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Background Groove pancreatitis (GP) is a rare form of chronic pancreatitis with limited data on its diagnostics and treatment outcomes. The aim of this study was to assess its diagnostics, natural course, and treatment options. Methods The study is a retrospective population-based study from Southern Finland, including all patients with suspected GP between January 2005 and December 2015. Two certified gastrointestinal radiologists re-reviewed the imaging studies. The radiological re-review, clinical judgment, and final histopathology confirmed the GP diagnoses. Results Out of 67 patients with possible GP, 39 patients were considered to have high radiological certainty of GP. Out of these 39, five patients had cancer instead. Thirty-three patients with confirmed GP formed the final study cohort. Patients with GP were mostly middle-aged (median 55 years) men. All had at least moderate alcohol consumption. No intervention was needed in 14 patients. In five-year follow-up all conservatively treated patients became asymptomatic, while 10 out of 16 patients undergoing at least one intervention were asymptomatic at five years. Conclusion The radiological diagnosis of GP is difficult, and a low threshold for cancer suspicion should be kept. Symptoms of GP decrease with time and suggest conservative treatment as the first-line option.

The fatigue strength of thermally cut edges shares many similar features with the fatigue strength of a welded joint. Current design standards are valid for geometrically simple, straight, flame-cut edges made of mild steel. However, the applicability of current recommendations is questionable if the geometry is more complicated, if a different (thermal) cutting process is employed, or if any high-strength steel is used. In this study, conventional fatigue analysis methods are applied in order to explain the experimental results obtained by conducting fatigue tests on a cut component made of different steel grades. Since those methods did not explain the experimental results properly, a novel fatigue analysis method for plates with a thermally cut edge was created. This method is a parallel approach to that recently developed at Lappeenranta University of Technology for analyzing fatigue of a welded joint. In addition to the general stress range, this method also takes into account the structural and local geometry of the cut detail, surface roughness, residual stresses due to the cutting process, the external stress ratio, and the effect of the steel grade. The method agreed well with the test results and can be recommended as a new general approach for analyzing the fatigue of cut edges.

Experimental fatigue data for ASW, HFMI and LTT treated joints under VA tensile loading were analyzed using the 3R-method that takes the local stress ratio into account. The main focus of the work was study of how the new approach predicts the fatigue strength of welded joint under VA loading. Equivalent CA notch stress ranges at failure were calculated using a mean master S-N-curve and Miner’s linear cumulative damage rule. All calculated equivalent stress ranges at failure were above the characteristic master S-N-curve, which corresponds to a damage sum of 0.174 at failure, in a case-independent reference notch stress system.

This study considers the effect of bending loading and the symmetry of joints on the fatigue strength of transverse non-load carrying attachments. Conventionally, the fatigue strength of a welded joint has been determined without taking these factors into account. Experimental and finite element analyses were carried out and both methods showed that both loading type and symmetry have an influence on the fatigue resistance of a welded joint. Under tensile loading, the fatigue strength of asymmetric T-joints was higher than that of symmetric X-joints. Respectively, the fatigue resistance of tested joints improved explicitly when the external loading was bending. The finite element analysis was in good agreement with the test results in the joints subjected to tension but gave very conservative results in the joints subjected to bending.

Recently, the capacity of welded joints made of direct-quenched ultra-high-strength steel (with nominal yield strength of 960 MPa) has been increasingly investigated. However, less attention has been paid to joints subjected to shear loading. In this research, work the punching shear capacity of a plated structure was studied. The effects of cold forming and welding were also included in the study. The capacities based on analytical calculations were compared with experimental results and values obtained by FEA. The results matched each other quite well. The experimental results proved that if the heat input is moderate the welding alone has only a small effect on the punching shear capacity. However, the heat input together with cold forming seems to decrease the load carrying capacity more significantly.

Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading were analysed using the effective notch stress system and a new master curve analysis that takes the local stress ratio, Rlocal, into account. The local stresses needed for computation of Rlocal are calculated with the notch strain approach in conjunction with the reference radius concept. The main focus was to predict with the derived master curve the fatigue strength of peened butt-welded joints. The lowest surface residual stresses after peening were first estimated based on reported measurements and an analytical lower bound result. The predictions showed quite similar strength dependences and FAT values as reported for high-frequency mechanical impact treated welds for applied stress ratio R = 0.1. The benefits of peening reduce faster for higher strength steels when R increases. When R = 0.5, the FATs are practically the same for all steel grades.

Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading (secondary bending included) were analyzed using the nominal stress system and the notch stress system. Two approaches were used; a standard fitting procedure and minimization of the sum of squared perpendicular distances from a line with a fixed and free slope. In all cases, the latter method gave better agreement between the experimental and predicted fatigue life and fatigue strength. The analyses showed both with all broken specimen data included and with reduced data that the FAT225 curve, as recommended by IIW, might be too optimistic for the notch stress approach in the case of butt-welded joints in as-welded condition. It was also found that use of the local stress ratio instead of the applied stress ratio might explain many issues concerning current observations and apparent inconsistencies in reported literature.

The capacity of the welded joint can be defined in terms of load-carrying and deformation capacities. For ultra-high-strength structural steels, such as S960 QC, the deformation capacity is a crucial structural property. In this paper, the rotation capacity of fillet weld joints was investigated experimentally and analytically. The rotation capacity of the fillet weld joints under pure bending load is calculated analytically by a model using the elastic peak stress and plastic limit state. The experimental test proved that the plastic load-carrying capacities required by the standards were reached. Additionally, the tests showed that sufficient deformation capacities can be obtained, although fully plastic rotation hinges could not always be reached. The experimental results were in good agreement with the analytically calculated capacities. However, there is a need for some design limitations before more results are available.

The effect of weaved weld toe geometry on the fatigue strength of S960 steel grade fillet welds has been studied by means of experimental testing and finite element analysis. The comparisons have been made between normal straight weld toe lines and weaved weld toe lines by using the weld toe radius and structural stress fatigue class (FAT) value as reference values. The effective notch stress approach was utilized to conduct finite element (FE) analyses on weaved weld toe geometry, and the results were compared with the experimental results. The FE analysis showed quite good agreement with the experimental test results, although residual stresses or heat-affected zone (HAZ) softening in welded joint were not included in the modeling. The experimental tests also indicated that it is possible to achieve high fatigue properties for ultra-high-strength steel (UHSS) fillet welded joints without any postweld treatments. By taking account all the essential factors—joint geometry, welding metallurgy, and residual stresses—the reached fatigue strength of UHSS weldments can be much higher than normal fatigue resistance values presented in standards and recommendations.

This study investigated the residual strength of a precracked cold-formed rectangular hollow section made of novel ultra-high-strength steel. The primary goal was to experimentally discover the residual strength of the structure when used in low temperature service conditions. The secondary goal was to predict the residual strength by using a J-integral approach with nonlinear finite element calculations and to compare these predictions with measured results. The experimental tests were carried out with a beam in four-point bending loading. The test specimens were taken from a cold-formed rectangular hollow section fabricated from direct quenched (untempered) ultra-high-strength steel S960 QC omitting the annealing in the fabrication process. The tests for final failure were carried out at −40 °C, with the exception of the first pilot test. There were two kinds of tests: (1) the beam was cyclically loaded until the final fracture or the fatigue precrack was first introduced and (2) the specimen was then subjected to a quasistatic bending loading condition until it failed. The new experimental results matched well with our predictions, and both confirmed the high toughness of ultra-high-strength steel in beam construction studied, even at a low ambient temperature.

The ultimate load-bearing capacity of typical fillet welded joints made of ultra high-strength steel (UHSS) S960 has been investigated. The aim of the work has been to assess the validity of current design rules for UHSS and possibly define new design criteria. Experimental testing and nonlinear finite element analysis (FEA) were applied to define the capacity of fillet welded joints. Joint geometries and material properties were measured for both filler and base materials. In comparison with current design rules, the experimental results showed that the fillet welded joints had adequate load-carrying capacity presuming that adequate weld quality is achieved in the joint fabrication. Load-carrying capacities and rupture modes in welds defined by FEA were in agreement with experimental results. The experimental deformation capacities of some of the joints were found to be critical, but the capacities can be improved by the use of undermatched filler metals. Heat input control is essential in the fabrication of welded connections made of UHSS and thus an additional failure criteria should be considered in design codes due to the softening effect in HAZ.

