bluuebunny/crossref_metadata_2025 huggingface dataset:
PVDF and PZT Piezoelectric Wafer Active Sensors for Structural Health Monitoring
Authors: Lin Bin , Giurgiutiu Victor
Published: April 2008

Piezoelectric wafer active sensors (PWAS) used in structural health monitoring (SHM) applications are able to detect structural damage using Lamb waves. PWAS are small, lightweight, unobtrusive and inexpensive. PWAS achieve direct transduction between electric and elastic wave energies. PWAS are essential elements in the Lamb-wave SHM with pitch-catch, pulse-echo, phased array system and electromechanical impedance methods. PWAS are charge mode sensors and they can be used as both transmitters and receivers. A model of PWAS is shown in this paper. In vibration, impact detections applications, the PWAS response is strong due to the large dynamic change of strain. In pitch-catch, pulse-echo and phased array applications, PWAS are used to generate and receive Lamb waves and the PWAS response is small. A charge amplifier for PWAS applications is introduced in this paper. PWAS are normally made of piezoceramic Lead Zirconate Titanate (PZT). The structural integrity tests require attachment of PWAS to the material surface and there are critical applications where the rigid piezoceramic wafers cannot conform to curved surfaces. As alternative one can use flexible piezopolymer such as polyvinylidene fluoride (PVDF); such PVDF-PWAS have been studied in this paper. PVDF-PWAS were mounted on a cantilever beam for the free vibration test and on a long rod for the longitudinal impact test. The experimental results of the PZT-PWAS and PVDF-PWAS have been compared with the conventional strain gauge. The theoretical and experimental results in this study gave the basic demonstration of the piezoelectricity of PZT-PWAS and PVDF-PWAS.
Infuence of the Friction Force, the Tooth Correction Coefficient and the Normal Force Radial Component in the Form Factor and the Stress in the Feet of Spur Gear’s Teeth
Authors: Quinones Aisman , Goytisolo Rafael , Moya Jorge , Ocampo Roger
Published: April 2008

In this paper, a theoretical research is made on the influence of the friction force, the correction coefficient of the tooth and the radial component of the normal force in the Form Factor applicable to the stress on spur gears’ teeth. The Industrial Standards AGMA, ISO and DIN use the Lewis factor as the Form Factor but it doesn’t consider the above mentioned effects. The Standard GOST uses a Form Factor that considers the effect of the correction coefficient of the tooth and the radial component of the normal strength, but it doesn’t include the effect of the friction force. In this paper, a Mathematical Model is developed that incorporates all those effects. The obtained values of the form factors were represented graphically in function of the number of teeth, the correction coefficient and the friction coefficient. A graph is drawn for the driver gear and the driven gear, in which a remarkable influence of the simultaneous action of friction and correction coefficients is appreciated. In this new approach, it is found that the correction coefficients needed to optimize the resistance to the stress fracture of the teeth, in dependence of the values of the friction coefficient, should be greater that those used in the traditional approach. On the other hand, it has always been considered that gears with small number of teeth are the weakest with respect to stress fracture; however, in multiplying transmissions it is possible for driver gears with high number of teeth to be the weakest gear, given the favourable effect of the friction force on Form Factor in the driven gear and unfavourable in the driver gear. For the validation of the obtained results the Program of Finite Elements Analysis COSMOS Design Start 4.0 was used, obtaining very good results. Using FEA and Multiple Lineal Regression, a new expression for the calculation of the stress concentration coefficient in the feet of the tooth, in function of the number of teeth and of the correction coefficient, was found: kσMEF=1.497+0.126−0.003933Z
A Six-Sigma Approach for Investment Plans in Process Plants
Authors: Ventura Gabriel , Aboites Fernando
Published: April 2008

It is possible to demonstrate that QFD (Quality Function Deployment) within a norm space permits to realize gap analysis and investment plans for a complex process plant, using its process capability (defects per million of opportunities: DPMO) in the last Quality house. The first step is to partition in six “master nodes” the plant: man power, materials, maintenance, machinery, environment and methods. It is important to realize the layout of the plant, to know the customer’s CTQ (Critical to Quality); according with the CTQ the “customer’s How” will be obtained using the six sigma methodology, the layout and process information. For the last quality house the weak form will be changed by the capability metric. The domain is obtained through Taguchi functions (rigorously: a norm space). For the use of the same metric: DPMO, it is possible to compare man power, materials, maintenance, machinery, environment and methods. In these terms get a benchmarking, Pareto’s diagrams, investment plans are feasible. This method was implemented by CIATEQ A. C. in the Mexican Petrochemical plants and some results are included; CIATEQ A. C. (Advanced Technology Center) is a research center in Me´xico and is part of the Technological centers in this country.
HYDROFORGING: A New Manufacturing Technology for Forged Lightweight Products of Aluminum
Authors: Roeper Matthias , Reinsch Steffen
Published: April 2008

