To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response a...To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response and crack closure effect is proposed.In line with the theory of mechanical vibration,a dynamic model of crane structure during the working cycle is constructed,and dynamic coefficients under diverse actions are analysed.Calculation models of the internal force dynamic change process of dangerous cross-sections and a simulation model of first principal stress-time history are established by using the steel structure design criteria,which is utilised to extract the change of first principal stress of danger points over time.Then,the double-parameter stress spectrum is obtained by the rain flow counting method.The fatigue life calculation formula is corrected by introducing a crack closure parameter that can be calculated by the stress ratio and the effective stress ratio.Under the finite element model imported into Msc.Patran,crack propagation analysis is performed by the growth method in the fatigue integration module Msc.Fatigue.Taking the metal structure of a 100/40t-28.5m foundry crane with track offset as an example,the accuracy of calculation results and the feasibility and applicability of the proposed method are verified by theoretical calculation and finite element simulation,which provide a theoretical basis for improvement of the fatigue resistance design of foundry cranes.展开更多
Static and dynamic compression tests were carried out on mortar and paste specimens of three sizes（Ф68 mm×32 mm,Ф59 mm×29.5 mm and Ф32 mm×16 mm）to study the influence of specimen size on the compre...Static and dynamic compression tests were carried out on mortar and paste specimens of three sizes（Ф68 mm×32 mm,Ф59 mm×29.5 mm and Ф32 mm×16 mm）to study the influence of specimen size on the compression behavior of cement-based materials under high strain rates.The static tests were applied using a universalservo-hydraulic system,and the dynamic tests were applied by a spilt Hopkinson pressure bar（SHPB）system.The experimentalresults show that for mortar and paste specimens,the dynamic compressive strength is greater than the quasi-static one,and the dynamic compressive strength for specimens of large size is lower than those of smallsize.However,the dynamic increase factors（DIF）has an opposite trend.Obviously,both strain rate and size effect exist in mortar and paste.The test results were then analyzed using Weibull,Carpinteriand Ba？ant＇s size effect laws.A good agreement between these three laws and the test results was reached on the compressive strength.However,for the experimentalresults of paste and cement mortar,the size effect is not evident for the peak strain and elastic modulus of paste and cement mortar.展开更多
基金the National Science-technology Support Projects for the 13th Five-year Plan(2017YFC0805703-4).
文摘To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response and crack closure effect is proposed.In line with the theory of mechanical vibration,a dynamic model of crane structure during the working cycle is constructed,and dynamic coefficients under diverse actions are analysed.Calculation models of the internal force dynamic change process of dangerous cross-sections and a simulation model of first principal stress-time history are established by using the steel structure design criteria,which is utilised to extract the change of first principal stress of danger points over time.Then,the double-parameter stress spectrum is obtained by the rain flow counting method.The fatigue life calculation formula is corrected by introducing a crack closure parameter that can be calculated by the stress ratio and the effective stress ratio.Under the finite element model imported into Msc.Patran,crack propagation analysis is performed by the growth method in the fatigue integration module Msc.Fatigue.Taking the metal structure of a 100/40t-28.5m foundry crane with track offset as an example,the accuracy of calculation results and the feasibility and applicability of the proposed method are verified by theoretical calculation and finite element simulation,which provide a theoretical basis for improvement of the fatigue resistance design of foundry cranes.
基金Funded by the National Natural Science Foundation of China(No.51509078)the Natural Science Foundation of Jiangsu Province(No.BK20150820)
文摘Static and dynamic compression tests were carried out on mortar and paste specimens of three sizes（Ф68 mm×32 mm,Ф59 mm×29.5 mm and Ф32 mm×16 mm）to study the influence of specimen size on the compression behavior of cement-based materials under high strain rates.The static tests were applied using a universalservo-hydraulic system,and the dynamic tests were applied by a spilt Hopkinson pressure bar（SHPB）system.The experimentalresults show that for mortar and paste specimens,the dynamic compressive strength is greater than the quasi-static one,and the dynamic compressive strength for specimens of large size is lower than those of smallsize.However,the dynamic increase factors（DIF）has an opposite trend.Obviously,both strain rate and size effect exist in mortar and paste.The test results were then analyzed using Weibull,Carpinteriand Ba？ant＇s size effect laws.A good agreement between these three laws and the test results was reached on the compressive strength.However,for the experimentalresults of paste and cement mortar,the size effect is not evident for the peak strain and elastic modulus of paste and cement mortar.
