Chapter 4. Surfaces, Tribology, Dimensions Inspection & Quality Dimensions, Inspection & Quality
Sung-Hoon Ahn
School of Mechanical and Aerospace Engineering Seoul National University
Seoul National University
Introduction
Surface properties affect
F i ti d
Friction and wear
Lubrication
Painting coating welding soldering adhesive bonding corrosion Painting, coating, welding, soldering, adhesive bonding, corrosion resistance
Crack initiation
Thermal and electrical conductivity
Tribology
Friction
Wear
Lubrication
Lubrication
Surface structure
Oxide layer (hard, brittle, abrasive)
I F O F O F O
Iron: FeO, Fe 3 O 4 , Fe 2 O 3
Aluminum: Al 2 O 3
Copper: Cu Copper: Cu 2 2 O CuO O, CuO
Stainless steel: CrO
Beilby layer: melting & surface flow-> rapid quenching y y g p q g
Work-hardened layer: residual stress
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Surface texture
Flaw (흠)/ defect (결함), lay (가공무늬), roughness (거칠기), waviness (파상도)
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Surface roughness
Surface profilometers (표면거칠기 측정기)
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
R a a and R q q
Arithmetic mean value
arithmetic ave. (AA) ( )
center-line ave. (CLA) Root-mean-square ave. (RMS)
1
⋅⋅ 1
⋅ + +
+ y y y ∑ ∫
y
b d n l12 2 2
2 2
2 2
1 0
1 1
1 1
⎥ ⎤
⎢ ⎡
=
⋅⋅ =
⋅ + +
+
= +
= + =
+
= +
∑ ∫
∑ ∫
=
dx y y y
y y
R y
dx l y
n y n
y y y R y
n l i d
c b
a
i i d
c b a a
Rough surface:
Lower precision short fatigue life higher electrical & thermal contact1
⎢⎣ ∫
0⎥⎦
∑
=dx l y
n y R n
i i q
Lower precision, short fatigue life, higher electrical & thermal contactresistance, lower corrosion resistance, better painting & coating, lower cost
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Atomic Force Microscope (AFM) Tip
piezoresistor
region PZT region Tip
High doping region
Before PZT process After PZT process
Friction
Adhesion theory of friction (응착이론)
Intimate contact of asperities creates an adhesive bond
Friction coefficient (마찰계수)
A
F τ
rτ
μ = = = friction ( shear ) factor , m = τ k
ihardness A
N
rμ τ
σ μ σ
=
=
=
=
2 . 3 0
3
2 / )
(
≅
=
=
=
Y Y h d
Y stress yield
shear k
k
μ τ
577 . 3 0
3
=
=
= Y
Y
Y hardness
σ μ τ
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Measuring Friction
Ring compression test
5 ) 39
4 ( 10 ) 15 30 4 (
2 2
2
2
− = −
= ID
volume π π
4 . 0 09
. 0
)
%(
13 15 100
13 15
4 4
=
=
=
− ×
= m and
decrease ID
in change
μ 0 . 09 and m 0 . 4 μ
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Wear (1)
Progressive loss of material from
a surface
Adhesive wear (응착마멸)
a surface
A h d l LW
p k LW V = 3
Archard wear law
i lb k
lb W
k
in V
/ 700 170 /
120 200
) 2 . 4 table from ( 10
001 . 0
2 2
3 3
=
=
=
−
ft kW in
L Vp
in lb mm
kg p
213 ) 2560
200 )(
10 (
) 700 , 170 )(
001 . 0 )(
3 ( 3
/ 700 , 170 /
120
3
2 2
=
=
=
=
=
=
− Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Wear (2)
Abrasive wear
Corrosive wear
Corrosive wear
Fatigue wear
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Lubrication
4 i f l b i ti G t i d f t
4 regimes of lubrication Geometric defects
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Surface Treatment (1)
Shot peening, water-jet peening, laser peening
Roller burnishing (surface rolling)
Roller burnishing (surface rolling)
Cladding (clad bonding)
Mechanical plating p g
Thermal spraying
Surface texturing
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Surface Treatment (2)
Vapor deposition (CVD/PVD/ Ion implantation)
Electroplating/ electroless plating p g p g
Electroforming
Anodizing
Diamond coating g
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Cold spray (1)
• High deposition rate at low temperature
• Accelerated powder particles are sprayed onto substrate.
• Fabrication type : constructive process
• Typical substrate materials : metal
Schematic diagram
Cold spray (2)
Repair of damaged mold
1. Mold fabrication 3. Deposition of
particles
2. Damaged mold 4. Machining
mold surface 5. Repaired mold
Nano particle deposition system (NPDS)
• High deposition rate at room temperature
• Aerosol with particles is accelerated by a gas flow and sprayed onto substrate.
• Fabrication type : constructive process
• Typical substrate materials : metal, ceramic
Fabrication envelop
yp
0 1
Mn-Zn ferrite coating on Al 6061 with niddles
0.17mm
0.1mm 1.03mm 0.46mm
2 5 μm 250 nm
TiO
2coating on Stainless steel
2.5 μm 250 nm
Schematic diagram
Measurement
Length: dial indicator, LVDT
Straightness : autocollimators
Straightness : autocollimators
Flatness: interferometry
Roundness: total indicator reading (TIR), full indicator movement
P fil
Profile
Coordinate measuring machines (CMM) and layout machines
Gages
g
Microscopes
Precision & Accuracy
Accuracy(정확도)
degree of conformity of a
degree of conformity of ameasure to a standard or a true
value(closeness to the true value,
Probability
density δ
mProbability
density δ
mδ
m
) Precision(정밀도) Precision(정밀도)
the degree of refinement with which an operation is performedσ
or a measurement stated(size of
standard deviation, σ)
Value
True value Value
True value
Precision & Accuracy – example
Accurate
Not precise
Accurate
Precise
Precise
Not accurate
Dimensional Tolerance
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Quality Assurance
Normal (Gaussian) Distribution
) (
) (
) (
) (
,
2 2
2 2
min max
3 2 1
−
=
+
⋅
⋅
⋅ + +
= +
x x
R Range
n
x x
x
x x
n1
) (
) (
) (
)
(
1 2 2 2 3 2 2−
− +
⋅
⋅
⋅ +
− +
− +
= −
n
x x x
x x
x x
x
nσ
Control Chart
R A x x
LCL
R A x x
UCL
x 23 )
( lmit control Lower
3 )
( lmit control
Upper = + = +
σ σ
Control Chart
R A x x
LCL
x) 3
2(
lmit control
Lower = − σ = −
Six sigma (3~4 ppm)
ISO 9000 (quality management &
(q y g quality assurance)
ISO 14000 (environmental
management)
management)
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials",
Control Chart
3 R
4
R
R D LCL
R D UCL
R=
=
d
2= R σ
Ref.
S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley
Process Capability Indices
LSL USL
Process Capability Index, C p
x p
LSL C USL
σ 6
= −
Minimum acceptable value for C p is 1
Desirable value : 1 ~ 2
σ
± 3
USL-LSL ① USL-LSL ② USL-LSL ① USL-LSL ②
Desirable value : 1 2
Process Capability Index, C pk
−
− =
= LSL
USL Z Z
x x LSL
x x
USL
σ
μ σ
μ
) (
, min
mean
process :
min
= −
Z
Z or
Z
Z
USL LSLμ
x0 . 3 1
min
≥
= Z
C
pkProcess Capability Indices - example
LSL USL
σ x =10
130
100 190
130 190
130
100 190