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Welding - Science topic

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Questions related to Welding
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Currently i am working on thermo-mechanical simulation of dissimilar welded materials in ABAQUS, during my work i am facing problem in simulating volumetric heat source in both the materials. After successfully applying the DFLUX, i am able to get the heat distribution in only one plate. Please, provide me some helpful suggestions.
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Dear Niraj Kumar,
You likely did something wrong somewhere, and your model needs to be checked. I can recommend you some tutorial videos, which I share their link below. You might find it useful.
Best wishes.
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How interpass temperature and TTT diagram are related to each other.
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AWS D1.6 specifies an interpass temperature of max. 175°C for stainless steels. This is mainly to avoid sensitisation. The interpass temperature is typically measured on the surface some distance from the weld (e.g. 1"/25mm). Thus, the actual temperature of the (bulk) weld may be significantly higher than the measured interpass temperature. This is why the max. interpass temperature is conservatively set well below the temperature where sensitisation can occur (above 500°C).
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i am doing welding simulation for that i have to import geometry file which should be in NASTRAN format (.bdf). Does anybody know how to create a geometry file in nastran format (by using any software), or is there any method to convert iGES or other file format into the nastran file format 
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You need to use APEX. You can create geometry in it and mesh it.
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hello everyone. In accordance with the Ti-Cu phase diagram, welding these two metals, forms brittle IMCs like Ti2Cu and TiCu. does anybody know if there is any post-heat treatment cycle to remove or at least decrease these IMCs?
thank you for your favor.
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No, heat treatment below 400°C will not affect the microstructure of the material. It only serves to reduce the residual stresses.
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Can anyone explain how the carbon dioxide gas is protecting the weldments in MAG welding. Since this gas is active/reactive in nature with the hot metal how does this affect the weldment. Further, can this be utilized to avoid oxidation in the sintering process?
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Carbon dioxide protects a weld pool from contamination with air gases. However, it is necessary to deoxidize the weld pool, i.e. remove oxygen from the liquid metal. In arc welding, it can be carried out in two ways: 1) using chemical reactions with deoxidizing elements (precipitating deoxidation); 2) physical and chemical processes between metal and slag (diffusion deoxidation).
Deoxidizers are chemical elements that have a greater affinity for oxygen than the metal being welded (easier to interact with it), they can be ranged by decreasing degree of deoxidation (affinity for oxygen): Ca, Mg, Al, Ti, Si, Mn, Cr, Mo, Fe, Ni, Cu.
The element position the series is determined by the oxide dissociation elasticity level. Elements in the row to the left of iron protect the weld pool from oxidation. Most often, manganese and silicon are used as deoxidizers in arc welding, since they are cheaper. They are added to the weld pool from coatings, flux and/or welding wire. In these cases, the following deoxidation reactions occur in the weld pool:
2Mn + O2 = 2MnO;
Si + O2 = SiO2;
FeO + Mn = MnO + Fe;
2FeO + Si = SiO2 + 2Fe.
Due to these reasons, only low-alloy steels can be welded while shielding the weld pool with carbon dioxide. Respectively, it is not the best option for sintering.
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hello everyone,
can you tell me what are the steps to simulate the ultrasonic bonding in ansys/abaqus ?just i want to know the starting steps how can i start?
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You can read my paper published in IJMT , Temperature and stress distribution in ultrasonic welding _ FEA based study. in that steps are explained in detail.
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Does anyone used the data logger other than DAQ(LabVIEW) for welding temperature measurement?
If yes
Can we get required data by using the data logger or do we need to use the DAQ itself?
(Apart from the cost comparison)
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I used the Agilent 34970A data acquisition/switch unit (see Fig. 2), together with the BenchLink Data Logger software, to record the temperature histories on selected points.
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I am simulating a welding process. Do I have to use merge nodes as well as the spot welding together?
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No you do not need to do this. If you merge the nodes the contact will lose its function.
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Dear researchers:
Through my read some of the papers, I find that the welding efficiency may reach 100%, so the separation of the metal occurs away from the welding area (during the tensile test).
From your point of view: How do you evaluate the microstructure of welding zone?
With Regards
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Observation of Microstructure and Mechanical Properties in
Heat Affected Zone of As-Welded Carbon Steel by Using
Plasma MIG Welding Process
It was seen that the use of plasma MIG welding process has resulted in the refinement of the microstructure in the CGHAZ region, thus improving the mechanical properties of the as-welded SPCC steel. The highest microhardness values were obtained for conventional MIG in the CGHAZ regions. Incorporation of the plasma arc reduces the hardness, potentially increasing the ductility of the joining by plasma MIG welds. Further reduction in hardness can be obtained by decreasing the plasma current values.
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Hi,
I'm working in FEM simulation of an arc welding process. Base and filler materials are steel S420MC in both cases. I'm using a elasto-plastic material with properties dependent on temperature. The simulation consists on two uncoupled models: thermal and mechanical. The thermal model results are very good but I'm having problems with the mechanical model accuracy.
The problem could be the mechanical properties. ¿Where can I find these properties dependent on temperature for the steel S420MC?
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The easiest solution is to use JMatPro software to generate the material data. Experimental determination of welding simulation is very time consuming and expensive. Though, the quality of JMatPro data may be questionable depending on your requirement of accuracy.
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Can any one suggest the articles that mentioning the selection of the filler materials for dissimilar welding. i.e. the variation of the young's modulus/yield stress/CTE with respect to the temperature?
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Thank you for the information.
To add
The below article, "Validated numerical analysis of residual stresses in Safety Relief Valve (SRV) nozzle mock-ups."
is using Lemaitre-Chaboche parameters to derive the material properties. Though I didn't understand the concept thoroughly, to an extent, I think we can make use of it to derive the properties.
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According to the great difference between titanium propreties and Aluminum ones, especially the melting temperature. We have to make an other alloy between Aluminum and Titanum to weld them using RFW technique, for example, we have thaught about the copper. Do you agree ?
