scholarly journals Dynamic failure of viscoplastic structures under ASB and micro-voiding

2018 ◽  
Vol 183 ◽  
pp. 01005
Author(s):  
Hannah Lois Dorothy ◽  
Patrice Longere
Keyword(s):  
Shear Banding ◽  
Shear Bands ◽  
High Strength ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Calibration Procedure ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Adiabatic Shear Banding ◽  
Initial Boundary Value

Adiabatic shear bands are known to cause premature structural failure in high strength metals and alloys. The observation of adiabatic shear bands inside partially fractured specimens evidences the presence of micro-voids as the precursor of the ultimate failure. An enriched model containing the effects of adiabatic shear banding and micro-voiding mechanisms was developed and it is here taken through a calibration procedure. The aim of the present work is to evaluate the performances of the enriched model considering an initial-boundary value problem. To that purpose, the model has been implemented as user material in the engineering finite element computation code LS-DYNA. Numerical simulation of the dynamic shearing of hat shaped structures is conducted and the interest of accounting for the pre-failure stage consisting of micro-voiding in the ASB wake is emphasized.

Adiabatic Shear Banding in Plane Strain Problems

1989 ◽  
Vol 56 (3) ◽  
pp. 527-534 ◽  
Author(s):  
R. C. Batra ◽  
De-Shin Liu
Keyword(s):  
Plane Strain ◽  
Shear Banding ◽  
Tangential Velocity ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Normal Velocity ◽  
Adiabatic Shear Banding ◽  
Shearing Strain ◽  
Initial Boundary Value ◽  
Narrow Bands

Plane strain thermomechanical deformations of a viscoplastic body are studied with the objective of analyzing the localization of deformation into narrow bands of intense straining. Two different loadings, namely, the top and bottom surfaces subjected to a prescribed tangential velocity, and these two surfaces subjected to a preassigned normal velocity, are considered. In each case a material defect, flaw, or inhomogeneity is modeled by introducing a temperature bump at the center of the specimen. The solution of the initial boundary value problem by the Galerkin-Adams method reveals that the deformation eventually localizes into a narrow band aligned along the direction of the maximum shearing strain. For both problems, bands of intense shearing appear to diffuse out from the center of the specimen.

An Investigation into the Microstructure of Adiabatic Shear Banding in AISI 1045 Hardened Steel due to High Speed Machining

2010 ◽  
Vol 154-155 ◽  
pp. 321-324 ◽  
Author(s):  
Chun Zheng Duan ◽  
Liang Chi Zhang ◽  
Hai Yang Yu ◽  
Min Jie Wang
Keyword(s):  
High Speed ◽  
Shear Banding ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
High Speed Machining ◽  
Adiabatic Shear Bands ◽  
Adiabatic Shear Banding ◽  
Aisi 1045 ◽  
Cutting Speeds ◽  
Electronic Microscope

Adiabatic shear banding during high speed machining is important to understand material removal mechanisms. This paper investigates the microstructure of adiabatic shear bands (ASBs) in the serrated chips produced during the high speed machining of AISI 1045 hardened steel. Optical microscope, scanning electronic microscope(SEM) and transmission electronic microscope(TEM) were used to explore the microstructural characteristics. It was found that there are two types of adiabatic shear bands. One is the deformed adiabatic shear band composed of a significantly deformed structure generated in a range of low cutting speeds, and the other is the transformed adiabatic shear band composed of very small equiaxed grains generated under high cutting speeds. The results indicated that the deformed band has a tempered martensite structure that formed through large plastic deformation and the transformed band has experienced a dynamic recrystallization process.

Penetration Damaging Behavior of TB17 Titanium Alloy

2020 ◽  
Vol 993 ◽  
pp. 100-107
Author(s):  
Jing Li ◽  
Yun Peng Xin ◽  
Tao Jiang ◽  
Xin Nan Wang ◽  
Zhi Shou Zhu
Keyword(s):  
Titanium Alloy ◽  
Adiabatic Shear Band ◽  
Shear Bands ◽  
High Strength ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Internal Wall ◽  
Micro Cracks ◽  
Opening Stage ◽  
River Pattern

The damage behavior of TB17 titanium alloy with ultra-high strength was studied by 12.7mm diameter armor piercing test. The characteristics and mechanism of damaging were analyzed by the observation of damage morphology of target board. The results indicated that the area was irregular at the opening stage, the internal wall were turtle-shell-like or poly-porous, a few cracks and no adiabatic shear band was observed. The zone was parabolic at the penetrating stage, the internal wall were granular or river pattern, adiabatic shear bands and fragments existed around the crater. A large number micro-pores and micro-cracks originating from the adiabatic shear bands expanded and formed macroscopic cracks. Finally, the target board fractured.

Study on the Evolution of Adiabatic Shear Band of a High Strength Steel

2015 ◽  
Vol 782 ◽  
pp. 143-150
Author(s):  
Wen Wen Du ◽  
Qian Wang ◽  
Deng Hui Zhao ◽  
Lin Wang
Keyword(s):  
High Strength Steel ◽  
Split Hopkinson Pressure Bar ◽  
Shear Bands ◽  
High Strength ◽  
Heat Treatments ◽  
Adiabatic Shear ◽  
Adiabatic Shear Bands ◽  
Hopkinson Pressure Bar ◽  
Static Tensile ◽  
Pressure Bar

The evolution process of a high strength steel which subjected with three different heat treatment proceedings and gets different quasi-static tensile properties was investigated in this paper. To precisely control the plastic deformation of the cylinder and capture the development process of adiabatic shear bands, stopper ring was used in Split Hopkinson Pressure Bar (SHPB). Combining the stress-strain curves and microstructures after SHPB tests, the microstructure evolution from the nucleation of adiabatic shear bands to fracture of the cylindrical steel were observed. The experimental results have demonstrated that there are similar fracture procedures of the steel treated through different heat treatments. Shear bands form firstly, then micro-cracks develop from shear bands, and lead to macro-crack finally. However, the critical strains for nucleation of ASBs and the time spending on the fracture procedure of the steel treated at different heat treatments are different. Samples treated at 900°C/AC exhibit the best resistance to adiabatic shear sensitivity when compressed under high strain rates.

Adiabatic Shear Banding in an Al-Mg-Si Alloy Processed by Equal Channel Angular Pressing

2010 ◽  
Vol 654-656 ◽  
pp. 1014-1017 ◽  
Author(s):  
Majid Vaseghi ◽  
Ali Karimi Taheri ◽  
Ji Hoon Yoo ◽  
Soo Hyun Joo ◽  
Hyoung Seop Kim
Keyword(s):  
Equal Channel Angular Pressing ◽  
Shear Banding ◽  
Effective Strain ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Processing Temperature ◽  
Adiabatic Shear Banding ◽  
Angular Pressing ◽  
Ram Speed ◽  
Number Of Passes

Equal channel angular pressing is an outstanding method for imposing large plastic deformation to metallic materials without any decreasing in cross section area of as processed samples. In this paper, the effect of working temperature, ram speed and the number of passes on the formation of adiabatic shear bands in Al6061 during equal channel angular pressing was investigated. Billets of the alloy were processed up to four passes via route BC from room temperature to 200oC with two ram speeds using a die that imparts an effective strain of ~1.1 per pass. The results have demonstrated that the onset of the adiabatic shear banding in this alloy strongly depends on the ram speed: more frequently observed at the higher ram speed than the lower speed. Although the geometry of the macroscopic view of shear band is similar in all cases, the development of bands depends on the number of passes as well as processing temperature.

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