bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermomechanical Model and Experimental Analysis of Progressive Fatigue Damage in Steel Specimens
Authors: Cura` Francesca , Curti Graziano , Sesana Raffaella
Published: September 2008

This paper presents a thermomechanical model to predict the surface temperature evolution of a specimen during a fatigue test. In particular, the aim of this theoretical approach is to evaluate the amount of accumulated fatigue damage in the material, on the basis of its temperature growth indicated as damage parameter. To do that, a thermomechanical model has been developed and applied to a unidimensional steel specimen, with rectangular cross-section, fatigued by alternate axial stresses. Temperature variation along the thickness of the specimen has been disregarded. Thermomechanical differential equation has been integrated by applying both initial and boundary conditions. Temperature evolution of steel specimens measured during fatigue tests by means of thermographic techniques has been compared to the corresponding predicted by the theoretical model.
Finite Element Simulation of Multilayer Metal Cylinder Head Gaskets
Authors: Durando Mario , Petronio Domenico , Rivilli Giuseppe , Virzi` Mariotti Gabriele
Published: September 2008

The ABAQUS gasket elements are an efficient and flexible tool to study gasket applications. Nevertheless their usage is not limited to gasket analysis, but it provides an effective improvement in structural analysis. The results point out that both the predicted contact pressure and the predicted stress distribution depend on the mesh topology. Several combinations of mesh dimension and topology are investigated. The purpose is the definition of a calculation methodology and the demonstration of the application efficiency. Complex models analysis highlights that the defined methodology represents an effective tool for the design and the optimisation of the head gasket, the cylinder head and the engine block. The methodology is then applied to an actual case. A layout modification to prevent a sealing issue is validated by the FEM analysis. The modification was introduced in the actual component. The qualitative and quantitative evidences provided by the calculation were confirmed by the experimental results obtained by colour films (not running engine with assembly loads at room temperature) and by the test bench (actual working conditions).
A Novel Simple and Low Cost 4-DOF Angular Indexing Calibrating Technique for High Precision Rotary Table
Authors: Chen Chun-Jen , Jywe Wenyuh , Teng Yun-Feng , Liu Chien-Huang
Published: September 2008

For calibrating an angular rotary table, either a high precision standard table or a laser interferometer and related optics are normally employed at high cost. This paper establishes a novel, simple and low cost technique to calibrate a 4-degrees-of-freedom errors of a rotary table (three angular motion errors and one displacement error) for a 360° full circle by employing one reference rotary table, one 1D grating and two 2D (2 dimensional) position-sensing-detectors. With this technique, no highly accurate reference table with good repeatability is needed. After two full circle tests, the 4 DOF errors of the target rotary table and the reference table can be calculated respectively. The angular uncertainty of the measurement system can be less than 1.5 arc sec, while the displacement uncertainty can be up to 1.5 μm.
Stochastic Analysis of Free Vibrations in Piezoelectric Bimorphs
Authors: Borboni Alberto , De Santis Diego , Faglia Rodolfo
Published: September 2008

Piezoelectric bimorph benders are a particular class of piezoelectric devices, which are characterized by the ability of producing flexural deformation greatly larger than the length or thickness deformation of a single piezoelectric layer. Piezoelectric bimorph benders were first developed by Sawyer in 1931 at the Brush Development Company. The performance of these actuators was rudimentary studied and improved much later, with the results of research on smart structures in 1980s. Piezoelectric benders have been used in different applications: in robotics, spoilers on missile fins, actuation for a quick-focusing lens, to control the vibration of a helicopter rotor blade and for many other purposes. Due to extensive dimensional reduction of devices and to high precision requested, the effect of erroneous parameter estimation and the fluctuation of parameters due to external reasons, sometimes, cannot be omitted. So, we consider mechanical, electrical and piezoelectric parameters as uniformly distributed around a nominal value and we calculate the distribution of natural frequencies of the device. We consider an efficient and accurate analytical model for piezoelectric bimorph. The model combines an equivalent single-layer theory for the mechanical displacements with layerwise-type approximation for the electric potential. First-order Timoshenko shear deformation theory kinematics and quadratic electric potentials are assumed in developing the analytical solution. Mechanical displacement and electric potential Fourier-series amplitudes are treated as fundamental variables, and full electromechanical coupling is maintained. Numerical analysis of simply supported bimorphs under free vibration conditions are presented for different length-to-thickness ratios (i.e., aspect ratio), and the results are verified by those obtained from the exact 2D solution. According to Timoshenko theory, a shear correction factor is introduced with a value proposed by Timoshenko (1922) and by Cowper (1966). Free vibration problem of simply supported piezoelectric bimorphs with series or parallel arrangement is investigated for the closed circuit condition, and the results for different length-to-thickness ratios are compared with those obtained from the exact 2D solution. Numerical examples are presented on bimorphs constituted by two orthotropic piezoceramic layers (PZT-5A material). The calculation of natural frequencies is based on a Weibull distribution, because it is capable to properly model a large class of stochastic behaviours. The effect of errors on the Weibull distribution of the natural frequencies is shown in terms of change of the Weibull parameters. The results show how the parameters errors are reflected on the natural frequencies and how an increment of the error is able to change the shape of the frequencies distribution.
FE Calculation Methodology for the Thermodynamic Fatigue Analysis of an Engine Component
Authors: Angileri Vito , Bonavolonta` Raffaele , Durando Mario , Garganese Massimiliano , Virzi` Mariotti Gabriele
Published: September 2008

