Active axial vibration control of a shaft-bearing system excited by the dynamic thrust force

The axial vibration of a shaft-bearing system induced by the thrust excitation is usually composed of multiple tones. To suppress the axial vibration of the shaft-bearing system, two inertial electro-magnetic actuators are mounted symmetrically at the thrust bearing and work in parallel to exert control forces. The control signal is generated by an adaptive algorithm with subband filtering, which aims to attenuate over a broadband the vibration of the thrust bearing and its foundation induced by the dynamic thrust force. To reduce computational complexity, the recursive computation is partly realized with the auto-regressive moving average (ARMA) model. The proposed active control approach is evaluated numerically at first with the dynamic model of the shaft-bearing system and then verified with an experimental system. It is demonstrated by the numerical and experimental results that the active control approach is able to suppress the multi-tone vibration of the thrust bearing and the foundation. Moreover, in comparison to the single-band adaptive feedback algorithm, the adaptive algorithm with subband filtering is more effective when the disturbance contains multiple tones.

The Study of CFRP Variable Feed Drilling Method Based on Sinusoidal Curve

In order to reduce the delamination damage of carbon fiber reinforced polymer (CFRP) drilling and improve the drilling quality. A variable feed drilling method based on sinusoidal curve was proposed, that is, when the drill at a distance of 1mm from the hole exit, the feed rate of the drill would be reduced according to the rule of sinusoidal curve. The method is compared with the traditional feed drilling by experiment, and the influence of the variable feed drilling on thrust force, delamination factor, surface quality, surface roughness of hole wall and exit hole wall morphology are analyzed. The results show that compared with constant-feed drilling, the variable-feed drilling based on sinusoidal curve reduces the thrust force near the hole exit, and greatly improves the delamination factor, surface quality and hole wall morphology at the exit. But the influence on the hole wall roughness is not particularly obvious.

Experimental Investigations into Assessment of Thrust Force and Temperature in Bone Drilling

Drilling of bone is a challenging task for surgeons due to its effect on bone tissues. During drilling, it is noted that the temperature of bone increases. This increase in temperature if above 47°C causes thermal necrosis. Experiments were conducted to study the effect of input drilling parameters and drill bit parameters on bone health. To plan experiments a full factorial design method was used. An analysis is done on the effect of input parameters on thrust force and temperature of bone. The analysis of results shows an increase in thrust force and temperature when the feed rate increases and the spindle speed decreases. Further, the analysis of results shows an increase in thrust force and temperature when point angle increases and helix angle decreases. The increase in thrust force results in temperature rise. Scanning electron microscopy is done to analyze the surface topography of drilled hole. SEM image analysis shows an increase micro-crack in the drilled area when the thrust force and temperature increases.

Numerical investigation of dimple-texturing on the turning performance of hardened AISI H-13 steel

Forming micro-dimples nearer to the cutting edge on the rack face of the tungsten carbide cutting inserts will positively influence the machinability. However, it is challenging to machine the perfect micro-dimple dimensions by utilizing the available machining techniques. Finite element analysis can be an efficient way to observe the influence of dimple-texture area density, micro-dimple size, and various micro-dimple shapes on cutting inserts' machinability. This paper numerically analyses the impact of micro-dimple-textured cutting inserts in dry machining of AISI H-13 steel using AdvantEdge (virtual machining and finite element analysis software). Micro-dimples are formed on the rack face of tungsten carbide cutting inserts to observe the effect of dimple-textured cutting inserts on machinability compared to non-textured cutting inserts in terms of micro-dimple shape, micro-dimple size, and micro-dimple area density ratio. Their outcomes are analysed in terms of chip-insert contact length, main cutting force, and thrust force. It is observed that micro-dimple textured cutting inserts exhibit minimal main cutting force and thrust force in line with increasing the cutting insert life span. The abrasive wear was reduced in dimple-textured cutting inserts due to minimal contact between the cutting insert and chip developed compared to non-textured cutting inserts.

Investigation on Thrust Force Conversion Method of Oscillating Caudal Fin Based on Wake Vortex Field Structure

The wake field of the flexible oscillating caudal fin is investigated using the Digital Particle Image Velocity (DPIV) system. The distributions of the vorticity with different Strouhal numbers are presented, and a self-developed program is used for calculating the velocity circulation of the vortex ring. Quantitative analysis of the wake field such as velocity circulation of the vortex ring, vortex radius, and the center-to-center spacing of vortex pair is presented. A three-dimensional vortex ring chain model of oscillating caudal fin is introduced. A conversion model between velocity circulation and dynamic moment of the vortex ring is presented according to the vortex dynamics theory, and a self-developed program is used for the calculation, in which the conversion of the thrust force based on wake field of oscillating caudal fin is carried out. Comparisons of the results of the two kinds flexible caudal fins thrust force conversion with the result of tricomponent balance system have been done in this paper. The relative errors are 5.86% and 3.44%, respectively. It is shown that the thrust force conversion model of flexible oscillating caudal fin is accurate and reliable, and the method presented in the paper provides an effective model for the quantitative conversion between the flow field and the thrust force of the caudal fin.

