On basic definitions of unified fracture mechanics terminology

The adoption of unified fracture mechanics terminology (UFMT) will promote efficient communication between specialists in different fields of fracture research, harmonization of national and international standards relating to fracture mechanics, and last but not least improvement of the existing methodology for teaching and education in fatigue and fracture. In this paper the definitions of some basic and related terms included in different standards on fracture mechanics terminology are confronted with one another. Alternative definitions of the same terms are offered. By this strategy the author tries to show that the definitions of basic and related terms appropriate for the UFMT should emerge as a consequence of harmonizing a crack model with an actual crack and then both taken together with a fracture model, laboratory test methods, and failure assessment codes.Published in Problemy Prochonsti, No. 1, pp. 17–29, January, 1996.This paper is published as a matter of discussion.     

Measurements of Stress Intensity Factors of an Interface Crack Under Mixed Mode Loading

The optical method of caustics has been utilised to measure both the stress intensity factor for a crack lying along the interface of an aluminium/epoxy bimaterial specimen, and the mode mixity arising from the difference in the elastic properties across the interface. Measurements were carried out by using a novel modification to the method whereby caustics are produced and measured from both sides of the specimen, so compensating automatically for the distortion induced in the specimen due to misaligned loading fixtures. A flat reflective surface across the interface was obtained by adhering a reflective coating to the specimen. Verification that this coating does not affect measurement accuracy was obtained by comparing stress intensity factors measured from coated and uncoated monolithic aluminium specimens where good agreement was found to exist between both measurements.     

几种高强度钢腐蚀疲劳裂纹扩展行为的研究

本文研究了ＧＣ－４，３０ＣｒＭｎＳｉＮｉ２Ａ和３００Ｍ超高强钢的腐蚀疲劳裂纹扩展行为。考虑了环境，热处理制度，应力比和频率对裂纹扩展的影响。研究结果表明：腐蚀环境和热处理制度对疲劳裂纹扩展有显著影响。在侵蚀性环境中随频率降低，裂纹扩展大幅度上升，随应力比提高，环境影响加剧。利用扫描电镜对试样断口形貌进行了分析，并讨论了高强钢的腐蚀疲劳机理。     

13SiMnNiCrMoV钢切口疲劳裂纹萌生门槛值

本文研究在13SiMnNiCrMoV 结构钢中用尖裂纹的应力强度因子来反映三点弯曲缺口试样的疲劳裂纹萌生规律。当 R=0.1,f=100Hz,试样尺寸 B×W×L=12.5×25×117mm 时,缺口名义应力幅的门槛值为Δσ_(th)=3315ρ~(0.352) MPa,0.5mm≤ρ≤5mmΔK_(th)=250ρ~(0.352) MPam~(1/2)门槛值与ρ有关。同时得到缺口裂纹萌生的循环次数 N_i 与名义应力幅Δσ、缺口曲率半径ρ的定量关系是N_i=3.98×10~(22)ρ~(1.62)/Δσ~(4.85),N_i≤10~(5.5)并讨论了(ΔK_1/ρ~(1/2))_(th)与ρ无关的结论。     

Microstructure and Its Influence on Mechanical Behaviour of Directionally Solidified DZ38G Superalloy

The features of microstructure and theirinfluence on mechanical properties onstress-rupture as well as thermal fatigue ofdirectionally solidified DZ38G nickel-base su-peralloy have been investigated.It has beenfound that the contents of carbides on grainboundaries are increased and morphology of γ'-precipitates has been changed after testing.Particularly γ'-precipitates coalesced intoraft-like in morphology perpendicular to theapplied stress-axis have been observed thathas no detrimental effect on the stress-rupturebehaviour.The tendency of σ-formation hasalso been discussed.The σ-phase can be avoidedwhen the process parameters are chosenappropriately during solidification.     

及时利用过喷粉末的涂装装置

对比了典型进口及国产粉末喷涂设备对过喷粉末的利用情况，介绍了一种获得实用新型专利权的涂装装置。该装置综合了进口及国产设备的优点，具有很高的性价比。     

Reticulated Porous Multiphase Ceramics with Improved Compressive Strength and Fracture Toughness

A multiphase reticulated porous ceramic (RPC) as Si₃N₄–Al₂O₃–SiO₂ was fabricated by replication techniques. Proper volumes of additives and twice sinter- twice immerse process endow the RPC an excellent crack healing and submerging property. The compressive strength and fracture toughness improved owing to the crack bridging behavior. The existence of pores in struts in RPC blunt the crack tip and increased the external force needed to propagate the crack. The mechanisms play a beneficial role in enhancing the compressive strength and fracture strength. Si₃N₄ RPC with additives of 5%Al and 5% Al₂O₃ yielded the compressive strength of 9.8 MPa and fracture toughness of 0.3 MPa m^1/2.     

疲劳裂纹的灰色残差预测

借助灰色理论，建立了预测疲劳裂纹扩展的灰色残差预测模型，并应用此模型预测了某不锈钢构件腐蚀疲劳裂纹的扩展，得到了较高精度的预测结果，为疲劳裂纹预测提供了一种简易而可靠的新途径。     

大体积砼产生裂缝的原因及防治措施

大体积砼裂缝问题是建筑业普通关心的问题.对砼裂缝进行控制,就必须研究砼结构中裂缝产生的原因以及在实际的设计和施工过程中采取合理的、经济的措施来控制裂缝.本文通过对大体积砼裂缝成因的理论研究,提出了合理的裂缝控制的设计和施工措施.     

Determination of Discrete-Structure Parameters of Coatings with Allowance for Residual Stresses

The authors suggest that the dimensions of a discrete section of a coating should be chosen on the basis of calculation of the critical crack spacing in cohesion cracking. This approach allows for residual stresses in the coating. The reliability of the calculation method has been verified experimentally by direct measurement of the crack spacing.