A variety of nonlinear dynamic responses for a new electro-vibro-impact system is presented, with indication of chaotic behavior. By mathematical modeling of the physical system, an insight is obtained to the global system dynamics. The modeling has established a good correlation with experimental data, and hence can be used as a numerical tool to optimize the system dynamics. In particular, with respect to impact forces and progression rate, may then be achieved with minimal computational cost.

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Agricultural residues are the most abundant biomass and forage resources. Chopping is a precondition for either use, and reducing the shearing force has been considered as one of the most effective way to save energy. A smaller force can also permit more compact mechanical parts of chopping devices. In several cases, power consumption may be large, even when the shearing force is small, if the corresponding cutting velocity is high. Consequently, it is important to minimize both cutting force and power consumption simultaneously. This paper presents a practical approach to solve the multi-objective optimization problem for chopping processes of corn stalks. Applying the Taguchi design of experiments, a plan of 27 chopping tests was conducted. Based on the grey relational grade analysis and analysis of variance technique, optimum levels as well as the percentage contribution of such parameters were identified. Experimental results showed that the multi-response optimization problem in chopping corn stalks can be effectively addressed through the combination of Taguchi design and grey relational analysis. The results can be expanded for practical applications in design and operation of chopping machines for agricultural residues.

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This paper presents an experimental study of the positive effects of vibration-assisted deep drilling of aluminum alloy Al-6061. The four most important evaluation criteria in drilling-machinability, workpiece temperature, torque, and material removal rate-were chosen to be investigated. Holes with a depth-to-diameter ratio of 13 were drilled by high speed steel (HSS) twist drill bits of 3 mm diameter, using both methods of conventional drilling (CD) and ultrasonic-assisted drilling (UAD). Three levels of axial force of 6 kgf, 9 kgf, and 12 kgf were kept constant for each pair of comparison experiments. It was found that workpiece temperature and torque not only changed from one drill to the other, but were also dependent on the hole depth being drilled. Comparisons were made in-pair between CD and UAD under the same axial force and at the same order of hole numbers. The result shows that the material removal rate with UAD was up to 3.5 times higher than that with CD and the average workpiece temperature and torque in UAD were reduced by 3.5 and 6 times, respectively. Moreover, tool life in UAD was observed to increase from 2.5 to 5 times, in terms of number of holes drilled, compared to that in CD. thrust force, morphology chip, built-up edge, exit burr, and hole oversize from UAD were reported as significantly improved compared with those from CD. In research by Chang and Bone [2], the authors predicted and compared thrust force induced in UAD and CD of Al-6061-T6. The conclusion shows that there is a vibration frequency that minimizes thrust force in different drills and cutting conditions. Burr height reduction of up to 85%, tool life increase (in terms of number of holes drilled), and an up to 20% reduction in the thrust force of UAD compared with those of CD have also been revealed in another study by these authors [3]. In other investigation, Li et al. [4] found that the thrust force of UAD is much smaller than that of CD, with a larger vibration amplitude resulting in the smaller thrust force of the cutting edge. A study by Babitsky et al. [5] verified several improvements in machining characteristics due to UAD in drilling, including faster penetration rates, reduction of tool wear, surface finish, roundness and straightness of holes, and the reduction or complete elimination of burrs when drilling ductile plates. Nevertheless, the effectiveness of UAD in deep hole drilling of aluminum alloys, where the depth-to-diameter ratios are larger than 5, have rarely been found in the literature.Investigations considering the reduction of torque and temperature as a primary factor which leads to major improvements in UAD compared with CD of other materials have also been limited in the literature. An experimental study from Azarhoushang and Akbari [6] drilling Inconel 738-LC considered on improvement in average surface roughness and circularity, hole oversize, and drill skidding, causing discontinuous and finer chips in UAD in contrast to in CD. Advantages of UAD such as reducing the thrust force and the cuttin...