bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigations for Characterization and Analysis of Rake Face of the WC-Co Inserts Using Taguchi Method
Authors: Prasad C. L. V. R. S. V. , Ramana S. V. , Srikiran S. , Ramji K.
Published: May 2012

In order to improve the performance of the cutting tool, it is required to model the metal cutting process at the system level. To predict and enhance the cutting tool performance the primary requirement of the system is the efficiency of the model explaining the interactions at the tool chip interface. The predominating parameters which influence the development of the system are work piece material and machining variables or sometimes both. Further the development of low cost methodology to study the chip tool interactions with minimum amount of testing is of more importance. Major part of the work is emphasized on the investigation and characterization of various zones on the rake face of tungsten carbide inserts. Tests have been carried out by machining AISI 1040 steel using WC inserts with variable dry conditions examining the chip flow phenomenon on the rake face of considerable number of samples. Taguchi method is adopted for the design of experimental conditions. Results have shown an acceptable chip flow patterns and authors were able to quantify the wear zones on the rake face. The rake face is then characterized to represent all the possible cases of chip flow patterns, crater wear and chipping of the cutting edge. Side and end cutting edges are taken as datum lines for locating the wear zones. The quantification and locations of the wear zones might help the researchers and tool makers to concentrate more on the defined areas instead of the rake face in total.
Methodology for Creating a Scale Model of an Assembly
Authors: Nininahazwe Linda , Hennessey Michael P.
Published: May 2012

This paper attempts to provide an understanding of some of the issues involved in creating a physical scale model of an assembly using (primarily) rapid prototyping (RP) technology and to develop a semi-formal methodology of interest to scale model builders that guides the process. The methodology starts with either the full scale assembly or the CAD files and all assembly liaison diagrams which are then transformed into the scaled versions assuming use of a nominal scale factor. In the process a “scaling structure table” is created that documents the transformation and it only needs to focus on scaling issues, vs. angular dimensions and other geometric constraints which are invariant with respect to scale. The case study assembly used in this effort is a previously designed hand-powered breadfruit shredder of modest complexity. For various reasons, the process was not as simple as applying the nominal scale factor to all relevant dimensions. The transformation process included strategically adding special scaling features such as ribs, wall thickening, and fillets to ensure adequate strength, and merging of a subassembly into a single part. The final step was to create the physical scale model using mostly plastic-based RP.
Turbulent Boundary Layer Separation Control by Using DBD Plasma Actuators: Part II—Numerical Model Validation and Parametric Study
Authors: Xu Xiaofei , Vo Huu Duc , Mureithi Njuki , Zhang Xue Feng
Published: May 2012

Following an experimental investigation into suppression of a 2-D turbulent boundary layer separation with dielectric barrier discharge (DBD) plasma actuators, the present work investigates the concept numerically. The purpose is to develop and validate a simulation tool that captures the flow physics and carry out a parametric study of the concept at flow regimes beyond the current flow control capability of plasma actuators of conventional strength. First, a plasma actuator model is integrated into the commercial computational fluid dynamics (CFD) code ANSYS CFX to simulate the effects of plasma actuation. This computational tool is validated through comparison of results with the experimental results for pulsed actuation in quiescent air and for the control of a turbulent boundary layer separation at low flow velocities. It is shown that CFX with an integrated plasma model can capture the main experimentally observed effects of DBD actuators on turbulent boundary layer separation. Subsequently, this numerical approach is used, with increased plasma actuator strength, to study the influence of different actuation parameters (e.g., actuation location, direction and frequency) on suppression of turbulent boundary layer separation at higher flow velocities.
Analysis of the Mechanical Properties of Pristine and Thermally Aged PC/PMMA Micro and Nanolayered Films
Authors: Shen Hui , Gannon N. D.
Published: May 2012

Microlayered polymer films are synthetic polymers with biomimicking layered structures which have been successfully commercialized. Nanolayered polymer films have been developed in recent years using advanced process technology. The innovative nanolayered polymer films have more complex hierarchical systems with truly biomimic nature. There are many potential applications for the nanolayered films such as gas barrier materials and spherical gradient refractive index lens. However, as polymers possess many properties that are different from metals and other traditional materials, the mechanical properties of the polymer films can vary widely depending on the material formulation, environmental temperature, and time. In this work, standard mechanical tests have been conducted to study the relationship between the mechanical properties and the layered structures. The impact of thermal aging on the mechanical behavior of the micro and nanolayered polymer films has also been investigated experimentally. The composition of the polymer films under study are 50vol% polycarbonate (PC) and 50vol% poly(methyl methacrylate) (PMMA). The layer thickness ranges from 31 nm to 32 μm and the film thickness 50.8 μm to 254 μm. These films were thermally aged at 115°C and 125°C in a constant temperature oven for up to four weeks. The mechanical properties, including the modulus of elasticity, tensile strength and ductility, have been tested on the pristine and thermally aged films. It has been observed that the mechanical properties of the films vary with the layered structure and film thickness. The thermal aging temperature and aging time have significant effects on the overall character of the stress-strain responses. Films with different thicknesses and layer formations respond to the thermal conditions differently.
Effect on Water Leak of Tiled Roofs by Wind Flow Over Japanese Residence
Authors: Okamoto Satoru
Published: May 2012

