Materials Engineering

Materials Engineering

  • Mohamed Abdelgawad Gebril added an answer:
    3
    How to confirm the deformation mechanism of spot welds with different Mn contents?

    Resistance spot welds with different Mn contents can be obtained by the resistance spot welding of TWIP steel with other steel (such as TRIP,DP, QP, etc.). How can we confirm the deformation mechanism of spot welds with different Mn contents? It is dislocation slip, twinning, martensitic transformation or the combination of some of them. 

    Mohamed Abdelgawad Gebril

    I support the idea of Professor ٍSirgei, you  must study the microscopic structure using (SEM or TEM), as well as study the complete feature of RSW for work piece welds, Nugget structure and diameter and ( HAZ).

  • Ivan Alexandrovich Komarov added an answer:
    3
    Any recommendation for analyzing graphene solution?

    Any recommendation for analyzing graphene solution?

    I want to compare graphene solution before my exfoliation process and after the process.

    it is my pretest. Thus I just want to check if it was exfoliated or reduced about size.

    AFM, TEM, Raman is excellent tool to analyze.

    However, I think it usually use supernatant after centrifugation. Therefore, it has some limitations for whole solution.

    Is there anyone who know other methods to analyze or technique to analyze whole sample with AFM,TEM,Raman?

    Thanks for reading and replying in advance.

    Ivan Alexandrovich Komarov

    You may also use SEM. By SEM you can look through larger area than with AFM or TEM that will give you more data about size of your graphene.

  • Ji Chang Chen added an answer:
    11
    How to reduce the shifting when performing EBSD ?

    The shifting is quite annoying during EBSD data accquring.How to reduce the shifting when performing EBSD ?High vacum?

    Ji Chang Chen

    Thanks Hilger.The drift does get worse while measuring for too long.Accroding to my experiences,the critical time would be half and an hour .There were no jump records in our system.It is a thermal filed emission SEM equipted with EBSD detector.Hopefully,you can find the solution.Good luck.  

  • Artavazd Kirakosyan added an answer:
    7
    How can I have a PVP concentration of 0.36M?

    I do not understand how can I have a concentration of 0.36molPVP K30/L EG if the molecular weight (Mw) of PVP is about 40.000, therefore I would need too many PVP to get to that concentration. Could anybody tell me if it is ok to have all that PVP or I am doing it wrong. Thank you.

    • [Show abstract] [Hide abstract]
      ABSTRACT: A rapid, simple and cost-effective polyol method has been developed for the synthesis of silver nanowires with high aspect ratio and high purity. The aspect ratios of the silver nanowires as high as ca. 1000 (average length 40 µm and some even as long as 80 µm, diameter 50–100 nm) were obtained via optimizing the reaction conditions. Transparent electrodes with excellent optoelectronic performances (optical transmittance of 90%, sheet resistance of 23.2 Ω/□ and optical transmittance of 87%, sheet resistance of 19.7 Ω/□) comparable to commercial ITO were fabricated via simple spin coating the resulting silver nanowires onto the glass substrates. The high optoelectronic performances and the facile all-solution process of the as-prepared transparent electrodes render them rather promising candidates for use in cost-effective large-area optoelectronic devices.
      No preview · Article · Nov 2014 · Chinese Journal of Chemistry
    Artavazd Kirakosyan

    Good question and good explanations, I was about to post the same issue. thank to everyone! Cheers!

  • Khairunnisa Ramli added an answer:
    9
    How can I determine the 0.2% yield stress from my stress-strain graphs?
    I plotted my stress - strain data with excel. Now I need to get the 0.2% (strain) offset in order to get my yield stress.
    Khairunnisa Ramli

     Hi,

    it is clearly explained here.

    https://www.mtu.edu/materials/k12/experiments/tensile/

  • Larbi Boukezzi added an answer:
    3
    How antioxidants improve the breakdown voltage of insulating oil?

    1. Karthik

    Larbi Boukezzi

    Hi,

    I think that the antioxidant can improve the breakdown voltage by its role in the inhibition of the oxidation process. It is well known that oxidation generate oxidized pieces like acid, Kitone and other polar groups which act as charge carriers.

