Abstract: An engineering diffractometer designed to solve many problems in materials science and
engineering including investigations of stresses and crystallographic structures within engineering
components is now being developed at J-PARC project. This instrument views a decoupled-poisoned
liquid H2 moderator providing neutrons with good symmetrical diffraction profiles in the acceptable
wavelength range. The primary flight path and the secondary flight path are 40 m and 2.0 m,
respectively, for 90 degree scattering detector banks. A curved supermirror neutron guide will be
installed to avoid intensity loss due to the long flight path and to reduce backgrounds from fast
neutrons and gamma rays. Therefore, stress measurements with sufficient accuracies in many
engineering studies are quite promising. The optimization of this instrument has been performed with
a Monte Carlo simulation, and an appropriate resolution of less than 0.2 % in d/d has been
confirmed. A prototyped radial collimator to define a gauge width of 1 mm has been designed and
manufactured. From performance tests conducted at the neutron diffractometer for residual stress
analysis RESA in JRR-3 of Japan Atomic Energy Agency, the normal distribution with a full width at
half maximum of 1 mm was obtained in a good agreement with the simulation.
Abstract: A large distance between the reactor core and the monochromator together with a take-off
angle of 90° leads to low flux but high angular resolution of the diffractometer around 90° scattering
angle. The sample-table consists of two goniometers for heavy loads. An x-y-z table for heavy loads
can be mounted, as well as different eulerian cradles, a mirror furnace or a tensile rig. The detector
is a 20x20cm2 position sensitive delay-line detector made by EMBL. A sophisticated primary and
secondary slit system together with the recently installed high-resolution camera system allows the
application of the high precision instrument alignment and calibration system recently developed at
HMI. Here some special features of the instrument are presented and the consequences are outlined.
Abstract: In response to the development of new materials and the application of materials and
components in new technologies the direct measurement, calculation and evaluation of textures and
residual stresses has gained worldwide significance in recent years. Non-destructive analysis for
phase specific residual stresses and textures is only possible by means of diffraction methods. In
order to cater for the development of these analytical techniques the new Materials Science
Diffractometer STRESS-SPEC at FRM-II is designed to be equally applied to texture and residual
stress analyses by virtue of its flexible configuration. The system compromises a highly flexible
monochromator setup using three different monochromators: Ge (511), bent silicon (400) and
pyrolitic graphite (PG). This range of monochromators and the possibility to vary the take-off angles
from 2θM = 35º to 110º allows wavelength adjustment such that measurements can be performed
around a scattering angle of 2θS ~ 90º. This is important in order to optimise neutron flux and
resolution, especially for stress analysis on components, since the gauge volume element in that case
is cubic and large vertical divergences due to focusing monochromators do not affect the spatial
The instrument is now available for routine operation and here we will present details of recent
experiments and instrument performance.
Abstract: SALSA (Strain Analyser for Large Scale engineering Applications) is a novel
instrument for strain imaging at the high flux neutron reactor of the Institut Max von Laue – Paul
Langevin (ILL) in Grenoble, France. It is the first of its kind that uses a precise robotic sample stage
for sample manipulation. In addition to standard xyz-translation it provides tilts up to ±30° about
any horizontal axis. Its load capacity is more than 500 kg and samples up to 1.5 m in length can be
scanned with high accuracy. Thanks to a double focusing monochromator and supermirror guide
count times are very short. A broad wavelength range, variable beam optics, including radial
focusing collimators for high lateral resolution, make it a very flexible instrument for a large variety
of strain imaging applications in small and large specimens. The instrument has been commissioned
in 2005 and is open for access by a peer review proposal system and as well by industry. The paper
describes the important aspects of the instrument and results from the first experiments.
Abstract: Recent progress in engineering includes the development of new materials and
innovations in their processing and treatments. Material technologies, like the study of metals,
alloys, ceramics and composites, especially non-destructive analyses of residual stresses profiles and
textures, have gained an increasing importance.
The dedicated residual stress diffractometers E3 and E7 at BENSC, HMI, Berlin are already
equipped with new two-dimensional position sensitive detectors. An upgrade of the monochromator
system is planned for 2006 which includes perfectly bent silicon crystals in order to optimise both
intensity and angular resolution yielding a large gain of the diffractometer efficiency for strain
measurements. A range of equipment for sample positioning is available, such as a closed Eulerian
cradle for samples with weights of up to 5 kg, a second cradle for heavy samples (up to 50 kg) with
the ability to tilt the samples up to 90° and a translation table carrying samples of up to 300 kg and
1000 mm in diameter. Gauge volumes can be adjusted by a new computer controlled variable slitsystem
in a range from 1x1x1 mm³ up to several mm³. In-situ residual stress analysis can be
performed within industrial components during mechanical or thermal loading (up to 2000 K).
