Modification of the Wilkins Method to Study the Dynamics of Axisymmetric Thick-Wall Shells with a Spiral Orthotropy

Modification of the Wilkins method has been performed for numerical investigation into dynamics of thick-wall cylindrical shells with a spiral orthotropy. Test calculations are shown to agree well with the known solutions. New physical effects have been found, which are absent from isotropic and cylindrically orthotropic bodies.     

Numerical studies on the dynamic behavior of multilayer thick-walled cylinders with helical orthotropy

The Wilkins two-dimensional algorithm-based method of numerical studies on the dynamic behavior of multilayer thick-walled cylindrical shells with different spiral reinforcement structures is developed. Test calculations are in good agreement with known solutions. The dynamic behavior of a two-layer cylinder with different spiral reinforcement structures is investigated.Translated from Problemy Prochnosti, No. 6, pp. 99–110, November–December, 2004     

On the Applicability of One-Dimensional Models to the Dynamic Strength Estimation for Axially Symmetric Bodies

A comparative analysis of the characteristics-difference method and the Wilkins algorithm with reference to problems of nonstationary deformation of one-dimensional cylindrical thick-walled shells has been carried out. On the basis of comparing one- and two-dimensional solutions of boundary problems of the dynamic theory of elasticity obtained by the Wilkins method, conclusions have been drawn about the validity limit of one-dimensional models for the estimation of the strength of female dies for impulse-pressure forming of closed cylindrical and conical shells.     

A numerical study of the nonlinear dynamics of multilayer spirally orthotropic cylinders

Based on the Wilkins two-dimensional algorithm, a method is developed for the numerical study of the geometrically and physically nonlinear axially symmetrical dynamic stress-strain state of multilayer thick-walled cylindrical elastoplastic shells with different spiral reinforcement structures. A numerical study of the specific features in the nonlinear dynamic behavior of single-and two-layer cylinders is carried out for different reinforcement configurations and loading amplitudes. Translated from Problemy Prochnosti, No. 6, pp. 110–121, November–December, 2008.     

Numerical investigation of the dynamic strength of thick-walled cylindrical shells with cracklike technological defects

A numerical method is proposed for the evaluation of the stress intensity factors in elastic thick-walled cylindrical shells with cracks subjected to dynamic loading. The method is based on the two-dimensional axially symmetric Wilkins algorithm and the equations of mechanics of brittle fracture. The strength of thick-walled cylinders loaded by pulses of internal pressure and containing technological defects (similar to mathematical cuts) formed at the sites of fixing of their ends by welding is investigated.Translated from Problemy Prochnosti, No. 1, pp. 76–87, January–February, 2005.     

Bounds on the Transverse Effective Conductivity of a Fiberreinforced Composite

A simple method for determination of the dynamic stress intensity factor (DSIF) variation with time during a four-point impact bend test has been proposed. A formula for DSIF calculation from the recorded loading has been obtained using modal superposition method. Results of calculations for different specimens have been compared with the experimental data and the results of the direct finite element analysis.     

Comment to “A method for smoothing multiple yield functions” by Wilkins,Spencer, Jain and Gencturk. Int J Numer Methods Eng. 2020; 121:434–449

This paper presents a comment to the article “A method for smoothing multiple yield functions” by Andy Wilkins, Benjamin W. Spencer, Amit Jain and Bora Gencturk. The article was published in International Journal for Numerical Methods in Engineering, 2020, issue 121, pages 434–449.     

水下刚硬体声散射场计算及分析

针对水下任意形状刚硬体,建立了其声散射T矩阵法计算模型。利用物体的几何对称性,提出了各种简化计算Q矩阵的方法。以两端有半椭球顶的有限长圆柱体为例,分别计算了具有不同长宽比或者是不同端部几何形状的有限长圆柱体的反向散射和前向散射函数。深入讨论了有限长圆柱体的镜反射波和Franz波的干涉物理模型,以及其圆柱体中段长度对散射场的影响,并对得到的计算结果给出了合理的物理解释。计算结果同时也表明T矩阵法是一种很简便实用的计算水下物体远场散射的方法。     

A Method for Evaluation of Two-point Resolution of Axially Symmetrical Filters

The rapid convergence of the recently developed series representation of the Fresnel diffraction pattern [1] enables us to evaluate the central intensity maximum of the focal patterns using only the first three terms. This fact leads to a simple graphical method of determining the two-point resolution achieved in the Fraunhofer focal plane by the filters with real pupil functions. The method is tested for the Fresnel and Gabor zone plates, the Wilkins filter and the central obstruction.     

Verification of the new viscoelastic method of thermal stress calculation in asphalt layers of pavements

The new viscoelastic method of thermal stress calculations in asphalt layers has been developed and published recently by the author. This paper presents verification of this method. The verification is based on the comparison of the results of calculations with results of testing of thermal stresses in Thermal Stress Restrained Specimen Test. The calculations of thermal stresses according to the new method were based on rheological parameters of the Burgers model. The parameters were measured in laboratory at different low temperatures, at long time creep under constant loading. Five asphalt mixes were tested. Three of them were high modulus asphalt concretes and two conventional asphalt concretes. Specimens were prepared in exactly the same way both for rheological creep tests and for the Thermal Stress Restrained Specimen Test. The results of measured thermal stresses were compared with thermal stresses calculated from the new viscoelastic method developed by the author and in most cases a good agreement was found. For comparison, the measured stresses were compared with results of calculations according to the existing methods. The viscoelastic Monismith method failed in prediction of thermal stresses. The prediction from the quasi-elastic Hills and Brien method was underestimated, but better than from the Monismith method and worse than from the new viscoelastic method. The reasons of discrepancies were discussed.     

