大力值拉向力传感器校准装置的研制

目前,大力值拉向力传感器的校准是国内的一大难题。本文基于对力值转换的准确性、装置的安全性和安装便捷性的考量,设计了一套用于60MN叠加式力标准机的大力值拉向校准装置,将力标准机的压向力转换为拉向力,并进行计量性能测试。实验证明:测量范围(2~30)MN内,装置重复性优于0.05%。

万能试验机检测拉向力和压向力的影响因素分析

总结了万能试验机在检定拉力和压力过程中出现的问题,并对问题产生的原因进行了分析和讨论,基于此,提出了保证检测结果准确可靠的措施。

Effects of parameters of asphalt concrete surfacing on mechanical property of paving layer

The important parameters that influence the mechanical property of the pavinglayer on an orthotropic steel bridge deck are the paving layer thickness and modulus of the asphaltconcrete surfacing. Three important indices that control the typical failures of the paving layerare the maximum tensile stress of paving layer, the maximum shear stress between the steel deck andthe paving layer, and the maximum deflection on the paving surface. In this paper, the analyticalmodel of paving systems on orthotropic steel bridge deck is established, and the finite elementmethod is adopted to study the stress and strain of paving system. With the variation of asphaltconcrete modulus in high or low temperature season, the influences of paving layer thickness onthree control indices are researched. The results provide a theoretical basis for the determinationof thickness of the paving layer on the steel bridge deck.

便携式漆膜附着力检测仪校准装置设计与研究

漆膜的附着力是指漆膜与被附着物体表面通过物理和化学力作用结合在一起的坚牢程度,是考核漆膜性能的重要指标,其主要测量仪器为便携式漆膜附着力测试仪。为解决该测试仪的溯源问题,本研究拟设计一套专用的校准装置,采用标准测力仪作为核心标准器具,通过设计辅助测量装置,实现与便携式漆膜附着力测试仪的连接,并通过辅助结构,将标准测力仪的显示力值转化为单位面积的压强,从而实现量程范围内的逐点、直观校准。;实验结果表明,该便携式漆膜附着力测试仪校准装置具备更高检测精度及准确度。

Hydrodynamic deep drawing of double layered conical cups

Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.

Extending application of asymmetric semi-circular bend specimen to investigate mixed mode Ⅰ/Ⅱ fracture behavior of granite

The asymmetric semi-circular bend(ASCB)specimen has been proposed to investigate the cracking behavior in different geo and construction materials and attracted the attention of researchers due to its advantages.However,there are few studies on the fracture toughness determination of rock materials.In this work,a series of fracture tests were performed with the ASCB specimens made of granite.The onset of fracture,crack initiation angle and crack propagating trajectory was analyzed in detail combined with several mixed mode fracture criteria.The influence of the crack length on the mode Ⅰ/Ⅱ fracture toughness was studied.A comparison between the fracture toughness ratios predicted by varying criteria and experimental results was conducted.The relationship between experimentally determined crack initiation angles and curves of the generalized maximum tangential stress(GMTS)criterion was obtained.The fracture process of the specimen was recorded with the high-speed camera.The shortcomings of the ASCB specimens for the fracture toughness determination of rock materials were discussed.The results may provide a reference for analysis of mixed mode I and II fracture behavior of brittle materials.

Effect of process parameters on tensile strength of friction stir welded cast A356 aluminium alloy joints

A356 is a high strength aluminium-silicon cast alloy used in food,chemical,marine,electrical and automotive industries.Fusion welding of this cast alloy will lead to many problems such as porosity,micro-fissuring,and hot cracking.However,friction stir welding（FSW） can be used to weld this cast alloy without above mentioned defects.An attempt was made to study the effect of FSW process parameters on the tensile strength of cast A356 aluminium alloy.Joints were made using different combinations of tool rotation speed,welding speed and axial force.The quality of weld zone was analyzed by macrostructure and microstructure analyses.Tensile strengths of the joints were evaluated and correlated with the weld zone hardness and microstructure.The joint fabricated using a rotational speed of 1000 r/min,a welding speed of 75 mm/min and an axial force of 5 kN showed a higher tensile strength compared to the other joints.

Modern tectonic stress field deeply in Xuzhou Coal Mine

By inverting fault slip data, the parameters of 12 tectonic stress tensors in the mine region can be determined. The following characteristics can be obtained for recent tectonic stress fields, which are found deep in the study region. The results show that the recent tectonic stress field mainly presents the characteristics of near NWW-SSE maximum compressional stress and near NE-SW minimum extensional stress, while the stress regimes are mainly of strike slip, part of the reverse-fault type. Recent tectonic stress field in the region is characterized by horizontal components. The maximum principal compression stress direction was from NEE to SEE, the average principal compression stress direction was near NWW-SSE maximum compres- sional stress and near NE-SW minimum extensional. The recent tectonic stress field of the studied area can be controlled by a large tectonic stress area.

