Characterisation of advanced high strength strip steels using electromagnetic sensor system

The mechanical properties of steel are strongly influenced by its microstructural features such as phase balance, grain size, dislocations and precipitates. In order to obtain accurate quality control of steel products, it is desirable to be able to monitor the mechanical properties non-destructively. It is known that the low frequency inductance (where the effect of eddy currents are negligible) measured using an EM sensor depends on the relative permeability of the sample and that the permeability is affected by microstructural parameters (i.e. phase fraction / distribution and, to a lesser extent, grain size are the important features in dual phase, DP, steel). A variety of electromagnetic sensors have been reported for non-destructively assessing the state of steel microstructures including; monitoring the recovery and recrystallisation processes in-situ during heat treatment, phase transformation and detecting decarburisation in steel rod both on-line and off-line, etc. Recently it has been shown that electromagnetic sensors can measure the phase fraction in DP steel but the effect of strip thickness was not assessed. This research work discusses the development of an EM sensor system that can be used to assess the microstructure (and hence mechanical properties) of commercially produced DP steels (in particular phase balance and grain size) with a range of thicknesses in a steel works test house environment, specifically, it focuses on employing an EM sensor system in the prediction of ultimate tensile strength for DP steels of any sheet thickness. In this project, a set of heat treated DP600 grade of 1.4mm thickness and commercial DP steel samples, including DP600, DP800 and DP1000 with a range of strength levels and thicknesses, and produced in different strip mills, have been assessed. The sensor outputs have been correlated to microstructural phase fraction and mechanical properties. Firstly, the magnetic properties of commercial DP steel samples were investigated through the major hysteresis loop and minor hysteresis loops. Measured coercivity from the major loop showed that the coercivity was affected by phase fraction (ferrite/martensite percentage) and ferrite grain size where the coercivity decreased with increased ferrite fraction. Three types of minor loop configurations were used to derive incremental permeability values; the minor loop deviations from the initial magnetisation curve (μIc); the minor loop deviations from the main B-H loop (μBH) and the minor loop deviations from amplitude sweep (μi). It was found that although the incremental permeability values are not precisely the same for the three sets of measurements, similar trends for the DP samples can be observed where the incremental permeability values are affected by the phase fraction and ferrite grain size. The effect of magnetic field on permeability for the DP steels was studied. It was shown that the incremental permeability increases with the applied field amplitude until reaching a maximum value at a certain applied field amplitude (i.e. very close to the coercivity values) and then drop at higher applied field amplitude and converge to a similar permeability value. The initial gradient and the peak position for the samples are different and would allow them to be distinguished from each other. It was observed in the commercial DP steels with a range of ferrite fraction (72 to 79%) and a range of average ferrite grain size (from 6 to 10μm), that the effect of ferrite grain boundaries on permeability is more significant than the effect of ferrite fraction within the range studied. Finally, the measured magnetic properties were used to develop a link between microstructure and mechanical properties for DP steels, using a readily deployable EM sensor that can be used with large strip steel samples. The deployable sensor geometry and operation rely on a relatively low magnetic field being generated in the sample and therefore low field incremental permeability being the relevant material parameter being assessed. Initially, the effect of ferrite fraction for the laboratory heat-treated DP600 samples, with the same thickness (1.4mm), on EM sensor output signal (i.e. mutual real inductance) was investigated. It was found that the real inductance value at a low frequency (below approx.100 Hz) is dominated by differences in the relative permeability of the samples, showing an approximately linear trend of increasing low frequency inductance value with increasing ferrite content. The increasing amount of ferrite, which possesses a much higher relative permeability than martensite, showed higher real inductance value (in the range of 35 -70% ferrite fraction in these DP steels). The measured real inductance at a frequency of 10Hz was compared with the mechanical property (hardness). An approximately linear decrease in real inductance at 10 Hz with the hardness value was found for these samples. EM sensor measurements were then carried out for the commercial DP600, DP800 and DP1000 samples with different thicknesses (1 to 4 mm). The EM sensor system showed a significant effect of thickness on the signal with thicker strip showing a much higher mutual inductance value for the same microstructure. This is due to the skin depth (for this sensor, operation frequency and material characteristics) being larger than the sample thickness, therefore a thicker sample gives a large sensor response. To deal with this problem, a calibration curve (a plot of real inductance versus permeability for different thickness of material) was constructed using a FE model for the sensor and sample geometry. Therefore, an electromagnetic sensor – sample FE model, developed in COMSOL multi-physics software, has been developed to determine the relationship between the low magnetic field relative permeability and microstructure (phase balance and grain size). The model has been validated using commercial DP steel sheets of 1 to 4 mm. It was found that the ferrite grain size affects the magnetic properties in DP steels as the grain boundaries act as effective pinning points to magnetic domain movement. Therefore, the magnetic permeability in DP steels is affected by ferrite grain size and ferrite fraction, both of which affect the tensile strength, therefore a single relationship between permeability and tensile strength results. The low field relative permeability, which is the permeability value derived from the EM sensor (e.g. U-shaped sensor), can therefore be used to predict the tensile strength in commercial DP steels. The relationship between permeability and field was employed to develop the technique. Therefore, U-shaped sensor modification was carried out to increase the accuracy of tensile strength determination, this was done as part of a case study for Tata Steel Jamshedpur to evaluate DP steels

