Analysis and Simulation of Residual Stresses

We develop recommendations and concepts for component design, choice of materials, and manufacturing processes by identifying manufacturing and usage-related residual stresses and evaluating them in terms of reliability, safety, and service life.

We develop optimization concepts for managing residual stresses resulting from: 

• Forming processes
• Casting processes
• Joining processes (welding, cold cracking)
• Additive manufacturing
• Surface treatments such as shot peening, hammering, and roll peening (cold rolling)
• Machining processes such as grinding, turning, and milling
• Hydrogen embrittlement

We implement a cost-effective measurement strategy for our clients that is tailored to their specific needs. Here, we can ensure an economical and reliable assessment of residual stress conditions, as we have various radiographic and mechanical methods at our disposal for determining residual stresses. In addition, we perform texture and phase analyses. Furthermore, we simulate and calculate residual stresses and derive their effects on component performance, for example, specifically on service life.

We work with position-sensitive X-ray detectors and 2D detectors, allowing many measurements to be performed in a short time. For highly deformed components and multiphase materials, we can perform analysis using our proprietary StressIWM software. We also offer point measurements with a small radius of 0.3 mm for measurements in notches, even on large specimens. For components with complex geometries, we offer a CAD routine to assess in advance the accessibility of the measurement position for the classic sin2ψ method used to determine residual stresses.

Radiographic Residual Stress Measurements – Our Portfolio

Stationary X-ray diffractometers

We prefer to perform near-surface residual stress analyses using X-ray diffraction (XRD). This method is based on the determination of strains in the crystal lattice and is therefore suitable for (partially) crystalline materials. The components examined range in size from millimeters to meters.

• Measurements on metals, ceramics, and various phases
• Depth profiles obtained by electrolytic etching
• Lateral resolution up to 100 µm
• Automated 4-point bending apparatus for determining specific X-ray elastic constants
  

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Mobile X-ray Diffractometers

Mobile diffractometers are available for on-site measurements. The long-wavelength X-rays typically used have a shallow penetration depth ranging from a few micrometers to several tens of micrometers. Greater depths can be achieved through step-by-step electrochemical ablation, with subsequent measurements taken after each step. In this case, the method is no longer non-destructive.

• Measurements on metals, ceramics, and various phases
• Large samples and on-site at the customer’s location
• Depth profiles at the customer’s location possible via electrolytic ablation with a mobile device
• Lateral resolution up to 300 µm
  

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Robotic Diffractometer

For complex surface geometries, mounting a mobile diffractometer on a robotic arm allows for the cost-effective and efficient measurement of large-area maps (e.g., 0.3 x 0.3 m).

• Metals, ceramics, various phases
• Lateral resolution up to 300 µm possible
• Automated measurements at multiple measurement points on large components

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Borehole Method

At depths of approximately 20 µm or greater, we also determine residual stresses in surface layers using a mechanical borehole method. To do this, the existing residual stress state is partially relieved step by step by high-speed milling of a blind hole or an annular groove, and the resulting strains are recorded using strain gauges. The original residual stresses can be calculated from the stress-depth profiles. Residual stress distributions down to approximately 1 mm can be determined in this way.

• Residual stress-depth profiles from approx. 0.04 mm to approx. 1 mm depth
• Hardness of the material up to 55 HRC (higher hardness upon request)
• Surface measurements can be performed using X-ray methods
• On-site measurements at the customer’s location and on large components are possible
• Measurements according to ASTM E837-13a

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