In this paper, a FITNET analysis of the structural element made of ultra high strength steel was performed. The critical loadings at failure were estimated at three levels of analysis and two temperatures, -40°C and +20°C. The results of the analysis were verified by full scale experiments at -40°C, which proved that the predictions of the critical moment provide a sufficient safety margin.

The primary goal of this study was to develop an equation relating the geometric parameters to fatigue strength which can be used is routine design assessment. To attain this, the influence of local geometrical weld variations on the fatigue strength of non-load-carrying cruciform fillet welded joints were systematically studied using plane strain linear elastic fracture mechanics (LEFM). The effects of weld toe radius, flank angle and weld size were considered. Both continuous weld toe cracks and semi-elliptical toe cracks with alternate pre-existing defect depths were considered. A previously developed experimental crack aspect ratio development curve was used for assessing the growth of the semi-elliptical cracks using 2D FE models. A total of 152 experimental fatigue data points from six published studies of welded cruciform joints were evaluated. Details of the actual weld toe radius, flank angle and weld size were available for these joints. For the high quality welds evaluated, an assumed initial crack depth of 0.05 mm was found to correlate best with the experimental data. Of all the geometric parameters considered analytically, weld toe radius was found to have the most dramatic influence on fatigue life. A simple equation is proposed which relates welded joint fatigue strength to the ratio weld toe radius/plate thickness for high quality welds.

— A single-crack evolution model with eight degrees of freedom and an isotropic Paris law constant was used to simulate fatigue crack growth at the surface of a plate, and from the toe of a transverse non-load-bearing fillet weld in a T-joint. A planar crack was assumed. In the simulated cases fatigue cracks usually propagate through the plate thickness under the dominant effect of the mode I stress system. The crack front shape was modelled as a broken line. The straight sided crack tip elements were tangential to the direction of an initial elliptical crack front. It was found that the simple eight degrees of freedom model performed well and the predicted aspect ratio development was in good agreement with experimental data.

The goal of this investigation was to study the effect of local geometrical variations of the weld on the fatigue strength. Therefore the fatigue behaviour of non-load-carrying cruciform fillet welded joint under tensile loading has been studied parametrically. Several two-dimensional (2D) finite element models of the joint were analysed using plane strain linear elastic fracture mechanics (LEFM) calculations in order to get the magnification function M k . A maximum tangential stress criterion was used to predict the crack growth direction under mixed mode K I – K II conditions. The derived M k solution was then applied both for continuous weld toe cracks and also for semi-elliptical toe cracks at the deepest point of the crack front. An experimental crack aspect ratio development curve was used for propagating semi-elliptical cracks. The as-welded condition was assumed with the result that no crack initiation period was considered and stress ranges were fully effective. The Paris crack growth law was used to predict the growth rate. The effects of weld toe radius, flank angle and weld size on the fatigue strength were systematically studied. Finally, predicted fatigue strength values corresponding to different assumed crack sizes were compared with the available test results.

Many welded lap joints are subject to fluctuating loads, and fatigue failure plays a dominant role in the failure of such structures. Based on the concepts of linear elastic fracture mechanics, the effects of weld geometry, load conditions and the boundary constraints on fatigue strength of a ferrite–pearlite steel lap joint were investigated in this paper using the finite element method. Paris's power law was used to predict the fatigue life of the joints. Various weld geometry including the leg length, flank angle and the size of lack-of-penetration were considered during the calculation of fatigue strengths. The loads include tension, bending and their combinations. It was found that the existence of a root crack has no influence on the fatigue strength of the joint, under the relevant load conditions. The existence of a toe crack is also of no influence on the fatigue strength of the joint if the applied loads, e.g. DOB>0 in this paper, produce a compressive stress field at the top region of the main plate. For a lap joint with a free transverse (Y direction in this paper) boundary constraint at the main plate, a joint with a smaller size of lack-of-penetration, a reasonably large weld leg and smaller flank angle is recommended to be used in engineering practice, in order to obtain a higher fatigue strength. For a lap joint, with transverse fixed boundary constraint at the main plate, the fatigue strength increases with a decrease of weld size but the influence of flank angle depends on the type of load carried. It was also found that the size reduction in FE model is a significant influence on the calculated fatigue strength; the use of reduced size FE model gives a much higher overestimate of fatigue strength of the joint.