Comparison of adding neostigmine and fentanyl to bupivacaine in caudal analgesia in pediatric inguinal herniorrhaphy

AbstractObjective: The aim of the present trial was to compare efficacy and adverse effects of neostigmine against fentanyl when used as adjuvant to bupivacaine in caudal anesthesia.Method: A total of 140 children, aged 1-6 year scheduled to elective herniorrhaphy, were enrolled. Exclusion criteria were sacral area infection, history of allergic reactions to local anesthetics, bleeding tendency, neurological or spinal disease and lack of parent consent. Patients were assigned, using permuted block randomization method, into four groups of 35. Children in the first group received a caudal injection of 0.5 ml/kg bupivacaine 0.25% plus fentanyl 1µ/kg. The second group received 0.5 ml/kg bupivacaine 0.25% plus neostigmine 1µ/kg. Patients in the third group received 0.5 ml/kg bupivacaine 0.25% plus combination of fentanyl 1µ/kg and neostigmine 1µ/kg, and those in the fourth group only received 0.5 ml/kg bupivacaine 0.25% concentration. To assess pain intensity, Wong-Baker Scale was used. Time to first analgesic request and the dosage of analgesic agent was recorded. Data were analyzed using SPSS 17.0.Results:Significant differences were observed among groups in terms of number of patients needing analgesic (p=0.01), time to first analgesic request (p=0.005) and analgesic dose. (p=0.05) The lowest number of requests for analgesia, lowest dose of pethidine and longest time to first analgesic request were in patients receiving combination of bupivacaine, neostigmine and fentanyl.Conclusion: The present study shows that the combination of fentanyl and neostigmine, could prolong duration of analgesia, and decrease severity of pain when added to bupivacain

Comparison the efficacy of pre-emptive oral celecoxib with acetaminophen in controlling post-operative pain and nausea after lower limb surgery under general anesthesia

