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# Mechanical Behavior of Materials - Science topic

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Questions related to Mechanical Behavior of Materials

Quasi-static indentation test conducted on Aluminium 5052-H32 sheet with 3 different thickness;0.5 mm,1 mm, 2 mm.

using 12.7 mm hemispherical indenter, speed 1.25 mm/minute, both edges clamped. The test was conducted until specimen perforated.

For 1 mm and 2 mm thickness there is a flat plateau as shown in the load-displacement graph.

can anyone explain this?

e.g. if f'c = 35MPa (AS3600) what would fcu = ? MPA (BS8110)

Method that used in most of automotive industries to detect cracks or damage

I sam earching a preporcessor program for fracture mechanics analysis using abaqus, I am doubting between zencrack and feacrack, I wonder if someone has experience with these programs and can help me to select which one (or another program) is better.

I want to use it for 3D studies

I would like to to know, is there any change in stacking fault energy with varying strain rate during deformation?

Hi, I am working micro mechanical analysis of the composite material by using GTN model. I am encountering the macroscopic and microscopic local phenomenon in the composite is completely depends on the type and arrangement of element. I would like to suppress this mesh dependency of solution in the GTN, could you please let me know is there is any possible method to over this issuse, without using UMAT or UEL. If possible , could any one share their UEL or UMAT code for nonlocal GTN model

I have done the tensile strength test on two kinds of tensile specimens with the same material, but the mechanical behaviors differ from each other.

My considerations are focused on the size effect factor of test specimens, but I don't know how this parameter manipulates the mechanical behavior.

I would be grateful for any suggestions.

I am doing subzero heat treatment after quenching for en24 steel. And after subzero heat treatment am tempering it for 450c. So is it ok to go for 6 hours for subzero heat treatment or do we have to go for 24 hours only?

Young's Modulus and Poisson's' ratio is not known for the material (in literature).

I had a question revolving around the friction hardening law based on UBCSAND model utilized in CY model embedded in FLAC3D-V5. Apropos of CY model, the users are supposed to define a table of the mobilized friction angle in terms of the plastic shear strain. Inasmuch as the ensuing equations, i.e. Eq.1 and Eq.2, were posited for the frictional soils, I have tended to think of modifying the aforesaid equations so as to harness in the cohesive frictional soils medium in light of the fact that the friction hardening table in CY model ought to be adjusted to reflect more realistic behavior for a cohesive material.

Eq.1

Eq.2

Having perused HS model in PLAXIS plus CY model in FLAC3D, the formula concomitant with the elastic shear modulus has been rectified for the clayey soils as follow:

Eq.3

As respects the plastic shear modulus formula, can I have your say whether or not Eq.1 is expected to be modified with the intention of adding the mobilized cohesion?

I am trying to find out how to identify specified parameters of ductile damage material in its stress-strain curve in Abaqus. I could identify the Young's modulus and the yield stress, but not the fracture energy. How do I identify this in my results?

For now I am simulating a simple tensile test in y-direction on a one-element model (1x0.2x1).

Suppose one side of the rope is closed and the other side is on the pulley. Force is applied to the free side of rope. How can I simulate this, since the rope does not bear shear force? Which element? Beam? Trus?

Thickness and diameter shrinkage percentage of the Al2O3 sample (after sintering):

Diameter 20%

Thickness 18%

Hello

We have certain high temperature oxidation/corrosion autoclaves for testing in aqueous or gaseous environments. I would like to check the creep resistance (qualitatively) of alloys by exposing the pre-stressed/strained specimens in the autoclave, as it is more demanding to build a creep-tester with load cell and extensometer exclusively for it. Are there any reported procedures to perform qualitative creep tests using pre-stressed/strained specimens (such as U-bend specimens for SCC testing)? I would check the creep damage through the evolution of creep cavities and cracks after the completion of the test. Any suggestions provided will be of great assistance.

Thank you in advance.

I’m searching for possible applications for magnesium wire and rods. I considered fasteners (for example, screws, rivets, and bolts), springs , grids and meshes and bioresorble implants. Also I would like to discuss their potential. I’m not sure if Mg springs could get to industrial use, because of its low Young modulus of 45 GPa. But springs from aluminium with a low Young modulus of 70 GPa is commercially available. In my opinion screws have the best chances because with increasing use of Mg sheets more fasteners of the same material will be needed (e.g. to reduce galvanic corrosion). Any ideas for other applications would also be appreciated. Thanks in advance.

