Evaluation of Deformable Boundary Condition Using Finite Element Method and Impact Test for Steel Tubes

Stainless steel pipelines are crucial components to transportation and storage in the oil and gas industry. However, the rise of random attacks and vandalism on these pipes for their valuable transport has led to more security and protection for incoming surface impacts. These surface impacts can lead to large global deformations of the pipe and place the pipe under strain, causing the eventual failure of the pipeline. Therefore, understanding how these surface impact loads affect the pipes is vital to improving the pipes’ security and protection. In this study, experimental test and finite element analysis (FEA) have been carried out on EN3B stainless steel specimens to study the impact behaviour. Low velocity impact tests at 9 m/s with 16 kg dome impactor was used to simulate for high momentum impact for localised failure. FEA models of clamped and deformable boundaries were modelled to study the effect of the boundaries on the pipes impact behaviour on its impact resistance, using experimental and FEA approach. Comparison of experimental and FE simulation shows good correlation to the deformable boundaries in order to validate the robustness of the FE model to be implemented in pipe models with complex anisotropic structure

A preliminary modelling investigation into the safe correction zone for high tibial osteotomy

Purpose: High tibial osteotomy (HTO) re-aligns the weight-bearing axis (WBA) of the lower limb. The surgery reduces medial load (reducing pain and slowing progression of cartilage damage) while avoiding overloading the lateral compartment. The optimal correction has not been established. This study investigated how different WBA re-alignments affected load distribu- tion in the knee, to consider the optimal post-surgery re-alignment. Methods: We collected motion analysis and 7T MRI data from 3 healthy sub- jects, and combined this data to create sets of subject-specific finite element models (total=45 models). Each set of models simulated a range of potential post-HTO knee re-alignments. We shifted the WBA from its native align- ment to between 40% and 80% medial-lateral tibial width (corresponding to 2.8◦-3.1◦ varus and 8.5◦-9.3◦ valgus), in 3% increments. We then compared stress/pressure distributions in the models. Results/Discussion: Correcting the WBA to 50% tibial width (0◦ varus- valgus) approximately halved medial compartment stresses, with minimal changes to lateral stress levels, but provided little margin for error in under- correction. Correcting the WBA to a more commonly-used 62%-65% tibial width (3.4◦-4.6◦ valgus) further reduced medial stresses but introduced the danger of damaging lateral compartment tissues. To balance optimal loading environment with that of the historical risk of under-correction, we propose a new target: WBA correction to 55% tibial width (1.7◦-1.9◦ valgus), which anatomically represented the apex of the lateral tibial spine. Conclusions: Finite element models can successfully simulate a variety of HTO re-alignments. Correcting the WBA to 55% tibial width (1.7◦-1.9◦ valgus) optimally distributes medial and lateral stresses/pressures