Fracture Definition and 73 Threads

Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displacement develops perpendicular to the surface of displacement, it is called a normal tensile crack or simply a crack; if a displacement develops tangentially to the surface of displacement, it is called a shear crack, slip band, or dislocation.Brittle fractures occur with no apparent deformation before fracture; ductile fractures occur when visible deformation does occur before separation. Fracture strength or breaking strength is the stress when a specimen fails or fractures. A detailed understanding of how fracture occurs in materials may be assisted by the study of fracture mechanics.

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  1. P

    So what is the precise role that thickness plays in the resistance of a specimen to deformation or fracture during a collision?

    From Stress-Strain curves in static loading conditions, we know the stress in force/cross-sectional area that's needed to deform a material. So with a bigger specimen, there's also a bigger cross-sectional area so you need a bigger force to generate the necessary stress. This same concept should...
  2. M

    I Why does the end of the fracture have a branch? (Fracking)

    Hello, I have seen some pictures about hydraulic fracturing, which is injecting water into the ground under high pressure, and when people draw the schematic, it looks like this I am wondering why the fracture will be branched. Thanks!
  3. Ozen

    Fracture Energy for JH2 Model (Ceramics and FEA)?

    This is a bit of a multi-part question on impact engineering and FEA usage. I am working on making my Alumina ceramic model as accurate as possible in ANSYS for impact simulations. But I am noticing a common theme, while using model parameters in scientific journals I am not getting any...
  4. Dario56

    Why is Material Toughness the Ability to Absorb Energy Before Fracture?

    Toughness is defined as ability of material to absorb energy when deforming before fracture. Materials with high ductility and strength will have high toughness. What is meant by ability of material to absorb energy? What is connection between strength, ductility and ability to absorb energy so...
  5. person123

    Derivation of Griffith's Criterion

    I did my derivation for a beam as shown with Young's Modulus ##E##, width ##w##, crack length ##a##, and surface energy density ##\gamma##. I understand that a crack will propagate when the free energy ##G## decreases with increase crack length ##a##. Free energy is the combination of the...
  6. Keval Patil

    What is the difference between failure and fracture?

    How did you find PF?: Google search How we can differentiate failure and fracture using Stress Strain Curve [Mentor Note -- thread moved from the New Member Introduction forum]
  7. S

    Fracture in Switch Rail: Investigating R260 Steel

    Hello everybody We saw a fracture in a switch rail, now we're trying to find the reason, may be you can help us. This rail is made of R260 steel. Let me know if any other information is needed. I have attached pictures of this rail. Thanks in advance
  8. D

    Fracture mechanics, stress intensity, fracture toughness

    I've been giving this some thought. It's clear that the stiffners will increase the resistance of the material so that the energy release is no longer high enough to cause further fracture. I'm just not sure what formula I can use to take into account the new resistance. I suspect part 1 of the...
  9. P

    Fracture Mechanics: Proving Stress Intensity Factor Superposition Principle

    I am trying to prove the superposition principle of stress intensity factors (SIFs). The superposition principle states that the stress intensity factors obtained from the boundary loading are equal to those obtained from the crack face traction loading. I used a flat plate model with the size...
  10. JTC

    B Tearing Tape: Understanding the Differences in Fracture Behavior

    (If this is posted in the wrong area, please feel free to move it.) If I take Scotch tape (using the product name), pull out a long strand and then, beginning at the free end, tear it down along its length (to get two strips of the same length, but thinner), the "fracture" (if I may call it...
  11. E

    Difference between brittle fracture and fatigue crack growth

    My question here is regarding fracture of materials. I have problems in understanding some concepts. Now, for static loading, there is a property called KIC (fracture toughness). By equating our stress from the static load to this KIC, we get the maximum length of the crack which does not...
  12. J

    Ansys Workbench Fracture and Cracking Behavior using Solid65

    I am trying to simulate concrete material under three-point bending in Ansys Workbench 16.0. The concrete beam (unnotched) will be under displacement load at the center while as the both ends will be fixed. The design geometry is simple which I have already completed. I ran the simulation using...
  13. C

    Why Brittle Fracture is More Common in Strain-Rate Dependent Materials

    Why are materials whose yield stresses are highly strain-rate dependent more susceptible to brittle fracture than those materials whose yield stresses do not exhibit marked strain-rate dependence
  14. Moayd Shagaf

    I Glass Breaking -- What causes this characteristic fracture pattern?

    Will, I have weird question , when the glass is broken for example, its take some shap like So Why this happen , I mean if i throw a ball on glass does the weakest place are broken ,does this right?
  15. B

    A Wooden vs iron sword causing bone fracture

    I'm trying to talk science to anthropologists and hope an academic physicist will let me quote him. Here is the data and my purpose is to prove that wood can't slice a skull the way a sword does . good grief ... " On this basis, the boomerang is the most probable candidate for the main trauma...
  16. A

    Modeling fracture flow in stress field in COMSOL

    I am new to COMSOL and I want to model fluid flow in stress field. As starting point I want a simple 2D box having a fracture from right to left while pressure gradient vertically. I want to know the threshold value of that pressure from top which allows flow of fluid in fracture. Can anyone...
  17. K

    Fracture mechanics - understanding required

    I had posted this in the General Engineering forum but perhaps it is a better question for mechanical engineering forum: 1) Consider a centre crack specimen subjected to a wedge load a shown in the figure: https://www.physicsforums.com/attachments/centre_crack_wedge_load-jpg.112584/ In such a...
  18. S

    Medical Why do osteoporotic bones fracture?

