单试样法测金属材料JR曲线及其条件起裂值

在单试样卸载柔度法及三曲线法基础上,提出了一种更简便的测定金属材料JR曲线及其条件起裂值的单试样三点柔度法,并用该方法测定了1Cr1/2Mo钢、16MnR钢和WCF62钢的JR曲线及其条件起裂值,与标准的多试样法相比,误差均在工程许可范围内。     

单试样三曲线法测定J积分阻力曲线及条件起裂值

用单试样三曲线法测定了16MnR 钢和某一焊缝金属的 J 积分阻力曲线及其条件起裂值,与标准的多试样测定结果基本吻合.实验表明,单试样三曲线的关联分析反映了带裂纹的三点弯曲试样的宏观断裂物理过程,裂纹的延性扩展符合幂函数规律.     

COD阻力曲线的单试样三曲线分析法

在三曲线分析的基础上,提出了一种新的单试样测定 COD 阻力曲线的方法和步骤,编制了计算机应用程序。用三曲线法测定了 C—Mn 钢,Cr-Mo 钢和一种焊缝金属的 COD 阻力曲线,与标准的多试样法实验结果符合较好。该方法使用方便经济。有推广使用的价值。     

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介绍降载柔度单试件法测量柱试件ＣＯＤ阻力曲线的基本原理和运用微机采集与处理数据的方法,测定圆试件ＨＱ６０钢的ＣＯＤ阻力曲线,试验结果表明用降载柔度法测量圆柱试件ＣＯＤ阻力曲线有高很精度。     

韧性材料J_R阻力曲线受试样尺寸因素影响的实验研究

本文应用不同尺寸的三点弯曲试样和带边侧槽试样,用实验方法研究了启裂J积分(J_(1C))和J_R阻力曲线的斜率(dJ/da)受试样尺寸的影响。结果表明,在满足GB2038-80所规定的试样尺寸要求的条件下,J_(1C)值受试样尺寸影响不大,但DJ/da值受试样尺寸影响较大。因此,在应用以J_R曲线理论为基础的裂纹扩展稳定性评定方法时,如撕裂模量理论及EPRI方法,要应用较大尺寸试样或带侧槽试样来测定J_R阻力曲线。     

-196℃奥氏体不锈钢母材与焊缝的动态断裂韧性

在-196 ℃对S30408奥氏体不锈钢的母材和焊缝进行了夏比摆锤冲击实验,采用改进的柔度变化率法得到了低温下不锈钢母材夏比试样的起裂点。结果表明,采用改进的柔度变化率法得到的结果比采用传统的柔度变化率法得到的结果更准确。根据实验得到的载荷-位移曲线,结合采用Schindler法和关键曲线法各自所得结果的优点,得到了不锈钢母材的动态裂纹扩展阻力曲线（动态J-R曲线）。依据不锈钢焊缝在低温动载下的载荷-位移曲线及其断裂特征,通过线弹性断裂力学计算获得其动态断裂韧性。     

动态弹塑性断裂韧性测试方法的比较研究

利用示波冲击试验,对动态弹塑性断裂韧性测试的不同方法（单试样法和多试样法）进行了研究．结果表明,单试样法（柔度变化率）测定材料的动态断裂韧性是一种简单、准确、适合于工程应用的好方法     

试验确定自增强圆筒的表面裂纹K1因子和疲劳扩展规律

本文提供了一种可以进行自增强处理的圆筒试样,通过实验用柔度法确定了该试样的表面裂纹的应力强度因子,介绍了含表面裂纹试样的柔度测试技术,导出了柔度与表面裂纹尖端前缘各点的应力强度因子的关系式,该式可作为各种含表面裂纹试样柔度法测表面裂纹 K_1因子的参考,本文还测定了不同自增强程度下,自增强圆筒的表面裂纹疲劳扩展规律。     

