A thermomechanical model for the analysis of disc brake using the finite element method in frictional contact

In this work, numerical simulations of the transient thermal and the static structural analysis were performed here sequentially, with the coupled thermo-structural method. Numerical procedure of calculation relies on important steps such that the CFD thermal analysis has been well illustrated in 3D, showing the effects of heat distribution over the brake disc. Three different brake disc materials were selected in this simulation and a comparative analysis of the results was conducted in order to derive the one with the best thermal behavior. Finally, the resolution of the coupled thermomechanical model allows us to visualize other important results of this research such as; the deformations, and the equivalent Von Mises stress of the disc, as well as the contact pressure of the brake pads. Following our analysis and the results we draw from it, we derive several conclusions. The choice allowed us to deliver the best suitable of the brake rotor to ensure and guarantee the good braking performance of vehicles.

A Multiphysics approach to constrain the dynamics of the Altiplano-Puna magmatic system

Continuous Interferometric Synthetic Aperture Radar (InSAR) monitoring (> 25 years) has revealed a concentric surface deformation pattern above the Altiplano-Puna magma body (APMB) in the central Andes. Here, we use a joint interpretation of seismic imaging, gravity anomalies and InSAR data to constrain location, 3D geometry and density of the magma body. By combining gravity modelling, thermomechanical modelling, scaling law analysis and Bayesian inference, we are able to create a relationship between the geometry of a mid-crustal magma body and surface observations. Furthermore, we can estimate the uncertainties associated with the geometry of the APMB and identify the most important parameters that control the dynamics of the system. We constrain the density contrast between the APMB and the surrounding host rock to 90 - 130 kg m−3 (2σ) and the associated melt fraction to 15 - 22 %. Our visco-elasto-plastic 3D thermomechanical model reproduces the observed surface deformation self-consistently by buoyancy driven magma transport without the need for additional pressure sources. The flow pattern is controlled by a central rise at the top of the APMB whose geometry can be constrained with the help of InSAR observations while Bouguer anomalies constrain the deeper parts of the APMB. Automated scaling law analysis shows that the rheology of the upper crust and the magma mush as well as the density contrast between the two are the most important parameters in the system and need to be constrained for a better understanding of the subsurface processes.

Thermo-Mechanical Simulation of Ti6Al4V-NiTi Dissimilar Laser Welding Process

Fiber Laser Welding (FLW) is a versatile joining technique of metals and alloys because it allows welding of dissimilar materials without filler material. FLW utilizes intensified heat energy to liquify the workpiece interface and joins when they are solidified. In this study, dissimilar joining between Ti6Al4V-Nitinol was performed using FLW process and the thermomechanical model was developed to understand the metallurgical mechanisms and investigate weldability of dissimilar alloys. The FLW of Ti6Al4V and Nitinol plates was performed with variable power density, welding speed, and focal distance. In this three-dimensional numerical model, heat flows in two different workpieces were computed during active laser welding and cooling process using a combined effect of radiation and convection. Both of the top and bottom surfaces of the welded zone were studied considering the combined effect from focused heat source and Argon shielding gas. Significant thermal cracks were produced through the welded interface. However, this numerical study illustrated thermomechanical foundation and discuss future challenges to improve the integrity and desirable FLW parameters in the dissimilar metal joining.

Analysis of the Industrial Process of Producing a Hub Forging Used in Motorcar Power Transmission Systems—A Case Study

The article refers to an analysis of the multi-operation process of manufacturing a hub type forging used to transmit power in motorcar gear boxes, by way of die forging on a crank press. The investigations were performed in order to improve the currently realized production technology, mainly with the use of numerical simulations. Through the determination of the key parameters/quantities during forging, which are difficult to determine directly during the industrial process, an in-depth and complex analysis was performed by way of FE (Finite Element) modelling. A thermomechanical model of producing a hub forging with deformable tools was developed with the use of the Qform 9.0.9 software. For the elaboration and construction of the forging tool CAD (Computer Aided Design) models, the Catia V5R20 program was applied. The results of the performed numerical modelling made it possible to determine the material flow and the properness of the filling of impressions, as well as the temperature field distributions and plastic deformations in the forging; it was also possible to detect the forging defects often observed in the industrial process. On this basis, the changes in the process were determined, which enabled an improvement of the presently realized technology and the obtaining of proper forgings, both in respect of quality and dimensions and shape.

