Applied Mechanics - Science topic

Thanks for the opportunity!

We provide G values for Double-Cantilever Beam (DCB) specimens that depend linearly on the crack length c: see " DOUBLE-CANTILEVER BEAM SPECIMEN BENT BY PAIRS OF OPPOSITE TERMINAL TRANSVERSE LOADS" (2024) in our contributions in Research Gate.

Automating biological functions such as childbirth with AI is a highly complex and ethically sensitive area. While AI can significantly enhance and assist in many aspects of healthcare, full automation of biological functions, especially something as intricate and personal as childbirth, presents numerous challenges and limitations. Here's a breakdown of how AI can be involved, and the specifics of its application:

1. Monitoring and Diagnosis

2. Assisting in Decision-Making

3. Automation of Procedures

4. AI in Healthcare Management

5. Ethical and Practical Considerations

Current State and Future Potential

Summary

AI can enhance and support various aspects of childbirth and prenatal care, such as monitoring, decision-making, and procedure assistance. However, the full automation of childbirth involves complex physiological, ethical, and human factors that cannot currently be fully addressed by AI alone. AI’s role is to complement and support human expertise rather than replace it.

May-be you have already solved your question.

I have made a similar work using formula taken from Love (1927) . I needed to introduce "Poisson effect" to correctly solved the crack system in this study entitled "FRACTURE MECHANICS IN A THREE-DIMENSIONAL ELASTIC HALF-SPACE UNDER THE RECTILINEAR CONTACT PRESSURE OF A CYLINDER" (2019). May-be introducing "Poisson effect" solve the problem.

Regards

1) Your answer is on a purely assumption level.

2) Assuming no pre-existing crack, le material would deform plastically only.

3) In presence of a pre-existing crack, expansion of the latter would be observed on the elastic applied stress range first until the blunting of the crack (crack arrest), clearly in a two-dimensional crack scheme.

Recent works confirm that elliptical cracks cannot expand under applied shearing stresses parallel to their planes. Please see: Conoidal crack with elliptic bases, within cubic crystals, under arbitrarily applied loadings-I. Dislocation, crack-tip stress, and crack extension force; -III. Application to brittle fracture systems of CoSi₂ single crystals (III). Theory and experiments completely agree.

Progress is achieved with respect to previous description:

1) The crack extension force G, per unit length of the crack front, is now available in analytical form

2) G value now includes the contribution of gravitational forces due to the earth.

Please refer to “BRITTLE CRACKS IN A THREE-DIMENSIONAL ELASTIC HALF-SPACE UNDER THE RECTILINEAR CONTACT PRESSURE OF A CYLINDER: INTRODUCING GRAVITATIONAL FORCES”.

Cross-slip, twinning, and fracture systems under applied loadings receive the same mathematical theory using continuous distributions of elliptical dislocations in the framework of linear elasticity. Essentially the theory provides a quantity G that is a ratio, defined as the decrease ΔE of the total energy of the system divided by the corresponding change ΔS of the surface of the dislocation distribution, after incremental infinitesimal time dt: G= -ΔE/ΔS. In fracture G is the energy release rate or crack-extension force per unit length of the crack-front. Stationary configurations under which d<G> = 0 are those observed experimentally. <G> is the value of G averaged over all the spatial positions on the defect front. Please refer to the following works for details: Conoidal crack with elliptic bases, within cubic crystals, under arbitrarily applied loadings-I. Dislocation, crack-tip stress, and crack extension force; -II, III, and IV: Application to systems of twinning in copper (II), fracture in CoSi2 (III), and cross-slip in copper (IV). Theory and experiments completely agree.

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.

The inertia tensor is a function of several geometric and material parameters. If they are assumed as random variables following a certain PDF, it should be possible - in principle - to compute the PDF of the inertia tensor in closed form by applying transformation formulas of random variables

The Thomson anisotropy parameter, denoted as ε or γ, is a measure of the degree of anisotropy in a material, specifically the difference in wave velocities in different directions. For orthotropic materials, which have different properties along three perpendicular axes, there are three Thomson parameters (ε1, ε2, ε3) corresponding to each axis.

