Materials Engineering

Materials Engineering

  • Sabyasachi Roy added an answer:
    Has anyone ever had the experience of having bumpy surface after making a zirconia /Alumina sample by SPS followed by thermal etch?

    After making composite out of zirconia and alumina by SPS followed by grinding, polishing and thermal etch, my samples get bumps over surface. I'm not sure about the possible reasons. Please see attached example.

    Sabyasachi Roy · ANTS Ceramics Pvt Ltd

    In production unit, we do get this type of bump by conventional sintering process also. This is due to entrapped gas. After Cutting across the bump will clarify the same. It happens when gases can not escape during their binder burn out stage ( can be due to high heating rate, minimum dwell time, high density on top surface compared to bottom part, improper  mixing or non uniform mixing of binder etc)

  • Ajeet Babu Kumar Parasumanna added an answer:
    Is anyone familiar with Carburizing nitrogen/methanol atmosphere system?

    We are making the assembly of the process in the foundry laboratory of the University of Antioquia (Medellin - Colombia), in order to supplement the training of students in the study of heat treatment of materials.

    I would like to consult on the most important aspects to keep in mind for execution and implementation of the system Nitrogen / methanol.

    Ajeet Babu Kumar Parasumanna · Automotive Research Association of India

    Mr.Oscar,Always welcome.

  • Ahmed Shawky added an answer:
    What will be the best solvent (other than acetone) to disperse CNT?

    This is for better dispersion and avoiding the CNT agglomeration

    Ahmed Shawky · Central Metallurgical Research and Development Institute

    My opinion is to disperse not dissolve, dissolving CNTs is quit impossible, please consider sodium dodecyl sulfate (SDS)

  • Milad Salarvand added an answer:
    Which process is the most reliable way for joining of Al to Alumina?

    According to literature, active brazing and diffusion bonding are the most reliable methods for joining of metals to ceramics. but in the case of joining of Al to Alumina there are two problems:

    1. In active brazing method, the brazing temperature is usually higher than 700 degree Celcius. therefore this method is not applicable for Al. 
    2. Sufficient information about diffusion bonding of Al to Alumina is not available.
    Milad Salarvand · Iran University of Science and Technology

    Thank you very much for your suggestions.

  • Junyoung Kwon added an answer:
    How can I etch the natural iron oxide grown on steel wire?

    I want to utilize a steel wire as a gate electrode of TFT. Then, I have to deposit the gate dielectic(Al2O3) on the wire by atomic layer deposition process. However, there is a iron oxide between the iron gate and the alumina which induces leakage current and lack of uniformity of surface. 

    So, I want to etch this oxide. What is the best etching technique for better uniformity of the ALD deposited alumina surface?

    Junyoung Kwon · Yonsei University

    Thank you for your clear answers. Have a nice day.

  • Chenghui Zeng added an answer:
    What is the cause of pure water flux variation in UF or NF polyethersulfone membrane?

    I have tried to fabricate NF membrane using PES and NMP. but, when I prepare a solution, for example (18 %wt), and cast it into several sheets, then test their water flux, I get quite different flux among these membranes and even within the same membrane ( differences are  sometimes double, 3 folds and  more)....many thanks.

    Chenghui Zeng · Kyoto University

    Now I get the same problem. I used the same membrane and same pressure. but the flux varies significantly. I think the problem might be caused by the membrane structure, especially for charged membranes. According to what I know, there are many functional groups at the surface of the membrane. and they can influence the permeate flux. But I dont know the exact reasons. Hope this could be helpful to you. If you get any new information on this issue, please share it with me. Thank you in advance.

  • Jaronie Mohd Jani added an answer:
    Can someone suggest how to determine the shape recoverability percentage of shape memory alloy?
    Shape memory alloys
    Jaronie Mohd Jani · University of Kuala Lumpur

    Please remind, that the strain also changes with number of cycles performed.

  • Zol Bahri Razali added an answer:
    How to get yield pressure sigma from a modified Heckel equation?
    A modified Heckel equation involves a term K1P/sigma. How can we get sigma at a particular pressure from this equation?
    Zol Bahri Razali · Universiti Malaysia Perlis

    I will explain in detail soon

  • Jim Boland added an answer:
    Why are residual stresses anisotropic ?

    I have done XRD test for a cylindrical component which is previously being turned in lathe machine. I got negative value of stress i.e.compressive residual stress in axial direction and positive value i.e. tensile stress in circumferential direction. Why nature of stress is changing with direction ?

    Jim Boland · The Commonwealth Scientific and Industrial Research Organisation

    It is essential  to know the following;

    (1) the material being machined and any prior treatment given to that material - annealed, normalised, case hardened, cold rolled, extruded, evidence of preferred orientation in the material

    (2) the cutting/machining conditions such as speed, depth of cut, use of a cutting fluid

    (3) What were the stress levels in the starting material itself prior to machining - stresses calculated from the x-ray data?

