Metal Forming - Science topic

No, heat treatment below 400°C will not affect the microstructure of the material. It only serves to reduce the residual stresses.

Electrodeposit a thin layer of nickel prior to Cu plating on it. It will work. But some stainless steel contain very high chromium contents and nickel plating also experiences adhesions problem.

Dear Pavan,

Please find the useful information from the following.

A non-associated plasticity model with anisotropic and nonlinear kinematic hardening for simulation of sheet metal forming,

by Aboozar Taherizadeh, Daniel E. Green, Jeong Whan Yoon,

International Journal of Solids and Structures,

Volumes 69–70,

2015,

Pages 370-382,

ISSN 0020-7683,

https://doi.org/10.1016/j.ijsolstr.2015.05.013.

Try latex preservative ;) Set your rubber dies with steel mandrel and powder up and put this setup in preservative, then pump it and seal it after vaccuum is achieved.

This should enable CIP procedure and your compact should stay dry..

Dear Surbhi Anand thank you for this interesting technical question. As already mentioned by Bikshandarkoil R Srinivasan thioacetamide normally serves as an easily handled source of H₂S in analytical chemistry. Thus I'm pretty sure that under hydrothermal conditions the thioacetamide completely decomposes and forms H₂S. A few transition metal complexes of thioacetamide have been reported in the previous literature e.g. for cobalt(II), nickel(II), copper(I), copper(II), zinc(II), cadmium(II), and mercury(II). In this context please have a look at the following useful links:

Unfortunately these articles have not been posted by the authors as public full texts on RG, but I think that the Abstracts contain sufficient information. Apparently, simple thioacetamide complexes of manganese and molybdenum have not been reported in the literature.

Good luck with your research!

Hello! We are engaged in modeling and creating materials with ordered porosity - https://www.scopus.com/record/display.uri?eid=2-s2.0-85013168155&origin=resultslist. To model an unordered porous structure, we created our own macro program.

Use high pressure water Descaler. Most of forgings and steel producers are using to remove scale from heated billets / slabs.

Water spray @ 200 bar is applied through flat jet nozzles. This reduces billet / slab temperature @ 5 to 10 degree, which is acceptable in these process.

Have you tried developing your model at same parameters like same material, laser parameters, and boundary conditions? Please share a pic or your simulated results ? I dont have much knowledge but i do have modeling experience of SLM process in Abaqus

Besides saving meshing effort and computing time, the 2D axisymmetric models show the complete solution, whereas the 3D solution is seen on the surface. Only after cutting the 3D solution can be seen on individual sections (again this is only a partial view). However, also the expected solution must be symmetric. Often a non-symmetric solution of a symmetric problem matters. Typical examples are instabilities (like buckling).

Hot rolling is preferable process with heat treatment by annealing and normalizing.

Speed of rotation ,feed and depth of cut.

I am proposing to work with Shape memory alloy NITI sputtering Target . Kindly suggest reliable suppliers in India or foreign manufacturers who will supply to India

Mostly I hear this problem in docking, it is necessary to track bond distance when you using every software, for example for maestro we normally for zero-bond for metal and ligand instead of coordination. but if you want to see your ligand have the ability to bind to the metal in protein, track the Bond distance (like Zn-n around 2-2.2A). simulation and docking forcefield couldn't recognize the metal coordination, but if there is it is possible to recognize it by distance

Au and Ag nanoparticles can be formed to absorb visible spectrum efficiently that's why its commonly used photocatalysts.

You can model powder by 90 percentage density by Gurson model available in Abaqus software.

I think the mentioned error comes from element dimensions, run the simulation by default element and check the results.

Dear Msebawi,

From stress-strain graph, using the data, the flow stress model is developed by entering the stress strain curve values. By using this, the new model is developed in DEFORM 3D

Is there any specific reason to use Tresca? It is only slighly more conservative than von Mises, but its failure domain is discontinuous

In my exprience, it is best to connect two different nodes (one on each mesh) to prevent over-constraints. Tie constraints, can basically allow you to select two sets (one on each mesh) and link their nodes together so that all the TIED nodes move with the same amount

Hi Hamid Reza Attar ,

according to the change of the behaviour at strain=1 this is purely mathematical since the exponent is n<1 (it's like the behaviour of square root). I believe that you care about cases with strain values much lower than 1. So, an increase in strain hardening exponent n results in less material necking since it represents a more "elastic" material behaviour. Check the following:

https://en.wikipedia.org/wiki/Strain_hardening_exponent

Hello Hamid Reza Attar ,

Basically, there are at least three methods to perform such task. The problem is that most of them works only for Explicit anylysis. Below is a brief description of them all.