To derive the elasticity matrix, you need to:

It's important to note that this process requires accurate measurements and calculations, as well as knowledge of some elastic constants beforehand. Additionally, it assumes that the material is linearly elastic, homogeneous, and orthotropic.

I think you can email the Publishing house (Springer), and the conference organizing committee all including in a single email (CC) to inform that you have nothing to do with the mentioned conference. The conference committee did not reach you and nor did you agree to be in the conference. You can also make a public statement in LinkedIn and/or twitter that you are not affiliated with the mention conference.

However, I would suggest you to be confirm first if the conference indeed use your name without your permission or was it a same name /similar name of researcher. Because people often make mistake researchers with same/similar name. Thank You.

Synergetic Control:

Synergetic control, often involving the theory of synergetics which is related to self-organization and pattern formation in complex systems, can be applied in both model-free and model-based contexts. However, its implementation tends to be more aligned with a model-based approach. This is because synergetic control often requires a good understanding of the system dynamics to design the control laws that guide the system towards a desired self-organized pattern or behavior. It leverages mathematical models to predict and orchestrate the dynamics of the system components cooperatively, aiming for an optimal performance through self-organization principles.

PID Control:

PID (Proportional-Integral-Derivative) control, on the other hand, is primarily a model-free control strategy. It does not require a model of the process to be controlled; instead, it relies on adjusting the control inputs based on the error between the desired setpoint and the actual output. The PID controller adjusts its output using three terms – proportional, integral, and derivative – which are tuned based on the error over time. This approach makes PID control widely applicable in various situations where a detailed model of the system is not available or is difficult to develop.

In summary:

- Synergetic control is typically more model-based, requiring knowledge of the system’s dynamics to effectively drive the system towards a desired behavior using principles of self-organization.

- PID control is model-free, relying solely on feedback from the system to adjust its outputs, making it versatile and straightforward to implement in many different applications without detailed knowledge of the underlying system dynamics.

Thank you so much

Dear Sarabjeet Kaur ，For more details please visit the conference website:

Phenomena such as the Al Naslaa Rock, Active cracks in Yosemite National Park find explanation from gravitational forces.

Dear Khamiss Cheikh The short answer is yes.

The somewhat longer answer is that the journal “Journal of Advanced Research in Applied Mechanics” was till this month listed as “Accepted Scopus title”, see enclosed file September 2023 (added in December 2022). In the latest update November 2023, see enclosed file the title is added to the current list of Scopus titles. This explains why in the Scopus link https://www.scopus.com/sourceid/21101152132 details like “Scopus content coverage” etc. are missing: they are too new.

Best regards.

still awaiting criticism

We refer to the work “NON-PLANAR CRACKS IN UNIFORM MOTION UNDER GENERAL LOADING” by ANONGBA (2020):

When the velocity v of planar cracks increases toward the terminal velocity ve = 0.52 ct (ct, the velocity of transverse sound wave), moving non-planar crack configurations have been found (0.33 ct < v < 0.55 ct, approximately) with average crack extension force < G > much larger than those of planar cracks. This indicates that non-planar cracks may be associated with larger decrease of the energy of the system on change of crack configuration. Hence, the starter planar crack transforms itself into a non-planar configuration to maintain higher speed motion during its evolution in steady motion.

With this work at hand (i.e. "ROUGH CONOIDAL CRACK GROWING UNIFORMLY UNDER GENERAL LOADING"), it becomes possible to follow the evolution (propagation) of highest complexity cracks that nucleate from defects (such as heterogeneities, inclusions ...) located inside materials. The provided G (the crack extension force per unit length of the crack front) is function of highest number of variables and parameters.

Again with this work at hand, it becomes possible to follow the evolution (propagation) of highest complexity cracks that nucleate from defects (such as heterogeneities, inclusions ...) located inside materials. The provided G (the crack extension force per unit length of the crack front) is function of highest number of variables and parameters.

