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1
Malena, Marialaura, and Gianmarco de Felice. "Analytical Modeling of Composite-to-Masonry Prisms Bond." Key Engineering Materials 624 (September 2014): 567–74. http://dx.doi.org/10.4028/www.scientific.net/kem.624.567.
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The composite-to-substrate interfacial stresses transfer mechanism is one of the critical issues in externally-bonded structural strengthening by means of composite fabrics. In this work, an analytical approach for modeling the debonding process of a composite on a non-homogeneous substrate is developed and applied to simulate the loss of bond of FRP on brick masonry. The analytical formulation is based on the experimental outcomes of bond shear tests, which are part of a Round Robin activity involving several laboratories. The experimental work is the follow up of a previous one [1], and comprises 12 single-lap shear tests of four kinds of unidirectional reinforcement, i.e., glass, carbon, basalt and steel, applied with epoxy resin to masonry prisms composed by five clay bricks and four mortar joints. The analytical simulations of the experimental tests rely upon a bi-linear non-homogeneous bond-slip law that was calibrated using the experimental population. Eventually, the analytical results are compared to experimental ones both, in terms of global (load to displacement curve) and local behavior (strain profile on the reinforcement for increasing load values).
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Irubetagoyena, I., M. Verset, S. Palierne, P. Swider, and A. Autefage. "Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model." Veterinary and Comparative Orthopaedics and Traumatology 26, no. 06 (2013): 479–88. http://dx.doi.org/10.3415/vcot-13-07-0089.
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SummaryObjectives: To compare the mechanical properties of locking compression plate (LCP) and limited contact dynamic compression plate (LC-DCP) constructs in an experimental model of comminuted fracture of the canine femur during eccentric cyclic loading.Methods: A 20 mm mid-diaphyseal gap was created in eighteen canine femora. A 10-hole, 2.4 mm stainless steel plate (LCP or LC-DCP) was applied with three bicortical screws in each bone fragment. Eccentric cyclic loadings were applied at 10 Hertz for 610,000 cycles. Quasistatic loading / unloading cycles were applied at 0 and 10,000 cycles, and then every 50,000 cycles. Structural stiffness was calculated as the slope of the linear portion of the load-displacement curves during quasistatic loading / unloading cycles.Results: No bone failure or screw loosening occurred. Two of the nine LCP constructs failed by plate breakage during fatigue testing, whereas no gross failure occurred with the LC-DCP constructs. The mean first stiffness of the LCP constructs over the course of testing was 24.0% lower than that of constructs stabilized by LC-DCP. Construct stiffness increased in some specimens during testing, presumably due to changes in boneplate contact. The first stiffness of LC-DCP constructs decreased by 19.4% and that of locked constructs by 34.3% during the cycling period. A biphasic stiffness profile was observed: the second stiffness was significantly greater than the first stiffness in both groups, which allowed progressive stabilization at elevated load levels.Clinical significance: Because LCP are not compressed to the bone, they may have a longer working length across a fracture, and thus be less stiff. However, this may cause them to be more susceptible to fatigue failure if healing is delayed.
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Singh, Rahul Kumar, Sun Woh Lye, and Jianmin Miao. "PVDF Nanofiber Sensor for Vibration Measurement in a String." Sensors 19, no. 17 (August 29, 2019): 3739. http://dx.doi.org/10.3390/s19173739.
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Flexible, self-powered and miniaturized sensors are extensively used in the areas of sports, soft robotics, health care and communication devices. Measurement of vibration is important for determining the mechanical properties of a structure, specifically the string tension in strings. In this work, a flexible, lightweight and self-powered sensor is developed and attached to a string to measure vibrations characteristics in strings. Electrospun poly(vinylidene) fluoride (PVDF) nanofibers are deposited on a flexible liquid crystal polymer (LCP) substrate for the development of the sensor. The electrospinning process is optimized for different needle sizes (0.34–0.84 mm) and flow rates (0.6–3 mL/h). The characterization of the sensor is done in a cantilever configuration and the test results indicate the sensor’s capability to measure the frequency and strain in the required range. The comparison of the results from the developed PVDF sensor and a commercial Laser Displacement Sensor (LDS) showed good resemblance (±0.2%) and a linear voltage profile (0.2 mV/με). The sensor, upon attachment to a racket string, is able to measure single impacts and sinusoidal vibrations. The repeatability of the results on the measurement of vibrations produced by an impact hammer and a mini shaker demonstrate an exciting new application for piezoelectric sensors.
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Wang, Yonghong, Wen Du, Guohui Zhang, and Yang Song. "The Longitudinal Deformation Profile of a Rock Tunnel: An Elastic Analysis." Mathematical Problems in Engineering 2021 (April 2, 2021): 1–12. http://dx.doi.org/10.1155/2021/6684035.
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The longitudinal deformation profile (LDP) is the profile of wall displacement versus the distance from the tunnel face. To develop LDP equations, numerical methods and in situ experiments have been used to obtain the deformation of a tunnel in three-dimensional space. However, extant approaches are inadequate in terms of explaining the mechanical relation between the wall displacement and the conditions of a tunnel (e.g., properties of rock). In this paper, an analytical approach is proposed to develop a new LDP equation. First, on the basis of the axisymmetric elastic model of a tunnel, a closed-form solution of wall displacement is derived. Then, a new LDP equation is presented according to the solution developed above; the coefficient β, defined as the ratio of the effective range of the “face effect” to the radius of the tunnel, is proposed for the first time. Finally, a case study is proposed to validate the practicability of this equation.
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Ha, Sang-gui, Abdul Muntaqim Naji, Hafeezur Rehaman, Kyoung-min Nam, Han-eol Kim, Jae-won Park, and Han-kyu Yoo. "Expanded Longitudinal Deformation Profile in Tunnel Excavations Considering Rock Mass Conditions via 3D Numerical Analyses." Applied Sciences 11, no. 12 (June 10, 2021): 5405. http://dx.doi.org/10.3390/app11125405.
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In the convergence–confinement method, the longitudinal deformation profile (LDP) serves as a graphical representation of the actual tunnel convergence (both ahead of and behind the face); therefore, it is considered important for determining the distance of support installation from the face or the timing after excavation in this method. The LDP is a function of the rock mass quality, excavation size, and state of in situ stresses; thus, obtaining the LDP according to the rock mass conditions is essential for analyzing the complete behavior of convergence during tunnel excavation. The famous LDP shows that the best fit for the measured values of tunnel internal displacement reported simply expresses the ratio of the preceding displacement as approximately 0.3. This can lead to an error when predicting the ratio of the preceding displacement while neglecting the rock conditions; consequently, a complete tunnel behavior analysis cannot be realized. To avoid such error, the finite difference method software FLAC 3D is used to develop an expanded longitudinal deformation profile (ELDP) according to the rock mass conditions. The ELDP is represented by graphs featuring different shapes according to the rock mass rating (RMR), and the empirical formula of the LDP best fitted for the tunnel convergence measurement values is expanded. This expanded LDP formula is proposed in a generalized form, including the parameters α and β from the empirical equation. These parameters α and β are expressed as functions of the RMR and initial stress. Statistical analysis results of the 3D numerical analysis of 35 cases were analyzed in the ranges of α = 0.898–2.416 and β = 1.361–2.851; this result is based on the empirical formula of Hoek (1999) (α = 1.1, β = 1.7), which was expanded in the current study according to the rock quality and initial stress conditions.
