square geometry of the array and component may be replaced with an equivalent axisymmetric geometry and (b) the stiffness of the solder joints is negligible with respect to that of the component and substrate. The “soft joint” assumption corresponds to low-modulus solders or to thermal excursions occurring at high temperatures or low frequencies, for which significant stress relaxation occurs in the solder. For arrays exhibiting higher stiffness characteristics, the model yields conservative estimates of shearing displacement. Results indicate that, unlike homogeneous-component models under uniform temperature changes, the critical joints are not necessarily at the outer corners of the array. Other candidate locations predicted by the model (and observed in experimental and numerical studies) include the inner corner joints and any joints positioned beneath the die corners. The analytical results, also presented graphically, are found to depend on only three dimensionless parameters: the ratio of inner to outer array dimension, the ratio of die size to outer array dimension, and a “mismatch parameter,” which depends on the material, geometry, and loading characteristics of the problem. The results can be used to quickly determine the location and magnitude of peak shearing displacement in the array, possibly minimizing or eliminating the need to perform expensive and time-consuming finite element macroanalyses on entire assemblies involving hundreds of joints. Thus, the analyst may proceed directly to a detailed finite element microanalysis of the critical joint for fatigue life estimation, using the calculated shearing displacement as a required boundary condition in the finite element model.
The Effect of Underfill Delamination on the Reliability of Flip Chip Modules
Authors: Rzepka Sven , Korhonen Matt A. , Meusel Ekkehard , Li Che-Yu
Published: March 2022

The stresses occurring in the solder joints during thermal loads have been studied by finite element analysis in order to determine the effect of underfill delaminations on the reliability of FC modules and to evaluate the feasibility of lifetime estimations by the damage integral method. Besides the cases of no underfill and perfect adhesion, underfill delaminations at various interfaces to the solder, to the chip or to the substrate surfaces have been considered. The analysis included four different types of epoxy underfill, three kinds of substrates (alumina, FR-4, and flexboard), and two different tin lead solders (Pb97Sn and eutectic SnPb). The major findings are as follows. (i) The stress analysis has to be based on models that include the inelastic behavior of solder. Otherwise, even the qualitative trends might be wrong. (ii) The major beneficial effect of the underfill is its ability to create a compressive stress within the solder joint that suppresses the tensile stress concentration, which otherwise would lead to opening crack mode conditions at the side of the solder joints. The tensile stress is created by bending, which is a result of the global shear deformation due to the expansion mismatch between chip and substrate. (iii) Since the compressive stress can still be generated, delaminations from solder surfaces are not critical. (iv) When soft underfill is used, an extreme tensile stress concentration is created in the solder at the edge of the bond pad when the underfill is delaminated from the adjacent chip or substrate surfaces. This leads to a complete failure of the FC module very rapidly. (v) Using hard underfill that has a lower CTE than solder, however, the tensile stress in the joint can be kept at a safely low level even when adhesion to chip passivation or substrate is completely lost. Thus, it is possible to design FC modules, for which delaminations are not disastrous. (vi) Since the ultimate failure is always caused by growing of a major crack in the solder or at the underfill/chip interface, the damage integral concept can be applied to all kinds of FC modules, i.e. with or without underfill, to estimate the time to failure.
Some Mechanics Issues Related to the Thermomechanical Reliability of Flip Chip DCA With Underfill Encapsulation
Authors: Gall Carole A. Le , Qu Jianmin , McDowell David L.
Published: March 2022

The objectives of this research were to address some reliability issues in flip chip applications by characterizing the stress and strain response of a flip chip assembly under various loading conditions. In particular, the issue of fundamental limits on chip size was addressed and the importance of appropriate material models and constitutive relationships was assessed. Linear thermoelasticity models, metal plasticity models, viscoelasticity models and creep models were implemented. Finally, parametric studies were performed to optimize some of the elastic properties of the underfill.