  • John Ågren added an answer:
    9
    Relative density increases or decreases after sintering (for all cases or there is any type of exception)

    For AMMCs the relative density increases or decreases...if it is decreasing then it is possible or not.

    John Ågren

    During sintering you can have either swelling or shrinkage. What type of behaviour you find depends on various factors and important empirical observations can be interpreted in terms of the phase diagram as shown by German in his books on sintering. Eg Cu gives swelling and C shrinkage when sintering iron powder.

  • Asit Baran Samui added an answer:
    2
    Apart from Hexane Solvent extraction of lipids/ fatty acids from bio-mass, are any popular methods are recently in place?

    Apart from Hexane Solvent extraction of lipids/ fatty acids from bio-mass, are any popular methods are recently in place for extraction of biomass from fresh water algae?

    Asit Baran Samui

    Hexane or hexane/ethanol solvents used in the popular method of extraction.

  • Vahideh Shahedifar added an answer:
    5
    Which method is the best for determination of being a stoichiometric compound or nonstoichiometric one?

    I have purchased TaC powder. I'm not sure that is stoichiometry or not.

    Vahideh Shahedifar

    Thank you very much Dr. Shabalin for your detailed answer

  • Ganesh Warkhade added an answer:
    3
    Why the few exhaust emission's unit are in ppm and few are in % volume of gas?

    Why the few exhaust emission's unit are in ppm and few are in % volume of gas?

    Ganesh Warkhade

    Thanks for answering the Q

  • Andrew Drach added an answer:
    3
    What's the proper way to plot a mean value graph of several stress-strain curves with different strengh and fracture strain?

    I did a test series and got the stress-strain relationship of 10 specimens. To compare different materials I just want one mean value curve of every test series. 

    Up to the point of the lowest fracture strain I just avarage. What to do from this point? Do I have to extrapolate every curve to the mean fracture strain?

    Andrew Drach

    I personally would not do any averaging. If you want to have some representative curve, I would only do that in the well-defined region for all specimens, i.e. up until the development of cracks. You can fit any of the elasto-plastic models or polynomials to the data and that would be a good thing to have for modeling purposes, and that could serve as a representative material behavior curve. Make sure to the define the upper limit on say max strain that is valid for this model, so it is clear that after that it is extrapolation.

    As for the fracture/strength values, those are usually modeled using distributions, so you could fit any of the standard distributions to that (start with Weibull for example). Then model parameters would be representative of the dataset that you have. Averaging those numbers algebraically has little practical value.

    If you combine those two things, it looks like a comprehensive material description which covers both stress-strain relationship and the strength distribution.

  • Sami Tehrani added an answer:
    7
    Please could someone suggest why the samples which have been processed in exactly the same way obtain different colour after sintering by SPS?

    Please could someone suggest what are the possible reasons that the samples (Alumina and zirconia) which have been processed in exactly the same way ( Ceramics Processing and also the same recipe in SPS) obtain different colour and different density after sintering by SPS/FAST.

    Sami Tehrani

    Thanks so much everyone!!

  • Sukhyeun Jang added an answer:
    7
    Does anyone know why the absorption coefficient for graphene is different when we calculate graphene concentration with UV-vis?

    Hi all who are studying graphene.

    Anyone know why absorption coefficient for graphene is not fixed value when we calculate graphene concentration?

    I know that it is calibrated value with absorbance/length and graphene concetration.

    I want to get concentration of unknown graphene dispersion with Uv-vis, if it has certain fixed absorption coefficient.

    But if it has different value depending on graphene layer, size and functional group, how can I know graphene concentration?

    Do you guys usually filtrate and weigh that mass and disperse in known volume DI?

    what else do you use to calculate graphene concentration when is very low concentration?  

    Sukhyeun Jang

    Dear Bruno,

    what do you mean by the third carbon of 3nm scale?

  • Sirous Khabbaz added an answer:
    11
    Why do UV-Vis spectroscopy and DLS give different sizes for the same sample of colloidal nanoparticles?

    Why do UV-Vis spectroscopy and DLS give different sizes for the same sample of colloidal nanoparticles?

    Sirous Khabbaz

    Thanks a bunch for your constructive comments. 

