Modes of Wave Propagation and Dispersion Relations in Inclusion Reinforced Composite Plates

This paper mainly analyzes the wave dispersion relations and associated modal pattens in the inclusion-reinforced composite plates including the effect of inclusion shapes, inclusion contents, inclusion elastic constants, and plate thickness. The shape of inclusion is modeled as spheroid that enables the composite reinforcement geometrical configurations ranging from sphere to short and continuous fiber. Using the Mori-Tanaka mean-field theory, the effective elastic moduli which are able to elucidate the effect of inclusion’s shape, stiffness, and volume fraction on the composite’s anisotropic elastic behavior can be predicted explicitly. Then, the dispersion relations and the modal patterns of Lamb waves determined from the effective elastic moduli can be obtained by using the dynamic stiffness matrix method. Numerical simulations have been given for the various inclusion types and the resulting dispersions in various wave types on the composite plate. The types (symmetric or antisymmetric) of Lamb waves in an isotropic plate can be classified according to the wave motions about the midplane of the plate. For an orthotropic composite plate, it can also be classified as either symmetric or antisymmetric waves by analyzing the dispersion curves and inspecting the calculated modal patterns. It is also found that the inclusion contents, aspect ratios and plate thickness affect propagation velocities, higher-order mode cutoff frequencies, and modal patterns.

Static Analysis of Moderately Thick Functionally Graded Plates With Various Boundary Conditions

The present study investigates static analyses of moderately thick FG plates. Using the First Order Shear Deformation Theory (FSDT), functionally graded plates subjected to transversely distributed loading with various boundary conditions are studied. Effective mechanical properties which vary from one surface of the plate to the other assumed to be defined by a power law form of distribution. Different ceramic-metal sets of materials are studied. Solution of the governing equations, including five equilibrium and eight constitutive equations, is obtained by the Extended Kantorovich Method (EKM). The system of thirteen Partial Differential Equations (PDEs) in terms of displacements, rotations, force and moment resultants are considered as multiplications of separable function of independent variables x and y. Then by successful utilization of the EKM these equations are converted to a double set of ODE systems in terms of x and y. The obtained ODE systems are then solved iteratively until final convergence is achieved. Closed form solution is presented for these ODE sets. It is shown that the method is very stable and provides fast convergence and highly accurate predictions for both thin and moderately thick plates. Comparison of the normal stresses at various points of rectangular plates and deflection of mid-point of the plate are presented and compared with available data in the literature. The effects of the volume fraction exponent n on the behavior of the normalized deflection, moment resultants and stresses of FG plates are also studied. To validate data for analysis fully clamped FG plates, another analysis was carried out using finite element code ANSYS. Close agreement is observed between predictions of the EKM and ANSYS.

A Study on the Development of a Practical Postprocessor for 5-Axis Machining

This paper deals with the development of a practical postprocessor for 5-axis machine tools. Recently, special 5-axis machine tools with non-orthogonal rotary axes as well as typical 5-axis machine tools with orthogonal rotary axes have been introduced. In the present work, the general equations of NC data for 5-axis configurations with non-orthogonal rotary axes are exactly expressed by the inverse kinematics, and a Windows-based postprocessor written in Visual Basic was developed according to the proposed algorithm. The developed postprocessor is a general system suitable for all kinds of 5-axis machine tools not only with orthogonal rotary axes but also with non-orthogonal rotary axes, thereby expanding the range of application of the developed postprocessor. In addition, through implementation of the developed postprocessor and verification by a cutting simulation and machining experiment, the effectiveness of the proposed algorithm was confirmed. Compatibility was improved by allowing exchange of data formats such as RTCP controlled NC data, Vector post NC data, and POF CL data, and convenience was increased by adding the function of work-piece origin offset. Consequently, a practical post-processor for 5-axis machining has been developed.

A Low Cost Velocity Measurement System Design for Rotary Machinery

Today, as the importance of system automation increases, measurement systems become more and more important. Consequently, in many applications, from washing machines, motorized vehicles, robots to nuclear turbine reactors, velocity measurement is inevitable. In industry, velocity is widespreadly needed to be measured. Besides that researchers through the globe need such measurement devices in their studies. On the other hand, to be able to make a correct measurement, it may be needed to pay much on measuring equipments while the economical issue is sometimes the reason for the research does not continue on or even not begin. So, it has always been a practical problem for both industry and researchers not to be able to measure the rotating velocity of machinery with both sufficient precision and low cost. In this paper, a very low cost but still precise velocity measurement system design is introduced, explained and discussed. First, building up of the sensor circuit and basic components of the system are introduced. Then, data acquisition and signal processing of the system are explained. Finally, advantages of the system are discussed and some conclusions are given.

A Methodological Approach to Radical Technological Changes and Improvements in Electron Beam Technology

Predicting of the optimal machining conditions for experimental results and dimensional accuracy plays an important role in process planning. In addition, whenever there is a new unknown process, great importance has to be placed on the estimation of all operative conditions with rational and logical planning methodologies. The aim of this work is to obtain feasible conditions for Electron Beam (EB) technology, using a welding machine, which is then converted for additive manufacturing processes. At the beginning of the research there was a state of uncertainty about the influencing parameters and the use of EB for rapid manufacturing process; a multi-disciplinary and integrated methodology was then performed in order to carry out the work. The proposed methodology is composed of several techniques, including a method to support multi-decision making problems and a statistical approach.

