Fracture Behavior of Welded Ductile Iron

Год: 2010
Автор: Hakan Cetinel
Издательство: LAP Lambert Academic Publishing
Описание:
In this study, fracture behavior of welded ductile iron was investigated experimentally and theoretically. Ferritic ductile irons were joined by cold arc welding method by using the nickel base electrode. In experimental part of the study, firstly, mechanical and metallographical properties of the welded specimens were identified. Then, J- Integral toughness values were determined by fracture toughness tests for different crack locations including base metal, heat affected zones and weld metal. In numerical part of the study, finite element analyses were conducted by fixing 3- D models precracked on different locations. After stress – strain analyses, stress triaxiality and plastic deformation characteristics around crack tip were determined for each crack locations and different crack sizes. It was found that stress triaxiality and plastic strain values increase with growing crack length. Different regions with different strength levels, affect the extension of …

173 Replies to “Fracture Behavior of Welded Ductile Iron”

  1. what is a series of the alumunium alloy that you have been used to tensile test ?

    1. Answer to Sorry for that… Could i get your file about this tensile test result ? And if you have more tensile test result file like material St 37 steel etc. Could you send me your file ? I am afraid again, that this is not intended here. On the other hand, we are thinking of creating a database for flow curves in the future, but there simply is too much work for us at the moment.

    2. Sorry for that… Could i get your file about this tensile test result ? And if you have more tensile test result file like material St 37 steel etc. Could you send me your file ?

    3. Answer to could i get your contact person like whatsapp, fb messenger, line or email ? Because i want to ask something about tensile test.. For your information i sincerely say thank you very much.. I am afraid, this is not intended (and not manageable) within this scope, sorry.

    4. could i get your contanct person like whatsapp, fb messenger, line or email ? Because i want to ask something about tensile test.. For your information i sincerely say thank you very much..

    5. Answer to what is a series of the alumunium alloy that you have been used to tensile test ? We have used the alloy AW 2007, so it is an example of the 2000 series.

    1. Answer to pls say how much load applied in this test: The tensile test machine actually does not apply a force, but instead the test piece grips are being moved apart. The force that the specimen is able to oppose to its being pulled apart is measured. In our tests the maximum forces are around 30 kN (for both tests).

  2. can you do tensile strength at the through thickness direction acc to EN 10164 ?

  3. Does cross section area decrease at the point of fracture only throughout the whole experiment(even when sample is in elastic limit)?

    1. Answer to Does cross section area decrease at the point of fracture only throughout the whole experiment (even when sample is in elastic limit)? The cross sectional area decreases from the beginning of the test. In the elastic region, this decrease is very small and barely noticeable. In the plastic region the decrease is important. The volume of the material here stays constant. The decrease of cross sectional area after fracture, an important material property, does not include the elastic part.

    1. It is a Hegewald und Peschke machine with a mechanical spindle drive and 200 kN maximum load.

  4. I have got good idea for this testing methods, parallel i have equation to ask tensile test for 6mm diameters of work pc what abut the length

    1. Answer to How much carbon does this steel have?: The carbon content is approximately 0.1 %.

  5. ludas effect??? anybody know?
    or im listening it wrong?

    1. Answer to ludas effect??? anybody know? or im listening it wrong? It is the Lüders effect, an effect closely connected with the yield point phenomenon

  6. This is an insteresting and informative video. Im a Mechanical Engineering and this information clarifies some concepts.

  7. No idea why this was in my recommendations, but I watched it and it was interesting. Props for Anneke Reinsperger for speaking English without even the hint of a German accent.

  8. why the force sometimes drops stay constant or drop again , is this dependent on the response of the material to the applied force

    1. Answer to Basically, the specimen was elongated gradually by the machine at a steady pace and then the extensometer measures changes in the length of the specimen. So, how could the machine obtain the force data? Which sensor or something like this helps us to record the force?: Yes, of course there is an additional force sensor, that measures the actual force on the specimen.

    2. Basically, the specimen was elongated gradually by the machine at a steady pace and then the extensometer measures changes in the length of the specimen. So, how could the machine obtain the force data? Which sensor or something like this helps us to record the force?

