What is Strain: Definition and 461 Discussions

In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are substantially smaller than the idealized value of approximately 109°. Because of their high strain, the heat of combustion for these small rings is elevated.Ring strain results from a combination of angle strain, conformational strain or Pitzer strain (torsional eclipsing interactions), and transannular strain, also known as van der Waals strain or Prelog strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane.

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  1. S

    Strain Energy due to Bending

    I can't work out the strain energy using the integral equation here, question (b)(i). I've got the bending moment for the first beam as 400kN. E and I are given, I'm guessing you can take '2EI' out of the integral and just integrate the M^2, is that correct?
  2. S

    Strain Energy in a Rod Question

    Unsure which dimensions to use to work out the force and strain energy here. I know that Force = yield strength * area Yield strength = 310 MPa Area, I'm unsure which radius to use. I assume 12 mm. For strain energy = (Force^2 * Length)/(2 * Area * Youngs Modulus) Unsure which length and...
  3. C

    Critical Buckling loads-how to plot?

    Homework Statement Hi all, I am an architect so engineering is not my strong point. for these equations I am unsure how to correctly determine the mode of failure and plot a graph. Any help would be greatly appreciated. Also the attached files have the formulas written and question written...
  4. REVIANNA

    Mechanical properties: strain

    Homework Statement A copper rod of length l_0 at 0 C is placed on a smooth surface.Now the rod is heated up to 100 C.FIND THE LONGITUDINAL STRAIN DEVELOPED ? The Attempt at a Solution What I did : strain = delta l/ l_0 = l_0 alpha(coefficient of linear expansion) delta T/l_0...
  5. H

    Displacement gradient same as strain?

    Hi, is displacement gradient du/dx same as strain? i though it would be until someone made a comment that they are not the same thing and now I am confused.
  6. M

    Rosetta gauge for stress strain

    Homework Statement Homework Equations The Attempt at a Solution I'm trying to find the principal strain, then from that find stress. The poisons ratio should be around 0.3 for this experiment. My result is about 100 micro strain higher than what my class mates got. Can anyone see...
  7. 1350-F

    Effective Strain of Frictionless Punch on Deep Plate

    I'm trying to figure out the effective strain of a frictionless punch on a deep plate. For simplicity's sake let's say it's in plane strain. Don't quite know where to start. Closest thing I can think of is the strain from a bulge test, but that involves a thin sheet. Looked at some indentor...
  8. J

    Graphing stress-strain plots on excel

    1. I'm given time (s), extension (mm), tensile stress (mPa), and tensile strain (%) in a table. I'm supposed to graph it on excel, but my graphs don't look at all like a stress-strain graph. 2. I think it's probably because I'm using tensile stress or strain? Or is it an excel error I'm doing...
  9. S

    How could change the energy band gap(E-K) using the strain?

    Hi! I'm sung dae with tensile strain, energy band structure could be changed. bang gap decrease with compressive strain, energy band structure could be changed. bang gap increase but I'm not sure why it could be changed .. Is there someone who explain in detail ? thanks. have a nice day! :)
  10. D

    How to Waterproof a Strain Gage?

    Hello all, Our project needs to implement a force (strain) gage underwater for one of our tests. Our budget is pretty tight and we can't afford a wash-down strain gage that can support the forces that we will be operating at (~500 lbs). Does anybody know a way to hermetically seal a strain...
  11. B

    Solving Shear Strain Problem: Find Vertical Displacement

    Homework Statement The support consists of three rigid plates, which are connected together using two symmetrically placed rubber pads. If a vertical force of 5 N is applied to plate A, determine the approximate vertical displacement of this plate due to shear strains in the rubber. Each pad...
  12. A

    Stress due to compression of 3D object

    Good day, I am trying to calculate the stress along the yy-direction for a 3D object compressed in the zz direction (perpendicular to it). The width of the object (in the yy direction) is constant, and the object can only deform along the xx direction. All stresses except for sigma_zz (known)...
  13. R