Thermo mechanical fatigue problem is treated to define an analysis methodology permitting the strength evaluation by reliability viewpoint. The main difficulty is the lack of both theoretical and experimental information; consequently the problem is treated verifying continually the validity and the limits of the developing solution method. The chosen application was the exhaust manifold of an IC engine; FE analyses were executed following the standard methodology consolidated by this time in CRF. In particular a time transient thermal analysis was performed taking into account the exhaust gas fluid dynamics inside the manifold; the thermo structural analysis took into account both geometrical and material non linearities; the contact between the manifold and the cylinder head was simulated and the bolts pre load was applied. The evaluation of the thermal fatigue damage is executed adapting methods developed to face isothermal fatigue, analysing also energetic criteria. A preliminary reliability evaluation was executed, on the base of numerical results and of experimental information. The results permitted the individuation of critical areas of the manifold and a preliminary evaluation of the number of cycles allowable before the rupture. Since the several criteria furnished different durations, a more accurate evaluation may be deferred to the execution of experimental tests.
Automatic Procedures as Help for Optimal Cam Design
Authors: Antonini Massimo , Borboni Alberto , Bussola Roberto , Faglia Rodolfo
Published: September 2008

In this work we suggest a synthesis of recent results obtained on the application of soft-computing techniques to solve typical automatic machines design problems. Particularly, here we show an optimization method based on the application of a specialized algorithms ruled by a generalized software procedures, which appears able to help the mechanical designer in the first part of the design process, when he has to choose among different wide classes of solutions. In this frame, among the different problems studied, we refer here about the choice of the best class of motion profiles, to be imposed to a cam follower, which must satisfy prefixed design specifications. A realistic behaviour of the system is considered and the parameter model identification is set up by a soft computing procedure. The design, based on theoretical knowledge, sometimes is not sufficient to fulfil desired dynamical performances, in this situation, a residual optimization is achieved with the help of another optimizing method. The problem of a cam-follower design is presented. A class of motion profiles and the best theoretical motion profile is selected by an evolutionary algorithm. A realistic model is considered and its parameter identification is achieved by a genetic algorithm. The residual optimization is achieved by a servomotor optimized by another genetic algorithm. Evolutionary approach is used during all the design process and, as was shown, it allows really interesting performance in terms of simplicity of the design process and in terms of performance of the product.
A Genetic Algorithm as Support in the Movement Optimisation of a Redundant Serial Robot
Authors: Antonini Massimo , Borboni Alberto , Bussola Roberto , Faglia Rodolfo
Published: September 2008

The paper illustrates the application of a genetic algorithm as a methodology to choose and improve the motion law governing the movement of a redundant robot. The subject of this research is an innovative system developed to introduce the laser ray technology in the on-line tube cutting. This technique allows a quality improvement in the pipe-cutting sector, thanks to the various goals. Firstly we underline the improvement of the working environment due to the elimination of cutting noise taking off the tool changing and the steel shaving creation. Secondarily there is a drastic reduction of the cutting cycle time and an improvement of the productivity accomplished by the use of brushless drives and linear motors. In the robot design, particular attention was dedicated to the masses distributions allowing a good natural machine dynamics. The ability of the robot to avoid the cutting object, the demand to maintain the laser torch orthogonal to the cutting surfaces, as well the necessity to impose a velocity behaviour as constant as possible during the cutting operation, suggested the introduction of a redundant degree of freedom. This aspect gives a lot of opportunities in the choose of movements because there are thousands motion profiles for the joints whichever satisfying the conditions imposed to the end-effector path. In this context, we have proposed the idea to combine the procedure to solve the inverse kinematics problem with the contemporaneous optimization of the trajectory. Literature offers a series of algorithms to solve well-known inverse kinematics problem of redundant robot. These are based on the inversion of the matrix representing the link between the end-effector co-ordinates and the joints. The presence of redundancy makes this matrix rectangular and requires the use of the pseudo-inverse matrix to solve the problem in several points of the trajectory. The introduction of some weights, one for each joint co-ordinate, allows to obtain a different distribution of the joint movements computing the pseudo-inverse matrix. If we change these weights in a continuous way in time domain, we can supervise the dynamic behaviors of the machine. The new idea we propose here is the use of an adapted multi-objective genetic algorithm to define a several of particular motion laws reducing vibrations and realizing “special harmonies” in the robot motion. The procedure, that will be completely discussed in the full paper, is actually working on a laser pipe cutting machine. This robot awarded the first prize between two thousand competitor at the EMO MILANO 2003 exhibition.
Design and Experimental Investigation of a Diffusion Absorption Refrigeration System
Authors: Xu Shiming , Liang Jian , He Yi Jian , Du Ru Xu
Published: September 2008

