RESUMEN
This paper describes the hardware and software upgrades, operation, and performance of the high intensity diffractometer for residual stress analysis (HIDRA) instrument, a residual stress mapping neutron diffractometer located at the High Flux Isotope Reactor at Oak Ridge National Laboratory in Oak Ridge Tennessee, USA. Following a major upgrade in 2018, the new instrument has a single 3He multiwire 2D 30 × 30 cm2 position sensitive detector, yielding a field of view of 17° 2θ. The increase in the field of view (from 4° 2θ) from the previous model instrument has contributed to the tremendous improvement in the out of plane solid angle such that the 3D count rate could be obtained easily. Accordingly, the hardware, software, Data Acquisition System (DAS), and so on have also been updated. Finally, all these enhanced features of HIDRA have been ably demonstrated by conducting multi directional diffraction measurements in the quenched 750-T74 aluminum, and the evolved and improved strain/stress mappings are presented.
RESUMEN
The crystallographic texture of polycrystalline materials is the result of how these materials are processed and what external forces materials have experienced. Neutron and X-ray diffraction are standard methods to characterize global crystallographic textures. However, conventional neutron and X-ray texture analyses rely on pole figure inversion routines derived from intensity analysis of individual reflections or powder Rietveld analysis to reconstruct and model the orientation distribution from slices through reciprocal space. In this work, we describe an original approach to directly probe the crystallographic texture information of rolled aluminum from the intensity distribution in 3-dimensional reciprocal space volumes measured simultaneously. Using the TOPAZ time-of-flight Laue neutron diffractometer, reciprocal space analysis allowed determination of "pole spheres" with <1° angular resolution. These pole spheres are compared with reconstructed pole figures from classic texture analysis.
RESUMEN
Pleiotrophin (PTN) was found to have potent effects on regulation of osteoblast recruitment, proliferation and differentiation. The present study examined the long-term effects of targeted PTN over-expression on bone development and repair in a transgenic mouse model. Femurs and tibiae from the PTN transgenic mice and the wild type mice at age 1, 2, 4, 6, 12 and 24 months were collected, and examined by radiography, peripheral quantitative computed tomography (pQCT), histology and mechanical testing. Age-matched PTN and the control mice received a standardized femoral fracture, followed by regular x-rays and sacrificed at day 16 post-fracture for histology examination. A cortical hole was drilled on the tibiae of age-matched PTN and wild type mice, collagen sponge with either saline, 100 ng of rhBMP-2 or rhPTN was implanted in the holes, and animals were sacrificed 10 days later, subject to pQCT and histology examinations. During early stages of bone development, the PTN mice had advanced bone growth in length and maturation, but the difference diminished in later life. The fracture healing was impaired in the PTN mice, and there was delayed callus formation and remodelling. The cortical holes treated with BMP-2 in the PTN mice had significantly less trabecular bone formation. The current study confirmed that the targeted PTN over-expression in mouse bone has moderate enhancing effects on early bone development; but the bones become brittle in later life. Fracture healing was impaired in the adult PTN mice and this may be due to inhibitory effects of PTN over-expression on BMP-2 mediated bone induction.