    How to plot stress - strain and work out the Young's modulus

    Homework Statement I have the following table Load 25 50 75 100 125 150 160 170 Extension 0.38 0.75 1.15 1.53 2.8 8.6 15 28 and I need to: 1. Plot the stress – strain or (load-extension) graph and determine (a) Approximate value of the elastic limit (b)...
  14. P

    Difference between Creep and Strain Rate Sensitivity

    Hello, recently I became interested in some basics of material science and there was one thing that I did not really understand. What is the difference (or what are things in common) between creep and strain rate sensitivity? I read about it in connection with indentation. - To measure the...
  15. PinkGeologist

    Is strain always recoverable in a viscoelastic solid?

    Is strain always recoverable in a viscoelastic solid? For instance, I thought in the single-branch Maxwell model, there was unrecoverable strain ... or am I wrong? And then if you use a two branch Maxwell model (one spring, one spring + dashpot), all strain must be recoverable, correct?
  16. B

    A question about strain in graphene

    Dear forum people The new position of the carbon atoms under uniaxial strain r in the framework of elastic theory is shown by the following equation: ri'=(I+ε).ri in which ri and ri' are the position of the carbon atoms before and after the strain is applied, respectively. I is the unit matrix...
  17. S

    Simple Calculation for Pressure Vessel Strain | 69.6 kPa Solution

    Homework Statement Homework Equations The Attempt at a Solution Not sure if I'm on the right track here at all. p=40*10-6*6*10-3*290*109/1=69600 Pa=69.6 kPa
  18. F

    How to plot stress-strain curve?

    Can we plot stress-strain curve if we only have yield strength, tensile strength, and elongation data? For example if i have: Yield strength = 300 MPa Tensile Strength = 600 MPa Elongation = 50% How to plot the stress-strain curve? Thanks
  19. B

    High strain rate testing using the SHPB -- Help please

    I am a part C mechanical engineering student and require some advice for my individual project, which is based on the high strain-rate testing of a particular glass filled composite material using a split-Hopkinson pressure bar (SHPB) experiment. I gathered the results on a SHPB test rig and...
  20. F

    Strain rate material modeling

    I want to create stress/strain curves for Higher Strain Rates from an available stress/strain curve? I am interested on the mathematical formulation aspect to generate a Dyna Material card.
  21. H

    Calculating strain from wave speed and tension in a wire

    Homework Statement Just wanted to check my work on this one. An aluminum wire is clamped at each end under zero tension at room temperature. The tension in the wire is increased by reducing the temperature which results in a decrease in the wire's equilibrium length. What strain (ΔL/L) will...
  22. T

    Converting stress-strain curve to shear stress-shear strain

    Homework Statement For a crystalline metal material - Elastic modulus E - Poisson ratio v - A table with test data of stresses vs. total strains, from a monotonic uniaxial tension test, which generates a stress-strain curve. How would you use this data to find the corresponding pure shear...
  23. Y

    Strain Gauge Formula Derivation

    Using R = ρL/A, I am trying to get this formula, which is the change in resistance due to change in length, area, and resistivity. ΔR = (∂R/∂L)ΔL + (∂R/∂A)ΔA + (∂R/∂ρ)Δρ I understand the above conceptually, but I am confused about why we are multiplying by terms ΔL, ΔA, and Δρ. Intuitively, I...
  24. A

    Hookes law for stress and strain

    I need help understanding a passage in my textbook, where the form of hookes law in continuous elastic media is explained. It says: "The absence of internal directions in isotopic matter tells us that there are only two tensors available to construct a linear relation between the the stress...
  25. 1

    The strain of a dog-bone specimen

    Homework Statement A dog-bone specimen made by aluminum alloy is used for tensile testing by a force of 4000N via two steel pins. The dimension of the specimen is shown in the following picture; the thickness of specimen and the length of pins are 4mm and 8mm, respectively. The mechanical...
  26. M

