bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discussion of the Worst Case Scenario of FLD0
Authors: Arwashan Naji 
Published: November 2021

Abstract
The Forming Limit Diagram is used in circle grid analysis to check the safety of a formed panel. The shape of the Forming Limit Diagram for steel is always the same, it is only the vertical position of the diagram that varies depending on the value of FLD0. For steel, FLD0 is widely accepted to be dependent on the thickness and n value which are both inherently indeterministic, and can exhibit variations, small or large, depending on the manufacturing process. To account for this variability in determining the safety of a formed panel, the engineering practice in many companies is to use a minimum value for FLD0 called Worst Case Scenario, because it is calculated using minimum values for both t and n. This paper presents a different and better approach to calculate the minimum value of FLD0. The approach is based on probabilistic concepts, and allows the calculation of a minimum value for FLD0 that is related to a certain probability of occurrence. The derivation technique used in the paper is borrowed from Reliability Analysis and tailored to solve our problem. The derivation leads to a simple formula that can be easily used. The minimum value of FLD0 calculated according to the paper is more accurate than the Worst Case Scenario, and provides better cost saving since it is always greater than the Worst Case Scenario value.
Improving Formability in Sheet Metal Stamping With Active Drawbead Technology
Authors: Bohn M. L. , Xu S. G. , Weinmann K. J. , Chen C. C. , Chandra A. 
Published: November 2021

Abstract
Aluminum is expected to gain popularity as material for the bodies of the next generation of lighter and more fuel-efficient vehicles. However, its lower formability compared with that of steel tends to create considerable problems. A controllable restraining force caused by adjusting the penetration of drawbeads can improve the formability. This paper describes the effects of temporal variations in drawbead penetration on the strain distribution in a symmetric stamped part. Comparison of the results of numerical simulations with the corresponding experimental results shows that the predictions of strain distribution on the panel are in very good agreement. Furthermore, forming limit diagram analysis indicates that the active drawbead concept is beneficial to the formability of AA 6111-T4.
In Process Control of Strain in a Stretch Forming Process
Authors: Hardt D. E. , Norfleet W. A. , Valentin V. M. , Parris A. 
Published: November 2021

Abstract
The process of stretch forming is used extensively in the aerospace industry to form large sheet panels of mild curvature. This has traditionally been a low precision process requiring considerable hand-working at assembly. However, recent demands for faster, less wasteful production have placed new demands on the accuracy and consistency (quality) of this process. In this paper the various modes of control for this process are examined, from both an analytical and experimental point of view. It is shown clearly that the process is least sensitive to material and machine property variations if controlled to a target level of strain in specific areas of the sheet. This method is compared with the conventional methods of controlling either the force applied to the sheet during stretching or the displacement of the stretch jaws.
A series of both lab scale and full production experiments concur with the analytical findings, demonstrating reduced process variation if strain feedback is used. Lab experiments and analysis indicate that far greater reductions are possible if a more precise form of strain control is used. In production trials forming wing leading edges, a manually implemented strain control showed a shape variation reduction of 50% over normal factory practice using force control.
Environmentally Conscious Investigation of Cutting Fluid Mist Behavior via Particle Image Velocimetry in Turning
Authors: Chiou Richard Y. , Chen Jim S.-J. , Cooper Derrek , Ciuciu Cristian 
Published: November 2021

Abstract
In this paper, Particle Image Velocimetry (PIV) monitoring approach for cutting fluid mist behavior in machining is proposed. Particle Image Velocimetry is a technique that uses a combination of lasers and a CCD camera to analyze the fluid flow field. Experiments were performed to investigate the transient mist patterns due to the impinging cutting fluid on a rotational workpiece in a turning operation. The measurements displayed the velocity profiles and sizes of the generated fluid mist both in the near-field and far-field. This paper contains the results of a preliminary experiment to measure and analyze mist generation mechanism on a lathe. The experimental investigation concerning the mist behavior in a turning operation can be used as basis for human exposure and health hazard analysis. Some preliminary results were obtained and recommendations were made for future research.
Theory of Torsional Chatter in Twist Drills: Model, Stability Analysis and Comparison to Test
Authors: Bayly Philip V. , Metzler Sandra A. , Schaut Adam J. , Young Keith A. 
Published: November 2021