Influence of the rotor propulsor on the characteristics of the power unit integrated with wing

Fan wing concept increased the efficiency of using the kinetic energy of the movement of air that flows around the wing. It allow generate thrust and lifting forces. But this scheme also has drawbacks. The most important associated with the significant drag force. The large diameter of the cross-flow fan, in case of failure of the power plant, the aerodynamic quality will be approximately 1: 3. To improve parameters and increase the feasibility of using this scheme, we need to review the existing concepts and change the basic geometric parameters of the cross-flow fan and try to reduce the diameter. It is advisable to increase the speed of its rotation. This work performed calculation and compare lift force and thrust force generated by the system. Compare various positions of the blades, and airflow rate at the outlet of the engine by numerical simulation. Also studied the effect of the profile shape of the blades and their amounts on the performance. As a result, analysis of the interaction of all these parameters to determine the model with the best aerodynamic performance. Numerical modeling turned out to be very resource-intensive. So the main focus on a series of physical experiments with real models. The results show that this scheme has more benefits when compared with before use. So, the proposed idea has good prospects for development and application.

Measurement and optimization of multi-attribute characteristics in milling epoxy granite composites using rsm and combined ahp-topsis

Epoxy granite composites with its wide range of applications in machine tool industries are manufactured by molding process and require post cast machining operations to meet the desired dimensional accuracy for assembly of machine tool structures. In this research work, milling of epoxy granite composites are carried out based on the experimental design from Response Surface Methodology (RSM) techniques and further the optimal solutions are determined by a novel hybrid algorithm AHP-TOPSIS. Central Composite Design (CCD) model is applied with three factors-three levels and the measured output responses are thrust force, tangential force and surface roughness. Experimental combinations of 20 different trials are performed using high speed steel end mill cutter of diameter 10mm with three levels of input parameters: speed; fibre content and feed rate at a uniform depth of cut. The relative importance matrix formulated proved to be highly consistent with its consistency ratio to a maximum of 0.000641 which lies below the higher range of 0.1. Consistency ratio of 0.000641 reveals that the optimal solutions determined will be highly reliable and the decision making is much more judicious. Optimal solution determined from hybrid AHP-TOPSIS methods are: speed 1800 rpm; feed rate 0.03 m/min and 0% percent fibre content. Functional relationships among parameters and responses established by RSM are consistent upto 95% and its significance is tested by analysis of variance. Comparison among predicted and experimental values of three measured responses convey that the percentage variations are minimum with up to 2.03% for surface roughness, 2.50% for thrust force and 2.71% for tangential force components. This research work provides a systematic procedure and clear framework for determination of optimal machining conditions by hybrid methodology on the basis of technique for order preference by similarity to ideal solution (TOPSIS) combined with analytical hierarchy procedure (AHP) for attribute weights and further analyzes the influence of machining parameters over measured responses.

Drilling Parameters Analysis on In-Situ Al/B4C/Mica Hybrid Composite and an Integrated Optimization Approach Using Fuzzy Model and Non-Dominated Sorting Genetic Algorithm

In-situ hybrid metal matrix composites were prepared by reinforcing AA6061 aluminium alloy with 10 wt.% of boron carbide (B4C) and 0 wt.% to 6 wt.% of mica. Machinability of the hybrid aluminium metal matrix composite was assessed by conducting drilling with varying input parameters. Surface texture of the hybrid composites and morphology of drill holes were examined through scanning electron microscope images. The influence of rotational speed, feed rate and % of mica reinforcement on thrust force and torque were studied and analysed. Statistical analysis and regression analysis were conducted to understand the significance of each input parameter. Reinforcement of mica is the key performance indicator in reducing the thrust force and torque in drilling of the selected material, irrespective of other parameter settings. Thrust force is minimum at mid-speed (2000 rpm) with the lowest feed rate (25 mm/min), but torque is minimum at highest speed (3000 rpm) with lowest feed rate (25 mm/min). Multi-objective optimization through a non-dominated sorting genetic algorithm has indicated that 1840 rpm of rotational speed, 25.3 mm/min of feed rate and 5.83% of mica reinforcement are the best parameters for obtaining the lowest thrust force of 339.68 N and torque of 68.98 N.m. Validation through experimental results confirms the predicted results with a negligible error (less than 0.1%). From the analysis and investigations, it is concluded that use of Al/10 wt.% B4C/5.83 wt.% mica composite is a good choice of material that comply with European Environmental Protection Directives: 2000/53/CE-ELV for the automotive sector. The energy and production cost of the components can be very much reduced if the found optimum drill parameters are adopted in the production.