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Furutani, Ryoshu. "UNCERTAINTY ESTIMATION OF CONSTRUCTED METROLOGY FRAME." International Journal "Advanced Quality" 45, no. 2 (June 22, 2017): 37. http://dx.doi.org/10.25137/ijaq.n2.v45.y2017.p37-42.
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In general, the profile measuring machine uses the displacement sensor attached on movable mechanism in order to measure the object. It could measure the object profile by the amount of movement of the displacement sensor and output of the displacement sensor. When measuring the object, metrological frame is important as a reference. If the metrological frame has some profile errors, the output of the displacement sensor includes the profile error of the metrological frame. We proposed a new method to distinguish the profile error of the metrological frame from the output of the displacement sensor. This method requires two linear stages and a displacement sensor. The object profile and profile error of the movable mechanism are determined by calculation using output of the displacement sensor. The validity of the new method was confirmed by the simulation andexperiment. It was confirmed to be possible to construct metrological frame below 1μm. As a lot of number of iteration are required, the reduction of iteration was discussed. As a result of reduction of measurement, the uncertainties of measurement are shown and compared.
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Goh, Ker Liang. "Displacement-Time Graph of a Point on a Wave Pulse." Physics Educator 03, no. 03 (September 2021): 2120001. http://dx.doi.org/10.1142/s2661339521200018.
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G. Yakubu, G. Sani, S. B. Abdulkadir, A. A.Jimoh, and M. Francis. "FULL CAR ACTIVE DAMPING SYSTEM FOR VIBRATION CONTROL." International Journal of Engineering Technologies and Management Research 6, no. 4 (March 25, 2020): 1–17. http://dx.doi.org/10.29121/ijetmr.v6.i4.2019.365.
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Full car passive and active damping system mathematical model was developed. Computer simulation using MATLAB was performed and analyzed. Two different road profile were used to check the performance of the passive and active damping using Linear Quadratic Regulator controller (LQR)Road profile 1 has three bumps with amplitude of 0.05m, 0.025 m and 0.05 m. Road profile 2 has a bump with amplitude of 0.05 m and a hole of -0.025 m. For all the road profiles, there were 100% amplitude reduction in Wheel displacement, Wheel deflection, Suspension travel and body displacement, and 97.5% amplitude reduction in body acceleration for active damping with LQR controller as compared to the road profile and 54.0% amplitude reduction in body acceleration as compared to the passive damping system. For the two road profiles, the settling time for all the observed parameters was less than two (2) seconds. The present work gave faster settling time for mass displacement, body acceleration and wheel displacement.
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Arai, Yoshikazu, Atsushi Shibuya, Y. Yoshikawa, and Wei Gao. "Online Measurement of Micro-Aspheric Surface Profile with Compensation of Scanning Error." Key Engineering Materials 381-382 (June 2008): 175–78. http://dx.doi.org/10.4028/www.scientific.net/kem.381-382.175.
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A novel scanning probe measurement system has been developed to achieve precise profile measurements of micro-aspheric surfaces. The system consists of a scanning stage (a spindle and a linear slide) and a sensor unit. The sensor unit consists of a ring artifact, two capacitance sensors and a contact-mode displacement sensor. The two capacitance sensors scan the surface of the ring artifact to measure and compensate the error motions of the scanning stage while the contact-mode displacement sensor scans the surface of a micro-aspheric. In this paper, a new contact-mode displacement sensor that has a small contact force of less than 2.3 mN and a stable output has been developed. After investigating the fundamental performance of the contact-mode displacement sensor, the sensor has been applied to the micro-aspheric surface profile measurement system. The effectiveness of the measurement system has been verified by the measurement results.
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Chen, Hong Niao, Jia Jian Chen, and Ray Kai Leung Su. "Detection of Crack Evolution in Plain Concrete by Electronic Speckle Pattern Interferometry." Key Engineering Materials 744 (July 2017): 92–96. http://dx.doi.org/10.4028/www.scientific.net/kem.744.92.
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In order to study crack evolution in concrete, Electronic Speckle Pattern Interferometry (ESPI) technique was applied to measure full-field displacement of concrete beam subjected to three-point bending. Basic principles of ESPI technique were introduced. Mid-span deflection and crack mouth opening displacement were measured by linear variable differential transformers (LVDTs) and clip gauge, respectively. Typical load-displacement curves measured by different methods were compared and analyzed. Analysis results indicated that ESPI results were in good agreement with that measured by LVDT (clip gauge), verifying the validity and accuracy of ESPI measurement. From displacement contours, crack evolution including its initiation and propagation was observed. Furthermore, strain profiles near the crack at different loading levels were determined. Strain profile was nearly linear before crack initiation and became nonlinear with crack growth.
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Carvajal, Juan-Carlos, William D. Liam Finn, and Carlos Estuardo Ventura. "Response spectrum-based seismic response of bridge embankments." Canadian Geotechnical Journal 57, no. 11 (November 2020): 1639–51. http://dx.doi.org/10.1139/cgj-2018-0674.
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A single degree of freedom model is presented for calculating the free-field seismic response of bridge embankments due to horizontal ground shaking using equivalent linear analysis and a design response spectrum. The shear wave velocity profile, base flexibility, 2D shape, and damping ratio of the embankment are accounted for in the model. A step-by-step procedure is presented for calculating the effective cyclic shear strain of the embankment, equivalent homogeneous shear modulus and damping ratio, fundamental period of vibration, peak crest acceleration, peak shear stress profile, peak shear strain profile, equivalent linear shear modulus profile, and peak relative displacement profile. Model calibration and verification of the proposed procedure is carried out with linear, equivalent linear, and nonlinear finite element analysis for embankments with fundamental periods of vibration between 0.1 and 1.0 s. The proposed model is simple, rational, and suitable for practical implementation using spreadsheets for a preliminary design phase of bridge embankments.
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Shimizu, Tsuyoshi, Yasutake Hramiishi, Takaaki Ishii, Yuzairi Abdul Rahim, Mohd Fadzil Ali Ahmad, and Hiromi Watanabe. "Geometrical consideration for mechanical contact between rolling circle and surface roughness as an improvement to the surface profile." Journal of Mechanical Engineering and Sciences 15, no. 1 (March 15, 2021): 7846–59. http://dx.doi.org/10.15282/jmes.15.1.2021.19.0619.
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This paper describes measurement methods of surface profiles that improve contact-type displacement sensor outputs by focusing on the contact point between the sphere tip of the sensor and the rough surface. We examined the geometry of a surface profile model and compared measurements using various methods with the measurement using a roughness meter. The spherical tip of the contact type displacement sensor touches the measurement surface and detects the displacement. The sphere tip radius of a typical contact-type displacement sensor ranges from 1–3 mm, causing the roughness curve to be “filtered” by the radius of the sphere. Three methods for estimating the valley portion of the surface profile are evaluated in this study: a) linear approximation of the concave portion of the surface profile, b) function approximation of the concave portion, and c) using the known nose radius of the machining tool. The following sphere tip radii were used to measure actual surface profiles: 0.25 mm, 0.5 mm, 1.0 mm and 1.5 mm. Given the conditions of the experimental model, we found that surface profiles with a roughness that approximates a predictable curve can be measured with a high degree of accuracy.
