The Battelle structural stress method is examined for the evaluation of multiaxial loading fatigue behavior in welded structures. Even though the structural stress and its master S-N curve approach have been mainly focused on normal loading dominant (Mode I) failure cases, the evaluations on multiaxial loading weld fatigue using structural stress parameters have been relatively recently performed such as using the modified Gough ellipse [1] and the path-dependent maximum range (PDMR) cycle counting procedure [2]. In this article, in order to evaluate the multiaxial fatigue behavior, an effective equivalent structural stress range (EESS) parameter is defined as a von Mises form of combined normal and in-plane shear equivalent structural stress ranges. The newly developed in-plane shear equivalent structural stress range for in-plane shear dominant loading (Mode III) is introduced. This in-plane shear equivalent structural stress range parameter has been formulated based on the evaluation of fatigue behavior under in-plane shear loading. Also, the EESS parameter is a function of damage parameter based on the PDMR procedure. In this article, the procedure employing the EESS parameter is evaluated and validated using published weld fatigue data. The multiaxial fatigue date is consolidated within a small scatter band regardless of in-phase, out-of-phase, and non-proportional loading as well as torsional loading. Finally, the design master S-N curve is proposed for multiaxial loading weld fatigue. It is found that the dimensionless bend ratio parameter, Iτ (rτ)1/mτ for in-plane shear loading is a much more significant correction than that for normal loading when the ratio of bending structural stress to the total structural stress, rτ increases. This procedure will be beneficial for fatigue design with preventing over-conservatism.

Purpose: the aim of the computational 3D-finite element study is to evaluate the influence of an augmented sinus lift with additional inserted bone grafting. The bone graft block stabilizes the implant in conjunction with conventional bone augmentation. Two finite element models were applied: the real geometry based bone models and the simplified geometry models. The bone graft block was placed in three different positions. The implants were loaded first with an axial force and then with forces simulating laterotrusion and protrusion. This study examines whether the calculated stress behavior is symmetrical for both models. Having established a symmetry between the primary axis, the laterotrusion and protrusion behavior reduces calculation efforts, by simplifying the model. Material and Methods: a simplified U-shaped 3D finite element model of the molar region of the upper jaw and a more complex anatomical model of the left maxilla with less cortical bone were created. The bone graft block was placed in the maxillary sinus. Then the von Mises stress distribution was calculated and analyzed at three block positions: at contact with the sinus floor, in the middle of the implant helix and in the upper third of the implant. The two finite element models were then compared to simplify the modelling. Results: the position of the bone graft block significantly influences the magnitude of stress distribution. A bone graft block positioned in the upper third or middle of the implant reduces the quantity of stress compared to the reference model without a bone graft block. The low bone graft block position is clearly associated with lower stress distribution in compact bone. We registered no significant differences in stress in compact bone with regard to laterotrusion or protrusion. Conclusions: maximum values of von Mises stresses in compact bone can be reduced significantly by using a bone graft block. The reduction of stress is nearly the same for positions in the upper third and the middle of the implant. It is much more pronounced when the bone graft block is in the lower third of the implant near the sinus floor, which appeared to be the best position in the present study.

Incident analyses over the last several decades consistently show that outside force is the largest single cause of reportable incidents for the hazardous-liquid- and gas-transmission pipeline systems throughout the world. This paper addresses outside-force incidents due to “acts of man” leading to mechanical damage in the form of dents. As such incidents are significant worldwide, there are worldwide efforts to prevent future incidents, and develop approaches to manage this threat. This paper evaluates the criticality of dents in a more general framework than acceptable dent depth used in codes. This analysis is done with reference to typical line pipe mechanical properties, as well as less know parameters like true -fracture ductility and fracture-initiation toughness. Analyses results characterize severity and rank criticality as a function of dent type in reference to the general PRCI model for mechanical damage. Results are presented that show current code-acceptance criteria for dents are over conservative in general, sometimes significantly, particularly for plain dents. Full-scale test data are introduced to support the analytical results. Results are also presented to assist in evaluating the utility and accuracy of ILI deformation tools, and their calibration with reference to measured field dent size.

2 AbstractPurpose: The aim of the present experimental 3D-finite element study was to evaluate the influence of an augmented sinus lift with an additional inserted bone graft block. The bone graft block stabilizes the implant in addition to conventional augmented bone. We placed the block in three different positions. The implants were loaded with axial force and forces secondary to laterotrusion and protrusion. Material and Methods:A simplified U-shaped 3D finite element model of the upper jaw and a more complex anatomical model of the left maxilla were created. The bone graft block was placed in three positions: in the lower third in contact with the sinus floor, the middle, and the upper third of the implant. Van Mises' stress distribution was calculated and analyzed for the different models. We also compared the complex anatomical model with the simplified one. Results:The position of the bone graft block significantly influences the magnitude of stress distribution. A bone graft block positioned in the upper third or middle of the implant reduces the quantity of stress compared to the reference model without a bone graft block. The low bone graft block position is clearly associated with lower stress distribution in compact bone.We registered no significant differences in stress in compact bone with regard to laterotrusion or protrusion. Conclusions:Maximum values of von Mises stresses in compact bone can be reduced significantly by using a bone graft block. The reduction of stress is nearly the same for positions in the upper third and the middle of the implant. It is much more pronounced when the bone graft block is in the lower third of the implant near the sinus floor, which appeared to be the best position in the present study.

Modern wind turbines, which are usually made of composite materials, are fatigue critical structures that are subjected to variable multi-axial fatigue loading. Therefore, they should be designed as safely as necessary to withstand the fatigue loads over the designed life time. Path-Dependent Maximum Range (PDMR) is a multi-axial fatigue life assessment tool developed by Battelle researchers. PDMR has been successfully applied to fatigue analysis of isotropic structures under general variable amplitude, multi-axial fatigue loading histories. The effectiveness of the PDMR method has been validated by its ability to correlate a large amount of fatigue data available in the literature. For uniaxial loading data, PDMR gives exactly the same results as ASTM standard Rainflow cycle counting method. In this paper, the PDMR method is extended to composite materials, such as glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP). The proposed multi-axial fatigue damage model effectively correlates fatigue lives of unidirectional composites for various off-axis ply angles under cyclic tensile loading. With this extended capability, the PDMR can now be used to assess the multi-axial fatigue life of composite structures used in wind energy industry.

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In this paper, a path-dependent maximum range (PDMR) multi-axial cycle counting method is presented for performing fatigue life assessment of engineering components under general variable-amplitude multi-axial loading conditions. The PDMR method has two distinct features: (a) multi-axial cycle counting, in which the cycle counting is conducted in an equivalent stress or strain space, and (b) explicit loading path dependency. For uniaxial loading data, the PDMR and the ASTM standard Rainflow methods both generate the same counting results. The path-length, a function of both normal and shear stress components on a critical crack plane, is proposed as a fatigue damage parameter for ductile materials. PDMR can be applied to welded structures, in which the crack plane is usually known in advance, as well as to non-welded structures, in which the critical plane approach can be implemented into PDMR to determine both the fatigue crack orientation and the associated fatigue damage. The effectiveness and robustness of the PDMR method have been validated by its ability to correlate nominal stress and Battelle structural stress fatigue data including pure-bending, pure-torsion, in-phase, and out-of-phase loading conditions for welded tube-to-flange steel structures. The relationship between the data correlations based on nominal stress and Battelle structural stress for these loading conditions is illustrated. Finally, one-parameter and two-parameter equivalency approaches for PDMR operation are also introduced and discussed.

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