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I'm using a nitrogen/argon gas mixture during welding with different mixtures.
How I can calculate the partial pressure of the nitrogen gas from the flow rate and mixtures percentage?
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I'm afraid you need to obtain a practical relation for the variation of the shielding gas mixture flow rate with the shielding gas mixture pressure (Ptotal) by connecting suitable pressure gauge and gas flow meter with your welding rig, then use Excel facilities to draw the function graphically with its equation. Now, by applying this equation , the partial pressure of nitrogen gas can be calculated by substituting the gas mixture pressure(PTotal) by nitrogen partial pressure (PN2) divided by its percent(XN2%) following the Dalton's law of gas partial pressures Ptotal = PN2/ XN2%
Best regards
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Hello everyone
I hope you doing well
  • Aluminum alloy after fusion welding has FZ containing dendritic structure. I want the dendrites to be identified separately and in the form of grains (whether it can be called grain or not is also a question for me). The figure shows the dendritic structure in the FZ, but it is difficult to separate dendrites from each other. (Figure shows the FZ in fusion welded AA7075 (not AA6061) etched with Keller).
  • On the other hand, what is the etchant solution for the SEM investigation of the PMZ and FZ grain boundaries of the AA6061 fusion weld sample?
  • If you have experience in this field, I would appreciate writing it there.
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Hi
The best way is electro-etching with Barker reagent
Good luck
MP
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Welding software
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A variety of software is available for simulating heat transfer in materials. I myself have found COMSOL Multiphysics to be more user-friendly than other software products.
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As a kind of renewable non-metallic material with excellent performance, polymer has been increasingly widely used in the design and manufacture of parts in various industries. Traditional metal parts are increasingly replaced by polymer parts with the same performance. In the automotive, aerospace, transportation and other industries, the demand for lightweight is particularly strong, which has spawned a variety of polymer products to replace metal, and also put forward higher requirements on the connection technology and quality between polymer parts. Welding has always been the most effective way to permanently connect polymer components. Traditional polymer welding processes are mostly ultrasonic welding, vibration friction welding, hot plate welding, etc. The problem lies in certain limitations of welding methods, such as: Poor welding quality, low production efficiency, difficult to achieve complex shape welding, serious environmental pollution, short life, follow-up treatment and other problems have been plaguing people in the polymer industry.
Nowadays, with the continuous innovation of laser processing technology and the continuous development of composite materials, the emergence of polymer laser welding just makes up for the defects in this aspect, and will gradually replace the traditional polymer connection with its obvious advantages.
However, material limitations remain an important issue in polymer welding. The researchers are looking at LTW in polymer combinations that are difficult to weld due to varying degrees of incompatibility.
Is there any new progress in the understanding of laser welding polymer?
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Hi folks
I want to know the best way to calculate or find the power consumed to produce a friction stor weld joint.
Thanks in advance
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calculate time in minutes you run the machine multiply by the wattage(w) of the machine divide by 60 to get in hours. you will get in watt hours. 1000 watts per hour makes one kilo watt hour which is metered for power consumption.
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How particle size of ferrochrome or any ferroalloy powders affect the hardfacing properties (hardness and wear resistance) in submerged arc weld overlay process for high chromium carbide alloys (Fe-30wt%Cr-5wt%C)?
Generally, particle size remains 0.2 to 0.8 mm for ferroalloy powders. Why? What if I use less than 0.2 mm size ferroalloy powder.
Material: Chromium carbide alloys
Manufacturing process: Submerged arc weld overlay
Substrate material: Mild steel
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Usually, fine grained particles will cause better results in phases microstructure formation and more homogenous mettalurgical properties. In SAW Hard-Facing this parameter will be more significant, due to the filling rate and specific process features of this welding process.
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My simulation topic is about resistance welding in abaqus. I finisher the part about Coulpled thermal-electrical-structural , now i want to simulation the melt pool , like solid change to liquid , but i have no idea that how can i start , and i cant't find any topic like this in online...
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Hi Li-Ying Chan,
In this case, you must use the heat transfer step as well. watch this video: https://www.youtube.com/watch?v=IqDGbYCQLMs
Also, you can find more information about the welding process, types of welding, methods of welding simulation, and theories behind them in the link below. I think it could be a great help in welding analysis.
Best wishes
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Hello, I'm working on a project related to weld overlays. As part of this, we performed TIG welding on Base Metal - Mild Steel 200 * 100 mm AND Filler rod AISI 316 L.
  • For single-layer and a double layer of welding, weld overlap is 25%.
  • After this, we did a microhardness test for the single-layer 420HV Was recorded
  • Whereas for the double layer it decreases to half around 216HV.
We could not able to figure out the reason behind the decrease in hardness for the double layer. idly hardness should increase. what might be the possible reason for this?
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AISI 316L has a very low thermal conductivity (almost three times lower than that of mild steel), so the second layer cools more slowly than the first. Slower cooling means better annealing, so the second layer is softer than the first.
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I am doing an uncoupled thermal-mechanical analysis of a welded plate in ANSYS MECHANICAL APDL. I want to apply constant amplitude cyclic loading on this model after the residual welding stress has been generated after the completion of the structural model. Could I know the process of defining the cyclic load and the welding residual stress together in one model?
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I have no idea about the residual welding stress analysis but it sounded could be solved using 'do' loop command with resume analysis if possible
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Dear all,
I am working on a 2D welding simulation. The welding plate is symmetric about the X-axis, and the welding is moving along the Z direction. The width of the plate is along the Y direction. I have applied the Dflux subroutine as the heat input in Abaqus software. When I use the X symmetry boundary conditions at the Symmetric plane, and the other two ends nodes are fixed along with all directions, the simulation works fine(but the percentage difference from results is more). But the end of the plate away from the heating side becomes more tensile. If I apply the Xsymmetry and encastering the bottom node in the same plane with the same mesh, the results are diverging. When I reduce the size of the mesh, the solutions will converge.
