A Methodology for the Robust Procedure Development of Fillet Welds

Though Gas Metal Arc Welding has been a basic component of fabrication in manufacturing over the last half-century, a standard methodology for optimizing welding procedures is lacking. A new procedure development method which minimizes trial runs, while maximizing accuracy has been recently developed by T.T. Allen, et al, in 2002. The use of the method is presently restricted to lap joint type welds. This work looked to extend this methodology to the application of fillet welds, test its effectiveness with different response variables, and study the effect of increasing the number of response variables. The development of a robust weld procedure that produces a consistent root penetration was used as the application for the developed methodology. The significance of this application lies in the fact that typical codes and standards currently give no consideration to root penetration when calculating joint strength from a lack of confidence in consistency and robustness. The benefits of incorporating penetration in strength calculations are numerous and consequential for industry. An increase in strength would result allowing welds to be made smaller, thus, resulting in decreases in weld time, filler wire used, and heat input, reducing distortion. Showing the capability of robust penetration through this statistical process procedure is the first step towards inclusion of penetration as a variable in joint strength calculations and the reaping of its benefits. Fillet welds were made on 12 mm thick A572 Grade 50 steel and cross-sectioned to allow for the critical response variables of penetration, undercut, convexity, maximum and minimum leg length, to be measured. Regression models were created along with contour plots displaying penetration and quality ratings on a plot of WFS/TS ratio versus travel speed. The optimization of travel speed against penetration and quality restrictions was also performed revealing a set of nominal procedural variables which produce sound welds for a range of noise variables. The optimized welding procedure included a travel speed of 11.3 in/min, a 1/16” arc length, a WFS/TS ratio of 28.4, and a contact-tip-to-work distance of 22 mm. The low travel speed resulted primarily from a need to maintain a minimum leg length in specification. It was also, observed from the contour plots that the robustness of the process was low from both the minimum leg length and convexity quality response factors. While the application conclusions show low robustness results, the significance of the developments with the process procedure were significant. The combination of optimization and the contour plots provides the engineer with a tool for determining the nominal input welding variables along with gaining an understanding of the robustness of the certain procedure, according to each significant quality issue. Also, the development of a rating scale based on code adds authenticity to the procedure, while at the same time increasing the ease at which the common scale is developed.John Deere Dubuque Work

The Development of LOX-Based Magnetic Fluid Technology and its Impact on Small Satellites

A magnetic fluid system could potentially replace mechanically moving parts in a satellite as a means of increasing system reliability and mission lifetime, but rather than a standard ferrofluid with magnetic particles, liquid oxygen (LOX) may be a more adequate working fluid. As a pure paramagnetic cryogen, LOX is already heavily used in space, but still requires basic research before being integrated into system development. The objectives of the research conducted were to verify LOX as a magnetic working fluid through experiment and establish a theoretical model to describe its behavior. This paper presents the theoretical, experimental, and numerical results of a slug of LOX being pulsed by a 1.1 T solenoid in a quartz tube with an inner diameter of 1.9 mm. The slug oscillated about the solenoid at 6-8 Hz, producing a pressure change of up to 1.2 kPa. System efficiency based on the Mason number was also studied for various geometric setups, and, using a one-dimensional, finite-differenced model in Matlab 2008a, the numerical analyses confirmed the theoretical model. The research provides groundwork for future applied studies using Comsol Multiphysics 3.5a with complex designs

On Smith normal forms of qq-Varchenko matrices

In this paper, we investigate $q$-Varchenko matrices for some hyperplane arrangements with symmetry in two and three dimensions, and prove that they have a Smith normal form over $\mathbb Z[q]$. In particular, we examine the hyperplane arrangement for the regular $n$-gon in the plane and the dihedral model in the space and Platonic polyhedra. In each case, we prove that the $q$-Varchenko matrix associated with the hyperplane arrangement has a Smith normal form over $\mathbb Z[q]$ and realize their congruent transformation matrices over $\mathbb Z[q]$ as well.Comment: 22 pages, 8 figure

GEODYN programmer's guide, volume 2, part 2

A computer program for executive control routine for orbit integration of artificial satellites is presented. At the beginning of each arc, the program initiates required constants as well as the variational partials at epoch. If epoch needs to be reset to a previous time, the program negates the stepsize, and calls for integration backward to the desired time. After backward integration is completed, the program resets the stepsize to the proper positive quantity

Massive Gravity Simplified: A Quadratic Action

We present a simplified formulation of massive gravity where the Higgs fields have quadratic kinetic term. This new formulation allows us to prove in a very explicit way that all massive gravity theories considered so far inevitably have Boulware-Deser ghost in non-trivial fluctuations of background metric.Comment: 8 pages, paragraph added proving that Bianchi identity does not imply vanishing of linearized curvatur

