Systematical Characterization of Material Response to Microscale Laser Shock Peening

2004 ◽  
Vol 126 (4) ◽  
pp. 740-749 ◽  
Author(s):  
Hongqiang Chen ◽  
Youneng Wang ◽  
Jeffrey W. Kysar ◽  
Y. Lawrence Yao
Keyword(s):  
Fourier Analysis ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Laser Shock Peening ◽  
Lattice Rotation ◽  
Strength Increase ◽  
Laser Shock ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
Shock Peening

The response of materials after microscale laser shock peening (μLSP) was experimentally characterized and compared with the theoretical prediction from FEM analysis in microlength level. Since μLSP is predominantly a mechanical process instead of a thermal process, the characterization focuses on mechanical properties and associated microstructures. An X-ray microdiffraction technique was applied on the postpeened single crystal aluminum of (001) and (110) orientations, and an X-ray profile was analyzed by subprofiling and Fourier analysis method. Spatially resolved residual stress and strain deviation was quantified and explained in terms of the heterogeneous dislocation cell structure. In-plane crystal lattice rotation induced by μLSP were measured by electron backscatter diffraction (EBSD) and compared with the FEM simulation. Average mosaic size was evaluated from X-ray profile Fourier analysis and compared with the result from EBSD. Surface strength increase and dislocation cell structure formation were studied. The systematical characterization helps develop more realistic simulation models and obtain better understanding in microlength level.

Spatially Resolved Characterization of Residual Stress Induced by Micro Scale Laser Shock Peening

2004 ◽  
Vol 126 (2) ◽  
pp. 226-236 ◽  
Author(s):  
Hongqiang Chen ◽  
Y. Lawrence Yao ◽  
Jeffrey W. Kysar
Keyword(s):  
Residual Stress ◽  
Cell Structure ◽  
Fem Analysis ◽  
Dislocation Cell ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
X Ray ◽  
Micro Scale ◽  
Spatially Resolved ◽  
Shock Peening

Single crystal aluminum and copper of (001) and (110) orientation were shock peened using laser beam of 12 micron diameter and observed with X-ray micro-diffraction techniques based on a synchrotron light source. The X-ray micro-diffraction affords micron level resolution as compared with conventional X-ray diffraction which has only mm level resolution. The asymmetric and broadened diffraction profiles registered at each location were analyzed by sub-profiling and explained in terms of the heterogeneous dislocation cell structure. For the first time, the spatial distribution of residual stress induced in micro-scale laser shock peening was experimentally quantified and compared with the simulation result obtained from FEM analysis. Difference in material response and microstructure evolution under shock peening were explained in terms of material property difference in stack fault energy and its relationship with cross slip under plastic deformation. Difference in response caused by different orientations (110 and 001) and active slip systems was also investigated.

Characterization of Plastic Deformation Induced by Microscale Laser Shock Peening

2004 ◽  
Vol 71 (5) ◽  
pp. 713-723 ◽  
Author(s):  
Hongqiang Chen ◽  
Jeffrey W. Kysar ◽  
Y. Lawrence Yao
Keyword(s):  
Plastic Deformation ◽  
Single Crystal ◽  
Crystal Lattice ◽  
Electron Backscatter Diffraction ◽  
Fem Analysis ◽  
Copper Sample ◽  
Laser Shock Peening ◽  
Lattice Rotation ◽  
Laser Shock ◽  
Shock Peening

Electron backscatter diffraction (EBSD) is used to investigate crystal lattice rotation caused by plastic deformation during high-strain rate laser shock peening in single crystal aluminum and copper sample on 110¯ and (001) surfaces. New experimental methodologies are employed which enable measurement of the in-plane lattice rotation under approximate plane-strain conditions. Crystal lattice rotation on and below the microscale laser shock peened sample surface was measured and compared with the simulation result obtained from FEM analysis, which account for single crystal plasticity. The lattice rotation measurements directly complement measurements of residual strain/stress with X-ray micro-diffraction using synchrotron light source and it also gives an indication of the extent of the plastic deformation induced by the microscale laser shock peening.

