Seoul National University

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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

(2)

Introduction

ƒ Surface properties affect

F i ti d

ƒ

Friction and wear

ƒ

Lubrication

ƒ

Painting coating welding soldering adhesive bonding corrosion Painting, coating, welding, soldering, adhesive bonding, corrosion resistance

ƒ

Crack initiation

ƒ

Thermal and electrical conductivity

ƒ Tribology

ƒ

Friction

ƒ

Wear

ƒ

Lubrication

ƒ

Lubrication

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Surface structure

ƒ Oxide layer (hard, brittle, abrasive)

I F O F O F O

ƒ

Iron: FeO, Fe 3 O 4 , Fe 2 O 3

ƒ

Aluminum: Al 2 O 3

ƒ

Copper: Cu Copper: Cu 2 2 O CuO O, CuO

ƒ

Stainless steel: CrO

ƒ Beilby layer: melting & surface flow-> rapid quenching y y g p q g

ƒ Work-hardened layer: residual stress

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley

(4)

Surface texture

ƒ Flaw (흠)/ defect (결함), lay (가공무늬), roughness (거칠기), waviness (파상도)

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials",

(5)

Surface roughness

ƒ Surface profilometers (표면거칠기 측정기)

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley

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R a a and R q q

ƒ Arithmetic mean value

ƒ

arithmetic ave. (AA) ( )

ƒ

center-line ave. (CLA)

ƒ Root-mean-square ave. (RMS)

1

⋅⋅ 1

⋅ + +

+ y y y ∑ ∫

y

b d n l

12 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

ƒ Rough surface:

ƒ

Lower precision short fatigue life higher electrical & thermal contact

1

⎢⎣ ∫

0

⎥⎦

=

dx l y

n y R n

i i q

ƒ

Lower precision, short fatigue life, higher electrical & thermal contact

resistance, lower corrosion resistance, better painting & coating, lower cost

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials",

(7)

Atomic Force Microscope (AFM) Tip

piezoresistor

region PZT region Tip

High doping region

Before PZT process After PZT process

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Friction

ƒ Adhesion theory of friction (응착이론)

ƒ Intimate contact of asperities creates an adhesive bond

ƒ Friction coefficient (마찰계수)

A

F τ

r

τ

μ = = = friction ( shear ) factor , m = τ k

i

hardness A

N

r

μ 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",

(9)

Measuring Friction

ƒ 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

(10)

Wear (1)

ƒ Progressive loss of material from

a surface

ƒ Adhesive wear (응착마멸)

a surface

A h d l LW

p k LW V = 3

ƒ 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",

(11)

Wear (2)

ƒ Abrasive wear

ƒ Corrosive wear

ƒ Corrosive wear

ƒ Fatigue wear

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley

(12)

Lubrication

4 i f l b i ti G t i d f t

ƒ 4 regimes of lubrication ƒ Geometric defects

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials",

(13)

Surface Treatment (1)

ƒ Shot peening, water-jet peening, laser peening

ƒ Roller burnishing (surface rolling)

ƒ Roller burnishing (surface rolling)

ƒ Cladding (clad bonding)

ƒ Mechanical plating p g

ƒ Thermal spraying

ƒ Surface texturing

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley

(14)

Surface Treatment (2)

ƒ Vapor deposition (CVD/PVD/ Ion implantation)

ƒ Electroplating/ electroless plating p g p g

ƒ Electroforming

ƒ Anodizing

ƒ Diamond coating g

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials",

(15)

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

(16)

Cold spray (2)

ƒ Repair of damaged mold

1. Mold fabrication 3. Deposition of

particles

2. Damaged mold 4. Machining

mold surface 5. Repaired mold

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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

2

coating on Stainless steel

2.5 μm 250 nm

Schematic diagram

(18)

Measurement

ƒ Length: dial indicator, LVDT

ƒ Straightness : autocollimators

Straightness : autocollimators

ƒ Flatness: interferometry

ƒ Roundness: total indicator reading (TIR), full indicator movement

P fil

ƒ Profile

ƒ Coordinate measuring machines (CMM) and layout machines

ƒ Gages

g

ƒ Microscopes

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Precision & Accuracy

ƒ Accuracy(정확도)

ƒ

degree of conformity of a

ƒ

degree of conformity of a

measure to a standard or a true

value(closeness to the true value,

Probability

density δ

m

Probability

density δ

m

δ

m

)

ƒ Precision(정밀도) Precision(정밀도)

ƒ

the degree of refinement with which an operation is performed

σ

or a measurement stated(size of

standard deviation, σ)

Value

True value Value

True value

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Precision & Accuracy – example

ƒ Accurate

ƒ Not precise

ƒ Accurate

ƒ Precise

ƒ Precise

ƒ Not accurate

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Dimensional Tolerance

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials", 3rd/4th ed. Addison Wesley

(22)

Quality Assurance

ƒ Normal (Gaussian) Distribution

) (

) (

) (

) (

,

2 2

2 2

min max

3 2 1

=

+

⋅ + +

= +

x x

R Range

n

x x

x

x x

n

1

) (

) (

) (

)

(

1 2 2 2 3 2 2

− +

⋅ +

− +

− +

= −

n

x x x

x x

x x

x

n

σ

ƒ Control Chart

R A x x

LCL

R A x x

UCL

x 2

3 )

( lmit control Lower

3 )

( lmit control

Upper = + = +

σ σ

ƒ Control Chart

R A x x

LCL

x

) 3

2

(

lmit control

Lower = − σ = −

ƒ Six sigma (3~4 ppm)

ƒ ISO 9000 (quality management &

(q y g quality assurance)

ƒ ISO 14000 (environmental

management)

management)

Ref.

S. Kalpakjian, "Manufacturing Processes for Engineering Materials",

(23)

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

(24)

Process Capability Indices

LSL USL

ƒ Process Capability Index, C p

x p

LSL C USL

σ 6

= −

ƒ Minimum acceptable value for C p is 1

ƒ Desirable value : 1 ~ 2

σ

± 3

USL-LSL ① USL-LSL ② USL-LSL ① USL-LSL ②

Desirable value : 1 2

ƒ 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 LSL

μ

x

0 . 3 1

min

= Z

C

pk

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Process Capability Indices - example

LSL USL

σ x =10

130

100 190

130 190

130

100 190

6

10 130 190

=

= − Z USL

3

) 3 ( , 6

min min

=

= Z

10 130 100

6

= −

Z LSL 1.0

3 3 =

pk = C

3

= −

Figure

Updating...

References

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