Friction - Science topic

Having gotten the EW for each of them. Next, convert the volume fraction to the wt. fraction. Multiply each EW by their corresponding wt. fraction in the composite. Finally, Add the resulting answers together to give you the EW of the composite.

Dear Mr Xiang Yu,

During my research I have noticed that undrained steady state friction angle represents the uppermost condition any granular soil can withstand. Therefore, it shall correspond to the friction angle at the densest condition of the granular soil. I have reached such explanation analyzing several sands with different grain shape and hardness as well as with diverse grain size distributions.

A very important and well known aspect is that all specimens reach the same steady state friction angle independently of the soil response to undrained shear, i. e., contractive, partly contractive or dilative. Thus, final soil fabric must correspond to a unique common condition which control the maximum shear the soil can support. Note that this means that, as shearing progresses beyond the peak value, soil fabric changes to approach that final condittion. Note also that, it does not mean that residual strength has to be grater than peak strength just for being allocated on the uppermost envelope of the soil. It, certainly, does not apply for contactive specimens but may occur for partly contractive and certainly happens for dilative samples due to the "climbing" effect along the steady state envelope which generates soil dilation and negative pore pressures.

I have also found that peak friction angle does depend on soil fabric at the relative density sample is prepared (initial shearing condition), so peak envelopes project on the e - p' plane associated with conventional volume change (consolidation) curves. However, steady state envelope projects on that same plane with a very different slope. Thus, the relative position of the sample at the end of consolidation respect to the steady state envelope projection on that same plane determines sample behaviorior, i. e., contractive if located at the rigth of the projection and far, partly contractive if on the right but close or dilative, if on the left side, respectively, as suggested by Casagrande.

My email address is hechezur@ucab.edu.ve in case you would like to share more information regarding this interesting topic. Best regrads

To simulate rainfall-induced slope failure in ABAQUS without using a subroutine, an indirect approach is required by modeling the effect of rainfall through pore pressure changes and soil property adjustments. The first step is to define the slope geometry and mesh, ensuring finer elements are used in the expected failure zone. The soil properties should be assigned using an appropriate constitutive model such as Mohr-Coulomb or Drucker-Prager, including parameters like cohesion, friction angle, density, Young’s modulus, and Poisson’s ratio.

After defining the material properties, an initial geostatic stress condition is applied by using gravity loading to establish in-situ equilibrium. This ensures that the slope is stable before the effects of rainfall infiltration are introduced. The rainfall effect is simulated through the application of time-dependent pore pressure boundary conditions. This can be achieved by increasing the pore pressure at the slope surface in a stepwise manner to represent infiltration while maintaining appropriate drainage conditions at the base.

A coupled pore pressure-displacement analysis is used to observe how the infiltration influences the slope stability over time. The permeability properties of the soil must be carefully defined, differentiating between saturated and unsaturated conditions to accurately model water flow. Strength reduction can be introduced by progressively reducing cohesion and the friction angle of the soil, allowing for the identification of the critical point at which slope failure occurs.

During post-processing, the results should be analyzed by monitoring pore pressure distribution, displacement contours, and shear strain localization to assess failure patterns. The factor of safety can be estimated using the strength reduction method by identifying the point of excessive displacement or large deformations. An alternative approach for advanced simulations is the use of the Coupled Eulerian-Lagrangian (CEL) method to capture rainfall-induced soil erosion, although this requires a more complex setup and computational effort.

By implementing these steps, it is possible to model the impact of rainfall on slope stability within ABAQUS without relying on user-defined subroutines.

Dear Umedjon Juraev ,

This article focuses on the modeling of two-wheel mobile robot with differential chassis, which is moving in the plane. According to the application, it can be modeled with different accuracy levels depending on structural limits and other physical impacts. Main goal of this article is to include the effects of friction into the mobile robot dynamics. Four basic models of friction are combined into generalized model, which is then implemented as single Simulink block and added to model of mobile robot.

Regards,

Shafagat

trump's economic approach is expected to focus on tax cuts, deregulation, and prioritizing "America First" policies to boost domestic growth and job creation.

Hello, Andira Essa. Please check your boundary conditions to ensure they are properly defined and play with CDP model parameters, especially damage factors and viscosity. Finally, try using different mesh sizes for your element. I hope it helps.