    Seriously, why? Bone is a composite, of apatite that provides rigidity and collagen which provides toughness. Bones of children are soft. They do fracture under excessive forces, but are liable to greenstick fractures. So soft bones of children may deform plastically, as in rickets. Both...
  19. G

    I Fracture and material strength

    Let's assume I have a large block of crystalline diamond, with reported compressive strength of 110 GPa. If the cross-sectional area of the block is 1 m2, then obviously if I apply a force of 110x10^9 N the material will begin to fracture. But what if the pressure of 110 GPa is applied locally...
  20. 9

    How does quenching affect the fracture energy of a material?

    Is it true that quenching will decrease the toughness of material and tempering the quenched material will then increase the toughness? I need an explanation in term of the effect of quenching and tempering on the structure of the material.
  21. R

    What are some approaches for estimating the work done up to fracture?

    Good day everyone! i have a problem dealing with the fracture analysis. We all know that the work done per unit volume is equal to the area under the curve of stress-strain curve or we can express it in terms of integral form, and if we're looking at necking point stress can be express in this...
  22. krater

    What is a Jones Fracture and How Can I Treat It?

    I have recently been fortunate and clumsy enough to suffer an acute injury leading to a break in my foot which ultimately might be diagnosed today as a "Jones Fracture". The demeanor of the AP that treated it last week was less than reassuring. Anybody have any anecdotal contributions of...
  23. B

    How to analyse a simple fracture with ANSYS WB?

    My tutor only knows how to do it with APDL and I seek for a more up to date Workbench solution. How do I evaluate stress concentration factor for a surface plate with a fracture going straight through it (like a slit - no crack width, only length)?
  24. PetePetePete

    How Does Changing MPa m^0.5 to MPa m^-0.5 Affect Calculations?

    I know the units of measurement for this are: MPa m^0.5 However a question I am working on has it as MPa m^-0.5 What is the difference and does it affect the way I calculate the answer? Would appreciate your insight. Thanks Pete
  25. TyroneTheDino

    Calculating Traction Force for Leg Fracture Treatment

    Homework Statement When the thigh is fractured, the patient's leg must be kept under traction. One method of doing so is a variation on the Russell traction apparatus. If the physical therapist specifies that the traction force directed along the leg must be 25N, what must W be? Homework...
  26. I

    How to determine fracture toughness Kic from a punch test?

    I am looking to determine fracture toughness for aluminium, from a punch test. I have the dimensions of the specimen and the load-displacement curve of the test. I have seen how to calculate Kic for brittle materials from a punch test but am struggling to find a formula for ductile materials...
  27. T

    How Does Impact Length Affect Dynamic Tensile Strength in Brittle Materials?

    Homework Statement Brittle materials as glass and ceramics have generally a much lower tensile strength than compressive strength. A rigid mass impacts the end of a bar (free-free) of such a material and a piece of the other end drops off. Is there a relation between the length of the piece...
  28. O

    Brittle Fracture Self Study Question

    Homework Statement [/B] A tensile load F is to be applied to a tie bar. The tie bar is 50 mm diameter. The surface of the bar has defects resulting from the manufacturing process, these have a maximum depth of 1.5 mm and have a shape factor of 1.4. If the fracture toughness of the material...
  29. J

    Strain Energy Release During Fracture -Where does it go?

    When a bolt is pulled in tension and eventually fractures, is all the built up strain energy dissipated in the formation of the new surfaces? Does any energy do into accelerating the broken halves of the bolt? Imagine that two plates are bolted together. As the two plates are forced apart...
  30. B

    Where to look for consulting on small fracture calculation project?

    I don't know if this is the right forum to be asking this question... Please feel free to redirect me if not. I want to calculate how far a fracture can propagate as part of a project I'm doing. The system is not so simple and I have never dealt with stress analysis and fracturing before. I...
  31. W

    Assumptions of Griffith's fracture theory

    Any experts on Griffith's fracture theory? I am studying the subject and I am having hard time finding out if the theory is valid for all possible initial crack lengths. I have heard from pretty reliable source that we must assume small crack length compared to the macroscopic length of the...
  32. R

    How Much Shear Force Can PVC Withstand Without Fracturing?

    Material: PVC E-modulus: 1300 N/mm^2 Poisson's ratio: 0.35 Applied shear force: 100 N Resisting area: 28 mm^2 Shear modulus: E = 2G(1+v) --> G = E/(2(1+v)) = 1300/(2(1+0.35) = 481 N/mm^2 Does this mean that a force which can be applied to the area without fracturing is 481 N/mm^2 * 28 mm^2? I...
  33. D

    Fracturing Material: Why 2 Opposing Forces?