    3. Answer to why the force sometimes drops stay constant or drop again, is this dependent on the response of the material to the applied force: This is an interesting question and at the moment part of the research going on in this area. The tensile testing machine actually does not apply a force (at least not predominantly), but rather moves the specimen grips apart (strain controlled). The ups and downs of the force that appear in the so-called Lüders region are the result of a dynamic equilibrium of the Lüders band formation and the material response. I am afraid it is quite complicated and may not be explained in a few lines …

  9. What happy as same the company in your industry, I am a China company, good video!

  10. after yield point, the video said the piece is strained uniformly , what does that mean exactly? (2) since here we use force, but if we consider the stress, do we just take the original area? shouldnt the area decrease with extension?

    1. Answer to after yield point, the video said the piece is strained uniformly , what does that mean exactly? (2) since here we use force, but if we consider the stress, do we just take the original area? shouldnt the area decrease with extension?: (1) Strained uniformly means that the strain within the specimen is the same at any point of the specimen, just as in the case of a rubber band being strained. This is only true in the region between the end of the Lüders strain and the maximum load point. (2) Yes, the cross sectional area decreases during the tensile test. The stress mentioned in the video is the nominal stress or engineering stress. It is always calculated by dividing the force F by the original cross sectional area A_sub_0, so it is not the true stress. The true stress is the force F divided by the true cross sectional area A.

  11. what will be the gauge length to thickness ratio for specimen mentioned in ASTM D 638.

    1. Answer to Is there any standard gauge length prescribed for the specimen: In the international standard ISO
      6892 the length to diameter ratio is normally 5 (and sometimes 10) for cylindrical specimens made from metallic materials. Things are more complicated in the case of rectangular cross sectional areas and in the case of polymers. It is explained in the respective standards. In ASTM D 638 the gauge length for cylindrical specimens made from certain polymers is not explicitly stated, but probably 50 mm.

    2. Is there any standard gauge length prescribed for the specimen

    3. Answer to what will be the gauge length to thickness ratio for specimen mentioned in ASTM D 638: ASTM D 638 refers to the testing of polymers. Polymers may show very different properties and the tensile test must be specially adapted to the different sorts of polymers. In most cases flat specimens with a prescribed shape are used for the testing of polymers. Cylindrical specimens are very rare and ASTM D 638 does not prescribe a fixed gauge length to diameter ratio in this case, but rather a fixed gauge length (and the diameter may be chosen freely).

  12. If i have to plot the stress-strain curve using this machine, Stress = Force / area. How does the system know the area to calculate the stress because diameter of specimen goes on decreasing on increase of load? Is there any instrument used to calculate the diameter of the specimen at varying loads to calculate the stress?

    1. How do we measure Stiffness of elastomers on this machine? Does elastomer also have a elastic region and plastic region like metals?

    2. Answer to Can this machine measure the elastic modulus and loss modulus, how will it measure?: Yes: The elastic modulus is simply the slope of the stress vs strain diagram in the elastic region. The loss modulus is more difficult to describe, but may be measured as well, as long as the load cycle frequency is below 1 Hz (slow cyclic loading).

    3. MaterialsScience2000 Can this machine measure the elastic modulus and loss modulus,how will it measure?

    4. Answer to Which instrument measures the true diameter of specimen under tensile loading? This is mostly done optically with a high quality camera focussed on the specimen, using a bright background. The analysis is then done by automated digital image processing.

    5. Which instrument measures the true diameter of specimen under tensile loading?

  13. i almost felt into tears when the Lüders effect happened

  14. Its very interesting to see how things work practically instead of just reading it from books.

  15. Never quite understood why we always had two different graphs but thanks to this video its very clear. Great stuff

  16. watching this video to know the strength of my bmx bike ,which is made from 4130 chromolly steel

  17. This is really interesting but the science and maths go way over my head.

  18. What does the term position between kraft and gauge length is telling us

    1. Answer to What does the term position between kraft and gauge length is telling us: Position means the (vertical) position of the crosshead of the machine relative to the machine frame. In most cases the position of the crosshead is not so important. The actual increase in length of the specimen is always smaller than the increase in position because of the elastic resilience of the machine. Also sorry for the late answer …

  19. i cant understand it clearly about that phenomenon with slight fluctuations. whats do you call that again?

