bluuebunny/crossref_metadata_2025_split huggingface dataset:
Refrigerative Stereolithography Using Sol-Gel Transformable Photopolymer Resin and Direct Masking
Authors: Murakami Tamotsu , Kamimura Akiya , Nakajima Naomasa 
Published: November 2021

Abstract
The authors have been studying a new fabrication method termed “refrigerative stereolithography” which uses a gel resin layer instead of a liquid layer used in conventional stereolithography. In this paper, we propose the “direct masking method” in which a masking pattern is drawn directly on a gel layer surface to block harmful light exposure of photopolymer resin. With such masks, we can avoid surplus growth only in the regions where it is unnecessary to improve height direction accuracy and resolution. The possibility of surplus growth in the width direction caused by light reflection from the mask surface is pointed out, and the effect is analyzed and confirmed by simulation and experiment. This new surplus growth is termed “reflective surplus growth”. Also, we can solidify the required section shape selectively using the masks and a lamp instead of laser scan patterns. The effectiveness of refrigerative stereolithography with the direct masking method is discussed and confirmed by some experimental results.
A Finite Element Based Die Design Algorithm for Sheet Metal Forming on Reconfigurable Tools
Authors: Socrate Simona , Boyce Mary C. 
Published: November 2021

Abstract
Tooling cost is a major contributor to the total cost of small-lot production of sheet metal components. Within the framework of an academic/industrial/ government partnership devoted to the development of a reconfigurable tool for stretch forming, we have implemented a Finite Element-based procedure to determine optimal die shape. In the reconfigurable forming tool [1], the die surface is created by the ends of an array of square pins, which can be individually repositioned by computer driven servo-mechanisms. An interpolating polymer layer is interposed between the part and the die surface to attain a smooth pressure distribution. The objective of the die design/algorithm is to determine optimal positions for the pin array, which will result in the desired part shape. The proposed “spring-forward” method was originally developed for matched-die forming [2, 3] and it is here extended and adapted to the reconfigurable tool geometry and stretch forming loading conditions. An essential prerequisite to the implementation of the die design procedure is the availability of an accurate FE model of the entire forming operation. The particular nature of the discrete die and issues related to the behavior of the interpolating layer introduce additional challenges. We have first simulated the process using a model which reproduces, as closely as possible, the actual geometry of the discrete tool. In order to optimize the delicate balance between model accuracy and computational requirements, we have then used the information gathered from the detailed analyses to develop an equivalent die model. An automated algorithm to construct the equivalent die model based on the discrete tool geometry (pin-positions) is integrated with the spring-forward method, to generate an iterative die design procedure that can be easily interfaced with the reconfiguring tool. The success of the proposed procedure in selecting an optimal die configuration is confirmed by comparison with experimental results.
Optimum Process Design in Sheet Metal Forming With Finite Element Analysis
Authors: Huh Hoon , Kim Se-Ho 
Published: November 2021

Abstract
Process optimization is carried out to determine process parameters which satisfy the given design requirements and constraint conditions in sheet metal forming processes. The scheme incorporates with a rigid-plastic finite element method for calculation of the final shape and the strain distribution. The optimization scheme adopts a direct differentiation method and a response surface methodology in order to seek for the optimum condition of process parameters. The algorithm developed is applied to design of the draw bead force and the die shapes in deep drawing processes. Results show that design of process parameters is well performed to increase the amount of strain for increasing the strength or to decrease the amount of strain for preventing fracture by tearing. The present algorithm also enhances the stable optimum solution with small number of iterations for optimization.
Stretch Forming Process Modeling: The Role of Modern Stretch Forming Machinery Design and Performance
Authors: Widmann James M. 
Published: November 2021

