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Mechanical Engineering

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Missouri University of Science and Technology

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2000

Articles 1 - 18 of 18

Full-Text Articles in Engineering

Investment Casting With Ice Patterns Made By Rapid Freeze Prototyping, Wei Zhang, Ming-Chuan Leu, Chao Feng, Rong Ren, Renjie Zhang, Qingping Lu, Jubu Jiang, Yongnian Yan Aug 2000

Investment Casting With Ice Patterns Made By Rapid Freeze Prototyping, Wei Zhang, Ming-Chuan Leu, Chao Feng, Rong Ren, Renjie Zhang, Qingping Lu, Jubu Jiang, Yongnian Yan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

One of the most promising applications of rapid freeze prototyping (RFP) is making metal parts by investment casting with the built ice parts. The integration of RFP and investment casting allows fast creation of complex net-shape metal parts directly from their CAD models. The advantages of doing so include no part geometric complexity limitation, no experience of parting line design and assembling needed, clean and low-cost of process operation, and good performance. In this paper, we will present our recent study on binder selection, slurry making, ceramic shell making, and the casting results of the metal parts.

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Laser Additive Manufacturing Process Planning And Automation, Jun Zhang, Jianzhong Ruan, Frank W. Liou Aug 2000

Laser Additive Manufacturing Process Planning And Automation, Jun Zhang, Jianzhong Ruan, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a Laser Additive Manufacturing Process Planning (LAMPP) being developed at the University of Missouri-Rolla. The off-line planning recognizes difficult-to-build features from an STL file, selects optimal part orientation and building directions based on the skeleton information of the object geometry, and optimizes the sub-process sequences for deposition and machining. During the optimization of the subpart building processes, collaboration between the deposition process planner and the machining process planner is needed to check the deposition availability and machinability. As a result, tool paths for both the laser head and the machining head are automatically generated.

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Determination And Improvement Of Building Speed In Rapid Freeze Prototyping, Wei Zhang, Guanghua Sui, Ming-Chuan Leu Aug 2000

Determination And Improvement Of Building Speed In Rapid Freeze Prototyping, Wei Zhang, Guanghua Sui, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Rapid freeze prototyping (RFP) is a solid freeform fabrication process that builds an ice part by rapidly freezing water in a layer by layer manner. One advantage of this process is the ability to build ice parts faster than other SFF processes. The factors that affect the speed of contour building and interior filling in RFP are identified. The influence of these factors is analyzed through heat transfer and material flow analyses. A model based on heat transfer analysis is proposed to determine the maximum achievable speed of contour building under stable conditions. Experiments are conducted to validate the performance …

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Study On Water Deposit In Rapid Freeze Prototyping Process, Guanghua Sui, Weihan Zhang, Ming-Chuan Leu Aug 2000

Study On Water Deposit In Rapid Freeze Prototyping Process, Guanghua Sui, Weihan Zhang, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Rapid Freeze Prototyping (RFP) builds a three-dimensional ice part according to its CAD model by depositing and rapidly freezing water in a layer-by-layer manner. To study the water deposit in RFP, assumptions are made based on the deformation of water droplet impinging on a flat substrate, the thermal analysis of a new layer of water deposit, and the characteristics of solidification of a water drop. The equations governing the cross-sectional profile of the water deposit are then established. A model of water deposit is proposed by simplifying the equations under our experimental conditions in RFP. By using this model, equations …

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Process Modeling, Monitoring And Control Of Laser Metal Forming, N. Munjuluri, Sanjeev Agarwal, Frank W. Liou Aug 2000

Process Modeling, Monitoring And Control Of Laser Metal Forming, N. Munjuluri, Sanjeev Agarwal, Frank W. Liou

Electrical and Computer Engineering Faculty Research & Creative Works

Laser Metal Forming (LMF) process is one of the prominent Rapid Prototyping (RP) process that can be used to develop functional and fully dense metal parts. This paper addresses process modeling, monitoring and control of a laser metal forming system currently under development at Laser Aided Manufacturing Processes (LAMP) laboratory at University of Missouri--Rolla. This LMF system is based on a 2.5kW Nd:YAG laser as energy source and integrates five axis metal deposition and five axis machining. The current paper is aimed at characterization of effects of operating parameters such as traverse speed, mass flow-rate and laser power on the …

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High-Temperature Characteristics Of 1.3 Μm Ingaasn:Sb/Gaas Multiple-Quantum-Well Lasers Grown By Molecular-Beam Epitaxy, Xiaodong Yang, J. B. Heroux, M. J. Jurkovic, W. I. Wang Feb 2000

