Mechanical Characterization - Science topic

You may find some useful information in the preprint article link http://dx.doi.org/10.13140/RG.2.2.23849.40808

Polyamide 12 powder thermal conductivity varies with packing density and temperature, with inter-particle bonding being the primary factor influencing its performance in laser sintering. Temperature and time exposure are the most influential factors for deteriorating polyamide powder properties in the laser sintering process, affecting the quality of produced parts.

Laser sintering of polyamide 12 powder significantly impacts the microstructure and mechanical properties of sintered parts, with particle size distribution and crystallization temperature being key parameters in porosity formation. Using different ambient conditions and pretreatment can reduce the degradation of polyamide 12 powder in selective laser melting processes, resulting in better part properties. High-temperature flow properties of polyamide 12 powder deteriorate significantly, but agglomeration is excluded in the 100-140°C range, making it safe for laser sintering applications.

Please Find out more researches that might be useful:

· Heliyon, 9 (10) 2023: e21042 DOI: 10.1016/j.heliyon. 2023.e21042

· e-Polymers, 22(1) 2022:858-869 DOI: 10.1515/epoly-2022-0078

Best regards,

Theoretically, it doesn't matter whether the specimen is rectangular or circular, But technically a problem may arise with circular specimens if you use knife edges on your transverse extensometer. The knives may bite into the specimen by an unpredictable depth, depending on radius. On flat surfaces their clamping force is distributed. It is not a coincidence that testing standards like ASTM E132 advise to use rectangular cross-section for measuring Poisson's ratio.

Also, it is beneficial to have specimens as wide as possible to increase gauge length of transverse measurement. At the same time it is not wise to increase greatly the overal cross-section, because that may require buying a new, testing machnie with bigger force limit ). Rectangular shape allows to vary with and thickness independently.

Regarding the 3rd question, the area under curve represents toughness (amount of work done /unit volume) of material specimen, In you case it is 96.1kPa %. The tensile strength is however, ~580.1 kPa = ~ 0.6 MPa. and the Youngs (elastic) modulus is ~ (580.1 /95.5)*(100/1000) = 0.61MPa

However, i am not sure if there are direct conversion units from Pa% to J/mm^3 .

Nanoindentation is a separate testing procedure that is often used in conjunction with Atomic Force Microscopy (AFM). It is used to measure properties at the nanoscale, such as Young's modulus, hardness, stiffness, and load vs. depth and load vs. hardness. Other properties can also be measured using nanoindentation, depending on the specific application. In India, there are several institutions that offer nanoindentation services. These include the Indian Institute of Technology (IIT) Delhi, IIT Bombay, IIT Madras, IIT Kanpur, IIT Hyderabad, and the National Institute of Technology (NIT) Surat. Additionally, there are several private companies that offer nanoindentation services, such as NanoTest India, NanoTest Solutions, and NanoTest Technologies. If you are having difficulty finding a nanoindentation service provider, it is possible that the machine is under maintenance or the operator is not available. In this case, it is best to contact the service provider directly to inquire about the availability of the machine and the operator.

Dear Dr. Nekin Joshua ,

a piston can be made more efficient with a ceramic coating, which improves the device’s heat reflection and transfers part of the detonation energy into the fuel burning phase. Ceramic coated pistons can assist higher fuel burning efficiency and reduced carbon accumulation, which in turn makes detonation more effective.

For more details, please see the source:

-Ceramic Coating of Automotive Components by THOMAS for Industry

Available at: https://www.thomasnet.com/articles/chemicals/automotive-ceramic-coating/

My best regards, Pierluigi Traverso.

Himadri Nath Saha whats the difference between this method in the article and simple multiple force to displacement one by one?

There is no physical meaning in a higher bending strength of a brittle isomorphic material than in compression strength. The compressive strength simply has to be higher. Could it be that the cross section of the compressive specimen is larger than that of the flexural specimen and therefore the cylindrical specimen is not fully cured? In order to exclude the effect of unequal curing on the strength measurement, both types of specimens would have to be made from the same piece of pre-cured material.