Abstract
Extrusion stretch forming is used extensively in the aerospace and architectural industries to add contour to extrusions and roll formed sections. Frame members, stringers, wing spars, curtain tracks and many other important aircraft parts are formed with this process. Forming is achieved by pulling an initially straight part in the tensile direction above the material’s yield point and then wrapping the section around a die to add contour. Local buckling and wrinkling that might appear in a pure bending operation can be avoided. There is current interest in improving the process for greater repeatability and less part rework to reduce cost while achieving tighter tolerances (e.g. [1,2]). The stretch forming die plays a significant role in the process. To this end researchers are interested in quicker die development techniques using non-linear beam theory and non-linear finite element modeling of the forming process. For a complete analytical picture of the process, a close look at the stretch forming machine’s performance must be included in the process model. Two major areas of machine performance are important; machine deflections and hydraulic control system performance. This paper provides a brief overview of the extrusion stretch forming process and then focuses on the structural and control system design of the modern stretch forming machine. Analytical models of the machine deflection as well as its hydraulic control system are developed. A short discussion concerning the difference between traditional “pressure forming” and modern CNC position forming is also included. Insight into the limitations of traditional PID control for the stretch forming machine can be seen from the analysis. It is evident that these machine models must be used to complete the process model to effectively create die designs for close tolerance and highly repetitive part production.
Aluminum Tailored Blank Welding Using Laser Beam Shaping and Twin-Spot Optics
Authors: Hsu Rey , Fliss Stefan , Heinemann Stefan 
Published: November 2021

Abstract
The use of aluminum tailor welded blanks in the automotive industry continues to grow due to the fact that aluminum is lightweight and the characteristics of the tailor welded blanks. It has been found that welding of aluminum blanks with a CO2 laser is difficult but doable in a production environment. By using a high power CW Nd:YAG (Neodynium dopped Yittrium Aluminum Garnet) laser. It is possible to obtain sound results with a much wider process parameter window. However, currently, high power CO2 lasers (in the range of 8 kW) are still the dominate laser source in North America steel tailor welded blank companies. Will these lasers be able to weld aluminum tailored blanks if the demand for aluminum tailor welded blanks increases? This study employed twin spot and beam shaping methods to weld 1mm and 2 mm tailored blanks together using a high power (9 kW maximum) CO2 laser for both 5754-O and 6111-T4 alloys. The results show that high power CO2 lasers can be used to weld 5754-O and 6111-T4 aluminum alloys with very precise parameter settings. However, using beam shaping is more critical than using twin spot for 1 mm thick aluminum blanks. Once the correct parameters are applied for using beam shaping, the cup test results are better than using twin spot.
Measurement and Analysis of Tip Growth
Authors: Steele Charles R. , Dumais Jacques , Shaw Sidney L. 
Published: November 2021

Abstract
Tip growth is basic and deceptively simple. A single cell has a wall that is cylindrical with a prolate spheroid as an end cap. The growth takes place in the end cap. The mechanical loading which drives the growth consists of turgor pressure of magnitude 5–10 atmospheres. We report recent measurements on the geometry of the growth that provide detail of the shape of the end cap. In addition, fluorescent beads were placed at points on the cap, whose positions with time were recorded.
A Lagrangian formulation provides the kinematics of the growth process, and indicates that for steady-state, axisymmetric growth, the current velocity of a bead depends on only the geometry and the stretch ratio. The ratio of current mean strain rate to mean stress provides a coefficient of growth rate. This depends on position, which can be interpreted as a dependence on the stretch ratio, i.e., the past history of the wall element. Thus a simple mechanical description appears to be appropriate. However, the stability of the process has not yet been considered.
Tensegrity and the Emergence of Complex Mechanical Behavior in Living Cells
Authors: Ingber Donald E. 
Published: November 2021

