A sequentially coupled thermal stress analysis approach is presented for modelling temperature and distortion profiles resulting from welding thin-walled structures. The material is modelled as thermo-elastic-plastic with isotropic strain hardening. The heat source is modelled as a threedimensional (3-D) double ellipsoid, and 3-D finite element (FE) models are employed for predicting ensuing distortions. Comparisons between the simulation results and experiments performed for eight weld configurations are presented. The weld configurations include bead-onplate, butt weld and tee joint welds with varying plate thicknesses. Temperature measurements using thermocouples and an infrared (IR) imaging radiometer are directly compared to the thermal simulations. Likewise, distortions measured directly on the experimental set-ups are compared to the FE distortion predictions. Very good correlation is obtained for temperature as well as distortion predictions between experimental and proposed numerical approaches. Lastly, details of a weld simulation for the rear section of a motorcycle frame are presented.

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This research work explores the connection of machining parameters, i.e. peak current (I p), pulse on-time (T on), pulse off-time (T off), tool material (copper, copper-chromium, graphite) and powder particles (tungsten carbide, cobalt, boron carbide) on surface roughness (SR) for Inconel-800 superalloy in powder mixed electrical discharge machining process (PMEDM). The Box-Behnken design had been applied to design the experiments, and response surface methodology (RSM) was employed to cultivate the empirical models. Forty-six experiments were conducted as per Box-Behnken method of RSM. The results indicated that when current increases from 4 to 12 A, SR increases from 4.23 to 12.57 μm, while with the increase of T off from 30 to 60 µs, SR decreased from 9.23 to 7.10 μm. Results also indicated that copper as a tool electrode and boron carbide as a powder additive has significantly effect on SR. The predicted results based on developed models are found to be in good agreement with the experimental results reasonably well with the coefficient of determination 0.96 for surface roughness. Furthermore, certain machined specimens were analyzed using energy-dispersive x-ray analysis (EDX) and scanning electron microscope (SEM) techniques.

Interior sampling of a reservoir illuminates its mixing characteristics and supports the assumption of stratification or partitioning. An extensive sampling study of reservoir water quality was conducted in Azusa, Calif. Primary emphasis was placed on providing a better understanding of the dynamics of hydraulic mixing and free chlorine residual concentration distribution in the reservoir. The reservoir approached completely mixed behavior with two exceptions: a degree of short‐circuiting between the inlet and outlet (which significantly affected the T10 time) and the presence of a stagnant zone in the center core of the reservoir where there was less mixing and thus older water. These results support the assumption of stratification or partitioning in reservoirs. Regular field sampling is recommended to facilitate the effective management of distribution system water quality. In particular, interior sampling of reservoirs can provide useful information that could not be inferred otherwise.

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