1) Using *FILTER "to stop the analysis when the value of any variable in the output request reaches a specified upper bound or lower bound".

For more information read this:

2) Using *EXTREME VALUE with *EXTREME ELEMENT VALUE "to stop the analysis at the first occurrence of a variable exceeding its user-specifed bound"

For more information read this:

3) Using utility routine XIT "within any Abaqus/Standard or Abaqus/Explicit user subroutine, respectively, to terminate an analysis."

You need to include this command in some user subroutine which would check the PEEQ value, and if it reach some extream value, run the command XIT. I would recommend to use USDFLD subroutine with utility routine GETVRM for Abaqus/Standard.

For more information read this:

Hope this information will help you.

Sincerely,

Pavlo

The value of MAX_PRINCIPAL+MID_PRINCIPAL+MIN_PRINCIPAL for LE could be considered as an indicator of volume relative change (>0 for expansion and <0 for contraction).

As above, friends have said about residual stresses and indicator of the breakage point will be helpful in the future.

In addition, I think that the highest tensile residual stress will help to find the cause of hair-cracks or deformations such as spring back, distortion and winkle during manufacturing process.

Hope be helpful.

polymers or plasticity (Plastic Behaviour of Material)?

When you start a new run, be sure that you have no stored results in your problem. I suppose that you have some stored initial values from previous runs.

Laser drilling or laser cutting are excellent technologies, but in both cases the process produce many types of deffects (spatter, HAZ zone, recast layer, burr, and so on). The magnitude of this type of deffects may be controlled by the laser parameters (for example, spot position, power percentage, laser speed).

It might be worth rechecking your EDX data to see if you found any oxygen associated with the analysed area. I assume that you carried out the EDX analysis in a SEM? If you haven't used any carbon coating you could also analyse your EDX data to see if carbon was detected. If you have access to a TEM with EDX you could sample small volumes of your sample to determine where the tungsten is sitting and what form it is in.

Hello,

just for understanding of the problem two questions from my side:

- what kind of friction model are we talking about? Straight Coulomb? Viscous approach? A combined approach?

- why the restriction to either 0.1 or 0.3?

At least the first question i mandatory, since without the type of modeling approach it is (from my humble point of view) impossible to interpret the given numbers. If if would be Coulomb I'd also say, that 0.3 seems rather high; if we're talking viscous, it's quite okay on the other hand.

Kind regards.

Hi,

The grain size may influence the biocompatibility, so the alloys co-exist better with human tissue. Also, strength is always important for the implants. SPD may give rise to better properties on those aspects.

There are many cobalt-copper alloys made for different applications.For the phase daigram please see the following reference.

The Co− Cu (Cobalt-Copper) system

T Nishizawa, K Ishida

Journal of Phase Equilibria 5 (2), 161-165, 1984

First of all, a higher rolling will help not only to reduce the roll separating force, but also to lowers the residual stress (which matters a lot in case of foils) in the processed materials. If there exist big difference int the linier velocity of foil and the roll velocity, complete slipping occurs between the roll surfaces and the foil, ie, there are no neutral points or lines in the deformed zone. This differs from current practices in the industry where the entry speed of the plate is generally controlled to match the horizontal component of the surface velocity of the roll in the feeding direction.

And also if the difference in the relative speed becomes too large, ie. the rolls rotate too fast, then the drawing capacity may disappear due to the friction loss. And this problem becomes cretical as the initial thickness becomes smaller and smaller. Industries prefer planetory roling mill most of the time for foil production. Hence to get good quality foils, its imp. to controll the entry speed(linier speed of foil or plate) and the roll velocity properly.

dear Abdul Basit, the star-like squared pattern that you see results from the circular (!) face of the cylinder which you want to change into a more or less squared shape. If you dont want it, because it is related to made properties, you can change the material flow by designing the intermediate forming steps in a way to enhance the flow as much as possible towards the straight sides of the square first before puching the material into the corners. Regarding the distribution of material properties, it depends very much on the properties of the initial cylinder and the alloy grade and casting properties. You can improve on some of the material properties by forming but also causing problems. It is hard to say from the scratch. Is also a question of design and application.

