Theses and Dissertations at Montana State University (MSU)
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Item Characterization and optimization of direct drive friction welding parameters in small stainless steel tube welds(Montana State University - Bozeman, College of Engineering, 2013) Adams, Alex Jackson; Chairperson, Graduate Committee: David A. MillerRotational friction welding is a common joining process used to join cylindrical metal components. Typically, one piece is rotated and a secondary piece is held rigid. The two samples are then forced together in a controlled manner, and the resulting friction generates enough heat to weld the two pieces. This process was characterized and optimized for 304 Stainless Steel tubes with a .317 cm (.125 in) outer diameter and .14 cm (.055 in) inner diameter. The goal was to characterize and optimize parameters around a weld with no leak, strong ultimate tensile strength, and proper through-hole integrity. Also, solid bars were welded to some tubes to analyze a capped system. Key parameters to the process that were monitored and/or controlled include rotational speed, applied force, temperature, duration, and material upset. Often times the applied force is divided into two steps. A lower force is applied during heating (friction force), and a larger force is applied once rotation stops (forging force). The material upset, maximum temperature, and forging fore were the primary controlling variables in this study. Other parameters were held constant. A testing setup was built to analyze these factors. Modifications were made to a three axis mill to perform friction welding in a controlled environment. Then, tests were run to understand the effects each parameter had on weld quality. Welds with an upset greater than .1 cm held a pressure at a much higher success rate than welds with lower upsets. In general, the forging force was shown to have a large positive impact on ultimate tensile force. The integrity of the through-hole was compromised in many of the tube to tube tests. Several welds were post-drilled to recreate the through-hole. Tests with this done held a pressure 66.67% of the time. It was found that successful welding can be accomplished with this process, and different adjustments to testing procedures can maximize different qualities in the weld.Item An experimental classification of energies necessary to crimp seal copper and stainless steel tubing(Montana State University - Bozeman, College of Engineering, 2011) Krob, Tyler James; Chairperson, Graduate Committee: David A. MillerCrimping by means of deformation is a process commonly performed which restricts the flow of a substance through a tube. This process is unique by requiring large amounts of deformation between the inner tube walls which must lock and seal together allowing no flow to occur. This research studies how much energy is required to seal tubes constructed of copper or stainless steel between 0.125" and 0.25" encompassing all wall thicknesses available. Each cross section of tubing was cut, tightened into the end of a compression fitting, and plumbed through an integral vacuum sensor via plastic tubing running back to an oil-filled vacuum pump. This setup was mounted into a crimping fixture with interchangeable die sets within an Instron 5882 load frame and compressed at a quasi-static rate while monitoring load, displacement and vacuum level through a LabVIEW data acquisition program. All testing was analyzed to identify which die set produced the most efficient seal and required the least amount of input energy. Several sets of crimped samples were laid on their sides, mounted within epoxy and ground down to expose the sealing interface of the inside walls. From all acquired information, a new die set was constructed in an optimizing attempt to minimize both the leak rate and the energy required in creating the seal. The shape and contours of the optimized die set were the parameters changed from the 3 original sets. Final results showed that a shear shaped die set required the least amount of energy to establish a seal. The flat die created the best seal having the lowest resulting leak rate. The optimized die set created did not minimize the energy, but did produce a comparable leak rate to the flat set. This research develops a strict testing regimen to be followed when crimping a tube using a quasi-static deformation technique.