IntroductionUp to now, there is no single opinion on how to control pain after surgeryand molecular and clinical research in this area has been continuing. This study aimed to compare the effect of premedication with oral administration of celecoxib and acetaminophen on postoperative pain relief in the lower extremity surgery under general anesthesia.                                                         Materials and methods:In a prospective, randomized, double-blinded, clinical trial study, 70 patients undergoing lower limb surgery under general anesthesia were distributed into two equal groups. In the first and second group, oral acetaminophen 1000 mg orcelecoxib 400 mg capsules were prescribed one hour before the operation, respectively. Postoperative painand nausea severity in both groups were evaluatedby VAS score and compared with each other. ResultsAssessment of pain intensity at 1, 2, 6, 12 and 24 hours after surgery revealed that acetaminophen group at the first hour had more intensity of  postoperative pain (5.46±1.17) compared with celecoxib group(4.31±1.32)(P <0.001). In the rest of the time, there was no significant difference between the two groups. Analysis of variance with repeated observations showed, the trend of postoperative pain intensity during the study in both groups had a significant difference (p = 0.013). The intensity of nausea in the first hour after surgery was significantly more in acetaminophen group compared with celecoxib group (2.8±1.1 vs. 2.2±1.3, p<0.034). Conclusions:Celecoxib may be a better choice in reducing pain and nausea after surgery compared with acetaminophen. Considering no significant adverse effects in many studies, celecoxib may be used as a pre-emptive medication to reduce pain after lower extremity surgery.Key words: Premedication, Post-operative, PONV, pain, Celecoxib, Acetaminophe

Efficacy of Glucose-Insulin-Potassium Infusion on Left Ventricular Performance in Type II Diabetic Patients Undergoing Elective Coronary Artery Bypass Graft.Dy

BACKGROUND: Glucose-insulin-potassium (GIK) may improve cardiovascular performance after coronary artery bypass graft surgery (CABG). Our study investigated whether an infusion of GIK during elective CABG surgery in type II diabetic patient improved left ventricular performance.    METHODS: We measured left ventricular ejection fraction and troponin (Tn), a myofibrillar structural protein. In this research, after ethics committee approval, 50 patients with type 2 diabetes mellitus (DM) were enrolled into a randomized simple sampling, prospective, double-blind clinical trial study. In the case group, 500 cc dextrose water 5% plus 80 IU regular insulin and 40 mEq KCL were infused at the rate of 30 cc/hr. Patients in control group received 5% dextrose solution at the rate of 30cc/hr. Venous blood samples were taken before induction of anesthesia, after removal of the aortic clamp and before discharging from hospital. The Mann-Whitney-test was used to test for differences in Tn concentration between the groups. Fisher’s exact test was used to determine whether there was a difference in the proportion of patients with a low ejection fraction (<45%) in the case group compared with that in the control group. Changes in potassium and glucose concentrations over time within the groups were examined by ANOVA and paired t-tests. P<0.05 was regarded as significant level for all tests.    RESULTS: In this study, 50 patients with type 2 DM were evaluated in case and control groups. The mean age ± SD in the case group was 57.7 ±9.9 years and in the other group was 61.2 ± 8.4 years. The groups were well-matched for age, sex and number of bypass grafts. Randomization did not give an equal distribution of male and female patients. There wasn’t any significant difference in ejection fraction between the case and control groups before and after CABG (P>0.05). Tn concentration in the case group was 3.3 ± 5.0 and in the control group was 3.9 ± 5.1. There was no significant difference in Tn between the two groups before and after CABG (P>0.05). There was not any significant difference in hospitalization time between the two groups.     CONCLUSION: The results suggested that GIK can’t improve left ventricular performance in routine CABG surgery.      Keywords: Cardiovascular surgery, Glucose-Insulin-Potassium, Cardiac troponin

Non-destructive evaluation of magnetic anisotropy associated with crystallographic texture of interstitial free steels

Interstitial free (IF) steels, as third generation of deep drawing steel, are used in the automotive industry for applications requiring good formability, strength and a superior surface quality. The formability is achieved by having a strong gamma fibre (γ-fibre) crystallographic texture and is quantified by measuring the r-value from tensile tests. Whereas the crystallographic texture is typically measured using EBSD or XRD on samples after careful surface preparation, it is desirable to be able to evaluate it non-destructively on production material. To do this aim, a magnetic anisotropy measurement is an attractive approach as the magnetic behaviour of steel is known to be affected by its crystallographic texture. A set of interstitial free steel samples, at different stages of recrystallisation process (i.e., commercially cold rolled and annealed to achieve fully and partially recrystallised microstructures) and consequently different texture components have been employed to study the measurement and possibility of model-wise predicting magnetic anisotropy in IF steels. In order to compare the predicted magnetic anisotropy to the measured values, a finite element (FE) microstructure model that takes into account crystallographic texture was applied

