bluuebunny/crossref_metadata_2025 huggingface dataset:
Polystyrene / Acrylic Blends and Their Application in Foam Production: Part Two — R134a Blowing Agent
Authors: Smith Peter J. , Cross Bernard J. , Corr Stuart , Gendron Richard , Daigneault Louis E.
Published: January 2022

Rheological data, at elevated temperature and pressure, for pure polystyrene, pure acrylic and polystyrene / acrylic blends containing R134a are contrasted with similar data for polymers containing R22 and R142b blowing agents. The variation of polymer melt viscosity with blowing agent concentration (R22, R142b and R134a) is interpreted in terms of equilibrium blowing agent solubility and molecular plasticization effects. Equilibrium solubility data for all blowing agents are presented.

Information on the variation of extruded foam density with blowing agent content for pure polystyrene, pure acrylic and polystyrene / acrylic polymer blends is described. Inclusion of modest quantities (∼10% w/w) of acrylic into the polystyrene is shown to allow the manufacture of reduced density foams using R134a blowing agent. Inclusion of the acrylic also stabilizes extruder pressure profiles and facilitates easier plant operation.

The observed reduced foam density, both with polymer composition and blowing agent content, and easier extruder operation are explained in terms of blowing agent solubility and secondary relaxation processes associated with the acrylic component.
More Experiments on Thermoplastic Foam Sheet Formation
Authors: Lee Shau-Tarng
Published: January 2022

This paper discusses effects of formula/processing parameters of polyethylene foam extrusion on foam sheet characteristics, such as: foaming efficiency and open cell percentage. The former arises economics issue, and the latter performance. Earlier publications suggest that surface to volume ratio has profound impacts on thermal and gas loss to become a key processing factor for foaming efficiency during sheet formation. More experiments were performed to investigate foam density, cell density and open cell percentage. It was found that foam density reaches a minimum then increases as cell density increases. Open cell percentage experiments offers a reasonable correlation between cell density and foam density. Therefore, cell wall strength becomes a limiting factor for optimal foaming, which was confirmed by the take-up speed experiments.
A Reactive Algorithm for Micro-Robotic Vehicles
Authors: Dohner Jeffrey L.
Published: January 2022

In this paper a guidance and control algorithm for a simple robotic vehicle (called a “bug”) cooperatively operating in a swarm of vehicles is presented. A bug is assumed to have limited communication, sensing, memory, and compute capability. Therefore, it is assumed that its behavior is reactive in nature. Bugs travel in swarms and track scent emanating from scent sources in unknown environments.

Since bug behavior is reactive, the guidance and control algorithm which is used to define its motion must not be computationally intensive. The guidance and control algorithm presented in this paper is subdivided into three, simple to implement, non-computationally intensive sub-algorithms. They are a sensory compensation sub-algorithm, a guidance sub-algorithm, and a control sub-algorithm. The sensory compensation sub-algorithm uses a simplified potential model of the local scent environment to cancel discovered scent source effects on its sensory perception, the guidance control algorithm produces a desired trajectory for bug motion which is based on a simplified friction model, and the control sub-algorithm forces the bugs actual trajectory to the desired trajectory. Bug cooperation is performed by using the concepts of social rank.
An Intelligent Tool With Adaptive Structure for L-Bending Process of Sheet Metals
Authors: Yang Ming , Manabe Ken-ichi
Published: January 2022

In this study, an intelligent tool system for flexible L-bending of sheet metals is developed. The punch and die are adaptively actuated by hydraulic cylinders incorporated in the punch and die, respectively. An adaptive structure with high stiffness and motion accuracy is designed and compared with a formerly developed one. The tool system can basically change the profile of the tools and pressure distribution along the workpiece during the L-bending process. The system is characterized by its capability to bend the workpiece to various bending radii and bend angles for different materials without tool change. Process control paths for obtaining desired bend radii and angles are determined off-line by a numerical simulation using the elasto-plastic model. The paths are stacked into a simulation database and used for real-time control of the L-bending process. The measured data from the sensors are input into a computer for controlling the actuators and learning the control model by comparing it with the simulated data. Several experiments have been carried out for obtaining various bend radii using two kinds of materials, SPC and aluminum alloy. The experimental results corresponded not only to various bending radii but also different materials. In addition, higher accuracy of the process control has been achieved by improving the structure of the tool system and learning the process control model. These results prove the validity and reliability of the proposed intelligent tool system.
Performance Comparison of Magnetorheological and Electrorheological Materials in Adaptive Structural Applications
Authors: Yalcintas Melek , Dai Heming
Published: January 2022

