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Thermal Analysis of Laser Chemical Machining: Part I: Static Irradiation

Materials Sciences and Applications 2017年第10期8卷 685-707页

作者： Hamza Messaoudi sandro eckert Frank Vollertsen BIAS—Bremer Institut für angewandte Strahltechnik Bremen Germany Faculty of Production Engineering-Mechanical Engineering & Process Engineering University of Bremen Bremen Germany

The laser chemical machining is a non-conventional substractive processing method. It is based on the laser-activation of a material dissolution of metals in electrolyte ambient via local-induced temperature gradients and allows a gentle and smooth processing of especially temperature-sensitive metals. However, the material removal is characterized by a narrow process window and is restricted by occurring disturbances, which are supposed to be related to the localized electrolyte boiling. In order to control the removal quality and avoid disturbances, the correlation between the laser-induced temperatures and the resulting removal geometry has to be better understood. In this work an analytical modeling of the laser-induced temperatures at the surface of titanium based on a Green-function approach is presented. The main influencing factors (laser, electrolyte, material) as well as possible heat transfer into the electrolyte are included and discussed. To verify the calculated temperatures, single spot experiments are performed and characterized for titanium in phosphoric acid solution within laser irradiation of 1 s. The correlation between the temperature distribution and the resulting removal geometry is investigated based on a spatial superposition. Thereby, the bottom limit temperature is found to range between 63°C and 70°C whereas the upper limit is related to the nucleate boiling regime. Based on the performed correlation an indicator is identified to predict the ruling removal regime and thereby to reduce the experimental expenditure.

关键词： Laser Micro Machining Laser Chemical Removal Modeling Temperature Process Stability Titanium

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Recent advancements in thermal conductivity of magnesium alloys

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Journal of Magnesium and Alloys 2024年第5期12卷 1687-1708页

作者： Hao Lv Jun Tan Qian Yuan Fanglei Wang Yunxuan Zhou Quan Dong Aitao Tang Jürgen eckert Bin Jiang Fusheng Pan National Engineering Research Center for Magnesium Alloys College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Key Laboratory of Advanced Casting Technologies Chongqing UniversityChongqing 400044China Department of Materials Science Chair of Materials PhysicsMontanuniversität LeobenJahnstraße 12Leoben A-8700Austria Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraße 12Leoben A-8700Austria

As highly integrated circuits continue to advance,accompanied by a growing demand for energy efficiency and weight reduction,materials are confronted with mounting challenges pertaining to thermal conductivity and lightweight *** virtue of numerous intrinsic mechanisms,as a result,the thermal conductivity and mechanical properties of the Mg alloys are often inversely related,which becomes a bottleneck limiting the application of Mg *** on several effective modification methods to improve the thermal conductivity of Mg alloys,this paper describes the law of how they affect the mechanical properties,and clearly indicates that peak aging treatment is one of the best ways to simultaneously enhance an alloy's thermal conductivity and mechanical *** the most frequently used Mg alloy,cast alloys exhibit substantial potential for achieving high thermal ***,recent reports indicate that hot deformation can significantly improve the mechanical properties while maintaining,and potentially slightly enhancing,the alloy's thermal *** presents a meaningful way to develop Mg alloys for applications in the field of small-volume heat dissipation components that require high *** comprehensive review begins by outlining standard testing and prediction methods,followed by the theoretical models used to predict thermal conductivity,and then explores the primary influencing factors affecting thermal *** review summarizes the current development status of Mg alloys,focusing on the quest for alloys that offer both high thermal conductivity and high *** concludes by providing insights into forthcoming prospects and challenges within this field.

关键词： Mg alloy Thermal conductivity Mechanical properties Solute atom Second phase

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Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1185-1200页

作者： Weicheng Zhang Andreas eckert Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and TechnologyRollaMOUSA

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life *** MA can significantly compromise wellbore integrity by establishing enhanced fluid flow *** study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole *** emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening *** resulting state of stress during the life cycle of a typical injection well(***,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole *** results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding *** summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is *** results are different compared to laboratory studies without considering/simulating downhole *** kno

关键词： Micro-annulus Debonding Staged finite element analysis Cement hardening Poro-elastic bulk shrinkage Pore pressure Temperature fluctuation

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Mechanical Properties,Damage and Fracture Mechanisms of Bulk Metallic Glass Materials

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Journal of Materials Science & Technology 2007年第6期23卷 I0003-I0006,747-767页

作者： Zhefeng ZHANG Fufa WU Guo HE eckert Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering Shanghai Jiaotong University Shanghai 200030 China IFW Dresden Institute for Complex Materials P.O. Box 270116 D-01171 Dresden Germany TU Dresden Institute for Materials Science D-01062 Dresden Germany

The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses （BMGs） and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension, and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.

