Mechanical Engineering Commons^™

Frequency Inspection Of Additively Manufactured Parts For Layer Defect Identification, Aimee Allen, Kevin Johnson, Jason R. Blough, Andrew Barnard, Troy Hartwig, Ben Brown, David Soine, Tristan Cullom, Douglas A. Bristow, Robert G. Landers, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Additive manufactured (AM) parts are produced at low volume or with complex geometries. Identifying internal defects is difficult as current testing techniques are not optimized for AM processes. The goal of this paper is to evaluate defects on multiple parts printed on the same build plate. The technique used was resonant frequency testing with the results verified through Finite Element Analysis. From these tests, it was found that the natural frequencies needed to detect the defects were higher than the excitation provided by a modal hammer. The deficiencies in this range led to the development of other excitation methods. Based …

Effective Elastic Properties Of Additively Manufactured Metallic Lattice Structures: Unit-Cell Modeling, Okanmisope Fashanu, David Murphy, Myranda Spratt, Joseph William Newkirk, K. Chandrashekhara, Ben Brown, John Porter

Materials Science and Engineering Faculty Research & Creative Works

Lattice structures are lightweight materials, which exhibit a unique combination of properties such as air and water permeability, energy and acoustic absorption, low thermal conductivity, and electrical insulation. In this work, unit-cell homogenization was used to predict the effective elastic moduli of octet-truss (OT) lattice structures manufactured using selective laser melting (SLM). OT structures were manufactured using a Renishaw AM 250 SLM machine with various relative densities. Compression test was carried out at strain rate 5 x 10^-3 m^-1 using an MTS frame. Finite element analysis was used in the determination of the OT’s effective elastic properties. Results …

In-Situ Local Part Qualification Of Slm 304l Stainless Steel Through Voxel Based Processing Of Swir Imaging Data, Cody S. Lough, Xin Wang, Robert G. Landers, Douglas A. Bristow, James A. Drallmeier, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper demonstrates the potential for qualification through local part property prediction of 304L stainless steel parts manufactured by Selective Laser Melting (SLM). This is accomplished through voxel based processing of SWIR imaging data measured in-situ. Thermal features are extracted from time-series SWIR imaging data recorded from layer-to-layer to generate 3D point cloud reconstructions of parts. The voxel based data is indexed with localized measurements of SLM part properties (light-to-dark microstructural feature ratio, microhardness, μCT data) to demonstrate the correlations. Various features are extracted from the thermal history for comparison of their respective abilities to predict the resulting local part …

Comparison Of Fatigue Performance Between Additively Manufactured And Wrought 304l Stainless Steel Using A Novel Fatigue Test Setup, M. M. Parvez, Y. Chen, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

In this research, a novel adaptive controlled fatigue testing machine was designed for bending type high cycle fatigue test. A unique dual gauge section Krouse type mini specimen was designed for simply supported transverse bending. Displacement controlled fatigue tests were implemented using an electromechanical actuator. The variation in the control signal and load observed during the test provides unique insights into realizing the deterioration of the specimen due to fatigue. These analyses were utilized to compare the fatigue performance of wrought and additively manufactured 304L stainless steel. The influence of the build direction on fatigue performance was also investigated by …

Frequency Domain Measurements Of Melt Pool Recoil Pressure Using Modal Analysis And Prospects For In-Situ Non-Destructive Testing, Tristan Cullom, Nicholas Altese, Douglas A. Bristow, Robert G. Landers, Ben Brown, Troy Hartwig, David Soine, Aimee Allen, Andrew Barnard, Jason Blough, Kevin Johnson, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Fielding Additively Manufactured (AM) parts requires evaluating both the part’s geometry and material state. This includes geometry that may be optically hidden. Both the geometry and material state affect the vibration response of the parts and modal analysis (identifying natural frequencies) has been shown to be effective for at least simple geometries using ex-situ methods (shaker table and impact hammer excitations). This paper investigates evaluation of the frequency response of metal parts inside the build chamber using the process laser to excite the parts during printing (Renishaw AM250). Vibrations in the part are measured with accelerometers connected to the build …

