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Semi-active systems using magnetorheological fluids have been realized in many novel devices such as linear dampers, rotary dampers, brakes, and so on. Rotary vane-type magnetorheological damper is one such device that uses magnetorheological fluid as a hydraulic medium and a controllable magnetorheological valve to generate variable resistance. This device, due to its limited angle motion, lends itself to a natural application for prosthetic knee joint. In this article, a bypass rotary vane-type magnetorheological damper suitable for prosthetic knee device is designed. In the proposed design, the rotary vane chamber and the bypass magnetorheological valve are connected using hydraulic cables and ports. The design of rotary cylinder is implemented based on the largest possible dimensions within the envelope of a healthy human knee, while the magnetorheological valve is designed optimally using a multi-objective genetic algorithm optimization. Off-state braking torque, induced on-state braking torque and mass of the valve are selected as three objectives. The torque and angular velocity requirements of the normal human knee are used as design limits. The optimal solution is chosen from the obtained Pareto fronts by prioritizing the objective of weight reduction of magnetorheological valve. The optimal solution is capable of producing a damping torque of 73 Nm at a design speed of 8.4 rpm and current supply of 1.9 A. Potential benefits offered by this design when compared with multi-plate magnetorheological brake are flow mode operation, large clearance gap, and fewer design components, thus reducing the manufacturing complexity.

The most promising technology in the field of semi-active suspension systems is the use of magnetorheological property of MR fluid, whose material behavior can be controlled through external magnetic field. Devices developed based on this principle are adaptive and controllable as desired for a specific application. It is important to understand the damping characteristics of these devices before employing them, using experimental or computational approaches. In the present work, both experimental and computational methods have been adopted for characterizing a twin-tube MR damper with an intention to develop a computational approach as an alternative to experimental test in the preliminary design stage. Initially, experimental characterization of MR damper was carried out at 1.5 and 2 Hz frequencies for damper stroke length of ± 5 mm under different DC currents ranging from 0.1 to 0.4 A. Later, coupled finite-element and computational fluid dynamic analysis has been carried out to estimate the damping force under same conditions as used in the experiment. The results of computation are in good agreement with experimental ones. Furthermore, using this computational approach, the damping force at different frequencies of 1.5, 2, 3, and 4 Hz has been estimated and its time histories are also plotted. The influence of fluid flow gap on the damping force has been determined and results revealed that damping force behaves inversely with fluid flow gap.

a b s t r a c tThis paper deals with the fault diagnosis of the face milling tool based on machine learning approach using histogram features and K-star algorithm technique. Vibration signals of the milling tool under healthy and different fault conditions are acquired during machining of steel alloy 42CrMo4. Histogram features are extracted from the acquired signals. The decision tree is used to select the salient features out of all the extracted features and these selected features are used as an input to the classifier. K-star algorithm is used as a classifier and the output of the model is utilised to study and classify the different conditions of the face milling tool. Based on the experimental results, K-star algorithm is provided a better classification accuracy in the range from 94% to 96% with histogram features and is acceptable for fault diagnosis.

Dynamic characterization of silicon carbide particles reinforced Al6082 alloy metal matrix composite sandwich beam with magnetorheological fluid core is experimentally investigated. The study is focused on determining the effect of magnetorheological fluid core on the dynamic behavior of the sandwich structure. The magnetorheological fluid core is enclosed between the top and bottom metal matrix composite beams. The metal matrix composite beams are cast with silicon carbide particles in Al6082 alloy varying from 0 to 20 wt%. The magnetorheological fluid is prepared in-house and contains 30 vol.% carbonyl iron powder and 70 vol.% silicone oil. The free vibration test is conducted to determine the natural frequencies and damping ratio. It is found that the natural frequencies and damping ratio of the sandwich beams increased with an increase in the applied magnetic flux density. The experimental forced dynamic response of sandwich beams is carried out using sine sweep excitation. Vibration amplitude suppression capabilities of the sandwich beams subjected to varying magnetic flux densities are determined. The experimental forced vibration results reveal that metal matrix composite–magnetorheological fluid core sandwich beams have excellent vibration amplitude suppression capabilities.

a comparative study of the optimised and non-optimised results was carried out.

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