Theory Of Stress Concentration Research Articles

Structural Optimization Design of Magnetoelectric Thin-Film Antenna for Bandwidth and Radiation Enhancement.

The acoustically actuated nanomechanical magnetoelectric (ME) antennas represent a promising new technology that can significantly reduce antenna size by 1-2 orders of magnitude compared to traditional antennas. However, current ME antennas face challenges such as low antenna gain and narrow operating bandwidth, limiting their engineering applications. In this paper, we enhance the bandwidth and radiation performance of ME antennas through structural optimization, leveraging theoretical analysis and numerical simulations. Our findings indicate that optimizing the inner diameter of the ring-shaped ME antenna can elevate the average stress of the magnetic layer, leading to improved radiation performance and bandwidth compared to circular ME antennas. We establish an optimization model for the radiation performance of the ME antenna and conduct shape optimization simulations using COMSOL Multiphysics. The results of the Multiphysics field optimization align with the stress concentration theory, demonstrating a strong correlation between the radiation performance and bandwidth of the ME antenna with the average stress of the magnetic film. The resonant frequency in the thickness vibration mode is determined to be 170 MHz. Furthermore, shape optimization can enhance the bandwidth by up to 104% compared to circular ME antenna structures of the same size.

Simulation Analysis and Experiment of Mechanical Performance of Bulge Formed Joint

In this paper, a new joint - bulge formed joint is proposed, which is designed for truss structure. Its mechanical performance is analyzed, and the finite element modeling and the simulation are carried on. The stress concentration theory is combined to obtain the stress concentration factor and compared with the direct intersecting joint, which shows superiority of bulge formed joint. On the basis of this, a test device is designed for stress test of the two kinds of joints. The results of the test verify the rationality of the result of the finite element simulation that the stress level of the bulge formed joint is small. Both the finite element simulation and the experiment show that the designed joint can improve the security of the joints.

Stress concentration in elastic bodies with multiple concentrators

The stress concentration is considered in the case of two and more elastic concentrators in an elastic body. A single concentrator, in the absence of the others, creates its stress field calculated using an external field with the aid of the concentration tensor operator. The stress field from several concentrators is replaced by the interaction of the stress fields of each of the concentrators. The tensor theory of stress concentration from several concentrators of various nature is used to describe their interaction. An approximate analytical expression for the stress concentration tensor is found in the plane with two circular holes and is compared with known solutions.

Study on Stress Field Distribution Characteristics under Coal Seam Pre-splitting Blasting

In order to analyze thoroughly cracks characteristics inside coal seam which are most important for improving the effect of methane extraction, according to ventage stress concentration theory and thick cylinder principle, this paper study the characteristics of various stress distribution under pre-splitting blasting in coal seam. The results show that on explosion cavity wall, radial stress of coal particle is equal in value and opposite in direction with blasting gases; tangent stress is related to differ position; cracks extension on explosion cavity wall will start along horizontal direction firstly. Therefore, methane extraction hole must be designed by cracks distribution characteristics so that obtaining most effect.

Orifices Stress Concentration Study by Static and Dynamic Combination Loads

By the use of the experimental system of Impact Rockburst, which was designed by State Key Laboratory for GeoMechanics and Deep Underground Engineering, the stress concentration for orifices in a cubic gypsum specimen subjected to static and dynamic combination loads was studied. The different triaxial precompression was loaded on gypsum specimen, then the dynamic cyclic loading is exerted in the direction of σ1, while the constant stress is exerted in σ2 and σ3. For the stress strain curve, the data of force and displacement were collected by the servo control system in real time. By the strain gauge near the orifices, the strain was recorded by the dynamic strain collecting device, that result in the orifices stress was obtained. In addition, the phenomenon of inner wall of the orifices was real-time photographed. Based on elastic theory and dynamic stress concentration theory, we calculated the stress near the orifices, which keep pace with the results of test.

Stress and Strain Locus of Perforated Plate in Inelastic Deformation—Strain-Controlled Loading Case