Joining Of Copper And Stainless Steel 304l Using Direct Metal Deposition, Xinchang Zhang, Yitao Chen, Tan Pan, Wenyuan Cui, Lan Li, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In the current study, the feasibility of joining pure copper (Cu) and stainless steel 304L (SS304L) through direct metal deposition process was investigated by material characterization. Samples were analyzed in terms of microstructure, elemental distribution, and tensile testing. Direct depositing pure copper on SS304L shows copper was mechanically rather than metallurgical bonded with SS304L due to the poor dissolubility of iron in copper. Iron was diffused into copper with a diluted distance of 1.5 mm and above that, pure copper deposits were obtained. Columnar structure was observed at the copper region near the interface while the columnar grains became finer …

Application Of Schlieren Technique In Additive Manufacturing: A Review, R. Bharadwaja, Aravind Murugan, Yitao Chen, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Additive manufacturing has gained a lot of attention in the past few decades due to its significant advantages in terms of design freedom, lower lead time, and ability to produce complex shapes. One of the pivotal factors affecting the process stability and hence the part quality is the shielding gas flow in additive manufacturing. As extremely beneficial for the process, the shielding gas flow is often set at maximum supply to achieve enough gas cover over the substrate. This causes excessive quantity of shielding gas to be unutilized. Realizing the importance of shielding gas, various studies have been carried out …

Applications Of Supervised Machine Learning Algorithms In Additive Manufacturing: A Review, M. S. Joshi, Aaron Flood, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Additive Manufacturing (AM) simplifies the fabrication of complex geometries. Its scope has rapidly expanded from the fabrication of pre-production visualization models to the manufacturing of end use parts driving the need for better part quality assurance in the additively manufactured parts. Machine learning (ML) is one of the promising techniques that can be used to achieve this goal. Current research in this field includes the use of supervised and unsupervised ML algorithms for quality control and prediction of mechanical properties of AM parts. This paper explores the applications of supervised learning algorithms - Support Vector Machines and Random Forests. Support …

Simulated Effect Of Laser Beam Quality On The Robustness Of Laser-Based Am System, Aaron Flood, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In many metal AM techniques, a laser is used as the heat source and in some applications, it can be advantageous to work off of the focal plane. When operating outside of focus, the beam quality of the laser can have drastic impacts on the ability to manufacture quality parts. This study investigates the effect of the beam quality and distance from the focal plan on the ability to deposit Ti-64, aluminum, and steel through the simulation of the blown powder process.

Compressive And Bending Performance Of Selectively Laser Melted Alsi10mg Structures, D. Murphy, O. Fashanu, Myranda Spratt, Joseph William Newkirk, K. Chandrashekhara, H. Misak, D. Klenosky

Materials Science and Engineering Faculty Research & Creative Works

Selective laser melting (SLM) is a widely used additive manufacturing technique that effectively manufactures complex geometries such as cellular structures. However, challenges such as anisotropy and mechanical property variation are commonly found due to process parameters. In a bid to utilize this method for the commercial production of cellular structures, it is important to understand the behavior of a material under different loading conditions. In this work, the behavior of additively manufactured AlSi10Mg under compression, bending, and tension loads was investigated. Vertical and horizontal build directions are compared for each type of loading. Specimens were manufactured using the reduced build …

Elevated Temperature Mechanical And Microstructural Characterization Of Slm Ss304l, G. R. Hecht, Sriram Praneeth Isanaka, Joseph William Newkirk

