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121.
122.
研究带中心刚体的作大范围运动的空间曲梁的刚-柔耦合动力学.结合混合坐标法和绝对坐标法的特点,取与中心刚体大范围运动有关的变量和柔性梁各单元节点相对中心刚体连体基的位移和斜率作为广义坐标,建立了一种新的柔性梁的刚柔耦合模型.基于精确的应变和位移的关系式,根据Jourdian速度变分原理,建立了带中心刚体柔性曲梁的有限元离散的动力学方程.数值对比了空间曲梁系统和空间直梁系统的刚柔耦合动力学性质,用能量守恒规律验证了文中曲梁模型的合理性.在此基础上,在应变能中计及热应变,研究温度增高引起的曲梁的热膨胀对系统的动力学性态的影响. 相似文献
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利用有限克尔变换得到了求面各向同笥球体的热冲击作用下的动态热应力解析表达式。从表达式中,可以看出球中向同性球体的动态热应力集中现象明显不同于各向同性球体。另外,所描述的动态热应力集中现象与文献「１,３」也有一定的区别。 相似文献
127.
热/均布载荷下双材料悬臂梁的解析解 总被引：1，自引：0，他引：1
基于弹性介质的二维本构关系和热传导理论,采用逆解法,研究了双材料悬臂梁在热/机械载荷作用下的问题,通过假设双材料悬臂梁构件的应力函数,利用应力、位移边界条件和连续性条件,给出了其位移、应力分布的表达式. 相似文献
128.
焊管的残余应力测试与研究 总被引：6，自引：1，他引：5
通过小孔法与分割法对Ф720mm螺旋埋弧焊管和Ф380mm对接焊管的残余应力测试,分析探讨了螺旋焊缝、环焊缝以及焊缝热影响区的残余应力分布.研究结果表明,不同工艺焊接成型的圆管,其焊缝纵向均为拉应力分布,焊缝横向均为压应力分布,焊缝热影响区的残余应力分布各异. 相似文献
129.
Ben LI;Jingfeng ZHOU;Yi WANG;Yang BAI 《光子学报》2022,51(2):127-138
A space-transmission high-power near-infrared semiconductor laser beam with a rectangular laser spot is one of the key tools to improve the efficiency and quality of laser surface heat treatment. However, this kind of laser is difficult to apply to the surface heat treatment of flexible lasers inside workpieces. This is because the volume of the lasers increases greatly with increasing laser power and is affected by the space transmission of the laser beam. The spot of the ultrahigh-power laser beam from a commercial high-power fiber laser or a fiber-transmitted semiconductor laser is circular, which makes it difficult to control the spot overlap rate during the laser surface heat treatment process. It is difficult to change the ultrahigh-power circular laser spot into a rectangular spot through beam shaping technology. Laser incoherent spatial combining based on multifiber transmission is an effective method to reduce the risk of high-power laser transmission in a single fiber and realize the flexible transmission of high-power lasers. It has quickly become a research hotspot in the field of ultrahigh power laser systems. To solve the spot overlap rate control problem of ultrahigh power lasers transmitted by fibers in flexible laser surface heat treatment, a design scheme of arranging 18 semiconductor laser beams at 972 nm transmitted by fibers according to a “staggered rectangle” and implementing space incoherent beam combination was proposed in this paper. Based on this, a set of 10 kW rectangular spot laser beam combiners was developed. The optical elements in the combiner are all optical lenses made of fused silica glass. It is widely known that the accumulation of heat generated by long-term ultrahigh-power laser beam irradiation will produce serious thermal effects inside the optical lens, resulting in reduced beam quality and even irreversible damage inside the optical lens, which will seriously affect the safety and reliability of the combiner for long-term operation. However, the structural shielding of the combiner often makes the thermodynamic properties of the optical lenses difficult to directly detect and evaluate with experimental methods. With the rapid development of computer technology and calculation methods, the establishment of temperature field models based on finite element analysis has become a simulation method widely used in the reliability analysis of laser irradiation optical components. At present, most thermodynamic finite element analysis studies on laser irradiation optical elements simplify the laser beam to an area heat source while ignoring the volume absorption of the laser beam by the optical element. However, the volume absorption of the laser beam by the optical lens itself is already one of the main factors affecting its thermodynamic properties with the continuous increase in laser incoherent space combining power. There is no report on the thermodynamic finite element analysis of multiple ultrahigh power laser beams transmitted through optical lenses under the premise that the laser beam is used as a volume heat source. To solve the above problems, the finite element thermodynamic model of the optical lens was established based on the mathematical model of the whole heat source of the 18 laser beams. The thermodynamic properties of all optical lenses under the condition of being irradiated by 18 laser beams participating in the combination for 1 000 s are simulated and analyzed using this model. The research results show that the maximum temperature, maximum thermal deformation and maximum equivalent thermal stress of the optical lens in the combiner stabilized after the 800 s time node. The simulated values of the maximum core temperature and the maximum equivalent thermal stress were 427.27 K and 12.68 MPa, respectively, which were significantly lower than the softening point temperature and thermal damage threshold of fused silica glass used to manufacture optical lenses. The maximum aperture of 0.1 corresponding to the simulated maximum thermal deformation of 4.53 μm was much smaller than the conventional machining tolerance of 2.0. The highest temperature on the exit surface of the window lens was measured during the laser beam combining time of 1 000 s. Both the experimental value and the simulated value of the highest temperature showed good consistency with the laser beam combining time. This shows that the established finite element thermal analysis model has good accuracy. The maximum combined power of 10.64 kW for the combined laser with a rectangular spot was measured when it was continuously operated for 1 000 s. The power instability of less than ±1.2% further experimentally verified the safety and reliability of the combiner under long-term operation. 相似文献
130.
赵宇涵;李雪;关海艳;杜金峰;张健;李传南;汪津 《发光学报》2017,38(8):1063-1068
采用快速热退火对ZnO薄膜进行后处理,制作了ITO/ZnO/PTB7：PC71BM/MoO3/Ag结构的倒置聚合物太阳能电池,器件能量转换效率达到了8.1%,与传统热退火工艺相比提高了11.26%。通过原子力显微镜、扫描电子显微镜、X光衍射谱、透射光谱和荧光谱对不同退火条件下制备的ZnO薄膜进行表征和分析。结果表明,经快速热退火处理的ZnO薄膜具有良好的c轴取向结晶特性、较大的晶粒尺寸和表面粗糙度,有效地降低了器件的串联电阻Rs,增大了器件的短路电流Jsc和填充因子FF。 相似文献