By the way in open die forming you should generate a mostly perfect circle pattern until you work towards the squared shape, but the distance from the edges of the former circular face to the final squared side edges can be manufactured constant on all sides as well corners in this way.

Hello Ashish

We used a modified Johnson-Cook model in an LS-Dyna simulation, it captures pretty well on the elastic strain recovery/ spring back effect during ring expansion. It is significantly evidenced during the low deformation case. A work presented in 7th International Conference on High Speed Forming (ICHSF 2016), have more detail of the simulation and experimental work available from the following link;

you can also see a simulation video of ring expansion test (obtained using LS-Dyna, showing the elastic spring back, available in the following link,

Amr Shaaban

Yes exactly!

Yes X-axis is the triaxiality! Is defined as the ratio between the idrostatic stress and the vM equivalent stress.

I am forwarding an article, hope that it may helpful.

https://www.dynalook.com/european-conf-2003/influence-of-the-effect-of-strain-rates-on.pdf

Yes, mass sclaing will help but you need to monitor kinetic energy, it should remain small compared to other energies in the model.

Or switch to implicit and don't bother with dynamics...

Dear all

I think you can try reducing thedimension of the minimum time increment.

Probably the problem is the mass scaling factor.

You can use edge guiders to extend the surface of sheet, it will stop the creation of negative pressure at the edges of sheet. But more easy option is try to use edge drop cold rolled coils. Try to drop the edges of sheet 10 to 15 microns from the center.

see

Multiaxial forming behaviour in the plane of sheet metal will be similar with respect to necking and failure against cracking. Also, if the FLCs are similar, similar hardening behaviour could be assumed too - according to modeling approaches, e.g. Keeler.

However, different yield stress will also cause different springback, playing an important role in any geometrical application. Moreover, forming forces will be significantly different, du to different yield stresses and as UTS is not considered.

Yes. When you plotted the contour, if you click on it, then you will see the tabular data is created on the bottom right corner. Depends on how you defined the time steps for the problem, you will see the strain results (time dependent strain results). Extract these results into an Excel file. Do the same thing for stress (Normal stress) and extract the result into excel file and then plot it.

It is also possible to create this chart directly in Ansys, However the graphs are not as nice as Excel, So I preffer to work with Excel. You can use "New Chart and Table" function and make everything in Ansys.

By the way if you defined only one time step then this method doesn't work for you!! make sure you have enough time step and increase the load gradually for creating a accurate stress-strain curve.

For creating stress-strain curve, you need to define non-linear material first by using plasticity options avaialble in "Engineering Data". I preffe "Multilinear Kinematic Hardening" . Then increase the load gragually by properly adjusting "Number of Steps" and "Timing steps".

Also the link above

Depend of the properties you need. Also depend of the characteristics metals you want to forming.I agree with the professor Omer Beganović

In this sense, cranck shafts, camshafts, hip prosthesis, and many many parts are made by forging.

Two prominent methods of converting raw material into a product have been metal forming and machining. Metal forming involves changing the shape of the material by permanent plastic deformation. After converting non-porous metal into product form by metal forming processes, the mass as well as the volume remains unchanged. However, in the case of metal forming of porous metal, volume does not remain unchanged. The advantages of metal forming processes include no wastage of the raw material, better mechanical properties of the product and faster production rate. Machining is the process of removing the material in the form of chips by means of a wedge shaped tool. In ductile materials, a significant amount of plastic deformation occurs before the material fractures. In brittle materials, very little plastic deformation takes place. Hence, the mechanics of machining is quite different for ductile and brittle materials. In machining, the work-piece is subjected to shear, bending and compression by the tool

The assessment of binding forms by sequential elution must be considered as an approach and should not be regarded to be specific for single mineralization forms (operational binding forms). However, it gives much more information on your sample than just doing total analyses (e.g. anthropogenic vs. geogenic loads in environmental questions). Since the procedure proposed by Tessier at al. (1979) there appeared lots of modifications, some of which are very specific designs to identify binding forms of single elements (e.g. As, P, U). The reagents used for identification of a specific binding form will co-extract to some extent other components. As an example, in procedures developed on the Tessier approach besides the release of exchangeable ions ammonium acetate will also etch carbonates on particle surfaces.

