Modal Advisor — ribbed_plate

Free-free vibration analysis · finite element analysis + energy methods · generated 2026-10-02 13:55 · v0.1.0

At a glance

Material
Aluminum 6061-T6
E 68900 MPa · ν 0.33 · ρ 2.70 g/cm³
Mass
241.5 g
volume 89429 mm³
Size
200.0 × 120.0 × 15.0 mm
16 CAD faces · typical wall ≈ 3.0 mm
First natural frequency
418.1 Hz
free-free · 12 flexible modes analysed
What was analysed
Stiffness & weight
the part's natural vibration, unsupported; 14 regions compared
Finite element model
11,216 elements
22,684 nodes · size 4.55 mm · quality 0.24
Consistency checks
pass
rigid-body modes ≤ 0.00329 Hz · energy balance 1.0000–1.0000 · model volume vs CAD -0.000 %

Want it stiffer? Add material in the regions listed first below (red in the viewer). Want it lighter without losing stiffness? Take material out of the regions listed second (blue in the viewer). The advice does not depend on the material you picked — only the mass does.

The part is analysed unsupported (free-free): its first vibration modes show where it is flexible and where mass is merely riding along. Every suggestion below is independent of the material chosen — only the Hz values and the mass depend on it.

What to change

Ranked by payoff. Click show on part to light the region up in the 3D viewer below; the bar shows each region's payoff relative to the best one.

Derived from the energy split of the first 3 flexible modes (equal weights). First-order sensitivities: reliable for ranking regions, indicative for sizing; a thin wall in bending gains up to 3× the material-scaling number quoted.

Want it stiffer? Add material hereAdd material here — most frequency per gram

Want it lighter without losing stiffness? Remove material hereRemove material here — mass that is riding along

Don't touch — this is where the part bendsLeave alone — the flexible links

Cheap weight — near-neutral regions

  • R8 mid X, +Y end, -Z endshow on part
    R8 (mid X, +Y end, -Z end): 10.5 % of the mass, near-neutral for stiffness (strain 10 % vs kinetic 9 %). Removing 10 % of its mass costs about 0.04 % of the first modes' frequencies -- a cheap place to save weight if the stiffness target has margin.
  • R10 +X end, -Y end, +Z endshow on part
    R10 (+X end, -Y end, +Z end): 6.4 % of the mass, near-neutral for stiffness (strain 5 % vs kinetic 4 %). Removing 10 % of its mass costs about 0.02 % of the first modes' frequencies -- a cheap place to save weight if the stiffness target has margin.

3D viewer

Click the part to identify a region.

Drag to orbit, wheel to zoom, right-drag to pan.

Flexible modes

ModeHzCharacterMotionMost strain energyMost kinetic energyElements carrying 50 % of ESEEnergy balance
1418.1global (3 regions carry half the KE)Z-dominant (0/1/99 % X/Y/Z)R8R326.8 %1.0000
21041.9global (3 regions carry half the KE)Z-dominant (1/1/99 % X/Y/Z)R5R68.2 %1.0000
31112.9global (4 regions carry half the KE)Z-dominant (0/3/97 % X/Y/Z)R2R115.6 %1.0000
41187.1global (3 regions carry half the KE)Z-dominant (1/1/99 % X/Y/Z)R8R620.1 %1.0000
51350.0global (4 regions carry half the KE)Z-dominant (0/4/96 % X/Y/Z)R2R117.1 %1.0000
62177.6global (4 regions carry half the KE)Z-dominant (1/2/97 % X/Y/Z)R1R621.2 %1.0000
72229.1global (2 regions carry half the KE)Z-dominant (0/1/99 % X/Y/Z)R3R311.1 %1.0000
82410.7global (2 regions carry half the KE)Z-dominant (2/1/97 % X/Y/Z)R6R612.1 %1.0000
92871.5global (5 regions carry half the KE)Z-dominant (0/2/98 % X/Y/Z)R1R114.0 %1.0000
103096.7global (4 regions carry half the KE)Z-dominant (0/4/96 % X/Y/Z)R13R110.0 %1.0000
113371.0global (3 regions carry half the KE)Z-dominant (2/1/98 % X/Y/Z)R8R816.4 %1.0000
123537.4global (4 regions carry half the KE)Z-dominant (2/1/97 % X/Y/Z)R1R118.1 %1.0000

Rigid-body modes found: 6 (|f| ≤ 0.00329 Hz). "Elements carrying 50 % of ESE" = how concentrated the mode's flexibility is — small means one flexible spot, large means a diffuse (global) mode. Energy balance = strain energy over kinetic energy per mode; 1.000 is exact.

Energy by region (% of each mode's total)

Red bars = element strain energy (ESE), green bars = element kinetic energy (EKE). A region high in both carries a local mode of its own; a mode whose strain energy is spread across many regions is global.

