1,721,000 research outputs found
Effect of surface integrity induced by machining on high cycle fatigue life of 7075-T6 aluminum alloy
No full textThe metallurgical, mechanical and topographical modifications induced by machining strongly influence the surface quality of the final components which, in turn, dictates the functional performance and service-life of engineered products. This paper aims to extensively discuss the effect of machining parameters and cooling/lubrication strategies on the high cycle fatigue strength of 7075-T6 aluminum alloy. More in detail, three different cutting speeds (90, 120 and 150 m/min) and four cooling/lubrication methodologies (dry, cryogenic, minimum quantity lubrication and high pressure air jet) have been analyzed. The obtained fatigue samples have been tested under fully reversed stress conditions in the high cycle fatigue regime. An adapted analytical model, taking into account the effect of the surface changes, is also proposed in order to drastically reduce the number of destructive tests needed assessing the effects of the processing parameters on the overall fatigue endurance
Fabrication and characterization of zeolite coatings on aluminum and magnesium alloys
No full textThis work presents a methodology to fabricate zeolite coating on aluminum and magnesium alloys. A procedure for coating AA 6082 aluminum and AZ31B magnesium alloys substrates with a homogeneous, adherent and anticorrosive layer of a zeolite filler embedded in a silane matrix is developed. The adhesion of the coating has been probed by scratch and shear tests. Furthermore, the coating strength at high strain rate has been tested by tensile impact testing method. Also, the corrosion resistance of the coated samples has been verified highlighting an improvement with respect to the uncoated materials. The overall results show a very good surface coverage grade and a good level of coating adhesion and strength
Surface Modifications Induced by Roller Burnishing of Ti6Al4V Under Different Cooling/Lubrication Conditions
No full textThe paper presents a deep analysis of surface modifications induced by roller burnishing process of Ti6Al4V titanium alloy. The extensive experimental campaign has been performed based on a Design of Experiments at varying lubrication/cooling strategies (dry, cryogenic and MQL), roller radius, burnishing speed and burnishing depth. The resulting surface integrity has been analyzed in terms of surface roughness, micro hard-ness, microstructural changes and tribological performance. In particular, the wear rate of the burnished sample has been evaluated as a quality indicator of the process. The overall results show the influence of burnishing process parameters on surface quality and wear resistance of Ti6Al4V highlighting the capability of the process to significantly improve the above performance especially when cryogenic cooling is applied. Finally, the extensive experimental activity allowed to find a combination of processing parameters and lubrication conditions able to significantly improve the surface quality of the final component
Fatigue life of machined Ti6Al4V alloy under different cooling conditions
No full textThis paper presents an extensive experimental study on the influence of machining parameters and cooling conditions on the overall fatigue life of a titanium component. In particular, dry, minimum quantity lubrication, cryogenic and high-pressure air jet were compared as cooling/lubrication strategies for the finishing operation. The obtained dog-bone cylindrical fatigue specimens were tested under uniaxial pull–pull cyclic loading in the high cycle fatigue range. An analytical model is proposed to predict the high cycle fatigue strength for the material under investigation demonstrating its effectiveness to reduce the number of tests needed
A physically based constitutive model of microstructural evolution of Ti6Al4V hard machining under different lubri-cooling conditions
No full textThe metallurgical phenomena taking place during machining processes affect the thermo-mechanical properties of the severely deformed materials, influencing, consequently, the process behavior. The microstructural modifications are difficult to be evaluated when the material is subjected to high speed deformations that are typical of material removal processes. Therefore, the microstructure-based numerical simulations can represent a useful tool able to properly predict their mechanics. Hard turning experiments were conducted on Ti6Al4V alloy, involving different process parameters and lubri-cooling conditions. The worked samples surfaces were assessed in terms of resulting microstructural changes and microhardness. The obtained results (cutting forces, temperature, and surface metallurgical modifications) were considered to develop and validate a physics-based model able to describe the microstructural phenomena occurring under large deformation processes, taking into account the influence of the physical phenomena that accommodate the material plastic strengthening and their resulting effects on the process variables. The dislocations reciprocal influence and their interaction with the material lattice were considered to understand the material viscoplastic flow. Moreover, also the recrystallization phenomena influencing the grain size related strengthening were considered to formulate the model. Then, the developed material model was implemented via user sub-routine in a commercial finite element (FE) software. The FE model was used to in-depth analyze the inner evolution of the processed material and to predict the variables of industrial interest. A good agreement was shown between the experimentally measured variables and the numerically predicted results. Moreover, the model was employed to investigate additional machining conditions via finite element analysis (FEA), demonstrating a huge capability to improve the manufacturing process performances, leading to a deeper knowledge of microstructural evolution and the material machinability under various process conditions
Tool Wear Characterization in Turning of a Nickel Superalloy Through Customized Pin-On-Disk Tests and Acoustic Emission Signals Analysis
No full textAdvanced finite element model for predicting surface integrity in high-speed turning of AA7075-T6 under dry and cryogenic conditions
No full textSurface modification of Ti6Al4V alloy by pulsed Yb-laser irradiation for enhanced adhesive bonding
No full textThis work presents a comprehensive experimental study on the effect of pulsed laser ablation (Yb-fiber) on Ti6Al4V titanium alloy substrates for adhesive bonding. The modification of surface morphology and chemistry is assessed by means of SEM, XRD and wettability measurements. In addition, surface and subsurface mechanical properties are probed through an extensive series of instrumented indentation tests. Based on the results of the aforementioned analyses, a suitable processing window is identified and adhesive bonded T-peel joints are fabricated and tested. The obtained results indicate that pulsed laser irradiation can substantially improve the performance of Ti6Al4V/epoxy joints
Development of customized physics-based predictive models for improved performance in turning of Ti6Al4V
No full textThis paper presents a combination of numerical and analytical models for selection of optimal parameters on turning Ti6Al4V. In particular, the work demonstrates the efficiency of the combined models to properly design the process tremendously reducing the time requested to verify the final product characteristics. The applied models include the prediction of surface integrity characteristics such as grain size, hardness changes and residual stresses but also fatigue life prediction based on surface characteristics. The above models have been modified and updated according to the material characteristics, centered on physics-based equations and assumptions, process and phenomena taken into consideration for the specific setup. In particular, the models follow the overall process starting from the cutting phase up to the final fatigue operational performance. The proposed approach demonstrates that it is possible to predict, with adequate accuracy, the influence of the machining process on surface state and final performance in terms of fatigue life. Thus, it is possible to drastically reduce the time and efforts to build up knowledge based on experimental trials including the proposed models into an industrial context
Innovative high-speed femtosecond laser nano-patterning for improved adhesive bonding of Ti6Al4V titanium alloy
No full textIn this work the effect of femtosecond Yb fiber laser irradiation on Ti6Al4V titanium alloy is assessed. An extensive experimental campaign is carried out to survey surface properties through the use of SEM, AFM, EDS mapping and contact angle measurements. It is shown that the generation of uniform nanoscale laser induced periodic surface structures (LIPSS) allows to tailor surface properties and improves adhesive bonding with epoxy resin. The potential of the technique to improve the durability of the joints against accelerated aging is also evaluated
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