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Search Publications by: Marvin Hamstad (Assoc)

Displaying 26 - 42 of 42

Finite Element and Plate Theory Methods for Modeling Acoustic Emission Waveforms

October 1, 2002

Author(s)

W H. Prosser, Marvin A. Hamstad, John M. Gary, Agnes O'Gallagher

A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the flexural plate mode response to a point source, step-function load, applied

Reflections of AE Waves in Finite Plates: Finite Element Modeling and Experimental Measurements

October 1, 2002

Author(s)

W H. Prosser, Marvin A. Hamstad, John M. Gary, Agnes O'Gallagher

We investigated the capability of a three-dimentional dynamic finite element method for predicting far-field acoustic emission (AE) signals in thin plates of finite lateral extent, including their reflections from the plate edges. A lead-break (Hsu-Neilsen

Examination of the Application of a Wavelet Transformation to Acoustic Emission Signals: part 1. Source Identification

January 1, 2002

Author(s)

Marvin A. Hamstad, Agnes O'Gallagher, John M. Gary

A database of wideband acoustic emission (AE) modeled signals was used in Part 1 to examine the application of a wavelet transform (WT) to accomplish identification of AE sources. The AE signals in the database were created by use of a validted three

Examination of the Application of a Wavelet Transformation to Acoustic Emission Signals: Part 2. Source Location

January 1, 2002

Author(s)

Marvin A. Hamstad, Agnes O'Gallagher, John M. Gary

In Part 2, (Part 1 Source Identification) the same finite-element-generated database of acoustic emission (AE) signals was used to examine the application of a wavelet transform (WT) to improve the accuracy of AE source location. The method utilizes a WT

Effects of Lateral Plate Dimensions on Acoustic Emission Signals From Dipole Sources

December 1, 2001

Author(s)

Marvin A. Hamstad, Agnes O'Gallagher, John M. Gary

Using a validated three-dimensional finite element code, the out-of-plane displacements corresponding to model sources of acoustic emission (AE) were calculated in aluminum plate samples of two different lateral dimensions. Both samples were 4.7 mm thick

Modeling of Buried Monopole and Dipole Sources of Acoustic Emission With a Finite Element Technique

December 1, 1999

Author(s)

Marvin A. Hamstad, Agnes O'Gallagher, John M. Gary

The requirements for dynamic finite element modeling of the source dynamics and wave propagation of buried acoustic emission point sources were examined. Maximum permissible source and cell sizes for point sources were determined as a function of the

Detectability of Slow Crack Growth in Bridge Seels by Acoustic Emission

December 1, 1998

Author(s)

Marvin A. Hamstad, Joseph D. McColskey

The detectabillity of slow crack growth of cracks in bridge steels has been studied by use of acoustic emission testing technology. Fatigue crack-growth rates of nominally 1x10 -4 mm/cycle (4x10 -6 in./cycle) and 1x10 -3 mm/cycle (4x10-5 in/cycle) were

Wideband Acoustic Emission Displacement Signals as a Function of Source Rise-Time and Plate Thickness

August 1, 1998

Author(s)

Marvin A. Hamstad, John M. Gary, Agnes O'Gallagher

Using a dynamic finite element model, we studied the interrelationships between acoustic source rise-time and plate thickness in steel plates. The source was typically a midplane vertical dipole, and the out-of-plane displacement was obtained in the far

Development of Practical Wideband High-Fidelity Acoustic Emission Sensors

June 1, 1995

Author(s)

Marvin A. Hamstad

The development of a series of wideband acoustic emission (AE) sensor/preamplifier systems is described. Key design factors are discussed along with the actual design and characterization of the sensors. These new sensors with integral amplification are