Dr. Abdulla Bin Rahaman in addition to the right and the elaborate answer of Prof. Dmitriy Shevchenko I can add that if we take into account the order of magnitude

T₀ ~ 16 /(N_F a³) * where a is the ratio in which a quantum state is a localization regime, but without external H. This expression is more realistic for metallic alloys where N(ε) ~ (ε - ε_F)² and it has to be with the Shklovsky B.I., Efros A.L. theory of percolation and conductivity in highly heterogeneous media.

Experimentally it has been found years ago T₀ ~ 300 K in the galvanomagnetic properties of epitaxial germanium films forming a part of planar heterostructures

* Kinetic effects of strong localization in planar heterostructures p-Ge/i-GaAe by O. Mironov and S. Ghistyakov. Ukrainian, 1987, Academic of Sciences Institute of RadioPhysics

Best Regards.

From a more general point of view, what you are asking for is generally called a "MRV", as in Minimum Representative Volume.

That is, the minimal volume you can work upon and have a representative result for bigger scales.

I can't help you with your specific issue but when MRV is not known, it should be researched : measure whatever you are measuring on different volumes of growing dimensions and look for when the result stabilizes. This would be your MRV for THAT measurement (not necessarily for others).

Hexagonal boron nitride nanosheets (BNNSs) are promising two-dimensional materials to boost the mechanical, thermal, electrical, and optical properties of polymer nanocomposites. Yet, BNNS-polymer composites face many challenges to meet the desired properties owing to agglomeration of BNNSs, incompatibility, and weak interactions of BNNSs with the host polymers.

Given the mass barrier properties of 2D nanosheets, the high surface area of BNNSs has the potential to reduce the oxygen and decomposed volatile gas flow within the nanocomposite matrix. Hence, reduced oxygen and decomposed gas flow promote the thermal stability of nanocomposites. On the other hand, the incorporation of BNNSs into polymer materials affects the optical properties of the corresponding composite materials. The main reason for the optical property changes is the light scattered by the BNNSs. The nanosheet size and agglomerates of BNNSs, and the defects formed within the nanocomposites are the source of such light scattering. Different strategies are developed to minimize the light scattering such as distributing the BNNSs uniformly within matrix, developing stronger interphase, and downsizing the BN nanosheet sizes. Such approaches require good control of downsizing BNNSs as well as modification of BNNSs. The surface modification includes functionalizing BNNSs with appropriate functional molecules in order to increase the miscibility of nanosheets into polymer matrix and form chemical bonding between nanocomposite constituents. The other optical properties such as UV and IR-wavelength blocking also require good control of the above-mentioned factors to develop the desired properties into polymer nanocomposites.

Dear Milad

The phenomenon of SCC normally occurrs in polycrystalline metallic alloys that are succeptible to a combined of corrosion,i.e.,chemical dissolution, and a tensile deformation. Therefore,the possibility of SCC of PLA is slim to impossible .

See the paper: How Nanofibers Carry the Load: Toward a Universal and Reliable Approach for Tensile Testing of Polymeric Nanofibrous Membranes

Macromolecular Materials and Engineering, 2021, 2100183

Currently, ASTM or ISO standards for tensile properties evaluation of electrospun nanofibers/nanofibrous mats are not available.

Most researchers recommend using a paper frame to fix the nanofibrous membrane for preventing nanofibers damage and better handling the specimen.

However, a more critical problem is the correct normalization of the force recorded by the load cell during the tensile test to obtain the stress-strain curve and, consequently, calculate elastic modulus (Young's modulus) and strength. Indeed, to calculate the stress, the membrane thickness measurement is necessary. However, the measured thickness is affected by the pressure applied to the porous mat during its measurement, so it is impossible to measure the "right" thickness and, as a consequence, the specimen section. To bypass this problem, a load normalization based on sample mass instead of its cross-section area is helpful.

Since the mass measurement is reliable, the calculated stress, elastic modulus, and strength are, in turn, reliable. Furthermore, this method reduces errors in load normalization owing to any thickness variation in the specimen, and the contribution of the mat porosity is discarded. Moreover, it is very powerful when dealing with membranes with a very low thickness, being in such cases the thickness measurement very tricky and completely not reliable.

