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This article presents a nonlinear vibration signature study of high-speed defective cylindrical roller bearings under unbalance rotor conditions. Qualitative analysis is conducted considering a spall defect of a specific size on major elements such as outer race, inner race, and rollers. A spring-mass model with nonlinear stiffness and damping is formulated to study the dynamic behavior of the rotor-bearing model. The set of nonlinear differential equations are solved using the fourth-order Runge–Kutta method to predict the characteristics of the discrete spectra and analyze the stability of the system. The results show that higher impulsive forces are generated because of outer race defects than defects in the inner race and roller. This can be explained as every time the roller passes through the defect in the outer race during rotation, the energy is released. However, in the case of both the roller and inner race defects, the impulsive force generated in the load zone is averaged because of the force generated in the unloading zone. The route to chaos from periodic to quasiperiodic response has been observed and analyzed that vibration signature is very much sensitive not only to the defects of bearing components but also to the rotor speed. [ABSTRACT FROM AUTHOR]

The manuscript aims to perform the free and forced vibration analysis considering the porosity and orthotropic foundation effect. For the first time, the study is conducted on a variable thickness FGM plate resting on an orthotropic foundation. This study uses the first-order shear deformation plate theory (FSDT) model to present an exact solution for free and forced vibration analysis of the functionally graded material (FGM) plate with variable thickness. The FGM plate, having exponentially varied material properties in the thickness direction, was restrained on simply supported (S-S-S-S) and clamped-clamped (C-C-C-C) boundary conditions. Three different types of microstructural defects (porosity) are taken into consideration during the establishment of the mathematical modeling. In addition, the effect of the orthotropic Pasternak foundation has been incorporated during the formulation. The governing differential equation for thick to thin plates is derived using a variational approach, and further, the Galerkin method is applied to solve the equation of motion. The results have been compared and validated with the existing literature available for a rectangular plate on an elastic foundation. The parametric studies have been done to explore the detailed understanding of the E-FGM (Exponentially graded material) plate including microstructural defects. Even the benchmark results have been investigated for free and forced vibration analysis of the E-FGM plate on the orthotropic elastic foundation. [ABSTRACT FROM AUTHOR]

Abstract: The present study investigates influences of vibration directions, vibration magnitudes, object sizes, object distances and angles of approach on producing errors while performing pointing and clicking activity on a laptop monitor similar to passengers working on moving trains. Attempts made outside the boundary of an object while performing the activity is registered as an error. The number of errors produced under different exposure conditions is computed. Higher vibration magnitudes, smaller size of the objects, and diagonal angular movements are found to create more errors and affected accuracy of the activity and hence showed difficulties to perform the activity. [Copyright &y& Elsevier]

This paper attempts to demonstrate the vibration response of porous Functionally Graded Material (FGM) plate with variable thickness. For the first time, the porous tapered FGM plate being considered is mathematically modeled and assumed to be resting on a linear, parabolic, sinusoidal, and exponential varying Winkler's elastic foundation. The even and uneven porosity distribution as a micro-defect is assumed in a tapered FGM plate that varies according to well-defined mathematical rules. The tapered FGM plate, across the edges, is supported with various boundary conditions. Simple Power (P-) and Sigmoid (S-) Law have been chosen for the homogenization of material properties that are tailored in the thickness direction. First-order shear deformation theory (FSDT) is applied to describe the displacement function for computing the strain field. The variational approach has been used to establish the formulation for free vibration response. The equation of motion has been derived using Hamilton's principle and solved by implementing Galerkin Vlasov's method. Parametric studies on elastic foundations have been done to explore the results and relevance to the real problems. It was observed that variable foundation has a significant effect on the tapered FGM plate rather than the tapered homogenous plate. In addition, it was witnessed that the effect of variable foundation effect diminishes as a constraint on the edges of the tapered FGM plate increases. Also, some benchmark results based on the porosity effect and the influence of variable elastic foundations are exhibited in this study for future reference. [ABSTRACT FROM AUTHOR]

