Retracted: “Numerical Studies of Extreme High-Speed Laser Material Deposition Processes at Powder-Scale” [ASME 2019 International Mechanical Engineering Congress and Exposition, Volume 2A: Advanced Manufacturing, Salt Lake City, Utah, USA, November 11–14, 2019, Conference Sponsors: ASME, ISBN: 978-0-7918-5937-7, Copyright © 2019 by ASME. Paper No. IMECE2019-10730, pp. V02AT02A045; 10 pages; doi: 10.1115/IMECE2019-10730]

The above referenced paper has been removed from publication. (April 21, 2020) Copyright © 2020 by ASME

Effect of Moisture on the Mechanical Properties of Additively Manufactured PLA, ABS and PLA/SiC Composites

In this study the tensile properties of additively manufactured Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS) and Silicon Carbide (SiC) particulate filled PLA composites were assessed after aging for 4.5 months at 50°C in distilled water. The maximum moisture gain in PLA was about 16% by weight, and ABS gained 0.65%. In PLA/SiC composites, the weight gain due to moisture absorption was inversely proportional to the weight percentage of SiC loading. The PLA specimens degraded completely during aging without measurable residual strength. While the addition of SiC to PLA increased the room temperature tensile strength at lower volume fractions of SiC, the degradation of aged strength was similar to that of the pure PLA. The PLA/SiC composites had no measurable strength after aging. The ABS specimens retained their strength and failure strain after aging.

Investigation on Deep Hole Trepanning of TC10 Titanium Alloy

Titanium alloy is a typical hard-to-machine material, and has a relatively expensive material price. For deep-hole tubes made of titanium alloys, the material utilization rate of direct deep-hole drilling is relatively low, especially for large diameter holes. Deep-hole trepanning provides an effective method that reduces manufacturing cost and improves the material utilization which is used on larger diameter bars. In this paper, deep-hole trepanning tests are carried out on the TC10 titanium alloys to resolve the key technical problems. The thrust force and torque, tool wear, and chip morphology are analyzed based on the different process parameters. The results show that appropriate process parameters can remove the chips easily and reduce the thrust force and tool wear. The titanium alloy deep-hole trepanning has a good drilling effect and solves the problem of drilling deep, large diameter holes in titanium alloy tubes, which has practical significance for reducing production cost and improving material utilization.

Numerical and Experimental Analysis of Attaching-Mandrel Process Under Multi-Pass Cold Spinning Process on Superalloy GH3030

The superalloy products formed by multi-pass conventional spinning are widely used in rotary forming parts with complex shapes. As the connection of each forming pass, the attaching-mandrel process has an important influence on forming quality and production efficiency. The hot spinning process is usually adopted in superalloy forming because its poor plasticity in normal temperature, meanwhile, it brings the poor surface quality of the parts and huge energy consumption. For this reason, the cold spinning and the attaching-mandrel process of nickel-base superalloy GH3030 are studied. The combination method of experiment and simulation is used to study the attaching-mandrel process based on one-forward-pass spinning process. The effects of pass pitch and the attaching-mandrel velocity on the tool forces, parts stress field, strain field and wall thickness distribution are analyzed. The microstructure of the part is divided into three layers: outer, middle and inner layer. The grain size of each layer is compared. Then the effect of different pass pitch on the grain structure is clarified. The results show that the reasonable pass pitch and the attaching-mandrel velocity can improve the forming quality and production efficiency. The multi-pass cold spinning process on superalloy GH3030 is feasible. The excessive pass pitch can cause seriously grain elongation, the grain boundaries are blurred, and even cracking.

Simulation and Experimental Investigation of Scallop Removal Using Friction Stir Processing and Complex Toolpath

Machining of complex geometries is conventionally accomplished through the use of a ball-end mill and a helical toolpath which follows along the contours of the geometry at incremental depths. While effective for the majority of geometries, this method produces scallops which result from the ball-end mill radius and the step size of the toolpath. The size of these scallops, which degrades the surface finish, can be minimized by utilizing a relatively small step size. However, this results in increased machining time. A novel method of scallop removal is simulated and experimentally tested herein on 6061-T6511 aluminum. This method applies a friction stir processing effect to the workpiece by rotating a ball-end mill tool in reverse over the surface of the material subsequent to ball-end mill cutting passes. Additionally, the path constructed for scallop removal was a self-intersecting epicycloid which plastically deforms the scallops in order to reduce the surface roughness and impart favorable compressive surface stress. In this study, the surface variability produced from this process is reported for several different tool paths, determined experimentally and through simulation. Future studies will investigate the microstructural effects of this process, as well as the resulting microhardness and residual stress profile.

