Weapon barrels experience rapid cyclic heating during firing. This study systematically examines the microstructural evolution of PCrNi3MoVA steel subjected to simulated thermal cycles using a Gleeble thermal simulator. The results indicate that under transient thermal cycling, PCrNi3MoVA steel displays distinct microstructural responses across various temperature regimes. Below Ac1, Cr-rich carbides precipitate and coarsen at grain boundaries, resulting in an initial increase followed by a decline in microhardness. Above Ac3, grain evolution diverges: refinement occurs at 850 degrees C due to VC pinning, while significant coarsening is observed at 920-1000 degrees C as enhanced diffusion surpasses precipitate pinning. These behaviors, associated with competing nucleation and coarsening mechanisms under repeated thermal pulses, clarify the microstructural factors contributing to performance degradation in barrel steels under service conditions.

针对压电陶瓷堆栈作为驱动元件时存在输出位移微小的局限，设计了由柔性机构与弧形杠杆机构级联而成的复合位移放大机构。通过理论分析推导各级机构的放大倍数模型，得到关键结构参数对放大性能的影响规律，求解柔性机构、弧形杠杆机构、复合位移放大机构的理论放大倍数分别为10.28、1.62、16.65。利用ANSYS软件对放大机构进行静力学分析与模态分析，仿真表明：在所选用的压电陶瓷堆栈输出最大位移情况下，放大机构最大应力低于材料许用值，仿真放大倍数为14.85，与理论值相差10.8%；一阶振型的稳定性、应力分布及抗共振能力更优。试制样件并进行位移放大性能测试，结果显示：放大机构实际放大倍数为13.95，最大输出位移0.4647mm，弧形杠杆最大输出角度为2.18°，适用于机械制造、光学工程、生物医疗等领域的大行程位移调控与微小角度精密调节。

PCrNi3MoV, a Cr-Ni-Mo-V high-strength alloy steel, is commonly utilized in harsh environments involving transient high-temperature conditions. Conventional methods face significant challenges in simulating the phase transformation processes of materials under transient high-energy pulse conditions. In this work, a high-temperature pulse experiment was conducted using Gleeble on PCrNi3MoV material, with holding temperature, holding time, and heating rate serving as independent variables. The potential damage of high-temperature pulse to microstructure was analyzed. Thermal expansion curves were used to create the phase transition equation for non-isothermal austenitization. The microstructure observation indicated that the primary factor influencing the microstructure was the peak temperature. At 700 degrees C, the microstructure consists of networked cementite and ferrite. At 800-900 degrees C, the microstructure is a kind of lath martensite with genetic initial microstructure characteristics. At 1000 degrees C, the microstructure is typical lath martensite. Finally, the changes in grain size were quantified, and the samples were examined following multiple thermal cycles.

为提升哈里斯鹰优化算法收敛精度，解决易陷入局部最优等问题，本文提出了一种基于迭代混沌精英反向学习和黄金正弦策略的哈里斯鹰优化算法（GSHHO）。首先，利用无限迭代混沌映射初始化种群，利用精英反向学习策略筛选优质种群，提高种群质量，增强算法的全局搜索能力；其次，使用一种收敛因子调整策略重新计算猎物能量，平衡算法的全局探索和局部开发能力；然后，在哈里斯鹰的开发阶段引入黄金正弦策略，替换原有的位置更新方法，提升算法的局部开发能力；最后，在9个测试函数上和不同规模的栅格地图上评估GSHHO的有效性。实验结果表明，GSHHO在不同测试函数中具有较好的寻优精度和稳定性能，在两次机器人路径规划中路径长度较原始HHO算法分别减少4.28%、2.42%，稳定性分别提升55.68%、63.12%。

Objective The circular structured light based measurement system can generate circular structured light by reflecting a laser beam through a conical reflector, and utilizing laser triangulation and close-view photogrammetry algorithms to calculate three-dimensional coordinates. This kind of measurement system has been widely studied by researchers due to its advantages such as high flexibility, high accuracy and simple structure. The current circular structured light system has certain problems in measuring roundness. It is difficult for the laser, the camera and the deep hole to be measured to be parallel or coaxial, which leads to the inability to measure the accurate circular cross-section. A measurement system based on circular structured light is constructed, the mechanism of systematic error is analyzed and a method based on the circular structured light system to measure circularity is proposed, which provides some compensation for systematic errors. Methods The mechanism that generates systematic errors in the measurement of roundness by the circular structured light system is analyzed (Fig.3). A high-precision electric linear slide is used to move the deep hole parts to be measured to complete the full-field measurement, and a high-resolution point cloud is obtained and fit the axis. Through the Rodrigues formula, the inner surface point cloud rigid body will be transformed to the point cloud axis and z-axis parallel to the location of the point cloud axis, searching for the z coordinate near the point as a cross-section of the roundness of the assessment point (Fig.4). The roundness evaluation is completed by the grid search algorithm (Fig.5). Results and Discussions The compensation by the proposed method works well in roundness measurement experiments, in which the measurement uncertainty is 4.78 µm (Tab.3). For the circular structured light measurement system, a long rod can be assembled after the laser to increase the axial measurement range of the system. For the proposed circular structured light roundness measurement method, the resolution of the 3D point cloud can be improved by reducing the step length of the motorized linear slide to further improve the measurement accuracy. Conclusions A three-dimensional measurement system of circular structured light is built, the error generated when the circular structured light system measures roundness is analyzed, and a method based on the circular structured light system to accurately measure roundness is proposed. It is verified that the use of the method to measure roundness has a good compensating effect through the measurement experiments. © 2024 Chinese Society of Astronautics. All rights reserved.