Experimental Characterization and Simulation of Three Dimensional Plastic Deformation Induced by Microscale Laser Shock Peening

2004 ◽  
Author(s):  
Hongqiang Chen ◽  
Jeffrey W. Kysar ◽  
Y. Lawrence Yao ◽  
Youneng Wang
Keyword(s):  
Plastic Deformation ◽  
Single Crystal ◽  
Three Dimensional ◽  
Finite Size ◽  
Fem Analysis ◽  
Laser Shock Peening ◽  
Lattice Rotation ◽  
Finite Size Effect ◽  
Laser Shock ◽  
Shock Peening

Different experimental techniques and 3D FEM simulations are employed to characterize and analyze the three dimensional plastic deformation and residual strain/stress distribution for single crystal Aluminum under microscale laser shock peening assuming finite geometry. Single pulse shock peening at individual locations was studied. X-ray micro-diffraction techniques based on a synchrotron light source affords micron scale spatial resolution and is used to measure the residual stress spatial distribution along different crystalline directions on the shocked surface. Crystal lattice rotation due to plastic deformation is also measured with electron backscatter diffraction (EBSD). The result is experimentally quantified and compared with the simulation result obtained from FEM analysis. The influence of the finite size effect, crystalline orientation are investigated using single crystal plasticity in FEM analysis. The result of the 3D simulations of a single shock peened indentation are compared with the FEM results for a shocked line under 2D plain strain deformation assumption. The prediction of overall character of the deformation and lattice rotation fields in three dimensions will lay the ground work for practical application of μLSP.

Microscale Laser Shock Peening of Thin Films, Part 2: High Spatial Resolution Material Characterization

2004 ◽  
Vol 126 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Wenwu Zhang ◽  
Y. Lawrence Yao ◽  
I. C. Noyan
Keyword(s):  
Thin Films ◽  
Spatial Resolution ◽  
Strain Field ◽  
High Spatial Resolution ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
Stress Strain ◽  
Crystal Silicon ◽  
X Ray ◽  
Shock Peening

Microscale Laser Shock Peening (LSP) is a technique that can be potentially applied to manipulate the residual stress distributions in metal film structures and thus improve the reliability of micro-devices. This paper reports high-spatial-resolution characterization of shock treated copper thin films on single-crystal silicon substrates, where scanning x-ray microtopography is used to map the relative variation of the stress/strain field with micron spatial resolution, and instrumented nanoindentation is applied to measure the distribution of hardness and deduce the sign of the stress/strain field. The measurement results are also compared with 3-D simulation results. The general trends in simulations agree with those from experimental measurements. Simulations and experiments show that there is a near linear correlation between strain energy density at the film-substrate interface and the X-ray diffraction intensity contrast.

Spatially Resolved Characterization of Geometrically Necessary Dislocation Dependent Deformation in Micro-Scale Laser Shock Peening

2008 ◽  
Author(s):  
Youneng Wang ◽  
Sinisa Vukelic ◽  
Jeffrey W. Kysar ◽  
Y. Lawrence Yao
Keyword(s):  
Scale Effects ◽  
Fem Simulation ◽  
Target Material ◽  
Material Point ◽  
Laser Shock Peening ◽  
Lattice Rotation ◽  
Length Scale ◽  
Laser Shock ◽  
Micro Scale ◽  
Shock Peening

As the laser spot size in micro-scale laser shock peening is in the order of magnitude of several microns, the anisotropic response of grains will have a dominant influence on its mechanical behavior of the target material. Furthermore, conventional plasticity theory employed in previous studies needs to be reexamined due to the length scale effect. In the present work, the length scale effects in microscale laser shock peening have been investigated. The crystal lattice rotation underneath the shocked surface was determined via Electron Backscatter Diffraction (EBSD). From these measurements, the geometrically necessary dislocations (GND) density that the material contains has been estimated. The yield strength increment was then calculated from the GND distribution by using Taylor model and integrated into each material point of the FEM simulation. Finite element simulations, based on single crystal plasticity, were performed of the process for both with and without considering the GND hardening and the comparison has been conducted.

X-ray determination of dislocation density and arrangement in plastically deformed copper

2000 ◽  
Vol 33 (5) ◽  
pp. 1284-1294 ◽  
Author(s):  
D. Breuer ◽  
P. Klimanek ◽  
W. Pantleon
Keyword(s):  
Dislocation Density ◽  
Profile Analysis ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Double Crystal ◽  
Mean Values ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
X Ray Scattering

