The effect of spring restraint on weld distortion in t-joint fillet welds

T-joint fillet welds are a very common occurrence found in industry today. Localized heating and cooling from the welding process lead to the rise of distortion and residual stresses. Weld fixturing is a common practice in industry used to address the problems associated with welding, however fixturing also creates problems of residual stresses being locked into the weldment. This research involves placing linear compression springs along the top of a t-joint fillet weld in an effort to gain an understanding of the contraction of the weld metal. The effect of different levels of restraint is also investigated. Variable restraint is a concept that could be used to reduce distortion while keeping residual stress at a minimal level. The idea behind this is that unnecessary force applied to a part could leave stress in that part; variable restraint would use force where it is needed. Residual stresses were obtained for the weldments by the x-ray diffraction process. The distortion and stress trends are presented and discussed in this work

Insulin resistance, subclinical left ventricular remodeling, and the obesity paradox: the multi-ethnic study of atherosclerosis

ObjectivesThis study assessed whether impaired fasting glucose (IFG), insulin resistance, and waist-to-hip ratio (WHR) had effects on cardiac remodeling, independent of obesity, in the MESA (Multi-Ethnic Study of Atherosclerosis) trial.BackgroundRecent studies have suggested that central obesity and insulin resistance may be primary mediators of obesity-related cardiac remodeling independent of body mass index (BMI).MethodsWe investigated 4,364 subjects without diabetes in the MESA trial. IFG (100 to 125 mg/dl) or insulin resistance (by homeostatic model assessment of insulin resistance [HOMA-IR]) and WHR were used for cardiometabolic phenotyping. Multivariate linear regression analysis was used to determine the effects of the cardiometabolic markers on left ventricular (LV) remodeling, assessed primarily through the LV mass-to-volume ratio obtained by cine cardiac magnetic resonance imaging.ResultsIndividuals with IFG were more likely to be older and hypertensive, with increased prevalence of cardiometabolic risk factors regardless of BMI. In each quartile of BMI, subjects with above-median HOMA-IR, above-median WHR, or IFG had a higher LV mass-to-volume ratio (p < 0.05 for all). HOMA-IR (p < 0.0001), WHR (p < 0.0001), and the presence of IFG (p = 0.04), but not BMI (p = 0.24), were independently associated with LV mass-to-volume ratio after adjustment for age, sex, hypertension, race, and dyslipidemia.ConclusionsInsulin resistance and WHR were associated with concentric LV remodeling independent of BMI. These results support the emerging hypothesis that the cardiometabolic phenotype, defined by insulin resistance and central obesity, may play a critical role in LV remodeling independently of BMI

Myocardial Tissue Remodeling in Adolescent Obesity

Background: Childhood obesity is a significant risk factor for cardiovascular disease in adulthood. Although ventricular remodeling has been reported in obese youth, early tissue‐level markers within the myocardium that precede organ‐level alterations have not been described. Methods and Results: We studied 21 obese adolescents (mean age, 17.7±2.6 years; mean body mass index [BMI], 41.9±9.5 kg/m2, including 11 patients with type 2 diabetes [T2D]) and 12 healthy volunteers (age, 15.1±4.5 years; BMI, 20.1±3.5 kg/m2) using biomarkers of cardiometabolic risk and cardiac magnetic resonance imaging (CMR) to phenotype cardiac structure, function, and interstitial matrix remodeling by standard techniques. Although left ventricular ejection fraction and left atrial volumes were similar in healthy volunteers and obese patients (and within normal body size‐adjusted limits), interstitial matrix expansion by CMR extracellular volume fraction (ECV) was significantly different between healthy volunteers (median, 0.264; interquartile range [IQR], 0.253 to 0.271), obese adolescents without T2D (median, 0.328; IQR, 0.278 to 0.345), and obese adolescents with T2D (median, 0.376; IQR, 0.336 to 0.407; P=0.0001). ECV was associated with BMI for the entire population (r=0.58, P<0.001) and with high‐sensitivity C‐reactive protein (r=0.47, P<0.05), serum triglycerides (r=0.51, P<0.05), and hemoglobin A1c (r=0.76, P<0.0001) in the obese stratum. Conclusions: Obese adolescents (particularly those with T2D) have subclinical alterations in myocardial tissue architecture associated with inflammation and insulin resistance. These alterations precede significant left ventricular hypertrophy or decreased cardiac function