bluuebunny/crossref_metadata_2025 huggingface dataset:
Complexity Analysis of Assembly Supply Chain Configurations
Authors: Wang Hui , Zhu Xiaowei , Hu S. Jack , Koren Yoram
Published: July 2009

This paper studies the complexity of assembly supply chains in mass customization environment. The high product variety from mass customization increases the complexity of assembly supply chains. The paper identifies the factors causing supply chain complexity and defines a complexity measure of an assembly supply chain based on these factors and the information entropy theory. Algorithms that determine the optimal supply chain configuration are developed to minimize the supply chain complexity (without and with assembly constraints). This analytical study of supply chain complexity will generate new insights on the influence of product variety on supply chains performance in mass customization. The model and algorithms developed in this paper can assist in making decisions such as when and how to implement a modular assembly supply chain and how much variety should be economically offered.
Characterization of Venous Graft Wall Motion as an Indicator of Distal Anastomosis Quality in Coronary Artery By-Pass Surgery
Authors: Ben-Hamo Nati , Milo Simcha , Gottlieb Oded , Hetsroni Gad
Published: July 2009

An essential parameter in assessing anastomosis quality and graft patency is associated with the graft flow rate measured at the end of a by-pass surgery. To date, no objective method to determine the quality of the anastomosis graft and to obtain graft flow rate has been endorsed by the medical community. This paper describes a non-invasive technique for measuring the integrity of a venal graft in a coronary artery bypass upon conclusion of surgery. An in vitro laboratory setup was designed to illustrate the dynamic conditions in a coronary by-pass graft. Experiments were conducted for a graft with constant flow and for a graft with pulsatile flow. The behavior of the vein wall was examined when both ends of the graft were open to flow, and also when one end of the graft was occluded. The dynamic behavior of the graft was found to change as a function of graft patency and venal pressure. A correlation was confirmed between the oscillation frequency at the graft mid span and the change in pressure at vein exit.
Digital Layer Manufacturing Chances and Challenges
Authors: Levy Gideon N.
Published: July 2009

The industrial expectation and future of the additive process, also DLM (Digital Layer Manufacturing) called, is the extensive use in Rapid Manufacturing (RM). These manufacturing technologies are at this point in time emerging. The tool-less economical manufacture of short runs plastic components is real life in several branches. These technologies emerge from the Rapid Prototyping and are on the way to Rapid Manufacturing, demonstrating great future chances. At the same time it puts forward several great research and development challenges. The paper, starting with background information, shows trends toward RM. Case studies from own research and experience as well as pioneer projects demonstrating the transition toward RM. The present challenges are discussed and considered alongside the technical and economical perspectives. Chances like “complexity for free”, individualization of design, mass customization and others are demonstrated, some final conclusions are stated.
Theoretical and Experimental Investigation of Plastic Hysteresis in Spherical Contact Under Combined Normal and Tangential Loading
Authors: Kligerman Yuri , Ovcharenko Andrey , Etsion Izhak , Halperin Gregory
Published: July 2009

The behavior of an elastic-plastic contact between a deformable sphere and a rigid flat under combined constant normal and reciprocating tangential loading is investigated theoretically and experimentally. The theoretical model is based on the assumptions of full stick contact condition and elastic–linear kinematic hardening of the sphere material. Hysteretic change of friction force versus tangential displacement during reciprocating tangential loading is investigated along with the study of the change of the contact area and stress state in the elastic-plastic sphere. Good agreement between theoretical and experimental results is obtained.
Info Gap Bayesian Classification
Authors: Keren Carmit , Zacksenhouse Miriam , Ben-Haim Yakov
Published: July 2009

Optimal decision methods and most notably the Bayesian decision are sensitive to uncertainty in the statistics of the patterns to be classified. Errors in the associated probabilities and distributions would degrade the performance of these methods. We present here a robust-satisficing decision-rule whose robustness to uncertainty in the priors is maximized given a performance demand. We apply the method to a two-class medical classification problem. We show that the robust-satisficing decision-rule is more robust to uncertainty in the priors than the optimal Bayesian decision-rule at sub-optimal performance levels. We present 4 propositions which characterize the robust-satisficing classifier. In addition we demonstrate the capabilities of this method when applied to uncertainty in the conditional probability density functions.
Dynamic Modeling and Control: Interdisciplinary Faculty Teamwork and Techniques
Authors: Rabb Robert , Chang David , Rogers John R.
Published: July 2009

