Investigation on photonic crystal nanobeam cavity based on mixed diamond–circular holes

A photonic crystal nanobeam cavity(M-PCNC)with a structure incorporating a mixture of diamond-shaped and circular air holes is pro-posed.The performance of the cavity is simulated and studied theoretically.Using thefinite-difference time-domain method,the parameters of the M-PCNC,including cavity thickness and width,lattice constant,and radii and numbers of holes,are optimized,with the quality factor Q and mode volume Vm as performance indicators.Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance.The optimized cavity possesses a high quality factor Q 1.45105 and an ultra-small mode=×volume Vm 0.01(λ/n)[Zeng et al.,Opt Lett 2023:48;3981–3984]in the telecommunications wavelength range.Light can be progres-=sively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure.Thereby,the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.

Fracture evolution characteristics of sandstone containing double fissures and a single circular hole under uniaxial compression

The uniaxial compression experiments on the sandstone samples containing double fissures and a single circular hole were carried out by using electro-hydraulic servo universal testing machine to investigate the effect of rock bridge angle β and fissure angle α on mechanical properties and evolution characteristics of cracks.The results show that the peak strength,peak strain and elastic modulus of defected specimens decrease comparing with those for intact sample,and show a decreased trend firstly and then increase with β changing from 0° to 90°.The peak strength and elastic modulus achieve the minimum value as the rock bridge angle is 60°,while the peak strain reaches the minimum value with the rock bridge angle of 45°.The crack initiation of tested rock samples occurs firstly in stress concentration areas at tips of prefabricated fissures under uniaxial compression,and then propagates constantly and coalescences with the prefabricated hole.Some secondary cracks initiate and propagate as well until buckling failure happens.The rock bridge angle has a great influence on crack initiation,coalescence,final failure mode,crack initiation stress and transfixion stress.The peak strength varies significantly,while the elastic modulus and peak strain change slightly,and the failure modes are also different due to the influence of fissure angle.

Anti-plane Analysis of a Circular Hole withThree Unequal Cracks in One-dimensionalHexagonal Piezoelectric Quasicrystals

This paper employes variable function method and the technique of conformal mappingto discuss the anti-plane problem of a circular hole with three unequal cracksin a one-dimensional （1D） hexagonal piezoelectric quasicrystal. Based on the piezoelectricityfundamental equations of quasicrystal materials and the symmetry of1D hexagonal quasicrystal and its linear piezoelectricity effect, 1D hexagonal quasicrystalcontrol equations of anti-plane problem are derived. Applying Cauchyintegral formula, the analytical expressions for the crack tip filed intensity factorsare presented with the assumption that the crack are electrical impermeable andelectrical permeable. With the variation of the hole-size and the crack length, someof the new model of crack are obtained. In the absence of the electric load, theresults match with the classical ones. The numerical results indicate the effects ofgeometric parameters on the field intensity factors. It is verified that the horizontalcrack length and the circle radius can easily promote crack growth. Researchon such issues will provide reliable theoretical value for the engineering materialspreparation and application.

Strength and failure characteristics of sandstone containing two circular holes filled with two types of inclusions under uniaxial compression

Plate shaped sandstones containing two fabricated circular holes that were filled with gypsum and high-strength concrete respectively were prepared for studying the effects of ligament length L ligament incline angle α, as well as filling modes on their strength properties and failure modes. The results show that the initial cracks can be categorized as wing crack, axial tensile crack and curved tensile crack. The failure modes of ligaments can be categorized as mode of single inclined crack, mode of single axial crack and mode of two parallel cracks. The final failure modes of all specimens can be categorized as the tension-shear mixed failure and shear failure. The strength of inclusions shows little influence on the final failure modes of specimens, while the failure modes vary with L and α. When α is a fixed value, the peak strength σc and elastic modulus Ec of tested specimens increase firstly with increasing L and reaches to the maximum value at L of 16 mm, then declines. When L is a fixed value, σc declines firstly and then turns to increase as α increases to 75° from 45°, while Ec increases linearly. The axial stress σp performs the similar variation trends with those of σc versus increasing L and α when ligaments fail.

Displacement of surrounding rock in a deep circular hole considering double moduli and strength-stiffness degradation

The problem of cavity stability widely exists in deep underground engineering and energy exploitation.First,the stress field of the surrounding rock under the uniform stress field is deduced based on a post-peak strength drop model considering the rock’s characteristics of constant modulus and double moduli.Then,the orthogonal non-associative flow rule is used to establish the displacement of the surrounding rock under constant modulus and double moduli,respectively,considering the stiffness degradation and dilatancy effects in the plastic region and assuming that the elastic strain in the plastic region satisfies the elastic constitutive relationship.Finally,the evolution of the displacement in the surrounding rock is analyzed under the effects of the double modulus characteristics,the strength drop,the stiffness degradation,and the dilatancy.The results show that the displacement solutions of the surrounding rock under constant modulus and double moduli have a unified expression.The coefficients of the expression are related to the stress field of the original rock,the elastic constant of the surrounding rock,the strength parameters,and the dilatancy angle.The strength drop,the stiffness degradation,and the dilatancy effects all have effects on the displacement.The effects can be characterized by quantitative relationships.