Materials Science and Engineering Faculty Research & Creative Works

SLM built SS304L was annealed and water quenched to minimize residual stress and avoid carbide precipitation. Mini-tensile characterization of strength and elongation at temperature conditions up to 800°C, along with observations of the associated microstructural transformations were utilized to understand the changes produced in SLM SS304L. As-built and annealed specimens were found to exhibit decreasing strength and elongation with increasing temperature as expected. Carbide precipitates appeared after short times at high temperatures within both as-built and annealed specimens for all cases, but no brittle intermetallic phase development was observed for any of the temperatures investigated. While the lack of Sigma, …

Dynamic Defect Detection In Additively Manufactured Parts Using Fea Simulation, Kevin Johnson, Aimee Allen, Jason R. Blough, Andrew Barnard, David Labyak, Troy Hartwig, Ben Brown, David Soine, Tristan Cullom, Edward C. Kinzel, Douglas A. Bristow, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The goal of this paper is to evaluate internal defects in additively manufactured (AM) parts using FEA simulation. The resonant frequencies of parts are determined by the stiffness and mass involved in the mode shape at each resonant frequency. Voids in AM parts will change the stiffness and mass therefore shift the resonant frequencies from nominal. This paper will investigate the use of FEA to determine how much a void size, shape, and location will change the resonant frequencies. Along with where the optimal input and response locations are in order to find these frequency changes. The AM part evaluated …

Part Remanufacturing Using Hybrid Manufacturing Processes, Xinchang Zhang, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Many users of high-performance metal parts, such as the aerospace industry, the mold/die casting industry, and heavy machinery consumers, extend the service of these damaged parts by employing remanufacturing technology. Additive manufacturing has unique capabilities, such as low heat input, a small heat-affected zone, free-form fabrication, and a near-net-shape. This paper summarizes the effort and the tested results to achieve an automated remanufacturing process using hybrid additive manufacturing and CNC machining processes. It will enable the robust remanufacturing-on-demand to significantly increase operational availability to reduce sustainment costs, thus will lead to robust and quality remanufacturing that is critical for remanufacturing …

The Effect Of Cell Size And Surface Roughness On The Compressive Properties Of Abs Lattice Structures Fabricated By Fused Deposition Modeling, Leah Mason, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Researchers looking to improve the surface roughness of acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling (FDM) have determined that acetone smoothing not only achieves improved surface roughness but increases compressive strength as well. However, the sensitivity of ABS parts to acetone smoothing has not been explored. In this study we investigated FDM-fabricated ABS lattice structures of various cell sizes subjected to cold acetone vapor smoothing to determine the combined effect of cell size and acetone smoothing on the compressive properties of the lattice structures. The acetone-smoothed specimens performed better than the as-built specimens in both compression modulus …

A Displacement Controlled Fatigue Test Method For Additively Manufactured Materials, Mohammad Masud Parvez, Yitao Chen, Sreekar Karnati, Connor Coward, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

A novel adaptive displacement-controlled test setup was developed for fatigue testing on mini specimens. In property characterization of additive manufacturing materials, mini specimens are preferred due to the specimen preparation, and manufacturing cost but mini specimens demonstrate higher fatigue strength than standard specimens due to the lower probability of material defects resulting in fatigue. In this study, a dual gauge section Krouse type mini specimen was designed to conduct fatigue tests on additively manufactured materials. The large surface area of the specimen with a constant stress distribution and increased control volume as the gauge section may capture all different types …

Bioprinting With Human Stem Cell-Laden Alginate-Gelatin Bioink And Bioactive Glass For Tissue Engineering, Krishna C. R. Kolan, Julie A. Semon, Bradley Bromet, D. E. Day, Ming-Chuan Leu

Biological Sciences Faculty Research & Creative Works

Three-dimensional (3D) bioprinting technologies have shown great potential in the fabrication of 3D models for different human tissues. Stem cells are an attractive cell source in tissue engineering as they can be directed by material and environmental cues to differentiate into multiple cell types for tissue repair and regeneration. In this study, we investigate the viability of human adipose-derived mesenchymal stem cells (ASCs) in alginate-gelatin (Alg-Gel) hydrogel bioprinted with or without bioactive glass. Highly angiogenic borate bioactive glass (13-93B3) in 50 wt% is added to polycaprolactone (PCL) to fabricate scaffolds using a solvent-based extrusion 3D bioprinting technique. The fabricated scaffolds …