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Israël, I., R. Grasso, P. Georges-François, T. Tsuzuku, and A. Berthoz. "Spatial Memory and Path Integration Studied by Self-Driven Passive Linear Displacement. I. Basic Properties." Journal of Neurophysiology 77, no. 6 (June 1, 1997): 3180–92. http://dx.doi.org/10.1152/jn.1997.77.6.3180.
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Israël, I., R. Grasso, P. Georges-François, T. Tsuzuku, and A. Berthoz. Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties. J. Neurophysiol. 77: 3180–3192, 1997. According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by passive transport can be used to build a dynamic as well as a static representation of the traveled path. We found a close quantitative similarity between the present findings on distance reproduction and those obtained from active locomotion experiments in which the same paradigm was used. This resemblance suggests that the two types of navigation tasks draw on common physiological processes and extends the relevance of our results to naturally occurring path integration.
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Ren, Chun, Haitao Min, Tianfei Ma, and Fangquan Wang. "An effective topology optimization method for crashworthiness of thin-walled structures using the equivalent linear static loads." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, no. 14 (July 21, 2020): 3239–55. http://dx.doi.org/10.1177/0954407020940138.
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The equivalent static loads method for nonlinear dynamic response structural optimization may be failed in large deformation crash conditions, due to topology optimization with the equivalent static loads mostly beyond the linear range and causing numerical defects such as high compliance of elements. To overcome the above disadvantage, an advanced structural topology optimization method for crashworthiness considering crash-reduced large deformation and plastic buckling is proposed using newly defined equivalent linear static loads. The equivalent linear static loads can adaptively scale to guarantee that the topology optimization is performed within linear range. At each cycle, the crash simulation is performed and the nonlinear nodal displacement vector at the time step with the maximum strain energy is scaled by an adaptive displacement-scaling factor. The equivalent linear static loads that are generated by multiplying the linear stiffness matrix and the scaled nodal displacement vector will be incorporated into topology optimization, which can guarantee the topology optimization to remain in linear range and further solve the numerical instability problems. The process is repeated until the convergence criteria are satisfied. The effectiveness of the proposed method is evaluated by solving a crashworthiness topology optimization of a crash box considering crash-induced plastic buckling to determine the location and profile of crash triggers. The results show that the proposed method can effectively solve the large deformation crashworthiness topology optimization of thin-walled structures and provides a feasible strategy for crash triggers design in crash box.
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Fung, Eric Hoi Kwun, Xin Zheng Zhang, Ming Zhu, and Wai On Wong. "Profile Estimation of Linear Slide in the Presence of Straightness, Yawing and Rolling Motion Errors." Applied Mechanics and Materials 421 (September 2013): 444–48. http://dx.doi.org/10.4028/www.scientific.net/amm.421.444.
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This paper presents a novel measurement system for the on-machine estimation of the profiles of a linear slide in the presence of three motion errors, i.e. straightness, yawing and rolling. The system consists of eight displacement sensors, a mounting stage and a data acquisition system. The Fourier Eight Sensor (F8S) method is employed for the error separation with software programs written in MATLAB codes. A prototype is designed, built and fitted to an axis of the precision slide. Experiments are performed to test the repeatability of the profile results under three different slide speeds. Results confirm that the proposed measurement system is capable of determining the profiles with good repeatability in the presence of straightness, yaw and roll errors of the slide.
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Manickam, O., and G. M. Homsy. "Fingering instabilities in vertical miscible displacement flows in porous media." Journal of Fluid Mechanics 288 (April 10, 1995): 75–102. http://dx.doi.org/10.1017/s0022112095001078.
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The fingering instabilities in vertical miscible displacement flows in porous media driven by both viscosity and density contrasts are studied using linear stability analysis and direct numerical simulations. The conditions under which vertical flows are different from horizontal flows are derived. A linear stability analysis of a sharp interface gives an expression for the critical velocity that determines the stability of the flow. It is shown that the critical velocity does not remain constant but changes as the two fluids disperse into each other. In a diffused profile, the flow can develop a potentially stable region followed downstream by a potentially unstable region or vice versa depending on the flow velocity, viscosity and density profiles, leading to the potential for ‘reverse’ fingering. As the flow evolves into the nonlinear regime, the strength and location of the stable region changes, which adds to the complexity and richness of finger propagation. The flow is numerically simulated using a Hartley-transform-based spectral method to study the nonlinear evolution of the instabilities. The simulations are validated by comparing to experiments. Miscible displacements with linear density and exponential viscosity dependencies on concentration are simulated to study the effects of stable zones on finger propagation. The growth rates of the mixing zone are parametrically obtained for various injection velocities and viscosity ratios.
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Nalini, D., and K. Dhanalakshmi. "Synergistically configured shape memory alloy for variable stiffness translational actuation." Journal of Intelligent Material Systems and Structures 30, no. 6 (February 22, 2019): 844–54. http://dx.doi.org/10.1177/1045389x19828487.
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The structural composition of two elastic elements, shape memory alloy wire (active actuating element) and spring (the passive bias), offers variable stiffness actuation. Based on this principle, a variable stiffness linear actuator is conceptually designed and developed. It is electromechanical by nature, that is, it is electrically activated and creates translational/linear motion. The variable stiffness linear actuator engages shape memory alloy wire(s) along with a passive compression spring to work synergistically. The biasing element offers recovery force to the shape memory alloy wire as well as compliance to the whole structure. The synergistic configuration exhibits an aiding force, thereby allowing an actuation with large displacement and a wide range of stiffness. The actuator mechanism is implemented through parallel action and further proposes two different modes of operation: pull mode (i.e. the disc moving along a fixed shaft) and push mode (i.e. linear reciprocating motion of the pushrod). The shape memory alloy configured actuator mechanism is analysed theoretically; the working model of the variable stiffness linear actuator is developed and investigated experimentally. The results apprise that the variable stiffness linear actuator is capable of offering large displacement and in reproducing the stiffness profile for active compliance control applications.
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Soong, M. F., Rahizar Ramli, and Wan Nor Liza Wan Mahadi. "Ride Evaluation of Vehicle Suspension Employing Non-Linear Inerter." Applied Mechanics and Materials 471 (December 2013): 9–13. http://dx.doi.org/10.4028/www.scientific.net/amm.471.9.
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Inerter is a recent element in suspension systems with the property that the generated force is proportional to the relative acceleration between its two terminals, which is similar to the way a spring reacts to relative displacement and a damper to relative velocity. This paper presents the analysis of a non-linear inerter working in parallel to passive spring and damper of a vehicle suspension to evaluate its effect on vehicles ride. The non-linear inerter was theoretically capable of switching between on and off states depending on whether or not the suspension deflection was beyond a specified free play. In the study, this behavior was represented mathematically as control law which depended on the relative displacement between the sprung and unsprung masses. A mathematical quarter vehicle model incorporating the non-linear inerter was simulated in MATLAB/Simulink to determine the vehicle responses due to road input in the form of step profile for different combinations of free play and inerters on-state proportionality constant called the inertance. Results showed improvements in vehicle ride comfort, as demonstrated by the lower root-mean-squared sprung mass accelerations compared to the ordinary passive suspension with only spring and damper. Additionally, implementation of non-linear inerter gave lower percentage overshoot to step input, indicating better transient response than ordinary passive suspension.
