Questions related to Mechanics

I am looking for information on the pressure tree roots (by expansion) can exert on structures as retaining walls and quay walls. Failure of retaining walls by root pressure is very common. Is there any way/model to determine this load?

What characterization required for automotive anti-roll bar applications?

Mechanical, Dynamic mechanical, thermal etc and what is range of vales of these properties

I am simulating a welding process. Do I have to use merge nodes as well as the spot welding together?

Hello,

One of my colleagues is working with piezoelectric components and couldn't find the shock response spectrum for various piezoelectric components. Can anyone please share your idea to deal with the calculation process of shock response spectrum (srs) of piezoelectric components? However, any informative links that contain useful resources or details will be very helpful.

Thank you for your time and guidance.

Best wishes,

**Faishal Rahaman**

What is the relationship between the polar moment of inertia and the torsional constant?

I have just designed a fuzzy system, and now I want to redesign it based on the fractional order. However, I have no idea where to start from and what to do. Could you please tell me what I should do and mention any related sources to study?

Please, see the attached file RPVM.pdf. Any comment will be wellcome.

More on this subject at:

You can find the wording in the attached file PR1-v3.pdf. Any comment will be wellcome.

More on this topic at:

In a stress-strain curve of an FRP composite, mostly it is represented strain in terms of (%) rather than in (mm). Why it is represented in such a way?

Assuming we have a piece of timber C16 - 100x100x1000mm and we apply UDL + a point load at middle point on it (parallel to the fibre) as shown below, how much will the timber compress between the force and the concrete surface ?

I have attached a sketch as well. Please see below.

If you could show a detailed calculation would be much appreciated. Thank you!

Hello all,

I´m currently working for a medical device company. We are trying to understand the buckling effect during an insertion force test.

We use a flexible PVC extrusion with these properties:

Hardness: 95 (ASTM D-2240)

Specific gravity: 1.73 (ASTM D-792)

Tensile strength psi: 3400 (ASTM D-638)

Elongation%: 250 (ASTM D-638)

100% Modulus psi: 2860 (ASTM D-638)

This extrusion is inserted into another medical device and the force required to insert the extrusion must be below 4 lbf. However, it is noted that during insertion procedure the extrusion buckles, losing force and failing test. The extrusion is inserted using a fixture to guarantee that 4lbf are being applied, there are some cases where the readings of the force tester are below 4lbf but the extrusion get stuck and didn't pass all the way thru the medical device not reaching the desired end position. Our guess is that the column force is lost as result of buckling.

Extrusion length is about 10 inches, OD is about .077” and ID is .035”, this isn’t a solid extrusion. For this case, we would like to know much force (lbf) can be applied to the extrusion before buckling. Seems like we might use Euler formula, but it is unclear to me how to use the formula adding the factor that this isn’t a solid column, I assume wall thickness may be considered.

I appreciate any help to solve this doubt.

Thanks!

how to create a custom output time (t) -Displacement (Uy) in a transient analysis ???

I want a macro gives the following output;

t-time y-disp

1 0.00000E+00

2 0.00000E+00

3 -0.18027E-01

4 -0.36054E-01

5 -0.54260E-01

.

.

.

I used this code in a static analysis it worked

*get,far,node,,count

*dim,matrice,array,far,3

/post1

set,last

*cfopen,temp,txt ! Create file called “temp.txt”

*vwrite

('x-dist',8x,'y-disp',10x,'z-disp')

*vget,matrice(1,1),node,1,loc,x

*vget,matrice(1,2),node,1,u,y

*vget,matrice(1,3),node,1,u,z

*vwrite,matrice(1,1),matrice(1,2),matrice(1,3)

finish

The above macro creates the following output:

x-dist y-disp z-disp

0.93 0.00000E+00 0.00000E+00

0.96 0.00000E+00 0.00000E+00

1.00 -0.45562E+00 0.00000E+00

1.00 -0.47383E+00 0.00000E+00

1.00 -0.49186E+00 0.00000E+00

0.96 -0.50988E+00 0.00000E+00

0.93 -0.50988E+00 0.00000E+00

0.89 -0.50988E+00 0.00000E+00

0.86 -0.50988E+00 0.00000E+00

0.82 -0.50988E+00 0.00000E+00

0.78 -0.50988E+00 0.00000E+00

0.75 -0.50988E+00 0.00000E+00

0.71 -0.50988E+00 0.00000E+00

0.68 -0.50988E+00 0.00000E+00

.