• Balls of misaligned bearing either follow offset or inclined trajectories. • Increase in radial and axial load has contrasting effect on vibrational response. • Vibrational response is more sensitive to offset case than inclined case. • Effect of defect's dimension and misalignment on depth achieved by balls analyzed. • System shows an intermittent behaviour with multi-periodicity having hidden chaos. Dynamic-misalignment beyond a specific limit suggests some abnormal systems' behaviour and, if not dealt with appropriately may lead to its sudden breakdown. To address this problem spherical rolling-element bearings are used which have the capacity to encounter such misalignment till a certain limit. Investigating this physical mechanism of such bearing's and quantifying the degree as well as nature of dynamic-misalignment can lead to diagnosing the root cause responsible for it. This paper thus aims at understanding the physics governing the vibration response of spherical rolling-element bearing with a localized defect and subjected to dynamic-misalignment at the same time, using numerical simulations and experimental validation. The numerically simulated results firstly show that an increase in radial and axial loads have a contrasting effect on the acceleration response and contact-load shared by the two bearing rows. Secondly, the rolling-elements while following an offset trajectory, significantly affect the bearing's vibration response as compared to an inclined trajectory and the depth achieved by rolling-elements inside defect also varies with varying misalignment angles. Thirdly. with an increase in misalignment, the strange attractors form intermittent behaviour with outer multi-periodic response having hidden chaos. The behaviour observed from the numerically simulated results was also validated from the vibration data obtained experimentally from the test-rig. [ABSTRACT FROM AUTHOR]

This paper aims at predicting the non-linear dynamic behavior of a self-aligning ball bearing supported on an unbalanced shaft system under varying shaft speed and radial load conditions. A mathematical model is developed for analyzing the behavior of the shaft-bearing system under dynamic conditions. The nonlinear stiffness, damping, and clearance act as the source of nonlinearity. The balls and the race contacts are considered as non-linear springs and the contact deformation is defined using Hertzian contact theory. A fully populated stiffness matrix characterizing the bearing stiffness in all 3 directions (x,y,z) has been used. The phase diagrams and Poincaré maps are used to characterize the vibrations response and it has been observed that the system undergoes gradual or sometimes sudden changes in the dynamic behavior with the variation in parameters. The route to chaos analysis with considering multi-periodic to chaotic response has been done with parametric variations. It was observed that the periodicity of the system tends to increase with the increase in shaft's rotational speed while it decreases with the increase in radial load. In order to validate the simulated results, a test-rig has been set up, where the vibration data of the rotor-bearing system is acquired and further analyzed. The results obtained from experimental data were found to be in good agreement with the numerical simulations. Hence, these observed results will provide the basic platform in designing of such double-row self-aligning shaft-bearing systems. • Dynamic analysis of double-row self-aligning ball-bearing on an unbalanced shaft is performed. • Parametric analysis includes variation in shaft's rotational speed and radial load on the bearing. • Periodicity increases with increase in shaft speed while with the increase in radial load, it decreases. • Phase plots, Poincare maps and orbit plots are used to characterize the dynamic behavior of system. • Further, computational results have been validated using experimental study performed. [ABSTRACT FROM AUTHOR]

Recent advancements in radiation detection and computer vision have enabled small unmanned aerial systems (sUASs) to produce 3-D radiation maps, for example, composed of gamma rays and neutrons, in real time. Currently, these state-of-the-art systems require two operators: one to pilot the sUAS and another operator to monitor the detected radiation. In this work, we present a system that integrates real-time 3-D radiation visualization with semi-autonomous sUAS control. Our virtual reality (VR) interface enables a single operator to define trajectories using waypoints to abstract complex flight control and utilize the semi-autonomous maneuvering capabilities of the sUAS. The interface also displays a fused radiation visualization and environment map, thereby enabling simultaneous remote operation and radiation monitoring by a single operator. This interface and its underlying framework serves as the basis for development of a single system that can deploy and autonomously control a fleet of radiation-mapping sUASs. [ABSTRACT FROM AUTHOR]

Discusses copolyamides and soluble aromatic polyamides. Syntheses of polyamides; Characterization of polyamides; Effect of structure on properties of polyamides.