Rapid data visualization as well as evaluation is performed by the specially designed software. The
powder diffraction pattern is calculated by summation over the scattering angle dependent Debye-
Scherrer lines on the two-dimensional 400*400 mm² planar area detector.
A large amount of beam time is exclusively used for industrial research. Among the components
that were investigated are crankshafts, impellers, pistons, cylinder heads, turbine blades and welds.
Both instruments are similarly designed, where E3 is set up for higher flux and therefore penetration
depths and E7 is designed for higher angular resolution.
Abstract: Although x-ray diffraction techniques have been applied to the measurement of residual
stress in the industry for decades, some of the related details are still unclear to many
production and mechanical testing engineers working in the field. This is because these
details, specifically those associated with the transition between diffraction and mechanics,
are not always emphasized in the literature. This paper will emphasize the appropriate
calculation methods and the steps necessary to perform high quality residual stress
measurements. Additionally, details are given regarding the difference between mechanical
and x-ray elastic constants, as well as the true meaning of stress and strain from both
diffraction and strain gage point of view. Cases where the material is subject to loading above
the yield limit are also included.
Abstract: A new method for calculation of the diffraction elastic constants, based on the selfconsistent
model, is proposed and tested. This method is especially useful in the interpretation of
the results of X-ray measurements since the ellipsoidal inclusion near the sample surface is
considered. In X-ray diffraction the information volume of the sample is defined by absorption,
causing unequal contribution of different crystallites to the intensity of the measured peak.
Consequently, the surface grains participate more effectively in diffraction than the grains which are
deeper in the sample.
Abstract: Residual stress can be found in engineering components as a result of non-uniform plastic
strain introduced through a variety of manufacturing processes such as rolling, casting, hot forging,
cold working, shot-peening, laser shock peening, welding, etc. The numerical simulation of the
resulting residual stress field requires the use of sophisticated coupled microstructural and thermomechanical
models that rely on profound understanding of the constitutive laws and detailed
knowledge of material parameters. In practice this level of understanding is not generally available,
leading to the use of simplified models that are unable to reproduce or predict reliably the real
residual stress distributions. This leads to the necessity of using increased safety factors and utilising
overly conservative designs. A rational approach to the description of residual stress states is
proposed that relies on the use of eigenstrain distributions as sources of residual stress. The problem
of residual stress evaluation can then be replaced by the problem of determining the underlying
eigenstrain distribution. An approach to this problem is proposed based on a simple variational
formulation. Some examples of its application are shown, and the difficulties and challenges that
may arise are discussed.
Abstract: In order to study the method of the neutron stress measurement using the
cosα method, a numerical simulation study was performed and the result was compared
with author's former experiment. The results of the simulation study agreed with those
obtained in the previous experiment, which suggests the validity of the present method
for neutron stress measurement.
Abstract: The stress distribution on the midsection of a pure bending beam where tensile strain
localization band initiates on the tensile side of the beam and propagates within the beam is analyzed.
Using the static equilibrium condition on the section of the midspan of the beam and the assumption
of plane section as well as the linear softening constitutive relation beyond the tensile strength, the
expressions for the length of tensile strain localization band and the distance from the tip of the band
to the neutral axis are derived. After superimposing a linear unloading stress distribution over the
initial stress distribution, the residual stress distribution on the midsection of the beam is investigated.
In the process of strain localization band’s propagation, strain-softening behavior of the band occurs
and neutral axis will shift. When the unloading moment is lower, the length of tensile strain
localization band remains a constant since the stress on the base side of the beam is tensile stress.
While, for larger unloading moment, with an increase of unloading moment, the length of tensile
strain localization band decreases and the distance from the initial neutral axis to the unloading
neutral axis increases. The neutral axis of midsection of the beam will shift in the unloading process.
The present analysis is applicable to some metal materials and many quasi-brittle geomaterials (rocks
and concrete, etc) in which tensile strength is lower than compressive strength. The present
investigation is limited to the case of no real crack. Moreover, the present investigation is limited to
the case that the length of strain localization band before unloading is less than half of depth of the
beam. Otherwise, the residual tensile stress above the elastic neutral axis will be greater than the
tensile strength, leading to the further development of tensile strain localization band in the unloading