Thank you, Aziz Khan and Stephan D A Hannot for your valuable suggestions.

YES! THIS HAS BEEN SHOWN IN “PLANAR CRACKS IN UNIFORM MOTION UNDER MODE I AND II LOADINGS” (ANONGBA 2020).

THIS IS WITHIN THE THEORY OF LINEAR ELASTICITY!!!

In mode I loading and in the subsonic velocity regime (v < ct, the velocity of transverse sound wave), G (I) increases continuously with v from the value in the static case G(I)0 (v = 0) to a maximum G(I)max = 1.32 G(I)0 at v = v (e) =0.52ct; then, G (I) decreases rapidly to zero when v tends to ct. In agreement with experiments, the value v (e) corresponding to the maximum of the crack extension force is identified to the terminal tensile crack velocity, observed in the fracture of brittle materials. No reference is made to the Rayleigh wave velocity cR. In the transonic speed regime (ct < v < cl), the crack characteristic functions are identical in form with those of the subsonic regime. However, for v < ct√2, we show that the faces of the crack, separated under load before the extension of the crack, close under motion; this indicates that the crack movement is hindered. for v > ct√2, the motion of the crack is possible. In mode II loading and in the subsonic regime (v < ct), G (II) increases continuously with v (when v < cR) from the value in the static case G(II)0(v = 0); when v approaches cR, G (II) increases very rapidly. Above cR (cR < v < ct), the relative displacement of the faces of the crack, formed under load before crack motion, closes in motion; this indicates that crack motion is impeded. The velocity of uniformly moving cracks is limited by the Rayleigh wave velocity. In the intermediate speed regime (ct < v < cl), the crack characteristic functions are similar in form to those below cR. The mouvement of the crack is possible.

YES, FRACTURE MECHANICS IS BEAUTIFULLY COMPLETED. It has been suggested and demonstrated that a crack in an elastic loaded solid in the framework of linear elasticity may be viewed as a continuous distribution of infinitesimal dislocations (For a review, see Bilby and Eshelby, 1968). These authors provide an expression for G, the crack extension force per unit length of the crack front (or energy release rate), for steady motion. G is sum of terms that are products of stresses and values of the relative displacement of the faces of the crack at the tip of the crack. We find in recent works (Anongba, 2021 and 2022) that for a dislocation in the form of an arbitrary closed loop, there exists only one singularity in the dislocation stress fields. This singularity is of the Cauchy type: i.e., 1 / │r - r₀│; r the position in the medium and r₀ the position on the dislocation where G is evaluated. These are terms involving that singularity which contribute a non-zero value to G. All the other additional terms in the dislocation stress fields are bounded and contribute nothing. In this sense, we may say that Fracture Mechanics is completed.

There are couple of sensors might be used for different purpose in automobile, for temperature, rain, speed, fuel, break and stability direction, knock, transmission, oxygen, proximation, traffic etc. depends on your requirements. You can use all or call on car is inbuilt with which sensors.

Hi

Does that mean you want to compare different bodies with a fixed underbody? If so, can't you consider the underbody rigid in your software? If not, can you ask your question more clearly?

A corresponding work (Anongba, 2021) is intitled ʺ Elliptical crack under general loading: dislocation, crack-tip stress, and crack extension forceʺ. The various physical quantities displayed there depend implicitly on time t through the dependence on time of the circular crack radius R ≡ vt (v= constant). We take ar = a1 / a2 = 1 where aiare the semiaxes of the elliptical crack; R = a1.

P.N.B. ANONGBA, Elliptical crack under arbitrarily applied loadings: dislocation, crack-tip stress and crack extension force, Rev. Ivoir. Sci. Technol., 38 (2021) 388 – 409; see also, http://dx.doi.org/10.13140/RG.2.2.27048.29446

Thank you Gaurav for your interest.

In aerospace the wake has always been a disadvantage from the design point. But is it possible to use it for solving the problem, or designing a device, may be the cooling mechanism.

Using the problem itself to generate the solution. Reverse engineering if I m correct.