The demand of parts with low weight, high material properties and relatively low cost leads to lightweight constructions. Especially hollow structures with a high stiffness and minimized weight are expected to have high potentials. In comparison to other manufacturing technologies, e.g. hydroforming or casting, characterized by their limitations of material thickness or mechanical strength, forging is a costeffective way to produce lightweight parts with excellent material properties and a balanced relation between strength and mass. Based on known flashless forging processes, a new technology to produce forged parts with hollow structures is developed at IPH — Institut fu¨r Integrierte Produktion Hannover, Germany. The hollow structure is filled by an incompressible liquid which is removed after the forming process. Maximum deformations are reached by using punches moving into the liquid.
Numerical Simulations by Detailed Chemistry and Experimental Measurements of Diesel Combustion in a Light Duty Common Rail Direct Injection Engine
Authors: Costa Michela , Vaglieco Bianca M. , Corcione Felice E. , Omote Hiroshi
Published: April 2008

Present paper couples the use of a modified version of the KIVA-3V code including a model for detailed chemistry to an experimental investigation performed on an optically accessible diesel engine. The engine is equipped with a commercial four valves cylinder head and a Common Rail injection system. Digital images and UV-visible flame emission measurements are compared with the visualization of the numerical results. The diesel fuel surrogate is considered within the numerical code, namely a blend consisting of n-heptane and toluene, approximating the physical and ignition properties of the diesel oil. Products, soot and NOx formation is described by a chain of 283 reactions involving 69 species. The Partially Stirred Reactor (PaSR) assumption is adopted to maintain the computational cost within acceptable limits. The collections of digital images of the spray evolution, the mixture formation and the combustion processes are undertaken by running the engine at 1000 rpm. Commercial diesel fuel is injected by using a single injection.
Determination of an Optimal Assembly Misalignment in Sugar Cane Mills
Authors: Arzola Nelson , Goytisolo Rafael , Fernandez Ariel
Published: April 2008

This paper analyzes the influence of the misalignment between the master gear shaft and the top shaft in the durability of the latter. Previous research papers describe that the harmful influence of an excessive flotation, fundamentally in the life of the top shaft, is due to an increase of contact forces in the square coupling. No previous papers include an analysis of the loads that would allow you to know the value of the installation misalignment for a flotation in a certain operation, in order to reach a tensional state more favorable in the more frequent areas of failure of these shafts. The described procedure permits you to know the optimum values of the installation misalignment for a certain mill and the acting load system with which the durability of the shafts of the sugar cane mills is increased. The tool used to reach these results, is the Fracture Mechanic applied along with a satisfactory analysis diagram from the point of view of the load system treatment, and the exactness reached in the calculations.
Dual Role of Nanoparticles in the Thermal Conductivity Enhancement of Nanoparticle Suspensions
Authors: Li Calvin H. , Peterson G. P.
Published: April 2008

Experimental evidence exists that the addition of a small quantity of nanoparticles to a base fluid, can have a significant impact on the effective thermal conductivity of the resulting suspension. The causes for this are currently thought to be due to a combination of two distinct mechanisms. The first is due to the change in the thermophysical properties of the suspension, resulting from the difference in the thermal conductivity of the fluid and the particles, and the second is thought to be due to the transport of thermal energy by the particles, due to the Brownian motion of the particles. In order to better understand these phenomena, a theoretical model has been developed that examines the effect of the Brownian motion. In this model, the well-known approach first presented by Maxwell, is combined with a new expression that incorporates the effect of the Brownian motion and describes the physical phenomena that occurs because of it. The results indicate that the enhanced thermal conductivity may not in fact be due to the transport of energy by the particles, but rather, due to the stirring motion caused by the movement of the nanoparticles which enhances the heat transfer within the fluid. The resulting model shows good agreement when compared with the existing experimental data and perhaps more importantly helps to explain the trends observed from a fundamental physical perspective. In addition, it provides a possible explanation for the differences that have been observed between the previously obtained experimental data, the predictions obtained from Maxwell’s equation and the theoretical models developed by other investigators.
Droplet and Bubble Dynamics in Saturated FC-72 Spray Cooling
Authors: Chen Ruey-Hung , Tan David S. , Lin Kuo-Chi , Chow Louis C. , Griffin Alison R. , Rini Daniel P.
Published: April 2008

Droplet and bubble dynamics and nucleate heat transfer in saturated FC-72 spray cooling were studied using a simulation model. Using the experimentally observed bubble growth rate, submodels were assumed based on physical reasoning for the number of secondary nuclei entrained by the impinging droplets, bubble puncturing by the impinging droplets, bubble merging and the spatial distribution of secondary nuclei. The predicted nucleate heat transfer was in agreement with experimental findings. Dynamic aspects of the droplets and bubbles, which had been difficult to observe experimentally, and their ability in enhancing nucleate heat transfer were then discussed based on the results of the simulation. These aspects include bubble merging, bubble puncturing by impinging droplets, secondary nucleation, bubble size distribution and bubble diameter at puncture. Simply increasing the number of secondary nuclei is not as effective in enhancing nucleate heat transfer as when it is also combined with increased bubble puncturing frequency by the impinging droplets. For heat transfer enhancement, it is desirable to have as many small bubbles and as high a bubble density as possible.
Understanding Air Flow Patterns and Thermal Behaviour in “King Tutankhamen Tomb”
Authors: Abdel-Aziz Omar A. A. , Khalil Essam E.
Published: April 2008