A crucial prerequisite of thorough identification of binding forms is to take in account the redox condition of the sediments. Many authors have demonstrated that some of the characteristics of these sediments change rapidly in contact with O2 and, therefore, also binding form proportions will change. Handling of sediments (e.g. lake sediments) from reducing conditions without preservation of the original conditions is waste of time and will result in fake numbers. However, starting with sampling in the field the handling under reducing conditions remains cumbersome. Cores should be regularly sliced already in the field into subsamples in an Ar-flushed box and immediately stored under Ar in airtight sample containers (glass). The tightened containers should be transferred immediately in a cooled box filled with Ar until finally stored in a fridge at the laboratory in the dark at 4 ºC. All samples should be processed and analyzed immediately after the sampling campaign. The slices are split in the laboratory into subsamples under Ar atmosphere in a glove box (one part remains under anoxic conditions (sequential elution), the other part is used for total element analysis, grain size, X-ray etc.).

In case of oxic conditions sampling is much easier; specific precautions must not be applied.

The method I applied is described in detail in Zachmann et al. (2009 and 2013; publication can be found in RG); it is a 6-step procedure and is based on Tessier et al. (1979) but it contains some modifications concerning the anoxic processing. In summary the procedure is as follows (Step - Phase – (Extractant) – Duration):

1 - Adsorbed cations – (Ammonium acetate (1 M, pH 7, 20 mL)) - 2 h;

2 - Carbonatic - (Na acetate (1 M, pH 5, 20 mL)) - 5 h:

3 - Easily reducible – (Hydroxyle ammonium chloride (0.1 M, pH 2, 100 mL)) - 12 h

4 - Less easily reducible – (Ammonium oxalate/oxalic acid (0.2 M, pH 3, 100 mL)) - 24 h

5 - Organic + sulphidic – ((a) Hydrogen peroxide (30 %), 30 mL, time depends on reactivity; followed by repetition of step 4: Ammonium oxalate/oxalic acid (0.2 M, pH 3, 100 mL) - 24 h);

6 - Residual - Hydroflouric acid digestion (standard procedure)

Additional remarks:

In case of anoxic conditions also the procedure the steps 1 – 4 of sequential elution must be performed under anoxic conditions with fresh sample material in the glove box in an Ar atmosphere. All solutions used in steps 1–4 were washed O2-free by purging with Ar for about 24 h. The solutions were controlled by an O2 sensor.

In case of oxic conditions these precautions must not be applied. However and in any case, due to the high concentrations of extraction solutions the detection of potentially harmful trace elements in the different elution steps (e.g. Cd, Pb) is heavily hampered by the high matrix load. The very high sensitivity of ICP-MS allows high dilutions by this suppressing the matrix effects and still allowing reliable element signals.

In the case of Pb the procedure may cause an artifact by shifting an elevated portion from step 5 to step 6, which yields an apparently non-reasonable stable binding form (step 6: ‘‘silicate’’); most likely this portion belongs to the sulfidic binding form. Therefore, in the case of Pb the ‘‘residual’’ binding form is included to the sulfidic (C-org.) binding form.

In electroforming, the concentration of metal ion in the electrolyte is higher than electroplating since higher thickness is required, the same with respect to current density.

Dear Jayesh M Sonawane,

There is a few things you can do/check:

1) Double check if you calibrated your mass spectrum correctly. Pick C, C2, O, O2 and Bi (or any other element if your primary ions are not bismuth). Don’t use hydrogen for the calibration.

2) Check the oxygen peak. There are quite a lot species that can match your measured values with oxygen in them.

3) I don’t think it’s a mass interference because MRP required to distinguish Cu from other species is low and I assume your system meets it but the real question is what is the width of your peaks? Are they perhaps broad? If yes then try to check what could have caused the peak broadening.

4) Do you have any confirmation from other methods that copper is indeed in your sample?

Best Regards

The more mechanical and forming tests you do, the better your final FE model.

I would think that tensile, coupled by forming limit curve tests; for a start. Then you could also investigate different strain paths.

It depends what type of plasticity model you want to develop. If you want to look at kinematic hardening as well you would need to do fully reversed cyclic loading/testing.

