Hill Engineering Blog

What is Residual Stress?

What is residual stress? That’s a very common question when you work at Hill Engineering. Many of our customers, friends, colleagues, and family members like to ask us questions about residual stress including: What is residual stress? How do you measure it? How does residual stress affect material performance? If you have questions about these topics, you’ve come to the right place. At Hill Engineering we love to talk about our work and we have a lot to share about residual stress. Continue reading What is Residual Stress?

Come see us at PS&S 2017

Hill Engineering will be presenting at the upcoming Propulsion Safety & Sustainment Conference (PS&S) in Phoenix, AZ on May 22nd through May 25th. We invite you to come see us. We will be sharing some recent work about experimental validation of process models for nickel engine disk design. Hill Engineering’s presentation will include a summary of residual stress measurements used to calibrate and validate process models for nickel engine disk applications. The abstract text is presented below. Continue reading Come see us at PS&S 2017

Aircraft Airworthiness & Sustainment 2017

Hill Engineering is presenting about residual stress engineering to support fleet management and life extensions of legacy fleets at the upcoming 2017 Aircraft Airworthiness & Sustainment Conference (AA&S) in Phoenix, AZ. The mission of this conference is to identify the challenges and the collaborative work being done within the aerospace community in improving the safety, airworthiness, availability and cost effectiveness of both our military and commercial aircraft fleets. Hill Engineering’s presentation will include a summary of recent work in airframe structures, demonstrating the use of residual stress engineering tools to support design and sustainment. The abstract text is presented below. Continue reading Aircraft Airworthiness & Sustainment 2017

Welcome Josh Hodges

We would like to welcome Josh Hodges to Hill Engineering. Josh has worked in the United States Air Force T-38 ASIP office (Hill Air Force Base) for the past 8+ years as a Structural Integrity Analyst. During his time in the T-38 ASIP office, Josh filled many roles including: developer of the Broad Application for Modeling Failure software and manager of the T-38 Damage Database, while also serving as a subject matter expert on the effects of residual stress on fracture and fatigue. Continue reading Welcome Josh Hodges

Fatigue Analysis

Fatigue is a material failure mechanism whereby repeated sub-critical loads nucleate and grow cracks that can ultimately lead to failure of a structure. Hill Engineering routinely performs fatigue analysis to quantify and predict fatigue performance of materials. State-of-the-art fatigue analysis is subdivided into categories, including durability (crack initiation) or damage tolerance (crack growth). The appropriate fatigue analysis for a given design depends on the application. Continue reading Fatigue Analysis

Come see us at AeroMat 2017

Hill Engineering is presenting about advanced manufacturing methods and their effects on residual stress at the upcoming 2017 AeroMat Conference in Charleston, SC. The event is organized by ASM International and is hosted by Arconic. Hill Engineering’s presentation will include a summary of recent programs where we evaluated the residual stress from a variety of advanced manufacturing methods. The abstract text is presented below. Continue reading Come see us at AeroMat 2017

Building a Quality System

As was previously discussed, Hill Engineering was recently awarded ISO17025:2005 accreditation for our Quality System. Developing a Quality System that is compliant with ISO is a significant effort, and at Hill Engineering we took it as an opportunity to improve the quality and documentation of our laboratory residual stress measurement services. Here’s a look back on some of the highlights in the development of our Quality System. Continue reading Building a Quality System

Cold expansion

Fatigue is one important failure mode that guides the design and engineering of aircraft structure. As we have discussed previously aircraft are often manufactured using rivets and fasteners, which require drilling many holes in the structure during assembly. The holes act as stress concentrations, which tend to be locations where fatigue cracks are found. Compressive residual stresses act to hold cracks shut and result in improved fatigue performance. This residual compressive stress can provide substantial benefits in terms of performance, safety, cost, and inspection requirements. To take advantage of the benefits of compressive residual stress, cold expansion is often applied to aircraft fastener holes. Continue reading Cold expansion