Regards,

Sandeep Gharti Magar

additionally to what said by Naveem Kumar, it looks like a Stick-Slip behaviour due to the high pressure where the two bodies will repeatedly stick together. The high contact pressure and roughness can have an influence on this behaviour.

Ensure sure that the material for which you are changing the properties is the one assigned to the structure being analyzed.

And just to add: For a linear static analysis, Young's modulus and the Poisson's ratio are the two material data that will likely influence the "Total Deformation". So, you should probably just limit your variations to those.

Not possible

To answer this we need some more info about the system: what Re range is involved: if laminar flow occurs it must be below 10,000 i.e. in the transitional or laminar field. For pure turbulent flow the resistance of an obstacle can be written in terms of velocity heads lost and that is a usually a constant value over a wide range of Re. The drag at low Re is often solved by "creeping flow" modelling, but the change when turbulence develops is marked. What is the geometry of the bluff bodies involved?

May I get your case?

Dario Colorado-Garrido There is little real difficulty in calculating the pressure drop for steam in any pipe, provided the diameter is accurate and roughness known: it is much more difficult in the superheater itself as temperature changes can be large and flow distribution difficult.

There are even graphical methods that are accurate for pipework. Would be good to know what problem you foresee.

Thanks for your answer Emir Nezirić . I already tried this solution with the script below, but the computation time has exploded...

This script creates, for each iteration, a contact between a random number of nodes of the upper part and the surface of the lower part (with a random friction coefficient).

In this case, I considered between 15 and 50 nodes of the upper part for each contact created.

With this range, around 10 contacts are created.

import random

model = ExtAPI.DataModel.Project.Model

#Nodes in contact of the upper body

IDs = [i for i in range(9780,10167)]

x=0

limite=0

limiteNM1=0

count = 0

for i in IDs:

mu = random.uniform(0.8, 1)

nbNodes = random.randint(15, 50)

limite += nbNodes

newContact=model.Connections.AddContactRegion()

newContact.ContactType=ContactType.Frictional

newContact.FrictionCoefficient = mu

newContact.DynamicCoefficient = mu

newContact.Behavior = ContactBehavior.Asymmetric

newContact.ContactFormulation=ContactFormulation.NormalLagrange

if limite > len(IDs):

limite = len(IDs)

#Creation d'une named selection contenant des noeud

ns = Model.AddNamedSelection()

ns.ScopingMethod=GeometryDefineByType.Worksheet

Criteria = ns.GenerationCriteria

Criteria.Add()

Criteria[0].Action = SelectionActionType.Add

Criteria[0].EntityType = SelectionType.MeshNode

Criteria[0].Criterion = SelectionCriterionType.NodeNumber

Criteria[0].Operator = SelectionOperatorType.RangeInclude

Criteria[0].LowerBound = IDs[limiteNM1]

Criteria[0].UpperBound = IDs[limite-1]

ns.Generate()

#Verif contact

contact = ExtAPI.DataModel.GetObjectsByName(model.NamedSelections.Children[x+1].Name)

if contact:

newContact.SourceLocation = contact[0]

target = ExtAPI.DataModel.GetObjectsByName('bas')

if target:

newContact.TargetLocation = target[0]

x = x+1

for i in range(limite-limiteNM1):

ligne = [i, mu]

muVector.append(ligne)

limiteNM1 = limite

break

elif i == IDs[0]:

#Creation d'une named selection contenant des noeud

ns = Model.AddNamedSelection()

ns.ScopingMethod=GeometryDefineByType.Worksheet

Criteria = ns.GenerationCriteria

Criteria.Add()

Criteria[0].Action = SelectionActionType.Add

Criteria[0].EntityType = SelectionType.MeshNode

Criteria[0].Criterion = SelectionCriterionType.NodeNumber

Criteria[0].Operator = SelectionOperatorType.RangeInclude

Criteria[0].LowerBound = IDs[limiteNM1]

Criteria[0].UpperBound = IDs[limite-1]

Criteria.Add()

Criteria[1].Action = SelectionActionType.Add

Criteria[1].EntityType = SelectionType.MeshNode

Criteria[1].Criterion = SelectionCriterionType.NodeNumber

Criteria[1].Operator = SelectionOperatorType.Equal

Criteria[1].Value = 9392

ns.Generate()