ELECTRIC FIELD GRADIENT EFFECTS IN ANTI-PLANE PROBLEMS OF A CIRCULAR CYLINDRICAL HOLE IN PIEZOELECTRIC MATERIALS OF 6 mm SYMMETRY

We study electromechanical felds in the anti-plane deformation of an infnite medium of piezoelectric materials of 6 mm symmetry with a circular cylindrical hole. The theory of electro- elastic dielectrics with electric feld gradient in the constitutive relations is used. Special attention is paid to the felds near the surface of the hole.

Interaction effects on heat conduction and thermal stress in an infinite elastic plane with two circular holes

Numerous researches have focused on the physical behavior of an elastic material in the vicinity of a single hole under the assumption that the interaction effects arising from the introduction of multiple holes remain negligible if the holes are placed sufficiently far from each other.In an effort to understand hole interaction effects on heat conduction and thermal stress,we consider the case when two circular holes are embedded in an infinite elastic material and use complex variable methods together with numerical analysis to obtain solutions describing temperature and elastic fields in the vicinity of the two circular holes.The results indicate that the interaction effects on temperature distribution and stress strongly depend on the relative size of the two holes and the distance placed between them but not on the actual size of the holes.

TORSION OF CIRCULAR CYLINDERS CONTAINING n CIRCULAR HOLES

In the present paper by using complex variable methods in linear elasticity and by-means of analytic continuation, the author obtains for this problem a complex torsional function, shear stress components, displacement components,the lorsional rigidity and shear stresses on boundaries expressed in terms of series.

Three-Dimensional Stress Concentration Factor in Finite Width Plates with a Circular Hole

The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickness, hole dimensions and material properties, such as the Poisson’s coefficient. This study employs three dimensional finite element modeling to numerically investigate the effect of plate width on the behavior of the SCF across the thickness of linear elastic isotropic plates with a through-the-thickness circular hole under remote tension. The problem is governed by two geometric non-dimensional parameters, i.e., the plate half-width to hole radius (W/r) and the plate thickness to hole radius (B/r) ratios. It is shown that for thin plates the value of the SCF is nearly constant throughout the thickness for any plate width. As the plate thickness increases, the point of maximum SCF shifts from the plate middle plane and approaches the free surface. When the ratio of plate half-width to hole radius (W/r) is greater than four, the maximum SCF was observed to approximate the theoretical value determined for infinite plates. When the plate width is reduced, the maximum SCF values significantly increase. A polynomial curve fitting was employed on the numerical results to generate empirical formulas for the maximum and surface SCFs as a function of W/r and B/r. These equations can be applied, with reasonable accuracy, to practical problems of structural strength and fatigue, for instance.

基于小孔应力集中的激光预钻孔条件下TBM滚刀侵岩模型建模与试验验证

激光发生器耦合安装到全断面岩石隧道掘进机(TBM)刀盘上,利用高能量激光辅助TBM掘进作业,理论上有望达到新型热-机械高效破岩之目的。针对激光辅助滚刀破岩,基于小孔应力集中理论的弹性应力状态计算方法,在空腔膨胀模型基础上,建立了一种考虑密实核衍生效应的激光预钻孔条件下滚刀侵岩理论模型,并对模型进行理论分析;随后开展双侧围压下的激光辅助缩尺比例滚刀侵岩试验,对理论模型进行试验验证。研究结果表明,刃宽及孔距均对侵岩垂直力有一定影响,且孔距较小时理论模型不再适用;经对比分析后,在理论模型与试验所得结果中,随着孔距的改变侵岩垂直力有着相同的变化趋势,侵岩垂直力大小较为符合,激光预钻孔条件下滚刀侵岩理论模型具有一定准确性。

钢拱架铰接孔视觉定位方法研究

针对钢拱架自动化拼接过程中需要对钢拱架铰接孔进行定位的实际问题,设计了一种基于双目视觉的钢拱架铰接孔定位方法。首先通过模板匹配对钢拱架铰接孔进行初定位,找到感兴趣区域;采用一种新的自适应阈值算法计算阈值,对感兴趣区域进行二值化处理;利用边缘检测和最小二乘法提取得到铰接孔椭圆轮廓特征;然后找到椭圆轮廓上特殊的两条弦,根据空间几何关系,计算空间圆平面的法向量;利用消影线和椭圆参数矩阵,计算铰接孔圆心在图像上的实际投影点;最后基于双目视觉成像模型计算铰接孔圆心的精确空间坐标。实验证明,本方法可实现钢拱架铰接孔高精度定位,满足实际工业需求,为钢拱架自动化拼接提供技术支撑。

基于phyphox软件的菲涅尔圆孔衍射实验的设计与实施

通过确定智能手机phyphox软件光传感器的位置,搭建菲涅尔圆孔衍射实验装置,解决传统实验成本高、不易开展的问题,利用智能手机APP对菲涅尔圆孔衍射特点及光强分布进行研究,提供了一种实验成本低、易操作、更直观研究衍射特性的新方法。

