Relaxation of metals: A model based on MD calculations

Domı́nguez-Vázquez, Javier; Pérez-Martı́n, A.M.C.; Jiménez-Rodrı́guez, J.J.; Gras‐Martí, A.

doi:10.1016/s0168-583x(97)00654-x

Cited by 3 publications

(1 citation statement)

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“…It has been demonstrated that metallic alloy creep fatigue is related to the defect rate located in welded joints considered as a metallic alloy zones [15]. In particular, a model based on molecular dynamics calculations, developed by Vazquez, has discussed on isotropic and anisotropic relaxation phenomenon from simulations of lattice relaxation of metallic alloys considering the sudden appearance of vacancy or an interstitial site in the crystal [16]. This microscopic relaxation model allows highlighting macroscopic effective displacement of system responsible of relaxation phase.…”

Section: Results Of Thermomechanical Simulationsmentioning

confidence: 99%

Simulations of Thermomechanical Stresses and Optical Misalignment in 1550-nm Transmitter Optoelectronic Modules Using FEM and Process Dispersions

Deshayes

Béchou

Verdier

et al. 2008

IEEE Trans. Comp. Packag. Technol.

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Expertise of packaging for optoelectronic components requires the solution of optical, mechanical, and electrical problems in the same way. The purpose of this paper is to present three-dimensional simulations using finite-element method (FEM) of thermomechanical stresses and strains in 1550-nm laser modules induced by Nd:YAG crystal laser welds and thermal cycles on main subassembly laser submount. Nonlinear FEM computations, taking into account of experimental ( ) measured curves, show that thew laser welding process can induce high level of strains in columns of the laser platform, bearing the laser diode, responsible of an optical axis shift and a gradual drop of the optical power in relation with relaxation of accumulated stresses in the subassembly (W. M. Sherry et al., "High performance optoelectronic packaging for 2.5 and 10 Gb/s laser modules," in Proc. Electron. Compon. Technol. Conf., 1996, pp. 620-627). Typical stresses are close to 160 MPa with drift about 5 MPa with the dispersion of energy level of the laser Nd: YAG beam. The introduction of both material and process dispersion in order to evaluate their impact on product lifetime distribution has been taking into account. In the case of thermal cycles, stresses can occur on elements sensitive to coefficient of thermal expansion mismatches such as solder joints between the laser platform and thermoelectric cooler and as fiber glued into the pigtail leading to crack propagation with sudden drop of optical power. A previous paper demonstrated that laser submount is the most sensitive part of optical system (Deshayes, et al., "Three-dimensional FEM simulations of thermal mechanical stresses in 1.55 m laser modules," Microelectron. Rel., vol. 43, no. 7, pp. 1125-1136, Jul. 2003). Experimental analyses were also conducted to correlate simulation results and monitor the output optical power of laser modules after 500 thermal cycles ( 40 C + 85 C VRT). Index Terms-Distributed feedback (DFB), finite-element model (FEM), laser YAG, neodymium-doped yttrium aluminium garnet (NdYAG), optical module, reliability, welding.

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Section: Results Of Thermomechanical Simulationsmentioning

confidence: 99%