07/21/2026
By Marley O'Neil

The Francis College of Engineering, Department of Mechanical Engineering, invites you to attend a doctoral dissertation defense by John Matthews titled: "On the Implementation of Fixture Neutralization with Enhanced Tools and Techniques."

Tuesday, August 4, 2026
1 to p.m.
Southwick 240

Committee:

  • Advisor: Peter Avitabile, DEng., Professor Emeritus, Mechanical Engineering, University of Massachusetts Lowell
  • Co-Advisor: Alessandro Sabato, Ph.D., Associate Professor, Mechanical Engineering, University of Massachusetts Lowell
  • Jesus Reyes-Blanco, Ph.D., Associate Teaching Professor, Mechanical Engineering, University of Massachusetts Lowell 
  • Javad Baqersad, Ph.D., Associate Professor, Mechanical Engineering, Kettering University

Abstract:
Structural systems need to be designed to withstand environmental in-service loadings. As such, testing standards are imposed to ensure equipment will properly function in service. While testing is routinely deployed, there is a serious concern that the test environment may not totally replicate the field condition. Recently, field to laboratory boundary condition compensation techniques have been deployed to allow for accurate and reliable environments testing. Fixture Neutralization (FINE) is one such technique being deployed, but there is little guidance as to what critical items are needed to effectively perform the steps required. Development of tools to better assist and understand the FINE process is critical to allow for more accurate recreation of target field responses in a laboratory environment. In this work, a multitude of tools and techniques were developed to help aid the FINE response recreation process; specifically, INSPECT, SAFE, extension of force reconstruction for FINE, and STRAC are tools developed in this work.

All these tools represent improvements in the overall FINE process. Utilization of all the tools together is useful for more accurate response recreation. Analytical cases were investigated to validate the accuracy of the tools. An experimental FINE process was performed to show how each of the techniques shown can be integrated into the overall FINE process. The FINE process requires a number of forces equal to the number of effective connections that exist in the configuration being tested. The number of effective connections does not necessarily equal the number of physical connections. Thus, a metric to determine the effective connections in the system was developed, called the Iterative Nullification of Singular-Value Process for Effective Connections Technique (INSPECT). Singular Value Decomposition is utilized in an iterative process to determine the effective connection set in a configuration, reducing the total number of inputs necessary for FINE testing. Force reconstruction is a research field that aims to recreate forces that produced a set of measured responses. A variety of tools, such as the Primary Locator Function (PLF), have been developed to aid the force reconstruction process. These tools are utilized to better condition the matrix inversion step that occurs and allow for more accurate input location determination. These force reconstruction techniques were morphed to be utilized for FINE field to laboratory response recreation. This allows for the adaptation of these tools, such as the PLF, for FINE testing. Both force reconstruction and FINE techniques are susceptible to modal truncation errors during the calculations. 

The Scaled Accumulation of FRF Error (SAFE) metric was developed to determine modal truncation effects in a system from a given mode set. SAFE uses target responses to scale FRF residual error to graphically represent FRF truncation error for given mode sets. The SAFE metric is useful to allow for better conditioning of inversion steps performed in the previous techniques developed. Finally, the Scale Time Response Assurance Criteria (STRAC) was developed to determine scale factors between two signals being compared. This allows for more robust correlation metrics to be found in conjunction with the traditional TRAC metric. Both the TRAC and STRAC must be utilized in unison for optimal results. Additional work extended the application of these techniques to modal response contributions as well as to subsections over time, allowing for a more complete understanding of the correlation of results performed. The FINE process is a major step forward in providing accurate recreation of field response in a laboratory setting but specific guidance in deployment was lacking. This work provided the tools necessary to augment the FINE process and ultimately provides a much clearer and better understanding of deployment of FINE for field to laboratory applications.