In order to achieve the optimized design of a cased telescoped ammunition(CTA) interior ballistic design,a genetic algorithm was introduced into the optimal design of CTA interior ballistics with coupling the CTA inte...In order to achieve the optimized design of a cased telescoped ammunition(CTA) interior ballistic design,a genetic algorithm was introduced into the optimal design of CTA interior ballistics with coupling the CTA interior ballistic model. Aiming at the interior ballistic characteristics of a CTA gun, the goal of CTA interior ballistic design is to obtain a projectile velocity as large as possible. The optimal design of CTA interior ballistic is carried out using a genetic algorithm by setting peak pressure, changing the chamber volume and gun powder charge density. A numerical simulation of interior ballistics based on a 35 mm CTA firing experimental scheme was conducted and then the genetic algorithm was used for numerical optimization. The projectile muzzle velocity of the optimized scheme is increased from 1168 m/s for the initial experimental scheme to 1182 m/s. Then four optimization schemes were obtained with several independent optimization processes. The schemes were compared with each other and the difference between these schemes is small. The peak pressure and muzzle velocity of these schemes are almost the same. The result shows that the genetic algorithm is effective in the optimal design of the CTA interior ballistics. This work will be lay the foundation for further CTA interior ballistic design.展开更多
7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal dire...7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal direction(ND)and rolling direction(RD)plane,was occasionally observed after the welding of thick plates,resulting in premature material failure.A vertically metal-inert gas(MIG)-welded laminar tearing component of a 30 mm thick plate was analyzed to determine the factors associated with this phenomenon.The texture,residual stress,microhardness,and tensile properties were also investigated.The results indicated that the crack extended along the RD as a transcrystalline fracture and terminated at the BM.The grains near the crack grew preferentially in the(001)crystal direction.Furthermore,the tensile strength(83 MPa)and elongation(6.8%)in the RD were relatively higher than those in the ND.In particular,the primary factors for crack initiation include stronger texture,higher dislocation density,increased Al_(7)Cu_(2)Fe phases,lower proportion of small-angle grain boundaries,and varying grain sizes in different regions,leading to the fragile microstructure.The higher residual stress of the BM promotes the formation and extension of cracks.The restraining force due to fixation and welding shrinkage force transformed the crack into laminar tearing.Preventive measures of laminar tearing were also proposed.展开更多
An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of stren...An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of strength of the target on the deformation patterns.The experimental results revealed slight mass loss in the first layer of the steel target during the transient entrance phase,with an extremely negligible loss in target mass during the quasi-steady penetration phase.The results of macro-analysis,micro-analysis and simulation show that the eroded target material migrated towards the periphery of the crater,causing an increase in the target's thickness,remained within the target,instead of flowing out of the crater.Therefore,the process of long rods penetrating the metal target is considered as a process of backward extrusion.By combining the backward extrusion theory with energy conservation,a penetration depth model for long rods penetrating a metal target,taking into account both the diameter of the crater and the friction coefficient between the rod and the target,has been established.Although the model is not yet perfect,it innovatively applies the principles of solid mechanics to the study of long rod penetration.Additionally,it takes into account the friction coefficient between the rod and the target during the penetration process.Therefore,this model provides a new research direction for future studies on long rod penetration.展开更多
Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue be...Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area,which is further influenced by the lubrication and surface roughness due to pressure fluctuations.In this study,a numerical model incorporating the lubrication state,tooth surface roughness,residual stress,and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear.The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test,respectively.The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution,highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler.The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation(DC-FFT)method.Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk.The effect of the root mean square(RMS)value of the surface roughness on the failure risk at critical material points were discussed in detail.Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area,and the maximum risk appears near the surface.展开更多
Erratum to Friction(2019)https://doi.org/10.1007/s40544-019-0277-3 The article“Study on contact fatigue of a wind turbine gear pair considering surface roughness”,written by Heli LIU,Huaiju LIU,Caichao ZHU,Zhangdong...Erratum to Friction(2019)https://doi.org/10.1007/s40544-019-0277-3 The article“Study on contact fatigue of a wind turbine gear pair considering surface roughness”,written by Heli LIU,Huaiju LIU,Caichao ZHU,Zhangdong SUN,Houyi BAI,was erroneously originally published online without open access.After online first publication this was corrected and the article is now an open access publication.The article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/).展开更多
Butterfly wings are closely related to the premature failure of rolling element bearings.In this study,butterfly formation is investigated using the developed semi-analytical three-dimensional(3D)contact model incorpo...Butterfly wings are closely related to the premature failure of rolling element bearings.In this study,butterfly formation is investigated using the developed semi-analytical three-dimensional(3D)contact model incorporating inclusion and material property degradation.The 3D elastic field introduced by inhomogeneous inclusion is solved by using numerical approaches,which include the equivalent inclusion method(EIM)and the conjugate gradient method(CGM).The accumulation of fatigue damage surrounding inclusions is described using continuum damage mechanics.The coupling between the development of the damaged zone and the stress field is considered.The effects of the inclusion properties on the contact status and butterfly formation are discussed in detail.The model provides a potential method for quantifying material defects and fatigue behavior in terms of the deterioration of material properties.展开更多
文摘In order to achieve the optimized design of a cased telescoped ammunition(CTA) interior ballistic design,a genetic algorithm was introduced into the optimal design of CTA interior ballistics with coupling the CTA interior ballistic model. Aiming at the interior ballistic characteristics of a CTA gun, the goal of CTA interior ballistic design is to obtain a projectile velocity as large as possible. The optimal design of CTA interior ballistic is carried out using a genetic algorithm by setting peak pressure, changing the chamber volume and gun powder charge density. A numerical simulation of interior ballistics based on a 35 mm CTA firing experimental scheme was conducted and then the genetic algorithm was used for numerical optimization. The projectile muzzle velocity of the optimized scheme is increased from 1168 m/s for the initial experimental scheme to 1182 m/s. Then four optimization schemes were obtained with several independent optimization processes. The schemes were compared with each other and the difference between these schemes is small. The peak pressure and muzzle velocity of these schemes are almost the same. The result shows that the genetic algorithm is effective in the optimal design of the CTA interior ballistics. This work will be lay the foundation for further CTA interior ballistic design.
