Arts et Métiers ParisTech

About: Arts et Métiers ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Machining. The organization has 3946 authors who have published 6693 publications receiving 142083 citations. The organization is also known as: École nationale supérieure d'arts et métiers & ENSAM.

Finite element analysis of the plane strain crack-tip mechanical fields in pseudoelastic shape memory alloys

Abstract: The plane strain mechanical fields near a stationary crack tip in a pseudoelastic shape memory alloy (SMA) are analyzed via the finite element method. The small scale transformation assumption is employed for the calculations using displacement boundary conditions on a circular region that encloses the stress-induced phase transformation zone. The constitutive law used adopts the classical rate-independent small strain flow theory for the evolution equations of both the transformation and plastic strains. Results on the size and shape of the stress-induced transformation and plastic zone formed near the stationary crack are obtained and a fracture toughness criterion based on the J-integral is discussed in view of the observed path-dependence of J. Moreover, the obtained results are discussed in relation to results for stationary cracks in conventional elastic–plastic materials.

Experimental Study of a Cavitating Centrifugal Pump During Fast Startups

Abstract: The start-up of rocket engine turbopumps is generally performed only in a few seconds It implies that these pumps reach their nominal operating conditions after only a few rotations During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution These phenomena progressively become negligible when the steady behavior is reached The pump transient behavior induces significant pressure fluctuations which may result in partial flow vaporization, ie cavitation An existing experimental test rig has been updated in the LML laboratory (Lille, France) for the start-ups of a centrifugal pump The study focuses on cavitation induced during the pump start-up Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods Three different types of fast start-up behaviors have been identified According to the final operating point, the start-up is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed both a the inlet and outlet of the pump A physical analysis is proposed to explain these three different types of transient flow behavior