Non-destructive evaluation of magnetic anisotropy associated with crystallographic texture of interstitial free steels using an electromagnetic sensor

Interstitial free (IF) steels, as third generation of deep drawing steel, are used in the automotive industry for applications requiring good formability, strength and a superior surface quality. The formability is achieved by having a desired strong gamma fibre (γ-fibre) crystallographic texture, which is typically measured using EBSD or XRD, and is quantified by measuring the r-value from tensile tests. It is desirable to be able to evaluate the crystallographic texture using non-destructive testing on production material. Magnetic anisotropy measurement is an attractive approach as the magnetic behaviour of steel is known to be affected by its crystallographic texture. A set of interstitial free steel samples, at different stages of recrystallisation process (i.e., commercially cold rolled and annealed to achieve fully recrystallised microstructures and partially recrystallised) and consequently different texture components have been employed to study the measurement and possibility of predicting magnetic anisotropy in IF steels. In order to compare the predicted magnetic anisotropy to the measured values, a finite element (FE) microstructure model that takes into account crystallographic texture was applied.The findings indicate that the deployable non-destructive technique - proposed U-shaped electromagnetic (EM) sensor that can be placed onto a sheet specimen, is promising for a rapid assessment of the magnetic anisotropy in IF steels

The Cardioprotective Effects of N acetylcysteine as an Additive to the Blood Cardioplegia During Coronary Artery Bypass Grafting

Abstract: Introduction: During coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass (CPB), the role of cardioplegic solution which results in cardiac arrest, is critical. This study was planned to evaluate the clinical impacts of N acetylcysteine (NAC) enriched cold-blood cardioplegia on early reperfusion injury in patients with ischaemic heart disease undergoing CABG. Methods: In a randomized double blind clinical trial, seventy patients undergoing elective CABG surgery with CPB were studied. They all underwent similar methods of preoperative medication, anaesthesia and cardiac surgery. Patients were randomly divided into the case group (cardioplegia plus 50 mg/kg NAC) and the control group (cardioplegia with the equal volume of normal saline). The incidence of arrhythmias, usage of DC-shock, pacemaker and inotropic agents during and twenty four hours after surgery, EF five days after surgery and ICU staying and hospitalization periods in the two groups were compared. Results: There were no statistically significant differences between the two groups according to demographic features, EF before surgery, CPB or aorta clamping times, intraoperative DC shock and pacemaker requirements and postoperative inotropic necessity (p >0.05). Two groups showed significant differences in regard to the incidence of arrhythmias (5.7% vs. 22.9%), the inotropic requirement (14.3% vs. 34.3%) during surgery, EF five days after surgery (51.4% vs. 45%) and the mean EF changes postoperatively in comparison with the preoperative period (0.88 vs. -2.28) (p <0.05). Conclusion: Addition of N-acetylcysteine to cardioplegic solution can reduce some of the clinical complications during and after surgery and has positive effects on the postoperative ejection fraction. Keywords: Coronary artery bypass grafting, N acetylcysteine, Cardiac surgery, Cardioplegi

Septic Thrombophlebitis of the Cephalic Vein Caused by a Peripherally Inserted Venous Catheter

Septic thrombophlebitis of a vein is a rare but life-threatening complication of an intravascular (IV) catheter placed percutaneously in the veins. Most published clinical experiences with IV catheters, mainly in the outpatient settings, have reported very low rates of catheter-related bloodstream infection compared to rates with central venous catheters placed in a subclavian or internal jugular vein. Most of the complications reported with IV catheters have been non-infectious, particularly sterile phlebitis or thrombosis. We report a case of cephalic vein suppurative thrombophlebitis from an intravascular catheter and offer guidelines for diagnosis and management of this complication.&#13; Key words: Septic thrombophlebitis, Intravascular catheter, Suppurative thrombophlebiti

