Browse Topic: Coatings, colorants, and finishes
This specification establishes the requirements for brush plating of cadmium by electrodeposition.
Hybrid additive manufacturing (AM) and subtractive manufacturing (SM) processes utilize the combination of AM (e.g., LPBF and DED) and SM (e.g., milling and turning operations) to produce the final part. Due to the poor surface roughness resulting from the uneven melting of powders in AM, the subtractive process is a necessary finishing operation to improve the surface roughness of the AM part. The hybrid AM/SM technology combines the benefits of AM and SM processes to create complex geometry while introducing good surface finish and compressive stress to prevent crack initiation. However, the relationship between large process parameter space and the residual stress/distortion in the part is not well understood, which impedes the adoption of hybrid AM/SM to minimize the residual stress in the final product. To expedite the process optimization, we establish a pipeline for the sequential modeling of additive manufacturing (AM) and subtractive manufacturing (SM) processes. Key accomplishments achieved under this study include (1) development of thermal abstraction technique for the AM process to speed up the macroscale level heat transfer analysis based on the manufacturing factors including scanning vector, laser power, dwelling time, etc.; (2) development of the sequentially coupled thermal-mechanical model to predict the residual stress and distortion after AM process by passing the temperature history obtained from heat transfer analysis to the mechanical analysis at each time point; (3) validation of the thermal-mechanical model for AM using thin-wall structure from literature and cantilever beam structure from UNT’s experiments data; (4) conduction of the parametric study on the chamber temperature and part design in the AM process to demonstrate how the temperature gradient and supporting structure affect the residual stress and distortion; (5) exploration of macro and micro scale models to predict the bulk and surface residual stress after cutting; (6) applying the developed modeling framework to tailoring the hybrid AM/SM process. To support model verification and demonstration, we print cantilever beam structure with different supporting structure designs and cutting strategies to study how these factors affect the final part residual stress and distortion. The data collected in the printing and cutting process is used to examine the applicability of the developed simulation tool.
A study into the effects of a low ice adhesion strength coating and combined low power thermal heater system was conducted. Preliminary tests determined the mass of ice necessary to shed from the low ice adhesion strength coating at a specific ambient temperature (-4°C, -8°C, -12°C, and-16°C). The heater tests were conducted at an ambient temperature of -20°C, where the same mass of ice was accreted for each specific case temperature. With the accreted mass, the heaters were turned on until a shed event occurred. The surface temperature at the shed event was recorded. For colder temperatures such as -12°C and-16°C, the surface needed to reach a temperature within 1°C of -12°C and-16°C, respectively, to initiate a shed event. For the warmer cases the replication of ice at -20°C was not feasible, as the type of ice influences adhesion strength. Ice accreted at -20°C has different physical properties than ice formed at warm temperatures, therefore the surface temperature required for shedding did not match between the two tests. Results from the heater tests led to a discovery of a value that describes the adhesion strength normalized with respect to shed surface temperature. The value was found to be -1.09 psi/°C, averaged over six cases with varying conditions. This value is dependent upon a wide range of adhesion strength values for the system but opens possibilities of a full understanding of the hybrid thermal/passive coating system. With the experimental characterization of the adhesion strength to shed surface temperature value, future coating development could rely on heating the surface and recording the surface temperature needed for shedding. With such value, the ice adhesion strength of the coating could be characterized without the need for ice adhesion strength measurements.
ABSTRACT
ABSTRACT
This specification covers a corrosion and heat-resistant steel in the form of bars, wire, forgings, mechanical tubing, flash welded rings, and stock for forging, flash welded rings, or heading.
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