Dear Ibrahim,

There is not any relationship between metal forming and gases.

The point is that plastic deformation during metal forming is related to the Arrhenius-type law and the strain rate follow such equation, as you present in the equation above. The exponential term of this equation is related to the Boltzman statistic and basically represents the probability of the mechanism to jump across the barrier of apparent energy Q at a given temperature T. Then, if you introduce an apparent energy Q measured in J/mol, then it should appear R measured in J/mol K and the temperature T in K. However, you may introduce this term as Q/k_B T, being k_B the Boltzman constant. In this case, it could be useful to introduce Q in eV, k_B in eV/K.

Then, in your equation, if the left term represents the strain rate, the proportionality constant A is the Zener-Hollomon parameter Z.

So the relationship of Z is not with gases, but with the Boltzman statistic and the Arrhenius equation.

I hope that this could be useful for you.

Kind regards.

Prof. Jose San juan

The phase fractions on your initial depend strongly on the pre-process it has been through. If you use steel as comming out of the production is different from material comming from a pre-heating process which might produce large amounts of austenite.

What is the pre-history of the components you are welding?

Dear,

The best example of benefits of statistical methods is 6 sigma approach!

Regards,

Looking again at the original problem, which Ayad Mutafi has stated, he is more interested in press forming thin sheets where there is extensive plastic flow of the sheet material. The sheet being thin the magnitude of bending stresses will be negligibly small compared to membrane (in-plane) stresses. In such a situation investigators have tried visco-plastic stress analysis using membrane shell elements with success.

Dear Ayad,

It all depends on the physics of your problem and degree of accuracy desired. Shell elements can indeed be used. But you have to consider that they formulation rely heavily on strict hypothesis in the thickness direction. Solid elements do not need these hypothesis, but they are prone to blocking and other unwanted deformations for very thin structures. That is why "solid-shell" (aka thick-shell) formulations are promising tools for modeling thin shells. Their formulation is more complex compared to classic bricks, but they need only one FE in the thickness direction.

I used a solid-shell formulation in my PhD thesis to simulate a forming process with strong stress gradients through the thickness, under localized contact. The shell element gave good predictions in terms of the deformation, but not as good as solid-shell elements. Classic bricks needed several layers through the thickness, increasing the CPU time heavily. You can check my thesis for more information.

Regards,

Carlos.

if you are interesting to invesitgate through-thickness stresses, then it is better to use solid/brick element.

Hi, What is the fps that you get in your EBSD system.... I suppose all you want is to incorporate the orientation information to individual tessellae, for your FEM simulation. If you say, EBSD scan takes roughly 3 days, it implies that your fps is: (1600*1600)/(3*3)/ (3*24*3600) ~ 1.1 fps. Most SEM's can now aquire scans at ~ 30-100 fps. So, the time taken for you scans can be significantly reduced. Since, you are mostly interested for the orientation of the grains, you can perform a transverse scan (perpendicular to orientation of columnar grains) with a coarse scan say, 5 microns. Now, the time required would be, (3500*3500)/(5*5)/50fps ~2.72 hrs..even for 50 fps. So, I was just wondering what is the maximum scan rate, in fps possible in your EBSD set-up .

Thanks

Sulphur causes hot shortness in steel. This is nothing but cracking caused inside the steel due to formation of FeS which is a low MP phase. When steel is hot worked, this FeS softenes and promotes cracking. Hence, % of Sulphur is kept below 0.05%

Thank you for sharing your wisdom with me.

I suggest the book X-ray diffraction by B.E. Warren. It's an older one and quite mathematical, but thetheories inside are fine.

Laser processing is often associated with a change of properties on the surface of impact. The degree of change depends on the time of the power of the laser treatment. It is possible to process a very thin layer of 0.005 to 0.060 mm that does not affect depth. In this case, a barium boundary that can be used for some processes and is harmful to other processes

Thanks   Bojidarka B. Ivanova and Nassim Oulamine for your help. 

I agree with Omar (direct metal printing)  But there is another form of additive manufacturing through 3D printed sand molds and casting. This would give better properties. ExOne or Voxeljet printers.

Fracture surface in Scanning Electron Microscopy (SEM). The ductile fracture appears as dimples and brittle fracture appears as rock candy morphology as shown by (SEM), after the fracture materials are different shapes as cup and cone.