High-Temperature Characteristics Of 1.3 Μm Ingaasn:Sb/Gaas Multiple-Quantum-Well Lasers Grown By Molecular-Beam Epitaxy, Xiaodong Yang, J. B. Heroux, M. J. Jurkovic, W. I. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

1.3 μm InGaAsN:Sb/GaAs multiple-quantum-well laser diodes have been grown by solid-source molecular-beam epitaxy using Sb as a surfactant. A low threshold of 1.1 kA/cm² was achieved for broad-area laser diodes under pulsed operation at room temperature. High-temperature device characterization revealed characteristic temperatures (T₀) of 92 and 54 K for operating temperatures below and above 75°C, respectively, as well as a lasing-wavelength temperature dependence of 0.36 nm/°C.

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Convergence Analysis Of Adaptive Critic Based Optimal Control, S. N. Balakrishnan, Xin Liu Jan 2000

Convergence Analysis Of Adaptive Critic Based Optimal Control, S. N. Balakrishnan, Xin Liu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive critic based neural networks have been found to be powerful tools in solving various optimal control problems. The adaptive critic approach consists of two neural networks which output the control values and the Lagrangian multipliers associated with optimal control. These networks are trained successively and when the outputs of the two networks are mutually consistent and satisfy the differential constraints, the controller network output produces optimal control. In this paper, we analyze the mechanics of convergence of the network solutions. We establish the necessary conditions for the network solutions to converge and show that the converged solution is optimal.

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Midcourse Guidance Law With Neural Networks, Dongchen Han, S. N. Balakrishnan Jan 2000

Midcourse Guidance Law With Neural Networks, Dongchen Han, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A neural network-based synthesis of an optimal midcourse guidance law is presented in this study. We use a set of two-neural networks; the first network called 'a critic' outputs the Lagrange's multipliers arising in an optimal control formulation and second network called 'an action network' outputs the optimal guidance/control. In this so-called 'adaptive critic' approach, the inputs to the networks are the current values of the states. This approach needs no external training. System equations, optimality conditions and the costate equations are used in conjunction with the network outputs to provide the targets for the neural networks. When the critic …

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Carryover For Hypersonic '+' And 'X' Configuration Delta Fin Missiles, Harlan F. Nelson Jan 2000

Carryover For Hypersonic '+' And 'X' Configuration Delta Fin Missiles, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Zonal Euler Solver code (ZEUS) is used to predict hypersonic missile flow fields and to determine the carryover factors for the effect of the body on wing lift, Kw(B), and for the effect of the wing on body lift, KB(w). Results are presented for Mach 4, 6, 8, and 10 at an angle of attack of 2 deg. The missile has a conical nose and a cylindrical fuselage with a 1-degree flair angle. Both 'x' and '+' fin configurations are considered. Results are given for 20 and 30 deg semi vertex angles as a function of fur span to …

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Editorial, Ahmed Noor, Victor Birman Jan 2000

Editorial, Ahmed Noor, Victor Birman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

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A Heuristic Method For Identifying Modules For Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford Jan 2000

A Heuristic Method For Identifying Modules For Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Developing product architectures is a key phase in design and development processes. It encompasses the transformation of product function to alternative product layouts. In this paper, we describe a new approach for identifying modules for product architectures. We begin by reviewing the terminology and motivation for modular products. The new concepts of a functional basis and time ordered function chains are used to formally derive functional models of products. Then, three heuristic methods for identifying modules from functional models are presented. Using the formal functional decomposition and heuristic methods, modular design can be executed earlier in the product development process, …

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Tuning Parameter Tolerance Design: Foundations, Methods, And Measures, Daniel A. Mcadams, Kristin L. Wood Jan 2000

Tuning Parameter Tolerance Design: Foundations, Methods, And Measures, Daniel A. Mcadams, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a novel technique is presented to solve tolerance design problems. To achieve the desired performance tolerance, the technique uses a subtle, but significant, change in the design: the addition of a tuning parameter in place of an increase in component precision. Statistical models are used to develop a framework for the tuning parameter design method. Also developed is a new, dimensionless design metric which ranks candidate tuning parameters. A step-by-step method is developed for the application of tuning parameters using this metric. The step-by-step tuning parameter design method is applied to a heavy-duty manual stapler as a …