Does a single-valued description exist for isotropic materials?

What is commonly used stress-strain material model for

**prestressed steel tendon/strand reinforcement**for computer modelling such as Abaqus?I have material model for concrete (such as Hognested) and steel reinforcement (such as Ramberg-Osgood), but would like to know theoretical/ideal material model for prestressed steel reinforcement to be used for

*nonlinear analysis*.Does the curve change in case of prestressed or post tensioning?

Cheers,

The material of the specimen is concrete. Three point bending test in my words is synonymous with a Crack mode opening displacement tests with a notch on the bottom surface of the concrete beam.

In hot forging process, when we heat the work piece up-to 1200oC. It surface begin to rupture, due to oxidation of iron. This oxide layer penetrates into the metal surface when we deform it with compressive forces. So, We are in the investigation of a best technique for descaling of hot metal. Our production is mixed and batch. Our product variety.

I am simulating on adhesive bonded multi-layer protective structure. To capture the adhesive effects, I am advised to use AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK to model the bonding strength without actually modeling the bulk adhesive. However, the contact surfaces are eroding surfaces due to projectile penetration. Could I use two contact cards simultaneously to simulate an eroding contact surface with initial bonding strength? if not, is there any other suggestion?

I need very recent (2010 onwards) technological advances that can allow magnesium to be used for Car body shells. Similar to how aluminium is used today at JLR. Thanks !

Hi guys

I am trying to implement Holzapfel material model (anisotropic hyperelastic) and have to define two families of fibre directions. Initially we ran Abaqus’s benchmark problem input files (section 3.1.7 Anisotropic hyperelastic modelling of arterial layers), but we did not get any of their results! (Keeping in mind the 1/8 th symmetry)!

Is there a problem with Abaqus input files for the mentioned section? I am planning to follow what they have done in this simulation, specifically with regards to their implementation of fibre directions, but it’s quit depressing to see that they are not working.

Thanks in advance

My "Concrete Damaged Plasticity" model in ABAQUS can't simulate the behavior of reinforced concrete structures in cyclic loading.

I have been trying to solve Stokes equation in 3D micro - geometrical meshed. I'm currently exploring the Fluid model>Creeping flow>stationary of COMSOL 4.4. Comsol failed to solve my problem. It continue showing me "Failed to find a solution. Divergence of the linear iterations. Returned solution is not converged". Going through discussion forum, someone suggested that unchecking "p" on "solver manager" in "solver paramters" would help solve the problem. Please, can anyone help me on how I can locate this solver manager in COMSOL 4.4? Or what is a suitable approach? Thank you all,

Otaru, A.J.

Dr Bin Yang asked an interesting question: https://www.researchgate.net/post/How_to_distinguish_between_creep_voids_and_dimples

I am currently working on a phenomenological creep damage model that takes account of (i) creep cavity nucleation, (ii) diffusion controlled creep cavity growth and (iii) plastic hole growth.

The model gives a good prediction of a wide range of creep-fatigue test data (164 tests) on; Cast 1CrMoV, Cast ½CrMoV, Wrought Grade 91, Cast Type 304L, Type 347 Weld Metal, Wrought Type 321, Wrought Type 316H and Type 316H Multi-Pass HAZ; Tested at Temperatures ranging from 538 to 650°C. (see attached plots).

(Note: The black lines show 1, 2 and 0.5, which are acceptable scatter bands. The red lines show a linear fit to the data and the upper and lower 95% prediction intervals to demonstrate whether the model meets the acceptance criterion. )

However, to achieve a good prediction for all of the 164 Creep-Fatigue tests I have to make some assumptions. I am therefore looking for other evidence (such as metallography or theoretical modelling) that supports these assumptions:

The main assumption that has been made is about the conditions under which Plastic Hole Growth dominates and when Plastic Hole Growth is negligible.

Are there any metallographic observations or theoretical modelling that suggests that; Plastic Hole Growth can only dominate; (i) when the total strain is monotonically increasing and/or (ii) when the total strain exceeds a certain value; or (iii) any other relevant observation regarding Plastic Hole Growth at elevated temperature?

Does Young's modulus of a material change with heat treatment?

Does the chemical composition affect Young's modulus?

If during heat treatment process the chemical composition remains constant and material only has a microstructural change, dose Young's modulus change?