Mathematical Modeling of Abrasive Waterjet Turning of Ductile Materials

In this paper, an erosion-based model for abrasive waterjet (AWJ) turning process is presented. In the AWJ turning process a particular volume of material is removed by impacting of abrasive particles to the surface of the rotating cylindrical workpiece. This volume is estimated according to the modified Hashish erosion model; thus radius reduction at each revolution is calculated. The distinctively proposed model considers the continuous change in local impact angle due to change in workpiece diameter, axial traverse speed of the jet, the abrasive particle roundness and density. The accuracy of the proposed model is approved by experimental tests under various traverse speeds. The final diameters estimated by the new model are in good accordance with the experiments.

Investigating Optimum Procedures Needed to Maintain a Model Satellite’s CG Stable About Design Point, Under Subsystem Configuration Changes

During design, microsatellites are subject to different changes like the changes in weight, location and dimension of parts and elements of subsystems and the payload. These changes should be accumulated by the structure subsystem in a way that some key structural parameters like the center of gravity (CG) and inertia moments remain unchanged. This subject is also important regarding the design of a modular structure of a satellite. In the present study it is tried to accommodate any changes in weight and location of any part(s) and element(s) of a microsatellite by optimum (minimum) rearrangement of other parts on their plane of rest in order to keep the CG and inertia moments unchanged. This is performed by a special mathematics modeling considering the existing constraints. Of course, no addition or subtractions of weight from the remaining parts are assumed. Also, in order to keep the original structural design intact, no movement of the parts except in the close neighborhood of their original location is allowed. At the end, this study shows that it is possible to move other subsystems on some suitable paths as a result of changing one subsystem mass from −100% (omitting that element) to 100% (doubling the weight of that element) to maintain the overall CG position in its previous position.

Life Cycle Cost Modeling of Pumps Using an Activity Based Costing Methodology

In order to survive in today’s competitive global business environment, implementation of life cycle costing methodology with a greater emphasis on cost control could be one of the convincing approaches for the manufacturing firms. The product life cycle costing approach can help track and analyse the cost implications associated with each phase of product life cycle. Life cycle costing (LCC) practices with traditional costing methods may provide results that have a severe deviation from the real product LCC as it focuses on the cost of materials, labor and a low portion of overheads apportioned by the absorption rate to the product. Activity based costing (ABC) has emerged as one of the several innovative and more accurate costing methods in recent years. It is based on the principle that products or services consume activities and activities consume resources that generate costs. Thus, the ABC system focuses on calculating the costs incurred on performing the activities to manufacture a product. This paper presents a LCC modeling approach for estimating life cycle cost of pumps using activity based costing method. The study was conducted in a large pump manufacturing company from India that has significant global standing within its industry. Firstly, all the activities and cost drivers associated with the life cycle of a pump have been identified. A methodology for LCC analysis using ABC is then developed and it is applied to two different pumps manufactured by the same industry and the results obtained are presented.

Investigation of Sectoral Scanning in Selective Laser Melting

Selective laser melting (SLM), a powder metallurgical (PM) additive manufacturing (AM) technology, is able to produce fully functional parts directly from standard metal powders without using any intermediate binders or any additional post-processing steps. During the process, a laser beam selectively scans a powder bed according to the CAD data of the part to be produced and completely melts the powder particles together. Stacking and bonding two-dimensional powder layers in this way, allows production of fully dense parts with any geometrical complexity. The scanning of the powder bed by the laser beam can be achieved in several different ways, one of which is island or sectoral scanning. In this way, the area to be scanned is divided in small square areas (‘sectors’) which are scanned in a random order. This study is carried out to explore the influence of sectoral scanning on density, surface quality, mechanical properties and residual stresses formed during SLM. The experiments are carried out on a machine with an Nd:YAG laser source using AISI 316L stainless steel powder. As a result of this experimental study, it is concluded that sectoral scanning has some advantages such as lower residual stresses and better surface quality. However, the selection of parameters related to sectoral scanning is a critical task since it may cause aligned porosity at the edges between sectors or scanned tracks, which is very undesired in terms of mechanical properties.

Effect of Material Properties and Thickness of Die Attach on Delamination of Die Attach/Die Paddle Interface in Electronic Package

The electronic package is a multi-layered structure that is consisted of several materials. Under the temperature loadings, the interfacial stresses between layered components are generated due to the CTE (coefficient of thermal expansion) mismatch between different materials. In die bonding process, the void or defect might exist at the die attach/die paddle interface. The void cause further delamination on the interface during the encapsulation process. In this study, the finite element method is used to construct the model of electronic package with a void on the die attach/die paddle interface. The energy release rate based on J integration, which is calculated by the stress and strain around the tip of crack, is used as a damage parameter to predict the tendency of further delamination during encapsulation. Effect of material properties (Young’s modulus and CTE) and die attach thickness on delamination of die attach/die paddle interface in package during encapsulation is studied.