针对高强铝合金毛细芯结构的高精度成形及传质功能需求,研究了常规激光粉末床熔融(Conventional laser powder bed fusion,c-LPBF)与微细激光粉末床熔融(Micro laser powder bed fusion,μ-LPBF)成形高强铝合金微特征结构的成形性与毛...针对高强铝合金毛细芯结构的高精度成形及传质功能需求,研究了常规激光粉末床熔融(Conventional laser powder bed fusion,c-LPBF)与微细激光粉末床熔融(Micro laser powder bed fusion,μ-LPBF)成形高强铝合金微特征结构的成形性与毛细性能。μ-LPBF成形高强铝合金结构的极限尺寸约为86μm,缺陷等效直径集中于25~40μm,平均缺陷体积和球形度分别为9.99×10^(-6)mm^(3)、0.76;远优于c-LPBF工艺(缺陷等效直径50~100μm,球形度降至0.48),且在200μm以下结构展现出优异的尺寸精度与缺陷抑制能力。基于数值模型揭示了颗粒飞溅和剥蚀行为的演化机制,c-LPBF因强金属蒸汽羽流导致粉末飞溅速度超过10 m/s、剥蚀带宽度为821~932μm;而μ-LPBF因蒸汽扰动减弱,飞溅速度降至5 m/s以下、剥蚀带宽度缩小至159~239μm,工艺稳定性显著提升。μ-LPBF结构获得了更高的毛细压差-渗透率乘积(ΔP_(cap)K=16.08×10^(-8)N)与毛细因子(K/R_(eff)=1.16μm),展现出更均衡的综合传质性能,为热控结构的优化设计与一体化成形提供了参考。展开更多
Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires d...Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires drilling and countersinking.Robotic machining systems are gradually used in the machining of holes due to their high flexibility.However,weakly rigid stacked structure and low-stiffness industrial robot system bring about complex and diverse countersinking depth errors,which significantly affects the fatigue life of components.In this paper,the influence mechanism of ultrasonic energy on the accuracy of robotic countersinking of stacked structure is investigated.Firstly,a workpiece deformation model is established with the thinwalled plate deformation theory,defined as static error.Then,the vibration of the industrial robot is calculated from the acceleration with the frequency domain integration,defined as dynamic error.The suppression of ultrasonic energy on the two kinds of errors were elucidated,respectively.Base on this,a depth compensation model of robotic ultrasonic countersinking is established.Finally,the feasibility of the accuracy compensation is experimentally verified,and the countersinking depth error can be controlled within±0.09 mm.展开更多
The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and redu...The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and reduce forming loads.However,the absence of compatible forming equipment makes it difficult to control the constraint in the unloaded zones during the forming process.This difficulty complicates coordination and control of deformation,particularly for asymmetric rib-web components.Additionally,the current implementation involves multi-fire heating,a long process flow,and high energy consumption,which limits the popularization and application of the local loading process.In this study,a new multi-pass local loading hydraulic forming apparatus that can quickly and reliably switch between heavy-load deformation and low-load constraint for different local loading sub-dies was developed.A 10-tonne laboratory prototype was developed,and the forming characteristics during the forming process as well as the response characteristics of the hydraulic system during the multi-pass intermittent local loading of rib-web component were investigated using numerical simulations and physical experiments.Results indicated that,compared to a whole loading process with the same initial geometry of billet,the total forming load(i.e.,the sum of loaded and restrained loads)is reduced by more than 40%with the local loading process,and by nearly 50%with multi-pass local loading.The multi-pass local loading process allows for more effective control of material flow compared to single-pass local loading,leading to improved cavity filling and reduced flow line disturbance.For a large-scale,complex titanium alloy bulkhead,the cavity filling problem was addressed by optimizing the multi-pass local loading path with an unequal thickness billet.The dynamic performance of the multi-pass local loading hydraulic system was found to be robust,with stable pressure transitions during motion and load switching for the sub-die(s).The dynamic characteristic of the hydraulic cylinder when switching from non-moving/unloaded state to a moving/loading state are consistent whether a load is present or not.However,the dynamic characteristics differ when switching from a moving/loading state to non-moving/unloaded state,showing opposite behavior.The developed hydraulic drive mechanism provides a way for implementation of multi-pass local loading without auxiliary operation and extra heating.The results of the study provide a foundation for the industrial production of large-scale,complex components with reduced force requirement and low-energy consumption.展开更多
基金co-supported by the National Key Research and Development Program of China(No.2024YFB4711201)National Natural Science Foundation of China(Nos.U22A20204,52305472)。
文摘Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires drilling and countersinking.Robotic machining systems are gradually used in the machining of holes due to their high flexibility.However,weakly rigid stacked structure and low-stiffness industrial robot system bring about complex and diverse countersinking depth errors,which significantly affects the fatigue life of components.In this paper,the influence mechanism of ultrasonic energy on the accuracy of robotic countersinking of stacked structure is investigated.Firstly,a workpiece deformation model is established with the thinwalled plate deformation theory,defined as static error.Then,the vibration of the industrial robot is calculated from the acceleration with the frequency domain integration,defined as dynamic error.The suppression of ultrasonic energy on the two kinds of errors were elucidated,respectively.Base on this,a depth compensation model of robotic ultrasonic countersinking is established.Finally,the feasibility of the accuracy compensation is experimentally verified,and the countersinking depth error can be controlled within±0.09 mm.
基金the supports of the National Natural Science Foundation of China(Grant No.52375378)。
文摘The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and reduce forming loads.However,the absence of compatible forming equipment makes it difficult to control the constraint in the unloaded zones during the forming process.This difficulty complicates coordination and control of deformation,particularly for asymmetric rib-web components.Additionally,the current implementation involves multi-fire heating,a long process flow,and high energy consumption,which limits the popularization and application of the local loading process.In this study,a new multi-pass local loading hydraulic forming apparatus that can quickly and reliably switch between heavy-load deformation and low-load constraint for different local loading sub-dies was developed.A 10-tonne laboratory prototype was developed,and the forming characteristics during the forming process as well as the response characteristics of the hydraulic system during the multi-pass intermittent local loading of rib-web component were investigated using numerical simulations and physical experiments.Results indicated that,compared to a whole loading process with the same initial geometry of billet,the total forming load(i.e.,the sum of loaded and restrained loads)is reduced by more than 40%with the local loading process,and by nearly 50%with multi-pass local loading.The multi-pass local loading process allows for more effective control of material flow compared to single-pass local loading,leading to improved cavity filling and reduced flow line disturbance.For a large-scale,complex titanium alloy bulkhead,the cavity filling problem was addressed by optimizing the multi-pass local loading path with an unequal thickness billet.The dynamic performance of the multi-pass local loading hydraulic system was found to be robust,with stable pressure transitions during motion and load switching for the sub-die(s).The dynamic characteristic of the hydraulic cylinder when switching from non-moving/unloaded state to a moving/loading state are consistent whether a load is present or not.However,the dynamic characteristics differ when switching from a moving/loading state to non-moving/unloaded state,showing opposite behavior.The developed hydraulic drive mechanism provides a way for implementation of multi-pass local loading without auxiliary operation and extra heating.The results of the study provide a foundation for the industrial production of large-scale,complex components with reduced force requirement and low-energy consumption.
