This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 9445
To cite this version:
Wehbe, Toufic and Arnaud, Lionel and Dessein, Gilles Faisabilité de la
mesure de champs par stéréo corrélation d’images en conditions restrictives. Application aux vibrations de pièces minces en Usinage Grande Vitesse Anglais : Analyzing feasibility of field measurement by digital image stereo correlation to flexible workpiece vibrations during high speed machining. (2013) In: 19th LAAS Internation Science
Conference, 05 April 2013 - 06 April 2013 (Beirut, Lebanon).
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Faisabilité de la mesure de champs par stéréo corrélation d’images en
conditions restrictives:
Analyzing feasibility of field measurements by Digital Image Stereo
Correlation in restrictive conditions:
Application to flexible work-piece vibrations during High Speed Machining
19
thLAAS International Science Conference.
Lebanese American University, Beirut, Lebanon, April 5 - 6, 2013
conditions restrictives:
Application aux vibrations de pièces minces en Usinage Grande Vitesse
Toufic WEHBE, PhD
Bureau Moyen-Orient
Agence universitaire de la Francophonie
Beyrouth - Liban
Gilles DESSEIN, full professor
Lionel ARNAUD, assistant professor
Ecole Nationale d’Ingénieurs de Tarbes
Tarbes - France
Presentation chronology
I.
Context and goal
II.
Digital Image Stereovision in machining
III. Machining tests and Measurements analysis method
III. Machining tests and Measurements analysis method
- Weight reducing
thin plates
I.
Context and goal
Thin plates milling = high risk of chatter
- Broken tools
- Scraped pieces
- Polishing
Results
thin plates
reduced stiffness compared to tool
- More and more resistant materials
Increased cutting forces
Costs
Risks
Scientific motivation
TOOL VIBRATIONS
THIN PART VIBRATIONS
I.
Context and goal
- No loss of material
- Constant characteristics - No modes transitions
… Scientists own deep knowledge
Complex scientific enigmas
- Loss of material - Nodes and antinodes - Many modes transitiosns
Material removal problematic
Complex dynamical
phenomenona
I.
Context and goal
Vibratory modes must be measured
during machining
Punctual sensors do not see the whole part
Necessity of displacement field measurement during machining
Loss of information on finished part
combination of 6 sensors
II. Digital Image Stereovision in machining
Very high cutting frequencies
Machining center access
Cameras snapping frequency: 5 images / second
Limitations
Displacement fields only allow to study permanent vibrations
II. Digital Image Stereovision in machining
Stereo correlation measurement
Optical Phenmena [KIM 05] [LIN 05]
Image coding Step 1: Grey pattern painting
Step 2:
Sample framing Step 3: Sharpness searching
Step 4: Cameras calibrating
Step 5: Test measuring
II. Digital Image Stereovision in machining
Stereo correlation measurement
No works about setting phases (2 and 3) + reduced accessibility
-> We developed a setting method
Border effects [HIR 2002] Calculus parameters [KIM 05] [BOR 2009] … Image coding FAZ [2009] Devices distorsion [KRU 03] [ZHA 09] Unexpected elements [SCH 03] Lighting [HEI 00]
Step 6: Calculus pram. adjusting
Step 7: Physical points
- Equipment choice - Shutter time - Objective - Diaphragm - Lighting device
- Angle between cameras - Measurement distance - Cameras spacing
II. Digital Image Stereovision in machining
Parameters to be adjusted
Constraints
- Vibration frequency
- Machining center accessibility - Poor ambient light
- Part’s horizontal framing - Part’s vertical framing - Parts sharpness
- Angle stereovision angle - . . .
