Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials

1994 ◽  
Vol 376 ◽  
Author(s):  
M. Vrána ◽  
P. Klimanek ◽  
T. Kschidock ◽  
P. Lukáš ◽  
P. Mikula
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Stacking Faults ◽  
Metallic Materials ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutron Diffractometer ◽  
Residual Strains ◽  
Good Agreement

ABSTRACTInvestigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.

scholarly journals Microstrain Measurement in Plastically Deformed Austenitic Steel

1999 ◽  
Vol 33 (1-4) ◽  
pp. 219-230 ◽  
Author(s):  
K. Hirschi ◽  
M. Ceretti ◽  
P. Lukás ◽  
N. Ji ◽  
C. Braham ◽  
...  
Keyword(s):  
Austenitic Steel ◽  
Metallic Materials ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Compressive Stresses ◽  
Cold Rolled ◽  
The Mean ◽  
Good Agreement

Some results of high-resolution neutron diffraction experiments resulting in determination of the microstrain in metallic materials are reported. The method of the diffraction line broadening analysis was verified in two materials, investigated earlier by X-ray diffraction: an austenitic steel prestrained up to 30% and a cold rolled aluminium magnesium alloy. For these materials, the mean-square microstrain and the dislocation density were determined, a good agreement was reached with the results of X-ray experiments. As an application of such analysis we investigated the influence of the shot-peening treatment on an austenitic steel. This treatment is commonly used to introduce compressive stresses in the surface of material, giving improved resistance to fatigue fracture. The microstrain distribution and the size of coherently diffracting blocks for a shot-peened sample of austenitic steel as a function of depth from the surface are determined by the above analysis and the results are presented.

Three-dimensional welding residual stresses evaluation based on the eigenstrain methodology via X-ray measurements at the surface

2014 ◽  
Vol 03 (04) ◽  
pp. 1450023
Author(s):  
Masaru Ogawa
Keyword(s):  
Neutron Diffraction ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain Gauges ◽  
X Ray Diffraction ◽  
Stress Evaluation ◽  
X Ray ◽  
Residual Strains ◽  
Non Destructive ◽  
Evaluation Accuracy

In order to assure structural integrity for operating welded structures, it is necessary to evaluate crack growth rate and crack propagation direction for each observed crack non-destructively. Here, three dimensional (3D) welding residual stresses must be evaluated to predict crack propagation. Today, X-ray diffraction is used and the ultrasonic method has been proposed as non-destructive method to measure residual stresses. However, it is impossible to determine residual stress distributions in the thickness direction. Although residual stresses through a depth of several tens of millimeters can be evaluated non-destructively by neutron diffraction, it cannot be used as an on-site measurement technique. This is because neutron diffraction is only available in special irradiation facilities. Author pays attention to the bead flush method based on the eigenstrain methodology. In this method, 3D welding residual stresses are calculated by an elastic Finite Element Method (FEM) analysis from eigenstrains which are evaluated by an inverse analysis from released strains by strain gauges in the removal of the reinforcement of the weld. Here, the removal of the excess metal can be regarded as non-destructive treatment because toe of weld which may become crack starters can be eliminated. The effectiveness of the method has been proven for welded plates and pipes even with relatively lower bead height. In actual measurements, stress evaluation accuracy becomes poorer because measured values of strain gauges are affected by processing strains on the machined surface. In the previous studies, the author has developed the bead flush method that is free from the influence of the affecting strains by using residual strains on surface by X-ray diffraction. However, stress evaluation accuracy is not good enough because of relatively poor measurement accuracy of X-ray diffraction. In this study, a method to improve the estimation accuracy of residual stresses in this method is formulated, and it is shown numerically that inner welding residual stresses can be estimated accurately from the residual strains measured by X-ray diffraction.

