Stress-strain state analysis and fatigue prediction of D16T alloy in the stress concentration zone under combined tension-torsion load

Engineering machines and components are proneto structural failures during their service time due to certaintechnical reasons and also due to some unforeseencircumstances. The technical breakdowns sometime lead tohigh economic imbalance and can also be fatal to life andproperty. Predicting the failure and evaluating the breakagecharacteristics of engineering components are crucial indetermining the life of the component and also increasetheir maintenance and safety in daily life. This research study deals with the modelling andnumerical simulations of an aluminium alloy specimen in3D stress-state and thereby predicting the fatigue failure ofthe material subjected to external cyclic loadings. Topredict the failure of a component, a specimen with aninduced crack can be evaluated through cyclic loadingprocess. It is based on the fact that the presence of a crackstends to modify the stresses present locally on thecomponent that the elastic deformation and the stressesattributed with them are totally insufficient for the designagainst fracture. It is based on the assumption that thespecimen undergoes complete fracture when the crackreaches its critical size even though the stress at the criticalcrack tip is much lower than the yield stress of thecomponent. The critical size of the crack is based on theapplication of the load and the number of load cycles itundergoes.The main aim of this research is to present andvalidate the numerical method for the study of theinfluence of cracks present in the engineering components.Finite element method was applied for numericalsimulation. In this study the tension, torsion, combined tension-torsion and fatigue loads was applied. Theexperimental testing data of mechanical properties wasused in numerical simulation as input data. This researchstudy investigates the three-dimensional stress-strain stateand fatigue prediction of D16T aluminium alloy which ispredominantly used in the aerospace and automobileindustries for their high strength-to-weight ratio and muchbetter physical properties. The different specimen modelsare then analysed and the most efficient one was selectedfor the preliminary experimental tests.

Oxidation Stabilization of ZrFe Alloys in Nitrogen Gas Atmosphere

A porous ZrFe alloy specimen was prepared as a 6 × 3 mm (diameter × thickness) disk. The reaction of the ZrFe alloy was confirmed while the whole system was maintained at a target temperature, which was increased from 150 oC to 950 oC in a 99.999% low purity nitrogen atmosphere, consisting of 10 ppm of impurity gas. Surface color, pore size, stabilized layer, and phase change were confirmed with optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Micro-Raman, according to temperature. The surface color of the ZrFe alloy changed from metallic silver to dark gray as the temperature increased. In the EDS and XPS results, nitrogen component was not observed, and oxygen content increased on each surface at the elevated temperatures. In this way, the ZrFe alloy was stabilized in a low purity nitrogen atmosphere, preventing rapid nitride reactions.

Oxidation Stabilization of ZrFe Alloys in Nitrogen Gas Atmosphere

A porous ZrFe alloy specimen was prepared as a 6 × 3 mm (diameter × thickness) disk. The reaction of the ZrFe alloy was confirmed while the whole system was maintained at a target temperature, which was increased from 150 oC to 950 oC in a 99.999% low purity nitrogen atmosphere, consisting of 10 ppm of impurity gas. Surface color, pore size, stabilized layer, and phase change were confirmed with optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Micro-Raman, according to temperature. The surface color of the ZrFe alloy changed from metallic silver to dark gray as the temperature increased. In the EDS and XPS results, nitrogen component was not observed, and oxygen content increased on each surface at the elevated temperatures. In this way, the ZrFe alloy was stabilized in a low purity nitrogen atmosphere, preventing rapid nitride reactions.

Influence of Sc Microalloying on the Microstructure of Al5083 Alloy and Its Strengthening Effect

In this study, we investigate the influence of Sc microalloying on the microstructure of the Al5083 alloy. Trace amounts of Sc addition drastically improve the mechanical properties of the Al5083 alloy from 216 MPa to 233 MPa. Macroscopically, the addition of Sc significantly reduces the grain size of Al by approximately 50%. Additionally, a microstructural investigation reveals that the Sc microalloying element induces fine Al3Sc nanoprecipitates in the Al matrix. The formation of Al3Sc nanoprecipitates results in a pinning effect on the dislocations, leading to accumulated dislocations. Compared to a Sc-free Al5083 alloy specimen, the number density of dislocations in the Sc-added Al5083 alloy significantly increases after hot rolling, enhancing the tensile properties. We reveal that the improved mechanical properties of Al5083 with Sc microalloying originate from the grain refinement and the formation of fine Al3Sc nanoprecipitates.

Fatigue Life of Ni-Based Single Crystal Super-Alloy Specimen with Single Hole

A method of predicting the fatigue life under multiaxis loads based on the Paris law and EIFS was proposed. And the fatigue life under different loading stress and stress ratio were investigated. The results show that when the loading stress increased from 450~800 MPa, the fatigue life decreased from 6762379 to 10056, as well as when the stress ratio increased from 0.1~1, the fatigue life increased from 6762379 to 14932368. It was validated by test eventually. And the fatigue life model presented here agrees well with test results. It is significant to the prediction of turbine of Ni-based single crystal super-alloy material with filming hole.

Investigation on Stress and Strain of Ni-Based Single Crystal Super-Alloy Specimen with Single Hole Based on Abacus

The Miss stress, Max.principal strain and Magnitude displacement have important influence on the fatigue life of the Ni-based single crystal super-alloy turbine blades. This work investigated The Miss stress, Max.principal strain and Magnitude displacement of Ni-based single crystal super-alloy specimen with single hole along dangerous path under different working conditions by Abacus. The results show that the initial crack length and loading stresses are larger, the crack growth on the specimen is faster, and then, the fatigue life is the shorter. Moreover, for the different stress ratios, smaller stress ratio can lead to lower fatigue life. The result is significant to design turbine of Ni-based single crystal super-alloy of high accuracy, high reliability and high strength.

Experimental Investigation on the Effect Due to Mould Vibrations on Mechanical and Metallurgical Properties of Aluminum Alloy (A-1050)

In the current research work performed, the consequences caused in the casting aluminum alloy specimen due to mechanical mould vibrations are examined. Mould vibration throughout the casting provides decreased rate of shrinkage, good morphology, surface finish and lesser probability of hot tear. In this research work, the effect of mould vibration during solidification of Aluminum A-1050 alloys for dissimilar values of wavelengths at a permanent pouring temperature has been investigated to understand the modification in microstructure and mechanical properties after casting. The Al A-1050 casting has been made in a metal mould with different vibrations. The frequencies are varied from 15Hz to 50 Hz during the casting process. A casting has been made with different vibration as well to compare the results of castings with vibration frequencies. The experimental outcomes exhibited substantial grain refinement and significant increase in tensile strength and hardness of the castings with mechanical mould vibration during the duration and after solidification.

Modeling and Numerical Simulation of the Effect of Temperature on the LCF Behaviour of a CuCrZr Alloy Specimen

The main originality of this work consists in investigating low cycle fatigue of cylindrical test piece with wings under imposed constraint and for the temperature 20°c, 200°c, 400°c. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles at break. It was found that the CuCrZr cylindrical test piece showed a reduction in fatigue life with increasing temperature.