More information about the tensile test data normalization based on specimen mass (and other very easy-to-measure quantities) can be found on the research article:

Macromolecular Materials and Engineering, 2021, 2100183

This paper also presents a data fitting model applicable to tensile test data of nanofibrous mats, as well as the effect of nanofiber diameter and nanofibers crossings on the tensile behaviour of membranes made of nanofibers.

See also the following videos:

---> How to correctly prepare nanofibrous mat specimens for tensile testing

---> Reliable tensile testing of nanofibrous mats

In the following papers, the proposed mass-based normalization method was positively applied to different nanofibrous mats, even rubber (elastomeric) nanofibers:

---> Rubbery nanofibers by co-electrospinning of almost immiscible NBR and PCL blends

---> Morphology, thermal, mechanical properties and ageing of nylon 6,6/graphene nanofibers as Nano2 materials

---> Rubbery-Modified CFRPs with Improved Mode I Fracture Toughness: Effect of Nanofibrous Mat Grammage and Positioning on Tanδ Behaviour

The interaction in your given state of polymer and 2D material is expected to increase which is surface, contaminants, and interaction capacity based.

Dear Mukesh Pandey many thanks for your interesring technical question. I'm certainly not a proven expert in this field. However, I can recommend to you the following useful article which might help answering your question:

This paper can be freely downloaded as public full text. Also please see the following relevant RG links:

and

Good luck with your research! 👍

Just an idea, use a dye, like fluorescein Na.

Regards,

Joachim

Dear Dr. Pardeep Saini ,

generally, increasing content of porosity will decrease the mechanical properties of MMC such as tensile strength, Young's modulus, Poisson ratio, and damping capacity. The presence of porosity decreased the mechanical properties of cast MMC as the failure process is initiated from the voids formed. Porosity has detrimental effects on the mechanical properties of castings because it introduces defects into the material composition. These defects are created by either shrinkage or trapped gases which both cause air pockets within the final cooled metal.

For more details, please see the following sources:

-EFFECTS OF POROSITY ON MECHANICAL PROPERTIES OF METAL MATRIX COMPOSITE: AN OVERVIEW

S. N. AQIDA, M. I. GHAZALI & J. HASHIM

Jurnal Teknologi, 40(A), 17–32 (2004)

Available at: http://eprints.utm.my/id/eprint/1529/1/JTJUN40A02.pdf

-THE EFFECT OF POROSITY ON FATIGUE FOR CAST METAL MATRIX COMPOSITES

S.N. Aqida, M. I. Ghazali, J. Hashim

No journal info. (2015)

Available at: https://www.researchgate.net/publication/266054224_THE_EFFECT_OF_POROSITY_ON_FATIGUE_FOR_CAST_METAL_MATRIX_COMPOSITES

-Porosity in aluminium matrix composites: cause, effect and defence

Devinder Priyadarshi, Rajesh Kumar Sharma

MS AIJ,14(4) (2016)

Avaliable at: https://www.tsijournals.com/articles/porosity-in-aluminium-matrix-composites-cause-effect-and-defence.pdf

-A Review on Properties of Aluminium Based Metal Matrix Composites via Stir Casting

V. Rama koteswara Rao, J. Rangaraya Chowdary, A.Balaji, D.Sai Krishna, B.P.R.Bhavabhuthi, G.Sreevatsava, K.Abhiram

International Journal of Scientific & Engineering Research, Volume 7, Issue 2 (2016)

Available at: https://www.ijser.org/researchpaper/A-Review-on-Properties-of-Aluminium-Based-Metal-Matrix-Composites-via-Stir-Casting.pdf

Enjoy reading and my best regards. Pierluigi Traverso.

Hey there,

you got any results on material model for PCL? :)

Stay healthy!

Thanks Soumitra Paul sir for your extensive in depth answer. I will surely go through the articles.

