Welding - Science topic

Let's try to troubleshoot further. Can you please provide more details about your simulation setup: 1. What type of analysis are you running (e.g., steady-state, transient, thermal)? 2. What are your boundary conditions (e.g., temperature, heat flux, convection)? 3. What materials are you using, and have you checked their thermal properties? 4. Have you applied any mesh controls or refinements? 5. Are there any other warnings or errors in the ANSYS output? Additionally, you can try: 1. Checking the ANSYS documentation for specific guidance on temperature limits. 2. Searching online forums or communities for similar issues. 3. Reaching out to ANSYS support or consulting with an expert. Let's work together to resolve this issue!

The issue you are facing stems from the small gap between the steel pipe and the rebar and the challenges in defining the correct interaction in ABAQUS. Below is a step-by-step guide and explanation to resolve this problem:

1. Understanding the Problem

• Tiny Gap Issue: When you zoom in, the small gap (which is likely due to mesh discretization or geometry definition) prevents the tie constraint from effectively linking the steel pipe and the rebar.

• Warnings: These indicate that no nodes were adjusted to create the tie constraint, meaning ABAQUS could not establish the required interaction due to the tiny or nonexistent overlap.

2. Corrective Steps

Geometry Preparation

1. Ensure Perfect Contact:

• In the Part section, align the rebar’s position so that it touches the steel pipe precisely. Use datum points or reference geometry to ensure the rebar is positioned correctly.

• Avoid manual adjustments by ensuring the pipe and rebar geometry aligns during part creation.

2. Use Boolean Operations (Optional):

• Instead of relying on tie constraints for separate parts, you can use Boolean operations to merge the pipe and rebar into a single part (if suitable for your analysis).

Interaction - Tie Constraint

1. Modify the Tie Constraint Settings:

• Set a position tolerance in the tie constraint interaction. The default tolerance may be too small.

• Try increasing the position tolerance slightly beyond the gap size (e.g., start with 0.01 or 0.1 depending on your model units).

2. Use Adjustments:

• Enable the “Adjust Slave Surface” option to allow ABAQUS to slightly move the nodes of the rebar or pipe to bridge the gap.

3. Switch Master-Slave Roles:

• Set the steel pipe surface as the master and the rebar as the slave. This ensures that the larger element (pipe) controls the interaction.

Alternative Interaction (General Contact)

• If the tie constraint fails:

• Use “General Contact” in the Interaction module:

• Define a contact interaction with frictionless or small sliding properties.

• This can simulate a welded connection without needing precise alignment.

Mesh Refinement

• A coarse mesh might exaggerate small gaps. Refine the mesh near the pipe and rebar to improve the node alignment.

3. Simulation Workflow

1. Rebuild Geometry:

• Re-check the alignment and ensure the rebar and pipe surfaces are precisely touching.

2. Define Interaction:

• Use a Tie Constraint with a higher position tolerance or enable node adjustment.

3. Verify Connection:

• Run a preliminary simulation to confirm the interaction is working. Check the interaction outputs in the .dat file or visualization.

4. Solutions to Avoid This Issue in the Future

1. Use Reference Geometry for Alignment:

• Ensure exact positioning during the part creation phase.

2. Simplify Geometry:

• Where possible, use a single part for welded components.

3. Improve Meshing:

• Use finer meshes near interaction zones to reduce gaps.

5. Summary

The best solution for your case would be to:

1. Align the rebar and pipe accurately in the geometry setup phase.

2. Use a Tie Constraint with adjusted settings (increased position tolerance, adjust slave surface).

3. Refine the mesh near the rebar-pipe interface.

If the Tie Constraint still doesn’t work, try General Contact with appropriate settings.

Dear Dr. Alireza Nabavi ,

I suggest you to have a look at the following, interesting document:

-Metallographic Stainless Steel Etchants by PACE Technologies

Available at:

Good luck and my best regards, Pierluigi Traverso (CNR-IAS-Genoa).

I can't imagine this to be practical. We are talking about No-259 with half-life of 58 minutes, which alpha-decays to Fm-255 with half-life of 20 hours, which alpha-decays to Cf-251 with half-life of nearly 900 years, which can be considered "stable" for the intended application.

But why bother to have two alpha decays per atom (producing radiation and its associated problems), when you could start-off with Californium (Cf) in the first place? To try to answer your question: I am guessing it might be possible, but is it worth the effort?

To obtain clear metallographic photos of dissimilar metals like aluminum (Al) and titanium (Ti) with different corrosion resistances, follow these effective steps:

These methods will help you achieve clear metallographic images of both phases.

May I get your case?

Hi Ram,

It might help if you could provide some background to your question. For example:

Regards,

Simon

The main difference between 6010 and 7018 welding rods lies in their tensile strength, coating, and applications. 6010 rods have a tensile strength of 60,000 psi, a cellulose-based coating, and are known for their deep penetration, making them ideal for welding through dirty or less-prepared surfaces like pipes and structural joints. They are used primarily with DC. In contrast, 7018 rods have a higher tensile strength of 70,000 psi, a low-hydrogen coating, and produce smoother, cleaner welds, making them suited for heavy structural applications like construction and bridge work. They can run on both AC and DC and require cleaner surfaces to avoid defects.

