Quantification of mesoscale deformation-induced surface roughness in α-titanium

The phenomenon of mesoscale deformation-induced surface roughening in titanium polycrystals is examined experimentally and numerically. The evolution of the surface morphology under uniaxial tension is analyzed in terms of the standard and ad hoc roughness parameters and the fractal dimension. The statistical estimates are compared to the grain-scale stress-strain fields in order to reveal an interrelation between the in-plane plastic strains and out-of-plane surface displacements. A strong correlation with a determination coefficient of 0.99 is revealed between the dimensionless roughness parameter Rd and the corresponding in-plane plastic strain. The standard roughness parameters Ra and RRMS are shown to correlate linearly with the in-plane strains, but only for moderate tensile deformation, which is due to filtering out low-frequency components in the surface profiles. The fractal dimension DF changes with the subsection strains in a sawtooth fashion, with an abrupt drop in the neck region. The descent portions of the DF dependences are supposedly related to the appearance of low-frequency components in the structure of the surface profiles

Damage of high-chromium steels under deformation in a wide temperature range

High-chromium steels have high strength properties, corrosion properties and resistance to neutron irradiation, thereby are considered as promising steels for nuclear reactors of generation IV. The deformation and damage of high chromium steels in a wide temperature range was studied by numerical simulation method. A model was proposed to predict the deformation and damage of high chromium steels under quasi–static loading within the temperature range from 295 to 1100 K. It is shown that the ductility of high-chromium steels increases proportionally to temperature in the range from 750 to 1100 K due to the growth of α′-phase precipitates

Mechanical aspects of nonhomogeneous deformation of aluminum single crystals under compression along [100] and [110] directions

The deformation behavior of aluminum single crystals subjected to compression along the [100] and [110] directions is numerically examined in terms of crystal plasticity. A constitutive model taking into account slip geometry in face-centered cubic crystals is developed using experimental data for the single-crystal samples with lateral sides coplanar to certain crystal planes. Two sets of calculations are performed using ABAQUS/Explicit to examine the features of plastic strain evolution in perfectly plastic and strain-hardened crystals. Special attention is given to the discussion of mechanical aspects of crystal fragmentation. Several distinct deformation stages are revealed in the calculations. In the first stage, narrow solitary fronts of plastic deformation are alternately formed near the top or bottom surfaces and then propagate towards opposite ends to save the symmetry of the crystal shape. The strain rate within the fronts is an order of magnitude higher than the average strain rate. The first stage lasts longer in the strain-hardened crystals, eventually giving way to an intermediate stage of multiple slips in different crystal parts. Finally, the crystal shape becomes asymmetrical, but no pronounced macroscopic strain localization has been revealed at any deformation stage. The second stage in perfectly plastic crystals relates to abrupt strain localization within a through-thickness band-shaped region, accompanied by macroscale crystal fragmentation. Stress analysis has shown that pure compression took place only in the first deformation stage. Once the crystal shape has lost its symmetry, the compressive stress in some regions progressively decreases to zero and eventually turns tensile

Clinical management of nausea and vomiting in pregnancy and hyperemesis gravidarum across primary and secondary care: a population based study

Objectives: To assess how nausea and vomiting in pregnancy (NVP) and hyperemesis gravidarum (HG) are managed and treated across primary and secondary care.Design: Population-based pregnancy cohortSetting: Medical records (CPRD-GOLD) from EnglandPopulation: 417,028 pregnancies, during 1998-2014 Methods: Proportions of pregnancies with recorded NVP/HG diagnoses, primary care treatment and hospital admissions were calculated. Multinomial logistic regression was employed to estimate adjusted relative risk ratios (aRRRs) with 99% confidence intervals (CIs) for the association between NVP/HG management paths and maternal characteristics.Main Outcome Measures: NVP/HG diagnoses, treatments and hospital admissions. Results: Overall prevalence of clinically recorded NVP/HG was 9.1%: 2.1% had hospital admissions, 3.4% were treated with antiemetics in primary care only, and 3.6% had only recorded diagnoses. Hospital admissions and antiemetic prescribing increased continuously during 1998-2013 (trend p less than 0.001). Younger age, deprivation, Black/Asian/Mixed ethnicity, multiple-pregnancy were associated with NVP/HG generally across all levels, but associations were strongest for hospital admissions. Most comorbidities had patterns of association with NVP/HG levels. Among women with NVP/HG who had no hospital admissions, 49% were prescribed antiemetics, mainly from first line treatment (21% prochlorperazine, 15% promethazine, 13% cyclizine) and metoclopramide (10%). Of those admitted, 38% had prior antiemetic prescriptions (34% first-line, 9% second-line, 1% third-line treatment).Conclusion: Previous focus on hospital admissions has greatly underestimated the NVP/HG burden. Although primary care prescribing has increased, most women admitted to hospital have no antiemetics prescribed before this. An urgent call is made to assess whether admissions could be prevented with better primary care recognition and timely treatment

Modeling of 3D microstructures produced by additive manufacturing

Two approaches to simulating microstructures typical of additively manufactured (AM) materials are presented. First approach relies on the mathematical description of the microstructure evolution during metal AM process, taking into account complex physical processes involved. The numerical solution is based on a combination of the finite difference method for modeling AM thermal processes and the cellular automata method for describing the grain growth. The other approach provides fast generation of artificial 3D microstructures similar to those produced by AM by geometrical characteristics of grains, using the step-by-step packing method