Magnetorheological (MR) and electrorheological (ER) materials show variations in their rheological properties when subjected to varying magnetic and electric fields respectively. They have quick time response, in the order of milliseconds, and thus are potentially applicable to structures and devices when tunable system response is required. When incorporated into an adaptive structural system, they can yield higher variations in the dynamic response of the structure. This study presents a detailed analysis of vibration control capabilities of adaptive structures based on MR and ER materials, and compares their vibration minimization rates, time responses, and energy consumption rates. Homogenous one-dimensional MR and ER adaptive beam configurations were considered. Structural dynamic modeling approach was discussed, and vibration characteristics of MR and ER adaptive beams were predicted for different magnetic and electric field levels. In addition to the model predictions, actual MR and ER adaptive beams were fabricated and tested. Both studies illustrated the vibration minimization capabilities of the MR and ER adaptive beams at different rates and environmental conditions. The relative performances of both MR and ER adaptive beams were discussed in detail and their advantages and disadvantages were listed.
Dynamic Characterization of Grid Stiffened Composite Panels for Active Structural-Acoustic Control
Authors: Newbury Kenneth , Glaese Roger , Leo Donald , Anderson Eric
Published: January 2022

This paper presents a dynamic characterization of a sample plate of a grid stiffened composite material being developed for use in launch vehicle payload fairings. First, experimental modal analysis is performed to identify the plate’s global modes. The global modes are used for finite element model correlation and for a sound power radiation study which identifies the dominant radiator modes. Next is a strain transfer study using piezoceramic actuators bonded to the plate surface and to the stiffener ribs. Efforts are focused on the ability to sense and excite the dominant radiator modes using the piezoceramic actuators.
Enhanced Piezoelectric Shunt Design
Authors: Park Chul H. , Kabeya Kazuhisa , Inman Daniel J.
Published: January 2022

Piezo ceramic patches connected to electronic shunt circuits have formed successful vibration reduction devices. Here a new shunt circuit design with additional capacitors is presented. One drawback of existing electronic shunt circuits is the large inductance required when suppressing low frequency vibration. Also, the large internal resistance associated with this high inductance value exceeds the optimal design resistance needed for vibration suppression. To solve these problems, a modified and improved piezoelectric shunt circuit is designed by connecting additional capacitors in parallel. This design is experimentally demonstrated for a desired tuned mode of an aluminum beam. The results indicate that improved electronic passive damping can significantly reduce the structural vibration response with half of the inductance previously required.
Adaptive Shape Control of Precision Membrane Antennae and Reflectors
Authors: Jenkins C. H. , Kalanovic V. D. , Faisal S. M. , Padmanabhan K. , Tampi M.
Published: January 2022

A resurgence of interest in membrane structures in space is developing after a brief period of activity about two decades ago. This renewal is motivated in large part by the great potential for reduced launch mass and stowed volume that membrane structures can afford. Applications for such structures range from planar configurations in solar sails, concentrators, and shields, to inflatable lenticulars for radar, radio, and optical purposes. Three key factors are paramount for the success and user acceptance of this technology: deployment, longevity, and performance. Performance hinges critically on the precision of the membrane surface.

Nonlinear controllers developed to improve performance of such systems are often dependent on state estimation and parameter identification procedures. The existence of these procedures, within the control strategy, increases the size of the algorithms, limiting the system performance in real-time. The research presented has as a main objective to create an intelligent controller, based on feedback error learning, which is capable of extracting performance information from precision large membrane deployables, and subsequently using this information to achieve maximum surface precision.

This paper addresses the problem of modeling and controlling a class of nonlinear systems that can be considered as highly compliant structures, specifically planar and inflatable membranes, which are represented by complex nonlinear multi-variable models. Methods of noncontact local state estimation are considered in order to provide feedback on the membrane shape, which would then be coupled with a mathematical model of boundary perturbation and/or thermal effects for control efforts.
Robust Position Control of Flexible Adaptive Structures With Embedded PZT Actuators
Authors: Wilson D. G. , Parker G. G. , Starr G. P. , Robinett R. D.
Published: January 2022

In this paper we present a hybrid Sliding Mode Control (SMC) and Constant Amplitude Feedback Control (CAFC) architecture for a slewing flexible adaptive structure. The SMC controller is used to servo the adaptive structure and the CAFC is used to suppress vibrations of the flexible structure. In addition a traditional Linear-Quadratic Regulator (LQR) controller was developed and tested. This system consists of 1) a single-axis servo DC motor and encoder for large angle slewing and 2) a graphite/epoxy composite structure with embedded strain sensors/actuators for active vibration suppression. The results of this study include the analytical development and numerical simulation verification. Minimum time maneuvers based on an equivalent rigid structure are used to slew the flexible active structure. Numerical simulation studies were performed to compare the SMC/CAFC controller with the LQR controller. A nonlinear optimization algorithm was used to determine optimal component weights for the LQR control weighting matrices Q and R. Both controllers were also compared to a passive SMC case to show benefits of using active vibration control. Several case studies are reviewed that involve minimizing tracking and residual tip deflection errors. The results showed a reduction in residual vibration for both cases studied. A final test was performed that investigated the robustness to parameter variations by increasing the tip mass. Both control architectures showed favorable results, but the LQR controller required larger control effort.
Quantization Effects on Digital Control of Structural Vibration
Authors: Sun Jian , Shahin Ali. R.
Published: January 2022