This paper describes a water leak test of roof tiles. The 100 roof tiles were set up on 10 lines and 10 rows on the pitched roof in the downstream of the flow from the wind tunnel. The flow velocity was increased gradually from the low velocity to the high velocity, and the effects of the wind on the roof tiles were investigated by the water leak test. The situation of the water leak test was filmed by video camera. Two accelerometers were simultaneously used. The roof tiles which showed significant vibration at any velocity were found in a series of experiments and the accelerometers were attached to the two neighboring roof tiles on the model roof. The water leak phenomena in the experiment by using the artificial rainfall apparatus are discussed in this paper. Some mechanisms with relatively large amplitudes at low-frequency vibrations, which caused water leak phenomena were made clear.
Concentration Measurement of Lithium Bromide Aqueous Solution by Electrical Resistivity
Authors: Sun Jian , Fu Lin , Zhang Shigang , Hou Wei
Published: May 2012

Absorption chillers have currently become an important device in saving energy because of its effectiveness in utilizing low grade heat. Lithium bromide is widely used as absorbent in this system. But there were few outstanding concentration measurement methods in practice before. In this paper, complete electrical resistivity data of lithium bromide aqueous solution for concentration measurement was given. The electrical resistivity of lithium bromide aqueous solution was measured at concentrations of 35–70 wt% of lithium bromide and temperatures of 10–100°C. Results of this work can meet the requirement of concentration measurement of lithium bromide in absorption chillers without extracting samples.
The Incremental Harmonic Balance Method Applied to Coupled Van der Pol Oscillators
Authors: Zhang Wei , Hu Hailiang , Qian Youhua
Published: May 2012

The incremental harmonic balance (IHB) method is used to investigate coupled Van der Pol oscillators. An effective way for calculating the coefficient matrices and selecting the appropriate initial values is presented. The results of the IHB method are in good agreement with the results of the numerical method.
A Mathematical Model and Experiments for the LiBr-H2O Absorption Heat Pump
Authors: Sun Jian , Fu Lin , Zhang Shigang
Published: May 2012

A theoretical analysis performed for a single-effect, water-LiBr absorption heat pump at steady conditions was presented in this paper. This model took into consideration crosscurrent flow of fluids for heat and mass exchangers and thermal parameter dependent physical properties of working fluids. A solar driven absorption heat pump was built and employed to justify this model. Results derived from this model show satisfying agreement with our experimental values.
Effect of Pulsed Film Cooling on Leading Edge Film Effectiveness
Authors: El-Gabry Lamyaa A. , Rivir Richard B.
Published: May 2012

Detailed film effectiveness measurements have been made on a cylindrical leading edge surface for steady and pulsating flow. The film hole is off-centered by 21.5° from the centerline and angled 20° to the surface and 90° from the stream wise direction. Two jet-to-cross-flow velocity ratios have been considered: VR = 1 and 2 which correspond to blowing ratio of 1 and 2, respectively. The pulsating frequency is 10 Hz and the duty cycle is 50%. Comparisons between film effectiveness with a pulsating film and a continuous film show that for the same blowing ratio, the effectiveness of the film drops by a factor of 2 when the flow is pulsed. Hotwire measurements are made to characterize the pulsating velocity waveform at the exit of the film exit and verify the integrity of the pulse. The variation in the measured surface adiabatic wall temperature over the pulsing duration is very small suggesting a large thermal inertia that keeps the wall surface largely unaffected by the time scale of the pulsations; this holds true for both blowing ratios tested.
Application of Reversed Modeling in the Measurement of the Power Plant Unburned Carbon in Fly Ash
Authors: Fu Zhongguang , Jin Tao , Yang Guoqiang
Published: May 2012

In the paper, the research on reversed modeling method and its application with operation data of power plant is presented with the consideration of nonlinear and multiple coupling characteristics of thermal system in large capacity of power plant. The paper focus on the partial least-squares regression and artificial neural networks method which were studied based on data-driven model. The PLS-ANN coupling model was proposed. The paper aimed at modeling of unburned carbon in fly ash occurred in the operation of power generating units. Finally, the unburned carbon in fly ash model based on PLS regression and ANN method was built under the consideration of the advantages of the above models. The simulation results indicated that the presented coupling model is good at the model of non-linear system with the characteristics of higher computing speed as well as high precision. By presented model, the analysis of the impact of the unburned carbon in fly ash could be carried out in consideration of the changes of operating parameters as well as coal quality. The model could also be expected to be used in guiding of the optimal operation of power plant boiler.
Application of Grey Correlation and Reversed Modeling Method on the Soft-Measuring of Ball Mill Level
Authors: Fu Zhongguang , Fu Guoxian , Jin Tao
Published: May 2012