Dear Sage,

Self-healing polymers are a new class of smart materials that have the capability to repair themselves when they are damaged without the need for detection or repair by manual intervention of any kind. One way to extend the lifetime of a material is to mitigate the mechanism leading to failure. Self-healing polymers and fiber-reinforced polymer composites possess the ability to heal in response to damage wherever and whenever it occurs in the material. This phenomenal material behavior is inspired by biological systems in which self-healing is commonplace.

Self-healing polymer composites possess the inherent ability to heal the damage event autonomically or non-autonomically with external intervention. These advanced materials can be commercialized if the challenges and limitations of different self-healing mechanisms are well known and considered. These include capsule-based healing systems, vascular healing systems, and intrinsic healing systems.

The concept of self-healing polymers relies on encapsulation of monomers and catalyst and incorporating these encapsulated healing precursors into the polymer. When cracks are initiated in the polymer, the capsules rupture and healing monomers fill the crack and polymerize there, allowing healing of the crack.

The best-known self-healing materials have built-in microcapsules (tiny embedded pockets) filled with a glue-like chemical that can repair damage. If the material cracks inside, the capsules break open, the repair material "wicks" out, and the crack seals up.

The researchers successfully created a material capable of restoring the functions in electronics after a break. Still there is scope to work in the areas of electrical resistivity, breakdown strength, ion-diploe interactions and combination with shape memory alloys as a developmental application in sensing materials etc. Other challenges for the work are capsule-based healing systems, vascular healing systems, and intrinsic healing systems where work can be carried out. .

Hope it is helpful to you.

Ashish

Dear Hossein Homayoun,

Let me introduce for your consideration an original method of studying the mechanical properties of polymeric materials.

Creep rate measurement with laser interferometer

Laser-interferometric creep rate meter (LICRM) is the original high-resolution method for investigation of the mechanical properties of solids, first of all, polymeric materials.

LICRM has been successfully applied to solving various problems of polymer physics and materials science. It allows to register precisely creep rates on the basis of deformation increment of 150–300 nm. This approach provided absolutely new experimental possibilities exhibiting the superiority in resolution and sensitivity to the conventional relaxation spectrometry techniques. Amongst such possibilities are creep studying on submicro-, micro- and meso-scale levels; revealing the connections between stepwise microplasticity and polymer morphology; getting kinetic information on creep at any temperature and deformation degree, the discrete analysis of dynamics within an each relaxation region; analyzing microplasticity, relaxations and phase transitions even in brittle materials; using creep rate spectra for non-destructive prediction of the temperature anomalies in mechanical behavior of materials, etc.

The report : <https://link.springer.com/chapter/10.1007/12_2009_36 >

represents this method and some (not all) results of numerous studies performed with applying of LICRM setups for different polymeric materials in the form of bulk specimens, films or thin fibers

We are ready to provide more detailed information on your request.

International Journal of Sustainable Engineering

Also, you can paste the abstract of your paper in the journal finder below to find the most suitable journal to publish on Elsevier

All the best

A tricky question. For me, it depends on many different things. If I have all data collected it can take at least 2 weeks, as after writing an article I usually put it aside.

The above answer does not seem satisfactory. Indeed, strain hardening, which is due to an increase of the dislocation, will occur whatever the loading direction is (i.e. tension or compression).

In my opinion, the most likely explanation for this asymmetry is the impact of processing. Indeed, during the fabrication of your alloy, a significant amount of plastic deformation has been used for forming (e.g. extrusion, rolling). Because this plastic deformation result in strain hardening, the yield surface of your alloy has significantly been altered by processing. Strain hardening is usually directional (i.e. kinematic hardening), which means that the evolution of the yield strength is direction dependent. The consequence is that, because of processing-induced hardening, the compression and tensile yield strength are different.

Answering w/o justification or complementing on questions are not welcome on an academic website. Here is not Linkedin or Facebook. Getting back to Shima's question. Usually Taguchi DOE is used in cases where you want to perform as minimum as possible number of iterations (or Cases). In my opinion, full factorial DOE provides the best accuracy, however, if you are limited in terms of time or expense associated with your analysis, then you can use other methods with less accuracy.

