Fatigue Analysis Of Ball t 2045a

“Fatigue Life cycle Analysis on Steering Knuckle Ball t”

GUIDE Mr.A.R.SURESH M.E Assistant professor (ss) Dr.MCET

S.PRADEEP ME(CAD/CAM) Dr.MECT-POLLACHI

OBJECTIVE OF THE PROJECT

Optimized design of a Steering Knuckle

Ball t with increased life condition.

Introduction to Ball t • The Ball t has three rotational DOFs. • This t is used to connect the knuckle to the steering rod and the short and long arm. • Ball ts – allows movement of steering components and suspension • Ball ts are a critical component to a car. • They are the part of the vehicle's chassis that connect the steering knuckles to the control arms next to the wheels.

Broken specimen of a ball t

Specimen preliminary investigations • From the broken samples it is found that maximum failure occurs at the neck region of the ball t. • Fractured parts are investigated for surface defects through SEM analysis, and results are collected.

Chemical Composition of SAE 4135 grade steel Elements

Symbol

Unit

Specified Values

Observed Values

Carbon

C

%

0.33-0.38

0.334

Silicon

Si

%

0.15-0.35

0.229

Manganese

Mn

%

0.70-0.90

0.774

Phosphorus

P

%

0.035 Max

0.013

Sulphur

S

%

0.040 Max

0.004

Chromium

Cr

%

0.80-1.10

1.06

Molybdenum

Mo

%

0.15-0.25

0.184

Mechanical Properties of SAE 4135 Grade Steel Mechanical Properties Properties

SAE4135

Diameter (d) mm

>16-40

Thickness (t) mm

8 <20

0.2℅ Proof stress (N/mm2)

min.650

Tensile Strength (Mpa)

900-1200

Fracture Elongation (℅)

min.15

Reduction of area Z (℅)

min.50

Notch Impact Energy ISO - V [J]

min.40

Density (×1000 kg/m3)

7.7-8.03

Poisson's Ratio

0.27-0.30

Elastic Modulus (Gpa)

190-210

Yield Strength (Mpa)

1034

SEM Analysis

a) Origin of the crack

b) Fracture features of origin

SEM - Result  There is enough evidence of micro crack on the surface of

the neck region just below ball.  The broken samples show that the crack originate from the

top surface as it experience a uni-directional knocking load.

EXPERIMENTAL DETAILS Fatigue test under cyclic loading

 INSTRON servo-hydraulic actuator of 25 KN capacity

 Constant amplitude cyclic loading with load ratio of 0.3

 The test frequency was 0.5 – 5 Hz

Fatigue test on steering knuckle ball t

EXPERIMENTAL DETAILS

(Contd…)

Constant amplitude completely reversed fatigue test results At midlife (N50%) Specimen ID

Test control mode

Load (KN)

Test control No.of.cycles

Freq (±5)

HZ

Δε/2, %

Δεp/2 [a]

Nf

%(calculated),

Failure Loaction

[b]

E Gpa

Ball10-1

strain

4

5

0.56

0.55

2.514E+05

NECK

190

Ball10-2

strain

4

5

0.79

0.78

2.544E+05

NECK

190

Ball10-3

strain

4

5

0.625

0.62

2.471E+05

NECK

190

Ball10-4

strain

4

5

0.6

0.6

2.504E+05

NECK

190

Ball10-5

strain

4

5

0.605

0.605

2.533E+05

NECK

190

[a] Δεp/2(calculated)=Δε/2-Δσ/2E. [b]Neck region NECK

CASE – I : Ball t (30°,R1.5,L-54mm)

Boundary and Loading Condition

Total Deformation

Stress distribution

Life cycle

CASE – II : Ball t (33°,R3,L-64mm)

Boundary and Loading Condition

Stress distribution

Log-Life cycle repeated Total Deformation

EXPERIMENTAL DETAILS

Existing neck region Von-Mises Stress (Mpa)

Total deformation (mm)

Angle

(Contd…)

