Current Issue : April - June Volume : 2018 Issue Number : 2 Articles : 5 Articles
Multilayered combination of protective structures is an importantmeans of effectively weakening the explosive shockwave. On this\nbasis, a ââ?¬Å?rigid-flexible-rigidââ?¬Â three-layer sealed structure was proposed in this paper and two models for the sealed structure were\ndesigned. Meanwhile, internal explosion tests of the two models were conducted. One model used foam concrete as the energy\nabsorbing material and the other used dense sand. The comparisons between the test results and the computed results obtained\nfrom the formulae were made, and the test results agreed well with the computed results. Test results showed that both models\nhad favorable energy-dissipating capacity, and the model that used foam concrete as the energy absorbing material had a superior\nenergy-dissipating capacity....
We doubt whether the monolithic precast concrete structure could be designed as the cast-in-place structure in high seismic\nintensity area. To solve the puzzle, the 1/5 scaled monolithic precast concrete structure model and cast-in-place structure model\nwere designed and tested by shake table. Comparative analysis between them was made to better understand their seismic behavior.\nBased on the experimental results, the failure pattern and mechanism were different, which was concentrated damage in coupling\nbeam and then extended to shear walls of CIPS, and the weak connections presented cracks between precast elements besides the\ndamage coupling beamof MPCS.Thenatural frequency of MPCS possessed a typical feature for theweakness of connections,which\nwas the initial one greater than that of CIPS and decreased fast after the first waves with PGA of 0.035 g. Acceleration amplifying\nfactors presented variation trend under the different earthquake waves. The distribution of seismic response presented linearity\nalong the height of models in plastic stage and turned into nonlinearity later for severe damage. In general, the MPCS and CIPS\nhad similar seismic responses, except typical characteristics. And they were proven to have better seismic performance without\ncollapse under the high-intensity earthquake waves....
A new impact testing system with an integrated magnetorheological (MR) damper is proposed, and its dynamic characteristics are\nanalyzed. The testing system consists of a velocity generator, impact mass, test mass, spring, and MR damper. In order to tune the\ndual shock-wave profile, a dynamic model was constructed, and the appropriate design parameters of the MR damper were then\ndetermined to produce the required damping force. Following this, an impact testing system was constructed to evaluate the design\nanalysis and field-dependent dual shock-wave profiles. The experimental results of impact test showed that the dual shock-wave\nprofile can be altered by changing the intensity of the magnetic field...
The car front bumper system needs to meet the requirements of both pedestrian safety and low-speed impact which are somewhat\ncontradicting. This study aims to design a new kind of modular self-adaptive energy absorber of the front bumper system which can\nbalance the two performances. The X-shaped energy-absorbing structure was proposed which can enhance the energy absorption\ncapacity during impact by changing its deformation mode based on the amount of external collision energy. Then, finite element\nsimulations with a realistic vehicle bumper system are performed to demonstrate its crashworthiness in comparison with the\ntraditional foam energy absorber, which presents a significant improvement of the two performances. Furthermore, the\nstructural parameters of the X-shaped energy-absorbing structure including thickness (tu), side arc radius (R), and clamping\nboost beam thickness (tb) are analyzed using a full factorial method, and a multiobjective optimization is implemented\nregarding evaluation indexes of both pedestrian safety and low-speed impact. The optimal parameters are then verified, and the\nfeasibility of the optimal results is confirmed. In conclusion, the new X-shaped energy absorber can meet both pedestrian safety\nand low-speed impact requirements well by altering the main deformation modes according to different impact energy levels....
The geometric modeling and finite element modeling of the whole structure of an electrostatic precipitator and its main\ncomponents consisting of top beam, column, bottom beam, and bracket were finished. The strength calculation was completed. As\na result, the design of the whole structure of the electrostatic precipitator and the main components were reasonable, the structure\nwas in a balance state, its working condition was safe and reliable, its stress variation was even, and the stress distribution was\nregular. The maximum von Mises stress of the whole structure is 20.14 MPa. The safety factor was large, resulting in a waste of\nmaterial. An optimization mathematical model is established. Using the ANSYS first-order method, the dimension parameters of\nthe main frame structure of the electrostatic precipitator were optimized. After optimization, more reasonable structural design\nparameters were obtained. The model weight is 72,344.11 kg, the optimal weight is 49,239.35 kg, and the revised weight is\n53,645.68 kg. Compared with the model weight, the optimal weight decreased by 23,104.76 kg and the objective function decreased\nby 31.94%, while the revised weight decreased by 18,698.43 kg and the objective function decreased by 25.84%....
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