The tombs of the Pharonic kings in “valley of the kings”, Thebes, Egypt are famous for their unique wall paintings and structure. KV62, King Tutankhamen tomb, is the most famous because of the treasures it held intact for over three thousand years. This tomb originally designed for a non-royal personage nevertheless was used for royal burial, and possessed a nearly intact set of burial equipment. The tomb was forgotten and a group of Rameside workmen’s huts were built over it later in antiquity. The walls of the tomb were smoother but, except for burial chamber, were left undecorated. The burial chamber is decorated with scenes from the Opening of the Mouth ritual, Book of the Dead, and representations of the king with various deities. The current status of the tomb is very critical as pink stain and black fungus spots have spread over decorated walls due to excessive moisture content in the air. Small portion of this moisture came from the ancient offerings placed in the tomb such as vegetation, and also from the gypsum plaster on which the decoration was painted, which may not have been fully dry when the tomb was sealed, visitors activities led to extra moisture production inside the tomb, this would naturally lead to an increase of those pink spots and fungus activities. For this purpose and in pursue of restoration operation it was suggested to design and install a special ventilation system that would reduce the relative humidity inside the tomb to normally acceptable environment for artifacts. Since this situation is novel and unique, the present work pursues a research plan to design and utilize a CFD model to numerically model the flow pattern, heat transfer and humidity in the tomb. A commercial CFD codes are also used in order to simulate the indoor air conditions, air flow velocities, temperatures and relative humidity patterns. In the present investigation, this technique is used in a parametric study to select the most suitable airside system design that doesn’t affect the archaeological theme of the tomb and that provides lower air velocities around the wall paintings as well as lower air humidity all over the tomb.
Model Based Damage Detection in an Automotive Exhaust Hanger Component
Authors: Mejia Paloma , Shukla Amit
Published: April 2008

The field of health monitoring of structures may have possible benefits for many industries. In this work, we analyze damage induced in an automotive exhaust hanger component. Damage in this system is defined as a crack development and propagation at a specific location. It is proposed and demonstrated in this work that a selected group of modal frequencies and their collective behavior is a suitable measure of tracking the damage. It is also shown in this work, via experimental and computational observations, that the second moment of inertia is very sensitive to the damage induced. Future work will include developing a predictive model for damage in this automotive exhaust system component.
Rapid Prototyping Systems: Types, Case Studies, and Integration in a Mechanical Engineering Technology Program
Authors: Davoud Mohammad S.
Published: April 2008

This paper describes the current types and applications of rapid prototyping (RP) systems. The capabilities of various types of RP systems are outlined, as are the benefits these systems offer when compared to traditional manufacturing methods, case studies are presented to show how some companies have reduced development costs and time-to-market by implementing RP technology. Finally, it outlines a plan for implementation of a RP system in a Mechanical Engineering Technology curriculum.
A Simple Mechanism to Teach a Complex Practitioner Knowledge Set
Authors: Harding Bruce A.
Published: April 2008

Mechanical engineering technology graduates must exhibit a number of skills as industrial practitioners. While certain skills are learned on the job, fundamental knowledge acquired in school coursework actually forms the basis for successful development of that necessary skills set. Within the skill set, one given great emphasis is that of communications. At Purdue University, the emphasis on communications skills crosses many courses but is divided among four veins: 1) written communications dealing with papers, reports, etc.; 2) oral communications dealing with effective presentations and interpersonal relationships; 3) computational communications, mathematical problem-solving, be it via hand, calculator or computer; and 4) graphics communications dealing with 3D modeling and the development and interpretation of specifications documented on engineering drawings. This paper describes a project where a simple mechanical device is used to teach complex topics, bridging multiple communications veins. In this case the project centers on the design and modification of an arbor press, but could be based on any number of devices. The simple arbor press forms the foundation for the development of a complex industry-driven knowledge set. Included are topics common to practitioners employed in design, manufacturing and quality - all of which are typical industrial assignments for MET graduates. The assignment is part of Production Design & Specifications (PD&S), a core course and the second in a two-course CAD-based freshman sequence. Where the first course teaches 3D modeling skills, PD&S concentrates on the cognitive aspects of problem-solving using modeling, calculations and extracted drawings. Students complete the project in three phases over an eight-week period. Each phase is driven by an Engineering Change Order (ECO), a common industrial practice. Contained in the ECOs are both detailed requirements and open-ended requirements. While fulfilling the ECOs, students must make decisions on interconnected requirements that ripple through design, manufacturing, and quality assurance. Requirements include: • Design based on ISO preferred numbers. • Selection of standard parts and stock materials. • Determination of cost/benefit ratios. • Manufacturing tolerances and tolerance stack-ups. • Fits calculations based on ASME B4.2 standards. • Calculation of mass properties. • Use of geometric dimensioning & tolerancing. • Documentation of product lifecycle changes. Together, these and other varied topics, when woven around the simplicity of an arbor press, give students real-world experiences without the process becoming daunting due to the sheer complexity of the mechanism.
Roll Plane Analysis of Interconnected Hydro-Pneumatic Suspension Struts
Authors: Cao Dongpu , Rakheja Subhash , Su Chun-Yi
Published: April 2008