    1. Answer to  i cant understand it clearly about that phenomenon with slight fluctuations. whats do you call that again?: It is called Lüders effect. It is closely connected with the yield point phenomenon.

  20. could you upload those diagrams for different materials please

    1. Answer to could you upload those diagrams for different materials please: I agree, this would be a good idea, since not many of these diagrams are freely available on the net. However, to do this means more work than most people think. It should be accompanied by other relevant data like microstructure and precise chemical analysis, and that makes the task tedious. But one day perhaps …

  21. This is extremely fascinating. Im super motivated to finish my remaining education. Working two full time jobs for school has been very tiresome.

  22. Please add izod impact test
    Bemding moment one and three point
    Thank you

    1. Answer to Please add izod impact test Bemding moment one and three Point. Thank you I am afraid we are not really active in this area at the moment, so we cannot make a good contribution.

  23. I’m in 6th grade and this was the first advanced thing I’ve learned like this so thx

  24. How do we find the young modulus from the plot of the load against elongation?

    1. Answer to How do we find the young modulus from the plot of the load against Elongation?: (i) Pick any point (F, Delta L) near the end of the elastic line. (ii) Calculate stress and elastic strain at this point. (iii) Calculate E = stress/strain. Good luck!

  25. I dont know how youtube recognized that Im studying civil engineering.

    1. lol- EVERYTHING you have googled, watched, and thought about in the last month… big brother is watching

    1. Answer to Why the material broke from middle? The fracture of a tensile test specimen is a complex phenomenon and not explained in a short way, Ill do my best. In ductile materials the fracture is initiated by necking. Necking principally may take place at any point along the cylindrical part of the specimen. In the case of good ductility (the structural steel in the video), the neck region is in most cases situated in the middle part of the specimen, because the grips have a certain influence. The actual fracture starts in the central part of the neck, roughly perpendicular to the longitudinal axis, and then spreads out towards the surface at an angle of about 45°.

  26. and this is college, basically not just “hey heres how to memorize shit” like hs which is dumb

    1. Answer to It is very useful to know the material: Quite correct, the steel is a typical plain low-carbon structural steel, type S235JR. The aluminium alloy is a 2014 precipitation hardened alloy with about 4 % Cu and some small additions of Si and Mg.

  27. phá hủy do mỏi. nó sẽ bị phá ở điểm yếu nhất. điểm này nằm trên đường chia độ dài. phụ thuộc vào lực bao nhiêu trong thời gian bao nhiêu. nếu lực rất lớn quá ngưỡng phá liên kết trong thời gian rất ngắn thì điểm phá rất gần 2 đầu. khi phá xong 2 điện cực truyền điện biết rõ thời điểm đút mất điện và mối quan hệ lực điểm phá thời gian truyền lực và kết cấu vật liệu… mở rộng cái này ra rất hay khi 1 nơron thần kinh phá do mỏi logic.

    1. nghĩa là rối loạn logic não bộ ko cần thuốc chữa mà cần cảm xúc để lối lại liên kết. và ta hiểu thế nào về thuốc làm trì độn logic.

  28. Hi,thx for the video,we are a die casting company,we want to change our micro structure to increase our tensile strength from 300 to say 400,can u tell us what we have to add to A356 aluminium to get increased tensile strength

  29. Good introduction, however you should have also explained how the extensometer is also used to calculate ductility properties.

    1. Answer to Good introduction, however you should have also explained how the extensometer is also used to calculate ductility properties.: You are absolutely right. The main idea of the video is to show the testing procedure. The calculation of the material properties from the raw data is very important, and much more extensive than most people think. So we just explain the most important strength properties.

    1. ours was like that too, it seems most are. why dont they use wire samples? Those can be cut instead of turned on a lathe?

