Abstract A collision between two bodies is a usual phenomenon in many engineering applications. The most important problem with the collision analysis is determining the hysteresis damping factor or the hysteresis damping ratio. The hysteresis damping ratio is related to the coefficient of restitution. In this paper, an explicit expression is determined for this relation. For this reason, a parametric

This paper presents a novel geometrical design of inserts to realize high-efficiency smooth-surface high-chatter-stability turning. Inserts with a nose radius are used in turning to realize a smooth surface since the theoretical surface roughness Rth=f2/(8r) where f is the feed rate and r is the radius of the nose part. Since the size of the nose radius is limited because of the chatter stability,

The effects of different boundary conditions on the composite laminate containing embedded and through-the-width delamination under bending load are investigated analytically based on a developed Layerwise Higher Order Shear Deformation Theory (LHSDT) and the results are compared with the three-dimensional Finite Element Method (FEM). Contact energy has been calculated. The results demonstrate the

In this work, thermally induced dynamic behaviors of functionally graded flexoelectric nanobeams (FGFNs) are analyzed theoretically while considering the neutral surface concept and the von Karman nonlinearity induced by thermal environment. The temperature field is assumed to vary only in the thickness direction by solving a simple steady state heat transfer equation and to be constant in the plane

In the context of a pedestrian-vehicle accident, the head of an adult pedestrian normally impacts the automotive windshield glazing, which mainly accounts for the pedestrian’s death. Consequently, it is of vital importance to investigate the head impact injury behaviour during interaction with the windshield glazing for the purpose of pedestrian safety protection. This paper presents a numerical approach

The aim of this experimental study is to determine the heat transfer coefficients in laminar regime of mechanically agitated vessel for Newtonian (water) and non-Newtonian fluids, i.e. CMC (carboxy methyl cellulose) solutions in mechanically agitated vessel. It is found that Dean number and Prandtl number play an important role with Nusselt number while determining heat transfer coefficients. Modified

Use of environmentally safe refrigerants is the need of the hour to minimize the carbon footprints and to reduce the ozone depletion. The application of such environmentally safe refrigerants in the thermosyphon with the micro/nanoporous coating is expected to operate efficiently. In this study, a simple cost-effective anodizing technique to form a uniform thin micro/nanoporous coating at the inner

In the present article, we intend to study quasi-analytically the unsteady three-dimensional squeezed flow of the magnetite–graphene oxide/water hybrid nanofluid inside a rotating channel with two horizontal and parallel sheets, in which the lower sheet is stationary, stretchable, and permeable, while the upper sheet is moving and impermeable. Our methodology is based on the single-phase Tiwari–Das

The solar irradiance received by the solar cell is partially lost as heat, which carries negative effect on its voltage and in turn, its generated power. This trapped heat within the photovoltaic module is considered waste energy. Hence, techniques to extract this heat to utilize it for thermal loads, such as water heating or drying, are presented throughout the literature. Most prominent technique

Based on the elastohydrodynamic theory, the nonlinear dynamic behavior of worn oil-lubricated rolling bearings is explored, and the dynamic response including the effect of trajectory of the axis center, the accelerated speed, and the film thickness is analyzed. The worn model is represented by the worn depth. The discrete iterative method and implicit Euler method are combined to solve the dynamic

In this paper, a new manufacturing method of pyramidal lattice cells has been suggested to produce lattice composite cylinders. Moreover, the effect of fiber volume fraction, vacuum molding, and fiber pre-tension has been investigated on the load-carrying capacity of the cylindrical pyramidal lattice structure of a carbon fiber composite. The carbon fiber composite cylindrical pyramidal lattice structure

Abstract The dynamic modeling for the foldable origami space membrane structure considering contact-impact during the deployment is studied in this paper. The membrane is discretized using the triangular elements of the Absolute Nodal Coordinate Formulation (ANCF), and the stress–strain relationship of the membrane is determined based on the Stiffness Reduction Model (SRM). A mixed method is proposed

Ultrasonic elliptical vibration cutting of titanium alloy Ti–6Al–4V is investigated in this research. Because products made of Ti–6Al–4V alloy are usually designed for possessing low-rigidity structures or good-quality cut surfaces, machining requirements such as low cutting forces and slow rate of tool wear need to be fulfilled for realization of their precision machining. Therefore, the ultrasonic

