Three-dimensional in situ observations of compressive damage mechanisms in syntactic foam using X-ray microcomputed tomography

Royal Society Grant number RG140680 Lloyd's Register Foundation (GB) Oil and Gas Academy of Scotland Open access via Springer Compact AgreementPeer reviewedPublisher PD

Representative volume element (RVE) based crystal plasticity study of void growth on phase boundary in titanium alloys

Author is thankful to University of Aberdeen for the award of Elphinstone Scholarship which covers the tuition fee of PhD study of author.Peer reviewedPostprin

Modelling Hydrogen Induced Stress Corrosion Cracking in Austenitic Stainless Steel

The authors are thankful to the University of Aberdeen and Apache North Sea for their support for this project.Peer reviewedPostprin

Atmospheric Pressure Mass Spectrometry by Single-Mode Nanoelectromechanical Systems

Weighing particles above MegaDalton mass range has been a persistent challenge in commercial mass spectrometry. Recently, nanoelectromechanical systems-based mass spectrometry (NEMS-MS) has shown remarkable performance in this mass range, especially with the advance of performing mass spectrometry under entirely atmospheric conditions. This advance reduces the overall complexity and cost, while improving the limit of detection. However, this technique required the tracking of two mechanical modes, and the accurate knowledge of mode shapes which may deviate from their ideal values especially due to air damping. Here, we used a NEMS architecture with a central platform, which enables the calculation of mass by single mode measurements. Experiments were conducted using polystyrene and gold nanoparticles to demonstrate the successful acquisition of mass spectra using a single mode, with improved areal capture efficiency. This advance represents a step forward in NEMS-MS, bringing it closer to becoming a practical application for mass sensing of nanoparticles.Comment: 24 pages, 4 figure

Friction of flat and micropatterned interfaces with nanoscale roughness

The dry friction of surfaces with nanoscale roughness and the possibility of using micropatterning to tailor friction by manipulating contact area is investigated. Square wave patterns produced on samples from silicon wafers (and their unstructured equivalent) were slid against unstructured silicon counter surfaces. The width of the square wave features was adjusted to vary the apparent feature contact area. The existence of nanoscale roughness was sufficient to ensure Amontons’ first law (F = μP) on both structured & unstructured samples. Somewhat counterintuitively, friction was independent of the apparent feature contact area making it difficult to tailor friction via the feature contact area. This occurred because, even though the apparent feature contact area was adjusted, the surface roughness and nominal flatness at the contact interface was preserved ensuring that the real contact area and thereby the friction, were likewise preserved. This is an interesting special case, but not universally applicable: friction can indeed be adjusted by structuring provided the intervention leads to a change in real contact area (or interlocking)– and this depends on the specific surface geometry and topography

Residual Stresses in Alloy IN718 Produced Through Modulated Laser Powder Bed Fusion

Background: Laser powder bed fusion (L-PBF) additive manufacturing (AM) is used for building metallic parts layer-by-layer and often generates non-uniform thermal gradients between layers during fabrication, resulting in the development of residual stresses when parts are cooled down. Objective: The impact of modulated laser used during the L-PBF process on residual stresses in Inconel 718 (IN718) material was investigated. The impact of build directions on residual stress is also determined. Methods: The contour method is employed to measure the full-field residual stress component on the cross-section of samples. A complementary residual stress measurement method, incremental hole drilling, was employed for obtaining in-plane residual stress components. Results: The results show that the residual stress distribution is sensitive to the build direction, with a higher magnitude of residual stress in the direction of build than that in the transverse direction. Multiple measurements with the same manufacturing parameters show good repeatability. Conclusion: Residual stresses in the as-built parts are significant and hence a further consideration regarding relieving residual stresses is required when post-thermal treatments are developed

Complete aromatase deficiency in four adult men: detection of a novel mutation and two known mutations in the CYP19A1 gene

The abstracts descibes four new cases of patients with aromatase deficiency. Both the clinical features and the results of the molecular studies are reported

The static friction peak in reciprocating sliding

This paper investigates why the static friction peak is mostly absent in reciprocating sliding and gross-slip fretting literature. Here, reciprocating sliding tests were conducted on ultra-smooth silicon surfaces. A prominent static friction peak was present in the initial cycles. However, a rapid wear-induced decay in the static friction peak occurred after the first cycle with the peak being mostly absent by about 30 cycles. Two possible explanations are proposed for the wear-induced decay: (1) that increasing surface roughness (with cycles) reduces the fully stuck contact area and (2) that wear reduces the bonding strength of the stuck interface by removing third body contaminant molecules. Predictions from a multi-asperity friction model are used to support these arguments