Flexible Base Plate Research Articles

Plastic limit analysis for eight-bolted base plate based on slip-line field theory

Eight-bolted base plates have gradually been employed in the UHV transmission lines. On the basis of slip-line field theory, this paper derived new calculation methods for predicting the uplift bearing capacities of rigid and flexible base plate, their reasonable accuracy has been validated by comparing with test observations and yield-line method results. The relevant parametric analysis demonstrated these two methods have consistent variation tendency and the thickness of base plates is of paramount impact on ultimate strength. Design suggestions considered four possible failure modes and their corresponding calculation formulae were presented for evaluating the controlling capacities of base plates, one of which associated with slip-line method adopted the least-square fitting to obtain correction coefficients so as to get explicit solutions for calculations. Their applicability and accuracy have been verified by comparing with the test and corresponding code.

Electrical and Thermal Conductivity of Polylactic Acid (PLA)-Based Biocomposites by Incorporation of Nano-Graphite Fabricated with Fused Deposition Modeling.

The aim of the study was to improve the electrical and thermal conductivity of the polylactic acid/wood flour/thermoplastic polyurethane composites by Fused Deposition Modeling (FDM). The results showed that, when the addition amount of nano-graphite reached 25 pbw, the volume resistivity of the composites decreased to 108 Ω·m, which was a significant reduction, indicating that the conductive network was already formed. It also had good thermal conductivity, mechanical properties, and thermal stability. The adding of the redox graphene (rGO) combined with graphite into the composites, compared to the tannic acid-functionalized graphite or the multi-walled carbon nanotubes, can be an effective method to improve the performance of the biocomposites, because the resistivity reduced by one order magnitude and the thermal conductivity increased by 25.71%. Models printed by FDM illustrated that the composite filaments have a certain flexibility and can be printed onto paper or flexible baseplates.

Capacity of exposed column base connections subjected to uniaxial and biaxial bending moments

ABSTRACT Current guidelines do not address the design of column base connections under combined biaxial bending moment and axial load. An analytical study is conducted to develop a biaxial moment-axial load interaction curve for design of exposed, unstiffened column base plates. First, a 3D finite element analysis model is developed for these connections. The response of the model is validated through a series of existing experimental data. Next, the model is used to investigate the response of a few connections subjected to various biaxial moments and axial loads. Based on simulation results, a simple and reasonably accurate interaction equation is proposed. Since the uniaxial capacities of the connection are involved in the interaction curve, an analytical method for predicting the uniaxial capacities, is also presented. This analytical method, which is based on formation of plastic mechanisms, is able to predict the strength of flexible base plates with high accuracy. The behavior of exposed base plates with I-shaped columns under minor-axis moments is also studied. Findings of this study assists practitioners with a reliable and convenient column base connection design.

Boundary element method based vibration analysis of elastic bottom plates of fluid storage tanks resting on Pasternak foundation

A higher-order boundary element procedure is presented for the free vibration analysis of flexible base plates of rigid fluid storage tanks resting on elastic foundation. The main principles of the procedure are replacing the biharmonic operator of the thin plate vibration problem by two successive harmonic operators, and representing the forcing terms (plate inertia, fluid loading and foundation influence) by applying the dual reciprocity boundary element formulation. The fluid effect on the plate dynamics is incorporated into the analysis by invoking another boundary element solution, which expresses the fluid pressure over the plate surface in terms of plate deflection. The performance of the method is thoroughly investigated and the nature of dynamic plate–foundation–fluid interaction is studied from several perspectives. The method provides excellent predictions, within the limits of Kirchhoff plate, potential flow, and Pasternak foundation models.

Dynamic behaviour and active sound radiation control of a two-stage vibration isolation system equipped on a flexible plate

This paper presents a general model of a two-stage vibration isolation system involving a flexible base plate with arbitrary boundary conditions. The dynamic behavior of the coupling system was obtained by using an impedance method in which the impedance matrix of the base plate was derived from a combined use of an improved Fourier series expansion and the Rayleigh-Ritz method. Subsequently, with the purpose of attenuation of sound radiation from the base plate structure, the optimal force information is formulated under various active control strategies including: 1) minimizing the total vibratory power of the coupled structure, 2) minimizing the sound power radiation from the base plate, 3) minimizing the vibratory power transmitted to the base plate, and 4) minimizing the mean square velocities at the isolator locations on the flexible plate. Numerical results were presented and discussed in detail. Finally, some concluding remarks are made.

Photo-induced evolution of copper sheets from cluster molecules and its application to photolithographic copper patterning

UV photoexcitation of (t-butylethynyl copper)24 cluster films induces segregation of the crystals into metallic and organic phases and leads to evolve the metallic sheets sandwiched by organic polymers. The growth of the metallic crystals in the plane of the photo-electromagnetic field is attributed due to plasmon-plasmon interaction among nanoparticles embedded in dielectric polymer matrices. The surface enhanced photochemical reaction of residual cluster molecules on the photon incident direction is expected to take an important role for joining the metal particles to produce a metallic sheet. We can apply this phenomenon for photolithographic copper pattern generation on a flexible base plate.

