in Vol. 12 - May Issue - Year 2011
Residual Stress Measurement Services in Spain
Dr. Jesus Ruiz-Hervias (Ph.D. in Physics), founder of ASM
Residual stress measurement in a shot-peened surface
Residual stress profiling in a shot-peened gear tooth (cut by EDM)
Residual stress measurement in large components
Accurate Stress Measurements (ASM) is a young company in the field of residual stresses. We offer consultancy, training and residual stress measurements in materials and components with the highest quality and reliability. The company was founded by Dr. Jesus Ruiz-Hervias (Ph.D. in Physics and Associate Professor at the Technical University of Madrid, UPM). He is one of the leading researchers in residual stresses in Spain and has broad experience (over 20 years) with diffraction methods, including laboratory X-ray, neutron and synchrotron sources.
Residual stresses are generated by the different thermal and mechanical treatments employed in fabrication or by the applied loads when a component is in service. They may cause dimensional changes and distortions which may render the component useless for engineering applications. Unlike applied stresses, residual stresses are not visible. Consequently, they are sometimes forgotten and this may cause unexpected failures. If residual stresses are high enough, cracks may develop in the component which may lead to catastrophic failure. In the case of high-risk components (power generation, nuclear, aeronautic, astronautics...), or in mass-production components (i.e. components for car engines) where the substitution of a defective component may be very costly, a precise assessment of residual stresses may save a lot of money.
Residual stress measurement techniques may be of two different kinds: destructive (i.e. hole drilling) or non-destructive (i.e. Barkhausen noise, interferometry, ultrasounds, and diffraction techniques). From the above-mentioned techniques, X-ray diffraction is the most accepted method for the non-destructive measurement of residual stresses, especially for the metallic materials used in engineering. With this technique, the lattice strain is measured and the residual stress is determined by using the diffraction elastic constants, which depend on the diffracting phase and lattice reflection employed.
Accurate Stress Measurements offers the following services:
Consulting: Our aim is to offer comprehensive advice to our customers concerning residual stress problems, mainly in fabrication processes. This includes a thorough analysis of the problem and a proposal to offer a solution, based on a better knowledge of residual stresses. Our company has highly skilled personnel with extensive experience in residual stress measurement. They can help our clients identify their problems and solve them adequately.
Residual stress measurement: We offer residual stress measurement by X-ray diffraction (a non-destructive technique), in our laboratory or on site. There is no limitation regarding the size of components that can be measured, since we have portable equipment especially designed for residual stress measurement.
There are two kinds of measurements:
Surface measurements: these measurements are carried out on the surface of the sample or component and they provide the residual stress value at a depth of a few microns below the surface. The method employed is 100% non-destructive and the component can be re-used after the measurement without any problem.
Sub-surface measurements: in this case a localized attack by electro-polishing is carried out in a surface region, and residual stresses are measured as the material is being removed. As a result, a residual stress profile is obtained as a function of depth, which provides more information than a single surface measurement. The maximum depth that can be achieved with this method is around 0.5 mm and, due to the layer removal technique employed, is mainly applied in metals. These profiles are very useful when a precise knowledge of the effect of thermo-mechanical treatments is needed, because steep stress gradients may exist in the vicinity of the surface. This is particularly interesting in shot peening, because it is the most efficient way to check the outcome of the process.
Training: The knowledge about residual stresses is usually insufficient, even among the technical managers in the companies. With the aim of improving this situation, courses and technical seminars will be given by the most renowned experts in this field, and the possibilities of the non-destructive techniques for residual stress measurements will be reviewed. This will help people to understand the possibilities of these techniques.
Our company values are aimed at our customers’ satisfaction. To achieve this goal we offer:
• Direct and personal communication.
• Highly qualified and reliable personnel.
• Respect for deadlines.
We provide residual stress characterization in engineering components in order to:
• Optimize component design.
• Validate numerical simulations.
• Control fabrication processes.
• Characterize the optimal surface treatment parameters (i.e. shot peening).
• Facilitate preventive maintenance.
• Ensure component quality and reliability.
Our company provides services to private companies, research institutes and research departments of universities. Some of our clients include the following:
• John Deere Iberica, Getafe, Madrid (Spain).
• GKN-Driveline, Vigo, Pontevedra (Spain).
• Metal Improvement Company (MIC), Sevilla (Spain).
• Universidad Rey Juan Carlos de Madrid, Móstoles, Madrid (Spain).
• Talleres Brimo, Granollers, Barcelona (Spain).
• Universidad del País Vasco, Bilbao (Spain).
Our company has the optimal technology and team staff to achieve the complete satisfaction of our clients. Our main objective is to offer a high-quality service and to provide our customers with reliable and useful results as promptly as possible. Trust ASM as your partner in residual stresses!