Bubble Behavior in Nucleate Boiling Experiment Aboard the Space Shuttle

Boiling dynamics in microgravity need to be better understood before heat transfer systems based on boiling mechanism can be developed for space applications. This paper presents the results of a nucleate boiling experiment aboard Space Shuttle Endeavor (STS- 108). The experiment utilized nickel-chromium resistance wire to boil water in microgravity, and the data was recorded with a CCD camera and six thermistors. This data was analyzed to determine the behavior of bubble formation, detachment from the heating wire, and travel in the water with effects of drag on bubble movement. Bubbles were observed to be ejected from the wire, travel through and eventually stop in the unsaturated water. The data from this experiment is in good agreement with the results of theoretical equations used to model bubble-fluid dynamics in microgravity. The primary conclusion from this experiment is that a bubble can be ejected from a heated wire in the absence of gravity, instead of the creation of a single large vapor bubble. Further conclusions from this research could be applied to the development of safe and efficient heat transfer systems for microgravity and terrestrial applications

Phase transitions in general gravity theories

Phase transitions between two competing vacua of a given theory are quite common in physics. We discuss how to construct the space-time solutions that allow the description of phase transitions between different branches (or asymptotics) of a given higher curvature gravity theory at finite temperature.Comment: 4 pages, 1 figure, Contribution to the Conference Proceedings of the Spanish Relativity Meeting in Portugal (ERE2012

Brane Cosmology from Heterotic String Theory

We consider brane cosmologies within the context of five-dimensional actions with O(a') higher curvature corrections. The actions are compatible with bulk string amplitude calculations from heterotic string theory. We find wrapped solutions that satisfy the field equations in an approximate but acceptable manner given their complexity, where the internal four-dimensional scale factor is naturally inflating, having an exponential De-Sitter form. The temporal dependence of the metric components is non-trivial so that this metric cannot be factored as in a conformally flat case. The effective Planck mass is finite and the brane solutions localize four-dimensional gravity, while the four-dimensional gravitational constant varies with time. The Hubble constant can be freely specified through the initial value of the scalar field, to conform with recent data.Comment: 15 pages, 3 figures, LaTeX, Accepted for Publication in IJT

The implications of autoantibodies to a single islet antigen in relatives with normal glucose tolerance:development of other autoantibodies and progression to type 1 diabetes

AIMS/HYPOTHESIS: Autoantibodies directed at single islet autoantigens are associated with lower overall risk of type 1 diabetes than multiple autoantibodies, but individuals with one autoantibody may progress to higher risk categories. We examined the characteristics of this progression in relatives followed prospectively in the TrialNet Pathway to Prevention. METHODS: The study population comprised 983 relatives who were single autoantibody positive with normal baseline glucose tolerance (median age 16.2 years). Samples were screened for antibodies to GAD, insulinoma-associated antigen 2 (IA-2) and insulin, and all positive samples tested for antibodies to zinc transporter 8 and islet cell antibodies. RESULTS: Antibodies to at least one additional islet autoantigen appeared in 118 of 983 relatives (overall 5 year risk 22%, 95% CI [17.9, 26.1]). At baseline, antibodies to GAD alone (68%) were more frequent than antibodies to insulin (26%) or IA-2 (6%), but all were associated with a similar risk of developing additional autoantibodies. Risk was associated with younger age (p = 0.002) and HLA class II genotype, but was similar in high and intermediate genetic risk groups (p = 0.65). Relatives who became multiple autoantibody positive during the follow-up had increased risk of developing diabetes comparable with the risk in relatives with multiple autoantibodies at study entry. CONCLUSIONS/INTERPRETATION: Progression of islet autoimmunity in single autoantibody positive relatives in late childhood/adult life is associated with a predominance of autoantibodies to GAD and a distinct HLA risk profile. This heterogeneity in type 1 diabetes autoimmunity has potentially important implications for disease prevention. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00125-015-3830-2) contains peer-reviewed but unedited supplementary material, which is available to authorised users

Cryogenic Experimentation on the Magnetohydrodynamics of Liquid Oxygen

The increasing demands of the small satellite industry are forcing the development of subsystems with increased reliability and robustness while maintaining harsh mass and volume constraints. Basic research has begun on the cryogenic magnetohydrodynamic properties of liquid oxygen to determine its feasibility as a working fluid in a magnetic system void of mechanically moving parts. A 1D finite-differenced numerical algorithm verified experimental data on the dynamics of a liquid oxygen slug propagated by pulsed magnetic fields. Up to 1.4 T was induced by electrically-sequenced solenoids wound with 30 gauge copper wire. The test section consisted of two solenoids and a 0.075 inch quartz tube and was completely submerged in liquid nitrogen. Because of this, visual confirmation of the slug size was difficult, and the algorithm was also used to determine its length. Using data obtained from upstream and downstream pressure sensors, the lengths were predicted as 3.75 inches for an oscillating slug test and as 2.2 inches for a propagating slug test. The maximum pressure differential obtained was 0.24 psi, which is comparable to ferrofluid-based experiments. The experiment resulted in the most detailed information to date on the paramagnetic susceptibility of liquid oxygen. It is anticipated that this basic research will eventually lead to the development of small satellite subsystems with significantly longer lifetimes