1.Why the solutions are converge when the mesh becomes finer?
2.Can anyone suggest the exact boundary conditions for the 2D welding analysis?
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We are doing an uncoupled thermal-mechanical analysis of a welded plate where we want to do a fatigue analysis. To do that, we want to obtain the structural stress-time history curve for the specimen. It would also be appreciated if we could get any help with the procedure to obtain the curve.
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Claudio Pedrazzi
Thank you for your advice, and I have followed it. But this process would help me in getting the time-history curve for a particular node. But I am concerned about the time history curve for a specific path where welding has been done.
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Multiple solidification modes can occur in metals. These modes describe the
different morphological forms that can exist at the S–L interface and in many
cases are still apparent when cooled to room temperature.
• Under conditions of low solidification rates, steep temperature gradients, or
both, plane front solidification can occur.
• In most practical cases, the plane front breaks down into other modes
described by either cellular or dendritic morphologies.
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I agreed with you
A planar solidification front first breaks down into a cellular front and then
into more complex dendritic morphologies, depending on solidification
conditions.
Most alloys solidify in either cellular, cellular dendritic, columnar dendritic
modes, or a combination of these. The solidification mode is determined by
the degree of constitutional supercooling , or undercooling, that exists in the
liquid immediately in front of the S–L interface. As the extent of supercooling
increases, more dendritic modes of solidification are favored.
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I need to measure residual stress in welded plastic parts. How can I do that? what is the method to measure residual stress in plastic accurately?
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Hi,
you can see in standards: ASTM D 4093: ASTM D 1939 and MTS3000 Restan. Best regards,
Dr. Gedvidas Bikulcius
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I created 50 interactions(welding-1 to welding-50) such that half of the region was reactivated through these interaction,which was previously deactivated , through the following code:
Tol=.00000000001
Speed=0.01
for i in range (1,51):
mdb.models['Model-2'].ModelChange(activeInStep=True,createStepName='welding_'+str(i),includeStrain=False,name='welding_'+str(i),region=Region(
elements=mdb.models['Model-2'].rootAssembly.instances['Part-1-1'].elements.getByBoundingBox(-Tol+Speed*(i-1),-Tol,-Tol,Tol+Speed*i,.0025+Tol,Tol+0.002)),
regionType=ELEMENTS)
But when I tried to view region reactivated in any of these newly created interaction,following error showed up,"At least part of the region of the selected interaction has been suppressed,deleted or excuded or is a part of reference representation".I am unable to understand the error.The deactivated region is a cuboid with X coordinate ranging from (0,0.5) ,Y coordinate ranging from (0,0.0025),Z coordinate value from (0,0.004).The direction of welding is positive X axis.Through these interactions I am trying to reactivate lower half of this cuboid with Z axis of the reactivated region ranging from (0,0.002) and range of X and Y coordinate being the same as that of the deactivated region.I have attached an image of abaqus model.
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Hi Atul,
I have the same problem in my modeling. could you finally resolve this error or not? I would appreciate it if you can share with me what you have done.
Regards,
Hossein
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what is the standard for peel test using laser beam welding (micro welding) process.
specimen size: 0.1mm and 1mm
overlap joint.
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A peel test is performed between two substrates bonded together with an adhesive. The substrates may be both flexible or one may be flexible while the other is rigid. The adhesive itself will generally take the form of a thin layer between the two substrates such as the adhesive located on the underside of a piece of tape that has been placed against a steel plate. To do peel tests for the measuring of adhesive strength are the T-peel, 90 degree peel, and the 180 degree peel. The T-peel test is a type of tensile test performed upon two flexible substrates that have been bonded together and placed into peel test grips such that one substrate sticks up and the other sticks down while the bonded area sticks out horizontally so that the entire setup forms a “T” shape. The 90 degree test requires a 90 degree peel test fixture to determine the adhesive strength between a flexible and rigid substrate, where the plate lies horizontally with the gripped end of the tape sticking up perpendicular while the rest is bonded to the plate so that it forms an “L” shape.
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Hello everyone,
  • So, as he mentioned in his paper that he neglected the Marangoni effect. Up until now, one can control the fluid flow with changing surface tension gradient. But since he neglected this effect, I don't know how I can enhance my fluid flow. I am having exactly the opposite fluid flow that he showed in the paper. (please see the attached screenshot of my simulation). His fluid flow is having curls in the molten pool clockwise but mine is anticlockwise. How else I can affect the fluid flow (Marangoni is out of discussion since he neglected and surface tension coefficient is assumed to be constant)?
  • He also neglected the latent heat in this paper and used recoil pressure to deform the free surface. But in order to apply the saturated vapor pressure in mass flux, latent heat of vaporization is used. You can comment on it too.
I have implemented all the boundary conditions and equations mentioned in the paper. Still, not able to generate the same results. If anyone can help me with it, I would really appreciate it. I am open to discussion as well through chat system or zoom.
paper link:
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as I explained in my previous answers, all these effects are considered, at least in the manuscript you refer to, as volume forces and their magnitude is obtained from empirical expressions. Both phenomena, the recoil pressure, and the vapor-induced shear stress occur due to the same physical effect, namely the rapid evaporation of material. Thereby, the recoil pressure is simply a pressure acting on the keyhole surface and directed in the inward normal direction of the free surface. The shear stress, however, acts in the tangential direction, which can be obtained with/from the normal inward vector.
Best,
Antoni Artinov
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Hello,
As part of my research activities, I wanted to measure the temperature during resistance welding with a K-type thermocouple.
The problem during the current passage the thermocouple is on a part with high potential gradients. The sphere of the thermocouple (Ø 400 μm) is thus itself in a potential gradient that can reach several hundred millivolts.
My measurement during the current flow is therefore erratic. Could you give me some advice on how to get around this problem?
Also, are there any thermocouples that can be used to measure the temperature in these conditions?