We present the macroscale three-dimensional numerical solution of anisotropic Biot's poroelasticity, with coefficients derived from a micromechanical analysis as prescribed by the asymptotic homogenisation technique. The system of partial differential equations (PDEs) is discretised by finite elements, exploiting a formal analogy with the fully coupled thermal displacement systems of PDEs implemented

Although being a popular approach for the modeling of laminated composites, mesoscale constitutive models often struggle to represent material response for arbitrary load cases. A better alternative in terms of accuracy is to use the FE2 technique to upscale microscopic material behavior without loss of generality, but the associated computational effort can be extreme. It is therefore interesting

In the present study, a new hydrokinetic energy harvester concept based on the tandem oscillating hydrofoils configuration is numerically investigated. Unsteady turbulent two dimensional flow simulations were performed, by using the commercial finite volume computational fluid dynamics code FLUENT, to study the power extraction from tandem hydrofoils oscillating inside a convergent duct. A sinusoidal

A simplified traction prediction approach has been developed for highly loaded EHL contacts accounting for non-Newtonian and thermal effects. For validation, a reference fluid squalane was used for traction measurements at high Hertzian contact pressures (1.25 to 2.66GPa) at three velocities of 5, 10 and 15m/s. Good agreement was seen for traction curves in a semi-log scale at a low speed of 5m/s,

Artificial saliva can benefit tooth degradation management; this study assesses the role of mucins in this process using a combination of techniques to assess wear and surface degradation. Different neutral and acidic artificial saliva solutions were investigated, focusing on the protective capability of mucins. Static immersion and reciprocating ball-on-flat tribometer tests were performed on bovine

Abstract A review of the current use of multibody dynamics methods in the analysis of the dynamics of vehicles is given. Railway vehicle dynamics as well as road vehicle dynamics are considered, where for the latter the dynamics of cars and trucks and the dynamics of single-track vehicles, in particular motorcycles and bicycles, are reviewed. Commonalities and differences are shown, and open questions

In this study, an elastic-plastic model with yielding described by a newly proposed orthotropic yield criterion was used to model the unusual deformation of a strongly textured AA6060 alloy. Available experimental data from tension tests and results of crystal plasticity simulations were used to determine the anisotropy coefficients involved in the yield criterion. Virtual material tests using a recent

We investigate the dynamic aeroelastic response of large but slow aircraft in low-altitude atmospheric turbulence. To this end, three turbulence models of increasing fidelity, namely, the one-dimensional von Kármán model, the two-dimensional Kaimal model and full three-dimensional wind fields extracted from large-eddy simulations (LES) are used to simulate ambient turbulence near the ground. Load calculations

Gallium based liquid metals are emerging as promising lubricant candidates due to their high thermal stability and conductivity. However, the oxidization and instability of liquid metal limit their practical application in lubricant field. In this work, to overcome such problems, the nanoscale liquid metal droplet wrapped by chitosan (NLMWC) was fabricated through the ball milling method, which could

The modified scuffing equations based on the adiabatic shear instability induced by friction effects are postulated. With the present equations, an alternative softening mechanism of the near-surface material undergoing adiabatic shear failure is proposed. This mechanism is dominated by the frictional work, rather than the plastic-deformation work. Based on the mechanism, a quantitative criterion is

Compliant hinges are one of the most widely used design elements in precision mechanism design. They enable higher precision rotation than multi-part hinges and facilitate the adaptation of macro-scale parallel mechanisms into micro-scale. Existing hinge designs offer either a large range at the expense of rotational accuracy or attempt to produce accuracy at the expense of range and stiffness. This

Microtexturing has been implemented to analyze its efficacy in improving the tribological performance of polymeric materials for potential marine applications. Textured and untextured pins were fabricated using aromatic thermosetting copolyester (ATSP) and tested against a copper alloy. Experiments were conducted under both starved and fully flooded (submerged) conditions. Constant pressure experiments