The implementation of a digital control system for the response of a structure will introduce nonlinearities due to the finite-word-length effects. This paper investigates regions of stability, possible existence of limit-cycles and unstable regions for a SISO digital control system for structural vibrations due to quantizer. A cantilever plate is modeled by the finite element method and controlled by a digital control system.
Crash Analysis of Two Vehicles in Frontal Impact Using Adaptive Artificial Neural Networks
Authors: Omar Tarek A. , Eskandarian Azim , Bedewi Nabih E.
Published: January 2022

An advanced recurrent Artificial Neural Network (ANN) was developed and used to model and analyze the frontal impact of two different vehicles. The main factors affecting the vehicle response — in case of frontal impacts — are the impact velocity and the structural characteristics of the vehicle. Each vehicle was represented by a corresponding ANN, and the mutual interaction between the two vehicles during the impact was considered in the ANN input. An adaptive learning technique was used to correct both the connections’ weights and the steepness factor of the neurons’ continuous activation functions to reduce the computation time during the supervised learning phase.

Nonlinear finite element (FE) simulations were performed for two different vehicle models in frontal impact scenarios using different impact velocities. The results obtained by the FE simulations were used in training and testing the proposed ANN model. The passenger compartment acceleration of the vehicle during the first 100 ms of the impact event was the main criteria considered in the crash analysis. The performance of the proposed ANN configuration was very good in both training and testing phases. The proposed technique explained the ability of the adapted ANNs to store the nonlinear structural characteristics of the two vehicles after a successful training phase. These two networks were then used together to predict a new different impact scenario. The predicted velocity and acceleration curves for the new impact scenario correlated well with the corresponding curves obtained from the FE simulation.

The current technique was applied only for frontal impact scenario, however, further research will be considered to extend the methodology to be applicable for both offset and oblique impact scenarios.
Sensitivity Analysis of Static Side Door Intrusion
Authors: ElHor Hassan H. , May Thomas A. , Jurosek Mike L.
Published: January 2022

This paper identifies the most important parameters that contribute to the strength of the door in a static intrusion, in order to satisfy the FMVSS 214 Standards. Side door intrusion requires the door to resist three stages of loading at several crash distances: initial (6″), intermediate (12″) and peak (18″). Thickness, shape and material of the side door beam are among the most important parameters considered in this study, latch and hinge strengths are also included.

A sensitivity evaluation analysis is performed where the main objective is to investigate the sensitivity of those parameters to changes, and their impact on the structural performance of the side door and its resistance. The various results are presented in tables and graphs to show the effect of each of those parameters.
Numerical Simulation on Turbulent Buoyant Jets in a Flowing Stratified Ambient
Authors: Hwang Robert R. , Chiang T. P.
Published: January 2022

In this study, an investigation using a 3-D numerical model, which treats conservation of mass, momentum and salinity simultaneously, was carried out to study the detailed flow field of a buoyant jet in a uniform cross-stream of stable linearly stratified environment. A k-ε turbulence model was used to simulate the turbulent phenomena and close the solving problem. Results indicate that the numerical computation simulates satisfactorily the plume behavior in a stratified crossflow. The ambient stratification tends to inhibit the flow development by inducing pairs of vortex as the plume flowing downstream and results in causing the jet-flow oscillation from its maximum height-of-rise.
Application of Embedded Parallelism to Large Scale Computations of Complex Industrial Flows
Authors: Tafti D. K. , Wang G.
Published: January 2022

The paper combines advances in computational fluid dynamics with advances in computer architectures and programming paradigms to extend the state-of-the-art in large-scale computations of complex industrial flows. The present work combines traditional distributed memory programming with shared memory programming, and hence has the advantage of imposed data locality of the former as well as the ease and flexibility of the latter. Conceptually, it manifests the architectural features of Distributed Shared Memory (DSM) and complements the concept of hierarchical domain decomposition for cache friendly algorithms on microprocessor based parallel systems. We demonstrate this concept through three-dimensional simulations of developing flow and heat transfer in a multilouvered fin array.
Isothermal Flow Distribution in Coupled Manifolds: Comparison of Results From CFD and an Integral Model
Authors: Jones G. F. , Galliera J. M.
Published: January 2022