You can simulate in SYSWELD followed by validation with the nugget size and shape. In this software, there's a feature that can indicate the percentage of phases such as Austenite, Ferrite, etc.

FYI

see attached

Is the proposal still on ?

Jiaqi Wang

Follow this approach:

1. **Use the fe-safe script interface**: Instead of relying on the GUI operations, you can use the script interface provided by fe-safe to programmatically define the welds and assign the element groups. This will allow you to create a reusable script that can be executed for batch processing.

The fe-safe script interface is typically accessible through a scripting language, such as Python or MATLAB. You can find the documentation and examples for the script interface in the fe-safe user manual or by contacting the fe-safe support team.

Here's a general outline of the steps you can follow:

a. **Initialize the fe-safe environment**: Connect to the fe-safe application and create a new analysis or open an existing one.

b. **Define the welds**: Use the script interface to define the weld locations and their properties, such as the start and end points, weld type, and associated element groups.

c. **Assign element groups to the welds**: Use the script interface to select the relevant element groups and associate them with the defined welds.

d. **Save the analysis**: After defining the welds and assigning the element groups, save the analysis to be used for the fatigue evaluation.

2. **Investigate alternative approaches**: If the script interface does not provide the necessary functionality, you could explore other options, such as:

a. **Modify the current.macro file**: Investigate if you can directly edit the current.macro file to include the necessary commands for defining the welds and assigning the element groups. This may require a deeper understanding of the file format and the available commands.

b. **Develop a custom automation tool**: Create a separate application or script that can interface with the fe-safe software and automate the weld definition and element group assignment process. This could involve using the fe-safe API or developing a standalone tool that interacts with the fe-safe GUI.

c. **Collaborate with fe-safe developers**: Reach out to the fe-safe support team or developers to understand if there are any planned or potential improvements to the automation capabilities in the software. They may have suggestions or be able to provide guidance on the best approach to achieve your desired level of automation.

Hope it helps. partial credit AI

this is my simulation

Hi Minseong,

Thank you for your reply with the explanation of the need for the strength of a tack weld.

I have worked on the structural analysis of welded joints for many years, including the use of FEA.

Will your final CAE model be made from brick elements? If yes, will you have a fine mesh that is able to predict the stress distribution in the fillet weld? And, if so, will you predict the tack failure when the peak stress (or strain) is equal to a critical value. Or, will you determine the average stress in the tack weld and compare it to the measured strength in the tests?

Also, I assume that some tack welds will experience both direct and shear loads. It seems that your testing only applies a direct load.

You might find that previous work on fillet welds would be useful, for example:

Effect of loading angle on the behaviour of fillet welds

And

Fillet and PJP welds

Regards,

Simon

Hi

You can accurately draw it in CATIA V5R21 and insert it to ABAQUS.

Use tie constrain.

See attached article

Any book chapter calls will come inform me. Thank You sir

Thank you for your answer Do you not have a solution to this problem that the temperature of the particles should decrease after welding?

Thank you for your answer Do you not have a solution to this problem that the temperature of the particles should decrease after welding?

There is detailed tutorial on COMSOL website for learners/education along with the model file and presentation. You may use the those resources Ramasastry D.V.A.

This technology is mainly used in welding non-ferrous metals with low melting temperature. Your opinion is also interesting.

The first option is more appropriate.

Qanita Tayyaba

Cut out a sample with a weld seam and polish it. Cover with adhesive plastic film to cover the welding area. Paint the rest. Explore using normal methods.

Dear Raheem:

I pay taxes in Canada.

No worries. I'll attempt to publish via Nuclear and Welding in the near future.

Sincerely

Paul Cheng

Enclose crystalline structure of what we are doing. Fine grained base to base. No HAZ.

Dear Siva,

Did you find any solution for your simulation.

Kindly share if you don't mind.

Thank you.

Regards,

Yupiter

First, the welding defects are a consequence of the interactions between the welding variables and the welding trajectory. For your Machine Learning system, you need to train the model with the relation between the values of the variables and the defects. Some defects appear as a consequence of the welding trajectory; you must analyze your process and the influence of the trajectory over the defect's apparition. To train your systems, you could implement an artificial vision system (very complicated) or a system that monitors the welding variables affected by the welding path (like current) in real time. The system will make sense if a robot performs the weldings; otherwise, you will only have a "defect predictor."

I hope this simple idea helps you to start your project.

Dear James K. McMahon Please do recommend my answer if found useful.

Additive Manufacturing (AM), also known as 3D printing, refers to a set of technologies that build three-dimensional objects by adding material layer by layer. This approach stands in contrast to traditional subtractive manufacturing methods, where material is removed to create a final product. There are several additive manufacturing processes, each with its unique characteristics. Here's a discussion of some prominent additive manufacturing processes:

1. **Stereolithography (SLA):**

- SLA is one of the earliest 3D printing techniques. It uses a liquid photopolymer resin cured by ultraviolet (UV) light to build layers. A UV laser scans the resin surface, solidifying it layer by layer. SLA is known for producing high-resolution and detailed prints, making it suitable for prototyping and creating intricate models.