EFFECT OF INTERPLEURAL MEPERIDINE WITH AND WITHOUT BUPI-VACAINE ON POSTOPERATIVE PAIN AFTER STERNOTOMY

Abstract &nbsp;&nbsp; INTRODUCTION: No unique technique has proved efficient enough in controlling post cardiothoracic surgery pain. A variety of agents and techniques have been used to control pain following cardiothoracic surgery; interpleural regional analgesia is one such technique. &nbsp;&nbsp; OBJECTIVE: There are many nerve endings in the pleural cavity. The local anesthetic action of meperidine administered interpleurally was evaluated in this study. &nbsp;&nbsp; METHODS: In a double blind clinical trial, 90 patients undergoing coronary artery bypass graft surgery were randomized into four groups as intravenous meperidine (G1), interpleural meperidine (G2), interpleural meperidine and bupivacaine (G3) and interpleural bupivacaine (G4) groups. At the end of surgery, interpleural catheter was placed in all groups and the medication was prescribed. In the cardiac intensive care unit, narcotic requirements and pain scores were registered. Collected data were analyzed by appropriate tests including t-test and chi-square test. P values below 0.05 were considered as significant. &nbsp;&nbsp; RESULTS: There were no significant differences in age, weight, sex and ASA (American Society of Anesthesiologists) class between the four groups. At all time periods, the pain levels measured by the visual analogue score (VAS) were significantly lower in the G3 and G4 groups (P&lt;0.05). The total narcotic requirements in the first 24 hours of postoperative period were significantly lower in the G3 and G4 groups (P&lt;0.05). &nbsp;&nbsp; CONCLUSION: In spite of analgesic effects of subarachnoid meperidine, intraarticular morphine and interpleural bupivacaine, interpleural meperidine does not change pain scores or narcotic requirements postoperatively. &nbsp;&nbsp; &nbsp; &nbsp;&nbsp; Keywords: Meperidine, bupivacaine, postoperative, pain, thoracic surgery, cardiac surgical procedure..</p

Correlation between timing of tracheostomy and duration of mechanical ventilation in patients with potentially normal lungs admitted to intensive care unit

Background: There is insufficient evidence to conclude that the timing of tracheostomy alters the duration of mechanical ventilation, hence this study was designed to investigate the correlation between timing of tracheostomy and duration of mechanical ventilation for patients admitted to intensive care unit (ICU) with potentially normal lungs. Materials and Methods: In a retrospective study for a period of 2 years, all adult patients admitted to the medical ICU of Al-Zahra Hospital in Isfahan University of Medical Sciences who needed endotracheal intubation and prolonged mechanical ventilation were considered for inclusion in this study. Data of underlying disease, causes of respiratory failure, age and gender, duration of mechanical ventilation, and interval between intubation time and tracheostomy were collected. The correlations between intubation period and ventilation period were analyzed using a Pearson correlation test. Results: Sixty-six percent of patients (100 patients) were men. The mean ± SD of age of patients was 56.2 ± 20.8 years (18-90 years.). The timing of tracheostomy (duration of endotracheal intubation until tracheostomy) did not exhibit any correlation with the length of mechanical ventilation ( P = 0.43, r = 0.08). The timing of tracheostomy had not any correlation with the age of patients ( P = 0.20, r = 0.129). The length of mechanical ventilation had not any correlation with the age of patients ( P = 0.83, r = 0.02). The timing of tracheostomy was similar in men and women ( P = 0.5). Mechanical ventilation period was not significantly different in both genders ( P = 0.89). Conclusion: Our study with mentioned sample size could not show any relationship between timing of tracheostomy and duration of mechanical ventilation in patients under mechanical ventilation with good pulmonary function in ICU