Relating Porosity With Ductility in a Commercial AA7075 Alloy: A Combined Experimental and Numerical Study

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Tawqeer Nasir Tak ◽  
Aditya Prakash ◽  
Arijit Lodh ◽  
Shyam M. Keralavarma ◽  
S. V. S. Narayana Murty ◽  
...  
Keyword(s):  
Numerical Study ◽  
Damage Model ◽  
High Strength ◽  
Compression Tests ◽  
Cast Material ◽  
Porosity Evolution ◽  
3 Dimensional ◽  
Mechanical Responses ◽  
Direct Observations ◽  
Spherical Voids

Abstract In this paper, the effect of porosity on the ductility of as-cast AA7075 (a commercial high-strength aluminum alloy) was investigated. The as-cast material was processed through hot upsetting, and specimens with different porosity content were achieved. These were then subjected to tensile and compression tests. It was shown that the tensile ductility exhibited a near sigmoidal dependence on the porosity content. Compressive ductility, on the other hand, was not affected by the initial porosity content. In addition, direct observations, on an X-ray microscope (XRM), enabled 3-dimensional imaging of the porosity evolution during plastic deformation. Numerical simulations using a homogenized damage model, the Gurson–Tvergaard–Needleman (GTN) approach, was used for predicting the mechanical responses. The continuum model, which accounted for the growth and coalescence of spherical voids, captured the overall experimental patterns reasonably well.

Numerical Prediction of Failure within Small Curvature Bending of Advanced High Strength Steels

2015 ◽  
Vol 639 ◽  
pp. 419-426
Author(s):  
Ioannis Tsoupis ◽  
Marion Merklein
Keyword(s):  
Crack Initiation ◽  
Damage Mechanics ◽  
Numerical Study ◽  
Damage Model ◽  
High Strength Steels ◽  
High Strength ◽  
Continuum Damage Mechanics ◽  
Calibration Method ◽  
Damage Parameter ◽  
Small Curvature

Within this paper a numerical study of the Continuum Damage Mechanics based damage model Lemaitre in commercial software LS-DYNA is performed in order to correctly predict failure in terms of crack occurrence within small curvature bending of AHSS steels. A strain based calibration method is used for the effective adaption of the Lemaitre model to the bending operation, which is based on the comparison and adaption of the numerically calculated and the experimentally measured deformation field on the outer surface of the bent specimen. Within this method the material dependent damage parameter S is systematically varied in the simulation in order to represent maximum major strain. The new method is proved by numerical simulation of experiments provoking crack initiation using smaller bending radii. It can be shown that failure in terms of crack initiation can be correctly predicted by the model with the damage parameters, which were determined by the method of strain based calibration and an additional optimisation of the parameter Dc. Thus, within this study a user friendly and effective way for the application of Lemaitre damage model to small curvature bending processes of AHSS steels is developed.

Void Growth and Coalescence in Porous Plastic Solids With Sigmoidal Hardening

2019 ◽  
Vol 86 (9) ◽  
Author(s):  
Padmeya P. Indurkar ◽  
Shailendra P. Joshi
Keyword(s):  
Void Growth ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Unit Cell ◽  
Porous Solid ◽  
Effective Response ◽  
Porosity Evolution ◽  
Aspect Ratios ◽  
Spherical Voids ◽  
Void Growth And Coalescence

Abstract This paper presents an analysis of void growth and coalescence in isotropic, elastoplastic materials exhibiting sigmoidal hardening using unit cell calculations and micromechanics-based damage modeling. Axisymmetric finite element unit cell calculations are carried out under tensile loading with constant nominal stress triaxiality conditions. These calculations reveal the characteristic role of material hardening in the evolution of the effective response of the porous solid. The local heterogeneous flow hardening around the void plays an important role, which manifests in the stress–strain response, porosity evolution, void aspect ratio evolution, and the coalescence characteristics that are qualitatively different from those of a conventional power-law hardening porous solid. A homogenization-based damage model based on the micromechanics of void growth and coalescence is presented with two simple, heuristic modifications that account for this effect. The model is calibrated to a small number of unit cell results with initially spherical voids, and its efficacy is demonstrated for a range of porosity fractions, hardening characteristics, and void aspect ratios.

scholarly journals CFRP Origami Metamaterial with Tunable Buckling Loads: A Numerical Study

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 917
Author(s):  
Houyao Zhu ◽  
Shouyan Chen ◽  
Teng Shen ◽  
Ruikun Wang ◽  
Jie Liu
Keyword(s):  
Numerical Study ◽  
Buckling Load ◽  
Fe Modelling ◽  
Buckling Loads ◽  
Folding Angle ◽  
Mechanical Responses ◽  
Reinforced Plastic ◽  
Rate Of Increase ◽  
Practical Engineering ◽  
Identical Rate

Origami has played an increasingly central role in designing a broad range of novel structures due to its simple concept and its lightweight and extraordinary mechanical properties. Nonetheless, most of the research focuses on mechanical responses by using homogeneous materials and limited studies involving buckling loads. In this study, we have designed a carbon fiber reinforced plastic (CFRP) origami metamaterial based on the classical Miura sheet and composite material. The finite element (FE) modelling process’s accuracy is first proved by utilizing a CFRP plate that has an analytical solution of the buckling load. Based on the validated FE modelling process, we then thoroughly study the buckling resistance ability of the proposed CFRP origami metamaterial numerically by varying the folding angle, layer order, and material properties, finding that the buckling loads can be tuned to as large as approximately 2.5 times for mode 5 by altering the folding angle from 10° to 130°. With the identical rate of increase, the shear modulus has a more significant influence on the buckling load than Young’s modulus. Outcomes reported reveal that tunable buckling loads can be achieved in two ways, i.e., origami technique and the CFRP material with fruitful design freedoms. This study provides an easy way of merely adjusting and controlling the buckling load of lightweight structures for practical engineering.