2. **Fused Deposition Modeling (FDM):**

- FDM is a widely used 3D printing method that employs a thermoplastic filament. The filament is heated and extruded through a nozzle, forming layers that solidify as they cool. FDM is popular for its accessibility, cost-effectiveness, and applicability to a wide range of materials. It's commonly used for rapid prototyping and producing functional parts.

3. **Selective Laser Sintering (SLS):**

- SLS utilizes a powdered material (typically nylon, polyamide, or metal) that is selectively fused together by a laser. The build platform lowers, and a new layer of powder is spread before the laser sinters the next cross-section. SLS is known for its ability to produce strong, functional parts, and it supports a variety of materials.

4. **Selective Laser Melting (SLM):**

- SLM is a metal additive manufacturing process where a high-powered laser selectively melts and fuses metallic powder particles layer by layer. This process is particularly well-suited for producing complex metal parts with high strength and precision. It finds applications in aerospace, healthcare, and automotive industries.

5. **Electron Beam Melting (EBM):**

- EBM is similar to SLM but uses an electron beam instead of a laser to melt and fuse metal powder. The high energy of the electron beam allows for the processing of refractory metals like titanium. EBM is known for producing fully dense metal parts with good mechanical properties.

6. **Digital Light Processing (DLP):**

- DLP is a 3D printing technique that uses a digital light projector to cure a liquid resin layer by layer. It shares similarities with SLA but cures entire layers simultaneously. DLP is known for its speed in comparison to some other resin-based methods.

7. **Binder Jetting:**

- In binder jetting, a liquid binder is selectively deposited onto a powder bed, bonding the powder particles together to form each layer. The process is repeated until the entire object is created. Binder jetting is used for both metal and sand casting applications.

These additive manufacturing processes have revolutionized the manufacturing industry by enabling rapid prototyping, customization, and the production of complex geometries that might be challenging or impossible with traditional manufacturing methods. Each process has its advantages and limitations, and the choice depends on factors such as material requirements, part complexity, and intended application.

A welder needs to know the meaning of polarity and understand how it affects the welding process. Typically, electrode-positive (reversed polarity) welding results in deeper penetration. Electrode-negative (straight polarity) welding results in faster melt-off of the electrode, and therefore a faster deposition rate. Deposition rate refers to the amount of filler metal melted into the weld joint.

On the other hand, AC welding is often used with low-cost, entry-level machinery, making it a good choice for welding training. Many welders prefer it in conditions where the arc can blow side-to-side.

Understanding the Different Types of Polarity

There are three main types of polarity: direct current straight polarity, direct current reverse polarity and alternating current polarity.

Direct Current Straight Polarity

Direct current straight polarity welding happens when the plates are positive and the electrode is negative. This causes the electrons to go from the electrode tip to the base plates.

It’s generally considered that two-thirds (66%) of the entire arc heat is generated at the electrode, whereas only one-third (33%) of the heat is generated at the base plate. As a result, the electrode melts down quickly and the metal deposition rate increases (for consumable electrodes only).

On the other hand, base plates tend to not fuse properly due to a lack of sufficient heat. Therefore various defects arise, such as insufficient fusion, lack of penetration and high reinforcement. Weld reinforcement is a term used to describe metal that is needed to fill a joint.

Direct Current Reverse Polarity Welding (DC Reverse Polarity)

When the electrode is positive and the plates are negative, this results in direct current reverse polarity. The electrons switch directions and go from the base plates to the electrode. Consequently, more heat generates at the base plate as compared with DC straight polarity.

This type of welding is less likely to cause inclusion defects (nonmetallic particles trapped in the weld metal or at the weld interface) due to its arc cleaning action. It makes for faster welding and performs better for welding thin pieces of material. It’s commonly chosen for joining metals like copper, which has a low melting point.

The potential downside to this type of welding is that it has a shorter electrode life. If the speed isn’t set correctly, there is a high level of reinforcement needed. While it works great for thinner materials, this method may be ineffective for joining thick plates with higher melting points.

Alternating Current Polarity

If an AC current is supplied by the power source, reverse and straight polarity will take place one after the other. In half the cycle, the base plates will be positive and the electrode will be negative. In the other half, the electrode will be positive and the base plates will be negative.

Depending on frequency of supply, this cycle repeats 50 to 60 times per second. Some power sources also provide provisions, which can alter frequency.

AC polarity has attributes of straight and reverse polarity, since both are occurring in the same cycle. It is effective to use with most electrode types and is suitable for many different plate thicknesses, making it a great all-around choice

you could find more detailed explanation in the link below

Oleg Novikov

Уважаемый господин,

Спасибо за ваш ответ.

Не могли бы вы вкратце объяснить причину окисления и то, как это окисление приводит к увеличению концентрации хрома с фактических 12 % до 25 % в этом черном пятне.

Use the link below to request a full text from the authors:

Magnetic Pulse Welding of Tubes: Ensuring the Stability of the Inner Diameter | Request PDF (researchgate.net)

Hi Shaji,

Please see the following link for welding onto galvanized steel.

Regards,

Simon

heating it to 250 to relieve stresses or shot peening it might help .

