Thank you very much. I am doing my university dissertation in the UK and I must let you know that you have saved me hours of frustration trying to find out how to use the Johnson Cook model. This was the only source I found that helped me and I have referenced you in my work.

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you so much

perfect,Thank you so much

This is a very useful video! I learned a lot with your detailed explanation and I could find the J-C parameters for my experimental material data combining your method with optimization in programming code. Thank you so much and great work!

@scienceandtechnologybygaya3535

Жыл бұрын

Thank you

you are like mother Terisa to me. Thank you

Very detailed. Thank you very much!

@scienceandtechnologybygaya3535

3 жыл бұрын

Thank you

Thank You..so much..for good presentation

@scienceandtechnologybygaya3535

3 жыл бұрын

Thank you

Thanks a lot!!

Very useful information...tq so much👍

@scienceandtechnologybygaya3535

3 жыл бұрын

Thank you

Thank you so much

thank u! this is what I need rn

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you

kindly keep video if you have idea on determining material parameters for Johnson Holmquist progressive damage model for ceramics. especially determining T, A and N of intact strength equation.

@scienceandtechnologybygaya3535

Жыл бұрын

Okay, I will try

thanks so much sister ..god bless u

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you so much

make a video on concrete damage plasticity also if possible

Can u explain Hollomon model strain hardening,

Very Useful and nicely explained, Thanks for the informations it is possible to share the example Excel sheet

@scienceandtechnologybygaya3535

3 жыл бұрын

Actually, data points are not allowed to me to share. If you have any doubt regrading to plot, you can ask me.

Hello and thank you for this video it was extremely helpful for me! Question: Why wasnt the linear curve equation not forced with an intercept of 1 for Thermal softening ?

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you

Thank you so much Miss, This is very useful. Can I get the excel sheet that you explained here? I'm also hoping to see the Johnson's Cook failure Parameters from you too. 🙃

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you very much for watching my video. Actually, these are not exact parameters. It's just for explain how to make graph. If you are having any data points, you can find these parameters.

Hello mam, you have explained it very nicely in the video. My senior learnt about JC parameters from your videos for his M.Tech. thesis and now he recommended your channel to me. I have one additional question: Do you know any source from where I can find the Stress-Strain data for a specific material? I need the data for AZ31B (Mg alloy) and AA-6061-T6 (Al alloy). Even if you guide me towards a website or a tool that I can use, I would be greatly helped. Thank you!

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you very much for watching my video. As per my knowledge, You can search stress- strain graph at particular strain rate from the paper. And request them for the data points. I have no Idea about any website ralated the data points.

Thanks a lot for your detailed explanation. I also need to find johnson cook parameters for my research, but I will use auxetic structure. Should I test auxetic geometries in split hopkinson or bulk structure is enough for johnson cook parameters? Also our test specimen size will be 6mm in radius for split hopkinson test, but our auxetic lattice cell size will be 4 or 5mm, what should I do?

@scienceandtechnologybygaya3535

3 жыл бұрын

Hi, Auxetic structure is having negative Poisson's ratio. And bulk structure shows the property of material lattice structure in static condition. If applied load through quasi static process (very slow). Then, some machines are available to see the behaviour of structure and also find true stress vs strain graph. When impact load (at high strain rate) is acting on the material then the true stress vs strain graph are different. J C parameters are used to provide the material properties to simulate the impact condition in any analysis software. Through the bulk structure, we can not find the true stress vs strain graph at high strain rate. As lattice cell size is very huge, 6 mm radius of specimen should not be enough. I have seen some papers in which they found the J C parameters for Auxetic material. You can contact them and asked what specimen size they used to find the true stress vs strain graph at different strain rate. Title of paper: Three-dimensional modelling of auxetic sandwich panels for localised impact resistance.

@oktaykaya5589

3 жыл бұрын

@@scienceandtechnologybygaya3535 Thank you for answer, I checked the paper you shared, and they found JC parameters from doi:10.1016/j.ijplas.2006.02.006 . In this paper, they had same geometric size problem, therefore they did high strain rate compression tests At Kolsky Bar at unit cell geometry. However, JC parameters results look like normal test results, I mean, the yield value of cell configuration at compression is 12 MPa but they use 310 MPa for A parameter of JC. Can I assume that JC model looking for just material property, not geometry. I want to use Ls-dyna modified JC model for ballistic test.

@scienceandtechnologybygaya3535

3 жыл бұрын

@@oktaykaya5589 Hi, J C parameters are used to give material properties in the simulation. The difference between normal test means you can find J C parameters for coupled effect of different strain rate and temperature on flow stress. You can find J C parameters through universal tensile machine but at low strain rates. You can go Split hopkinson bar for high strain rate.