By using the real operation data of the thermal power plant, a new modeling method, which is called the reversed modeling method, is presented, so that accurate model of double-ball mill was established by the method. In order to solve the problem which is how to select modeling variables, gray relational analysis such as the slope, relative variability and uniform association method is presented and used to variables selecting. As an example, double ball-mill level was used as the research object, using the above three kinds of gray correlation to select preferable variables. Meanwhile, analysis the effect of applying the gray correlation to reversed modeling in two ways, such as the variable selection results and modeling accuracy. The analysis results show that the reversed model method could achieved the higher precision results when gray correlation method is applied to select the input variables of the model. The slope association method is not only simple in calculation and easy to understand the meaning, but also with reasonable result of variable selection and higher model accuracy.
Combining Variation Simulation With Welding Simulation for Prediction of Deformation
Authors: Pahkamaa Andreas , Wa¨rmefjord Kristina , Karlsson Lennart , So¨derberg Rikard , Goldak John
Published: May 2012

In most variation simulations, i.e. simulations of geometric variations in assemblies, the influence from the heating and cooling processes, generated when two parts are welded together, is not taken into consideration. In most welding simulations the influence from geometric tolerances on parts is not taken into consideration, i.e. the simulations are based on nominal parts. In this paper these two aspects, both crucial for predicting the final outcome of an assembly, are combined by linking two commercial software packages for variation simulation and for welding simulation together. Monte Carlo simulation is used to generate a number of different non-nominal parts in the variation simulation software. The translation and rotation matrices, representing the deviations from the nominal geometry due to positioning error, are exported to the welding simulation software, where the effects from welding are applied. Thereafter, the results from the welding simulation are exported back to the variation simulation software in order to compute and illustrate the deviations and variations of the final subassembly. The method is applied on a simple case, a T-weld joint, with available measurements of residual stresses and deformations. The effect of the different sources of deviation on the final outcome is analyzed and the difference between welding simulations applied to nominal parts and to disturbed parts is investigated.
Active Vibration Control for Milling Processes
Authors: Jiang Hao , Long Xinhua , Meng Guang
Published: May 2012

In this paper, a study on the active control of vibration for peripheral milling is presented. Different from the control for the vibrations of cutting tool or workpiece, in this effort, the relative vibration between the workpiece and tool is selected as the control target. To reduce the relative vibration, a two-axis active work-holding stage, which is droved by two piezo-actuators, is designed and the control system synthesis method is used to determine the control gain. By this method, the dynamical stage is considered as plant while the complicated cutting process is treated as disturbance. The cutting vibration control can be considered as a robust disturbance rejection problem (RDRP), and the controller design is based on robust servo-mechanism method. Without the requirement on the model of disturbance, this method simplifies the vibration control problem and only the knowledge of frequencies of disturbance is required. Numerical results indicate the implemented system works well in cutting vibration cancellation.
A Hybrid Approach for the Modal Analysis of Continuous Systems With Localized Nonlinear Constraints
Authors: Brake M. R.
Published: May 2012

The analysis of continuous systems with nonlinearities in their domain have previously been limited to either numerical approaches, or analytical methods that are constrained in the parameter space, boundary conditions, or order of the system. The present analysis develops a robust method for studying continuous systems with arbitrary boundary conditions and nonlinearities using the assumption that the nonlinear constraint can be modeled with a piecewise-linear force-deflection constitutive relationship. Under this assumption, a superposition method is used to generate homogeneous boundary conditions, and modal analysis is used to find the displacement of the system in each state of the piecewise-linear nonlinearity. In order to map across each nonlinearity in the piecewise-linear force-deflection profile, a variational calculus approach is taken that minimizes the L2 energy norm between the previous and current states. To illustrate this method, a leaf spring coupled with a connector pin immersed in a viscous fluid is modeled as a beam with a piecewise-linear constraint. From the results of the convergence and parameter studies, a high correlation between the finite-time Lyapunov exponents and the contact time per period of the excitation is observed. The parameter studies also indicate that when the system’s parameters are changed in order to reduce the magnitude of the velocity impact between the leaf spring and connector pin, the extent of the regions over which a chaotic response is observed increases.
Design of a Pultruded Steel-GFRP Hybrid Structural Member
Authors: Honickman Hart , Johrendt Jennifer , Northwood Derek , Frise Peter
Published: May 2012