Plastic strain of structures having stress concentration is estimated by using the simplified method or the finite element elastic solutions. As the simplified methods used in codes and standards, we can cite Neuber’s formula in the work by American Society of Mechanical Engineers (1995, “Boiler and Pressure Vessel Code,” ASME-Code, Section 3, Division 1, Subsection NH) and by Neuber (1961, “Theory of Stress Concentration for Shear Strained Prismatic Bodies With Arbitrary Nonlinear Stress-Strain Law,” ASME, J. Appl. Mech., 28, pp.544–550) and elastic follow-up procedure in the work by Japan Society of Mechanical Engineers [2005, “Rules on Design and Construction for Nuclear Power Plants, 2005, Division 2: Fast Breeder Reactor” (in Japanese)]. Also, we will cite stress redistribution locus (SRL) method recently proposed as the other simplified method in the work by Shimakawa et al. [2002, “Creep-Fatigue Life Evaluation Based on Stress Redistribution Locus (SRL) Method,” JPVRC Symposium 2002, JPVRC/EPERC/JPVRC Joint Workshop sponsored by JPVRC, Tokyo, Japan, pp. 87–95] ad by High Pressure Institute of Japan [2005, “Creep-Fatigue Life Evaluation Scheme for Ferritic Component at Elevated Temperature,” HPIS C 107 TR 2005 (in Japanese)]. In the present paper, inelastic finite element analysis of perforated plate, whose stress concentration is about 2.2–2.5, is carried out, and stress and strain locus in inelastic range by the detailed finite element solutions is investigated to compare accuracy of the simplified methods. As strain-controlled loading conditions, monotonic loading, cyclic loading, and cyclic loading having hold time in tension under strain-controlled loading are assumed. The inelastic strain affects significantly life evaluation of fatigue and creep-fatigue failure modes, and the stress and strain locus is discussed from the detailed inelastic finite element solutions.

高強度鋼を用いた有孔梁の応力集中を考慮した許容耐力と繰返し性状

This study researches how stress concentration has an effect on cyclic behavior of H-shaped beam with web perforation made of high strength steel “H-SA700”. It is examined and compared with the same shaped beam made of “SN400” by cyclic loading tests. Cyclic elastic deformation of H-SA700 increases even under constant-amplitude cyclic loading. This property may amplify the local plasticity near a circular hole. So new yield strength, Qc and QF, by means of elastic theory of stress concentration, are suggested. Qc is a minimum strength when somewehre in a hole edge will be plastic. Similarly QF is a minimum strength in a minimum section. In addition large deformation behavior of H-SA700 is shown.

Seismicity and seismotectonics of Libya: as an example of intraplate environment

This investigation covers the area bounded by latitudes 20° to 33° N and longitudes 9.5° to 25°E.The seismicity of area for the period 1900–2005 is evaluated. Libyan earthquake catalog is complete for the 4.4 M and greater over a 70-year span. The overall seismicity of Libya is found to be low to intermediate. The seismic activity is concentrated in three zones of the northern Libya. Outside of these zones, epicenters are scattered and sparsely distributed. The b value for Libya is –0.71. This low b value is a characteristic feature for intraplate environment. A seismotectonics map is constructed for Libya. It shows that the epicenters agree well with the distribution of the major tectonic features. Majority of seismic activity in Libya is concentrated near Hun Graben and Cyrenaica, and the locations of earthquakes are near the transition zones between the stress domains in northern Libya. These transition zones are locations of stress concentration. This investigation suggests that the stress concentration theory is generally considered as causative mechanism for seismicity of Libya.

Integrable Structure in the Theory of Stress Concentration in Shear-Strained Nonlinear Elastic Materials

It is shown that the Neuber equations governing the stress and deformation in a shear-strained prismatical nonlinear elastic body may be completely characterized in terms of eigenfunctions of the integrable mNVN hierarchy. A Backlund transformation and nonlinear superposition principle are derived, whereby privileged constitutive laws may be generated iteratively.

A Mechanics Analysis of Formation and Expansion of Fatigue Crack in Laser Cladding on Repeated Impact Load

Coating samples prepared by laser cladding were subjected to repeated impact fatigue experiment. It is observed through phenomenological analysis that most coating cracks are original from the surface. And then, the cracks extend by the combined action of coating inner stress and repeated impact compression stress. The formation of crack is close related to performance of coating material. It can be divided to traversed crack and reticular crack from surface side; it also can be divided to vertical extend crack and reticular extend crack from the cross section side. Rigid and brickle coating has a shorter repeated impact life because a kind of linear crack is formed easily in it. On the other hand, tougher coating has a long life. Mechanics of nucleation and expansion of crack was explained by using stress concentration theory and vacancy concentration theory. The anti-repeated impact fatigue performance of laser cladding part could be improved by increasing toughness and reducing hardness of the coating material. Furthermore, suitable dispersion strengthening and fine-crystal strengthening can obtain the same purpose.