    2. Answer to why dont they use a smaller specimen and thus a smaller machine?: Smaller specimens with smaller cross sectional areas may be used. And then the tensile test machine can be much smaller, as you point out quite correctly. Here we have a tensile test machine that we can use for many applications at our university, so it has to be as versatile as possible. Under these conditions 10 mm Diameter is a common value.

  30. Metals are malleable and ductile materials with high electrical conductivity, high thermal conductivity, and high density. They are widely used in buildings, infrastructures, ships and automobile industry.

    1. Answer to also shouldnt the piece snap back a bit after breaking?: Yes it does, it is the elastic spring back that also causes the typical sound at failure.

    2. must check my android app for highway material app, it may be helpful for you 🙂

  31. Hello. I am a Korean student studying for tensile tests. Id like to better understand this video. Could you send me a script if you have a script file?

    1. Answer to Hello. I am a Korean student studying for tensile tests. Id like to better understand this video. Could you send me a script if you have a script file?: Sorry, there is no script file available, in any case not in English. The German book Werkstoffkunde und Werkstoffprüfung für Dummies describes the tensile test in some detail, alas, in German …

  32. when a bolt tensile strength is 60,000PSI, what does it mean? is it a constant through the material? do this value vary with bolt diameter?

    1. Answer to when a bolt tensile strength is 60,000 PSI, what does it mean? is it a constant through the material? do this value vary with bolt diameter?: The tensile strength does not vary much with the diameter of a part. So when, for instance, the diameter is increased to twice its value, the cross sectional area will increase to four times the original value. As a consequence, the maximum force will be almost exactly four times the original maximum force. However, it is generally more difficult to produce parts with a large diameter with the same quality in comparison to parts with a smaller diameter.

  33. who can present what thaey say for me pls? i am vietnamese and my english knowledge is not good
    Thanks

    1. Answer to wait, did the alluminim seriously take more force to break?: Yes, this is true. In the video a low carbon structural steel is tested in the first part. This steel is not very strong, but very ductile. There are also steels on the market with about five times the strength compared with this rather basic steel. The aluminium alloy in the second part is a precipitation-strengthened material with comparatively high strength (and low ductility). As regards strength this alloy ranges near the top end of common aluminium alloys. Sorry for the late answer, too busy.

  34. Hello,
    I would like to ask you a question. Basically, the first test and its diagram are for ductile material and the second ones are for brittle material. is that right?
    Thank you.

    1. Hello sir,
      Its been about six months since the last time I made questions. I hope youre still there. I would like to ask you a question about input data for Plasticity in some cae software. Taking cae software using true stress-strain for example, in the case of without yield point phenomenon, It is easy to insert data to the software because there is only one yield point and stress and strain keep increasing up to the fracture point. Its a little bit confusing for the case of with yield point phenomenon because there are two yield point. the specimen starts yielding at upper yield point, then stress decreases to lower yield point, then it increases up to the fracture point. My question is how could we choose which yield point is appropriate for input data of Plasticity?
      Thank you so much for your time.

    2. I try my best:1. In the first test, the upper yield point and the elastic limit are the same, arent they? Practically yes, but depending on the material there may be some small plastic deformations before the upper yield point. In the case of slowly cooled ferritic steels these plastic deformations are extremely small, hardly detectable.
      2. Up to now, this has still confused me. In the strain-hardening region, when the force is just unloaded, the point will drop down along a line parallel to the elastic line. Yes. But does it drop to the strain axis at which the stress value is 0 or its just hanging on that line? It is hanging on that parallel elastic line (hope I understood you correctly).  And What happens when the force is unloaded in the region between the upper yield point and the lower yield point or in the necking region? Exactly the same, elastic spring-back along an elastic line which is (almost) parallel to the first elastic line.
      3. For metals, are there only two kinds of diagrams as yield point phenomenon and without yield phenomenon when it comes to stress-strain diagram for uniaxial test (in this case)? For most of the metallic materials, yes. However, there may be certain anomalies, for example the Portevin-le-Chatelier-effect.