It has been shown that (1) the chip major dimension is not the limiting factor in determining the maximum chip size for underfilled flip chip interconnections; (2) non-linear material behavior (e.g., creep, viscoplasticity, etc.) and detailed geometry need to be considered in the modeling to accurately predict the stress and strain fields; (3) there is an window for selecting optimal thermal expansion coefficient and modulus values which minimize stress and strain fields in the solder and silicon chip.
Effect of Thermal Residual Stress on the Measurement of the Adhesion Between Polyimide and Underfill Using an Asymmetric Double Cantilever Beam Specimen
Authors: Jiao Jinbao , Gurumurthy Charan K. , Kramer Edward J. , Sha Yan , Hui Chung-Yuen , Børgesen Peter
Published: March 2022

An asymmetric double cantilever beam (ADCB) technique was used to measure the interfacial adhesion of polyimide passivation to underfill materials. A thin layer of polyimide was coated on a standard diglycidyl ether of bisphenol-A (DGEBA) epoxy plate as one of the beams and an underfill epoxy was flowed over the polyimide film and cured to form the second beam. Due to the large difference in the coefficients of thermal expansion (CTE) between the two beams, a new term in critical strain energy release rate GT caused by the thermal residual stress becomes significant. This fact has been demonstrated experimentally by varying the thickness ratio of the two beams. The interfacial fracture energies of different underfill materials with polyimide were also measured. The results indicate that the effect of thermal residual stress must be taken into account in the calculation of critical strain energy release rate to achieve the realistic interfacial fracture energy Gc*.
Investigation of Interfacial Fracture Behavior of a Flip-Chip Package Under a Constant Concentrated Load
Authors: Wang Jianjun , Lu Minfu , Zou Daqing , Liu Sheng
Published: March 2022

In this paper, the interfacial fracture behavior of a flip-chip package subjected to a constant concentrated line load was investigated using a unique 6-axis submicron tester coupled with a high density laser moiré interferometry. The real-scale three-point bending flip-chip specimen, capable of measuring the crack growth rate (along the interface) and the interfacial fracture toughness was developed. The results show that the crack propagation along the interface of the passivated silicon chip/underfill under a constant concentrated load can be categorized into three stages: (1) stable crack propagation stage, (2) unstable crack propagation stage, and (3) quasi-crack arrest stage. There exist two obvious transition points between the stable crack propagation stage and the unstable crack propagation stage, and between the unstable crack propagation stage and the quasi-crack arrest stage. The moiré interferometry technique was used to monitor and measure the crack length during the test. The crack growth rate along the interface of the passivated silicon chip/underfill was calculated in terms of the load line deflection vs. time curve obtained from the test. In addition, the relationship between the crack length and the load line deflection was calibrated by using finite element analysis. The near tip displacement fields of the flip-chip package was also determined by the same method. The energy release rate was computed by using these near tip displacement variables through an analytical expression derived by authors. The interfacial fracture toughness Gc was determined by the energy release rate corresponding to the crack length at the quasi-crack arrest stage measured in the test. The interfacial fracture toughness Gc and the phase angle ϕ of the flip-chip package considered at the interface where the passivated silicon chip meets the underfill are about 35 J/m2 and −65° respectively.
Investigation of Underfill Adhesion in Plastic Flip-Chip Packages
Authors: Dai Xiang , Brillhart Mark V. , Ho Paul S.
Published: March 2022

The adhesion performance of underfill/printed circuit board (PCB) and underfill/chip interfaces are crucial for the reliability of plastic flip-chip packages. Delamination at either of these interfaces can drastically reduce the ability of the underfill to reinforce the flip-chip system resulting in premature assembly failure. This paper presents reproducible experimental techniques based on fracture mechanics for quantitatively determining the interfacial performance of underfill/polymer substrates and underfill/chip junctions. These techniques can be employed to rapidly evaluate new materials and process modification impact on adhesion performance of plastic flip-chip assemblies.
Fracture and Damage Evaluation in Chip Scale Packages and Flip-Chip-Assemblies by FEA and MicroDAC
Authors: Auersperg Jürgen , Schubert Andreas , Vogel Dietmar , Michel Bernd , Reichl Herbert
Published: March 2022

The thermo-mechanical reliability of electronic packages such as flip chip assemblies and chip scale packages is one of the most important conditions for adopting these technologies in industrial applications. On the other hand, various kinds of inhomogeneities, localized stresses and thermal mismatch between the silicon die and the substrate lead to interface delaminations, chip cracking and fatigue of solder interconnects.

