scholarly journals The origin of the boundary strengthening in polycrystal-inspired architected materials

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chen Liu ◽  
Jedsada Lertthanasarn ◽  
Minh-Son Pham
Keyword(s):  
Shear Band ◽  
Mechanical Strength ◽  
Deformation Behaviour ◽  
Shear Bands ◽  
High Strength ◽  
Local Deformation ◽  
Great Capacity ◽  
Boundary Type ◽  
Underlying Mechanisms ◽  
Damage Tolerant

AbstractCrystal-inspired approach is found to be highly successful in designing extraordinarily damage-tolerant architected materials. i.e. meta-crystals, necessitating in-depth fundamental studies to reveal the underlying mechanisms responsible for the strengthening in meta-crystals. Such understanding will enable greater confidence to control not only strength, but also spatial local deformation. In this study, the mechanisms underlying shear band activities were investigated and discussed to provide a solid basis for predicting and controlling the local deformation behaviour in meta-crystals. The boundary strengthening in polycrystal-like meta-crystals was found to relate to the interaction between shear bands and polygrain-like boundaries. More importantly, the boundary type and coherency were found to be influential as they govern the transmission of shear bands across meta-grains boundaries. The obtained insights in this study provide crucial knowledge in developing high strength architected materials with great capacity in controlling and programming the mechanical strength and damage path.

Effect of Structure Relaxation on the Plastic Deformation Behaviour in a Zr-Based BMG under Indenter

2009 ◽  
Vol 618-619 ◽  
pp. 437-441
Author(s):  
Hao Wen Xie ◽  
Peter D. Hodgson ◽  
Cui E Wen
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Cast Alloy ◽  
Deformation Behaviour ◽  
Shear Bands ◽  
Structure Relaxation ◽  
Effect Of Structure

Vickers and nano indentations were performed on a structurally relaxed Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG), and the evolution of the shear bands in the relaxed BMG was investigated and compared to that in the as-cast alloy. Results indicate that the plastic deformation in the BMG with structure relaxation is accommodated by the semicircular (primary) and radial (secondary) as well as tertiary shear bands. Quantitatively, the shear band density in the relaxed alloy was much lower than that in the as-cast alloy. The annihilation of free volume caused by the annealing was responsible for the embrittlement of the sample with structure relaxation.

Analytical Modeling of Shear Localization in Orthogonal Cutting Processes

2021 ◽  
pp. 1-45
Author(s):  
Mohammadreza Fazlali ◽  
Mauricio Ponga ◽  
Xiaoliang Jin
Keyword(s):  
Shear Band ◽  
Orthogonal Cutting ◽  
Shear Bands ◽  
Chip Morphology ◽  
High Strength ◽  
Shear Localization ◽  
Shear Band Formation ◽  
Workpiece Material ◽  
Band Formation ◽  
Cutting Processes

Abstract This paper presents an analytical thermo-mechanical model of shear localization and shear band formation in orthogonal cutting of high-strength metallic alloys. The deformation process of the workpiece material includes three stages: homogeneous deformation, shear localization, and chip segmentation. A boundary layer analysis is used to analytically predict the temperature, stress, and strain rate variations in the primary shear zone associated with the shear localization. The predictions of shear band spacing and width from the proposed model are verified by experimental characterization of the chip morphology. The rolling of shear bands on the tool rake face is discussed from the experimental observations. The cutting tool temperature, which is influenced by the heat generated during the shear band formation, is simulated and compared with the finite element simulations. The proposed analytical model reveals the fundamental mechanism of the complete shear localization process in orthogonal cutting, and predicts the stress and temperature variations with high computational efficiency.

scholarly journals Shear band-driven precipitate dispersion for ultrastrong ductile medium-entropy alloys

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tae Jin Jang ◽  
Won Seok Choi ◽  
Dae Woong Kim ◽  
Gwanghyo Choi ◽  
Hosun Jun ◽  
...  
Keyword(s):  
Shear Band ◽  
Shear Bands ◽  
High Strength ◽  
Physical Metallurgy ◽  
Strengthening Effect ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Nucleation Sites ◽  
Cubic Structure ◽  
Face Centered

AbstractPrecipitation strengthening has been the basis of physical metallurgy since more than 100 years owing to its excellent strengthening effects. This approach generally employs coherent and nano-sized precipitates, as incoherent precipitates energetically become coarse due to their incompatibility with matrix and provide a negligible strengthening effect or even cause brittleness. Here we propose a shear band-driven dispersion of nano-sized and semicoherent precipitates, which show significant strengthening effects. We add aluminum to a model CoNiV medium-entropy alloy with a face-centered cubic structure to form the L21 Heusler phase with an ordered body-centered cubic structure, as predicted by ab initio calculations. Micro-shear bands act as heterogeneous nucleation sites and generate finely dispersed intragranular precipitates with a semicoherent interface, which leads to a remarkable strength-ductility balance. This work suggests that the structurally dissimilar precipitates, which are generally avoided in conventional alloys, can be a useful design concept in developing high-strength ductile structural materials.

