Institute Of Mechanics,Chinese Academy of Sciences
Not a member yet
33838 research outputs found
Sort by
一种基于准动态的亚格子动能方程模型的大涡模拟方法
No full text本发明是一种基于准动态的亚格子动能方程模型的大涡模拟方法，包括如下步骤：步骤1、推导亚格子动能的输运方程，并使用无限展开关系式对能流进行建模，得到能流关系式；步骤2、将涡粘模型代入能流关系式后，得到涡粘模型所计算得到的能流，使涡粘模型计算得到的能流与建模得到的能流的真实值相等，动态获得涡粘模型的系数；并展开亚格子应力的各项同性部分，基于亚格子动能与亚格子应力的各项同性部分的关系，得到能流关系式中的未知系数；步骤3、计算得到动态亚格子热流以及亚格子组分通量项的系数；步骤4、基于无限展开将亚格子动能输运方程中的未封闭项进行建模，使得整个方程组封闭
一种用于火焰辐射光谱及强度三维测量的实验系统
No full text本发明公开了一种用于火焰辐射光谱及强度三维测量的实验系统，火焰燃烧装置用于产生火焰；数据采集装置包括第一光纤、第一光纤光谱仪和平移旋转位移机构；第一光纤的感应端朝向火焰，第一光纤光谱仪得到火焰的辐射强度，且第一光纤设置在平移旋转位移机构，可实现空间多角度对火焰进行光谱扫描采集；标定装置包括标准光源、第二光纤和第二光纤光谱仪；第二光纤的感应端朝向标准光源；第二光纤光谱仪得到标准光源的辐射强度；将第二光纤光谱仪所得到标准光源的辐射强度与标准光源出厂辐射信息对比，修正第二光纤光谱仪和第一光纤光谱仪存在的波长响应系统误差，降低了测试系统的误差，提高了后续计算所得到的火焰温度的精度
Towards fatigue-resistant steels: Interfacial fatigue crack mechanisms in complex inclusions revealed by TEM and atomic simulations
No full textDespite the significance of inclusions on fatigue properties, a thorough and physics-based understanding of the failure behavior of complex inclusions is still missing due to experimental limitations. An atomic-scale simulation approach is proposed for investigating the interfacial cracking behavior of Ca2Al2SiO7/CaS complex inclusion in steel under tensile-compressive cyclic loading conditions. The results show that regular parallel lattice distortions are induced in CaS to generate stable interfacial structures. Interestingly, these distortion rows will gradually disappear under compression and eventually deteriorate the distortions adjacent to the interfacial region, which become the crack nucleation sites under tension. This study provides an in-depth understanding of the fatigue mechanism of modern steels with complex inclusions and potentially offers a physics-based bottom-up method to determine the fatigue life of materials
Opposed flame spread over a thermally-thin charring material under varied flow velocities and ambient pressures in a narrow channel apparatus
No full textThe opposed flame spread over thermally-thin filter paper under constrained buoyancy at varied flow velocities and ambient pressures was investigated, which will be conducive to develop ground-based techniques for simulating microgravity. With increasing flow velocity, three regimes can be roughly identified: 1) near quenching regime, the periodic fingering flamelets appear for oxygen starvation, expanding the flammability range; 2) steady-state spreading regime, symmetric flames occur among the sample surface due to buoyancy suppression, and the flame spread rate reaches its peak; 3) near blow-off regime, the flame is affected by finite chemical kinetics. The whole pyrolysis region is identified into the primary/secondary pyrolysis regions characterized by blue/orange attached flames, and the frequent transformation between them intensifies the flame instability. With increasing flow velocity, the global equivalence ratio increases firstly and decreases finally under higher pressures, while decreases monotonously under lower pressures. The optimal utilization of the narrow channel apparatus for suppressing the buoyancy effect should be located in the range of moderate flow velocities far away from the extinction limits, where the heat loss effect of the parallel plates can be neglected. By tracking the extinction limit, the flammability boundary under different pressures was obtained. It is found that the quenching boundary is dependent on the diffusion rate of fuel vapor, while the blow-off boundary is determined by the critical global equivalence ratio. The flammability range narrows with the decreasing pressure, and relatively higher ambient pressure is required to achieve better effectiveness of simulating microgravity in future space missions
A bead random generation method revealing structure-function relation of magnetorheological fluids with arbitrary morphology particles
No full textThe structure-function relation is crucial for guiding the preparation of magnetic intelligent materials with arbitrary particle morphologies. However, from the experimental perspective, it is both challenging and inefficient to elucidate this relationship, given the experimental scale and the randomness of particle preparation. Here, we propose a multiscale computational method through the superellipsoid morphology constraint equation and bead random generation method, ensuring the force-magnet coupling simulation for arbitrary particle morphologies with an error of only 2.24 %. The mechanical behaviors, including magnetic-induced stress, dynamic response, and anti-settlement, are systematically calculated and comprehensively analyzed. The derived morphology constraint dimensionless numbers exhibit a strong correlation with particle interactions, thereby revealing the structure-function relation between mechanical behaviors and particle morphologies. This work develops an accurate and efficient computational method for investigating the structure-function relation and provides deep insights into morphology-induced interactions, demonstrating significant potential to accelerate customized material design for next-generation magnetic intelligent materials
A data-driven approach to identify the optimal sub-laminates for homogeneity design under the concept of double-double composites