Abstract This paper proposes a systematic methodology to obtain a closed-form formulation for dynamics analysis of a new design of a fully spherical robot that is called a 3(RSS)-S parallel manipulator with real co-axial actuated shafts. The proposed robot can completely rotate about a vertical axis and can be used in celestial orientation and rehabilitation applications. After describing the robot

In this study, a highly efficient method for chemical mechanical polishing (CMP) of silicon carbide (SiC) substrates using enhanced slurry was proposed and developed. The enhanced slurry contains bubbles of ozone gas generated by ozone gas generator in pure water mixed with a conventional commercially available slurry. Therefore, the enhanced slurry has an oxidizing effect on the Si-face of SiC substrates

The present study deals with aeroelastic stability analysis of sandwich plates, containing magnetorheological fluid as the core layer, subjected to the supersonic airflow. The classical plate theory, Hamilton's principle and linear first-order piston theory have been employed to extract the governing equations of motion of the structure. The assumed mode method is used to solve the derived equations

Predicting the response of air-backed panels to impulsive hydrodynamic loading is essential to the design of marine structures operating in extreme conditions. Despite significant effort in this area of research, the lack of full-field measurement techniques of structural dynamics and flow physics hinders our understanding of the fluid–structure interaction. To fill this gap in knowledge, we designed

Manufacturing processes of natural fiber reinforced polymer (NFRP) composites are becoming the interest of industrials and scientists because these eco-friendly materials are emerging in automotive and aerospace industries. In this context, machining processes of NFRP composites present significant issues related to the complex structure of natural fibers that need thorough tribological studies. This

Laser welded–brazed Al/steel lapped joint was successfully obtained under various shielding gas contents (pure Ar, CO2+Ar and pure CO2) with laser power of 2000W. Influence of shielding gas contents on weld formation, interfacial microstructure and tensile–shear strength was investigated. The addition of CO2 in the shielding gas would not only enhance the total fusion volume but also improve the wettability

Abstract If robots can merge the appearance-based place knowledge of other robots with their own, they can relate to these places even if they have not previously visited them. We have investigated this problem using robots with compatible visual sensing capabilities and with each robot having its individual long-term place memory. Here, each place refers to a spatial region as defined by a collection

Abstract Graphene is a promising material as a lubricant additive for reducing friction and wear. Here, a dispersing method which combines chemical modification of graphene by octadecylamine and dicyclohexylcarbodiimide with a kind of effective dispersant has been successfully developed to achieve the remarkable dispersion stability of graphene in base oil. The stable dispersion time of modified graphene

Time series models have been popularly used in structural damage identification because the model coefficients and residual errors are sensitive to structural damages. As the direct relationship between the time series model coefficients (or residual errors) and damage severity is hard to be established, these methods provide limited information about the location or severity of damage. This study

This study aimed to explore the adaptability of coated tools with green cutting technologies. The cutting performance of five AlTiN-based coated tools, including tool life, wear model, and penetration mechanisms, were studied under six cooling methods in sustainable machining of 316L stainless steel. The results showed that the optimal cooling method for the coated tools was determined by the combined

Abstract This paper presents a novel approach for control and motion planning of formations of multiple unmanned micro aerial vehicles (multi-rotor helicopters, in the literature also often called unmanned aerial vehicles—UAVs or unmanned aerial system—UAS) in cluttered GPS-denied on straitened environments. The proposed method enables us to autonomously design complex maneuvers of a compact Micro

Research on the process and its mechanism of dam failure is a long‐term focus in dam engineering field. The reasonable analysis and prediction of dam failure are of great significance to improve the level of dam emergency management and reduce the risk of dam break. A cellular automata (CA)‐based approach is introduced to implement the simulation analysis for the process of piping failure and its induced

COVID-19 may drive sustained research in robotics to address risks of infectious diseases.