关键词： Bulk metallic glasses (BMGs) criterion Plastic deformation Mechanical properties Shear fracture Failure Melting phenomenon

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Localization of rare earth ions in an inhomogeneous magnetic field toward their magnetic separation

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Journal of Rare Earths 2022年第10期40卷 1598-1605页

作者： Barbara Fritzsche Zhe Lei Xuegeng Yang Kerstin eckert TU Dresden Institute of Process Engineering and Environmental Technology01062DresdenGermany Helmholtz-Zentrum Dresden-Rossendorf(HZDR) Institute of Fluid DynamicsBautzner Landstrasse 40001328DresdenGermany

Efficient extraction and recycling methods are an important issue for rare earth elements(REE). The significant differences in their magnetic moments make magnetic separation a promising step. Although the magnetic field gradient manipulation of ions seemed to be impossible, the robust enrichment of some paramagnetic RE ions was found in the vicinity of the magnet. The studies in recent years resolved the physical paradox of why, despite the Brownian motion of the ions, there is a reproducible enrichment of RE ions in magnetic field gradients. The existence of trigger process and energy barrier was ***, these studies usually used only high paramagnetic ions, e.g., Dy(Ⅲ) or Ho(Ⅲ). This work verifies the theory of the possible magnetic separation for 8 different rare earth ions, respectively. For this purpose, concentration distribution in rare earth chloride solutions were measured using a MachZehnder interferometer. The magnetic field was assured by a Halbach configuration to enhance the effect. The results show the classification of RE solutions into 2 classes: Class I contains the REs with low magnetic moment, whereas Class II includes the REs of high magnetic moment. Only the latter group shows the enrichment of ions in the vicinity of the magnet which encourages the implementation of magnetic separation into existing hydrometallurgical technology to enhance the selectivity of REE.

关键词： Magnetic separation Paramagnetic rare earth ions Enrichment Halbach array Interferometry Aqueous solution

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Modeling and Measurements of Heat Transfer Phenomena in Two-Phase PbSn Alloy Solidification in an External Magnetic Field

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Journal of Thermal Science 2003年第4期12卷 357-362页

作者： P.A.Nikrityuk K.eckert R.Grundmann B. Willers S. eckert Institute for Aerospace Engineering Dresden University of Technology D-01062 Dresden GermanyInstitute for Aerospace Engineering Dresden University of Technology D-01062 Dresden GermanyInstitute for Aerospace Engineering Dresden University of Technology D-01062 Dresden GermanyResearch Center Rossendorf P.O. Box 510119 D-01314 Dresden GermanyResearch Center Rossendorf P.O. Box 510119 D-01314 Dresden Germany

The main aim of this work is to study numerically the influence of an external magnetic field on the solidification processes of two-component materials. Based on the continuum model of two-phase flow a mathematical model for the directional solidification of a binary alloy in a magnetic field is presented. The model includes mass, momentum, energy and species mass conservation equations written in compressible form and additional relationships describing the temperature-solute coupling. The geometry under study is a cylindrical mold with adiabatic walls and cooled bottom. The macroscale transport in the solidification of alloys is governed by the progress of the two-phase mushy zone, which is treated by means of a porous medium approach. The volume fraction of liquid and solid phases, respectively, is calculated from a 2D approximation of the phase diagram. The results of calculation are compared with experimental data.

关键词： solidification measurements mushy zone Lorentz force rotating magnetic field.

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Orientation-dependent Hydrodynamic Instabilities from Chemo-Marangoni Cells to Large Scale Interfacial Deformations

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Chinese Journal of Chemical Engineering 2007年第5期15卷 748-753页

作者：石英 Kerstin eckert State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China Institute for Aerospace Engineering Technische Universitat Dresden D-01062 Dresden Germany

The interplay between chemistry and interfacial-tension-driven hydrodynamic instabilities has been studied experimentally. The system on hand consists of two immiscible liquids separated along an initially plane interface at which an interfacial reaction takes place to produce in situ a surfactant. It is identified that the dynamics of the system depends on the orientation of the Hele-Shaw cell with respect to the vector of gravity. If the nele-Shaw cell is placed vertically, Marangoni cells with vigorous convection develop in both phases along a nearly planar interface. However, if the Hele-Shaw cell is tilted off the gravity, the instabilities in the system are characterized by the large scale interracial deformation with a spatio-temporal periodicity together with the chemo-Marangoni convection. The focus is on the exploration of the transition from the cellular mode to the large scale interfacial deformation.

