A new method based on energy principle to predict uniaxial stress–strain relations of ductile materials by small punch testing

2018 ◽  
Vol 138-139 ◽  
pp. 244-249 ◽  
Author(s):  
Yun-qiang Peng ◽  
Li-xun Cai ◽  
Hui Chen ◽  
Chen Bao
Keyword(s):  
Uniaxial Stress ◽  
New Method ◽  
Stress Strain ◽  
Energy Principle ◽  
Small Punch ◽  
Ductile Materials

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.

Three Types of Stress-Strain Relationship’s Comparison of Circular Tubed Reinforced Concrete in FEA

2012 ◽  
Vol 204-208 ◽  
pp. 930-933
Author(s):  
Xiao Hu ◽  
Zhen Lin Chen
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Uniaxial Stress ◽  
Steel Tube ◽  
Finite Element Analyses ◽  
Stress Strain ◽  
Concrete Filled Steel Tube ◽  
Bearing Analysis

The paper introduces 3 types of uniaxial stress-strain relationships of concrete filled steel tube by Pan Youguang, Susantha and Saenz, and performs finite element analyses of the axial strengths of 18 CTRC columns, studies the characters of three models, and comprises between the axial strengths from FEA and existed experiments. Results show these 3 types of model are all suitable for bearing analysis, but Pan’s model is more accurate.

A New Method Developed for Brittle and Ductile Materials to Evaluate Mechanical Properties of a Lump Specimen in the Use of Indentation Test

2006 ◽  
Vol 129 (2) ◽  
pp. 284-292 ◽  
Author(s):  
Pal Jen Wei ◽  
Jen Fin Lin
Keyword(s):  
Yield Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Elastic Recovery ◽  
Indentation Test ◽  
New Method ◽  
Ductile Materials ◽  
Conventional Material ◽  
Loading And Unloading ◽  
Logarithm Function

In this study, the load-depth (P‐h) relationships matching the experimental results of the nanoindentation tests exhibited at the subregions of small and large depths are obtained, respectively. The relationships associated with these two subregions are then linked by the hyperbolic logarithm function to attain a single expression that is applied in the evaluation of the specimen’s elastic recovery ability, as shown in the unloading process. A new method is developed in the present study to evaluate both Young’s modulus and the yield strength of either a ductile or brittle material through the uses of the appropriate P‐h relationships developed in the load and unloading processes. The results of the Young’s modulus and the yield strength achieved by the present method are compared to those obtained from the conventional material tests for a lump material. The scattering of the experimental data shown in the loading and unloading processes are also interpreted by different causes.

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