1. * Department of Mechanical Engineering Technology, Purdue University
Finite Element Simulation And Experimental Study Of The Effect Of Combining Ultrasonic Vibration With ECAP Process Of Pure Aluminum 1050
Presented by:
Yanfei Liu
Authors:
Saeed Bagherzadeh1,*, Yanfei Liu, Qingyou Han, Karen Abrinia
* Department of Mechanical Engineering Technology, Purdue University
October 14-17, 2016  Seattle, Washington, USA

2. Table of content
Introduction to UFG materials, severe plastic deformation methods
Introduction to industrial applications of ultrasonic vibration
Ultrasonic-assisted ECAP: method, aim and scope
Finite element modeling
Experiments
Results and discussion
Conclusion
October 14-17, 2016  Seattle, Washington, USA

3. Fine-grained metals Advantages:
Grain size (μm)
d<0.1
0.1 <d<1
1 <d<10
10<d<100
d>100
Description NS
UFG FG MG CG
Advantages:
Higher strength, Superplastic properties, high fatigue strength, Corrosion resistance
𝜎 𝑌 = 𝜎 𝑌𝟎 +𝐴. 𝑑 −1/2
Two main methods for grain refinement:
Bottom-Up: Powder metallurgy, Alloy development, etc.
Top-down: severe plastic deformation (SPD) methods, i.e.: ECAP
𝜎 𝑌 = 𝜎 𝑌𝟎 +𝐴. 𝑑 −1/2
Such applications of UFG metals:
October 14-17, 2016  Seattle, Washington, USA

4. High heterogeneous structure
SPD methods & ECAP
Grain refinement due to applying high shear plastic strain without any change in the sample dimensions (applicable on the sheet an bulk metals)
ECAP is one of the most common SPD process to produce UFG metals
High friction forces
High forming load
High heterogeneous structure
Limited efficiency
Low surface quality
ECAP
limitations
Spd processes
Equal Channel Angular Pressing (ECAP)
Idea for enhancing ECAP efficiency and reducing of the limitations?
“Ultrasonic-assisted ECAP”
October 14-17, 2016  Seattle, Washington, USA

5. Literature review: Ultrasonic assisted Material Processing
UA-tensile test (Duad et al., 2007)
UA-FSW (Park, 2009)
UA- micro extrusion (Bunget & Ngaile, 2011)
UA-indentation (Siu et al., 2011)
UA-spinning (Rasoli et al., 2013)
UA-upsetting (Liu, et al., 2013)
October 14-17, 2016  Seattle, Washington, USA

6. Ultrasonic-assisted ECAP (UAE)
Apply high-intensity ultrasonic vibration directly in PDZ
Using both volume and surface effects of ultrasonic vibration during metal deformation
New ECAP die with one extra channel for locating vibrated horn
LUAE
PDZ
VUAE
October 14-17, 2016  Seattle, Washington, USA

7. Finite element simulation: Material properties
Compression behavior of AL under ultrasonic excitation
- Constitutive Model (based on DD/CP): Kinetic equation
𝜀 𝑃 = 𝜀 0 𝑒𝑥𝑝(− ∆𝐺 𝐾𝑇 )
∆𝐺=∆𝐹 1−( 𝜏 𝜏 )
𝜏 = 𝜏 0 +𝛼𝐺𝑏 𝜌
𝑀= 𝜎 𝜏 𝑟 = 𝛾 𝑟 𝜀
Relationship
(𝜎, 𝜀)
DD:
𝑑𝜌 𝑑𝛾 = 𝑘 1 𝜌 − 𝑘 2 𝜌
CP (Taylor model):
Acoustic softening :
- Flow stress reduction (function of acoustic intensity)
δ= 𝜏 𝜏
( 𝜏 𝜏 ) 𝑉 = ( 𝜏 𝜏 ) 0 +∆𝛿
∆δ=−β ( 𝐸 𝑈 𝜏 ) 𝑠
DD: dislocation density
CP: crystal plasticity
∆δ= δ V − δ 0
Relationship
( 𝜎 𝑣 ,𝜀 𝑣 )
𝐸 𝑈 = 𝜆 𝑠 2 . 𝜔 2 . 𝜌 𝑠 (Acoustic energy density)
Stress-Strain curves ( both with and without ultrasonic excitation)
USE as a User-material in the ABAQUS model
7/35

8. Finite element simulation : Modeling
Modeling vibration: displacement as “ u0.sin(ωt)”
Material properties under UV excitation: UMAT
Validation with experiments
Commercial code: ABAQUS 6.14
Analysis: Dynamic\Explicit
Planar model and plain strain condition
Geometry
90 °
Die angle (Ф)
AL 1050-O
Billet material
3 °
Die corner angle (ψ)
5×5 mm2
Billet section (a×a)
0.25 mm
Die inner redious (r)
32 mm
Billet length (Lt)
Process condition
20 KHz
Vibration frequency (f)
5 mm/min
Ram speed (v0)
u0.sin(ωt)
Horn displacement (U)
20 mm
Punch displacement (H)
0, 4, 8, 12, 15 μm
Vibration amplitude (λ)
0.13
Friction factor (m)
Mesh
R2D2
Rigid parts
1600 elements, CPE4R
Billet
Outputs:
Force-Stroke curve
Strain and stress distribution
Strain inhomogeneity
Final sample geometry
October 14-17, 2016  Seattle, Washington, USA