    (4) What levels of stress - compressive and tensile - were calculated in the machined component based on the x-ray data?

    (5) I presume the person means axial as in the direction parallel to the cylindrical sample itself.

    (6) Anisotropy would be readily explained if the material had a preferred crystallographic orientation  and an anisotropic grain structure.

  • W. Porzio added an answer:
    How accurate is the measurement of grain size using XRD?
    Additionally, I want to know the ways to improve the accuracy.
    W. Porzio · National Research Council

    the main problem of crystallite size in materials resides in the range. From 3 to 70 nm the methods based on Hosemann or Warren-Averback approches are quite reliable for organics or inorganics respectively, provided that accurate measurements are performed. The problems arise when the upper limit is exceeded in this case are HRTEM, AFM/STM or SEM are clearly preferable.

  • Peiliang Cong added an answer:
    Which organization or group give the specifications for the calcined bauxite used in road construction? What is the requirement for it?

    Why the chemical composition of calcined bauxite using road are limited. such as aluminum oxide, silica, ferric and titanium dioxide.

    Thanks!

    Peiliang Cong · Chang'an University

    There are an frenquce measurement for calcined bauxite in road application is chemical component. such as Al2O3 is not less than 88%. i don't know why the chemical component is be required. 

  • Jonathan Mcculfor added an answer:
    Why can graphite not be used for an anode in aqueous solution electrolytes?
    Regarding electrochemical characterization aqueous rechargeable lithium batteries.
    Jonathan Mcculfor

    Not sure if this is what you mean; but in acidic solutions, using a graphite anode will sometimes result in it decomposing via exfoliation.

  • Şakir Bor added an answer:
    Does volume fraction of ordered grains in polymer follow the power law as well?

    I was wondering whether the volume fraction of grains in polymer during recrystallization followed the power law as well assuming the volume evolution followed power law, any publication described this? 

    Şakir Bor · Middle East Technical University

    Thank you for the informative answer which made me recall 40 years ago when I first get acquainted with these subjects in your lectures.

    Although long chain molecule crystals is not in my area of interest I raised the question of definittion of "crystalline" because of a long time curiosity but more over because of my disappointment in intentional mis-usage of scientific terminology during the last ten or maybe twenty years. In powder metallurgy for example, it took me couple of days to find out that "dissolution and recrystallization" is being used for Oswald ripening (coarsening); "sinter hardening" means sintering and then quenching; "continuous and discontinuous recrystallization" in place of recrystallization with or without prior recovery despite the fact that they are two distinct transformations. And many more such incorrect terms just to be the first in using that term to get more citation.

    Best regards.

  • Fernando Almeida Costa Oliveira added an answer:
    What is the difference between grain and crystal in solid materials?

    materials engineering, materials science, solid, metallurgy 

    Fernando Almeida Costa Oliveira · Laboratório Nacional de Energia e Geologia

    When atoms or ions are arranged in a pattern that repeats itself in three dimensions, they form a solid which is said to have a crystal structure and is referred to as crystalline material. Upon solidification of metals, several stages do occur: a) formation of nuclei, b) growth of nuclei into crystals and c) joining together of crystals to form grains and associated grain boundaries. Typically grains are randomly oriented. Solidified metal containing many crystals is said to be polycrystalline. The crystals in the solidified metal are called grains and the surfaces between them are named grain boundaries.

    I hope this answers your question.

    Fernando Costa Oliveira

    Lisboa, 3rd June 2015

  • Monsur Ahmed added an answer:
    Can anyone suggest a solution for the electroless deposition of tin (Sn) onto Silicon wafer?

    Need a chemical solution containing Tin (Sn) which will deposit onto silicon by galvanic deposition. 

    Monsur Ahmed · Politecnico di Milano

    Thank you. It helps. But more specifically i need electroless deposition of tin on silicon.

  • Markus Lukacevic added an answer:
    Is it possible to evaluate multi crack propagation using Abaqus?

    Hi everyone.

    I am trying to perform crack propagation analysis using abaqus XFem. Some increments after the crack initialization, I got a inconsistent stress profile results (other regions show stresses value above the fracture limit criterion). In fact, the analysis does not start a new crack when the fracture criterion is reached.

    Please note that I am using linear elastic material behavior.

    Does anyone had this problem in your analysis?

    Thanks

    Markus Lukacevic · Vienna University of Technology

    If you have a single part, just partition it to get multiple cells. Then you can assign an individual crack region to each of them.

  • Letian Wang added an answer:
    Phase field or level set, which is better for modeling crystallization with capillary effect?