Eccentric compression tests and design of welded steel tube strengthened RC stub columns with high-strength grout

2021 ◽  
Vol 35 ◽  
pp. 102072
Author(s):  
Benhao Gao ◽  
Jingfeng Wang ◽  
Qihan Shen ◽  
Chenggang Wang ◽  
Zhonghua Yu
Keyword(s):  
High Strength ◽  
Steel Tube ◽  
Compression Tests ◽  
Welded Steel ◽  
Eccentric Compression ◽  
Stub Columns

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

2002 ◽  
Vol 17 (5) ◽  
pp. 991-1001 ◽  
Author(s):  
X. Y. Qin ◽  
J. S. Lee ◽  
C. S. Lee
Keyword(s):  
Yield Strength ◽  
Mechanical Behavior ◽  
Light Emission ◽  
Hot Isostatic Pressing ◽  
Microstructural Analysis ◽  
High Strength ◽  
Compression Tests ◽  
Mechanochemical Method ◽  
Force Microscopy ◽  
Bulk Nanocrystalline

The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.

Numerical Investigation of Ductile Fracture in Pipelines Under Complex Loading Using a Phenomenological Damage Model

2021 ◽  
Author(s):  
Iago S. Santos ◽  
Diego F. B. Sarzosa
Keyword(s):  
Ductile Fracture ◽  
Mechanical Response ◽  
Numerical Study ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Complex Loading ◽  
Experimental Tests ◽  
Compact Tension ◽  
Axial Tensile

Abstract This paper presents a numerical study on pipes ductile fracture mechanical response using a phenomenological computational damage model. The damage is controlled by an initiation criterion dependent on the stress triaxiality and the Lode angle parameter, and a post-initiation damage law to eliminate each finite element from the mesh. Experimental tests were carried out to calibrate the elastoplastic response, damage parameters and validate the FEM models. The tested geometries were round bars having smooth and notched cross-section, flat notched specimens under axial tensile loads, and fracture toughness tests in deeply cracked bending specimens SE(B) and compact tension samples C(T). The calibrated numerical procedure was applied to execute a parametric study in pipes with circumferential surface cracks subjected to tensile and internal pressure loads simultaneously. The effects of the variation of geometric parameters and the load applications on the pipes strain capacity were investigated. The influence of longitudinal misalignment between adjacent pipes was also investigated.

scholarly journals Axial compression behavior of concrete masonry wallettes strengthened with cement mortar overlays

2008 ◽  
Vol 1 (2) ◽  
pp. 158-170 ◽  
Author(s):  
F. L. De Oliveira ◽  
J. B. De Hanai
Keyword(s):  
Axial Compression ◽  
Cement Mortar ◽  
High Strength ◽  
Concrete Block ◽  
Masonry Wall ◽  
Compression Tests ◽  
Steel Mesh ◽  
Mortar Strength ◽  
Theoretical Approaches ◽  
Wall Strength

This paper presents the results of a series of axial compression tests on concrete block wallettes coated with cement mortar overlays. Different types of mortars and combinations with steel welded meshes and fibers were tested. The experimental results were discussed based on different theoretical approaches: analytical and Finite Element Method models. The main conclusions are: a) the application of mortar overlays increases the wall strength, but not in a uniform manner; b) the strengthening efficiency of wallettes loaded in axial compression is not proportional to the overlay mortar strength because it can be affected by the failure mechanisms of the wall; c) steel mesh reinforced overlays in combination with high strength mortar show better efficiency, because the steel mesh mitigates the damage effects in the block wall and in the overlays themselves; d) simplified theoretical methods of analysis as described in this paper can give satisfactory predictions of masonry wall behavior up to a certain level.

Modeling of Solder Fatigue Failure due to Ductile Damage

2010 ◽  
Vol 26 (4) ◽  
pp. N23-N27 ◽  
Author(s):  
K. Aluru ◽  
F.-L. Wen ◽  
Y.-L. Shen
Keyword(s):  
Numerical Study ◽  
Fatigue Cracks ◽  
Damage Model ◽  
Quantitative Information ◽  
Ductile Damage ◽  
Element Analysis ◽  
Cyclic Shear ◽  
Rate Dependent ◽  
Solder Fatigue ◽  
Temporal And Spatial

ABSTRACTA numerical study is undertaken to simulate failure of solder joint caused by cyclic shear deformation. A progressive ductile damage model is incorporated into the rate-dependent elastic-viscoplastic finite element analysis, resulting in the capability of simulating damage evolution and eventual failure through crack formation. It is demonstrated that quantitative information of fatigue life, as well as the temporal and spatial evolution of fatigue cracks, can be explicitly obtained.

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