Element strain energy (ESE) % by region

ModeHzR1R2R3R4R5R6R7R8R9R10R11R12R13R14
14187.710.55.22.12.411.414.115.02.11.79.74.98.74.6
210423.34.52.613.014.45.112.29.812.69.75.02.44.01.4
311137.219.02.41.64.63.516.35.31.63.217.51.615.30.8
411879.08.57.97.98.47.33.29.17.25.48.77.46.33.8
513509.023.95.60.70.88.25.610.10.60.615.33.713.72.4
6217819.56.65.04.82.49.311.77.21.97.96.58.04.54.7
722291.58.322.87.90.20.61.421.311.70.27.615.40.80.3
8241115.21.91.02.213.418.07.62.40.48.54.23.310.311.8
9287218.214.410.80.10.16.110.013.00.10.310.14.011.51.4
10309715.111.310.10.10.42.32.33.10.11.218.79.423.42.6
1133715.93.415.13.81.18.65.022.82.82.85.315.33.44.8
12353714.95.113.42.61.712.13.87.92.56.94.79.36.68.5

Element kinetic energy (EKE) % by region

ModeHzR1R2R3R4R5R6R7R8R9R10R11R12R13R14
141821.42.822.51.31.12.50.31.81.35.74.618.82.912.9
210427.910.16.91.81.820.31.619.91.72.77.66.76.64.2
3111316.94.510.81.31.82.115.45.91.44.75.014.34.311.8
4118711.91.415.31.11.120.61.618.11.02.32.015.92.35.4
5135016.314.016.21.41.53.41.21.71.44.28.014.06.99.9
6217814.29.54.12.01.317.311.410.31.13.74.67.97.74.8
722291.71.635.90.80.30.80.920.31.40.14.431.30.40.1
8241125.03.50.40.81.926.64.83.90.83.03.03.53.019.8
9287216.79.412.74.24.57.27.010.02.73.66.27.04.94.0
10309714.67.910.52.62.60.91.51.84.37.912.713.210.88.7
1133717.31.819.51.10.611.11.423.70.92.72.219.53.25.1
12353716.43.816.31.20.313.82.18.30.64.41.613.34.613.4

Average (ESE+EKE)/2 % by region — self-contained modes stand out

ModeHzR1R2R3R4R5R6R7R8R9R10R11R12R13R14
141814.56.613.81.71.86.97.28.41.73.77.111.95.88.7
210425.67.34.87.48.112.76.914.97.26.26.34.65.32.8
3111312.111.86.61.43.22.815.85.61.53.911.27.99.86.3
4118710.54.911.64.54.813.92.413.64.13.95.311.74.34.6
5135012.718.910.91.01.15.83.45.91.02.411.68.810.36.1
6217816.98.14.53.41.913.311.58.81.55.85.67.96.14.8
722291.64.929.44.30.20.71.120.86.60.26.023.40.60.2
8241120.12.70.71.57.722.36.23.20.65.73.63.46.615.8
9287217.411.911.82.12.36.68.511.51.41.98.25.58.22.7
10309714.99.610.31.31.51.61.92.52.24.615.711.317.15.7
1133716.62.617.32.40.89.83.223.21.82.83.817.43.35.0
12353715.64.414.81.91.012.93.08.11.55.73.211.35.610.9