As the future of engineering education emphasizes more interdisciplinary work and more work performed in teams, one logical starting point for this evolution is for faculty from different academic departments to work together. Engineering educators cannot ignore the real world’s shifting focus to interdisciplinary engineering, and they should adapt as well. Similar to the total engineering process as a team effort, the engineering education process also benefits from excellent communications among a diversity of team members. This paper highlights a classical dynamical modeling and controls course with students from two different disciplines: electrical engineering and mechanical engineering. Faculty from both departments teach every semester. Sections are assigned to individual instructors but all activities are planned jointly. Course administration is the role of a course director and this role alternates between the two departments each semester. Responsibilities throughout the semester are shared between the instructors. This organizational structure is important, allowing the interdisciplinary faculty team to synchronize their efforts, each contributing their individual strengths and resources to promote student learning and faculty development. The instructors engage in meaningful dialogue concerning their assignments, lesson preparations, laboratory exercises, and their results. The information flow between instructors from different departments encourages faculty learning by pushing the instructors beyond their own discipline. This paper provides details that illustrate the structure and benefits of the course. Advantages to empowering an interdisciplinary faculty are also described. The approach described allows the students to benefit from the work of an interdisciplinary faculty team enriching the students’ understanding through real world projects and examples that have aspects of multiple disciplines.
Holistic Design of Sustainable Systems With Improved Lifecycle Performance
Authors: Stiassnie Eli , Molcho Gila , Shpitalni Moshe
Published: July 2009

The rampant changes marking modern manufacturing are driven by: (a) excess manufacturing capacity and the consequent increase in competition, and (b) rising environmental awareness and legislation. This green legislation (WEEE, EuP, RoHS, etc.) has arisen in an attempt to resolve the inherent conflict between a number of competing needs: (1) environmental requirements and constraints, (2) consumer demands and (3) industrial profitability constraints. Consequently, modern industries seeking to maintain corporate profits while complying with new legislation have begun to shift from product delivery to through-life service support. That is, companies supply products and continue to maintain them throughout the product’s lifetime. Industrial profitability in such a paradigm requires technological adaption and innovation as well as enhanced product performance control. All these changes and requirements are dictating change in design approaches and practices. This paper presents a new design methodology and supporting tools to analyze and improve product design, while taking into account environmental impact and the selling-of-services business paradigm. The analysis is based on dynamic product models aimed at extending life span while reducing complexities and internal interdependencies by means of component periodicity planning and uncoupling activities.
Boiling of Water and Surfactants in Confined Space
Authors: Hetsroni G.
Published: July 2009

Natural convection boiling of water and surfactant solutions at atmospheric pressure in narrow horizontal annular channels was studied experimentally. The Alkyl (8–16) Glucoside with molecular weight of 390 g/mol was used in the experiments. It is a nonionic surfactant with negligible environmental impact. The length of the horizontal channels was 24 mm and 36 mm, the gape size was in the range of 0.45–3.7 mm, the heat flux was in the range of 20–500 kW/m2, the concentration of surfactant solutions was varied from 10 to 600 ppm. The gap size of the vertical channels was changed in the range of 1–80 mm. The flow pattern was visualized by high-speed video recording to identify the different regimes of boiling of water and surfactant solutions with different concentrations. At heat flux q<100 kW/m2 the rapid growth of elongated bubble was observed in the water. The rapid bubble growth pushes the liquid-vapor interface on both open sides of the channel. When a bubble departs from a nucleus cavity, its cavity is then recovered by liquid, and next bubble will appear on the heated tube after a certain interval. The behavior of the long vapor bubbles occurring in small size annular channels is not similar to annular flow with intermitted slugs between two vapor trains. Surfactant solution promotes activation of nucleation sites in a clustered mode. The cluster contains a number of small bubbles, the location of nucleation sites and time behavior of each bubble cannot be traced exactly. At higher values of heat flux coalescence process was observed during boiling of water and surfactant solutions. For water boiling in horizontal channels at Bond numbers Bo<1 the CHF in restricted space is lower than that in unconfined apace. This effect increases with increasing the channel length. For water at Bond number Bo = 1.52, boiling can be considered as unconfined. Additive of surfactant led to enhancement of heat transfer compared to water boiling in the same gap size, however, this effect decreased with decreasing gap size. For the same gap size, CHF in surfactant solutions was significantly lower than that in water. Hysteresis was observed for boiling in degraded surfactant solutions.
Virtual Fusion: Hybrid Process Simulation and Emulation-in-the-Loop
Authors: Harrison William S. , Tilbury Dawn
Published: July 2009

