Rigid-flexible composite pavement has gained significant popularity in recent decades.This paper provides a comprehensive review of the research progress concerning rigid-flexible composite pavement,aiming to promote ...Rigid-flexible composite pavement has gained significant popularity in recent decades.This paper provides a comprehensive review of the research progress concerning rigid-flexible composite pavement,aiming to promote its application and address key issues while identifying future directions.The design theory and methodology of rigid-flexible composite pavement are discussed,followed by a description of its structural and mechanical behavior characteristics.The load stress,temperature stress,and their interactive effects between the asphalt layer and the rigid base were analyzed.It is clarified that the asphalt layer serves a dual role as both a“functional layer”and a“structural layer”.Typical distresses of rigid-flexible composite pavement,which primarily occur in the asphalt layer,were discussed.These distresses include reflective cracking,top-down cracking,rutting,and compressive-shear failure.Generally,the integrity of the rigid base and the interlaminar bonding conditions significantly impact the performance and distress of the asphalt layer.The technology for enhancing the performance of rigid-flexible composite pavement is summarized in three aspects:asphalt layer properties,rigid base integrity,and interlaminar bonding condition.The study concludes that developing high-performance pavement materials based on their structural behaviors is an effective approach to improve the performance and durability of rigid-flexible composite pavement.The integrated design of structure and materials represents the future direction of road design.展开更多
The microstructure and mechanical properties of as-cast A356（Al–Si） alloy castings were investigated. A356 alloy was cast into three different molds composed of sand, ferrochrome（Fe–Cr） slag, and a mixture of sa...The microstructure and mechanical properties of as-cast A356（Al–Si） alloy castings were investigated. A356 alloy was cast into three different molds composed of sand, ferrochrome（Fe–Cr） slag, and a mixture of sand and Fe–Cr. A sodium silicate–CO_2 process was used to make the necessary molds. Cylindrical-shaped castings were prepared. Cast products with no porosity and a good surface finish were achieved in all of the molds. These castings were evaluated for their metallography, secondary dendrite arm spacing（SDAS）, and mechanical properties, including hardness, compression, tensile, and impact properties. Furthermore, the tensile and impact samples were analyzed by fractography. The results show that faster heat transfer in the Fe–Cr slag molds than in either the silica sand or mixed molds led to lower SDAS values with a refined microstructure in the products cast in Fe–Cr slag molds. Consistent and enhanced mechanical properties were observed in the slag mold products than in the castings obtained from either sand or mixed molds. The fracture surface of the slag mold castings shows a dimple fracture morphology with a transgranular fracture nature. However, the fracture surfaces of the sand mold castings display brittle fracture. In conclusion, products cast in Fe–Cr slag molds exhibit an improved surface finish and enhanced mechanical properties compared to those of products cast in sand and mixed molds.展开更多
为提高汽车工艺涂胶质量及机械臂作业效率,针对基于深度学习的双目视觉车顶焊缝涂胶机械臂系统,提出了一种SEmYOLOv5算法,在主干网络上增加SE(squeeze and excitation)注意力机制,同时在颈部网络上增加一组采样模块,提高焊缝的识别能力...为提高汽车工艺涂胶质量及机械臂作业效率,针对基于深度学习的双目视觉车顶焊缝涂胶机械臂系统,提出了一种SEmYOLOv5算法,在主干网络上增加SE(squeeze and excitation)注意力机制,同时在颈部网络上增加一组采样模块,提高焊缝的识别能力。对提取到的图像进行图像处理,使得更好的提取车顶焊缝的特征信息从而得到特征点坐标,采用B样条曲线法对机械臂进行轨迹规划。改进后的算法相较原YOLOv5算法的mAP值提升了6.76%,针对该系统进行实验并验证了提出的基于深度学习的双目视觉车顶焊缝涂胶机械臂系统的有效性。展开更多
基金This manuscript is supported by the National Key Research and Development Program of China(Grant No.2021YFB2601000)the National Natural Science Foundation of China(Grant Nos.52278437,52008044)+2 种基金the Natural Science Foundation of Hunan Province(Grant No.2022JJ40479)the Science and Technology Innovation Program of Hunan Provincial Department of Transportation(Grant No.202236)the Changsha Outstanding Innovative Youth Training Program Project(Grant No.kq2306009).
文摘Rigid-flexible composite pavement has gained significant popularity in recent decades.This paper provides a comprehensive review of the research progress concerning rigid-flexible composite pavement,aiming to promote its application and address key issues while identifying future directions.The design theory and methodology of rigid-flexible composite pavement are discussed,followed by a description of its structural and mechanical behavior characteristics.The load stress,temperature stress,and their interactive effects between the asphalt layer and the rigid base were analyzed.It is clarified that the asphalt layer serves a dual role as both a“functional layer”and a“structural layer”.Typical distresses of rigid-flexible composite pavement,which primarily occur in the asphalt layer,were discussed.These distresses include reflective cracking,top-down cracking,rutting,and compressive-shear failure.Generally,the integrity of the rigid base and the interlaminar bonding conditions significantly impact the performance and distress of the asphalt layer.The technology for enhancing the performance of rigid-flexible composite pavement is summarized in three aspects:asphalt layer properties,rigid base integrity,and interlaminar bonding condition.The study concludes that developing high-performance pavement materials based on their structural behaviors is an effective approach to improve the performance and durability of rigid-flexible composite pavement.The integrated design of structure and materials represents the future direction of road design.
基金the DST–Fly Ash unit, New Delhi, India for their financial support (Grant Ref No.FAU/DST/600(52)/2012-13)Advance Analytical laboratory, Andhra University, India for the support in SEM–EDS studies
文摘The microstructure and mechanical properties of as-cast A356（Al–Si） alloy castings were investigated. A356 alloy was cast into three different molds composed of sand, ferrochrome（Fe–Cr） slag, and a mixture of sand and Fe–Cr. A sodium silicate–CO_2 process was used to make the necessary molds. Cylindrical-shaped castings were prepared. Cast products with no porosity and a good surface finish were achieved in all of the molds. These castings were evaluated for their metallography, secondary dendrite arm spacing（SDAS）, and mechanical properties, including hardness, compression, tensile, and impact properties. Furthermore, the tensile and impact samples were analyzed by fractography. The results show that faster heat transfer in the Fe–Cr slag molds than in either the silica sand or mixed molds led to lower SDAS values with a refined microstructure in the products cast in Fe–Cr slag molds. Consistent and enhanced mechanical properties were observed in the slag mold products than in the castings obtained from either sand or mixed molds. The fracture surface of the slag mold castings shows a dimple fracture morphology with a transgranular fracture nature. However, the fracture surfaces of the sand mold castings display brittle fracture. In conclusion, products cast in Fe–Cr slag molds exhibit an improved surface finish and enhanced mechanical properties compared to those of products cast in sand and mixed molds.
文摘为提高汽车工艺涂胶质量及机械臂作业效率,针对基于深度学习的双目视觉车顶焊缝涂胶机械臂系统,提出了一种SEmYOLOv5算法,在主干网络上增加SE(squeeze and excitation)注意力机制,同时在颈部网络上增加一组采样模块,提高焊缝的识别能力。对提取到的图像进行图像处理,使得更好的提取车顶焊缝的特征信息从而得到特征点坐标,采用B样条曲线法对机械臂进行轨迹规划。改进后的算法相较原YOLOv5算法的mAP值提升了6.76%,针对该系统进行实验并验证了提出的基于深度学习的双目视觉车顶焊缝涂胶机械臂系统的有效性。