The contribution shows the use of nonlinear finite element simulations with respect to the nonlinear, temperature and rate dependent behavior of the different materials used (metals, polymeric and solder materials) and the combination with experimental investigations. The development and application of failure models (e.g. thermal fatigue, life time prediction by Coffin-Manson type equations, integral fracture mechanics approaches — J–, J^–, ΔT*– integral — and evaluation of critical regions) is explained, in detail.

Furthermore, the simulation of damage growth in solder interconnects by an automatic adaptive finite element technique is performed. Inherent local damage models allow us to study the correctness of crack- and damage models. For this reason, some results have been compared to micrographs from damaged interconnects and to strain measurement results obtained by experimental methods. In particular, the microDAC measurement method is a powerful tool which inspects the displacement fields on the basis of the gray scale correlation method applied to micrographs from scanning electron microscopy, laser scanning microscopy and optical microscopy.

The application of those combined investigations should help to better understand the failure mechanisms especially in solder joints and directly support further applications for enhancing the thermo-mechanical reliability of advanced electronic assemblies.
Free-Edge Stress Intensity Factors for Edge-Loaded Bimaterial Layers
Authors: Klingbeil Nathan W. , Beuth Jack L.
Published: March 2022

Structures composed of bonded layers of dissimilar materials are common in a variety of applications. Designing such structures to resist debonding at free edges is often of critical importance. In this work, the problem of initiation of free-edge debonding is considered for use in designing debond-resistant layered structures. It is well known that the local elastic stress fields near the free edge of bonded dissimilar quarter planes can exhibit singular behavior, with the power of the stress singularity determined by the material mismatch. A fracture mechanics-type approach is adopted here which assumes that the local interface tractions governing initiation of debonding can be characterized by the power of the stress singularity and a suitably defined stress intensity factor. The global problem considered in this study is that of a bimaterial strip composed of isotropic layers with a uniform edge pressure applied to the top layer. A dimensionless free-edge stress intensity factor is introduced from which stress intensity factors can be derived for either uniform edge or thermal loadings applied to either or both of the layers. Finite element results are presented for the dimensionless free-edge stress intensity factor over a wide range of material mismatches and relative layer thicknesses. Trends in the dimensionless stress intensity factor are used to identify strategies for designing debond-resistant bimaterials. Finally, the trends are shown to be well approximated by the analytically calculated stress resultants transmitted across the interface, which suggests a simplified approach for designing debond-resistant multilayer structures.
Direct Measurement of the Adhesive Fracture Resistance of CVD Diamond Particles
Authors: Kamiya Shoji , Takahashi Hironori , Saka Masumi , Abé Hiroyuki
Published: March 2022

Diamond film produced by chemical vapor deposition (CVD) is being used in the electronics industry because of its excellent properties. In order to measure the adhesive strength of CVD diamond, external load is directly applied in a scanning electron microscope to the CVD diamond particles which sparsely appear on silicon substrate in the early stage of deposition. These particles are called nuclei when they are small and grow into contact with each other to form polycrystalline CVD diamond film. Diamond film was supposed to adhere to the substrate at only these discrete nucleation points, which might result in weak adhesive strength. We measure the maximum load, as the adhesive fracture resistance, required to scratch off the particles with 2–13 μm diameter. Adhesive fracture resistance is found to increase with the diameter of the particle. Hence we conclude that CVD diamond does not adhere only at the nucleation points but that the whole contact area to the substrate is responsible for its adhesive strength.
Two Interpretations of Rigidity in Rigid Body Collisions
Authors: Chatterjee Anindya , Ruina Andy L.
Published: March 2022

We distinguish between, and discuss the applicability of, two levels of rigidity in rigid-body collision modeling.

For rigidity in the strong, force-response, sense collisional contact deformations must be highly localized. The bodies then move according to 2nd order rigid-body mechanics during the collision. Incremental collision laws and most collision models using continuum mechanics for the contact region depend on force-response rigidity.