Thank you in advance for your answer
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Thanks so much for your answer Farhad
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Tensile strength performance and optimization of Al 7068 using TIG welding process is done by the previous researcher.
Please suggest the aluminium or stainless steel material other than Al 7068 for my future project. I like to follow the same methodology of previous researcher. But changing the material.
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You can try TIG to weld aluminum alloys AA6082
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I have a streel structure and the welds need to be merged in share topology in SpaceClaim in order for the elements of both parts to match.
But the contact between beam must no be merged in shared topology so that I can make a contact frictionless in Mechanical.
I can only manage to either separate all bodies so that they all make contacts (but mesh does not match) or merge all bodies so that mesh matches (but no contact surfaces are created and I cannot make the beam-beam contact frictionless).
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I have found a solution for the above said problem. Bodies grouped under a single part in Design modeller can have selective shared topology using the option of 'Connect'. You may refer to this under the section of 'Selective Shared Topology: Using Connect after Share Topology' in Design Modeller User's Guide for further information.
Thanks.
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I want to do MATLAB simulation for the MIAB welding process. In the process the arc play a very important role. So I want to understand the arc simulation in MATLAB. Kindly help me with that.
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I would like to know which is the most influential parameter of the weld bead (especially penetration depth) in laser welding simulation(irrespective of joint type)). How?
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As per the Specification for Structural Steel Buildings from AISC, the design related to the partial joint penetration welding for the weld metal (Table J2.5) includes apart from the LRFD resistance factor (φ=0.80), another factor equal to 0.6 along with its nominal stress (0.6Fexx).
From some searching I have understood that the strength of the weld metal is underestimated due to the experience of the welder or temperature effect, but they are not clearly related to this 0.6 factor.
Any help about the source of this 0.6 factor would be very helpful.
I would appreciate any opinion.
Thank you
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Answer found, but any further suggestions are welcomed.
The factor of 0.6 on FEXX for the tensile strength of PJP groove welds has been used since the early 1960s to compensate for factors such as the notch effect of the unfused area of the joint and uncertain quality in the root of the weld due to the difficulty in performing nondestructive evaluation. It does not imply presence of shear as in fillet welds.
[Specification for structural steel buildings, AISC, p.429].
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Hello everyone,
I want to model three dimensional conical heat source. But there are some parameters I am not sure about how to choose such as ze,zi,re,ri (please see the attached pic to see those parameters)
If anyone has any idea about it, please comment.
Thank you.
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Sunil Suthar : Thank you for your reply. But I think you missed my question. I was asking about modelling a heat source and its parameters. You will find all the information in the questions above.
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What's the campaign of strength of flash butt welding and thermite welding ?
Any research please share .
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Dear all,
How can we calculate the heat source fitting parameters for welding in Abaqus when we are using the Goldak double ellipsoidal heat source model?
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Hello Mr.Anoop, The Goldak parameter can be calculated from the weld bead width and penetration. The goldak model can be easily implement in the Abaqus using the dflux subroutine. best wishes
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the graph i have plotted is 304 SS but different slag is there on the top surface of weld zone.
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In this case, you need to calculate the Icoor and Ecoor, and then calculate the tafel slopes of each samples. You can then determine the polarization resistance Rp for each sample. This is how you can make a comparative (quantitative) study of the corrosion behavior of your samples.
all the best
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Recently, I am working on a study about PWHT. I curious on when did PWHT first appear? How did PWHT develop with history time ? Which research institutions have made outstanding contributions in this regard?
hope to update the knowledge of PWHT, looking foward for your reply.
Thanks in advance.
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Please check the attached file, I hope it would help
Thanks
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Hello everyone,
There is a porosity formation at the end of the process right in the middle of the workpiece. I know porosities formation depends on several factors such as laser power, solidification rate, welding speed, backfilling speed, etc. So, my question is:
I actually want to see the porosities scattered throughout at the Solid/liquid interface or nearby to that location. Any suggestions would be appreciated. I am attaching the GIF, please download to watch since researchgate isnt supporting it.
I am using COMSOL and doing a simulation on Laser keyhole welding. Thank You.
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Hi Akash,
in my opinion, you will not be able to see any porosity during the process at the S/L interface as long as you are using a well-distributed Gaussian heat source. Process porosity occurs mainly due to transient collapses of the keyhole, and you will only be able to reproduce that behavior by using a more realistic beam-matter coupling, e.g. as provided by the ray-tracing method. By doing so, you end up in multiple reflection points along the keyhole wall being associated to a more local energy input and thus ares of different temperatures and recoil pressure values in the end.
Best,
MB
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I need measure residual stresses in the welded joint
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Contact Prof M Mohapatra, from IIT, Bhuwaneswar.
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My research was focused on the nanomechanical characterisation of welded aerospace alloys. I have one publication. I am looking for a funded PhD position in a good university. What should be the approach to apply for PhDs and which country should focused in relation to the subject that I have mentioned?
Thank you for the responses in advance.
Regards
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PWHT (post weld heat treatment) is widely used to eliminate welding residual stress, but how to evaluate the effectiveness? what are the commonly used methods to measure welding residual stress in a component in or to be in service? Any standards?
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You could also check the Blind Hole Drilling technique for components in service. The technique is a bit old-fashioned maybe and less accurate than XRD but the equipment can easily be carried on site. Also, take in mind that it is semi-destructive cause you drill a small hole on the sample. Maybe in some cases can be repaired with cladding or even not depending on the application. Good luck!
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With the development of large size heavy section pressure vessel, local post wed heat treatment(PWHT) instead of furnace PWHT must be used. Absloutely, there are differences between furnace PWHT and local PWHT. For example, the structural constraints, the temperature distribution field will be significantly different. Obviously,The effect of PWHT will also be different. So, my questions are :What's the essential difference between furnace post weld heat treatment (PWHT) and local PWHT?How does this difference affect the release of residual stress and the change of microstructure and properties?
