摘要：The purpose of this study was to prepare high-quality Al-Si-Mg-Mn alloy with a good combination of strength and ductility employing the vacuum-assisted high-pressure die cast process. An orthogonal study of heat treatments was conducted to design an optimized T6 heat treatment process for both Al-10%Si-0.3%Mg-Mn and Al-11%Si-0.6%Mg-Mn alloys. The results demonstrate that no obvious blisters and warpage were observed in these two alloys with solid solution treatment. After the optimal T6 heat treatment of 530°C×3 h + 165°C×6 h, Al-11%Si-0.6%Mg-Mn alloy has better mechanical properties, of which tensile strength, yield strength and elongation reached 377.3 MPa, 307.8 MPa and 9%, respectively. The improvement of mechanical properties can be attributed to the high density of needle-like β″(Mg_5Si_6) precipitation after aging treatment and the fine and spherical eutectic Si particles uniformly distributed in the α-Al matrix.

摘要：BACKGROUND: With the social and economic development and aging, coronary heart disease has become the primary cause of death endangering human life and health, while cardiovascular intervention (especially stenting) in the treatment of cardiovascular disease is at a growing status. OBJECTIVE: To describe the development, research progress and latest clinical application of heart interventional materials as well as advantages and disadvantages of biodegradable stents, and meanwhile to prospect for its future development and improvement. METHODS: A computer-based online search was conducted in PubMed for English language publications from January 1999 to April 2014 using the key words of "stent, scaffold, bioabsorbable, bioresorbable, biodegradable, biocompatibility, material properties" in English. RESULTS AND CONCLUSION: The new fully biodegradable stents are considered as another major progress in the cardiac intervention, which brings a new gospel for patients with coronary heart disease. In the initial stage of implantation, biodegradable stents exhibit the same mechanical support as bare metal stents; after implantation, anti-proliferative drugs are released to prevent thrombosis and restenosis, and the stent is completely degraded within a specified period, which significantly reduces the late-stage and very late-stage thrombosis and the risk of in-stent restenosis. However, long-term safety and efficacy of biodegradable stents need further studies. Innovation of stent design and materials science is the key to overcome the current shortcomings of biodegradable stents.

摘要：The mechanism and the design parameters of blasting with air-decking are studied. The theory of detonation waves is used to investigate the processes of the one-dimensional plane detonation wave within a borehole. The interac- tion of the rarefaction wave with an interface and reflection on a rigid wall is also analyzed. The same courses of the shock wave are also investigated. This decides the distribution of the pressure of the explosion products changing with time along the borehole. Based on the above theoretical analysis, two conditions should be met for a reasonable range of values of the air-decking ratio in blasting rock. First, the rarefaction wave from the contact interface between detonation products and air reaches the bottom earlier than that of the reflected shock wave from the end of the stemming. Second, the reflected shock wave reaches the contact interface between the detonation products and air earlier than that of the reflected rarefaction wave from the bottom of the borehole. Finally, the reasonable value of the air-decking ratio must be decided theoretically in air-decking blasting. For different explosives, the reasonable range of air-decking ratio varies from 0.15 to 0.4. This result is well consistent with what was obtained by previous researchers.

摘要：针对现有高压共轨柴油机电控单元高度依赖进口芯片、自主不足的问题,提出了基于全国产芯片的高压共轨柴油机电控单元方案。所设计的国产控制单元选用兆易创新的GD32F450芯片为控制核心,承担发动机数据采样、处理、存储与控制任务。首先,采用boost升压电路提供喷油器峰值电流,利用分立器件设计双边驱动与电流反馈电路,在不依赖进口专用芯片的条件下,对喷油器驱动电流进行闭环控制;然后,基于FreeRTOS操作系统,开发高压共轨柴油机底层驱动软件,实现对不同任务调度周期的精准控制;最后,对所设计的电控单元进行了实验验证。结果表明,所设计的国产高压共轨柴油机电控单元功能齐全、工作稳定,双边驱动电路典型峰值电流为22 A,维持电流为10 A,最小喷射间隔时间为200μs,多次喷射性能与bosch系统相当。发动机不同转速条件下任务调度周期精准、实时性好,研究证实了高压共轨柴油机电控单元全国产化方案的可行性,对推动发动机电控技术自主可控提供了有益参考。

摘要：吊卡作为钻井提升系统的重要结构,强度与可靠性要求极高。为提高吊卡的强度与安全可靠性,对吊卡吊臂部位进行结构优化。利用有限元软件ANSYS workbench对吊卡的静态特性进行了研究分析;在此分析基础上,对吊臂结构优化设计参数进行了灵敏度分析与实验设计;并基于响应面法建立了优化的数学模型,再通过遗传算法得到最优设计方案。结果表明:当吊臂截面厚度b为94mm,吊臂截面半径R为87mm,吊臂截面偏离角度β为37°时,吊臂的最大应力值降低12.5%,并通过试验进行了验证。提高了吊卡的强度与安全储备,为吊卡结构改进设计提供了理论指导。

