Planning the Process Parameters During Direct Metal Deposition of Functionally Graded Thin-Walled Parts Based on a 2D Model

The need for functionally graded material (FGM) parts has surfaced with the development of material science and additive manufacturing techniques. Direct Metal Deposition (DMD) processes can locally deposit different metallic powders to produce FGM parts. Yet inappropriate mixing of materials without considering the influence of varying dilution rates and the variation of material properties can result in inaccurate material composition ratios when compared to the desired or computed compositions. Within such a context, this paper proposes a 2D simulation based design method for planning the process parameters in the DMD manufacturing of designed thin-walled parts. The proposed scheme is illustrated through two case studies, one of which is a part with one-dimensional varying composition and the other with two dimensional variation. Using the proposed method, the process parameters can be planned prior to the manufacturing process, and the material distribution deviation from the desired one can be reduced.Mechanical Engineerin

Performance of Stainless Steel AlSi 304 Wire Reinforced Metal Matrix Composites Made Using Ultrasonic Additive Manufacturing in Bending

Ultrasonic additive manufacturing (UAM) is a solid-state additive and subtractive manufacturing process that utilizes ultrasonic energy to produce layered metallic parts. The process is easily extended to create advanced multi-material structures, e.g., metal matrix composites, functionally graded metallic components, and shape memory alloys. This research utilizes a three point bending test to compare the elastic modulus in metal matrix composites (MMC’s) specimens consisting of stainless steel wire reinforcements with an aluminum matrix to unreinforced test specimens; both specimens are produced by UAM. In the MMC the volume fraction of wire is relatively low, 0.77%, yet yields an average increase in modulus of 8.9%.Mechanical Engineerin

Examination of Build Height in Ultrasonic Consolidation for Foil Width Specimens Using Supports

Ultrasonic consolidation (UC) is a novel, solid-state, additive manufacturing fabrication process. It consists of ultrasonic joining of thin metal foils and contour milling to directly produce functional components in a variety of geometries. The bond between layers forms when an ultrasonic horn creates a local oscillating stress field at the mating surfaces. It is commonly theorized that the high frequency vibration under pressure produces a metallurgical bond without melting the base material. The mechanism behind the bond is believed to be due to interfacial motion and friction that disrupts surface contaminants, arguably allowing direct metal to metal contact, and producing sufficient stress to induce plastic flow and promote the growth of grains across the mating surfaces. Ignored in this explanation is the role of substrate dimensions on the quality and strength of the joining process. Researchers have previously examined the effective height limitations of the build process, i.e., the limiting height to width ratio of one of the component features being fabricated. This paper extends the experimental work on using support materials to extend build height on specimens using two different candidate materials, tin bismuth, and a mixture of sugar, corn syrup, and water, referred to as “candy”. Tin bismuth and candy the represent the extremes of a tradeoff between convenience and stiffness that a support material must possess.Mechanical Engineerin

The Clemson Intelligent Design Environment For Stereolithography-Cides 2.0

There are a large number of commercial Rapid Prototyping (RP) devices available today. All ofthese machines begin with a Computer-Aided Design (CAD) model, which is tessellated, sliced and then built layer-by-Iayer on the RP device. All ofthese operations, except the actual building ofthe part, are completed on a computer. Therefore, many improvements to the RP processes can be achieved through software, without affecting the RP devices or the warranties on them. This has led to the development of a front-end software product to support the task of preparing the part to be built. The Clemson Intelligent Design Environment for Stereolithography (CIDES) is a user-centered interface between the CAD system and RP systems, primarily the Stereolithography Apparatus (SLA). CIDES 2.0 is designed to provide a variety oftools which are valuable to the users ofRP systems, including the ability to view and modify tessellated (STL) files, generate supports, and slice STL files into layer (SLI) files for use on an SLA. It also provides the ability to view SLI and merged (V) files. Furthermore, CIDES offers additional translation capabilities that make it valuable for other RP processes. The package has proven useful in the Laboratory to Advance Industrial Prototyping (LAIP) at Clemson University. CIDES 2.0 is a new X Windows-based release based on the original version ofCIDES with many additional features. A new HumanComputer Interface is the major improvement to this release.Mechanical Engineerin