  • Ernesto Davidson added an answer:
    2
    How can I find out the expression for rate of propagation for a particular reaction?

    I need to find out rate of propagation in the expression of time for the following reaction-

    P(i) + M   = P(i+1)    where rate constant is Kp

    P(i) - Polymer chain attached with 'i' monomer

    M - monomer

    Ernesto Davidson

    uSE THE EXPRESSION:

    Rp= Kp[M][P(i)]

  • Bassim Shaheen Bachy added an answer:
    4
    How to use Element Birth and Death technique in ANSYS APDL to simulate layer wise LASER deposition of material?

    My model is a 3-D plate of Titanium alloy which is to be deposited layer-wise by a LASER heat source. The procedure I have followed is-

    1: Build the model and apply boundary conditions.

    2: Kill all the elements using EKILL, ALL Command.

    3: Apply Heat Flux on the top face of the first element in the form of a 2-D Gaussian model.

    4: Activate the first element.

    5: Solve the first load step.

    6: Restart the analysis and repeat step 3,4,5 for the second element and solve the second load step, and so on.

    I have not been able to obtain a proper melt pool and the temperature of the model keeps on increasing greatly with each load step. Is the approach correct? If not, what is the correct procedure to do so? Any help will be greatly appreciated.

  • Márcio Mafra added an answer:
    2
    What is cost difference between SAE 15B41 and SAE 5140?

    mention in % difference

    Márcio Mafra

    About cost difference, it will change by Country or Region, 

  • Stanislav Levyakov added an answer:
    5
    How can I calculate the moment of inertia of the sinusoidal cross section in sinusoidally corrugated plate?

    I want to find the equivalent orthotropic model for a sinusoidal corrugated plate. During this process I need to find the moment of inertia of the sinusoidal cross section. Any one can help me in calculating this moment of inerta? 

    Stanislav Levyakov

    It is unclear from the question whether the cross section is of exact sinusoidal shape or not. If yes, the answer is quite trivial (see, for example,  above comments by Gordon). If the section geometry is described by another function or given in terms of discrete data like x and y values, employ a numerical technique. Please remember that the principal moment of inertia should be calculated with respect to the central axis. That is, you have to determine centroid of the cross section.

    Regards.

  • Ravi Ananth added an answer:
    14
    Hi I want to know if is possible to see any preferential crystalline orientation in freestand nanotubes only by x-ray diffraction study? If yes, why?

    xray difraction

    Ravi Ananth

    It is virtually impossible to have no residual preferred orientation. The question is about the ability of the XRD technique and data acquisition system to detect and resolve it. You may pick up these "Nano tubes" (how did you confirm this?) with scotch tape and then use transmission Laue mode to detect the preferred orientation if any, with a piece of dental film. The film may be quantified subsequently using any old scanner in place of the dinosaur photodensitometer.

  • Mohamad Johari Abu added an answer:
    4
    How do I create an equation from two projection point in the ternary system?

    The tie line between basis point to solid solution. for example, in CaO-CuO-TiO2 ternary system; the projection tie line from CaO (1,0,0) to solid solution type (12.75, 37.25, 50), so how to create an equation from this line.

    tqvm

    Mohamad Johari Abu

    Thank you. very helpful for my understanding.

  • Hu wen gang added an answer:
    4
    Any advice on the damage of cohesive element?

     I simulate the DBC with cohesive elment , the glued-line was modeled with thickness of 0.01mm,but the results show that the glued-line did not damage (like the picture attached), I had tried to change my parameters but it did not work . Hoping someone helo me solve this probleme or give some advise.

    Hu wen gang

     @Alaa Al-Mosawe , Panaj Biswas ; I have defined it wth COH2D4, but it also did not work,

  • Leonid V Vladimirov added an answer:
    1
    Hydrophilic silica aerogels: it is the structure preserved after immersion in water?

    The question is related to hydrophilic silica aerogels with or without calcium and magnesium in granular form. I'd also like to know if there are chemical modification useful to preserve the damage due to water contact or to the contact between the aerogels granules in water.

    Leonid V Vladimirov

    Water will NOT affect your "hydrophilic silica aerogels with or without calcium and magnesium in granular form."  Thus you do not need any chemical modification to protect the granules from action (there will be no effect of action) of water.