Exoskeletons that reduce energetic cost could make recreational running more enjoyable and improve running performance. Although there are many ways to assist runners, the best approaches remain unclear. In our study, we used a tethered ankle exoskeleton emulator to optimize both powered and spring-like exoskeleton characteristics while participants ran on a treadmill. We expected powered conditions

The integrity of moment-resisting timber framed structures can be compromised in a seismic event due to damage of the joint region. Externally bonded carbon fibre-reinforced polymer (CFRP) composites offers an effective retrofit strategy for such joints and the concept has been proven in a limited number of experimental studies to date. There is a, however, a distinct lack of numerical modelling studies

h-BN matrix solid-lubricating composites containing SiC were fabricated by the spark plasma sintering technique. The prepared h-BN/SiC composites exhibited excellent lubricating performance in the wide temperature range from room temperature to 900 °C. With the content of the h-BN increasing from 50 to 75 vol%, the friction coefficients at room temperature decreased from 0.53 to 0.25. Up to 900 °C

The variability of applied load and the integrity of lubrication are crucial factors dictating the durability of wind turbine gearbox bearings. In this work, new ultrasonic reflectometry techniques have been implemented to measure both load and lubrication in the high-speed shaft bearing of a field operational Vestas V42 wind turbine gearbox. Miniature piezoelectric transducers were bonded onto the

MAX phase composites Ti3SiC2–TiCx and Ti3SiC2–(TiCx + TiC) were synthesized and consolidated via a powder metallurgy spark plasma sintering (SPS) technique. The bulk compositions and microstructural evolution of the resulting SPS discs were analyzed using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM) paired with an energy-dispersive spectroscopy (EDS) system. The tribological

Abstract Many exciting robotic applications require multiple robots with many degrees of freedom, such as manipulators, to coordinate their motion in a shared workspace. Discovering high-quality paths in such scenarios can be achieved, in principle, by exploring the composite space of all robots. Sampling-based planners do so by building a roadmap or a tree data structure in the corresponding configuration

Abstract This paper addresses the problem of Multi-robot Coverage Path Planning for unknown environments in the presence of robot failures. Unexpected robot failures can seriously degrade the performance of a robot team and in extreme cases jeopardize the overall operation. Therefore, this paper presents a distributed algorithm, called Cooperative Autonomy for Resilience and Efficiency, which not only

Cloud Manufacturing (CMfg) is a state-of-the-art manufacturing paradigm implementing the concept of service-oriented manufacturing. Machine tools are one kind of the critical manufacturing resources in Cloud Manufacturing, however machine tool matching is still immature owning to customization manufacturing service demands from users and various disturbing factors in production. This paper proposes

The quality of cold-rolled aluminum products is dependent on a low surface roughness and a high surface finish. Accordingly, the present study develops a mixed lubrication model to examine the effects of the main rolling parameters. Cold rolling experiments are then performed on laboratory-scale high-speed cold mill system to evaluate the surface roughness and surface gloss of aluminum sheets processed

Shear-induced chemical etching reactions of single-crystalline Si(100), Si(110), and Si(111) surfaces were studied in acidic, neutral, and basic aqueous solutions. Measuring the applied load dependence of substrate etching yield and analyzing the data with the mechanically-assisted thermal activation model, the critical activation volume and activation barrier were determined for mechanochemical etching

In recent years, advances in nanotechnology have been positively reflected in the manufacturing industry, as in many other fields. Owing to their physical and chemical aspects, the nano-sized solid lubricants can help to improve the tribological and thermal properties when added to aerosols, suspensions and emulsions. In order to achieve high efficiency in machining operations, this phenomenon provides

The interaction between tubes and anti-vibration bars (AVBs) can cause fretting wear of the tubes. The impact-sliding wear caused by random excitation could not be predicted accurately by current models, therefore an energy-based wear model was proposed in this paper to obtain a better prediction. Statistical analysis was established to obtain parameters such as the impact angle and the energy loss

Path planning in robotics often requires finding high-quality solutions to continuously valued and/or high-dimensional problems. These problems are challenging and most planning algorithms instead solve simplified approximations. Popular approximations include graphs and random samples, as used by informed graph-based searches and anytime sampling-based planners, respectively. Informed graph-based

This work develops a novel high-dimensional inverse reinforcement learning (IRL) algorithm for human motion analysis in medical, clinical, and robotics applications. The method is based on the assumption that a surgical robot operators’ skill or a patient’s motor skill is encoded into the innate reward function during motion planning and recovered by an IRL algorithm from motion demonstrations. This