Tài liệu miễn phí Cơ khí - Chế tạo máy
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Self-propelled capsule endoscopy for small-bowel examination: Proof-of-concept and model verification
This paper reports the experimental study of a vibro-impact self-propulsion technique applying for small-bowel endoscopy by using a mesoscale capsule prototype, which is 56.9 mm in length and 19.4 mm in diameter. Based on nonsmooth multibody dynamics, a mathematical model is developed for studying the dynamical characteristics of the prototype.
4/5/2023 4:15:34 AM +00:00
Effects of strain stiffening and electrostriction on tunable elastic waves in compressible dielectric elastomer laminates
This paper presents an electromechanical analysis of the nonlinear static response and the superimposed smallamplitude wave characteristics in an infinite periodic compressible dielectric elastomer (DE) laminate subjected to electrostatic excitations and prestress in the thickness direction.
4/5/2023 4:15:27 AM +00:00
Mechanical behavior of steel and aluminum foams at elevated temperatures. Local buckling based approach toward understanding of the material system behavior
The computational model shows that plastic buckling of cells with progressive plasticity of the contact area is the key local failure mechanism. As expected, due to the plastic buckling of the unit cells, thermal degradations of the tested metallic foams follow similar trends as does the yield stress of their bulk metals.
4/5/2023 4:15:16 AM +00:00
Theoretical modeling and experimental verification of chip flow angle catastrophe in double-edged cutting considering non-linear effects
The end face of 6061-T6 workpiece is turned transversely by straight double-edged turning tools with different tool geometry. Comparing the experimental results with the predicted results, it is found that the two have good consistency.
4/5/2023 4:15:00 AM +00:00
Energy recovery from a pendulum tuned mass damper with two independent harvesting sources
This paper focuses on vibration mitigation and energy harvesting in a coupled oscillator-pendulum system. Generally, the concept of a vibration-based energy harvester is similar to a vibration absorber, it is naturally desired to use the same system for simultaneous vibration reduction and energy recovery.
4/5/2023 4:14:52 AM +00:00
Hardening vs. softening dichotomy of a hinged-simply supported beam with one end axial linear spring: Experimental and numerical studies
The aim of this paper is to validate experimentally a nonlinear model of a kinematically excited hinged-simply supported beam with a spring subjected to one end. An experimental setup configuration enables to test different variants of axial boundary conditions: first a typical simply supported beam (no spring), and next two different spring systems.
4/5/2023 4:14:41 AM +00:00
On selected aspects of space-fractional continuum mechanics model approximation
The main goal of this paper is to study selected aspects of the space-Fractional Continuum Mechanical model (s-FCM) approximation. The considerations include the in-depth analysis of three generalized finite difference schemes, which are based on: (i) The rectangle rule, (ii) the trapezoidal rule, and (iii) Simpson’s (parabolas) rule, respectively. The analysis includes the dynamic (eigenvalues) response of the 1D s-FCM body.
4/5/2023 4:14:32 AM +00:00
Application of neutron imaging to detect and quantify fatigue cracking
The neutron tomography, although lower in spatial resolution compared with the X-ray synchrotron tomography and requiring higher acquisition time, is sensitive to the phase chemistry, and has the potential to study engineering size components. Bragg edge neutron transmission imaging allows for the mapping of two-dimensional elastic strains and was used to identify the fatigue crack from the reduction in the strain in the region where the crack propagated.
4/5/2023 4:14:20 AM +00:00
Design of dielectric elastomer actuators for vibration control at high frequencies
This study evaluates the basic characteristics of smart structures composed of dielectric elastomer actuators (DEAs) to suppress vibrations. A DEA, which is a lightweight, flexible polymer that can induce high deformations, should realize next-generation actuators. Additionally, DEA can achieve vibration control of structures with complex shapes or curved surfaces.