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Experimental Characterization Of Hygrothermal And Aging Effects In Textile Composites, Lokeswarappa R. Dharani, Samit Roy, V. Gupta, Weiqun Xu, N. Dixon Jan 2000

Experimental Characterization Of Hygrothermal And Aging Effects In Textile Composites, Lokeswarappa R. Dharani, Samit Roy, V. Gupta, Weiqun Xu, N. Dixon

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper summarizes the hygrothermal and physical aging tests that were conducted on AS4/PR500 5HS textile composite laminates. The objectives of the hygrothermal tests were to determine the diffusivity and maximum moisture content of the laminate. Three temperatures and three relative humidity levels (RH) were used in combination to create seven test conditions. In addition, three stress levels and three damage levels were imposed to examine the combined effects of stress and damage on moisture absorption. Short-term creep tests were performed on neat resin at different test temperatures to characterize physical aging of the resin matrix. In addition, creep and …

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Development Of A Functional Basis For Design, Robert B. Stone, Kristin L. Wood Jan 2000

Development Of A Functional Basis For Design, Robert B. Stone, Kristin L. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Functional models represent a form independent blueprint of a product. As with any blueprint or schematic, a consistent language or coding system is required to ensure others can read it. This paper introduces such a design language, called a functional basis, where product function is characterized in a verb-object (function-flow) format. The set of functions and flows is intended to comprehensively describe the mechanical design space. Clear definitions are provided for each function and flow. The functional basis is compared to previous functional representations and is shown to subsume these attempts as well as offer a more consistent classification scheme. …

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Using Quantitative Functional Models To Develop Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford Jan 2000

Using Quantitative Functional Models To Develop Product Architectures, Robert B. Stone, Kristin L. Wood, Richard H. Crawford

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Developing product architectures is a key phase in design and development processes. It encompasses the transformation from functional model to alternative product layouts. In this paper, we introduce a methodology for representing a functional model of a product in a quantitative manner. In addition to describing product functionality, the quantitative functional model also incorporates customer need ratings. Product design knowledge can be archived and transmitted in databases using this novel representation. Numerical manipulations of such a database assist in developing product architectures. In particular, product families and customer need ratings for modules are easily computed. Prior to the methodology, a …

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Infinite Time Optimal Neuro Control For Distributed Parameter Systems, S. N. Balakrishnan, Radhakant Padhi Jan 2000

Infinite Time Optimal Neuro Control For Distributed Parameter Systems, S. N. Balakrishnan, Radhakant Padhi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The conventional dynamic programming methodology for the solution of optimal control, despite having many desirable features, is severely restricted by its computational requirements. However, in recent times, an alternate formulation, known as the adaptive-critic synthesis, has given it a new perspective. In this paper, we have attempted to use the philosophy of adaptive-critic design to the optimal control of distributed parameter systems. An important contribution of this study is the derivation of the necessary conditions of optimality for distributed parameter systems, described in discrete domain, following the principle of approximate dynamic programming. Then the derived necessary conditions of optimality are …

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Lifecycle Analysis For Environmentally Conscious Solid Freeform Manufacturing, Yanchun Luo, Ji Zhiming, Ming-Chuan Leu, R. J. Caudill Jan 2000

Lifecycle Analysis For Environmentally Conscious Solid Freeform Manufacturing, Yanchun Luo, Ji Zhiming, Ming-Chuan Leu, R. J. Caudill

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A lifecycle based process model for analyzing the environmental performance of SFM processes and SFM based rapid tooling processes is presented in this paper. The process environmental performance assessment model considers material, energy and disposal scenarios. The material use, process parameters (e.g. scanning speed) and power use can affect the environmental consequence of a process when material resource, energy, human health and environmental damage are taken into account. The presented method is applied to the SLA process and two SLA based rapid tooling processes. The method can be used to compare different rapid prototyping (RP) and RT processes in terms …

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Robust Adaptive Critic Based Neurocontrollers For Systems With Input Uncertainties, S. N. Balakrishnan, Zhongwu Huang Jan 2000

Robust Adaptive Critic Based Neurocontrollers For Systems With Input Uncertainties, S. N. Balakrishnan, Zhongwu Huang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A two-neural network approach to solving optimal control problems is described in this study. This approach called the adaptive critic method consists of two neural networks: one is called the supervisor or critic, and the other is called an action network or controller. The inputs to both these networks are the current states of the system to be controlled. Each network is trained through an output of the other network and the conditions for optimal control. When their outputs are mutually consistent, the controller network output is optimal. The optimality is limited to the underlying model. Hence, we develop a …

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