一种弹塑性材料动态起裂韧度的J表征和测试方法

在数值计算的基础上提出了一个弹塑性材料动态起裂韧度的J表征和测试方法．这一方法利用自行研制的间接杆-杆型冲击拉伸试验装置，对周边切口的短圆柱试件实施基于一维试验原理的弹塑性材料动态断裂试验；利用试件两端的平均载荷—相对位移曲线(P-δ)或平均载荷-裂纹张开位移曲线(P-△)，推广Bice远场公式获得动态J积分；采用柔度变化率法确定裂纹起裂点，从而得到动态起裂韧度JJD．这一方法的优点在于利用P-δ或P-△曲线将外力对试件所做的与裂纹运动无关的质心惯性运动动能近似地从总能量中分离出来，且平均载荷P在起裂前以至失稳扩展前是单调增的，同时试验获得的P-δ和P-△曲线光滑，这使得用J积分作为裂纹尖端的表征参量以及用柔度变化率法确定起裂点和失稳点具有坚实的物理基础．     

40Cr材料动态起裂韧性KId（）的实验测试

描述了利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试４０Ｃｒ，材料动态起裂韧性ＫＩｄ（）的试验方法。试样上的动态载荷历程由Ｈｏｐｋｉｎｓｏｎ杆直接测得，并分别代入动态有限元程序及近似公式求得动态应力强度因子历史；由贴在试样裂尖附近的应变片确定起裂时间，最终确定起裂时的动态应力强度因子值，即动态起裂韧性ＫＩｄ（）。试验结果表明:利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试材料动态起裂韧性的方法是可行的，起裂时，动态有限元的位移法、应力法及近似公式法求得的动态应力强度因子值比较吻合；在本文的载荷速率下，４０Ｃｒ材料动态起裂韧性ＫＩｄ（）与准静态裂韧性ＫＩｄ（）相比，降低了约２８％。     

Oscillatory measurements of silicone oils —Loss and storage modulus master curves

The work describes a way to obtain loss modulus and storage modulus master curves from oscillatory measurements of silicone oils.The loss modulus master curve represents the dependence of the viscous flow behavior on · ₀ ^* and the storage modulus master curve — the dependence of the elastic flow behavior on · ₀ ^* .The relation between the values of the loss modulus and storage modulus master curves (at a certain frequency) is a measurement of the viscoelastic behavior of a system. The G/G-ratio depends on · ₀ ^* which leads to a viscoelastic master curve. The viscoelastic master curve represents the relation between the elastic and viscous oscillatory flow behavior.     

混凝土分段曲线损伤模型

在对比分析国内外现有的混凝土受拉损伤模型基础上，结合素混凝土受拉应力应变曲线的试验结果，提出了一个新的混凝土分段曲线损伤模型，并利用应力连续条件确定了损伤模型中各系数的值。运用该模型到力学分析中，推导了矩形截面的混凝土梁在纯弯矩作用下，在损伤较小和损伤较大时的力学方程，算出了梁的最大承载能力，并与材料力学计算的梁承载能力进行了对比。详细分析了损伤区域及损伤应力在横截面上的变化过程，确定了极限状态下含损伤混凝土梁的应力分布和相应的承载能力，画出了损伤状态梁截面的应力分布图。     

水工混凝土S-N和P-S-N曲线特性研究

在已知混凝土静压强度分布的基础上使用S－N曲线模型推导出一种疲劳寿命满足的分布，并对水工混凝土做了大量的等幅抗压疲劳试验。通过分析发现，实验数据能较好地符合该分布，同时得出了该种混凝土的S－N曲线和P－S－N曲线。     

基于正弦曲线拟合法实现陀螺罗盘快速精寻北

在对陀螺罗盘精寻北进行研究的过程中,发现陀螺罗盘精寻北耗时很长,不能满足要求,而在保证精度的前提下缩短其精寻北时间是作战需要。为了兼顾陀螺罗盘精寻北的精度和效率,分析了精寻北时陀螺灵敏部摆动模型,发现陀螺灵敏部绕当地子午面做有偏移的正弦摆动,于是提出了一种正弦曲线拟合算法以解算陀螺罗盘仪器中心的方位角。实验表明,利用1/4周期的数据进行正弦曲线拟合寻北,精度略低于积分法,精寻北时间却可由传统积分法的150 s减至37.5 s,大幅缩减了寻北时间。因此,正弦曲线拟合算法是提高陀螺罗盘寻北效率的有效途径。     