Dear Chandra Bhanu Basak and Sergei Tarasov,

Thank you very much for your information. Actually, I am interested in increasing the cooling rate to avoid the formation of unnecessary compounds which eventually reduce the mechanical properties of joint.  I suppose conduction is the better way to take way the heat rather convection. However, we are providing natural convection by blowing air. Hence please suggest me what is the thickness of pure copper backing plate which can withstand around 5000N load.   

I am glad if you provide any alternate solution. 

It will be hard to observe precipitates using OM or SEM. TEM is better to observe precipitates. 

If it is a tensile test and the sample is fixed well, this effect could be due to exeeding a force required for moving some element of the clamping system. This effect can occur when movable traverse is loose. Its weight should be exceeded to displace it.

Thanks, will go thru and understand it.

For validate the software, I think that you need to test with the "Compression ring test". The sample have the following relation: 6 (outer diameter), 3 (inner diameter) and 2 (thickness). If you make the virtual test (with Abaqus), when you use friction factor =0, with the compresion of the sample, the outer and inner diameter increase (figure a). When you use friction factor greater, the inner diameter reduce its value (figure b).

Thank you Dear William, this was so helpful

Basically, trying to simulate your forming process before starting to actually excerise tests on your material would be a good idea to get a first glimpse of what is particularly happening. As you already started to let your material undergo certain tests, you should at least start to simulate its material behavior and the development of elongation and tension [...] now. Anyway, to get an impression of the correlation of structure and properties of your steel, using divergent forming parameters (temperature, speed of forming, true strain...) would be a good idea. Don't forget to quench after forming to freeze the current state of microstructure. Then, try to evaluate the microstructure by taking a closer look on the micrographs of your specimens. Maybe you can already see the effects of certain changes in the forming conditions? Secondly, take a closer look on the mechanical parameters saved by your forming device. There should be a correlation between the changing conditions and the force needed to form etc... It would be best to argument by developing flow curves for each condition you took a closer look on, if possible.

As always, please talk to your professor about the things you're planing to do in advance. And always try to remember that the specimen's microstructure will always determine its properties - not the other way around.

Dr. Gupta,

I really appreciate your comments and your really valuable information. Im gonna make the simulations and try to analyze all possible variables.

Thank you again.

It is actually really simple to write this routine, here is an example for a simple material law with (A* eps**n + B) * (1-C*TEMP)

[Note that correct fortran formatting was lost, lines with $ are continuation lines]

SUBROUTINE UHARD(SYIELD,HARD,EQPLAS,EQPLASRT,TIME,DTIME,TEMP,

$ DTEMP,NOEL,NPT,LAYER,KSPT,KSTEP,KINC,

$ CMNAME,NSTATV,STATEV,NUMFIELDV,

$ PREDEF,DPREDEF,NUMPROPS,PROPS)

C

INCLUDE 'ABA_PARAM.INC'

C

CHARACTER*80 CMNAME

C

DIMENSION HARD(3),STATEV(NSTATV),TIME(*),

$ PREDEF(NUMFIELDV),DPREDEF(*),PROPS(*)

C

real*8 A,n, B,C

c write(*,*) 'nprecd', nprecd

A=PROPS(1)

n=PROPS(2)

B=PROPS(3)

C=PROPS(4)

C Calculate yield stress and derivatives

C

syield = (A * (eqplas+1.e-5)**n + B ) * ( 1 - C*temp)

hard(1) = A* n * (eqplas+1.e-5)**(n-1) * ( 1 - C*temp)

hard(2) = 0.D0

hard(3) = (A * (eqplas+1.e-5)**n + B )* (-C)

if (syield.le.(B/100.)) then

syield=B/100.

hard(1)=0.

hard(3)=0.

end if

c$$$ if (NOEL .eq. 1) then

c$$$ write(*,*) A, n, B, C

c$$$ write(*,*) TIME(1), DTIME, syield, hard(1), hard(2), hard(3)

c$$$ end if

RETURN

END

Use the commented lines at the end to output everything at one element.

it depend your as received material, if the al-alloys mechanical properties be standard (not rolled, extruded,..) you can enhance temperature to 0.5*melt temperture to increasing properties and if you use worked material , predicting it is difficult.

Good luck

Thank you Dr K. Aliakbari