Abstract

In this paper, a novel approach, proposed for predicting residual stresses induced on materials treated with high pressure water jets, i.e. water jet peening, is presented. This approach considers the impact pressure distribution due to high velocity droplets impinging on the material surface instead of stationary pressure distribution considered in Trans ASME J Eng Mat Technol 121 (1999) 336 for prediction of residual stresses on water jet peened surfaces. It makes use of Reichardt’s theory for predicting the velocity distribution of droplets and liquid impact theory for predicting the impact pressure and duration of impact of high velocity droplets. For predicting residual stresses on the surface and sub surface of material subjected to water jet peening, finite element modelling approach was adopted by considering the transient, dynamic nature of droplets for analysis. The effectiveness of the proposed approach was demonstrated by comparing the predicted residual stresses with those predicted employing the approach proposed in Trans ASME J Eng Mat Technol 121 (1999) 336. Finally, the practical relevance of the proposed approach was shown by comparing the predicted results with the experimental results obtained by water peening of 6063-T6 aluminium alloy.

Author Keywords: Author Keywords: Water jet peening; Surface treatment; Residual stresses; Numerical modelling; Transient dynamic analysis

Nomenclature

A

cross-sectional area of water jet (m²)

C₁

shock velocity of water (m/s)

C₀

Acoustic velocity of water (m/s)

E

Young’s modulus (GPa)

E_t

Tangent modulus (GPa)

F

total force (N) of water jet

K

constant for water in the velocity range up to 1000 ms⁻¹

P_imp

impact pressure (GPa)

p

intensifier pressure (MPa)

p_o

stagnation pressure (MPa)

p_s

stationary pressure (MPa)

r

arbitrary radial distance from the center of impinging jet (mm)

r^*

outer radius of the circular region exposed by the jet (mm)

r_n

radius of the nozzle (mm)

r_w

radius of the water droplet (μm)

r_c

contact radius of droplet (μm)

r_eff

effective contact radius of droplet (μm)

t_l

loading time (seconds)

t_u

unloading time (seconds)

u_max

maximum exit velocity of water jet (m/s)

u

average exit velocity of water jet (m/s)

σ_y

yield stress (MPa)

ρ

density of water (kg/m³)

ν

Poisson’s ratio

Article Outline

Nomenclature

1. Introduction

2. Methodology

2.1. Distribution of impact pressures generated by water jet

2.2. Residual stresses on water peened surface

3. Results and discussion

3.1. Validation of the proposed model

3.2. Experimental validation

4. Conclusions

References