Cost Affecting Factors Related to Fillet Joints

Fillet welds are by far the most frequent arc welding joint type in the fabrication industry with about 80% of all arc welded joints worldwide. Alt-hough the joint is well established, there are many aspects to consider when pro-ducing an ideal weld. This paper reveals and connects several problematic issues related to the joint type and the difficulties to fabricate a weld with correct strength, cost, and quality. Excessive welding of fillet welds is common, resulting in increased fabrication cost. There could be several causes for this; the designers do not customize the weld demand for the different stress levels and the production adds even more to handle the variation in the process. Previous studies shows that the combination of these factors can result in 100% extra weld metal, compared to what should be needed to fulfil the strength demands. Inspections are another contributor to excess welding. The capability of the weld size measurement method used by welders and inspectors is unsatisfactory. Measurement system analyses show that the scatter from the measurement system itself is in the same range as the scatter from the process. A critical summary of the current state-of-the-art is that fillet welds are hard to specify and fabricate with the right size, that the measuring method is incapable and the connection between size and strength is weak

Projected sensitivity to sub-GeV dark matter of next-generation semiconductor detectors

We compute the projected sensitivity to dark matter (DM) particles in the sub-GeV mass range of future direct detection experiments using germanium and silicon semiconductor targets. We perform this calculation within the dark photon model for DM-electron interactions using the likelihood ratio as a test statistic, Monte Carlo simulations, and background models that we extract from recent experimental data. We present our results in terms of DM-electron scattering cross section values required to reject the background only hypothesis in favour of the background plus DM signal hypothesis with a statistical significance, $\mathcal{Z}$, corresponding to 3 or 5 standard deviations. We also test the stability of our conclusions under changes in the astrophysical parameters governing the local space and velocity distribution of DM in the Milky Way. In the best-case scenario, when a high-voltage germanium detector with an exposure of $50$ kg-year and a CCD silicon detector with an exposure of $1$ kg-year and a dark current rate of $1\times10^{-7}$ counts/pixel/day have simultaneously reported a DM signal, we find that the smallest cross section value compatible with $\mathcal{Z}=3$ ($\mathcal{Z}=5$) is about $8\times10^{-42}$ cm$^2$ ($1\times10^{-41}$ cm$^2$) for contact interactions, and $4\times10^{-41}$ cm$^2$ ($7\times10^{-41}$ cm$^2$) for long-range interactions. Our sensitivity study extends and refine previous works in terms of background models, statistical methods, and treatment of the underlying astrophysical uncertainties.Comment: 17 pages, 4 figure

Predictors of stable return-to-work in non-acute, non-specific spinal pain: low total prior sick-listing, high self prediction and young age. A two-year prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Non-specific spinal pain (NSP), comprising back and/or neck pain, is one of the leading disorders in long-term sick-listing. During 2000-2004, 125 Swedish primary-care patients with non-acute NSP, full-time sick-listed 6 weeks-2 years, were included in a randomized controlled trial to compare a cognitive-behavioural programme with traditional primary care. This prospective cohort study is a re-assessment of the data from the randomized trial with the 2 treatment groups considered as a single cohort. The aim was to investigate which baseline variables predict a stable return-to-work during a 2-year period after baseline: objective variables from function tests, socioeconomic, subjective and/or treatment variables. Stable return-to-work was a return-to-work lasting for at least 1 month from the start of follow-up.</p> <p>Methods</p> <p><it>Stable return-to-work </it>was the outcome variable, the above-mentioned factors were the predictive variables in multiple-logistic regression models, one per follow-up at 6, 12, 18 and 24 months after baseline. The factors from univariate analyzes with a <it>p</it>-value of at most .10 were included. The non-significant variables were excluded stepwise to yield models comprising only significant factors (<it>p </it>< .05). As the comparatively few cases made it risky to associate certain predictors with certain time-points, we finally considered the predictors which were represented in at least 3 follow-ups. They are presented with odds ratios (OR) and 95% confidence intervals.</p> <p>Results</p> <p>Three variables qualified, all of them represented in 3 follow-ups: <it>Low total prior sick-listing </it>(including all diagnoses) was the strongest predictor in 2 follow-ups, 18 and 24 months, OR 4.8 [1.9-12.3] and 3.8 [1.6-8.7] respectively, <it>High self prediction </it>(the patients' own belief in return-to-work) was the strongest at 12 months, OR 5.2 [1.5-17.5] and <it>Young age </it>(max 44 years) the second strongest at 18 months, OR 3.5 [1.3-9.1].</p> <p>Conclusions</p> <p>In primary-care patients with non-acute NSP, the strong predictors of stable return-to-work were 2 socioeconomic variables, <it>Low total prior sick-listing </it>and <it>Young age</it>, and 1 subjective variable, <it>High self-prediction</it>. Objective variables from function tests and treatment variables were non-predictors. Except for <it>Young age</it>, the predictors have previously been insufficiently studied, and so our study should widen knowledge within clinical practice.</p> <p>Trial registration</p> <p>Trial registration number for the original trial NCT00488735.</p

Weld procedures and demands for improved fatigue strength of single load carrying fillet welds

Traditional weld demands on throat size and leg length does not support a welding process for improved penetration. This paper includes theoretical analysis of welded samples showing the potential with welds that have a prescribed asymmetry. Weld with a larger leg length against the web plate offer in this study improved fatigue properties and could also offer potential for reduced welding time, a smaller amount of filler material and potentially make the quality inspection more relevant

A Framework for optimised welding of fatigue loaded structures : Applied to gas metal arc welding of fillet welds

Welding is a key process for heavy steel structures, but it is also a weak link in the structure since fatigue fractures in welds are a common cause of failure. This thesis proposes several changes in order to improve the fatigue properties in acost effective way, enabling reduced weight and reduced cost of welded structures. The main idea is to adapt the weld requirements and welding procedures to the load conditions of the weld. This approach ensures that the main focus in the welding process is the critical characteristics of the welds fatigue life properties. The fatigue life critical properties are most often related to the geometrical factors of the weld such as the radius at the weld toe or the penetration in the root. The thesis describes a holistic view of the subject and covers fatigue, weld quality, weld requirements and welding procedures. It becomes evident that the traditional way of working without a direct connection to fatigue is not the best. With an adaptation to the load conditions and fatigue, it is possible to enhance the fatigue life and reduce the welding cost. The main challenge is to connect the welding process, weld requirements and fatigue life properties. It is needed for an optimised welding process of heavy structures subjected to fatigue and toget a predictable fatigue life. Welds optimised for enhanced fatigue life properties are not necessary accepted according to the requirements in a current standard. Several welding procedures are proposed for improving the fatigue life properties of the weld, which indicate a high potential for enhanced fatigue lifeof fillet welds. The idea is to replace the "standard" fillet weld with three different weld types: (i) Welds with deep penetration, (ii) Welds with large weld toe radius and (iii) Welds produced with low cost. Together with customised requirements and reduced over-welding there is a vast potential for reduced weight, reduced cost and increased productivity.The main contribution of this thesis work is the cross-functional studies including design, analysis, production and quality control. This gives a framework for improvements supporting reduced cost and reduced weight of VIII welded structures without reducing the fatigue strength. Many shortcomings have been highlighted to change the welding from a state where welds are done in a way as they "always" have, by tradition, to a more contemporary situation where weld requirements and welding procedures are actively chosen to match the load conditions of the weld. This result in requirements and welding procedures which actually are connected to the fatigue properties as defined by the loading conditions, and where auditors with high probability can say that an accepted weld actually is better than a rejected weld