4/5/2023 4:14:12 AM +00:00
Strain energy spectral density and information content of materials deformation
Spectral entropy is a basic measure of information available in the material interior about surface loads, or a measure of disorder introduced into elastic medium by the deformation. An exact analytical entropy function is derived for an isotropic plane solid under Gauss-distributed and point loads.
4/5/2023 4:14:01 AM +00:00
Correlating and evaluating the functionality-related properties with surface texture parameters and specific characteristics of machined components
This study emphasized on the effectiveness and veracity of the 3D surface texture parameters and statistical functions in characterizing and evaluating machined-surface performance along with the traditional 2D parameters. It is especially suitable for machining materials whose functionality-related properties are machining-process-sensitive and surface-texturedependent.
4/5/2023 4:13:48 AM +00:00
Localised prior strain-hardening increases the tearing resistance of ductile steel
This depends on a material’s microstructure and its stress–strain response. By introducing a spatiallyvarying distribution of prior strain-hardening into a material, we can modify the stress field which develops around a crack as it is loaded, producing an increased resistance to ductile tearing.
4/5/2023 4:13:40 AM +00:00
Elastic imperfect tip-loaded cantilever cylinders of varying length
This paper presents a comprehensive computational investigation into the nonlinear elastic buckling response of perfect and imperfect thin cantilever cylinders under global transverse shear. A complete range of practical lengths was investigated, from short cylinders which fail by shear buckling to very long ones which exhibit local meridional compression buckling with significant prior cross-section ovalisation.
4/5/2023 4:13:26 AM +00:00
A confinement-dependent load-induced thermal strain constitutive model for concrete subjected to temperatures up to 500°C
This paper proves that, given a Load-Induced Thermal Strain (LITS) curve able to accurately describe the uniaxial LITS development for a specific type of concrete and temperatures up to 500 °C, a more accurate prediction of the 3D LITS state is obtained through a confinement-dependent 3D implementation than through the classic confinement-independent approach.
4/5/2023 4:13:14 AM +00:00
An origami-inspired structure with graded stiffness
Origami-inspired structures and mechanical metamaterials are often made up of individual tessellating repeat units, the folding and relative geometry of which determine the overall mechanical properties. If these units are identical, then the mechanical behaviour of the structure is uniform throughout, meaning that it is not able to adapt to changeable loading conditions.
4/5/2023 4:13:06 AM +00:00
Non-contact and non-destructive Lamb wave generation using laser-induced plasma shock wave
This paper proposes a non-contact and non-destructive method to generate Lamb waves against a target structure using the impulse excitation force generated by laser-induced plasma (LIP). When a high power pulse laser is irradiated in air and its laser fluence exceeds 1015 W/m2, a plasma is formed.
4/5/2023 4:12:56 AM +00:00
Effect of nodal mass on macroscopic mechanical properties of nanoporous metals
The current work investigates the effect of the nodal mass on the macroscopic mechanical behavior of nanoporous metals using the Finite Element Method. A nodal corrected beam modeling concept is introduced that allows local incorporation of the effective elastoplastic mechanical behavior of the nodal mass in the nodal area of a representative volume element (RVE).
4/5/2023 4:12:48 AM +00:00
A semi-analytical approach towards plane wave analysis of local resonance metamaterials using a multiscale enriched continuum description
This work presents a novel multiscale semi-analytical technique for the acoustic plane wave analysis of (negative) dynamic mass density type local resonance metamaterials with complex micro-structural geometry. A two step solution strategy is adopted, in which the unit cell problem at the micro-scale is solved once numerically, whereas the macro-scale problem is solved using an analytical plane wave expansion.
4/5/2023 4:12:40 AM +00:00
Gaussian and non-Gaussian stochastic response of slender continua with time-varying length deployed in tall structures
This paper presents a study to predict the probabilistic characteristics of lateral dynamic motions of a long heavy cable moving at speed within a tall host structure. The cable is subjected to a base-motion (kinematic) excitation due to a low frequency sway of the structure.