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Lohar, Hareram, Anirban Mitra, and Sarmila Sahoo. "Natural Frequency and Mode Shapes of Exponential Tapered AFG Beams on Elastic Foundation." International Frontier Science Letters 9 (August 2016): 9–25. http://dx.doi.org/10.18052/www.scipress.com/ifsl.9.9.
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A displacement based semi-analytical method is utilized to study non-linear free vibration and mode shapes of an exponential tapered axially functionally graded (AFG) beam resting on an elastic foundation. In the present study geometric nonlinearity induced through large displacement is taken care of by non-linear strain-displacement relations. The beam is considered to be slender to neglect the rotary inertia and shear deformation effects. In the present paper at first the static problem is solved through an iterative scheme using a relaxation parameter and later on the subsequent dynamic analysis is carried out as a standard eigen value problem. Energy principles are used for the formulation of both the problems. The static problem is solved by using minimum potential energy principle whereas in case of dynamic problem Hamilton’s principle is employed. The free vibrational frequencies are tabulated for exponential taper profile subject to various boundary conditions and foundation stiffness. The dynamic behaviour of the system is presented in the form of backbone curves in dimensionless frequency-amplitude plane and in some particular case the mode shape results are furnished.
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Gao, Wei, J. Yokoyama, S. Kiyono, and N. Hitomi. "A Scanning Multi-Probe Straightness Measurement System for Alignment of Linear Collider Accelerator." Key Engineering Materials 295-296 (October 2005): 253–58. http://dx.doi.org/10.4028/www.scientific.net/kem.295-296.253.
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This paper describes a scanning multi-probe measurement system for local alignment of linac components. The system consists of two probe-units, each having three displacement probes. The two probe-units, which are placed on the two sides of the cylindrical linac components, are moved by a scanning stage with a scanning range of 5 m to simultaneously scan the two opposed straightness profiles of the linac cylinders. A differential output calculated from the probe outputs in each probe-unit cancels the influence of error motions of the scanning stage, and a double ntegration of the differential output gives the straightness profile. The difference between the unknown zero-values of the probes in each probe-unit of zero-difference, which introduces a parabolic error term in the profile evaluation result, is calculated and compensated for by a zero-adjustment method so that accurate straightness profiles of the linac cylinders can be obtained. The effectiveness of the measuring system is confirmed by experimental results.
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Li, Xin, Yu Rong Chen, and Sheng Huai Wang. "One Kind of High Precision Non-Contact Displacement Sensor and its Application." Advanced Materials Research 328-330 (September 2011): 2102–7. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.2102.
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In this article, one new non-contact displacement sensor and its principle has been introduced; it is based upon improved Foucault focus detection and equipped with diffraction grating measuring system. Driven by piezoelectric actuator instead of voice coil motor and diffraction grating metrology system being adopted, the non-contact displacement sensor avoids non-linear error and other measurement error caused by the movement of the voice coil motor and therefore has higher measurement accuracy, which has be proved by series of experiments. During measuring the workpiece surface contour profiles, piezoelectric actuator drives focus object lens to make vertical displacement, and ensures focus in every sampling interval to go to the workpiece surface. In the mean time the focus error signal can be set to zero. The sensor has large range and high resolution, which can be applied in profile measurement. This non-contact displacement sensor resolution can reach 10nm.
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Ghafoori, E., and M. Asghari. "Three-dimensional elasticity analysis of functionally graded rotating cylinders with variable thickness profile." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, no. 3 (September 14, 2011): 585–94. http://dx.doi.org/10.1177/0954406211416916.
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A three-dimensional elasticity solution for the analysis of functionally graded rotating cylinders with variable thickness profile is proposed. The axisymmetric structure has been divided in several divisions in the radial direction. Constant mechanical properties and thickness profile are assumed within each division. The solution is considered for four different thickness profiles, namely constant, linear, concave, and convex. It is shown that the linear, concave, and convex thickness profiles have smaller stress values compared to a constant thickness profile. The effects of various grading indices as well as different boundary conditions, namely solid, free–free hollow and fixed–free hollow structures are discussed. A series of numerical results using zirconia as outer surface ceramic and aluminium as inner surface metal are presented. Parametric study has then been carried out to give a better understanding of how different stress, strain, and displacement components change along radial and axial directions of the rotating structures. Numerical results show that for a given grading index, the structures with a concave thickness profile have the smaller circumferential strain and stress compared to other thickness profiles.
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Yang, Xu Dong, Jia Chun Li, and Tie Bang Xie. "A Large Measuring Range Profilometer for Three-Dimensional Surface Topography Measurement." Key Engineering Materials 364-366 (December 2007): 750–55. http://dx.doi.org/10.4028/www.scientific.net/kem.364-366.750.
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A novel profilometer for three-dimensional (3D) surface topography measurement is presented. The profilometer has large measuring range, high precision and small measuring touch force. It is composed of a two-dimensional (2D) displacement sensor, a 3D platform based on vertical scanning, measuring and control circuits and an industrial control computer. When a workpiece is measured, the vertical undulation of the profile at a sampling point leads to a zero offset of the 2D displacement sensor. According to the zero offset, a piezoelectric actuator and a servo motor drive the vertical scanning platform to move vertically to ensure that the lever returns to its balance position. So the non-linear error caused by the rotation of the lever is very small even if the measuring range is large. When the stylus barges up against a steep wall, the horizontal resistance force results in another zero offset of the 2D displacement sensor. If the zero offset exceeds a quota, the vertical scanning platform descends to make the stylus climb the steep wall successfully. According to the theoretical and experimental analysis, the profilometer can measure roughness, profile of sphere, step, groove and other 3D surfaces with curvature precisely.
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Gannel, Leonid. "Velocity Profiler Optimization for High Precision Linear Servo Drives." Известия высших учебных заведений. Электромеханика 64, no. 2 (2021): 50–55. http://dx.doi.org/10.17213/0136-3360-2021-2-50-55.
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When installing a servo linear electric drive on platforms with supports of passive vibration isolation during positioning, elastic vibrations occur with the natural frequency of the elastic platform. The features of the velocity profile of such an electric drive with the ability to limit the jerk are considered. A mathematical model and a structural diagram of an elastic system are presented. When simulating such a system, the dependences of overshoot on the relative period of vibrations were obtained. It is shown that the optimal jerk time - from the point of view of minimizing the overshoot - is its value equal to the period of the 1st resonance of the "elastic" platform. The calculation of the minimum value of the displacement, at which the efficiency of the choice of the optimal value of the jerk, is ensured. The proposed choice of the optimal jerk time is confirmed by the experimental study.
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Yoo, S. H., and J. Pan. "Approximate Crack Opening Displacement Solutions for Long Circumferential Cracks in Pipes Subjected to Bending and Tension." Journal of Pressure Vessel Technology 114, no. 2 (May 1, 1992): 178–80. http://dx.doi.org/10.1115/1.2929026.
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A simple parabolic formula that describes the opening profile of a sufficiently long circumferential crack in a pipe subjected to bending and tension was found after a proper normalization of the second-order asymptotic expansion of the solutions of Sanders and Alabi [5-9]. Here the crack is sufficiently long in the sense that approximately the crack angle is larger than a small parameter which has the same order of magnitude as the ratio of the wall thickness to the pipe radius, and the pipe is sufficiently long enough not to consider the end effects. These linear elastic solutions can be superposed for combined bending and tension loading. The smile parabolic formula is shown to be a good approximation of the crack opening profile and can be used to evaluate the leak rate for crack length up to one-half of the circumference.