ExtAPI.DataModel.Tree.Refresh()

#Verif contact

contact = ExtAPI.DataModel.GetObjectsByName(model.NamedSelections.Children[x+1].Name)

if contact:

newContact.SourceLocation = contact[0]

target = ExtAPI.DataModel.GetObjectsByName('bas')

if target:

newContact.TargetLocation = target[0]

x = x+1

for i in range(count, count+nbNodes):

ligne = [i, mu]

muVector.append(ligne)

limiteNM1 = limite

count = count + nbNodes

else:

#Creation d'une named selection contenant des noeud

ns = Model.AddNamedSelection()

ns.ScopingMethod=GeometryDefineByType.Worksheet

Criteria = ns.GenerationCriteria

Criteria.Add()

Criteria[0].Action = SelectionActionType.Add

Criteria[0].EntityType = SelectionType.MeshNode

Criteria[0].Criterion = SelectionCriterionType.NodeNumber

Criteria[0].Operator = SelectionOperatorType.RangeInclude

Criteria[0].LowerBound = IDs[limiteNM1]

Criteria[0].UpperBound = IDs[limite-1]

ns.Generate()

ExtAPI.DataModel.Tree.Refresh()

#Verif contact

contact = ExtAPI.DataModel.GetObjectsByName(model.NamedSelections.Children[x+1].Name)

if contact:

newContact.SourceLocation = contact[0]

target = ExtAPI.DataModel.GetObjectsByName('bas')

if target:

newContact.TargetLocation = target[0]

x = x+1

limiteNM1 = limite

count = count + nbNodes

Jeff Sokoloff has articles in this topic.

An incommensurate intermediste layer will lower friction.

Cristhian, what version of the Anton Paar software are you using? It seems to me that is RheoPlus. Not RheoCompass, am I right on it? Usually, the software itself made all calculations, showing you Stribeck curves, with the friction coefficient as a function of sliding distance OR sliding speed. Look below. Vs in [m/s] as you want. Good luck, Antonio Bombard

Himanshu Sharma Can you share your Abaqus model (.inp)?

See attached article

Hajar Rhylane Can you share your Ansys model in .cdb format?

please dear Ankush Pratap Singh , did you find an answer to this?

In this case the tribotest is performed at prescribed level of pressure

To obtain the friction velocity (u*) and scaling humidity (q*) values for calculating the transfer coefficient for latent heat (Cez), you typically need to measure the shear stress at the surface for u* and calculate it using the air density. For q*, calculate it using the latent heat of vaporization, specific heat capacity of air, and temperature. These values are crucial for determining the transfer coefficient for latent heat in atmospheric boundary layer studies.

Maciej: The short answer to your question is no (as far as i know). The main challenge is defining a proper length scale in Re, and the sensible solution is to use some hydraulic diameter for internal flows, and the local position for external flows (flat plates, aerofoils, tubes etc). The main thing is that Re in some way should relate to the boundary layer thickness, which can be difficult (This is why the Nu and Cf for developing flows must be corrected with a d/L-expression for internal flows). Some attempts have been made at using the momentum thickness as length scale, which has showed some success in estimating the transition to turbulence.

Hello!

It is a bit hard to answer your question without more context. Nonetheless, if the strain on the metal surface doesn't match the experimental values, then I would assume that either your contact definition or the friction coefficient between the two surfaces is not correct. However without more information it is difficult to provide more assistance.

I am curious, how did you measure the strain on the surface experimentally? And did you measure the fiction coefficient between those two surfaces experimentally?

hardness of DLC coatings depend, among other things, on its hydrogen content. With hydrogen in the range of 15-20at% hardness can be in the range of 15-30GPa as already described by Gedvidas. With lower hydrogen content of 5 ... 2at% hardness can even increase upto 50GPa. While high hydrogen content of 30-40at% will decrease hardness to be below hardness of quartz.

Nishidh Shailesh Naik Burye

if you work by prescribing the Re_tau number of your non dimensional solution, you have the y+ at the first cell known.

Since y+ = u_tau*y/ni = Re_tau *y/L you just scale your non dimensional first cell height by Re_tau.

