Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality.In this paper,material repla...Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality.In this paper,material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight.Through finite element simulations,full frontal,offset frontal,and side crashes of a full car model are evaluated for peak acceleration,intrusion distance,and the internal energy absorbed by the structural parts.In addition,the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints.The wall thicknesses of twenty-two parts are considered as the design variables.Latin Hypercube Sampling is used to sample the design space,while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies.A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints.Using Sequential Quadratic Programming,the design optimization problem is solved with the results verified by finite element simulations.The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.展开更多
The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） tec...The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.展开更多
A version of an electric vehicle was developed and designed for the US market on the basis of the required domestic body structure.When compared with the original car,the new car body design leads to two major technic...A version of an electric vehicle was developed and designed for the US market on the basis of the required domestic body structure.When compared with the original car,the new car body design leads to two major technical difficulties.First,the installation of high-voltage components such as the battery pack and other new energy sources increases the vehicle weight and occupies a great deal of its structural space;this limits the impact paths and the use of traditional structural designs,which greatly increases the design difficulty.Second,the USA,as an advanced automobile-using country,has well-developed laws and regulations for collision standards,vehicle operating conditions and evaluation standards.Using a combination of butterfly diagram analysis,bending moment management,section forces and other computer-aided simulation and analysis techniques,this paper presents a body structure design that can achieve a“GOOD”evaluation under the US Insurance Institute for Highway Safety(IIHS)side impact body structure conditions by optimizing the force transfer path,the B-pillar deformation mode and the threshold support structure.The threshold support structure supports realization of the“GOOD”rating for IIHS side impact and helps the body to meet the crash requirements of the Federal Motor Vehicle Safety Standard FMVSS214 and the US New Car Assessment Program(NCAP)requirements for side impact at 32 km/h and 75°angular pole impact.展开更多
基金This material is based on the work supported by the U.S.Department of Energy under Award number DE-EE0002323.
文摘Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality.In this paper,material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight.Through finite element simulations,full frontal,offset frontal,and side crashes of a full car model are evaluated for peak acceleration,intrusion distance,and the internal energy absorbed by the structural parts.In addition,the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints.The wall thicknesses of twenty-two parts are considered as the design variables.Latin Hypercube Sampling is used to sample the design space,while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies.A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints.Using Sequential Quadratic Programming,the design optimization problem is solved with the results verified by finite element simulations.The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673211 and 21203047)the Foundation of Heilongjiang Bayi Agricultural University,China(Grant No.XZR2014-16)the Science Challenging Program of China(Grant No.JCKY2016212A501)
文摘The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.
文摘A version of an electric vehicle was developed and designed for the US market on the basis of the required domestic body structure.When compared with the original car,the new car body design leads to two major technical difficulties.First,the installation of high-voltage components such as the battery pack and other new energy sources increases the vehicle weight and occupies a great deal of its structural space;this limits the impact paths and the use of traditional structural designs,which greatly increases the design difficulty.Second,the USA,as an advanced automobile-using country,has well-developed laws and regulations for collision standards,vehicle operating conditions and evaluation standards.Using a combination of butterfly diagram analysis,bending moment management,section forces and other computer-aided simulation and analysis techniques,this paper presents a body structure design that can achieve a“GOOD”evaluation under the US Insurance Institute for Highway Safety(IIHS)side impact body structure conditions by optimizing the force transfer path,the B-pillar deformation mode and the threshold support structure.The threshold support structure supports realization of the“GOOD”rating for IIHS side impact and helps the body to meet the crash requirements of the Federal Motor Vehicle Safety Standard FMVSS214 and the US New Car Assessment Program(NCAP)requirements for side impact at 32 km/h and 75°angular pole impact.
