Influence Of Surface Imperfections Research Articles

The influence of surface imperfections on phosphate coating performance of nodular cast iron substrates

<p>The service performance of the nodular cast iron wheel hub was modelled by investigating the effect of surface morphology and characteristics on the phosphate coating size, morphology, and corrosion resistance properties of the zinc phosphate conversion coated cast iron substrates. The machined and unmachined surfaces as well as the coatings were examined by a scanning electron microscope coupled with an energy-dispersive X-ray spectrometer (SEM-EXD). The influence of the substrates’ surface imperfections on the phosphate coating and the subsequent corrosion resistance was assessed and rated according to the standard procedures. Surface analysis of the machined and unmachined cast iron hubs reveals the existence of graphite and foreign material inclusions on the substrate surface that impact the phosphate coating properties and resistance to corrosion. The average phosphate coating crystal size is 1.74 µm and 2.58 µm for the unmachined and machined cast iron substrates, respectively. The corrosion resistance of the coated unmachined wheel hub surfaces was rated poor and disapproved based on the application requirements. The poor corrosion resistance was ascribed to the influence of the substrates’ surface characteristics on the coating adhesion to the substrate. However, the cast surfaces should be properly shot-blasted to remove any adhere foreign materials on the as-cast skin to enhance the coating adhesion.</p>

The influence of surface imperfections on phosphate coating performance of nodular cast iron substrates

<p>The service performance of the nodular cast iron wheel hub was modelled by investigating the effect of surface morphology and characteristics on the phosphate coating size, morphology, and corrosion resistance properties of the zinc phosphate conversion coated cast iron substrates. The machined and unmachined surfaces as well as the coatings were examined by a scanning electron microscope coupled with an energy-dispersive X-ray spectrometer (SEM-EXD). The influence of the substrates’ surface imperfections on the phosphate coating and the subsequent corrosion resistance was assessed and rated according to the standard procedures. Surface analysis of the machined and unmachined cast iron hubs reveals the existence of graphite and foreign material inclusions on the substrate surface that impact the phosphate coating properties and resistance to corrosion. The average phosphate coating crystal size is 1.74 µm and 2.58 µm for the unmachined and machined cast iron substrates, respectively. The corrosion resistance of the coated unmachined wheel hub surfaces was rated poor and disapproved based on the application requirements. The poor corrosion resistance was ascribed to the influence of the substrates’ surface characteristics on the coating adhesion to the substrate. However, the cast surfaces should be properly shot-blasted to remove any adhere foreign materials on the as-cast skin to enhance the coating adhesion.</p>

A rheological model for immersed corrugated elastic plates

The influence of surface imperfections on the propagation of guided waves in an immersed elastic plate can be interpreted by means of a rheological model. The corrugated surface is modeled by a very thin interface, similar to a Jones spring model, which replaces the continuity boundary conditions at the liquid – corrugated solid-plate interface. As the surrounding liquid is considered to be perfect, only one complex stiffness is used for the model of Jones. The selection of the plate guided mode and the test frequency are motivated by the detectability and non-interference with other modes. The spring stiffness is obtained by a best fit procedure, between the analytical solution and the results obtained by the finite elements method (FEM). One way ensuring the agreement of the two approaches, rheological and FEM, is to consider angular resonances provided by the transmission coefficients. Small changes in the parameters of the roughness keep the positions of the angular resonances of the plate practically unchanged, while at the same time large variations of the half width of the transmission coefficient curve is observed. The effect of corrugation parameters on the guided modes in the plate can be predicted by using the rheological model with the deduced spring complex stiffness.

Experimental and numerical modeling of flatness defects in strip cold rolling

The manufacturing of sheets with high mechanical yield stress, low thickness and minimal flatness defects is a major challenge in the cold rolling of aluminum alloys or steels. Compressive residual stress may appear due to the manufacturing process and induce elastic wave buckling, leading to flatness defects. This study proposes an experimental setup to analyze the interaction between residual stress and buckling for wavy edge flatness defects. The residual stress is simulated by thermal stress. High-resolution full-field measurements are used to measure the wrinkling shape and thermal field. The influence of surface imperfections and global tension on the wrinkling characteristics is highlighted. Finite element tests are used for test validation.

Influence of surface imperfections caused by thruster elements on the aerodynamics of a supersonic projectile

Pulsed side jet thrusters can be used to correct the trajectory of supersonic projectiles. After their time-of-action, these pyrotechnical thrusters leave a hole in the shaft, which sometimes also features a protuberance or burr at its rim. The current work quantifies the aerodynamic interference caused by this sub-boundary-layer disturbance by means of 3-axis-force balance measurements in a supersonic wind tunnel at Mach 3 at angles of attack between 0 and 10 degrees. Supplementary numerical time- and scale-resolving detached eddy simulations (DES) of the wind tunnel setup as well as basic theoretical correlations also support the experimental result that aerodynamic coefficients change by less than 2%, if the hole diameter is in the order of half a calibre and surface deformations protrude less than 2.5% of the calibre.

Theoretical study on the influence of surface imperfections on the properties of ferroelectric thin films in first‐order ferroelectric systems

AbstractA generalized Ginzburg–Landau–Devonshire (GLD) theory is used to study the properties of ferroelectric thin films sandwiched between two metal electrodes with a first‐order phase transition. By taking into account the effect of the imperfect surface layer and a natural boundary condition, the temperature and film‐thickness dependence of the spontaneous polarization and the dielectric susceptibility are calculated. The depolarization field makes the polarization distribution more uniform. In addition, an asymmetric hysteresis loop can be obtained due to the existence of asymmetrical imperfect surface layers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of surface imperfections on the epitaxy of gold on silver and the coherence of a carbon film deposited on silver

Influence of surface imperfections on the epitaxy of gold on silver and the coherence of a carbon film deposited on silver