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Vadim Verlotski ,I‘m sorry I forgot to state that the materials I want to study are low alloy steels and stainless steels,such as Cr-Mo-V steel,9% Cr steel ,304 stainless steel ,316 stainless steel,etc. According to what I have learn, it is hard to release the welding residual stress completely by PWHT (including furnace PWHT). That's why I curious about the stress relief mechanism of PWHT. Meanwhile, that's also my motivtion for the topic of the disscussion. In other words, I want to know the difference of stress reilef mechaism between furnace PWHT and local PWHT.
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Hello everyone,
Just a general doubt, I have seen a lot of papers on welding using Gaussian heat-source to model their welding process. But either it's a plasma arc welding or laser welding, they are using the same gaussian heat source, if we can use the same heat source for both the processes, what would be the difference numerically since almost all the physics are pretty much the same.
Please share your thoughts!
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Because laser welding and plasma arc welding have large energy density and relatively small molten pools. Their energy distribution are almost symmetric on the moving direction.
Both of them can be described via Gaussian heat source model.
In comparison, TIG and MIG have large molten pools, which has a longer tail and the energy density is more distributed on this region. In this situation, the Goldak double ellipsoidal heat source model is more suitable since it has more shape parameters to reproduce the actual energy distribution.
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If R squared values is exactly equal to 0.95, is that significant or insignificant for Taguchi method in case of Mechanical testing of welded joints? Some authors have reported R square values 99.98% and Adjusted R square value 99.97%??
Please share your thought.
Your opinion is highly appreciated
Regards
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Dear Sudhir Kumar,
The R squared is not enough to verify your model. I think you should add a confirmation test and compare the results of obtained value with the model and experiment.
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I was at a Nano-Technology conference some years ago and a concept was introduced which was intended for welding dissimilar metal objects that are difficult to fuse. This uses a nano "flash paper" which is placed between the objects and lit like you would flash paper. The reaction progresses quickly through the material and creates enough heat to produce a weld joint between the metals. Can anyone point me to any companies that may be offering this sort of thing?
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Thanks Madhukar. I vaguely recall this material was made with alternating atoms thick layers of aluminum and titanium. I had made notes during the conference, but they were lost.
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I conducted a tensile test on a welded joint and have plotted its stress-strain behavior(attached file). Unfortunately, I have not been able to identify the Young's Modulus due to the graph's behavior. If I am to do a linear fit on the graph, which data points should I include?
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The term Young modulus for a welded joint is inappropriate, because E is a material property, whereas a joint is an assembly. The term "joint stiffness" is more correct, and it should refer to the load vs displacement curve. It is defined as the tangent of the curve; in your case it is clearly non linear, that is, the stiffness increases during the test.
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Some theories of physics require (not merely allow) magnetic monopoles. [See, for example, David J. Griffiths, Introduction to Electrodynamics, Fourth (Kindle) Edition (Cambridge University Press, Cambridge, UK, 2017.] But how can a theory that requires (not merely allows) magnetic monopoles be consistent with the fact that magnets with circular magnetic fields — and hence with no poles (neither a north pole nor a south pole) — exist? Two examples: (i) A horseshoe iron, alnico, or other permanent magnet bent into a circle, with the poles cold-welded together. (Cold welding is possible in a vacuum for surfaces planed very smooth.) (ii) A toroidal-solenoid electromagnet (with or without an enclosed iron core for increased strength). The magnetic field lines in such magnets are circular — and hence with no poles — neither a north pole nor a south pole.
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As I understand, your question is not about horseshoe magnet.
First of all, there is no problem with existence of circular magnetic fields even if there are magnetic monopoles (somwhere else). Such fields can be produced by electric currents. Simplest example of the circular magnetic field produced without magnetic monopoles is the field around the wire with electric current.
As for theories that require (or, at least, admit) existence of magnetis charges, their consistency with experimental data depends on the viewpoint.
For instance, there is an interesting theory of superluminal particles developed by Italian physicists (see e.g. Recami, E., & Mignani, R. (1974). Classical theory of tachyons (special relativity extended to superluminal frames and objects). La Rivista Del Nuovo Cimento Series 2, 4(2), 209–290).
According to this theory, superluminal velocity flips electric and magnetic fields, i.e. electric fields become magnetic and vice versa. Prticularly, superluminal magnetic charge will be seen as electric charge (i.e. the divergence of the electric field (div E) will be non-zero).
To undestand this, consider (again) the simplest example of magnetic field around the wire with electric current. In fact, this is the case of superluminal electric charge: it's time-like component (charge density in the wire) is zero, while space-like component (electric current) is non-zero. And, as we know, this "superluminal" electric charge produces magnetic field, not electric.
Similarly, superluminal magnetic charges (if exist) will produce electric field.
According to Recami & Mignani referred above, protons can be regarded as superluminal magnetic currents inside the proton. Since these currents are superluminal, they are seen as electric charges (not magnetic).
What are the reasons to think that currents inside the proton are superluminal? Well, according to experiments on inelastic scattering of electrons on protons, the number of proton constituents (termed partons) that scatter electrons is dependent on the reference frame. The faster the observer is moving with respect to scattering particles, the more proton constituents will be observed (you can read about this here: https://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/).
But according to Special relativity, this can only happen if proton constituents are moving faster than light. As you certainly know, slower-than-light objects can be at the same place at different times. Similarly, in Special relativity faster-than-light objects can be at different places at the same time. And the "number of places" where superluminal objects can be observed at the same time depend on the reference frame of the observer.
If we accept the idea of Recami & Mignani, we obtain very nice picture of the world with both electric charges (subluminal, inside electrons, muons and tau) and magnetic charges (superluminal. inside protons). But they both look like electric charges from our frame, hence we have an impression that there are no magnetic charges in nature.
I hope this is a good example of the theory that admits magnetic charges and is consistent with our experimental observations.
