Vývoj fenomenologického modelu pro popis chování bezolovnatých pájecích past při tepelně-mechanickém namáhání

Abstract

This dissertation thesis deals with the solution of designing a phenomenological model for the description of the lead-free solder paste Sn-3.5Ag-0.75Cu behavior during numerical modeling of soldered joints. The proposed methodology includes the design of axi-symmetric samples of soldered joints intended for experimental investigation of static strength and low-cycle fatigue, which also considers the production and dimensional constraints. The mechanical properties of the solder paste with monotonic tension, torsion and creep behavior were investigated on the proposed samples. Furthermore, low-cycle fatigue in tension-compression, torsion and in combination under disproportionate loading with a phase shift of 90 ° was investigated. The influence of stress amplitude on the accumulation of plastic deformation in a soldered joint under uniaxial and multiaxial loading, so-called uniaxial and biaxial ratcheting, was also investigated. The proposed methodology also includes the optimization of a numerical viscoplastic model based on measured data using optiSlang software. Based on the achieved results, a proposal of the methodology for the calculation of lifetime prediction of soldered joints based on fatigue tests performed directly on real products.