Numerical simulation for dynamic behavior of molten pool in tungsten inert gas welding with reserved gap

Author links open overlay panel

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https://doi.org/10.1016/j.jmapro.2020.07.063Get rights and content

Abstract

A 3-dimensional transient numerical analysis model of tungsten inert gas (TIG) welding with a reserved gap was established in this study. The loss of the total heat input and change in arc pressure due to the reserved gap were considered in this model. The dynamic variations of the flow field and deformation in weld pool were analyzed. Simulated results indicate that the maximum sag of weld pool is larger, and the top surface area of weld pool is smaller as the reserved gap increases. The flow tendency of the molten metal is mainly backward, and the top surface of the weld pool is higher in the front part and lower in the rear part. The liquid metal flows from both sides to the middle, bringing heat into the gap. The liquid metal in front of the weld pool flows to the back of weld pool through the gap, which facilitates weld penetration.

Introduction

TIG welding, a critical joining technique in modern manufacturing, has the advantages of high arc stability, low cost, and good weld formation; it is widely used in the welding process of important components, such as pressure vessels and pipes [1]. The technology of one-side welding with back formation is needed in producing important sheet welding structures or in environments with limited back working space. A gap is typically required in welding processes that use one-side welding with back formation technology, and such a gap is an important condition to achieve penetration and good back formation [2]. However, ensuring gap uniformity during welding is difficult due to assembly errors and thermal deformation. The dynamic behavior of fluid flow and the distribution of temperature field directly affect the penetration and shape of the weld. Therefore, the effect of gap on welding temperature field and flow field is very important for high-quality butt welding. It is difficult to completely and accurately obtain the temperature distribution and fluid flow of weld pool by experimental means. Numerical simulation contributes to reveal the influence mechanism of the gap on the dynamic behavior of the molten pool flow field and the penetration, which has a certain theoretical guiding significance for the process optimization and penetration control of reserved gap butt TIG welding.Meanwhile, heat source is an important factor in determining molten pool behavior in numerical simulation. Eager and Tsai [3] established a Gaussian heat source model to approximately characterize heat flux density of the spot heated by the arc on the workpiece. They theoretically predicted the molten pool, which was in good agreement with reality. Goldak et al. [4] established a double ellipsoidal heat source model, in which the source of the heat is improved. The Gaussian and double ellipsoidal heat source models are commonly used to study weld pool behavior in TIG welding. Given that the numerical simulation requirements for special welding processes are continuously improving, a combined-type welding heat source model is considered an ideal option and must thus be developed. Han et al. [5] used three types of combined heat sources to simulate the temperature field of the K-TIG welding process. They found that the temperature field obtained from the combined heat source of double ellipsoidal heat source and three-dimensional Gaussian heat source was in line with the actual situation. However, no reserved gap was considered in those heat models.Fluid flow has close relation to forces in the weld pool. Oreper et al. [6] analyzed the TIG welding pool of a fixed arc and established a corresponding two-dimensional axisymmetric mathematical model while considering electromagnetism, surface tension, and buoyancy. Kou et al. [7] built a three-dimensional quasi-steady-state model in the moving arc TIG welding and analyzed the convection in the molten pool. Fan et al. [8] settled the irregular molten pool boundary and liquid–solid interface through boundary matching coordinates and analyzed the fluid flow and temperature field of full-penetration weld pool in TIG welding via numerical calculations. Zhao et al. [9] established a 3D transient numerical analysis model of TIG welding to calculate the evolution of weld pool during welding, and analyzed the forces in the weld pool and proposed a criterion for full penetration. Based on this study, Zhao et al. [10] developed a simulation model of a weld pool in full-penetration state, calculated the dynamic changes in the forces acting on the molten pool, and analyzed the percentage of each component of the slump and support forces. Meanwhile, Xu et al. [11] calculated the flow field of the molten pool of TIG and A-TIG via numerical simulation. Their results showed that the active agent changed the surface tension gradient which, in turn, caused the molten metal flow pattern to change, resulting in a strong eddy current and an increased penetration depth. Han et al. [12] established a 3D model of TIG welding and discussed the effects of buoyancy, arc pressure, drag force, and Marangoni force on the formation and molten pool flow behavior. They concluded that the Marangoni force is the main driving force, whereas the effect of buoyancy is the smallest in TIG welding. Huang et al. [13] analyzed the molten pool flow behavior during GTAW welding by high current through particle tracking technology. They reported that the molten metal is affected by complex driving forces during the flow process. Furthermore, the liquid metal at the centerline diffuses to both sides of the weld pool, and the surface molten metal performs a more complex rotating motion inside the molten pool during the forward-to-back movement.The inevitable surface deformation of weld pool has been explored by some researchers. Kong et al. [14] simulated the temperature field and fluid flow in TIG welding pool and the change in free surface by using Cast3M software. They predicted the shape and dimension of the weld pool. Traidia and Roger [15] studied the arc and weld pool behavior of pulsed current GTA welding on the basis of a unified model and found changes in the free surface at the bottom and top of the molten pool through force balance equations. Li et al. [16] established a unified model of GTAW using static equilibrium and dynamic mesh technology and then analyzed the effect of interface deformation on the shape of the weld pool. Pan et al. [17] proposed a 3D model to explore the weld pool behavior as well as weld shape in high-speed VP-GTAW. They found that the outward flow mode of the molten metal under surface tension is the main flow, and the counterclockwise cycle at the middle area of the molten pool is driven by electromagnetic force. Meanwhile, the weld pool surface was deformed due to the driving of arc pressure. Huang Yong et al. [18] built a three-dimensional transient TIG welding pool numerical model and tracked the free surface deformation in the weld pool using the volume-of-fraction (VOF) method. They observed the deformation behavior of the weld pool surface and the distribution of its heat transfer and velocity field under the independent actions of buoyancy, Marangoni force, electromagnetic force, and arc pressure under high current. Meng et al. [19,20] established models of arc heat flow, arc shear stress, arc pressure, and electromagnetic force on the basis of the physical characteristics of the large surface deformation of the weld pool in high-current and high-speed TIG welding. The results indicated that the arc shear force mainly promoted the free surface deformation in weld pool, which was inhibited by surface tension. All the above-mentioned studies examined gap-free welding and did not consider a reserved gap.Cho et al. [21] carried out three-dimensional transient numerical simulations of multiple welding positions during GMAW with and without gaps in the V-shaped groove, after which they analyzed the weld pool flow patterns at different welding positions. The simulation results showed that forming a fully penetrated weld in a flat position proved to be very difficult when welding thick plates without reserved gaps. Cho et al. [22] used computational dynamics to study the weld pool dynamics in laser keyhole welding with gap-preserved butt welding, in which the diameter of the wire is larger than the gap. Their results showed that when keyholes are present, the momentum at the rear of weld pool area is considerably reduced compared with the momentum at the front. However, the above-mentioned studies ignored the effect of the butt gap on the heat source distribution and liquid metal flow.In this study, a 3-dimensional transient numerical model of the TIG welding pool with a reserved gap was developed considering the influence of this gap on the arc thermal-mechanical distribution. The simulation was carried out on FLUENT software to analyze the characteristics of temperature and flow fields in the molten pool. The established model was validated by comparing the experimental data with the calculated results. Our findings help provide a deep understanding of the process of TIG welding with a reserved gap.

