New publication – An Uncertainty Estimator for Slitting Method Residual Stress Measurements Including the Influence of Regularization

Hill Engineering recently published new research detailing our efforts to quantify uncertainty for slitting method residual stress measurements. This new approach provides a more accurate estimate of the measurement uncertainty associated with the slitting method, which is very helpful for probabilistic performance assessments. The paper is titled An Uncertainty Estimator for Slitting Method Residual Stress Measurements Including the Influence of Regularization and appears in Experimental Mechanics. The abstract text is available here along with a link to the publication.

This paper describes the development of a new uncertainty estimator for slitting method residual stress measurements. The new uncertainty estimator accounts for uncertainty in the regularization-based smoothing included in the residual stress calculation procedure, which is called regularization uncertainty. The work describes a means to quantify regularization uncertainty and then, in the context of a numerical experiment, compares estimated uncertainty to known errors. The paper further compares a first order uncertainty estimate, established by a repeatability experiment, to the new uncertainty estimator and finds good correlation between the two estimates of precision. Furthermore, the work establishes a procedure for automated determination of the regularization parameter value that minimizes total uncertainty. In summary, the work shows that uncertainty in the regularization parameter is a significant contributor to the total uncertainty in slitting method measurements and that the new uncertainty estimator provides a reasonable estimate of single measurement uncertainty.

If you are interested, the full publication is available here.

Illustration of estimated uncertainty for slitting method residual stress measurements on specimens removed from a quenched aluminum plate.

Additive Manufacturing Benchmark Publication

Hill Engineering recently contributed to a publication related to residual stress measurement in additive manufacturing (AM) test specimens titled, Elastic Residual Strain and Stress Measurements and Corresponding Part Deflections of 3D Additive Manufacturing Builds of IN625 AM‑Bench Artifacts Using Neutron Diffraction, Synchrotron X‑Ray Diffraction, and Contour Method. The work was performed under the NIST AM-Bench program in collaboration with researchers from NIST, Los Alamos National Laboratory, University of California Davis, and Cornell High Energy Synchrotron Source. The abstract text is available here along with a link to the publication. Continue reading Additive Manufacturing Benchmark Publication

ASIP Conference 2019

Hill Engineering is presenting about residual stress aerospace forgings at the upcoming 2019 United States Air Force Structural Integrity Program Conference (ASIP) in San Antonio, TX. The 2019 ASIP Conference is specifically designed to bring together the world leaders in the area of aircraft structural integrity and to disseminate information on state-of-the-art technologies for aircraft structures in both the military and civilian fleets. Hill Engineering’s presentation will include a summary of recent work to quantify the residual stress variability in aerospace forgings. The abstract text is presented below. Continue reading ASIP Conference 2019

Welcome Dallen Andrew

We would like to welcome Dallen Andrew to Hill Engineering. Dallen has 10 years of experience as a mechanical engineer supporting aircraft structural integrity programs. He received a BS degree in Mechanical Engineering from Utah State University in 2009, and a MS degree in Mechanical Engineering from the University of Utah in 2011.

During his career, Dallen has gained experience in many aspects of aircraft structural integrity, with specialization in the fatigue and fracture of metals. He has worked on many projects requiring him to utilize his capabilities in  fatigue crack growth analysis, fracture mechanics, durability and damage tolerance analysis (DADTA), fatigue testing, continuing damage, residual stress, finite element analysis (FEA), and non-destructive inspection.

Dallen is an organizer of the Engineered Residual Stress Implementation (ERSI) working group developing the analytical framework to allow the benefits from deep engineered residual stresses to be applied to aircraft inspection intervals for the United States Air Force. Dallen has significant experience supporting the A-10 and T-38 aircraft fleets. He also has significant expertise in the use of AFGROW and NASGRO fracture mechanics and damage tolerance software packages.

Please contact us today for additional information about Hill Engineering and the services we offer.

Hill Engineering announces agreement with VEQTER for Deep-Hole Drilling technology

Hill Engineering, answering strong demand for its residual stress measurement services, would like to announce our agreement with VEQTER, Ltd to license the Deep-Hole Drilling (DHD) technology. VEQTER, along with the University of Bristol, aided in the development of the DHD technique, and have practiced the technology for over 25 years. With this agreement, VEQTER will provide Hill Engineering with the equipment, technology, and support to deliver state-of-the-art DHD measurements within the North and South American Continents. Continue reading Hill Engineering announces agreement with VEQTER for Deep-Hole Drilling technology

Engineered Residual Stress Implementation workshop

Hill Engineering is proud to support the USAF and their objective to advance damage tolerance analysis methods through the Engineered Residual Stress Implementation (ERSI) workshop. At this year’s ERSI meeting (September 12-13), Hill Engineering will meet with other stakeholders in the USAF aircraft community to review progress over the past year towards implementation of engineered residual stress in the USAF fleet. Continue reading Engineered Residual Stress Implementation workshop

Welcome John Watton

We would like to welcome John Watton to Hill Engineering. John comes with more than 30 years of experience, most recently from Arconic where he worked at the Arconic Technical Center. John obtained an undergraduate degree in mechanical engineering jointly with Acadia University and the Technical University of Nova Scotia, and earned graduate degrees in mechanical engineering at Stanford University (masters, applied mechanics) and Carnegie Mellon University (Ph.D., design and expert systems).

Continue reading Welcome John Watton

Additive Manufacturing Benchmark Test Series

As a follow-up to our previous post about additive manufacturing (AM) we wanted to highlight some other activities in the additive manufacturing space.

One such activity that Hill Engineering has been involved in is the NIST AM-Bench program. AM-Bench is developing a continuing series of controlled benchmark tests with two initial goals: 1) to allow modelers to test their simulations against rigorous, highly controlled additive manufacturing benchmark test data, and 2) to encourage additive manufacturing practitioners to develop novel mitigation strategies for challenging build scenarios. As part of this program, Hill Engineering has been working in collaboration with UC Davis to support residual stress measurement activities using the contour method. Continue reading Additive Manufacturing Benchmark Test Series

BAMF webinar

Hill Engineering will be participating in an upcoming webinar related to 3D fatigue analysis using our Broad Application for Modeling Failure (BAMF) software. BAMF is a software tool for predicting the growth of fatigue cracks in 3D parts. Starting from an assumed initial flaw, BAMF combines stress and crack growth analyses to predict the evolution of crack shape and size in 3D. BAMF provides a robust and automated link between two leading tools: AFGROW and StressCheck™. Continue reading BAMF webinar