Due to many positive properties aluminium alloys have great potential in the automotive industry. Their susceptibility to defect occurence is, however, a known and frustrating obstacle. Defects such as inclusions and porosity have a major impact on the functionality and reliability of the product. This thesis presents a method for predicting the fatigue life and it's scatter of castings containing defects. The method is based on experimental data and results of numerical stress-strain analysis of castings containing structural inhomogenities. The characteristic of the presented method is that it predicts fatigue life based on fatigue curves of sound material and statsitical distribustion of the studied inhomogenity. After the adequacy of the method was verified for cases of porous specimens, it was then applied to specimens containing inclusions. The proposed method gives good estimates of order of magnitude of fatigue life for castings containing defects. The main advantage of this method is that it uses fatigue properties of sound material for it's prediction and that it is highly time efficient.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 13280027Advanced numerical simulation of a longitudinal whiplash crash for a front seat and its passanger was performed. The applied boundary conditions were in accordance to the ECE and EuroNCAP norms. During te simulation the passanger was modelled using a BIORID crash-test dummy. The seat structure, its foam and lining were modelled in detail. The simulation results agree well with the experiments from the viewpoints of a crash-test dummy traveling and a seat deformation.
F.06 Development of a new product
COBISS.SI-ID: 13006107Fatigue lifetime evaluation is an important part of the design process, since sudden failures of structural components can cause substantial material damage or even take human lives. There are many methods available that in different ways obtain fatigue lifetime. A new fatigue damage model based on concepts of energy methods has been developed in which dissipated energy is used as fatigue damage parameter. On the basis of energy balance in the segment of the Prandtl type operator, normally used in simulations of material response, a new multiaxial damage model and an upgrade of the previously developed methodology is proposed. By means of numerical simulation we have shown that the developed operator type model is better than the established integration model. This is due the fact that closed cycles and transformation of multiaxial stress-strain states into uniaxial stress-strain states are no longer needed, as well as dissipated energy is obtained independently and continuously, which is a great advantage. By comparing the simulated fatigue lifetimes with the measured ones, we have shown that the developed method is appropriate.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 13047835In automotive industry a great amount of effort is invested to reduce mass and to lower production costs of assembly parts. Therefore, air spring manufacturers invest in the development of new products that are lighter and cheaper as compared to the generation before. An analysis of potential use of alternative materials for production of pistons that are traditionally made of steel or aluminium has been conducted with cooperation with the Veyance Technologies Inc. The analysis has shown that fibre glass reinforced polymer (Poliamid) is economically viable. Along with the change of material alters the design of a piston which has to fit the selected material. Consequently, a completely new design of the piston with the same outer shell as compared to the original steel one has been developed. Many design studies and testings’ have been done on the new piston and they confirm the required structural strength of it. By choosing an alternative material the weight is reduced from 3.96 kg to 1.42 kg which represents 64 % mass reduction. Along mass reduction a 10 % reduction of a production costs has also been achieved. As such, the goal of the research has been met; therefore the transition from steel to polymers for other pistons and bead plates is to be expected in near future.
F.06 Development of a new product
COBISS.SI-ID: 13045275Material properties and the response of a material to different load conditions need to be defined properly to correctly evaluate the fatigue life as much as possible. Special attention needs to be given to parts which are exposed to combined load conditions, such as thermo-mechanical loads. This doctoral thesis presents the fatigue life evaluation of material with designation 1.4512 (EN 10088-2) for low and high cycle fatigue at different temperatures, which provides a wide range of material durability. A welded joint, which represents an increasingly used technique of combining different parts, is observed in order to define the influence on material durability. Weld decreases the durability of the basic material. Additionally, material aging is characterised as the influence on durability, where the parameters of aging temperature and time are observed. The analyses of experimental data are then conducted, after which durability curves are drawn for the low and high cycle fatigue regimes. Special attention is given to low cycle fatigue and the definition of fatigue crack growth, which is important when designing parts with low mass.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 13284635