Small-Scale Morphological Features on a Solid Surface Processed by High-Pressure Abrasive Water Jet
Being subjected to a high-pressure abrasive water jet, solid samples will experience an essential variation of both internal stress and physical characteristics, which is closely associated with the kinetic energy attached to the abrasive particles involved in the jet stream. Here, experiments were performed, with particular emphasis being placed on the kinetic energy attenuation and turbulent features in the jet stream. At jet pressure of 260 MPa, mean velocity and root-mean-square (RMS) velocity on two jet-stream sections were acquired by utilizing the phase Doppler anemometry (PDA) technique. A jet-cutting experiment was then carried out with Al-Mg alloy samples being cut by an abrasive water jet. Morphological features and roughness on the cut surface were quantitatively examined through scanning electron microscopy (SEM) and optical profiling techniques. The results indicate that the high-pressure water jet is characterized by remarkably high mean flow velocities and distinct velocity fluctuations. Those irregular pits and grooves on the cut surfaces indicate both the energy attenuation and the development of radial velocity components in the jet stream. When the sample is positioned with different distances from the nozzle outlet, the obtained quantitative surface roughness varies accordingly. A descriptive model highlighting the behaviors of abrasive particles in jet-cutting process is established in light of the experimental results and correlation analysis.
Investigation of removing thermal barrier coatings from Nickel based super-alloy using abrasive water jet
Thermal barrier coatings (TBCs) are commonly coated at components of aero engines to protect them from high temperature corrosion. However, there are needs to remove TBCs to provide opportunities to drill cooling holes at metal substrate of these components using electro-discharge machining (EDM). This paper investigated the process of removing TBCs at Nickel based super-alloy by low pressure abrasive water jet machining (AWJM). The geometric features of drilled hole at TBCs were analysed. The effect of process parameters, such as incident angle, dwell time and abrasive concentration, were investigated using single factor experiment. The results revealed that AWJM with low pressure can effectively remove TBCs and expose metal substrate for subsequent EDM drilling.
Frank Must Marry Money: Men, Women, and Property in Trollope's Novels
There is a continuing debate about the extent to which women in the 19th century were involved in economic life. The paper uses a reading of a number of novels by the English author Anthony Trollop...