Formability Characterization of a New Generation High Strength Steels

Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength

Heat transfer analysis of a micro satellite

Satellites have been used to support variety of applications and the trend of using micro satellites is increasing because of various factors such as cost, size, manufacturing time, and efficiency when compared with big satellites. For a successful mission, it is very important to design micro satellites to work in the space environment. The skills needed to design micro satellites span many disciplines such as, mechanical, structural, electronics and thermal.Master of Science (Precision Engineering

Study On Metal Sheet Ductile Fracture Using Square Punch Test

This study introduces a new practical calibration approach of ductile fracture models by performing square punch tests on metal sheets. During square punch tests, ductile fracture occurs at either the corner of die or punch radius when applying different clamping loads and lubrication conditions. At the corner of die radius, in-plane pure shear is induced at the intersection between the side-walls and the flange by combined tension and compression. On the other hand, the material at the corner of the punch radius is under combined bending and biaxial tension. The material studied in this paper is advanced high strength steel (AHSS) DP780 from ArcelorMittal. Isotropic J2 plasticity model with mixed Swift-Voce hardening rule is calibrated from uniaxial tensile tests. The four-parameter modified Mohr-Coulomb (MMC4) fracture locus [1] was converted to all-strain-based modified Mohr-Coulomb (eMMC) fracture locus and fracture forming limit diagram (FFLD) in the space of principal strains under plane stress condition. The eMMC and FFLD [2] can be calibrated directly from measured fracture strains at die and punch radius of the AHSS sheets in square punch tests, as well as from uniaxial tensile tests. For analyzing possible close to shear-induced fracture by different combinations of tension and compression at the die radius, the DP780 sheets were arranged at 45° with respect to the orientation of the square punch. The square punch tests were simulated in Abaqus/Explicit. The finite element results show that the force-displacement response of the punch, the fracture initiation and crack propagation at the critical locations in square punch tests were correctly predicted. The load path of the mid-surface at the die radius was found close to proportional loading of in-plane shear

Immediate, intermediate and long term clinical outcomes of percutaneous transvenous mitral commissurotomy

Percutaneous transvenous mitral commissurotomy (PTMC) is one of the nonsurgical commissurotomy in patients with hemodynamically significant mitral stenosis. The aim of the present study is to assess the immediate, intermediate and long term outcomes of PTMC in relation to initial mitral valve score and to assess its impact on mitral valve area (MVA), clinical and hemodynamic parameters. It is a retrospective study on a total of 303 patients who underwent successful PTMC between 1994 and 2001, were called back and their preprocedural, immediate post and follow-up (4, 7 and 10 year.) data were analyzed. Echo was performed in patients before and after PTMC. The patients were divided into two groups, group-I with Wilkins score of ≤ 8 and group-II with Wilkins score between 8 and 12. PTMC patients who have completed 4, 7 and 10 years of follow up revealed the mitral valve area, mean transmitral gradient and pulmonary artery pressures to be significantly different in both group-I and group-II. At all follow-up periods group-II showed higher restenosis than group-I, but its distribution between the groups was not statistically significant (χ2 = 0.029, p = 0.986). Furthermore, losses of the MVA during different periods of follow-up revealed a gradual increase in attrition. MV score, Mitral valve area, mitral gradient and pulmonary artery pressures appeared to influence the outcome of PTMC. A clear-cut prospective assessment of individual components of the mitral valve apparatus using 3-D echocardiographic images may provide a more precise prediction of the PTMC outcome based on its morphological abnormalities

Formability Characterization of a New Generation High Strength Steels

Advanced high strength steels (AHSS) are being progressively explored by the automotive industry all around the world for cost-effective solutions to accomplish vehicle lightweighting, improve fuel economy, and consequently reduce greenhouse emissions. Because of their inherent high strength, attractive crash energy management properties, and good formability, the effective use of AHSS such as Duel Phase and TRIP (Transformation Induced Plasticity) steels, will significantly contribute to vehicle lightweighting and fuel economy. To further the application of these steels in automotive body and structural parts, a good knowledge and experience base must be developed regarding the press formability of these materials. This project provides data on relevant intrinsic mechanical behavior, splitting limits, and springback behavior of several lots of mild steel, conventional high strength steel (HSS), advanced high strength steel (AHSS) and ultra-high strength steel (UHSS), supplied by the member companies of the Automotive Applications Committee (AAC) of the American Iron and Steel Institute (AISI). Two lots of TRIP600, which were supplied by ThyssenKrupp Stahl, were also included in the study. Since sheet metal forming encompasses a very diverse range of forming processes and deformation modes, a number of simulative tests were used to characterize the forming behavior of these steel grades. In general, it was found that formability, as determined by the different tests, decreased with increased tensile strength. Consistant with previous findings, the formability of TRIP600 was found to be exceptionally good for its tensile strength

Immediate, intermediate and long term clinical outcomes of percutaneous transvenous mitral commissurotomy

Introduction: Percutaneous transvenous mitral commissurotomy (PTMC) is one of the nonsurgical commissurotomy in patients with hemodynamically significant mitral stenosis. The aim of the present study is to assess the immediate, intermediate and long term outcomes of PTMC in relation to initial mitral valve score and to assess its impact on mitral valve area (MVA), clinical and hemodynamic parameters. Methods: It is a retrospective study on a total of 303 patients who underwent successful PTMC between 1994 and 2001, were called back and their preprocedural, immediate post and follow-up (4, 7 and 10 year.) data were analyzed. Echo was performed in patients before and after PTMC. The patients were divided into two groups, group-I with Wilkins score of ≤8 and group-II with Wilkins score between 8 and 12. Results: PTMC patients who have completed 4, 7 and 10 years of follow up revealed the mitral valve area, mean transmitral gradient and pulmonary artery pressures to be significantly different in both group-I and group-II. At all follow-up periods group-II showed higher restenosis than group-I, but its distribution between the groups was not statistically significant (χ2 = 0.029; p = 0.986). Furthermore, losses of the MVA during different periods of follow-up revealed a gradual increase in attrition. Conclusions: MV score, Mitral valve area, mitral gradient and pulmonary artery pressures appeared to influence the outcome of PTMC. A clear-cut prospective assessment of individual components of the mitral valve apparatus using 3-D echocardiographic images may provide a more precise prediction of the PTMC outcome based on its morphological abnormalities

Post-Surgical Prognosis of Patients with Pineoblastoma: A Systematic Review and Individual Patient Data Analysis with Trends over Time.

Most of the literature on pineoblastoma consists of case reports and single-institution series. The goal of this systematic review and individual patient data (IPD) analysis was to summarize the existing literature, identify factors associated with overall survival (OS), and provide a contemporary update on prognosis for patients with pineoblastoma. Forty-four studies were identified with 298 patients having IPD. Kaplan-Meier analyses were used to report survival outcomes based on age, tumor metastases, extent of resection (EOR), adjuvant therapy, and publication year. Cox regression was performed to identify independent predictors of time to mortality. Multivariable recursive partitioning analysis was used to identify the most important subgroups associated with mortality. Patients were classified based on publication year before and after the last systematic review on this topic (pre-2012 and 2012 onwards) and compared using univariate and multivariable analyses. This study demonstrates that EOR less-than-gross total resection, metastatic presentation, adjuvant chemotherapy without radiation, and tumor presentation in children less than three years old are associated with poorer prognosis. Since 2012, the 5-year actuarial OS has improved from 32.8% to 56.1%, which remained significant even after accounting for EOR, age, and adjuvant therapy. Pineoblastoma remains a severe rare disease, but survival outcomes are improving