When developing a new manufacturing system or reconfiguring an existing system, it is desirable to have a simulation model for test and evaluation. However, there is often a disconnect between the real system and the simulation model; it is difficult for them to have exactly equivalent behavior. The highest-fidelity “model” is always the system itself. In this paper we propose a framework in which modular models of the manufacturing system components (robots, machines, conveyors, controllers) can be interchanged with their real counterparts, forming a hybrid process. We focus on both the connections between components and the most pertinent aspects of the processed parts. The transfer of parts between the real and virtual domains is particularly challenging; we describe how parts can transition between real and virtual without making substantial changes to the system itself. We discuss how the proposed hybrid process simulation can be used for the design of new manufacturing systems. As the new machines and components are built and installed, they can be “swapped” in for the virtual machines, and testing can be done incrementally. We also discuss how the proposed hybrid process simulation can be used for the upgrade or reconfiguration of existing manufacturing systems. When a new machine or cell is added, or the part flow is reconfigured, the relevant new parts of the system can first be built in simulation and tested as part of the hybrid process, with the new machines. A case study describing the implementation of the hybrid process simulation on the Reconfigurable Factory Testbed at the University of Michigan is presented.
The Study of Cutting Forces About Dynamic Stability of Milling Machine Tools
Authors: Pop Petru A.
Published: July 2009

The paper has presented a study of cutting forces about dynamic stability of milling machine tools. For that has required the analysis of dynamic machining system (DMS), represented by the interaction between elastic structure of machine tool and cutting process. The cutting force occurred during cutting process is dependent by a certain factors as thickness cut, physics-mechanics properties of workpiece, geometry of shaped edge tool, etc. An important factor, which has direct influenced about DMS, is present of vibration, in special at chatter frequency due to real perturbation and damages of DMS. The magnitude of cutting force depends largely on the tool-work engagement and depth of cut. The dynamic installation has used for study of milling cutting process assured the acquisition of vibration and cutting force on each three axes of milling machine tool. The calculus and interpretation of dynamic tests had done by MATLAB R14.v7.01 Program. Dynamic tests have been more that 150 recordings, by variation of cutting depth for each spindle speeds of machine until occurring chatter. It had used for testing four milling cutters with different geometric parameters and differential pitch of cutter. These dynamic tests are emphasizing the direct influences of cutting forces about dynamic machining system. Thus, by reducing, the magnitude of cutting forces due to suppressing the vibrations and implicit enhanced the dynamic stability of milling machine and quality of machining workpiece.
Methodical Approach to Factory Planning Regarding a Lean Production System
Authors: Dombrowski Uwe , Palluck Markus
Published: July 2009

Factory planning has been developed from a unique and infrequently performed activity to a permanent management task with an immense complexity. Furthermore the meaning of human-social and organizational aspects becomes more crucial, because of the linkage of different processes (e.g. product development and oder processing). A new type of lean production system (LPS), that is currently implemented in many european enterprises, offers a holistic approach to arrange enterprise-specifically methods in order to design the production in a comprehensive and consistent way. Now, the challenge of factory planning is to configure the elements of the factory in a way, that they support the fulfilment of the purposes of the production system in the best possible way. Based on the described challenges for factory planning, this paper offers a methodology to identify and illustrate the influences of the elements of an LPS on the elements of a factory. These influences are structured in a matrix. Therefore the interdependencies between the requirement areas (methods/tools of an LPS) and the scopes for design (elements of a factory) are structured hierarchically by various levels.
Mechatronics as a Learning Platform
Authors: Ben-Hanan Uri , Reichsfeld Oded
Published: July 2009

A new model for professional development training in the field of mechatronics is presented in this paper. According to this model, students’ first steps in the mechatronic track will be made while they are still in high school. Here they will be exposed to the field of mechatronics, using basic engineering tools such as reverse engineering and design process procedures. Through the reverse engineering process students will get insight into how both everyday and hi-tech products are engineered. Students will study the basic building blocks of a system, how they are connected, and the kind of interfaces being used. In addition, the high school program will show students how a system is designed. The design process is based on engineering methodology, which includes writing specifications, seeking a few alternative solutions and choosing the best one for the given problem. After determining which is the best system, students build it using the available technical tools such as Lego® bricks and a Lego microcontroller. This basic introduction to mechatronics, when given to high school students, is liable to lead them to seriously consider this field when deciding about their future careers. Such a program will present students with an overview of the broad knowledge needed by mechatronic systems designers. The model presented in this article can be represented using the letter “I”, where the lower horizontal line of the letter symbolizes the high school program, the long vertical line symbolizes both basic and disciplinary academic studies, and the top horizontal line symbolizes the interdisciplinary mechatronic broadening.
The Evaluation of Strain, Microstructural Aspects and Some Mechanical Properties of Nano-Grained Aluminum Processed by Accumulative Roll Bonding Using 2, 3 and 4 Initial Strips
Authors: Zaharia Luchian , Comaneci Radu , Baciu Constantin , Cimpoesu Nicanor
Published: July 2009