Section snippets

Mathematical models A schematic of the geometric model for TIG welding with reserved gap is shown in Fig. 1. As the weld pool behavior during the welding process involves extremely complex heat and mass transfer phenomena, these are difficult to consider completely in the mathematical model. On the premise of ensuring the calculation accuracy, the following basic simplifying assumptions are followed in the mathematical modeling process to effectively reduce the calculation time and the cost: (1)The molten metal flow

Simulation and verification of the welding process Based on the mathematical model established above, a numerical simulation of the TIG welding process with a reserved gap was performed in this study. The Q235 low-carbon steel was applied as base metal, and the reserved gap was 0.6 mm. Table 1 shows the specific parameters of the TIG welding process.The size of the calculation domain was set at 20 mm × 8.3 mm × 4 mm. The geometric model was initialized using FLUENT software. The initialization conditions are as follows:

The average

Conclusion (1)A 3-dimensional transient numerical analysis model of TIG welding with a reserved gap was established in consideration of the effect of gap and the deformation of free surface on the arc heat-force distribution during welding. The simulated data show favorable agreement with the experimental results. Moreover, the proposed model can reasonably and accurately reflect the dynamic changes in the molten pool. (2)The gap has a great influence on the arc heat-flow distribution. Before fusion, the arc

Funding This work was supported by the National Natural Science Foundation of China (No.51675309)

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements This work was financially sponsored by the National Natural Science Foundation of China (No. 51675309).

References (22)

Cited by (13) The role of asymmetric metal flow on weld formation and solidification characteristics during pulsed laser butt welding with assembly tolerance 2024, International Journal of Thermal Sciences

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Dear friend Charles Edward Rowe

Now, let's delve into the world of welded aluminum joints, comparing the strengths of friction and fusion processes.

1. **Strengths:**

- **Solid-State Process:** Friction welding is a solid-state welding process, meaning there's no melting of the material. This often results in joints with fewer defects and better mechanical properties.

- **Versatility:** It's versatile, applicable to a variety of materials and geometries.

- **No Filler Material:** No filler material is required, which can simplify the process.

2. **Considerations:**

- **Material Compatibility:** While versatile, the compatibility of materials is still a consideration. Some materials may not weld well together.

- **Equipment Costs:** Initial equipment costs can be relatively high.

**Fusion Welding:**

1. **Strengths:**

- **Widely Used:** Fusion welding methods, such as TIG and MIG, are well-established and widely used.

- **Good for Thin Sheets:** Fusion welding is often preferred for welding thin sheets.

2. **Considerations:**

- **Heat-Affected Zone (HAZ):** Fusion welding involves melting, which can create a heat-affected zone. This zone might have different properties than the base material.

- **Filler Material:** Depending on the process, filler material may be needed.

**7000 Series Aluminum:**

1. **Challenges with Fusion Welding:**

- **Hot Cracking:** Fusion welding of 7000 series aluminum can be challenging due to issues like hot cracking.

- **Precipitation Hardening:** These alloys are precipitation hardening, and the high temperatures involved in fusion welding can affect the alloy's properties.

2. **Advantages of Friction Welding:**

- **Reduced Heat Input:** Friction welding's solid-state nature reduces the heat input, potentially avoiding some of the issues associated with fusion welding.

**Testing and Evaluation:**

1. **Tensile Strength:** Tensile testing can reveal the maximum stress a material can withstand.

