by increasing the applied magnetic field strength. However, because the fluid response to the applied field is limited in the high-flux regime by magnetic saturation, the ability to correct thermorheological changes are limited and it becomes necessary to explore and understand the intrinsic limitations of the fluid at elevated temperature. We describe a new magnetorheological fixture that is designed as a removable accessory to a commercial torsional shear rheometer. Careful consideration of the mechanical, thermal and electromagnetic design constraints enabled us to extend the operating range of the device.The assembled fixture is capable of applying magnetic flux densities up to 1T and controlling 2 the sample temperature up to 150°C. During the design of the instrument, close attention was given to the uniformity of the magnetic field applied to the sample by using finite element simulations. Incorporation of a custom-built magnetic flux sensor which matches the environmental capabilities of the fixture enables in-situ measurement of the local magnetic field at each temperature. The numerical results are also validated by spatially-resolved measurements of the local magnetic field throughout the sample. Finally, we explore the ability of a shift factor between fluid magnetization and yield strength to describe the measured variation in the MR fluid response at elevated temperatures.

The interaction between magnetorheological (MR) fluid particles and the walls of the device that retain the fluid is critical as this interaction provides the means for coupling the physical device to the field-controllable properties of the fluid. This interaction is often enhanced in actuators by the use of ferromagnetic walls which generate an attractive force on the particles in the field-on state. In this paper, the aggregation dynamics of MR fluid particles and the evolution of the microstructure in pressure-driven flow through ferromagnetic channels are studied using customfabricated microfluidic devices with ferromagnetic side walls. The aggregation of the particles and the time-dependent evolution in the microstructure is studied in rectilinear, expansion and contraction channel geometries. These observations help identify methods for improving MR actuator design and performance.

Real-time leak monitoring of pipelines is a need that is growing with the aging of the assets and the rise of the population living in their close proximity. While traditional deployment of external monitoring solutions on legacy assets may require extensive construction and trenching on the pipeline right-of-way, a new class of self-powered and wirelessly communicating devices provides an intriguing alternative. These devices are installed on the right-of-way with no need for mechanical excavation and allow continuous monitoring of a pipeline over long distances. Their low-power requirement makes it possible to operate the monitoring system continuously on battery power and their wireless communication is established through a self-forming network. These attributes make real-time monitoring possible without requiring any wiring to be deployed on the right-of way. The devices take advantage of the pipe’s characteristics that guide the acoustic waves generated by the leak along the pipeline to detect leaks. These characteristics make the detection possible even from a device that is not in close proximity of the leak. Since device spacing is a key parameter in the cost of monitoring with the leak detection system, it is important to understand the parameters that govern the propagation of leak sound on pipelines. Testing was performed for this purpose to validate the ability of these novel acoustic sensors in an outdoor test facility under a variety of leak conditions. This testing evaluated the propagation of acoustic waves emanating from small leaks on a buried pipe. This was achieved by pressurizing the pipeline to different levels of pressure and inducing leaks through various orifice sizes. The acoustic disturbances induced by these leaks were measured by sensors deployed at various stations on the pipe. The results of this testing demonstrated the ability of such an approach to be used for detecting very small disturbances in soil from an offset position caused by leaking liquids.