Regions

RegionWhereCAD faces (by boundary area)ElementsMass %Wall proxy mmExtent mm
R1 show-X end, -Y end, -Z end
centre (29.64, 23.15, 1.73)
F7 (2755.1), F3 (2384.5), F4 (226.5)11739.92.9365.9 × 44.5 × 5.8
R2 show-X end, mid Y, -Z end
centre (30.91, 66.85, 1.8)
F7 (2518.8), F4 (2224.6), F5 (238.3)10269.33.0272.2 × 39.0 × 5.8
R3 show-X end, +Y end, -Z end
centre (31.9, 103.64, 1.5)
F7 (2360.6), F5 (2236.5), F6 (218.2)8697.72.8171.1 × 34.0 × 2.3
R4 show-X end, mid Y, mid Z
centre (49.06, 80.5, 10.05)
F13 (695.1), F15 (688.4), F14 (300.0)3622.32.44100.0 × 2.2 × 7.0
R5 show-X end, mid Y, mid Z
centre (52.32, 39.5, 10.03)
F9 (745.5), F12 (732.4), F11 (317.0)3852.52.47109.6 × 2.2 × 7.0
R6 showmid X, -Y end, -Z end
centre (95.58, 14.99, 1.49)
F7 (2343.1), F3 (2181.7), F2 (218.2)8787.72.8974.4 × 32.3 × 2.2
R7 showmid X, mid Y, -Z end
centre (95.84, 51.01, 1.78)
F7 (2672.2), F4 (2187.5), F3 (347.4)10509.83.1179.6 × 40.6 × 5.9
R8 showmid X, +Y end, -Z end
centre (97.46, 95.51, 1.73)
F7 (2922.8), F5 (2505.7), F4 (272.3)112610.53.0174.9 × 45.6 × 5.4
R9 show+X end, mid Y, mid Z
centre (152.88, 80.5, 10.07)
F13 (671.7), F15 (663.2), F14 (300.0)3482.22.4398.3 × 2.2 × 6.3
R10 show+X end, -Y end, +Z end
centre (162.89, 32.77, 10.67)
F10 (638.2), F12 (615.9), F9 (609.7)5916.44.3792.6 × 26.6 × 8.1
R11 show+X end, mid Y, -Z end
centre (165.07, 75.27, 1.87)
F7 (2349.3), F4 (1452.5), F5 (634.5)9368.63.0778.0 × 32.7 × 5.8
R12 show+X end, +Y end, -Z end
centre (165.43, 106.68, 1.5)
F7 (2119.2), F5 (1985.0), F6 (231.8)7796.92.7975.6 × 28.7 × 2.3
R13 show+X end, mid Y, -Z end
centre (166.14, 41.81, 2.04)
F7 (2045.1), F4 (1236.6), F3 (634.7)9399.03.4672.6 × 34.3 × 5.9
R14 show+X end, -Y end, -Z end
centre (166.18, 12.56, 1.69)
F7 (1913.9), F3 (1609.5), F2 (211.4)7547.13.2469.9 × 27.4 × 6.0

Regions are automatic clusters of the finite element model (k = 14); "CAD faces" are the STEP face numbers with the boundary area each contributes (mm²).

Sensitivity by region

"Add material" = first-mode frequency gain per +1 % of part mass added in the region (efficiency). "Remove 10 %" = first-mode frequency change when 10 % of the region's mass is removed (positive = frequency rises). Weighted columns use the first 3 modes equally.

RegionMass %ESE % (m1)EKE % (m1)Add material: Δf % per +1 % mass (m1)Add material (weighted)Remove 10 %: Δf % (m1)Remove 10 % (weighted)Mass saved %
R1 -X end, -Y end, -Z end9.97.721.4-0.69-0.47+0.69+0.470.99
R2 -X end, mid Y, -Z end9.310.52.8+0.41+0.30-0.39-0.280.93
R3 -X end, +Y end, -Z end7.75.222.5-1.12-0.65+0.87+0.500.77
R4 -X end, mid Y, mid Z2.32.11.3+0.17+0.88-0.04-0.210.23
R5 -X end, mid Y, mid Z2.52.41.1+0.26+1.11-0.07-0.280.25
R6 mid X, -Y end, -Z end7.711.42.5+0.59-0.11-0.45+0.080.77
R7 mid X, mid Y, -Z end9.814.10.3+0.70+0.43-0.69-0.420.98
R8 mid X, +Y end, -Z end10.515.01.8+0.63+0.04-0.66-0.041.05
R9 +X end, mid Y, mid Z2.22.11.3+0.18+0.87-0.04-0.200.22
R10 +X end, -Y end, +Z end6.41.75.7-0.32+0.04+0.20-0.020.64
R11 +X end, mid Y, -Z end8.69.74.6+0.30+0.29-0.26-0.250.86
R12 +X end, +Y end, -Z end6.94.918.8-1.01-0.75+0.70+0.520.69
R13 +X end, mid Y, -Z end9.08.72.9+0.32+0.26-0.29-0.240.90
R14 +X end, -Y end, -Z end7.14.612.9-0.59-0.52+0.42+0.370.71

Strain-energy hot spots

Per mode, the smallest set of elements that carries 50 % and 80 % of the strain energy. Elements in the 80 % set of every one of the first 3 modes form the core stiffness zone (15.5 % of elements, 16.9 % of mass) — change several modes at once by working there.

ModeHzElements for 50 % ESEElements for 80 % ESE
1418.13007 (26.8 %)5925 (52.8 %)
21041.9920 (8.2 %)3715 (33.1 %)
31112.91749 (15.6 %)3898 (34.8 %)
41187.12255 (20.1 %)5390 (48.1 %)
51350.01916 (17.1 %)4667 (41.6 %)
62177.62373 (21.2 %)5329 (47.5 %)
72229.11247 (11.1 %)2836 (25.3 %)
82410.71356 (12.1 %)3786 (33.8 %)
92871.51568 (14.0 %)3508 (31.3 %)
103096.71125 (10.0 %)3272 (29.2 %)
113371.01844 (16.4 %)4374 (39.0 %)
123537.42027 (18.1 %)4826 (43.0 %)

Scope and limits