Calculation Model of Equivalent Strength for Induced Crack Based on Double-K Fracture Theory and Its Optimizing Setting in RCC Arch Dam

By means of fracture testing on roller-compacted concrete （RCC） three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer′s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.

Incompleted Field Strength Calculation of the Potential Term Adopted from Landau-Ginzberg Theory Applied in Particle Physics

Completion of field strength calculation of the potential term originated in theories of condensed matter applied in particle physics is discussed.

Temperature field calculation of rail flash welding

The forging stage of rail flash welding has a decisive influence on joint strength,and the study of the temperature distribution in the process has an important role in further improving joint strength.In this paper,three calculation methods for the temperature field are given.First,the finite element model of the temperature field before forging rail flash welding is established by using the transient heat module of Ansys software and verified by infrared temperature measurement.Second,the temperature distribution of different parts of the rail before flash welding is obtained by using infrared thermal imaging equipment.Third,Matlab software is used to calculate the temperature of the non-measured part.Finally,the temperature distribution function along the rail axis is fitted through the temperature measurement data.The temperature distribution before the top forging of the rail flash welding can be used to analyze the joint and heat-affected zone organization and properties effectively and to guide the parameter setting and industrial production.

Relativistic calculations of 3s^2 ~1S_0-3s3p ~1P_1 and 3s^2 ~1S_0-3s3p ~3P_(1,2) transition probabilities in the Mg isoelectronic sequence

Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration-interaction method, calculations of transition energies, oscillator strengths and rates are performed for the 3s2 1S0-3s3p 1P1 spinallowed transition, 3s2 1S0-3s3p 3P1,2 intercombination and magnetic quadrupole transition in the Mg isoelectronic sequence （Mg I, A1 II, Si III, P IV and S V）. Electron correlations are treated adequately, including intravalence electron correlations. The influence of the Breit interaction on oscillator strengths and transition energies are investigated. Quantum eleetrodynamics corrections are added as corrections. The calculation results are found to be in good agreement with the experimental data and other theoretical calculations.

First principles calculation of stable structure and adhesive strength of plated Ni/Fe(100) or Cu/Fe(100) interfaces

A study the with first principles calculation of the interfaces of the Ni layer or Cu layer on the Fe(100) surface formed with metal plating was performed.Ni or Cu atoms were shown to adopt the corresponding position to the bcc structure of the Fe(100) substrate.Other calculations showed that the interfaces of Ni(5 atomic layers)/Fe(100)(5 layers) or Cu(5 atomic layers)/Fe(100)(5 layers) had square lattices.The orientation relationship of Ni/Fe(100) interface corresponds to fcc-Ni(100)//bcc-Fe(100),Ni[011]//Fe[010],and Ni[011]//Fe[001].Similar results were obtained for Cu/Fe(100) interfaces.This structure was supported by TEM analysis of plated Ni layer on Fe(100) surfaces.The adhesion strength of the Ni/Fe(100) interface evaluated by first principles calculation was higher than that of the Cu/Fe(100) interface.The experimental results of Hull cell iron plated with Ni or Cu supported the results of the calculation.These results indicate that the first principles calculation,which deals with the ideal interface at the atomic scale,has the potential to evaluate the adhesion strength of metallic material interfaces.

MECHANICAL ANALYSIS AND NUMERICAL CALCULATION OF BONDING STRENGTH MEASUREMENT BY INTERFACIAL INDENTATION METHOD

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CALCULATION ON THE YIELD STRENGTH OF A PRECIPITATION STRENGTHENING Ni－BASE ALLOYS

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Anisotropic elastic properties and ideal uniaxial compressive strength of TiB_2 from first principles calculations

The structural, anisotropic elastic properties and the ideal compressive and tensile strengths of titanium diboride （TiB2） were investigated using first-principles calculations based on density functional theory. The stress-strain relationships of TiB2 under 〈10i0〉, 〈12i0〉, and 〈0001〉 compressive loads were calculated. Our results showed that the ideal uniaxial compressive strengths are ｜σ〈02i0〉）｜ = 142.96 GPa, ｜σ〈0001〉 ] = 188.75 GPa, and ｜σ〈10i0〉｜ = 245.33 GPa, at strains -0.16, -0.32, and -0.24, respectively. The variational trend is just the opposite to that of the ideal tensile strength with σ〈10i0〉 = 44.13 GPa, σ〈0001〉 = 47.03 GPa, and σ〈i2i0〉 = 56.09 GPa, at strains 0.14, 0.28, and 0.22, respectively. Furthermore, it was found that TiB2 is much stronger under compression than in tension. The ratios of the ideal compressive to tensile strengths are 5.56, 2.55, and 4.01 for crystallographic directions （10i0）, 〈12i0〉, and 〈0001〉, respectively. The present results are in excellent agreement with the most recent experimental data and should be helpful to the understanding of the compressive property of TiB2.