    Hi, Dear researchers!

    I am considering modeling the Si crystallization using matlab code. The capillary effect will also be considered.

    I found there is general difference in phase field and level set method. In the following paper, both of them can work well. But just not sure how these two methods works with the capillary effect.

    Thanks!

    Letian Wang · University of California, Berkeley

    Sorry for getting back to you two late. I was doing some side simulations. After your comments, I read some papers. I found level set is more complex in the surface tension modeling (Thanks Henrique). Also, literature indicates that the phase field could be used to simulate the droplet spreading, therefore the three-phase contact line could be solved. (Thanks George!) I will give phase field a vote.

    Thank you again.

    Letian

  • Peiliang Cong added an answer:
    How to bend a steel-polymer-steel composite on a press brake without distortion of the legs?

    How to bend a steel composite with a very thin visco-elastic interlayer (0,05mm) and a total thickness of 3mm? When bending with a small =2,7mm and a large=20 mm bending radius distortion of the legs occurs. This causes damage to the polymer interlayer, and reduces the vibration damping behaviour.
    Is the polymer suitable for bending or welding? Or is it just applicable as sheet cover and deep-drawing applications.

    Peiliang Cong · Chang'an University

    The temperature and strain velocity is two important factor for you bending polymer.

  • Karar Abdali added an answer:
    In which case can the crystallite size be the same as grain size?

    Thank you.

    Karar Abdali · University of Babylon

    In Xtal. wisker.

  • Jeremy S Robinson added an answer:
    Is it correct to affirm that pure Al has better fatigue behavior/fracture toughness than common commercial Al alloys like 2024, 6061 and 7075?

    I would expect that commercial Al alloys like 2024, 6061 and 7075, which have been heat-treated (age-hardened), have lower ductility than pure Al, and thus the fatigue behavior/fracture toughness for pure Al is better than for the alloys. Is this correct?

    Thanks

    Jeremy S Robinson · University of Limerick

    It is harder to initiate a fatigue crack in a stronger material than a weaker material. Crack initiation is driven by slip at the surface or a defect. If the dislocations find it harder to move then it will be more difficult for persistent slip bands to form and eventually form a crack. A good example of this is the strong aluminium alloy 2024 when clad in pure aluminium for enhanced corrosion resistance. This is the stuff aircraft fuselage is made from btw. The initiation fatigue performance of the clad alloy is a lot worse than the unclad alloy.

  • Abdelkrim Azzouz added an answer:
    What happened to absorbent colorless silica gel if in effect when heated it turned to brown?

    Colorless silica gel heating in 120-140 oC for resuscitation. After it was observed that some of the granules change the color and turned to brown. Does it change color on absorption is effective or not?

    Abdelkrim Azzouz · Université du Québec à Montréal

    What was the heating temperature? Was your silica already used or contacted with organic compound before? High temperature beyond 250oC triggers organic compounds decomposition (pyrolysis in the absence of air). Controlled heating at 300-350oC under air (oxygen)  stream may completely regenerate your silica. If not, you may be dealing with an inorganic impurity, than can be easily removed through acid-leaching.

  • Taha Ibrahim added an answer:
    How can we model fatigue in ABAQUS? How can I create amplitude?
    I have read many things about this, but could not find any tutorial on fatigue simulation for example fatigue simulation of round specimen (dog bone) under constant amplitude loading, and need to get stress-life curve.
    Taha Ibrahim · Benha University

    You may check: http://www.egr.msu.edu/software/abaqus/Documentation/docs/v6.7/books/usb/default.htm?startat=pt03ch06s02at05.html

  • Thomas Korimort added an answer:
    Hello. I am doing single screw extrusion simulation in polyflow and I am getting the following error message. Can anyone help me in resolving it.?

    *summary of simulation*
    ************************
    the computation failed.


    ****************************
    *expert tool diagnostics*
    ****************************
    stack error

    *****************************
    *expert tool suggestions*
    ********************************

    a serious internal error has occurred (in DPGETB) please, contact Polyflow s.a. and send us , if possible, the mesh and data files.
    we apologize for the inconvenience.

    Thomas Korimort · Not affiliated

    Stack usually can mean execution stack or it can be used as a data structure by the program itself. Maybe execution stack ran out of memory because of (unexpected) memory requirements?

  • Amirhosein Ghavimi added an answer:
    What are the industrial applications of Aluminum/Brass bimetals?

    Nowadays there is a high interest to use bimetals like Aluminum/Magnesium, Aluminum/Cast iron, and etc. that provide several propeties in one component.