This study presents a compact hydro-pneumatic strut design with enhanced working area to reduce the design pressure requirements for suspension applications. The two struts are interconnected in the roll plane to realize enhanced roll properties of the suspension. The feedback effects of the interconnecting pipes on the suspension stiffness and damping properties are derived and discussed. The influences of fluid compressibility on the effective ride and roll properties are also investigated. Asymmetric and variable damping valves are further introduced to realize adequately damped and soft ride, and high low speed damping in the roll mode. Fundamental properties of the proposed interconnected configurations are derived and compared with those of the unconnected struts with an anti-roll bar, in terms of suspension vertical stiffness, roll stiffness, and vertical and roll mode damping. Parametric studies are also performed to study the role of interconnecting parameters on the essential suspension properties. The results indicate that interconnected suspension with inherent enhanced roll stiffness and damping characteristics offers significant potential to improve the dynamic roll performance of heavy vehicles, while retaining soft vertical ride. The effectiveness of the proposed concept is further illustrated through simulation results attained under two different deterministic excitations.
Biological Fluid Separation in Microfluidic Channels Using Flow Rate Control
Authors: Yang Sung , U¨ndar Akif , Zahn Jeffrey D.
Published: April 2008

A microfluidic device for continuous, real time blood plasma separation is introduced. This device is composed of a blood inlet, a purified plasma outlet, and a concentrated blood cell outlet. It is designed to separate blood plasma from an initial blood sample of up to 45 % hematocrit (Hct). The microfluidic device is designed and analyzed using an analogous electrical circuit, analytical and numerical studies. The numerical study results show that 27 % and 25 % of plasma volume can be separated from a total inlet blood volume of 45 % and 39 % hematocrit, respectively. The functionality of this device was demonstrated using defibrinated sheep blood (Hct=36 %). During 2 hrs. of continuous blood infusion through the device, all the blood cells traveled through the device toward the concentrated blood outlet while only the plasma flowed towards the plasma outlet without any clogging or lysis of cells. The experimentally measured plasma skimming volume was about 33 % for a 36 % inlet hematocrit. Due to the device’s simple structure and control mechanism, this microdevice is expected to be used for highly efficient continuous, real time cell-free blood plasma separation device.
Miniature Creep Testing for Sn-37Pb and Sn-3.5Ag Solders
Authors: Takada Akio , Sakane Masao , Tsukada Yutaka
Published: April 2008

This paper studies the effect of specimen diameter on creep and creep rupture time for Sn-37Pb and Sn-3.5Ag solders. Creep tests using miniature specimens with gage diameters ranging from 7.5 and 0.3 mm were carried out at 313 K and the effect of specimen diameter was discussed. The scatter of the creep rupture time was increased with decreasing the specimen diameter. The rupture ductility was decreased by the reduction of the diameter but the reduction of area did not decreased. This indicates that the reduction of area at local parts caused the larger scatter of rupture time for the miniature specimens.
Fabrication of Inkjet Printed Flexible Electronics by Low Temperature Subtractive Laser Processing
Authors: Ko Seung Hwan , Chung Jaewon , Choi Yeonho , Griogoropoulos Costas P. , Poulikakos Dimos
Published: April 2008

The low temperature fabrication of passive electrical components (resistor, capacitor) on flexible substrates is presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print passive electrical components from gold nano-particles suspended in Alpha-Terpineol solution on a flexible polymer substrate. PVP (poly-4-vinylphenol) in PGMEA (propylene glycol monomethyl ether acetate) solvent was inkjet-printed as dielectric layer for capacitor. A pulsed laser beam was irradiated to produce finer electrical components, thereby overcoming the inherent limitation of inkjet processing. A continuous Ar laser beam was irradiated locally to evaporate carrier solvent as well as to cure the gold nano-particles in order to improve the electrical resistivity. Conductor lines and capacitors were fabricated on polymer substrate and their performance was analyzed.
Using System Engineering Approach to Implement Value Stream Mapping (VSM) Tool in Manufacturing Service Environment
Authors: Wang Z. Y. , Koripelli Rama S. , Aekula Sucharitha
Published: April 2008