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we want to produce VAR electrode (d=150 mm) from scraps (Ti 6-4) for melting (with attached shape). what is best solution for producing of initial electrode? can we cut it to small pieces and pressing in related mold and welding final discs together? is this way practical?
please guide me if you please.
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CIP
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Kindly provide any technical papers/patents.
Thanks and regards
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Does anyone know the effects of Si and Ni contents on the mechanical properties (strength, impact and creep properties of 9Cr heat resistant steel weld metal?
Thank you.
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The added Silicon (Si) will help as it is a basically a deoxidizer and degasifier. In fact, It increases tensile strength and yield strength and moreover the hardness, and magnetic permeability. As far as clarity is concerned, Silicon helps to purify the iron ore during the smelting process because of the deoxidization and thus removing other kinds of impurities from it. Also, the Excess addition of Si may also improve the creep resistance and ductility of the steel. In welding, silicon is detrimental to surface quality in the low carbon like metals. It actually aggravates cracking effects when the carbon content is high. Slicon content if not exceed 0.10% welds are good including impact strength.
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I have been etching with picric modified to reveal the HAZ, specifically the fusion lines but it is restricted in my country. I tried with differents option from the Handbook (Metallography and microstructures) but I haven't been good results.
I wondering if someone have one suggestion.
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I suggest you to have a look at the following paper:
- INVESTIGATION OF EFFECTS OF MIG WELDING ON CORROSION BEHAVIOUR OF AISI 1010 CARBON STEEL
Nur Azhani Abd Razak and Shing Shian Ng
Journal of Mechanical Engineering and Sciences (JMES), Vol. 7, pp. 1168-1178 (2014)
Good luck and my best regards, Pierluigi Traverso.
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Any dedicated formula for conical heat source of high energy welding simulation.
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Formula for 3 dimensional conical heat source for simulating is easily available, however i feel approximating the z coordinate parameters is the real hard question here.
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I have some problems with welding omniprobe needle to sample. I am really frustrated when I convince that I make out and do freecut for pulling out the chunk, right after freecut the chunk twist and fall off the needle. I really want to know the reason to make the chunk twist and fall off.
Can shape of needle tip cause to fail welding?
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Kindly suggest a best fusion welding method (GTAW or EBW) for joining Cast alloy Inconel 718 with Inconel X750
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Selection of a welding method depends on various factors. If you are trying to do a very general fabrication weld of a component, then just simple GTAW process with IN718 weld filler wire would just work fine. I am assuming the material is in solution HT condition. But be aware that cast IN718 could have laves phases that might cause some issues. If the cast IN718 has been properly heat treated to dissolve laves phases, and the material is generally "metallurgically clean" then you should have no problems.
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I am doing a welding simulation and using element birth/death in the following way:
Thermal analysis:-
1) Conductivity matrix, Convective matrix and Heat capacity matrix of kill.ed elements are multiplied by a factor of 10^(-6).
2) Heat input vectors (load vectors) are made zero for kill.ed elements
3) After solving a particular load step, fictitious values of temperature are obtained for the nodes within the kill.ed elemental zone. These fictitious temperature values of kill.ed nodes are made equal to ambient temperature at that load step.
Structural analysis (small deformation theory):-
1) Stiffness matrix of kill.ed elements are multiplied by a factor of 10^(-6).
2) Thermal load vectors of kill.ed elements are made zero.
3) After solving a particular load step, fictitious values of displacement are obtained for the nodes within the kill.ed elemental zone. These fictitious displacement values of kill.ed nodes are made equal to zero at that load step.
4) The fictitious elastic and plastic strains for the nodes in the kill.ed zone are made zero, at that load step.
5) The stresses in the kill.ed zone are made zero at that load step.
6) Apart from the elements in the small gap between plates, the other bulk elements that melt are also kill.ed in that load step, and points 1 to 5 (structural analysis) above are applied on them.
7) Elements are made to born structurally once their temperature starts dropping down from the solidus temperature. (i.e from start of solidification). The incremental stresses in the non-linear simulation are added from this start of solidification.
Can anyone provide their insights on how correct is my above approach?
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Can there any alternative way to implement this process?
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Heating, due to welding causes microstructural changes in duplex stainless steel. Besides changing the 50:50 balance ratio of austenite: ferrite, hard phases such as sigma are formed at specific temperatures.
Why sigma phase reduces the corrosion and/or pitting resistance of the DSS in seawater?
How to avoid the formation of the sigma phase during welding?
Is there any procedure or heat treatment that could be done to get rid of the sigma phase from the HAZ!!
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sigma phase is a chromium rich intermetallic phase found in duplex stainless steels, that forms when steel is cooled slowly through the range from around 1000degC to 550degC. Upon controlled heat input results very less inter pass temperature followed by PWHT ( Solution annealing at 1050 °C ) might be avoid sigma or intermetallic phases at high rich chromium in two phase materials
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I am simulating arc welding where, my initially I perform a non-linear transient thermal analysis and then I do a non-linear elasto-plastic analysis under thermal loads.
During thermal analysis, full Newton-Raphson method converges successfully at all times (i.e heat source starting, moving, stopping and post stopping).
However, during the quasi static elasto-plastic analysis, the full newton raphson method is unable to converge the solution when the material starts to cool after welding. (i.e when, temperatures at all the nodes of the model start to monotonically decrease).
Can anyone provide some expert insights into this matter. Thanks
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There is no guarantee that N-R or any other method of solving one or more nonlinear equations will ever converge. With a reasonable starting value and a smart implementation with checks and restarting will often yield the desired result, but that's not a given. Many nonlinear equations have multiple solutions, which may be local minima when you are seeking a global minimum. This is why it is helpful to have full control over the calculations. Building a task inside MATLAB and depending on the algorithms provided may often work, but this is not always the case, as in your present example. This is one of many reasons why I would never use MATLAB to do anything. If you're stuck with MATLAB and have no other options, I suggest you try other methods, including: Regula-Falsi, Secant Method, Davidon-Fletcher-Powel, Broyden, and evolutionary, to name a few.
