On the stress distribution at scratching of thin film structures

Abstract

Scratching of thin film/substrate structures is studied theoretically and numerically. In most cases, the material behavior of the film as well as the substrate is described by classical elastoplasticity accounting for large deformations; further, pressuresensitive flow models are considered. The main efforts are devoted toward an understanding of the influence from the film/substrate boundary on the stress distribution at scratching but for comparative reasons, scratching of homogeneous materials are also studied and pertinent results presented. Among other things, the results are discussed in relation to delamination initiation and growth at scratching. The numerical investigation is performed using the finite element method, and the numerical strategy is discussed in some detail. The most important finding given by the present study is that high shear stresses are the main driving force for delamination initiation and growth along the film/substrate interface. It was also noted that the influence from pressure-sensitive flow on the stress fields related to delamination initiation is small, both quantitatively and qualitatively.

On the stability of delamination growth at scratching of thin film structures

“…Further developments regarding this matter were presented by Wredenberg and Larsson. 33 In reference (33), the details concerning the stress fields at thin film scratching were analyzed and it was concluded that high shear stresses were the driving force for both crack initiation and continued growth along the film/substrate interface. In this investigation, the load at crack forming and subsequent growth is not of immediate interest but instead, the stability of delamination growth in such a situation is studied.…”

“…Also, thin film scratching has been studied quite frequently, cf., e.g., references (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) considering different aspects of the problem such as fracture, delamination, the behavior of different global and local scratch variables (global scratch variables include normal and tangential hardness, apparent coefficient of friction and contact area) and alternative constitutive behavior. In reference (33), the local stress fields at thin film scratching were examined in some detail and an important conclusion from this study was that high shear stresses are the dominant factor leading to delamination initiation and growth.…”

“…In reference (33), the local stress fields at thin film scratching were examined in some detail and an important conclusion from this study was that high shear stresses are the dominant factor leading to delamination initiation and growth. However, in this context some preliminary results, briefly discussed in reference (33), indicated that delamination growth is a stable process and crack arrest will occur at constant or decreasing load. This feature was for brevity not investigated further in reference (33) but is indeed very important as it suggests that damage at scratching can be contained in a practical situation.…”

“…However, in this context some preliminary results, briefly discussed in reference (33), indicated that delamination growth is a stable process and crack arrest will occur at constant or decreasing load. This feature was for brevity not investigated further in reference (33) but is indeed very important as it suggests that damage at scratching can be contained in a practical situation. The stability of delamination growth at scratching has not been investigated in full previously and it is the present intention to remedy this shortcoming.…”

Comportamento mecânico de sistemas revestidos submetidos a esforços de contato normais e tangenciais.

“…Os modos de falha associados com o ensaio de riscamento têm sido identificados com base em observações e análise do sulco gerado durante o teste [15,16,37,38,42,48,49,51,[53][54][55][56][57][58]. Desta forma, alguns modos de falha envolvem o destacamento do revestimento do substrato, sendo, portanto, de importância direta durante uso do ensaio de riscamento como avaliação da adesão.…”