Value Stream Mapping (VSM) is the one of the techniques used in lean manufacturing; it is a method of visually mapping a product’s production path (including materials and information) from door-to-door. Value Stream Mapping can serve as a starting point to help managers, engineers, suppliers and customers recognize waste and identify its causes. Traditionally VSM tool is used in manufacturing environment. In this study it has been applied for the distribution system. This study is conducted on a distribution company delivering automotive parts to the customers in and around Las Vegas. The primary objective of this system engineering approach is to create the present and future state Value Stream Mapping for a small sampling of three different categories of parts based on average monthly usage from the time they arrive on the receiving dock to the time they are placed into the delivery vehicle. In this work the value added and non-value added activities in the distribution process are identified. The future state map has been suggested with a set of short-term and long-term recommendations.
Distinct Element Simulation of Laser Assisted Machining of Silicon Nitride Ceramics: Surface/Subsurface Cracks and Damage
Authors: Shen X. , Lei S.
Published: April 2008

This paper applies distinct element method (DEM) to simulate the material removal process of laser assisted machining of silicon nitride ceramics and show the formation and propagation of surface/sub-surface cracks and damage. A synthetic specimen is created using particle clusters to approximate the granular microstructure of β-type silicon nitride ceramics. The effect of temperature on machining is considered by its influence on the material properties. In addition, some other parameters such as rake angle, depth of cut, local damping coefficient and cluster size are also considered in a parametric study. It shows that all these parameters influence surface/sub-surface cracks and chip formation of silicon nitride ceramics in laser assisted machining.
Methodology for Intrinsic Exergy Analysis as Guide for Process Improvement With a Fuel Droplet Combustion Example
Authors: Sarmiento-Darkin Wladimir , Lior Noam
Published: April 2008

While exergy analysis is by now commonly used on the system level to identify losses and recommend ways for reducing them, its use on the “intrinsic”, field, level where the exergy of a process is calculated as a function of location and time, is still developing. Intrinsic exergy analysis is a most useful method for identifying and understanding the specific reasons for exergy losses in a process, and in devising methods for their reduction. A good example, which is the sample case of this paper, is the analysis of exergy losses in combustion processes, which are known to be responsible for around 30 % of the fuel potential to produce power. In this paper we develop a methodology for intrinsic exergy analysis and for its use for process improvement, using the case of combustion of a n-heptane droplet as example. The time-dependent continuity, energy and species conservation equations together with the reaction kinetics, state equations, and temperature and concentration dependent transport properties, are solved numerically to determine the temperature and concentrations fields. These results are then used to calculate the rates of local entropy generation to determine the spatial and temporal irreversibilities produced during the combustion process, as well as the exergy efficiency. The results obtained indicate, among other things, that after ignition has taken place, the exergy loss (or entropy generation) component most responsible for the overall exergy loss is the chemical entropy, having the same order of magnitude as the rest of the entropy generation terms combined for all the cases evaluated. The computed exergy efficiency for the base case is 68.4%, in agreement with previous droplet combustion exergy studies. To develop guidelines for the process improvement, the sensitivity of the second law efficiency to the initial gas temperature (Tgi), reaction rate (ω), and combustion duration were analyzed. The results generated several promising improvement avenues.
Flow Physics in Microchannels
Authors: Pidugu S. B. , Bayraktar T.
Published: April 2008

Even though microfluidic devices are slowly becoming commercial reality (e.g. Inkjet printers), the challenges in the design of microfluidic devices remain since not all aspects of fluid flow in microchannels have been fully understood yet. This paper presents an extensive review of studies on flow physics for both pressure-driven and electrokinetic flows in microchannels. The primary goal of the present paper is to provide a wide overview of findings on underlying principles of microflow physics. The issues discussed include the effect of pressure drop and friction measurements; mixing and flow control methods for microfluidic systems; and joule heating and viscous dissipation effects in microchannel flows. No agreement has been found among studies focusing on the characterization of friction factor/pressure drop for microflow systems. Further investigation requires understanding how entrance effects differ in the case of microflows when compared to macro scale flow. There is a clear need to investigate characteristics of non-Newtonian fluid flow in microchannels.
An Application of the Self-Excited Oscillation Method to a Hydraulic Motor Angular Velocity System
Authors: Ichiyanagi Takayoshi , Nishiumi Takao
Published: April 2008

It has been known that a hydraulic servo system can be generally dealt with a second order delay element for designing an adequate controller. In the previous work, our research group developed a simple method utilizing the self-excited oscillation of a hydraulic servo system to directly estimate the dynamic parameters such as the damping ratio and undamped natural frequency. The advantage of this method is the “on-line” ability that is able to identify these parameters instantaneously with changing the operating conditions. Although this method was found to be very useful, it is available only when the spool valve is close to the neutral position. This paper proposes an online parameter estimation method for the hydraulic motor angular velocity system. In this method, the self-excited oscillation around the displaced position from the neutral spool position is utilized. In order to demonstrate the effectiveness, the experimental work is conducted by giving the various input voltages, system pressures and angular velocities. The resulting frequency characteristics of these identified transfer functions are then compared with those of the measured data by the frequency characteristics method in order to confirm coincidence.
Topology Optimization of Carbon Nanotube Reinforced Damping Layers
Authors: Lumsdaine Arnold , Damu Mohan
Published: April 2008