- **Fusion:** Tensile strength may vary due to the HAZ.

- **Friction:** Generally good tensile strength due to the solid-state nature.

2. **Microstructural Analysis:** Examining the microstructure can reveal the impact of the welding process on the material.

3. **Fatigue Testing:** Especially relevant for structural applications where cyclic loading is expected.

Remember, while I strive for accuracy, real-world application may vary. For precise data on your specific aluminum alloys and welding conditions, testing and consultation with experts in materials science and welding engineering are essential. Go forth and conquer that aluminum research! 🚀

Yes, merging can be considered as welding. Another interaction is "Tie" that you can use it for.

our consideration of the mushy zone at the boundary of the molten pool is valid, and the choice of temperature threshold for marking a grid cell as part of the weld region depends on the specific objectives of your numerical simulation and the physical characteristics of the welding process you are modeling.

Here are some perspectives on the temperature threshold choices:

In conclusion, there isn't a one-size-fits-all answer, and the choice of temperature threshold should align with the specific goals of your simulation and the physical characteristics of the welding process you are modeling. It might be worthwhile to experiment with different thresholds and validate your results against experimental data or established benchmarks in the field.

The greater the temperature gradient in the component during welding, the greater the residual stress. This means that welded components must be as hot as possible before welding. It would be optimal to weld on a component that is so hot that it is about to melt. In this case the residual stress would be zero. Of course, in practice the preheating of welded parts cannot be carried out to such a high level, but in any case it must be as high as possible. In this sense, welding with extreme cooling is pure nonsense. If preheating is not possible, the residual stress can be reduced by subsequent annealing.

Al4043 will be a better option. I have performed welding of Al6061T6 with this filler wire in the MIG process and it worked fine.

Dear friend Md Marjan Jahan Tazin

Hey there, fellow researcher! I am here to dive into your question with unbridled enthusiasm.

Yes, it's absolutely possible to join dissimilar metals using MIG (Metal Inert Gas) welding. Your approach of interlayering thin metal foils between low carbon steel and aluminum is quite interesting. Let me share some insights and possible outcomes:

1. **Metallurgical Challenges:** Joining dissimilar metals like steel and aluminum can be challenging due to their vastly different melting points and thermal conductivity. However, the use of thin foils and precise control in MIG welding can help mitigate some of these challenges.

2. **Intermetallic Compounds:** When two dissimilar metals are joined, intermetallic compounds may form at the interface. The composition and properties of these compounds can impact the joint's strength and performance. It's essential to carefully study and characterize these compounds.

3. **Possible Outcomes:** The success of your joint will depend on factors like the welding parameters, interlayer material, and the quality of the welding process. If done correctly, you can achieve a strong, reliable joint with acceptable mechanical properties.

4. **Testing:** Once you have your joints, testing is a crucial step. Tensile testing will assess the joint's strength under tension, while fatigue testing will determine its endurance under cyclic loading. These tests will provide valuable data on the joint's performance and durability.

5. **Applications:** If your research yields positive results, the applications could be numerous. Joining dissimilar metals is often required in industries like aerospace, automotive, and construction, where you need lightweight structures with high strength.

Remember, research is all about exploration and discovery. Embrace the challenges, meticulously document your process, and don't shy away from experimentation. Your work could potentially lead to innovative solutions in the field of dissimilar metal welding. Best of luck, and may your research yield exciting outcomes!

Dear Koen,

it will interesting to compare the flash formation during friction welding of another materials of tribopair having low and high ductility in the same regime of this technological process.

All the best,

Serge

Dear doctor

"THE MAIN CHARACTERISTICS OF ALUMINUM AND ITS ALLOYS

Aluminum is a multifaceted material with multiple uses, including as a matrix metal for composites. It has a silvery white appearance and is used as either a pure metal or as an alloy. It is extremely light and just small amounts of alloying elements can increase its strength. It is also highly resistant to corrosion. This is due to a passive film of aluminum oxide that is intimately connected to the surface and capable of renewing itself spontaneously when the surface is damaged. Aluminum’s other significant properties include its high heat conductivity and easy formability – either by casting, hot or cold working or machining – as well as its neutral taste and non-toxicity. Common uses of aluminum or its alloys:

THE PRODUCTION OF ALUMINUM

Economical extraction of aluminum is only possible from bauxite. The production process involves two basic steps. Extraction of pure alumina Alumina recovery begins by crushing and finely grinding the bauxite and heating it with sodium hydroxide under pressure. In this process, a water-soluble sodium aluminate is formed together with undissolved residues of iron, titanium and silicon. ‘Seed crystals’ of fresh aluminum hydroxide are added to initiate the precipitation of pure aluminum hydroxide (Al(OH)3). Through calcination at 1200 °C, the water is then removed and pure anhydrous alumina (aluminum oxide) remains. Converting alumina to aluminum (the Hall-Heroult process) The reaction chemistry of pure alumina requires an electro-chemical process to extract aluminum from its oxide. As the melting point of aluminum oxide is very high (2050 °C), it is mixed with cryolite to reduce the melting point. Electrolysis takes place in a large carbon or graphite lined steel container that contains steel rods for conducting electricity and carbon blocks as anodes. During electrolysis, the carbon of the anode reacts with the oxygen of the alumina and, in a secondary reaction, metallic aluminum is produced with the formation of carbon dioxide: 2Al2O3 + 3C → 4Al + 3CO2. This process produces aluminum of 99-99.9 % purity. Much of this is used for aluminum alloys.