Pressure‐induced ferroelectric to antiferroelectric phase transformation in porous PZT95/5 ceramics

AbstractThe hydrostatic pressure‐induced ferroelectric to antiferroelectric (FE–AFE) phase transformation of PZT95/5 ceramics was investigated as a function of porosity, pore shape and pore size. FE–AFE phase transformations were more diffuse and occurred at lower hydrostatic pressures with increasing porosity. The porous PZT95/5 ceramics with spherical pores exhibited higher transformation pressures than those with irregular pores. Moreover, FE–AFE phase transformations of porous PZT95/5 ceramics with polydisperse irregular pores were more diffuse than those of porous PZT95/5 ceramics with monodisperse irregular pores. The relation between pore structure and hydrostatic pressure‐induced FE–AFE transformation was established according to stress concentration theory. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On the theory of stress concentration for shear‐strained prismatical bodies with a non‐linear stress‐strain law

The system of equations governing the stress in a shear-strained prismatical body are examined and it is shown that, provided the stress-strain law adopts certain multi-parameter forms, the system may be reduced to the Cauchy-Riemann equations. Integration of the system is then immediate and the analysis of the stress concentration round certain notches thereby facilitated.

The Role of Stress Concentration in Slab Avalanche Release

AbstractSlab avalanches are shown to be released by brittle fracture. An analogy is drawn in which the snow-pack is considered to be a macroscopic, molecular model of glass. The analogy is examined qualitatively from two viewpoints: the Griffith fracture criterion, and stress concentration theory. The details of fracture propagation in a layered snow-pack are explained by means of stress concentration theory, and many details of slab avalanches are shown to be consistent with the proposed mechanism. The significance of various fracture surface markings is pointed out.

The Role of Stress Concentration in Slab Avalanche Release

AbstractSlab avalanches are shown to be released by brittle fracture. An analogy is drawn in which the snow-pack is considered to be a macroscopic, molecular model of glass. The analogy is examined qualitatively from two viewpoints: the Griffith fracture criterion, and stress concentration theory. The details of fracture propagation in a layered snow-pack are explained by means of stress concentration theory, and many details of slab avalanches are shown to be consistent with the proposed mechanism. The significance of various fracture surface markings is pointed out.

Theory of Stress Concentration of Two Normally Intersecting Cylindrical Shells

Stress distributions in two normally intersecting cylindrical shells subjected to internal pressure are discussed on the basis of Donnell's equation for the intersected shell, and Flugge's equation for the intersecting one. A rational boundary condition along the intersection curve is derived by using Energy Principles. Numerical computation was conducted, and the results are compared with experiments.

Approximate solution of axially symmetric problems

A variety of physical problems in such diverse fields as electrostatic field theory, heat and ideal fluid flow, and stress concentration theory reduce, under the assumption of axial symmetry, to the study of the elliptic partial differential equation ∂ 2 u/∂x 2 + ∂ 2 u/∂y 2 + k/y(∂u/∂y) = 0. Dirichlet-type problems associated with this equation are studied on regions whose boundaries include a nondegenerate portion of the x-axis and exceedingly accurate numerical methods are given for approximating solutions.

Theory of Stress Concentration for Shear-Strained Prismatical Bodies With Arbitrary Nonlinear Stress-Strain Law

Knowledge of stress concentration is very important for engineers in many practical cases. But the stress-concentration factors for Hooke’s law often cannot be used because most technical materials have stress-strain laws deviating from Hooke’s law. In the second edition of his book “Kerbspannungslehre” the author gave a calculation method for a special nonlinear deformation law. In the present paper a general theory for arbitrary stress-strain laws is established which leads to a calculation method for the real values of the concentrated stresses in the material.

Comparison of Semi-Empirical Solutions for Crack Propagation With Experiments

Abstract The crack-propagation characteristics of two aluminum alloys and several steels have been investigated in sheet materials under uniaxial tension. Empirical formulas based on ultimate strength and initial crack length were found to be a sufficiently effective method for establishing the relative merit of a material in its resistance to crack propagation. Comparison of experimental data with criteria obtained from the energy-release rate or stress-concentration theory shows that neither method yields reliable material constants.

Some Problems Associated with Stress Concentration

The theory of stress concentration is such a fascinating study that the whole of this lecture could be most happily devoted to discussion of the stress distribution round all sorts of special boundaries. At the same time the most detailed knowledge of elastic stress distribution is of little value unless we can be sure how the stresses computed will be reflected in the actual strength of the part. For that reason this paper is divided into three sections: the first deals with certain moderately simple cases of stress and load concentration and shows how the stress analysis is confirmed by static and fatigue tests: the second describes some investigations of special two–dimensional boundaries and indicates, some fairly general theoretical conclusions which can be drawn: in the third I shall try to review the possible reasons why, in practice, the best found conclusions are not always borne out.