Abstract
Existing engineering models of cell mechanics fail to incorporate current knowledge of the molecular intricacy of living cells. An alternative model of cell structure based on tensegrity architecture suggests that complex mechanical behaviors emerge in cells from collective interactions among different cytoskeletal filaments which are organized within hierarchical networks that are tensionally prestressed to ensure shape stability. This discrete network model has been controversial because it goes against prevailing views. In this article, I will review the concept behind cellular tensegrity, explain how it has become translated into mathematical terms over time, and provide reference to recent studies which provide experimental verification of predictions that have arisen from this theoretical model. Taken together, these findings suggest that tensegrity represents a robust and unified model of cell mechanics which, in contrast to alternative approaches, may facilitate future understanding of the link between mechanics and biochemistry.
Mechanics of Angioplasty: Wall, Balloon and Stent
Authors: Holzapfel Gerhard A. , Schulze-Bauer Christian A. J. , Stadler Michael 
Published: November 2021

Abstract
Studying the solid mechanics of angioplasty provides essential insight in the mechanisms of angioplasty such as overstretching the disease-free tissue, plaque disruption or dissection, redistribution inside the wall and lipid extrusion etc. We desribe our current understanding of the mechanics of angioplasty based on the example of a human iliac artery with an eccentric stenosis. We outline a new approach which has the potential to improve interventional treatment planning, to predict the balloon and stent-induced wall stresses as well as the dilation success. In particular, we use MRI to obtain accurate geometrical data for the vessel wall and plaque architecture and to identify their different types of soft (biological) tissues and calcifications. One issue is to characterize the quasistatic stress-strain response of these components in both axial and circumferential directions. We present new experimental results showing strong nonlinearity and anisotropy. Another issue is to identify predominant directions of each component by analyzing orientations of cellular nuclei. The morphological and mechanical information is used for the elastoplastic constitutive model designed to capture the finite strains of the stenotic artery during angioplasty. The three-dimensional model is fitted to the experimental data. Associated material parameters, corresponding to the different tissues of the stenosis, are presented. The numerical part outlines briefly the concept of the finite element model and, based on a computational structural analysis, discusses the mechanism of angioplasty for the considered type of stenosis.
Friction Effects in Pipe Flow of Phan-Thien-Tanner Fluids
Authors: Letelier Mario F. , Siginer Dennis A. 
Published: November 2021

Abstract
An analytical study of the friction law for rectilinear flow a Phan-Thien-Tanner fluid is presented. The flow is assumed steady and the pipe circular. The equations of motion are solved and the velocity, rate of flow, and friction factor are determined. Friction effects are related to the Reynolds number and to other flow parameters, such as the Deborah number.
Appraisal of an ESF Radial Plate Clutch With Cooling Flow Using a NNF CFD Solver
Authors: Ellam Darren J. , Atkin Raymond J. , Bullough William A. 
Published: November 2021

Abstract
To aid the application of electro-structured fluid (ESF) devices, a virtual two plate radial clutch is examined in a pre-prototyping exercise to estimate the effect of a radial cooling flow on pre-set torque transmission. A throughflow of ESF will act to keep the fluid temperature under control making such devices more reliable over a wider operating range.
The ESF is treated as a Bingham viscoplastic material and clutch behaviour is investigated under steady state isothermal conditions. The resulting two-dimensional non-Newtonian fluid (NNF) model is solved using a computational fluid dynamics (CFD) package. The results are partially verified using analytical analysis and compared with sparse experimental data. This work is expected to lead to a more complex CFD model for which analytical methods will not be available.
Indications are that, for realistic rates of throughflow, torque transmission should not be overtly affected. Hence the cooling of slipping ESF clutches by throughflow can be contemplated.
Symmetry Breaking in ER and MR Fluids Under Shear
Authors: Tao R. , Zhang J. , Shiroyanagi Y. , Tang X. , Zhang X. 
Published: November 2021

Abstract
The behavior of an electtorheological (ER) chain under a shear force is investigated theoretically and experimentally. Contrary to the conventional assumption that the ER chain under a shear force becomes slanted and breaks at the middle, we have found that there is symmetry breaking. When the shear strain is small, the chain becomes slanted with a space gap between the first and second particles (or between the last and next last particles). As the shear strain increases, the gap becomes wider and wider. When the shear strain exceeds a critical value, the chain breaks at the gap. The experiment also confirms that an ER chain under the shear breaks at either end, not at the middle. This symmetry breaking reflects the space’s anisotropy, which is the result of the applied electric field.
The Control of Impulsive Forces Using Electrorheological and Magnetorheological Fluids
Authors: El Wahed Ali K. , Sproston John L. 
Published: November 2021

