Fatigue of continuous fiber reinforced metallic materials

The complex damage mechanisms that occur in fiber reinforced advanced metallic materials are discussed. As examples, results for several layups of SCS-6/Ti-15-3 composites are presented. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room and elevated temperatures. Test conditions included isothermal, non-isothermal, and simulated mission profile thermomechanical fatigue. Test results indicated that the stress in the 0 degree fibers is the controlling factor for fatigue life for a given test condition. An effective strain approach is presented for predicting crack initiation at notches. Fiber bridging models were applied to crack growth behavior

Modeling and life prediction methodology for Titanium Matrix Composites subjected to mission profiles

Titanium matrix composites (TMC) are being evaluated as structural materials for elevated temperature applications in future generation hypersonic vehicles. In such applications, TMC components are subjected to complex thermomechanical loading profiles at various elevated temperatures. Therefore, thermomechanical fatigue (TMF) testing, using a simulated mission profile, is essential for evaluation and development of life prediction methodologies. The objective of the research presented in this paper was to evaluate the TMF response of the (0/90)2s SCS-6/Timetal-21S subjected to a generic hypersonic flight profile and its portions with a temperature ranging from -130 C to 816 C. It was found that the composite modulus, prior to rapid degradation, had consistent values for all the profiles tested. A micromechanics based analysis was used to predict the stress-strain response of the laminate and of the constituents in each ply during thermomechanical loading conditions by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. In the analysis, the composite modulus degradation was assumed to result from matrix cracking and was modeled by reducing the matrix modulus. Fatigue lives of the composite subjected to the complex generic hypersonic flight profile were well correlated using the predicted stress in 0 degree fibers

The Frequency of Opium Addiction and Cofactors in Diabetic Patients Referred to Karaj Dr. Shariati Hospital in 1389-90

Background: Diabetes mellitus is one of the most common and complicate endocrine disease in Iran. Also, opium addiction is one of the most prevalent social problems in Iran. The goal of this study was to determine the frequency of opium addiction and diabetic vascular complications in diabetic patients. Methods: This study was a cross-sectional study conducted in two years (1389- 90) in Karaj Dr. Shariati hospital. Sampling method was non-probability convenience sampling. Sample size was 384 patients. Data collection forms filled with patient’s files evidences. Statistical analysis of data was performed with SPSS. Results: 384 diabetic patients with age ranging from 13 to 91 years old (mean age 59.1 years) were evaluated. 40 patients (10.4%) were opium addict and 75 patients (19.5%) were smoker. After elimination of smoking effect, frequency of retinopathy, neuropathy and diabetic foot ulcer were significantly more in opium addicts than other diabetic patients. Conclusion: Opium abuse in diabetic patients can accelerates and progresses some of diabetic vascular complications

Analysis of thermomechanical fatigue of unidirectional titanium metal matrix composites

Thermomechanical fatigue (TMF) data was generated for a Ti-15V-3Cr-3Al-3Sn (Ti-15-3) material reinforced with SCS-6 silicon carbide fibers for both in-phase and out-of-phase thermomechanical cycling. Significant differences in failure mechanisms and fatigue life were noted for in-phase and out-of-phase testing. The purpose of the research is to apply a micromechanical model to the analysis of the data. The analysis predicts the stresses in the fiber and the matrix during the thermal and mechanical cycling by calculating both the thermal and mechanical stresses and their rate-dependent behavior. The rate-dependent behavior of the matrix was characterized and was used to calculate the constituent stresses in the composite. The predicted 0 degree fiber stress range was used to explain the composite failure. It was found that for a given condition, temperature, loading frequency, and time at temperature, the 0 degree fiber stress range may control the fatigue life of the unidirectional composite

Axial and torsional fatigue behavior of Waspaloy

The cyclic flow response and crack growth behavior of Waspaloy at room temperature and 650 C under tensile loading and torsional loading was studied, for two conditions of Waspaloy: fine grain, large gamma prime size; coarse grain, small gamma prime size. The fine grain material showed 5 to 10 percent hardening after about 10 percent of life, with sequent softening to failure at both themperature levels. The coarse grain material showed either stable response or monotonic softening to failure. Early crack initiation was observed on planes of maximum shear, with eventual branching to principle planes under torsional loading; cracks were always normal to load axis under tensile loading. Also, crack paths were intergranular at 650 C, mostly transgranular at room temperature

A case report of total anomalous pulmonary vein connection in an adult through application of multi-modality imaging

