- One-sided tensile or compressive load: 20 kN
- Alternating load: ±10 kN
- Frequency depending on specimen stiffness and structure: 35–240 Hz
In the Department of Mechanical Properties, we investigate the mechanical properties of specimens and components and their relation to other material and component properties. This includes studying material behavior under monotonic and cyclic loading on undamaged specimens, fracture mechanics specimens, and components.
Accompanying microstructural investigations are conducted on both the initial state and the loaded state, with a primary focus on clarifying failure mechanisms. Based on these studies, we derive models and quantitative descriptions for component failure, enabling us to predict strength and durability under mechanical loading. We also collaborate with other working groups within the institute to develop and investigate methods for increasing strength.
The Department of Mechanical Properties has two main areas of focus. Firstly, we carry out mechanical testing of materials and components as part of research projects and on behalf of industrial companies. Our particular emphasis lies in vibrational stress testing. Secondly, we develop models based on these test results to predict material behavior. The department's research primarily revolves around three key areas:
Calculation of the stressability
Considering the existing microstructure, local hardness, and residual stresses, we are working on a material model for stressability under vibrational stress. This model can be integrated into the simulation of the process chain using common equivalent stress hypotheses. Our ultimate goal is to account for complex microstructures, such as those found in carbonitrided surface layers.
Building upon the already successful flaw modeling that allows for the calculation of fatigue strength, we are developing a model for discrete lifetime prediction at stress levels within the fatigue strength range. This model is based on locally existing strengths and stresses.
Competing failure mechanisms
We are also working towards consolidating the description of different types of defects into a unified model. Different materials fail under vibrational stress due to various types of defects, such as pores, blowholes, precipitates, dispersions, and structural inhomogeneities. The multiple flaw approach will be employed to create a differentiated description of these defects.
The overall objective of these research areas is to verify the generalizability of our models concerning material, stress, and geometry. This will help reduce the testing effort in the future and allow the implementation of these models as building blocks in simulation tools.
In addition to the primary research, the department is involved in further projects that investigate stress interactions during component processing, develop test methods for unusual specimen geometries, and work on meaningful data structures for the structured storage of research data.
The Department of Mechanical Properties is equipped with 21 vibration testing machines covering different load and frequency ranges, along with 5 rollover test stands. Our testing capacities span a wide range, from large sample testing in a horizontal pulser with +/- 100 kN at 30 Hz to ultrasonic pulser testing at 20 kHz under alternating and pulsating loads. Our experienced technical staff is proficient in performing stress and strain-controlled vibration tests, while our scientific staff provides support in test planning and evaluation. Emphasizing the evaluation and classification of results, we also offer support through digital image evaluation, local temperature measurement, and a system for recording crack growth rates.
With a well-preserved fracture surface, our team can meticulously trace the history of a crack through detailed detective work. Supported by microstructure investigations and residual stress measurements, we uncover the causes of failure and recommend remedial measures for practical applications. In addition to examining in-house tested samples, we specialize in assessing damage caused by vibrational stress, collaborating with the metallographic and physical analysis department to investigate various cases, from broken springs to large gearwheels.