For rigidity in the weaker, impulse-response, sense the deformations need not be localized but displacements during the collision need to be small everywhere. Only the time-integrated rigid-body equations, involving before-collision and after-collision velocities, then need apply. Although a force-response rigid body is also impulse-response rigid the converse is not true. Algebraic collision laws depend only on impulse-response rigidity. Elastic vibration models of collisions are also generally consistent with impulse-response rigidity.
Strength and Stability Analyses of Retaining Structure Models for the Fracturing Fluid Characterization Facility
Authors: Striz Alfred G. , Thakore Keyur
Published: March 2022

Millions of dollars are spent annually on hydraulic fracturing for oil and gas well stimulation. Various researchers have proposed models to optimize the stimulation treatment, with limited success due to a lack of understanding of the behavior of critical parameters in the models, especially the fracturing fluids. Thus, the Gas Research Institute and the U.S. Department of Energy are sponsoring a project at the University of Oklahoma to investigate fracturing fluids in a large physical fracture model, the Fracturing Fluid Characterization Facility (FFCF). This simulator was initially expected to consist of a parallel plate simulator as large as 16 ft high by 100 ft long, with an internal pressure as high as 1200 psi, to determine critical fluid parameters under full-scale operating conditions. A smaller and more economical version of the simulator (7 ft high by 9 1/3 ft long) has since been built and moved to its own facility. As the reaction forces of the originally intended structure were tremendous (over 275,000,000 lbf for a full-scale simulator), structural analyses were essential.

Thus, static strength and stability (buckling) analyses were performed on various full-scale models and on the smaller final version of the pressure retaining structure for the FFCF simulator. An interior segment of each structural model consisting of the pressure chamber and the reaction beam/ plate/tie rod assemblies was modeled in detail and analyzed by the finite element method using the industry standard code MSC/NASTRAN together with the MSC/XL pre- and postprocessor. In addition to the linear analyses for all models, a material nonlinear analysis was run for Model 1. General buckling analyses by the finite element method were performed on square plates and on retaining structure plates with various boundary conditions to determine the influence of these conditions on the critical buckling loads. Finally, the full final model was analyzed for buckling proving the stability of the design.
Simplified Methodologies for the Characterization of Fatigue Crack Propagation in Metallic Structural Materials
Authors: Soboyejo Alfred B. O. , Soboyejo Winston O.
Published: March 2022

In several important engineering applications, the need to develop simplified mechanistically-based methodologies has become a significant factor in the development of appropriate techniques in the choice of suitable components, structures and infrastructures. Several metallic structural materials which have been used in such systems have suffered severe structural damages, due to the initiation of fatigue cracks, and in several instances, these have resulted in catastrophic structural and mechanical failures. In addition to the above, the importance of environmental and climatological considerations, including the effects of other essential variables, which can contribute significantly to fatigue crack initiation, propagation and structural failures, need to be addressed and incorporated into the formulation of any new methodologies, which may be proposed to solve the practical engineering problems in this field.

The successful results of recent research work in this field are hereby presented, in order to provide practically acceptable and simple engineering methodologies, which can provide the much needed solutions to problems in several structural and mechanical engineering design applications. The important technical contributions from the recent results of engineering research in this field are hereby presented in this technical paper.
An Integrated Micro/Macro Approach for Structural Analysis of Laminate Composites With Applications to Turbine Blades
Authors: Ávila Antonio F.
Published: March 2022

An integrated micro/macro mechanical procedure for structural analysis of unidirectional metal matrix composites is proposed. The micromechanical analysis is performed via the Composite Cylinder Assemblage model (CCA) or the Representative Volume Element approach (RVE). The macroscopic stress-strain relation is based on a modification of the Vanishing Fiber Diameter theory (VFD), and the concept of “smeared” finite element. The fibers are considered to be linear elastic, and the matrix viscoplastic behavior is described by the Bodner and Partom model. The overall composite behavior is assumed to be elastic-viscoplastic.

