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  • Users: gio1
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  1. gio1

    accelerated vibration test

    Hello I am planning an accelerated vibration test on a shaker rig, starting from time-history data of measured accelerations. My approach is as follows: - calculate gRMS of measured data - calculate gRMS of profile to be used on rig for a (say) 3x accelerated testing time, using Coffin-Manson...
  2. gio1

    frequency response FEA

    Hi I have carried out a FE frequency sweep analysis of an assembly using modal superimposition. The assembly is shaken using the same acceleration amplitude across a frequency range along one direction only. When plotting the response (acceleration) Vs frequency for several nodes there are...
  3. gio1

    crush analysis

    Hello I am doing some dynamic analyses (with Abaqus/Explicit) to correlate the crushing of an extruded aluminum cylindrical tube with experimental results. The tube is mounted around a steel rod (assumed rigid) with no clearance. It is supported rigidly at one end and is impacted at the other...
  4. gio1

    fatigue calculations on shaft in torsion

    Hello Which equivalent stress should I use for fatigue calculations on a shaft subject to pure torsion? Von Mises and Maximum principal differ significantly in this case and give hugely different fatigue lifes. Thanks Gio1
  5. gio1

    fatigue-sizing a shaft subject to torsion

    Hello Which equivalent stress should I use for fatigue calculations on a shaft subject to pure torsion? Von Mises and Maximum principal differ significantly in this case and give hugely different fatigue lifes. Thanks Gio1
  6. gio1

    reaction consuming CO2

    A sealed tank is filled with gaseous CO2 at 200F and 200Psi. Is there any substance which if introduced in the tank could react with CO2 and reduce the pressure? Thanks Gio1
  7. gio1

    unsteady mass flow calculation

    Hello I am having a hard time with the following problem: Two vessels full of air at different pressures are connected through an orifice with a tap. I need to size the orifice so that when the tap is open the pressures equalise after a given time t. The flow is choked to start with and only...
  8. gio1

    endind a STEP upon reaching a predefined displacement/reaction force

    Hello My /Explicit analysis consists of two steps. The first applies a load by means of displacing the free end of a restrained structure. I need the analysis to progress to step 2 only when the reaction force at the restraints has reached a predetermined value (i.e. the displacement...
  9. gio1

    composite pressure vessel

    I need to carry out a FEA on a carbon fibre pressure vessel subject to high pressure. The vessel consists of an inner aluminum thin liner core which is used as a mandrel for the filament winding process. I have not much experience of composite FEA, although I am familiar with laminar classical...
  10. gio1

    amplitude of fft harmonics

    Hello I'm having a small problem in handling the results from a simple fft analysis of a signal (I don't do them everyday) I am interested in finding the actual amplitude value of some harmonics. I managed to plot the spectrum: if I remember well I need to drop the first value (as this is the...
  11. gio1

    trivial question?

    Hello I have meshed a coil spring (with hexaedral elements) and loaded it in compression (prescribed displacement of one end, with the other fixed) Looking at the results (VM) I am somewhat suprised to observe that the inner side of the coil is more stressed than the outside. Is the coil...
  12. gio1

    FEA of roller bearing assembly

    Hello I'm about to start a FEA on an assembly consisting of a flange mounted around a rotating shaft through a roller bearing and loaded radially. I would be interested in hearing your thoughts about a possible analysis approach (contact modelling for all the rollers? How to model the cage...
  13. gio1

    air reservoir and valve problem

    Hello, An air reservoir (volume V at pressure P) is connected to a pneumatic system of volume v<V, operating at a max pressure p<P, through a valve with a given maximum volumetric flow rate (at a certain pressure drop). Pipes section area is known. The system needs a minimum mass flow rate to...
  14. gio1

    contact stress

    Hi I am looking at the sensitivity of contact stress between a piston and its gudgeon pin to different pin diameters. The piston is loaded by inertia force and bending+shear develops on the pin. The analysis is in Abaqus/standard and the contacting elements are C3D10M on one side and linear...
  15. gio1

    deflection of short beams

    Can anybody please suggest a formula for the deflection of cantilever beams with very short spans (L/D around 1) subject to concentrated end load?. This would contain a shear term (the highest contribution?) and a bending term (negligible?) I struggle to find such a formula in literature Thanks
  16. gio1

    trumpet length

    Hello An engine with inlet system consisting of individual trumpets for each cylinder develops peak power at a speed of X rpm. The total length of each inlect duct (from valve seat to trumpet edge) is L. Assuming a new target engine speed Y>X for peak power I would like to (approximately)...
  17. gio1

    unbalance of 4 cylinder engines

    Hello It is known that in-line 4 cylinder engines have fully balanced 1st order forces and moments and also 2nd order moments, but second order forces are unbalanced. If you sketch the crankshaft and draw the second order forces you will see that they will point all in the same direction, and...
  18. gio1

    coil spring FEA

    Hello I am planning a FEA of a dynamic system which includes some steel coil springs, using an explicit solver. Before starting the dynamic analysis I have done some static and free modal analyses on the spring FE models, to ensure that their stiffness and first natural frequency is similar to...
  19. gio1

    torsional spring in ABAQUS

    Hello, Is there anybody who could give me an example on how to define a torsional stiffness between two nodes in ABAQUS/Explicit? Apparently this is not possible with SPRING elements, and requires the use of Connectors instead. However I can't find a suitable definition for type and behavior...
  20. gio1

    effect of backlash on durability of straight gears

    Hi, I am analysing a gear train consisting of straight gears. Briefly the method I am using is as follows: 1- Dynamic simulation of the entire system (torsional model of engine) to calculate critical speeds corresponding to peaks in crankshaft / camshaft /geartrain torsional amplitudes. 2- At...

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