applications

X-Ray Diffraction Systems and Services Can Be Utilized for a Wide Range of Applications

Proto's application scientists are skilled in a variety of x-ray diffraction (XRD) applications. Whether you need to verify the effectiveness of shot peening on a spring or prevent stress corrosion cracking (SCC) on a pipeline, Proto® can provide you with an effective system or measurement service. Some of the most common applications of XRD are listed below, but feel free to contact us to learn how we can help with your specific requirements.

residual stress software

RESIDUAL STRESS overview

Residual stress is defined as the stress present inside a component or structure after all applied forces have been removed. Compressive residual stress acts by pushing the material together, while tensile residual stress pulls the material apart. Mathematically, compressive stress is negative and tensile stress is positive. Stresses can also be characterized as normal stresses that act perpendicular to the face of a material or shear stresses that act parallel to the face of a material. There are a total of six independent stresses at any point inside a material represented by σij where i is the direction that the stress is acting and j is the face the stress is acting on.

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Geology xrd measurement

geology

Geologists study the earth in order to understand its processes and to extract valuable resources. X-ray diffraction (XRD) analysis provides a multitude of information about crystalline phases within rocks, which is essential to understanding their mineralogy, chemistry, and formation conditions. XRD data provides direct information aboutthe identity of crystalline phases, their relative abundances, crystallitesize, strain, and site chemistry.

Historically, the mineralogy of rocks was evaluated via polarized light microscopy (PLM) of thin sections or back-calculated from chemical data. The error in these methods is much larger than that of XRD, and preparation of samples for XRD is much simpler and less time-consuming than for optical methods. XRD data can be used to distinguish between polymorphs and accurately identify the distribution of cations within the minerals making it the preferred method of geoscientists.

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corrosion xrd measurement

corrosion

Corrosion reduces structural integrity and can ultimately lead to part failure. Furthermore, both scale and corrosion products can result in blockages and result in costly downtime and repairs. Powder x-ray diffraction is a powerful technique which allows rapid identification of scale and corrosion products. While chemical analysis methods can be used to determine elemental composition, they cannot identify what phases are present in scale and corrosion products. In addition, powder XRD can also distinguish between polymorphic phases with the same chemical composition.

For example, calcium carbonate (CaCO3), a common scale product, is mainly found in the form of calcite; however, it is also found as other polymorphs, such as aragonite or vaterite, depending on the environmental conditions present during formation. Iron-based corrosion products (e.g., rust) are perhaps the most common type of corrosion products analyzed. Iron(III) oxide-hydroxides can also be found in various polymorphic types such as lepidocrocite, feroxyhyte, and ferrihydrite, which can only be identified using XRD.

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cement xrd measurement

cement

The performance characteristics of cement are directly related to its phase composition. For example, ASTM type III cement develops high early strength and is characterized by having a larger mass fraction of alite. In comparison, ASTM type IV cement is known to have a low heat of hydration and is characterized by having a much lower mass fraction of alite. Therefore, having prior knowledge of the phases in a cement mixture and their relative amounts allows one to have control over the physical characteristics of the final product.

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automotive xrd measurementaerospace measurementautomotive xrd measurement

automotive

X-ray diffraction has become the industry standard for residual stress characterization of automotive components. It is an essential tool for process optimization, design improvements, and failure analysis.

Verify Surface Enhancements

The fatigue life of a component is often enhanced by cold-working processes such as shot peening. XRD residual stress measurement can be used to verify that these locations have been enhanced to the specified residual stress level.

Machining

Aggressive or abusive machining can create regions of tensile stress that can make certain areas of a component susceptible to crack initiation and increase the rate of crack propagation.

Validation of Finite Element Models 

Residual stress measurement can be used to verify that finite element models are predicting the correct residual stress in a component. When deficient, the known residual stress can be used to improve the FEA models.

Fatigue Life And Stress Concentrations 

When issues of fatigue cracking are considered, potentially harmful tensile residual stresses alone or in combination with stress concentrations can lead to fatigue crack initiation and propagation.

Heat Treatment Processes

Heat treatment processes are commonly applied to automotive components to lower or reduce the residual stresses present. Residual stress measurement can be used to ensure that such processes have been correctly applied and that any harmful residual stresses have been reduced to an acceptable level.