A novel hybrid structural member is under development for vehicle applications. The new structure is comprised of a pultruded glass fibre reinforced polymer (GFRP) shell structure with embedded longitudinal steel rods. The rods will resist the majority of flexural and axial stresses, and serve as hard points for connection to other components; the GFRP webs between the rods will primarily be responsible for resisting shear flow. It is expected that this structural system will offer many of the benefits of carbon fibre reinforced polymer (CFRP) structures, while remaining cost effective for mass production. This paper details the process used to design physical specimens that will be fabricated and tested to experimentally assess the behaviour and performance of this hybrid structural system. Since the intended application of this technology is for vehicle structures, the specimens were designed as though they would be required to endure the environments typically seen by an automotive structure. The design was largely carried out using conventional design and analysis techniques for fibre composite laminates; however, some provisions and design innovations were necessary in order to account for the highly heterogeneous and anisotropic qualities of the hybrid members, and to ensure manufacturability using existing pultrusion equipment. Differential thermal expansion coefficients raised concerns regarding prestressing that could be induced during the pultrusion process. The quality of the bond between the steel rods and the polymer matrix was another matter that received attention. Another critical aspect of the design was the displacement and discontinuity of the GFRP laminae in the regions of the embedded steel rods.
Development of a High-Speed On-Off Valve for Switch-Mode Control of Hydraulic Circuits With Four-Quadrant Control
Authors: Wu Jeslin J. , Van de Ven James D.
Published: May 2012

Hydraulic circuits are typically controlled by throttling valves or variable displacement pump/motors. The first method throttles fluid for a desired pressure output and excess energy is lost through heat. While variable displacement pumps are more efficient, they are often large and expensive. An alternate method is the switch-mode control of hydraulic circuits through high-speed on-off valves. The proposed on-off valve design makes use of a continuously rotating disc to modulate flow between on and off states; the average power output or pulse duration is determined by the relative phase shift between the input and output ports. The addition of a directional valve to the the high-speed three-way valve allows any fixed displacement actuator to behave like a virtually variable displacement unit that is capable of four-quadrant control. In this paper a mathematical model focusing on the throttling, compressibility, internal leakage and viscous friction losses is developed and utilized to optimize the valve design for highest efficiency.
A Thermo-Mechanically Coupled Large-Deformation Theory for Amorphous Polymers Across the Glass Transition Temperature
Authors: Chester Shawn A. , Srivastava Vikas , Anand Lallit
Published: May 2012

Amorphous thermoplastic polymers are important engineering materials; however, their nonlinear, strongly temperature- and rate-dependent elastic-viscoplastic behavior is still not very well understood, and is modeled by existing constitutive theories with varying degrees of success. There is no generally agreed upon theory to model the large-deformation, thermo-mechanically-coupled, elastic-viscoplastic response of these materials in a temperature range which spans their glass transition temperature. Such a theory is crucial for the development of a numerical capability for the simulation and design of important polymer processing operations, and also for predicting the relationship between processing methods and the subsequent mechanical properties of polymeric products. In this manuscript we briefly summarize a few results from our own recent research [1–4] which is intended to fill this need.
Piston Pump Noise Attenuation Through Modification of Piston Travel Trajectory
Authors: Mehta Viral S. , Manring Noah D.
Published: May 2012

Piston pumps are widely used in industrial and mobile applications to transmit power. These pumps emit loud and objectionable noise when operated at high pressure and high speeds. It is generally accepted that large amplitude of flow ripple causes pumps to produce unacceptable noise level. The flow ripple could be thought of composed of two components — a kinematic component resulting out of periodic nature of flow and a dynamic component resulting due to compression and decompression of fluid. There has been considerable research activity to reduce the noise induced by the dynamic component however very little is done to attenuate the noise generated due to the periodic nature of flow. This research investigated one method to reduce noise associated with kinematic component for axial and radial type piston pumps. A theoretical analysis is presented deriving the equations defining the motion of pistons on their regular trajectory as well as their modified trajectory. It is shown here that by altering the trajectory of the piston travel the amplitude of the kinematic flow component could be reduced by up to 85% in some conditions. While effectiveness of the techniques aimed at reducing the dynamic flow component are speed and pressure dependent, the techniques presented here work with same effectiveness throughout the entire spectrum of speed and pressure towards reducing the noise.
Realizing Self-Manufacture of Large Hydro-Generating Unit Through Technology Transfer and Innovation in Three Gorges Project
Authors: Gong Jingkun
Published: May 2012

In this paper, the situation of technology transfer, assimilation and independence innovation of key technology, the self-manufacture of large hydro-generating unit in Three Gorges Project by Harbin Electric Corporation (HE) are presented, as well as the experience of self-innovation in Three Gorges Project is summarized.
Urban Energy System Analysis by MARKAL Model in China
Authors: Hou Wei , Sun Jian , Fu Lin , Liu Lequn
Published: May 2012

The Chinese government has planned to reduce domestic energy consumption by 20% by 2010. In order to analysis the energy saving potential in the city’s energy system from different aspects, an energy consumption model of China energy system was provided based on bottom-up MARKAL model, which assessed the future competitiveness of different types of energy supplications and the future growth in energy service demand in China under different scenarios and conditions. The modeled results were also analyzed and discussed. The model established the foundation for the study of energy technology development and energy policy in the future.
Intrinsic Finite Element Modeling of Nonlinear Dynamic Response in Helical Springs
Authors: Leamy Michael J.
Published: May 2012

