VOL. 24 July ISSUE YEAR 2023
in Vol. 24 - July Issue - Year 2023
An Affordable and Accurate New Solution for Residual Stress Measurement
Michael Brauss, President of Proto Manufacturing
The iXRD Mini measuring the residual stress of a part
MFN had the opportunity to have a conversation with Michael Brauss, President of Proto Manufacturing.
(?) MFN: Michael, thank you for taking the time to be interviewed today. Has Proto been working on developing any new residual stress x-ray diffraction (XRD) technology lately?
(!) M. B.: Thanks for the opportunity to communicate with the readers at MFN, many of whom are our customers. Yes, we have been busy developing new technologies; of particular interest to MFN readers would be our new iXRD Mini, a spin-off of our popular iXRD portable diffractometer, that is an affordable entry-level instrument for residual stress XRD measurements. We’re especially excited to launch this system because we think that it will make XRD measurements more accessible to our customers.
(?) MFN: How will the iXRD Mini make XRD residual stress measurements more accessible?
(!) M. B.: It was important to us to design a system that utilized the most reliable residual stress XRD method (the sin2ψ method) rather than less accurate methods such as cosα, all while remaining affordable for our customers. The iXRD Mini is a compact, low-maintenance instrument that is easy to set up and use. It’s an ideal balance between convenient features and a reasonable price point, allowing more engineers and technicians the opportunity to collect residual stress data and optimize their components.
(?) MFN: What kind of user do you think would benefit most from using an iXRD Mini?
(!) M. B.: A wide range of users could benefit from using the iXRD Mini – in particular, users with less experience, users with simpler measurement needs, and users with lower measurement throughput requirements. Although we sell a full range of advanced residual stress measurement systems with high power and extensive configurations, not every user requires that level of adaptability for their measurements. The streamlined design of the Mini means that users can expect a system that is very easy to use, with slightly reduced speeds and power compared to our other systems – but these reductions come with a lower price point. For users who are doing R&D or quality control on a routine part, or who have standard residual stress measurement needs and no tight time constraints, the iXRD Mini is a more affordable solution that doesn’t sacrifice the accuracy of data.
(?) MFN: What kind of information do the results provide?
(!) M. B.: Data from the iXRD Mini provides information about the residual stress state of components, which gives users direct information about performance and safety: for example, fatigue life, corrosion resistance, distortion, or dimensional stability. Even small changes in residual stress can have a significant effect on the life of a component, so it’s incredibly important to monitor residual stress. Knowledge of the residual stress state can help identify and correct issues prior to in-service failure, ensuring the safety and stability of components. The compact nature of this system also makes it ideal for field use on large in-service components, such as vehicles, bridges, and structures.
(?) MFN: What are the main features of the new system?
(!) M. B.: The iXRD Mini has dual x-ray detectors and a full-range goniometer for sin2ψ multiple exposure measurement. It allows for data to be collected from both positive and negative psi tilts to ensure correct shear stress evaluation. X-ray tubes are user replaceable and are made in-house by Proto with a range of different anodes to provide the best results possible for each application. The entire system is packed into a single travel case, making it extremely convenient for field measurements. Finally, a nice bonus of the iXRD Mini is its built-in linear translation slide that enables residual stress profiles to be created, which helps users identify stress gradients along the surface of a part automatically without tedious setup. This is a handy and time-saving feature that is not typically found in this level of equipment. The translation slide coupled with the most accurate measurement method makes the iXRD Mini the ideal residual stress measurement instrument in its price range.
(?) MFN: Why is identifying surface residual stress gradients important?
(!) M. B.: Gradients show us the distribution of residual stress along the surface of a part. These linear profiles are extremely helpful because the distribution of residual stress within a part is not always obvious just from its appearance, meaning that it can be challenging to locate the specific problem area within a component. While the net sum of all residual stresses across any cross section of a component is always zero, balancing tensile and compressive stresses exist, either internally or across the surface of a part. Because of the potential for areas of high tensile residual stress, it is important to understand the magnitude and location of the stress in order to prevent issues such as stress corrosion cracking.
However, it can be challenging to get a complete understanding of the residual stress present in any region of a component because the area could be large, or we may not have any clues about where to start measuring. In addition, the setup that is required to measure residual stress at several different locations, especially within a complex part, can be cumbersome and time consuming. With the iXRD Mini’s linear mapping slide, you can select specific points along a line for measurements and also greatly reduce instrument setup requirements. The resultant residual stress profiles are great for observing residual stress changes that are often present when moving away from an area such as a bolt hole or weld. Many problems related to residual stress can be adequately investigated with just this linear mapping feature.
(?) MFN: Once users generate residual stress profiles, how can they use the data to improve their components?
(!) M. B.: Residual stress profiles can identify areas of high tensile stress, which could lead to premature component failure or other serious issues. Once the locations of the harmful stresses have been determined, decisions can be made in order to optimize the part’s performance. For instance, users might decide that they want to use a method like shot peening or ultrasonic impact treatment (UIT) to impart beneficial compressive residual stress and thus mitigate the stress-related issues present in the component. Alternatively, the information gained through residual stress measurement could lead to changes within the design or manufacturing process to prevent the issue from recurring. The data may even be used to create a new specification for the part, as it could provide a better understanding of the part’s in-service performance so that it can be removed from service before it fails.
(?) MFN: If a method such as shot peening or UIT is used to impart beneficial residual stress, can XRD measurements help us verify that it has had the desired effect?
(!) M. B.: Yes, XRD residual stress measurement is a highly effective method for verifying that processes such as shot peening and UIT have been applied correctly. XRD measurements are non-destructive (at the surface, where shot peening imparts beneficial stresses), as well as accurate and repeatable, which means that many companies rely on XRD measurements to characterize the residual stress state of their components at all stages of their lives, including after any cold-working processes are applied.
(?) MFN: It sounds like Proto specializes in making residual stress measurements more efficient via mapping technology. Aside from the iXRD Mini’s line mapping feature, do your other residual stress measurement systems have mapping capabilities?
(!) M. B.: Yes, they do. From built-in mapping stages to accessories and add-on systems, we make efficient mapping a priority in all of our residual stress instruments. Our laboratory system, the LXRD, and our most popular portable system, the iXRD, both have speciality Modular Mapping editions with built-in mapping capabilities for convenient and comprehensive residual stress mapping of large parts. The LXRD is also compatible with our patented ball-mapping apparatus for characterizing the residual stress within spherical objects such as ball bearings. Finally, the LP200 Profilometer is a great add-on that is compatible with all of our residual stress systems. It can be used to generate maps in a variety of different shapes, as well as characterize the depth of a component for the creation of stress-versus-depth profiles.
(?) MFN: Have you introduced other novel design elements lately?
(!) M. B.: Our roboXRD system is the first of our residual stress measurement systems to incorporate robotics, making it very flexible for parts with complex geometries. The roboXRD features a six-axis robot that can collect data at many different angles, so it is ideal for both small and large parts. At the end of the day, our top priority in all of our residual stress measurement systems is accuracy of the data collected, and this system provides an impressive level of precision.
(?) MFN: Michael, thank you for speaking with us about your recent technological improvements in the area of XRD residual stress measurement.
(!) M. B.: Thank you very much for allowing me to share our latest developments. We look forward to seeing the important results that the iXRD Mini will deliver for our customers in the years to come.
MFN would like to thank Michael Brauss for this interview!
Proto Mfg. Inc.
12350 Universal Drive, Taylor, Michigan