The main objective of the paper is to present the refinement of grains when aluminum strips are exposed to Severe Plastic Deformation (SPD) by Accumulative Roll-Bonding (ARB). Also, the relationship between nano-grain size and the increase of some mechanical characteristics (yield stress, tensile strength) is investigated. The work presents a theoretical analysis of ARB process taking into account the effect of the initial number of strips stacked before rolling on the strain evolution. We proposed the ARB process analysis when the number of strips initially stacked is 2, 3 and 4 and the initial thickness of each strip before rolling is equal with the thickness of the laminated strip, so the thickness of initial strip is a multiple of thickness resulting from rolling. It is obvious that in the case of rolling with a multilayer initial stacked, each layer will be deformed with a bigger strain, so the bond will be realised easier, at lower working temperature and the grain refinement will be achieved by a smaller number of passes. For each case (2, 3 and 4 initial layers) the engineer and equivalent (von Mises) strain are calculated. From this analysis results that increasing the number of strips initially stacked increases the total strain and the grain size from the laminated strip achieve submicronic values after a smaller pass number. The micro-structural investigations, made with Atomic Force Microscope (AFM), show that nanometric grain appear at 5–6 equivalent strain for 2 initial stacked strips and at 3–4 equivalent strain for 4 initial stacked strips. The stress – strain curves for each case and evolution of yield stress, tensile strength and micro-hardness with the number of passes are presented.
A Novel Gas-Assist Atomizer for Power Stations
Authors: Levitsky M. P. , Korin E. , Haddad J. , Levitsky S. P. , Levy Y. , Sherbaum V. , Ovcharenko V. , Bercovich Y.
Published: July 2009

A novel high flow rate gas-assist atomizer for liquid atomization was developed. The method of liquid supply in the zone of maximal air velocity is used. It is shown that it is possible to achieve fine atomization as the relative velocity between gas and liquid is very high. However actual sprays have droplets with larger size due to the rapid decrease of the difference between air and liquid velocities. So droplets disintegrate mainly due to the turbulent velocity fluctuations of the air flow. The experimental study included two stages: laboratory tests and field tests inside a full size boiler of a 220 MW power station. At the first stage, several atomizer modifications were tested using water and compressed air. Droplet size was measured by a special Laser Light Scattering method. Liquid flow rate was equal to 3500 kg/hr. The liquid atomization quality at each cross-section of the spray was estimated by measuring the liquid-droplets sizes at several stations across the spray. The tests were carried out for two distances, 30 and 40 cm, downstream of the nozzle. The tests show that for the proposed atomizer droplets SMD was reduced from 135 to 67 microns. Droplets SMD maintains constant value when liquid flow rate is reduced by 50%. The spray angle was kept as in a standard atomizer and equal to 110 degrees under all operating conditions. It was found that to obtain this angle, the pressure downstream of the nozzle core should be atmospheric. The atomizer with the best performances was selected for the field tests. It was assumed that the atomizer which shows the best results for air-water mixture would be superior also for steam-fuel mixture. Field tests of the atomizer within the burner of an actual power station in Israel (boiler by Babcock Borsig Company), demonstrated a significant reduction in NOx content, from 540 to 270 ppmv as well as better service conditions.
Seismic Analysis of a Large Oil Tank With Floating Roof
Authors: Kultsep Alexander V. , Berkovsky Alexey M.
Published: July 2009

Seismic qualification of the large oil tanks requires consideration of a lot of specific failure modes. One of them is the failure induced by dynamic behaviour of the floating roofs or pontoons: a collision between floating steel roof and tank wall during an earthquake can lead to the post crash fire with severe system fault. Seismic behaviour of a 50000 m3 tank with floating pontoon has been investigated in a numeric study. Seismic safety limits of the considered tank including floating roof movement are presented. A validation study using numerical experiments of the tank with floating pontoon has been performed in order to verify the analytical approach. An influence of the tank anchorage on the tank seismic behaviour and specific failure modes connected with tank bottom uplift has been also investigated.
High Order Theories for Elastic Modules Identification of Composite Plates
Authors: Diveyev Bohdan M. , Butyter Ihor B. , Shcherbyna Natalie N.
Published: July 2009

The study aims to predict elastic and damping properties of composite laminated plates from the measured dynamical properties. Elastic constants of laminates and damping properties have been determined by using an identification procedure based on experiment design, and multi-level theoretical approach. The present paper is the first attempt at proposing a novel adaptive procedure to derive stiffness parameters from forced sandwich plate’s vibration experiments.
Coupled Structural-Electromagnetic Optimization and Analysis of Space Intelligent Antenna Structural Systems
Authors: Wang C. S. , Bao H. , Wang W.
Published: July 2009

For high electromagnetic performances, large space truss antennas should have reflector surface with an extremely high precision. Due to the varied load and some random disturbances, active control strategy is always used in the kind of structure for the precise surface. For the improvement of the electromagnetic performances, an electromechanical synthesis optimization model of space antenna structure systems is developed based on the antenna’s characteristics, which adopts the axial gain of antenna and power consumption of actuators as the objective functions, and structural material strength and actuator’s capability as constraint conditions. The application of model to an 8-m antenna structure demonstrates the potential for significant improvement. The analysis results indicate the benefit of including electrical performance in model for necessary effort for shape control of large space antenna reflectors.
Data-Mining Dynamical Systems: Automated Symbolic System Identification for Exploratory Analysis
Authors: Schmidt Michael D. , Lipson Hod
Published: July 2009

