Manufacturing and Materials Processing Research at the School of Mechanical Engineering, Purdue University
Laser-based Manufacturing. Laser-based manufacturing is one of the most rapidly growing areas in manufacturing. The faculty and students at the Center for Laser-based Manufacturing focus on developing various new and novel laser-based processing techniques along with predictive models for these processes. The laser-based manufacturing processes currently under research include laser-assisted machining, laser hardening, laser cladding, laser 3D deposition, laser surface alloying, laser shock peening, laser direct writing and laser micromachining. The state-of-the-art facilities include a range of lasers from high power direct diode lasers to pico-second pulsed lasers. The integrated laser-processing set-up shown in Fig. 1 provides the flexibility of performing various surface enhancement processes such as laser hardening of complex surfaces and laser cladding.
Researchers in the MMP area are developing modeling and prediction capabilities for high speed machining and grinding processes. The analytical and simulation tools that researchers design from their models provide the means of predicting various machining process conditions without expensive and time-consuming experiments on actual machines. This helps significantly reduce process design lead time and manufacturing costs. The examples of modeling efforts include finite element simulation of material deformation during machining processes, mechanistic modeling of cutting force and vibration, prediction of chatter in various machining and grinding processes, and heat transfer modeling during machining processes. These modeling tools have been adopted by several industrial companies. These process simulation models are geared towards developing a digital manufacturing system, which people in industry can use for simultaneous engineering of product and process design.
Integrated Laser Processing Setup
Intelligent Manufacturing. In the Intelligent Manufacturing Laboratory, several projects on intelligent modeling, optimization, monitoring and control techniques are under way. Researchers are developing a methodology that can automatically optimize grinding processes based on heuristic rules, experimental data and models. This intelligent optimization method is to determine the optimal operating conditions instead of relying on human experts. They are also working on developing various in-process sensing and diagnostic techniques to monitor the conditions and health of the process and the machine. The monitoring technique determines the optimal configuration of sensors and sensor features to minimize the cost and yet maximize the effectiveness of monitoring. Various sensors and sensing techniques used include acoustic emission sensors, a power meter, force dynamometers, accelerometers, ultrasonic sensors, a laser-triangulation, capacitance probes and infrared temperature measurement sensors.
Laser based micro and nano manufacturing. The Center for Laser Micro-Fabrication at Purdue University carries out combined experimental and theoretical studies on laser-based manufacturing and materials processing. The Center has eight state-of-the-art laser systems including an ultrafast laser (an ultrafast laser normally refers to a laser with a pulse width less than 1 picosecond), an excimer laser, Nd:YLF/YAG/VA lasers, a fiber laser, an argon ion laser, and a CO2 laser. These laser systems together with the computerized precision motion control systems are being used for laser micro and nano-machining, laser fabrication of MEMS (micro-electro-mechanical systems) components, laser printing of microelectronic circuits, micro and sub-micro scale 3D stereo lithography, and development of integrated MEMS systems. In parallel, fundamental studies are being carried out to investigate thermal, thermomechanical, optical, and control aspects of the problems arising from the laser micro and nano manufacturing processes.
Boiling and Two-Phase Flow Laboratory (BTPFL). Quenching represents one of the most critical stages in the production of metallic alloys. This process influences the internal microstructure of the alloy and hence the part’s mechanical properties. If the final product does not meet the required specifications, a costly post-treatment operation is required, consisting of additional heat treatment and mechanical straightening of warped sections. In addition, the effect of post-treatment operations on the final metallurgical properties can seldom be predicted with accuracy. Researchers at the Purdue University Boiling and Two-Phase Flow Laboratory (BTPFL) have developed a large-scale test bed whose primary objective is optimize the quenching process to achieve superior part quality and consistency between production runs with minimal cost. Another related facility is dedicated to the study of the effects of temperature, heating time and composition on the spectral emissivity of aluminum alloys. Radiation thermometry theory and techniques are being used to develop new emissivity algorithms for accurate temperature measurement of aluminum surfaces.
Microstructure Testing and Analysis Laboratory. Research in this facility is in the area of micromechanics of materials. Professor Thomas Siegmund and his graduate students apply principles of mechanics to the micro structural level of materials and their interfaces, and to the development of relationships between the internal features of a material and its macroscopic behavior. The goal of his work is (1) to obtain a fundamental understanding of deformation and failure processes in materials, and (2) to develop and manufacture new high performance materials that will allow for the design of engineering structures with improved properties and higher reliability. the composite material might become affordable enough for a wide range of new applications, including engine parts such as pistons, biomedical devices and electronic components, such as new types of electrical transformers, and circuit boards capable of withstanding high temperatures. The team of researchers has shown that it is possible to use robotic manufacturing technology to develop a process that leads to a new way of producing carbon-carbon composite materials.
