Prediction of the Strength of Steel Pipes Damaged by Aqueous Corrosion

We demonstrate the possibility of prediction of the durability of damaged steel pipes. The electrochemical reactions between the metal and water lead to the appearance of slotlike corrosion defects playing the role of stress concentrators and leading to the local overstressing of the material and fracture of the pipes. The durability of the pipes is found as a function of the growth rate of corrosion defects and the degree of stress concentration. The rate of electrochemical corrosion increases with temperature, which decreases the durability of the pipes.     

A Method for the Strength Prediction of Porous Ceramics

We present a fracture model for ceramic materials, according to which ceramics is regarded as a porous inhomogeneous material with a composite structure. The role of pores as stress raisers is taken into account, and their size, geometric shape, and orientation with respect to the direction of the maximum tensile stresses are shown to be important factors. The stress on the pore surface at the places of highest stress concentration, which is equal to the ultimate strength of the ceramics bonding phase, was taken as limiting (failure) stress. Probable pore sizes and shapes have been considered in terms of filler crystal size and volume content. A fracture model and a method for the mathematical determination of the strength of ceramics have been proposed, the method taking into account the strength of the constituents, their volume content, and the shape and size of possible internal defects.     

Prediction of the Long-Term Strength of Various Classes of Metallic Materials

We apply the method of base diagrams to analyze more than 200 diagrams of long-term strength for dispersion-hardened nickel and aluminum alloys. By using only two close numerical values of a single constant, we attain a practically acceptable accuracy of prediction of long-term strength.     

Application of the Method of Base Diagrams for the Prediction of Long-Term Strength in Notched Specimen Tests

The influence of stress concentrators on long-term strength relationships for heat-resistant steels and alloys is investigated in view of known data on strengthening and weakening effects of these concentrators. The method of base diagrams is substantiated to be appropriate for use to significantly refine their effects. The results of experimental data processing are cited, according to these results, with longer times of loading of notched specimens, hardening mainly gives way to softening.     

Analytical Prediction of Crack Coalesce in Multiple Site Damaged Structures

An analytical methodology for predicting the condition when interacting cracks coalesce and estimate the residual strength under Multiple Site Damage situations is proposed. Dominating magnitudes of the criterion are the changes in elastic and plastic strain energy due to crack ligament fracture. The strain energy magnitudes of interest are calculated using analytical formulations, such that the methodology is efficiently applicable in the design of real aircraft panels. Link-up stress predictions using the present methodology are in very good correlation to the experiments and in most cases better, as compared to the alternative crack link-up prediction models.     

复合材料层合板冲击损伤及剩余强度研究进展

综述了受低速冲击后复合材料层合板的损伤研究进展,重点介绍了倍受复合材料工程结构设计师所关注的含损复合材料层合板的剩余拉伸及压缩强度问题,最后对有待于进一步研究的问题进行了展望.     

High-Temperature Strength of Niobium Alloy 5VMTs with a Silicide-Ceramic Coating. Part 2. Characteristics of Short-Term Creep

The regularities of variation in the characteristics of short-term (second) creep and long-term strength of niobium alloy 5VMTs and a composite (alloy 5VMTs/silicide ceramic coating) have been studied using short test durations in the temperature range from 1770 to 2020 K. The creep strength values of the alloy and the composite have been obtained for residual strain tolerances of 0.5 and 1.0% for test durations of 0.1, 1.0, and 10 h at temperatures of 1770, 1970, and 2020 K in vacuum, an inert atmosphere, and in air.     

On the Statistical Theory of Long-Term Strength of Glass

We present new methods for the evaluation of the statistical parameters of long-term strength of glass and describe the procedure of preparation of specimens (glass disks) for testing, the method of loading, and the experimental procedure. The statistical model of fracture of glass is presented and the conclusions concerning the evaluation of the parameters of strength are made.__________Translated from Problemy Prochnosti, No. 3, pp. 75 – 85, May – June, 2005.     

有损伤框架结构中的波动分析

基于回传射线矩阵法，研究了有损伤框架结构在水平方波脉冲作用下脉冲作用点的速度波，结构的局部损伤用减小受损单元的横截面面积来模拟。结果表明：改变脉冲作用点位置，通过脉冲作用点横向速度波首波波幅的变化可以确定受损单元的起始位置；当脉冲作用点在受损单元的起始位置时，脉冲作用点横向速度波首波波幅变化越大，损伤越大，脉冲作用点横向速度波的第一个波谷到达时间越晚，损伤单元越长。     

含分层损伤缝合复合材料层板的剩余压缩强度

基于渐进损伤方法,研究了含单脱层缝合复合材料层板在压缩载荷下的剩余强度。通过商用软件ABAQUS建立了含单脱层缝合复合材料层板剩余压缩强度计算模型,考虑了子层屈曲和分层扩展对剩余强度的影响。通过UMAT子程序实现了层板失效、层间失效和缝线失效的模拟。通过嵌入式杆单元结构模拟了缝线桥联作用及失效。采用Hashin准则及刚度折减法对纤维拉压、基体拉压失效进行了模拟。通过渐进损伤分析,揭示了缝合情况下含单脱层复合材料层板的失效机理,讨论了缝合参数对剩余压缩强度的影响。所预测的破坏模式和剩余强度结果与实验能较好地吻合。分析表明缝合可以明显提高含分层损伤复合材料层板的子层屈曲载荷,抑制分层扩展,并提高层板的剩余压缩强度。     

