Three-Dimensional Elastoplastic Contact Analysis of Rough Surface Considering a Micro-Scale Effect

2021 ◽  
Vol 144 (1) ◽  
Author(s):  
Shengyu You ◽  
Jinyuan Tang ◽  
Yuqin Wen
Keyword(s):  
Constitutive Model ◽  
Rough Surface ◽  
Scale Effect ◽  
Three Dimensional ◽  
Nano Indentation ◽  
Micro Scale ◽  
Finite Element Software ◽  
Elastoplastic Contact ◽  
Macro Scale ◽  
Indentation Experiment

Abstract The micro-surface asperity scale of grinding metal parts is within several microns. When two grinding surfaces are in contact, the unevenness of the plastic deformation of the asperities at the micro-scale leads to greater plastic hardening strength of the material. The results of the nano-indentation experiment conducted in this paper confirmed this phenomenon. Based on conventional mechanism-based strain gradient (CMSG) plasticity theory, the micro-scale plastic constitutive equation of materials is given and then is verified by the nano-indentation experiment. Finite element software abaqus and the user-defined element (UEL) subroutine are used to build three-dimensional rough surface elastoplastic contact models. By calculating the grinding rough surface contact in the macro-scale constitutive model based on J2 theory and in the CMSG plasticity constitutive model, the influence law of plastic micro-scale effect on contact performance is obtained.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

Multi-Scale Stereolithography Using Shaped Beams

2017 ◽  
Author(s):  
Huachao Mao ◽  
Yuen-Shan Leung ◽  
Yuanrui Li ◽  
Pan Hu ◽  
Wei Wu ◽  
...  
Keyword(s):  
Laser Beam ◽  
Tool Path ◽  
Three Dimensional ◽  
Laser Exposure ◽  
Micro Scale ◽  
Multi Scale ◽  
Good Surface ◽  
Single Scale ◽  
Macro Scale ◽  
Micro Patterns

Current Stereolithography (SL) can fabricate three-dimensional (3D) objects in a single scale level, e.g. printing macro-scale or micro-scale objects. However, it is difficult for the SL printers to fabricate a 3D macro-scale object with micro-scale features. In the paper a novel SL-based multi-scale fabrication method is presented to address such a problem. The developed SL process can fabricate multi-scale features by dynamically changing the shape and size of a laser beam. Different shaped beams are realized by switching apertures with different micro-patterns. The laser beam without using any micro-patterns is used to fabricate the macro-scale features, while the shaped laser beams with smaller sizes are used to fabricate micro-patterned features. Accordingly, the tool path planning method for the multi-scale fabrication process are developed so that macro-scale and micro-scale features can be built by using different layer thicknesses, laser exposure time, and scanning paths. Compared with the conventional SL process based on a fixed laser beam size, our process can fabricate multi-scale features in a 3D object. It also has fast fabrication speed and good surface quality.

scholarly journals Micro- and Macro-Scale Measurement of Flow Velocity in Porous Media: A Shadow Imaging Approach for 2D and 3D

Optics ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 71-87 ◽  
Author(s):  
Reza Sabbagh ◽  
Mohammad Amin Kazemi ◽  
Hirad Soltani ◽  
David S. Nobes
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Pattern ◽  
Flow Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Detailed Knowledge ◽  
Micro Scale ◽  
Macro Scale

Flow measurement in porous media is a challenging subject, especially when it comes to performing a three-dimensional (3D) velocimetry at the micro scale. Volumetric flow measurement techniques such as defocusing and tomographic imaging generally involve rigorous procedures, complex experimental setups, and multi-part data processing procedures. However, detailed knowledge of the flow pattern at the pore and subpore scales is important in interpreting the phenomena that occur inside the porous media and understanding the macro-scale behaviors. In this work, the flow of an oil inside a porous medium is measured at the pore and subpore scales using refractive index matching (RIM) and shadowgraph imaging techniques. At the macro scale, flow is measured using the particle image velocimetry (PIV) method in two dimensions (2D) to confirm the volumetric nature of the flow and obtain the overall flow pattern in the vicinity of the flow entrance and at the far field. At the micro scale, the three-dimensional (3D) flow within an arbitrary volume of the porous medium was quantified using 2D particle-tracking velocimetry (PTV) utilizing the law of conservation of mass. Using the shadowgraphy method and a single camera makes the flow measurement much less complex than the approaches using laser light sheets or multiple cameras with multiple viewing angles.