Isothermal, incompressible flow distribution in the coupled manifold continues to be of interest to the industrial, engineering, and scientific communities. Several investigations carried out in the past have considered the suitability of a CFD code (Fluent) for predicting detailed velocity and pressure distributions for three dimensional dividing flow in a 90° tee junction. Results from these cast doubt on the successful use of CFD to model the complex flow in a tee. The focus of the present work is to determine if the same code can accurately predict the larger-scale features of three dimensional branching flows and in a coupled manifold having three risers. Simulations were performed for flow in the coupled manifold and for both laminar and turbulent, dividing and combining flow in a tee section for a broad range of flow branching conditions. The ratio of riser diameter to manifold diameter is fixed at 0.75 for this study. The turbulent models used are the standard and renormalization group k-ϵ models. All constants in these models are set to their respective default values. Static pressure re-gain factors are calculated from the results of CFD simulations and are favorably compared with the data of others. These data are then used in an existing integral model for flow in coupled manifolds. The good agreement between the results from the integral model and the CFD model for flow in the coupled manifold attests to the suitability of the integral model for this problem. The advantage of the integral approach is the speed at which the problem can be solved by the computer, and the fact that there is no need for the time-consuming and expensive geometrical modeling and mesh generation normally associated with finite element and finite difference models.
Skin Friction Measurement in Low Reynolds Number Shallow Open Channel Flows
Authors: Ramachandran Shyam S. , Balachandar Ram
Published: January 2022

The present study was conducted to measure skin friction in shallow open channel flows at low Reynolds numbers. The study was aimed at extending the database towards lower values of Reynolds number (180 ≤ Reθ ≤ 480) based on the momentum thickness. The validity of the semi-empirical laws characterizing the turbulent boundary layer is examined. The method for accurately determining the wall shear stress and hence the skin-friction coefficient in an open channel is verified.
Integration Methodology for Implementing a Teleservice Engineering System
Authors: Lee Jay , Tsai John
Published: January 2022

Machine maintenance is a critical task to assure operations’ efficiency, reliability, and safety. As manufacturing becomes more globalized, the challenge is how to leverage information technologies to sustain high-quality and just-in,-time maintenance services to global facilities.

This paper introduces a methodology for implementing a teleservice engineering system. This methodology provides manufacturers with a multi-level systematic framework to monitor any highly complex manufacturing system such as a distributed automated storage and retrieval or materials handling system.
A Mechanistic Force Model for Contour Turning
Authors: Gajjela Rohit R. , Kapoor Shiv G. , DeVor Richard E.
Published: January 2022

In this paper a mechanistic model for contour turning is presented. A chip load model is developed for general contour turning process. Analytical expressions are derived for chip thickness and chip load in a simple case of contour turning. A generalized numerical procedure is also developed for evaluation of various cutting parameters like cutting velocity, effective lead angle, chip thickness, chip load, normal rake angle, and chip flow angle. The effects of these parameter variations on the cutting forces are analyzed. As a special case hemispherical turning is considered for model validation. Simple straight turning tests are employed for model calibration. The interference between tool and workpiece and ploughing are identified as possible causes for an abrupt increase observed in the cutting forces. Use of circular inserts with large nose radius eliminates this problem. Experimental validation is done with circular inserts.
On the Forces and Temperatures due to Flank Wear in Hard Turning
Authors: Wang J. Y. , Liu C. R.
Published: January 2022

The computation of cutting temperatures under flank-worn condition needs the knowledge of the forces due to flank wear and chip formation. Methods determining forces due to flank wear have been based on the assumption that the chip formation process remains constant as the tool flank is progressively worn, such that the force due to flank wear can be isolated from the total cutting force measured. This assumption continues to be used in literature despite the fact that there is evidence disproving it. Error introduced by this assumption for computing work surface temperature can be significant, as shown by the result of this paper.

In this study, the forces and temperatures due to flank wear were investigated using a newly developed thermal model and orthogonal hard turning experiments without the above assumption. First, the microstructural change in chips was used to determine the heat carried by the work and chip. Then the heat generated and the heat partition coefficients at both tool-work and tool-chip interfaces were obtained by solving the heat partition equations of the thermal model. Finally, shear forces at the tool-work interface and tool-chip interface that were coupled in the cutting process were determined independently without using cutting force measurement. The results also show that, as flank wear increases, the force due to flank wear determined by this method is larger and the interface temperatures are higher than those obtained based on the conventional assumption.
Effect of the DCEP and DCEN Duration Time on the Penetration in AC Plasma Arc Welding of Aluminum Alloys
Authors: Zheng B. , Wang Q. L. , Kovacevic R.
Published: January 2022

The heat transferred to the workpiece plays a main role in the control of the full penetration weld bead during AC plasma arc welding of aluminum alloys in the keyhole mode. In order to better understand the effect of the heat generated by the AC arc on the weld formation, a low frequency-changed AC welding power source was developed. When the direct current electrode positive (DCEP) arc initiates, the heat generated in the cathodic region by the high cathodic potential is greater than that in the anodic region when the direct current electrode negative (DCEN) arc initiates. The role of the DCEP arc is not only to remove the oxide film on the workpiece, but also to provide the coming DCEN arc with more heat to melt and penetrate the workpiece. To guarantee the weld formation, the rule of maximum-width cleaning area is not acceptable during AC PAW of aluminum alloys in the keyhole mode.
Technologies for Flexible Fixturing and Higher Speed Part Handling in Automated Automotive Sheet Metal Assembly
Authors: Bone Gary M. , Yuen Ka-Ming
Published: January 2022