.

.

Is there any defined radii ratio with respect to the plate thickness exceeding to which an annular plate may be treated as a ring? Moreover what changes in vibrational behaviour may be observed when we increase the radii ratio of an annular plate and make it a ring?

Hi. I have a gel aspirated in a rectangular tapered microchannel at deltaP pressure. The channel has the same height everywhere. But the width changes uniformly. The purpose of the experiment is to find Young's modulus from Hook's law. For that I will need stress along x, y and z axis. Along x axis, the stress is deltaP. Along y axis the stress arises from the wall stress which is a function of deltaP and angle alpha as shown in the figure. I am not sure how to calculate wall stress along z axis. Should it be equal to stress along y axis? Also, should I sum two wall stresses in the y axis as there are two walls to calculate overall stress?

Dear Sirs,

The elevator example in general relativity is used to show that gravitational force and an inertial force are not distinguishable. In other words the 2nd Newton's law is the same in the two frames: inertial frame with homogenous gravitational field and the elevator's frame without gravitational field which has constant acceleration in respect to the inertial frame.

But every one knows that an inertial force is a force which does not obey the 3rd Newton's law. For example such forces are cetrifugal force and Coriolis force existing in the Earth reference frame. Gravitational force satisfies the 3rd Newton's law. So one can conclude that the gravitational force is not inertial.

Could you clarify the above controversy.

Dear Sirs,

R Feynman in his lectures, vol 1, chapter 12, Characteristics of force wrote:

"The real content of Newton’s laws is this: that the force is supposed to have some

*independent properties*, in addition to the law F=ma; but the*specific*independent properties that the force has were not completely described by Newton or by anybody else, and therefore the physical law F=ma is an incomplete law. ".Other researchers may consider the 2nd Newton's law as a definition of force or mass. But R. Feynman did not agree with them in the above chapter.

What is your view on the 2nd Newton's law?

Hello,

I'm trying to model a transient heating process in COMSOL with a thin metal film on a polymer substrate. I'm trying to gain intuition into the mechanical and thermal properties as a function of temperature. In particular, how do the heat capacity and Young's modulus of polyimide change with temperature especially near or above the glass transition temperature.

Regards,

Adam

Hi,

I wonder how torque changes with different angles of the torsion axis. Please find the attached figure. I can see how to find out T1 (Blue colour) but not T2. Do I have to compare cross-sectional areas? It would be great if someone can share your thought on this or any formula on this.

Regards

Dear Sirs,

Everyone knows the derivation of Lorentz transformations from electromagnetic wave front propagation. But Lorentz transformations are the basis of the general mechanics theory. It seems to me it is logically correct to derive the transformations from purely mechanical grounds. But how to do this? Mechanical (sound) waves are not of course applicable here. Or there is only purely mathematical approach? I The later is also not good in physics. Could it be derived from gravitational wave propagation? If it is so is there any controversy because General relativity is based on special relativity? I would be grateful for your suggestions.

Dear Sirs,

I would like to find out whether galilean relativity principle (which means the same

form of three Newton's laws in all inertial frames) is derived from the three Newton's laws or

any other classical mechanics statements.

Are tire damping co-efficient and stiffness material-dependent properties or related to tire pressure?

Hi everyone, recently i have a question about how to calculate the orthotropic elastic matrix of cancellous bone cube. I really need the help!!!!

I applied six stress states to the cancellous bone cube by ABAQUS and got an anisotropic stiffness matrix whose every element has value (because the material coordinate axis is not consistent with the local axis) as shown in figure.

