Browsing by Subject "tensile strength"

Now showing 1 - 8 of 8

A Comparison of Binder Burnout and Mechanical Characteristics of Printed and Chemically Bonded Sand Molds
(University of Texas at Austin, 2014) Snelling, Dean; Williams, Christopher; Druschitz, Alan
Various material systems have been created for Binder Jetting of sand molds; however, a formal analysis comparing the materials to commonly used foundry molding materials has not been conducted. In this paper the authors investigate potential differences in the material properties from four different commercially available binders systems for chemically bonded sand molds. Specifically, the authors compared the binder burnout characteristics and the tensile strength of sand created by 3D printing and conventional chemically bonded molding materials. Increased binder content can strengthen the mold but have adverse effect on part quality. Understanding the binder characteristics of printed molds are essential due to the potential defects from large amounts of gas generated from binder while pouring molten metal.
Determination of the Optimum Joint Design for LENS Fabricated Ti6Al4V and Ti6Al4V/TiC Dual-Material Structures
(University of Texas at Austin, 2010-09-23) Obielodan, J.O.; Stucker, B.E.
Joints between dissimilar material systems made using laser metal deposition processes have been investigated. The fusion of materials with different physical properties and chemical compositions under high laser power often results in defects at the joints. Although some solutions have been suggested in previous work for defect-free fabrications, most of the joints studied have been characterized using qualitative techniques only. Quantitative study is imperative for predicting the mechanical behavior of fabricated structures for real life applications. In this work, tensile and flexural specimens made of different Ti6Al4V and Ti6Al4V/10%TiC dual-material transition joint designs were fabricated using laser engineered net shaping (LENS) and tested. It was found that transition joint design has a significant effect on the tensile strengths of dual-material structures.
Effects of Powder Variation on the Microstructure and Tensile Strength of Ti6Al4V Parts Fabricated by Selective Laser Melting
(University of Texas at Austin, 2014) Gu, Hengfeng; Gong, Haijun; Dilip, J.J.S.; Pal, Deepankar
Metallic powders are used as raw materials in the Selective Laser Melting (SLM) process. These metal powders are typically available from more than one powder vendor. Even when powders have the same nominal chemical compositions, powders produced by different companies typically result in different powder particle size distributions and morphologies. These powder differences result in different powder bed thermophysical properties, which affect how the powder melts and solidifies. This paper studies the effect of powder variation on the microstructure and tensile strength of as-built SLM Ti6Al4V parts. Ti6Al4V powders from different vendors were used to fabricate parts via SLM. Powder characteristics, such as particle size distribution, morphology, and flowability, were obtained. Powder bed densities and thermal conductivities were measured and compared. The microstructures and tensile strengths were investigated by standard metallographic and tensile testing methods. Based on the experimental results, a correlation between the powder characteristics and part properties are discussed.
Efficient Sampling for Design Optimization of an SLS Product
(University of Texas at Austin, 2017) Xu, Nancy; Tutum, Cem C.
In this work an efficient constrained surrogate-based sampling algorithm is implemented to optimize Selective Laser Sintering (SLS) process parameters for maximizing the tensile strength of a tensile specimen. Two variations of the algorithm have been implemented and tested on a Farsoon HT251P machine using (polyamid) PA3300 polymer powder. The algorithm is based on building a statistical predictive model of the objective response (i.e., maximization of tensile strength), aggregating the constraint function (i.e., limited amount of warping), in an iterative manner by simultaneously improving the accuracy of the predictive model as well as searching for the optimum set of process parameters. The difference in two algorithmic variations is the number of samples to update at each iteration. While the first method is based on a single sample update, the latter searches for multiple simultaneous updates to let the manufacturer try several potentially good sets of parameters in the same machine to eventually speed up the experimental evaluation procedure.
Elevated Temperature Mechanical and Microstructural Characterization of SLM SS304L
(University of Texas at Austin, 2019) Hecht, G.R.; Isanaka, S.P.; Newkirk, J.W.
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, Chi or Laves phases were anticipated, the premature formation of carbides is unexpected behavior for this composition of SS 304L. It is an indication of higher sensitivity of SLM made material. An additional change in the etch response was also observed between as-built and annealed specimens. It is theorized that annealing caused all ferritic and other residual phases present in as-built SLM SS 304L to fully transform into austenite. The cellular structure observed in the as-built specimen was also dissolved due to annealing and water quenching possibly leading to the strength loss observed.
Influence of Embedding Process on Mechanical Properties of Material Extrusion Parts
(University of Texas at Austin, 2016) Sinha, Swapnil; Meisel, Nicholas A.
The layer-by- layer deposition of material in Additive Manufacturing (AM) introduces the capability for in-situ embedding of functional components into printed parts. The typical embedding process involves, i) designing the cavity for the embedded component, ii) pausing the print when the top layer of the cavity is reached, iii) manually inserting the component, and iv) resuming the build process. However, the effect of different interfacial materials (due to the presence or absence of a shape converter) and the pause time during the build process on a part’s material properties is not well-understood. Therefore, the tensile strength of 3D-printed embedded specimens with and without shape converters and with different intervals of pause time is tested in this study. The results from this experimental analysis can be useful for the design guidelines for AM with embedded components as they provide an initial understanding of mechanical properties of these parts.
Influence of Gage Length on Miniature Tensile Characterization of Powder Bed Fabricated 304L Stainless Steel
(University of Texas at Austin, 2017) Karnati, S.; Hoerchler, J.L.; Liou, F.; Newkirk, J.W.
Miniature tensile specimens with varying aspect ratios were fabricated from 304L stainless steel (SS) made using powder bed additive manufacturing (AM) process. The tensile characteristics measured from these specimens were analyzed to assess the impact of gage length. The study found no impact upon varying gage length on yield and ultimate strength measurements. However, a significant impact was observed on strain measurements. This data was also used to perform Weibull statistics to estimate the stochastic performance of the material. Fractography was performed to visually identify the types of flaws. A comparative study with specimens fabricated from cold rolled annealed 304 SS was also performed. The Weibull parameters were used to compare the variability within cold rolled annealed and AM 304L SS. This study indicates miniature tensile testing is a robust characterization technique for obtaining representative material properties.
Processing and Characterization of 3D-Printed Polymer Matrix Composites Reinforced with Discontinuous Fibers
(University of Texas at Austin, 2019) Gupta, Ankit; Hasanov, Seymur; Fidan, Ismail
The objective of this study is to fabricate discontinuous fiber (short fiber) reinforced polymer matrix composite material (CM) by additive manufacturing (AM) technology using single extruder 3D printer. For this study, short carbon fibers (diameter = 7.2μm, length = 150μm) reinforced filaments were extruded with fiber concentrations of 3% - 7.5% in volume. Input process parameters used for 3D printing to obtain good quality short carbon fiber (SCF) reinforced polymer specimens are reinforcement percentage and printing speed by fixing nozzle temperature, layer thickness, bed temperature and print orientation. It was analyzed that the surface characteristics and mechanical performance of 3D printed samples are greatly influenced by varying input process parameters. Scanning electron microscopy was performed to observe microstructural behavior of 3D printed samples. Tensile strength, ductility, and toughness were examined to validate the adhesiveness of the matrix and reinforcement. From the microhardness test, it was observed that the hardness properties are significantly affected by increasing the reinforcement percentage. The results obtained in this study could be quite useful in fabricating polymer matrix composites (PMCs) with improved overall characteristics for applications in automotive industry and medical field.