Finite-element modelling of multilayer X-ray optics

2017 ◽  
Vol 24 (3) ◽  
pp. 717-724
Author(s):  
Xianchao Cheng ◽  
Lin Zhang
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Photon Flux ◽  
Attractive Alternative ◽  
Geometrical Parameters ◽  
X Rays ◽  
Element Analysis ◽  
Ray Optics ◽  
X Ray ◽  
Fea Model

Multilayer optical elements for hard X-rays are an attractive alternative to crystals whenever high photon flux and moderate energy resolution are required. Prediction of the temperature, strain and stress distribution in the multilayer optics is essential in designing the cooling scheme and optimizing geometrical parameters for multilayer optics. The finite-element analysis (FEA) model of the multilayer optics is a well established tool for doing so. Multilayers used in X-ray optics typically consist of hundreds of periods of two types of materials. The thickness of one period is a few nanometers. Most multilayers are coated on silicon substrates of typical size 60 mm × 60 mm × 100–300 mm. The high aspect ratio between the size of the optics and the thickness of the multilayer (107) can lead to a huge number of elements for the finite-element model. For instance, meshing by the size of the layers will require more than 1016 elements, which is an impossible task for present-day computers. Conversely, meshing by the size of the substrate will produce a too high element shape ratio (element geometry width/height > 106), which causes low solution accuracy; and the number of elements is still very large (106). In this work, by use of ANSYS layer-functioned elements, a thermal-structural FEA model has been implemented for multilayer X-ray optics. The possible number of layers that can be computed by presently available computers is increased considerably.

A Finite Element Analysis Study of Non-Linear Behavior in a Bolted Connection

1999 ◽  
Author(s):  
Richard B. Englund ◽  
David H. Johnson ◽  
Shannon K. Sweeney
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sliding Friction ◽  
Element Model ◽  
Element Analysis ◽  
Bolted Connection ◽  
Fea Model ◽  
Linear Behavior ◽  
Radial Loading ◽  
The Finite Element Model

Abstract A finite element analysis (FEA) model of the interaction of a nut and bolt was used to investigate the effects of sliding, friction, and yielding in a bolted connection. The finite element model was developed as a two-dimensional, axisymmetric system, which allowed the study of axial and radial loading and displacements. This model did not permit evaluation of hoop or torsional effects such as tightening or the helical thread form. Results presented in this paper include the distribution of load between consecutive threads, the relative sliding along thread faces, and the stress distribution and regions of yielding in the model. Finally, a comparison to previous, linear analysis work and to published experimental data is made to conclude the paper.

Finite Element Analysis of Fixation System Influence on the Thoracolumbar Spine Stability

2016 ◽  
Vol 821 ◽  
pp. 685-692 ◽  
Author(s):  
Klaudia Szkoda ◽  
Celina Pezowicz
Keyword(s):  
Finite Element ◽  
Sagittal Plane ◽  
Thoracolumbar Spine ◽  
Element Model ◽  
Intervertebral Discs ◽  
Vertebral Compression Fractures ◽  
Geometrical Parameters ◽  
Element Analysis ◽  
Transpedicular Fixation ◽  
The Stability

All segments of the spine are characterized by a corresponding curvature in the sagittal plane and different geometrical parameters of vertebrae, which affects the complicated structure of transition between subsequent segments. The aim of the study was to assess changes occurring in the thoracolumbar spine, as a result of application of the transpedicular fixation. The research was conducted on finite element model, which was constructed on the basis of CT images. Five different configurations of the model were analyzed: focusing on vertebral compression fractures and degeneration of intervertebral discs. The analysis showed that the highest displacement occurred for a segment with intervertebral disc degeneration. Transpedicular fixation of injured thoracolumbar spine is given the opportunity to improve the stability and stiffness of the segment under consideration.

Study of Alternative Assembly Patterns Using Finite Element Analysis and Lab Tests

2018 ◽  
Author(s):  
Gong H. Jung ◽  
Wesley Pudwill ◽  
Elysia J. Sheu
Keyword(s):  
Finite Element ◽  
Elastic Interaction ◽  
Element Model ◽  
Potential Method ◽  
Test Results ◽  
Element Analysis ◽  
Fea Model ◽  
Assembly Method ◽  
Bolt Stress ◽  
Lab Test

A total of 24 lab tests were performed to evaluate two different joint assembly patterns (legacy and an alternative pattern), two lubricant types (Nickel based and Moly-Disulphide based), and two types of torque wrenches (Hydraulic and Pneumatic). Bolt stress was measured during assembly using load indicating bolts (SPC4). Assembly time was also measured since alternative assembly patterns have been recognized as a potential method for improving assembly efficiency without negatively impacting bolt pre-load scatter. In order to understand the bolt stress distribution in both of the legacy and alternative assembly patterns, a finite element model was developed to simulate wrench sequences specified by ASME PCC-1. The FEA model included the effect of elastic interaction of the bolts and flange. The FEA results indicate similar behavior when compared to the lab test results, and the FEA study was extended to two other alternative assembly patterns. This paper summarizes the results of the FEA and lab tests on a 24” NPS Class 300 flange and may provide validation and supporting information for users who are considering the use of a more efficient assembly method such as the alternative assembly patterns presented in ASME PCC-1.

