Mechanics - Science topic

Thanks for the opportunity!

AI:

Tensile tests of rolled sheets are preferably performed on samples taken parallel to the transverse direction (TD) rather than the rolling direction (RD) due to the following reasons:

By testing in the transverse direction, engineers and material scientists can ensure that the rolled sheets will perform adequately under various service conditions, thereby improving safety, reliability, and performance in their intended applications.

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.

@sunil Bhat, with UTS, what do you mean?

The best book that would suit your requirement is 'Fatigue of Materials' by Dr. Subra Suresh. The google book link is below:

Happy reading!

And why sparse matrix has computational benefits than diagonal matrix for large sizes ?

As I just figured out, it's basically the strain energy of a body divided by its volume.

the following link gives a good explanation:

Strain Energy Density: What, Why and How? | OnScale

There are some experimental papers on force measurement by plant tree roots:

A: https://academic.oup.com/jxb/article-abstract/45/1/95/476383?redirectedFrom=fulltext#no-access-message

B: https://academic.oup.com/jxb/article/67/19/5605/2236186

You may use an inverted analysis of paper B with rod theory to derive root pressure.

Hope it helps

Dear Karthika P,

Don’t copy paste articles from Google on a subject which you don’t know anything. To understand Automotive Dynamic Systems is beyond your capability.

regards

jasbir s ryait

No you do not need to do this. If you merge the nodes the contact will lose its function.

The results seemed to go against the laws of physics: The vacuum, by definition, is completely empty space and does not exert friction on objects within it.

Hello Md. Faishal Rahaman ,

I have a RG write-up for the impulse excitation of a piezoelectric shock sensor (PSS), which you may find of interest for your current problem, see, . I just uploaded this Method today, 3/2/2022. I hope this helps.

Regards,

Thomas Cuff

Prof. Mostafa Shabani

I guess is * τ = T r / J_p0, where:

τ - is the shear stress.

T - is torque.

r - is the distance from the axis of the torsion.

J_p0 - is the polar moment of inertia.

so J_p0 ~ τ^-1 T r

Dear s.Milad:

You can benefit from this valuable article about your topic:

"Fuzzy Fractional-Order PID Controller for Fractional Model of Pneumatic Pressure System".

Abstract:

This article presents a fuzzy fractional-order PID (FFOPID) controller scheme for a pneumatic pressure regulating system. The industrial pneumatic pressure systems are having strong dynamic and nonlinearity characteristics; further, these systems come across frequent load variations and external disturbances. Hence, for the smooth and trouble-free operation of the industrial pressure system, an effective control mechanism could be adopted. The objective of this work is to design an intelligent fuzzy-based fractional-order PID control scheme to ensure a robust performance with respect to load variation and external disturbances. A novel model of a pilot pressure regulating system is developed to validate the effectiveness of the proposed control scheme. Simulation studies are carried out in a delayed nonlinear pressure regulating system under different operating conditions using fractional-order PID (FOPID) controller with fuzzy online gain tuning mechanism. The results demonstrate the usefulness of the proposed strategy and confirm the performance improvement for the pneumatic pressure system. To highlight the advantages of the proposed scheme a comparative study with conventional PID and FOPID control schemes is made.

@https://www.hindawi.com/journals/mpe/2018/5478781/

I hope it will be helpful...

Best wishes....

Strain is any kind of deformation, including elongation. Elongation is the word used if we're talking specifically about tensile strain which the sample deforms by stretching and becoming longer. Usually the percent elongation is calculated, which is just the length of the polymer sample after it is stretched (L), divided by the original length of the sample (L0), and then multiplied by 100.

Kindly find my working if you need more tutorials you can follow me on research gate. I can teach you for free.

A quick check with pens and papers-

Use Euler's Buckling formula

max load P= EI*(pi)^2/L^2. L is the insertion point (into hole, box, whatever) to holding point (where the pipe is gripped and applied force. E is young's modulus. I is area moment of inertia, I=(pi/64)* (D^4-d^4). D is outer and d is inner dia of tube

This bold portion would work just fine to use the area moment of inertia of a hollow column.

For eccentric loading, use the Secant formula instead

(https://lh3.googleusercontent.com/proxy/g8_baZStGvHyY_kjl9HELONHz1gqJddFMcZayzbGxs98fjs8RGCh2SOdBy_3t-736KBrYl3BRgVjUwCGnuauyvL2x7_9N84G8L0imQal66A9UQ4hKcWBlV8o25Z5fBTBABo_HA0AeIPa54ezgH2sCeR2P4U2_G3x-Y2d4w)

But wait! if PVC tube is way too flexible to be considered to be elastomeric rather than linear elastic, there can be error, because Euler's formula was derived for linear elastic deformation of columns.