基金supported by the National Key Research and Development Program of China(No.SQ2021YFF 0600011).
文摘7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal direction(ND)and rolling direction(RD)plane,was occasionally observed after the welding of thick plates,resulting in premature material failure.A vertically metal-inert gas(MIG)-welded laminar tearing component of a 30 mm thick plate was analyzed to determine the factors associated with this phenomenon.The texture,residual stress,microhardness,and tensile properties were also investigated.The results indicated that the crack extended along the RD as a transcrystalline fracture and terminated at the BM.The grains near the crack grew preferentially in the(001)crystal direction.Furthermore,the tensile strength(83 MPa)and elongation(6.8%)in the RD were relatively higher than those in the ND.In particular,the primary factors for crack initiation include stronger texture,higher dislocation density,increased Al_(7)Cu_(2)Fe phases,lower proportion of small-angle grain boundaries,and varying grain sizes in different regions,leading to the fragile microstructure.The higher residual stress of the BM promotes the formation and extension of cracks.The restraining force due to fixation and welding shrinkage force transformed the crack into laminar tearing.Preventive measures of laminar tearing were also proposed.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102201,U2341244).
文摘An experimental and finite element simulation investigation are conducted to study the deformation patterns of steel targets during the penetration process of tungsten alloy long rods,as well as the influence of strength of the target on the deformation patterns.The experimental results revealed slight mass loss in the first layer of the steel target during the transient entrance phase,with an extremely negligible loss in target mass during the quasi-steady penetration phase.The results of macro-analysis,micro-analysis and simulation show that the eroded target material migrated towards the periphery of the crater,causing an increase in the target's thickness,remained within the target,instead of flowing out of the crater.Therefore,the process of long rods penetrating the metal target is considered as a process of backward extrusion.By combining the backward extrusion theory with energy conservation,a penetration depth model for long rods penetrating a metal target,taking into account both the diameter of the crater and the friction coefficient between the rod and the target,has been established.Although the model is not yet perfect,it innovatively applies the principles of solid mechanics to the study of long rod penetration.Additionally,it takes into account the friction coefficient between the rod and the target during the penetration process.Therefore,this model provides a new research direction for future studies on long rod penetration.
基金The work was supported by the National Natural Science Foundation of China(Nos.U1864210,51775060,and 51705043)Chongqing Research Program on Technology Innovation and Application Demonstration(No.cstc2018jszx-cyzdX0053).
文摘Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area,which is further influenced by the lubrication and surface roughness due to pressure fluctuations.In this study,a numerical model incorporating the lubrication state,tooth surface roughness,residual stress,and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear.The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test,respectively.The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution,highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler.The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation(DC-FFT)method.Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk.The effect of the root mean square(RMS)value of the surface roughness on the failure risk at critical material points were discussed in detail.Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area,and the maximum risk appears near the surface.
文摘Erratum to Friction(2019)https://doi.org/10.1007/s40544-019-0277-3 The article“Study on contact fatigue of a wind turbine gear pair considering surface roughness”,written by Heli LIU,Huaiju LIU,Caichao ZHU,Zhangdong SUN,Houyi BAI,was erroneously originally published online without open access.After online first publication this was corrected and the article is now an open access publication.The article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/).
基金This project is supported by National Natural Science Foundation of China(Nos.52005057 and 51975063)the Fundamental Research Funds for the Central Universities(Nos.2020CDJQY-A069 and 2021CDJGXB 008).
文摘Butterfly wings are closely related to the premature failure of rolling element bearings.In this study,butterfly formation is investigated using the developed semi-analytical three-dimensional(3D)contact model incorporating inclusion and material property degradation.The 3D elastic field introduced by inhomogeneous inclusion is solved by using numerical approaches,which include the equivalent inclusion method(EIM)and the conjugate gradient method(CGM).The accumulation of fatigue damage surrounding inclusions is described using continuum damage mechanics.The coupling between the development of the damaged zone and the stress field is considered.The effects of the inclusion properties on the contact status and butterfly formation are discussed in detail.The model provides a potential method for quantifying material defects and fatigue behavior in terms of the deterioration of material properties.
