Papers by Keyword: Nanomechanics

Abstract: The paper delves into various aspects of nanotechnology in mechanical engineering, including the fabrication of nanomaterials and advanced manufacturing techniques. Nanomanufacturing methods offer unprecedented precision and control, enhancing efficiency and performance across industries. From nanoscale manipulation to intricate structure fabrication, nanotechnology is transforming manufacturing processes profoundly. Furthermore, the paper explores the applications of nanotechnology in nano mechanics and nanotribology, elucidating how it enables us to understand and manipulate mechanical behaviours at the nanoscale. Additionally, it discusses the role of nanotechnology in energy systems, where nanomaterials contribute to improved energy storage and conversion efficiency. Beyond traditional mechanical engineering, nanotechnology finds applications in biomechanics, shaping advancements in healthcare through innovative biomedical devices and materials. The interdisciplinary nature of nanotechnology is evident in its potential to address global challenges, such as environmental remediation, by developing nanomaterials for water purification, air filtration, and soil remediation. Looking ahead, the paper discusses future directions for nanotechnology in mechanical engineering, emphasizing the importance of interdisciplinary collaboration, ethical considerations, and responsible governance. It highlights the potential for transformative breakthroughs in medicine, energy systems, and materials science, guided by ongoing research and innovation. In conclusion, nanotechnology is poised to reshape the landscape of mechanical engineering, offering unprecedented possibilities for efficiency, sustainability, and technological advancement. Through careful exploration and application, nanotechnology holds the promise of addressing societal needs while pushing the boundaries of what is possible in mechanical engineering.

Abstract: A continuum model for GO membranes is developed in this study. The model is built representing the membrane as a two-dimensional, heterogeneous, two-phase continuum and the constitutive behavior of each phase (graphitic or oxidized) is built based on DFTB simulations of representative patches. A hyper-elastic continuum model is employed for the graphene areas, while a continuum damage model is more adequate for representing the behavior of oxidized regions. A finite element implementation for GO membranes subjected to degradation and failure is then implemented and, to avoid localization instabilities and spurious mesh sensitivity, a simple crack band model is adopted. The developed implementation is then used to investigate the existence of GO nano-representative volume elements.

Abstract: This project investigated the tribological properties and nanomechanics of Cu-benzotriazole (BTA) composite nanooils. Cu-BTA nanoparticles were synthesized by a thermal decomposition process. Cu-BTA nanoparticles were added into paraffin oil to form the nanooils. Cu-BTA explores the nanomechanics of sphere geometry functions as a rolling medium for friction lower. BTA nanoparticles functions as a protector from oxidation of the Cu nanoparticles in various test circumstances. Tribological experiments were conducted using a pin-on-disk (ASTM G99) test for the wear scar diameter, friction coefficient, and morphology of worn surfaces. The experiment results revealed the dispersion capability of the benzotriazole-capped Cu nanoparticles and indicated the dispersing stability in liquid paraffin oil for the BTA-capped surface of Cu nanoparticles. The testing results show that the Cu-BTA nanoparticle used as an additive in paraffin oil at an appropriate concentration exhibits better tribological properties than those of pure paraffin oil. Cu-BTA functioning as an additives have different anti-wear abilities due to its small size effect and a high absolute viscosity given high Herser number, corresponds to relatively thick lubricant film and an larged elastohydrodynamic lubrication area. A thin film or powder consisting of spherical Cu-BTA nanoparticles on pin-on-disk (ASTM G99) test iron surface protests against damage from relative rolling movement, which reduces friction and wear.

Abstract: There have been increasing research interests in the measurement of the mechanical properties of nanoscale materials by pressing a spherical tip into surfaces of the tested materials. To acquire a better understanding of this process, a model of adhesive contact between a spherical tip and a flat surface is developed by employing the Hamaker hypotheses and molecular dynamics (MD) method. With this model, the deformation characteristics of the tested surface are illustrated by the key snapshots of the deformed surface and the corresponding curves of pressure distribution. The results indicate that the contact can be formed before the tip impresses into the surface. Moreover, the variation of the adhesive force with the distance is recorded during the approach and separation processes, and the adhesion hysteresis is demonstrated by the force-distance curve. Additionally, the stepwise increase of the contact radius with a decrease in the distance is revealed and investigated.