I am trying to model friction in a cracked structure by using contact feature. I have used contact pair algorithm option and used Dynamic Explicit analysis method. If you suspect any modeling error, I would appreciate your suggestion.

I am using ductile damage in FE model for steel material. the damage evolution law should be specified in terms of equivalent plastic displacement (U

_{pl}) or in terms of fracture energy dissipation (G_{f})Is the correct to use the following relation for calculating equivalent plastic displacement (U

_{pl})?Where L is the characteristic length of element, "epsilon.f.pl" is the equivalent plastic strain at failure and "epsilon.0.pl" is the equivalent plastic strain at the onset of damage.

or it should be calculated using this equation?

U

_{pl}=L(epsilon.f.pl)based on abaqus documentation the fracture energy can be calculated using the following relation

G

_{f}=(U_{pl}*sigma_{yo})/2where sigma

_{yo}is the value of the yield stress at the time when the failure criterion is reachedIn the material assignment section, I am not able to define the strain life properties of materials (i.e. Strength Coefficient, Strength Exponent, Ductility Coefficient, Ductility Exponent, Cyclic Strength Coefficient, Cyclic Strain Hardening Exponent). Please help me for the same.

Please explain with reference to that of an undergrad level.

Please share your thought.

Your opinion is highly appreciated

Regards

For N-H creep, creep rate is inversely proportional to d

^{2}, whereas for Coble creep, creep rate is inversely proportional to d^{3 }. What can be the possible explanation for d^{2 }or^{ }d^{3 }?- Generally, fracture mechanics parameters and terms (CTOD, J, C*, stress, load line displacement, plastic zone size) have relevant & respective dimensional units. The physical significance of their units is easily understandable like, energy per unit area or energy rate per unit area of crack growth. In case of K, why its (meter)
^{1/2 }i.e. square root of crack size, a and not simple a or 1/a or a^{-2 }? What is the physical significance of including square root of crack size, a in K formula?

I want to know the reason for the impression as shown in figure after hot forging of composite material. I have done a step wise hot forging of cylindrical shape ingot and after hot forging the rectangular shape as shown in figure has obtained with impression of top and bottom side. I want to know the reason for that if anyone can explain this.

thanks

It's seems that addition of carbon atoms increase the hardness by solid solution strengthening. However I do not know why it will have more effect on ferrite than on Austenite.

We are trying to manufacture fasteners made of A286 steel. The fasteners were forged and solid solution treated at 900

^{o}C for 2.5hours followed by 680, 720, or 740^{o}C aging for 16hours, which is well-known heat-treatment process for gamma' precipitation of A286. After then, hardness in the range of 30-32HRC was obtained.This result is pretty much unsatisfactory to us because we need to make A286 fasteners with 34HRC or above. I heard that maximum hardness of A286 would be around 35-36HRC but our heat-treatment couldn't lead to the value.

Can anybody suggest any heat-treatment process to improve hardness of A286 steel? Unfortunately, we cannot conduct cold rolling more after solid solution treatment due to client's request. For your information, grain size of our materials is around 12-13 micro meter.

Any assistance would be greatly appreciated.

Thank you,

JH Kim

Since strains measured in the middle of the bars of SHPB by gauges don't represent what happens at specimen/bar interfaces, we must establish calibration files for both incident and transmitted bars. These files will be introduced to a post processing program.

I'm doing the characterization of composites materials at high strain rates by SHPB. I need to know if there is a way to validate the method. In other words how can I know that the Stress-Strain curve is correct?

Can anyone help me to make the user subroutine UMATHT used in ABAQUS simulation for lithiation process in lithium ion battery (LIB)? I am working on anode part of LIB and need to run an FEM simulation. However, I am not aware of the programming part of this subroutine. I would really appreciate comments from people who know about it.

I have diagram of cyclic voltammogram, seeking to understand how to define the diagram voltammogram.

I model and simulate a simple plate in 2D form, to analysis the tensile test in WB. However, by increasing the load, nothing happened and just stress and deflection increased. Even stress passes the ultimate strength of steel. I defined the plasticity in Engineering material and its ultimate tension strength is defined there too. I am new to Ansys and I do not know how to accomplish the tensile test.

Aim is to introduce different amounts of oxygen into Zr and study its deformation behaviour.

Dear engineers, scientists and experts in the field of plasticity,

In the literature, the terms strain hardening and work hardening are often used under the theory of istropic hardening. Mostly these terms are used in the same context or even equated.