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.

Fine Crystalline Phase Dispersion in Zr-Based Bulk Metallic Glass by Laser Irradiation

2007 ◽  
Vol 26-28 ◽  
pp. 747-750
Author(s):  
R. Ikutomo ◽  
Masato Tsujikawa ◽  
Makoto Hino ◽  
Hisamichi Kimura ◽  
Kunio Yubuta ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Shear Band ◽  
Metallic Glass ◽  
Laser Irradiation ◽  
Bulk Metallic Glass ◽  
Crystalline Phase ◽  
Shear Bands ◽  
High Strength ◽  
Band Formation ◽  
Phase Dispersion

Bulk metallic glass (BMG) exhibits remarkable properties such as high strength, good stiffness and good corrosion resistance. However, the wear resistance of amorphous metals is not excellent as expected their high strength. It is thought that large local shear bands easily change into cracks for debris formation. The effective obstruction of shear band formation might be applied to improve the wear resistance of BMG. In this study, we tried to suppress shear band deformation by fine crystalline phase dispersion formed by semi-conductor laser irradiation. The microstructures of irradiated Zr-based BMG specimens were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The fine dispersions of crystalline phases are observed in the amorphous matrix. The optimum condition for laser irradiation was discussed.

scholarly journals An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4384
Author(s):  
Mohd Aidy Faizal Johari ◽  
Asmawan Mohd Sarman ◽  
Saiful Amri Mazlan ◽  
Ubaidillah U ◽  
Nur Azmah Nordin ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Shear Band ◽  
Shear Bands ◽  
Test Duration ◽  
Phase Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Matrix ◽  
Relaxation Stress ◽  
Band Deformation

Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.

scholarly journals High-strength and fibrous capsule–resistant zwitterionic elastomers

2021 ◽  
Vol 7 (1) ◽  
pp. eabc5442
Author(s):  
Dianyu Dong ◽  
Caroline Tsao ◽  
Hsiang-Chieh Hung ◽  
Fanglian Yao ◽  
Chenjue Tang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Strength ◽  
High Strength ◽  
Design Principles ◽  
Fibrous Capsule ◽  
High Mechanical Strength ◽  
Capsule Formation ◽  
Locking Mechanism ◽  
Fibrous Capsule Formation

The high mechanical strength and long-term resistance to the fibrous capsule formation are two major challenges for implantable materials. Unfortunately, these two distinct properties do not come together and instead compromise each other. Here, we report a unique class of materials by integrating two weak zwitterionic hydrogels into an elastomer-like high-strength pure zwitterionic hydrogel via a “swelling” and “locking” mechanism. These zwitterionic-elastomeric-networked (ZEN) hydrogels are further shown to efficaciously resist the fibrous capsule formation upon implantation in mice for up to 1 year. Such materials with both high mechanical properties and long-term fibrous capsule resistance have never been achieved before. This work not only demonstrates a class of durable and fibrous capsule–resistant materials but also provides design principles for zwitterionic elastomeric hydrogels.

scholarly journals Are We Able to Print Components as Strong as Injection Molded?—Comparing the Properties of 3D Printed and Injection Molded Components Made from ABS Thermoplastic

2021 ◽  
Vol 11 (15) ◽  
pp. 6946
Author(s):  
Bartłomiej Podsiadły ◽  
Andrzej Skalski ◽  
Wiktor Rozpiórski ◽  
Marcin Słoma
Keyword(s):  
Tensile Strength ◽  
Injection Molding ◽  
Mechanical Strength ◽  
Cross Section ◽  
Fused Deposition Modeling ◽  
High Strength ◽  
Large Cross Section ◽  
Fused Deposition ◽  
Injection Molded ◽  
The Cross

In this paper, we are focusing on comparing results obtained for polymer elements manufactured with injection molding and additive manufacturing techniques. The analysis was performed for fused deposition modeling (FDM) and single screw injection molding with regards to the standards used in thermoplastics processing technology. We argue that the cross-section structure of the sample obtained via FDM is the key factor in the fabrication of high-strength components and that the dimensions of the samples have a strong influence on the mechanical properties. Large cross-section samples, 4 × 10 mm2, with three perimeter layers and 50% infill, have lower mechanical strength than injection molded reference samples—less than 60% of the strength. However, if we reduce the cross-section dimensions down to 2 × 4 mm2, the samples will be more durable, reaching up to 110% of the tensile strength observed for the injection molded samples. In the case of large cross-section samples, strength increases with the number of contour layers, leading to an increase of up to 97% of the tensile strength value for 11 perimeter layer samples. The mechanical strength of the printed components can also be improved by using lower values of the thickness of the deposited layers.

Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test

2021 ◽  
pp. 030932472110212
Author(s):  
Mohammad Mehdi Kasaei ◽  
Marta C Oliveira
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Rate ◽  
Contact Pressure ◽  
Deformation Behaviour ◽  
High Strength Steels ◽  
High Strength ◽  
Advanced High Strength Steels ◽  
Deformation Mechanics ◽  
Nakajima Test

This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.

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