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.

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.

Surface accuracy optimization of mechanical parts with multiple circular holes for additive manufacturing based on triangular fuzzy number

Surface accuracy directly affects the surface quality and performance of mechanical parts.Circular hole,especially spatial non-planar hole set is the typical feature and working surface of mechanical parts.Compared with traditional machining methods,additive manufacturing(AM)technology can decrease the surface accuracy errors of circular holes during fabrication.However,an accuracy error may still exist on the surface of circular holes fabricated by AM due to the influence of staircase effect.This study proposes a surface accuracy optimization approach for mechanical parts with multiple circular holes for AM based on triangular fuzzy number(TFN).First,the feature lines on the manifold mesh are extracted using the dihedral angle method and normal tensor voting to detect the circular holes.Second,the optimal AM part build orientation is determined using the genetic algorithm to optimize the surface accuracy of the circular holes by minimizing the weighted volumetric error of the part.Third,the corresponding weights of the circular holes are calculated with the TFN analytic hierarchy process in accordance with the surface accuracy requirements.Lastly,an improved adaptive slicing algorithm is utilized to reduce the entire build time while maintaining the forming surface accuracy of the circular holes using digital twins via virtual printing.The effectiveness of the proposed approach is experimentally validated using two mechanical models.

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.

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.

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.

Research of the Issue of Lightening the Construction of the Gin Saw Cylinder

The article investigates the problem of lightening the construction of the saw cylinder of the gin by drilling a central longitudinal through hole on the shaft and cutting circular holes on the saw blades. This is accompanied by a relatively large decrease in the mass of the saw cylinder and a relatively smaller decrease in the axial moment of inertia of the cross-sectional area of the shaft, which provides the maximum deflection of the saw cylinder under the action of its own gravity in the middle of the span is from 0.450 mm to 0.406 mm.

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.

A generalized plane strain theory for transversely isotropic piezoelectric plates

Study of generalized plane strain has so far been limited to elasticity. The present is aimed at parallel development of transversely isotropic piezoelasticity. By assuming that the along depth distribution of electric potential is linear, and that com- monly used Kane-Mindlin kinematical assumption is valid, two dimensional solution systems were deduced, for which, explicit solutions of the out-of-plane constraint factor, as well as the stress resultant concentration factor around a circular hole in a transversely isotropic piezoelectric plate subjected to remote biaxial tension are obtained. Comparisons of these formulas with their counterparts for elastic case yielded suggestions that whether the piezoelectric effect exacerbates or mitigates the stress resultant concentration greatly depends on material properties, particularly, the piezoelectric coefficients; the effect of plate thickness was extensively investigated.

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.

Stress concentration in a finite functionally graded material plate

This paper is to study the two-dimensional stress distribution of a finite functionally graded material (FGM) plate with a circular hole under arbitrary constant loads. Using the method of piece-wise homogeneous layers, the stress analysis of the finite FGM plate having radial arbitrary elastic properties is made based on the complex variable method combined with the least square boundary collocation technique. Numerical results of stress distribution around the hole are then presented for different loading conditions, different material properties and different plate sizes, respectively. It is shown that the stress concentration in the finite plate is generally enhanced compared with the case of an infinite plate, but it can be significantly reduced by choosing proper change ways of the radial elastic modulus.

Analysis of stress and failure in rock specimens with closed and open flaws on the surface

The influence of closed and open surface flaws on the stress distribution and failure in rock specimens is investigated.Heterogeneous finite element models are developed to simulate the compression tests on flawed rock specimens.The simulated specimens include those with closed flaws and those with open flaws on the surface.Systematic analyses are conducted to investigate the influences of the flaw inclination,friction coefficient and the confining stress on failure behavior.Numerical results show significant differences in the stress,displacement,and failure behavior of the closed and open flaws when they are subjected to pure compression;however,their behaviors under shear and tensile loads are similar.According to the results,when compression is the dominant mode of stress applied to the flaw surface,an open flaw may play a destressing role in the rock and relocate the stress concentration and failure zones.The presented results in this article suggest that failure at the rock surface may be managed in a favorable manner by fabricating open flaws on the rock surface.The insights gained from this research can be helpful in managing failure at the boundaries of rock structures.