Fire behaviors along timber linings affixed to tunnel walls in mines.

Timber linings are applied as primary supports in the tunnel fault and fracture zones of mines. These linings are essential to prevent broken rock from falling during the occurrence of exogenous fires. In this study, experiments and numerical simulations were carried out using a fire dynamics simulator to investigate the flame-spread rate, flame characteristics, smoke movement, and spread process of timber-lining fires under different wind speeds of 0, 0.25, 0.5, and 0.75 m/s. It was found that cross-section flame spreading follows the three-stage sidewall-ceiling-sidewall pattern. Moreover, the average flame-spread rate increases along the vertical flame-spreading direction and decreases when the flame reaches the timber-lining corners. Moreover, the flame lengths underneath the timber-lining ceiling in the x-direction are longer than those in the y-direction. As the wind speed increases, the normalized flame lengths R(f) in the two directions decrease, and the maximum temperature underneath the ceiling decreases. In addition, the maximum temperature in the three tunnel sections of interest is first recorded in the tunnel cross-section in the initial fire stage. Higher wind speeds correspond to farther distances of the maximum-temperature points of the three timber-lining sections from the fire source

Process planning strategy for wire and ARC additive manufacturing

Additive manufacturing has gained worldwide popularity in the last 20 years as many different methods and technologies for adding materials have been developed. Among them, wire and arc additive manufacturing (WAAM) is a promising alternative for fabricating high quality aerospace metal components economically. This study introduces a process planning strategy for WAAM that produces the path and parameters for the deposition process from CAD and process models. After introducing the framework for process planning, two important steps, tool-path generation and optimization of welding parameters, will be presented in detail. Based on the general requirements for a good quality AM tool-path, including high geometrical accuracy and a minimal number of tool-path passes and elements, two novel tool-path patterns suitable for various geometries are introduced. Using the proposed weld bead model and the overlapping model, appropriate welding parameters, such as the travel speed, wire-feed rate, and layer thickness, can be determined. The performance of the proposed process planning strategy is verified through building a sample impeller