Theoretical Calculation Model of Single Rip Tearing Strength for the Nonwoven Composites

The nonwoven composites have sandwich structure, with the first and third layers being nonwovens and the middle layer of woven fabric. On the basis of tests of the single rip tearing strength and drawing out resistances of both the nonwoven composites and the woven fabric, the single rip tearing failure mechanism of the composites were analyzed. Then theoretical calculation model for the single rip tearing strength was established, which indicates that the breaking strength of warp and weft yams in the nonwoven composites, the density of warp and weft yarns and drawing out resistances are the main influencing factors. In the end, experimental verification was made, which shows that theoretical values conform to the measured values well.

Calculation on uniaxial compressive strength of high strength concrete after wrapped by FRP

A theoretical calculation method of the axial compressive strength of a high strength concrete with fibre reinforced plastics (FRP) constraint is proposed. It is shown by test verification that the FRP strength devotion factor used for this method is in accordance with actual conditions. FRP is not up to the ultimate strength when the concrete reaches the ultimate strength, whose strength devotion factor is in the range of 0.28 to 0.59, which is related to an elastic modulus. The method can be used to estimate axial compressive strength of the concrete strengthened with FRP. The theoretical strength is 10% to 30% higher than the measured one. The deviation comes mainly from a non-ideal bonding condition of FRP-concrete interfaces and discrete property of the testing data of compressive strength.

TENSILE STRENGTH OF RANDOM ORIENTED SHORT FIBER COMPOSITE

This paper shows a calculation model and a method for predicting the tensile strength of the random distributed short fiber composite.On the basis of Renjie Mao's model,the longitudinal tensile strength of the aligned short fiber composite is formulated.Considering the transverse tensile strength and in plane shear strength of the unidirectional fiber composite,and the stress transformation relations of two couples of axes,the stress of the unidirectional fiber composite when it is loaded at an arbitrary angle is obtained.With the aid of an equivalence relation,the calculation formulation of the tensile strength of the random short fiber reinforced composite is deduced.

First-principles investigation on ideal strength of B2 NiAl and NiTi alloys

For B2 NiAl and NiTi intermetallic compounds, the ideal stress–strain image is lack from the perspective of elastic constants. We use first-principles calculation to investigate the ideal strength and elastic behavior under the tensile and shear loads. The relation between the ideal strength and elastic constants is found. The uniaxial tension of NiAl and NiTi along <001> crystal direction leads to the change from tetragonal path to orthogonal path, which is driven by the vanishing of the shear constant C(66). The shear failure under {110}{111} shear deformation occurring in process of tension may result in a small ideal tensile strength(~ 2 GPa) for NiTi. The unlikeness in the ideal strength of Ni Al and Ni Ti alloys is discussed based on the charge density difference.

Ideal strength of Mg_(2)X(X¼Si,Ge,Sn and Pb)from first-principles

First-principles calculations within generalized gradient approximation have been performed to investigate ideal strengths of anti-fluorite structured Mg_(2)X(X¼Si,Ge,Sn and Pb)compounds.The present calculations showed that the ideal tensile strengths of Mg_(2)X occur in the[111]directions while the ideal shear strengths appear in the(111)[11-2]systems.Both ideal tensile strength and shear strength of Mg_(2)X(X¼Si,Ge,Sn and Pb)decreased gradually with the increase of atomic number of X.The microscopic process and inherent mechanisms of mechanical properties were discussed from the evolution of electronic structures during strain.

Analysis of complete plasticity assumption for solid circular shaft under pure torsion and calculation of shear stress

The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding, the applicability of complete plastic model assumption and the shear stress formula were researched. Based on the shear stress formula of circular shaft under pure torsion in elastic stage, the formula of torque in elastic stage and the definition of yield, it is obtained that the yielding stage of plastic metal shaft under pure torsion is only a surface phenomenon of torque-torsion angle relationship, and the distribution of shear stress is essentially different from that of tensile stress when yielding under uniaxial tension. The pure torsion platform-torsion angle and the shape of torque-torsion angle curve cannot change the distribution of shear stress on the shaft cross-section. The distribution of shear stress is still linear with the maximum shear stress ts. The complete plasticity model assumption is not in accordance with the actual situation of shaft under torsion. The experimental strength data of nine plastic metals are consistent with the calculated results of the new limiting strain energy strength theory （LSEST）. The traditional yield stress formula for plastic shaft under torsion is reasonable. The shear stress formula based on the plane assumption in material mechanics is applicable for all loaded stages of torsion shaft.