If standard simulations (Solidworks, Comsol, Ansys) seem too hard for you, go to some user friendly online simulation interfaces like simscale. Just upload 3D image of files in their simulation IDE, give input parameters, and you are done within a few minutes to hours.

Go for it.

This is a good question.

Nitish Kumar Guru I have added the example to the PERMAS4EDU project. See the project log at https://www.researchgate.net/project/PERMAS4EDU

Dear Mr khripov,

I prefer that we agree on the questions you ask.

For me F'=-kx is Hook's law.

For me F=ma is Newton's second law.

If in a given problem F=F', then -kx=ma.It is Newton's law particularized to the case where the force applied is that of a spring (Hook's law).

At static equilibrium, we have theoretically kx=mg. The theory tells you that kx=mg.

You want to check this relation experimentally. Fabricate identical objects of the same mass m. Hang on the spring one object, then two objects, then three objects, etc.... At the first elongation mark the elongation with a pen x=X0. You will notice experimentally that for 2m you will have an elongation of 2(X0), for 3m you will have 3(X0), etc ..... Plot on a graph the elongation of the spring as a function of the hooked mass. You will see that the curve is a straight line and that the slope of this line is (1/k) in the system of units you have used.

Conclusion:

1) You have therefore verified the linearity of x as a function of m and this is the verification you wanted to make.

2) You have deduced the value of k.

Important remark:

I hope I have answered your question.

Adam Ww please follow the link attached herewith , i hope this article will help you lot

Sorry Jelong Lee, now a understand your question. There will be two component for the torque: one in the direction of 1 and other in the direction 2. In the direction 2 is a different deformation, I am not sure if the formula above applies, I think L should be much bigger than the other 2 dimensions of the beam.

Length contraction CAN be deduced by purely mechanical processes. The other Transformations are substituted by other mechanical means. For example, time dilation can be speed of light changes in different media density.

Dear Anatoly,

If you are satisfied by the 1st Newton's law, which is basically equivalent to Galilean relativity, there is nothing to prove.

But if you mean to axiomatically construct a logically self-consistent mechanics without Galilean relativity, like non-Euclidean geometries proposed by mathematicians in 19th century, that should be possible, of course.

There are plenty of mechanical systems without translation invariance - a pendulum, a bent railway, a body in an "irremovable potential field", etc. But they are used to be well handled by existing formalism: systems with nonlinear constraints - by Lagrangian, potential motions - by Hamiltonian.

So, it is unobvious whether there is need for something new physically. And mathematically, it must be just part of non-Euclidean geometry, already well developed.

Both the parameters are considered. However, many more parameters are taken into account while varying the stiffness and damping coefficient.

check the uploaded doc maybe it will help

The first mechanistic model of self-replication was given by John von Neumann by his self-replicating cellular automaton. He was followed by others: Langdon, Reggia, ...

It would be interesting to study this research stream as it provides great insights into creation of mechanistic description of certain properties of living structures.

Hi Sirenia,

My message is probably too late. How is your experience with those swivels?

We use a similar swivel for recording rats. They work well mostly but one of three or four makes some noise during spinning. But in generally we are satisfied. Now fortunately there is a big selection of different swivels in amazon. I guess that a bit more expensive one conducts a a better quality signal.

Have you got answer about it?

1)Berkeley Physics Course

2)Alonso-Finn Fundamental University Physics

3)A.N.Matveev 4 volumes; Mechanics, Electricity and Magnetism, Molecular Physics and Optics

The first option is a special case of the second one.

In other words, if the stiffness of the springs is too high, both formulas will give you the same answer.

The Galilean invariance, Dr. Anatoly A Khripov, the laws of motion are the same in all inertial frames if there is no acceleration due to an external force. But sometimes a conservation law (momentum, or energy) is needed experimentally to be tested.

For example, the capillary movement without viscosity of the ⁴He isotope is based on the Galilean invariance of energy and momentum, despite it is a quantum liquid, showing how general is the Galilean invariance.

Abdul Baqi Ahady Ketan Ajay

Does anyone know the exact name of the following equation used for friction factor calculation?

f=16/Re_k

1/√f= G log (Re_k√f)-H

that G, H, k are constants that have different values.

what dose the index of k shows?

i want to know how i should choose the correct value for each constant

We activate alkali activated hybrid cement in standard cement ball mill already couple of years as mentioned in older answer

Conclusion: Were indeed purely numerical issues. To my surprise beam length errors and node position errors of a magnitude of 10E-6 [m] resulted in a rank deficient Stiffness Matrix.

Of course you need to calibrate your equipment and perform good maintenance. Like the pipetting error in the old days, there will always be an analyser error nowadays, mainly bias for wrong settings but also imprecision due to wear.