Two types of material systems are employed, namely, SCS-6/Ti-15-3 and SCS-6/Tiβ21-S. Both set of material systems exhibit isotropic and/or kinematic hardening under specific conditions of temperature and loading. The proposed methodology is validated with experimental and analytical results available in the literature. After the validation process, this methodology is applied to a 3-D finite element model of a [0/90]2s SCS-6/Tiβ21-S turbine blade tip. Aerodynamic and centrifugal loading are considered acting at the same time. The turbine blade tip inelastic strain field is presented.
Simulation of Deformation in Nial Single Crystals
Authors: Yang Chulho , Kumar Ashok V.
Published: March 2022

Deformation of NiAl single crystals during tensile testing was simulated using finite element analysis to investigate the modes of localized deformation. The effect of varying the loading direction with respect to lattice was studied to understand the deformation mechanism. Three-dimensional finite element models of tensile testing were created to study the effect of latent hardening when multiple slip systems are active. In particular, necking, neck diffusion and kink band formation were studied and the material and geometric characteristics that influence the deformation mode were investigated.
Vibration Control of Tubes With Internally Moving Loads Using Active Constrained Layer Damping
Authors: Ro J. , El-Din K. S. , Baz A.
Published: March 2022

The vibration of a flexible tube with internally moving load is controlled using patches of Active Constrained Layer Damping (ACLD) bonded to the tube surface. The damping characteristics of the tube/ACLD system are modeled by Golla-Hughes-McTavish (GHM) method in order to predict the tube response in the time domain. The transient response of tube/ACLD system is calculated using the finite element method. The predicted response is compared with that of a tube controlled with conventional Passive Constrained Layer Damping (PCLD) treatments. Such comparisons are essential in quantifying the individual contribution of the active and passive damping components to the overall damping characteristics of the system.

The predictions of the finite element model are validated experimentally using a cantilevered PVC plastic tube treated with an ACLD patch placed parallel to the tube longitudinal axis. The tube vibration due to an internally moving load is controlled by the ACLD patch using a simple velocity feedback controller. The effectiveness of the controller in damping out the tube vibration is determined experimentally and theoretically for different control gains. Close agreement is obtained between theory and experiments. The results obtained suggest the effectiveness of the ACLD treatment in controlling the vibration of precision pointing systems such as weapon systems.
Integrating Active-Passive Hybrid Piezoelectric Networks With Active Constrained Layer Treatments for Structural Damping
Authors: Tsai M. S. , Wang K. W.
Published: March 2022

The goals of the research reported in this paper are to investigate the feasibility of integrating Active-Passive Hybrid Piezoelectric Networks (APPN) with the Active Coristrained Layer (ACL) or Enhanced Active Constrained Layer (EACL) treatments, identify the benefits or limitations of the approach, and provide insights toward designing such systems. It is shown that integration of APPN with ACL cannot obtain much extra damping because of low inverse transmissibility, while the APPN-EACL configuration can achieve high damping around the shunt frequency. The APPN-EACL can be synthesized to outperform the APPN, EACL and APPN-ACL configurations under both narrowband and broadband excitations. The study indicates that while EACL can outperform ACL when the demand on performance is high, it will become less effective than ACL when control effort is very limited. However, with the help of the shunt circuit, APPN-EACL can outperform the APPN-ACL system even when the limitation on control effort is high.
Localization of Vibration Propagation in Randomly Disordered Weakly Coupled Two-Dimensional Cantilever-Spring Arrays
Authors: Xie Wei-Chau
Published: March 2022

In this paper, the method of regular perturbation for a linear algebraic system is applied to study localization of vibration propagation in randomly disordered weakly coupled two-dimensional cantilever-spring arrays under external harmonic excitations. Iterative equations are obtained to express the displacement vector of the cantilevers on the Mth “layer” in the Mth-order perturbation in terms of those on the (M − 1)th “layer” in the (M − 1)th-order perturbation. Localization factors, which characterize the average exponential rates of decay of the amplitudes of vibration, are defined in terms of the angles of orientation. First-order approximate results of the localization factors are obtained using a combined analytical-numerical approach. The localization factors are symmetric about the horizontal and vertical axes passing through the cantilever that is being externally excited. For the systems under consideration, the direction in which vibration is dominant corresponds to the smallest localization factor; whereas the “diagonal” directions correspond to the largest localization factor.
P-Bifurcations in the Stochastic Version of the Duffing-van der Pol Equation
Authors: Liang Yan , Namachchivaya N. Sri
Published: March 2022

