Accepted Manuscripts

reem Yassine, Ali Fakhreddine, Mohammad Sayegh, Samir Mustapha and Ramsey Hamade
ASME J Nondestructive Evaluation   doi: 10.1115/1.4040797
Thirteen long tibia (bovine) bones were utilized in vitro to experimentally extract modal frequencies in Cranial-Caudal (C-C) and Medial-Lateral (M-L) planes. Bones were instrumented with four single-axis accelerometers uniformly placed along the length of the bone and hammer impacted at different locations in both planes. Frequency response function (FRF) and Complex Mode Indicator Function (CMIF) techniques were used to identify the modal frequencies. CMIF has an advantage of detecting closely spaced modes by excluding misinterpreted peaks. It was found that the difference between the two methods did not exceed 2.98 %. CMIF data was more consistent when varying impact location. Effect of bone's geometrical attributes on modal frequencies was statistically scrutinized and highly correlated parameters were identified. Bone length exhibited high correspondence to frequencies (p< 0.05) for practically all modes. Also, four simple equations were developed, relating modes 1 and 2 in the C-C and M-L planes to bone length. To determine the first and second modal shapes, subset of 6 tibia bones was further instrumented. Mode shapes were extracted in C-C and M-L planes.
TOPICS: Nondestructive evaluation, Modeling, Shapes, Bone, Accelerometers, Hammers, Mode shapes, Frequency response
Elizabeth Gregory and Peter Juarez
ASME J Nondestructive Evaluation   doi: 10.1115/1.4040764
This paper presents data from an innovative nondestructive evaluation method for automated composite fiber placement fabrication. Using Infrared images of the fiber as it was being placed we are able to provide valuable information about the quality of the part during fabrication. Herein, we discuss the methodology for data collection and processing. The described in-situ thermal nondestructive evaluation process is found to be applicable for identifying fiber tow overlaps, gaps, twists, puckering and poor ply adhesion prior to cure, thereby reducing the time and cost associated with post cure flaw repair or scrapping parts. This paper also describes the process of assembling data sets for an entire part beyond simple frame by frame analysis. Example data sets for both a flat part and a larger cylindrical part are presented to demonstrate the type of defect characterization information that can be obtained.
TOPICS: Composite materials, Fibers, Nondestructive evaluation, Manufacturing, Adhesion, Maintenance, Data collection
Ali Mirala, Ali Foudazi, Mohammad Tayeb Ghasr and Kristen M. Donnell
ASME J Nondestructive Evaluation   doi: 10.1115/1.4040673
Active Microwave Thermography (AMT) is an integrated nondestructive testing (NDT) technique that utilizes a microwave-based thermal excitation and subsequent thermal measurement. AMT has shown potential for applications in the transportation, infrastructure, and aerospace industries. This paper investigates the potential of AMT for detection of defects referred to as flat-bottom holes (FBHs) in composites with high electrical conductivity such as carbon fiber-based composites. Specifically, FBHs of different dimensions machined in a carbon fiber reinforced polymer (CFRP) composite sheet are considered. Simulation and measurement results illustrate the potential for AMT as a nondestructive testing (NDT) tool for inspection of CFRP structures. In addition, a dimensional analysis of detectable defects is provided including a radius-to-depth ratio threshold for successful detection.
TOPICS: Microwaves, Composite materials, Nondestructive evaluation, Thermography, Carbon reinforced plastics, Aerospace industry, Carbon, Transportation systems, Excitation, Fibers, Inspection, Dimensions, Dimensional analysis, Simulation, Electrical conductivity

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