关键词： interfacial reaction in situ produced surfactant Marangoni convection interfacial deformation

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Indigenous knowledge as data for modern fishery management:a case study of Dungeness crab in Pacific Canada

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Ecosystem Health and Sustainability 2017年第8期3卷 32-42页

作者： Natalie C Ban Lauren eckert Madeleine McGreer Alejandro Frid School of Environmental Studies University of VictoriaVictoriaBCCanada Central Coast Indigenous Resource Aliance Campbell RiverBCCanada

Introduction:F isheries management is often data-limited,and conducted at spatial scales that are too large to address the needs of Indigenous peoples,whose cultures depend upon the local availability of marine ***:We combined Indigenous ecological knowledge with simulation modelling to inform modern fishery ***-structured interviews with Indigenous fishers in coastal British Columbia,Canada,uncovered severe declines in the abundance and catches of Dungeness crab(Cancer magister)since the *** modelled the current probability of"successful"crab harvesting trips-as defined by expectations from past catches by Indigenous fishers-using fishery-independent data from nine *** probabilities were very low(<20%)for all sites except ***:Our study highlights that local depletions,which Indigenous fishers attribute to commercial and recreational fisheries,have been widespread and undetected by federal managers who manage Dungeness crab at regional scales without fishery-independent ***,local depletions impacted the ability of Indigenous fishers to access traditional ***:Integrating Indigenous knowledge with scientific research is crucial to inform locally-relevant fisheries management and conservation.

关键词： Indigenous knowledge marine conservation .Dungeness crab spatial management co-management stewardship

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New para-magnetic(CoFeNi)(50)(CrMo)(50-x)(CB)x(x=20,25,30)non-equiatomic high entropy metallic glasses with wide supercooled liquid region and excellent mechanical properties

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Journal of Materials Science & Technology 2020年第8期36卷 135-143页

作者： Jeong Tae Kim Sung Hwan Hong Jin Man Park Jürgen eckert Ki Buem Kim Erich Schmid Institute of Materials Science Austrian Academy of Sciences(ÖAW)Jahnstrae 128700LeobenAustria Hybrid Materials Center(HMC) Department of Nanotechnology and Advanced Materials EngineeringSejong University209Neungdong-roGwangjin-guSeoul143-747Republic of Korea Global Technology Center(GTC) Samsung Electronics Co.Ltd129 Samsung-roYeongtong-guSuwonsiGyeonggi-do443-742Republic of Korea Department of Materials Science Chair of Materials PhysicsMontanuniversität LeobenJahnstraße 128700LeobenAustria

In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five elements,each element having an atomic concentration between 5 at.%and 35 at.%).The developed metallic glass alloys are composed of Co-Fe-Ni main elements,transition metals(Cr,Mo)and metalloid elements(C,B).Moreover,the present work reports the thermal,mechanical and magnetic properties of(CoFeNi)(50)(CrMo)(50-x)(CB)x alloys with x=20,25,*** developed as-spun HEMGs exhibit typical paramagnetic properties even for a high amount of ferromagnetic elements(Co,Fe,and Ni)and have high elastic modulus(103–160 GPa)and hardness(14–27 GPa),thus possessing mechanical properties similar to well-known Co-based metallic glasses(Co-Cr-Mo-C-B system).In addition,some of the bulk samples prepared with a diameter of 2 mm form bulk metallic glasses with a high compressive strength around 3.5 *** mechanisms determining the stability of the supercooled liquid,as well as the paramagnetic and mechanical properties for the developed non-equiatomic HEMGs,are discussed.

关键词： Metallic glasses Paramagnetism High entropy alloys Phase stability

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Numerical estimates of the maximum sustainable pore pressure in anticline formations using the tensor based concept of pore pressure-stress coupling

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第1期7卷 60-72页

作者： Andreas eckert Weicheng Zhang Xiaolong Liu Matthew Paradeis Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and Technology

The advanced tensor based concept of pore pressure-stress coupling is used to provide pre-injection analytical estimates of the maximum sustainable pore pressure change, ΔPc, for fluid injection scenarios into generic anticline geometries. The heterogeneous stress distribution for different prevailing stress regimes in combination with the Young's modulus(E) contrast between the injection layer and the cap rock and the interbedding friction coefficient, m, may result in large spatial and directional differences of ΔP c. A single value characterizing the cap rock as for horizontal layered injection scenarios is not obtained. It is observed that a higher Young's modulus in the cap rock and/or a weak mechanical coupling between layers amplifies the maximum and minimum ΔPc values in the valley and limb,respectively. These differences in ΔPc imposed by E and m are further ampli fied by different stress regimes. The more compressional the stress regime is, the larger the differences between the maximum and minimum ΔPc values become. The results of this study show that, in general compressional stress regimes yield the largest magnitudes of ΔPc and extensional stress regimes provide the lowest values of ΔPc for anticline formations. Yet this conclusion has to be considered with care when folded anticline layers are characterized by flexural slip and the friction coefficient between layers is low, i.e.μ=0.1. For such cases of weak mechanical coupling, ΔPc magnitudes may range from 0 MPa to 27 MPa, indicating imminent risk of fault reactivation in the cap rock.

关键词： Pore pressure-stress coupling Anticlines Stress regimes Friction coefficient

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