Engineering Papers⌕ Search

Engineering topics

Ehmann, Kornel

Publications and source records attributed to Ehmann, Kornel.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Method and apparatus for double-sided incremental flanging

Flanges formed on sheet metal parts to increase the part stiffness or create mating surface for further assembly are created in an incremental sheet forming process using forming tool and supporting tool that move along a specified tool path so as to gradually deform a peripherally-clamped sheet metal work piece into the desired geometry. With two universal tools moving along the designed toolpath on the both sides of the part, the process is very flexible. Process time is can also be reduced by utilizing an accumulative double-sided incremental hole-flanging strategy, in which the flange is formed in only one step.

Zhang, Huan↗
DOE OSTI2022

A deep learning framework for layer-wise porosity prediction in metal powder bed fusion using thermal signatures

Abstract Part quality manufactured by the laser powder bed fusion process is significantly affected by porosity. Existing works of process–property relationships for porosity prediction require many experiments or computationally expensive simulations without considering environmental variations. While efforts that adopt real-time monitoring sensors can only detect porosity after its occurrence rather than predicting it ahead of time. In this study, a novel porosity detection-prediction framework is proposed based on deep learning that predicts porosity in the next layer based on thermal signatures of the previous layers. The proposed framework is validated in terms of its ability to accurately predict lack of fusion porosity using computerized tomography (CT) scans, which achieves a F1-score of 0.75. The framework presented in this work can be effectively applied to quality control in additive manufacturing. As a function of the predicted porosity positions, laser process parameters in the next layer can be adjusted to avoid more part porosity in the future or the existing porosity could be filled. If the predicted part porosity is not acceptable regardless of laser parameters, the building process can be stopped to minimize the loss.

42 ENGINEERING↗
DOE OSTI2022

Method and apparatus for double-sided incremental flanging

Flanges formed on sheet metal parts to increase the part stiffness or create mating surface for further assembly are created in an incremental sheet forming process using forming tool and supporting tool that move along a specified tool path so as to gradually deform a peripherally-clamped sheet metal work piece into the desired geometry. With two universal tools moving along the designed toolpath on the both sides of the part, the process is very flexible. Process time is can also be reduced by utilizing an accumulative double-sided incremental hole-flanging strategy, in which the flange is formed in only one step.

Zhang, Huan↗
DOE OSTI2022

High-throughput, in situ imaging of multi-layer powder-blown directed energy deposition with angled nozzle

Laser metal additive manufacturing (AM) has become an increasingly popular technology due to its flexibility in geometry and materials. As one of the commercialized additive processes, powder-blown directed energy deposition (DED) has been used in multiple industries such as aerospace, automotive, medical device, etc. However, a lack of fundamental understanding remains for this process, and many opportunities for alloy development and implementation can be identified. A high-throughput, in situ DED system capable of multi-layer builds that can address these issues is presented here. In this work, implications of layer heights and energy density are investigated through an extensive process parameter sweep, showcasing the power of a high-throughput setup while also discussing multi-layer interactions.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Incremental rotary rolling mill and method

A rolling mill system for Incremental rotary shaping of an elongated workpiece is provided that includes first and second workpiece holders. A support frame has a track with the first and second workpiece holders being movably associated with the track, the workpiece holders and an associated workpiece being movable in unison along the track. A radial chuck is mounted to the frame that includes a plurality of jaws that are movable radially inwardly and outwardly. Each jaw has a tool mounted thereto that is rotatable about an axis of rotation, with the axis of rotation of each tool being oriented at a skew angle relative to the longitudinal axis of a workpiece. A source of electric current and an electrically conductive flow path are provided for flowing electrical current through a workpiece. A controller is provided that is configured to control the operation of each of the first motor, second motor and third motor, and to control the flow of current flowing through the tools to the workpiece.

Zeng, Qiang↗