Hill Engineering, McClellan, CA. Adrian T. DeWald. Engineered Residual Stress.
Engineered residual stress is emerging as a tool for enhancing the performance, safety, and
reliability of metallic structure. Hill Engineering in an engineering services organization that
helps customers develop engineered residual stress solutions to solve challenges in material and
mechanical performance. As a first step, our engineers work carefully with a customer’s staff to
carefully understand the challenges. We provide a preliminary evaluation summarizing the
expected performance benefits against a range of costs for alternative surface treatments. Hill
Engineering is qualified for this service through its extensive experience with surface treatments
and its proven record of quick response.
Throughout the development process, Hill Engineering provides a range of capabilities to support residual stress engineering. These include a residual stress measurement laboratory, with expertise in both contour and slitting methods. We operate a fatigue testing laboratory which specializes in surface treated coupons and parts. We use finite element based modeling tools that predict full-field residual stresses induced by surface treatments of complex 3D parts, and we have extensive experience in fatigue analysis and prediction for residual stress bearing materials.
Lambda Technologies, Cincinnati, OH. Douglas J. Hornbach.
Residual Stress Design for Optimal Component Life.
Residual compressive stresses in metallic components have long been recognized to enhance
fatigue strength. Engineering components have been shot-peened or cold worked to create
a surface layer of residual compressive stress with fatigue strength enhancement
as the primary objective, or as a by-product of a surface hardening treatment like
carburizing, nitriding, induction hardening, etc. Additional surface enhancement methods
including LPB and laser shock peening have emerged, capable of placing relatively deep
compression into a component, furthering the potential benefit of compressive residual
stresses. Typically, surface enhancement processes are applied with little to no
preliminary design of the compression required to produce a given fatigue strength or
protection against stress corrosion cracking. No scientific means of precisely determining
the compressive zone in terms of magnitude and size has been available. In the absence
of a proper residual stress design, surface enhancement processes can produce too little or
too much compression leading to an undesirable fatigue strength, high compensatory
tensile stresses and/or unacceptable distortion.
A detailed design protocol has been developed to allow the compressive residual stress to be tailored for a given component. The protocol comprises of a series of successive design steps that ultimately allow the engineer to converge on a unique compressive residual stress field for a given application. Using a patented fatigue design diagram (FDD) a customized compressive field can be developed to produce a targeted high cycle fatigue performance given the mean and alternating applied stresses, and the damage in terms of Kf. Finite element analysis is used to predict the level of distortion and compensatory tension. A customized compressive field is placed into the work piece using CNC controlled mills, lathes or robots driven by CNC code to manipulate the low plasticity burnishing (LPB) tool onto the work piece. Residual stresses are measured using x-ray diffraction equipment and software developed to apply the corrections required for accurate results. High cycle fatigue tests are conducted to confirm the fatigue strength and damage tolerance is achieved. Finally, production LPB tooling and equipment are manufactured and integrated onto the CNC equipment to provide a turnkey system that consistently produces the desired compression in a production environment.
ORNL, Oak Ridge, TN. Thomas Watkins.
User Centers at the High Temperature Materials Laboratory.
The Department of Energy, through the office of FreedomCar and Vehicle
Technologies, supports the six user centers within the High Temperature
Materials Laboratory (HTML) located at Oak Ridge National Laboratory (ORNL).
A wide variety of characterization tools for materials exist in the areas of
microscopy, thermo-physical properties, mechanical properties, diffraction,
residual stress and tribology. This poster will provide an overview of the
capabilities at the HTML and discuss ways industry, small business and academia
can access them.
PROTO Manufacturing. Robert Drake.
X-ray Diffraction Residual Stress Measurements
PROTO Mfg. will display some of their latest x-ray diffraction residual stress
measurement equipment. For over 25 years, PROTO has been manufacturing a full
line of portable, laboratory, in-line production and custom x-ray diffraction
systems for the measurement of residual stress. PROTO also provides residual
stress measurement services in-house in their measurement laboratories, and
on-site on large components at their customer's facilities.
TEC. Beth Matlock. Portable X-ray Diffraction Stress Analysis.
Residual stresses play an important role in the life of a part. After a component
is manufactured and/or put in service, if may be necessary to check the stresses
nondestructively. It may also be preferable to measure these stresses on an i
nstalled part in a field environment. Portable x-ray diffraction systems such as
the TEC 4000 and MAX are uniquely
suited for measuring stresses in a non-laboratory environment. These systems are
low-powered (3-90W) devices that can measure residual stresses non-destructively
in a matter of minutes on parts in difficult to access locations. This ability
gives the customer the advantage of determining stresses in situ and possibly
avoiding removal of the part from service.
Practical examples of how portable XRD systems can be used in the field and laboratory will be presented. The measurement results along with how these results were used to problem solve will be discussed. Specifically, the logistics of making measurements on top of a large transport aircraft will be discussed. This aircraft was on the flight line when the measurements were made. Portable equipment made these measurements possible and provided precise residual stresses on top of the fuselage. The measurements were used to access the condition of the aircraft after many years of service.