This paper presents an efficient intrinsic finite element approach for modeling and analyzing the forced dynamic response of helical springs. The finite element treatment employs intrinsic curvature (and strain) interpolation vice rotation (and displacement) interpolation, and thus can accurately and efficiently represent initially curved and twisted beams with a sparse number of elements. The governing equations of motion contain nonlinearities necessary for large curvatures. In addition, a constitutive model is developed which captures coupling due to non-zero initial curvature and strain. The method is employed to efficiently study dynamically-loaded helical springs. Convergence studies demonstrate that a sparse number of elements accurately capture spring dynamic response, with more elements required to resolve higher frequency content, as expected. Presented results also document rich, amplitude-dependent frequency response. In particular, moderate amplitude response leads to the presence of secondary resonances not captured by linearized models.
Development of Water Lubricated Compressor-Expander for Fuel Cell Application
Authors: Stosic Nikola , Smith Ian K. , Kovacevic Ahmed , Mujic E.
Published: May 2012

Fuel cells, currently being developed for automotive and stationary applications, require a supply of pressurized air at about 3 bars abs. This is expelled in the reaction products, mainly as water steam and nitrogen, at approximately 100 °C. The power input required to compress the air is typically 20–25% of the cell electrical output. Hence, for the cell efficiency to be acceptable and to recover water conveniently from the reaction products, power needs to be generated by expansion of the reaction products and used to reduce the electrical output from the cell that is consumed by the compressor. Then water may be condensed in a flue gas cooler and returned to process. Screw compressor is a good choice to supply pressurized air at about 3 bars for fuel cell application. It is shown that a twin screw machine can perform both the compression and expansion functions using only one pair of rotors. Moreover, by proper location of the ports, mechanical friction losses within it will be less than if the two functions are performed in separate machines. However, due to strict requirements for oil contamination, the rotors and bearings in such a machine have to be either absolutely sealed or left open and lubricated by water. A research performed at City University is described in the paper on the rotors and bearings lubricated exclusively by water which then can be used in the combined compressor-expander screw machines which are suitable for fuel cell application.
An Industry-University Collaboration Experience on a Senior Project
Authors: Dave Janak , Dong Janet
Published: May 2012

Students working toward a baccalaureate degree in Mechanical/Electrical Engineering Technology at the University of Cincinnati are required to complete a “Design, Build, and Test” senior capstone design project. Some of these capstone design projects are done in collaboration with industries to meet their needs. One of the projects during 2009–2010 academic year is to meet the needs of the packaging industry. The student team will design and recommend a specialized End of Arm Tool for palletizing applications. They will build a scaled model and the industrial sponsor may build the full product at the later date. A team of three students from Mechanical Engineering Technology at the University of Cincinnati are working on this project, which gives them an opportunity to showcase the knowledge and skills learned in their coursework and during the co-op (cooperative) experience, as well as to develop the additional skills needed to be successful in a team oriented business world. This team is working on a technically complex project from concept-to-design, build, test, and then to have the possibility of their product being used in commercial applications. This paper will give a description of the MET senior capstone design course sequence at University of Cincinnati and the list of pre-requisites for the capstone design sequence. It will also describe the design of 2009–2010 End of Arm Tool (EOAT) project and the plans for building a scaled model. Included too, is a description of how Industry-University Collaboration can improve student learning.
Biodynamic Modeling of a Pedestrian Impact With a Rigid Frontal Guard of a Utility Vehicle
Authors: Moradi Rasoul , Thorbole Chandrashekhar K. , McCoy Michael , Lankarani Hamid M.
Published: May 2012

Accident data reveals that in most pedestrian accidents, the pedestrian head and lower extremity are vulnerable to serious injuries. The vehicle front geometry profile as well as the impact speed are important factors affecting the pedestrian kinematics and injury potential. In the US, accident data also shows that the fatality rate for pedestrian/light trucks and vans (LTV) impact is greater than that for the pedestrian/passenger-car impact. Addition of a front guard on light trucks and sports utility vehicles to mitigate damage during off-road activity or to provide mounting points for extra lights, makes the pedestrian more vulnerable to the impact. In this paper, a computational technique is utilized to study the influence of the added front guard on the impacted pedestrian. A CAD model of a typical commercial frontal guard is developed and converted into a rigid facet model, and attached to the vehicle front. The validated standing dummy model in the MADYMO code is used to simulate a pedestrian, and the rigid facet-surface model of a pickup truck is used to generate a vehicle front surface. This computational model is validated by comparing the pedestrian kinematics with the published data. This study demonstrates that the pedestrian mid body region is more vulnerable with the addition of guard on the vehicle. The result from this study facilitates a better understanding of a guard design and its geometry profile as required to protect vulnerable road users.
Data Modeling Using NURBs Curves and Modified Genetic Algorithms
Authors: Hammond Christopher , Turner Cameron J.
Published: May 2012