This paper describes a new algorithm for automatically reverse-engineering symbolic analytical models of dynamical systems directly from experimental observations, for the purpose of modeling, control and exploratory analysis. The new algorithm builds on genetic programming techniques used in symbolic regression to infer differential equations from time series data. We introduce the core algorithm for building coherent mathematical models efficiently and then describe its application to system identification. The method is demonstrated on a number of nonlinear mechanical and biological systems.
Knowledge Flow in Product Design
Authors: Zhang Zhinan , Xie Youbai
Published: July 2009

Product design (PD) is viewed as a knowledge-based, socially mediated, technical activity, and knowledge represents the critical resource in the PD. As knowledge is action enabled, knowledge flows can improve product performance. However, Knowledge flow (KF) has been defined and developed in the organization domain. Unfortunately, the knowledge management field does not have the benefit of strong theory on knowledge flows to inform the enhancement of Knowledge flows to enable and support PD. This paper presents the definition of KF in the domain of PD and analyzes types of KF. The key elements of KF have been introduced respectively and the four types of KF in a distributed resource environment (DRE) are presented and analyzed. We put forward a four-level knowledge flow model (KFM) and establish a novel framework of knowledge flow engine for PD in a DRE. The model has been employed for a case study directly. The proposed model and framework provide a new way to enhance KF in PD under a DRE.
Educating the Engineer of 2020
Authors: Agogino Alice M.
Published: July 2009

How will engineering practice change in the next twenty years? What are the implications to engineering education? Will we have achieved gender equity? These questions will be discussed in the context of three recent reports of the US. National Academy of Engineering – The Engineer of 2020: Global Visions of Engineering in the New Century; Educating the Engineer of 2020: Adapting Engineering Education to the New Century; and Beyond Bias and Barriers: Fulfilling the Potential of Women in Academic Science and Engineering.
The Error Modeling and Accuracy Synthesis of a 3-DOF Parallel Robot Delta-S
Authors: Mei Jiangping , Li Yi , Zhang Ce
Published: July 2009

The error modeling and precision synthesis of a 3-DOF translational parallel robot named Delta-S are presented. An error model of the system is achieved, ready for precision synthesis. The un-compensable pose error and the compensable pose error are classified according to the error modeling. Based on precision synthesis, the error-coefficient system was built. It indicated the relation between source errors and end errors. An example was taken to demonstrate how to finish above studies. The result shows that the error modeling and the precision-synthesis method have good performance. The work is available for all parallel robots with similar mechanism.
Computer Aided Modelling and Simulation of Lathe Centre Spindle Assembly Process
Authors: Ciszak Olaf
Published: July 2009

The paper presents the issue of rationalization (task of assembly line balancing) of the final assembly process on an example of main spindle of lathe centre CTX-210 (taken from the industry practice). The task of selecting the most favorable technological assembly organizational structure from the point of view of productivity using the modern tools for modeling a simulation of production processes Flexsim software is presented. The hitherto structure of a main spindle unit assembly process will be presented, together with a developed precedence constraint graph as well as algorithms making it possible to optimize utilization rate of assembly stations and their number. The final part of the paper presents the results and conclusions from conducted tests and analyses.
The SciMED RADIUS™ Stent-Artery Interaction
Authors: Brand Moshe , Ryvkin Michael , Einav Shmuel
Published: July 2009

Main cause of restenosis after balloon angioplasty is due to the stresses generated in the artery as well as from the stent artery interaction. Understanding the factors that are involved in this interaction and the ability to evaluate the stresses that are formed in the artery, could help to lessen the number of failures. The goal of the present study is to develop computationally efficient analytical model for estimating the potential damage factor as the contact stresses, and to investigate their influence upon stent design, artery and plaque parameters. The artery was stipulated to be thick walled cylinder and its stress-strain state was determined from analytic solution of Lame problem. An analytic model based on the analysis of the beams deformation in the framework Euler-Bernoulli assumptions was formulated for the stent. The radial pressure, which is exerted on the inner surface of the artery, is assumed to be an average of contact stresses applied by the stent and the blood pressure. The variation in the Potential Damage Factor value as a function of the mismatch between stent’s and artery’s diameters is linear, and as much as the diameter of the artery increases, the Potential Damage Factor for the same mismatch decreases. For arteries with 75% blocking and mismatch of 1mm, the potential damage factor is 4.5.
Numerical Analysis of a Three Element Microbeam Array Subject to Electrodynamical Parametric Excitation
Authors: Gutschmidt Stefanie , Gottlieb Oded
Published: July 2009