A lack of fixturing flexibility and of high speed handling of non-rigid parts are two important problems in automotive sheet metal assembly operations. This paper describes the development of two unique grippers for flexible fixturing of automotive sheet metal parts, and of two methods for the vibration control needed for high speed handling of non-rigid parts. Each gripper is designed to execute a 3-D fixturing strategy which does not require accurate initial part placement, and provides a large number of valid fixturing solutions. Both grippers are tested on several automotive parts. With the first design, the average standard deviation of the parts’ location before fixturing of 0.5 mm was reduced to 0.01 mm after fixturing. The methods of vibration control may be used with most of the industrial robots used for part handling. At a speed of 1 m/s the LEC method reduced the vibration amplitude by 33% after four learning trials. At 0.5 m/s the ICS method reduced the vibration amplitude by 60% and the settling time by 67%.
Planning and Control of Automated Assembly Systems
Authors: Reinhart G. , Cuiper R.
Published: January 2022

This contribution describes an assembly planning methodology in a concurrent engineering environment and a supporting computer system featuring continuous data management and standardized data exchange. The assembly planning is related to results available from the product’s designer and suitable computer tools provide support for each task. There are 5 major groups of input information that is needed for the various tasks of assembly planning. Data created during planning are stored in an object-oriented database to avoid conversion and can even be re-used directly for start-up or production. Therefore the communication between the computer tools themselves and between the tools and the real automated devices has been standardized according to MMS and implemented as CORBA-objects. An equally important system characteristic is represented by the analyses based on the planning status; they can be applied throughout the planning process. Increasingly detailed and realistic analyses are thus possible during the whole planning process.
A Structured Approach for Assembly Planning
Authors: Rea Heather J. , Falconer Richard A. , Murray James L. , Simmons John E. L.
Published: January 2022

Instructions on how to assemble a product, known as assembly plans, are traditionally presented to operators in the form of a paper document. The quality, clarity and format of this documentation rely largely on planning engineers’ experience and expertise. Inconsistencies can occur from planner to planner or across project departments which effect product quality. This paper presents a novel structured approach to assembly planning for initial application in the small batch, high technology, precision products sector (eg avionics, mechatronics, electronics). The structured approach capturing best practice is designed to assist experienced planners as well as providing a mechanism for training new planners. The common and variable requirements of assembly planning and information delivery systems in the application sector have been researched and defined.
A Study on the Life Cycle Simulation for the Post Mass Production Paradigm
Authors: Umeda Yasushi , Nonomura Akira , Tomiyama Tetsuo
Published: January 2022

The environmental issues require a new manufacturing paradigm, because they are caused inevitably by the current mass production and mass consumption paradigm. This paper proposes a new manufacturing paradigm called the “Post Mass Production Paradigm (PMPP).” PMPP advocates sustainable production by decoupling economic growth from material and energy consumption. For examining feasibility of PMPP, this paper describes a life cycle simulation tool. Examples of simulation results illustrate that the environmental impacts can be drastically reduced without decreasing profits of a company by executing services of maintenance and reclamation.
Environmentally Conscious Manufacturing Project Contingency Planning
Authors: Olson Walter W.
Published: January 2022

The framework for environmentally conscious manufacturing in industry is the life cycle assessment structure developed by the Society of Environmental Toxicology and Chemistry and incorporated into ISO 14000 Environmental Management Systems. Plant managers subject to this standard have the responsibility for environmental improvement projects. Often, applying these projects creates significant risks, particularly if the project is unsuccessful or requires a new technology that has not been widely applied. Therefore, plant managers need a method of identifying the risks such that contingency plans can be drafted. In this paper, a method for identifying potential environmental states in light of improvement projects is illustrated.
An Adaptive Tool Path Generation Algorithm for Precision Surface Machining
Authors: Lin Y. J. , Lee T. S.
Published: January 2022

In this paper an adaptive CNC tool path generation algorithm for precision machining of parts with free-form surfaces is proposed. It is aimed at developing a generic CNC tool path generation methodology suitable for machining parts having analytical curves/surfaces and/or sculptured (parametric) surfaces, as opposed to most existing NC programming techniques which are unable to handle free-form surface cutting. The proposed algorithm is desired to be robust that it can be applied to generate tool paths for CAD models having both two- and three-dimensional curves and/or surfaces. In the method, a parametric surface curve on a three-dimensional sculptured surface is approximated by a sequence of linear segments. From the current reference point of the cutting tool, the method has the capability of predicting the next reference point of the tool for a given feed. If the predicted reference point does not satisfy a specified dimension tolerance, then the method will adjust itself according to the adaptive rules. Based on the adjustment information together with the current position of the cutter, a corrected position of the cutter can be obtained.