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Allen, Stephen P., and Alena M. Grabowski. "Hopping with degressive spring stiffness in a full-leg exoskeleton lowers metabolic cost compared with progressive spring stiffness and hopping without assistance." Journal of Applied Physiology 127, no. 2 (August 1, 2019): 520–30. http://dx.doi.org/10.1152/japplphysiol.01003.2018.
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When humans hop with a passive-elastic exoskeleton with springs in parallel with both legs, net metabolic power (Pmet) decreases compared with normal hopping (NH). Furthermore, humans retain near-constant total vertical stiffness ( ktot) when hopping with such an exoskeleton. To determine how spring stiffness profile affects Pmet and biomechanics, 10 subjects hopped on both legs normally and with three full-leg exoskeletons that each used a different spring stiffness profile at 2.4, 2.6, 2.8, and 3.0 Hz. Each subject hopped with an exoskeleton that had a degressive spring stiffness (DGexo), where stiffness, the slope of force vs. displacement, is initially high but decreases with greater displacement, linear spring stiffness (LNexo), where stiffness is constant, or progressive spring stiffness (PGexo), where stiffness is initially low but increases with greater displacement. Compared with NH, use of the DGexo, LNexo, and PGexo numerically resulted in 13–24% lower, 4–12% lower, and 0–8% higher Pmet, respectively, at 2.4–3.0 Hz. Hopping with the DGexo reduced Pmet compared with NH at 2.4–2.6 Hz ( P ≤ 0.0457) and reduced Pmet compared with the PGexo at 2.4–2.8 Hz ( P < 0.001). ktot while hopping with each exoskeleton was not different compared with NH, suggesting that humans adjust leg stiffness to maintain overall stiffness regardless of the spring stiffness profile in an exoskeleton. Furthermore, the DGexo provided the greatest elastic energy return, followed by LNexo and PGexo ( P ≤ 0.001). Future full-leg, passive-elastic exoskeleton designs for hopping, and presumably running, should use a DGexo rather than an LNexo or a PGexo to minimize metabolic demand. NEW & NOTEWORTHY When humans hop at 2.4–3.0 Hz normally and with an exoskeleton with different spring stiffness profiles in parallel to the legs, net metabolic power is lowest when hopping with an exoskeleton with degressive spring stiffness. Total vertical stiffness is constant when using an exoskeleton with linear or nonlinear spring stiffness compared with normal hopping. In-parallel spring stiffness influences net metabolic power and biomechanics and should be considered when designing passive-elastic exoskeletons for hopping and running.
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Astafiev, V. I., M. G. Kakhidze, V. I. Popkov, and A. V. Popkova. "MULTI-SCALE STRESS-DEFORMATION STATUS OF POROUS GEOLOGICAL STRUCTURE AS RELATED TO WELL FILTRATION FLOWS." Vestnik of Samara University. Natural Science Series 19, no. 9.2 (June 6, 2017): 153–69. http://dx.doi.org/10.18287/2541-7525-2013-19-9.2-153-169.
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Mono-harmonic junction in the interaction of porous space rock stress in oil/gas saturated reservoirs and averaged hydro-dynamic flows of viscous oil towards wells obtained as a result of innovative decisions in oil industry in general is presented. Within the frames of block homogeneous models of a well through the application of 3D linear theory of wave diffusion along the surface of geophysical emission layer, mathematical statement of asymmetrical filtration challenge with finite velocity of effect is presented. Dispersive ratios for constrained and resonant dissipative structures in a shear layer of viscous-elastic filtration at the edge of a slug of water-oil displacement are given. The redistribution results for the averaged inflow profile of viscous Newtonian filtration into asymmetrical energy-stable stress-deformation status inside the saturated porous media at various constraints: in conditions of enclosed or capillary-clamped boundary and in non-constrained conditions - at the frontier of displacement or with stimulation of water-flood displacement in zones of stagnation is presented.
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SURYANTO, A., and E. VAN GROESEN. "ON THE SWING EFFECT OF SPATIAL INHOMOGENEOUS NLS SOLITONS." Journal of Nonlinear Optical Physics & Materials 10, no. 02 (June 2001): 143–52. http://dx.doi.org/10.1142/s0218863501000498.
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In this paper, we consider the propagation of a spatial soliton in a waveguide with triangular linear refractive index profile. We propose a model that is obtained by starting with a small perturbation of the constant linear refractive index in the displacement vector of the Maxwell equation, and then deriving the NLS equation for this case. Using this model it is shown, both analytically and numerically, that the soliton beam oscillates inside the waveguide. This is as expected, but differs from the model found in the literature in which the inhomogeneity is introduced directly in the standard NLS equation. Finally, the proposed model is used to study the breakup of bound N-soliton in a triangular waveguide.
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Yiming, Fu, and Li Sheng. "The analysis of inter-laminar stress and electric potential for a laminated piezoelectric plate with interfacial damage." Mathematics and Mechanics of Solids 16, no. 8 (July 7, 2011): 793–811. http://dx.doi.org/10.1177/1081286510375346.
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This paper presents a non-linear model for laminated piezoelectric plates with inter-laminar mechanical and electrical damage. The model is based on the general six-degrees-of-freedom plate theory, and the discontinuity of displacement and electric potential on the interfaces are depicted by three shape functions. By using the variation principle, the three-dimensional non-linear equilibrium differential equations of simply supported laminated piezoelectric plates with interfacial damage are derived. Then, an analytical solution is presented by using the finite difference method. In numerical examples, the effects of different damage values, load models, and electric boundary conditions on the inter-laminar stress and electric potential profile of a laminated piezoelectric plate with interfacial imperfections are investigated.
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Zhao, Guo Yong, Yu Gang Zhao, and Rong Guo Hou. "Research on Motion Profile Smooth Control Algorithm Based on Continuous Jerk." Applied Mechanics and Materials 29-32 (August 2010): 2002–7. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.2002.
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Motion profile smooth control is significant to reduce the obvious impact on machine tool in high speed and high accuracy CNC machining. However, the jerk is discontinuous and brings about flexible impact on machine tool in the linear Acceleration/Deceleration (ab. Acc/Dec), exponent Acc/Dec and S curve Acc/Dec approach. In the paper, the CNC machine tool dynamic model is built up to analyze the cause of machine impact, to describe the mathematics and physics meanings of jerk. Then a new Acc/Dec approach in which the jerk is continuous is put forward. And the motion profile smooth control algorithm based on continuous jerk is developed in details according to the permissible maximum acceleration, the permissible maximum jerk, the machining program segment displacement and the instruction feedrate. The motion profile smooth control algorithm can achieve continuous jerk, reduce impact on machine tool effectively, and be important to high speed and high accuracy CNC machining.
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Zhang, Xiaoshuang, Xiuchuan Zhang, and Yunshan Han. "A Case Study on Field Monitoring Analysis of Deep Foundation Pit in Soft Soils." Advances in Civil Engineering 2019 (May 2, 2019): 1–10. http://dx.doi.org/10.1155/2019/9342341.
