Laser shock peening produces a compressive residual stress in the surface of metallic materials, which significantly increases fatigue life in applications where failure is caused by surface-initi ated cracks. Laser shock peening is applied by using a high energy pulsed laser to create a high amplitude stress wave or shock wave on the surface to be treated. This stress wave propagates into the material, causing the surface layer to yield and plastically deform, and thereby, develop a residual compressive stress. Where comparisons have been made to shot peening, the magnitude of the residual stresses at the surface are similar, but the compressive stresses from laser peening extend much deeper below the surface than those from shot peening. The resulting fatigue life enhancement is often greater for laser peering than it is for shot peening. In addition to fatigue strength improvement, laser peering can also locally strain harden thin sections of parts or strain harden a surface

1. LASER SHOCK PEENING
KOTA MANISH KUMAR
(1602-17-745-002)

2. CONTENTS
 Introduction
 Literature Review
 Experimental Setup
 Working Process
 What are residual stresses
 Incremental hole drilling method
 Factors influencing residual stresses
 Advantages
 Conclusion
 References

3. INTRODUCTION
 Peening is the process of working a metals‘ s
surface to improve its material properties
 It is a cold working process.
 Mechanical working processes
1. Hammers
2. Shots
3. Laser

4. WHAT IS LASER PEENING?
 Laser peening is a surface enhancement method
for extending the life of metal components
 Laser peening improves fatigue life
 residual stresses generated by LSP typically
extend 5to 10 times deeper than those produced
by shot peening.
 longer service lifetimes

5. RESIDUAL STRESS ANALYSIS ON
TITANIUM ALLOY TC4 BY LASER
SHOCK PEENING
 This test was performed by jun hong li ,he is
from china.
 He is done LSP test on TC4 material
 the residual stresses using x-ray stress analyser
 Results indicates that there was large residual
stresses are induced on the surface of material.

6. PARAMETRIC STUDY ON SINGLE SHOT
AND OVERLAPPING LASER SHOCK
PEENING ON VARIOUS METALS VIA
MODELLING AND EXPERIMENTS
 This paper is written by yunfeng cao and yung
c.shin.
this experiment performed on 4140 steel and TI-
6AL-4V materials
 These are underwater confinement process
 And he used 3-d finite element for analyse
residual stresses in the materials

7. AN ANALYTICAL MODEL TO PREDICT
RESIDUAL STRESS FIELD INDUCED BY
LASER SHOCK PEENING
 This paper was published by yongxiang hu and
zheqiang yao and jun hu
 He proposed a complete analytical model of LSP
 He used FEM to calculate residual stresses in the
material

8. EXPERIMENTAL AND NUMERICAL
INVESTIGATION OF RESIDUAL
STRESSES IN LASER PEENED AA2198
 This paper was published by s.keller,s.chupakhin,
p.staron,e.maawad,n.kashaev
 Lsp is done on AA2198 material
 Experimental and numerical investigation are done
using different investigating models
 Using hole drilling method and x-ray diffraction test

9. FINITE ELEMENT ANALYSIS OF
VARIATION IN RESIDUAL STRESS
DISTRIBUTION IN LASER SHOCK
PEENING OF STEELS
 This paper was published rohit voothaluru and
c.Richard liu gary j.cheng
 This experiment was done on 1053STEEL &
52100 AISI STEELS
 By using ansys software he compared residual
stresses of 1053 STEEL and 52100 AISI
STEELS

10. EXPERIMENTAL SETUP

11. EXPERIMENTAL DETAILS
 Laser characteristics
1. Neodymium glass (Nd) laser (1054 nm wavelength)
2. 0.6 - 5 J energy per pulse
3. 1 - 3mm spot diameter
4. 2.78- 25GW/cm2 power density
 Opaque used
1. Paint
2. Tape
 Coolant used
1. water

12. • Specimen used
1. AA2198-T3, AA2198-T5
2. Specimen thickness : 3.2 mm
• Base layer used:
1. Steel plate
2. Air

13. •PROCEDURE
 A high-energy, short-duration laser pulse
produces a rapidly expanding plasma burst on
the part surface
 The rapid rise of pressure generates a powerful
compressive shockwave that propagates into the
material.

14. TYPICAL LSP PROCESSING PARAMETERS FROM THE LITERATURE USED FOR
DIFFERENT MATERIALS WITH CONCLUDING REMARKS.

15. WHAT ARE RESIDUAL STRESSES?
 Residual stresses are stresses that remain in a
solid material after the original cause of the
stresses has been removed
 Residual stress may be desirable or undesirable
 Undesirable residual stresses cause premature
failures

16. WHY ARE RESIDUAL STRESSES
BENEFICIAL?
 When a component is enhanced with
compressive residual stresses, it can withstand
greater tensile forces before cracking and failure
occur.
 buffer against tensile strain,
 deeper compressive stresses inhibit crack
initiation

17. METHODS TO FIND RESIDUAL
STRESSES
 Nano-indentation,
 X-ray diffraction,
 metallographic microscope,
 SEM,
 TEM
 Incremental hole drilling method
 Fem

18. INCREMENTAL HOLE DRILLING
METHOD
 Residual stresses were determined by the
measurement system Prism from Stress-tech by
1. electronic speckle pattern interferometry
(ESPI) or Strain gauges.
1. Drilling a hole incrementally.
2. Measurement of the surface deformation after
each increment using ESPI or Strain gauges
3. Calculation of the residual stresses from surface
deformations(Integral method)

19. ESPI SETUP

20. STRAIN GUAGE SETUP

21. FACTORS INFLUENCING RESIDUAL
STRESSES DURING EXPERIMENT
 Temper condition
 Focal size
 Laser power density
 Base layer

22. TEMPER CONDITION

23. FOCAL SIZE
• Low focus size
1. high overlapping stresses
2. spherical wavefront
• High focus size
1. high depth of penetration
2. linear wave front
Laser power density
1. Higher power density leads to high pressure pulse
irrespective of pulse energy

25. Influence of base layer
 Base layer is placed at the back of the work
piece as a support.
 This will reflect back the wave into material to
increase residual stresses.

26. Influence of specimen thickness
1. Increase in the thickness the shock wave
intensity decreases at the end of plate
2. Reflected shock wave intensity also decreases

27. X-RAY DIFFRACTIONS TEST
 The photon energy: 87.1 kev
 Wave length:0.1419 Aº
 Pixel size :200μm
 Beam is 1.5 mt from work-piece

28. HDM VS XRD METHOD

29. ADVANTAGES
o increases the strength
o high fatigue resistance
o High wear properties
o Low cold work

30. DIS-ADVANTAGES
 High capital cost
 Repeated coating
 Difficult to control process variables

31. APPLICATIONS
 Engine components
 Turbine, fan, and compressor blades
 Bulkheads, wing attachments, flight control
mechanisms, wheels
 Brakes, landing gear
 Welded titanium and aluminum components for
improved reliability
 Welded aging aircraft parts for improved
reliability

32. CONCLUSION
 As the LSP power density increased, the residual
compressive stresses on the surface were also
increased.
 fatigue resistance of material would be greatly
improved
 Laser shock processing can make high residual
compressive stress on the surface and deep
inside of the material.
 Compressive stresses decreased gradually with
the depth increased,