Characterization of Wear Modes in Orthogonal Milling of 15-5PH Stainless Steel

Tool wear remains of high interest for industry, as it influences process costs and part’s surface integrity. Although experimental and analytical investigations have been the main ways to investigate wear, the growing development of computational power enables predicting tool wear based on chip formation simulations. If this has been quite successful in turning, developments in milling are still limited due to the specific nature of this machining operation characterized by an interrupted cutting process leading to mechanical and thermal cyclic loadings onto the cutting tool. Wear modes are often not well characterized and become even more difficult to model as far as hard to machine material such as martensitic stainless steels are concerned. The present work propose to investigate wear in orthogonal milling of a 15-5PH martensitic stainless steel. An experimental campaign is first performed to identify the wear modes when cutting this material with uncoated and coated carbide tools. Milling forces, tool wear and material transfer are especially studied. A multi-scale numerical procedure is then developed by combining an Arbitrary-Lagrangian-Eulerian (ALE) thermomechanical model to a pure thermal sub-model in order to predict the thermomechanical loadings withstood by the tool. The thermal sub-model is applied at the scale of the coating in order to extract the thermal gradients generated by the interrupted cutting. These loadings are finally compared to the reported wear modes to identify a correlation and improve their understanding.

The role of sliding in ice stream formation

Ice streams are bands of fast-flowing ice in ice sheets. We investigate their formation as an example of spontaneous pattern formation, based on positive feedbacks between dissipation and basal sliding. Our focus is on temperature-dependent subtemperate sliding, where faster sliding leads to enhanced dissipation and hence warmer temperatures, weak- ening the bed further, and on a similar feedback driven by basal melt water production. Using a novel thermomechanical model, we show that formation of a steady pattern of fast and slow flow can occur through the downstream amplification of noise in basal conditions. This process can lead to the establishment of a clearly defined ice stream separated from slowly flowing, cold-based ice ridges by narrow shear margins. Our model is also able to predict the downstream widening of ice streams due to dissipation and heat transport in these margins. We also show that downward advection of cold ice induced by accelerated sliding is the primary stabilizing mechanism that can suppress ice steam formation altogether, and give an approximate, analytical criterion for pattern formation.

A validated asymptotic thermomechanical model for air-gap formation in tapered moulds in the continuous casting of steel

A recent asymptotics-based thermomechanical model is adapted and applied to the mould region in the continuous casting of round steel billets, with a view to describing the complex interplay between air-gap formation, mould taper, cooling channel width and cooling water velocity. Although the situation is steady state, the analysis leads to what is mathematically a dual moving-boundary problem for the solid–melt and solid–air interfaces, where the distance from the top of the mould region is the time-like variable in the problem. Moreover, the two interfaces are initiated at different locations. In addition, the thermal and mechanical problems are found to decouple and it is possible to solve the first ahead of the second. The model equations are solved numerically using a finite-difference method, and the approach is subsequently successfully validated against a previous finite-element model and experimental data from temperature measurements taken within the mould.

The influence of lithospheric rheology on escarpment evolution at divergent margins: a numerical approach

<p>The evolution of escarpments bordering the coast during the post-rift phase is numerically simulated mostly by landscape surface processes models. However, there are few thermomechanical models that were applied to study the post-rift evolution of these escarpments. In the present work, we used a finite element thermomechanical model to simulate lithospheric extension and evaluate the sensitivity of escarpment amplitude over time under different geological and rheological conditions from the onset of lithospheric extension to the post-rift phase. The results showed that the evolution of escarpment amplitude and its preservation for tens of millions of years are sensitive to crustal and lithospheric thicknesses. We observed that escarpment preservation is higher for scenarios with a thinner crust with a strong lower crust and a thicker lithospheric mantle. This behavior is related to the degree of coupling between the crust and lithospheric mantle that affect the vertical displacement of the lithosphere due to flexural and isostatic response. Additionally, even without surface processes of erosion and sedimentation, the amplitude of the escarpment can monotonically decrease with time due to the lateral flow of the lower crust. This effect is expressive in the scenarios where the effective viscosity of the lower crust is relatively low and the upper crust is rheologically decoupled from the lithospheric mantle. In these cases, the amplitude of the escarpment can decrease from 2-3 km during the rifting phase to less 1 km after 40 Myr after the onset of lithospheric extension. On the other hand, in scenarios where the crust is rheologically coupled, the amplitude of the escarpment after 100 Myr since the lithospheric stretching is only ~25% smaller than maximum amplitude observed during the rifting phase. We conclude that the rheological structure of the lithosphere can play an important role in the formation and preservation of escarpments at divergent margins simultaneously with surface process.</p>