This paper presents the design and experimental analysis of a compact Diffusion Absorption Air Cooler (DAAC) system, in which the Diffusion Absorption Refrigeration (DAR) technology is utilized. The system uses a bubble pump to replace the mechanical pump, uses three-component working fluid (NH3+H2O+He), and operates under the same system pressure level. Hence, it is quiet, long lasting and environmental friendly. To investigate the practicality of using the DAAC system for regional air conditioning, the thermodynamic model is derived to guide the system design first, and then a DAAC experimental prototype is built for validation. Since the bubble pump is the kernel component, a series of experiments are conducted to investigate the bubble pump performance. From the experimental results under various operation conditions, it is found that the bubble pump dominates the system performance and should be designed carefully to match the designed cooling capacity and operation condition. The experimental results also show that the DAAC can work smoothly under various ambient temperatures when the input power of bubble pump is over 200W.
The Effect of Cavitation on the Vibration Behaviour of Nonlinear Rotor Bearing Systems
Authors: Pham Duc , Feng Ningsheng , Hahn Eric
Published: September 2008

Rotor bearing systems frequently utilise hydrodynamic bearings whose dynamic properties are generally influenced by the bearing reaction forces (which determine the bearing stiffness and damping coefficients). These reaction forces are frequently unknown and are generally determined from the solution of the Reynolds equation using rotor motion measurements as input. Of interest is the attainable accuracy of such bearing force determinations, and for experimental evaluation, a test rig was fabricated, the design specification of which required that the rotor system run stably over its operating speed range. This paper describes the commissioning of this rig for stability purposes with the aid of natural frequency analyses, noting the required design modifications to ensure stable operation. Stability was found to be significantly influenced by the extent of the continuous fluid film in the hydrodynamic circumferentially grooved bearings. It was concluded that the assumption of a 180 degree film extent was totally inappropriate even though the bearing ends were open to the atmosphere, whereas the assumption of fluid film break up at the lubricant saturation vapour pressure proved appropriate for stability predictions provided one ensured that the bearings were flooded. Preliminary bearing force evaluations proved inconclusive, primarily because the self aligning bearings nevertheless experienced angular misalignment; and because there was uncertainty as to how much air was entrained in the bearings, in spite of attempts to prevent air ingress.
Optimization Analysis of Alternate Tube Section for Pulse Tube Refrigerators
Authors: Jafarian A. , Saidi M. H. , Hannani S. K.
Published: September 2008

In spite of numerous attempts which have been made during the last decade to optimize pulse tube refrigerators, still theoretical and analytical realization of this device needs to be thoroughly explained. In this paper, in addition to the oscillatory flow analysis in the pulse tube refrigerator through a simple analytical model, the performance of the alternate tube section of this device is analyzed using a generalized efficiency, based on the entropy generation rate. In this model, in order to extract the entropy generation rate and the dissipative terms caused by fluid friction and heat flow in alternate tube, simplified momentum and energy equations are solved analytically and velocity and temperature fields for the oscillatory flow are obtained. The method of entropy generation minimization is used to determine the optimum operation conditions that minimize process irreversibility. Based on the developed theoretical model, the influence of important parameters such as kinetic Reynolds number, ratio of tube length to its diameter, frequency of oscillations and temperature gradient along the tube on the pulse tube performance is investigated.
Parameterization of a Piezoelectric Nanomanipulation Device
Authors: Patel Ravi , Legum Benjamin , Gogotsi Yury , Layton Bradley
Published: September 2008

Through measurement of hysteresis and drift in a piezoelectrically driven multi-axis multi-positioner nanomanipulator, we have quantified error over ranges of three primary operating parameters: gain, duty cycle, and actuation time. A total of sixty-nine curves were plotted, and error and drift measured in a single operating plane. All data shown were collected on the Zyvex L-100 nanomanipulator operating in an open-loop programmed method, in both coarse (12mm range, 2–5 μm precision) and fine mode (100 μm range, 10–50 nm precision). In general, the normalized error was reduced at larger actuation distances and in coarse mode. These results may be used to define optimum operating conditions for piezoelectrically actuated nanomanipulators and micromanipulators whereby the goal is to find a balance between speed and accuracy. The results also are intended to allow for optimal control in closed-loop operation and for task-oriented and pick-and-place operations.
Automatic Positioning for Optical Scanning of Overlapping Fan-Blades
Authors: Lin Alan C. , Wu Jun-Chung
Published: September 2008