    Hi,I have thought about this question for the whole night but I couldn't solve it. I want to ask why we need at least 2 forces(they are in opposite direction) to separatre an object. 1 force or several forces act at the same direction could never divide an object.(but the object will accelerate)...
  34. F

    How Is Theoretical Fracture Strength Calculated for Glass?

    Hi, I was wondering what the equation is to calculate theoretical fracture strength if you know the elastic modulus and flexural fracture stress? Homework Statement The flexural fracture stress for ordinary (i.e., soda-lime) glass is around 30–70 MPa. Based purely on the elastic...
  35. T

    Hip Fracture Falls: Reduce Speed with Elastic Hip Pads

    Homework Statement Falls result in hip fractures are a major cause of injury and even death to the elderly. Typically, the hip's speed at impact is about 2.0 m/s. If this can be reduced to 1.3 m/s or less, the hip will usually not fracture. One way to do this is by wearing elastic hip pads. If...
  36. L

    Is Polycarbonate the Best Material for Durable CD Cases?

    Polycarbonate fracture toughness? I am doing a project in which I have to make a cd case out of a material which is transparent, has a young's modulus not too different to polystyrene, can't cost more than twice polystyrene and has a fracture toughness better than polystyrene! Polycarbonate...
  37. R

    Fracture Mechanics Problem: Max Slit Length Without Fracture

    Hi everyone, I have a problem that I hope someone can help me with, the question is. A mass of 500kg induces a tensile stress in a glass sheet restrained at the top. Given that the fracture strength of sound glass is 170MPa what is the maximum length of slit that can be tolerated without...
  38. T

    Calculate the total amount of strain at fracture?

    Homework Statement The question is: calculate the total amount of strain at fracture? How much of this is recoverable strain? Explain your answer Homework Equations strain = (change in length)/ (initial length) The Attempt at a Solution I'm not sure about my answer but i just...
  39. M

    Value of fracture toughness for a finite plate

    Hiii heeeeeelp please. I am new here and hope to find a solution and an easy to understand explanation to my problem:confused:. Thank you all :smile: a. A specimen corresponding to a finite plate of width W = 65 mm is made from a steel with a yield strength of 650 MN m^-2 and contains an edge...
  40. C

    At what temperature range can brittle fracture be expected in low carbon steels?

    Hi. At what temperature range can brittle fracture be expected in low carbon steels? Are there other parameters which govern its occurance? Thanks.
  41. T

    Pump Jack force - fracture mechanics

    Hey everyone, Im having some major trouble with an assignment that I just can't figure out what to do with it. we have been given a pump jack similar to below: http://en.wikipedia.org/wiki/File:Pump_Jack_labelled.png Ignore the belt attachment and gearbox, ours just has motor to...
  42. J

    Potential energy term in fracture

    Hi I have a simple question about thin-film peeling physics. A lot of papers say that the potential energy term in peeling off a tape is F(1-cos@)del c in the picture attached. It says that the potential energy term arises due to the movement of the applied force, which i don't really...
  43. C

    Why Does Fracture Toughness Decrease as Material Strength Increases?

    Hi, why does fracture toughness decrease when a material increases in strength? How do one explain this relationship? Does it have to do with stress vs. strain curve? Thanks.
  44. A

    Fracture Toughness: Stress Intensity Factor Formula

    Reference is to the formula for stress intensity factor : K_I(mode I) = beta*nominal stress*(pi*crack dimension)^1/2 now the question is that 1.ductile: if I use the value of fracture toughness K_c in place of K_I and yield strength in place of nominal stress what will the value of...
  45. C

    HELP Fracture Toughness Question

    The Question I'm Trying to Solve Is: Aluminum alloy (7075-T651) is used for aircraft wing. The largest flaw size monitored in the wing was 9mm. What is the maximum allowable loading so that any catastrophic failure can be avoided? The fracture toughness of aluminum is 26MPa*m^0.5. Assume the...
  46. M

    Stress and Strain fracture and flow

    Stress and Strain...fracture and flow If a material has a maximum tensile fracture stress of S, and a maximum shear stress of T which causes plastic flow, how will it deform: If T=S and if 3T=S ?? Its not an important question, but I am just curious? I can't get my head...
  47. L

    Is the Fracture Energy Equation for Ice Valid?

    Homework Statement i have been told i can use the equation potential energy/cross sectional area to work out fracture energy of ice after dropping weights on it till it breaks. is this true? Homework Equations fracture energy = potential energy/cross sectional area The Attempt at a...
  48. A

    Fracture Toughness Test: Understanding ASTM E399-09 vs BS 7448 Methods

    Hello, What is the general differences betwen the ASTM E399-09 method and the BS 7448 method? Thanks, Alexisonsmith
  49. N

    Representing this complex fracture into exponent

    \frac{2i}{2+i} i don know how to separate the complex and imaginary part of this fracture?
  50. 5

    Effect of Temp on yield stress and fracture toughness

    Homework Statement I am given the trends for yield stress and fracture toughness as functions of temperature for steel. I need to explain the trends Homework Equations none The Attempt at a Solution I am guessing the yield stress is the stress that the material can withstand...
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