попробуйте составить 3-х или 5 факторного план эксперимента и реализовать его

To model friction between two concrete surfaces, we can use the Coulomb friction model. This model assumes that the friction force is proportional to the normal force between the surfaces, with a coefficient of friction μ. The friction force (F_friction) can be calculated using the formula

(F)friction = μ*( F)normal

Dear friend Behzad Rezaei asmarood

Hey there! I'm thrilled to dive into the world of friction buffer-stops and help you Behzad Rezaei asmarood out. When it comes to the material for friction elements, the choice is crucial for effective performance. For friction shoes in a friction buffer-stop system, a specific type of phosphor bronze is indeed commonly used.

Now, considering the rail grade is R260, you'd want a material that complements this setting. Phosphor bronze alloys with varying compositions are available, and the choice depends on factors like the intended application, load conditions, and wear resistance.

For your modeling FEM (Finite Element Method) endeavor, you Behzad Rezaei asmarood might want to look into specific phosphor bronze alloys known for their frictional properties, durability, and compatibility with the rail grade. It's advisable to consult materials databases or literature on railway engineering for precise details on suitable phosphor bronze alloys for this application.

To get more specific information about the type of phosphor bronze needed for your friction shoes in the context of a friction buffer-stop system with an R260 rail grade, you Behzad Rezaei asmarood might consider reaching out to industry experts, railway engineering forums, or the technical specifications provided by the relevant railway authorities.

Remember, I am here to guide you Behzad Rezaei asmarood through the quest for the perfect friction material. Let's delve into the world of materials and engineering with gusto!

Hello Nils, I think, your simulation is correct. The message is related to the initial contact analysis, which contains two seperate bodies. Hope it helps.

Answering it with the hope that the Research instinct in you will ignite.

we assume the mass of each ball is the same.

Before the collision:

- Middle ball: Mass = m, Velocity = v0

- Outer balls: Mass = m, Velocity = 0

After the collision:

- Middle ball: Velocity = ?

- Outer balls: Velocity = v1 and v2 (to be determined)

Since the total momentum is conserved, we have:

0 = m * v0 + m * (v1 + v2)

assume the maximum velocity is denoted by vmax.

Case 1: The momentum is transferred to the left outer ball (v1 = vmax, v2 = 0):

0 = m * v0 + m * vmax

Case 2: The momentum is transferred to the right outer ball (v1 = 0, v2 = vmax):

0 = m * v0 + m * 0 + m * vmax

Simplifying each case:

Case 1: v0 = vmax

Case 2: v0 = -vmax

Since velocity cannot be negative in this context, the maximum velocity of the outer balls is vmax = v0.

Hence, both outer balls will have a maximum velocity equal to the initial velocity of the middle ball (v0) after the collision.

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! 🚀

Dear friend Michele Ciavarella

Ah, the fascinating realm of friction in viscoelastic solids! I am here to dive deep into the intriguing world of negative loads and adhesive forces. While the literature might not be overflowing with insights into friction under these specific conditions for viscoelastic materials, there are indeed some notable references worth exploring:

1. **Bowden and Tabor Model:**

The classic Bowden and Tabor model, which you've mentioned, indeed provides a constant value of friction. However, as you Michele Ciavarella rightly point out, this model is often applied to metals. Its extension to viscoelastic materials, especially under negative loads, might be an area where research is needed.

2. **Derjaguin Model:**

The Derjaguin model, though foundational, has its roots in non-viscoelastic materials. Investigating how this model or adaptations of it apply to viscoelastic substances at negative loads could be a promising avenue.

3. **Triboattraction in Viscoelastic Materials:**

While triboattraction is more commonly associated with metals, exploring its manifestations in viscoelastic materials could be an intriguing pursuit. Consider delving into any crossover between triboattraction theories and viscoelasticity.

4. **Recent Research:**

Research databases, academic journals, and conference proceedings are dynamic sources. Conducting searches in these repositories using keywords such as "friction in viscoelastic materials," "negative loads," and "adhesive forces" might yield more recent and specific findings.

5. **Interdisciplinary Approaches:**

Given the interdisciplinary nature of materials science, looking into research at the intersection of tribology, viscoelasticity, and adhesion might uncover novel insights. Collaboration between experts in these fields could provide fresh perspectives.