This research applies ATOS, an optical scanning device, to scan fan blades which possess overlapped geometry between blades. The surfaces to be investigated include a pressure surface, a suction surface and two hub surfaces adjacent to the pressure and suction surfaces respectively. Through numerous scanning practices, rules are found to position the fan blades in proper orientations so that data points of the four types of fan-blade surfaces can be completely obtained. The scanning sequence include: (1) rotate the fan with respect to the z-axis so that the fan can be set parallel to the straight-line connecting the two cameras of ATOS, (2) rotate the fan with respect to the x-axis so that the whole pressure surface can be located inside the scanning region of cameras, (3) rotate the fan w.r.t. the z-axis to let the suction surface be completely scanned, (4) rotate the fan w.r.t. the y-axis so that the hub surface can be located inside the camera scanning region, and (5) rotate the fan w.r.t. the z-axis so that the other hub surface can be scanned. To verify the proposed scanning sequence, this research uses Pro/Toolkit and Visual C++ to develop the programming codes so that the positioning angles for the four different types of surfaces can be automatically found from the Pro/ENGINEER part model of a fan. The goal of automatic positioning for scanning of fan blades can thus be achieved. It is concluded that the research results contribute the possibility of scanning overlapped fan blades in an automation manner, and also in little time-span.
Diagnosing Faults of Angular Contact Ball Bearing
Authors: Ghanbari Ahmad , Khanmohamadi Sohrab , Alizadeh Ghasem , Bahrami Mohsen
Published: September 2008

This paper presents experimental results for diagnosing faults in angular contact ball bearing in rotating systems such as motors or space actuators that nowadays can be found in a variety of consumer products. Some measuring methods of torque in small motors have been summarized. All these methods are not suitable for the extremely low torques and depend on dimensions of the systems. Therefore a completely new Frictional Torque Tester Device (FTTD) with applies axial loading at applicable speed, is designed and developed. This device allows us to gauge ball bearing quality and integrity, ensuring that precision specifications are under control, and the maximum efficiency can be gained. Through this FTTD the user ensures maximum performance of ball bearing by physically diagnosing of problems in bearing prior to use. Problems such as retainer hang-up, ball or race surface problems, contamination, internal geometry and structural defects can be determined on a bearing through different samplings.
Some Peculiarities in Behavior of Electrosensitive Fluids Under Electric Field
Authors: Korobko Evguenia V. , Mansurov Valery A. , Kaberdina Elena B. , Bilyk Vyacheslav A.
Published: September 2008

Rheological behavior of electrorheological fluid (ERF) under electric field is investigated experimentally and structural strengthening and viscoplastic characteristics are evaluated at different intensities of electric field and various concentrations of solid phase in ERF under its deformation in the system of disk parallel surfaces. An increase of the first difference of normal stresses is found at the increase of intensity of electric field applied, and also its change in time. At that the change of the sign of normal stresses takes place depending on magnitude of electric field and deformation.
Electrostructured Lubricants for Friction Devices
Authors: Basinuk Vladimir L. , Kaberdina Elena B. , Mardosevich Elena I. , Sushko Marina I. , Karabko Aliaksandra O.
Published: September 2008

In this work it is proposed to use special lubricant materials with the properties manageable by electric field. Such lubricant materials allow to provide the viscosity needed for liquid friction adaptive to the conditions of the loading interaction of the contacting interfaces of bearings and sliding supports. The coefficients of friction were evaluated by means of modified friction machine with planar parallel scheme of the sample interaction realization. At that the sliding speed of the sample relative to the counter body increased smoothly according to the sinusoidal law from zero up to maximum value. Then it decreased smoothly to the full stop and the movement reversed; contact pressures after working out the given number of cycles increased stepwise from 0.5 to 3.2 MPa. The range of the optimal intensities lain in between 120–150V. An increase in the relative resource of efficiency of the frictional device up to 3 times was found in these conditions.
Performance and Fuel Consumption of “CVT-Hybrid-Driveline”
Authors: Ho¨hn Bernd-Robert , Pflaum Hermann , Tomic Daniel
Published: September 2008

This paper presents results of a research project which is carried out at the Technical University Munich, Germany. In this project the “CVT-Hybrid-Driveline” is designed, manufactured and investigated in close cooperation with OEM (GM Powertrain Europe) and suppliers (EPCOS AG, ZF Friedrichshafen AG and ZF SACHS AG). The focus is put on reduction of fuel consumption at low additional cost for hybrid components. The “CVT-Hybrid-Driveline” is a hybrid car driveline using Diesel-engine, electric motor with double layer capacitors and a CVT-type transmission. The driveline is assembled into an OPEL VECTRA vehicle for investigations on practical use of this hybrid system. In addition the driveline is installed at test rig for detailed investigations on consumption, energy flow and control system behavior. The concept is presented and explained in this document. Based on simulation of the hybrid system the drivability is shown for various situations of driving; fuel consumption of the CVT-Hybrid is evaluated and discussed both for standard cycle and for specific driving course.
The Effect of the Electrostatic Field on the Deflection of Microcantilever Biosensors
Authors: Merlo Manuele , Negretto Fabio , Montevecchi Franco Maria
Published: September 2008