When using Abaqus or other finite element analysis software, it is not uncommon to encounter elements that become highly distorted and remain connected by only one node. This can occur for various reasons, such as meshing errors, modeling inaccuracies, or material instability.

To address this issue, you can try the following steps:

The GIc method is already outdated by non linear plastic principles such as GF.

I think Praveen meant stable solutions and not steady. To get unstable solutions you can integrate backward in time or use continuation methods to trace steady-state stable and unstable solutions including bifurcations.

The nano layer thickness is very very small layer, otherwise it's cannot use by Resistivity method and it has VES limitation.

Best regards.

P. Hakaew

Hello, I have a problem with Ansys for composite prototyping. Does anyone know how to add the ACP (pre) module in Ansys 2018?

The regular polygons of trigonal and hexagonal symmetry as yield criteria are summarized in Altenbach, H., Kolupaev, V. A., General Forms of Limit Surface: Application for Isotropic Materials, in Altenbach, H., Beitelschmidt, M., Kästner, M., Naumenko, K., Wallmersperger, Th. (eds.), Material Modeling and Structural Mechanics, Advanced Structured Materials, pp. 1-76, Springer, Cham, 2022. Both 24-gons are called the Rosendahl criteria.

Dear colleague

the research in title may help to find the answers

'Serviceability of Reinforced Concrete Gable Roof

Beams with Openings under Static Loads '

Bob Senyange Sir and Victor Krasnoshchekov Sir, thank you for your comments.

Hello!

You can use the Tabor equation: H=3S, here H (MPa) - hardness & S (MPa) - yield stress.

Also you can use the next equation describing indentation h (mm) of a cylindrical object (indenter) into a material with HV (MPa):

h=(P/HV/l)^2/(2R), here P - load (N), l - length (mm), R - radius (mm) of a cylindrical object. This equation can be easily transformed into a equation for a case of a spherical object (indenter) indentation.

Best regards, Michael.

property module>special (at top of screen)>inertia>create>anisotropic

me too, i need to know, How can estimate the Abaqus chaboche parameters, please ?

I think this job will help you

Theories for triboelectric nanogenerators: A comprehensive review (https://doi.org/10.1515/ntrev-2020-0049)

Dear Zmour,

It can be better in term of diffusion convection reaction. My opinion is little different, the least-squares method has better control of the streamline derivative than the SUPG.

Ashish

When the crack (be it planar or non-planar) is associated with crack-tip plasticity, the relations between the failure stresses in specimens tested in tension, compression and bending given above (see our answer 1) remain valid, except that σ_T is now multiplied by a quantity that contains the crack-tip plastic zone size, crack-front shape and orientation of average crack surface. Please see “NON-PLANAR CRACK WITH CRACK-FRONT PLASTIC YIELDING UNDER GENERAL LOADING” in our contributions in ResearchGate.

Almost all modern instruments have an option to measure the OC potential of solutions (sometimes called the rest potential) in 3 electrode configuration. You don't need to remove or disconnect any electrode. Don't stir the solution during measurements. I don't understand what means "electrosorption" experiment. If this is a kind of bulk electrolysis, you must stir the solution as fast as possible.

I also need to use this feature but the problem is when I use it the values of stress are changing. How can I use the view cut feature without changing the values?? and Is there another way to do it??

I suggest you that take a look at following link.

Dear Al B. Kounga, piezochromic polymers are known with regard to this feature. Please check the following documents. My Regards

10.1007/978-3-642-36199-9_6-4

10.1002/chem.201800194

Attached is the paper.

Hi, SLM-ed SS316L does not need damage model. Based on numerous experiences working with the compression of SS316L lattices no fracture will occur even up to densification. In addition, bulk SS316L (cylinder) sample does not even fracture up to 80 % compressive strain. A solely bilinear or multilinear plasticity model will work for SS316L.

If you are interested in damage model for a less ductile metal, such as Ti64, high strength steel etc, you can consider the Johnson-Cook damage model nontheless. If you are not planning to obtain them experimentally, you can reference them easily from various lattice papers.

this is a simple Code i have done while ago hope will help :

NDIV=10

PI=3.14

!