The dynamic response of parametrically excited microbeam arrays is governed by nonlinear effects which directly influence their performance. To date, documented theoretical models consist of lumped-mass models. While a lumped-mass approach is useful for a qualitative understanding of the system response it does not resolve the spatio-temporal interaction of the individual elements in the array. Thus, we employ a consistent nonlinear continuum model to investigate the nonlinear dynamic behavior of an array of N nonlinearly coupled microbeams. Investigations focus on the behavior of a small size array in its 1:1:1 internal, parametric, and 3:1 internal resonances, which correspond to low, medium and high DC-voltage input, respectively. The dynamic equations of motion are solved numerically. The dynamic behavior of the three beam systems reveals coexisting periodic and aperiodic solutions. Similarities in the comprehensive bifurcation structures of the three beam systems provide insight to the nearest neighbor response of multi-element microbeam arrays subject to electrodynamic parametric excitation.
Nondestructive Evaluation of Some Medical Prosthesis Components Made From Syntherized Zirconium Oxides Using US Spectroscopy
Authors: Grimberg Raimond , Savin Adriana , Steigmann Rozina , Bruma Alina , Leitoiu Sorin
Published: July 2009

This paper presents the resonant ultrasound spectroscopy method that allows, in principle, the determination of the density changing, elastic and geometrical properties of the object to be examined. The method is applied at the noninvasive evaluation of the femoral head prosthetic and of the artificial cervical discs made from yttria stabilized tetragonal zirconia. In the case of density changing, the spectral lines are displacing to smaller frequencies and in the case of the cracks, supplementary peaks appear.
Modeling of Surface Topography for Reduced Friction
Authors: Sedlacˇek Marko , Podgornik Bojan , Vizˇintin Jozˇe
Published: July 2009

The aim of the present research was to investigate surface topography in terms of different surface roughness parameters and to correlate surface topography change to friction of contact surfaces. For this purpose, different 100Cr6 plate samples with different surface topography were prepared. Using different grades and combinations of grinding and polishing samples with similar Ra values, but different Rku and Rsk values were obtained. To evaluate influence of roughness parameters on friction and wear, dry and lubricated pin-on-disc tests were carried out under different contact conditions. Test results indicate that high Rku and negative Rsk values lead to decrease in friction. To investigate the effect of surface texturing on surface roughness parameters, real roughness profiles were virtually altered to achieve virtually textured surfaces. Using NIST SMATS softgauge for calculation of surface roughness parameters, virtually altered roughness profiles were investigated in terms of texture size, shape and spacing, and their influence on surface roughness parameters, especially on skewness and kurtosis. Lower diameter, higher spacing and wedge-shaped dimples reflect in higher Rku and more negative Rsk parameters.
A New Concept of a Large-Workspace Small-Size Bending Bellow Actuator
Authors: Wolf Alon , Ko´sa Ga´bor
Published: July 2009

Ask a mechanical designer, especially those dealing with robotics, what are the two main limitations when designing a new autonomous small mechanism. The answer will most likely be the need for better small-size actuation devices and better and smaller energy sources. Indeed, these two factors impose most of the constraints to designers, reflected in the size of the device, the forces it can apply, its achievable workspace, and the time duration it can work when not connected to a permanent energy source. Usually these parameters are in conflict with each other, that is, a small motor has somewhat low output torque and power, while a motor that can generate a large amount of torque is usually large in size and consumes a lot of power. Consequently, every mechanism designer is eager to design a small actuator that generates a large amount of torque while it simultaneously consumes a reasonable amount of energy. This report explains our efforts in developing an inflatable actuator having a small size yet can apply relatively large torque where at the same time can cover a large workspace. The inflatable actuator is shaped as a bellow which is composed of two materials with different shear modulus—one has high elasticity and the other low. By applying pressure inside the bellow, each of the materials tends to deform according to Hooke’s law, resulting in the bending effect due to the elongation differences between the two materials which are constrained to deform simultaneously. We describe the mechanical concept of the bellow actuator; we also provide an analytical model for the bellow deformation. Experimental results for verification of the model are also presented.
Experimental Analysis of Process and Laser Parameters in Laser Marking
Authors: Kruth Jean-Pierre , Yasa Evren
Published: July 2009