    3. Thank you so much for your prompt answer. I would like to ask you some more questions.
      1. In the first test, the upper yield point and the elastic limit are the same, arent they?
      2. Up to now, this has still confused me. In the strain-hardening region, when the force is just unloaded, the point will drop down along a line parallel to the elastic line. But does it drop to the strain axis at which the stress value is 0 or its just hanging on that line? And What happens when the force is unloaded in the region between the upper yield point and the lower yield point or in the necking region?
      3. For metals, are there only two kinds of diagrams as yield point phenomenon and without yield phenomenon when it comes to stress-strain diagram for uniaxial test (in this case)?
      Looking forward to hearing from you.

    4. Answer to I would like to ask you a question. Basically, the first test and its diagram are for ductile material and the second ones are for brittle material. is that right?: There is a smooth transition between perfectly ductile and perfectly brittle materials. One would call a material very ductile, when it shows a percentage elongation after fracture of about 30 or 40 %, which was the case in the first tensile test. A perfectly brittle material would have a value of 0 %. Our precipitation hardened aluminium material had a percentage elongation after fracture of about 10 %, so it is neither a very ductile nor a brittle material. Let us say it is a moderately ductile material. Many people would draw a blurred line between ductile and brittle at around 5 %. By the way: Whether a material shows a yield point phenomenon or not has principally nothing to do with ductility.

    1. Answer to Is the second tested metal brittle type?: The aluminium material is precipitation hardened and not as ductile as the structural steel, but one would not call it brittle yet.

  35. nice video.this video is much more suitable for professionals than students. this is widely used in industries. well we had this experiment done during my engg time.

    1. Answer to What is being displayed in middle reading, titled as position?: Position means the vertical position of the crosshead relative to a reference point. The reference point may be chosen freely by the operator. The position is a good feature to move the crosshead after a tensile test to the same position where it started, for instance, to carry out another tensile test.

  36. MaterialsScience2000, Would you put a translation to Brazilian Portuguese in the video if I send it to you?

  37. Can you please elaborate more on Ludus Effect or Ludar Effect or whatever that effect is? It would be really helpful.

    1. MaterialsScience2000 You guys are the best! Thanks a tonne for the reading recommendation.

    2. Answer to Can you please elaborate more on Ludus Effect or Ludar Effect or whatever that effect is? It would be really helpful.: It is called Lüders effect and it is closely connected with the yield point phenomenon. I am afraid it is too extensive to be explained here. A good (and old) book is Yield point phenomena in Metals and Alloys by E. O. Hall. A recent scientific publication is R. Schwab and V. Ruff: On the Nature of the Yield Point Phenomenon, Acta Materialia 61 (2013) 1798-1808

  38. How to calculate stress and strain?
    Used total length or parallel leng? Tq

    1. answer to How to calculate stress and strain? Used total length or parallel leng? Tq The nominal stress is always calculated as force/(original cross sectional area). The nominal strain is calculated as (elongation of original gauge length)/(original gauge length). The original gauge length is always smaller than the parallel length.

  39. which is the yield point of carbon steel??? (number)
    please help

    1. As MaterialsScience2000 already answered, it has a wide range depending upon the alloy. As a quick reference, ASTM A36 has 250MPa yeld point.

    2. Answer to which is the yield point of carbon steel??? (number) please help: The yield point of carbon steel may be very different, depending on the carbon content, the heat treatment and plastic deformation by forming. It ranges from around 180 MPa to more than 1000 MPa.

  40. I am trying to calculate the Stress of this experiment using the formula shown at 8:33. I presume the tube is hollow, if so what is its thickness?

    1. Answer to I am trying to calculate the Stress of this experiment using the formula shown at 8:33. I presume the tube is hollow, if so what is its thickness? The specimen is completely solid, no tube. The original cross sectional are is the area of the circle, (pi*d^2)/4.

    1. Answer to Why lines have been drawn in the specimen?: The lines on the specimen have been drawn on the original specimen in equal spacing of 10 mm . After fracture they are used to visualise the strain distribution along the specimen. The plastic strain in the neck area is much larger than the plastic strain outside the neck region. Percentage elongation after fracture and maximum uniform plastic strain can also be measured.

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