4/5/2023 4:12:29 AM +00:00
Serial-EMD: Fast empirical mode decomposition method for multi-dimensional signals based on serialization
Empirical mode decomposition (EMD) has developed into a prominent tool for adaptive, scale-based signal analysis in various fields like robotics, security and biomedical engineering. Since the dramatic increase in amount of data puts forward higher requirements for the capability of real-time signal analysis.
4/5/2023 4:10:28 AM +00:00
Machine learning classifiers for surface crack detection in fracture experiments
It is found that a small subset of the investigated texture features is highly significant for all experiments. Using this feature subset in conjunction with multi-layer, nonlinear and low complexity feed-forward network architectures classification accuracies in the order of 99% are obtained.
4/5/2023 4:08:43 AM +00:00
Mesh-free micromechanical modeling of inverse opal structures
The developed and implemented DEM-based strategy is applied to analyze stiffness and strength of inverse opals made of pure silica and inverse opals coated with titania layers of various thicknesses. Also, the influence of the porosity of the initial packing on the properties of the material is investigated.
4/5/2023 4:08:33 AM +00:00
Biofidelic finite element modelling of brain trauma: Importance of the scalp in simulating head impact
The model was validated using published experimental data and subsequently used to simulate three well-documented real-world concussive head injury accidents. Results showed that the brain stresses and strains predicted using the current version (V2.0) of the UCDBTM correspond well with values for concussion reported in literature.
4/5/2023 4:08:16 AM +00:00
Monitoring power-law creep using the failure forecast method
The methodology has been demonstrated using experiment data sets that are pertinent to creep in high temperature pressure vessels and piping; it is shown that failure times are accurately predicted shortly after the minimum creep strain rate.
4/5/2023 4:08:09 AM +00:00
Modelling and simulation of a stationary high-rise elevator system to predict the dynamic interactions between its components
A case study is presented when the car is parked at a landing level where the fundamental natural frequencies of the car, suspension and compensating rope system coincide with one of the natural frequencies of the high-rise building. The results show a range of nonlinear dynamic interactions between the components of the elevator system that play a significant role in the operation of the entire installation.
4/5/2023 4:08:00 AM +00:00
Inherent and induced anisotropic finite visco-plasticity with applications to the forming of DC06 sheets
In the current work we present a finite visco-plasticity model accounting for inherent and induced plastic anisotropy as well as Bauschinger effect for the interstitial free (IF) steels and its application to a forming process simulation of DC06 sheets.
4/5/2023 3:38:36 AM +00:00
Asymptotic analysis of cold sandwich rolling
This model relaxes the assumption, crucial to slab methods, that the stresses are uniformly distributed through the thickness of each material layer. Thus, our model is able to predict the through-thickness velocity and stress distributions.
4/5/2023 3:38:28 AM +00:00
Modeling of fracture in small punch tests for small- and large-scale yielding conditions at various temperatures
The brittle fracture mode by cleavage is accounted for by Ritchie–Knott–Rice's deterministic maximum principal stress criterion (Ritchie et al., 1973). The wellknown problem of mesh dependence associated with softening material behavior is remedied by using an integral type nonlocal formulation similar to that presented in Tvergaard and Needleman (1995).
4/5/2023 3:38:15 AM +00:00
Non-linear energy harvesting from coupled impacting beams
The power generated by the coupled system from the non-linear impact is sensitive to the thickness ratio of the beams and the clearance. The variation in thickness ratio alters the spacing of the natural frequencies of the system which causes modes to interact. This study shows that higher power is produced than the linear system, depending on the dissimilarity in the mode shapes of the interacting close modes.
4/5/2023 3:38:08 AM +00:00
Design and analysis of pioneering high supersonic axial turbines
This paper provides for the first time in the open literature the design procedure, and subsequent analysis of the turbine performance of a turbine adequate for supersonic axial pulsating flows, as those encountered in innovative combustors.
4/5/2023 3:37:53 AM +00:00