A refinement of the Karman-Pohlhausen integral method in boundary layer theory

A basis relation for boundary layer calculations has been obtained by double integration of the Prandtl equations. It is shown that this method leads to more accurate results than the Karman-Pohlhausen method.     

Thermal effects in the contact fusion of the antimony-tellurium system

We have investigated the contact fusion in a binary system with a complex state diagram for different techniques of heating the contact of massive antimony and tellurium specimens with the use of the autothermal e.m.f. method. A decrease in the contact fusion temperature compared to the fusion temperature of the metastable eutectic due to the action of metastable processes has been revealed by experiment. We have established the formation of a metastable Sb + Te eutectic by X-ray structural, X-ray microspectrum, and microstructural analyses and by microhardness measurements of contact interlayers as well as by secondary fusion. Theoretical calculations of the heat released as a result of the exothermal reaction of intermediate Sb₂Te₃ phase formation have been performed.     

Simulation of explosive welding using the Williamsburg equation of state to model low detonation velocity explosives

Explosive welding is a process for producing bi-metallic plates and tubes. Whilst well established it has been essentially an empirical process. In most welding operations, low-speed explosives such as ammonium nitrate fuel oil (ANFO) mixtures, are used. Such explosives have a low velocity of detonation with an appreciable detonation zone. The usual Jones–Wilkins–Lee equation of state (EOS) is not valid. A more representative EOS is the Williamsburg EOS.Recent work to numerically model the process is described. A notable advance is the use of the finite difference engineering package AUTODYN with a Williamsburg-type EOS to model low detonation velocity ANFO explosive and perlite mixtures. In this work, the Williamsburg EOS was coded as a subroutine in the AUTODYN software package which was then used to simulate most aspects of the explosive welding process. The computed results were validated by explosive welding trials.The phenomenon of jetting and the interfacial waves usually observed in explosive welding were successfully reproduced.     

Numerical-analytical method for 3D dynamics study of spirally orthotropic multilayer cylinders

Based on the combination of the Fourier series expansions of variables with respect to the angular coordinate and a two-dimensional Wilkins algorithm, a numerical analytical method is developed to study the three-dimensional non-axisymmetric dynamics of multilayer thick-walled elastic spirally orthotropic cylinders of finite length. Verification of the proposed method is performed based on the comparison of the results with those obtained using the computational kernel of the LS-DYNA combined with the ANSYS/ED (an educational version of ANSYS finite element software). Some features of the dynamic behavior of a two-layer spirally reinforced cylinder under internal pulse loading produced by concentrated explosive charges are studied numerically.     

Binding energy of liquid4He calculated by the hypernetted-chain method

The hypernetted-chain (HNC) method for quantum many-body calculations is investigated in some detail by means of calculations of the binding energy and the equilibrium density for liquid⁴He. The calculations are done for six different two-body potentials, and the results are compared with experimental results and other theoretical results obtained by the lowest order constrained variation (LOCV) method. Our HNC results are, in general, quite different from the results obtained by the LOCV method—the LOCV binding energies are generally reduced by 2–5 K in the HNC calculations. The results are also very dependent on the chosen potential, especially at high densities.     

水压爆破拆除钢筋混凝土酸罐池

用水压爆破方法拆除一个全埋式钢筋混凝土酸罐池。以不同的公式计算药量 ,再结合经验 ,最终选取实际的药量。爆破达到预期目的。对于多药包水压爆破 ,由计算和实际爆破效果来看 ,以注水体积法计算药量较为合理。     

水压爆破拆除钢筋混凝土酸罐池

用水压爆破方法拆除一个全埋式钢筋混凝土酸罐池。以不同的公式计算药量 ,再结合经验 ,最终选取实际的药量。爆破达到预期目的。对于多药包水压爆破 ,由计算和实际爆破效果来看 ,以注水体积法计算药量较为合理。     

Hydrothermal synthesized bismuth ferrites particles: thermodynamic, structural, and magnetic properties

A family of bismuth ferrites (BFO), including Bi2Fe4O9, BiFeO3, and Bi25FeO39 with different morphologies, has been prepared by the hydrothermal method assisted by different alkaline mineralizers. X-ray diffraction refinement calculations are carried out to study the crystal structures of bismuth ferrites. A thermodynamic calculation based on the dissolution-precipitation model was carried out to analyze the hydrothermal synthesis of BFO powders. Magnetic measurements of the obtained bismuth ferrites show different magnetic properties from 5 K to 350 K.     

Measurement of the Kossovich number for thawing frozen soil

Successive approximation has been used to consider the thawing (freezing) of moist soil in an unbounded cylinder. A solution has been used in a method for determining the Kossovich number. The measurements agree with calculations.