Mr. Shen Shang Profile

Shen Shang

at Univ of Akron

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Publications (2)

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Proceedings Article | 9 April 2010 Paper

A low-cost digital image correlation based constitutive sensor

Gun-Jin Yun, Shen Shang, Shilpa Kunchum, Joan Carletta, Si-Byung Nam

Proceedings Volume 7648, 76480H (2010) https://doi.org/10.1117/12.848184

KEYWORDS: Digital image correlation, Sensors, Image sensors, Cameras, Digital imaging, Finite element methods, Genetic algorithms, Optimization (mathematics), Experimental mechanics, Image processing

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In this paper, a low-cost digital image correlation-based constitutive sensor with a novel identification algorithm that is deployable and scalable in the field is proposed. The term 'constitutive sensor' is coined herein to describe a sensor that is capable of determining the target material constitutive parameters. The proposed method is different from existing identification methods in that it does not need to solve boundary value problems of the target materials using updated parameters. Since the development of the digital image correlation (DIC) technique in the 1980s, the DIC technique has been broadly evaluated and improved for measuring full-field displacements of test specimens, mainly in laboratory settings. Although its potential in damage and mechanical identification is immense, the high cost of current commercial DIC systems makes it difficult to apply the DIC technique to in-field health monitoring of structures. To realize a first ever application of DIC in the field, a prototypical low-cost sensing unit consisting of a high performance embedded microprocessor board, a low-cost web camera, and a communication module is suggested. In the proposed constitutive sensor, DIC displacement fields considered as true values are used in computing stress fields satisfying the equilibrium condition and strain fields using finite element concepts. The unknown constitutive law is initially assumed to be fully anisotropic and linear elastic. A steady state genetic algorithm is utilized to search for the material parameters by minimizing a cost function that measures energy residuals. The main features that allow the sensor to be deployable in the field are introduced, and a validation of the proposed constitutive sensor concept using synthetic data is presented.

Proceedings Article | 8 April 2009 Paper

Fast inverse identification of delamination of E-glass/epoxy laminated composite panels

Gun-Jin Yun, Shen Shang, Pizhong Qiao

Proceedings Volume 7294, 72940H (2009) https://doi.org/10.1117/12.821525

KEYWORDS: Composites, Finite element methods, Sensors, Actuators, Modal analysis, Matrices, Chemical elements, Ferroelectric polymers, Aerospace engineering

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In this paper, a novel vibration-based methodology for fast inverse identification of delamination in E-glass/epoxy composite panels has been proposed with experimental demonstration using a scanning laser vibrometer (SLV). The methodology consists of 1) a parameter subset selection for delamination damage localization and 2) iterative inverse eigenvalue analysis for damage quantification. It can potentially lead to a functional formulation relating spatial and global damage indices such as curvature damage factor to local damage parameters. The functional relationship will be suitable to fast or real-time in-situ delamination damage identification. To accomplish the objectives, a shear-locking free higher-order finite element model has been combined with a micromechanics theory-based continuum damage model as an identification model for locating delamination. Applications of the proposed methodology to an Eglass/ epoxy panel [CSM/UM1208/3 layers of C1800]s = [CSM/0/(90/0)3]s with delamination have been demonstrated both numerically and experimentally using a piezoelectric actuator, a PVDF sensor and non-contact measuring SLV. Experimental modal analysis has been successfully conducted using the sample specimen to demonstrate the proposed methodology.

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