Stagnation zone during the turning of Duplex SAF 2205 stainless steels alloy

Duplex stainless alloys are extremely sensitive to cutting speed for strain hardening during machining. Tool wear for these materials is dominated by the adhesion wear because of formation of built-up edge (BUE) that upsurges the flank wear considerably. In addition, flute damage is a significant problem during drilling of those alloys. To address this issue, this paper investigates the mechanism of BUE creation in stagnation region of duplex SAF 2205 alloys during material removal by turning process. The investigation of chip root through SEM and electron backscatter diffraction (EBSD) revealed build-up of ferritic bands at the stagnation zone. Higher capacity of austenite phase to deform plastically is accountable for the ferrite build-up. This was detected as a possible activating mechanism of built-up edge. The flow pattern of austenite phase designates faster deforming compare to that of ferrite phases

Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite

Incidence of first stroke and ethnic differences in stroke pattern in Bradford, UK: Bradford Stroke Study

Background: Information on ethnic disparities in stroke between White and Pakistani population in Europe is scarce. Bradford District has the largest proportion of Pakistani people in England; this provides a unique opportunity to study the difference in stroke between the two major ethnic groups. Aim: To determine the first-ever-stroke incidence and examine the disparities in stroke patterns between Whites and Pakistanis in Bradford. Methods: Prospective 12 months study consisting of 273,327 adults (≥18 years) residents. Stroke cases were identified by multiple overlapping approaches. Results: In the study period, 541 first-ever-strokes were recorded. The crude incidence rate was 198 per 100,000 person-years. Age adjusted-standardized rate to the World Health Organization world population of first-ever-stroke is 155 and 101 per 100,000 person-years in Pakistanis and Whites respectively. Four hundred and thirty-eight patients (81%) were Whites, 83 (15.3%) were Pakistanis, 11 (2%) were Indian and Bangladeshis, and 9 (1.7%) were of other ethnic origin. Pakistanis were significantly younger and had more obesity (p = 0.049), and diabetes mellitus (DM) (p = <0.001). They were less likely to suffer from atrial fibrillation (p = <0.001), be ex- or current smokers (p = <0.001), and drink alcohol above the recommended level (p = 0.007) compared with Whites. In comparison with Whites, higher rates of age-adjusted stroke (1.5-fold), lacunar infarction (threefold), and ischemic infarction due to large artery disease (twofold) were found in the Pakistanis. Conclusions: The incidence of first-ever-stroke is higher in the Pakistanis compared with the Whites in Bradford, UK. Etiology and vascular risk factors vary between the ethnic groups. This information should be considered when investigating stroke etiology, and when planning prevention and care provision to improve outcomes after stroke

A Reliability Model for Safety Instrumented System

Safety analysis in the companies is an important issue besides the quality, productivity and profitability. Safety integrity function in many industries is based on safety instrumented systems. Uncertainty is the main problem of safety analysis. In this paper, a new mathematical model is developed to compute the probability of failure on demand (PFD) following the three steps. First, KHALFI (Characteristics of Hazard Analysis based on Logic Frequency Initiative) mathematical model is formulated to identify the real PFD at any geographical location considering five intermediate factors: temperature, humidity, pressure, wind speed and time which can affect the PFD. Second, probability binary state (PROBIST) is used to precise the values of PFD. Third, Bowtie method is employed to carry out the safety analysis for examining the safety of some scenarios by determining the PFD of safeguards, where new classification for the safety integrity level is proposed. Finally, Simulink model is developed implementing the proposed model to facilitate the automatic computation and analysis. Results indicate that all the atmospheric elements are significant and need to be taken into consideration to attain the best reliability in the calculation of PFD. The effectiveness of the proposed model gives the opportunity for the analysts to conduct safety analysis at any geographical location

Lie Group Analysis and Numerical Solution of Magnetohydrodynamic Free Convective Slip Flow of Micropolar Fluid Over a Moving Plate With Heat Transfer

In this paper, we investigate magnetohydrodynamic free convective flow of micropolar fluid over a moving flat plate using the Lie group transformations and numerical methods. Instead of using conventional no-slip boundary conditions, we used both the velocity and thermal slip boundary conditions to achieve physically realistic and practically useful results. The governing boundary layer equations are non-dimensionalized and transformed into a set of coupled ordinary differential equations (ODEs) using similarity transformations generated by the Lie group, before being solved numerically using Matlab stiff ODE solver ode15s and Matlab trust-region-reflective algorithm lsqnonlin. The effects of governing parameters on the dimensionless velocity, angular velocity, temperature, skin friction and heat transfer rate are investigated. Our analysis revealed that the dimensionless velocity and angular velocity decrease whilst the dimensionless temperature increases with the velocity slip parameter. Thermal slip reduces the dimensionless velocity and temperature but raises the dimensionless angular velocity. Magnetic field suppresses the velocity but elevates the temperature and angular velocity. Results reported in this paper are in good agreement with the ones reported by the previous authors

Slot machining of TI6AL4V with trochoidal milling technique

Titanium usage for aerospace growing day by day as application of titanium and its alloys covers wide range. Most of the aerospace components made up of wall structure involves lot of pocket slot milling since those components are monolithic components, eliminating need to manufacture multiple pieces for assembly into one final part. The increasing complexity of titanium parts used in aviation industry, increasing demand for productive manufacturing methods like trochoidal milling. This paper aims at evaluating its potential in slot milling for Ti6Al4V component by conducting experiments on 5-axis CNC machine. This study focuses on Productivity, Quality and Machine Tool Dynamics