Non-Uniform Rational B-Splines (NURBS) curves have long been used to model 1D and 2D data because they are efficient to calculate, easy to manipulate, and capable of handling discontinuities and drastic changes in the general topology of the data. However, the user must assist in defining the control points, weights, knots and an order for the curve in order to fit the curve to the data. This paper uses a modified Genetic Algorithm (GA) to choose and manipulate these various parameters to produce a NURBS curve that minimizes the error between the data and the curve and also minimizes the time it takes the algorithm to compute the solution. The algorithm is tested on several 1D trial data sets and the results are explained. Then, several general difficulties for this application of the GA are explained and possible methods for overcoming them are discussed.
Research on Heat Exchange Characteristics Between Rock and High-Pressure Fluid Through the Cranny Among Dry Hot Rocks
Authors: Li Lun , Li Jishun , Zhang Shengqi , Ma Wei , Xue Yujun
Published: May 2012

Owing to energy crisis and global warming, people have to seek for new energy sources to substitute fossil fuels. Human being would maintain persistent development by means of new replaceable energy sources. As a kind of replaceable energy source, geothermal power is attracting people more and more attention. The technology of geothermal power generation has been gradually recognized and applied around the world. Heat exchange is the basic principle of geothermal power generation. A lot of heats stored in dry hot rocks under the ground can be carried out by high-pressure medium. The heat energy drives the steam turbine generator to work. Therefore, the heat exchange between rock and high-pressure fluid through the dry hot rock crannies is a key problem which needs to be solved. Based on the geological structure of rocks, the hypothetical cranny among dry hot rocks is put forward in this paper. The model of a single cranny is established too. The heat exchange between rock and high-pressure fluid through the dry hot rock crannies is analyzed based on the theory of heat transfer and hydrodynamics. The relationship among high-pressure fluid temperature, fluid velocity, dry hot rock crannies length and dry hot rock temperature field is obtained using the single cranny model. It may be useful for the development and application of geothermal resources.
Dynamic Stress Intensity Factor for an Interfacial Crack on a Circular Cavity in Piezoelectric Media
Authors: Song Tianshu , Li Dong , Merhej Tamman
Published: May 2012

Dynamic stress intensity factor is investigated theoretically on two dissimilar piezoelectric media with an interfacial crack at the edge of a circular cavity subjected to time-harmonic incident anti-plane shearing in present paper. The formulations are based on the methods of Green’s function and conjunction. Dynamic stress intensity factor at the crack’s tip are obtained by solving boundary value problems with the methods of conjunction and crack-division technique. The calculating results are plotted so as to show how the frequencies of incident wave, all kinds of physical parameters of two dissimilar piezoelectric materials, applied electric loads and geometric parameters influence on the dynamic stress intensity factor (DSIF). While some of the calculating results are compared with other published documents.
Cohesive Laws for Delamination of CFRP: Experiments and Model
Authors: Stigh Ulf
Published: May 2012

In the present paper, we study delamination of a carbon fibre reinforced composite at a small length scale, i.e. without consideration of crack bridging. The study is performed within the framework of cohesive modelling. We propose methods based on the applications of the path independent J-integral to measure the cohesive law for delamination. With a DCB-specimen, the cohesive law corresponding to mode I loading is measured and with an ENF-specimen, the law corresponding to mode II loading is measured. These laws are used to calibrate a mixed-mode cohesive law. It is argued that the most important parameters of a cohesive law are the ability to provide the correct fracture energy and strength. The cohesive law is developed using a minimum of adjustable parameters to provide a transparent calibration process.
Integrated Process Planning Based on a Federative Factory Data Management
Authors: Mosch Christian , Anderl Reiner , Moura Antonio A´lvaro de Assis , Schuetzer Klaus
Published: May 2012

