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On the interior ballistics of an underwater personal gun

This paper deals with solving the problem of interior ballistics for a concrete personal underwater gun. The governing equations of the problem are carefully discussed because the water resistance force acting on the bullet is quite different from that of the air. These equations are used to create software for analyzing and designing an underwater gun. The calculated results are in very good agreement with the experimental data.

Stationary values of the transmission ratio of the planar fourbar

The transmission ratio of the planar fourbar, i.e. the ratio of the angular velocities of input link and output link, is a function of the input angle. Freudenstein [1] showed how to calculate stationary values of the transmission ratio. In the present paper a new method is described. Like Freudenstein’s method it results in a sixth-order polynomial equation.

On shakedown and ratchetting of conforming frictional systems

The theorems can also be considered the extension to cyclic loadings of the Dundurs results for conforming contacts under monotonic loading, in which case the contact area doesn’t vary in time and hence the problem is linear (from which the denomination "receding contacts").

An approximate secular equation of rayleigh waves in an elastic half space coated by a thin weakly inhomogeneous elastic layer

. In this paper, the propagation of Rayleigh waves in a homogeneous isotropic elastic half-space coated with a thin weakly inhomogeneous isotropic elastic layer is investigated. The material parameters of the layer is assumed to depend arbitrarily continuously on the thickness variable. The contact between the layer and the half space is perfectly bonded.

On the design of an optimum active mass-spring-inverted pendulum dynamic vibration absorber for the inverted pendulum type structure

The paper presents a design of an active massspring-inverted pendulum DVA for the inverted pendulum type structure in case the external force is white noise process. The design is based on the optimum passive DVA as carried out in [4] and apply the optimum control force by minimizing the performance index.

Equivalent-inclusion approach for estimating the elastic moduli of matrix composites with non-circular inclusions

A novel approach to predict the effective elastic moduli of matrix composites made from non-circular inclusions embedded in a continuous matrix is proposed. In this approach, those inhomogeneities are substituted by simple equivalent circularinclusions with modified elastic properties obtained from comparing the dilute solution results.

Improved estimates for the effective elastic bulk modulus of random tetragonal crystal aggregates

Particular expressions of upper and lower estimates for the macroscopic elastic bulk modulus of random cell tetragonal polycrystalline materials are derived and computed for a number of practical crystals. The cell-shape-unspecified bounds, based on minimum energy principles and generalized polarization trial fields, appear close to the simple bounds for specific spherical cell polycrystals.

Frequency response of a beam like structure to moving harmonic forces

The spectral approach is employed for spectral analysis of a beam subjected to an arbitrary force traveling along the beam with constant speed. First, an expression for exact frequency response of a beam subjected to moving arbitrary force and general boundary conditions has been constructed.

Postbuckling of thick FGM cylindrical panels with tangential edge constraints and temperature dependent properties

This paper investigates postbuckling behavior of thick FGM cylindrical panels resting on elastic foundations and subjected to thermal, mechanical and thermomechanical loading conditions. Material properties are assumed to be temperature dependent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of constituents.

Free vibration of a cracked double beam-carrying a concentrated mass

This paper presents the free vibration of a cracked double-beam carrying a concentrated mass located at an arbitrary position. The double-beam consisting of two different simply supported beams connected by an elastic medium is modelled by using finite element method.

Numerical simulation of solidification around a circular cylinder with natural convection

The solidification interface is represented by connected elements that move on the fixed background grid. Code validations are carried out through various problems. Finally, the temporal dependence of the solid area ratio of the solid phase to the cylinder upon various dimensionless parameters, such as Rayleigh number, Prandtl number, Stefan number, thermal property ratios as well as a parameter indicating the effect of superheat is studied.

An evolutionary-based optimization algorithm for truss sizing design

In this paper, the optimal sizing of truss structures is solved using a novel evolutionary-based optimization algorithm. The efficiency of the proposed method lies in the combination of global search and local search, in which the global move is applied for a set of random solutions whereas the local move is performed on the other solutions in the search population.

Free vibration of functionally graded sandwich plates with stiffeners based on the third-order shear deformation theory

In this paper, the free vibration of functionally sandwich grades plates with stiffeners is investigated by using the finite element method. The material properties are assumed to be graded in the thickness direction by a power-law distribution. Based on the third-order shear deformation theory, the governing equations of motion are derived from the Hamilton’s principle.

Can dislocations accelerate through the shear wave speed ”barrier”

The question of whether a dislocation can accelerate through the shear-wave speed “barrier” is addressed by analyzing the transient motion of a Volterra dislocation at the instant when the velocity equals the shear-wave speed in the presence of acceleration, which requires an asymptotic analysis at a double root (–at the transition from subsonic to supersonic a pair of complex conjugate roots becomes a double real —).

About the edge - based smoothed finite element method for the reissner - mindlin plate - bending problem

The paper further develops the edge-based smoothed finite element method (ES-FEM) for analysis of Reissner - Mindlin plates using triangular meshes. The bending and shearing stiffness matrices are obtained using strain smoothing technique over the smoothing domains associated with edges of elements.

Crack analysis for some structures subjected to thermal and dynamic loads

The influence of the temperature, dynamic loads or position of the crack on fracture parameters for these structures are investigated. The given programs may be useful for estimating the failure of dams, tunnels or other structures.