9. Experiments October 14-17, 2016 Seattle, Washington, USA
Design vibrating horn (Material : AL 7075-T6)
Frequency analysis in ABAQUS
Resonance freq.:
Design: Hz
Test: Hz
Measuring vibration amplitude: GAP-SENSOR
October 14-17, 2016  Seattle, Washington, USA

10. Experiments October 14-17, 2016 Seattle, Washington, USA
Aluminum 1050-O, 5×5×32 mm3
Specimen
Ф=90 °, ψ=3 °, r=0.25 mm
ECAP die
V0=5 mm/min
Ram speed
S=25 mm
Punch displacement
f=20,000 Hz, U=λ.sin(ωt) , λ= 0, 4, 8, 15, 20 μm
Ultrasonic vibration
Polished by sandpapers & lubricated by MoS2
Surface condition
October 14-17, 2016  Seattle, Washington, USA

11. FEM: Forming load October 14-17, 2016 Seattle, Washington, USA
Reduction of the forming force by using ultrasonic vib. VS. conventional ECAP
More forming load reduction by increasing vibration amplitude (energy)
Vertical vibration (VUAE method) is more efficient than lateral vibration (LUAE) due to back pressure
LUAE
VUAE
October 14-17, 2016  Seattle, Washington, USA

12. FEM VS. EXP: Forming load
Good agreement between FEM and EXP
FEM results was lower bound because of errors in:
material model
Ignore hardening effect after deformation
*MPFF: Max. peak forming force
October 14-17, 2016  Seattle, Washington, USA

13. FEM: Plastic strain (Value and distribution)
Higher plastic strain in the ultrasonic assisted ECAP (VUAE) VS. Conventional ECAP (CE)
Increasing maximum and average value of PEEQ by using higher vibration amplitude (energy)
Improve strain homogeneity in the longitudinal direction of sample but weakening homogeneity in thickness direction
Inhomogeneity factor
𝐶 𝑖 = ( 𝜀 𝑚𝑎𝑥 − 𝜀 𝑚𝑖𝑛 ) 𝜀 𝑎𝑣𝑒
VUAE CE
Process 20 15 12 8 4
Amplitude (μm)
2.14
2.09
2.04
1.86
1.75
1.60
𝜀 𝑚𝑎𝑥. 𝑃
length In
1.82
1.84
1.76
1.6
1.66
1.15
𝜀 𝑎𝑣𝑒. 𝑃
0.37
0.38
0.42
0.43
0.41
0.66
CiL
1.99
2.03
1.74
1.78
1.45
In thickness
1.55
1.54
1.49
1.48
1.46
1.3
0.31
0.26
0.29
0.16
CiW
October 14-17, 2016  Seattle, Washington, USA

14. EXP: Microhardness measurement
نتایج اندازه گیری های تجربی
Higher microhardness values by using ultrasonic vibration in both direction vertical (VUAE) and lateral (LUAE) than CECAP
More Inhomogeneity by using LUAE method due to localized vibration effect on the bottom surface of sample
Average microhardness value by one pass of VUAE method is higher even from two passes of CECAP aluminum samples Y
Top Y X Z
Bottom
October 14-17, 2016  Seattle, Washington, USA

15. EXP: Optical Microscopy (OM) images
Initial grains after annealing: equiaxed with ave. grain size 160μm
Formation of grains in lower angle by using lateral vibration (LUAE) and higher angle by using vertical vibration (VUAE)
More straining and grain refinement by using ultrasonic vibration during ECAP vertically (VUAE)
Annealed
First Pass CE
LUAE
VUAE
October 14-17, 2016  Seattle, Washington, USA

16. EXP: SEM images and grain size
Enhancement of the grain refinement by using ultrasonic than conventional ECAP (CE) method
VUAE-Pass 4
VUAE-Pass 1
VUAE-Pass 2
Material & Ref.
Process
Die angle
Route
No. of
passes
Hardness (Hv)
Grain size (μm)
Initial
After
Pure AL 99.5%, [118] CE
Φ=90°, ψ=10° C 2 -
150 4
Pure AL 1050, [113]
Φ=90°, ψ=0° Bc 50
600
2.1
Pure AL 1050, [119] 54
300
2.3
Pure AL 1050, [113] 59
0.85
Pure AL1050, Present work
Φ=90°, ψ=3°
48.0
160
~ 5
VUAE 1
50.7
~ 3
55.3
~ 1.7
62.0
~ 0.9
October 14-17, 2016  Seattle, Washington, USA
16/47

17. Conclusion
The combining of high-intensity ultrasonic vibration with ECAP method was resulted in:
Decrease in the required forming force (with λ=15 μm: 16% reduction by using LUAE method and 31% reduction by using VUAE method)
Increasing the maximum and average values of plastic strain (PEEQ) in thickness direction of sample
Improve strain distribution (decrease inhomogeneity factor) in length
Needs sample rotation in next passes or increase ultrasonic power to overcome strain inhomogeneity in sample thickness
Increase microhardness of samples (with λ=15 μm: 15% reduction by using LUAE method and 22% reduction by using VUAE method)
More grain refinement that means improvement of the ECAP efficiency
Reach Ave. grain size around 3 μm by one pass of VUAE better than even two passes of conventional ECAP
Generally, vertical vibration (VUAE method) was more efficient than lateral vibration (LUAE method) to improve ECAP limitations
October 14-17, 2016  Seattle, Washington, USA

18. Thank you all! “you never fail until you stop trying” Albert Einstein
October 14-17, 2016  Seattle, Washington, USA