    Interfacial Strain Calculation: BaTiO3 on SrTiO3

    Hello everyone, I have a question on the calculation of interfacial strain. If we know the elastic constants of BaTiO3 (1 dimension), how to give a quantitative estimation of the elastic energy per unit cell layer grown with a c-axis orientation on SrTiO3? Thanks very much
  27. P

    Calculate Elastic Strain Energy in Solid State Physics

    Homework Statement A think film of ErAs(rock salt structure, a=0.574nm) is grown on top of a thick GaAs (Zn-blend structure, a=0.565nm) substrate. The substrate orientation and the film growth direction are both <001>. For very thin films, the ErAs is tetragonally distorted such that its...
  28. A

    Engineering Help with Wheatstone Bridge Strain Gauge Circuit

    Homework Statement Given your average Wheatstone Bridge with R1 R2 and R3 unknown resistor values and R4=RG= strain gauge, how to solve for the resistor values given only input voltage and the value of the resistances between the resistors?[/B]Homework Equations Not Sure[/B]The Attempt at a...
  29. R

    Shear in fluids: What is measured and called - strain?

    It's about shear stress and strain. We are talking about Newtonian fluids, a situation where we are lubricating a rotating shaft with oil. I cannot understand what we are measuring that we use as the strain. SOLIDS. As far as I know we can say: Stress (F/A) = G x (Δ l / l) Where G is shear...
  30. A

    Mud contraction - stress, strain

    I am trying to solve the problem of the mud cracks in the attached pdf, but I am not really sure I have the right understanding of the problem. As far as I can understand we look at what will happen when mud dries and contract. The contraction of the mud modifies the strain by a term β on the...
  31. A

    Solving Stress and Strain: A Guide to Understanding

    I am so confused about these quantities. For many theoretical setups you assume a linear relation (elastic materials) such that for example if you press on the side of a rectangular box, it makes the box contract in the normal direction to the induced stress. Also the box will expand in the...
  32. G

    Direction of max shear strain

    Homework Statement Hi Everyone, I am going to be doing an experiment soon using strain gauges on a beam and I will have to, among other things, calculate the direction of the maximum shear strain with respect to the axis of the beam. I am trying to find the correct equation to use. Homework...
  33. gracy

    Which Stress vs Strain Curve Has a Larger Slope?

    How can we determine which curve has larger slope just by looking at curves. http://www.meritnation.com/img/shared/userimages/mn_images/image/a_2_12_2.png Which curve has larger slope?
  34. F

    Calculating Strain and Stress in a Steel Plate Under Tensile Load

    Homework Statement A 2.75 KN tensile load is applied to at test coupon made from 1.6 mm flat steel plate (E=200 GPa, v=0.30). Determine the resulting change in the 50 mm gage length. Homework Equations εx = (σx/E) + (-Vσy/E) - (Vσz/E) εy = (-vσx/E) + (σy/E) - (Vσz/E) εz = (-vσx/E) - (Vσy/E)...
  35. A

    Finding Strain Without Extension: A Guide

    Homework Statement hi guys i have a sheet of i have the W,L and T a force and also the elastic modules etc now my issue is i need to find the strain i have the stress etc but the is no extension figure given i have the usual strain equation e=x/l can anyone point me in the right direction in...
  36. J

    Mohr's Circle and Strain Gauges

    Hi Guys, I have been given a lab report to complete on Torsion of a beam. - Beam was subjected to torsion under increments of weight - Strain gauge rosette was placed, A B and C where there is 90 deg between A and C, B at 45 deg in between. - The angle from Gauge A and the "x" axis was given...
  37. G

    Direction of max strain from Mohr's circle

    Homework Statement Hi, I am doing some things with Mohr's circle. I am trying to find the direction of max strain but I am a bit confused. How can I do this? Homework EquationsThe Attempt at a Solution I always assumed that the max strain occurs at 90O from the normal axis or 45O in real...
  38. G

    Can Mohr's Circle be Constructed with Only xx and yy Strain Values?

