W. H. Peters

Application of an optimized digital correlation method to planar deformation analysis

Abstract An optimized digital correlation method (DCM) has been developed to improve previously reported iterative DCMs. The optimized method is shown to be much faster than previous methods while achieving accuracy equivalent to that obtained via simple coarse-fine iterative techniques. The optimized correlation routine employs the Newton-Raphson method with differential corrections to minimize search time. The paper illustrates the optimized DCM and presents a simple flowchart of a practical program. Experiments indicate that the optimized DCM is successful in displacement measurement. In direct strain measurement, however, both DCMs using a coarse-fine search routine and those using the proposed optimized correlation procedure are shown to have large variability in the computed strains.

Determination of plastic strains at notches by image-proceessing methods

An image-processing method was developed to quantitatively extract the level of plastic deformation in metal specimen made of 304 stainless steel under remote tensile loading. The effective strain distribution around the notch tip was obtained and compared with the finite-element results. An exponential decay of the plastic strain concentration with distance from the notch tip was observed.

A study of mixed mode fracture by photoelasticity and digital image analysis

Abstract In this paper, the results from two experimental methodologies, photoelasticity aided by digital image processing and precision digital image correlation, are presented for a mixed mode fracture problem. The mixed mode fracture problem was a three-point-bend edge-crack specimen which was loaded at various off-crack-line locations between the crack line and the specimen support line. The estimations of KI and KII from both methodologies indicate that the crack tip stress field is strongly intensified by KI but not KII.

A study of plastic zone formation by digital image processing

Abstract A simple experimental technique is presented to directly measure the plastic zone in engineering structural materials by using both digital image processing and optical techniques. Standard image processing procedures were performed on images obtainted from laser illumination of polished stainless steel specimens to obtain predictions of the onset and size of plastic zone formation. The finite element program, ANSYS, was used to obtain numerical solutions for comparison with the experimental data. It is shown that the experimental method discussed in this paper is capable of predicting plastic zone size as a function of loading.

Improved digital image processing technique to investigate plastic zone formation in steel

Abstract An improved digital image processing procedure is developed to extract the size and shape of the plastic zone formation at the tip of a notched metal specimen based on the characteristics of the variation of intensity in a digitized image. The result is compared with the result from finite element analysis, and with that from a previously developed image processing procedure. Comparison shows that this method provides a faster and more accurate result than previously.

The faculty perspective on holistic and systems thinking in American and Australian mechanical engineering programmes

This research effort examined current mechanical engineering educational programmes in America and Australia to determine the degree of holistic, systems thinking of each programme. Faculty from ten American universities and ten Australian universities participated in online surveys and interviews. Resulting data analysis and interpretation suggest that holistic, systems thinking is present in both American and Australian engineering educational programmes, although it is more prevalent in Australian programmes. Specific examples of educational opportunities (courses, projects, extracurricular activities, research experiences) that integrate complex systems study are described in the full paper. This study is currently limited a small sample size within two countries, but it would be very useful to expand the study to a larger population and to include European sites to gain a fuller picture of the state of holistic, systems thinking in higher education.

Benchmarking the Integration of Complex Systems Study in Mechanical Engineering Programs in the Southeastern United States

Complex systems study, defined as an understanding of interrelationships between engineered, technical, and non-technical (e.g., social or environmental) systems, has been identified as a critical component of undergraduate engineering education. This paper assesses the extent to which complex systems study has been integrated into undergraduate mechanical engineering programs in the southeastern United States. Engineering administrators and faculty were surveyed and university websites associated with engineering education were examined. The results suggest engineering administrators and faculty believe that undergraduate engineering education remains focused on traditional engineering topics. However, the review of university websites indicates a significant level of activity in complex systems study integration at the university level, although less so at college and department levels.

Hybrid Methods in Experimental Mechanics

Hybrid procedures can be broadly defined as the synthesis of a variety of available methodologies into a composite techinque, which, taken as a whole, is more useful than any of the individal methods. In experimental mechanics, the most common form of hybrid approach is one utilizing both numerical and experimental data to quantify the behavior of a structure. In this paper, the finite element method is combined with laser speckle, holographic interferometry, and photoelasticity and the boundary element method is combined with a new experimental method, digital image correlation, for measuring displacements. These hybrid methods are used to address several problems in mechanics.

Digital Image Correlation Of White Light Speckle Including The Effects Of Image Distortion

An image correlation theory of white light speckle is presented which describes the light intensity as a continuous function for both the reference and deformed images. The reference image is divided into small regions corresponding to small subimages of the object surface. The subimage forms the basic element of the process of image correlation. The subimage of the undeformed intensity pattern is mapped to the deformed surface in order to compare its location to a corresponding location on the deformed intensity surface. This mapping function mathematically translates, rotates and deforms small subimages until the best fit is obtained with the recorded data. The following is thus obtained: (1) translation, (2) rotation, and (3) deformation.

Microprocessor‐based data‐acquisition system

This article describes the development of an automated microprocessor‐based data‐acquisition system and, in particular, the use of an inexpensive microcomputer to automate an acoustic experiment. Specifically, it explains the use of a Motorola MC6801 in the single‐chip mode to control a rather complex experimental process. The system is configured to provide for automated, two‐dimensional data acquisition of ultrasonic transmissibility through a specimen surface. Results to evaluate the accuracy and the performance of the system with known analytical predictions will be presented.