用有限元确定起重机裂纹补强板的参数

采用ANSYS有限元分析软件，对因出现裂纹的起重机主梁而添加的补强板进行系列计算，得出修补后主梁裂纹的应力及应力强度因子的变化规律。结果表明，采用参数适当的补强板，可降低起重机主梁裂纹尖端的应力，从而保证起重机的安全。     

A time series approach to fatigue crack propagation

The inherently nonlinear phenomenon of fatigue crack propagation is modeled as a linear random process. To a first approximation, simple, nonstationary time series models are introduced and standard techniques for determining the parameters of autoregressive integrated moving-average processes are applied. Multiplicative time series models are next utilised for the representation of a group of crack history curves. Implementation of the models on the Virkler experimental data set yields satisfactory results. Reliable Gaussian approximations to the distribution of the time required by a crack to reach a specified critical length are obtained, and the usefulness of the approach is demonstrated when updating lifetime predictions after periodic inspections.     

Oscillatory crack tip triangular elements for finite element analysis of interface cracks

In this paper a special crack tip element has been developed in which displacements and stresses have the same behaviour as those of bi‐material interface cracks with open tips. The element degenerates into a traditional triangular quarter point element in cases of homogeneous cracks. An isoparametric co‐ordinate system (ρ, t) is defined in this study, and numerical techniques using these co‐ordinates to evaluate Jacobian matrices, shape function derivatives, and element stiffness matrices are developed. Also, equations calculating the complex stress intensity factor using displacements are obtained in this study. Numerical results are in good agreement with known analytical solutions in two examples. Copyright © 2003 John Wiley & Sons, Ltd.     

An investigation of crack closure and the propagation of semi-elliptical fatigue cracks in Q1N (HY80) pressure vessel steel

The results of an experimental investigation of the effect of crack closure on the propagation of semi-elliptical fatigue cracks are presented. Load-shedding fatigue threshold tests were carried out at stress ratios of 0.2, 0.35, 0.5 and 0.7. Crack closure was measured at the surface and depth positions using backface strain gauges, near-tip gauges, and a clip gauge. Differences between the surface and depth growth behaviour are explained by considerations of the effects of the transition from plane stress conditions at the surface to plane strain conditions at the depth. The effects of stress ratios are attributed largely to differences in the crack opening displacement, which result in asperities coming into contact to induce roughness-induced crack closure.     

Fatigue crack growth analysis of welded aluminium RHS T-joints with manipulated residual stress level

The fatigue life of a welded aluminium T‐joint made from beams with rectangular hollow section (RHS) has been predicted using a crack propagation analysis and compared with experimental results from joints with different residual stress levels. To include the effect of the residual stresses, the stress ratio was calculated at the weld toe and, via Walker's equation, introduced into the analysis. How to obtain the Walker exponent has been discussed in detail. The introduction of a stress ratio at the weld toe provides good agreement between the experimentally and analytically found S–N curves. The effect of the residual stress was successfully included in the analysis.     

广州港起重机械裂纹诊断系统的应用及改进

从港口起重机金属结构的故障管理与实践出发，通过对故障原理的分析，在断裂力学的基础上，对存在宏观裂纹构件的使用寿命和巡检周期进行预测，并开发出了港口起重机械金属结构裂纹诊断系统。通过在广州等大港口的推广，方便了维修、管理人员的使用。最后对该系统在应力测试操作中的经验和教训进行了总结。     

A new numerical analysis for a semi-circular surface crack

This note is concerned with a surface semi-circular crack by using the fracture analysis software FRANC3D developed by a fracture mechanics investigation group of Cornell University. Attention is specifically paid to the effect of the boundaries parallel to the crack on the stress intensity factors (SIFs).     

现浇钢筋混凝土楼板裂缝原因及施工控制

阐述了现浇混凝土楼板产生裂缝的很多原因，针对炎热干燥气候条件下现浇钢筋混凝土楼板产生裂缝的原因进行了分析，提出施工预防措施，经实践证明，对裂缝的控制是有效的。     

钢筋混凝土非正常裂缝的产生原因及应对措施

根据钢筋混凝土结构中非正常裂缝的种类，分析了各种裂缝的产生原因，并有针对性地提出了应对措施，以保证建筑物和构件安全和稳定地工作。     

Creep Crack Growth in Polypropylene Film with Various Crack Lengths at Diverse Stresses and Temperatures

Creep crack growth rates were measured using centrally cracked tension specimens of thin polypropylene film with different crack lengths at various stresses and temperatures. The creep crack growth rates were correlated with the stress intensity factor. There was the region of the minimum constant crack growth rate which occupied more than 70% of the total creep failure life. This constant creep crack growth rate characteristics were analyzed on the basis of the stress-dependent Arrhenius type thermally activated process.