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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

(3)

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

(6)

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

(8)

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

(17)

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

(19)

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

(20)

Precision & Accuracy – example

ƒ Accurate

ƒ Not precise

ƒ Accurate

ƒ Precise

ƒ Precise

ƒ Not accurate

(21)

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

(25)

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

= −

참조

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