Core level photoelectron spectroscopy is a widely used technique to study amino acids. Interpretation of the individual contributions from functional groups and their local chemical environments to overall spectra requires both high-resolution reference spectra and theoretical insights, for example from density functional theory calculations. This is a particular challenge for crystalline amino acids due to the lack of experimental data and the limitation of previous calculations to gas phase molecules. Here, a state of the art multiresolution approach is used for high precision gas phase calculations and to validate core hole pseudopotentials for plane-wave calculations. This powerful combination of complementary numerical techniques provides a framework for accurate ΔSCF calculations for molecules and solids in systematic basis sets. It is used to successfully predict C and O 1s core level spectra of glycine, alanine and serine and identify chemical state contributions to experimental spectra of crystalline amino acids. File list (3) download file view on ChemRxiv amino_paper.pdf (2.77 MiB) download file view on ChemRxiv amino_paper_SI.pdf (2.92 MiB) download file view on ChemRxiv amino_structures.zip (12.01 KiB)

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Abstract. Springback behaviour of surface-machined 7B04-T651 aluminium plates of 3 to 8 mm thicknesses, creep-age formed under a single curvature bending radius of 1200 mm, has been experimentally investigated. The surface residual stress levels of the plates have been measured and the typical residual stress distribution and values in 7000-series aluminium alloys have been reviewed and analysed. Finite element models have been developed to simulate creep-age forming (CAF) processes and predict the amount of springback in the physical CAF test. Machining-induced residual stresses and distortion have been considered in the finite element models. This paper presents a first attempt to study the effect of machining-induced residual stresses on the errors of springback prediction in CAF of 7000-series aluminium alloy panel components. It has been found that the effect of machininginduced residual stresses on the accuracy of springback prediction is related to the initial loading stress levels in CAF. In addition, when the initial distortion conforms to the loading curvature, an opposing effect on the material's deformation is observed. Creep-ageing material constant related to effective creep strain rate.1 Creep-ageing material constant related to rate of age hardening.2 Creep-ageing material constant related to the depletion of solute into precipitate.3 Creep-ageing material constant related to rate of precipitate growth.4 Creep-ageing material constant controlling the effect of dislocation density (or creep) on precipitate nucleation and growth.5 Creep-ageing material constant related to rate of dislocation density.Creep-ageing material constant related to rate of dislocation hardening.Bending radius of forming tool.̅ , ̅ Normalised precipitate size and its rate term respectively. ̅ 0 Initial value for normalised precipitate size.Radius of revolvement of workheads of the flexible form tool.Creep-ageing time.1 , 2 , 3 , 4 Time of loading, heating, cooling and unloading respectively. Artificial ageing time.Solution heat treatment time., , Translational degrees of freedom in Cartesian coordinates., , Rotational degrees of freedom in Cartesian coordinates.Poisson's ratio., , Cartesian coordinates., positions of the lower and upper splines respectively.

Creep-age forming (CAF) is a proven forming technique in the aerospace industry for the production of large integrally stiffened panels. One of the most urgent issues to be addressed in CAF is the development of flexible tooling. Flexible tools already have a long-standing reputation for the economic impact they have brought to the aircraft industry. However, with the rising need to establish comprehensive springback prediction models for CAF, the need for flexible CAF tools is now stronger than ever. In this article, an existing state-of-the-art CAF tool is described followed by the introduction of a novel design concept for flexible tooling. Based on the proposed design method, which utilises mechanical splines and sparsely spaced controlling points, a proof-of-concept prototype is built and characterised using corresponding analytical and finite element models that have been developed. Three parameters that can influence forming surface error: (i) the number of control points, (ii) spaces between control points and (iii) spline thickness are identified and optimised. Finally, an integrated optimisation process for tool offsetting is introduced, and its use is demonstrated. It is confirmed that this design method can be used to make flexible CAF tools with less than ± 1 mm error (defined as vertical difference from prediction) in the forming surface. In addition, this error can eventually be compensated and thus eliminated from CA-formed parts by using the developed optimisation technique. This article provides CAF tool designers confirmed advices for making new flexible CAF tools. Lightweight and flexible CAF tools can now be constructed through the use of mechanical splines and sparse controlling points.

Abstract. The creep-ageing behaviour of a peak-aged aluminium alloy 7050 was investigated under different stress levels at 174• C for up to 8 h. Interrupted creep tests and tensile tests were performed to investigate the influences of creep-ageing time and applied stress on yield strength. The mechanical testing results indicate that the material exhibits an over-ageing behaviour which increases with the applied stress level during creep-ageing. As creep-ageing time approaches 8 h, the material's yield strength under different stress levels gradually converge, which suggests that the difference in mechanical properties under different stress conditions can be minimised. This feature can be advantageous in creep-age forming to the formed components such that uniformed mechanical properties across part area can be achieved. A set of constitutive equations was calibrated using the mechanical test results and the alloy-specific material constants were obtained. A good agreement is observed between the experimental and calibrated results.