Is that always correct, even using Drucker-Prager flow rule?

We use Vickers indentation method for estimation of the fracture toughness. We use the following formula, Fig. 1. The calculation requires the average length of cracks. If there is only one 8 μm crack (Fig. 2), then we take the average 8 μm? Or (8+0+0+0)/4 = 2 μm?

I want to explore the dynamics of parametrically excited (nonlinear) beam whose material's Young's modulus (E) and loss tangent (tan(delta)) are known. It is convenient to use the simple Kelvin-Viogt model in the evaluation nonlinear dynamics. Hence, I want to find out viscoelastic coefficient (eta) in the model, sigma = E*(epsilon)+eta*(d/dt(epsilon)) where, sigma is time varying stress, epsilon is time varying strain. d/dt is differentiation with respect to time. Please, give me some suggestions for the calculation of viscoelastic coefficient or any other alternative modelings using loss tangent and Young's modulus.

hello

im a new abaqus user and i want to model a viscoelastic material (asphalt) in abaqus . i have uniaxial creep test data for characterize viscoelastic behaviour . my question is how can i enter viscoelastic parameters in abaqus?is there any way to put creep test data directely in abaqus??

in abaqus for modelling viscoelastic material in time domain there are three ways:

1)combined test data

2)shear test data

3)volumetric test data

i have unaxial creep test data so what shoud i do?how can i obtain long-tern normalized shear compliance and elastic modulus for elastic modelling?

i attached my test data .

thank you

best regards

Hello to all the members of the world of science!

It's a tensile-related question and kind of a basic one; but I'd really like to know the answer. So here we go:

Notwithstanding the fact that for most of the iron-based alloys, a rapid fall from upper yield point to lower yield point is witnessed (in addition to the Lüders bands), some iron-based "superalloys" exhibit an almost straight, fall-free form of curve. What is the reason?

Thanks in advance!

Specifically electropolishing reagent and conditions.

Normally, representative volume element (RVE) of the composite is independent of geometry. There are several homogenization methods available that defines regular shaped like rectangular, quadrilateral with inclusions of rectangular,circular,ellipsoidal, spherical shapes. Is there any analytical methods defined for irregular shaped RVE?

Is there any element type available to model viscoelastic material ?

There is only option available to model viscoelastic material in ANSYS is using prony series but that couldn't help me.

I am doing quasi static and high strain rate compression and tension test but the yield value are different. Compression yield is grater than tensile yield. What is the reason behind it.

Is there any extensive literature, dataset or open source/free software for generating CCT and TTT diagrams for steels

I collect data concerning Poisson's ratio of different types of geopolymer concrete. I would appreciate if you recommend any articles that include the results of tests in which the value of Poisson's ratio of geopolymer concrete is determined.

Thank you.

I am trying to correlate the experimental and modeling results of micro-indentation. The indent shapes are not matching because the amount of springback and material rise the model is predicting is different than that from the experiment. I tried changing the BCs, refining the mesh in the region of indentation. I didn't experiment with the contact behavior yet. But,these solutions didn't help. I am guessing the differences are due to improper material definition (using Abaqus for modeling). I am using tensile test data for the same. I wanted to know if Al 1100 H14 behaves differently in compression. If yes, how to incorporate that in Abaqus material definition?

I am currently investigating the load-carrying mechanism of a driven pile (hollow bar) and trying to install strain gauge on the pile for measurement of stress distribution. I have tried to install the strain gauges on both outer and inner surface of the pile with sealant and protective tape on but they all fail due to the large driving force applying on the pile. Most of the gauges broke at the lead wire connections. Is there a way to install the gauges that can withstand large driving force?

Regards, Philip

Hello all ! I'm working on the formability of different aluminium alloys by ironing process. And I want to know how does the strain hardening exponent 'n' influence the formability by this process?

Thank you !

Where is the stress-strain diagram of brass forging at different temperatures and strain rates?

Does anyone have experience in writing UMAT Subroutine in Abaqus?

I wish to open a discussion on the way that Plastic Instabilities influence the results of Mechanical Tests. For example, tensile tests, creep tests, torsion tests, pressurised tubes test, etc..

It might be interesting to also discuss tests that are not affected by plastic instabilities; this category might include high cycle fatigue and fracture toughness tests. However, it would be interesting to hear any views to the contrary, such as the need to use side grooves in fracture testing being because of plastic instabilities.