scholarly journals Nondestructive Evaluation Of A Polymer Composite Hip Implant Using Lock-In Thermography

2021 ◽  
Author(s):  
Ehsan Rahim
Keyword(s):  
Finite Element ◽  
Experimental Testing ◽  
Element Model ◽  
Element Analysis ◽  
Hip Implant ◽  
Polyamide 12 ◽  
Strain Pattern ◽  
Fea Model ◽  
Lock In ◽  
Good Agreement

Lock-in thermography, combined with finite element analysis and experimental testing, was used to investigate the stress/strain pattern in a novel composite hip implant made of carbon fibre and polyamide 12 (CF/PA12). In this study, the geometry of the hip implant was first modelled and analysed in ANSYS workbench 11. Different virtual loads of 800N, 1400N and 2200N were applied on the finite element model of the hip stem at an adduction angle of 15º, thereby replicating the present experimental setup. The values of strains obtained were confirmed by replicating the experiment by using strain gauges. A Pearson's correlation (R²=0.98) was obtained, which indicated good agreement between the FEA model and experimental hip stem. The hip implant was again subjected to similar loading conditions, and stresses were recorded by using a thermal camera at corresponding vertices. The comparison of results showed good agreement between the values of stress calculated from the strain gauge experiment and stress obtained from thermography. This study showed that it was possible to find stresses in a hip implant reliably by thermography.

Experimental Measurement and Finite Element Analysis of Screw Spike Fatigue Loads

2007 ◽  
Author(s):  
Matthew G. Dick ◽  
David S. McConnell ◽  
Hans C. Iwand
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Failure ◽  
High Strength Steels ◽  
High Strength ◽  
Element Model ◽  
Element Analysis ◽  
Bending Fatigue ◽  
Fea Model ◽  
Bending Loads

Screw spikes, also known as coach screws, are an advanced alternative to common cut spikes for track fastening. Despite their ability to secure tie plates with a clamp load and utilization of high strength steels, they are still susceptible to bending fatigue failure from lateral wheel loads. A novel method of measuring these bending loads on screw spikes was developed and implemented to characterize the load environment of the screw spikes. Results indicated that measured peak bending loads under lateral wheel loads reached as high as 10,000 lbs for individual spikes, while others carried no load whatsoever. A finite element model was developed to determine the tensile stress fields created by the measured bending loads. A good correlation was found between the FEA model predicted point of highest stress and the location of fracture. Through the testing and analysis it was determined that lateral wheel loads are not distributed evenly among the four screw spikes of a single tie plate. Instead, it was found that one spike carried nearly no load while the spike opposite of it carried more load. Using the finite element analysis it was determined that the spike exposed to the higher loading was subjected to tensile stresses above its endurance limit, which would eventually lead to a bending fatigue failure.

Finite Element Study of a Micro-Opto-XRay Imaging Lens for Biomedical Applications

2007 ◽  
Author(s):  
H. Ostadi ◽  
Marino Arroyo ◽  
P. D. Prewett ◽  
S. E. Huq
Keyword(s):  
Finite Element ◽  
Bystander Effect ◽  
Focal Length ◽  
Broad Band ◽  
Spherical Geometry ◽  
Length Variation ◽  
X Rays ◽  
Element Analysis ◽  
X Ray ◽  
Micro Lens

Micro-Electro-Opto-Mechanical-Systems or MOEMS have potential applications inter alia in biomedical research. For instance, studies of the Bystander Effect require controlled irradiation of biological cells with focused X-rays to reveal the mechanisms occurring. X-ray focusing may be achieved using an adaptive optic micro-lens in which focusing is entirely reflective and therefore compatible with broad band illumination, an improvement over diffractive systems such as zone plates. Such a micro-lens can be microfabricated in the form of a bent-cantilever beam made from two dissimilar materials (polyimide and gold) in a thermal bimorph configuration, actuated with a micro heater. The parallel horizontal slots on the beam provide the transmission and focusing functions, while the heater provides control of the focal length through variation of the beam’s curvature. This novel system has been named 1D-MOXI (Micro-Opto-X-ray Imaging) and a basic system has already been made and tested thermo-mechanically. The present paper focuses on details of the geometry of the deformed slotted micro-beam lens element under thermally derived strain, using finite element analysis, and suggests an optimized MOEMS design, giving prescribed curvature of the lens through changing the number and the dimensions of the slots. The study reveals the localized stress and the small deviations of the micro-lens behavior from that of perfect spherical geometry. The focal length variation with temperature is compared with the experimental values and those predicted by an analytical model.

scholarly journals Nondestructive Evaluation Of A Polymer Composite Hip Implant Using Lock-In Thermography

2021 ◽  
Author(s):  
Ehsan Rahim
Keyword(s):  
Finite Element ◽  
Experimental Testing ◽  
Element Model ◽  
Element Analysis ◽  
Hip Implant ◽  
Polyamide 12 ◽  
Strain Pattern ◽  
Fea Model ◽  
Lock In ◽  
Good Agreement

