A comparison of modal flexibility method and modal curvature method in structural damage detection

Vibration based damage detection techniques examines the changes in dynamic properties of a structure such as frequency, mode shape and damping to indicate the presence of damage. This method is preferred for its ease of implementation, non-destructive nature and its ability to identify damage that is invisible to the surface. Two vibration based damage detection methods are used in this study, namely Modal Flexibility Method and Modal Curvature Method. Although there have been numerous publications on these two methods, there is lack of study on the direct comparison of the methods. Finite element modal analysis of a reinforced concrete slab and steel frame was carried out to obtain the dynamic responses that were used to calculate the Modal Flexibility and Modal Curvature. The structural models were simulated using four damage cases: damage at single location, damage at multiple locations, damage at support location and damage at different damage severities. The comparison of the sensitivity and reliability of Modal Flexibility and Modal Curvature were evaluated using the results of these four damage cases. The results show that the sensitivity and reliability of both methods are affected by the size of the damaged area, its location relative to the support location and the number of damaged segments

Certification of damage tolerant composite structure

A reliability based certification testing methodology for impact damage tolerant composite structure was developed. Cocured, adhesively bonded, and impact damaged composite static strength and fatigue life data were statistically analyzed to determine the influence of test parameters on the data scatter. The impact damage resistance and damage tolerance of various structural configurations were characterized through the analysis of an industry wide database of impact test results. Realistic impact damage certification requirements were proposed based on actual fleet aircraft data. The capabilities of available impact damage analysis methods were determined through correlation with experimental data. Probabilistic methods were developed to estimate the reliability of impact damaged composite structures

On systematic approaches for interpreted information transfer of inspection data from bridge models to structural analysis

In conjunction with the improved methods of monitoring damage and degradation processes, the interest in reliability assessment of reinforced concrete bridges is increasing in recent years. Automated imagebased inspections of the structural surface provide valuable data to extract quantitative information about deteriorations, such as crack patterns. However, the knowledge gain results from processing this information in a structural context, i.e. relating the damage artifacts to building components. This way, transformation to structural analysis is enabled. This approach sets two further requirements: availability of structural bridge information and a standardized storage for interoperability with subsequent analysis tools. Since the involved large datasets are only efficiently processed in an automated manner, the implementation of the complete workflow from damage and building data to structural analysis is targeted in this work. First, domain concepts are derived from the back-end tasks: structural analysis, damage modeling, and life-cycle assessment. The common interoperability format, the Industry Foundation Class (IFC), and processes in these domains are further assessed. The need for usercontrolled interpretation steps is identified and the developed prototype thus allows interaction at subsequent model stages. The latter has the advantage that interpretation steps can be individually separated into either a structural analysis or a damage information model or a combination of both. This approach to damage information processing from the perspective of structural analysis is then validated in different case studies

Plasma damage in floating metal-insulator-metal capacitors

In this paper, charging induced damage (CID) to metal-insulator-metal capacitors (MIMCs), is reported. CID does not necessarily lead to direct yield loss, but may also induce latent damage leading to reliability losses. The damage is caused by the build up of a voltage potential difference between the two plates of the capacitor. A simple logarithmic relation is discovered between the damage by this voltage potential and the ratio of the area of the exposed antennas connected to the plates of the MIMC. This function allows anticipation of damage in MIMCs with long interconnect

Enabling electronic prognostics using thermal data

Prognostics is a process of assessing the extent of deviation or degradation of a product from its expected normal operating condition, and then, based on continuous monitoring, predicting the future reliability of the product. By being able to determine when a product will fail, procedures can be developed to provide advanced warning of failures, optimize maintenance, reduce life cycle costs, and improve the design, qualification and logistical support of fielded and future systems. In the case of electronics, the reliability is often influenced by thermal loads, in the form of steady-state temperatures, power cycles, temperature gradients, ramp rates, and dwell times. If one can continuously monitor the thermal loads, in-situ, this data can be used in conjunction with precursor reasoning algorithms and stress-and-damage models to enable prognostics. This paper discusses approaches to enable electronic prognostics and provides a case study of prognostics using thermal data.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

The Discontinuous Carbon Fiber Composite: a Review of the Damage Characteristics

Discontinuous carbon fiber composite (DCFC) is one of new low-cost material product form that had applied for commercial component such as window frames of the Boeing 787 Dreamliner. Study on DCFC was very challenging since it did not have the same nature behavior like conventional composite nor isotropic materials. In this work several studies on damage characteristics of DCFC material were presented. The damage characteristics of DCFC were investigated while undergoing static and fatigue loading. In particular, the damage mechanisms of DCFC were also observed through several nondestructive testing (NDT) methods. The review had shown that the study of DCFC specimen gives an interesting challenges for the future work to understand its damage characteristics and the reliability of the NDT method to study the damage of DCFC material