    Homework Statement I have used a strain rosette with two gauges at 0 and 90 degrees to find strain on a beam under force and an trying to plot Mohr's circle for the problem. As the gauges are at right angles finding the xx and yy strain is easy but I am lost about how to find the xy strain...
  39. W

    Can strain exist without deflection?

    Lets take an example of a person pushing a thick wall, of course no deflection in the line of action of force is seen but can strains be induced in it, like surface slips?
  40. K

    Hysteresis in helical coils springs

    Hi, Do helical springs have hysteresis. Say I do an exercise of plotting deformation Vs load curve of a helical spring, one way will be starting from load zero and increasing till the spring achieves solid length. The other way will be loading the spring till solid length and measuring...
  41. S

    Calculating Stress & Strain in Compressive Force on Component

    Homework Statement The component shown in Fig 1 is made from a material with the following properties and is subjected to a compressive force of 5kN. Material Properties : Young’s Modulus of Elasticity – 200 GNm-2 Modulus of Rigidity – 90 GNm-2 Poisons ratio – 0.32 Calculate : (a) The stress...
  42. Ganesh Ujwal

    Why do small fonts strain the eyes?

    I understand that too much close reading will strain the ciliary muscles of the eyes. But what about small fonts? The contraction of the ciliary muscles is dependent on the distance not font size. In other words, it is better to read from a closer monitor with bigger font or from a further...
  43. E

    Stresses & Strains: Solving for W & F on Steel Pillar

    Homework Statement A 45 degree strain rosette is fixed to a short rectangular section pillar. The gauge reads εa =72x10^6, εb=100x10^6, εc=-240x10^-6. What are the values of W and F? The cross section area is 600mm2 and is made out of steel which E=207GN/m2 and v=0.3. The maximum shear stress...
  44. W

    Poisson's ratio for a rigid rod

    I have a conceptual misunderstanding it seems. Poisson's ratio is the ratio of elastic strain deformation of the transverse and longitudinal components. That being said, if I were to induce thermal stress (heating up) to a rod by keeping its ends (longitudinal component) rigid, would there be a...
  45. kelvin490

    Same E for true stress true strain?

    Before yield we know that stress/strain= E. Can we obtain the same E if we substitute true stress and true strain in the equation? Why
  46. B

    How does eye strain affect the length of the eyeball?

    Ever since I learned that short-sightedness is due to the eyeball being too long, and far-sightedness is due to the eyeball being too short, I've wondered what the point of avoiding eye strain is. How could straining the eyes possibly have the effect of changing the length of the eyeball? By...
  47. A

    Prove Poisson's Ratio is .5 for Small Strains

    Homework Statement Poisson's ratio v is the negative ratio of the transverse strain to the axial strain. For an incompressible (density doesn't change), homogeneous (everything is the same molecule), isotropic (it doesn't matter which direction you pull or push on it, it will act the same way)...
  48. R

    Anisotropic Modulus of elasticity and Poisson's ratio

    Hi, I have some experimental data and I am interested to use this data to calculated modulus of elasticiy (young's modulus) and Poisson's ratio. The material for which the data is given in an anisotropic material, therefore I need to calculate modulus of elasticity and poisson's ration is x,y...
  49. kelvin490

    Strain hardening exponent Question

    For some metals and alloys the region of the true stress–strain curve from the onset of plastic deformation to the point at which necking begins may be approximated by σ=Kεn where n is strain hardening exponent. I wonder whether this equation can be applied to engineering stress-strain curve or...
  50. N

    How Do You Calculate Elastic Modulus and Strengths from a Stress-Strain Curve?

    Hello I'm having trouble wrapping my head around finding things from stress strain curvesI need to find: Elastic modulus (Young’s modulus) •Yield strength •Tensile strength •Uniform and total elongation (ductility) elastic modulus I think is 1240/0.02 = 62000 but I'm unsure of how to find...
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