X-ray diffraction characterization of the microstructure of close-packed hexagonal nanomaterials

2008 ◽  
Vol 23 (3) ◽  
pp. 213-223 ◽  
Author(s):  
Zhao-hui Pu ◽  
Chuan-zheng Yang ◽  
Pei Qin ◽  
Yu-wan Lou ◽  
Li-fang Cheng
Keyword(s):  
Stacking Faults ◽  
Triple Line ◽  
Stacking Fault ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Nano Zno ◽  
X Ray ◽  
Crystallite Sizes ◽  
Small Crystallite ◽  
Charge Discharge

A general least-squares technique for X-ray diffraction line broadening analysis has been developed. The technique can be used to determine single, double, and triple line broadening effects caused by small particle sizes, microstrain, stacking faults, or all three presented in a closed-packed hexagonal nanomaterial. The technique was applied to characterize the microstructure of β-Ni(OH)2, a negative electrode material in nickel-metal hydride (NiMH) batteries. Double line broadening effects caused by both small crystallite sizes and stacking faults in β-Ni(OH)2 were detected and analyzed. Triple line broadening effects caused simultaneously by small crystallite sizes, microstrain, and stacking faults were detected in β-Ni(OH)2 after activation and charge-discharge cycle tests. The triple line broadening effects were found to be selective and most pronounced for diffraction lines with h−k=3n±1. The broadening effects were larger when l=even, but smaller when l=odd. The shape and the average size of the crystallites, microstrain, and stacking fault probability in β-Ni(OH)2 changed dramatically after activation and charge-discharge cycles. The method was also applied to characterize and investigate the microstructure of nano ZnO materials. Results indicate that no selective broadening appears in the XRD patterns of the nano ZnO materials. The average crystallite sizes were different slightly, and the stacking fault probabilities differed significantly with different dopants.

X-Ray diffraction line broadening by stacking faults in SrBi2Nb2O9/SrTiO3 epitaxial thin films

2001 ◽  
Vol 391 (1) ◽  
pp. 42-46 ◽  
Author(s):  
A. Boulle ◽  
C. Legrand ◽  
R. Guinebretière ◽  
J.P. Mercurio ◽  
A. Dauger
Keyword(s):  
Thin Films ◽  
Stacking Faults ◽  
Diffraction Line ◽  
Epitaxial Thin Films ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals The Australian High Resolution Neutron Powder Diffractometer

1983 ◽  
Vol 36 (4) ◽  
pp. 507 ◽  
Author(s):  
CJ Howard ◽  
CJ Ball ◽  
RL Davis ◽  
MM Elcombe
Keyword(s):  
High Resolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Diffractometer ◽  
Neutron Powder Diffractometer ◽  
Good Agreement

The high resolution neutron powder diffractometer installed on the AAEC HIFAR reactor at Lucas Heights is described. The resolution is in good agreement with predictions and, although below the most optimistic estimates, the intensities are usable. Examples are given of problems solved using the diffractometer which could not have been solved either by X-ray diffraction or by use of a conventional neutron powder diffractometer. Plans for diffractometer development are outlined.

The whole range of hydrogen bonds in one crystal structure: neutron diffraction and charge-density studies of N,N-dimethylbiguanidinium bis(hydrogensquarate)

2011 ◽  
Vol 67 (6) ◽  
pp. 552-559 ◽  
Author(s):  
Mihaela-Diana Şerb ◽  
Ruimin Wang ◽  
Martin Meven ◽  
Ulli Englert
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
High Resolution ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Electron Density ◽  
Organic Salt ◽  
X Ray Diffraction ◽  
Covalent Character ◽  
X Ray

N,N-Dimethylbiguanidinium bis(hydrogensquarate) features an impressive range of hydrogen bonds within the same crystal structure: neighbouring anions aggregate to a dianionic pair through two strong O—H...O interactions; one of these can be classified among the shortest hydrogen bonds ever studied. Cations and anions in this organic salt further interact via conventional N—H...O and nonclassical C—H...O contacts to an extended structure. As all these interactions occur in the same sample, the title compound is particularly suitable to monitor even subtle trends in hydrogen bonds. Neutron and high-resolution X-ray diffraction experiments have enabled us to determine the electron density precisely and to address its properties with an emphasis on the nature of the X—H...O interactions. Sensitive criteria such as the Laplacian of the electron density and energy densities in the bond-critical points reveal the incipient covalent character of the shortest O—H...O bond. These findings are in agreement with the precise geometry from neutron diffraction: the shortest hydrogen bond is also significantly more symmetric than the longer interactions.