Calculation of the wave parameters for sea dyke design and upgrading

In the paper, the authors present the results of the project concerning the input data, wave models and the calculated wave parameters with different returning periods for 5 sectors along the coastal line from Quang Ninh to Quang Nam. The obtained results afford the promising of using in the sea dyke design and upgrading.

Shear strengthening of reinforced concrete beams using epoxy bonded steel plates, cfrp sheets and externally anchored stirrups

This research presents the effectiveness of different shear strengthening methods using epoxy bonded steel plates, steel strips, carbon fiber reinforced plastics (CFRP) sheets and externally anchored stirrups for enhancing the shear strength of RC beams. In this study, an experimental program including two series of twelve specimens was carried out to investigate the behavior of RC beams strengthened with the above methods.

Định lượng 5-hydroxymethylfurfural trong mật ong bằng phương pháp sắc ký lỏng hiệu năng cao (HPLC-DAD)

Trong nghiên cứu này, HMF được nghiên cứu định lượng bằng phương pháp sắc ký lỏng hiệu năng cao, một kỹ thuật đã được xem là phổ biến tại các cơ sở kiểm tra chất lượng ở Việt Nam hiện nay.

About an approximate method to solve the static boundary value problems in the isotropic hardening elastic plastic solid

The paper presents the theory, model, weak form, finite element method and return-mapping algorithm for the isotropic hardening elastic-plastic problem. Then applying the algorithm to numerically simulate a variety of plane strain problems.

Slip-shakedown analysis and the assumption of small coupling in frictional contact

The pressure is thus a given time-dependent function and the Coulomb criterion is reduced to a Mises-like standard law of friction. It is shown here that Melan and Koiter theorems can be applied again as in standard plasticity. The dependence of the yield limit on the loading amplitude is however not classical and the extension of the static and kinematic approaches is discussed to obtain the critical shakedown load or the limit load. The validity of the assumption of small coupling is also explored by numerical simulation in an practicle example.

Determining reaction forces in planar mechanisms

In the paper, it is introduced a method to det ermine joint reaction forces, constraint forces and internal forces at the cross section of linkages. Based on the principle of compatibility and the ideality of constraints, the methodology is presented to analyze and determine reaction forces in planar mechanisms.

An interesting material that appears to be fit to possibly all future mechanical vibration textbooks

A material is suggested for future mechanical vibration textbooks. Both mathematically and conceptually it is simpler than most of the material that is already included in the existing textbooks. It pertains to the inverse vibration problem for inhomogeneous beam, i.e. the beam with the modulus of elasticity that varies along the axial coordinate. Specifically, the solution of the following problem is presented: Find a distribution of the modulus of elasticity of an inhomogeneous beam such that the beam would possess the preselected simple, polynomial vibration mode shape.

Dynamic absorber for ropeway gondola using coriolis force

The mass moves in the radius direction (up and down) and it induces Coriolis force in the circumference direction to prevent the swing of gondola. If the natural frequency of the absorber is tuned to twice that of the gondola, the absorber moves spontaneously with a large amplitude due the resonance. This absorber is more effective when it is located at lower positions. The experiment with a small model and an actual gondola for 10 passengers were carried out and the results agreed well with the theoretical predictions.

On the convergence of a coupling successive approximation method for solving duffing equation

In the present paper the convergence of mentioned method is proven and a condition relating coefficients of Duffing equation to provide the convergence procedure is formulated. Emphasize that the assumption of small parameters is not used in the proving. Some examples are presented to illustrate the proposed method, particularly exact solutions of some problems are compared with analytical approximate ones found by CSAM.

Thermal buckling of imperfect functionally graded cylindrical shells according to wan-donnell model

The thermal loads include the uniform temperature rise and nonlinear temperature change across the thickness of shell. A closed form solution for the thermal buckling of simply supported cylindrical FG shell under the described thermal loads is obtained. The influences of the relative thickness, the imperfection size and the power law index on buckling thermal loads are all discussed.

Shakedown and collapse of elastic-plastic structures under variable and cyclic loads

The paper presents an introduction to the results obtained mainly by the author in shakedown analysis of elastic plastic structures, with the shakedown theorems for elastic plastic kinematic hardening materials playing the central role. Some illustrative examples of application are given.

Mô phỏng số quá trình hàn ma sát quay của hợp kim titan

Bài báo này trình bày một phương pháp mô phỏng số cho quá trình hàn ma sát quay bằng mô hình 2D dùng phần mềm thương mại Abaqus/Standard. Mô hình cơ nhiệt được sử dụng trên cơ sở mô hình vật liệu Johnson-Cook.

A cell-based smoothed discrete shear gap method (CS-FEM-DSG3) for dynamic response of laminated composite plate subjected to blast loading

The paper investigates the dynamic response of laminated composite plate under the effect of blast loading. The cell-based smoothed discrete shear gap method (CSFEM-DSG3) based on the first-order shear deformation theory (FSDT) and the equivalent layer theory (ELT) is used to model the behavior of the laminated composite plate.

Các mũi cắt/ Kim chuyên may da

Trình bày đầy đủ Các mũi cắt/ Kim chuyên may da. Nhận biết khả năng cắt gọt của mũi cắt, mài và kiểm tra phần cắt gọt đúng yêu cầu kỹ thuật thời gian. Phải đam bảo an toàn lao động và bảo dưỡng máy móc tốt.

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