Manufacturing companies are confronted with short product life cycles, more variety of products and short cycles of leap innovations. This results in a higher frequency of changes in factory structures and an increasing importance of factory planning processes. Factory planning processes are characterized by participative and interdisciplinary processes due to various actors dealing in different domains and working in distributed environments. The result is a heterogeneous IT-landscape based on increasing use of multiple isolated and domain-specific IT tools and systems and hereby an increasing redundant, inhomogeneous and inconsistent data-holding. The control of these factory planning processes can be reached by holistic approaches and consistent system integration. The mean of system integration is the consideration of all domains involved in planning processes, used IT tools and systems and business processes. In this paper, the approach of a Federative Factory Data Management (FFDM) based on Service Oriented Architecture (SOA) and Semantic Model funded by the DFG (Germany) and CAPES (Brazil) will be described, which faces up the described challenges of factory planning processes. The focus of this approach is on the integration of isolated used IT tools for the dimensioning and structuring of factory systems, the generated domain-specific partial models as well as the coordination and synchronization of engineering workflows. In order of the control of factory planning processes the integration and coupling of the views of products, processes and resources on metadata level is required for a communication between different isolated and domain-specific IT tools of the various involved domains without losses or redundancies. The integration and coupling of these three views is based on a document independent factory structure description linked with factory defining metadata. In order to integrate and couple these different views, the relevant information and independencies are identified. Current reference process models for production and factory planning as well as the current methods to describe domain-specific models are analyzed. This is the basis for the development of the FFDM to build up a semantically coherent information model as a common communication and integration framework to represent the factory and to define and to access factory data. The goal of the presented approach is the increasing of planning harmonization, certainty, quality and frequency by a consistent information flow as well as the reduction of time of product development and factory planning processes.
Lessons Learned From Avionics Integrity Program (AVIP) Durability Life Testing (DLT)
Authors: Lide Charles , Kunc Chris , Glista Stefan , Barnett Kent , Alexander Ric , Bielefeld David
Published: May 2012

In the late 1980s the United States Air Force began requiring the implementation of the Avionics/ Electronics Integrity Program (AVIP). The purpose of AVIP was to utilize physics of failure analysis and test methods during development to eliminate fatigue and wearout failure mechanisms when systems are fielded. One of the key features of AVIP is the durability life test (DLT). The F-22 program was the first major weapons system to comprehensively require AVIP or the Mechanical Systems Integrity Program (MECSIP) for all equipment. The paper documents the findings and lessons learned from the F-22 program DLT for avionics and electronics. The paper discusses the driving environments of vibration and thermal cycling and test compression for those environments. Also discussed are test specifications, sample size, test setup, combined environments, failure criteria, and test instrumentation. Programmatic issues with DLT are presented. The data reduction for a large sample of tests is reported by failure type and as a function of test duration. Corrective action and corrective action verification is discussed and statistics presented. Finally, a cost-benefit analysis shows the benefit of DLT.
Synthesis, Characterization and Mechanical Properties of Silicon Carbide Nanowires
Authors: Zhang Huan , Ding Weiqiang , Aidun Daryush
Published: May 2012

Silicon carbide (SiC) material has many outstanding physical and mechanical properties such as high strength, high hardness, low density, high thermal conductivity, low thermal expansion coefficient, large band-gap, and excellent oxidation and corrosion resistances [1–3]. It is a leading material for components and devices operating at high temperature, high power and under harsh environments [4–5]. Micro-sized SiC particles and whiskers are commonly used as reinforcement materials for ceramics, metals and alloys in various structural and tribological applications [6–7].
A CFD Investigation of Window Cooling for an Optically Accessible Combustion Rig
Authors: Chen S.
Published: May 2012

Numerical simulation was performed for the window cooling system of a new facility, the High Pressure Optically Accessible Combustion Rig, at Institute for Aerospace Research, National Research Council Canada. The Shear-Stress Transport k-ω two-equation model in FLUENT was used to solve the complex flows. The numerical results revealed that a cooling film was formed along the window glass. However, because of the presence of the bridge blocks the cooling film was not quite uniform. The bridge blocks for the cooling slots induced complex flow patterns and thus reduced the cooling effectiveness for the window. The maximum surface temperature was found to be at the trailing edge of the inner window surface. The cooling flow exiting from the downstream end cooling slot formed a large and strong vortex, which entrained hot air from the combustion air flow and caused the described high surface temperature. At the current flow condition, the maximum value of the temperature on the window surface was slightly higher than the allowable temperature for the designed window material.
Tractive Efficiency Analysis for an Intelligent Air-Cushion Tracked Vehicle
Authors: Mohiuddin A. K. M. , Hossain Altab , Rahman Ataur , Aminanda Yulfian
Published: May 2012

This study presents the tractive efficiency of an intelligent air-cushion tracked vehicle (IACTV) working on swamp terrain. Based on the total power consumption and optimum load distribution for IACTV, two main issues are studied in this paper. First, a theoretical model is developed for optimizing total power consumption of the vehicle and tractive efficiency has been investigated with the effects of load distribution on the vehicle performance. Secondly, the vehicle has the ability to response for the changeable cushion pressure based on the cushion height from the ground. The system is effective to control the intelligent air–cushion system by measuring the vehicle tractive efficiency (TE), volume flow rate (Q), cushion height (CH) and cushion pressure (CP). Experiment and simulation results showed that the optimal power consumption can be obtained and maintained by using the designed fuzzy logic system (FLS) with the load distribution ratio of 0.2 and tractive efficiency of 62%. The mean relative error of actual and predicted values from the FLS model on tractive efficiency is found as 9.2%, which is less than the acceptable limit of 10%. The goodness of fit of the prediction value from FLS is found as 0.96.
VAT Based Modeling of Heat Exchanger and Obtaining Closure From CFD Solution
Authors: Zhou Feng , Hansen Nicholas , Catton Ivan
Published: May 2012