    Leonid

    P.S. Of course, my prediction - is "time-dependent". But for reasonably short, say 1 day - time - it will work OK

  • Dirk Lehmhus added an answer:
    10
    Are there any manufacturing machine for heterogeneous objects?

    Fabrication of heterogeneous objects

    Dirk Lehmhus

    ... unless you manage to do that in SLM through the laser used for consolidation ... which is difficult in practice, I guess, because the current layer will typically overlap with the previous one, so the latter is at least partly remelted ...

  • Erik Carton added an answer:
    9
    How can I change cone crack angle in brittle material with Herzian stress distribution ?

    Compressive point loading of brittle material generates a ring crack and subsequent cone crack due to the Herzian stress distribution in the material.

    Are there ways to influence the cone crack angle by intrinsic material properties or extrinsic solutions like a coating on the surface?

    Erik Carton

    In order to get a Herzian cone crack in the materials, they need to be brittle.

    Do you know about any ceramic materials that are auxetic?

  • Belma Fakić added an answer:
    2
    What could be an explanation for UNS S17400 (17-4PH) to have areas of low hardness (measuring about 94 HRB)?

    I have found small areas of low hardness on a sample of UNS S17400 machined from rod supplied in condition A and then heat treated to H1100. Bulk of the sample is in the appropiate range. Nothing i have seen in standard literature reports hardnesses in this range.

    Belma Fakić

    i agree with Mr Anil, some amount of retained austenite in the matrix, may be result in lower hardness in these areas, which can depend of diameter of rod.

  • Ji Chen added an answer:
    7
    Anyone have experience exfoliating graphite to graphene by electrochemical method? What type of graphite did you use?

    Which type of graphite did you use?

    I've done experiment with method on this paper.

    I was using graphite foil instead of flake type graphite on conductive carbon tape.

    When I've done with flake on carbon tape. It didn't even have a current, that would mean that resistance was too big.

    Can anyone give some advice for it?

    http://pubs.acs.org/doi/abs/10.1021/ja5017156

    Ji Chen

    Dear Jang,
    Thank you for your kind reply.

    Best,
    Ji

  • Flap Bester added an answer:
    3
    Is it ok to do the sub-zero heat treatment (liquid nitrogen) for 6 hours to increase the hardness and toughness or 24 hours?

    I am doing subzero heat treatment after quenching for en24 steel. And after subzero heat treatment am tempering it for 450c. So is it ok to go for 6 hours for subzero heat treatment or do we have to go for 24 hours only? 

    Flap Bester

    Sub-zero treatment changes retained austenite into un-tempered martensite.  Hence the improvement in mechanical properties.  During the change from austenite to martensite a volumetric change takes place (the volume increases).  This leads to the generation of internal stresses. The "new" martensite will be under compressive stress and the surrounding "old" martensite will experience tensile stress.  At the temperatures involved the material may be below its ductile to brittle transition temperature and therefore susceptible to cracking.  I would recommend that you keep the time to a minimum, depending on the size of the component.

  • Yves Rémond added an answer:
    17
    Are thermal fatigue and mechanical fatigue really equivalent?
    I have heard several times from different people that thermal fatigue could be studied in a more simplified way if you just consider that temperature gradients are the fonts of stresses and then act like the sample is under mechanical fatigue with an multiaxial loading.
    Is this really the truth? What should be taken as an unique feature of thermal fatigue and what could not be applied to it from the concepts of mechanical fatigue?
    It would really help me if someone could cite some references.

    P.S.: I'm studying thermal fatigue in hot forming tools.
    Yves Rémond

    First of all, I wish you a happy new year for everybody!

    In addition to your clever answers, I just want to say that for composites (with polymer matrix) and polymer materials, thermal fatigue and mechanical fatigue are very different. Polymer materials are very sensitive to temperature and strain rate as you know. Their thermal conductivity is also very bad. That induces specific phenomena which do not appear in the case of metallic materials.

    These specific behaviors were studied in the past, not so often in my point of view, and should be improved. The understanding of these phenomena induced mainly useful phenomenological laws, but are quite poor.

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