A general surface curve is used to test the effectiveness of the method. At the respective feedrates of 10 mm/s and 30 mm/s, the method is not only able to replicate the contour of the desired curve but also to steer the path generated to constantly stay within an allowable range with a specified tolerance. Therefore, the proposed algorithm is proved to be robust and effective in generating precision tool paths due to its adaptive error correction mechanism.
Multi-Milling-Insert Wear Assessment Using Nonlinear Virtual Sensor, Time-Frequency Distribution and Neural Networks
Authors: Li C. James , Tzeng Tzong-Chyi
Published: January 2022

The objective of this study is to establish a signal processing methodology that can infer the state of milling insert wear from translational vibration measured on the spindle housing of a milling machine. First, the tool wear signature in a translational vibration is accentuated by mapping the translational vibration into a torsional vibration using a previously identified nonlinear relationship between the two, i.e., a virtual sensor. Second, a time-frequency distribution, i.e., a Choi-Williams distribution, is calculated from the torsional vibration. Third, scattering matrices and orthogonalization are employed to identify the time-frequency components that are best correlated to the state of wear. Fourth, a neural network is trained to estimate the extent of wear from these critical time-frequency components. The combination of the virtual sensor, time frequency analysis and neural network is then validated with data obtained from real cutting tests.
Modeling and Control of Ablative Thermal Layered Manufacturing Processes
Authors: Fourligkas Nikolaos , Doumanidis Charalabos
Published: January 2022

This article establishes a general thermal modeling and control methodology for ablative processing of layered materials for rapid prototyping technologies. An analytical multivariable model of lumped temperature outputs generated by heat inputs on a surface grid is developed, based on Green’s function and state-space descriptions. The few independent parameters needed in such a linearized formulation are experimentally identified, and their time-variability reflects the heat transfer nonlinearities and process disturbances. A robust controller with thermal feedback is designed by pole placement methods, to obtain a specified dynamic temperature field yielding the desired material structure and properties. The regulated thermal processing is optimized in real time by proper heat source power modulation and torch guidance through a simulated annealing strategy. Its performance is tested on both the computer model and a laboratory station in regulating the sensitized zone during blanking of an elementary contour pattern on stainless steel, using robotically guided plasma-arc cutting and infrared thermal sensing.
Eclipse: An Overactuated Parallel Mechanism for Rapid Machining
Authors: Ryu Seon-Joong , Kim Jin Wook , Hwang Jae Chul , Park Changbeom , Cho Han Sang , Lee Kiha , Lee Yonghoon , Cornel U. , Park F. C. , Kim Jongwon
Published: January 2022

This paper describes the design, construction, and experimental results of the Eclipse, a novel 6 d.o.f. parallel mechanism designed for rapid machining. The Eclipse is designed to be capable of performing 5-face machining while retaining the advantages of high stiffness, high accuracy, and compact size characteristic of parallel mechanisms. We describe the kinematic structure of the Eclipse, including computational procedures for the forward and inverse kinematics, as well as results of workspace, stiffness, and singularity analysis. The Eclipse has 8 actuators. The overactuation is necessary in order to eliminate kinematic singularities present in the internal workspace of the mechanism. Experimental results obtained with a prototype capable of machining plastic stock are described. We conclude with a summary of what we believe are some of the criticial issues in designing parallel mechanism-based machine tools.
Development of Parallel Mechanism Based Milling Machine [HexaM]
Authors: Shibukawa Tetsuro , Tooyama Taizo , Hattori Kazuya , Ohta Hiromichi
Published: January 2022

Recently, it is required to reduce not only the net cutting time but also the non-cutting time in order to improve productivity in the cutting process. It is important to develop a new machine tool for high-speed cutting operations, which provides a high speed feed mechanism and a high rotational speed spindle. To obtain a greater level than the conventional feed rate, a parallel mechanism is applied as a high-speed spatial positioning mechanism in a newly developed milling machine. Six ball screw drives are used to actuate this parallel mechanism. One end of the rod is connected to a slider of the ball screw drive with a joint having two degrees of freedom, and the other end of the rod is connected to an end effector with another joint having three degrees of freedom. Six sets of these links are slung down from a fixed base, and support the end effector. Maximum feed rate of 100 m/min and maximum acceleration of 14.7 m/sec2 are achieved.

