Mechanical Sciences

Mechanical engineering is one of the three most important engineering branches that have played the primary role in bringing the First Industrial Revolution that is responsible for the present-day human civilization. However, whether this branch of engineering is a result of gradual evolution over the millennia or it was almost ‘born’ during a relatively short period of time is a point that has been discussed in this article. The article also attempts to provide a very brief account of the possible current and future trends of development. How the different branches of engineering have evolved and the possible course that will be followed by the futuristic engineering have also been discussed in brief.

Nonlinearity plays an important role in the dynamics of microelectromechanical resonator. On the one hand, presence of nonlinearity may lead to poor performance of the device. On the other hand, the same nonlinear terms can improve other characteristics of the system. Nonlinearity is, thus, sometimes unwanted while at the other occasions is welcome. Whatever be the reason is, nonlinear dynamics of MEMS device, especially resonator, needs further understanding. In this review work, different aspects of nonlinear dynamics of a single-degree-of-freedom MEMS resonators are discussed. Not only deterministic response under various kinds of excitation, but also noise characteristics of the nonlinear system have been scrutinized. Different methods, which are mostly of recent origin, of tailoring nonlinearity in MEMS resonators have been reviewed. Care has been taken to present a complete picture of the nonlinear dynamics of the simplest type of resonator, namely, the one which can be modelled as a single-degree-of-freedom oscillator.

A tensor-based general order full-discretization method which can be automated to preempt all manual case-by-case symbolic analyses associated with chatter stability identification is upgraded with the capacity for model order reduction of elastic thin-walled workpieces. The implemented method is then exploited for studying the sensitivity of the precision of stability lobes of a reduced elastic thin-walled workpiece to arbitrary variation of interpolation order of both the current and delayed regenerative chatter states. The studied system shows almost identical results for unidirectional and bidirectional models. It was further found that within the numerically stable interpolation orders which are usually from 0 to 9, stability lobes are mildly sensitive to the variation of the order of the current state but strongly sensitive to the variation of the order of the delayed state. Though no combination of orders of current and delayed states is seen to outperform the others in all spindle speed ranges, it is recommended to keep the order of the delayed state at 3 while the order of the current state is varied to get the best results. Error surfaces and time-domain simulations were instrumental in the deductions and discussions of results. The programmed method offers potential industrial benefit of making use of stability lobes for precise selection of productive chatter-free process parameters more user-friendly.

Space elevators are expected to change significantly the method of deployment of Earth-orbiting satellites, offering a more efficient and elegant approach than chemical rockets. A space elevator consists of one or more ribbons (tethers) stretching from the surface of the Earth to a counterweight located beyond the geosynchronous altitude. Before a full space elevator is deployed, it is likely that a partial space elevator will be deployed. One of the key requirements for the design of a space elevator is the understanding of its mechanics. This article discusses the statics and dynamics of space elevators.

This chapter highlights the recent advances in free-surface flows. The governing equations and the boundary conditions associated with free-surface flows involving multiple fluids have been discussed. It is interesting to note that the kinematic boundary conditions are not explicitly applied at the interfaces. A brief review of the numerical methods deployed to investigate the interfacial flows is given. This is followed by the discussions of few examples of free-surface flows involving interesting dynamical scenario and underlying intricate physics. This is a vast and emerging area of research. Several researchers have contributed on different aspects of interfacial flows for about a century. Thus, it is difficult to do justice to all the previous studies in a short review. In this chapter, we mainly review the research work we have been involved with in this subject.

The study of deformable channels finds particular interest among the biofluid dynamists as models to physiological vessels, especially arteries. They serve as a convenient laboratory platform in which experiments can be conducted in controlled settings. This is important when the actual tests on living subjects become difficult to perform due to ethical constraints and poor control over multiple experimental and theoretical parameters. Starting from the earliest findings of William Harvey on the circulation of blood, we have evolved a great extent up to solving complex mathematical models pertaining to arterial mechanics using supercomputers. With the advent of rapid prototyping, robotics, image processing, and high-end digital capabilities, detailed investigations can be carried out in a fast and accurate manner with the least human intervention. To this end, microfluidics technology offers a great advantage due to its inherent capabilities of addressing many fundamental issues that affect the biofluid mechanics in physiological conduits. The present chapter deals with these aspects starting with the history of biofluid mechanics to the state of the art of microfluidics addressing it from both theoretical and experimental perspectives.

Blood is one of the most common human tissues required to assess the human health condition. In a conventional setup, disease diagnosis includes consultation with a health practitioner, blood analysis, and follow up. Overall, the diagnosis process is time consuming and delays the timely treatment of the patients. Point-of-care technology (POCT) is rapidly progressing toward providing innovative and efficient solutions for diagnosing. Point-of-care (POC) devices are portable, provide on-site testing of the blood within few minutes, and utilize small volume of blood. Lab-on-chip microfluidic devices play a key role in the progress of POCT. Several lab-on-chip (LOC) microdevices have been reported in literature for the successful detection of various diseases using blood as a sample fluid. Here, we review blood-based lab-on-chip microfluidics devices dedicated to the point-of-care technology. Our review focuses on the technologies and designs of various dedicated microdevices toward disease diagnostics in reference with blood components such as plasma, red blood cells, white blood cells, platelets, and circulating tumor cells. The review should therefore serve as a useful reference for the development of future blood-based POC devices.

Origami, folding of two-dimensional sheets to create three-dimensional shapes, is well equipped for creating almost any conceivable macroscale shape. As far as its engineering aspects are concerned, origami offers several valuable traits such as easy packaging and moderate material consumption. Unlike at macroscale, folding is a nontrivial process at submillimeter regime. The goal of this chapter is to help acquaint our readers with various micro-origami/origami MEMS fabrication strategies, and origami MEMS applications. Here, we systematically explain different logical routes to achieve folding using various materials and fabrication methods. These strategies are intended to be foundations, upon which various other techniques may be built. A brief note on the fabrication of permanent folds and carbon-based origami is also included in this chapter.

Modelling of micromachining is a challenging but much-needed task of modern science and technology era. In this chapter, salient issues related to modelling are illustrated through some case studies of machining of single-crystal material. Two micro-scale machining processes of a single-crystal metal—conventional machining (CM) and ultrasonically assisted machining (UAM)—are investigated using a crystal-plasticity-based approach. Differences between CM and UAM are elucidated employing three case studies with different cutting velocities. The emphasis of this research is placed on a comparison of the levels of cutting force, chip morphology and dissipated plastic energy between CM and UAM. The simulation results indicate that respective improvements of UAM compared to CM depend significantly on a ratio of the nominal velocity to a critical oscillatory speed. This study ultimately enhanced the understanding of micro-mechanisms, inherent in UAM at the micro-scale.

Laser, an acronym of “Light Amplification by Stimulated Emission of Radiation,” is one of the most convenient forms of energies. Since its invention, its application has been continuously increasing. This article presents an insight on different applications of laser, viz., heat treatment, material removal, finishing, cutting, welding, and cleaning. The specialty of laser lies in its ability to be used at different levels of intensity as per requirement. The applicability of laser can be found in entire manufacturing field, starting from traditional manufacturing (machining, welding) to modern manufacturing (3D printing).