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Field monitoring in the process of excavation of foundation pit is an important measure to reduce the risk. This paper describes a case study of the filed monitoring data during the process of deep foundation pit excavation in soft soil areas. The displacements of the diaphragm wall top were analysed and found that the horizontal displacement showed the convex shape, while the vertical displacement showed the concave shape. Based on the field monitoring data, the deformation mode of lateral displacement of the diaphragm wall belonged to the composite mode. The relationship between maximum lateral displacement and excavation depth showed a strong linear correlation. The horizontal displacements of bracing pillar decreased with the increasing of bracing stiffness, while the effect of bracing stiffness on vertical displacements of bracing pillar could be ignored. The settlement profile computed using the method of Hsieh and Ou was in good agreement with the field observations and better described the development trend of the ground surface settlement. The ratio of the maximum ground surface settlement (δvm) to the maximum lateral displacement of the diaphragm wall (δhm) was in the range of 0.74∼0.88, belonging to the range of 0.5∼1.0 proposed by Hsieh and Ou. This paper provides a reference basis and related guidance for similar projects.
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Ma, Yu Zhen, Xin Hua Wang, Hong Min Li, Xiao Dong, and Yan Hui Kang. "A New Capacitive Sensing System for Roundness Measurement." Advanced Materials Research 662 (February 2013): 754–57. http://dx.doi.org/10.4028/www.scientific.net/amr.662.754.
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A capacitive sensing system for measuring spindle roundness was proposed in this paper, it was different with the past method using inductive sensors and laser displacement sensors. Three capacitive displacement probes were installed circularly on the measured shaft, because of capacitive sensor with average effect in two electrode plates, it is able to overcome the affect of microscopic factors. while the shaft was rotating with a certain speed, the probes measured the shaft’s profile in non-contact mode simultaneously, then through linear combination for three output signals, the spindle error of the rotating shaft was eliminated, and the roundness error was effectively separated from the measurement results. The experiment results have verified the effectiveness of roundness error measuring system based on mutiple capacitive probes, this capacitive sensing system can be used for rotating shaft roundness measurement.
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Cocchetti, Giuseppe, Claudio di Prisco, and Andrea Galli. "Soil–pipeline interaction along unstable slopes: a coupled three-dimensional approach. Part 2: Numerical analyses." Canadian Geotechnical Journal 46, no. 11 (November 2009): 1305–21. http://dx.doi.org/10.1139/t09-102.
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The soil–pipe interaction constitutive model, based on the concept of the “macroelement” described in a companion paper, has been implemented according to a piecewise linear (PWL) formulation in a three-dimensional finite element code in which the pipe is discretised by means of beam elements. To draw an interpretative theoretical framework for the structural response of the system, some ideal problems in which the pipeline is assumed to be straight and the displacement profile simple are discussed. Both large and small displacement approaches are employed, and the problem of axial instability of pipelines is also analysed. Monitoring data from three real case studies have also been numerically simulated: the first two concern pipelines subject to transversal slow soil movements and the third one refers to a small diameter pipeline subject to failure due to axial instability.
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Ito, So, Ming Lei Li, Zhi Gang Jia, Yuan Liu Chen, Yuki Shimizu, and Wei Gao. "Surface Profile Measurement of Micro-Optics by Using a Long Stroke Atomic Force Microscope." Applied Mechanics and Materials 870 (September 2017): 102–7. http://dx.doi.org/10.4028/www.scientific.net/amm.870.102.
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In this study, a long stroke atomic force microscope (LS-AFM) has been developed for the measurement of the micro-optics which have micrometric amplitude surface structures. An electrochemically polished tungsten wire is used as the AFM probe tip. Since the effective length of the tungsten probe is more than 100 μm, the probe tip can access valley part without the interference between the steep slope and the sidewall of the probe tip. By using the long stroke PZT Z scanner whose long stroke of 70 μm and a resolution of 1 nm, micrometric amplitude of the optical elements can be measured. A linear encoder is employed to measure the displacement of Z scanner in Z direction. A well-detected result of a prism sheet film profile has been obtained by the LS-AFM and its tapping mode.
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BRISCHETTO, S. "EFFECT OF THE THROUGH-THE-THICKNESS TEMPERATURE DISTRIBUTION ON THE RESPONSE OF LAYERED AND COMPOSITE SHELLS." International Journal of Applied Mechanics 01, no. 04 (December 2009): 581–605. http://dx.doi.org/10.1142/s1758825109000393.
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This paper considers the thermal stress problem of thick and thin multilayered cylindrical and spherical shells including carbon fiber reinforced layers and/or a central soft core. The following two cases are considered: (i) the temperature distribution in thickness direction is assumed linear; (ii) the temperature distribution in thickness direction is calculated via Fourier's heat conduction equation. Carrera's Unified Formulation and the Principle of Virtual Displacements are used to obtain the governing equations in the case of shells with constant radii of curvature subjected to established temperature conditions on their upper and lower surfaces. Both Equivalent Single Layer and Layer Wise models with an order of expansion in the thickness direction from linear to fourth order are considered. The importance of refined models for a correct evaluation of displacement and stress fields in multilayered shells can be noted. Furthermore, it has been shown that results obtained assuming a linear temperature profile in the thickness direction can be meaningless.
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Mehta, Parth Dinesh, and Manoj Sahni. "Thermo-Mechanical Analysis for an Axisymmetric Functionally Graded Rotating Disc under Linear and Quadratic Thermal Loading." International Journal of Mathematical, Engineering and Management Sciences 5, no. 4 (August 1, 2020): 744–57. http://dx.doi.org/10.33889/ijmems.2020.5.4.059.
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The study presents thermo-mechanical analysis of functionally graded (FG) rotating disc whose material properties, namely, Young’s modulus, density and coefficient of thermal expansion in radial direction are tailored from inner to outer radius using power law form. The disc is considered to be under the influence of internal pressure, centrifugal body force and thermal loading of the form linear as well as quadratic. Response of FG disc under linear and quadratic temperature profile subjected to internal pressure as well as centrifugal body force is analysed. An exact solution for stress in radial and tangential directions, under mechanical and thermal loading is presented. Numerical solutions for stresses under internal pressure with uniform thermal loading are obtained using finite element method and its comparison with analytical results is presented graphically. Results for radial displacement, radial stress and tangential stress are depicted graphically and their interpretation has been discussed.
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MacLennan, L. D. "An analytical method to determine the influence of shape deviation on load distribution and mesh stiffness for spur gears." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 216, no. 10 (October 1, 2002): 1005–16. http://dx.doi.org/10.1243/095440602760400977.
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A method for analysing the influence of profile errors upon load-sharing capabilities and mesh stiffness of spur gears is proposed. The analysis is based upon a static, two-dimensional finite element approach. The contacts between mating gear teeth are identified in the deformed state, and the nodal point density permits contact pressure distribution emulation for moderate to high load levels. In addition, artificial neural networks are employed for system identification in order to calculate load-sharing capabilities and mesh stiffness trends for low tooth load levels. The effect of tip relief on load-sharing properties is discussed. The contact force and the transmission error are simulated for two medium-quality spur gears where the profile and pitch errors are known. Experimental data validate the reliability of the approach. The contact ratio is shown to be highly load dependent due to profile and pitch errors. The discussion is focused upon the size of the area where the relation between torque and angular displacement is highly non-linear, i.e. load depending. Hence, the contact ratio is shown to be load depending due to geometrical errors, such as profile and pitch errors, in addition to material elasticity.