In this paper, we shall re-examine the stochastic version of the Duffing-van der Pol equation. As in [2], [9], [19], [22], we shall introduce a multiplicative and an additive stochastic excitation in our case, i.e.x¨=(α+σ1ξ1)x+βx˙+ax3+bx2x˙+σ2ξ2, where, α and β are the bifurcation parameters, ζ1 and ζ2 are white noise processes with intensities σ1 and σ2, respectively. The existence of the extrema of the probability density function is presented for the stochastic system. The method used in this paper is essentially the same as what has been used in [19]. We first reduce the above system to a weakly perturbed conservative system by introducing an appropriate scaling. The corresponding unperturbed system is then studied. Subsequently, by transforming the variables and performing stochastic averaging, we obtain a one-dimensional Itv equation of the Hamiltonian H. The probability density function is found by solving the Fokker-Planck equation. The extrema of the probability density function are then calculated in order to study the so-called P-Bifurcation. The bifurcation pictures for the stochastic version Duffing-van der Pol oscillator with a = −1.0, b = −1.0 over the whole (α, β)-plane are given. The related mean exit time problem has also been studied.
Stochastic and Resonant Layers in a Periodically Driven Pendulum
Authors: Luo Albert C. J. , Han Ray P. S.
Published: March 2022

The stochastic and resonant layers in a periodically driven pendulum are investigated in this paper. The analytical solutions and nonlinear natural frequencies of the non-driven pendulum are first derived, and then the energy increments in the stochastic and resonant layers for the driven pendulum are approximated by the work done by the external excitation along the heteroclinic and resonant orbits, respectively. From these results, the approximate analytical conditions for the predictions of stochastic and resonant layers are constructed. Based on these conditions, input parameters are computed for the numerical simulations of the stochastic and resonant layers. The stochastic and resonant layers associated with the librational and rotational motions are illustrated via the Poincare mapping sections.
An Experimental Study About the Bouncing Vibration of a Contact Slider
Authors: Ono Kyosuke , Maruyama Hideki
Published: March 2022

In this paper, we described an experimental study about the fundamental characteristics of the bouncing vibration of contact slider which is composed of a small stainless steel suspension and a glass or lead ball. The behavior of the contact slider was analyzed by using a laser doppler vibrometer. We found that the bouncing vibration was always low when the slider load was large, the coefficient of restitution was low and the suspension damping was high. For lead contact sliders that had a low coefficient of restitution, smaller mass can reduce the bouncing vibration more than the larger mass can. On the other hand, for glass sliders with a high coefficient of restitution, larger mass can reduce the bouncing vibration due to the increase in the inertia effect. Almost all of our experimental results agreed qualitatively with our analytical ones.
Fast Seek Servo Method Using Two-Degree-of-Freedom Control for Magneto-Optical Disk Drives
Authors: Toyama Souichi , Yanagihara Norihisa , Saegusa Shozo , Saito Atsushi
Published: March 2022

The seek speed of magneto-optical disk drives is greater than that of other optical disk drives. To design a high-speed seek servo system that will be an improvement over the traditional system, we must achieve following two goals. One is to drive the coarse-positioning actuator as fast as possible. The other is to restrain shift and vibration of the lens during the seek. We propose to apply two-degree-of-freedom (2-DOF) seek-velocity control and lens-shift restriction control. The 2-DOF seek-velocity control uses acceleration feedforward of the lens motion as well as target velocity signal of the lens velocity. This method can work the coarse actuator quickly. Further, the lens-shift restriction control uses the controlling input to cancel the inertial force that acts on the lens during the seek. By simulating this method, we discovered that such control systems provide the prospect of average seek time shorter than 19 ms.
Acoustic Identification of a Spun Cone Roller Bearing Defect
Authors: Anderson Gerald B. , Smith Richard L.
Published: March 2022