Lock-in thermography, combined with finite element analysis and experimental testing, was used to investigate the stress/strain pattern in a novel composite hip implant made of carbon fibre and polyamide 12 (CF/PA12). In this study, the geometry of the hip implant was first modelled and analysed in ANSYS workbench 11. Different virtual loads of 800N, 1400N and 2200N were applied on the finite element model of the hip stem at an adduction angle of 15º, thereby replicating the present experimental setup. The values of strains obtained were confirmed by replicating the experiment by using strain gauges. A Pearson's correlation (R²=0.98) was obtained, which indicated good agreement between the FEA model and experimental hip stem. The hip implant was again subjected to similar loading conditions, and stresses were recorded by using a thermal camera at corresponding vertices. The comparison of results showed good agreement between the values of stress calculated from the strain gauge experiment and stress obtained from thermography. This study showed that it was possible to find stresses in a hip implant reliably by thermography.

A minimisation algorithm with application to optimal design of reinforcements in textiles and garments

2007 ◽  
Vol 19 (3/4) ◽  
pp. 159-166
Author(s):  
Željko Šomodi ◽  
Anica Hursa ◽  
Dubravko Rogale
Keyword(s):  
Finite Element ◽  
Optimal Design ◽  
Objective Function ◽  
Influence Factors ◽  
Element Model ◽  
Geometrical Parameters ◽  
Elastic Model ◽  
Element Analysis ◽  
Elliptic Paraboloid ◽  
Content Type

PurposeThis paper aims to develop an efficient two‐variable minimisation algorithm and to apply it in engineering optimisation of buttonhole reinforcements.Design/methodology/approachAn iterative extreme search is based on quadratic approximation of objective function, locating approximate solution at the minimum of corresponding elliptic paraboloid. Stress analysis is performed using plane stress finite element model. Optimal selection of geometrical parameters of buttonhole‐type reinforcement is done in terms of balance between maximum stress and material consumption.FindingsAdopted minimisation algorithm is assessed in a selected test example and proven to perform well in comparison with methods available in literature. In the selected case two local minima have been found within the predefined optimisation domain, with slight difference in objective function values.Research limitations/implicationsResearch is limited to homogeneous isotropic elastic model and a single representative load case. Objective function is restricted to two influence factors and predefined optimisation domain.Practical implicationsThe method can be useful for engineers/practitioners in the branch of clothing technology as a tool for computational estimate of optimal design of structural reinforcements.Originality/valueThe main quality of the paper is in software fusion of finite element analysis and advanced optimisation algorithm. The proposed theoretical‐numerical model is discussed in terms of applicability in parameter setting on buttonholer in garment production.

Prolog for Finite-Element Model Definition

1992 ◽  
Author(s):  
P. A. Strooper ◽  
M. Stylianou ◽  
B. Tabarrok
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Logic Programming ◽  
Programming Language ◽  
Element Model ◽  
Element Analysis ◽  
Novice User ◽  
Fea Model ◽  
Expert User

Abstract Finite-Element Analysis (FEA) program vendors go to great lengths to provide their customers with powerful input languages for model definition. The result is a multitude of incompatible input languages. An expert user of one FEA program is merely a novice user of another, primarily because of the different ways vendors implement their input languages. We propose and evaluate the logic programming language Prolog as a language for FEA model definition.

Thermal stress prediction in mirror and multilayer coatings

2015 ◽  
Vol 22 (2) ◽  
pp. 317-327 ◽  
Author(s):  
Xianchao Cheng ◽  
Lin Zhang ◽  
Christian Morawe ◽  
Manuel Sanchez del Rio
Keyword(s):  
Finite Element ◽  
Liquid Nitrogen ◽  
Thermal Stresses ◽  
Single Layer ◽  
Element Model ◽  
Critical Issue ◽  
X Rays ◽  
Element Analysis ◽  
Thermal Expansion Coefficients ◽  
Liquid Nitrogen Cooling

Multilayer optics for X-rays typically consist of hundreds of periods of two types of alternating sub-layers which are coated on a silicon substrate. The thickness of the coating is well below 1 µm (tens or hundreds of nanometers). The high aspect ratio (∼107) between the size of the optics and the thickness of the multilayer can lead to a huge number of elements (∼1016) for the numerical simulation (by finite-element analysis usingANSYScode). In this work, the finite-element model for thermal-structural analysis of multilayer optics has been implemented using theANSYSlayer-functioned elements. The number of meshed elements is considerably reduced and the number of sub-layers feasible for the present computers is increased significantly. Based on this technique, single-layer coated mirrors and multilayer monochromators cooled by water or liquid nitrogen are studied with typical parameters of heat-load, cooling and geometry. The effects of cooling-down of the optics and heating of the X-ray beam are described. It is shown that the influences from the coating on temperature and deformation are negligible. However, large stresses are induced in the layers due to the different thermal expansion coefficients between the layer and the substrate materials, which is the critical issue for the survival of the optics. This is particularly true for the liquid-nitrogen cooling condition. The material properties of thin multilayer films are applied in the simulation to predict the layer thermal stresses with more precision.

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