No full textThis paper presents the design of the sub-laminate under the concept of the double-double composite using the data-driven method. As the key advantage of the double-double composites is the reduced repeat number of sub-laminates necessary to achieve homogeneity, it is therefore crucial to determine the best pattern of sub-laminates which ensures the optimal lightweight design with the minimum thickness. In the data-driven framework, first, a generative neural network model was built for generating the sub-laminates fitting in the scope of the homogeneous criterion. Then, a symbolic regression model was built for quantitatively finding the hidden layup patterns in the dataset of these sub-laminates. It is found that the form of double-double and triple-double stands out in the vast design space of all the possible layup sequences. The 4-layer sub-laminate of [B/ - /i//i/ - B] and 6-layer sub-laminate of [B/ - /i/ - y/ + y/ + /i/ - B] are most recommended as they meet the homogeneous criterion with less thickness and offer larger design space of mechanical properties. The established data-driven framework can be extended to other scenarios especially in finding the common design rules of laminates
Size- and stability-dependent fracture scaling in nanoscale metallic glass
No full textExperiments show a significant size effect in the fracture modes of the metallic glass (MG) nanowires, while simulations often diverge due to differences in thermal histories caused by timescale issue of the classical molecular dynamics quenching methods. This leads to disparities between computational and experimental results. To address this, we used a hybrid molecular dynamics (MD) and Monte Carlo thermal cycling method to fabricate well-annealed MG nanowires with effective quenching rates significantly lower than those of MD-prepared samples. Our findings reveal that fracture mode transitions are strongly tied to thermal history. For high quenching rate samples, the fracture mode is only dictated by the aspect ratio (L/D) of nanowires, aligning with existing simulations. For low quenching rate samples, the critical factor determining fracture is the diameter (D), matching experimental observations. This resolves the discrepancies between simulations and experiments on size-dependent fractures in nanoscale MGs. Microscopic analysis links this variation to the intrinsic plastic zone width (delta 0), influenced by the aspect ratio in high rates but correlated solely with diameter in low rates. We propose a universal model for fracture scaling with size and thermal stability in nanostructured MGs
Study of microbubble defects in high-NA silicate-glass multi-core imaging fibers fabricated by the stack-and-draw method
No full textThe fabrication of multicore imaging fiber (MCIF)/fiber bundle by the stack-and-draw method is favorable to achieve a hyperfine spatial imaging resolution without the rise of lattice defectw, such as core breakage and dislocation. MCIFs made of silicate glasses as host materials usually present a high numerical aperture (NA), lower bend loss, and low inter-core crosstalk, giving an excellent imaging capability. In this paper, we focus on the microbubble defect (MD) in the high-NA silicate-glass MCIF fabricated by the stack-and-draw method. MDs are a type of local defect in a scale of micrometers or smaller, distributed randomly along the fiber length. Some MD would cause the abrupt variation of the core shape in the neighbor, which gives rise to a local scattering loss up to 103 dB/m according to the numerical simulation. The origin of MD is still uncertain, and our investigation shows that MD could possibly be mitigated or even eliminated in principle by minimizing the difference in softening the temperature between core and cladding glasses. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreemen
Multi-parameter optimisation of optical bonding for the ultra-stable optical measurement bench in space-based platform
No full textTo enhance the measurement accuracy of space-based platforms, the construction of optical platforms imposes higher performance demands on optical bonding technology. Hydroxide Catalysis Bonding (HCB) technology, with its advantages of low stress and high precision, has emerged as a critical technique for achieving this objective. However, the performance optimisation and application of HCB under multi-parameter influences still require further systematic investigation. This study, using the developed mathematical model and experimental validation, systematically examines the effects of solution concentration, solution volume, curing temperature, and surface shape error on bonding time, strength, and stability. The experiments identified the optimal process parameters: 1:300 Molar ratio, 0.8 mu L solution volume, 0.1 lambda surface shape error, and a bonding area of 2 cm2, while confirming the pronounced impact of high-temperature curing in accelerating bonding time and enhancing bonding strength. The research reveals that a plane-convex combination exhibits superior strength performance under low RMS error (<= 0.6 lambda), while spot displacement tests indicate that the deflection angle of the bonding structure during curing can be maintained stably within 10 arcsec. Based on the optimised parameters and conclusions, the Chinese "Taiji" ultra-stable optical measurement bench (USOMB) achieved optical bonding, and passed noise stability measurement. The results demonstrate that the platform achieves noise levels below 10 pm/ / in the 0.1 Hz to 1 Hz range, reaching pm/ Hz /Hzat 1 Hz, a reduction of approximately two orders of magnitude compared to "Taiji-1". These findings provide technical support for the construction of the USOMB in the "Taiji Program"