Microcantilever biosensors offer the capability to detect specific molecular binding like complementary DNA fragment hybridization or specific antibody-antigen binding. The cantilever deflection, which can be optically detected, is caused by the adsorption of biological molecules like DNA fragments upon the microcantilever surface and the subsequent specific binding to the complementary species. The cantilever deflection is due to the surface stress induced by the free energy variation on the cantilever surface. Contributions to the free energy variation come from a number of interactions within the molecules, such as electrostatic interactions, biomolecule conformational entropy and internal energy variation, hydration forces. In the present work the effect of the electrostatic field within DNA biomolecules on the cantilever deflection is investigated. The electrostatic field within double strand DNA molecules is studied by means of a Finite Element (FE) analysis aimed at numerically solving the non linear Poisson Boltzmann equation (PBE) in the domain representing the biomolecule system. The electrostatic analysis has been coupled to a FE structural analysis in order to evaluate the influence of the electrostatic field on the cantilever deflection. The double strand DNA molecules are modelled as a periodic disposition of cylinders negatively charged at the surface. The hexagonal and square DNA molecule patterns were compared, and the Manning condensation hypothesis was discussed. The results are shown for different operating conditions and compared with experimental data from literature.
Identification of Distributed Unbalanced Mass in Flexible Rotors
Authors: Alasty Aria , Malekian Mohammad
Published: September 2008

This paper presents a new method for identification of distributed unbalanced mass (DUM) of flexible rotors. To this end, a circular section rotor with constant area, distributed parameters, and a spatial distributed unbalanced mass is considered. Rotary inertia and gyroscopic effects are included in the dynamic of system. Then, by measuring the deflection of shaft at some points while rotating in a specific angular speed, an identification method is proposed to obtain the amount of DUM. This information can be used in balancing procedure of the rotor. The method is justified by two numerical simulations.
Machining of Rotational Asymmetric Components With a Single Turning Centre
Authors: Yusof Y. , Case K. , Newman S. T.
Published: September 2008

The key to successful manufacturing of complicated geometry in numerically controlled machines lies in the control and quality of operations planning. Process planning, as it is considered plays an important role in the innovation process. It is the interface between product development and manufacturing system development. Hence, in this paper, process planning is considered to be an active part in the concurrent development of products and their manufacturing systems, not only as an activity where manufacturing resources are selected. The authors focus on the use of the new standard; ISO 14649, to address the process planning and machining of turn/mill discrete components. This paper identifies a view of how ISO 14649 can be used to combine turning and milling operations to achieve the complete machining of rotational asymmetric components at a single turning centre. The use of the individual parts of the evolving standard ISO 14649, namely Parts 10, 11, 12, 111 and 121 has been investigated to provide the means to represent STEP-compliant turn/mill component programs.
Prediction and Analysis of Size Tolerances Achievable in Peripheral End Milling
Authors: Islam M. N. , Lee Han Ul , Cho Dong-Woo
Published: September 2008

This paper details the current research on size tolerances of component parts machined through peripheral end milling using a prototype simulation software for virtual end milling based on previously reported cutting force and surface generation models. Firstly, the simulation software was employed for predicting the size tolerances of a prismatic component by varying one controllable variable at a time and then, the relationship between the size tolerance and the variable changed was monitored. When a distinct relationship was noted it was verified both analytically and experimentally. The results indicated that while the average size variation, which contributed to the variation of the basic size of component parts, was always proportional to the metal removal rate, the range of size variations that contributed to the size tolerance was not. Thus, there is scope for increasing the metal removal rate without sacrificing the size tolerances. The knowledge acquired through this research can be applied for selecting an optimum cutting condition using the simulation software when the size tolerances of component parts are specified.
Fault Diagnosis Competitive Neural Network Training Through Condition Monitoring of Industrial Machines and Stock Exchange Prediction
Authors: Khanmohammadi Sohrab , Hosseini Sayyed Mahdi
Published: September 2008

In this paper a new way for neural network training is introduced where the output of middle (hidden) layer of neural network is used to update weights in a competition procedure. Output layer’s weights are modified with multi layer perceptron (MLP) policy. This learning method is applied to two systems as case studies. First one is the monitoring of industrial machine where the results are compared with other training methods such as MLP or Radial Basis Function (RBF). Oil analysis data is used for condition monitoring. The data is gathered by using ten stages technique. The second one is the Stock prediction where the data are highly nonlinear and normally unpredictable especially when the markets are affected by political facts. The simulation results are analyzed and compared with other methods.
Feasibility Studies on the Modeling and Evaluation of Residual Stresses in Arc Welded Butt Joints
Authors: Satyambabu K. , Ramachandran N.
Published: September 2008