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Meng, Li Xia, Nian Li Lu, and Shi Ming Liu. "Exact Expression of Element Stiffness Matrix for a Tapered Beam and its Application in Stability Analysis." Advanced Materials Research 255-260 (May 2011): 1968–73. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1968.
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The exact stiffness matrix of a tapered Bernoulli-Euler beam is proposed, whose profile is assumed linear variation. Classical finite element method to get stiffness matrix through interpolation theory and the principle of virtual displacement is abandoned. Starting from the governing differential equation with second-order effect, the exact stiffness matrix of tapered beam can be obtained. In the formulation of finite element method, the stiffness matrix derived has the same accuracy with the solution of exact differential equation method. As is demonstrated in the numerical examples, the presented method can yield, in a very efficient way, accurate results for single tapered beam or structures consisting of tapered elements.
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Sundaresan, S., K. Ishii, and D. R. Houser. "A Procedure Using Manufacturing Variance to Design Gears With Minimum Transmission Error." Journal of Mechanical Design 113, no. 3 (September 1, 1991): 318–24. http://dx.doi.org/10.1115/1.2912785.
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This paper deals with the design of spur gears that have minimum transmission error and are insensitive to manufacturing variance. We address two stages of design: (1) generation of candidate designs (selection of number of teeth, pressure angle, etc.), and (2) tooth profile modification. The first stage involves a search of discrete combinations of design variables, while the second stage utilizes numerical optimization techniques. The key research issue is finding a candidate design and its profile modification that not only has low transmission error, but is insensitive to variations in the design values caused by the manufacturing process. To achieve this goal, the procedure applies Taguchi’s concept of parameter design. In this paper, we consider a design problem with a set specification: fixed center distance, speed ratio, and transmission torque. We seek to find a limited number of candidate designs by applying conventional design generation techniques and some design heuristics. For each candidate design, the procedure determines the optimum profile modification (linear tip relief) by linking the Load Distribution Program (LDP) for gears with an optimization program package (OPTPAK). From the resulting peak optimum, we further seek the statistical optimum using an algorithm developed in this paper. The statistical optimum shows a nominal increase in the transmission error, but is quite insensitive to typical process error associated with gear manufacturing. The developed algorithm readily applies to other gear designs as well as other types of machine elements. In particular, we foresee our procedure to be particularly effective for helical gears. We hope to further our method by developing a means to add statistical heuristics to the discrete design generation stage.
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Thangaratnam, Kari, Divya, and Evangeline Kumar. "Integrated Thermal Structural Analysis of Advanced Composite Plates and Shells." Applied Mechanics and Materials 877 (February 2018): 335–40. http://dx.doi.org/10.4028/www.scientific.net/amm.877.335.
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Thermo-structural analysis with advanced composite plates and shells has been performed using Finite element method in order to determine temperature response and associated thermal stress. On solving the Fourier’s heat conduction equation, temperature profile is arrived at, with the assumption of linear/uniform temperature distribution through the thickness. Finite element program is developed for steady-state heat transfer problems using Semiloof shell element. Validation for integrated thermo-structural analysis has been done and compared with the available results from literature. The new results thus obtained are presented in terms of temperature, thermal stress, and displacement. The results obtained will be useful particularly in nuclear reactor vessels and Thermal Protection System (TPS) in aeronautical engineering.
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Chen, M., Q. Zhao, S. Dong, and D. Li. "Development of an ultra-precision grinding system for machining optical aspheric components with a large depth—diameter ratio." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 216, no. 11 (November 1, 2002): 1471–79. http://dx.doi.org/10.1243/095440502320783404.
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When grinding a large depth—diameter ratio aspheric part of high precision and high quality, the factors influencing surface roughness and profile accuracy of machined surfaces were theoretically analysed first. Afterwards the authors designed and manufactured the ultra-precision aspheric grinding system. The workpiece spindle, transverse guideway, longitudinal guideway and the grinder spindle are in aerostatic form. Turning accuracy of the workpiece spindle is 0.05 μm, the maximum rotational speed of the grinder is 80 000 r/min and the turning accuracy is 0.1 μm, and the resolution of linear displacement of the transverse and longitudinal guideway is 4.9 nm. The accuracy of the precise adjusting mechanism is 0.1 μm. The discharge principle of the dressing mechanism was developed in order to dress the diamond wheel. The ball-headed wheel has high profile accuracy after dressing. This mechanism solved the problem of on-position dressing of the case iron bonded diamond wheels and reduced the machining errors for aspheric surface components. Finally, grinding experiments for machining aspheric components were carried out. The grinding results indicated that the achieved profile accuracy is 0.3 μm and the surface roughness is less than 0.01 μm.
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Bai, Jiao, Xinghui Li, Xiaohao Wang, Qian Zhou, and Kai Ni. "Chromatic Confocal Displacement Sensor with Optimized Dispersion Probe and Modified Centroid Peak Extraction Algorithm." Sensors 19, no. 16 (August 18, 2019): 3592. http://dx.doi.org/10.3390/s19163592.
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Chromatic confocal technology (CCT) is one of the most promising methods for the contactless and accurate measurement of structure profiles. Based on the principles of chromatic dispersion and confocal theory, a dispersion probe is proposed and optimized with several commercial and cheap refractive index lenses. The probe provides 0.3× magnification and a dispersion range of 400 μm with a commercial LED source with an effective bandwidth of ca. 450–623 nm. Since the noise fluctuation can affect the extraction stability of the focal wavelength, a modification to the centroid peak extraction algorithm is proposed in this paper, where several virtual pixels are interpolated among the real pixels of the spectrometer before thresholding. In addition, a series of experiments were carried out to test the system’s displacement measurement performance. The results clearly show that stability is improved by the modified algorithm, and the calibration repeatability is ±0.3 μm in the full measurement range with a linear stage. The standard deviation at the fixed position has an optimal value of 0.009 μm. The section profile of a Fresnel lens is measured by the CCT system to demonstrate its high feasibility and efficiency.
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Medvecká-Beňová, Silvia, Martin Mantič, and Robert Grega. "The Stress Analysis in Dangerous Section of Gear Teeth." Applied Mechanics and Materials 611 (August 2014): 279–83. http://dx.doi.org/10.4028/www.scientific.net/amm.611.279.
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The calculation of the stress in the tooth is based on a number of assumptions. Here is calculated so-called comparative stress. This is useful if they are used in calculating the results and findings from research and practice in the determination of any effects that affect the actual teeth stress. The complicated shape of the teeth is the theoretical determination of stress in the teeth difficult. The starting assumption is highly idealized notion of a linear displacement of the tooth for and tooth load is considered as a beam loaded by bending. The paper deals with the problems of stress examining in a dangerous section of the foot tooth with asymmetrical profile. The stress of tooth is solution by finite element method.
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Moss, E. A., and A. H. Abbot. "The Effect of Finite Amplitude Disturbance Magnitude on Departures From Laminar Conditions in Impulsively Started and Steady Pipe Entrance Flows." Journal of Fluids Engineering 124, no. 1 (November 7, 2001): 235–40. http://dx.doi.org/10.1115/1.1445137.