Topology optimization has been successfully used for improving vibration damping in constrained layer damping structures with viscoelastic materials. Reinforcing carbon nanotubes in a polymer matrix greatly influences the mechanical properties of the polymer. Such nanotube-reinforced polymers (NRP) can be used to further enhance the damping properties of the constrained layer structures. The inclusion of nanotubes into a polymer matrix provides a new design variable in the topology optimization studies on such structures. In this work, the topology optimization of structures using such NRP as the damping material is performed. The resulting structures show a phenomenal improvement in damping. Moreover, a more efficient method is used for the optimization process.
Active and Event-Driven Passive Mechanical Fault Identifcation in Ground Vehicle Suspension Systems
Authors: Haroon Muhammad , Adams Douglas E.
Published: April 2008

Data interrogation methodologies are needed for identifying loads and faults in suspensions, tires, and other vehicle components to help design more durable systems and reduce the total cost of ownership. The application of passive and active data interrogation methodologies to passenger vehicle suspension systems is discussed here. For passive diagnostics, operating acceleration response data in conjunction with fundamental mechanics models are utilized. Mechanical faults in suspension components, e.g. degradation to shock, are identified using force state maps and transmissibility functions. First, it is shown that damage causes changes in the frequency characteristics of restoring forces, provided by the force state maps, which help to detect damage. Second, autoregressive nonlinear transmissibility models are used to locate faults and also characterize the degree to which faults alter nonlinear correlations in the response data. Force state maps are suited to narrow band inputs (e.g., sinusoidal) and transmissibility models are suited to broad-band inputs (e.g., random). This difference in preferential bandwidth for the two different data analysis methods motivates the selection of the diagnostic algorithm in an event-driven manner. For active diagnostics, experimental sensitivity functions, which are algebraic combinations of measured frequency response data, estimate the change in the forced response of the system with perturbation in stiffness or damping. By comparing the sensitivity functions to finite difference functions, faults can be detected, located, and quantified. The passive and active techniques are applied to experimental vehicle data and various issues (e.g., quantifying faults) are discussed.
Control of Industrial Robot Joint Flexibility Using Acceleration Feedback
Authors: Zaki Ahmed S.
Published: April 2008

Many industrial robotic arms are used for general pick and place operations. These particular robotic arms are usually driven by timing belts, which limit the speed of the pick and place operation due to undesirable vibration at the end of the motion. This undesirable vibration is attributed to the timing belt’s flexibility, which introduces resonance inside the servo bandwidth. The objective of this paper is to demonstrate a simple and robust approach, which can be easily implemented in real time, to control robot belt flexibility. By using standard industrial accelerometers and a sliding observer, all the information required to implement a control can be estimated. A description of the sliding observer design and the vibration suppression controller are presented in this paper. Simulation results show how this technique can successfully reduce the robot end-point vibration and improve the bandwidth of the servo controller.
The Microstructure Control and Rolling Contact Fatigue Behavior of a Hot Worked Automotive Application
Authors: Lee Jae-Seong , Son Chan-Hyun , Song Bok-Han , Han Hyo-Seup
Published: April 2008

Once hot forgings for automotive parts such as wheel bearing flange to which cyclic asymmetric bending stress is continuously applied are produced, their microstructure, such as ferrite, should be controlled appropriately for obtaining of superior mechanical properties. However, it is hard to control the microstructure uniformly because mechanical strength is reduced as coarsening of ferrite grains. To investigate the microstructural alteration based on process parameters during hot working, the variation of the ferrite grain size, hereafter FGS, was investigated by utilizing of the computer-controlled servo-hydraulic Gleeble tester which can reproduce hot deformation behavior. In addition, the effect of ferrite grain size of raw material on austenite grain behavior of hot forgings was also examined. The rolling contact fatigue resistance of induction-hardened SAE1055 steel was compared with the result of induction-hardened SAE52100 bearing steel. As a result, it was confirmed that ferrite grain sizes of hot forging depend on heating temperature and cooling-start temperature during hot forging and cooling operations. Induction-hardened SAE1055 steel showed superior rolling contact fatigue resistance to induction-hardened SAE52100 steel. This fact appears that SAE1055 steel is freer from material defects such as segregateion than comparative steel.
Deformation Behavior of Bellows Pipes for Laying Cables Under Ground by Axial Load and Bending Moment
Authors: Tehara Satoshi , Naoi Hisashi , Okada Hideki , Osaku Makoto
Published: April 2008