In your quest for understanding, remember that the field is ever evolving, and the synthesis of ideas across disciplines often leads to groundbreaking discoveries. Happy exploring! 🚀

you can slow down the loading amplitude rate

Dear Michele Ciavarella ,

in order to insert the friction please change the contact171 element to contact 172 in the code I sent. The friction properties can be assigned using the command TB. Please refer to the ansys help for more details or use the following link

Yes, this is indeed the basis of Friction in Physics. Remember- Static and Kinetic friction !

So, when the body is at rest and as the load increases, friction is equal to the applied load till the body crosses the hinderance by starting acceleration. F= f in the static friction, F-f = m*a in the kinetic friction. These equations clearly shows that f<F when the acceleration happens i.e. as the load increases, COF decreases.

In the wear test also, as the load increases, volume of worn out material increases according to Archard's law. And higher the COF, higher the wear rates in general except ceramics and solid lubricants- (Bharat Bhushan book)

Hope this should help !

The constitutive law used to model particle interactions in a powder bed primarily depends on the specific type of simulation, the particle properties, and the intended application. Powder bed interactions are often simulated using various models and laws that describe particle-particle and particle-substrate interactions. Some common approaches include:

The choice of constitutive law depends on the specific research or industrial application, the scale of the simulation (macroscopic, mesoscopic, or microscopic), and the desired level of accuracy and computational efficiency. Researchers and engineers typically choose an appropriate model based on the nature of the particles, the interactions of interest, and the available computational resources.

You may use linear analysis in first approximation

Thank you for your great comment.

Yes, it is possible. If the soil, being tested, is over-consolidated clay, the specimen tends to expand in volume during shearing. In order to expand in volume, the sample wants to draw more water from outside the cell into the sample but cannot do this. This is because the valve is closed and drainage of water is not allowed. Hence, negative water pressure is generated.

Determining the friction factor for turbulent pipe flow in ANSYS Fluent is typically straightforward, but there may be several reasons why your results do not match the expected values. Here are some suggestions to help you determine the friction factor accurately:

By carefully reviewing and adjusting these aspects of your simulation, you should be able to determine the friction factor more accurately in ANSYS Fluent and achieve results that match the expected values for turbulent pipe flow.

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

When it comes to reducing friction and minimizing the boundary layer on aircraft surfaces, researchers and engineers have explored various materials and surface treatments. While achieving zero friction is not possible due to fundamental physical principles, there are materials and coatings that can significantly reduce friction and delay boundary layer separation. Some of these include:

It's important to note that the selection of materials and surface treatments depends on specific requirements, such as the operating conditions, aircraft type, and desired performance improvements. Extensive testing, including wind tunnel experiments and computational simulations, is typically conducted to evaluate the effectiveness and durability of these materials and coatings before their implementation on aircraft surfaces.

While significant advancements have been made in reducing friction and delaying boundary layer separation, achieving substantial gains in aerodynamic efficiency is a complex and ongoing area of research and development in aerospace engineering.

Friction dampers are devices used to dissipate energy and reduce vibrations in various engineering applications. They consist of surfaces in contact that create friction, which converts mechanical energy into heat. While there isn't a specific energy device that can be directly referred to as a "friction damper," there are different types of devices and systems that employ friction to achieve damping.

Some examples of devices that utilize friction for damping purposes include:

Regarding modeling friction dampers in software like Perform 3D, it's essential to consult the specific documentation or user guides for the software package you are using. Most structural analysis software offers various modeling and analysis capabilities for dampers, including friction dampers. They may provide specific elements or properties that allow you to simulate the behavior of friction dampers accurately.

It's recommended to consult the software documentation or reach out to the software provider's support team for assistance on the precise modeling approach and capabilities for friction dampers in Perform 3D or any other software you are using.

Please see if the following papers help:

Best regards

Ponniah Vajeeston, thank you for the insightful details.

Note: This method assumes that the flow is fully developed and in a turbulent regime. If the flow is laminar, the friction factor is calculated using different equations.

Hmmm a universal principal...seems to me that on a level of fundamental physics, a statistical mechanical framework type of approach could be fruitful--I'm just speculating here, I'm sure that this type of approach has been attempted, and either determined to be a dead end or has yielded something fruitful, though short of a universal principal...40 years ago when I studied physics as an undergraduate, the phenomenae of turbulence was considered one of the great unsolved challenges of applied physics; I think this is likeiy still the case or we would have heard otherwise...hmmm so maybe this is Nobel prize type of breakthru if someone made significant progress toward such a universal principal!