Statistical Model of the 3-D Braided Composites Strength

Based on the statistical model for the tensile statistical strength of unidirectional composite materials and the stress analysis of 3-D braided composites, a new method is proposed to calculate the tensile statistical strength of the 3-D braided compos- ites. With this method, the strength of 3-D braided composites can be calculated with very large accuracy, and the statistical parameters of 3-D braided composites can be determined. The numerical result shows that the tensile statistical strength of 3-D braided composites can be predicted using this method.

Physical Methods and Parameters for Assessing the Strength, Fatigue, Durability and Damage to a Structural Material

The methods and criteria of the physical theory of strength are used. The initial physical and mechanical parameters of the strength of steel 45 were determined analytically. Strength, fatigue and damage to steel were calculated for non-stationary mechanical and various thermal loads. The ratio between the physical and generally accepted mechanical parameters of the material strength is determined analytically. The result of the calculation of the new characteristics of the strength of the damaged material is given. The method takes into account plastic deformation, an arbitrary form of stress cycle, temperature mode. Additional physical criteria for evaluating the strength properties are proposed. We use our own calculation programs, which allow us to take into account the changed characteristics of the damaged material for various stress functions. The physical method allows you to analyze and quickly process the rheological data of sensors that control the parameters of the material under load. A method for rapid analysis and comparison of the results of indentation into the material in accordance with ISO 14577 using various indenters is proposed. Physical parameters of the material and new theoretical methods of calculation can be used to assess the properties of materials, monitor the condition and predict the strength and durability of the material of machines during operation.

Composition design of high yield strength points in single-phase Co-Cr-Fe-Ni-Mo multi-principal element alloys system based on electronegativity,thermodynamic calculations,and machine learning

A method which combines electronegativity difference,CALculation of PHAse Diagrams(CALPHAD) and machine learning has been proposed to efficiently screen the high yield strength regions in Co-Cr-Fe-Ni-Mo multi-component phase diagram.First,the single-phase region at a certain annealing temperature is obtained by combining CALPHAD method and machine learning,to avoid the formation of brittle phases.Then high yield strength points in the single-phase region are selected by electronegativity difference.The yield strength and plastic deformation behavior of the designed Co_(14)Cr_(30)Ni_(50)Mo_(6)alloy are measured to evaluate the proposed method.The validation experiments indicate this method is effective to predict high yield strength points in the whole compositional space.Meanwhile,the interactions between the high density of shear bands and dislocations contribute to the high ductility and good work hardening ability of Co_(14)Cr_(30)Ni_(50)Mo_(6)alloy.The method is helpful and instructive to property-oriented compositional design for multi-principal element alloys.

First-principles study on mechanical properties of LaMg_3 and LaCuMg_2

Abstract： With the substitution of part Mg in LaMg3 by Cu, the elastic constants CH and C12 increase while C44 decreases, implying an enhanced Poisson effect and smaller resistance to 〈001〉（100） shear. Furthermore, the bulk modulus B increases, while the shear modulus G, elastic modulus E and anisotropie ratio A are reduced. The calculated Debye temperature of LaCuMg2 is lower, implying the weaker interaction between atoms in LaCuMg2. Then, the stress-strain curves in entire range and the ideal strength at critical strain are studied. The present results show that the lowest ideal tensile strength for LaMg3 and LaCuMg2 is in the 〈100〉 direction. The ideal shear strength on the 〈 1 ^-1 0〉（110） slip system of LaMg3 is greater than LaCuMg2. The density of states and charge density distribution are further studied to understand the inherent mechanism of the mechanical properties.

The Study of CAD ＆ Processing Error for End-Gear with Arc Tooth

This paper presents methods for determining the basic geometry of end-gear with arc tooth external diameter, width of tooth, end module, number of teeth, pressure angle, tooth, tooth clearance parameters; at the same time gives the tooth bearing strength calculation method, and the formulas to calculate the tooth shear stress, surface stress and bolt fastening force of equivalent stress is established; finally write the software error simulation analysis.

FRP筋混凝土双向板冲切强度公式评估

为评价现有FRP筋混凝土双向板冲切强度计算公式的精度,采用数理统计的方法对收集到的38组FRP筋混凝土双向板冲切强度试验数据进行评估。结果表明,影响FRP筋混凝土双向板冲切强度的主要因素有混凝土强度、临界冲切截面周长、有效板厚、FRP筋配筋率及其弹性模量、尺寸效应;在所评价的10个计算公式中,规范公式的预测结果大多比较保守,且其精度均低于文献公式;Ospina公式预测结果与试验结果最为接近,且精度最高,预测结果与试验结果比值的均值为1.03,标准差为16.04%,变异系数为15.53%。研究结果为FRP筋混凝土双向板冲切强度计算公式的进一步优化提供了参考。