A holistic approach to thermomechanical processing of alloys

New process design and control methods are needed for significantly improving productivity and reducing costs of thermomechanical processes such as hot metal forging. Current practices for accomplishing basic design tasks such as selecting the number of forming steps and specifying the processing conditions for each thermomechanical operation produce feasible solutions that are often far from optimal. Substantial improvements in effectiveness and efficiency can be realized through holistic approaches that optimize the whole system performance and not just individual subsystems such as workpiece material behavior, material flow in dies, and equipment responses. Recent progress in the application of dynamical modelling and process design techniques using ideal forming concepts and trajectory optimization are discussed. Monitoring methods for the on-line monitoring of the process and an intelligent forging system has been proposed

Magnetic Barkhausen emission analysis for assessment of microstructures and damage

Application of magnetic Barkhausen emission (MBE) analysis for assessment of microstructures and damage in various materials including carbon steel, Cr-Mo ferritic steels, 17-4 PH steel and metastable austenitic stainless steel. Thermally-induced microstructural changes in Cr-Mo steels have been correlated with MBE, based on a two-stage magnetisation process model. The MBE parameters have also been used to characterise different stages of tensile deformation and to assess tensile strength. Charpy impact energy, quality of induction hardening process, progress of carburisation in reformer tubes and fatigue damage

Physics of Flow Mechanism of Scour around Submerged Pipelines on an Erodible Bed

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Study of dimensionless quantities to analyse front and rear wall of keyhole formed during laser beam welding

Fluid flow mechanisms present in Keyhole (KH) during Laser Beam Welding (LBW) process influence the associated heat and mass transfer. In an attempt to describe these complexities for eventual optimization of LBW parameters, a dimensionless analysis using Mach (Ma), Raleigh (Ra), Reynolds (Re) and Marangoni (Mg) numbers have been carried out. This analysis describes hydrodynamics of melt and vapour phase appearing in the front and rear wall of KH. The non-dimensional hydrodynamic quantities describe the mechanism behind flow pattern present in melt-vapour in terms of ratio of convection–conduction heat transfer occurring within KH. The analysis shows that the higher Marangoni number indicates stronger Marangoni convection in the KH causing relatively higher capillary flow in the melt pool. The laminar-turbulent flow of melt-vapour in KH medium is described in terms of ratio of Reynolds and Mach numbers (Re/Ma). The pressure distribution in the KH accounts for the melt-vapour ejection rate. A relationship between depth and radius of KH has been obtained as a function of delivered laser power

Determination of Satisfaction Index as a tool in evaluation of CME Program

Continuing Medical Education is an indispensable part of physician's learning. Welldesigned program based on andragogy principles can enhance learning by motivatingthe learner and providing platform to encourage self directed learning. The presentstudy aimed to explore the impact of program “NAMS-AIIMS Regional Symposiumon Sleep Medicine” in changing the behavior and attitude of participants using“Satisfaction Index” and descriptive analysis of responses as evaluation tools forprogram effectiveness. This descriptive cross sectional study captured the response ofparticipants through a pre-tested and validated questionnaire administered at the end ofsymposium. The result showed almost equal sex distribution (M: F- 27: 34) withmajority being UG students (86%). Reliability of data showed Cronbach's Alpha of0.98 indicating high reliability. Satisfaction index (SI) calculated as per WHOEducational Handbook for Health Personnel showed highest satisfaction for conduciveenvironment of symposium (87.87 %) followed by provision for time to seekclarifications (87.21%), provision of appropriate Learning Resource material (85.90%) and handling of critical comments by organizers (85.57%). Descriptive analysisshowed majority responses as highly positive to our questionnaire with suggestions formore such activity, inclusion of clinical cases and other aspects of practical relevance.Key words : evaluation, program, satisfaction index, Kirkpatrick Model, studentsatisfaction, adult learning, Knowles Theory

Platelet indices and their correlation with HbA1c and association with microvascular complications in type-2 diabetes mellitus

Background: Depending on the aetiology of the DM, factors contributing to hyperglycaemia include reduced insulin secretion, decreased glucose utilization, and increased glucose production. Mean platelet volume (MPV) and platelet distribution width (PDW) are important, simple, effortless, and cost-effective tools measured by hematology analyser which assess the volume and function of platelets. Analysing the platelet parameters can act as an alarm for progression of complications of DM. Hence, we studied the platelet parameters in diabetic patients with good and poor glycaemic control and their association in microvascular complications. Methods: This study was conducted on 100 patients having diabetes mellitus. All the patients were subjected to detailed history regarding age, sex, occupation, socioeconomic status, GPE and systemic examination. Results: Out of 100 cases, 29 patients had a good glycemic control (HbA1c<7%) and 71 had poor glycemic control (HbA1c>7%). Mean FBS was 118.59±19.36 mg/dl in good control group and 158.79±29.21 mg/dl in poor control (p<0.001). Mean PPBS was 159.86±37.78 mg/dl in good control group and 235.80±53.28 mg/dl in poor control group (p<0.001). Good glycemic control group had mean MPV of 7.89±0.63 fl and poor glycemic control group had mean MPV 10.06 fl (p<0.001). Mean PDW was 12.32±1.94 in good control group and 13.81±2.25 in poor control group. Conclusions: Our study indicates that MPV and PDW are increased in diabetic patients, more so in patients with microvascular complications than in those without complications. Hence, they can be used as markers in predicting the microvascular complications in diabetes mellitus.

Dynamics of plasma expansion in the pulsed laser material interaction

A pulse Nd: YAG laser with pulse duration 5-10 ns, beam radius at focal point 0.2-0.4 mm, wavelengths 1064 nm, 532 nm and 238 nm with linearly polarized radiation and Gaussian beam profile, was impacted on a thin foil of titanium metal for generating plasma plume. Numerically, the above parameters were linked with average kinetic energy of the electrons and ions in the laser-induced plasma. In the present model, electrons having higher velocities are assumed to escape from plasma, that forms a negatively charged sheath around the plasma. It is seen from present computations that the forward directed nature of the laser evaporation process results from the anisotropic expansion velocities associated with different species. These velocities are mainly controlled by the initial dimension of the expanding plasma. An attempt was undertaken to estimate the length of the plume at different ambient gas pressures using an adiabatic expansion model. The rate of the plasma expansion for various Ar ion energies was derived from numerical calculations. A numerical definition of this plasma includes events like collisional/radiative, excitation/de-excitation and ionization/recombination processes involving multiples of energy levels with several ionization stages. Finally, based on a kinetic model, the plasma expansion rate across the laser beam axis was investigated

Melt pool vorticity in deep penetration laser material welding

In the present study, the vorticity of melt motion in the keyhole and weld pool has been evaluated in case of high power CO2 laser beam welding. The circulation of vorticity is obtained as a function of Reynolds number for a given keyhole volume which is linked to Mach number variation. The shear stress and thermal fluxes present in the turbulent pool are linked to diffusivity and Prandtl number variation. It was shown that below a critical value of Rayleigh number, the conduction mode of melt transfer signifying beam absorption becomes dominant. Above this value, convective heat transfer indicates melting and evaporation occurring in the weld pool during laser welding. The evaporative recoil pressure expels the liquid while surface tension and hydrostatic pressure help to retain the melt in the keyhole cavity in this high power laser beam welding. The understanding of several hydrodynamic phenomena occuring in the weld pool is valuable not only for understanding basic mechanistic aspects but also for process optimization involved in laser beam welding