<p>Unexplained acoustic emission spikes have been reported to occur at the workpiece entry and exit in interrupted machining operations, most notably during grinding. These AE spikes have yet to be fully explained in terms of their cause, or interpreted to yield useful information regarding the grinding process. This thesis research hence focuses on investigating this phenomenon. What started as a curiosity-driven project has resulted in an experimental technique to measure the actual contact length between the workpiece and the grinding wheel, as well as a technique for detecting grinding burn, which are of remarkable practical significance.</p> / Master of Applied Science (MASc)

This work deals with the thermal load during cut-off grinding of high-strength bearing rings. Linear cut-off operations lead to a high rise in temperature over the cutting process. These leads, together with the limited material volume, in a heat build-up and the resulting grinding burn. The aim of this work was to prevent this head build-up by using two-axis cut-off operations. Therefore, known methods were theoretically considered and from this, alternative two-axis strategies were determined. For testing, experiments were carried out on a test set-up developed in this work. The tests showed that the two-axis strategies lead to significantly reduced temperatures, as well as non-grinding burn and partially burr-free cutting surfaces. However, the two-axis methods lead to increased process times, which is why approaches for their optimization have been discussed.

Coolant application is critically important in grinding, preventing workpiece damage and increasing the quality of manufactured components. However, delivery of grinding fluids is difficult to achieve, due to issues unique to grinding processes such as the air layer that surrounds the wheel. Coherent jets, which maintain their shape over a significant distance, are one of the most effective methods of coolant delivery and a significant amount of research has been devoted to developing them. Results of this work, which has largely focused on contoured nozzles, have been modest. Inspired by laminar fountains and wind tunnel design, the present work focuses on the development of a coherent, laminar jet. The developed jet possesses extreme coherence, and appears to resemble a glass rod with its stability and clarity. Investigations were carried out, comparing the coherence and cooling ability of the developed system to that of a commercially available coherent nozzle. Models for the structure of the air layer and to predict the conditions necessary for a jet to penetrate the air layer were also developed. The developed jet outperformed the commercial system both in terms of coherence and manufacturing productivity. The model was validated with experimental values, and appears to provide excellent agreement to those results. This work details the background, design, and experimentation involved in creating these innovative systems. / Thesis / Master of Applied Science (MASc)

Generating gear grinding is a method used for hard machining of gearbox gears. It facilitates a productive gear manufacturing with tight tolerances regarding surface roughness and geometrical accuracy. However, if the grinding is done with incorrect parameters, so called grinding burns can arise with consequences such as changes in surface hardness, changes in residual stress levels, surface embrittlement and compromised fatigue strength. This thesis investigates the gear tooth quality resulting from grinding parameters contributing to an improved grinding time. A literature study will cover gear geometries and material, grinding wheel properties, influences by grinding parameters and several verification methods. An experimental test will then be used to put four different grinding parameters to the test. The results showed that an increased cutting speed indicated finer surface roughness andincreased Barkhausen noise but showed no influence on gear geometry. Increasing both rough and fine feed rates resulted in a minor increase in geometry deviation but no significant difference in surface roughness. Large variations within the different verification method results related to grinding burns madeit difficult to draw conclusions regarding the experimental factors chosen. However, several factors apart from the experimental ones varied in the testing were believed to have significant influence, such as the flow of the cooling fluidand the amount of retained austenite from the carburizing process. In fact, the trends which seemed to be connected to these factors could be seen in both Barkhausen noise analysis, hardness measurementsand microstructure.