Also, ±3-sigma repeatability of ±0.001 mm and circularity of 0.016 mm are obtained.
Constraint-Based Modular Fixture Assembly Modeling and Automated Design
Authors: Kang Y. , Rong Y. , Sun M.
Published: January 2022

Modular fixtures are used as flexible fixtures for holding a variety of workpieces in manufacturing processes where standard fixture elements are assembled into different configurations to adapt to different workpiece geometry. This paper presents a constraint-based modeling and automated design of modular fixture configuration design. Assembly constraints are defined in two levels so that the spatial relationships between fixture elements can be modeled and further inferred in terms of a set of constraints. The advantages of this method compared with our previous work include the associativity in fixture design. Once the constraints are specified, the assembly relationships are maintained even if other conditions may change, especially in the process of design modification. The constraint definitions and constraint satisfaction are presented. The application of the method to modular fixture configuration design is introduced.
Non-Linear Finite Element Analysis Support Testing for Gaskets and Seals
Authors: Pannikottu Abraham , Seiler Joseph A. , Leyden Jerry J.
Published: January 2022

Computer-Aided Engineering (CAE) refers to the use of computers to perform design calculations for determining an optimum shape and size for a variety of engineering applications. This modern concept of engineering management has led to important advances in the design and production of components used in aerospace, automotive, electronics and other industries throughout the world.

Computer-Aided Engineering enables an engineer to test design ideas by simulating the function of the part on the computer. Finite Element Analysis (FEA) is one of these computer simulation techniques which is most accurate, versatile and comprehensive technique for solving complex design problems. FEA permits the analysis of these complex structures without the necessity of developing and applying complex equations.

FEA program for non-linear stress analysis of elastomers is performed by applying two material models:

* Mooney-Rivlin Model

* Ogden Model

The Mooney-Rivlin model is the most widely used model for elastomer analysis. The basic problem facing the design engineer is how to obtain the material coefficients needed to use these two models in FEA. As expected, the effectiveness of design analysis is directly related to the quality of the material input material coefficients.

Akron Rubber Development Laboratory, Inc. (ARDL) has developed a reliable history of standard procedures for determination of these coefficients from experimental test data. This paper will discuss various testing techniques used for developing elastomer material constants. Also, the intent of this paper is to show how aging or service conditions can be incorporated to obtain material coefficients for elastomer parts.
Free Vibration of Symmetric Cross-Ply Laminated Cylindrical Helical Springs
Authors: Yildirim Vebil , Sancaktar Erol , Kiral Erhan
Published: January 2022

The first three free vibration frequencies of symmetric cross-ply laminated cylindrical helical springs with square section and fixed-fixed ends are theoretically computed based on the transfer matrix method. The rotary inertia, shear and axial deformation effects are taken into account in the solution. A parametric study is performed. to analyze the effects of the ratio of the extensional modulus to the shearing modulus, helix pitch angle and the number of active turns on the natural frequencies of such springs. The results are given in graphical forms.
Elastoplastic FEM Stress Analysis and Strength Evaluation of Adhesive Tapered Lap Joints of Hollow Shafts Subjected to Tensile Loads
Authors: Kawawaki Masataka , Nakano Yuichi , Sawa Toshiyuki
Published: January 2022

Tensile strength of adhesively bonded tapered lap joints of hollow shafts is investigated in this study. In tapered lap joint, the bonded area is increased even in hollow shafts which are relatively thin. Furthermore, assembling and adjusting the axes of the shafts are easier because of the self-aligning effect. In the experiments, the elastoplastic stress-strain behavior of the adhesive was measured by the uni-axial tensile test of the bulk specimen. The tensile strength of the joints with various taper angles was tested subsequently. In the analysis, the stress distributions at the interface between the shafts and the adhesive are calculated using the finite element method by taking the elastoplastic behaviors of the adhesive and the shafts into consideration. A tensile strength prediction method is proposed based on the numerically obtained stress distributions and its features are discussed by comparing the measured strengths with the predicted ones.
A Study on the Effects of Surface Roughness on the Strength of Single Lap Joints
Authors: Sancaktar Erol , Gomatam Rajesh
Published: January 2022

Many surface treatments that improve adhesion have the effect of roughening the surface involved. Treatments such as abrasion and etching remove the weak boundary layer and improve the wetting behavior. Liquid adhesives that are spread during the application do not ensure removal of air from the cavities present on the surface of the adherend. The penetration of adhesive into the pores of the substrate is influenced by capillary forces and is retarded by the viscosity. Surface roughness and surface irregularities can effect the spread of adhesive and thereby its contact angle.
Mechanical Behavior of Bolted Joints Under Thermal Changes
Authors: Sawa Toshiyuki , Muramatsu Akira , Kumano Hiroyuki
Published: January 2022