Stereo correlation device setting parameters
Analysis work: cameras spacing impact on sample sharpness
- Parameter effet may reverse
- Interaction of all the parameters
Cameras spacing
-> raises the Depth of Field (DOF), AND -> makes the D. o F. first plan cross the part
H’
D.o.F’
D.o.F
D
D’
H
α
α
'
Analytical formalizing of constraints
« … The grey pattern must sharply appears during the whole machining… »
II. Digital Image Stereovision in machining
ࡲࡽ > ࡲࢁ′
.∗∗ࡲ࢛࢈ࢋ࢘∗ࢉࢌ࢛࢙ࢌ ∗൫ሺ.∗ሻ+൯ ቆࡲ࢛࢈ࢋ࢘∗ࢉࢌ࢛࢙ࢌ ቇ−ሺሺ.∗ሻ+ሻ−
.∗ࡸ∗−ሺ∆−ࢾሻ∗ ሺሺ.∗ሻ+ሻൗ> 0
Machining center accessibility
>
Cameras spacing
< ࢇ࢞
Stereo correlation angles
∗ ∗ ࢚ࢇ ∝− ≤
− ∗ ∗ ࢚ࢇ ∝ࢇ࢞ ≤
Right border framing
൫ሺ.∗ሻ++ሺ∆−ࢾሻ∗−.ࡸ∗൯∗ࢎ࢘ࢠ∗࢘ࢎ࢘ࢠ
∗ࢌ −.∗∗ሺ∆−ࢾሻ−.∗ࡸ∗
ሺሺ.∗ሻ+ሻൗ > 0 Left border framing
ൣ+ሺ.∗ሻ∗+ሺ∆−ࢾሻ∗൫−ሺ.∗ሻ൯+.∗∗ࡸ∗൧∗ࢎ࢘ࢠ∗࢘ࢎ࢘ࢠ∗ࢌ −.∗ࡸ∗+ሺ∆−ࢾሻ∗.∗∗
∗ሺሺ.∗ሻ + ሻ > 0
Problem synthesis
8 inequalities
8 parameters
II. Digital Image Stereovision in machining
൛ ; ; ࢌ ; ࡲ
࢙࢚; ∆ ; ࢾ ; ࡸ ; ൟ
To be chosen by the scientist
ሺሺ.∗ሻ + ሻ > 0 ൣ+ሺ.∗ሻ∗+ሺ∆−ࢾሻ∗൫−ሺ.∗ሻ൯+.∗∗ࡸ∗൧∗ࢎ࢘ࢠ∗࢘ࢎ࢘ࢠ∗ࢌ −.∗ࡸ∗+ሺ∆−ࢾሻ∗.∗∗ ∗ሺሺ.∗ሻ+ሻൗ > 0 Vertical framing ൫ሺ.∗ሻ++ሺ∆−ࢾሻ∗−.∗ࡸ∗൯∗࢜ࢋ࢚࢘ࢉ∗࢘࢜ࢋ࢚࢘ࢉ∗ࢌ −∗൫ሺ.∗ሻ+൯ൗ ሺሺ.∗ሻ+ሻൗ > 0 Right border sharpness
.∗∗ܨݏݐ∗ܥ݂ܿ݊ݑݏ݂݅݊2 ∗൫ሺ.∗ሻ+൯ ࡴ࢟ࢊ࢙࢚−ሺሺ.∗ሻ+ሻ −
.∗ࡸ∗−ሺ∆−ࢾሻ∗
ሺሺ.∗ሻ+ሻൗ > 0 Left border sharpness
.∗∗ܨݏݐ∗ܥ݂ܿ݊ݑݏ݂݅݊2 ∗൫ሺ.∗ሻ+൯ ࡴ࢟ࢊ࢙࢚−ሺሺ.∗ሻ+ሻ −
ሺ∆+ࢾሻ∗+.∗ࡸ∗
ሺሺ.∗ሻ+ሻൗ > 0
Graphical solution chart
Advised angle
II. Digital Image Stereovision in machining
Includes the measurement technique, the sensors characteristics, the
lighting, the part dimensions, the machine, …
Feasibility island Best solution
Interesting benefits
- Optimal settings choice
before tests
- A complex experimental
problem simplified
-
Fast chart plotting
II. Digital Image Stereovision in machining
Method synthesis
Limitations
- Needs to consider ambient light « in situ » to choose diaphragm aperture
- Can include human factor, cameras dissymetry, …
- May be
transposed to other process
Measurements during radial milling tests
III. Machining tests and Measurements analysis method
Ap= 6 mm
N = 10900 rot/ min
FE Model
ࢌሺࢻ, ࢞, ࢟ሻ = ࢻ ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯
ࢌሺࢻ, ࢞, ࢟ሻ = ࢻ ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯
Modal analysis
Interpolation with polynoms
Measurement of cutting force F
F
ࢌሺࢻ, ࢞, ࢟ሻ࢞ ࢛࢚ = ࢻ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯
III. Machining tests and Measurements analysis method
Measurements analysis method
ࢌሺࢻ, ࢞, ࢟ሻ = ࢻ ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯ ࢌሺࢻ, ࢞, ࢟ሻ = ࢻ ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯ . . . ࢌሺࢻ, ࢞, ࢟ሻ = ࢻ ∗ ൫ࢇ,࢞࢟+ ⋯ + ࢇ,࢞࢟൯ ࢌሺࢻ, ࢞, ࢟ሻ࢞ ࢛࢚ = ࢻ∗ ൫ࢇ,ૢ࢞ૢ࢟ૢ+ ⋯ + ࢇ,࢞࢟൯ ࡿሺ࢞, ࢟ሻ࢞ ࢛࢚ = ࢌ ሺࢻ, ࢞, ࢟ሻ + ࢌሺࢻ, ࢞, ࢟ሻ࢞ ࢛࢚
Modal shapes + statical deflexion
Interpolation of
Measured shape
20 N < F < 30 N
Instantaneous shape
Part’s structural modes of the free part (FEM)
Frequencies
Shape
Modes weights
Dissimilarities
Not vibratory
Some analysis results
III. Machining tests and Measurements analysis method
Dissimilarities
Mean cutting force
Vibratory shapes from cameras Vibratory shapes from laser vibrometer