scholarly journals Quantifying magnetic anisotropy using X-ray and neutron diffraction

IUCrJ ◽  
2021 ◽  
Vol 8 (5) ◽  
Author(s):  
Emil Andreasen Klahn ◽  
Emil Damgaard-Møller ◽  
Lennard Krause ◽  
Iurii Kibalin ◽  
Arsen Gukasov ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Magnetic Anisotropy ◽  
Ab Initio ◽  
Single Molecule ◽  
Ligand Field ◽  
Zero Field ◽  
X Ray Diffraction ◽  
Zero Field Splitting ◽  
X Ray

In this work, the magnetic anisotropy in two iso-structural distorted tetrahedral Co(II) complexes, CoX 2tmtu2 [X = Cl(1) and Br(2), tmtu = tetramethylthiourea] is investigated, using a combination of polarized neutron diffraction (PND), very low-temperature high-resolution synchrotron X-ray diffraction and CASSCF/NEVPT2 ab initio calculations. Here, it was found consistently among all methods that the compounds have an easy axis of magnetization pointing nearly along the bisector of the compression angle, with minute deviations between PND and theory. Importantly, this work represents the first derivation of the atomic susceptibility tensor based on powder PND for a single-molecule magnet and the comparison thereof with ab initio calculations and high-resolution X-ray diffraction. Theoretical ab initio ligand field theory (AILFT) analysis finds the d xy orbital to be stabilized relative to the d xz and d yz orbitals, thus providing the intuitive explanation for the presence of a negative zero-field splitting parameter, D, from coupling and thus mixing of d xy and d x 2  −  y 2 . Experimental d-orbital populations support this interpretation, showing in addition that the metal–ligand covalency is larger for Br-ligated 2 than for Cl-ligated 1.

scholarly journals Depth dependence of residual strains in polycrystalline Mo thin films using high‐resolution x‐ray diffraction

1996 ◽  
Vol 79 (9) ◽  
pp. 6872-6879 ◽  
Author(s):  
S. G. Malhotra ◽  
Z. U. Rek ◽  
S. M. Yalisove ◽  
J. C. Bilello
Keyword(s):  
Thin Films ◽  
High Resolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Depth Dependence ◽  
Residual Strains

Spin-resolved charge density and wavefunction refinements using MOLLYNX: a review

2021 ◽  
Vol 77 (5) ◽  
Author(s):  
Mohamed Souhassou ◽  
Iurii Kiblin ◽  
Maxime Deutsch ◽  
Ariste Bolivar Voufack ◽  
Claude Lecomte ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Spherical Harmonics ◽  
Experimental Information ◽  
Theoretical Ground ◽  
X Ray Diffraction ◽  
Precise Description ◽  
New Approach ◽  
X Ray ◽  
Atomic Orbitals

MOLLYNX is a new crystallographic tool developed to access a more precise description of the spin-dependent electron density of magnetic crystals, taking advantage of the richness of experimental information from high-resolution X-ray diffraction (XRD), unpolarized neutron (UND) and polarized neutron diffraction (PND). This new program is based either on the well known Hansen–Coppens multipolar model (MOLLYNX-mult) or on a new expansion over a set of atomic orbitals (MOLLYNX-orb). The main difference between the two models is the basis of the expansion: in MOLLYNX-mult the expansion is over atom centered real spherical harmonics, in MOLLYNX-orb the expansion is over a set of atomic orbitals with which mono and bicentric contributions are calculated. This new approach of MOLLYNX-orb can also be applied to nonmagnetic crystals. This paper summarizes the theoretical ground of two models and describes the first applications to organic, organometallic and inorganic magnetic materials

Sign in / Sign up

Export Citation Format

Share Document