Correlation Dependences between Short-Term/Long-Term Static Strength Characteristics and Creep Resistance of Tungsten at High Temperatures

Experimental data on high-temperature mechanical properties under uniaxial tension of commercially pure tungsten obtained by powder metallurgy have been analyzed. It has been found that for powder metallurgy tungsten in the high-temperature region ∼(0.5 –0.8)T_melt' there is a close correlation among the characteristics of short- and long-term static strengths and creep resistance, which are described by a single functional relation. __________ Translated from Problemy Prochnosti, No. 6, pp. 50 – 60, November – December, 2005.     

压制压力对Ni3Al金属间化合物多孔材料孔结构及抗拉强度的影响

以Ni、Al元素粉末为原料,采用粉末冶金的方法制备Ni3Al多孔金属间化合物。研究了压制压力对Ni3Al多孔金属间化合物孔结构和抗拉强度的影响。研究结果表明,随着压制压力的增大,Ni3Al多孔金属间化合物的孔隙度呈线性减小的趋势;当压制压力达到220MPa以上时,随着压制压力的增大,Ni3Al多孔金属间化合物的最大孔径和透气度减小幅度趋缓;最大孔径是决定透气度大小的主要因素;抗拉强度与压制压力之间的关系式为sb=600(0.06P-41.51)2.45。     

一种超高强度钢构件抗疲劳实验研究

提出了超高强度钢“无应力集中”抗疲劳概念。喷丸、孔挤压、螺纹滚压等表面层组织再造改性造成的残余压应力和高位错密度胞状结构将裂纹推移至亚表面萌生并阻滞其扩展，回复不同应力集中处的疲劳强度至接近钢的固有疲劳强度，形成“无应力集中”表面完整性状态。“无应力集中”抗疲劳概念表述为构件表面形成完整的接近于钢固有疲劳强度的等疲劳强度包络     

High-Temperature Strength of KTTs-110 Zirconium Alloy

We describe the methods and results of investigation of the characteristics of strength and plasticity of a pilot batch of tubes made of KTTs-110 zirconium alloy under the conditions of short- and long-term static loading. The obtained results are compared with the same characteristics of É-110 alloy extensively used in the active zones of WWÉR-1000-type nuclear reactors.     

养护温度对核防护用地聚合物早期强度影响研究

分析了养护温度、养护时间及砂子种类对核防护用地聚合物强度性能的影响,并进行了一系列的温度响应实验,实验结果表明,养护温度对核防护用地聚合物的早期强度影响巨大,温度越高,早期强度越高,强度提升越快;发现养护温度对养护时间6.5小时以上地聚合物样品的影响不大,且不能改变地聚合物的最终强度;掺合湖北砂的地聚合物样品强度最高,性能最好。     

钢结构用10.9S扭剪型高强螺栓连接副紧固轴力偏低原因分析

通过化学成分分析、硬度测试、楔载荷、保证载荷和紧固轴力检验,对某批规格为M20mm×80mm的10.9S扭剪型高强螺栓连接副紧固轴力偏低的原因进行了分析。结果表明：该批高强螺栓连接副质量合格,但在包装和运输过程中受干燥环境影响,导致其表面磷化膜风化,润滑性下降,轴向摩擦力增大,因而紧固轴力下降。     

Prediction of Fatigue Characteristics of Metals at Different Loading Frequences

The procedure for predicting fatigue characteristics by high-frequency test results over lifetime ranges up to 10¹⁰ cycles is proposed. The procedure is based on the fatigue fracture model accounting for the loading frequency and stress ratio. The potentials of the method are exemplified by the tests of smooth specimens and specimens with a stress concentrator from different materials (nickel-, aluminum-, and titanium-base alloys). The prediction results for different loading frequencies (35–10,000 Hz) and stress ratios (from -1 to 0.5) are shown to vary by about 10% from experimentally obtained data.     

10.9级高强度螺钉断裂分析

某单位生产的汽车门窗用10.9级20钢高强度螺钉在服役约一个月后相继出现多个断裂现象。利用光学显微镜、扫描电子显微镜、直读光谱仪、能谱分析仪和显微硬度计等对螺钉的断裂原因进行了分析。结果表明:该螺钉断裂的主要原因是其在使用之前就存在微裂纹,造成应力集中,在静载荷拉应力的作用下,材料中的氢原子向裂纹尖端移动、富集,使局部氢浓度较高,导致螺钉发生了氢致延迟脆性断裂;另螺钉表面硬度过高也增加了其对氢脆断裂的敏感性。     

New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints

A new welding electrode, low transformation temperature electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods. It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve th