Initial transgritical behavior in a compressed rod under creep conditions

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 2, pp. 152–156, March–April, 1993.     

Studying the nonlinear vibrations of statically compressed plates

The paper outlines a method for studying the vibrations of plates of complex geometry subjected to in-plane loading. The method is based on the R-function and variational methods. It is used to plot frequency response of plates with complex geometry and different boundary conditions __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 12, pp. 124–132, December, 2006.     

Solution of the problem of the initial postcritical behavior of cylindrical shells reinforced by stringers

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 27, No. 8, pp. 81–88, August, 1991.     

The creep behavior of ideally atactic and commercial polymethylmethacrylate

Summary The shear creep behavior of polymethylmethacrylate, PMMA, samples has been studied in the neighborhood of and above their glass temperatures. One of the materials studied was ideally atactic with equal numbers of random isotactic and syndiotactic placements, while the other was a commercial or conventional PMMA which was about 76% syndiotactic. The glass temperatures,T _g , were found to be 106 and 117 °C respectively. Evacuation above the glass temperature for several weeks was necessary before reproducible creep compliance,J (t), curves could be obtained. It is believed that absorbed water plasticized the polar materials and its removal led to the shifting of theJ (t) curves to longer times. For both materials apparently successful temperature reduction was found to be possible within the temperature range of our investigations, i.e. up to 200 °C. Retardation spectra were calculated from the reduced curves and are compared. The temperature dependences, as described by the time scale shift factors,a _T , were similar when allowance is made for the different glass temperature. Botha _T curves could not be fitted to theWilliams, Landel, andFerry, WLF, free volume expression. These are the first examples of such a deviation for amorphous high polymers. It is proposed that the primary softening dispersion has two distinctly different groups of viscoelastic mechanisms contributing to it. On this basis the primary dispersion was decomposed into the two contributions. Both of the resulting temperature dependences were satisfactorily fitted to the WLF equation. Differences in the retardation spectra are noted. The glassy compliance of the commercial PMMA appears to be about twice that of the atactic PMMA.Data on commercial PMMA is incorporated in a thesis which has been submitted in partial fulfillment of the requirements for the degree of Master of Science in Materials Engineering, University of Pittsburgh, 1970.With 12 figures and 1 table     

Anticlastic behavior of flat plates

The purpose of this paper is to show that the readings from strain gages can be used effectively to compute small transverse deflections in a rectangular plate and, further, show that the theory developed by Lamb for the rectangular-plate problem agrees with experiment. A numerical procedure is developed, based on the trapezoidal rule, which determines the transverse deflections from the readings of strain gages mounted to the top and bottom surface of a rectangular plate subjected to large longitudinal curvatures. It is shown using the strain-gage technique that experiment agrees with Lamb's theory forb ² /Rt ratios up to 50.     

Geometrically non-linear eccentrically compressed columns of uniform creep strength vs optimal columns

Optimality of geometrically non-linear eccentrically compressed columns of uniform strength in creep conditions is investigated. A third-order theory with siretehability of axis taken into account is employed. Norton's non-linear creep law and Kachanov's hypothesis of brittle creeprupture is used and an I-column of uniform strength for a given life-time is numerically evaluated. Then this column is. found to be non-optimal and a futher parametrical optimization is performed under the constraint of constant volume of the constant volume of the column. The life-time of the optimal column is considerably increased.     

Postbuckling behavior of rectangular moderately thick plates and sandwich plates

ＰＯＳＴＢＵＣＫＬＩＮＧＢＥＨＡＶｉＯＲＯＦＲＥＣＴＡＮＧＵＬＡＲＭＯＤＥＲＡＴＥＬＹＴＨＩＣＫＰＬＡＴＥＳＡＮＤＳＡＮＤＷＩＣＨＰＬＡＴＥＳＣｈｅｎｇＺｈｅｎ－ｑｉａｎｇ（成振强）ＷａｎｇＸｉｕ－ｘｉ（王秀喜）ＨｕａｎｇＭａｏ－ｇｕａｎｇ（黄茂光）...     

径向压缩单壁碳纳米管的力学行为

寻求具有卓越性能而又易于制造的纳米开关是纳米科技界的一个研究热点. 首先基于碳纳米管的结构双稳性提出了一种纳米开关的原型设计, 其由关到开的转换可通过径向压缩实现; 然后利用基于REBO-II作用势的分子动力学模拟, 系统分析了径向压缩单壁碳纳米管的力学行为和不同纳米管的双稳性特征, 给出了一些纳米管双稳性的特征参数, 对于工程设计具有一定的指导意义.     

基于有限元法的轮轨蠕滑特性研究

轮轨滚动接触蠕滑率／力理论是轮轨相互作用一系列问题研究的基础．现有的几种计算蠕滑力的理论模型均建立在Hertz接触条件和半空间假设的基础上，已经无法完成对复杂的接触问题的进一步研究．使用有限元参数二次规划法来求解轮轨的三维弹性／弹塑性接触问题，得出了在不同的轴重、牵引力矩、摩擦系数、踏面形状、横向力条件下的轮轨接触力．提出用轮轨接触的轮周位移计算蠕滑率的新方法，并对在各种参数下所得到的蠕滑率进行了分析比较．     

The creep behavior of simple structures with a stress range-dependent constitutive model

High temperature design remains an issue for many components in a variety of industries. Although finite element analysis for creep is now an accessible tool, most analyses outside the research domain use long standing and very simple constitutive models—in particular based on a power law representation. However, for many years, it has been known that a range of materials exhibit different behaviors at low and moderate stress levels. Recently, studies of the behavior of high temperature structures with such a stress range-dependent constitutive model have begun to emerge. The aim of this paper is to examine further the detailed behavior of simple structures with a modified power law constitutive model in order to instigate a deeper understanding of such a constitutive model’s effect on stress and deformation and the implications for high temperature design. The structures examined are elementary—a beam in bending and a pressurized thick cylinder—but have long been used to demonstrate the basic characteristics of nonlinear creep.