What kind of equipment / kind of lab are you dealing with? Best option is to perform regular (time interval dependent on the purpose) both internal and external quality control and keep your equipment within the specs your manufacturer and your professional organisation have laid down

Dear Kanticha,

You can easily get the answer by parsing the reaction vector A.

you can see in following PDF.

Also note that under the same loading the deformation of material with rectilinear orthotropy differs from the deformation of materials with cylindrical orthotropy.

hi Andrew

i have some ideas about your question but i am not sure about them.

for apply nodal force in Abaqus you can use input file. in input file you can apply concentrated force to any point you want.

📷Preston Guynn. added a reply on June 19, 2019:

Force, mass, and energy are a parallel set of descriptions of the effects of special relativistic Thomas Precession. All matter and space, and their interactions are described with distance in three dimensions, time, and their derivatives.

Newton's first law of motion is , "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."

Yet the concept of motion requires at least two objects, and if there are two objects, then there is always an external force, which is gravitation.

So the idea of rewriting Newton's laws without force (or mass or energy) is good, but it should be extended to incorporate the most basic non-linear effects of motion in space time, which are special relativity and Thomas Precession.

See my article describing the recent discovery of the effects of Thomas Precession the particle and galactic scales.

Article Thomas Precession is the Basis for the Structure of Matter and Space

Recommended / Share

Dear Fatemeh Pourhashem,

The ECU( Engine Control Unit (ECU) uses the camshaft and crankshaft position sensors to determine where the pistons and valves in the engine are at any given time. The ECU uses all of this information to start and keep the engine running.

ROM displaying method of automatically identifying sensor locations in an ECU’s can be effective. This can be able to create a data representation of the functions within a binary and their internal control flow graphs. Adding ECU can be effective for engine family. Addition can be able to successfully locate 95% of all candidate functions and was able to successfully recover 100% of likely sensor addresses within each of those functions.

Ashish

I agree with Abdulrahman Dahash

Dear Amir M Shamaei

Hi Hamid Reza Attar ,

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

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

Unfortunately, what you have here is a classic case of "jerk". It will not matter how well you calculate the theoretical torque required for the nut to hold fast, in practice it will always come loose. It is the same principle as the tool used to remove wheel nuts. You have to change the physics of your assembly. If you can, reverse the thread direction of the nut. If you cannot, you have to find a way of clamping the nut. Solutions depend on the size of the nut. How big is it? Knowing this, I can give you a way of locking the nut that does not depend on the torque that you are using.

Thank you Ashish and Alpesh. The toughness and resilience are calculated when tensile load is applied. Will a material absorb same energy when a impact load is applied such as bullet fired on the material front face?

Contact problems have improved in Comsol since recent releases. You can define the penalty stiffness/ coefficient (very high) to overcome the solids penetration issues.

Optimization looks a promising start for machine learning in mechanics. Even in expensive simulations like crack propagation u can build few models to get the results and then train ur models based on input data. Which can be further used for collecting more results or for optimization purposes.

Hassan, its a bit more complicated than that. Because, the accelerometer measures acceleration (in meters per second squared), whilst the load cell measures the force in N (kg.m.s^-2).

Of course the force (which the load cell will measure) of the impact will cause an acceleration on both bodies. But whilst the force is equal and opposite, the acceleration won’t be. Even more issues arise if the helpmeet deforms irreversibly to absorb the impact - which I guess is the idea of it. I would both sensors....

Thank you Sriram Ganesan

Maybe it is more intuitive to think about it on a stress-level.

Think about a body with weight F [N] that is placed on a surface with friction. Let the contact area be A [m^2].

The normal stress in the contact area then follows to:

sigma [N/m^2] = F / A (1)

This leads to a resistance against movement due to friction (mu [-]) of:

tau [N/m^2] = mu * sigma (2)

So every part of the contact area contributes to the resistance against movement. However, for the resisting force V [N] you have to sum up the stresses.

V = tau * A = mu * F (3)

So I think you could say that the contact area matters in a way. But what really matters is the product of the contact area and the normal stresses and that product stays the same for different geometries as long as your body has the same weight.

Hope that helps :)

Regards,

Stefan

I am not aware of any sources for historical return-to-service rates; you would probably have to do a study by recruiting Mechanics and looking at their current rates, or asking if shops have data of when the planes went in vs when they went back to service. Granted, the type of service will affect the results. If a mechanic is highly certified and regarded and is only given the complex problems to solve, of course their solutions will take longer, so maybe you can consider a way to classify the work done on the aircraft.

Hi, Apart from axial guiding function, there is perpendicular load to resist as well, which is a combination of temperature and pressure.

The U bolt has to be sufficient strength and stiffness.

is it possible to extract mode shapes from ansys mechanical apdl to a spreadsheet on excel.

additive manufacturing have the vast scope including some specified rapid prototype strategy...SLS, SLM, SGC, SDM, LRP,Mold SDM, DLF, BPM, 3DP etc.