Abstract
This paper is concerned with an experimental assessment of the application of both Electrorheological (ER) and Magnetorheological (MR) fluids in the control of impulsively applied loads. The ER device was built as a squeeze cell incorporating a chemically simple ER fluid, consisting of a suspension of a polymeric compound in a dielectric liquid carrier, sandwiched between two electrodes which, during impact, move towards each other, whilst the MR device was a commercially available vibration absorber. Each device was mounted in an experimental drop-hammer rig, which was capable of determining the instantaneous responses of the fluids for a range of applied loads.
The transient characteristics of the devices were assessed for various mechanical force levels and, for the ER device, under DC excitation of the fluid in conjunction with a digital controller to provide a constant applied electrical field.
Input and output force levels were monitored using a dedicated data acquisition system in conjunction with a PC enabling the dynamic response of the devices to be determined using a combination of displacement, force, velocity and acceleration measurements.
A Novel Design for Producing Fine-Celled Foams of Plastic/Wood-Fiber Composites
Authors: Rizvi Ghaus M. , Park Chul B. 
Published: November 2021

Abstract
This paper presents an innovative system design for production of plastic/wood-fiber composite foams based on a chemical blowing agent (CBA). Wood-fiber inherently contains moisture, which adversely affects the foam processing and the resultant cell morphology. To improve the cell morphology, the moisture content in the final foam should be minimized. A novel system design is presented for achieving this goal. Undried wood-fibers were processed together with HDPE, CBA and a coupling agent (CA) in a tandem extrusion system. At the interconnection of the two extruders, a vent was provided to purge the moisture into the atmosphere. HDPE/wood-fiber composite foams were produced on this system and on a single extruder without the vent, for comparison. The cellular morphology and volume expansion ratios of the foamed composites were characterized. The foams produced on the newly developed tandem system exhibited significantly improved cell morphology and surface quality.
Failure Analysis of Hybrid Armor Under High Velocity Impact
Authors: Mahfuz Hassan , Zhu Yuehui , Mamun Wahid A. , Haque Anwarul , Jeelani Shaik 
Published: November 2021

Abstract
Failure analysis of hybrid integral armor has been performed using finite element method. LS-DYNA3D code has been employed to investigate the response of an integral armor under high velocity impact. A 3-D FE model consisting of the various layers of the armor has been developed and subjected to transient dynamic loading. The analysis is based on actual experiments conducted in a gas gun set up. V50 velocity for a Fragment Simulating Projectile (FSP) has been considered, and the corresponding responses have been investigated to assess the failure of the armor at the ballistic limit. The investigation consisted of three successive studies; first, a base model was developed to have preliminary ideas about the energy absorption and the depth of penetration. Second, interface gap elements were introduced at the rubber interfaces, as the delamination across the rubber layer seemed critical in the failure of the armor. Third, a user defined material model has been introduced to account for the fracture behavior of ceramic. Details of the development of the models, and the analysis of failure are presented in this paper.
Control of a Hydraulically Driven Flexible Manipulator Using Sliding Mode
Authors: Liu Y. , Handroos H. 
Published: November 2021

Abstract
A class of multi-link, structurally flexible and hydraulically powered manipulators are considered for an application of using sliding mode control to track a trajectory of end-tip. Due to the particularity of dynamic model of system and for the purpose of control synthesis, it is required to a modification mapping from the generalized coordinate to the task space, and position of end tip is defined as output of system for the tracking target in the task space. The control based on the model is developed to exploit the full potential of flexible hydraulic manipulator. In the paper, the control performance is demonstrated by simulation on PATU 655 log crane, that is a three flexible links manipulator with the actuation of the lift and jib hydraulic servo systems in the presence of considerable uncertainty.
Pneumatic Pipe Modeling: Theory and Experimental Approach—Part II
Authors: Bideaux E. , Scavarda S. 
Published: November 2021