Hi,

It can depend on your material microstructure. Grain size and grain boundaries can significantly affect the strain behavior of any metal. When you apply shear load, the grain can slide on top of each other while, when you apply tensile load, the fracture mechanism is totally different.

The width of the process window is determined by the plunging force value so that wider welding speed may be used at higher force values. Holes arise due to insufficient flow of plasticized metal into a zone behind the tool. 5083 may have strong adhesion to the tool and therefore bad stirring and flow capacity. We use 0.5 m/min welding speed at 550 rpm and 2600 kg force for welding 5083 5 mm thickness butt joints.

Dear Sir,

For Epoxy composites You can do four main Mechanical Test such as Tensile test, Compression Test, flexural test, Impact test. Further u can check its hardness property.

For fiber alone u can take tensile test, moisture absorption test, other than physical characterization of fibers are also possible by checking fiber density and determining fiber constituents.

What will happen if the test is done in displacement control mode, with like 1 mm/min? Will it give different result compared to force control?

Thank you.

Agree with the answer above but for the small error in calculation, 0.5^2 is 0.25, therefore the difference in Poisson's ratio for 0.1 and 0.5 will result in about 30% error in the measured modulus, assuming you have used a very stiff indenter material (typically diamond). Typically errors up to 10 % in calculated moduli are expected from indentation experiments, so may be the sensitivity to Poisson's ratio is therefore not significant.

As prof said we have to follow the ASTM standard

If you have enough date, that would be possible. Use any statistical software to do the comparison. Also, i think any equation is suitable for a specific material and for certain condations. It is deffecult to generalize a mathematical equation for all materials

It is important that the rheological quantities measured for the solid and the gel are comparable. For example, a modulus (hardness) is something completely different from yield stress or breaking strength (strength): a cookie may be hard but have low strength, i.e. it breaks or crumbles easily. Modulus is measured in a small deformation test (linear range) whereas strength is evaluated in a large deformation test (non-linear range).

Your tensile tester operates in the creep mode (deformation vs. time at imposed constant stress). This gives the tensile compliance roughly equal to 1/E (Young's modulus). Ideally, for the gel this should be compared to the output of a stress-controlled rheometer, operating at imposed constant (small) stress. This gives the shear creep compliance J roughly equal to 1/G (shear modulus). Please note that E and G are generally time dependent. Equivalent results on the gel can be obtained in an oscillatory rheometer. If only a steady shear rheometer is available, the best experiment is to measure shear stress of the gel as a function of time at a given constant shear rate. G can be approximately calculated as the ratio of shear stress and total shear (= shear rate x time) at a range of as short as possible times.

A classical textbook on polymer rheology (linear behaviour) is J.D. Ferry, Viscoelastic properties of polymers, Wiley (1980).     

Hello Arvind,

Please have a look at the attached reference materials and let me know if they come in handy in line with your query.

I think tensile stress relaxation is governed by particle rearrangement and fluid redistribution. An increased packing density inhibits particle rearrangement and only leaves fluid redistribution as the major process that governs tensile stress relaxation.

Useful link:https://www.nature.com/nature/journal/v217/n5130/pdf/217736a0.pdf

Sand blasting is a fundamental and age old technique compared to chemical finishing. As said in earlier comments/answers, it depends on the application. Sand blasting is a good technique to remove the corrosive/rusted layers of metals right from the root and it is non reactive to the parent material. Chemical processing is a compulsion where one needs to preserve the thickness of the metals and further removal of the metal will render the design useless example fuel tanks.

generally the hardness (Brinell hardness-HB) and tensile strength(TS)  of cast iron, brass and steel related according to: TS (in MPa )= 3.45 x HB (Ref. Materials Sience and Engineering by Callister)

In fact, your current load fashion is harsher than the strain gage specification.

There is a standard you should follow

ASTM E111 Standard Test Method for Young's Modulus, Tangent Modulus, and Chord Modulus

Depends on what exactly the composite is, But below are a few links to the ASTM Standards for Polymer Matrix Composites compression testing using different fixtures:

Material anisotropy , filament winding angle and ratio of  hoop stress to longitudinal stress will play an important role in the failure mechanism. Pl refer attached papers.