I changed the anisotropic matix

**to a fourth order tensor***(6×6)***.***C*_{mnpq}I really want to rotate

*to an orthotropic fourth tensor***C**_{mnpq }*by the following relation:***C**_{ijkl}*=*

**C**_{ijkl}*,*

**R**_{im}R_{jn}R_{kp}R_{lq}C_{mnpq}the

**is an rotation***R*_{im}**matrix as shown in figure. The***(3×3)***,***α***and***β***is the angle of rotation ( euler angle) about***γ***,***z-***and***x-***.***y-axes*Now my idea is that, we can calculate brute-force the all rotation angle

**,***α***and***β***by 1 degree increments. When***γ***of***sum***of matrix is minimum closely to***C*_{14}, C_{15}, C_{16}, C_{24}, C_{25}, C_{26}, C_{34}, C_{35}, C_{36}, C_{55}, C_{56}, C_{66}**ZERO**,**the****is orthotropic tensor. And my question is:***C*_{ijkl}- what scope of
,*α*and*β*should I give in Python procedure? I can get all rotation situation.*γ* - If I can use any optimization algorithm? rather than brute-force calculating by 1degree increments. Such as
**POWELL**algorithm and how to use?

Thank you very much!

Dear Sirs,

I did not find this material on the internet. There are only mechanical models of some aspects of self-replication. Full mechanical model is absent. Of course it is enourmous problem if one precisely build it. But maybe there are simple and simultaneously more complete mechanical models? I prefer purely mechanical self-replicating machine but self-replicating robots are also good.

Hello!

Could you tell me - I need to simulate what forces are generated in the rotor of an electric machine when it rotates. Also, inserts of other materials are made in the rotor and this must be taken into account. As I understand it, you can take this into account by setting a Contact Pair, but the model takes a very long time and does not produce a result.

Please tell me if I'm doing everything right and what else is needed for a full analysis?

Thanks in advance!

Hello,

I would like to know what are the

**commutator systems**that are being used in other labs for**in-vivo neural recording (and stimulation) in rodents?**In the lab we tested some cheap non-motorized commutators such as adafruit's and moflon's. The initial mechanical resistance is very high for a mouse to easily make it turn.

I know there are some motorized options but they are super expensive (>4k) and/or super big (need to be installed in the ceiling)

Thank you!

I need the basics for including energy loss in Hamilton formulation for Finite element analysis for vibration of viscoelastic materials. The papers I read use complex modulus to represent viscoelastic losses or convolution integrals. Can someone give me a link where the formulation starts from Hamilton's principle?

I would like to know, which books are internationally recognized for studying Mechanics, Molecular Physics, Waves, Electricity and Magnetism, Optics and Atomic Physics. Russian favorite authors are Irodov and Saveliev. But I want to know what books are traditional for English speaking auditory?

I have a block of mass 'm' modelled as a spring-mass-damper system. A horizontal force F is acting on the mass as shown.

- spring constant = k;
- damping coefficient = c.

**Most of the models I see has a vertical push/pull force on the mass. Then the free body diagrams becomes easy. How do I make a free body diagram in this case? Also, I am mainly interested in Moment induced on the bottom hinge point.**

Dear Sirs,

The 1st law in Newton`s principia are now understood as two statements: the determination of inertial frame reference (if F=0 then a=0 and if F is not equal 0 then there is some body accelleration "a"); there is in nature at least one inertial frame reference. Theoretically I can understand it a little bit. As we have such a determination of inertial frame reference then the 2 nd Newton law is not directly followed from the 1 st law, or this determination is partly independent of the 2nd law. So it looks like logically good.

But what we have in experiment? I do not know whether there is any research on experimental determination of any particular inertial system (like International Celestial Reference System) using the 1 st Newton law. So in practice we use the 2 nd law (e.g. school example - foucault pendulum plane rotation). Could you clarify on the experimental and theoretical determination of inertial frame reference. You know there are teachers that see the 1st law as the consequence of the 2nd law.

I am confused with co-efficient of friction and friction factor.

A part of a Fluid Mechanics text book says that in Darcy-Weisbach equation

h

_{f}=(f L V^{2})/(2g D)f is friction factor.

