Fretting fatigue occurs when there is a small amplitude oscillatory movement between two contacting surfaces while the bodies are undergoing fatigue loading. Fretting fatigue conditions can substantially reduce the fatigue life of a component. Many engineering components such as Ti-6Al-4V gas turbine engine disks in military aircraft commonly experience fretting fatigue conditions that can potentially lead to catastrophic failure of critical components. The aim of this study is to characterize the behavior of Ti-6Al-4V under fretting fatigue conditions. Experiments are performed to analyze the influence of stress amplitude, stress ratio, and contact geometry. The effect of surface treatments such as low plasticity burnishing on the fretting fatigue life is also explored. The experimental results are being used to validate a proposed crack nucleation life prediction model. The proposed model utilizes a crack nucleation parameter H that is based on the strength of the singular stress field at the contact boundary. An advantage of this singular parameter is that neither a coefficient of friction nor the location of the stick/slip boundary needs to be determined. These two parameters are often difficult to define with certainty a priori. H is also independent of geometry making it well suited for use as a design parameter for designing structural joints and other fitted connections between components.

To ensure that manufactured cartridges is safe to use, a tensile test is performed. The frictional force between the bullet and the case is required according to Normas standard to be between 15 – 75 Kg. Variations of the frictional force, with values outside of the standard had been noted by Norma Precision without understanding the cause. The aim of this report was to investigate and evaluate possible causes of the variations measured by tensile tests, difference between extreme values and to find a solution to what can be done to prevent the variations. Two different cases and three different bullets were used by request from Norma in the scope of this report. Different combinations of the bullets and cases was tested by alternating process parameter, surfaces and loading procedures. The loaded cartridges went through tensile tests to investigate differences. Bullets and cases with extreme values from the measured frictional force were chosen for further investigation in SEM and profilometer. To be able to draw further conclusions four different simulation models was created in Abaqus and different parameters was calculated. The dimensions and shape of the bullet resulted as the cause of changes of the tensile test curves. The smallest frictional force was found to differ from the largest by a change in wear mechanism from mainly abrasive ploughing to cutting and adhesion that caused transfer of material from the bullet to the case. The change in wear mechanism was found to be caused by an increased bullet diameter. The loading procedure was found to cause variations in plastic deformation on the neck of the case and damage the bottom of the bullet. The loading procedure was assumed to have the largest impact on the variations in frictional force. To minimize the variations the central axis of the case was suggested to be in line with the central axis of the bullet.

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The goal of the project is a static provision design of Drnovice castle. This castle (today a municipal office and a restaurant) is violated by vertical cracks. There is a significant horizontal displacement vector. That’s why horizontal prestress redevelopment (using prestressed cables) was chosen. A drawing documentation is an integral part of the project.