220kV变压器线圈现场施压及压板强度研究

对ＳＦＰＳＺ９－１５０ ０００／２２０特大型变压器线圈现场施压进行了探讨性的试验，提供了 一些可行性的计算方法，分析了试验结果并提出了存在问题与一些合理建议。

对ZQYC型油压机主机压板结构的刚度与强度分析

利用解决弹性力学问题的能量法对 ZQYC型油压机主机压板结构刚度与强度的计算进行了研究 ,导出了合理估算压板厚度的近似公式 ,为压板设计提供了理论依据。

复合材料层压板强度与损伤评估研究

现代飞机发展趋势表明,复合材料在飞机结构中的应用越来越广,使用比例越来越高,复材的应用已成为衡量现代飞机先进性的重要标志之一。复合材料具有比强度高、比刚度大、材料性能可设计性等优点,已在航空领域得到较为广泛的应用。但在实际结构中,不可避免地会遇到各种应力集中情况,如开孔、加工缺陷等。

对四柱式油压机主机线性变截面压板结构设计的研究

利用弹性力学的变分原理,采用Galerkin方法,通过求解积分方程,对四柱式平板压榨挤水(油)机主机线性变截面压板的结构设计进行了研究,给出了可供工程应用的结果。

板式热交换器强度计算

随着我国工业化水平的不断发展,国家对能源的利用率提出了更高的要求,未来我国板式热交换器(以下简称板换)的使用会越来越多。板换的行业标准NB/T 47004.1-2017中没有明确规定板换压板计算方法,目前业内都是参考GB/T 150.3-2011平盖计算方法来计算压板厚度。经过多年的现场使用表明,通过GB/T 150.3-2011平盖计算的方法得到的结果过于保守。本文通过调整安全系数的方法来降低压板的厚度,同时利用ANSYS分析及试验验证计算结果。

A numerical method for multiple cracks in an infinite elastic plate

This article examines the interaction of multiple cracks in an infinite plate by using a numerical method. The numerical method consists of the non-singular displacement discontinuity element presented by Crouch and Startled and the crack tip displacement discontinuity elements proposed by the author. In the numerical method implementation, the left or the right crack tip element is placed locally at the corresponding left or right crack tip on top of the constant displacement discontinuity elements that cover the entire crack surface and the other boundaries. The numerical method is called a hybrid displacement discontinuity method. The following test examples of crack problems in an infinite plate under tension are included： “ center-inclined cracked plate”, “interaction of two collinear cracks with equal length”, “interaction of three collinear cracks with equal length”, “interaction of two parallel cracks with equal length”, and “interaction of one horizontal crack and one inclined crack”. The present numerical results show that the numerical method is simple yet very accurate for analyzing the interaction of multiple cracks in an infinite plate.

Prediction of representative deformation modulus of longwall panel roof rock strata using Mamdani fuzzy system

Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining struc- tures. In this paper, two predictive models including Mamdani fuzzy system （MFS） and multivariable regression analysis （MVRA） were developed to predict deformation modulus based on data obtained from dilatometer tests carried out in Bakhtiary dam site and additional data collected from longwall coal mines. Models inputs were considered to be rock quality designation, overburden height, weathering, unconfined compressive strength, bedding inclination to core axis, joint roughness coefficient and fill thickness. To control the models performance, calculating indices such as root mean square error （RMSE）, variance account for （VAF） and determination coefficient （R^2） were used. The MFS results show the significant prediction accuracy along with high performance compared to MVRA results. Finally, the sensitivity analysis of MFS results shows that the most and the least effective parameters on deformation modulus are weatherin~ and overburden height, respectively.

Dynamic analysis of double racks gear 3D roll forming machine

3 D roll-forming for high strength steel sheets is a new technology at present.Double racks gear 3D roll forming machine developed by our research group can be used to perform variable cross section roll forming for high strength steel.In the paper,a dynamic model of 8-DOF double rack gear 3D roll-forming machine is established by the method of Lagrange equation.The expression of the angle acceleration of the system response is obtained by solving the dynamic equations.Through an actual engineering example,the dynamical characters of the 3D roll forming machine are revealed.The results can support the design of 3D roll forming machine.Meanwhile,the research will play an active role in the development of control system.

Fatigue properties of rolled AZ31B magnesium alloy plate

Fatigue strength,crack initiation and propagation behavior of rolled AZ31B magnesium alloy plate were investigated. Axial tension-compression fatigue tests were carried out with cylindrical smooth specimens.Two types of specimens were machined with the loading axis parallel(L-specimen)and perpendicular(T-specimen)to rolling direction.Monotonic compressive 0.2%proof stress,tensile strength and tensile elongation were similar for both specimens.On the other hand,monotonic tensile 0.2%proof stress of the L-specimen was slightly higher than that of the T-specimen.Moreover,monotonic compressive 0.2%proof stresses were lower than tensile ones for both specimens.The fatigue strengths of 107cycles of the L-and T-specimens were 95 and 85 MPa,respectively. Compared with the monotonic compressive 0.2%proof stresses,the fatigue strengths were higher for both specimens.In other words, the fatigue crack did not initiate and propagate even though deformation twins were formed in compressive stress under the cyclic tension-compression loading.The fatigue crack initiated at early stage of the fatigue life in low cycle regime regardless of specimen direction.The crack growth rate of the L-specimen was slightly lower than of the T-specimen.Consequently,the fatigue lives of the L-specimen were longer than those of the T-specimen in low cycle regime.

Mechanical property of single-bolted composite laminates

In order to investigate the effects of different geometrical parameters and pretightening loads on failure mode and bearing strength,a large number of single-bolted T300/QY8911 composite laminates were tested under static tension load.Box-plot was used to extract the singular testing values of bearing strength and effective statistical values were obtained.T-test method of independent samples was used to study how much pretightening loads influence bearing strength.The results show that the geometrical parameters,such as ratios of width to hole diameter(w/d) and edge distance to hole diameter(e/d),remarkably influence failure mode and bearing strength.Net-section failure will occur when w/d is smaller than 4,and shear-out failure will occur when e/d is smaller than 2.Bearing failure or bearing and shear-out combined failure will occur when w/d is greater than 4 and e/d is greater than 2.There is an optimal combination of geometrical parameters to achieve the highest bearing strength.For most of specimens,pretightening loads do not explicitly influence bearing strength.

Square concrete columns strengthened with carbon fiber reinforced plastics sheets at low temperatures

Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.

A study on mechanical behavior of the carbon fiber composite sandwich panel with pyramidal truss cores at different temperatures

A series of compression tests were conducted to investigate the mechanical properties and failure mechanisms of carbon fiber composite sandwich panels using pyramidal truss cores subjected to temperatures ranging from 100℃ to 350℃.The compressive strength and stiffness of sandwich panels decreased as temperature increased.Cryogenic temperatures caused an increase in strength and stiffness,while elevated temperatures resulted in a reduction of strength and stiffness.The effect of temperature on the failure mode of the sandwich panel was revealed as well.The interface between the fiber and matrix was examined by a scanning electron microscope(SEM) in order to study the effect of temperature on strengthening the mechanism and good bonding conditions within the fiber-matrix interface was observed at cryogenic temperatures.The comparison of the predicted and experimental data indicated that the stiffness and strength of the composite sandwich panels for temperature variation was consistent.