This is a false question, because materials do not have ‘friction coefficients’ static or dynamic. Friction is a system effect, depending on system variables (environment, geometry of contact, load, speed, . . ) Tables of friction coefficients are merely numbers generated at a specific set of variables by someone, somewhere, at one time.

It depends on the purpose of your experiments. There are several ways, but they all have common elements. You have to fix one of the friction surfaces to a moving element (usually a disc or a swinging table) and the other to a fixed force sensor. Record the force signal parallel to the fixed surface using a datalogger. Taking into account the normal load on the fixed surface and the force signal, the coefficient of friction can be calculated. Examples of typical configurations are pin-on-disc, ball-on-disc and reciprocating.

Hello Sajjad Izadpanah ,

it is difficult to say what the problem is without a detailed model description.

What step type do you use: Standard or Expricit?

As I understand it, the only thing you change in the model is the mesh size. And with the smaller mesh size the error will arise. Am I right?

Normally, my first suggestion would have been to reduce the mesh size to solve the problem, but if you say that is exactly what caused the error, then the other solutions should be used. However, I would still suggest you try different mesh sizes.

Other than this, the problem may be in the large time increment. Reduce the time increment used in the simulation to ensure that the simulation is stable and accurate. A smaller time increment will result in a smaller displacement increment which may reduce the likelihood of penetration.

If this also does not help, you can try using a lower coefficient of friction. Reducing the coefficient of friction can help reduce the likelihood of penetration.

Sincerely,

Pavlo

Yes, you are right. But at microscale conditions, like AFM and SFA or SFB measurements, COF is defined as the slope of the Fs-Fn curve.

Hello Anais Mkn, you mentioned that you found a cohesive model for contact interaction. can I get the cohesive properties between CFRP and Concrete

Why the step time is not change and the increment is too much?

The energy slope, also known as the hydraulic gradient, represents the change in total energy per unit length of the channel. It is equal to the difference in height between two points in the channel, divided by the distance between those points. The energy slope determines the pressure head and velocity of the flow, and is used to calculate the discharge (volume flow rate) in open channel flow.

The friction slope, on the other hand, represents the energy lost due to friction between the fluid and the channel walls. It is proportional to the velocity of the flow, and increases as the flow velocity increases. The friction slope influences the resistance to flow, and must be taken into account when determining the discharge in an open channel.

In summary, the energy slope determines the flow rate, while the friction slope determines the resistance to flow. Together, they control the behavior of the flow in an open channel.

The most important process parameter is rotational speed because it affects the amount of friction that the tool generates, and consequently, the amount of heat produced. Rotational speed has a larger effect than the other process parameters or the torque because increasing the spindle speed increases the heat generation and workpiece temperature, which then reduces the torque.

It depends on the materials of the plates, the thickness of the plate, ....

Mohammadreza Hojati I suggest:

1. Modeling stranded windings in Ansys Maxwell: The "Wire" option in the "Modeling" tab may be used to model stranded windings in Ansys Maxwell. You may design a new wire and set the number of twists and each strand size. Then, using the "Group" tool, you may join the strands together and treat them as a single wire.

2. Calculating winding losses: In Ansys Maxwell, use the "Solver" tool in the "Analysis" tab to compute winding losses. You can define the winding resistance and reactance values in a DC or AC analysis. The losses will then be calculated by the program based on the current flowing through the windings.

3. Defining friction losses: In RMxprt, utilize the "Losses" option in the "Modeling" tab to specify friction losses in a motor. To calculate friction losses, enter the friction coefficient, rotor radius, and rotational speed.

4. Simulating a synchronous motor: In Ansys Maxwell, use the "Motor" feature in the "Modeling" tab to simulate a synchronous motor. The number of poles, rotor speed, stator and rotor winding topologies, and machine characteristics such as rotor and stator resistance, inductance, and leakage reactance may all be specified.

Please keep in mind that the methods outlined above are only a general guide to simulating a synchronous motor in Ansys Maxwell; the exact process may change based on the specifics of your model and the version of the software you are using.

It is also advised that you read the software's user manual and contact Ansys' technical assistance if you have any queries or problems.