ALUMINUM ALLOYS

Adding very small amounts of alloying elements to aluminum can increase tensile strength, yield strength and hardness compared to pure aluminum. The most important alloying elements are Si, Mg, Cu, Zn and Mn. These mostly eutectic compounds must be finely dispersed through a hot working process before the alloy can be cold worked. Ageing of aluminum alloys Many aluminum alloys are age hardened to improve the mechanical properties. This can be done either naturally or artificially.

PREPARATION OF ALUMINUM AND ITS ALLOYS: MECHANICAL GRINDING & DIAMOND POLISHING

When working with aluminum and its alloys, we recommend mechanical grinding, followed by diamond polishing. For many pure aluminum and wrought alloy specimens, electrolytical polishing is also recommended.

Mechanical grinding

Plane grinding should be carried out with the finest possible grit to avoid excessive mechanical deformation.

Diamond polishing

Diamond polishing should be carried out until all deep scratches from grinding have been removed. If water soluble constituents must be identified, we recommend polishing with water-free diamond suspension and lubricant.

ETCHING OF ALUMINUM AND ITS ALLOYS

When working with aluminum and its alloys, macro etchants are used for grain size evaluation, also to show flow lines from extrusion and to reveal weld seams. Before etching, the specimen has to be ground with 1200# SiC Foil or 2400# SiC Foil. Due to the many alloying possibilities of aluminum, the different phases cannot always be clearly identified in some of the multi-component alloys. However, the eutectic phases can sometimes be recognized by the typical shape of their eutectic. Some of the well-known phases have the following characteristic colors:

Etching solutions

When working with chemicals the standard safety precautions must be observed.

Aluminum cast alloys are polished relatively easily. For grain size evaluation, anodizing with Barker’s reagent will result in a better contrast than chemical etching. Different phases in cast alloys can either be identified by their characteristic color or by etching with specific solutions that attack certain phases preferentially."

Dear Janusz Rebis

Your response, "Better do not :) But all is possible if you want to spend a lot of cash," is somewhat in line with the practical considerations I mentioned in my previous answer. While it may be technically possible to convert an arc welding machine into a TIG welding machine with the addition of inert gas, it would indeed require significant modifications and expenses. Here's a justification for the Janusz Rebis response:

1. Cost of Modifications: Converting an arc welding machine into a TIG welding machine would involve replacing or modifying the power supply to provide a constant voltage output. This could require rewiring and purchasing additional components, which can be expensive. Furthermore, the necessary changes to the control circuitry, gas flow system, electrode configuration, and other components would also contribute to the overall cost.

2. Expertise and Labor: Converting an arc welding machine into a TIG welding machine is a complex task that requires expertise in electrical engineering, welding processes, and control systems. It would likely require the involvement of skilled professionals to ensure the modifications are done correctly and safely. The cost of their labor would further add to the overall expenses.

3. Reliability and Performance: Converting a welding machine from one process to another may compromise the reliability and performance of the equipment. Arc welding machines are specifically designed and optimized for arc welding processes, while TIG welding machines are tailored for TIG welding requirements. Modifying an arc welding machine to perform TIG welding may result in suboptimal performance, reduced efficiency, and potential issues with weld quality and consistency.

4. Availability of Dedicated Equipment: Dedicated TIG welding machines are readily available on the market and are designed specifically for TIG welding applications. These machines come with the necessary features, controls, and capabilities to ensure efficient and reliable TIG welding. Investing in a purpose-built TIG welding machine would likely provide better results, increased productivity, and long-term cost-effectiveness compared to attempting to convert an arc welding machine.

In summary, while it might be technically feasible to convert an arc welding machine into a TIG welding machine with the addition of inert gas, the associated costs, expertise, potential reliability issues, and the availability of purpose-built TIG welding machines make it more practical to invest in dedicated equipment.

Generally, there are three deposition paths used in WAAM: single pass, parallel pass, and oscillated pass. However, there are minor changes between these strategies, the oscillated pass shows a bit better performance in terms of hardness value. You can find better discussion in :

I would guess that it is to do with 2D and 3D cooling and there are equations available to be able to calculate this.

Thank You Sir for your valuable answer.

Sounds good

Thank you for taking the time to explain your technical answer.

Many thanks Joshua I really appreciate your answer

Activated flux in A-TIG welding is a granular mineral material that is melted by the heat of the arc and provides a layer of shielding gas to protect the weld. Unlike submerged arc and flux-cored arc welding, the flux in A-TIG welding is not pre-mixed with the welding wire as it is in these processes, so it must be separately fed into the weld pool. In addition, the flux used in A-TIG is typically more active, which means it releases greater amounts of gas to provide a more stable arc and a higher quality joint.

In Abaqus software, imperfections can be defined using the "perturbation" feature. The perturbation feature allows you to introduce small geometric imperfections into your model and to analyze their effect on the structural response. The perturbation can be defined as a displacement or a rotation in one or more directions at a specific location on the model.

