# Rectangular plate modal analysis **URL:** \ **Category:** Uncategorized\ **Created:** [July 15, 2023, 4:43pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734 "2023-07-15T16:43:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 4:43pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/1 "2023-07-15T16:43:41Z")
Hello CalculiX users, I have a question about calculix frequency step. I wanted to know the Eigenfrequencies of a rectangular plate, When I make free-free BC and let calculix calculate the first 20 Eigenfrequencies it always skip alot of them. How to avoid such a thing? ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [July 15, 2023, 5:34pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/2 "2023-07-15T17:34:04Z")
Hi Aly and welcome, That’s most probably a lack of refinement. Specially if you are requesting a large number of modes (High frequencies). Keep in mind your model should have a mesh size small enough to capture the smallest expected deformation pattern. Refine by x2 or x4 and let us know. ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 5:39pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/3 "2023-07-15T17:39:55Z")
The mesh was 60x60 structured shell elements ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 5:42pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/4 "2023-07-15T17:42:14Z")
Also, I care about the low Eigenfrequencies not the large ones… calculix skips the low Eigenfrequencies ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [July 15, 2023, 6:03pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/5 "2023-07-15T18:03:53Z")
Dimensions of the plate, element , solver ?. Will be easier and will be able to compare. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [July 15, 2023, 6:07pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/6 "2023-07-15T18:07:19Z")
Did you try setting the lower and upper bound for the frequency step ? ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 7:14pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/7 "2023-07-15T19:14:34Z")
430x302x1.5 mm³ , aluminium , spooles solver ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 7:15pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/8 "2023-07-15T19:15:59Z")
I’m not sure if i do that correctly… But i think in ccx manual its written that the software will solve normally as always but will just extract the frequencies between the limits ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 15, 2023, 7:37pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/9 "2023-07-15T19:37:27Z")
Can you post your \*.inp files? I’ve experienced issues with free-free modal requests in the past with pastix and spooles. So far, in my experience, pardiso performs much better in these requests. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [July 15, 2023, 7:43pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/10 "2023-07-15T19:43:05Z")
You can try requesting frequencies in the lower range (starting from 0 Hz to capture the rigid body modes too) and reducing the number of frequencies to be calculated. Issues with modal analyses are quite common in CalculiX (especially when using PaStiX but also with other solvers). ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 15, 2023, 9:30pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/11 "2023-07-15T21:30:45Z")
How to use pardiso on windows? Or how to install calculix correctly on windows? I was only able to install calculix on linux but currently im using windows and I don’t know how to get all its features ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [July 15, 2023, 10:18pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/12 "2023-07-15T22:18:49Z")
This is what I get with PArdiso (Spools the same). | Mode | EIGENVALUE | RAD/TIME | Hz | E | 6.90E+10 | [Pa] | | --- | --- | --- | --- | --- | --- | --- | | 1.00 | 54,881 | 234.27 | 37.28 | Poisson | 0.334 | | | 2.00 | 70,564 | 265.64 | 42.28 | a | 430 | [m] | | 3.00 | 301,490 | 549.08 | 87.39 | b | 302 | [m] | | 4.00 | 319,186 | 564.97 | 89.92 | r | 2700 | [Kg/m3] | | 5.00 | 472,551 | 687.42 | 109.41 | h | 1.50E-03 | [m] | | 6.00 | 649,317 | 805.80 | 128.25 | | | | | 7.00 | 1,074,194 | 1,036.43 | 164.95 | m | 4.05 | [Kg/m2] | | 8.00 | 1,326,581 | 1,151.77 | 183.31 | | | | | 9.00 | 2,276,238 | 1,508.72 | 240.12 | | | | | 10.00 | 2,368,427 | 1,538.97 | 244.93 | | | | | 11.00 | 2,917,362 | 1,708.03 | 271.84 | | | | | 12.00 | 3,057,290 | 1,748.51 | 278.28 | | | | | 13.00 | 3,158,500 | 1,777.22 | 282.85 | | | | | 14.00 | 4,700,708 | 2,168.11 | 345.07 | | | | | 15.00 | 6,227,352 | 2,495.47 | 397.17 | | | | | 16.00 | 6,388,353 | 2,527.52 | 402.27 | | | | | 17.00 | 7,387,391 | 2,717.98 | 432.58 | | | | | 18.00 | 8,196,915 | 2,863.03 | 455.66 | | | | | 19.00 | 9,397,854 | 3,065.59 | 487.90 | | | | | 20.00 | 10,165,630 | 3,188.36 | 507.44 | | | | | 21.00 | 12,625,010 | 3,553.17 | 565.50 | | | | | 22.00 | 13,049,210 | 3,612.37 | 574.93 | | | | | 23.00 | 13,462,920 | 3,669.19 | 583.97 | | | | | 24.00 | 14,393,790 | 3,793.92 | 603.82 | | | | | | | | Pardiso | | | | ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [July 15, 2023, 10:41pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/13 "2023-07-15T22:41:44Z")