Dear Akhil,

Under the condition of constant total length (or, equivalently, total strain), the plastic length change of the sample is equal and opposite to any elastic length change, which reduces the stress in the sample. The plastic deformation rate can, therefore, be found as

$\dot\epsilon_p = - \dot\sigma / E_{eff}$

with $E_{eff}$ being the combined stiffness of the sample and the dilatometer. Machine contributions to the stiffness are usually not negligible and should be quantified beforehand by using, for instance, an elastic (ceramic) sample.

Once the relation between plastic deformation rate and stress, i.e. $\dot\epsilon_p(\sigma)$ is established, you can start to analyze this relation and draw your conclusions.

The question is not only with the stiffness of plates, you should know the stiffness of the whole deformation machine. The simliest way to estimate the stiffness of the machine  is to make stress-strain test with the massive hard sample (hardened steel of similar) or even directly anvil to anvil. You should write the result of this calibration test in coordinates "shift of anvil" - "load". Afterwords, in experiment with the your sample, to each value of load correspond the value "shift of anvil", which is sum of  shift of sample and shift of machine, so you can easyly remove the contribution of machine to stress-strain curve.

Dear Juan,

Let me elaborate my problem precisely.While performing

While performing the experiment, one uses the Ti-6Al-4V material and deposit it by using additive manufacturing (specially DMLS) and thus print the material. The same above condition I want to model in Softwares like (ANSYS/COMSOL/SOLIDWORKS or any) and then afterward, I want to go for fatigue simulation.

Thank You,

Thanks Alan for the hint,

I got the ASTM document directly from the internet, without being a member of ASTM nor being an active member of a licenced institution.

But for sake I will remove the document.

@ Nabeel; please see the link at the section  "Selected Test Standards":

You can click on "ASTM F383 Static Bend and Torsion Testing of Intramedullary Rods".

However, I do not know what the term "intramedullar" is. But The ASTM F383 may help you.  Unfortunately I got not access to that document. Good luck.

If you want to enhance tribological properties of any surface using composite/ single layer coatings, you should use PVD/HiPIMS for super hard/protective coating.

Ray, thanks for your detailed explanation. I will try to use these theoretical models and see if it works for my material. I already have some frequency and deflection data for the material. Let me try to correlate.

 Hello Yun thanks for your kind reply. I will contact you through email.

As Bing said, it should be possible, but there are a couple of potential problems about TTS:

1. thermal degradation of your material might occur faster than you anticipate, which will falsify any TTS attempt

2. depending on the material you are using you might change the structure of your material when heating it. This includes changes of crystalline structure (melting), ageing (shifts Tg and does not happen in a way that it can be shifted with TTS), and evaporation of solvents and/or low molecular substances.

In principle, I would prefer a DMA over a tensile tester, if you can allow for testing long enough to get appropriate creep data, i.e. if the DMA is not overbooked. You have a better chance to do the tests in N2-atmosphere than in a tensile tester, as a modern DMA has this feature built-in.

The best answer is to use a more robust extensometer which would not get damaged when the specimen breaks.  This is because only extensometers which are attached to the specimen over a known gauge length can correctly measure engineering strain (extension/original gauge length).   However, I guess that such a device is not available to you.  

Some test machines have a LVDT which measures the movement of the actuator if your machine has one of these then you could make use of this data.  Alternatively you could attached your own LVDT to measure the displacement of the grips or the cross head.  

Now you must remember that measuring displacement at some point of the rig is not the same as measuring extension on the specimen and there would be an error in any calculated engineering strain.   Much of this error comes from the fact that the displacement is the sum all displacements (and not only due to the strain in the specimen).  You should do your best to estimate all these other displacements and minimise this error.  For example, the extensometer measures

strain*gauge length.  

Whereas any remote measurement will measure;

strain*(effective gauge length) + (elastic displacement of load train)*length of load train.  

