Adhesion of elastic punch to confined elastic layer

This research has been supported by the ÚNKP-18-4-BME-199 "New National Excellence Program of the Ministry of Human Capacities"

Integration method for constitutive equation of von Mises elastoplasticity with linear hardening

This paper presents a summary of the new semi-analytical integration method presented in [10] for von Mises elastoplasticity model with combined linear isotropic-kinematic hardening within a small deformation range. Solutions for the case of constant strain rate and constant stress rate assumptions are also presented. Furthemore, it is shown how the general solution reduces to the particular cases of purely kinematic hardening, purely isotropic hardening and perfect plasticity, respectively

The impact of macrofinancial variables on covered interest parity violations after the 2008 global financial crisis

Ce mémoire analyse les déterminants des déviations à la parité des taux d’intérêts couverts(PTIC) après la crise financière de 2008. Notre modèle analyse la relation de long terme entre certaines variables macroéconomiques et les déviations mesurées à la PTIC. Nous utilisons les données sur les instruments du marché financier, l’offre de monnaie ainsi que le PIB réel entre 2009 et 2019, pour le Canada et les États-Unis, comme déterminants de ces déviations. Notre approche méthodologique utilise des techniques d’économétrie des séries temporelles. Les paramètres du modèle sont estimés à l’aide des méthodes Fully-Modified OLS (FM-OLS),Dynamic OLS (DOLS) et Integrated modified OLS (IM-OLS). Pour les données couvrant l’horizon de 5 ans, nous trouvons des résultats contradictoires pour l’offre de monnaie, mais établissent une relation négative entre le PIB réel et les déviations observées à la PTIC. Sur un horizon plus long (10 et 20 ans), l’offre de monnaie et le PIB réel ont tous deux un effet négatif sur les déviations de la PTIC mais celui du PIB réel est plus important. En outre, l’inclusion dans le modèle de l’indice de volatilité du marché américain s’est montré significatif dans la plupart des cas.We analyze the macroeconomic determinants to the deviations from Covered Interest RateParity (CIP) after the 2008 financial crisis. Our model analyzes the long-term relationship between some macroeconomic variables and measured CIP deviations. We use data on financial market instruments, on relative money supply and relative real GDP between 2009 and 2019for Canada and the United States. Our theoretical approach uses time series econometrics tools adapted to non-stationary series and the model parameters are estimated using fully modifiedOLS (FM-OLS), dynamic OLS (DOLS) and integrated modified OLS (IM-OLS) regressions.On the 5 year horizon, the estimated effect of relative money supply on the deviations is mixed.On the other hand, there is a negative relationship between real GDP and the deviations observed. For longer-term horizons (10 and 20 years), both money supply and real output have a negative effect on the deviations. Yet, that of real GDP is stronger. In addition, the inclusion of the VIX volatility index in the model was significant in most cases

Characterization of Impacts of Elastic-plastic Spheres

This work presents explicit dynamic finite element simulations of various impacts of elastic-plastic solid spheres with flat walls. Different  analytical models describing the mechanics of the impact phenomenon are also presented. Elastic and elastic-plastic material models for the sphere and the wall are considered during the analyses. The applicability of these different models is demonstrated and their accuracies are investigated. Closed-form analytical functions are proposed to describe the relationship between the initial velocity of the sphere and the investigated contact characteristics for the given material models. Analysis is carried out to study the effect of the friction coefficient as well as the angle of impact for various cases

Effect of Subsurface Microstructures on Adhesion of Highly Confined Elastic Films

Polymer adhesive films sandwiched between two rigid solids are a common bonding strategy. The mechanics and consequently the adhesion of such geometrically confined films depend mainly on their thickness, Young's modulus, and the Poisson's ratio of the material. In this work, we explore the effect of a micropatterned subsurface embedded into the adhesive layer. We compare experiments with three-dimensional numerical simulations to evaluate the impact of the microstructure on the contact stiffness and effective modulus. The results are used to extend a previously proposed size scaling argument on adhesion from incompressible to slightly compressible films to account for the silicone used in our study with a Poisson's ratio of 0.495. In addition, interfacial stress distributions between the elastic film and the glass disc are obtained from plane strain simulations to evaluate characteristic adhesion failures such as edge cracks and cavitation. Overall, the micropatterned subsurface has a large impact on the contact stiffness, the interfacial stress distribution, and the detachment behavior; however, the adhesion performance is only slightly improved in comparison to a non-patterned subsurface

Analyzing the Effect of Temperature on Squash Ball Impacts Using High-Speed Camera Recordings

Description of the impact characteristics of different types of balls has a great importance in sport science and in engineering. The primary objective of the present paper is to investigate the effect of the temperature on the impacts of different types of squash balls from a given company. The shots were performed using a self-built air-cannon. The impacts were recorded by a high-speed camera and the recorded videos were analyzed by an image-processing method based on a background subtraction technique. Summarizing the main dynamical parameters, we can conclude that increasing the initial speed will decrease the contact time, the coefficient of restitution (COR) and the rebound resilience, whereas these parameters increase at elevated temperatures. The compression tests revealed that within the low velocity range the deformation of the ball’s material and not the compression of the inner gas is the main contribution in the force needed to compress the ball. However, when the ball suffers large deformations, the internal air pressure has a huge effect on the rebound behavior. The measurements revealed that there is an optimal initial velocity distinct from the maximum one where the rebound velocity of the ball is higher than in all other cases. From the results we can state that the ball's overall stiffness grows as the temperature increases