Bulk-Explosion-Induced Metal Spattering During Laser Processing, Cang Zhao, Qilin Guo, Xuxiao Li, Niranjan Parab, Kamel Fezzaa, Wenda Tan, Lianyi Chen, Tao Sun

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Spattering has been a problem in metal processing involving high-power lasers, like laser welding, machining, and recently, additive manufacturing. Limited by the capabilities of in situ diagnostic techniques, typically imaging with visible light or laboratory x-ray sources, a comprehensive understanding of the laser-spattering phenomenon, particularly the extremely fast spatters, has not been achieved yet. Here, using MHz single-pulse synchrotron-x-ray imaging, we probe the spattering behavior of Ti-6Al-4V with micrometer spatial resolution and subnanosecond temporal resolution. Combining direct experimental observations, quantitative image analysis, as well as numerical simulations, our study unravels a novel mechanism of laser spattering: The bulk explosion of …

Method And Apparatus For Fabricating Ceramic And Metal Components Via Additive Manufacturing With Uniform Layered Radiation Drying, Ming-Chuan Leu, Amir Ghazanfari, Wenbin Li, Greg Hilmas, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A freeform extrusion fabrication process for producing three - dimensional ceramic, metal and functionally gradient composite objects, including the steps of filling a plurality of paste sources with a respective plurality of aqueous paste compositions, operationally connecting respective syringes containing respective aqueous paste compositions to a mix ing chamber, moving a first aqueous paste composition from a first respective paste source into the mixing chamber, moving a second aqueous paste composition from a second respective paste source into the mixing chamber, mixing the first and second aqueous paste compositions to define a first admixture having a first admixture composition, extruding …

Laser Machining Countersinks In Carbon Fiber Reinforced Polymer, Leon James Neely Hill

Masters Theses

“Laser machining countersinks with a frequency doubled Q-switched diode pumped Nd:YAG laser is demonstrated. Tests were conducted in 0.100" thick IM7 prepreg CFRP with [0,90]3S orientation. The HAZ is minimized to avoid stress concentrations in the epoxy matrix. A chamber and filtration system was designed and built to contain the byproducts produced in the machining process. The variables investigated are the number of repetitions in the offset path, the plunge rate, and the line energy. The research was performed over one baseline study, one parameter space exercise, two full factorial experiments, and one repeatability study. Assessment was done under an …

Light Touch Based Virtual Cane For Balance Assistance During Standing, Sindhu Reddy Alluri

Masters Theses

"Can additional information about one's body kinematics provided through hands improve human balance? Light-Touch (LT) through hands helps improve balance in a wide range of populations, both healthy and impaired. The force is too small to provide any meaningful mechanical assistance -- rather, it is suggested that the additional sensory information through hands helps the body improve balance.

To investigate the potential for improving human balance through biofeedback through hands, we developed a Virtual Cane (VC) for balance assistance during standing. The VC mimics the physical cane's function of providing information about one's body in space. Balance experiments on 10 …

Remanufacturing Of Precision Metal Components Using Additive Manufacturing Technology, Xinchang Zhang

Doctoral Dissertations

"Critical metallic components such as jet engine turbine blades and casting die/mold may be damaged after servicing for a period at harsh working environments such as elevated temperature and pressure, impact with foreign objects, wear, corrosion, and fatigue. Additive manufacturing has a promising application for the refurbishment of such high-costly parts by depositing materials at the damaged zone to restore the nominal geometry. However, several issues such as pre-processing of worn parts to assure the repairability, reconstructing the repair volume to generate a repair tool path for material deposition, and inspection of repaired parts are challenging. The current research aims …