For Several years, the Association of American Railroads (AAR) has been developing new techniques to detect defective roller bearings as part of their new generation wayside acoustic detector program. This paper discusses data collected from several bearings with spun cone defects under both laboratory and simulated revenue service environments. The AAR performed the laboratory tests in July 1996 and the simulated revenue service test was completed in November 1996. Of all bearing defect types to be detected, the most challenging and highest priority is that of a bearing with a loose inner raceway (spinning cone) which rotates about the axle mount. Normal roller bearings have “press fit” inner raceways which keep them from rotating or sliding about the axle. The “Spun Cone” bearing defect is responsible for many of today’s bearing related derailments.
Application of the

W

COBRA/TRAC Best Estimate Methodology to the AP600 Large-Break LOCA Analysis
Authors: Zhang Jinzhao , Bajorek S. M. , Kemper R. M. , Nissley M. E. , Petkov N. , Hochreiter L. E.
Published: March 2022

The AP600 is a simplified advanced pressurized water reactor (PWR) design incorporating passive safety systems that perform the same function as the active emergency core cooling systems (ECCSs) on the current reactors. In order to verify the effectiveness of the AP600 design features for mitigation of a postulated large-break loss-of-coolant accident (LOCA), the recently USNRC-approved best-estimate LOCA methodology (BELOCA) was applied to perform the AP600 standard safety analysis report large-break LOCA analysis. The applicability of the WCOBRA/TRAC code to model the AP600 unique features was validated against CCTF and UFTE downcomer injection tests, the blowdown and reflood cooling heat transfer uncertainties were re-assessed for the AP600 large-break LOCA conditions, and a conservative minimum film boiling temperature was applied as a bounded parameter for blowdown cooling. The BELOCA methodology was simplified to quantify the code uncertainties due to local and global models as well as the statistical approximation methods, with the other uncertainties being bounded by limiting assumptions on the initial and boundary conditions. The final 95 percentile peak cladding temperature (PCT95%) was 1186 K, which meets the 10CFR50.46 criteria with a considerable margin. It is therefore concluded that the AP600 design is effective in mitigation of a postulated large-break LOCA.
Simulation of Some Emergency Operating Procedure for VVER-440 Reactors
Authors: Bánáti József , Ézsöl György
Published: March 2022

During the last few years the safety of the Hungarian Paks Nuclear Power Plant was reassessed in the framework of the AGNES project. Results of the program revealed that the safety of VVER-440/213 type reactors could be enhanced by modernizing a number of event oriented emergency operating procedures (EOPs) and the implementation of accident management (AM). Before the accomplishment of systematic AM all the possible thermal-hydraulic effects and consequences should be considered and experimentally verified.

This paper summarizes the most important findings of the relevant tests performed in the PMK-2 facility, which is a full-pressure, integral-type model of the Paks NPP. The present analysis concentrates on a particular method, the bleed-and-feed, applied in the primary or secondary circuit and conclusions are drawn for the effectiveness of this AM measure. Modelling of the thermal-hydraulic processes is extended with computer simulations using the RELAP5/MOD3.2 system code. Finally, a short assessment is given for the code capabilities to represent some significant phenomena of the transients.
Computational Fluid Dynamics Analysis of Thermal Mixing in the AP600 Upper Head
Authors: Schwirian R. E.
Published: March 2022

The paper discusses studies conducted to determine the extent of thermal mixing in the upper head region of the AP600 pressurized water reactor (PWR). This information is ultimately useful in the assessment of thermally-induced stresses in the upper head itself and the components adjacent to it. Coolant temperature profiles in the upper head region are also of interest in the evaluation of transients in which buoyancy forces are significant, such as natural circulation (NC) cooldown.
Scaling Analysis of AP600 Long Term Cooling Performance
Authors: Ortiz Marcos G. , Nielson Constance E. , Teerlink Laura
Published: March 2022

Westinghouse’s AP600 thermohydraulic design, with passive safety features, poses new challenges to computer simulation and analyses, the design of experimental test facilities to represent it, and to the proper interpretation of the data from these facilities. The conventional approach of modeling the reactor thermohydraulic system as a closed, steady state, natural circulation loop from which non-dimensional groups of parameters can be derived and used in the design of integral tests, is limited and can not capture the abrupt time-varying open system nature of the new design.