Many important engineering applications such as nuclear reactors, ships, pipes and pressure vessels are shell-like structures made with weldments. For such a structure, a major problem is the development of residual stress and distortion due to welding. Residual stresses in weldments significantly affect stress corrosion cracking, hydrogen-induced cracking and fatigue strength in welded structures. As-welded components generally have certain amount of residual stresses caused by the application of intense heat or thermal loading at the weld joint, formed due to non-uniform cooling rates at different points in the weld metal and heat affected zones. Presence of residual stresses in a component is detrimental as they may lead to failure below the design stress value and also affect many important properties including the life of a welded component. Welding induced residual stresses can significantly increase the fracture driving force in a weldment and also contribute to brittle fracture. The thermal cycle imposed on any welded object causes thermal expansions and contractions which are not uniform. Quantitative measurement of residual stresses is essential to take remedial measures such as change in the welding technique, optimizing welding parameters (heat input, electrode diameter etc,), change in the weld groove design and post-weld heat treatment for minimizing the residual stresses. Residual stress measurements after post-weld treatment would also ensure the adequacy of stress relief treatment. To have an investigation into these aspects, residual stresses due to Manual Metal Arc Welding and Submerged Arc Welding were measured nondestructively with Ultrasonic technique. Residual stress distribution for Shielded Metal Arc Welding and Submerged Arc Welding were compared and the present studies emphasized, that Shielded Metal Arc Welding gave higher compressive stresses than Submerged Arc Welding. Further, to substantiate the studies, commercial finite element analysis software ANSYS 5.6 was used for modeling of manual metal arc welded joint. The results obtained by ANSYS were compared with those by Ultrasonic method.
A Device to Test the Primary Stability in Cementless Hip Arthroplasty Through Mechanical Vibrations
Authors: Varini Elena , Lannocca Maurizio , Bialoblocka Ewa , Cappello Angelo , Cristofolini Luca
Published: September 2008

Primary stability of cementless prostheses is critical for the long term outcome of the operation. Cementless implants are mechanically stabilized during surgery through a press-fitting procedure. To achieve a good initial stability, it is important that the surgeon performs an optimal press-fitting, avoiding both problems of stem loosening, and micro-cracking of the host bone. A possible approach to solve this problem and assist the surgeon in achieving the optimal compromise, involves the use of the vibration analysis. This technique was used in the presented study, which was aimed to design and test a prototype device able to evaluate the primary stability of a cementless prosthesis, at the femoral level. In particular, the goal was to discriminate between stable and quasi-stable implants; thus the stem-bone system was assumed linear in both cases. For that reason, it was decided to study the frequency responses of the system, instead of the harmonic distortion. The prototype was developed. It is mainly composed by a piezoelectric exciter connected to the stem and an accelerometer attached to the femur. Preliminary tests were performed on a composite femur implanted with a conventional stem. The results showed that the input signal is repeatable and the output can be accurately recorded. The parameters that seem to be more sensitive to stability are the resonance frequency and the amplitude at the resonance frequency.
Biomechanical Testing of the Proximal Femoral Epiphysis: Intact and Implanted Condition
Authors: Cristofolini Luca , Pallini Francesco , Schileo Enrico , Juszczyk Mateusz , Varini Elena , Martelli Saulo , Taddei Fulvia
Published: September 2008

There is renewed interest in resurfacing hip prostheses. While stemmed prostheses have been extensively studied in the past, little is known about the biomechanics of epiphyseal prostheses. Our aim was to develop a combined experimental-numerical tool to study the intact and operated epiphysis. Bone and implant stress, relative micromotion and failure mode in the intact and implanted bone were investigated. Twelve pairs of cadaver human femurs were studied intact, to fully characterize the proximal epiphysis. Four were then implanted with a commercial resurfacing prosthesis. They were tested in the elastic range, while strains were measured with 15 rosettes. Implant micromotions were measured in the operated condition. A total of 7 loading scenarios were simulated to cover the range of typical motor tasks. Additionally, Finite Element (FE) models were built using a validated procedure for assigning inhomogeneous material properties based on CT data. To allow extensive validation of the FE model, additional measurements were taken in vitro: bone deflection in various points, indirect measurement of load application point, digitizing of the bone surface and gauge locations. The FE models were also used to identify the most critical load scenario to recreate in vitro spontaneous head-neck fractures. Strain measurements were successfully obtained in intact and implanted femurs, providing the natural strain pattern, and indicating moderate stress-shielding in the operated condition. Results on the 6 femurs that were modeled showed that FE can predict overall displacements with an accuracy of 0.4mm, and principal stress with an accuracy of 10% (Root Mean Squared, RMSE). In vitro failure tests were successful: all specimens fractured, with a variety of failures ranging from sub-capital to trans-trochanteric. This confirms the suitability of this test model to replicate spontaneous fractures in elderly subjects. In conclusion, an experimentally validated FE method was developed, that run in parallel with an optimized in vitro simulation. These tools can successfully predict the stress distribution and the failure mode in the proximal femur both in its natural condition and with a resurfacing prosthesis.
Optimal Feedback-Adaptive Feedforward Controller for Vibration Suppression of a Cantilever Beam Using Piezo-Actuators
Authors: Kazemi Omid , Sayyaadi Hassan , Behzad Mehdi
Published: September 2008