Honeycomb Structures for High Shear Flexure

The present invention provides an improved shear band for use in non-pneumatic tires, pneumatic tires, and other technologies. The improved shear band is uniquely constructed of honeycomb shaped units that can replace the elastomeric continuum materials such as natural or synthetic rubber or polyurethane that are typically used. In particular, honeycomb structures made of high modulus materials such as metals or polycarbonates are used that provide the desired shear strains and shear modulus when subjected to stress. When used in tire construction, improvements in rolling resistance can be obtained because of less mass being deformed and reduced hysteresis provided by these materials. The resulting mass of the shear band is greatly reduced if using low density materials. Higher density materials can be used (such as metals) without increasing mass while utilizing their characteristic low energy loss

Simulation of a domestic heat pump using a nonazeotropic working fluid and impact of parallel computers on the simulation of thermal systems

Ph.D.Sheldon M. Jete

Application of Genetic Algorithms in the Design of Multi-Material Structures Manufactured in Rapid Prototyping

Recent developments in the Rapid Prototyping technology establish it as a new manufacturing technique, enabling localized material addition to build a part. Thus, heterogeneous structures, consisting of more than one material can be produced. The aim of this paper is to present an optimization tool to find the best material distribution in a multi-material structure due to given objectives and constraints. The tool is based on genetic algorithms using a discrete material model and FE"'analysis to evaluate the objective functions. It can optimize the distribution materials in 2D-structures with up to 1500 DOF's at reasonable computational costs. Its performance is shown on a bi-objective optimization of a turbine blade.Mechanical Engineerin

IVECS, Interactively Correcting .STL Files in a Virtual Environment

Free Form Fabrication (FFF) machines transform objects merely existing as Os or 1s in a computer into a tangible object. FFF machines shift the paradigm of standard 2 Dimensional printers/paper printouts to 3 Dimensional printers/volumetric printouts (or 3D hardcopies). Currently, this technology is weakened by the link between computers and FFF machines: the .STL file, which contains a series oftriangles representing the skin ofthe object to be prototyped. A prototype, reflecting precisely the evolution of a concept within a design cycle and allowing a systematic inspection/verification, is essential. A system responding to this need was designed at Clemson University for the inspection and the correction ofsuch a file. IVECS, the Interactive Virtual Environment for the Correction of.STL files, is a tool that allows minute surgery to be performed on faulty tessellated models. IVECS allows STL files to be imported, tessellation errors to be detected and automatically or manually fixed. This paper expands on the use of IVECS for the inspection and the correction of .STL files. It extends the usefulness of the STL format by allowing designers to virtually prototype before actually building a physical model, thus contributing to a shorter design cycle.Mechanical Engineerin

Heterogeneous Solids: Possible Representation Schemes

Solid freeform fabrication processes allow parts to be built with accuracy and mechanical integrity, permittingthem to be used in tooling or fOrlnandfit applications. There is already a need form~lti ..color Parts.for surgical applications, which will eventually lead to. multi-material RP .machines.WhetherJor on the spot color deposition or for functionally tailored multiple materials parts,.RPmachines with such capabilities are becoming available. They will eventually lead to the trtiepromise of Solid Freeform Fabrication: a system that can build a functional mechanism without assembly, and from multiple materials. This paper is aimed at understanding the new challenges raised from representing solids whose material distribution is changing gradually from one material to another (HC), and those made of a collection .of discrete materials (HD). Several representation schemes are reviewed and critiqued. Techniques borrowed from medical imaging and geoscience modeling are used to better understand the modeling of heterogeneous and gradient solids, from a geometric standpoint.Mechanical Engineerin