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I am having difficulty understanding the stresses present at the weld point during the tensile test and which area to consider.
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This is not a familiar situation, for me, but I'd start with an area estimate of the spot welded joint(s) then consider the shear strength of the weakest material, (if the tube and bushing are dissimilar materials), given that area. For visualization purposes, imagine drilling a small hole through both tubes, at the site of the arrow, then inserting a snug fit shear pin and loading, longitudinally, to failure.
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Is it possible to change or form new chemical bonding using frictional heating during high sliding operations?
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Yes, it is possible. It depends against which material the friction occures. For instence, PI against SS creats a new chemical bond, etc.
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I have a specimen which is arc welded in a single pass. For simulation, I use a moving heat source and get the temperature vs time distribution. I have used quiet elements technique for the filler material.
During structural stress simulation, I use the same quiet element technique again, assuming small displacement theory.
However, during the structural stress simulation, the elements are born with some initial displacements, strains and stresses. Besides this happens for all those elements whose temperature has exceeded melting point.
Hence, I have a doubt regarding the following:
1) In my code, should I forcefully make the artificial displacements, strains and stresses as zero, for all elements which are not born?
2) For other bulk elements near the weld line, what should I do for displacements, strains and stresses, if the elements melts and becomes liquid?
(Note: I have assumed small displacement theory only, to keep my code simpler)
"Awaiting for kind insights from experts. Thanks"
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You need to reset the deformations/strains to zero when an element is activated in “liquid” state. This is a little bit trickier in a small deformation formulation, but it is doable. Especially, as in your case, when you have the source code :)
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Heating, due to welding causes microstructural changes in duplex stainless steel. Besides changing the 50:50 balance ratio of austenite: ferrite, hard phases such as sigma are formed at specific temperatures.
Why sigma phase reduces the corrosion and/or pitting resistance of the DSS in seawater?
How to avoid the formation of the sigma phase during welding?
Is there any procedure or heat treatment that could be done to get rid of the sigma phase from the HAZ!!
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The only way to remove sigma from the weld zone is a full solution anneal at minimum 1080C and rapid water quench. This is usually impractical for welded fabrications of complex shapes. A number of questions come to mind, How do you know that you have sigma in the HAZ? What is the geometry of the joint, how much sigma is present. An option is to carry out a fitness for purpose evaluation by quantifying the amount of sigma and what effect this has on properties. A number of successful studies have previously been carried out for modest sigma levels around 1 to 1 1/2%. Sigma itself does not reduce corrosion resistance but it is the denudation of the ferrite of Chromium and Molybdenum that locally reduces the PREN value. Sigma precipitates that form during welding are usually quite fine and do not have a large denuded area and so do not greatly affect corrosion properties. However the do still have an effect on toughness.
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We know that the formula of the Heat Input of a moving heat source in welding operation is:
Heat Input = (Voltage X Ampere X Process Efficiency)/(Weld Speed)
Is this formula is really accurate??!!
I mean should we include the material's thermal conductivity in that formula?!! Don't you think so!!
If we think in one material that has a high thermal conductivity then we should expect some heat loss in the weld pool area due to fast thermal conductivity, While in other materials with poor thermal conductivity the heat in the weld pool will be trapped and build up where the heat input from the source is the same, which means the longer weld line the higher the heat input will be created in the weld pool. In other words, the beginning of the weld line will form a weld pool with lower heat input than the end of the weld line since the amount of heat coming from the source is constant and as well as the weld speed.
What do you think?!! Please share your opinion
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An interesting questions. We can discuss it from two perspectives.
1. The line energy of welding process is defined by the equation you mentioned. It determines how many energy will be applied on the unit length of weld structure. While, the heat generation just has relationship with the heat source, which is not affected by the materials itself.
2. After the energy is loaded on material, the thermal behaviors, such as temperature variation, thermal conduction and thermal loss, are influenced by the thermal property of materials. E.g. the density and specific heat capacity determines the temperature variation. The thermal conduction is influenced by the conductivity and dT.
Indeed, when you solve the FEM formula to calculate transient temperature and its rate, the equivalent heat and thermal properties matrix are located at the two sides of equation. Both of them can affect the accuracy of thermal analysis, but they are individual with each other.
For your case, if we used a same line energy to make a long welding bead, the maximum temperature at the start and end are different. It is induced by the average temperature of the whole structure. Some Joule heat is employed to heat the material with lower average temperature at start, thereby the maximum temperature and weld pool size are lower. The situation at the end is opposite. This phenomenon is induced by the heat transfer rather than the heat generation.
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I have prepared metal joints using microwave energy. Can someone suggest on how to prepare specimen for mechanical testing and SEM/XRD/ TEM analysis? The problem is, after joining, the sample is not getting cut using wire EDM. Secondly, the joint is getting distorted/ damaged upon sample preparation through mechanical working/ machining. Please suggest a solution.
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Waterjet cutting is suitable for almost any materials, including very fragile materials such as glass and ceramics.
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I have a piece of old channel-shaped steel from the late 1800s, and I need to know if that steel is strong enough to take new loads and the type of welding that should be used. See the picture attached.
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Strengthening techniques of existing metal structures can be accomplished by shortening the span of the existing members, adding new structural members, replacing the existing structural members, post-tensioning (external prestressing) the existing members, and/or enlarging the structural member’s section by welding new reinforcing steel or by introducing composite action.
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Dear scholars,
my topic of interest is the numerical analysis of weldments with special interest in material heterogeneitiy (base material, coarse- & fine-grain-zone, filler material). For this purpose, i modeled a quarter of a 3D-butt-welded sample under displacement load. Each particular zone was modelled with specific material-data (for all in general: multilinear-plasticity; isotropic hardening), Hollomon-extrapolation was used to obtain realistic results.