scholarly journals Three-dimensional laser printing of macro-scale glass objects at a micro-scale resolution

2020 ◽  
Author(s):  
Peng Wang ◽  
Wei Chu ◽  
Xiaolong Li ◽  
Zijie Lin ◽  
Jian Xu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Micro Scale ◽  
Laser Printing ◽  
Macro Scale

scholarly journals Homogenization of fully nonlinear rod lattice structures: on the size of the RVE and micro structural instabilities

2021 ◽  
Author(s):  
Ludwig Herrnböck ◽  
Paul Steinmann
Keyword(s):  
Large Deformations ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Homogenization Method ◽  
Volume Element ◽  
Lattice Structures ◽  
Micro Scale ◽  
Macro Scale ◽  
Unit Cells ◽  
Structural Instabilities

AbstractThis work investigates the possibility of applying two-scale computational homogenization to rod lattice structures emerging, for instance, from additive manufacturing. The influence of the number of unit cells within the representative volume element (RVE), thus, the RVE’s size on the homogenized mechanical response is studied for occurring microscopic structural instabilities. Therein, the macro-scale, described in terms of three-dimensional continuum mechanics, is coupled to the micro-scale described by geometrically exact rods, enabling arbitrary large deformations and rotations. A special feature of the presented framework is that the rods building the lattice structures are not restricted to deform purely elastically but may deform inelastically. The mechanical response of lattice structures is investigated by applying the developed homogenization method to an exemplary lattice. Under special loads the structure reaches an instable state and may buckle. The appearance of instabilities depends on the geometric properties of the lattice’s underlying rods and the RVE’s size.

An Efficient, Non-Regularized Solution Algorithm for a Finite Strain Shape Memory Alloy Constitutive Model

2010 ◽  
Author(s):  
Jamal Arghavani ◽  
Ferdinando Auricchio ◽  
Reza Naghdabadi ◽  
Alessandro Reali ◽  
Saeed Sohrabpour
Keyword(s):  
Constitutive Model ◽  
Finite Strain ◽  
Three Dimensional ◽  
Solution Algorithm ◽  
Nonlinear Finite Element ◽  
Integration Algorithm ◽  
Finite Element Software ◽  
Cpu Time ◽  
Algorithm Implementation ◽  
Regularized Solution

In this paper we investigate a three-dimensional finite-strain phenomenological constitutive model and propose an efficient solution algorithm by properly defining the variables and by avoiding extensively-used regularization schemes which increase the solution time. We define a nucleation-completion criterion and modify the regularized solution algorithm. Implementation of the proposed integration algorithm within a user-defined subroutine UMAT in the commercial nonlinear finite element software ABAQUS has made possible the solution of boundary value problems. The obtained results show the efficiency of the proposed solution algorithm and confirm the improved efficiency (in terms of solution CPU time) when a nucleation-completion criterion is used instead of regularization schemes.

Indentation in F.C.C. Single Crystals

2012 ◽  
Vol 188 ◽  
pp. 219-225 ◽  
Author(s):  
Abolfazl Zahedi ◽  
Murat Demiral ◽  
Anish Roy ◽  
Vladimir I. Babitsky ◽  
Vadim V. Silberschmidt
Keyword(s):  
Finite Element ◽  
Single Crystal ◽  
Three Dimensional ◽  
Element Model ◽  
Workpiece Material ◽  
Contact Conditions ◽  
Nano Indentation ◽  
Crystal Plasticity Finite Element ◽  
Finite Element Software ◽  
Dimensional Crystal

A three-dimensional crystal-plasticity finite element model of nano-indentation is developed in this paper to analyze deformation of a face-centred cubic (f.c.c.) high-purity single crystal of copper. This model was implemented as a user-defined subroutine in the commercial finite element software ABAQUS/Standard and used to study cases with different crystallographic orientations of the single crystal. The effects of various factors – crystallographic orientation of the indented material, an indenter angle and contact conditions between the indenter and workpiece material – on the load-displacement characteristics are studied. The obtained results show an anisotropic nature of surface topography around the obtained indents.

The role of rough surface in the size-dependent behavior upon nano-indentation

2021 ◽  
pp. 103836
Author(s):  
Ding Tang ◽  
Leilei Zhao ◽  
Huamiao Wang ◽  
Dayong Li ◽  
Yinghong Peng ◽  
...  
Keyword(s):  
Rough Surface ◽  
Nano Indentation ◽  
Size Dependent ◽  
Dependent Behavior
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