In order to evaluate the ride quality of the soil compactor cab supplemented by the auxiliary hydraulic mounts (AHM), a nonlinear dynamic model of the soil compactor interacting with the off-road deformable terrain is...In order to evaluate the ride quality of the soil compactor cab supplemented by the auxiliary hydraulic mounts (AHM), a nonlinear dynamic model of the soil compactor interacting with the off-road deformable terrain is established based on Matlab/Simulink sofware. The power spectral density (PSD) and the weighted root mean square (RMS) of acceleration responses of the vertical driver s seat, the cab s pitch and roll angle are chosen as objective functions in low-frequency range. Experimental investigation is also used to verify the accuracy of the model. The influence of the damping coefficients of the AHM on the cab s ride quality is analyzed, and damping coefficients are then optimized via a genetic algorithm program. The research results show that the cab s rubber mounts added by the AHM clearly improve the ride quality under various operating conditions. Particularly, with the optimal damping coefficients of the front-end mounts c a 1,2 = 1 500 N · s/m and of the rear-end mounts c a 3,4 =2 335 N · s/m, the weighted RMS values of the driver s seat, the cab s pitch and roll angle are reduced by 22.2%, 18.8%, 58.7%, respectively. Under the condition of the vehicle travelling, with the optimal damping coefficients of c a 1,2 = 1 500 N · s/m and c a 3,4 =1 882 N · s/m, the maximum PSD values of the driver s seat, the cab s pitch and roll angle are clearly decreased by 36.7%, 54.7% and 50.6% under the condition of the vehicle working.展开更多
The hot deformation behaviors of two medium carbon ultra-high strength steels with different niobium contents were investigated by using Zener-Hollmom parameter and processing map,and the effect of niobium addition on...The hot deformation behaviors of two medium carbon ultra-high strength steels with different niobium contents were investigated by using Zener-Hollmom parameter and processing map,and the effect of niobium addition on the hot deformation behavior of medium carbon steel was determined.The hot compression tests were conducted on a Gleeble-3500 thermo-mechanical simulator deformed at temperatures from 850 to 1 200 ℃ and strain rates from 0.001 to 1 s^-1.The processing maps of two test steels were built at a true strain of 0.7 based on dynamic materials model（DMM）.There are two peak efficiency domains and two flow instability regions in both test steels.However,the peak efficiency domains of Nb-bearing steel move to higher temperature due to the inhibition of dynamic recrystaUization（DRX）,and the instability domains of Nb-bearing steel are enlarged due to the precipitation of Nb-containing particles during hot deformation.The optimum process parameters of Nb-bearing and Nb-free steels for industrial production were determined according to the processing map and the microstructural observation.展开更多
The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of opt...The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope（OM）, scanning electron microscope（SEM）, electron backscattering diffraction（EBSD） and transmission electron microscope（TEM）, and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. With decreasing heat input, both bainite packet and block are significantly refined, and the toughness has an increasing tendency due to the grain refinement. The fracture surfaces all present cleavage or fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of high strength bridge steel.展开更多
基金The Science and Technology Support Program of Jiangsu Province(No.BE2014133)the Prospective Joint Research Program of Jiangsu Province(No.BY2014127-01)
文摘In order to evaluate the ride quality of the soil compactor cab supplemented by the auxiliary hydraulic mounts (AHM), a nonlinear dynamic model of the soil compactor interacting with the off-road deformable terrain is established based on Matlab/Simulink sofware. The power spectral density (PSD) and the weighted root mean square (RMS) of acceleration responses of the vertical driver s seat, the cab s pitch and roll angle are chosen as objective functions in low-frequency range. Experimental investigation is also used to verify the accuracy of the model. The influence of the damping coefficients of the AHM on the cab s ride quality is analyzed, and damping coefficients are then optimized via a genetic algorithm program. The research results show that the cab s rubber mounts added by the AHM clearly improve the ride quality under various operating conditions. Particularly, with the optimal damping coefficients of the front-end mounts c a 1,2 = 1 500 N · s/m and of the rear-end mounts c a 3,4 =2 335 N · s/m, the weighted RMS values of the driver s seat, the cab s pitch and roll angle are reduced by 22.2%, 18.8%, 58.7%, respectively. Under the condition of the vehicle travelling, with the optimal damping coefficients of c a 1,2 = 1 500 N · s/m and c a 3,4 =1 882 N · s/m, the maximum PSD values of the driver s seat, the cab s pitch and roll angle are clearly decreased by 36.7%, 54.7% and 50.6% under the condition of the vehicle working.
基金Supported by the National 863 Program of China(No.2015AA042505)Hubei Department of Education Youth Program(No.Q20123001)+1 种基金Hubei Province Natural Science Foundation(No.2014 cfb177)Wuhan Huaxia Fine Blanking Technology Co.,LTD Program(No.YYYY2014-015)
文摘The hot deformation behaviors of two medium carbon ultra-high strength steels with different niobium contents were investigated by using Zener-Hollmom parameter and processing map,and the effect of niobium addition on the hot deformation behavior of medium carbon steel was determined.The hot compression tests were conducted on a Gleeble-3500 thermo-mechanical simulator deformed at temperatures from 850 to 1 200 ℃ and strain rates from 0.001 to 1 s^-1.The processing maps of two test steels were built at a true strain of 0.7 based on dynamic materials model（DMM）.There are two peak efficiency domains and two flow instability regions in both test steels.However,the peak efficiency domains of Nb-bearing steel move to higher temperature due to the inhibition of dynamic recrystaUization（DRX）,and the instability domains of Nb-bearing steel are enlarged due to the precipitation of Nb-containing particles during hot deformation.The optimum process parameters of Nb-bearing and Nb-free steels for industrial production were determined according to the processing map and the microstructural observation.
基金Supported by the National 863 Program of China(No.2015AA042505)State Key Laboratory of Materials Processing and Die&Mould Technology of Huazhong University of Science and Technology(No.P2018-014)Major Science and Technology Project in Guangdong Province(No.2014B010130001)
文摘The high strength bridge steel was processed with the simulated coarse grain heat affected zone（CGHAZ） thermal cycle with heat input varying from 30 to 60 kJ/cm, the microstructures were investigated by means of optical microscope（OM）, scanning electron microscope（SEM）, electron backscattering diffraction（EBSD） and transmission electron microscope（TEM）, and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. With decreasing heat input, both bainite packet and block are significantly refined, and the toughness has an increasing tendency due to the grain refinement. The fracture surfaces all present cleavage or fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of high strength bridge steel.