The results of the numerical simulation show huge discontinuities in zones of material transition when it comes to the internal stresses (for von-Mises-stress, see the attached PDF). In my opinion, these discontinuities have their origin in the simple fact, that the nodes on the borders between two different materials can't "smooth out" the two differing material behaviours. This arises from the fundamentals of FEA and can't be "improved" by ANSYS-specific modelling steps.
Am I right with my conclusion or does anyone have any advice for me in this context? Any advice is highly appreciated. In case there are still questions, I have attached my APDL script. Otherwise don't hesitate to ask, if more information is needed.
The basic facts of my numerical approach:
- Calculation using APDL script in ANSYS
- Notch stress analysis on 2D/3D bodies
- Meshed with quadratic elements
>>> 2D: Plane183
>>> 3D: Solid186 & Solid 187
- Multilinear-plasticity material models with isotropic hardening
- Due to lack of experimental data: stress-strain diagrams of the 4 material domains from secondary source.
>>> Hollomon extrapolation already performed there
Many thanks for any help.
Timo Siemer
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Your output is a result of FEM theory, which ensures only force equilibrium at nodes and displacement compatibility across adjacent elements, but not equilibrium of stress. Given a deformed mesh, the stress in a node changes depending on whether that node belongs to one element or to the adjacent one.
In addition, it seems that yor model has a geometrical singularity (zero notch radius), where the theoretical stress is clearly infinite (whilst the FE stress is finite, no matter how fine is the mesh).
Finally, it is not clear to me the purpose of your analysis and what result you expect from it.
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I am doing research involving the characterization of MIG welded mild steel plates of 8mm thickness and one of the characterization of the weldment is its tensile strength.
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Please follow ASTM E8/E8M-21 standard in which the standard specimen size characteristics are: overall length-200 mm, gauge length-50 mm, and width-12.5 mm. If you need the pdf of the standard. Please message me your email.
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Sometimes we employ single objective optimization algorithms to solve a single objective optimization problem with a set of constraints. For explaining, if we need to optimize an engineering design problem i.e. welded beam design problem to get the optimal parameters that achieve the lowest cost, in the same situation we have limitations about other parameters such as the used metal weight, height, and width of the required shape that also needed to be achieved during the optimization process.
The important point is it better to deal with the previous engineering design problem (welded beam design) as a multi-objective optimization problem, since that we need to minimize the cost and maximize let me say the shape width or height? and is there any challenges to convert constrained single optimization problem into multi-objective?
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Hi Mohamed,
It really depends on what you want from the optimization process. You can't really say one approach is better than the other. In the realm of engineering optimization, the decision of whether to adopt single vs. multi-objective optimization is largely based on the functionality of the optimized product and it's intended audience. Most optimization objectives are conflicting. Ergo, the first task is to select important aspects you wish to optimize and reduce them as much as possible. If this reduction process results in only one objective, then that is all you need. One example is the optimization of aircraft profile for minimum air drag and minimum radar cross-section (radar susceptibility). For commercial aircrafts, minimizing drag is the only objective that needs consideration since no stealth missions are to be expected using them. The opposite can be said with military jets where both drag and radar cross-section need to be minimized and therefore a multi-objective problem is expected. A common mistake many people make is the presupposition that since multi-objective optimization involves more objectives, therefore results are more realistic. This is far from true. The choice is really problem dependent.
As to whether there are challenges converting single objective optimization processes to multi-objective, I can cite none. Researchers nowadays have the privilege to select from a number of Pareto or Non-Pareto methodologies to choose from. For a more in-depth explanation on this matter, I refer you to this video link:
Good Luck!
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All the parameters remain the same!
If Yes
What might be the reason for the same? (other than the influence of longitudinal heat flow).
If No
Can anyone suggest an article with 2D(plane stress) and 3D thermal analysis using the Goldak double ellipsoidal model in the arc welding process?
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Basicaly, both results should have the same value, if the simulation went correctly because the 2d is the simplest face of the 3d.
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FSW of dissimilar alloys or materials having various defects, therefore by doing FSP on FSW will it make helpful?
Please suggest advantages and disadvantage of above mentioned technique along with field of applications.
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Roshan Vijay Marode, yes reinforcement FSP can be done on FSW joints. Certain metals having higher thermal conductivity such as Cu in which, it will be difficult to retain the mechanical properties and microstructure just after the Friction Stir Welding, and to improve the mechanical properties by addition of reinforcement particles it can be done. In fact, this can be the solution for many applications if the results will be satisfactory. Or Depending upon the application and the requirement it can be done. The second thing FSW can not improve the wear resistance in that case also this kind of FSP can be employed. As far as dissimilar metal joining is concerned, Certainly this kind of FSP can be done which can provide metallurgical compatibility in the joints like for Cu to SS FSW, one can add Ni particles which are having compatibility with steel and Cu both respectively, Using the Ni powder the properties of Cu HAZ can also be improved using FSP. THIS IS JUST MY OPINION but I certainly favor this type of processing of FSW joints.
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I want to model resistance spot welding in ANSYS APDL. How to model heat generation, which happens in the highest amount at contact of two sheets? How to model electrical contact resistance or conductance?
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What I have suggested is the general procedure for implementing the heat generation due to contact resistance which always works. I have not gone through the coupling feature of the solid element you have mentioned. In order to know why the program is not able to implement effect of contact resistance, you will have to go through the help and 'theory manual' where they might have explained how they are considering contact resistance, if at all.
Additionally, heating also takes place due to bulk heat generated by bulk resistivity of the material and during the later part of the heating process when the contact resistance drops considerably, it is the bulk heating which generates the heat.
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I am trying to weld a K-thermocouple on a 6013 aluminium alloy sample, for dilatometry tests, but I am having a lot of problems to welding this thermocouple on the welding machine that I have on our Dilatometer from TA Instruments. The sample have 10mm of lenght and 5mm of diameter, and I have tried to weld with and without helium gas to protect the weld but we don't have sucess. How can I obtain a good thermocouple's weld in this case?
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