    Amirhosein Ghavimi · Iran University of Science and Technology

    Aluminum brass tubes are highly accepted and one of the extensively used material for various industrial applications. This alloy develops a protective film that has self-healing properties. This film is dependent on oxygen, which is dissolved in the water and does not renew itself in polluted or stagnant water. High resistance to corrosion in clean seawater or in land conditions is difficult.

    Aluminum Brass tubes resists the action of high velocity salt and brackish water. The outstanding characteristic of this alloy is its superior resistance to impingement attack.

    High strength combined with good general corrosion resistance and low susceptibility to stress corrosion cracking of aluminum brass tubes make it a highly preferred material for load bearing masonry fixings.

    In case, the brass tubes are used in hard drawn conditions, or if they have been severely cold worked through bending or swaging in assembly, they should generally be heat treated to ensure freedom from stress corrosion cracking.

  • Emerson Escobar Nunez added an answer:
    What is the suitable pressure supply for polyphenylene sulfide in pin on disc test?

    In pin on disc test , I have polyphenylene sulfide as a pin , what is the suitable pressure supply for polyphenylene sulfide? d=6mm

    Emerson Escobar Nunez · Autonomous University of the West
    • Look into the hertzian solution for a sphere in contact with a flat surface. The normal load necessary to cause yielding can be found as W=[0.78*(phi)3*R2*Sy3]/E*2

    Where R is the radius of the sphere, Sy is the yield strength of the material of interest and E* is the combined Young´s modulus

  • Zol Bahri Razali added an answer:
    Are there other Mössbauer spectra at RT and 5K ?

    Good evening,

    I am glad to see our spectrum collected at 6K (not published) looks quite like yours. However, we simply couldn't measure any splitting for the other positions (we measured them all at 6K later on).

    The limited capacity we observed seemed to fit with the limited capacity observed by other folks in Tours who worked on a Na/Fe-Sb system you may have heard of.

    By curiosity, did your spectra collected at RT look like ours at all?

    Moreover, did you have the chance to measure other spectra at 5 K ?

    Anyways, congrats on your nice work !

    Zol Bahri Razali · Universiti Malaysia Perlis

    You can get the similar or apropriate answer by searching the keyword in the GOOGLE SCHOLAR page. Usually you will get the first paper similar to your keyword.

    From my experience, this way will help you a lot. If you still have a problem, do not hasitate to let me know.

    Kind regards, Dr ZOL BAHRI - Universiti Malaysia Perlis, MALAYSIA

  • Salah Gariani added an answer:
    Is there any way of increasing the tool life of lathe machine without changing machining parameters?

    I want to increase tool life (cutting tool) of lathe machine without changing machining parameters like speed, feed etc. The change should be in terms of material (material should not be very costly) or design of tool.

    Salah Gariani · Northumbria University

    Increasing tool life depending upon the following factors:

    1. Cutting tools

    2. Cutting conditions ( speed, feedrate , DOC)

    3. Cutting fluids

    4. Chatter ( Machine vibration) 

    However the senstivity of these factors are different for each materils. In your condition you have Cutting condition constant , But you need to state the material after that you conduct  an experiments using Taguchi and ANOVA to assess the senstivity of each for improving tool life.

  • Ravi Bollina added an answer:
    Is anyone aware of any references with pictures on Defects in Refractories?

    Hi

    I am looking into defects in refractories that are used in furnaces. I would like to analyze the defects that generally arise during manufacturing of these refractories.  Specifically looking for books in this field. Any suggestions?

    Ravi Bollina · Mahindra Ecole Centrale

    Mostly arise from Thermal cracking. Best is the above books mentioned by Mr. Sahu

  • Hao Kun Yang added an answer:
    Is there an effective method to observe dynamic strain aging effect in TWIP steel?

    Recently I find that the dynamic strain aging effect has an effect on the mechanical properties of TWIP steel. Is there any effective method to observe the DSA phenomenon?

    Hao Kun Yang · Chinese Academy of Sciences

    Thanks so much for your blessing, Professor Phaniraj!

  • A. Abdi added an answer:
    What will happen if I make a multiple-metal galvanic cell?

    From learning the galvanic corrosion theory, I know that when two dissimilar metals are in electric contact and are surrounded by electrolyte, the metal with lower electrode potential will corrode. My question is what will happen if there are more than two dissimilar metals which are in direct electric contact and are surrounded with electrolytes?

    A. Abdi · Ecole Militarie Polytechnique

    It is interesting to make a predictive study of galvanic coupling by plotting the current-potential curve of each material and then superimpose all curves. We can detect the behavior of each material (polarity), by drawing a line parallel to the axis of the current intensity and intersecting the axis of the potential at the value obtained experimentally from the galvanic coupling. It is imperative to consider the report of the different surfaces of materials. For this it is only necessary to multiply the values of current densities obtained independently for each material by the actual surfaces upon superposition.

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