During elastic loading of the specimen strain is proportional to load.  

Also (elastic displacement of load train) is proportional to the same load.  

Therefore, it should be possible to estimate the

(elastic displacement of load train)*length of load train, and therefore it is possible to estimate strain*(effective gauge length).  

During elastic loading both strain estimates should be the same (after subtracting (elastic displacement of load train)*length of load train).  

Therefore, this gives you an estimate for the (effective gauge length) necessary to make your Modulus measurement from the extensometer equal to the  Modulus measurement from the remote displacement.  

Once, you know

1. The effective gauge length and

2. The (elastic displacement of load train)*length of load train

Then you can use the remote displacement to estimate strain after you have taken the extensometer off.  I would suggest you always use the extensometer to measure Modulus.  and to keep a check that your estimates of 1. & 2. are reasonable.  

Dear Thomas Wu

ASTM A 370 specification give approximate hardness conversion numbers for some materials see it i hope it useful for you, also you can use chart to convert BHN to tensile strength value.

Best Regards 

Thank You Fukada. It was helpful

Of course D638 is still used, and may prove more efective than D3039 in obtaining valid results (e.g., failure away from the grip area) depending on the particular composite. As I mentioned before, D3039 is recommended for composites with high-modulus fibres (E> 20 GPa according to the standard). Concerning impact, it depends on your objective: D256 (Izod), D6110 (Charpy),  D4812 (Unnotched Cantilever Beam), D5628 (impact of plates by falling mass), D6395 ( Flatwise Flexural Impact), D1822 (Tensile-Impact Energy), etc.

 I saw people normally do rheology test on viscoelastic materials. But that is more like a shear modulus as they put shear stress on the material and find out its displacement. So, it sounds not sensible to assume it to be similar to its Young's modulus.  

Following the Carolan 's answer it is usual using the following equation for random "in plane" filler distribution:

Ec=3/8*E11+5/8*E22

where Ec= modulus of composite

E11=modulus obtained using H-T with the shape factor =2w/t 

E22= modulus obtained using H-T with the shape factor=2

However, as pointed out by Carolan, Ec  gets values close to E22 because of the formation of clusters of fillers that decrease the effectiveness of the reinforcing phase.

If the dispersion is good (i.e. filles do not aggregate) then the above equation is a reliable estimation of composite's modulus. 

One more equation is used when the filler is three-dimensionallly dispersed

Ec = 0.184 E11 + 0.816 E22

Dear Wei Shin Cheng!

If the surfase of the specimen (or gripers) can be photographed, you can use digital image correlation instead of extensometer for elongation measurement (https://www.researchgate.net/publication/257619818_Application_of_the_Method_of_Digital_Image_Correlation_to_the_Construction_of_Stress-Strain_Diagrams). This is optical measurement, so it is not influenced by temperature changes.

It looks perfect to me.

Dear Shanti,

I experienced before, the overhanging parts bend opposite direction when I tested sandwich specimens. As Pramod commented, overhanging parts do not affect to bending properties for ordinal materials, but if it is soft in shear---like sandwiches---, overhangings surely affect. It must be long enough so that the shear deformation at the support point can be negligible. Laminated-composites are normally soft in shear, so you must be careful. FEA may help you to ensure your sample design. 

There is no or very little correlation between strain energy dissipated under monotonic tensile test and energy dissipated during the cyclic test till failure - at least for standard metallic materials. The mechanisms of damage are different in those two tests.  However, your material is not standard, so without the fatigue tests, there is no clear answer.  

commercially pure titanium is OK? http://www.epj-conferences.org/articles/epjconf/pdf/2015/13/epjconf-dymat2015_01011.pdf

First, one should plot load-elongation or stress-strain; you put stress-elongation. Answer to your questions are as follows -

1. In order to evaluate YS one needs to fix a predefined offset strain, it is not possible to find any such standard YS (e.g. 0.05% or 0.2% YS) from your graph. Because you put elongation and not strain in x-axis.

2. Young's modulus (E) can be found out from the slope of the curve if it is stress-strain and your machine rigidity is much higher than your sample rigidity.