描述非线性振动的一个数学模型

本文运用保守振动系统的能量守恒定律，论述了一种确定振动系统运动微分方程阻尼函数的方法，以求得与保守系统运动微分方程的解相一致的相平面边界曲线。     

BUCKLING LOADS AND EIGENFREQUENCIES OF A BRACED BEAM RESTING ON AN ELASTIC FOUNDATION

The eigenvalue problems of the buckling loads and natural frequencies of a braced beam on an elastic foundation are investigated. The exact solutions for the eigenvalues are presented. The eigenvalues vary with the different parameters and are especially sensitive to the brace location. As the beam of a continuous system has infinite eigenvalues and these eigenvalues are influenced differently by a brace, the eigenvalues show rich variation patterns. Because these eigenvalues physically correspond to the structure buckling loads and natural frequencies, the study on the eigenvalues variation patterns can offer a design guidance of using a lateral brace of translation spring to strengthen the structure.     

Instability of the liquid equilibrium state in an ice-water system with account for radiation heating

The problem of the stability of the equilibrium state of a weakly compressible fluid bounded from below by a stationary rigid wall and from above by a heat-conducting finite-thickness wall is studied. The thermal state of the system is investigated with account for volume heat sources due to radiation. It is shown that the mechanical equilibrium of the system is unstable. The neutral curves are plotted and the critical Rayleigh numbers are found.     

Einsatz rheologischer Messungen zur Beschreibung der Beschaffenheit der Korninhaltsstoffe des Getreides

Zusammenfassung In der vorliegenden Arbeit wird über die Anwendung eines Universal-Rotationsviskosimeters für Forschungszwecke in einem Getreidelaboratorium berichtet und einige dabei gewonnenen Ergebnisse diskutiert. Die Messungen wurden sowohl an niedrigviskosen Wasserextrakten und Suspensionen als auch an hochviskosen Teigen durchgeführt. Als Meßart wurden Fließ- und Viskositätskurven zur Beschreibung eines Zustandes und kontinuierliche Messungen über die Zeit und bei steigenden Temperaturen zur Erfassung der Viskositätsveränderungen durchgeführt. Mit den dabei gewonnenen Ergebnissen wird versucht, die Struktur und Beschaffenheit der Korninhaltsstoffe zu beschreiben und die Wechselwirkung dieser Merkmale und der Enzymolyse zu verdeutlichen.Schlüsselwörter Rotationsviskosimeter, Fließkurve, Viskositätskurve, kontinuierliche Viskositätsmessung, Getreidequalität

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Summary In the present paper the possibilities for using a universal rotational viscometer for research purposes in cereal laboratories have been described and discussed. This kind of instrument is suitable as well for viscosity measurements in low viscous water-extracts and water-fluor slures as in high viscous doughs of such a consistency, as used in the practical breadmaking. Drawing up flow and viscosity curves for describing the condition of chemical matters in cereal grain, continuous measurements over the time at constant or defined increasing temperatures have been choosen to record the changes of the viscosity. The obtained results have been utilised to describe the structure and the state of the main constituents of cereal grains (starch, protein, pentosan) and to make evident the alternating effect between those characteristics and the enzymolysis.

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Stability of steady nonisothermal flow in a vertical layer with permeable boundaries in the microconvection model

The problem of the stability of steady convective viscous incompressible fluid flow in a vertical layer with boundaries at different temperatures is considered in the presence of transverse blowing through the layer. The complete spectral problem is solved for a silicon melt. The neutral curve is constructed and the critical Grashof number is found. The numerical calculations show that the presence of transverse blowing significantly affects the flow stability. As compared with the Oberbeck-Boussinesq model, in the microconvection model the instability develops at lower wavenumbers.     

Convective instability of a system of horizontal layers of slightly compressible liquids

The convective stability of a system of two immiscible liquids with close densities is studied. The densities of the liquids depend nonlinearly on temperature and pressure. It is shown that the state of mechanical equilibrium is unstable. Neutral curves are plotted, and the critical values of the Rayleigh number are found. The calculations are performed for physical parameters characteristic of various northern, central, and southern zones of lake Baikal. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 15–22, July–August, 2007.