Your videos on johnson cook are great Can you do a video on damage parameters of jc? Also maybe on von missus? Thanks!

@scienceandtechnologybygaya3535

3 жыл бұрын

Okay I will do.

@scienceandtechnologybygaya3535

3 жыл бұрын

Thank you

@manop919

3 жыл бұрын

​@@scienceandtechnologybygaya3535 I'd like to request too. Moreover, I'd like to know that JC failure model (D1,D2,D3) is able to calculate on tensile test? Finally, Could you mind to provide me your email address please? I'm stuck in trouble on my thesis. Thank you so much, Ma'am

@scienceandtechnologybygaya3535

3 жыл бұрын

@@manop919 Yes, you can find the JC damage parameters (D1, D2, D3) through tensile test. My mail id is gayatri.uiet@gmail.com

@yunsongguo584

3 жыл бұрын

@@scienceandtechnologybygaya3535 You are the best！

Dear Madam, it is a wonderful lecture. I have learned so many things. One thing is not clear that whether we have to conduct testing at different strain rates along with different temperatures for determining 'm' value or we just have to keep the same reference rate of 1/s at different temperatures?? Please clarify this doubt.

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you for watching my video. You can keep same strain rate for different temperatures value. And also you can do for different strain rate too. Suppose, you are having three strain rates and three temperatures value then you can find three m values for three strain rates. And you can do average of these three value. Or which one will give you very close results for experimental values. That you can take. Similarly, for 'C' parameter.

It is good if you can show how to determine strain rate as well.

@scienceandtechnologybygaya3535

3 жыл бұрын

Strain rate is dependent on your requirements. Just like, if a car is hitting another car with speed of 200 kmph and other car is in the rest. Then you have to see the body of car which is going to hit. Suppose the thickness of the body is 12 mm then strainrate will be 200kmph/12mm just match the units before division. If you converted in mm/s and mm then division will be (/s). It will come very high because it is not a point impact, it is a surface impact. But you can get a idea of the range of strain rate. I hope you get the answer. If you are having any confusion please ask me. And thank you very much for asking the question.

Dear Ms Bajpai, Thank you very much for the very good explained video. I have a question about the calculation. Why is it possible to disregard the 2nd and 3rd term when determining A, B and n, and the 3rd term when determining C and the 2nd term when determining m? Are they not related to each other?

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you very much for watching my video. This is a JC constitutive material model. Yes, they are related to each other. A, B, n these parameters are defined at quasistatic process which are using as reference at high strain rate range to define C parameter. At this time taking m parameter as constant or not taking. It is general way to solve the equation having more than one variables. As you know how to solve the equation having more than one variables by using Lagrange method. It's a simple mathematics.

Thank you very much for the very good explained video. I have a question about the definition. Is the strain rate of ε ̇0 defined as the strain rate at(of) 1 s-1?

@scienceandtechnologybygaya3535

2 жыл бұрын

This is the reference strain rate. Generally, minimum strain rate take as a reference strain rate in strain rate range choosen for experiment. If minimum strain rate is 1 / sec. in your strain rate range then can take as a reference strain rate.

@user-rv9re5cf7m

2 жыл бұрын

@@scienceandtechnologybygaya3535 Thank you, you give me a wonderful lecture.

Hi,Dear Miss , thanks for a useful calculation link, i have one question ,if you can explain, it will be very helpful, how you out the rend line after getting the high strain rate plots ,,,at your video time of 19.08

@scienceandtechnologybygaya3535

3 жыл бұрын

I have explained through the excel sheet.

Dear Gayatri Bajpai, thank you for the very informative video. I have a question for you. During the determination of B and n constants, you used the graph of ln (true stress-yield stress) - ln (true strain). Don't you think it is more appropriate to use true plastic strain (εpl=εtrue-εy) instead of true strain? Can you explain? In addition, I am trying the obtain these constants (B and n)according to my experimental data thanks to your video. I have a problem that according to my results, the graph of ln (true stress-yield stress) - ln (true strain) starting from minus in y axis, goes to vertical and then turns to a data line as in your video (I can share the image of the graph if you can share your email). I am wondering am I doing something wrong or should I consider the only the data line. Thank you very much!

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you for watching my video. Determination of parameters B, n and also A are there. True strain means strain at that moment, up to elastic limit, it will regain their position after removing the load and after that (plastic limit), it will not. A will find at elastic limit and B, n will at plastic limit. Hence, ln(true strain) at x-axis for both first elastic limit then plastic. Yes, you can share your graph. My email id is gayatri.uiet@gmail.com

Hi, im stucked at min 17 when you're finding the C parameter at different strain rates. My strain rates are 0,0001, 0,001 and 0,01 but I can manage to get a graph like yours after finding sigma/(Sigma-A+Be^n). What should I plot? sigma/(Sigma-A+Be^n) vs (ln(True strain/strain rate))?