Abstract: In the case of possible using carbon nanotubes in nanoelectronics and nanodevices the dynamic behavior is the key property. Various methods used in the derivation of eigenfrequencies of carbon nanotubes are presented and discussed herein. In particular, the atomistic, continuum mechanics and the numerical modeling are described. The most important factors that characterize the values of the free vibration of carbon nanotubes are summarized. It is worth to mention that the eigenfrequencies for carbon nanotubes lie in the range from GHz to even THz.

Abstract: Understanding major mechanisms affecting material strength such as grain size, grain orientation and dislocation mechanism from atomistic viewpoint can empower scientists and engineers with the capability to produce vastly strengthened materials. Computational studies can offer the possibility of carrying out simulations of material properties at both larger length scales and longer times than direct atomistic calculations. The study has conducted theoretical modeling and experimental testing to investigate nanoscale mechanisms related to material strength and interfacial performance. Various computational algorithms in nanomechanics including energy minimization, molecular dynamics and hybrid approaches that mix atomistic and continuum methods to bridge the length and time scales have been used to thoroughly study the deformation and strengthening mechanisms. Our study has also performed experiments including depth-sensing indentation technique and in-situ pico-indentation to characterize the nanomechanisms related to material strength and tribological performance. In this project, we have developed the innovative mutil-scale algorithms in the area of nanomechanics. These approaches were used to studies the defect effect on the mechanical properties of thin film, mechanical properties of nanotubes, and tribological phenomena at nanoscale interfaces.

Abstract: Vimentin intermediate filament (IF) is one of the major proteins which built the cytoskeleton network alongside with the microtubule and actin filament. Though it was known that the vimentin IF network plays an important role in the mechanical behaviours of cells, it is surprised that its mechanical behaviours are not fully understood to date. The aim of this paper is to study the nanomechanical properties of vimentin IF using the atomic force spectroscopy (AFM) which allows the manipulation and force spectroscopy of filaments. The vimentin intermediate filaments were attached to the APTES (3-aminopropyltriethoxy) functionalized mica which offered better adhesive force. In the force spectroscopy study, the AFM tip was allowed to clamp filaments and then retraced. The force-displacement curve of the process was obtained for analysis. The curves can be grouped into two major groups – sewtooth and plateau. The appearance of sewtooth was more frequent than the plateau. The sudden force changes (jumps from higher to lower force) in sewtooth and plateau curves were also analyzed. It was shown that the partial ruptures which denoted by the jumps favoured small force (~100 pN) and short range (separation of jumps below 25 nm). This result also demonstrated the probability of different modes of partial IF ruptures.

Abstract: The effect of diameter, chirality and volume fraction of SWCNTs on the tensile behavior of nanocomposites is studied. Multi-scale material modeling is applied to assemble different RVEs composed of various SWCNTs embedded in polymer. Nanotubes are modeled in continuum mechanics, based on their atomic structures as space frame structures. Beam elements in this structure are defined based on carbon bonds characteristics in molecular mechanics. Polymer portion of the RVE is modeled as a linear elastic continuum material, with lower accuracy regarding to the multi-scale modeling technique. Attained stress-strain curves obtained from modeled nanocomposites revealed that using Armchair SWCNTs in RVEs makes nanocomposites tougher rather than Zigzags. Also, diameter of CNT has an inverse effect on the curves level. Moreover, the effect of diameter is more obvious at higher volume fraction of CNTs.

Abstract: Nanometer size mechanical devices, which utilize dynamic force interaction, such as friction, may provide basis for new generation of electromechanical applications with superior speed and energy effectiveness compared to conventional semiconductor electronics. Experimental verification of theoretical model systems for friction force on nanoscale is difficult since the interaction is sensitive to exact chemical composition of interacting materials as well as precise definition of the contact geometry. In this work we address the geometrical and electrostatic aspect of dynamic shear force interaction between two nanometer size objects. An atomic force microscope (AFM) tip is attached to a quartz tuning fork (TF) in a way, which minimizes the added mass to the TF prongs and allows accurate control of the contact potential. The nanogap to the mating electrode is established by in-situ piezoelectric manipulator in a scanning electron microscope (SEM). The TF oscillation signal recorded at various gap distances shows distinct dependency on applied electrostatic potential.

Abstract: Gradient nanomechanics is a generalized continuum mechanics framework accounting for “bulk-surface” interactions in the form of gradient terms that enter in the evolution equations of the relevant constitutive variables and/or in the governing field equations. This approach is discussed in the paper by developing appropriate differential equations for the plastic strain and/or the structural defects that bring this about. The effectiveness of the approach is illustrated by considering size-dependent stress-strain curves for nanopolycrystals with varying grain size.