Longitudinal forces of continuously welded track on high-speed railway cable-stayed bridge considering impact of adjacent bridges

A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.

Evaluation of in-plane shear test methods for composite material laminates

In-plane shear properties of composite material laminates are very important in structural design of composite material. Four commonly used in-plane shear test methods were introduced in this paper. In order to study the differences of various shear test methods, two ASTM standard in-plane shear test methods for composite material laminates were experimentally investigated. They are ±45° tensile shear test (ASTM D3518) and V-notched rail shear test (ASTM D7078). Five types of composite material laminates composed of E-glass fiber fabric and vinyl ester resin were utilized, whose stacking sequences are 03s, 0/903s, CSM/0/902s, ±453s and (0/90)2/(±45)2/(0/90)2s, respectively. The test results indicate that the ±45° tensile shear test can predict shear moduli of composite material laminates accurately. However, the predictions of shear strength using ±45° tensile shear test are significantly lower than those of V-notched rail shear test.

Transverse vibration of pre-tensioned nonlocal nanobeams with precise internal axial loads

This paper investigates the transverse vibration of a simply supported nanobeam with an initial axial tension based on the nonlocal stress field theory with a nonlocal size parameter. Considering an axial elongation due to transverse vibration, the internal axial tension is not precisely equal to the external initial tension. A sixth-order nonlinear partial differential equation that governs the transverse vibration for such nonlocal nanobeam is derived. Using a perturbation method, the relation between natural frequency and nonlocal nanoscale parameter is derived and the transverse vibration mode is solved. The external axial tension and nonlocal nanoscale parameter are proven to play significant roles in the nonlinear vibration behavior of nonlocal nanobeams. Such effects enhance the natural frequency and stiffness as compared to the predictions of the classical continuum mechanics models. Additionally, the frequency is higher if the precise internal axial load is considered with respect to that when only the approximate internal axial tension is assumed.

An approach for shape optimization of stratosphere airships based on multidisciplinary design optimization

Airship shape is crucial to the design of stratosphere airships. In this paper, multidisciplinary design optimization (MDO) technology is introduced into the design of airship shape. We devise a composite objective function, based on this technology, which takes account of various factors which influence airship performance, including aerodynamics, structures, energy and weight to determine the optimal airship shape. A shape generation algorithm is proposed and appropriate mathematical models are constructed. Simulation results show that the optimized shape gives an improvement in the value of the composite objective function compared with a reference shape.

Polymorph and anisotropic Raman spectroscopy of Phz-Hca cocrystals

The nucleation and growth mechanism and polymorph-property correlations in the molecular cocrystal field are widely sought but currently remain unclear. Herein, a new wire-like morphology of phenazine(Phz)-chloranilic acid(H2ca) cocrystal(PHC) is demonstrated for the first time, and the self-assembly of Phz and H2ca is controlled to selectively prepare kinetically stable wires and thermodynamically stable plates. Specifically, low precursor concentration is beneficial for one-dimensional(1D) self-assembly along the [010] crystallographic direction, while only supersaturation can trigger 2D self-assembly along the [100] and [010] directions, respectively. This is understandable in terms of the(020) face showing the largest attachment energy(Eatt) and the(002) face possessing the smallest surface energy(Esurf). Moreover, anisotropic Raman spectra related to the mode symmetry and atomic displacements in two types of PHCs are revealed, and the same Raman-active vibrational bands of PHC wire and plate show different polarization responses, which is intrinsically ascribed to their different molecular orientations.Overall, this is the first case that morphologies of cocrystal are precisely tuned with comprehensive investigations of their anisotropic vibrational characteristics.

On f-bi-harmonic maps and bi-f-harmonic maps between Riemannian manifolds

Both bi-harmonic maps and f-harmonic maps have some nice physical motivation and applications.Motivated largely by f-tension field not involving Riemannian curvature tensor, we attempt to formalize some large objects so as to broaden the notions of f-tension field and bi-tension field. We introduce a very large generalization of harmonic maps called f-bi-harmonic maps as the critical points of f-bi-energy functional, and then derive the Euler-Lagrange equation of f-bi-energy functional given by the vanishing of f-bi-tension field.Subsequently, we study some properties of f-bi-harmonic maps between the same dimensional manifolds and give a non-trivial example. Furthermore, we also study the basic properties of f-bi-harmonic maps on a warped product manifold so that we could find some interesting and complicated examples.