VELO=10

TIM=Lbr/NDIV/VELO

delta=1/100

!

*CREATE,FORCE

FDELE,ALL

TIME,ARG1

Force=node(ARG2,Wbr/2,Hbr) !! Load position

amplitude=-1e2*cos(45*2*3.14*ARG1) !! load amplitude

!amplitude=-10e2

F,Force,FZ,amplitude

solve

*END

/SOLU

ANTYPE,4

TRNOPT,FULL,,DAMP

LUMPM,0

OUTRES,ALL,ALL

DELTIM,TIM ! Specifies the time step sizes

TINTP,,0.25,0.5,0.5

KBC,1 ! Ramped load step

*DO,K,1,100,1

*USE,FORCE,TIM*(K),(K)*delta

*ENDDO

Thanks again to you all, you helped me and pushed to keep on researching about the problem. And I finally solved it!

The problem was not on the B matrix, but it was on the order of the 8 displacements of the 4 nodes, on the vector that multiplies B. I called it nodes_displacements.

To be coherent with my B matrix, the order of the nodes have to be physically anti-clockwise: down-left, down-right, up-right, up-left. This is also the order used on many books.

However, as I had all the displacements of all the nodes of the mesh on a big vector, ordered from up to down, I inconsistently took the elements from up to down to build up the nodes_displacements vector, which corresponded to low index to high index and that was incorrect.

All in all, I recommend to anyone having my same problem to verify the order of the indexed displacements.

I think the mentioned error comes from element dimensions, run the simulation by default element and check the results.

Dear Mohammad Reza Amiri,

You can certainly use nano-indentation to measure the hardness of a particle less than 120 um in diameter. First, minimize the mismatch between the modulus of elasticity and yield strength associated with the particle and the modulus and yield strength associated with the mounting resin. Once the material is mounted, use standard polishing and grinding procedures to minimize the surface roughness, achieve a mirror finish, and expose the cross-section of the particle. Once you've calibrated your nanoindenter frame stiffness, compliance, and tip's contact area function using a reference material such as fused silica, determine the particle-dominated depth limit using the criteria proposed by Yan et al. such that indentation depth is less than or equal to 0.02 * R, where R is the radius of a given particle. Otherwise, David Mercier et al. appear to have had success when using the guiding principal established by Constantinides et al., which advocates for a depth limit of 10% of the particle size. From my own experience, when the mismatch between a particle's stiffness and the stiffness of a given mounting material is very large, then Constantinides 10% rule no longer holds and the 2% particle radius rule from Yan et al. remains reasonable.

With the aforementioned in mind you will still face a significant challenge in so far as the indentation size effect is concerned. Depending upon the radius of your particle, when you abide by Yan et al.'s approach then you may not obtain enough values of hardness as a function of indentation depth to apply the Nix-Gao relation before surpassing the particle-dominated depth limit. Therefore, care needs to be taken in interpreting the results. In other words, the hardness will not be the "true" hardness without the Nix-Gao analysis unless your particle is 120 um in diameter, then you could potentially solve for the true hardness by fitting the hardness vs. depth data between depths of 100 nm and 1200 nm. Such a range would likely be sufficient for indentation size effect analysis.

Lastly, one could take an alternative approach. You could acquire a flat-punch indenter tip and compress the micro-particles using an indenter. See Assadi et al. for more information surrounding this alternative approach.

Best,

Bryer C. Sousa

Materials Science and Eng.

Worcester Polytechnic Institute

Yan et al.

Mercier et al.

Assadi et al.

Good Answer Vaibhav Balkrishna Jadhav

Hi Karan,

Aside from the suggested answers, you can also use AceGen in Mathematica.

http://symech.fgg.uni-lj.si/User/AceGenPrint.pdf

Best,

Romik

Corresponding Python script

In Poland, there is now a trend in which we all have to duplicate our research and analysis in magazines that have relevant points on the list from our Ministry of Science and Higher Education - unfortunately I can't find you in our list :-(

Please look at ASME B31.3 Code Table A1 for minimum design temperature of materials. But Low temperature carbon steel ASTM A350 LF2 is very common forging carbon steel rather than A105.

