Off-axis fatigue cracking behaviour in notched fibre metal laminates

The off‐axis fatigue cracking behaviour of notched fibre metal laminates under constant amplitude loading conditions was investigated experimentally and numerically. It was found that the off‐axis fatigue crack initiation life decreased as the off‐axis angles increased. This indicated that the off‐axis laminates raised the applied stress level in the aluminium (Al) layer and subsequently resulted in earlier cracking in the Al layer. The off‐axis fatigue crack initiation lives of notched fibre metal laminates were predicted using lamination theory and an energy‐based critical plane fatigue damage analysis from the literature. After a crack initiated in the Al layer, it was observed that the crack path angles of the off‐axis specimens were neither perpendicular to the fibre nor to the loading direction. A finite‐element model was established for predicting the crack path angles.     

Crack closure in fibre metal laminates

GLARE is a fibre metal laminate (FML) built up of alternating layers of S2-glass/FM94 prepreg and aluminium 2024-T3. The excellent fatigue behaviour of GLARE can be described with a recently published analytical prediction model. This model is based on linear elastic fracture mechanics and the assumption that a similar stress state in the aluminium layers of GLARE and monolithic aluminium result in the same crack growth behaviour. It therefore describes the crack growth with an effective stress intensity factor (SIF) range at the crack tip in the aluminium layers, including the effect of internal residual stress as result of curing and the stiffness differences between the individual layers. In that model, an empirical relation is used to calculate the effective SIF range, which had been determined without sufficiently investigating the effect of crack closure. This paper presents the research performed on crack closure in GLARE. It is assumed that crack closure in FMLs is determined by the actual stress cycles in the metal layers and that it can be described with the available relations for monolithic aluminium published in the literature. Fatigue crack growth experiments have been performed on GLARE specimens in which crack growth rates and crack opening stresses have been recorded. The prediction model incorporating the crack closure relation for aluminium 2024-T3 obtained from the literature has been validated with the test results. It is concluded that crack growth in GLARE can be correlated with the effective SIF range at the crack tip in the aluminium layers, if it is determined with the crack closure relation for aluminium 2024-T3 based on actual stresses in the aluminium layers.     

S-N-P curves in 7075 T7351 and 2024 T3 aluminium alloys subjected to surface treatments

The S-N-P (stress, number of cycles, failure probability) curves for 2024 T3 and 7075 T7351 aluminium alloys were obtained. Previously, surface treatments of degreasing and different types of anodizing were applied to samples, evaluating the influence of these treatments on the fatigue life of the alloys. The determination of the S-N-P curves was done using Maennig's method. Rotary fatigue was used because this technique produces greater stress on the sample surfaces, the zone in which it is important to evaluate fatigue resistance. Both the transition range and the finite life range were evaluated, calculating the 1, 50 and 99% fracture probability. SEM was performed in order to characterize the fracture micromechanism. The conclusions were that Maennig's method is useful to evaluate fatigue life of these materials in a fast and efficient manner. Moreover, surface treatments produce a decrease in the fatigue life of both alloys, associating this effect with the surface damage produced on each sample during the treatment.     

Finite-element analysis and experimental study on tensile fatigue behaviour of bitumen–stone adhesion

Tensile fatigue behaviours of bitumen–stone adhesion were investigated using a dynamic mechanics analyser under stress‐controlled mode at two temperatures of 5 and 25°C and various controlled‐stress levels. Failure characteristics including interfacial failure and cohesive failure were examined using image analysis of fracture surfaces. Finite‐element analysis on stress distributions was conducted under different temperatures, film thickness and interfacial bonding conditions. A Coulomb–Mohr like criterion in combination with shear and normal stresses is proposed to deal with the extreme thin adhesive layer, which can be further simplified into an adhesive zone without significant loss of accuracy for stress analysis.     

改进的基于TMS320DM642的疲劳检测系统

针对疲劳检测算法中大数据量、高速传输、复杂运算的实际需要，设计了以SAA7115为视频采集A／D、DSPTMS320DM642为核心处理器、SAA7105为视频输出D／A，并以FPGA控制输出来实现增强显示功能的实时视频处理系统。该系统采用双摄像头控制采集数据，可以满足多路视频的实时采集、处理、显示需求，可以作为疲劳检测算法、视频处理和图像处理的硬件平台。     

CFRP强度复合Weibull分布的物理特征分析

本文对ＣＦＲＰ材料疲劳后剩余强度的复合Ｗｅｉｂｕｌｌ分布的物理特征进行了初步分析。指出树脂基复合材料失效（破坏）机理的双重性（基体和纤维失效模型）决定了剩余强度（累积损伤程度）测试结果的分布特征。复合Ｗｅｉｂｕｌｌ分布曲线的特征与分析结果对设计、使用及材料研究都有重要参考意义。     

往复式压缩机管道的防振设计

分析了往复式压缩机管道产生振动的原因及影响因素,提出解决管道振动的方法及对策。     

高速冷带轧机垂直自激振动稳定性分析的数值计算方法

本文在充分考虑轧机垂直振动过程中辊缝非线性的基础上，利用轧制理论方程和机械振动理论中的能量判据，给出了更精确的分析高速冷轧机垂直自激振动稳定性的数值计算方法。     

非线性隔振理论初探

本文以线必阻尼，立方刚度非线性系统为例，对非线性隔振理论进行了初步探讨，导出了系统的无量纲运动响应和传递率，并与线性隔振系统进行了比较，着重讨论了非线性对它们的影响，获得了一些有用的结论。