Smart manufacturing

Nano-manufacturing

Molecular level manufacturing

Atomic level fracture continuum mechanics

Mechatronics still it has very good research challenges and opportunities.

Control and precision engineering

Generation of electricity sustainable energy approach

Hope it work out for you.

Sorry to disagree. There are two ways how stress triaxiality can build up at the material point: under quasi-static loading it is the result of the stress gradient associated to geometry changes and stress concentration. The upper bound value for this is 3. The second way is because of stress waves interactions in dynamic impact. Under planar impact (uniaxial strain condition) stress triaxiality increases linearly with the uniaxial strain. Depending on the ratio of the bulk modulus and the flow stress. To give you an idea in pure copper it reaches 22 and more. Under ideally hydrostatic condition it becomes infinite ;)

The necessary information contains the attached paper:

Following with great interest.... Thank you so much for sharing this article. Regards, Emad

You can use COMBIN39 elements.

- When calculating ephemeris in the most accurate models of EPM and in some DE models, only miserable corrections are obtained from the PPN formalism. The Newtonian gravitation remains in the basement of celestial mechanics and of the GR. To my point of view, and stem from the fact, that geodetic lines in the presence of masses get bent, the Newton’s gravitation law suffers from a fundamental flaw due to violation of the inverse square law, underlying it. Let's try to go down from generalizations to specifics.

For example, discussing the modification of the law of Newton, I will argue that the mass is not an invariant, and the APPARENT gravitational mass depends on the distance to the observer Ma = M (1+ KR), where, for particular body, K = const. To verify the validity of the modified law, one will have to a) recalculate the masses of all celestial bodies in accordance with modified law, and b) get the Shapiro amendment, which will also depend on the (apparent) mass. As a result, using appropriate Shapiro delay values, we may get confirmation of the modified law.

Dear Sir,

To the point how to construct.

Let us take component wise

Forces = Air frictional force if your relative velocity is high like 1m/s, frictional force from ground and touching surfaces, EM forces, Temperature gradients, Electrical Gradients, Gravitational forces.

Maintain constant Temperature that is generally room temperature- If temperature gradients exist then, source of it should be eliminated or considered in the system.

Use Glass material polished with talcum powder.

If any EM material Exist that is taken care by glass itself.

If high velocity Evacuate the chamber i.e. create vacuum.

Cover other surfaces also with talcum powder.

X & Z components are taken care by these.

Y component gravity is left that comes vey expensive.

So to eliminate gravity either use Archemedies Principle or do it simulation if real is not compulsory.

Dear Preston,

Thank you very much for your papers

Anatoly

Could you please explain more what you want

Richard Moran , thanks for your explanation.

see

Hello:

According to professor Brandmark in his article

J Rehabil Res DevVol. 38 No. 2, March/April 2001

He gives definition to osseointegration as follows

Definition of Osseointegration Osseointegration was originally defined as a direct structural and functional connection between ordered living bone and the surface of a load-carrying implant (4). It is now said that an implant is regarded as Osseo integrated when there is no progressive relative movement between the implant and the bone with which it has direct contact (2). In practice, this means that in osseointegration there is an anchorage mechanism whereby nonvital components can be reliably and predictably incorporated into living bone and that this anchorage can persist under all normal conditions of loading (5).

Now if you want to know what is happening on the level of histological level then I can refer to Raghavendra S. Jayesh and V. Dhinakarsamy article on osteointegration (listed below as an attachment) where they showed histological steps where osteointegration become a bond between titanium and bone see fig 3 (two parts)osseointegration mechanism .

📷📷

Based on many literature review I read would like to define osteointegration as

A bio-mechanical bond (a new terminology by me ) which explains both the mechanical and biological properties

I think your question lacks a bit of context as the K-V model can be applied to a variety of situations, from actual spring-damper system in mechanical devices to fluids and solids under loads, and more. As you specified that it is for materials, you may want to specify which materials and conditions, or at least the material phase to get a detailed answer.

Nevertheless, I think that from a general standpoint, Mr. Hernández answer's is right. You usually curve fit the model to actual test data. However, the test will depend on the type of material and conditions.

You may want to search the web for ''basic elasticity and viscoelasticity princeton university press'' for a primer on materials mechanics and the relation of the K-V model to actual behaviour (although fitting is not really discussed).

Test standards as ''ASTM D6048—07 (Reapproved 2012) Standard Practice for Stress Relaxation Testing of Raw Rubber, Unvulcanized Rubber Compounds, and Thermoplastic Elastomers1'' may also help you.

Best regards,

Laurent

Hi Alex,

Try checking with with Adam A. Pepi . He has some some work measuring leaf toughness.

Good luck,

Hannah