ABSTRACT Total Anomalous Pulmonary Vein Connection (TAPVC) is often reported in neonates and children. This report demonstrates an unusual adult TAPVC that the patient is survived in the fourth decade of life. It was diagnosed via application of echocardiography paired with multi detector-row computed tomography angiography. A 39-year-old man was referred for evaluation of dyspnea and cyanosis at rest worsening with exertion. On physical examination, decreased oxygen saturation, clubbing, and central and peripheral cyanosis were detected. In primary evaluation, large Atrial Septal Defect (ASD) was discovered. Cardiac catheterization showed a large ASD and benign variant of Persistent Left Superior Vena Cava (PLSVC). On Trans-Thoracic Echocardiography (TTE), no pulmonary hypertension was defined in direct contradiction of Eisenmenger syndrome. Due to suspicion of a complex shunt, he underwent Trans-Esophageal Echocardiography (TEE) followed by CT-angiography. Both of these image modalities clearly demonstrated the presence of TAPVC in addition to ostium secundum ASD. Due to the change in the main diagnosis, he underwent surgical correction with immediate and complete relief of both cyanosis and dyspnea after operation. Although some complex congenital heart diseases are usually seen in newborns and infants, their presence in adulthood is not impossible. Thus, some unusual findings similar to presence of cyanosis in the absence of pulmonary hypertension should be questioning. In such cases, alternative imaging studies can provide additional guidance in diagnosis. It is not an infrequent occurrence, as this case underscores, where more complete imaging overturns an initial diagnosis leading to completely different management. Keywords: Computed Tomography Angiography Atrial Septal Defect Echocardiograph

Time-dependent deformation of titanium metal matrix composites

A three-dimensional finite element program called VISCOPAC was developed and used to conduct a micromechanics analysis of titanium metal matrix composites. The VISCOPAC program uses a modified Eisenberg-Yen thermo-viscoplastic constitutive model to predict matrix behavior under thermomechanical fatigue loading. The analysis incorporated temperature-dependent elastic properties in the fiber and temperature-dependent viscoplastic properties in the matrix. The material model was described and the necessary material constants were determined experimentally. Fiber-matrix interfacial behavior was analyzed using a discrete fiber-matrix model. The thermal residual stresses due to the fabrication cycle were predicted with a failed interface, The failed interface resulted in lower thermal residual stresses in the matrix and fiber. Stresses due to a uniform transverse load were calculated at two temperatures, room temperature and an elevated temperature of 650 C. At both temperatures, a large stress concentration was calculated when the interface had failed. The results indicate the importance of accuracy accounting for fiber-matrix interface failure and the need for a micromechanics-based analytical technique to understand and predict the behavior of titanium metal matrix composites

Timely diagnosis of left ventricular posterior wall rupture by echocardiography: A case report

Left ventricular free wall rupture is responsible for up to 10 of in-hospital deaths following myocardial infarction. It is mainly associated with posterolateral myocardial infarction, and its antemortem diagnosis is rarely made. One of the medical complications of myocardial infarction is the rupture of the free wall, which occurs more frequently in the anterolateral wall in hypertensives, women, and those with relatively large transmural myocardial infarction usually 1-4 days after myocardial infarction. We herein present the case of a 66-year-old man suffering inferior wall myocardial infarction with abrupt hemodynamic decompensation 9 days after myocardial infarction. Emergent transthoracic echocardiography revealed massive pericardial effusion with tamponade, containing a large elongated mass measuring 1 x 8cm suggestive of hematoma secondary to cardiac rupture. In urgent cardiac surgery, the posterior wall between the left coronary artery branches was ruptured

A facile route for preparation of CdS nanoparticles

CdS nanoparticles have been synthesized by a chemical reaction route using ethylenediamine as a complexing agent. The nanoparticles were characterized using techniques such as X-ray powder diffraction (XRD), scanning electron microscope (SEM), UV–VIS absorption spectroscopy, and photoluminescence spectroscopy. The absorption edge for the bulk hexagonal CdS is at 512 nm (2.42 eV). Comparing with the bulk CdS, it is believed that the blue shift in the absorption peak was caused by the quantum confinement effect. Photoluminescence measurements indicate CdS nanoparticles show fluorescence band with a maximum close to 315 nm

Analysis and determination of mercury, cadmium and lead in canned tuna fish marketed in Iran

The objective of this study is to determine mercury, cadmium and lead concentrations in 60 canned tuna fish samples produced and distributed in Iran after digestion by the standard methods of the Association of Official Analytical Chemists. Mercury contents in canned tuna fish were determined by cold vapor atomic absorption spectrophotometry while cadmium and lead were determined by graphite furnace atomic absorption spectrophotometry. The metal contents, expressed in μg g-1wet weight for mercury, cadmium and lead varied from 0.010 to 0.401 (average of 0.125), 0.008 to 0.150 (average of 0.050) and 0.021 to 0.301 (average of 0.096), respectively. The values  were comparable and in the range of the literature values. The results of this study indicate that tuna fish produced and marketed in Iran have concentrations well below the standards of FAO/WHO levels of these toxic metals.Key words: Canned tuna fish, heavy metals, mercury, cadmium, lead