Recently, electricity demand is rising steeply with advance of science. Additionally quantity of cables such as telephone and optical fiber is rising with communications development and increase of residence. These cables are untidily wired in the air with telephone pole. They impair cityscape and disturb pedestrian safety. Therefore improvement of procedures installing cables is requested. In order to solve it, the plan [1] which buries cables protected in pipes under ground is progressing. They are called buried pipes and consist of straight pipe made from stainless steel or plastic. However there is concern that the buried pipe is crushed and broken by the complex load due to earthquake and ground subsidence. Thus, it is necessary to develop the buried pipe with function of flexibly against damage or rupture. We focus attention to U-type bellows pipe with function of flexibly. In this study, we conduct tensile, compressive, bending test and numerical analysis of those tests using finite element method. From result, we investigate for the relationship between mechanical characteristic and deformation behavior. We study application of bellows pipe to buried pipe. In this study, we examined and analyzed deformation behavior when axial load and bending moment were given to specimens. Examinations items are as (1) we measured load, elongation bending radius by using are experimental device which modeled ground subsidence. (2) We obtained deformation behavior by numerical analysis by using constituted equations of solid mechanics. (3) We conducted simulation analysis of models constructed by finite element method. By comparing these three items, the deformation behavior is clarified.
A Fracture Mechanics Approach to the Prediction of Tool Wear in Dry High Speed Machining of Aluminum Cast Alloys: Part 2 — Model Calibration and Verification
Authors: Bardetsky Alexander , Attia Helmi , Elbestawi Mohamed
Published: April 2008

Experimental study has been carried out to establish the effect of cutting conditions (speed, feed, and depth of cut) on the cutting forces and time variation of carbide tool wear data in high-speed machining (face milling) of Al-Si cast alloys that are commonly used in the automotive industry. The experimental setup and force measurement system are described. The test results are used to calibrate and validate the fracture mechanics-based tool wear model developed in Part 1 of this work. The model calibration is conducted for two combinations of cutting speed and a feed rate, which represent a lower and upper limit of the range of cutting conditions. The calibrated model is then validated for a wide range of cutting conditions. This validation is performed by comparing the experimental tool wear data with the tool wear predicted by calibrated cutting tool wear model. The prediction errors were found to be less then 7%, demonstrating the accuracy of the object oriented finite element (OOFE) modeling of the crack propagation process in the cobalt binder. It also demonstrates its capability in capturing the physics of the wear process. This is attributed to the fact that the OOF model incorporates the real microstructure of the tool material.
Triological Aspects and Fluidity of Dense Granular Flow
Authors: Lu Kevin , Brodsky Emily E. , Kavehpour H. Pirouz
Published: April 2008

A key difficulty in describing the fluid-like behavior of granular materials is the transitional regime between the fully dynamic regime, i.e. the grain-inertial regime, to a quasi-static one. In the present investigation, we aim to establish a constitutive relation between stress and strain rate for a granular layer over a range of deformation rates within the transition/mixed regime. Our objective is to understand the relationship between granular flow and tribological-related issues, such as friction and stress behaviors, in terms of dependences on packing density, shear rate, and grain size. For the experimental setup, we utilize a Tribo-Rheometer to infer shear stress directly from the applied torque through steps of constant velocities. The configuration is a torsional-plane-shear geometry between two plates and the granular layer is confined laterally by a self-lubricating Teflon cylindrical sleeve. To analyze granular motion, we consider the powder layer as a compressible, frictional, athermal, and elasto-plastic material with solid, fluid, and gas-like properties. The granular flow regimes, defined by the dominant mode of interaction, are then analyzed as a function of different dimensionless parameters to illustrate the process that is controlling the tribological behavior. We find that shear stress and normal stress both decrease with increasing shear rate within the transition regime between the two limiting regimes. Also, the granular flow up to the grain-inertial regime shows a Coulomb-like friction behavior with no correlation to shear rate. However, the granular sample displays a quadratic rate-dependence of friction coefficient leading into and within the grain-inertial regime. A decrease in grain-size results in a dramatic increase in friction at the boundary.
Numerical Simulation of High-Temperature Air Direct-Ignition of Pulverized Coal
Authors: Kang Z. Z. , Sun B. M. , Guo Y. H. , Zhang W. , Wei H. Q.
Published: April 2008

Numerical simulation method is employed in this article to investigate various high-temperature air direct-ignition processes of pulverized coal (PC). Several important factors are analyzed, which are the inlet velocity of primary air flow, PC concentration and the velocity and temperature of high temperature air. The flow, combustion and heat transfer in high temperature air oil-free ignition burner can also be obtained from the simulation results, which are in accordance with the experimental data. The research provides guidance for structure improvement and operation optimization of burner.
Analysis of Consolidation of Matrix-Coated Fibre Composite by Power Law Creep
Authors: Carmai J. , Dunne F. P. E.
Published: April 2008