Abstract
In fluid power systems, lines or pipes can have a predominant effect on dynamics. Although many studies have been carried out on hydraulic pipe modeling, there are only a few existing approaches for such problems in pneumatics. This paper proposes an experimental work in modeling of pneumatic pipes. A short state of the art situation, the nature of this problem, and different approaches of modeling pneumatic pipes are presented in Pneumatic Pipe Modeling: Theory and Experimental Approach (PART I). As the simulation of system with pipes may need an important computing time, it is crucial to use the adequate model. While it is not difficult to develop theoretical models, we need to tune them by adjusting the unknown parameters such friction factor and the thermal exchange parameter. We introduce then an experimental method to evaluate these parameters. The robustness of the models is proved through several examples and in order to validate our propositions, we compare experimental trails to the results given by the simulation.
On the Response of Modulated Doublet Modes to Traveling Wave Excitation
Authors: Chang J. Y. , Wickert J. A. 
Published: November 2021

Abstract
The forced vibration of arotationally periodic structure when subjected to traveling wave excitation is discussed, with emphasis placed on the steady-state response of doublet modes having either repeated or split frequencies. Such vibration modes have spatially modulated shapes defined by (i) the numbers of nodal diameters present in the limiting case of axisymmetry, and (ii) certain additional, superposed, contaminating Fourier harmonics which distort their appearances. The natural frequency and mode structure of a model periodic structure is discussed in the context of an otherwise axisymmetric disk having evenly-spaced, sector-shaped, line distributions of stiffness and inertia. Through a perturbation analysis, the contamination wavenumbers present in a doublet having repeated frequency are shown to comprise two subsets, the members of which have sine and cosine coefficients of the same, or of differing, signs for each wavenumber present in the mode shape’s Fourier expansion. That structure for the wavenumber content is explored further with respect to the response of repeated and split doublets to a harmonic traveling wave excitation. The individual Fourier components comprising a modulated doublet mode shape can propagate in the same direction as the excitation, or opposite to it, depending on the wavenumber of the excitation and the subset to which the contamination wavenumber belongs. The response of the split frequency doublets and the circumstances under which traveling or standing wave responses, or a blend of the two, can occur in the structure’s reference frame are examined and discussed in the context of the model periodic structure. The qualitative character of the response, the forward or backward propagation direction of each mode’s constituent wavenumber components, and the phase speeds of those components are discussed in illustrative case studies.
Modal Control of Flexible Systems Using Distributed Sensing
Authors: Nagarkatti Siddharth P. , Rahn Christopher O. , Dawson Darren M. , Zergeroglu Erkan , Malatpure Aniket A. 
Published: November 2021

Abstract
In this paper, we design a modal controller for conservative flexible systems that uses distributed sensing. Spatial filtering of the distributed displacement and velocity measurements based on the system eigenfunctions prevents spillover instabilities in the closed-loop system. The proposed control is proven to stabilize a discrete set of controlled modes without destabilizing the remaining, residual modes. We then apply the theory to a single flexible link robot arm and experimentally demonstrate the feasibility of the proposed control strategy. The experiments use high speed video feedback with image processing to determine the spatial beam curve. The controller quickly damps the first modal response without causing instability in the remaining modes.
Design Curves for 3D Reinforced Composite Laminated Double Cantilever Beams
Authors: Mabson Gerald E. , Deobald Lyle R. 
Published: November 2021

Abstract
Design curves for 3D reinforced composite laminated double cantilever beams (DCB) are developed and presented. Z-pin and stitch reinforcements are considered. These curves may be used by designers and analysts in specifying Z-pin and stitch fields for preliminary design to arrest the progression of delaminations in laminated composite structures.