Finally, perhapse I should have re-phrased this question as:

Do plastic instabilities influence the outcome of all mechanical property tests?

Angle of internal friction of sand is found to decrease with increased overburden pressure (see attached figure). The curved nature of actual Mohr-Coulomb failure envelope (the straight line that we plot for Mohr-Coulomb failure envelope is merely a linear approximation) also indicates the same, i.e. a decrease in friction angle at higher normal stress.

In physical terms friction angle represents particle interlocking. Greater the interlocking between the particles, larger should be the friction angle and vice versa. At higher normal stress better interlocking is to be expected, which should translate into a higher friction angle but it isn't the case (considering the density remains constant). Particle crushing at high normal stress, might be one reason leading to low friction angle. My question is what are the other physical explanations of the decrease in friction angle at higher normal stress/overburden pressure?

I performed a Crack Propagation analysis using XFEA in Abaqus. The result is showing that the crack is propagated and the crack length is increased, however when I plot the result, I see the crack is all the way propagated. I could not see the crack propagation gradually. I think my visualization setting needs to be adjusted and then I will be able to see the crack propagation element by element. Any help will be appreciated.

Hamid

I have problems to running data of damage parameter (d

_{t}) coming from formula of Birtel article (2006 ABAQUS Users’ Conference )[1].But, with formula below ABAQUS running very well and, i take result in figure attached.

- d
_{t}= 1-exp(-strain inelastic * ac) ....... Bashar [2]

or

- d
_{t}= 1 - tension / fcm ........................ Jankowiak [3]

Someone can tell me how can i make data made with Birtel formula running in ABAQUS?

[3] Identification of parameter of Concrete Damaged Plasticity Model

In Abaqus I have an axisymmetric model of the rotor for a steel seal with a thin ceramic face. I want to get the circumferential stress induced by friction on the rotor face, when the seal is spinning at steady state, to determine interfacial stresses between the main body of the seal and the film. I see that this can be done in Abaqus, but I can't seem to find a way to specify spinning along the correct axis of rotation.

I have a question about cyclic hardening .

Are the values of Yeild stress at zero plastic strain and equiv stress identical?

The experimental data test will be used in conjunction with the numerical results of a counterpart model in an optimization procedure. The cost function will be built using the difference between the numerical and experimental data then minimized in a least squares sense.

let's say we are after strength and ductility of a structure with gradient of grain size (bimodal microstructure), and micro tensile test setup is not available. Is it possible to somehow manage to get stress-strain curve that represent mechanical behavior of all the microstructure from micro-hardness test or nano-indentation test? I know it is possible to get several indentation test along the sample and get a stress-strain curve for each point. However, the sample has gradient of grain size lets say from 400nm up to 5um, so depending on the indent location we are expecting different mechanical behavior. Also I am not sure if just averaging all these curves would be a very scientific way of getting the final stress-strain curve. Any idea along these thoughts is highly appreciated.

Thanks

**Which theory is used to calculate shear stress in Ansys workbench?**

because I like to determine shear stress for a brittle material through Ansys.

Dear all researchers,

I observed that Fracture Strain and Fracture Toughness of Aluminum Alloys depends upon the strain rate, as we increase the stain rate Fracture Strain and Fracture Toughness also increases. I don't able to find the reason behind this.

In mechanics of materials the engineering stress & strain (

**Cauchy**) are defined by the original area and original gauge length respectively. Is this by definition, at room temperature at which the original measurements are likely to be made?During tensile testing (creep testing etc) at elevated temperatures thermal expansion will affect the area and gauge length. However, it is common practice to use the values measured at room temperature to calculate the engineering stress and engineering strain.

It is clearly, possible to take this thermal expansion into account and I often do so when calculating true stress and strain (Hencky).

However, I don't do so for engineering stress and strain and instead use the room temperature values. Thereby treating the engineering definitions as approximations and the true stress and strain as the more "correct" definition of stress and strain.

In my mind I consider the engineering stress and strain to use the original area and original gauge length as measured at room temperature as a

**definition**of "engineering" stress and strain. However, I have never seen this written down explicitly and wondered if anybody knew if the "engineering" stress and strain were actually**defined**differently such as "original area and original gauge length,**measured under appropriate conditions**".Please note for the calculation of "true stress" and "true strain" I am fairly convinced that the correct thing to do is to use the "original area and original gauge length,

**measured under appropriate conditions**". My question is about the engineering definitions!I know this is very pedantic!