摘要：为了提高CDZ500型钻杆吊卡的机械强度,对其结构关键承载部位—吊臂进行优化设计,研究吊臂截面横向厚度b、吊臂截面半径R的改变对吊卡应力的影响,优化吊臂结构,并对优化后的吊卡进行有限元分析和应力贴片试验。结果表明:当b为98mm,R为81mm,吊臂的最大弯曲应力降低了4.8%,有限元、贴片试验结果验证了结构优化的合理性。计算结果为提高吊卡安全性能提供了依据,为海洋石油钻井设备的设计提供了理论基础,确保其在深海石油开采平台安全使用。

摘要：格构梁节点荷载简化分配方法的不足在于无法考虑2个方向的梁上其他节点荷载的影响且对文克尔(Winkler)地基上梁的类型进行了主观假定。为克服格构梁节点荷载简化分配方法的上述缺点,提出了一种基于力法的格构梁节点荷载分配方法。根据节点静力平衡条件及变形协调条件,新的格构梁节点荷载分配方法通过构建并求解线性方程组,能够合理地将作用在节点的集中力分别分配给2个方向的纵梁和横梁。进一步地,引入一个格构梁边坡锚固案例并等比例地增加纵梁和横梁的悬臂长度。不同基床系数条件下,基于新的节点荷载分配方法将格构梁节点荷载分配给纵梁和横梁,然后对各梁单独进行弯矩计算。以悬臂最大正弯矩与跨中最大负弯矩比值的绝对值接近1为评价指标,对格构梁最优悬臂长度进行了评价。节点荷载分配结果表明,随着悬臂长度的增加,分配给纵梁和横梁的荷载逐渐趋于稳定。弯矩计算结果表明,随着基床系数的增大,悬臂长度对格构梁弯矩的影响逐渐减弱。不同边坡基床系数条件下,当悬跨比在0.2~0.4之间时,悬臂各梁最大正弯矩与跨中最大负弯矩趋于均衡。因此,基于力法理论的节点荷载分配方法的提出为格构梁内力的精确分析及悬臂长度优化设计提供了可靠的理论依据。

摘要：采用数值模拟方法建立单层和双层电磁感应线圈的仿真模型,分析线圈几何构型对空间磁场分布、金属球体表面的麦克斯韦应力张量分布和线圈悬浮性能的作用规律。选取Al和Ti两种金属作为实验对象,研究线圈匝数、金属质量与最小悬浮电流之间的本征关系。设计多种用于大体积金属无容器处理的电磁悬浮线圈,并实现直径10～50mm的三种球状金属在空气中的悬浮加热。利用优化设计的线圈成功悬浮Al、Ti和Cu三种不同密度的典型金属,其中悬浮起质量高达807 g的纯铜。

摘要：提出一种求解任意边界条件下经典Timoshenko梁以及修正Timoshenko梁自振频率和振型的新方法。利用改进的傅立叶级数消除传统傅立叶级数的边界不收敛问题,然后通过Rayleigh-Ritz法导出Timoshenko梁的拉格朗日泛函,根据Hamilton原理将原问题转化为求解矩阵广义特征值问题。通过与解析解对比,本文采用的方法具有较好的收敛性以及较高的计算精度;通过数值计算发现,经典Timoshenko梁的自振频率略高于修正的Timoshenko梁,随着振型阶数的提高,经典Timoshenko梁的计算结果逐渐偏离文献解和有限元结果,而修正的Timoshenko梁能够保持较好的一致性;对于不同边界条件下修正Timoshenko梁的计算结果均能与有限元的计算结果吻合得很好。最后运用MATLAB编程软件将程序设计为App,对于不同情形的梁只需要修改参数即可,可为实际工程提供高效便捷的计算方案和可靠理论依据。

摘要：钻杆在作业过程中,需要通过卡瓦夹持,才能顺利作业,但卡瓦在钻杆表面会留下作业损伤。为了防止损伤导致的钻杆断裂,影响结构安全性,以某深井作业钻杆实际工况为例,创建含横向半椭圆形表面裂纹的钻杆有限元模型,数值研究拉扭复合载荷下,3种类型的形状因子沿裂纹前缘的变化规律;通过多项式拟合得到形状因子表达式中对应的系数,进而推导出等效应力强度因子的表达式。仿真计算结果表明,在(0.6~0.8)之间存在一临界形状比,裂纹最深点和边界相邻点处的等效应力强度因子值在此处相等。拟合得到的等效应力强度因子表达式,为进一步研究损伤钻杆表面裂纹扩展和寿命预测提供参考。