Search results for "Friction."

When is there more employment, with individual or collective wage bargaining?

2019

Abstract In a standard Diamond-Mortensen-Pissarides labour market with frictions, the authors seek to determine when there is more employment with individual wage bargaining than with collective wage bargaining, using a wage equation generated by the standard total surplus sharing rule. Using a Cobb-Douglas production function, they find that if the bargaining power of the individual is high compared to the bargaining power of the union, there is more unemployment with individual wage setting and vice versa. When the individual worker and the union have the same bargaining power, if the cost of opening a vacancy is sufficiently high, there is more unemployment with individual wage setting. …

Experimental and numerical study on Linear Friction Welding of AA2011 Aluminum Alloy

2014

COMPUTER AIDED ENGINEERING OF SOLID BONDING PHENOMENA

2014

Joining is a fundamental technological process in manufacturing used to create a single piece from two or more parts. Welding is still today one of the most popular joining techniques used in manufacturing allowing a permanent junction. Traditional welding processes are based on the melting of the materials to be joined. In this way, several defects may arise because of solidification problems, joints deformation due to elevated residual stress and metallurgical integrity of the joints (intermetallic, porosities, etc). As an example, some aluminum alloys present considerable problems the junction is carried out by traditional fusion welding methods. During the melting process, in fact, the …

Effective Linear Friction Welding Machine Redesign through Process Analysis

2014

Linear friction welding is a solid-state joining process developed for non-axisymmetric components in which the joining of the specimens is obtained through reciprocating motion and pressure. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. In order to design an effective machine, relevant issues derive from the high frequency and the large inertial forces involved in the process. In this study, the authors describe the redesign of a preexisting prototypal machine for LFW processes. A machine redesign is needed when welding high resistant materials, i.e. steels or titanium alloys, with high …

ADV measurements of velocity distributions in a gravel-bed flume

2003

Velocity measurements carried out by an acoustic doppler velocimeter (ADV) in a rectangular laboratory flume having a gravel bed are presented. The velocity profiles are measured in six verticals of the channel cross-section having an increasing distance (from 4 to 38.5 cm) from the flume wall. The experimental runs are carried out for five different bed arrangements, characterized by different concentrations of coarser elements, and for the two conditions of small- and large-scale roughness. For both hydraulic conditions, the velocity measurements are first used to test the applicability of the Dean profile and of the logarithmic profile corrected by a divergence function proposed in this …

Theory of Differential Inclusions and Its Application in Mechanics

2017

The following chapter deals with systems of differential equations with discontinuous right-hand sides. The key question is how to define the solutions of such systems. The most adequate approach is to treat discontinuous systems as systems with multivalued right-hand sides (differential inclusions). In this work, three well-known definitions of solution of discontinuous system are considered. We will demonstrate the difference between these definitions and their application to different mechanical problems. Mathematical models of drilling systems with discontinuous friction torque characteristics are considered. Here, opposite to classical Coulomb symmetric friction law, the friction torqu…

Experimental and numerical analysis on post welding formability of FSWed AZ31 magnesium alloy thin joints obtained using a "Pinless" tool configurati…

2012

The post welding formability of friction stir welded AZ31 magnesium alloy thin sheets (1.5 mm thick), obtained using a “pinless” tool configuration, was widely investigated by means of the hemispherical punch method at 350°C, with a constant crosshead speed of 0.1 mm/s. The results were compared with those obtained on the base material. It has shown that formability of the joints is lower than the one of the base material. The experimental work was supported by a numerical investigation based on FEM in order to highlight the material flow occurring during the welding process. Additionally, hemispherical punch tests were simulated starting from the calculated conditions, in terms of accumula…

Experimental and numerical analysis on FSWed magnesium alloy thin sheets obtained using “pin” and “pinless” tool

2012

Fixation-free incisional hernia repair in the elderly: our experience with a tentacle-shaped implant.

2016

Background: Incisional hernia in aged patients represents a challenge even for experienced surgeons. Besides increased risk of complications due to comorbidities, mesh fixation and assuring a sufficient mesh overlap of the defect are the main issues in carrying out the repair. Aims: In order to assure broader coverage of the abdominal wall and a tension- and fixation-free repair, a specifically designed prosthesis was developed for the surgical treatment of incisional hernias. The results of a fixation-free incisional hernia repair carried out in elderly patients using a tentacle-shaped implant are reported herewith. Methods: A tentacle-shaped flat mesh with a large central body and integra…

A Theoretical Approach to the Shift Mechanics of Rubber Belt Variators

2008

This paper proposes a theoretical description of the mechanical behavior of rubber belt variators during the speed ratio shift. Comparing with the steady operation, the mass conservation of the belt is completely reformulated considering an elementary dihedral control volume between two planes through the pulley axis and balancing the inside mass variation with the total mass flux through the control surface. On the other hand, the belt equilibrium conditions are similar to the steady case, as the inertia forces due to the shifting motion are negligible with respect to the other forces. Assuming a one-dimensional belt model, it is shown that adhesive regions may appear inside the arc of con…