scholarly journals Experimental and numerical analyses of the dynamic failure processes of symmetric Taylor impact specimens

2018 ◽  
Vol 183 ◽  
pp. 01043
Author(s):  
Hervé Couque
Keyword(s):  
Shear Failure ◽  
Failure Process ◽  
Shear Bands ◽  
High Strength ◽  
Adiabatic Shear ◽  
Tungsten Alloy ◽  
Three Dimension ◽  
Impact Specimen ◽  
Taylor Impact ◽  
Loading Procedure

Failure processes encountered in the Taylor impact specimen are of two kinds, Mode II cracks initiating within adiabatic shear bands and tensile cracks. Because friction occurring with the single Taylor configuration influences the failure processes, it is necessary to use the symmetric loading procedure providing frictionless interfaces. Numerical simulations of the symmetric Taylor test have been conducted to reproduce the failure processes observed with a highly ductile nickel and a high strength tungsten alloy. Because the adiabatic shear failure process is occurring along a three dimension path, the 3D module of the hydrocode AUTODYN was used.

Inspection of Adiabatic Shear Bands in High Manganese TRIP Steels

2013 ◽  
Vol 753 ◽  
pp. 72-75 ◽  
Author(s):  
Hui Zhen Wang ◽  
Xiu Rong Sun ◽  
Ping Yang ◽  
Wei Min Mao
Keyword(s):  
Shear Failure ◽  
High Strain ◽  
Shear Bands ◽  
Adiabatic Shear ◽  
Strain Rates ◽  
Trip Effect ◽  
Adiabatic Shear Bands ◽  
High Manganese ◽  
High Strain Rates ◽  
Trip Steels

Adiabatic shear bands (ASBs) develop generally during high strain rates. This paper investigates the transformation induced plasticity (TRIP) effect during ASBs formation at high strain rates in high manganese TRIP steels containing initial austenite and ferrite by EBSD technique. Results show that TRIP effect takes place mainly before the formation of ASBs. After ASBs formation, TRIP effect is strongly restricted by the size effect, the increase of stacking fault energy (SFE) and even inverse martensitic transformation due to the rise of temperature. The TRIP effect before ASBs formation contributes to the resistance of adiabatic shear failure. Dynamic recrystallization driven by subgrains rotation occurs within ASBs, and ultrafine grains often show strong shear textures with twin relationship owing to slip mechanism.

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.

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.

scholarly journals Dynamic crack arrest capability of some metallic alloys and polymers

2018 ◽  
Vol 183 ◽  
pp. 02002
Author(s):  
Gunasilan Manar ◽  
Norazrina Mat Jali ◽  
Patrice Longère
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Shear Failure ◽  
Failure Process ◽  
Shear Bands ◽  
Ductile Failure ◽  
Crack Arrest ◽  
Dynamic Crack ◽  
Impact Tests ◽  
The Impact

We are here interested in the crack arrest capability under impact loading of metals and polymers used as structural and/or protection materials in aerospace engineering. Kalthoff and Winkler-type impact tests are carried out to that purpose on high strength AA7175 aluminum alloy and shock resistant polymethyl methacrylate (PMMA). Impact tests are carried out at impact velocities ranging from 50 m/s to 250 m/s and high speed camera is used to record the different steps of the failure process. For AA7175, early Mode II shear failure followed by late Mode I opening failure are seen. The premature ductile failure of the alloy is shown to result from a preceding stage of dynamic localization in the form of adiabatic shear bands. Impact tests on shock-resistant PMMA evidence the brittle feature of the material failure. It is notably shown that the higher the impact velocity (in the range 50-100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen.

Component Analysis of Adiabatic Shear Band Formed in High Speed Cutting of High Strength Alloy Steel

2011 ◽  
Vol 52-54 ◽  
pp. 1482-1485
Author(s):  
Chun Zheng Duan ◽  
Zhao Xi Wang ◽  
Min Jie Wang ◽  
Wei Sen Kong
Keyword(s):  
Shear Band ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Diffusion Mechanism ◽  
Shear Bands ◽  
Cutting Speed ◽  
High Strength ◽  
Adiabatic Shear ◽  
Serrated Chip ◽  
High Speed Cutting

The component distribution of adiabatic shear banding during high speed cutting(HSC) is important to understand the phase transformation during formation of adiabatic shear band and mechanism of serrated chip formation. This paper analyzed element distribution inside and near the adiabatic shear bands formed during HSC of 30CrNi3MoV high strength steel using electronic probe. It was found that there is no obvious element segregation, but carbon element tends to gather towards adiabatic shear band’s boundaries. The density of carbon inside the shear bands tends to increase with the increase of cutting speed. The results indicated that the diffusion and gather of carbon may occur during formation of adiabatic shear band. The diffusion mechanism may be short-range diffusion driven by high-speed deformation and high temperature rise.

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