Modified neck region ε-N

S-N

Min

Max

Min

Max

30

0

918.63

0

0.01065

18553

1.87E+05

2.91E+05

0.3

31

0

611.87

0

0.064

35114

3.65E+06

3.89E+06

0.3

32

0.0003

621.87

0

0.0644

33233

3.24E+06

3.47E+06

0.3

33

7.55E-05

599.37

0

0.0683

37876

4.22E+06

4.46E+06

0.3

35

0.00013

609.41

0

0.069

35635

3.68E+06

3.92E+06

0.3

36

0.0002

604.26

0

0.0694

36763

3.94E+06

4.18E+06

0.3

37

0.00015

608.39

0

0.0694

35855

3.73E+06

3.97E+06

0.3

38

0.00015

865.2

0

0.106

10326

2.28E+05

3.21E+05

0.3

Fatigue Strength factor -1

Type – Full Reversed

Marrow- Fatigue life

SWT Fatigue life

Ratio

Fatigue Life (Gerber)

Case study 1- Experimental Results Vs Software result Life Specimen ID Experimental

Software Result

Ball 1-1

2.514E+05

4.222E+06

Ball 1-2

2.544E+05

Ball 1-3

2.471E+05

Ball 1-4

2.504E+05

Ball 1-5

2.533E+05

4.222E+06

4.222E+06 4.222E+06 4.222E+06

S-N Curve

Results of design for Infinite number of cycles Design for Infinite number of cycles Existing Design Parameter Min Max 7.55E-05 599.37 Von mises stress 0 0.0683 Total deformation 0 0.93 Stress ratio 0.071 14 Safety margin 0.933 15 Stress safety factor 37876 1.00E+06 Life cycle (cycle) Equivalent Alternating stress 2.26E-05 179.81 S-N Life (Gerber) (Mpa) Safety factor 4.79E-01 15 Bi-axiality Indication -1 0.9879 Fatigue Sensitivity 9.17E+03 7.85E+05 4.21E+06 1.00E+12 Life cycle (cycle) 1.00E-03 2.37E+02 Damage ε-N - Life (Marrow ) Safety factor 5.34E-01 15 Bi-axiality Indication -1 0.9879 Fatigue Sensitivity 2.15E+05 1.83E+09 4.46E+06 1.00E+09 Life cycle (cycle) 1.00E+00 2.24E+02 Damage ε-N – Life (SWT ) Safety factor 5.34E-01 15 Bi-axiality Indication -1 0.9879 Fatigue Sensitivity 2.51E+05 1.00E+09

Improved Design Min Max 7.41E-10 380.78 0 0.043 2.18E-12 1.5231 -0.343 14 0.656 15 1.98E+05 1.00E+06 2.23E-10

114.23

0.7546 -1 4.52E+04 2.06E+08 1.00E-03 0.84 -1 6.24E+06 2.06E+08 1.00E-03 0.84 -1 6.53E+06

15 0.978 1.00E+06 1.00E+12 4.81E+00 15 0.978 1.24E+11 1.00E+12 4.84E+00 15 0.978 1.24E+11

Results from analysis • A maximum load of 4000 N applied perpendicular to the

axis of the of the ball t . • Maximum deformation of 0.010 mm occur at Edge of the surface. • Maximum stress of 380.3Mpa ( Von Mises )is found out in the necked region. • When the parameter viz. Radius, angle, length and diameter increase the fatigue life is increased.

Conclusion • The software results which were obtained for fatigue life

predictions reasonably good agreement with the experimental results. • The increase in the taper angle (ø) the radius ® but, the life is decrease first and then increase for the increase in the taper angle. • For the given tapper angle and radius increase in the length (L) increase the life of the component. • With the limits of the parameters considered the tapper angle 33° radius 3mm and the length 64mm gives the better life.

Future Works • The

same design study can be utilized for other composition of materials. • This design study can be tried for the variable load application also. • This design study can be tried for fracture surface on bending and torsion loading.

Thank You