Using the kinematical theory of X-ray scattering by crystals with dislocations as developed by Krivoglazet al.and Wilkens, the dislocation content of compressed copper single and polycrystals was investigated by means of profile analysis of selected diffraction peaks. Measurements of radial intensity distributionsI(2θ) were performed with a double-crystal spectrometer in the case of the single crystals and with conventional polycrystal diffractometers in the case of the polycrystals. Additionally, the misorientations Θ occurring within the dislocation cell structure because of the accumulation of excess dislocations of one sign were investigated by means of rocking curves of the single-crystal reflections and by evaluation of electron backscattering patterns (EBSPs). Within a wide deformation range, the mean total dislocation density ρdcan be related well to the flow stressviathe Taylor relationship. Assuming a random distribution of the misorientations Θ between adjacent dislocation cells, the evaluation of the rocking curves gives mean values 〈|Θ|〉 much smaller than those determined by EBSP analysis. For this reason, a model of a dislocation cell structure with restrictedly correlated misorientations, which leads to better agreement of the X-ray and the EBSP data, is proposed.

Characterization of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Titanium Alloy by Laser Shock Peening

2011 ◽  
Vol 697-698 ◽  
pp. 466-469 ◽  
Author(s):  
Yu Qin Li ◽  
Wei Feng He ◽  
Ying Hong Li ◽  
Qi Peng Li ◽  
Xiang Fan Nie
Keyword(s):  
Titanium Alloy ◽  
Laser Shock Peening ◽  
Laser Shock ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Transmission Electron ◽  
Crystallization Surface ◽  
Shock Peening

In this paper, the microstructure and microhardness of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy with and without laser shock peening (LSP) were examined and compared. The titanium alloy samples were treated with different layers, at the same power density. X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and microhardness techniques were used to analyse microstructure and mechanical. X-ray diffraction analysis shows that there was not any phase transformation and no new crystalline phases have been formed. TEM studies demonstrate that both α and β phase can been refined in the surface layer with LSP. The microhardness measurements with LSP demonstrate that Hardness of crystallization surface is high up to 418MPa, which is more than the sample without LSP, the shock wave improved the microhardness for about 8%, and the affected depth is about 400 microns from the surface.

Spatially Resolved Characterization of Geometrically Necessary Dislocation Dependent Deformation in Microscale Laser Shock Peening

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Youneng Wang ◽  
Jeffrey W. Kysar ◽  
Sinisa Vukelic ◽  
Y. Lawrence Yao
Keyword(s):  
Finite Element ◽  
Scale Effects ◽  
Target Material ◽  
Material Point ◽  
Laser Shock Peening ◽  
Lattice Rotation ◽  
Length Scale ◽  
Laser Shock ◽  
Geometrically Necessary Dislocation ◽  
Shock Peening

As the laser spot size in microscale laser shock peening is in the order of magnitude of several microns, the anisotropic response of grains will have a dominant influence on its mechanical behavior of the target material. Furthermore, conventional plasticity theory employed in previous studies needs to be re-examined due to the length scale effect. In the present work, the length scale effects in microscale laser shock peening have been investigated. The crystal lattice rotation underneath the shocked surface was determined via electron backscatter diffraction. From these measurements, the geometrically necessary dislocation (GND) density that the material contains has been estimated. The yield strength increment was then calculated from the GND distribution by using the Taylor model and integrated into each material point of the finite element method (FEM) simulation. Finite element simulations, based on single crystal plasticity, were performed for the process both with and without considering the GND hardening, and the comparison has been conducted.

Asymmetric X-ray line broadening of plastically deformed crystals. II. Evaluation procedure and application to [001]-Cu crystals

1989 ◽  
Vol 22 (1) ◽  
pp. 26-34 ◽  
Author(s):  
T. Ungár ◽  
I. Groma ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Dislocation Structure ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Line Profiles ◽  
Line Broadening ◽  
Spatial Fluctuation ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
Dipole Polarization

In paper I [Groma, Ungár & Wilkens (1988). J. Appl. Cryst. 21, 47–53] a theory was developed to interpret the asymmetric X-ray line broadening of plastically deformed crystals. It was shown that the dislocation structure can be described by five distinct parameters, namely the dislocation density, the mean quadratic spatial fluctuation of the dislocation density, the effective outer cut-off radius, the dipole polarization and the spatial fluctuation of the dipole polarization of the dislocation structure. In this paper a procedure is developed to evaluate these parameters from the Fourier transform of the line profiles. The theory and this procedure are tested by applying it to the asymmetric line profiles of tensile-deformed Cu single crystals orientated for ideal multiple slip. The asymmetry of these profiles is assigned to the dipole polarization of the dislocation cell structure and is directly correlated to residual long-range internal stresses. It is shown that the data can be interpreted in terms of the quasi-composite model of the dislocation cell structure developed earlier for the same material.

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