Today's machine elements are exposed to ever greater loads and correspondingly higher demands. This development has resulted in greater deformation of the components. In dynamically loaded Due to different stiffnesses of the connected parts, these deformations occur as relative movements appear. In contact, these initiate the damage process of the frictional fatigue as a function of the joint pressure. The research at the institute is therefore concerned with the topic of strength calculation under additional continuous frictional stress.
Quantification of the fatigue strength as a function of the tribological contact variables joint pressure and slip. In addition to the basic research of the contact parameters, the further consideration focuses on the influencing factors of the coefficient of friction, the wear and the material. Depending on the influences mentioned above, the aim is to determine the fatigue behaviour of joints subjected to long-term friction loads. generally valid and to be implemented in a strength analysis.
Experimental determination of fatigue strength on the test bench RKP100 (left) and at the connecting rod device of the HPP250 (right).
Conversion of the system-specific nominal stress related fatigue strength into a local stress state by means of contact simulation, taking into account the experimental friction values as well as the measured motion sequences between the contact partners. The simulations are carried out with the FE software ABAQUS.
Extension of the fretting fatigue calculation concept to cast iron and aluminium
|Start time:||Jan 2020|
|Further Information:||FVV-Nr.: M2518|
Established standards such as DIN 743 for shafts and axles or the FKM guideline are giving the user a clearly structured guideline for fatigue strength calculations and lifetime predictions of components for static and dynamic strength verification. This is a purely mechanical stress approach. Due to the additional surface damage, e.g. by fretting corrosion, the connections in this case do not fall within the scope of the mentioned standards and are difficult to evaluate quantitatively. A suitable concept for the integration of tribological damage could be successfully implemented into the FKM calculation algorithm through research work at IKAT in recent years. The calculation concept is based on empirically determined fretting factors, based on the tribologically most critical impact from slip and joint pressure. The previous investigations and validations of the concept mainly focused on the material group of steels. In the course of lightweight construction and the well-known problem of fretting corrosion in the field of aviation, aluminium materials are increasingly coming into focus. Furthermore, cast iron components in internal combustion engines are affected by tribological damage and are potentially endangered by fretting fatigue effects. With regard to a closed verification procedure, it is essential to extend the existing concept across materials in order to ensure an evaluation of cast iron and aluminium materials. Furthermore, the accuracy of the calculation results is essentially determined by the determination of the potential failure location. Currently existing calculation methods do not yet provide adequate results for the crack location. Therefore a validation and further development of existing failure hypotheses for the determination of the failure location is an essential part of the planned research project.
Investigation for the development of a generally valid calculation specification for joints subjected to permanent friction loads
|End time:||Jun 2019|
|Further Information:||FVV-Nr.: 1237|
Calculated strength evaluation for the design of machine components subject to friction fatigue loading
|End time:||Aug 2015|
Design Guidelines for Preventing Friction Corrosion Damage to Joints in Reciprocating Internal Combustion Engines
|End time:||Aug 2011|