Hierarchical Design and Characterization Lab. The computational research in the lab is generally focused on developing top-down approaches to designing complex systems from system lengthscales down to material microstructure lengthscales. Several specific issues are addressed in this research including: a) the development of a meshfree computational analysis framework for studying changing sizes and topologies b) computationally efficient optimal shape and topology design at component lengthscales using the meshfree framework c) optimal design of material microstructure to achieve the required performance d) optimal design of components as well as microstructures that resist crack propagation through explicit meshfree simulation of interactions between cracks and pores or inclusions e) probabilistic design of systems under uncertainty and e) formal frameworks for design of complex systems in a decomposed manner in which issues of data encapsulation, security, sensitivity and uncertainty are addressed.
The research is applied to solve specific microelectronics related problems including developing nanostructured particulate thermal interface materials, characterizing the fracture behavior of low-k dielectric films, characterizing creep and high strain rate behavior of lead-free SnAgCu solder alloys, modeling (using cohesive zone theory) and experimentally characterizing fatigue fracture at SnAgCu solder joint interfaces, stochastic modeling and design of fiber-optic systems, developing thermodynamically consistent multiphysics models of stress and electromigration in interconnects.
The equipment available in the lab include a Nanonics Multiview 3000 dualprobe Nanoindenter/AFM, an Instron 5848 Micromechanical tester with Eurotherm EC 1615 environmental chamber, Thermotron 2800 Environmental Test Chamber, Linkam THMS 600 thermal stage and controller, a Photomechanics PEMI I four-beam laser Moire interferometer, a Nikon SMZ 1500 microscope and other metallographic sample preparation equipment.
Facility for Experimental Nonlinear Dynamics and Diagnostics. FEND2 at Ray W. Herrick Laboratories, combines first principle models of mechanical systems with dynamic pre/post-manufacturing data to develop health monitoring and prognosis systems, which aid in formulating design solutions to problems in noise/vibration and structural durability. For example, diagnostic methods for assessing how integrally manufactured suspension systems for automobiles degrade have been developed using a full-scale two post road simulator. Similar methods are being applied to predict the potential for squeak and rattle in manufactured automotive interiors. Other experimentation facilities include: a 9200 high velocity drop tower for studying the durability of advanced weapon systems manufactured with filament wound composite materials; a combined vibration-acoustic-thermal apparatus for exposing aircraft structural materials equipped with automated health monitoring sensors and data analysis software to hot engine exhaust and launch/reentry environments; a rolling dynamometer that exposes tires to operating loads for assessing the effects of manufacturing variability on tire durability predictions; and, 100’s of channels of dynamic instrumentation for sensing component response (strain, acceleration) to dynamic loads. Recent technical achievements include the deployment of a measurement system for detecting cracks in military ground vehicles and the development of health monitoring technology for wire harnesses and connectors in gas turbine engines.
ConfigLAB at Purdue Research and Education Center for Information Systems in Engineering (PRECISE) conducts research in the product configuration area which ties design closely to manufacturing. One area of research is development of spell checking paradigms for manufacturability during design time to enable manufacturability at design time. Intelligent Design Engineering Advisory Systems (IDEAS) is an example. Studies have indicated that the cost of product design is only around 5% of the total product cost, while decisions made during the design stage affect as much as 70-80% of the final product cost. IDEAS enables engineers/designers to make informed decisions in the early design about processes and part/tooling for manufacturability. It will also serve as an on-demand “what-if” and manufacturing educational tool for engineers/designers.
Solidification Heat Transfer Laboratory (SHTL). Solidification/melting phenomena are critical to wide variety of engineering applications such as casting, energy storage, and electronics cooling. Research efforts in the Solidification Heat Transfer Laboratory (SHTL) are focused on advancement of the scientific understanding of solid/liquid phase change phenomena through theoretical analysis, experimental investigation and numerical simulation, and application of these principles to advanced manufacturing and materials processing (MMP). Specific research areas include: 1) theoretical and experimental analysis of formation and suppression of channels in directional solidification of alloys; 2) experimental investigation of solidification/melting of phase change materials (Figure 1); 3) development of advanced numerical algorithms for multiscale simulation of solidification phenomena; 4) development of three-dimensional front tracking algorithms for free/moving surface problems; and 5) mathematical modeling of solidification of particle-laden melts.
Figure 1. Experimental setups for the study of solid-liquid phase change.
Research in the SHTL has led to significant progress in the MMP area, including microscale simulation of the solidification of binary-alloy Metal Matrix Composites (MMCs), crystal growth under terrestrial or microgravity conditions, and analysis and control of the casting of energetic materials. Use of phase change materials for transient thermal management of microelectronics components is also a related thrust area.