In this paper the combined optimal feedback-adaptive feedforward controller proposed to attain better performance of active vibration suppression of flexible structures subjected to different type of disturbances. The structure considered here is a cantilever beam actuated with a PZT patch actuator. The proposed controller consists of two individual parts, a filtered-x controller as a feedforward part and an optimal linear controller as a feedback part. Recursive Least Square algorithm (RLS) is used for the adaptive filtering scheme in Filtered-x adaptive feedforward controller. LQG optimal controller is also used in the feedback part of the controller. This research investigates the effectiveness of the proposed controller in comparison with other types of applied controllers. In this regard, the simulation study is performed on a finite element model to evaluate the performance of the proposed controller under different disturbances. It has been shown that this method can reduce the vibration caused by random disturbances due to its broad-band disturbance rejecting performance. Also, it can fully suppress the vibration caused by a harmonic disturbance in a small decay time because of its narrow-band disturbance rejecting performance with the fast parameter adaptation algorithm (RLS).
Heat Transfer by Mixed Convection Opposing Laminar Flow From the Inside Surface of Uniformly Heated Inclined Circular Tube
Authors: Mohammed H. , Yusaf T.
Published: September 2008

This paper aims to investigate the effect of the flow pattern on the mixed convection heat transfer. A 28 thermocouples wire were installed along a 900mm copper tube to measure the temperature distribution. Three insulation layers of fiber glass, asbestos and gypsum were used to minimize to heat lost to the surrounding. A forced convection at the entrance region of a fully developed opposing laminar air flow was investigated to evaluate the flow direction effect on the Nusselt number. The investigation covered a wide range of Reynolds number from 410 to 1600 and heat flux varied from 63W/m2 to 1260W/m2, with different angles of tube inclination of 30°, 45°, 60°, and 90°. It was found that the surface temperature variation along the tube for opposed flow higher than the assisted flow but lower than the horizontal orientation. The Reynolds number has a significant effect on Nusselt number in opposed flow while the effect of Reynolds number was found to be small in the case of assisted flow. The Nusselt number values were lower for opposed flow than the assisted flow. The temperature profiles results have revealed that the secondary flows created by natural convection have a significant effect on the heat transfer process. The obtained average Nusselt number values were correlated by dimensionless groups as Log Nu against Log Ra/Re.
Phase Interaction in Hydroxylapatite/CaTiO3 Composite
Authors: Ergun Celaletdin , Halloran John W. , Bae Chang-Jun
Published: September 2008

Hydroxylapatite composites with calcium titanium oxide were prepared with pressureless air sintering for 2 hours at different temperatures between 500°C and 1300°C. The interaction between the phases was monitored with XRD analysis. At sintering temperatures near 1100°C, slight decomposition of hydroxylapatite and formation of tricalcium phosphate was observed. However, sintering at the temperature higher than 1100°C, tricalcium phosphate disappeared most probably due to the incorporation of CaTiO3 in the hydroxylapatite structure.
Modeling and Analysis of a Power Transmission System: Influences in Tooth Contact Analysis of the Gears
Authors: Garci´a-Masia´ Carlos , Ceresa Pierre , Morillas-A´lvarez Juan D.
Published: September 2008

The simulation of the operating conditions of gears transmissions are strongly influenced so much by the unavoidable presence of several kind of errors or tolerances, manufacturing and assembly process, in kinematic simulation, as by the elastic deformations, in the contact zone under load and on the power transmission shafts, in dynamic simulation. As a result, the path of contact is shifted and the transmission errors arise increasing the dynamic overload and the level of noise and vibration. In this work is presented modeling and analysis of a power transmission system, considering the assembly conditions of the elements located on the shaft; as elements of support, bearings, and as power transmission elements, gears. After the modeling, performed considering the finite elements method, the stiffness analysis allows to study the deflection, longitudinal and angular, and the modal analysis the vibrations and critical speeds. The results allows to compare the magnitude of elastic deformations on the shaft, longitudinal and angular, opposite to the considered on the zone of contact under load, in the tooth contact analysis. Also the analysis can be extended opposed to other types of errors or tolerances considered in kinematic simulation.
Double-Cage Constant Power Continuously Variable Transmission (CP-CVT)
Authors: Glovnea Romeo P. , Cretu Ovidiu S.
Published: September 2008