The paper is concerned with the establishment of constitutive modelling approach for analysis of the consolidation processing of matrix-coated fibre composites. The constitutive modeling approach makes use of a repeating unit cell technique and is based on a variational method employing Hill’s minimum principle for velocities. In addition, the existing porous material model is adopted for generalisation of the resulting constitutive equations to make it applicable to practical consolidation process in which the stress states are mutiaxial. The model requires only the creep properties of matrix material. It has been verified by comparing predicted results with those obtained from independently developed micromechanical models. The resulting constitutive model has been used to simulate the uniaxial consolidation experiment. Good comparison has been achieved.
Tool Wear Monitoring in Turning Operation Using Vibration and Strain Measurement With Neural Network
Authors: Al-Sahib Nabeel Kadim Abid , Bachaa Aimen Mohammed
Published: April 2008

The selection of appropriate monitoring processes is an important decision to be made. Monitoring of manufacturing processes plays a very important role to avoid down time of the machine, or prevent unwanted conditions such as chatter, excessive tool wear or breakage. Most monitoring systems developed up to date employ force, acoustic emission and vibration, or a combination of these and other techniques with a sensor integration strategy. In this work, the implementation of a monitoring system utilizing simultaneous vibration and strain measurements on the tool tip is investigated for the average flank wear of coated carbide tools which are used in finishing turning process, with cast iron shaft as a work-piece. Data from the manufacturing processes were recorded with one piezoelectric strain sensor and an accelerometer, each coupled to the data acquisition card. There are 24 features indicative of tool wear were extracted from the original signal. These include features from the time domain, frequency domains, time-series model coefficients and four packet features extracted from wavelet packet analysis. The (2 × 3) self organizing map (SOM) neural network was employed to identify the tool state as a result of the present work, the tool wear classified by applied two independent wear test as a training tests, and checked the results of the SOM by applied an independent test, finally we have an SOM model can classifying the tool wear with minimal error.
Numerical Analysis of the Lubrication Performances for Ultra-Thin Gas Film Lubrication of Magnetic Head/Disk With a New Finite Difference Method
Authors: Huang Ping , Wang Hongzhi , Xu Langui , Meng Yonggang , Wen Shizhu
Published: April 2008

In the present paper, a new iterative algorithm of finite difference method to numerically solve the lubrication problems of magnetic head/disks under ultra thin gas film thickness is introduced. Pressure distributions are calculated when a slider deviates slowly or abruptly from the balance position due to perturbations. The results show that when the slider moves in the film thickness direction, the pressure always tends to force the slider back to the balance position. Steady flying simulations show that the pitch angle is the sensitive parameter to the load carrying capacity of the slider, which should be carefully controlled in design. Squeeze effect is apparent when abrupt movements or rotations happen, which can avoid, to some extent, fatal damages due to vibration or uncertain interferences.
Parametric Resonance Convection in a Modulated Gravity Field
Authors: Putin Gennady F. , Zavarykin Mikhail P. , Zyuzgin Alexey V.
Published: April 2008

Experiments were performed to examine the influence of vertical oscillations of inertia field on convection instability and flows patterns in a horizontal fluid layer heated from one wide side and cooled from another one. Two cases are considered: when the fluid layer was heated from below and from above. The temperature sensors were used for measurement of heat transport across the layer. Visualization of flow patterns was provided by stroboscopic lighting and powdered aluminum. The parametric resonance excitation of convection under heating from above, as well as dynamical stabilization of statically unstable states, long-wave mode and parametric resonance under heating from below realized. The earlier unknown instability regions and convection structures are discovered. The results indicate that with the use of an oscillating inertia field it is possible to control the convection stability, intensity of the heat transfer and the structure of convection motions.
Modular Lumped-Parameters Dynamic Model for Gas Turbines: Validation and Application to a Small Scale Externally Fired Gas Turbine
Authors: Gnutek Radoslaw , Colonna Piero
Published: April 2008

This paper presents a lumped-parameters modular dynamic model based on physical equations applicable to gas turbine systems. Dynamic simulations performed with the described model are suitable for process and control design purposes. The model is developed using the SimECS (Simulation Toolbox for Energy Conversion Systems) software library currently under development at the Delft University of Technology. The model is validated using reported dynamic trends of operating variables for a commercial aero propulsive turbine. The model of a small scale externally fired gas turbine for biomass conversion is also presented. The effort is part of an envisaged project to realize a prototype in the Netherlands. In the developing market of distributed power generation, the externally fired gas turbine is a promising technology for utilizing biomass in the small to medium power range and especially in cogeneration. One of the crucial issues to be addressed for such systems is its non-steady operation. This can be due both to the changing composition of the fuel source and to the load following operation mode which seems to be the most likely, especially for the foreseen application in developing countries. Thermal and fluid dynamic response times of the EFGT are widely different and computer simulations can provide a valuable tool to study control and design issues.