VAT is used to rigorously cast the point-wise conservation of energy, momentum and mass equations into a form that represents the thermal and hydraulic properties of heat exchanger channel morphology. At the lower level, the media is described by a representative elementary volume (REV). Closure terms in the VAT equations are related to a local friction factor and a heat transfer coefficient of the REV. The terms in the closure expressions are complex and relating experimental data to the closure terms resulting from Volume Averaging Theory (VAT) is difficult. In this work we use CFD to obtain detailed solutions to flow through an element of a heat exchanger and use these results to evaluate the closure terms needed for a fast running VAT based code. The VAT based code can then be used to solve the heat transfer characteristics of the higher level heat exchanger. A comparison is then made of the CFD closure and experimental data rescaled by VAT scaling. The objective is to show how heat exchangers can be modeled as porous media based on Volume Averaging Theory and how CFD can be used in place of a detailed, often formidable, experimental effort.
Study of Heat Transfer and Fluid Flow in Transitional Regime Inside a Channel With Offset Plates Heated by Radiation for Photovoltaic/Thermal System
Authors: Ali Ahmed Hamza H. , Youssef M. S. , Ahmed Mahmoud
Published: May 2012

This study investigates experimentally and theoretically both the effects of operating and configuration parameters on convection heat transfer process and fluid flow characteristics for air flowing in transitional regime through parallel plate channel with offset plate segments heated by a radiation heat flux. This configuration is intended to be applied into air heater solar collectors and/or a combined photovoltaic and air heater solar collector system (PV/T). In the experimental measurements, the operating parameters tested were Re values ranging from 2580 to 4650 with combination of incident radiation heat flux (qinc) values of 400, 700, and 1000 W/m2, respectively. The experimental results show that the local Nusselt number (Nux) is not unique function in the axial distance. In addition, a linear relationship between Re and apparent friction factor is observed. Moreover, in case of Re = 2600, increasing the incident radiation flux values by 175% and 250% leads to an increase in Nux values by 20% and 35%, respectively. The theoretical results indicate that, combinations of Re values inside the channel falling within the laminar regime with selections of both the plate’s length and thickness can lead to the convection heat transfer enhancement with avoiding of additional pumping power penalty when the channel flow falls in transitional regime.
Fluctuating Shear Stress Calibration Method Using a Channel Flow
Authors: Cole Daniel C. , Jonson Michael L. , Sharp Kendra V.
Published: May 2012

Fluctuating wall shear stress causes vibration and radiated noise from a structure. In the past wall shear stress has been measured indirectly using hot wires and hot films. Recently direct shear sensors have been developed. In this paper a calibration device consisting of a 305 mm × 60 mm × 5 mm channel filled with glycerin is used to calibrate a direct shear stress sensor with amplitudes up to 10 Pa of shear stress over a frequency range from 10 Hz to 1 kHz. The analytically known flow field caused by an oscillating plate 5 mm from the sensor is verified using laser Doppler velocimetry (LDV). The flow field is derived using a frequency-wavenumber approach thereby allowing for a known spatial and temporal field to be generated by specifying a derived plate vibration.
Experimental Investigation of Porous-Media Combustion Characteristics of Biodiesel Blends
Authors: Dahifale Balasaheb S. , Parthasarathy Ramkumar N. , Gollahalli Subramanyam R.
Published: May 2012

The use of porous-media burners in air-heating systems, gas turbine combustors, and steam generators is a potential method to reduce pollutant emission levels. Biofuels, such as canola methyl ester (CME), are an attractive alternate energy resource; however, pure biofuels have lower energy content than petroleum-based fuels. Therefore, the combustion characteristics of blends of Jet A and CME were studied in a porous-media burner. Two silicon carbide coated carbon-carbon matrix porous media of square section were used. The upstream porous medium with a pore size of 8 pores per centimeter (20 pores per inch) served as the evaporation porous medium; the downstream porous medium with a pore size of 31 ppcm (80 ppi) was used as the combustion porous medium. The CME-Jet A fuel blends were injected from an air-blast atomizer into a coflow of hot air, which entered the evaporation porous medium. The combustion characteristics of three blends (volume percentages of CME equal to 25%, 50% and 75%) were studied at four different initial equivalence ratios. The global pollutant emissions, axial temperature profiles and the radiative heat fraction of the flame downstream of the combustion porous medium were measured. The results indicated that for lean air-fuel mixtures, the addition of CME to Jet A resulted in a reduction of the CO emission index. However, the NOx emission index was increased with the CME content in the blend for a given equivalence ratio. Also, the maximum flame temperature increased with equivalence ratio. In general, it was found that the porous-media burner was useful in reducing emissions and controlling flame temperatures.