Selected issues concerning calculations and experimental tests of transport means construction elements fatigue life

Development of an algorithm of fatigue life of structural components of road and rail vehicles as well as sea vessels and aircrafts involves three groups of activities connected with: development of fatigue load spectra on the basis measurement of service loads, determination of the construction material fatigue properties and a selection of the best hypothesis for estimating the fatigue damage to be used for a phenomenological description of the fatigue process. The above listed groups of problems include the main causes of differences that occur between the calculation results and the results of fatigue life experimental tests. Evaluation of these differences is the main goal of this article

Mechanical properties comparison of Ti6Al4V produced by different technologies under static load conditions

The most commonly used technology among the additive manufacturing is Direct Metal Laser Sintering (DMLS). This process is based on selective laser sintering (SLS). The method gained its popularity due to the possibility of producing metal parts of any geometry, which would be difficult or impossible to obtain by the use of conventional manufacturing techniques. Materials used in the elements manufacturing process are: titanium alloys (e.g. Ti6Al4V), aluminium alloy AlSi10Mg, etc. Elements printed from Ti6Al4V titanium alloy find their application in many industries. Details produced by additive technology are often used in medicine as skeletal, and dental implants. Another example of the DMLS elements use is the aerospace industry. In this area, the additive manufacturing technology produces, i.a. parts of turbines. In addition to the aerospace and medical industries, DMLS technology is also used in motorsport for exhaust pipes or the gearbox parts. The research objects are samples for static tests. These samples were made of Ti6Al4V alloy by the DMLS method and the rolling method from a drawn rod. The aim of the paper is the mechanical properties comparative analysis of the Ti6Al4V alloy produced by the DMLS method under static loading conditions and microstructure analysis of this material

MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF), high cycle fatigue (HCF), fatigue limit (FL) and giga cycle fatigue (GCF) appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys

Analysis of a Simplified Method for Determining Fatigue Charts ΔS-N on the Example of Welded and Soldered Connectors

The paper describes the method of determining fatigue charts ΔS-N, which is particularly useful in the description of fatigue properties of welded and soldered joints. This method is based on IIW (International Institute of Welding) guidelines and FITNET procedures. This method makes it possible to design ΔS-N charts in a probabilistic approach, which is important in the reliability analysis of structural elements. The work also contains examples of charts resulting from the development of test results for selected welded and soldered joints

3D heart model of the trainer for cardiology percutaneous treatments

W artykule omówiono budowę serca, trenażer do zabiegów przezskórnych na sercu oraz przykładowe modele serc opracowywanych w czasie projektowania i budowy trenażera. Zdefiniowano również niezbędne parametry modelu serca.The article discusses the construction of the heart, the trainer for percutaneous treatments on the heart and examples of hearts models developed at the time of designing and construction of the trainer. The necessary parameters of the heart model was defined

Verification of the method of equivalent amplitude determination based on two - parameter fatigue characteristic

In the most causes the loads which are affected on structural components are various over time and their character changes is stochastic. The stochastic character of operational loads of construction elements in various machine types is depended on many factors, included : work forces variability, environmental conditions, physical properties of components etc. Fatigue life calculation for this type of loads are conducted on the basis of determined sinusoidal cycles set through to use of the cycles counting method. The cycles which are contained to the sinusoidal cycles set are characterized by extensive range of amplitude Sai variation and mean values Smi. Application of Sa-N curve in fatigue life calculations caused disregard of the cycle mean value. This may affect the accuracy of calculations. Taking into account the cycle mean value Sm in the calculations may be realized by determining a substitute cycle with an average value Sm=0 and a substitute amplitude Saz≠Sa

EVALUATION OF ASSUMPTIONS IN FITNET FATIGUE LIFE CALCULATIONS – CHOSEN PROBLEMS

Development and the need of unification of fatigue life calculation methods of structural elements led to elaborate proper calculation procedures. The procedures were initially developed to apply in specialist areas of technique such as: aviation, ship building industry and power engineering. The attempt of elaboration of a universal procedure was released in 2006 and called FITNET. In the paper there was performed an analysis of chosen problems connected with the fatigue life calculation procedure. A m exponent of a power applied in a description of fatigue life calculation and the fatigue limit were chosen for the analysis. The mentioned parameters essentially influence the description of a fatigue life curve that is a base for the fatigue life calculation method. The analysis of literature data was completed with own research results in the shape of fatigue life curves of chosen grades of steel and aluminum alloys

Verification of the method of equivalent amplitude determination based on two - parameter fatigue characteristic

In the most causes the loads which are affected on structural components are various over time and their character changes is stochastic. The stochastic character of operational loads of construction elements in various machine types is depended on many factors, included : work forces variability, environmental conditions, physical properties of components etc. Fatigue life calculation for this type of loads are conducted on the basis of determined sinusoidal cycles set through to use of the cycles counting method. The cycles which are contained to the sinusoidal cycles set are characterized by extensive range of amplitude Sai variation and mean values Smi. Application of Sa-N curve in fatigue life calculations caused disregard of the cycle mean value. This may affect the accuracy of calculations. Taking into account the cycle mean value Sm in the calculations may be realized by determining a substitute cycle with an average value Sm=0 and a substitute amplitude Saz≠Sa

Problems of Equivalent Load Amplitude in Fatigue Life Calculations

This paper presents issues of fatigue life calculations in operational load conditions. The assumed runs were so processed as to get a set of sinusoidal cycles by using the following methods: full cycles counting method and rainflow counting method. On the basis of such sets of cycles of the varying parameters Sm i and Sa i were prepared block load spectra of equivalent amplitudes Saz , obtained with the use of an original method of these authors, in which two-parameter fatigue characteristics were applied. The work resulted in comparison of fatigue life results for load spectra determined by using the assumed cycles counting methods and the assumed two-parameter fatigue characteristics: the model IM, model II, model III and model IV, respectively

SOURCES OF DIFFERENCES IN CALCULATIONS AND EXPERIMENTAL TEST RESULTS OF FATIGUE LIFE OF STRUCTURAL ELEMENTS

Calculation results are the base for evaluation of fatigue life of structural elements during machine design processes. It results from the fact that there are no material objects in the phase of existence of a product. Reliability of tests results is an essential element in the calculation fatigue life evaluation method and it can be evaluated by comparison of the results with experimental ones. In the paper there was performed an analysis of the chosen factors essentially influencing conformity of calculation results and experimental test ones connected with basic elements of a calculation algorithm including: - elaboration and analysis of service loadings of a structural element, - determination and analysis of cyclic properties of structural elements, - selection of fatigue damage accumulation hypothesis being a description of fatigue life processes. The mentioned analysis was illustrated with examples of fatigue life tests performed in the Machine Design Department of the University of Technology and Agriculture within the research grant no. 2221/B/T02/2010/39 financed by The Ministry of Science and Higher Education and National Science Centre