In the same time, it says that in below equation the f is co-efficient of fraction.

h

_{f}=(4f L V^{2})/(2g D).In this case, we see that (Friction factor = 4 x co-efficient of friction).

I am looking for information on advanced characterisation of mechanically activated fly ash. Advanced characterisation I mean, quantitative XRD for estimation of amorphous phase, IR, NMR and XPS for bonding, etc, Can anyone help about publication(s) on the subject?

Hi,

I am trying to model a free-free body (aircraft) as a stick-model only consisting of beam elements. For certain configurations I observed that my Stiffness Matrix loses singularities / my model has an insufficient number of rigid body modes. I broke the problem down to a simple 2-D Beam configuration shown in the attached picture. The model consists of 5 Nodes with 3 degrees of freedom per Node all connected via Euler-Bernoulli-Beams with the analytical Stiffness Matrix shown in the picture. The left configuration exhibits the expected behaviour having 3 rigid body modes. Introducing the additional stiffening beam element for some reason reduces the number of rigid body modes, as indicated by the higher Mode 3 Frequency and the higher Rank of the Stiffness Matrix. Is such behaviour expected? And if yes, what are ways to workaround this problem other than building the model from 3D solid elements?

Thanks for your help!

Find the reaction at Point A and B.

I want to convert the Young's modulus and Poisson ratio of an orthotropic material given in Cartesian coordinates into cylindrical coordinates. Please suggest me the way or provide me the link or document where I can get these things. Thanks in advance

Hi everyone,

As far as I know, the user-defined forces can only be applied to elements (VDLOAD). I could not find in the manual any subroutine to apply user-defined forces to the individual nodes instead of elements. I thought about adapting the VDISP to provide "forces" in the form of incremental displacements/accelerations, but I was hoping that there is some other way to achieve this. On a related note, how about Abaqus Standard?

Thanks!

Dear Sirs,

I think many knows the ideas due to Jules Henri Poincaré that the physics laws can be formally rewriten as a space-time curvature or as new geometry solely without forces. It is because the physics laws and geometry laws only together are verified in the experiment. So we can arbitrary choose the one of them.

Do you know any works, researchers who realized this idea. I understand that it is just fantasy as it is not proved in the experiment for all forces excepting gravitation.

Do you know works where three Newtons laws are rewritten as just space-time curvature or 5D space curvature or the like without FORCES. Kaluzi-Klein theory is only about electricity.

Is ECU connected to can? Can we program it through AUTOSAR?

And if we have up to 70's ECU in car so it means we don't have a brain here?

What is sbw-Center ECU then?

Why many scientists use the term mathematical model ?

If you have a certain phenomenon and you want to model it, you will describe its, more or less, approximate behaviour by applying to it laws which can be physical, chemical, economical, geometrical and so on, depending on the phenomenon.

Mathematics is only a tool to describe these laws, so you should speak of physical, chemical, economical, geometrical ... models and not of mathematical ones.

Most of the models I encounter in my research are physical models because, to build them up, the laws of physics are used.

Each time I hear the term mathematical model, my nose gets wrinkled.

What is your opinion ?

One of my friends is studying a bachelor's degree in mechanical engineering and going to finish it at the end of this year. he wants to continue his studies; therefore, I am searching for him exciting areas.

Could you please give me a piece of advice to find proper topics or draw an outline of trending fields in mechanical engineering?

PS: he does not have an academic email to sign up in RG.

Hello,

According to the power law, Stress=K*strain^n. Could someone please explain why an increase in strain hardening exponent n results in less material necking from this equation?

Please see the attached plot, here I used K=1 to ignore it's effect and I have varied n for n different values.

It seems that for the same stress put into the material, the curve at n=0.1 produces the smallest strain, where as the curve at n=0.5 produces the largest strain, up to strain=1. If the stiffest material is desired, is n=0.1 not more favourable here?

This behaviour changes at strains greater than 1, this has also left me confused.

Any clarification on this will be very much appreciated.

Thank you!

DIssipation is the reflection of irreversibility in the processes of nature. How does it reflect itself in various laws an principles ?

