DSpace Collection:https://hdl.handle.net/10171/556842024-03-28T23:59:08Z2024-03-28T23:59:08ZNew strategies based on liquid phase sintering for manufacturing of diamond impregnated bitshttps://hdl.handle.net/10171/691982024-03-11T06:06:56Z2024-01-01T00:00:00ZTitle: New strategies based on liquid phase sintering for manufacturing of diamond impregnated bits
Abstract: Infiltration is an extensively used technique in the production of Diamond Impregnated Bits (DIBs) commonly used for drilling in both mineral exploration and the Oil&Gas industry. This paper describes research into liquid phase sintering (LPS) as an alternative to commonly used infiltration processes. The great wear resistance and high cutting ability necessary for these tools in turn requires a high diamond concentration and a large volume fraction of wear-resistant components, such as tungsten carbide and/or eutectic tungsten carbide particles. With relatively large particles that do not contribute to densification, the LPS system researched was designed with a relatively large amount of permanent liquid phase sintering, with, rearrangement being selected as the primary densification mechanism owing to the stability of the hard phases. After testing various binder phases and evaluating the influence of the liquid phase volume fraction and presence of some sintering aids, results are promising. Bonds with better sintering behaviour were characterized, while hardness, microstructure, abrasive wear resistance, and interaction with diamonds were studied. The proposed 35NiP25Cu40WC bond processed by LPS attained hardness of 66 HRA and wear coefficient of 20 mm3/MPa, levels similar to those obtained by hot pressed components currently used in the diamond drilling tool industry (19 mm3/MPa).2024-01-01T00:00:00ZCollaborative human–robot interaction interface: development for a spinal surgery robotic assistanhttps://hdl.handle.net/10171/691882024-03-04T06:06:37Z2021-01-01T00:00:00ZTitle: Collaborative human–robot interaction interface: development for a spinal surgery robotic assistan
Abstract: The growing introduction of robotics in non-industrial applications where the environment is unstructured and changing, has led to the need of development of safer and more intuitive, human-robot interfaces. In such environments, the use of collaborative robots has potential benefits, due to the combination of user experience, knowledge and flexibility with the robot's accuracy, stiffness and repeatability. Nevertheless, in order to guarantee a functional collaboration in these environments, the interaction between user and robot must be intuitive, natural, fast and easy to use. On one hand, commercial collaborative robots are less accurate and less stiff than the traditional industrial ones, on the other hand, the later have not intuitive interaction interfaces. There are tasks in which the stiffness of industrial robots and the intuitive interaction interfaces of collaborative commercial robots, are desirable. This is the case of some robotic assisted surgical procedures, such as robotic assisted spine surgery, with high accuracy demands and with the need of intuitive surgeon-robot interaction. This paper presents a hand guiding methodology for functional human-robot collaboration and the introduction of novel algorithms to enhance its behavior. Also its implementation on a robotic surgical assistant for spine procedures is presented. It is emphasized how a traditional industrial robot can be used as a collaborative one when the available commercial collaborative robots do not have the required accuracy and stiffness for the task.2021-01-01T00:00:00ZExperimental quantitative comparison of different control architectures for master-slave teleoperation.https://hdl.handle.net/10171/691862024-03-04T06:06:36Z2004-01-01T00:00:00ZTitle: Experimental quantitative comparison of different control architectures for master-slave teleoperation.2004-01-01T00:00:00ZAn EBSD-based methodology for the characterization of intercritically deformed low carbon steelhttps://hdl.handle.net/10171/686862024-02-05T06:06:08Z2019-01-01T00:00:00ZTitle: An EBSD-based methodology for the characterization of intercritically deformed low carbon steel
Abstract: Heavy gauge structural plates has been widely rolled in the austenite/ferrite two phase region, in order to meet the demanding market requirements regarding tensile properties. Even though strength levels can be increased by intercritical rolling, toughness properties may be impaired. Therefore, a greater knowledge of how different austenite-ferrite balances affect the microstructural evolution during intercritical deformation is required. With the aim of gaining a deep comprehension of the evolution of the microstructure during intercritical deformation, dilatometry tests were performed simulating intercritical rolling conditions. Different ferrite populations are identified in the resulting microstructures, composed of intercritically deformed ferrite and non-deformed ferrite transformed during final air cooling. In the deformed ferrite grains well defined substructure is clearly noticed, whereas the non-deformed grains formed during air cooling step do not show any evidence of substructure. In the current work, EBSD advanced characterization technique was used to develop a methodology that is able to differentiate the intercritically deformed ferrite from non-deformed ferrite for low carbon steels. Based on the Grain Orientation Spread (GOS) parameter, a threshold value of 2 degrees was defined to distinguish deformed and non deformed ferrite grains. The proposed procedure allows distinguishing both ferrite populations and quantifying microstructural parameters of each family. The effect of the addition of C and austenite-ferrite balance on the microstructural evolution of each ferrite type was analyzed.2019-01-01T00:00:00Z