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The aim of this study was to investigate first departures from laminar conditions in both impulsively started and steady pipe entrance flows. Wall shear stress measurements were conducted of transition in impulsively started pipe flows with large disturbances. These results were reconciled in a framework of displacement thickness Reynolds number and a velocity profile shape parameter, with existing measurements of pipe entrance flow instability, pipe-Poiseuille and boundary layer flow responses to large disturbances, and linear stability predictions. Limiting critical Reynolds number variations for each type of flow were thus inferred, corresponding to the small and gross disturbance limits respectively. Consequently, insights have been provided regarding the effect of disturbance levels on the stability of both steady and unsteady pipe flows.
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Zhang, Ting, Xuan Li, Yawen Wang, and Lining Sun. "A Semi-Analytical Load Distribution Model for Cycloid Drives with Tooth Profile and Longitudinal Modifications." Applied Sciences 10, no. 14 (July 15, 2020): 4859. http://dx.doi.org/10.3390/app10144859.
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The current load distribution model for cycloid drives based on the Hertz contact stiffness typically assumes a two-dimensional planar problem without considering the tooth longitudinal modification effects, which fails to comply with the practical situation. In this paper, this issue is clarified by developing a semi-analytical load distribution model based on a three-dimensional and linear elastic solution. Unloaded tooth contact analysis is introduced to determine the instantaneous mesh information. The tooth compliance model considering tooth contact deformation is established by combining the Boussinesq force–displacement relationships in elastic half-space with an influence coefficient method. With this, the loads, contact patterns, and loaded transmission error are calculated by enforcing the compatibility and equilibrium conditions. Comparisons to predictions made with the assumption of Hertz contact stiffness are presented to demonstrate the effectiveness of the proposed model, which shows good agreement. At the end, the effect of tooth longitudinal modifications on load distributions is investigated along with various loading conditions. This study yields an in-depth understanding of the multi-tooth contact characteristics of cycloid drives and provides an effective tool for extensive parameter sensitivity analysis and design optimization studies.
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PANKIEWITZ, CHRISTIAN, and ECKART MEIBURG. "Miscible porous media displacements in the quarter five-spot configuration. Part 3. Non-monotonic viscosity profiles." Journal of Fluid Mechanics 388 (June 10, 1999): 171–95. http://dx.doi.org/10.1017/s0022112099004735.
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The influence of a non-monotonic viscosity–concentration relationship on miscible displacements in porous media is studied for radial source flows and the quarter five-spot configuration. Based on linear stability results, a parametric study is presented that demonstrates the dependence of the dispersion relations on both the Péclet number and the parameters of the viscosity profile. The stability analysis suggests that any displacement can become unstable provided only that the Péclet number is sufficiently high. In contrast to rectilinear flows, for a given end-point viscosity ratio an increase of the maximum viscosity generally has a destabilizing effect on the flow. The physical mechanisms behind this behaviour are examined by inspecting the eigensolutions to the linear stability problem. Nonlinear simulations of quarter five-spot displacements, which for small times correspond to radial source flows, confirm the linear stability results. Surprisingly, displacements characterized by the largest instability growth rates, and consequently by vigorous viscous fingering, lead to the highest breakthrough recoveries, which can even exceed that of a unit mobility ratio flow. It can be concluded that, for non-monotonic viscosity profiles, the interaction of viscous fingers with the base-flow vorticity can result in improved recovery rates.
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Narkhede, Dilip I., and Ravi Sinha. "Influence of shock impulse characteristics on vibration control using nonlinear fluid viscous dampers." Journal of Vibration and Control 23, no. 9 (August 25, 2015): 1463–79. http://dx.doi.org/10.1177/1077546315594062.
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Energy dissipating damping devices such as fluid viscous dampers (FVDs) often have applications in shock vibration control of structural and mechanical systems. Nonlinear FVDs are more suitable compared to the linear FVDs for applications where large force and velocities are exerted, such as in structures subjected to shock excitations. This paper discusses the influence of shock impulse characteristics on vibration control of a single-degree-of-freedom system with linear and nonlinear fluid viscous dampers for three types of shock excitation profile, viz. half-cycle sine, initial-peak saw tooth and rectangular. The following response parameters have been considered: (1) maximum acceleration of the structure, (2) maximum displacement of the structure, and (3) time required for attenuation of response below a specified threshold. An approximation based on the concept of equal energy dissipation to determine the response of the structure with nonlinear fluid viscous dampers subjected to shock excitation has been proposed. The paper also presents non-dimensional design charts for above shock pulses for linear and nonlinear fluid viscous dampers, which can be used for preliminary decision on damper parameters to be used in design.
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Sparling, Bruce F., and Alan G. Davenport. "Nonlinear dynamic behaviour of guy cables in turbulent winds." Canadian Journal of Civil Engineering 28, no. 1 (February 1, 2001): 98–110. http://dx.doi.org/10.1139/l00-089.
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Large amplitude cable vibrations are difficult to predict using linear theory due to the presence of sag in the suspended profile. A numerical study was therefore undertaken to investigate the dynamic behaviour of inclined cables excited by imposed displacements. To model the nonlinear nature of cable response, a time domain finite element approach was adopted using nonlinear catenary cable elements. Two types of horizontal displacement patterns were enforced at the upper end of the guy. In the first phase of the study, harmonic displacement histories with a wide range of forcing frequencies were considered. In the second phase, random enforced displacements were used to simulate the motion of a guyed mast in gusty winds. The influence of aerodynamic drag and damping forces was investigated by performing analyses under still air, steady wind, and turbulent wind conditions. It was found that nonlinear coupling of related harmonic response components was significant at certain critical frequencies, particular when the excitation was harmonic and acted in the plane of the guy. Positive aerodynamic damping was shown to effectively suppress resonant and nonlinear coupling response.Key words: cables, structural dynamics, wind loading, finite element method, nonlinear analysis, guyed towers.
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Gao, Cun Fa, Pin Tong, and Tong Yi Zhang. "Effect of Columbic Force on Piezoelectric Fracture." Key Engineering Materials 261-263 (April 2004): 81–86. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.81.
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This paper studies the effect of the Columbic force on piezoelectric fracture. Bound charges emerge on the upper and lower surfaces of a permeable crack when a piezoelectric solid with the crack is subjected to far-field mechanical/electric loading. Taking into account the Columbic force between the bound charges, we obtain a non-linear equation governing the normal component of electric displacement D2(x1)on the crack faces. The results show that D2(x1)is, in general, not a constant along the crack faces and depends on the mechanical/electric loading conditions, the crack profile and the material properties outside and inside the crack. Furthermore, we examine the Columbic force under low mechanical/electric loads and then discuss the effect of the Columbic force on the fracture behaviour of piezoelectric materials.
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Uddin, Nur. "Optimal Control Design of Active Suspension System Based on Quarter Car Model." JURNAL INFOTEL 11, no. 2 (June 30, 2019): 55. http://dx.doi.org/10.20895/infotel.v11i2.429.
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The optimal control design of the ground-vehicle active suspension system is presented. The active suspension system is to improve the vehicle ride comfort by isolating vibrations induced by the road profile and vehicle velocity. The vehicle suspension system is approached by a quarter car model. Dynamic equations of the system are derived by applying Newton’s second law. The control law of the active suspension system is designed using linear quadratic regulator (LQR) method. Performance evaluation is done by benchmarking the active suspension system to a passive suspension system. Both suspension systems are simulated in computer. The simulation results show that the active suspension system significantly improves the vehicle ride comfort of the passive suspension system by reducing 50.37% RMS of vertical displacement, 45.29% RMS of vertical velocity, and 1.77% RMS of vertical acceleration.