Residual Stress in Welds

Tensile residual stresses created during the welding process can lead to cracking. Components can be measured before welding, after welding, and after post-welding processes to ensure that stresses are properly managed.

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aerospace measurementaerospace measurement

aerospace

Residual stresses play a key role in the life of aerospace structures. Proto provides both measurement services and x-ray diffraction residual stress measurement instruments, enabling our customers to obtain residual stress measurements in the lab or in the field on aerospace components:

  • Skins
  • Wings
  • Frames
  • Landing gears
  • Engine supports
  • Landing gears
  • Engine casings
  • Engine cowlings

Some of the platforms Proto has worked on include C-141, B-2, Space Shuttle, Joint Strike Fighter, Boeing 777, and Dash 7.

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automotive xrd measurement

Power generation

Residual stresses created during the manufacturing process can lead to stress corrosion cracking, distortion, fatigue cracking, premature failures in components, and instances of over design. The nondestructive nature of the x-ray diffraction technique has made the residual stress characterization of power generation components a useful tool for process optimization, design improvements, and failure analysis.

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pipeline xrd measurement

pipelines

Residual stress plays an important role in many of the issues found in pipelines such as stress corrosion cracking (SCC), hydrogen induced cracking (HIC), fatigue cracking, welding stresses, heat treatment effectiveness, surface enhancements due to cold work, ending due to seismic activity and installation stresses. The significant effect that residual stress has on the performance and life of a component makes it extremely important to characterize these stresses.

The full benefit of a design can only be achieved when favorable residual stresses have been introduced into a component and harmful residual stresses have been minimized. X-ray diffraction is a portable, non-destructive, quantitative, highly accurate, and robust method to quantify residual stress. Modern equipment makes it quick and easy to do measurements in the laboratory, in line, and in the field. Proto’s portable measurement systems enable measurements to be easily performed on pipelines in the field.

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bridges xrd measurement

bridges

The weight of the concrete and the steel superstructure in a bridge and thus the resultant dead load in each of the critical members are well known when it is initially constructed, assuming all goes to plan. However, major maintenance, repair, or any significant damage to the structure can cause the loads to redistribute and thus change the dead loads and the load path. Therefore, it is important to know what these new dead loads and load paths are to ensure safe and reliable operation of the bridge. The in-service dead loads in metal bridge components can be measured using Proto’s x-ray diffraction (XRD) systems quickly and cost effectively without disrupting structure use.

Deadload Measurement

  • XRD measures total strain in the member
  • At the surface, most strains are due to fabrication. These strains quickly decrease with depth.
  • Electropolishing a small spot on the member to a depth of 0.020” (0.5 mm) exposes an area of the member where strain is mainly present due to the dead loads
  • XRD strain x Elastic constant x Cross sectional area of the member = Dead load (kips)
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3d printing

additive manufacturing

3D printing is increasingly being used as an alternative route to manufacturing components. In particular, replacement parts that were manufactured via traditional methods such as casting are now being made using additive manufacturing processes. While a printer can produce a dimensionally identical part, the process may not produce the same residual stress distribution in the part. The repeated cycles of heating and cooling that are required to deposit the layers of metal cause localized expansion and contraction, which in turn can create residual stress.

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shot peening map

shot peening

Peening effectiveness is normally characterized via the Almen intensity and the % coverage. It should be noted that many potentially different residual stress gradients can result from what may appear to be the same deflection of the Almen strip and observed % coverage. The % coverage is an optical assessment of the as-peened surface and is generally thought of as a measure of the uniformity of peening on the component surface.

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welding xrd measurement

Welds

Residual stresses created during the welding process can lead to stress corrosion cracking, distortion, fatigue cracking, premature failures in components, and instances of over design. The nondestructive nature of the x-ray diffraction technique has made the residual stress characterization of welds a useful tool for process optimization and failure analysis, particularly since components can be measured before welding, after welding and after post-welding processes.

Numerous techniques such as heat treating and shot peening are available to help manage potentially harmful residual stresses created during the welding process. Knowledge of the residual stress state is required to ensure that these post-welding processes have been correctly applied.

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