Structural optimum design of bistable cylindrical shell for broadband energy harvesting application

The shallow cylindrical structure is suitable to develop broadband vibration energy harvesters due to the property of the inherent mechanical bistability. In this letter, the optimum design of the bistable cylindrical shell for broadband energy harvesting application is investigated from the structural point of view. The output power is evaluated by the concept of the harvestable power, which balances the frequency of snap through and the referred output energy associated with each snap through. The non- dimensional harvestable power is analytically expressed as the function of the non-dimensional curvature parameter and one constructed parameter. The universal dependence of the optimal curvature parameter and the associated optimal harvestable power on the constructed parameter is derived, which can be well aooroximated by the linear relation in double logarithmic coordinate.

Optimum structural design of full-scale steel buildings using drift-tribe-charged system search

In this paper,the potential of utilizing improved metaheuristic approaches in optimal design of building structures is concerned.In this regard,the drift-tribe-charged system search algorithm is proposed that the position and velocity updating processes of the charged system search is developed by implementing the mathematical presentation of the free-electron model utilized for metal conductors.In addition,the searching phase of the developed algorithm is also divided into three separate phases in order to improve the convergence capability of the algorithm.By means of these modifications,the exploitation and exploration rates of the standard algorithm are enhanced.In order to determine the ability of the proposed improved metaheuristic method considering some complex optimization problems,a 10-story steel building structure with 1026 structural members alongside a 60-story structure with 8272 members are utilized as numerical examples.The overall capability of the developed metaheuristic approach is compared with other metaheuristics.A total number of 30 independent runs have been conducted for each of the standard and proposed methods while a statistical analysis is also conducted for comparative purposes.The obtained optimum results demonstrated that the proposed metaheuristic approach is capable of preparing better outcomes than other metaheuristics.

Experimental study on driver seat vibration characteristics of crawler-type combine harvester

To improve the driving comfort of combine harvesters,driver seat low-frequency vibration and related driver ride-comfort problems were investigated on a Chinese CFFL-850 crawler-type full-feed combine harvester based on ISO2631.Driver vibration and driving seat transmission characteristics were measured under the following conditions:no-load idling,driving on the road,driving in the field,and simulated harvesting.The root mean square values composite vibration under four conditions were 3.63 m/s^(2),2.35 m/s^(2),3.34 m/s^(2),and 2.67 m/s^(2),respectively.For the same condition,the maximum root mean square scores of vibration component on driver whole-body occurred in the seat support surface(test point 1)and vertical direction(Z direction),which were 3.56 m/s^(2),2.05 m/s^(2),3.15 m/s^(2),and 2.43 m/s^(2),respectively.The test point 2 to test point 1 vertical-transfer function curve trends were nearly identical.Nearly all of the transfer coefficients were greater than 1 in the range of 1-50 Hz,therefore,the seat vibration attenuation performance was poor.Based on the analysis results,the driver seat structure was altered and a verification test was performed.The test results indicated that after an X-damping mechanism was installed,vibration acceleration,on the surface of the seat support under the road-driving conditions,decreased from 2.35 m/s^(2) to 1.68 m/s^(2).Under the simulated harvesting condition,the vibration acceleration decreased from 2.56 m/s^(2) to 1.46 m/s^(2).Nearly all of the seat vertical transfer coefficients were less than 1 within the frequency range of 1-80 Hz,therefore the dynamic comfort of the seat was ameliorated after structural improvement.