航空发动机环形零件高精度孔位测具

针对航空发动机环形零件高精度孔位测具加工困难、加工周期长的现状,设计了一种航空发动机环形零件高精度孔位测具。介绍了测具的技术方案,分析了关键技术和优点。测具采用高精度电气分度技术,可以实现准确、高效检测,通用性强,适用范围广。

基于机器视觉的圆形部件中心点定位系统研究

为实现通过机器视觉对气门导管、闷盖孔、护套孔等零部件的定位,特设计一种适用于圆形部件中心点的检测方法。首先,使用阈值分割、膨胀、腐蚀等算法对图像进行预处理,筛选出圆形部件所在的区域。其次,找到圆形部件所在区域的中心,将此中心作为圆形卡尺工具的测量中心,设置卡尺的检测半径和动态测量范围,使测量范围覆盖圆形部件的外轮廓。利用卡尺测量算子找到圆形轮廓与卡尺栅格的交点集。最后,通过最小二乘圆弧逼近的方法得到圆的中心点,实现对圆形部件的定位。研究表明,该方法的鲁棒性较强,精确度较高,提高了装配的准确率。

Three-Dimensional Stress Fields in Finite Thickness Plate with Hole Under Shear Load

The theoretical solutions are obtained for the three-dimensional(3-D)stress field in an infinite isotropic elastic plate with a through-the-thickness circular hole subjected to shear load at far field by using Kane and Mindlin′s assumption based on the stress function method.Based on the present solutions,the characteristics of 3-D stress field are analyzed and the emphasis is placed on the effects of the plate thickness and Poisson′s ratio on the deviation of the present 3-D in-plane stress from the related plane stress solutions,the stress concentration and the out-of-plane constraint.The present solutions show that the stress concentration factor reaches its peak value of about 8.9% which is higher than that of the plane stress solutions.As expected,the out-of-plane stress constraint factor can reach 1on the surface of the hole when the plate is a very thick one.

Field of Stresses in an Isotropic Plane with Circular Inclusion under Tensile Stress

Within the framework of the linear theory of elasticity, the analytical equations for the components of the stress tensor for а plane with а circular inclusion under tensile loading have been derived using the method of superposition. The given approach allows one to describe the plane-stress state of the plane both for the case of rigid and “soft” inclusions.

Research on the control technology of medium-length hole blasting fragmentation in underground mine

The scalloped medium-length hole blasting mining method used in Dahongshan Copper Mine accounted for more than 61%of the total amount of mining,but the large boulder yield restricted the intensity of ore supply for mines,and the average boulder yield was as high as 22.7%.In order to develop the mine production efficiency,the circular medium-length hole blasting technology was proposed and field tests were carried out.The test results showed that circular medium-length hole blasting mining can reduce the average boulder yield to 10.3%.Compared with the traditional scalloped medium-length hole blasting mining,the average boulder yield was decreased by 12.4%.The daily yield of ore for the panel on duty was increased by 152.29 t,and the growth rate was 51.1%.The new technology can reduce the time for the handling of boulder and the consumption of explosives and detonators for recrushing,and increase the efficiency of mining while reduce the mining cost,which has received good blasting effects.

Analysis on Micro Complex Shape Via Hole Punching on Low Temperature Co-Fired Ceramics

The quality of a via hole on a multilayer stack of Low Temperature Co-fired Ceramic (LTCC) tape is of utmost importance to its functionality. This paper investigates a substitute for the commonly used circular shape hole to a more complex one and its implications when different parameters such as sheet thickness, punch speed, travel distance and tool clearance are?changed. Fabrication of the punch tools and the punching process is carried out at the same machine, ensuring alignment. Two types of non-circular shape are chosen to carry out the experiment. Pre-sintered complex shape hole measurements show that while punch conditions such as speed and tool gap have?little effect on the size, sheet thickness and travel depth play a vital role in the overall dimension. Albeit having only a slight effect on the size, those parameters are significant in other aspects of hole quality. Post-sintering investigation is also observed and discussed.

含圆孔有限八次对称二维准晶的边界元分析

利用推广的Stroh方法,得到含有圆孔无限八次对称二维准晶材料的格林函数。进一步采用半解析半数值的边界元方法,获得在均匀边界加载作用下,有限八次对称二维准晶体内的圆形孔口所引起的应力解答,并分析半径尺寸以及不同加载情况对圆孔边应力的影响。

基于关节臂测量机的群孔位置度检测研究

具有圆周均布群孔的零件在机床设备中应用十分广泛,其孔系位置度直接关系到机器整体的装配质量。针对其位置度检测快速准确的要求,采用关节臂式测量机进行检测。描述了关节臂式测量机的基本组成及测量原理,建立了关节臂的运动学模型,详细介绍了使用关节臂测量的测量流程及关键技术要点。根据检测结果,圆孔直径及位置度最大偏差为0.022 mm和0.046 mm,均满足测量标准,反映出关节臂式测量机应用于精密检测的技术优势。