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  1. jhardy1

    Calculating Axial Load in a Tire Beam

    If the main frame is moment-fixed at the apex, the problem is indeterminate, and the force in the tie beam will be a function of the relative stiffness of the main frame members and the tie beam. Think about it, if you remove the tie beam (i.e. zero force in the tie beam), the frame will still...
  2. jhardy1

    Topology Optimization queries

    The best way of enforcing symmetry would be to create a half-model with BCs of symmetry. Another key point to note: you say you are modelling a concrete beam (presumably reinforced concrete?) - but your results suggest the shape optimisation is based on an isotropic material, with tensile...
  3. jhardy1

    Keep getting e-mail notifications despite disabling them all in preferences

    Add me to the list of extremely disappointed users - getting heaps of email notifications for threads that I have no interest in. A very poorly implemented "upgrade" to the forums, in my opinion!
  4. jhardy1

    Boundary condition on a burst pressure test

    Surely the applied load case of internal pressure is self-equilibrating? Upward load equals downward load; longitudinal loads are equal and opposite; lateral loads are equal and opposite. http://julianh72.blogspot.com
  5. jhardy1

    Boundary condition on a burst pressure test

    Use the standard "3-2-1" restraint system. Assume xy is the horizontal plane, and z is vertical. Fix z at three nodes on the bottom of the box - three of the corner nodes, say. Now fix x at two of the corners which lie on the y axis, and then add a y restraint to one of those two nodes. All...
  6. jhardy1

    Too many bolts removed from pylon footings

    I learnt the lesson of reading the entire procedure completely before commencing the task many years ago, when I was still in high school. I had acquired an old bicycle with a Sturmey Archer 5-speed hub, which I wanted to refurbish. I got hold of a workshop maintenance guide, and was following...
  7. jhardy1

    FE modelling of three-edge supported plate under simply-support

    With respect to the upper corners moving apart: yes, that is indeed a common animation artefact that you'll often see when linear solutions are animated from -1 to +1 times the applied load. The animation routine has only two sets of actual displacements to work with: zero load / zero...
  8. jhardy1

    CALCULATION OF THRUST FORCE

    @rb1957: I believe the analogy between a wind turbine and a helicopter rotor or aeroplane propeller (or even a boat propeller for that matter) is entirely valid. A helicopter rotor or aeroplane propeller is designed to generate the maximum amount of axial thrust (i.e. axial air flow) using the...
  9. jhardy1

    CALCULATION OF THRUST FORCE

    And nobody has said the entire force is drag ("fwd" as you call it). Yes, the design of the blade is designed to maximise torque (by maximising the tangential force), but this must be accompanied by a significant drag force component as well. 800 kN (about 80 tonnes) of down-wind drag force...
  10. jhardy1

    CALCULATION OF THRUST FORCE

    The useful work done on a turbine is indeed in the form of torque to turn the generator, but that cannot be achieved without also generating downwind drag. Think about it - the turbine absorbs energy from the wind, reducing the free air speed downwind of the turbine. That loss of momentum...
  11. jhardy1

    CALCULATION OF THRUST FORCE

    162 metre diameter is a BIG wind turbine - quite a few megawatts generating capacity! 800 kN doesn't sound unreasonable to me. By way of comparison, a "typical" 3.5 MW offshore wind turbine might have a 100 metre diameter rotor, with a design operating horizontal wind load of around 1 MN. If...
  12. jhardy1

    3-2-1 method for cylindrical pressure vessel

    You have a slight imbalance in load in the negative Y direction, equal to the internal pressure times the area of the open neck. Effectively, you are anchoring an open "rocket bottle" by two point restraints, so it is not surprising that you have non-zero restraint forces, and local stress...
  13. jhardy1

    3-2-1 method for cylindrical pressure vessel

    I'm not defining any mid-thickness nodes - I merely modified BioRes' original restraint set-up for the open-ended pipe. The suggested restraints would work equally well on a mesh of plate / shell elements, or solid elements, or whatever. Yes, any set of 6 restrained DOF which prevent free body...
  14. jhardy1

    3-2-1 method for cylindrical pressure vessel

    @BioMes: Here's one way of restraining the pipe model so it will "breathe" about its center of mass: Define three new nodes D, E & F at the midplane, being the +X, +Y and -X points of the outside diameter respectively. Then Fix Y at A, D & F, fix X at C & E, and fix Z at E. There are many...
  15. jhardy1

    3-2-1 method for cylindrical pressure vessel

    @BioMes: You said "The only problem is that it’s not a 3-2-1 method per se but it’s a great way to constrain the model anyway." I don't understand why you don't think it's a valid 3-2-1 restraint set? You've restrained 3 x Z, 2 x X and 1 x Y; the vessel is restrained against free body motion...
  16. jhardy1

    3-2-1 method for cylindrical pressure vessel

    BioMes, Yes, sorry, I got confused - but in my defence, you rotated your global axes from your original pressure vessel (Y longitudinal), and the later open-ended pipe Z longitudinal)! http://julianh72.blogspot.com
  17. jhardy1

    3-2-1 method for cylindrical pressure vessel

    I've always used the philosophy that if the structure has symmetry, the 3-2-1 restraints should be symmetric as well. That way, when a symmetric load case is applied (e.g. internal pressure in a pipe or vessel), the displacements will also be symmetric. This doesn't affect the accuracy of the...
  18. jhardy1

    Acapulco now modern ruins

    TugBoatEng: In an interglacial period (such as the modern age), the annual rate of deposition of new ice onto an icefield is less than the annual melt, so there is a net loss of ice each year. This is true today of the majority of glacier fields around the globe, and also for Antarctica and...
  19. jhardy1

    Acapulco now modern ruins

    TugBoatEng, you're the only person who claims new ice doesn't form during periods of higher temperatures. The annual rate of deposition of snow / ice reduces as temperatures rise, but new snow / ice is still deposited each winter in the coldest areas (tops of mountains, inland Greenland, on...
  20. jhardy1

    Acapulco now modern ruins

    TugBoatEng said: "Nice dodge on the ice core question. If CO2 causes warming that reduces ice levels then ice samples would never show high levels of CO2." Not so; snow / ice is still deposited in periods of "interglaciation", but at a reduced rate. Ice cores exist which go back hundreds of...

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