Effects of mechanical stress and high glucose on pericyte proliferation, apoptosis and contractile phenotype

Pericyte loss is an early step of diabetic retinopathy. High glucose induces apoptosis in retinal pericytes, but systemic and capillary hypertension are also believed to be important in the onset and progression of diabetic retinopathy. The haemodynamic insult of retinal capillary hypertension can be mimicked by exposing pericytes to mechanical stretch. We investigated the effect of stretch combined with high glucose on pericyte proliferation/apoptosis and morphology. Bovine retinal pericytes, cultured in either normal or high glucose concentrations in flexible-base plates, were exposed to mechanical stretch for 48/72 h. Cell replication was determined by both cell counting and DNA synthesis, apoptosis by ELISA, cell morphology and actin cytoskeleton distribution by immunofluorescence. Both reduction in cell proliferation and increase in apoptosis were confirmed in high glucose alone. When cells were subjected to stretch, proliferation was reduced and apoptosis increased in both normal and high glucose in comparison with unstretched controls. In both cases, a synergistic effect of hyperglycaemia combined with stretch was shown. Cell morphology showed modifications of cytoskeleton in all experimental conditions; in particular, cells subjected to stretch showed a clear elongation and translocation of actin fibres. In conclusion, our results show that stretch, alone or combined with high glucose, reduces cell proliferation, increases apoptosis and induces morphological changes in pericyte cytoskeleton. Further elucidations of the mechanisms on the basis of reduced proliferation of pericytes subjected to high glucose and stretch could help to clarify the effects of combined hyperglycaemia and hypertension in the pathogenesis of diabetic retinopathy.

Finite element modal analysis of a rotating disk–spindle system in a HDD with hydrodynamic bearings considering the flexibility of a complicated supporting structure

This paper presents a method to analyze the free vibration of a rotating disk–spindle system in a HDD with hydrodynamic bearings (HDBs) considering the flexibility of a complicated base structure by using finite element method. Finite element equations of each component of a HDD spindle system from the spinning flexible disk to the flexible base plate are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between the sleeve and hydrodynamic bearings to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. The validity of the proposed method is verified by comparing the calculated damped natural frequencies and modes with the experimental results. This research also shows that the supporting structure which includes the stator, housing and base plate plays an important role in determining the natural frequencies and mode shapes of a HDD spindle system

Multichannel feedback control for the isolation of equipment from base vibration

Passive systems for the isolation of equipment from base vibration involve an inherent compromise between good high-frequency isolation, which requires low values of isolator damping, and limited excitation of the rigid body modes, which requires high values of isolator damping. It is known that a single-channel active control system using ‘‘skyhook damping,’’ in which a secondary force acts in proportion to the absolute velocity of the equipment, can give good damping in a lumped mass-spring-damper system without compromising the high-frequency isolation. In this experimental study a multichannel skyhook damper was used to study the isolation of a rigid mass from the vibrations of a flexible base plate. With the actuators and sensors wired together and the system excited symmetrically, a single-channel controller was initially implemented which not only showed reductions in the equipment vibration of up to 40 dB at the heave resonance at 15 Hz, but also showed substantial reductions at modes of the flexible base plate below about 200 Hz. The multichannel controller was also able to control the pitching mode of the equipment which is apparent when the system is not excited symmetrically.

Strain distribution in steel base plates under eccentric loads

Experiments have been conducted on steel column base plates subjected to eccentric loads and the strain distributions in the base plates at various stages of loading have been determined. The thickness of the base plate and the eccentricity of load have been treated as parameters. Test results for the maximum bending strains, which always occurred at the column–base plate junction on the side of the load, compare reasonably well with those from a finite element analysis. However, the present results for the bending strains in the cantilever portions of the base plates which failed by yielding are greater than those obtained from classical theory, which is, therefore, seen to be conservative for these cases. Longitudinal and lateral strain distributions, strain contour plans, maximum bending strain variation with load, and interaction diagrams are presented and the results discussed. From these results it is evident that flexible base plates, especially when loaded at higher eccentricities, behave somewhat differently from what is assumed in classical methods.

Base Plates Under Axial Loads and Moments

Experiments are conducted to study the behavior of base plates under the action of axial loads and moments by eccentric loading on the column. The parameters in the study are the thickness of the base plate and the eccentricity of the load. At the lowest eccentricity, failure was by cracking of the concrete, while at other eccentricities the primary mode of failure was by the yielding of the base plate. Comparisons of the test results with the predictions from the Working Stress Method gave a range of 1.09–1.89 for the factor of safety with a mean value of 1.35 for specimens that failed by yielding of the base plate. The strain distributions in the base plate were obtained at various stages of loading. They indicate the existence of a critical section of maximum strain, a section of zero strain and strain reversal. The eccentricity of the load seems to have a greater influence on the strains than the thickness of the base plate. The test results show that flexible base plates when loaded at high eccentric...