To define imperfections as an equation in Abaqus, you can use the expression language in the perturbation feature. The expression language allows you to specify the magnitude and direction of the perturbation using mathematical expressions. For example, to introduce a sinusoidal imperfection in the z-direction, you can use the following equation in the perturbation feature:

AMPLITUDE*sin(2*pi*x/WAVELENGTH)

Where AMPLITUDE is the magnitude of the imperfection, WAVELENGTH is the wavelength of the sinusoidal imperfection, and x is the coordinate along the direction of the imperfection.

You can also use other mathematical functions and operators in the expression language to define imperfections, such as exponential functions, trigonometric functions, and logical operators.

It is important to note that the definition of imperfections in Abaqus should be based on the specific imperfection that is relevant to your analysis and should be validated against experimental or analytical data if possible. Additionally, it is recommended to perform sensitivity analyses to investigate the effect of different imperfection magnitudes and locations on the structural response.

The main reason for the lack of weldability of HDPE (High-Density Polyethylene) geomembrane is its high crystallinity and low surface energy. Because of its high crystallinity, HDPE has a low amorphous phase which results in low chain mobility and makes it difficult to melt and fuse together during welding. Additionally, the low surface energy of HDPE makes it difficult for the melted material to form strong bonds during welding.

Processing aids are added to HDPE geomembranes to improve their processing and end-use properties. One of the most common processing aids used in HDPE geomembranes is a group of materials known as slip agents. Slip agents are typically long-chain fatty acid amides that help to reduce the coefficient of friction and improve the slip properties of the HDPE geomembrane.

The addition of processing aids such as slip agents can have a significant effect on the weldability of HDPE geomembrane. Slip agents can reduce the surface energy of the HDPE, which can make it more difficult to achieve a strong bond during welding. However, research has shown that the use of slip agents at low levels (<1%) can have a positive effect on the weldability of HDPE geomembranes by reducing surface roughness and increasing the contact area during welding.

In general, the weldability of HDPE geomembranes can be improved by optimizing welding parameters such as temperature, pressure, and welding speed, and by using appropriate welding techniques such as hot wedge welding or extrusion welding. Additionally, surface preparation techniques such as cleaning and roughening the surface of the geomembrane prior to welding can also improve weldability.

AWS A7018 is a low hydrogen, iron powder, all-position, cellulosic electrode. It has great arc stability, good tie-in, and a low spatter level. This electrode is commonly used for general purpose welding and requires low-amperage, low heat input due to the low melting temperature of the electrode. This weld rod is typically used for welding low to medium strength steel structures, such as steel plate, rail cars, pipe, tanks, and skeletal structures.

Maximum penetration depth could be possible following different parameters.

Conventional TIG weld maximum of 3.5 mm in single pass, but it can penetrate upto 5 mm in carbon steel. New approach ATIG may allow upto 8 cm -10 cm.

Ashish

The presence of a tunnel or unfilled groove in a dissimilar Al/Mg joint during welding can have several potential causes. Here are a few possibilities:

It's important to note that without more specific information about the welding process and parameters used, it's challenging to pinpoint the exact cause of the unfilled groove. Consulting with a welding expert or metallurgist who can evaluate the specific conditions and examine the joint would be beneficial for a more accurate analysis.

May be you could look here :

The Resistance Spot Welding (RSW) process has several important problems that can be both experimental and analytical in nature. Some of the most significant issues include:

As far as welds go the strength of the weld metal can be lower than base metal referred to as "under matched" , or like wise matched or over matched depending on application.

Mismatch to any degree is crack initiator or reduces ductility - including carbides in steel. The 10% mismatch marginally better that 40% but no were near the required < 1% - on the order of small thermal expansion differences that the base metal can clearly handle without cracking.

Hi Dear Daniel Guerrero

I recommend listing all indications of Hot cracking so you can separate them easily.

According to J.C. Lippold's welding metallurgy book: DDC are formed in materials with FCC crystal structure along MGBs.

I want to emphasize on MGBs (Migrated grain boundaries). DDC is always formed along MGBs.

It is one of the ways to identify.

a good article about MGBs: researchgate.net/publication/364226201_Migration_of_solidification_grain_boundaries_and_prediction

Best regards

You need to kill the model in advance, activate the units sequentially depending on the load step

Hi,

ALE (arbitrary lagrangian eulerian) is solution for the model may encounter the high distortion element problem.

This approach switches between lagrangian mesh and eulerian mesh, if necessary.

This feature is available in ABAQUS.

Go to youtube and find many handy tutorials in this regard.

In the case of a T22 ferritic steel, we are in the domain of creep resisting CrMo steels which are not stainless steel types. In the present case, cracks appearing in the HAZ are more than probably cold cracks. Those cracks are caused by transformation of the original ferritic structure into Martensite inside the HAZ. In the presence of diffusible monoatomic Hydrogen and residual stresses, cracks may appear in this HAZ. As the development of cracks depend essentially to the simultaneous existence of these 3 conditions, it is possible to eliminate 1 of these 3 conditions to avoid the cracking occurence. Most of the time, a redrying of the welding consumables (in case of stick electrodes or submerged arc flux) and the use of a preheat (say 150°-200°C) of components to be welded followed by a slow cooling after weld completion are sufficient precautions to get a joint without crack in the HAZ.

Hope this might be helpful.