Abstract
The mechanism of torsional chatter in drilling differs qualitatively and quantitatively from other types of chatter. In this paper we show that torsional chatter can be explained by the torsional-axial coupling inherent in a twisted beam; the beam “untwists” and extends in response to an increase in cutting torque. Based on a model of this mechanism, predictions of stability boundaries and chatter frequencies are derived by frequency domain analysis, and confirmed by numerical simulation and experimental tests. The effect of the torsional-axial coupling is opposite that of traditional cutting in that an increase in cutting forces leads to axial extension and greater chip load. Because of this sign difference, the limiting depth of cut is governed by the positive real part of the frequency response function, which explains the unexpected fact that torsional chatter occurs below the natural frequency of the tool.
The Effect of Dynamic Consistency in Spindles on Cutting Performance
Authors: Smith Scott , Winfough W. R. , Young Keith , Halley Jeremiah 
Published: November 2021

Abstract
This paper presents the results of three measurements of dynamic consistency in machine tool spindles. First the effect of reclamping and of the rotational orientation of a tool in a single spindle (40,000 rpm 40 kW) was evaluated. Then 5 different spindles of the same model (20,000 rpm 75 kW) were compared, first with a flexible tool and then with a stiff tool. It was seen that in all the tests the natural frequencies did not vary greatly, but that in some situations the damping showed significant variability. The effect of this damping variation on stability and cutting performance is evaluated for both conventional and for high speed machining.
Computational Biomechanics of Human Spine Under Wrapping Compression Loading
Authors: Shirazi-Adl A. , Parnianpour M. 
Published: November 2021

Abstract
Computational biomechanics of the human spine under a novel compression loading that follows the curvature of the spine is performed by evaluation and comparison of the detailed response of the spine under various types of compression loading at different postures. The nonlinear finite element formulation of wrapping elements sliding without friction over solid body edges is developed and used to study the load-bearing capacity of thoracolumbar (T1-S1) and lumbosacral (L1-S1) spines under one or several wrapping compression forces. Follower load at the L1, axially-fixed compression at the L1, and combined axially-fixed compression plus constrained rotations are also considered for comparison. Moreover, for the detailed lumbosacral model, the effect of changes in the position of wrapping elements and in the lumbar curvature on results are considered. The idealized wrapping loading substantially stiffens the spine allowing it to carry very large compression loads without hypermobility. It diminishes local segmental shear forces and moments as well as tissue stresses. In comparison to fixed axial compression, therefore, the compression loading by wrapping elements that follow the spinal curvatures increases the load-bearing capacity in compression and provides a greater margin of safety against both instability and tissue injury. These findings suggest a plausible mechanism in which postural changes and muscle activation patterns could be exploited to yield a loading configuration similar to that of the wrapping loading. To alleviate hypermobility in compression, the wrapping loading could also allow for the application of meaningful compression loads in experimental as well as model studies of the multi-segmental spinal biomechanics.
Use of Finite Elasticity in Abdominal Aortic Aneurysm Research
Authors: Vorp David A. , Wang David H.-J. 
Published: November 2021

Abstract
Abdominal aortic aneurysm (AAA) is a condition whereby the terminal aorta permanently dilates to dangerous proportions, risking rupture. Rupture of AAA is a significant cause of death in this country that is generally avoided by surgical repair. In order to improve our understanding and diagnosis of this disease, we call upon first principles of finite elasticity. We use such principles to estimate the AAA wall strength and acting wall stress, which in turn allow evaluation of an individual aneurysm’s risk of rupture. In this paper, we summarize the work that has been performed to date in applying finite elasticity to abdominal aortic aneurysm research.
Effects of Inhomogeneous Fixed Charge Density on the Electrical Signals for Chondrocytes in Cartilage
Authors: Lai W. M. , Sun D. D. , Ateshian G. A. , Guo X. E. , Mow V. C. 
Published: November 2021

Abstract
An important step toward understanding the signal transduction mechanisms that modulate cellular activities is the accurate prediction of the mechanical and electro-chemical environment of the cells in well-defined experimental configurations. One such configuration is the steady permeation experiment (e.g., bioreactors) in the open circuit condition. Using our triphasic theory, we have calculated the strain, velocity and the electric potential fields inside a layer of charged articular cartilage, through which a uni-univalent salt (e.g., NaCl) solution permeates under a constant pressure difference across the layer. The fluid flow through the tissue gives rise to an electrical potential difference across the tissue. This potential difference is the well-known “streaming potential” that is measured by Ag/AgCl electrodes placed across the tissue on the outside. Our results show that inside the tissue, in addition to the streaming potential caused by fluid convection, there is also a “diffusion potential” caused by cation and anion concentration gradients that are induced by the gradient of fixed charge density (FCD) inside the tissue. The gradient of FCD may be intrinsic, i.e., the tissue has an inhomogeneous FCD distribution, or it may also be caused by a non-uniform compaction of the solid matrix as is the case in steady permeation where the drag force exerted by the permeating fluid onto the solid matrix causes a compressive strain field inside the tissue. In this experimental configuration, the diffusion potential would compete against the streaming potential. The magnitude and the polarity of the electric field depend, amongst other material parameters, on the compressive stiffness of the tissue. For softer tissue (e.g., aggregate modulus &lt;0.54 MPa for a set of realistic material and testing parameters), the diffusion potential dominates over the streaming potential and vice versa for stiffer tissue. For articular cartilage what the cells see in situ is the combined electrical effect of intrinsic and deformation induced inhomogeneity of FCD. The present results provide not only quantitative information, but also new insight into an important problem in biotechnology. These results also demonstrate that for proper interpretation of the mechano-electrochemical signal transduction mechanisms that is needed for modulating cellular biosynthetic activities, one must not ignore the important effects of diffusion potential.
Modeling Flow Properties in Biofluids
Authors: Kee Daniel De , Sun Ning 
Published: November 2021