A rigorous and systematic, eight-step methodology has been developed to scale and interpret the results from three different integral test facilities, and to relate them to the full scale plant. In this paper, the aforementioned scaling methodology is applied to the analysis of the long term cooling phase of the AP600 behavior. This long term cooling phase, which appears independent of the initiating event, is divided for its analysis into two sub-phases. A first sub-phase dominated by the draining of the large In-Containment Refueling Water Storage Tank through the primary systems, and a second sub-phase characterized by the quasi-steady recirculation of coolant through the reactor vessel and the outside of the primary system. The analysis shows that with a few verifiable assumptions one can determine the key parameters and non-dimensional groups that govern the behavior in either of these sub-phases. One then uses these parameters and non-dimensional groups to evaluate the relevancy of existing test data.
The Influence of Processing on Structural Behaviour: An Interface Between Moldflow and ABAQUS
Authors: Bruijs Wim , Brounné Rob
Published: March 2022

It is well known that the injection molding process has an influence on the structural behaviour of the final plastic part. Due to shrinkage- and warpage effects, the final part does not have the same geometry as the mold, and it contains stresses. Nowadays cost and weight restrictions force part designers to use materials up to their mechanical limits. This puts very stringent requirements on the computer aided engineering of the parts and it becomes more and more important to account for the influence of the injection molding process on the part performance.

Moldflow is a versatile processing simulation program which, among others, is capable of predicting the warped shape and the molded-in stresses in a part. ABAQUS is a general purpose structural finite element program that is used to predict the behaviour of the part under a specific load. This paper describes an interface between the two programs which transforms the warped shape and the internal stresses as calculated by Moldflow to ABAQUS. A structural analysis can be performed based on the warped shape and taking into account the stresses.

The interface has been used to predict the shape of an injection molded thermoplastic fender. For this application, tight gap and flush requirements put strict requirements on the shape of the fender after mounting it on the vehicle. To be able to judge this shape, a special measurement method has been developed by RENAULT. In this method the plastic fender is placed on a measurement jig and fixed in a prescribed order. Afterwards the fender is measured and based on the results of these measurements the shape of the fender can be judged.

This procedure is simulated using the interface and taking into account warpage and molded-in stresses. For reasons of comparison, this simulation is also done without taking into account the molded-in stresses. The results of both simulations are compared with actual test data supplied by RENAULT and it can be concluded that accounting for the actual warpage results in a more accurate prediction of the fender shape.

The use of the interface can help in finding the optimal fender shape and the best molding conditions at a stage in the design phase where the final fixing system is not yet decided and tools still have to be made. In this way it helps to shorten the design cycle considerably.
An Optimization Scheme for Part Quality in Injection Molding
Authors: Ye Hua , Wu YingHui , Wang K. K.
Published: March 2022

In this paper, a mathematical definition of part warpage is presented by strain tensors and part quality is quantified via numerical simulation. An objective function of part quality is proposed that must be optimized. The resulting optimum is obtained by iterative search in the constrained space based on an numerical optimization algorithm — Simulated Annealing method, which is a global and robust method. The efficiency of the simulated Annealing method is in between calculus-based methods, such as DFP, BFGS, MFD and common search schemes, such as, simplex and exhaust search method, etc. (Goffe, 1994). The results are shown by a number of numerical examples where the part warpage is significantly reduced after optimization.
Prototype Design and Process Optimization Procedure for Products From Glass-Fiber Reinforced Polymer Blends
Authors: Narh K. A. , Xanthos M.
Published: March 2022

In order to minimize the effects of compositional variation in multiphase, multicomponent polymer mixtures equivalent to those found in commingled waste streams, such as those obtained from reclamation/recycling operations of post-consumer containers, several plastic composites containing varying amounts of glass fiber and different compatibilizers/coupling agents are studied. The glass-fiber reinforced composites, based on characteristic compositions simulating post-consumer “curbside tailings”, have been designed and molded into thin-section parts. Structural, and flow analyses were performed with commercial software on different types of plastic parts. Most of the data used in the simulation were experimentally generated on the compatibilized HDPE based polymer blends containing 20% short glass fibers. Issues concerned with injection molding and product performance are discussed.