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Numerically investigating the crushing of sandstone by a tooth hob

《结构与土木工程前沿（英文）》页码 964-979 doi: 10.1007/s11709-023-0978-6

摘要： To investigate the mechanical process that occurs between rocks and tooth hobs, the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-sized sandstone samples. When a piece of sandstone is crushed by the tooth of a hob rolling at a constant speed, the resultant reaction forces of the sandstone on the tooth first hinder and then contribute to the rolling of the hob. The absolute value of the longitudinal reaction force is significantly higher than that of the lateral reaction force. Because the tooth was subjected to reaction forces from the sandstone, forces and moments were applied to the hob in order to keep the hob rolling. The applied forces were equal in value and opposite in direction to the reaction forces of the sandstone on the tooth. Three typical curves of the work done by the applied forces and moment were obtained, and the contribution of the applied lateral force and moment to the total work done for crushing sandstones was variable; however, no work was done by the applied longitudinal force. Moreover, the applied longitudinal force and total work were positively correlated with the strength of sandstone samples. The total work, applied forces, and moment increased with the maximum penetration depth of the tooth in the sandstone.

关键词： sandstone tooth hob crushing process reaction force numerical simulation

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Coordinated shift control of nonsynchronizer transmission for electric vehicles based on dynamic tooth

《机械工程前沿（英文）》 2021年第16卷第4期页码 887-900 doi: 10.1007/s11465-021-0653-3

摘要： Multispeed transmissions can enhance the dynamics and economic performance of electric vehicles (EVs), but the coordinated control of the drive motor and gear shift mechanism during gear shifting is still a difficult challenge because gear shifting may cause discomfort to the occupants. To improve the swiftness of gear shifting, this paper proposes a coordinated shift control method based on the dynamic tooth alignment (DTA) algorithm for nonsynchronizer automated mechanical transmissions (NSAMTs) of EVs. After the speed difference between the sleeve (SL) and target dog gear is reduced to a certain value by speed synchronization, angle synchronization is adopted to synchronize the SL quickly to the target tooth slot’s angular position predicted by the DTA. A two-speed planetary NSAMT is taken as an example to carry out comparative simulations and bench experiments. Results show that gear shifting duration and maximum jerk are reduced under the shift control with the proposed method, which proves the effectiveness of the proposed coordinated shift control method with DTA.

关键词： electric vehicle nonsynchronizer automated mechanical transmission (NSAMT) planetary gear coordinated shift control dynamic tooth alignment

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Experimental investigation of fatigue behavior of spur gear in altered tooth-sum gearing

H. K. SACHIDANANDA, Joseph GONSALVIS, H. R. PRAKASH

《机械工程前沿（英文）》 2012年第7卷第3期页码 268-278 doi: 10.1007/s11465-012-0331-6

摘要：

This paper deals with the contact stress, power loss, and pitting of spur gear tooth in altered tooth-sum gearing for a tooth-sum of 100 teeth when altered by±4% tooth-sum. Analytical and experimental methods were performed to investigate and compare the altered tooth-sum gearing against the standard tooth-sum gearing. The experiments were performed using a power recirculating type test rig. The tooth loads for the experimental investigations were determined considering the surface durability of gears. A clear picture of the surface damage was obtained using a scanning electron microphotograph. The negative alteration in the tooth-sum performed better than the positive alteration in a tooth-sum operating between specified center distances.

关键词： spur gear power recirculating test rig altered tooth-sum gearing scanning electron microscopy (SEM)

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Primary cilia in hard tissue development and diseases

《医学前沿（英文）》 2021年第15卷第5期页码 657-678 doi: 10.1007/s11684-021-0829-6

摘要： Bone and teeth are hard tissues. Hard tissue diseases have a serious effect on human survival and quality of life. Primary cilia are protrusions on the surfaces of cells. As antennas, they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis. Mutations in cilium-related genes result in a variety of developmental and even lethal diseases. Patients with multiple ciliary gene mutations present overt changes in the skeletal system, suggesting that primary cilia are involved in hard tissue development and reconstruction. Furthermore, primary cilia act as sensors of external stimuli and regulate bone homeostasis. Specifically, substances are trafficked through primary cilia by intraflagellar transport, which affects key signaling pathways during hard tissue development. In this review, we summarize the roles of primary cilia in long bone development and remodeling from two perspectives: primary cilia signaling and sensory mechanisms. In addition, the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described. We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

关键词： primary cilia bone mechanical sensing hard tissue cilium-related bone disease tooth

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Mathematical model and manufacture programming of loxodromic-type normal circular-arc spiral bevel gear

Zhenyun DUAN, Houjun CHEN, Zhilan JU, Jian LIU

《机械工程前沿（英文）》 2012年第7卷第3期页码 312-321 doi: 10.1007/s11465-012-0308-5

摘要：

In this paper, loxodromic-type normal circular-arc spiral bevel gear is proposed as a novel application of the circular-arc tooth profile at the gear transmission with intersecting axes. Based on the principle of molding-surface conjugation, the study develops a mathematical model for the tooth alignment curve and the computational flow at the design stage to enable the generation of the tooth surface. Machining of the tooth surface is then carried out to determine the interference-free tool path of the numerical control (NC). Moreover, a pair of loxodromic-type normal circular-arc spiral bevel gears is manufactured on computer numerical control (CNC) machine tools. The proposed theory and method are experimentally investigated, and the obtained results primarily reflect the superior performance of the proposed novel gear.

关键词： loxodrome circular-arc tooth profile Wildhaber-Novikov (W-N) gear spiral bevel gear

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预应力梁桥齿板锚固区配筋设计新方法

张向群,林波,刘钊

《中国工程科学》 2010年第12卷第4期页码 82-85

摘要：

预应力混凝土梁桥的齿板锚固区，由于存在着几何形体上的突变，集中锚固力的作用以及预应力钢束局部弯曲引起的径向力作用，易产生开裂甚至剥落破坏，因此齿板锚固区的抗裂配筋设计十分重要。以7种典型局部作用效应刻画齿板锚固区内拉应力的集中分布特征，并在此基础上形成了齿板锚固区拉压杆模型，初步形成预应力混凝土梁桥的抗裂钢筋设计新方法。

关键词：齿板锚固区 D区拉压杆模型

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生成锁P<G,X,X'>和它的中央加密系统

史开泉,陈泽雄

《中国工程科学》 2000年第2卷第2期页码 41-46

摘要：

利用数据生成技术，提出生成锁P <G ,X, X´>的概念和由P <G ,X, X´>构成的中央加密系统。这些系统是：生成锁P <G ,X, X´>与单齿中央加密系统，生成锁P <G ,X, X´>与多齿中央加密系统。给出单齿加密-解密算法，多齿加密-解密算法，多齿静态加密-解密算法，多齿动态加密-解密算法，中央加密系统的结构特性。研究指出：任意两个秘密通讯的双方A和B，它们各自选择无规则分布的正整数集合X_A={x₁，x₂，…，x_n}，X_B={x₁，x₂，…，x_m}，m,n≥4，X_A≠X_B，利用P <G ,X, X´>完成双方之间的秘密通讯。研究结果表明，所提出的方法具有良好的应用性，安全性。