Abstract
Biofluids such as blood, as well as other structured materials, exhibit rather complex rheological behavior. In this paper, starting from a first order kinetic model introduced by Soong et al., we developed a constitutive equation and studied its applicability to model biofluids. In particular, we studied the cases of steady shear flow, hysteresis, yield stress and small amplitude oscillatory flow. Model predictions were successfully compared with experimental data on complex materials such as blood and a penicillin suspension.
Functional Macroporous poly(dicyclopentadiene)
Authors: Della Martina A. , Hilborn J. G. 
Published: November 2021

Abstract
The synthesis and processing of functional macroporous poly(dicyclopentadiene) is addressed in this paper. The basic principle of chemically induced phase separation, which can produce either closed or open pore materials, is described. The produced materials showed narrow pore size distributions and micrometric average access diameters. Linearity between the initial porogen contents and the final porosity was observed, allowing easy tailoring of the final materials. The wide possibilities of this technique are presented. Porous monoliths as well as porosity gradient rods and porous microspheres have been produced. Pore sizes distributions modification as well as surface functionalization have also been performed.
Flow-Forces Effect on the Behavior of an Open Center Hydraulic Distributor
Authors: Borghi M. , Milani M. , Sedoni E. 
Published: November 2021

Abstract
The effect of steady-state axial flow-forces on the motion of an open center hydraulic distributor notched spool is considered.
More in details, the spring driven spool centering is considered, in which undesired axial flow-forces could overcome the spring action.
A steady-state analysis of the forces influencing the spool motion is reported, calculating the axial flow-force for different positions of the spool.
Different notched shapes of the metering edge are considered, and an optimized solution for the notched edge of the spool is proposed at last.
Elastic-Plastic Behavior of Filamentary Networks
Authors: Baesu Eveline 
Published: November 2021

Abstract
The finite elastic-plastic deformation of thin sheets formed by several families of perfectly flexible extensible fibers is described using an idealized theory in which fibers are assumed to be continuously distributed and fastened together at nodes which deform as material points. The constitutive properties of the associated surface are deduced directly from those of the constituent fibers. An incremental formulation of the equilibrium equations for two families of fibers is presented and used to generate extremum principles based on primary bounds on the exact global force-deflection response.
Plane Steady Flows of Dilute Magnetic Fluids
Authors: Venkatasubramanian S. , Kaloni P. N. 
Published: November 2021

Abstract
In this article, steady plane flows of dilute magnetic fluids are studied. A solution procedure for a general flow is developed using transformation techniques. Macroscopic effects due to the rotation of the suspended particles are taken into account, while neglecting their diffusion. Effectiveness of this method is illustrated by solving two rectilinear flows in different coordinate systems. In an uniform applied magnetic field, the magnetic torque displays itself as an apparent viscosity affecting the flow of a dilute magnetic fluid. Importance of not neglecting the particle rotation effects are shown by comparing the results with that of the corresponding equilibrium model.
Spatial Discretization of Axially Moving Media Vibration Problems
Authors: Jha Rajesh K. , Parker Robert G. 
Published: November 2021

Abstract
Spatial discretization of axially moving media eigenvalue problems is examined from the perspectives of moving versus stationary system basis functions, configuration space versus state space form discretization, and subcritical versus supercritical speed convergence. The moving string eigenfunctions, which have previously been shown to give excellent discretization convergence under certain conditions, become linearly dependent and cause numerical problems as the number of terms increases. This problem does not occur in a discretization of the state space form of the eigenvalue problem, although convergence is slower, not monotonic, and not necessarily from above. Use of the moving string basis at supercritical speeds yields strikingly poor results with either the configuration or state space discretizations. The stationary system eigenfunctions provide reliable eigenvalue predictions across the range of problems examined. Because they have known, exact solutions, the moving string on elastic foundation and the traveling, tensioned beam are used as illustrative examples. Many of the findings, however, apply to more complex moving media problems, including non-trivial equilibria of nonlinear models.
Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model
Authors: Bažant Zdeněk P. , Brocca Michele 
Published: November 2021

