Materials Science Forum Vols. 490-491

Abstract: The Australian Nuclear Science and Technology Organisation, ANSTO, (http:\\www.ansto.gov.au) has initiated a “Neutrons for Engineering” project to provide an integrated residual stress service to Australian industry and academia. The service is based around measurements of residual stress using neutrons on a newly-refurbished instrument on the HIFAR research reactor. In addition to the neutron measurements there is a range of expertise available on the ANSTO site to solve residual stress problems using other techniques including hole-drilling, strain-gauging, and x-ray diffraction, as well as capabilities for finite element modeling and mechanical testing. In this paper we describe briefly the existing and future facilities at ANSTO for neutron strain scanning and present some benchmark results for the HIFAR strain scanner.

Abstract: The residual stress field in a VPPA welded AA2024 coupon sample was measured by neutron diffraction. A similar sample was measured using synchrotron X-rays to determine the inplane strain directions. The macrostrain obtained from both sources compares well in spite of the significant difference in gauge volume and diffraction geometry. The result confirms the repeatability of the weld process and also shows good correspondence between the two diffraction processes.

Abstract: Using our long experience in Bragg diffraction optics we successfully used focusing principles for substantial increasing both luminosity and resolution of the strain scanners with respect to the conventional devices. Monochromatic neutrons are selected by the cylindrically bent monochromator from the reactor spectrum. There is a strong correlation between divergences of incoming and outgoing beams with respect to the polycrystalline sample, which can be easily manipulated by changing the monochromator bending radius. By setting a proper value of the radius, a narrow, quasiparallel and highly luminous output beam can by adjusted. The strong correlation between wavelength and direction of incoming and outgoing beams depending on the monochromator bending radius can be as well used for suppression of surface effect in residual strain scanning. In scanning near a sample surface aberration peak shifts arise due to the fact that the gauge volume defined by input and output slits is partially out of the sample and its value can be of the same order as the residual strain effects. In this work we demonstrate that by changing of the bending radius of monochromator, this surface effect can be suppressed to values smaller then experimental errors in residual strain scanning.

Abstract: The internal stresses in the continuous tungsten-fiber reinforced copper-matrix composite were examined by the Neutron stress measurement method. The Neutron diffraction apparatus ND1, which is abbreviated from the Neutron Diffraction system No.1 designed and manufactured by the National Nuclear Energy Agency in Indonesia (Badan Tenage Nuklir Nasional, BATAN), was used in the present study. The most common 3-axes measurement method with Hooke’s equation was only possible to measure about 110 plane, because the tungsten fiber became the situation of heavy 110 orientation. Thermal stress alterations caused form low temperature cycling was measured by in-situ stress measurement method making use of a cryostat system. The thermal residual stresses in tungsten-fiber longitudinal direction were compressive state in every stage. Results of in-situ thermal stress measurement were good agreed with a calculated result of simple elastic theory in elastic area.

Abstract: In this study, we proposed the high-versatility stress measurement method using neutron diffraction which can determine the residual stress states by measuring the lattice strains in two or three orthogonal directions even if the measured diffraction families were different in all three directions. In addition, we also proposed the stress measurement method without using the stress-free lattice spacing d0 which was measured using the powder sample or annealed sample. To verify this method, the residual stress distributions in a shrink-fit ring and plug specimen of aluminum alloy A7075 with texture were measured. The profile of the measured stress distributions almost agreed with the simulated stress distributions in the assumption of the plane stress condition. Our method which can determine the tri-axial stress states using observed lattice strains in two orthogonal directions was secondly applied to evaluate the stress states of A7075, high tensile strength steel HT1000, and Ni-base alloy NCF600 loaded in-situ. Measured stresses almost agreed with theoretical value with 10 MPa to 60 MPa error. On the other hand, the residual stress states of NCF600 were measured under the uni-axial loading condition by the stress measurement method without using the measured d0. Estimated lattice constant a was almost agreed with the lattice constant of its annealed sample, and changes in stress states evaluated using the proposed method coincided with the theoretical value.

Abstract: Nitriding is an hardening thermomechanical treatment generally used to improve fatigue life of steel parts, like gear for example. Another effect of this treatment is generating superficial stress, influenced by nitriding conditions, composition of steel and geometry of the part. This work deals with the effect of shape on the residual stress profile obtain after nitriding on a gear tooth. The residual stress profile was determined using neutrons diffraction technique.

Abstract: Neutron diffraction has been used to study the progress of deformation twinning and intergranular strain evolution in extruded magnesium during cyclic and monotonic loading at two temperatures. Differences in the intergranular strains generated during tensile and compressive tests are attributed to the operation of twinning in compression. Twinning activity is reduced relative to slip at higher temperature, leading to greater similarities between tension and compression. During cyclic loading, a distinct Bauschinger effect is observed after each compressive loading stage. The origin of this effect is identified as the reversal of twinning during unloading and subsequent tensile loading.

Abstract: Neutron diffraction measurements were used in this study in order to determine the axial stress state in loaded screw from a specific assembly. The knowing of stress gradient is need to qualify a standard gauge used to calibrate the response of in-situ measurements using ultrasonic nondestructive technique. US is well adapted to perform measurements of the evolution of stress state on industrial screws during service life of the bolded assemblies.