Laser marking is a relatively new process to produce a mark on a product by the energy of a laser beam, mostly for the purpose of product identification and traceability. Compared to other techniques such as ink-marking, mechanical engraving and electro-chemical methods, laser marking has many advantages. In this study, laser marking is done with the laser of a standard RP/RM machine, i.e. a selective laser melting machine. This makes laser marking especially suited for marking parts produced by laser RP/RM techniques. On the other hand, the major difficulty in the process is the number of parameters and their complex relations which have not yet been investigated thoroughly. In the current study, the influences of scan speed, laser pump current (laser power) and pulse frequency of a Q-switched Nd:YAG laser on the mark qualities were investigated by single-factor experiments on stainless steel parts. It was found that these parameters substantially affect mark width, depth and rim formation which is caused by the expelled molten material due to the recoil pressure during the marking process. In order to investigate the influence of cross interactions, a design of experiment methodology was used to evaluate the effects of the same parameters on the success of the laser marking process in terms of removed material and clarity of the mark (visibility, sharpness, etc.).
System Parameters Identifying and Performance Predicting of ICEs Combining Multidisciplinary Model With System Responding Data
Authors: Meng Xianghui , Xie Youbai
Published: July 2009

For complex equipments, the phenomena of system declining such as wear and fatigue often takes place and spreads after a period of running. So it is important to identify the interior structural change of system during maintenance to avoid the system to be broken abruptly. Traditionally there are two methods to analyze and predict the structural change of system. One is from the monitoring data of equipments. Another is from the mechanism of structural changing and the interior working process of equipments. In this paper a combining method, which combining the advantages of the above two methods, is used to identify the structural change of internal combustion engines. The principle of the method is to firstly build an analytical system model, in which the system parameters stand for the structural parameters or constraints. Then the current value of system parameters in the model can be identified by comparing the calculating responding results and the detected responding data. From the varying of system parameters the structural change of system can be deduced. For internal combustion engines (ICEs), the most important CPSR (combustion Chamber-Piston-cylinder Sleeve-piston Rings) system is taken as the research object. A multidisciplinary model is built to simulate the interior working processes, especially the combustion process, the structural dynamics process, the tribology process and the coupling processes among them. Then the seeking-roots method (SRM) is used to identify the value of system parameters. A case study on a low power gasoline engine verifies the above method. In the case study, the blow by gap, which stands for the wear of piston rings and cylinder sleeve, is identified with the detected combustion pressure. The case study shows that the method of this paper can identify the structural change of complex equipments. It can provide accurate information for equipments maintenance as well as the residual life prediction.
Advanced Ferroelectric MFC Actuators: The Effect of Ferro-Elastic Domain Switching
Authors: Kushnir Uri , Rabinovitch Oded
Published: July 2009

Macro Fiber Composite (MFC) actuators, which are commonly integrated in modern smart structures, may be subjected to high levels of mechanical loads. Opposed to the electrical actuation, these loads are not always controlled or anticipated by the user. Thus, they may yield a response that is beyond the linear range due to a stress induced ferro-elastic domain switching. In this paper, the phenomenon of domain switching and mechanical depolarization in the MFC actuator and the resulting degradation of the actuation capabilities are investigated. As an illustrative numerical example, the response of MFC layers in an active beam element is analyzed. Emphasis is placed on the location of the fiber segment along the active beam with a distinction between the compressed and the tensed layers. The results highlight the range of effects associated with the potential nonlinear response of the active structure under high levels of mechanical load.
A Semianalytical Solution for Normal Contacts Involving a Thin Elastic Layer
Authors: Diaconescu E. N. , Glovnea M. L.
Published: July 2009

Many technical assemblies can be modelled by a constant thickness elastic layer pressed between two elastic bodies. These models are solved up to date either by numerical methods or analytically, when the outer bodies are rigid cylinders. This paper advances a semi-analytical solution for the case the outer bodies are identical elastic paraboloids. It is shown that contact area is elliptical having semi-axes dependent on layer thickness and the pressure distribution is half-ellipsoidal.
A Reexamination of the Extraction of Material Properties Using Nanoindentation
Authors: Poon B. , Rittel D. , Ravichandran G.
Published: July 2009

The paper reexamines the extraction of material properties using nanoindentation for linearly elastic and elastic-plastic materials. The paper considers indentation performed using a rigid conical indenter, as follows. Linearly elastic solids: The reduction of nanoindentation test data of elastic solids is usually processed using Sneddon’s relation [1], which assumes a linearly elastic infinite half space and an infinitely sharp indenter tip. These assumptions are violated in practical indentation experiments. Since most of the research on the extraction of material properties relies heavily on numerical simulations, we used them to investigate the specimen dimensions required for it to qualify as an infinite body, and the indentation conditions for finite tip radius effect to be negligible. The outcome of this part is firstly, the definition of a “converged” 2D geometry so that additional magnification of the numerical model does not influence the load-displacement curve, and secondly, an explicit relationship between the measured load and displacement that takes into account the finite tip radius. Elastic-plastic solids: Here, the main data reduction technique was proposed by Pharr et al. [2], assuming elastic unloading of a plastic nanoindentation. We investigated the effects of finite tip radius in elastic-plastic indentations and found that the accuracy of the prediction is currently limited by the accurate determination of the projected contact area. This point will be discussed and a new experimental technique to measure the projected contact area will be proposed. The Poisson’s ratio effect in elastic-plastic indentations is found to be different from the linearly elastic case. This leads to the discussion on the applicability of the correction factor (for Poisson’s ratio effect) derived in linear elastic indentations, on elastic-plastic indentations. Finally, a technique to obtain an upper bound estimate of the yield stress for the indented elastic-plastic material (which is an exact estimation for non-hardening materials), will be presented.
Sampling Point Sequential Determination by Kriging for Tolerance Verification With CMM
Authors: Barbato G. , Barini E. M. , Pedone P. , Romano D. , Vicario G.
Published: July 2009