@scienceandtechnologybygaya3535

3 жыл бұрын

Hi, sigma/(Sigma-A+Be^n) this formula is not correct. The correct formula is "sigma/(A+Be^n)". You have shown sigma both in numerator and denominator but it will be only in the numerator. You can plot "sigma/(A+Be^n)" vs ln( strain rate / reference strain rate). Sigma value (true stress) and e(strain) values will be for a particular strain rate graph. Reference strain rate will be fixed for all three strain rates. You are having three strain rates. you can take 0.00001/s as reference strain rate for all three strain rate graph. Basically, you will get two graphs for 0.001 and 0.01 same as my video. Then you can fit a trend line for these two graphs. I hope you will get it now. If you will get any difficulty. Please let me know.

@armandomatosmendez4948

3 жыл бұрын

@@scienceandtechnologybygaya3535 Yes, I'm sorry, this was a typing error I meant sigma/(A+Be^n). I will try to plot what you suggested. Thanks for answering!

Thanks very much for sharing this. I have a question about finding m. Do we have to force the equation to intercept 0? Hope you have your feedback soon.

@scienceandtechnologybygaya3535

3 жыл бұрын

Hi, No, I didn't give forcefully intercept '0'. Whatever slope was coming that I have taken as value 'm'. Thank you very much for asking the question.

@endorphinsaddict

3 жыл бұрын

@@scienceandtechnologybygaya3535 Noted and thanks for the feedback. Nevertheless, do you reckon we ought to force the equation to intercept 0, and then find m? Pardon my repeat question.

@scienceandtechnologybygaya3535

3 жыл бұрын

If you do it forcefully to intercept '0' then your slope will change. And 'm' value will also change. In my work, and other lots of paper, I found they didn't do forcefully intercept to '0'. While the equation x axis and y axis are same.

@endorphinsaddict

3 жыл бұрын

@@scienceandtechnologybygaya3535 Thanks again for your feedback. I shall take heed of your advice :)

17:00 The C parameter you have calculated at different strain rates for a particular temperature. If there is a different set of strain rates for different temperatures then how C parameter should be calculated? Will it be calculated only for the reference temperature condition?

@scienceandtechnologybygaya3535

2 жыл бұрын

C parameter is calculated at different strain rates for room temperature. And 'm' parameter is calculated at different temperatures for a strain rate. Suppose, you have take three strain rates (100/s, 500/s, 1000/s) and temperature ( 300K, 400K, 450K). Assume 300K is your room temperature. Then you can calculate three 'C' parameters for all three temperatures. Ans similarly you can calculate three 'm' parameters by taking three strain rates. You have to do lots of experiments but you can get best results. You have to check the best results for particular C and m parameters. Best results means, your simulation and experimental results match exactly for particular C and m parameters. I hope, able to explain you properly. If you having any doubt you can ask . Thank you

@barman5186

2 жыл бұрын

@@scienceandtechnologybygaya3535 thanks a lot 🙏

Hell :) In the second analysis for the strain rate dependency, the regression is not working on my project. Excel asks me to choose the trendline for one specific strain rate so I am not getting a line of the type y = 1 + C+ln(eps.). Can you maybe help me?

@scienceandtechnologybygaya3535

3 жыл бұрын

How many strain rates have taken for finding C parameter?

@NR-uc7oj

3 жыл бұрын

@@scienceandtechnologybygaya3535 We did the tensile testing for 4 strain rates (10 %/h,, 100 %/h, 1000 %/h and 10000%/h). The 10 &/h strain rate is our reference condition, because it's the lowest. So I used the other 3 to model the strain rate dependency in Excel. The same difficulty occured in finding the parameter m. I have data for 3 temperatures but I cannot add a trendline for all 3 curves. Could you maybe show again how you add the trendline for parameter C and m?

@scienceandtechnologybygaya3535

3 жыл бұрын

@@NR-uc7oj kzread.info/dash/bejne/paGI2saQnM2elKw.html

@scienceandtechnologybygaya3535

3 жыл бұрын

I have made the video for your query. Hope, It will be helpful for you. Still, you are having any problem, please let me know. And thank you for asking.

If Possible, Make the Quasi static Finite element analysis through any software.

@scienceandtechnologybygaya3535

3 жыл бұрын

Sure, I will do the same.

hello, mam true strain corresponds to true plastic strain or true plastic strain +true elastic strain. Thanks

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you for watching my video. Next one means both.