You don’t have to install it on Windows. Just put the solver’s executable file (ccx\_static.exe) in the same folder as the input file for the analysis that you want to run. Then open the command window in that directory and type ccx\_static input\_file\_name. Of course, you can also add an environment variable to avoid the necessity of placing the solver’s file in the same directory as the input file. Pardiso requires some additional libraries but try with other solvers first. ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 16, 2023, 3:36am UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/14 "2023-07-16T03:36:27Z")
Very similar values- attached are the input and result files using pardiso, spooles, and pastix: > **[Download PlateResults](https://filetransfer.io/data-package/tm2zjSoz#link)** > > Size of the data package: 9.95 MB. Free transfer of up to 6 GB of photos, videos and documents. Send large files via email or a link to share. No registration, no ads, just simple file sharing! ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 16, 2023, 7:27am UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/15 "2023-07-16T07:27:02Z")
![Screenshot_2023-07-16-10-21-14-49_1883c7f851f01ba16e32f0f357d2f56b](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/2/28948658772b519fce3f1952565161fea2dc22e5.jpeg) Can you please explain briefly the meaning of the 1e-9 and the second line? Also, the results are missing lower frequencies as i said. I don’t know why solid sections gives less accurate results than shell elements in this example I mean the “37 Hz” here should be around “35 Hz” . I’m exciting that plate harmonically in the laboratory and i got about 3 frequencies below that 35 Hz ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [July 16, 2023, 2:32pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/16 "2023-07-16T14:32:51Z")
> [@Aly](#): > > Can you please explain briefly the meaning of the 1e-9 and the second line? The second item of the second line of the \*FREQUENCY keyword is the lower bound of the requested frequency range. It’s set to 1e-9 which is almost zero but not exactly zero - apparently an attempt to obtain rigis body modes (with eigenfrequencies close to 0). The \*OUTPUT, FREQUENCY=1 keyword means that the results of every increment are saved. It’s primarily meant for nonlinear analyses, this way you can make sure that you don’t skip any increments in results. ---
**Author:** ![Aly](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Aly](https://calculix.discourse.group/u/Aly)\ **Post date:** [July 16, 2023, 2:36pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/17 "2023-07-16T14:36:17Z")
Okayyy, thanks alot… can you tell me what libraries are needed to be able to use pardiso ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [July 16, 2023, 2:40pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/18 "2023-07-16T14:40:21Z")
You can find them here: [PrePoMax](https://staff.tu.kielce.pl/rokach/instr/ppm_main.htm) ![IMG_2579](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/3/3781dcbe71a5231916e7f8a3315eb474b6062900.jpeg) ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 16, 2023, 2:57pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/19 "2023-07-16T14:57:48Z")
> [@Calc\_em](#): > > It’s set to 1e-9 which is almost zero but not exactly zero - apparently an attempt to obtain rigid body modes (with eigenfrequencies close to 0). Precisely. Thanks @Calc_em! ---
**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://calculix.discourse.group/u/jbr)\ **Post date:** [July 16, 2023, 3:06pm UTC](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734/20 "2023-07-16T15:06:14Z")
> [@Aly](#): > > can you tell me what libraries are needed to be able to use pardiso I followed this guide and script: [FEA Cluster](https://www.feacluster.com/calculix.php) Section: v2.19 Linux executable with the Intel Pardiso Solver [Next page](https://calculix.discourse.group/t/rectangular-plate-modal-analysis/1734.md?page=2)