Coordinate Measuring Machines (CMM) are widely used in industry, mainly for assessing product’s compliance to geometrical specifications. They are a de-facto standard for such a control, owing to their high accuracy and flexibility in catering to different measurement tasks with fast and easy setup change. One of the key aspects of any CMM inspection plan, affecting accuracy and cost, is the choice of the measurement strategy, namely the definition of the number and the location of the points sampled on the part’s surface. In the industrial practice, such important decisions are usually left to the experience of qualified operators. A method is presented here, based upon an innovative application of Kriging models to coordinate metrology, that defines an adaptive sampling strategy with the goal of obtaining accurate estimates of form errors using relatively small samples. Exploitation of kriging models (originated for geostatistics investigations, then successfully applied to the sector of Computer Experiments) in dimensional metrology entails however some adjustments. Two practical cases of form error estimation have been investigated, the first dealing with flatness verification, and the second with roundness.
Production and Material Requirements Planning in Manufacturing-to-Order Environments: An Application to Machining Centers Production
Authors: Tolio Tullio , Urgo Marcello , Alfieri Arianna
Published: July 2009

Long and medium-term production planning are tools to match production orders and resources capability but can also be used as baseline for material procurement. In some systems, however, to reduce the complexity of the planning problem, distinct production operations are aggregated into activities which normally represent production phases. This is the case of some Manufacturing-to-Order and Engineering-to-Order Systems. The lack of a detailed schedule of the manufacturing operations can cause difficulties in providing a proper Material Requirements Planning and can affect the feasibility of the production plan. The paper proposes an approach to extract scheduling information from a production plan, grounding on the knowledge of the production process, to support material procurement. Once a criterion to aggregate operations is chosen and the plan devised, the description of production operations and their precedence relations are used to obtain temporal ranges for production operations and, hence, deadline ranges are provided for the MRP. The proposed approach is applied to an industrial environment producing machining centers.
3D Finite Element Modeling of Molybdenum Equal Channel Angular Pressing
Authors: Padan Royi , Gorni David , Rubinson Leonid , Faran Eilon , Gilad Ilan , Weissberg Shani , Yosibash Zohar
Published: July 2009

Equal-channel angular pressing (ECAP) is a manufacturing process in which a material is subjected to a severe plastic shear strain with negligible change in the cross-sectional dimensions of the work-piece. Due to the severe plastic deformation, the ECAP process was investigated experimentally mainly on ductile materials such as Cu-99% and Al-4%Cu. Application of ECAP to harder metals (such as CP-Ti or Mo) imposes several problems due to the elevated temperature involved, cracks that may appear in the material and the large forces required. Furthermore, several cycles of the ECAP are required to obtain a uniform residual strain field in the workpiece. To optimize and gain scientific insight into the ECAP process of a Mo workpiece, a combined experimental–numerical investigation was conducted. A three dimensional finite element analysis (FEA) that simulates an ECAP BC4 process of hard metal at elevated temperature was performed. Both quantitative (final simulated geometry was compared to the shape of the workpiece after ECAP) qualitative (hardness and grain size were compared to effective-strain) methods were used for FE results validation.
Project Scheduling With Feeding Precedence Relations: An Application to Production Planning
Authors: Tolio Tullio , Urgo Marcello , Alfieri Arianna
Published: July 2009

Production planning in Manufacturing-to-Order environments producing complex items must manage the execution of fabrication and/or assembling activities. In case of activities executed by workers, the committed effort can vary over time. To model this behavior, the Variable Intensity formulation has been proposed in the literature. In addition, the activities to be scheduled often represent whole production phases made of distinct production operations. Hence, the utilization of simple finish-to-start precedence relations does not correctly represent the real production process. In such cases Generalized Precedence Relations are used to allow overlapping among activities. However, since in Variable Intensity formulations the percentage execution of the activities is no more univocally related to their time execution, Generalized Precedence Relations cannot completely describe the constraints among activities. In this paper two mathematical formulations of precedence relations based on processing execution are presented to model overlapping between activities. The formulations are applied to an industrial case of production of machining centers and compared in terms of computational efficiency.