为提高深孔加工精度，解决深孔中难排屑问题，在分析负压抽屑装置原理的基础上，求解出负压装置的最速降线方程，设计一种带有膛线的最速降线负压装置来提高排屑效率，利用方程驱动曲线建立其三维模型进行流体仿真，并通过正交试验找出膛线的最优参数。Fluent仿真结果表明，最速降线负压装置的负压效果比普通的锥面负压装置提高了4.2倍，切削液流速提高了3.6倍，湍流动能提高了2.5倍；当膛线数量为8根，膛线深度为0.15 mm,螺旋角度为9°时能最大幅度地提高排屑动力。该结构有效提高了深孔加工排屑动力，证明了最速降线能有效促进流体流动。

The generating conditions and affecting elements of oil film pressure of deep hole drilling are investigated based on the idea of hydrodynamic lubrication. A new kind of BTA deep hole drilling connector with tilting pads was created based on meeting the cutting parameters and structure requirements. The connector may change the tilting pad angle by adjusting the voltage of the piezoelectric ceramic stack, allowing for real-time control of the oil film pressure, counteracting the radial force generated by the tool during the cutting operation, and reducing roundness error. The range of oil film pressure was determined theoretically to be 0–9.809 N, and a link between the tilting angle and the stack voltage was found. 24 sets of comparative experiments were conducted, using the Φ37.8×500mm, Φ38.3×500mm, and Φ38.8×500mm deep hole as an example, to confirm the impact of connector presence or absence on the deep hole processing. The findings demonstrated that when the wedge gap is 0.45 mm, the latter radial force was decreased by 3.20 %~47.50 % while maintaining the same drilling circumstances. After 120 sets of cross-sections of a split deep hole specimen were found using a roundness tester, it was discovered that the roundness error of the latter had decreased by 27.98 %–49.73 %. © 2024 The Society of Manufacturing Engineers

The flow stress and microstructure evolution of 9Cr oxide dispersion strengthened (ODS) steels were investigated by isothermal compression at 1000-1150 degrees C with strain rates from 0.001 to 1 s(-1). Microstructure characteristics of ODS steels under various condition were studied using the EBSD and TEM techniques. At each deformation temperature, PortevinLe-Chatelier (PLC) effect characteristics of repeated serrated stress was observed, as the strain rates were 0.01, 0.1 and 1s(-1). The serrations fluctuated about the mean flow curve in quick succession, and the critical strain for the PLC effect was related to both the deformation temperature and strain rates. The stress drops at strain rates of 0.01 and 0.1 s(-1) were smaller than those at 1 s(-1). The strain rate affected the dynamic recovery and recrystallization of austenite grains, as well as the texture components of martensite transformed from austenite. Cap-shaped oxide particles in as-fabricated and hot deformed steels were characterized in detail. The cap parts of cap-shaped oxide particles were depleted of alloying elements, and the caps were crystal or amorphous. Large-sized oxide particles were easier to be deformed than small-sized ones. Despite of the oxide deformation, the PLC effect was still suggested to be related to the solute-dislocation interaction.

针对4-URU型柔性并联机构,提出了一种对支链刚度的新型求解方法,应用软件仿真结果验证该方法的有效性。首先,利用螺旋理论对4-URU刚性并联机构进行自由度分析,采用柔性铰链替换法设计相应的柔性并联机构。基于柔性铰链刚度矩阵,利用转

针对并联机床摆角小，难以加工复杂曲面零件的缺点，提出一种新型（2PSR+PUU）＆RP混联机床的机构构型。首先运用螺旋理论以及修正的K-G公式对机构自由度进行分析计算与验证。运用闭环矢量法对机构进行运动学分析，给出该机构的位置逆解以及基于粒子群算法的正解，确定驱动块和动平台的位姿关系。在SolidWorks软件中采用动静结合法绘制出其工作空间，并利用ADAMS对其摆角进行测算，验证了机构模型的正确性以及机构运动的可实现性。研究表明，混联机床具有3T2R这5个自由度，有较大的工作空间，且其刀具摆角可达（0°～90°）,通过刀具的大摆角转动和五轴联动可应用于部分汽轮机，水轮机和航空发动机的叶片和复杂曲面零件的加工。