Search

Background: The aim of this study is to conduct a comparative evaluation of different designs of clear aligners and examine the disparities between clear aligners and fixed appliances. Methods: 3D digital models were created, consisting of a maxillary dentition without first premolars, maxilla, periodontal ligaments, attachments, micro-implant, 3D printed lingual retractor, brackets, archwire and clear aligner. The study involved the creation of five design models for clear aligner maxillary anterior internal retraction and one design model for fixed appliance maxillary anterior internal retraction, which were subsequently subjected to finite element analysis. These design models included: (1) Model C0 Control, (2) Model C1 Posterior Micro-implant, (3) Model C2 Anterior Micro-implant, (4) Model C3 Palatal Plate, (5) Model C4 Lingual Retractor, and (6) Model F0 Fixed Appliance. Results: In the clear aligner models, a consistent pattern of tooth movement was observed. Notably, among all tested models, the modified clear aligner Model C3 exhibited the smallest differences in sagittal displacement of the crown-root of the central incisor, vertical displacement of the central incisor, sagittal displacement of the second premolar and second molar, as well as vertical displacement of posterior teeth. However, distinct variations in tooth movement trends were observed between the clear aligner models and the fixed appliance model. Furthermore, compared to the fixed appliance model, significant increases in tooth displacement were achieved with the use of clear aligner models. Conclusions: In the clear aligner models, the movement trend of the teeth remained consistent, but there were variations in the amount of tooth displacement. Overall, the Model C3 exhibited better torque control and provided greater protection for posterior anchorage teeth compared to the other four clear aligner models. On the other hand, the fixed appliance model provides superior anterior torque control and better protection of the posterior anchorage teeth compared to clear aligner models. The clear aligner approach and the fixed appliance approach still exhibit a disparity; nevertheless, this study offers a developmental direction and establishes a theoretical foundation for future non-invasive, aesthetically pleasing, comfortable, and efficient modalities of clear aligner treatment. [ABSTRACT FROM AUTHOR]

Bridge structures are often vulnerable to vehicle collisions, necessitating innovative solutions to enhance safety. This paper introduces a concept employing energy-absorbing crash dampers to safeguard bridge structures. The primary objective is to optimize energy dissipation while ensuring uninterrupted bridge functionality. Utilizing the finite element modeling approach, and incorporating realistic constitutive relationships and boundary conditions, simulations were performed to encompass X-shaped damper impact tests and collisions involving trucks with steel-reinforced concrete columns. The study affirms the effectiveness of the numerical model in simulating the dynamic response of steel dampers and column structures under vehicle impacts. Leveraging this modeling approach, this research compares the anti-collision performance of urban bridge structures, both with and without the proposed bridge pier. The methodology involves two key steps: first, a response surface optimization analysis is conducted for the primary energy-absorbing component, the anti-collision hollow diamond-shaped damper, determining optimal dimensions for the device at varying vehicle collision speeds. Second, a comparative study explores failure modes, collision capabilities, deflection changes, and energy absorption of bridge structures with and without the energy-absorbing crash dampers under vehicle impacts. Subsequently, this study performs an optimization design and calculation for the bridge structures. The outcomes reveal that the bridge with the pier experiences a substantial reduction in impact peak force. The damper effectively absorbs part of impact energy, with the optimized damper demonstrating superior energy absorption. • This paper presents for the first employing energy-absorbing crash dampers to safeguard bridge structures against impact. • The optimal dimensions of anti-collision hollow diamond-shaped damper is determined at varying vehicle collision speeds. • The dynamic responses of bridge structure with energy-absorbing crash dampers under lateral impact were obtained and analyzed. [ABSTRACT FROM AUTHOR]

To obtain the optimal size and shape of X-type energy dissipation device, 20 specimens were tested using a drop hammer impact test machine, then the finite element model was established by using the software LS-DYNA. The dynamic responses of X-type energy dissipation device including failure mode, impact force, displacement and energy absorption were obtained and analyzed with emphasis on the effect of the height reduction parameter a , length reduction coefficient b and high span ratio c. The effectiveness of the finite element model is verified by comparing the simulation results with the experimental results. The finite element model is then used to optimize the X-type energy dissipation device. The height reduction parameter a and high span ratio c were taken as the optimization parameters, and the strain uniformity was taken as the target for improvement. Through regression analysis, the formulas of height reduction parameter a , height span ratio c and strain uniformity degree are derived. After four levels of optimizations, the optimized shape of the X-type energy dissipation device is obtained, and its energy dissipation performance is significantly improved compared with that of the traditional X-type energy dissipation device. • It is a pioneering study on the lateral impact responses of X-type energy dissipation devices. • This paper presents the experimental study and FEA results of X-type energy dissipation devices under drop hammer impact. • The dynamic responses of X-type energy dissipation devices under lateral impact were obtained and analyzed. • The X-type energy dissipation devices optimized to achieve the best impact resistance. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the impact resistance and energy dissipation capacity of a new type of multi-cell sandwich aluminum alloy plate filled with aluminum foam, in comparison to the single-cell structure. To achieve this goal, 30 sandwich aluminum alloy plates were tested using a drop hammer test machine, varying impact velocity, wall thickness, and the number of internal diaphragms. The results were analyzed and finite element analysis was conducted to explore the energy dissipation mechanisms and the effect of aluminum foam on multi-cell plates. The findings revealed three failure modes and three stages of the impact force time history curve. Multi-cell plate exhibited showed much better specific energy absorption compared with the single-cell plate. Taking an example displacement of 22.5 mm, which differentiates the specific energy absorption the most between the two types of structures, the multi-cell plate exhibited an average increase of 332% in specific energy absorption compared to the single-cell plate. The numerical simulations were consistent with experimental results and highlighted the contribution of different components to energy dissipation in both structures. • This paper presents a new type of multi-cell sandwich aluminum alloy plate filled with aluminum foam. • The experiments and FEA are carried out on single-cell and multi-cell sandwich aluminum alloy plates filled with aluminum foam. • The dynamic responses of single-cell and multi-cell plates under impact were obtained and analyzed. • The FEA was carried out to explore the energy dissipation mechanism of single-cell and multi-cell plates. [ABSTRACT FROM AUTHOR]