scholarly journals Gradient material model in analysis of mechanical joints of CFRP laminate

2018 ◽  
Author(s):  
Krzysztof Puchała ◽  
Szymczyk Elżbieta ◽  
Jerzy Jachimowicz ◽  
Paweł Bogusz
Keyword(s):  
Material Model ◽  
Gradient Material ◽  
Cfrp Laminate ◽  
Mechanical Joints

scholarly journals The Influence of Selected Local Phenomena in CFRP Laminate on Global Characteristics of Bolted Joints

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4139 ◽  
Author(s):  
Krzysztof Puchała ◽  
Elżbieta Szymczyk ◽  
Jerzy Jachimowicz ◽  
Paweł Bogusz ◽  
Michał Sałaciński
Keyword(s):  
Aerospace Industry ◽  
Testing Machine ◽  
Material Model ◽  
Gradient Material ◽  
Drilling Process ◽  
Mechanical Joints ◽  
Joint Characteristics ◽  
Mechanically Fastened ◽  
Large Aircraft ◽  
Properties Of Composites

High specific mechanical properties of composites are the reason for their use in various fields, e.g., the aerospace industry. Mechanical joints are still used in the aerospace industry to assembly large aircraft structures. The properties of laminate around the hole can be, however, weakened, compared to their nominal values as a result of a drilling process or cyclic loading. This paper aims at the classification and analysis of imperfections affecting mechanically fastened joints in a laminate structure. A method of modeling the hole vicinity, a gradient material model, as well as the numerical and experimental estimation of laminate deterioration in this area, were proposed and analyzed. Comparative analysis of numerical and experimental results based on displacements of the testing machine grip and the extensometer length confirmed the aforementioned results as consistent in linear ranges. Therefore, joint characteristics obtained based upon measurement of the grip displacement and the ratio of stiffness in linear ranges are sufficient to determine the parameters of a gradient material model. Some imperfections resulting from, e.g., asymmetry, were included in the gradient material model; thus, the obtained weakening of laminate properties in the hole vicinity can be overestimated. Therefore, further analyses of the gradient material model for laminate structures are necessary.

scholarly journals Measuring the effect of residual stress on the machined subsurface of Inconel 718 by nanoindentation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245391
Author(s):  
Ling Chen ◽  
Qirui Du ◽  
Miao Yu ◽  
Xin Guo ◽  
Wu Zhao
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Inconel 718 ◽  
Material Model ◽  
Hardened Layer ◽  
Gradient Material ◽  
Material Surface ◽  
Inconel 718 Alloy ◽  
Finite Element Software ◽  
Stress States

Inconel 718 alloy is widely used in aero-engines and high-temperature environments. However, residual stress caused by processing and molding leads to an uneven distribution of internal pressure, which reduces the reliability of service process. Therefore, numerical simulation of the nanoindentation process was applied to evaluate the effect of residual stress on the machined subsurface of Inconel 718. A gradient material model of Inconel 718 was established in ABAQUS finite element software. Mechanical properties based on nanoindentation testing showed an influence of residual stress in combination with indenter geometry. The orthogonal experimental results show that under diverse residual stress states, the indenter’s geometry can affect the pile-up of the material surface after nanoindentation and significantly influence the test results. With increases in piling-up, the error caused by residual stress on the characterization of the mechanical properties of the hardened layer increases. Through the establishment of a numerical model, the influence of residual stress can be predicted within nanoindentation depths of 300 nm.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

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