Applied Mechanics and Materials Vols. 52-54

Abstract: A linear differential equation is adopted to account for the complexity of honeycomb paperboard properties under static and dynamic conditions. Based on the Laplace transform, honeycomb paperboard is modeled as a linear material with viscoelastic property. The free response of the mass loaded honeycomb paperboard system is expressed as the sum of complex exponentials. The residues and eigenvalues are obtained accurately using the structured nonlinear total least norm(SNTLN) method. A parameters estimation procedure is formulated using a substitution strategy. A experiment system is set up, a series of tests is carried out under different load condition, the free response data of the mass loaded honeycomb paperboard system are recorded and they are used to estimate the parameters. The stiffness coefficients, damping coefficients and viscoelastic coefficients are presented as the function of the load. The model in this work can be used to simulate the response of the mass loaded honeycomb paperboard system under shock condition.

Abstract: An accurate model of pneumatic isolators is important for its structure optimization and controller design. Previous researches show that an isolator model including the diaphragm effect which is neglected before can predict the isolator response more accurately. Since the diaphragm is often made of reinforced rubber material and has an irregular shape, it is not easy to obtain its parameters with experimental or computing method. A finite element analysis method for estimating the diaphragm stiffness is proposed in this paper, and experimental results suggest that a new model including the diaphragm stiffness correspond to the isolator behaviors more accurately.

Abstract: One-stage light gas gun is used to study the dynamic mechanical properties of reinforced concrete (SFRC) subjected to shock loading. The material of projectile is the same as of the target. The stress-time curves are recorded by three manganin pressure transducers embedded in the targets beforehand. The data of experiment are analyzed by self-designed program using the path line principle of Lagrangian analysis method. With the stress records, complete histories of particle velocity, density (and thus strain) and specific internal energy can be obtained at any point within the gaged region of the material. Moreover, the numerical constitutive relations of RC are obtained and the strain rate ranges from 104 to 105 per second. The result of experiment indicates that the stress-strain curves of SFRC present stagnant-return properties. And some other dynamic properties can be gained, such as rate dependent, waveform dissipation etc.

Abstract: This paper Shamir threshold scheme based on the protection of private keys, by constructing a Lagrange interpolating polynomial to achieve in the real environment using the key shared information systems, computation and communication in the case of less , the program can prevent the system key is lost, damaged, and from the enemy's attack, reduce the responsibility of the key holder, but also can reduce the success rate of an adversary to decipher the key. An example is the feasibility of the program.

Abstract: Based on the TNC architecture, using a trusted network of repair techniques in the trusted network access scenario does not meet the requirements of integrity verification solution for end users. Put forward a credible fix the overall network design, reliable model restoration and repair services, network workflow. The system is in need of restoration to provide safe and reliable repair end-user data transmission, providing a humane, reasonable repair services to ensure the credibility of fixed network and the isolation effect of the terminal to be repaired and strengthened the security of fixed server. Realized the classification of various types of repair resources management, restoration of resources in ensuring the transfer of fast, reliable, based on the performance with a certain extension.

Abstract: An exact and closed-form solution is obtained for free vibration problems of homogeneous isotropic cylindrical shells, which is under arbitrary boundary conditions and with varied initial stresses in different longitudinal sections. First, the cylindrical shell is divided into multiple sub-shells according to their thicknesses and initial stresses. And the displacement functions of the sub-shell’s middle plane are expanded as trigonometric series in circumferential direction. Then, based on the simplified Donnell shell theory, a set of fundamental dynamic equations, which take initial stresses into accounts, is derived through Hamilton’s principle for each sub-shell. Correspondingly, boundary conditions and connection conditions are derived too. These equations and conditions are simplified through setting the displacements varied in harmonic form. Finally, through defining the state vector, the dynamic equations and solution-determine conditions are described as state-space forms and solved conveniently. Numerical examples validate this method. Driving process of analytical solutions show that it is convenient for introducing and dealing with solution-determine conditions and solving the dynamic problems of cylindrical shells with varied initial stresses in different longitudinal sections.

Abstract: This article is to provide a method to make the structure of machine tools lightened and improve its anti-vibration capacity. Modal analysis with pre-stress of High-speed Turning Center’s spindle box was performed using ANSYS Workbench; based on the above results, we optimized the spindle box using topological optimization and dimensional optimization methods. Finally, we make the spindle box’s weight reduce by 4.44%, its first order frequency increase by 15.82%, its first mode maximum amplitude decrease by 9.18%.

Abstract: This paper mainly presents the study on the properties of cement treated aggregate with different coarse aggregate content. The test specimens which contain 75%, 70%, 65%, 60% and 55% of coarse aggregates were made and the 7d, 28d, and 90d unconfined compressive strengths (UCS), 28d thremal shrinkage coefficient, as well as 90d anti-erosion performance were tested. Results show that with the increase of coarse aggregate, the maximum dry density (MDD)of the cement treated aggregate mixture increased slowly at first to reached the peak value and then decreased rapidly; The optimum moisture content (OMC) declined with the increase of coarse aggregate content; In order to enhance the UCS of cement treated aggregate, coarse aggregate of mixture can be increased to some extent, but too much coarse aggregate will increase the void of the specimen and lead to lower UCS; Increasing the content of coarse aggregate is able to decrease the thermal shrinkage coefficient and erosion quantity of 30 min of the specimens. This is favourable to enhance the cracking resistance and anti-erosion performance of cement treated aggregate base course.

Abstract: Under seismic actions, reinforced concrete columns are generally damaged by a combination of repeated stress reversals and high stress excursions. An experimental study was undertaken to investigate cumulative damage in reinforced concrete rectangular columns subjected to repeated cyclic loadings. Fourteen identical half-scale concrete columns were fabricated and tested to failure. This paper summarizes the results of Phase I testing that consisted of benchmark tests to establish the monotonic force-deformation envelope, and constant amplitude tests to determine the low-cycle fatigue characteristics of typical flexural columns. A companion paper will present the results of variable amplitude tests to develop an analytical model of cumulative damage for rectangular reinforced concrete columns. Test observations indicate two potential failure modes: low cycle fatigue of the longitudinal reinforcing bars; and confinement failure due to rupture of the confining hoops. The former failure mode is associated with relatively large displacement amplitudes, while the latter is associated with a larger number of smaller amplitude cycles. A fatigue life expression is developed that can be used in damage-based seismic design of rectangular, flexural concrete columns.

Abstract: The findings from an experimental study to investigate cumulative seismic damage in reinforced concrete columns are presented. Fourteen identical half-scale concrete columns were fabricated and tested to failure. Results from Phase I testing, which included constant amplitude tests to determine the low-cycle fatigue characteristics of the rectangular concrete column, were presented in a companion paper. This paper summarizes results of variable amplitude tests. The imposed displacement histories were obtained from analytical simulations of the model column subjected to a series of earthquakes. Test observations indicate that failure is generally initiated by confinement inadequacy and the rupture of the transverse hoop reinforcement. The tests also demonstrated the potential for low-cycle fatigue fracture of the main longitudinal steel when the specimen was subjected to relatively larger displacement amplitudes. A fatigue-based damage model, derived from the constant-amplitude tests completed in Phase I testing, was applied to the observed response of the three specimens tested in this phase. Findings from the study indicate that the energy capacity of members is ductility-dependent and that fatigue-based damage models offer a reliable means of assessing seismic structural performance.