Micro-Indentation Assessment of Near Surface Material Properties and Sub-Surface Damage in Precision Machining

1988 ◽  
pp. 271-286 ◽  
Author(s):  
Robert S. Polvani ◽  
Chris Evans
Keyword(s):  
Material Properties ◽  
Surface Damage ◽  
Precision Machining ◽  
Surface Material ◽  
Near Surface ◽  
Micro Indentation

Nanomechanical Properties of Aluminum 390-T6 Rough Surfaces Undergoing Tribological Testing

2004 ◽  
Vol 126 (3) ◽  
pp. 573-582 ◽  
Author(s):  
Shaun R. Pergande ◽  
Andreas A. Polycarpou ◽  
Thomas F. Conry
Keyword(s):  
Surface Roughness ◽  
Material Properties ◽  
Bulk Material ◽  
Normal Load ◽  
Effective Elastic Modulus ◽  
Surface Microstructure ◽  
Surface Material ◽  
Surface Layers ◽  
Near Surface ◽  
Nanomechanical Properties

The nanoindentation technique was used to quantify nano-scale changes in material properties (effective elastic modulus and hardness) of Al390-T6 samples that have undergone tribological testing under a protocol in a high-pressure tribometer where the applied normal load was step-wise increased until failure by scuffing occurred. The test was highly repeatable, so additional tests were run to three intermediate fractions of the total-time-to-scuffing-failure, which provided data on the progressive wear of the surfaces preparatory to reaching the scuffed condition. The samples were engineering surfaces with significant surface roughness, nonhomogeneous surface microstructure and unknown, nonuniform surface layers. This study demonstrated that nanomechanical techniques can be extended to characterize the material properties of rough engineering surfaces. For the samples subjected to tribological testing, the material at the surface, and to approximately 60 nm below the surface, exhibited significantly higher hardness than the bulk material. Also, progressive wear of the surfaces resulted in a corresponding weakening of the near-surface material below the surface to a depth of 60 nm, while the hardness of material below the 60 nm depth remained relatively unchanged. The hardness data for the scuffed samples showed a large amount of scatter in the data, indicating that the surface is not homogeneous and that the protective surface layer is removed, at least at some points on the surface.

scholarly journals Impact of Enzymatic Degradation on the Material Properties of Poly(Ethylene Terephthalate)

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3885
Author(s):  
Teresa Menzel ◽  
Sebastian Weigert ◽  
Andreas Gagsteiger ◽  
Yannik Eich ◽  
Sebastian Sittl ◽  
...  
Keyword(s):  
Material Properties ◽  
Enzymatic Degradation ◽  
Ethylene Terephthalate ◽  
Compact Tension ◽  
Time Dependent ◽  
Material Failure ◽  
Near Surface ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
The Impact

With macroscopic litter and its degradation into secondary microplastic as a major source of environmental pollution, one key challenge is understanding the pathways from macro- to microplastic by abiotic and biotic environmental impact. So far, little is known about the impact of biota on material properties. This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-PET) and the degrading enzyme PETase from Ideonella sakaiensis. Compact tension (CT) specimens were incubated in an enzymatic solution and thermally and mechanically characterized. A time-dependent study up to 96 h revealed the formation of steadily growing colloidal structures. After 96 h incubation, high amounts of BHET dimer were found in a near-surface layer, affecting crack propagation and leading to faster material failure. The results of this pilot study show that enzymatic activity accelerates embrittlement and favors fragmentation. We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation.

Defects Introduced by Plasma Processing of Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
J. L. Benton
Keyword(s):  
Bulk Material ◽  
Surface Region ◽  
Surface Damage ◽  
Near Surface ◽  
Enhanced Diffusion ◽  
Interstitial Defect ◽  
Comprehensive Picture ◽  
Reaction Region ◽  
Defect Reactions ◽  
P Type

ABSTRACTThe electrical and optical properties of defects introduced by Reactive Ion Etching (RIE) in the near surface region of Si after dry etching with various gases and plasma conditions is studied with spreading Resistance (SR), photoluminescence (PL), and capacitance-voltage profiling (C-V). Plasma etching in chlorine and fluorine based gases produce donors at the surface in both n-type and p-type, Czochralski and float-zone silicon. Isochronal annealing reveals the presence of two distinct regions of dopant compensation. The surface damage region is confined to 1000 Å and survives heat treatment at 400°C, while the defect reaction region extends ≥ 1 μm in depth and recovers by 250°C. A comprehensive picture of the interstitial defect reactions in RIE silicon is completed. The interstitial defects, Ci and Bi, created in the ion damaged near surface region, undergo recombination enhanced diffusion caused by the presence of ultraviolet light in the plasma, resulting in the long range diffusion into the Si bulk. Subsequently, the interstitial atoms are trapped by the background impurities forming the defect pairs, CiOi, CSCi, or BiOi, which are observed experimentally. The depth of the diffusion-limited trapping and the probability of forming specific pairs depends on the relative concentrations of the reactants, oxygen, carbon or boron, present in the bulk material.

Interaction of a Sliding Wedge and a Metallic Specimen With a Near-Surface Inhomogeneity

2018 ◽  
Author(s):  
Vandana A. Salilkumar ◽  
Narayan K. Sundaram
Keyword(s):  
Sliding Wear ◽  
Surface Damage ◽  
Metal Substrate ◽  
Surface Plastic ◽  
Deformation Processing ◽  
Near Surface ◽  
Lagrangian Finite Element ◽  
Wedge Sliding ◽  
Metallic Specimen ◽  
Indenter Geometry

The problem of a hard wedge sliding against a metal substrate has been studied extensively for its importance in tribo-plasticity and deformation processing. Here we explore the effect of introducing a single, near-surface plastic inhomogeneity (termed as a pseudograin) in a metal substrate using Lagrangian finite element (FE) analysis. The pseudograin is allowed to be softer or harder than the surrounding material. The effects of sliding parameters like the size and location of the pseudograin, friction and indenter geometry are also studied. Interestingly, the introduction of the pseudograin can lead to production of surface folds / self-contacts, and acutely-inclined, near-surface, crack-like features, which cannot be reproduced by homogeneous specimens. In fact, this tribosystem is phenomenologically very rich, despite differing from classical triboplastic systems of Challen, Oxley and Torrance only by way of the inhomogeneity. Despite its simplicity, the model replicates several experimentally observed features of surface folding, and is a minimal model to obtain folding in sliding. The occurrence of surface folds and concomitant residual surface damage points to the important role played by microstructure-related inhomogeneities in determining surface quality in deformation processing operations (e.g. repeated sliding to generate UFG surfaces) and is also a potentially new mode of sliding wear.

Sign in / Sign up

Export Citation Format

Share Document