Experimental Investigation of PolyJet 3D Printing Process: Effects of Finish Type and Material Color on Color Appearance

The Stratasys J750 PolyJet printer is capable of printing full-color parts. However, little information is currently available about the effects of finish type and material color on color appearance of parts printed by the PolyJet process. In this study, the effects of finish type and material color on color appearance of PolyJet printed parts are investigated; two finish types (glossy and matte) and four material colors (cyan, magenta, yellow, and black) are considered. The results suggest that the main effects of finish type and its interactions with material color are significant. Especially, the effects of finish type when material color is black are more significant among the material colors. These results would be valuable to users of the full-color PolyJet 3D printer.

Mechanical Response and Incomplete Filling in Compression Molding With Microscale Double-Punch Sets

Forming nano-/micro-scale surface patterns on metal surfaces by direct compression molding is an important means for achieving small scale surface features with potential usage in wide ranging technological applications. Geometric fidelity of molded features and the corresponding molding response are of critical importance in determining the usefulness of the molding replication technique. In this paper, two series of microscale punches made of tool steels were fabricated using Ga+ focused ion beam (FIB). In one series, the punch consists of a single protruding rectangular strip of different width, w (dubbed the “single punch”). In the other series, the punch consists of two rectangular strips of identical dimensions separated by a spacing in between, s (dubbed the “double punch”). These so-fabricated punches were used to mold elemental single crystal Al. The mechanical response during compression molding was measured and analyzed. For the double-punch experiments, measured characteristic molding pressure exhibited a significant dependence on the spacing to punch width ratio, λ = s/w, as well as a significant dependence on s when λ was fixed. The molded features were examined and the phenomenon of incomplete filling was observed to occur at λ < 0.5.

Deformation Mechanics of Tube in Variation of Process Sequence During Low Pressure Tube Hydroforming

Tube hydroforming is the successful manufacturing process to create a variety of shapes using fluid pressure. In this process, the tube was filled with the fluid and further pressurized to deform to various shapes. Tube hydroforming is categorized into three types: higher pressure, pressure sequencing and low-pressure tube hydroforming. Ferrous and non-ferrous metals are formed using these processes. Due to uniform thinning in the formed part, the parts can be lower weight and thus proven to be the technology to create lightweight parts for automotive and aerospace industries. This process has gained popularity due to its many advantages such as part consolidation, quality of the formed part and the possibility of unique shapes with indents or angles. This paper focuses on low-pressure tube hydroforming. In low-pressure tube hydroforming, during the closing of the die the tube is marginally pressurized to a fixed volume. The focus of this paper is to investigate the deformation mechanics of the tube due to variation in the process sequence during low-pressure tube hydroforming. The circular tube was formed in a square shape. The four sides of die edges were considered as individual edges and the motion of these edges will be varied to achieve the final shape. The deformation mechanics in each condition was presented and analyzed. The thickness and strain distribution were studied. The change of tube profile pattern from the start to the end of the process were presented and compared.

Improving the Surface Characteristics by Employing FSP on the Composites for the Automobile Brake Pad Application

Looking at the background of the recent research on the area of the brake friction materials, composites are gaining the trust in being a potential replacement among the automobile sectors. The fabrication of the AA 2024 composites reinforced with 3 wt % Al2O3 is done using powder metallurgy technique followed by hot extrusion process. Current research work focuses on friction stir processed surface modified composites evaluated for the replacement of the currently used brake pads materials in automobile sectors. Surface characterization is carried out on the worn-out tracks of both brake materials developed and the counterpart employed using scanning electron microscope and XRD. The counterpart used in pin on disc configuration is exactly the material used in the automobile application (i.e. automobile brake disc plate material). Impact characteristics and tensile studies after friction stir processing (FSP) is studied as well. Coefficient of friction and wear loss characteristics in aspect of the tribological life of the composites developed is compared with the existing automobile brake pad components and found that FSP on composites served the purpose of the materials used in existing brake pads material.

On Characterizing Uncertainty Sources in Laser Powder Bed Fusion Additive Manufacturing Models

Tremendous effort has been dedicated to computational models and simulations of Additive Manufacturing (AM) processes to better understand process complexities and better realize high-quality parts. However, understanding whether a model is an acceptable representation for a given scenario is a difficult proposition. With metals, the laser powder bed fusion (L-PBF) process involves complex physical phenomena such as powder packing, heat transfer, phase transformation, and fluid flow. Models based on these phenomena will possess different degrees of fidelity as they often rely on assumptions that may neglect or simplify process physics, resulting in uncertainty in their prediction accuracy. Predictive uncertainty and its characterization can vary greatly between models. This paper characterizes sources of L-PBF model uncertainty, including those due to modeling assumptions (model form uncertainty), numerical approximation (numerical uncertainty), and model input parameters (input parameter uncertainty) for low and high-fidelity models. The characterization of input uncertainty in terms of probability density function (PDF) and its propagation through L-PBF models, is discussed in detail. The systematic representation of such uncertainty sources is achieved by leveraging the Web Ontology Language (OWL) to capture relevant knowledge used for interoperability and reusability. The topology and mapping of the uncertainty sources establish fundamental requirements for measuring model fidelity and guiding the selection of a model suitable for its intended purpose.