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The impact dynamics and drying of paint films sprayed on steel were experimentally investigated. The rupture of sprayed liquid films was first photographed on different substrates. The critical film thickness, below which a film would break, was observed to increase with increasing advancing liquid-solid contact angle, and was unaffected by liquid viscosity for a given substrate. For viscous paint, it was observed that there is no rupture or splashing from a paint droplet impacting a solid substrate or another paint drop or film. For paint films drying at room temperature, mass fluxes were measured and correlated with a simple analytical model based on transient diffusion, and showed good agreement. The mass flux of sprayed paint films decreased slightly with time, and the volatile concentration decreased appreciably. For sprayed paint films cured with heat, there is a minimum stand-time in order to cure a film without any entrapped bubbles.

The impact dynamics and drying of paint films sprayed on steel were experimentally investigated. The rupture of sprayed liquid films was first photographed on different substrates. The critical film thickness, below which a film would break, was observed to increase with increasing advancing liquid-solid contact angle, and was unaffected by liquid viscosity for a given substrate. For viscous paint, it was observed that there is no rupture or splashing from a paint droplet impacting a solid substrate or another paint drop or film. For paint films drying at room temperature, mass fluxes were measured and correlated with a simple analytical model based on transient diffusion, and showed good agreement. The mass flux of sprayed paint films decreased slightly with time, and the volatile concentration decreased appreciably. For sprayed paint films cured with heat, there is a minimum stand-time in order to cure a film without any entrapped bubbles.

No description available.

abstract: Over the past couple of decades, quality has been an area of increased focus. Multiple models and approaches have been proposed to measure the quality in the construction industry. This paper focuses on determining the quality of one of the types of roofing systems used in the construction industry, i.e. Sprayed Polyurethane Foam Roofs (SPF roofs). Thirty seven urethane coated SPF roofs that were installed in 2005 / 2006 were visually inspected to measure the percentage of blisters and repairs three times over a period of 4 year, 6 year and 7 year marks. A repairing criteria was established after a 6 year mark based on the data that were reported to contractors as vulnerable roofs. Furthermore, the relation between four possible contributing time of installation factors i.e. contractor, demographics, season, and difficulty (number of penetrations and size of the roof in square feet) that could affect the quality of the roof was determined. Demographics and difficulty did not affect the quality of the roofs whereas the contractor and the season when the roof was installed did affect the quality of the roofs. / Dissertation/Thesis / M.S. Construction 2013

Yttria Partially Stabilized Zirconia (Y-PSZ) plasma-sprayed coatings are widely used in turbine engines as thermal barrier coatings. However, in diesel engines Y-PSZ TBCs have not met with wide success. To reach the desirable temperature of 850-900˚C in the combustion chamber from the current temperature of 400-600˚C, a coating with a thickness of approximately 1mm is required. This introduces different considerations than in the case of turbine blade coatings, which are on the order of 100µm thick. Of the many factors affecting the durability and failure mechanism of TBCs, in service and residual stresses play an especially important role as the thickness of the coating increases. For decreasing the residual stress in the system, a multi-layer coating is helpful. The design of a multilayer coating employing relatively low cost materials with complementary thermal properties is described. Numerical models were used to describe the residual stress after deposition and under operating conditions for a multilayer coating that exhibited the desired temperature gradient. Results showed that the multilayer coating had a lower maximum stress under service conditions than a conventional Y-PSZ coating. Model validation with experiments showed a good match between the two.

Yttria Partially Stabilized Zirconia (Y-PSZ) plasma-sprayed coatings are widely used in turbine engines as thermal barrier coatings. However, in diesel engines Y-PSZ TBCs have not met with wide success. To reach the desirable temperature of 850-900˚C in the combustion chamber from the current temperature of 400-600˚C, a coating with a thickness of approximately 1mm is required. This introduces different considerations than in the case of turbine blade coatings, which are on the order of 100µm thick. Of the many factors affecting the durability and failure mechanism of TBCs, in service and residual stresses play an especially important role as the thickness of the coating increases. For decreasing the residual stress in the system, a multi-layer coating is helpful. The design of a multilayer coating employing relatively low cost materials with complementary thermal properties is described. Numerical models were used to describe the residual stress after deposition and under operating conditions for a multilayer coating that exhibited the desired temperature gradient. Results showed that the multilayer coating had a lower maximum stress under service conditions than a conventional Y-PSZ coating. Model validation with experiments showed a good match between the two.

A novel flame spray collar called the Coanda Assisted Spray Manipulation collar (CSM) has been tested for use on the Sulzer Metco 5P II combustion flame spray gun. A comparison study of the stock nozzle and the CSM has been performed by evaluating the porosity, surface roughness, microhardness, tensile strength and microscopy of normal and off-normal sprayed NiAl deposits. The use of the CSM collar resulted in the need to position the sprayed coupons closer to the gun, which in turn affected the particle impact energy and particle temperatures of the NiAl powder. For the CSM, porosities had a larger scatterband, surface roughness was comparably the same, microhardness was lower, and tensile strength was higher. The microscopy analysis revealed a greater presence of unmelted particles and steeper intersplat boundaries for the CSM. For both processes, the porosity and surface roughness increased and the microhardness decreased as the spray angle decreased.

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