Bolted joints in heat exchangers, cylinder head in combustion engines and so on are subjected to a heat flux. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. In the experiments, the bolted joints mentioned above were put in a furnace. Next, rectangular thick plates fastened by a bolt and nut were heated by an electric heater. Then, the temperatures on the surfaces of the clamped parts and the bolts were measured with thermocouples. The increase in axial bolt force, the maximum stress in the bolts and the strains in the clamped parts were measured under steady heat conduction or thermal changes. In addition, analyses we are carried out on the above load factors using the finite difference method. The analytical results are consistent with the experimental ones.
Proper Selection of Auxiliary Heat Source for Reducing Thermal Residual Stresses During Welding Process
Authors: Kunde Raghu Ram , Kuppa Padmalakshmi V. , Jahanian Shahriar
Published: January 2022

In this paper a method is proposed to reduce the residual stress distribution at the area close to the HAZ. Initially the temperature distribution in an AISI 304 stainless steel, which undergoes gas metal arc welding process, is evaluated using FEM. For this purpose general purpose FEM code ABAQUS is used. The results were compared with the experimental data and a reasonable agreement is observed. Across the thickness of the weldment high temperature gradient which is a function of space and time is observed. An auxiliary moving heat source is placed on the top surface of the weldment, close to welding heat source. It was observed that if the place of auxiliary heat source and time of application are not carefully selected it may create a thermal shock and may have adverse affect on the temperature distribution. This may result in high residual stress distribution. However when the heat input for the auxiliary heat source, its location, time of application, speed and magnitude of the auxiliary heat input are carefully selected, then the temperature gradient, both spatially and temporally at area close to HAZ will reduce considerably. Even though the affect at area very close to fusion zone is trivial, our results indicate residual stresses in general may reduce due to more uniform temperature distribution.
CFD Analysis of a Direct Vessel Injection (DVI) Transient to Calculate AP600 Reactor Vessel Shell Temperatures
Authors: Matarazzo John C. , Schwirian Richard E.
Published: January 2022

Computational Fluid Dynamics (CFD) was used to evaluate Reactor Vessel (RV) shell temperatures during a Direct Vessel Injection (DVI) transient for the Advanced Passive 600 mW Pressurized Water Reactor (AP600). The circumferential, axial and radial temperature distributions were calculated for the RV shell using CFD methods.
How to Get Second-Order Accurate Solutions From the First-Order Accurate RELAP5 Code
Authors: Tiselj Iztok , Petelin Stojan
Published: January 2022

Equations of the typical ID two-fluid model of two-phase flow, which is used in today’s computer codes for the simulations in nuclear thermal-hydraulics (RELAP5, TRAC), can be written in vectorial form as:∂ψ∂t+C∂ψ∂x=P Numerical scheme in RELAP5 is based on direct discretization of the equations using first-order accurate temporal and spatial discretizations. Staggered grid is used and upwind scheme for the spatial discretization of the convection terms in the equations. Second-order accurate central differences are used only for the discretization of the pressure gradients in the momentum equations.

In this paper we have demonstrated the capability of the RELAP5/MOD3 code to trace the acoustic waves with second-order accuracy, if a very small time step is chosen for the simulations. This feature of the RELAP5 code is important especially for the simulations of the fast transients describing pressure waves, i.e. shocks, rarefaction waves, water hammer... Second-order accuracy cannot be achieved for the propagation of the temperature and void fraction waves.
Uncertainty Quantification of SB LOCA With CSAU Using Optimal Statistical Estimator
Authors: Prošek Andrej , Mavko Borut
Published: January 2022

When performing best estimate calculations uncertainty needs to be quantified. An optimal statistical estimator algorithm was adapted, extended and used for response surface generation. The objective of the study was to demonstrate optimal statistical estimator for uncertainty evaluation of single value or time dependent parameters when Code Scaling, Applicability and Uncertainty (CSAU) method is used for uncertainty quantification. The scenario selected was small-break loss-of-coolant accident with break in cold leg of a two-loop pressurized water reactor Westinghouse type. The uncertainty was quantified for RELAP5/MOD3.2 thermalhydraulic computer code.

The results showed that peak cladding temperature selected as one of primary safety criteria with added uncertainty does not exceed the safety limit. Uncertainty was additionally evaluated for nine time dependent parameters. This finding indicate that CSAU method can be applied to transients other than loss-of-coolant accident.
Boundary Layer Two-Phase Bubbly Flow Equation
Authors: Troshko Andrey A. , Hassan Yassin A.
Published: January 2022

Experimental data indicate that bubbly, turbulent, boundary layer has the same structure as its single-phase counterpart. The modified logarithmic law of the wall for the bubbly turbulent log layer is obtained. Eddy viscosity concept is used to obtain boundary layer equation. Total turbulent stress in the inner layer is assumed to be the sum of the local stress caused by bubbles in the log layer and the stress taking into account the inherent liquid turbulence and bubble-liquid interaction in the outer layer. The proposed two-phase law of the wall can be used as a boundary condition in multidimensional models of two-phase turbulent flows. It is applicable to the upward and downward flows with the value of void fractions in the log layer not more than 10%.