Study on the characteristics of pipe buckling strength under pure bending and external stress using nonlinear finite element analysis

Buckling and collapse are important failure modes for laying and operating conditions in a subsea position. The pipe will be subjected to various kinds of loads, i.e., bending moment, external pressure, and tension. Nonlinear finite element analysis was used to analyze the buckling strength of the pipe under pure bending and external pressure. The buckling of elastic and elasto-plastic materials was also studied in this work. The buckling strength due to external pressure had decreased and become constant on the long pipe when the length-to-diameter ratio (L/D) was increased. The non-dimensional parameter (β), which is proportionate to (D/t) (σy/E), is used to study the yielding influence on the buckling strength of pipe under combined bending and external pressure loading. The interaction curves of the buckling strength of pipe were obtained, with various the diameter-to-thickness ratio (D/t) under combination loads of external pressure and bending moment. For straight pipes L/D = 2.5 to 40, D = 1000 to 4000 mm, and D/t = 50 to 200 were set. The curved pipes D/t = 200, L/D =2.5 to 30 have been investigated by changing the radius of curvature-to-diameter ratio (R/D) from 50 to ∞, for each one. With decreasing R/D, the buckling strength under external pressure decreases slightly. This is in contrast to the bending of a curved pipe. When the value of R/D was decreased, the flexibility of the pipe was increased. However, the buckling strength of the pipe during bending was decreased due to the oval deformation at the cross-section.

Nonlinear finite element analysis of lumbar spine under mechanical load

Nonlinear Finite Element Analysis of lumbar spine is carried out using the optimisation software, to determine the effect of accidents on the human spine under mechanical loading. The lower two lumbar section – L4 and L5 of spinal cord is focussed in the present study. A simplified model of the L4-L5 vertebra was prepared. Bone material was taken as nonlinear and disc centre was modelled as hyper elastic. The ligaments are modelled as 1D truss elements. 2 D triangular mesh was generated and converted to 3D tetrahedral mesh. The range of force of 500 N to 1600N and moment of 7500 Nm was given as an input. The relationship of displacement, stress and strain with force is studied. The analysis was carried out and the results obtained depicted that the force varies depending on the impact of accidents. Conclusions are drawn and the relationship at different values of force was obtained.

Application of Nonlinear Finite Element Analysis on Shear-Critical Reinforced Concrete Beams

This paper presents the application of a smeared fixed crack approach for nonlinear finite element analysis of shear-critical reinforced concrete beams. The experimental data was adopted from tests undertaken on twelve reinforced concrete beams by Bresler and Scordelis in 1963, and from duplicate tests undertaken by Vecchio and Shim in 2004. To this end, all beams were modeled in 3D using the software package ATENA-GiD. In the modeling, the nonlinear behaviors of the concrete were represented by fracture-plastic constitutive models, which were formulated within the smeared crack and crack/crush band approaches. The applicability of nonlinear analysis was demonstrated through accurate simulations of the full load-deflection responses, underlying mechanisms, crack patterns, and failure modes of all 24 beams. Detailed documentation of the results is presented to demonstrate the potential and practical value of nonlinear finite element analysis in providing an informed assessment of the safety and performance of reinforced concrete structures.