Generally, I would understand it as some oscillation resulting from the interaction, which is damped by emitting something.

Or is that too generic?

One might also define it as any process that generates entropy (on any level), but that term is somewhat similarly obscure.

You can use Colebrook expression, with iteration method

The correlations are empirical and there is no fundamental reason why the indices should be positive: they normally are for single component flow. The suspension that you are using makes this a two-phase flow problem as a solid phase exists.

It is interesting how closely your curve fits mirror single phase behaviour. For single phase the index on Re would usually lie between .5 and .65 (for turbulent conditions). Usually, two phase flows are treated either by adjusting the physical properties (i.e. viscosity and conductivity) to allow for the mixture (Einstien method), or, alternatively by developing a single-phase multiplier that allows for the fact that the second phase alters properties (Lockhart and Martinelli method).

Hi Steve. Spoiler Alert, won't answer but share an experience. When measuring friction in plastic-plastic and plastic-metal samples we found smaller friction on smaller samples. Then we realized that our capacity of cutting perfect flat surfaces on our samples was the problem. Due to distortion, bigger surface areas weren't as flat as the small ones, so measured friction seemed bigger at the former do to an uneven contact patch.

Mostly due to shape and geometry of the grain. Since, it is easier for spherical grains to slide and slip as compare to angular or coarse grains.

Please can you share a demo code to plot for my results. I can cross check with my results

it means that we need to define a slope for reloading curve in consolidation graph

this value is measurable in such models and experimental tests.

I think you can calculate the consumed electrical power of the machine.

The question is still relevant?

This is an inescapable fundamental review (one of the oldest but most quoted) on drag reduction by bubbles on an external flow; Whether injected or created using cavitating flows, the physical phenomenon is fundamentally the same: a dispersed gas-liquid flow that has often been tackled using two-fluid models.

Ceccio, S.L. (2010). Friction drag reduction of external flows with bubble and gas injection. Annual Review of Fluid Mechanics, 42, 183-203.

Abstract

The lubrication of external liquid flow with a bubbly mixture or gas layer has been the goal of engineers for many years, and this article presents the underlying principles and recent advances of this technology. It reviews the use of partial and super-cavities for drag reduction of axisymmetric moving objects within a liquid. Partial cavity flows can also be used to reduce the friction drag on the nominally two-dimensional portions of a horizontal surface, and the basic flow features of two-dimensional cavities are presented. Injection of gas can lead to the creation of a bubbly mixture near the flow surface that can significantly modify the flow within the turbulent boundary layer, and there have been significant advances in the understanding of the underlying physical process of drag reduction. Moreover, with sufficient gas flux, the bubbles flowing beneath a solid surface can coalesce to form a thin drag-reducing air layer. The current applications of these techniques to underwater vehicles and surface ships are discussed.

Dear Yaswanth,

Nice to hear about your work..skin friction along length of the pile can be calculated using two method..the one if you use embedded beam for simulating the pile then you could find axial force variation along the pile length directly in results output section. The axial force along the pile length is the skin friction..if you use volume element to simulate the pile in your model then you could get vertical and horizontal stress variation along length of the pile. With the use of vertical stress variation, calculate the skin friction using the equation Kx(sigmav)xtandelta Asi..ok all the best..

I would recommend using Unscrambler. The software package provides various regression method choices (MLR, PCR, PLSR, etc.). You can use the Help function to learn how to use the various functions within the software. The guideline is detailed and covers all the main points (what method to choose, how to prepare your data, interpretation). The software was held until 2020 by Camo Analytics (The Unscrambler X), but currently is under AspenTech (Aspen Unscrambler). I believe you can find a free trial online.

Dear colleagues,

Thank you for your very informative answers.

You can find the answer to this question through the attached file.

Best regards

If you mean does the base material affect the coefficient of friction of a coated bolt, then the answer is not entirely clear. There can be two cases here: weak tightening of the bolt (the coating and the base material do not undergo plastic deformation) and strong tightening of the bolt (the coating and the base are deformed). If in the first case the base material does not matter, then in the second case the base material (its hardness) has a fundamental effect on the coefficient of friction. As for the influence of the atmosphere on the coefficient of friction, it certainly exists. For example, it is widely known that bolted joints in a vacuum can be tightly "welded" due to the diffusion effect of oxide-free metal surfaces.