I have a Scenario where my lock nut is tightend using a prevailing torque of 14 Nm (as mentioned by the manufacturer) on to the rotor placed between bearings (But the tightening direction and the rotor rotating direction is same unfortunately). The lock nut is loosened after particular life cycle of usage as the rotor rotates with a acceleration of 1230 rad/sec and every time it starts, the sudden acceleration loosens the lock nut. Is there a simple approch to calculate a appropriate prevailing torque for this situation, so that the lock nut does not loosen up when the rotor starts accelerating towards it's max RPM of 9400 in 1 second?

The material should be stiff, tough or Young modulus should be more or which property should be significant for excellent energy absorption?

Hello, world

I've run a 3D simulation of solid mechanic when I'm trying to use contact pairs.In the model I have three parts, the first is constrained, the second is the membrane which is in contact with the first part and the thirth is where I prescribe a displacement and I'm looking the deformation of the membrane.

My issue is that the solids don't interact with each other, one go through the other one like a ghost.

Does anyone here have any experience with contact modeling in COMSOL? Anyone know how to fix this issue?

I basically want to know know any connection if machine learning in Mechanics.

I am designing a helmet impact machine. Does the accelerometer placed inside helmet and load cell placed under anvil give the same peak force value?

I would like to know a finite element software which provides open source codes for large deformation analysis for beam and shell elements.

For a hard surface, it is commanly assumed that the maximum value of friction only depends on the coefficient of friction and the normal reaction force. However, intution suggest that is should also depend on the contact surface area, as it does in the case of skin friction drag force (friction between a solid and fluid) which indeed depends on the surface area under concideration. So the question is what is the fundamental microscopic reasoning for this assumption that it the friction is independent of contact area?

I am wondering and doing a research project to find out if having personnel who are cross-qualified like A&P Mechanics with pilot training or pilots who have mechanic training make a difference. Do Aircraft maintenance release teams who have no, or limited, pilot training negatively affect aircraft return-to-service rates or is there no affect on how the return-to-service rate. Where could I possibly find information regarding the return-to-service rates for the aviation community?

As shown in illustration, I have a pipe with details listed below and it is clamped at both ends. Clamps are tightened by applying a torque of 15Nm. How could i find out if the support provided between the clamps, in this case a U bolt supporting at a length from one end of Clamp would be sufficient under 1G loading condition.

Total length of pipe = 4 meters

OD=5"

Wall thickness = 1.5mm

Total mass of pipe = 5 kg

Thank you all folks out here..

Appreciate your help.

i have generated some graph using ansys mechanical apdl.....now, i have to find FFT transformation of the figure which is in time domain............i can do it once i get x and y data value of figure............if anyone knows to extract x and y data from graph or perfom FFT of function from graph, then pl. help me

I wanna to calculate the fatigue life of rotational structures, first I need to know their mechanical loads

specialy in mechanical engineering

Why and How the stress triaxiality in a material becomes greater than 1? What is the physical significance of it?

Kindly throw a light on it.

Regards

Aditya

Please suggest some papers for Elastic constants of polymethylmethacrylate (PMMA)?

TIA

I have a fluid mechanics questions. Suppose that we a submillimeter needle that is already inserted in the soft tissue. water can run through this needle if the pump is on. suppose we turn the pump on. Waterjet with initial velocity of v0 starts to cut a channel in soft tissue. There is also backflow as this cuts the tissue (backflow from the same cut channel). my question is what happen to the velocity of the waterjet when it hits tissue and goes through backflow. Is it time dependent? Is it depth dependent? Experiments showed that it is velocity dependent since the depth of cut reached from 0 to say 4 mm in 30 second and after that it increases with the order of like 0.01 mm. So it got me thinking that velocity is depth and time dependent. My pump provided volumetric flow rate Q ml/min so the average velocity of waterjet at the nozzle is v = Q/A.

I have developed a mechanics based model for waterjet based on tissue properties and waterjet needle properties including velocity of waterjet. However for Q = 50 ml/min and 0.32 mm needle the velocity is approx. 10 m/s. including this velocity in model predicts a depth of cut in the order of meter which it should be in the order of mm. How can I include the effect of depth and time in my velocity. Any help is greatly appreciated.

