Key Engineering Materials Vols. 525-526

Abstract: In this paper, flatwise tensile test (FWT) and modified double cantilever beam (DCB) experiment were conducted to investigated the debond fracture of sandwich plate with corrugated core. In the experiment, the crack always stays at the face/core interfacial. Tensile bond strength of face core can be given from the flatwise tensile test and we can get the mode I fracture toughness G_IC from DCB tests. It is found that the trends of curves change greatly at the beginning, with the propagation of crack, load against open displacement curves change smoothly. In order to simulate the face/core failure of sandwich plate with corrugated core, the cohesive element model is used. Tensile strength and strain energy release rate measured by the experiments presented in this paper are used in as parameters for simulation of the debond fracture. By comparing with the experiment results, the model can express the face/core failure of sandwich plate with corrugated core validly.

Abstract: GLARE (Aluminium with glass fibres) has become known since it was successfully and widely used in aircraft structure for its excellent fatigue and damage tolerance behavior. In this study, fatigue testing samples with 3/2 Glare were designed according to the standard. The finite element method was used to build the numerical model of the sample; the fibre bridging was modeled and the bridging stress was calculated. The delamination growth behavior can be predicted based on the energy release rate. This numerical method considered both damage modes (fatigue and delamination) at the same time.

Abstract: This paper was retracted by the authors and publisher since it contained material used without the permission of Cranfield University, the copyright owner.

Abstract: Before friction stir welded integral panels are used in main aircraft structure, the corrosion behavior of welded joint need to be studied in detail. 2024 T3 samples were designed and welded by friction stir welding; the microstructure crossing the weld zone was observed by scanning electron microscopy (SEM), the feature of different zones (base material, thermo-mechanical affected zone, nugget) was seen; the corrosion testing in NaCl smoking box was carried out, and microstructure was observed after corrosion, localized corrosion predominantly occurs in the thermo-mechanical affected zone.

Abstract: Induced forces in secondary steel bridge members such as diaphragms and cross-bracing can cause out-of-plane distortion in webs that may lead to fatigue cracking. Such cracking is most likely to occur if the distortion must be accommodated in a short length of the web, such as in the gap between the end of transverse stiffeners and girder flanges, thats because the web gap is subject to double curvature. In this paper, the numerical analysis models of the curved continue steel bridges were established using ANSYS software to calculate the fatigue stress at the web gaps. The numerical analysis results show that both the bottom web gap at middle span area and the top web gap at supported were poor fatigue details, and web thickness and web gap depth give the great affection on the out-of-plane distortion fatigue stress at web gaps of curved steel bridges.

Abstract: Lanzhou Zhongshan Bridge, which is located in the center of Lanzhou city, is a rivet truss bridge built in 1909. It is the first iron bridge over the Yellow River as well as a national cultural relic. An original steel angel cut off from Lanzhou Zhongshan Bridge was used to carry out a series of tests including material mechanics, fracture and fatigue property. Based on the test results, the fatigue and fracture safety was evaluated during the bridge remaining service life. Whats more, remaining service life of Lanzhou Zhongshan Bridge was calculated and found that the trucks weight more than 120 kN should be limited to ensure the safety.

Abstract: The existing concrete bridges are often required to carry an increasing volume of traffic, higher speed and heavier trucks, so the bridge owners pay more attention to the actual fatigue damage and service safety of such structures. In this paper, Acoustic Emission (AE) sensors are used to monitor and evaluate the fatigue and damage of Yaoxian Bridge, which is the first field AE monitoring using Physical Acoustics Company equipment and sensors in China existing concrete bridge. This AE sensor has fine frequency bandwidth of interest to bridge monitoring, which is applicable to local cracking and damage positions and can monitor fatigue cracks and damage in close-range. In the field inspection, healthy monitoring was conducted at several locations, including the box concrete girder webs, bottom plates and deck plates using AE sensors. Based on AE monitoring data, the fatigue and damage conditions of box concrete girders was analyzed in order to propose theoretical basis and the rational advices for Yaoxian Bridge maintenance.

Abstract: The Yao Zhou downlink Viaduct damaged in a fire accident was repaired using steel plate and concrete composite strengthening (SPCCS) technique. After strengthening and servicing normally for 1.5 years, two loading tests, meanwhile, a three-day traffic information observation and dynamic strain monitoring were carried out. The static loading test and monitoring results all showed that the Yao Zhou downlink Viaduct had good service condition since reinforcement, which satisfying the safety requirement. In order to evaluate the effectiveness of the SPCCS technique in-depth, structural behaviour under the ultimate limit state (ULS) and the serviceability limit state (SLS) were analyzed. The SLS and ULC of the key sections before and after reinforcement were calculated using the simplified formula and the finite element models calibrated by filed test results. The post-evaluation results showed that the behaviour of the spans damaged in fire accident could be improved obviously under the SLS using SPCCS technique, as well as the bridge stiffness enlarged than the original bridge structure. The ultimate bearing capacity (UBC) of the key sections was improved about 75% using SPCCS technique, which was two times as the most disadvantageous load effect combinations. Whats more, the fatigue life of fire damaged box girders strengthened using SPCCS technique was evaluated based on monitoring strain data, and the further bridge maintenance suggestions were proposed based on the assessment results.

Abstract: The primary objective of this paper is to illustrate the effects of weak-link scaling on the tensile behaviour of fiber-reinforced composites. The proposed model takes into account the random nature of fiber strength, which is given by a two-parameter Weibull distribution function. Several hundred Monte-Carlo replications are executed to simulate the statistical strength distributions of the composites. It is shown that probabilistic tensile strength distributions and size scaling is dependent on both the stress redistribution and the fiber strength statistics.

Abstract: Through analyzing the characteristic of concrete freezing-thawing cumulative damage, concrete freezing-thawing damage can be with fatigue problems with similar methods to analysis. Coagulation Earth material property discrete and cause damage in a given amount of state natural freeze-thaw cycle times is a random variable, analysis found that it is better to obey three-parameter Weibull distribution. Based on three parameters Weibull distribution model, the test data in had established, on the basis of freezing-thawing environment concrete damage and freeze-thaw cycles of the probability of the relation curve, and regression to obtain different guarantee rate of freezing-thawing damage cumulative model for freezing-thawing environment,which could be provides reference for concrete service life prediction and health diagnosis.