Author: Adrian DeWald

Welcome Josh Hodges

by Adrian DeWald

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

by Adrian DeWald

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

by Adrian DeWald

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

by Adrian DeWald

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

by Adrian DeWald

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

The Prime Room

by Adrian DeWald

Hill Engineering recently moved into a new facility in Rancho Cordova, CA. The new facility features a combination of laboratory, research and development, and office space; all of which are important as we work tenaciously to meet the needs of our current projects, while at the same time keeping an eye towards innovation and new opportunities. We have proudly named the primary conference room in our new facility the Prime Room, a fitting tribute to a special Hill Engineering collaborator, the inventor of the contour method, and inspirational figure, Mike Prime. Continue reading The Prime Room

Hill Engineering achieves ISO 17025 certification

by Adrian DeWald

We are excited to announce that Hill Engineering was recently awarded ISO17025:2005 accreditation!

ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories is the primary ISO standard used by testing and calibration laboratories. Hill Engineering was accredited by the American Association for Laboratory Accreditation (A2LA). Compliance with the ISO/IEC 17025:2005 standard provides an internationally recognized basis for laboratory accreditation. The standard is used to govern Hill Engineering’s Quality System and entails adherence to rigorous technical requirements. Continue reading Hill Engineering achieves ISO 17025 certification

Residual stress in linear frictions welds

by Adrian DeWald

In a previous blog post we discussed, in general, issues related to residual stress in welding. In this post, we’ll follow up with a more detailed look at a specific welding application – linear friction welding of titanium alloys.

Titanium alloys are widely used in aerospace applications for their high strength to weight ratio, good corrosion resistance, and metallurgical stability. New joining methods are being implemented that allow for more efficient manufacture of titanium components. Linear friction welding (LFW) is a solid phase bonding process, which is particularly appropriate for titanium alloys. Due to the titanium’s great affinity for oxygen, nitrogen, and hydrogen, protective atmospheres must be used to prevent contamination of the welded material. LFW avoids the formation of a liquid phase during the welding process, and can therefore be carried out in air. Likewise, the typical defects caused by melting and solidification during traditional welding process such as pores, pinholes, shrinkage cracks and grain coarsening are avoided. However, as with all welding and deformation processes, understanding the weld residual stress is important. Continue reading Residual stress in linear frictions welds

ASIP Conference

by Adrian DeWald

Hill Engineering is presenting about fatigue analysis methods for cold expanded aircraft fastener holes at the upcoming 2016 Aircraft Structural Integrity Program (ASIP) Conference in San Antonio, TX. Cold hole expansion is a method commonly used to induce compressive residual stress around the perimeter of fastener holes, which are common in aircraft structure. The compressive residual stress has significant benefits related to fracture and fatigue of the structure. Hill Engineering’s presentation will include a summary of current analysis methods and a plan for how these methods can evolve to allow for improvements in aircraft design and sustainment. The abstract text is presented below. Continue reading ASIP Conference