1 / 14

Compounding and Composites

Compounding and Composites. Rene Herrmann. FEM static load analyzes. The purpose of the static test is to define areas of large strain . It is these areas that need stiffering in order to prevent formation of stress.

evan-hopkins
Download Presentation

Compounding and Composites

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Compounding and Composites Rene Herrmann

  2. FEM staticloadanalyzes • The purpose of the static test is to define areas of largestrain. It is these areas that needstiffering in order to prevent formation of stress. • For developing light weightstructures the engineershould try to keep the mass to a minimum and maximizestiffnesswhilekeeping the complexity for manufacturinglow. • The nextslideswillillustrate HOW such an analysiscouldproceed. The user is howeverrequired to have an basicunderstanding of beamdeflectiontheory.

  3. FEM staticloading (comsol 1) • Start COMSOL and load Exercise02.mph • The plate dimensions are 250 x 250 mm, the thickness is 5mm • Select under SOLVE the Solver parameter option and chooseStatic • Select in PHYSICS the Boundery Settings option and arrest the sides of the panel in all directions by selectingsurfaces 1, 2,5 and 6. For thesesurfaces the CONSTRAINT seen in the right field must be ticked. • Select under PHYSICS the Point Settings option and selectpoint 5 whichthenturns red in color. Select on the right side the load option and apply a 555555N load in Z – direction.

  4. FEM staticloading (comsol2) • Select under PHYSICS the Subdomain Settings (F8) and chooseobject 1 and define the material properties as 10000000000Pa and Poissionratio as 0.33 and Density as 2300kg/m^3 • Select under POSTPROCESSING the Plot Parameters option (F12) and select under General only the Subdomain and Max/Min Marker plottype option. Selectalso under Subdomain the predefinedquantities as Strainenergydensityor (later) First principlestrain. Select under Max/Min predefinedquantities as First principlestrain.

  5. FEM staticloading (comsol3) • Select under MESH the Free Mesh Parameters Option (F9) and select under Global a predefinedmeshsize of NORMAL and choose APPLY beforepressing OK • Choose under MESH the InitialzeMeshoption • Select under SOLVE the Solve problem option. • Verify that the strainenergydensity is largest in the center of the platewhere the point force is applied. Realize ALSO that the diagonal direction of the plate is less strainedthan the ortogonal direction. Ortogonal direction has to be stiffened and the fibers must thereforehave diagonal directions. To stiffenershowevershould be ortogonal. (Use different view options)

  6. FEM staticloading (comsol4) • Redo this staticloadanalysis and plotinstead First principlestrain. To do this select POSTPROCESSING and Plot parameter option and fieldSubdomainwherepredefinedquanties is First principlestrain. • Verify that the Strain maximum in the center of the plate is about 3.257 meaning the plate has surely broken because the material increaseditslength 3.2 fold. The realistic limit is 100 times less.

  7. FEM Eigenfrequencyanalysis • The purpose of the Eigenfrequencyanalysis is to find the resonancefrequencies and the modes of vibration. The resultwilldepend on the DENSITY of the material defined in PHYSICS, Subdomain Settings. The angularfrequency of a mass spring system analyzed by FEM calculates the mass by usingvolumen and density of the material. • The followingslideswillillustrate HOW such an analysiscouldproceed.

  8. Eigenfrequencyanalysis (1) • Select under SOLVE the Solver Parameter option and choose as AnalysistypeEigenfrequency. Choose to the right side in General the Desirednumbers of Eigenfrequencies as 20. Press APPLY and OK. • Select under SOLVE the Solve Problem option. • Selectthen the POSTPROCESSING and Plot parameter option. Find under General on the right topside the field Solution to use and the fieldEigenfrequency. In the dropdownmenu you find the first 20 resonantfrequenciescalculated. The lowestfrequency is found to be 294.5 Hz.

  9. Eigenfrequencyanalysis (1) • Redo this analysisbutchange in PHYSICS under Subdomain Settings (F8) the materials density from 2300 to 1150. • Find that an deceaseddensitymeans less mass and thereforehigherfrequencies. Find the lowestfrequency to be 416.5 Hz • Test the opposite to producelowerfrequencies by selecting a high density.

  10. FEM transientanalysis • The transientanalysis is the mostcomplexanalysisbecause it is time dependent. The test analyseshow an vibration decreases in amplitudewhencaused by an extrenal time dependent excitation. • The followingslideswillanalyse HOW a vibration caused by an impactinghammer in the center of the platewill cause vibrational oscillations and howthey are damped.

  11. Transientanalysis (1) • Choose under PHYSICS the Subdomain Option and verify that the density of the plate is 2300. • Redo the Eigenfrequencyanalysis and measure the first Eigenfrequency to 294.5 Hz. Calcualte that tehinverse of this frequency is the oscillation time, meaningabout 0.0034s. We make an transientanalysis for 10 periods with 10 points per period. Time t willtherefore be defined from 0:0.00034:0.034. (Veryimportant!!!) • Select SOLVE and Solver Parameters to AnalysistypeTransient. For General select Time Stepping, Times as the aboveexample. Selectalso Time Steps taken by solver to INTERMEDIATE. Select APPLY and OK.

  12. Transientanalysis(2) • Select under OPTIONS the Functionmenu. Press New. Give as Functionname: My_first_hammer and select interpolation, Use data from: Table and press OK. • You are no provided with a table to be filled in. X is the time and f(x) is RELATIVE AMPLITUDE, meaning 1 is 100% and -0.3 is 30% in oppositedirection. • Define an piecewisefunction that fullfills the follwing pairs, (x,f(x)=(0,0);(0.00034,0.5); (0.00068,1);(0.00102,-0.2); (0.00136,0) • Select under PHYSICS and Subdomain Settings option the materials Damping as No damping (important you return to this).

  13. Transientanalysis(3) • Select SOLVE and Solve Problem (Now you reallycanhave small pause – no smoking please!) • Select POSTPROCESSING and DomainPlot Parameters, find under General, Point Plotwhich you tick and select under Solutions to use all points given.Use in the same window the folder POINT and select for pointplot for Predefinedquantities the z-displacementand Point selection is Point 5. Whenpressing APPLY you are provided with a windowshowing you 10 undamped oscillations at the center of the platebecause the time of analysis is 10 periods with 10 points per period.

  14. Transientanalysis(4) • Redo the same analysisbutchange in PHYSICS, Subdomain Settings the Damping of the Material from No Damping to RayleigthDamping. Parameter alfa=0.003 and beta 0.0003 and find that the oscillation nowdiesout after 2-3 vibrations. • For composite light weight materials the value alfa is between 0.15 and 0.45. Beta can be calculatedusing beta=alfa/w_res^2.

More Related