The following article is relevant:

This paper presents a novel method of space-based geoengineering which uses the mass of a captured near Earth asteroid to gravitationally anchor a cloud of unprocessed dust in the vicinity of the L1 position to reduce the level of solar insolation at Earth. It has subsequently been shown that a cloud contained within the zero-velocity curve of the largest near Earth asteroid, Ganymed, can lead to an insolation reduction of 6.58% on Earth, which is significantly larger than the 1.7% required to offset a 2 °C increase in mean global temperature. The masses of the next largest near Earth asteroids are found to be too small to achieve the required level of insolation reduction, however, they are significant enough to be used as part of a portfolio of geoengineering schemes.

Cheers

There is no general valid answer, because materials do not respond equally to different typs of projectiles.

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.

Hi A. A. Ab.,

When we find stresses σ_ij corresponding to displacement vector U=grad f, then boundary loads will be p_i=σ_ijn_j, where n is unit external normal vector to the boundary of the body, and volume loads will be b_i=-σ_ij,_j. These loads cause the infinitesimal rotation tensor to be equal to zero. The case of symmetric displacement field is only particular.

Hello @Robert Shour,

On the question, "Does society lose or forget these old insights that are discarded once new conceptual reference frames take hold?" Yes, in the sense that too much "knowledge" eclipses common sense. A case in point is what I call the "Wimbledon Phenomenon". A couple years ago, British social scientists conducted a survey among 1) Housewives, and 2) Tennis trainers, asking who would win the next Wimbledon championship. The housewives out-performed the tennis trainers by a large margin.

It could also be argued that the Friedman-Robertson-Walker metric (as "a new conceptual reference frame") and its attendant big bang theory and LambdaCDM cosmological model have eclipsed all common sense about the nature of the universe, insofar as huge contradictions now exist in standard cosmology, for example related to Dark Energy, which has a phantom equation of state p<-rho and therefore behaves like anti-gravity. Yet this does not undermine the Mainstream Physicist's continuing belief in their objections to refutations of LambdaCDM!

Chee Loong Chin Thanks a lot for your helpful answer.

Units were not consistent. The mimics soft had defined density in g/cm3 but because distances was in mm; the consistent unit for density was tonne/mm3.

Problem solved and thank you again.

thanks Abhimanyu Kumar

Khaled Megahed Khaled, there is much to it then stated here. To answer your question, yes, it should not have softening part. By your terminology, it seems you are dealing with concrete or some similar material, since for metals, true stress is the one without softening. True stress could be expressed mathematically (usually without perfect matching), and damage also can be expressed through some sort of function. But it depends on many more parameters, firstly material and type of degradation that is causing damage, than triaxility, Lode parameter, than strain rate etc. Then, you probably need this for numerical analysis, and by using Abaqus or similar software, you will need to make a choice about yield law, hardening law, damage type and law (if any), or simply use damage as a multi-linear for some points you choose. This choice is highly influenced by the experiment you did, for example, is the strain rate important and varied etc, or did you used extensometers so you have only global softening, or you used DIC so you already know the true stress-strain relation for your material. If the latter is not the case, I suggest you follow the advice Charles gave, and iteratively obtain satisfactory P-delta through numerical analysis. Some papers that might help would be:

An Experimental-Numerical Combined Method to Determine the True Constitutive Relation of Tensile Specimens after Necking, You-de Wang, Shan-hua Xu, Song-bo Ren, and Hao Wang

True Stress-True Strain Models for Structural Steel Elements P. Arasaratnam K. S. Sivakumaran and M. J. Tait

Bolted shear connectors vs. headed studs behaviour in push-out tests, Marko Pavlović, Zlatko Marković , Milan Veljković , Dragan Buđevac

ELse, if you used Aramis, then maybe take a look at:

Strain and stress relation for non-linear finite element simulations, Sohren Ehlers , Petri Varsta