Planar deposition flow modeling of fiber filled composites in large area additive manufacturing

Cadaveric decellularized bone tissue is utilized as an allograft in many musculoskeletal surgical procedures. Typically, the allograft acts as a scaffold to guide tissue regeneration with superior biocompatibility relative to synthetic scaffolds. Traditionally these scaffolds are machined into the required dimensions and shapes. However, the geometrical simplicity and, in some cases, limited dimensions of the donated tissue restrict the use of allograft scaffolds. This could be overcome by additive manufacturing using granulated bone that is both decellularized and demineralized. In this study, the large area projection sintering (LAPS) method is evaluated as a fabrication method to build porous structures composed of granulated cortical bone bound by polycaprolactone (PCL). This additive manufacturing method utilizes visible light to selectively cure the deposited material layer-by-layer to create 3D geometry. First, the spreading behavior of the composite mixtures is evaluated and the conditions to attain improved powder bed density to fabricate the test specimens are determined. The tensile strength of the LAPS fabricated samples in both dry and hydrated states are determined and compared to the demineralized cancellous bone allograft and the heat treated demineralized-bone/PCL mixture in mold. The results indicated that the projection sintered composites of 45–55 wt %. Demineralized bone matrix (DBM) particulates produced strength comparable to processed and demineralized cancellous bone.

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Heat retention modeling of large area additive manufacturing

Additive Manufacturing ◽

10.1016/j.addma.2019.04.014 ◽

2019 ◽

Vol 28 ◽

pp. 325-332 ◽

Cited By ~ 1

Author(s):

Kyosung Choo ◽

Brian Friedrich ◽

Tim Daugherty ◽

Austin Schmidt ◽

Clark Patterson ◽

...

Keyword(s):

Additive Manufacturing ◽

Large Area

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Mechanical Characterization of High-Temperature Carbon Fiber-Polyphenylene Sulfide Composites for Large Area Extrusion Deposition Additive Manufacturing

Additive Manufacturing ◽

10.1016/j.addma.2020.101255 ◽

2020 ◽

Vol 34 ◽

pp. 101255 ◽

Cited By ~ 1

Author(s):

Pritesh Yeole ◽

Ahmed Arabi Hassen ◽

Seokpum Kim ◽

John Lindahl ◽

Vlastimil Kunc ◽

...

Keyword(s):

High Temperature ◽

Additive Manufacturing ◽

Carbon Fiber ◽

Mechanical Characterization ◽

Polyphenylene Sulfide ◽

Large Area

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Residual Stress Reduction Technology in Heterogeneous Metal Additive Manufacturing

Materials ◽

10.3390/ma13235516 ◽

2020 ◽

Vol 13 (23) ◽

pp. 5516

Author(s):

Myoung-Pyo Hong ◽

Young-Suk Kim

Keyword(s):

Residual Stress ◽

Additive Manufacturing ◽

Real Time ◽

Stress Reduction ◽

Room Temperature ◽

High Hardness ◽

Large Area ◽

Metal Additive Manufacturing ◽

Thermal Deviation ◽

Metal Additive

Metal additive manufacturing (AM) is a low-cost, high-efficiency functional mold manufacturing technology. However, when the functional section of the mold or part is not a partial area, and large-area additive processing of high-hardness metal is required, cracks occur frequently in AM and substrate materials owing to thermal stress and the accumulation of residual stresses. Hence, research on residual stress reduction technologies is required. In this study, we investigated the effect of reducing residual stress due to thermal deviation reduction using a real-time heating device as well as changes in laser power in the AM process for both high-hardness cold and hot work mold steel. The residual stress was measured using an X-ray stress diffraction device before and after AM. Compared to the AM processing conditions at room temperature (25 °C), residual stress decreased by 57% when the thermal deviation was reduced. The microstructures and mechanical properties of AM specimens manufactured under room-temperature and real-time preheating and heating conditions were analyzed using an optical microscope. Qualitative evaluation of the effect of reducing residual stress, which was quantitatively verified in a small specimen, confirmed that the residual stress decreased for a large-area curved specimen in which concentrated stress was generated during AM processing.

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Application Intensity and Spatial Distribution of Three Major Herbicides from Agricultural and Nonagricultural Practices in the Central Plain of Thailand

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18063046 ◽

2021 ◽

Vol 18 (6) ◽

pp. 3046

Author(s):

Suphaphat Kwonpongsagoon ◽

Chanokwan Katasila ◽

Pornpimol Kongtip ◽

Susan Woskie

Keyword(s):

Spatial Analysis ◽

Health Risks ◽

Material Flow ◽

Human Exposure ◽

Flow Analysis ◽

Material Flow Analysis ◽

Flow Modeling ◽

Herbicide Application ◽

Large Area ◽

Simplified Method

The herbicides glyphosate, paraquat, and 2,4-D play a significant role in Thailand. This paper is among the first study to describe the intensity of herbicide application and illustrate how the herbicides are extensively distributed over a large area through both agricultural and nonagricultural practices. Using a quick, economical, and simplified method of Material Flow Analysis together with spatial analysis, better data for the analysis of possible environmental herbicide contamination, human exposure, and related health risks for the general public and applicators can be developed. The findings from this study showed that in the study province, about 2.2 million kg of the active ingredients from the three targeted herbicides is applied annually. Pathway flow modeling with spatial analysis identified several local hotspots of concern based on the type of herbicide and crop/activity where it was used. Cassava planting was found to have the highest herbicide application activity, whereas rice cultivation was the major contributor of total herbicide mass, due to the wide area of cultivation in the province. The herbicide most likely to be applied at rates higher than recommended was 2,4-D, particularly on cassava and sugarcane farms.

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