The paper focuses on the internal construction of an original Constant Power Continuously Variable Transmission (CP-CVT). In a recent publication the authors have introduced the fundamentals of the kinematics and dynamics of the CP-CVT. The present study focuses on the optimisation of the CP-CVT’s internal geometry and the size of its active elements in order to obtain maximum power transmitted with least variation over a range of transmission ratio. The paper concludes that for a specific geometry the CP-CVT presented offers promising characteristics that recommend it as a good candidate in the race of developing a new generation of the automobiles’ powertrain.
Dynamical Analysis of a Flexible Multibody System: Lagrangian Approach
Authors: Mouhingou Alexis , Azouz Naoufel
Published: September 2008

This work presents the dynamical modelling of a flying multibody system. We consider a quadrirotor Helicopter composed of flexible and rigid components. We use the Lagrangian approach to define the equations governing the motion. Deformation modes are used to represent elastic deformation of the substructure relative to a body reference frame. The dynamic model of the whole body interconnected by links is made taking into account the inertial coupling between the rigid body motion and the deformation. The numerical application is related to the quadrirotor XSF developed in the LSC (Laboratory of Complex Systems).
Free Vibration Characteristics of SPR Joints
Authors: He Xiaocong , Pearson Ian , Young Ken
Published: September 2008

Self-piercing riveting (SPR) has drawn more attention in recent years because it can join some advanced materials that are hard to weld, such as aluminum alloy sheets. In this paper, the free torsional vibration characteristics of single lap-jointed encastre SPR beam are investigated in detail. The focus of the analysis is to reveal the influence on the torsional natural frequencies and mode shapes of the single lap-jointed encastre SPR beam of different characteristics of sheets to be jointed. Numerical examples show that the torsional natural frequencies increase significantly as the Young’s modulus of the sheets increase, but almost no change corresponding to the change in Poisson’s ratio of the sheets to be joint. The mode shapes show that there are different deformations in the jointed section of SPR beam compared with the reference encastre beam without joint. These different deformations may cause different natural frequency values and different stress distributions.
Experimental Determination of Special Frequencies With Constant SL (Sound’s Level) in Noise of a Centrifugal Pump That Lead or Lag Due to the Speed Fluctuation
Authors: Hashemian Natanzi M. S. , Rahimzadeh H. , Chini S. F.
Published: September 2008

In this work, an experimental study about the hydrodynamic tonal noise in an industrial centrifugal pump with seven blades has been carried out. Noise measurements on the casing surface have been made for different flow rates with constant shaft speed. The experiment explains that in the frequency domain, the noise of centrifugal pump can be categorized in to two parts. First, as was expected, those frequencies which sound level of them is related to the flow rate and second, those ones that the sound level of them is constant and related to the pump structure. The experiment determines that the frequencies at the second type are so few, and they have correlation with BPF fluctuations. Also with deep notification, it can be considered that these special frequencies, lead or lag due to the speed fluctuations which produced by flow rate changes in nearly constant shaft speed.
A Compact Dynamic Model for Vapor Compression Refrigerated Systems
Authors: Tagliafico Luca A. , Scarpa Federico , Senarega Maurizio
Published: September 2008

In the paper a simplified dynamic lumped model for the simulation of a refrigerator working according to an inverse cycle between two thermal sources with finite thermal capacity is presented. A variable capacity compressor (VCC) is considered. The model is compact enough to be employed in actual regulation systems, but sufficient to describe all the underlying physical phenomena relevant to the transient response of the refrigerated cell. The dynamic behaviour of the system is simulated taking into account all the heat capacities involved in the heat transfer processes between the system, the refrigerating fluid and the outside. On the other hand the dynamic of the physical phenomena having time constants smaller than a few seconds has been neglected. The validity of this approach is proved by comparing the numerical results with the transient experimental data coming from an instrumented chest-freezer (one kind of small refrigerator often used in household and super-market applications).
Control of Different FEM Based Musculoskeletal Models of Human Lumbar Spine Under Different Loading Conditions Using Optimization Method
Authors: Kiapour A. , Parnianpour M. , Shirazi-Adl A.
Published: September 2008

In this study the effects of using different musculoskeletal models on load-displacement behavior of FE models of the human lumbar spine under external loads and moments have been analyzed in terms of equilibrium and clinical stability. A simplified and a complex architecture of muscles have been integrated to FE based models of lumbar spine and were loaded to simulate the load carrying behavior of human lumbar spine in flexion, extension and lateral bending. The displacement values as well as muscle forces have been computed and compared in both cases using optimization methods with different cost functions. The models showed similar kinematics in pure flexion but the simplified model showed instability in flexion-lateral bending and pure lateral bending conditions. The complex model was loaded and analyzed with different cost function and it was observed that displacements in the model are lower while the angle between the load vector and spine curvature at each level is minimized. It was shown that the model is less stable in case an asymmetric loading condition is applied.