Abstract
The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this ‘first-principles’ approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.
Comparative Study of Two Different Conceptual Design Principles for Non-Circular Pressurized Sandwich Fuselage Sections Using a High-Order Sandwich Theory Formulation
Authors: Thomsen Ole T. , Vinson Jack R. 
Published: November 2021

Abstract
Results obtained as part of a design study regarding a non-circular pressurized sandwich fuselage section are presented. The originating problem is associated with preliminary studies for the “Global Range Transport” envisaged by the “New World Vistas” program of the United States Air Force. The modeling and analysis is conducted using a high-order sandwich theory formulation in which the elastic response of each face laminate is accounted for, including bending-stretching coupling and transverse shear deformations, and where the transverse flexibility of the core is included. The sandwich fuselage envisaged may contain flat, tapered and curved sandwich elements, and a high-order sandwich theory formulation is developed to analyze each of these configurations. The paper includes a brief presentation of the adopted high-order sandwich theory with special emphasis on the application for the analysis of sandwich panels with variable core thickness, and for the analysis of curved sandwich panels. Numerical results obtained for two different mid-plane asymmetric fuselage sections are presented and compared; one with constant core thickness, and one with varying core thickness.
High-Order Analysis of Unidirectional Sandwich Panels With Flat and Generally Piecewise Curved Faces and a “Soft” Core
Authors: Rabinovich Oded , Frostig Yeoshua 
Published: November 2021

Abstract
The bending behavior of a unidirectional sandwich panel with flat and generally piecewise curved faces and a flexible core in the vertical direction is investigated. The studied panels consist of an upper flat face sheet, a core of a variable thickness, and a lower face sheet that can take any geometrical layout described by a piecewise analytical function. The core is assumed to be a two-dimensional elastic medium with vertical and shear rigidities only, and the faces are considered to have membrane and bending rigidities and are made of metallic or composite materials. The field equations and the boundary conditions are rigorously derived using the variational principle of virtual work. The continuity conditions between the various regions of the generally piecewise curved face are presented. Higher order effects in the form of nonlinear deformation distributions through the thickness due to flexibility of the core are incorporated in the proposed analysis. Numerical results in terms of deformations, stresses, and stress resultants are presented for some typical cases of piecewise flat-curved panels. The results demonstrate the capabilities and generality of the proposed model, especially in the ability to predict the high-order localized effects and the high stress concentrations that characterize these panels.
Implication of Anisotropy of Face-Sheets and Core Layer Materials on the Load Carrying Capacity of Advanced Sandwich Panels: Linear and Nonlinear Responses
Authors: Librescu Liviu 
Published: November 2021

Abstract
This paper deals with a comprehensive geometrically nonlinear theory of shallow sandwich shells that includes also the effect of the initial geometric imperfections. It is assumed that the face-sheets of the sandwich structure are built-up from anisotropic materials layers, whereas the core layer from an orthotropic material. As a result of its features the structural model can provide important information related to the load carrying capacity of sandwich structures in the pre- and postbuckling ranges. Moreover, by using the directionality properties of face-sheets materials, possibilities of enhancing the load carrying capacity of sandwich shells/plates are reached. Selected numerical illustrations emphasizing these features are presented and pertinent conclusions on the beneficial implications of anisotropy of face-sheets and core layer materials upon the load-carrying capacity of sandwich panels are emphasized.
Under the present study, the sandwich structure consists of a thick core-layer bonded by the face-sheets that consist of composite anisotropic materials, symmetrically laminated with respect to the mid-surface of the core-layer. The initial geometric imperfection consisting of a stress free initial transversal deflection, will be also incorporated in the study. The loads under which the nonlinear response will be analyzed consist basically of uniaxial/biaxial compressive edge and lateral loads.
A Novel Micro Capacitance Sensor for Studying Hydrodynamics of Particle Laden Flow
Authors: Pokusevski Z. , Evans I. G. , York T. A. , Dyakowski T. 
Published: November 2021

Abstract
Particle laden flows occur in a wide range of industrial applications. Detection of dispersed particles and drops is of enormous importance since they may cause “erosion-corrosion effects” in industrial equipment. This paper presents a novel technique for particle detection. The results show 20 and 50 micron particles detected in the static tests. CFD simulations were carried out in order to design the sensor mounting and its optimal inclination to the flow. It was shown that sensor inclination of 5 or 10 degrees to the flow is highly beneficial. Dynamic tests were carried out and the full results show good agreement with the predicted particle tracks. 50 and 20 micron polyamide particles were detected at air velocities up to 12 metres per second.