Hi your video is very good and informative. can you do similar video for Rubber as well with ogden and prony series

@scienceandtechnologybygaya3535

3 жыл бұрын

Thank you for watching my video. I will try to do the same.

@1986karthik1986

3 жыл бұрын

Thanks a lot

@1986karthik1986

3 жыл бұрын

Thanks a lot

Mam can we have the value of C and m for single high strain rate and temperature.

@scienceandtechnologybygaya3535

3 жыл бұрын

'C' value and 'm' value comes from the slope of the curve. So it is not possible from one point.

Plz can tell me how you jave drawn the last chart for temperature plz

@scienceandtechnologybygaya3535

3 жыл бұрын

Hi, First, find the stress vs strain graph at different temperatures (T) by using any machine. Then you have to know the melting temperature (Tm) of the particular material and take room temperature as a reference temperature (Tref). Then put into the formula " T*= (T -T ref)/( Tm - Tref). After that you can see again the video @ 20.06 min. I have shown T in the video in place of T* at the calculation time. Please careful. And thank you very much for asking the question. Sorry for late reply. If you are having any doubt further please let me know.

@perlagulbeyazibrahim7780

3 жыл бұрын

@@scienceandtechnologybygaya3535 many thanks ❤️❤️

Hello mam.... Greeting of the day! I am working on new material for simulation work, I need the Johnson-Cook material model and damage parameters. This weekend, I complete my tensile test work, after that if any difficulties mean please guide me to find the model and parameters. Thank you, mam.

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you very much for watching my video. Sure.

Mam from where we can get stress-strain data points of AlSiC alloy. Please replay

@scienceandtechnologybygaya3535

3 жыл бұрын

You can search through papers. And for data points, you can request to author.

Can you share this excel sheet for practice purpose? Thanks in advance.

@scienceandtechnologybygaya3535

3 жыл бұрын

Actually, data points are not allowed to me to share. If you have any doubt regrading to plot, you can ask me.

excuse me, is johnson-cook can be use for elastomer material?

@scienceandtechnologybygaya3535

3 жыл бұрын

Yes, You can use Johnson Cook Model for elastomer material. A title of paper is given below, in which they have compared the responses of three different model for elastomer material. Hyper-viscoelastic constitutive models for predicting the material behaviour of polyurethane under varying strain rates and uni-axial tensile loading

@bimaanggoro8936

3 жыл бұрын

@@scienceandtechnologybygaya3535 thankyou for the reply ma'am. anyway, i just tried to use johnson-cook to my tensile test, and I got this error 'PARAMETERS A, B, M AND N FOR THE *PLASTIC, HARDENING=JOHNSON COOK OPTION MUST BE GREATER THAN OR EQUAL TO ZERO', my m value was negative like your example in this video, is that common? is there any solution for this problem, ma'am?

Mam you had put how to obtain jc parameters. Can you explain how to take parameters from the SS graph, without experiment values

@scienceandtechnologybygaya3535

2 жыл бұрын

Thank you very much for watching my video.

@scienceandtechnologybygaya3535

2 жыл бұрын

For generating the SS graph, it is required to have data points, which will come from experiments.

@sanjaykannan9276

2 жыл бұрын

@@scienceandtechnologybygaya3535 mam how to take graph for any material at elevated temperatures in abaqus especially for tensile use JC parameters

@sanjaykannan9276

2 жыл бұрын

Mam can u pls reply

How could I calculate true stress and strain at different strain rate

@scienceandtechnologybygaya3535

3 жыл бұрын

True stress and their corresponding strain at different strain rates can be found through experiments. Suppose, your material is Stainless steel and you have to find true stess vs strain graph at 1000/s strain rate. You can do the experiments any high strain machine i.e SHPB ( Split Hopkinson Pressure bar). Here, you can set the strain rates through high pressure impact on the specimen.

@prasadraul507

3 жыл бұрын

@@scienceandtechnologybygaya3535 thanks you for reply. I’m not able to experiment due to Pandamic. Is it any possibility I get such a value with the help of simulation ?

@prasadraul507

3 жыл бұрын

I have data point of reference stress vs strain. But I couldn’t able to go somewhere else for the experiment.

@scienceandtechnologybygaya3535

3 жыл бұрын

Experiment data, we can not find through any analysis software. We use these data to calculate Johnson cook material model which is used for simulation. You want some reverse thing. You can follow some paper in which they have found the data for same experimental conditions for same material. First, you have ask to your guide.

hi, could you please explain about material triaxiality

@scienceandtechnologybygaya3535

2 жыл бұрын

kzread.info/dash/bejne/eGx2s7CmXd2_g7A.html

@scienceandtechnologybygaya3535

2 жыл бұрын

Stress triaxiality explain in the following video.