Please also see the attached cartoon for a simple demonstration.

Dear All,

I am working on micro mechanical modeling of metals (X65 grade steel). I just have some questions that I am wondering if anyone can help me by answering them.

1. How can I find the the parameters in traction-separation: Knn, Kss, Ktt ( should I consider module of shear and elasticity for them?)

- In damage initiation: normal, shear 1, shear 2

- In damage evolution: fracture energy. mix-mode ratio 1 and 2

2. I know that for cohesive element , it is important to have the match meshes in boundaries of the surfaces but my question is that is it also important to have match meshes in boundaries when we define surface base cohesive?

I'm looking forward to hearing from you soon.

Thank you,

In mechanical APDL, combin39,14 elements can be used. But how to use multiple spring elements in ANSYS workbench.

Dear Sirs,

I would like to find out more precisely whether the 2nd Newton law is valid or not in wide range of masses, accelerations, forces. Particulary I have a question whether the inertial property of body (inertial mass) is able to stop the body for small external forces or not. I have found in the Internet the fresh articles with tests of the 2nd Newton law for small accelerations (10^-10), small forces (10^-13) and SMALL masses (about 1 kg). The articles deal with the question of dark matter and MOND theory in astrophysics.

But I am interested in BIG masses. Could the test be carried out in planetary scale? Maybe for the Moon or asteroids? Or for masses like 1000 kg? Thank you very much for any references.

Dear Sirs,

1, 2, 3 laws of Newtons need closed system (net force is zero). How do we practically realize, create such closed system?

One example. Let us look at a body motion. One can say If the body velocity is constant, e.g. zero then no forces act to it. Is it true? I think no. According to the 1st Newton law the velocity constance is the CONSEQUENCE of F=0.

So are there precise ways to construct closed system? Or all physical theory is just a mean to generate a hypothesis which has more higher probability to be true then other random thought?

Could you give references on mass measurement from the 3rd law (with different forces: gravitational, elastic, etc)? E.g. old articles by

**Saint-Venant.**I'm looking for a good intro for cantilever beam mechanics.

We are given a length and radius of a fixed rod and we apply a force F at the free end.

How can one calculate forces and slopes at each point of the rod?

I am planning to conduct four-point bending tests on tubes with

**different lengths and diameters**. Do you know of any method to decide the proper loading rate/speed?There are shell theories like Love's, Donnell-Vlasov, Sander's,etc genrally used. Which theory is applicable here based on the limiting ratio mentioned above ?

I have a ceramic crucible, which is pressed from the sides to hold the weight, for this material, which failure theory can be used from Ansys?

Mohr-Coulomb theory or Max Tensile Theory, which among two will be more accurate for failure prediction?

Is there any procedure to evaluate the viscoelastic coefficient of a material ?

You have a cylindrical structure that you want to preserve under impact loading (the force below which the cylindrical structure stays intact is 5kN). How do you design another energy absorbing structure to put between the impactor (which generates a force of 25kN) and the cylindrical structure to make sure that the later stays intact?

Dear RG members,

Why shear fracturing occurs in the rock compression test where no shear stress is applied?

I am trying to measure the toughness of leaves. I have rigged up a system where I put a leaf on a cube of agar (15g agar per liter water) and drop an empty syringe with a piece of wire (not a needle) through a tube to puncture the leaf. Unfortunately, the weight of the empty syringe is sufficient to penetrate the leaf so I figured a tougher leaf would cause the wire to enter the agar less, thus making a shallower hole. Is there an equation to relate the force required to puncture the leaf to the amount of slowing the leaf exerts on the wire? I also don't know if the difference will be perceptible and perhaps I should find a lighter puncture object

Dear RG members,

As shown in the attached picture, If the study objects are not rod-shapped, will cracks and fractures occur under gravity?

If crack appear, how to decribe it? how to determine the location of fracture face? and which yiled criteria is applicable in this case?