3. If your sample actually breaks at C then it is the stress at breaking.

The gauge length of your specimen should always be larger than the area tracked by your extensometer (or at least equal). So yes, you can design a specimen with a larger gauge length that the one of your extensometer. Besides, the larger it is, the easier the installation process will be.

Plastic and surface

links

You need to know the name of the materials.

The specimens made of uncompressible elastomeric materials like a rubber often demonstrate the slippage in grips, even in case of enough strong initial tightening. The slippage causes the "step-wised" force diagram and, correspondingly, "step-wised" strain - stress curve. If  this reason as well testing machine peculiarity may be exluded, the possibility of serrate curve formation due to microfailures in specimen at the beginning of plastic part of the curve should be take into account.  Good luck! 

Go for dilatometric test

The standard ASTM E8

Thank you so much..

Hi, 

I'd like to use ramp-and-hold procedure to test the increase and the relaxation, and to regress the data by rheological model. If you use fluctuation test, you should care about the frequency to avoid the inertial effect and should check if there is any software supplement to address this effect under high frequency in your device.

Hi

A low tech way to measure the axial travel of the mandrel might be to take a fixed thin diameter object, e.g. a steel wire and use a fixed position light source to cast a shadow across the dimension pattern you have on the mandrel. Alternatively, you can tape a mm scale to the mandrel. This would show mandrel extension.

On the same note, a scale that is able to stretch taped to the mandrel can be compared with an unloaded scale attached at one of the ends to show relative displacement. This might be implemented by printing a pattern on a plastic sheet.

As stated, low tech, but maybe enough to get at least part of the job done.

If you  wish to go more high tech. Why not use a FE model, measure deflection e.g. using image analysis or multiple measurement locations of your measurement clock (if the process is static) and work loads out from inverse analysis, i.e. apply displacements as loads and compute force/stress?

Sincerely

Claes

Hi,

you can use the single fiber tensile test to determine the mechanical properties of fibers using the single filament tensile tests procedure described in ASTM D-3322-01 standard test method.

Regards,

BELOUADAH Zouheyr

Dear Pramod,

At such high strength the plastic behavior tends to vanish .

Anyway I would try with much lower crosshead speed.

I think you can try with AFM and nanoindentation. They both can work on this scale. However, for nanoindentation, to get indent on this thickness, you may have to have a good optical system accompanying the nanoindenter.

What kind of mechanical properties are you trying to get? Nanoindentation can provide you Young's modulus and hardness. And to some extent, you can predict the yield strength and strain hardening exponent.

If you want to know the interfacial strength of the interface, then something like the lap-shear test or peel test may help you.

Good luck!!

you can attach the fiber or coir to each clamp and put a strain rate, Please the fiber or coir have to be well attach, because during the analysis they can go away of the clamp.

 here is the chemical composition

Using trigonometry, you can easily find the theoretical radius. You know 3 points, I suppose: both extremities and the mid span point after deflection. Thus, you only have to use the formula in the attached picture. The picture is the representation of your theoretical model. 

You can compare this result and the one using the method suggested by Mr. Biswas.

If it is porous or cellular metal, you could use the definition of plateau stress in ISO 13314:2011 standard (see enclosed abstract). Then at first view your computed plateau stress value = 19 MPa could be OK (strain interval 20-30%). See definition 3.4. And the corresponding plateau end at 24.7 MPa (1.3 x 19 MPa, as indicated in definition 3.5) couldindeed match.    

You can get to large shear strains using a technique like equal-channel angular pressing (ECAP). In this technique, you force the sample through an angled channel, which effectively imposes a shear strain. You could manufacture a die with an angled channel and then use your compression apparatus to force the sample through the die. The nice thing about ECAP is that you can pass your sample through the die multiple times, potentially reaching very large strains.

For a recent review of this technique, see:

Review: Processing of metals by equal-channel angular pressing

M. Furukawa, Z. Horita, M. Nemoto, T. G. Langdon

Journal of Materials Science

June 2001, Volume 36, Issue 12, pp 2835-2843