scholarly journals Identification of Material Constitutive Laws Representative of Machining Conditions for Two Titanium Alloys: Ti6Al4V and Ti555-3

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
G. Germain ◽  
A. Morel ◽  
T. Braham-Bouchnak
Keyword(s):  
Strain Rate ◽  
Titanium Alloys ◽  
Shear Bands ◽  
Shear Zones ◽  
Material Behavior ◽  
Constitutive Law ◽  
Β Phase ◽  
Cutting Zone ◽  
Machining Operations ◽  
Material Constitutive Law

Determining a material constitutive law that is representative of the extreme conditions found in the cutting zone during machining operations is a very challenging problem. In this study, dynamic shear tests, which reproduce, as faithfully as possible, these conditions in terms of strain, strain rate, and temperature, have been developed using hat-shaped specimens. The objective was to identify the parameters of a Johnson–Cook material behavior model by an inverse method for two titanium alloys: Ti6Al4V and Ti555-3. In order to be as representative as possible of the experimental results, the parameters of the Johnson–Cook model were not considered to be constant over the total range of the strain rate and temperature investigated. This reflects a change in the mechanisms governing the deformation. The shear zones observed in hat-shaped specimens were analyzed and compared to those produced in chips during conventional machining for both materials. It is concluded that the observed shear bands can be classified as white-etching bands only for the Ti555-3 alloy. These white bands are assumed to form more easily in the Ti555-3 alloy due to its predominately β phase microstructure compared to the Ti6Al4V alloy with a α + β microstructure.

scholarly journals Effect of High Strain Rate on Adiabatic Shearing of α+β Dual-Phase Ti Alloy

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2044
Author(s):  
Fang Hao ◽  
Yuxuan Du ◽  
Peixuan Li ◽  
Youchuan Mao ◽  
Deye Lin ◽  
...  
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Damage Tolerance ◽  
Shear Bands ◽  
Dual Phase ◽  
Ti Alloy ◽  
Hopkinson Pressure Bar ◽  
Β Phase ◽  
Schmid Factor ◽  
Pressure Bar

In the present work, the localized features of adiabatic shear bands (ASBs) of our recently designed damage tolerance α+β dual-phase Ti alloy are investigated by the integration of electron backscattering diffraction and experimental and theoretical Schmid factor analysis. At the strain rate of 1.8 × 104 s−1 induced by a split Hopkinson pressure bar, the shear stress reaches a maximum of 1951 MPa with the shear strain of 1.27. It is found that the α+β dual-phase colony structures mediate the extensive plastic deformations along α/β phase boundaries, contributing to the formations of ASBs, microvoids, and cracks, and resulting in stable and unstable softening behaviors. Moreover, the dynamic recrystallization yields the dispersion of a great amount of fine α grains along the shearing paths and in the ASBs, promoting the softening and shear localization. On the contrary, low-angle grain boundaries present good resistance to the formation of cracks and the thermal softening, while the non-basal slipping dramatically contributes to the strain hardening, supporting the promising approaches to fabricate the advanced damage tolerance dual-phase Ti alloy.

Plastic deformation and fracture characteristics of Hadfield steel subjected to high-velocity impact loading

2002 ◽  
Vol 216 (10) ◽  
pp. 971-982 ◽  
Author(s):  
W-S Lee ◽  
T-H Chen
Keyword(s):  
Strain Rate ◽  
Work Hardening ◽  
Shear Bands ◽  
Rate Sensitivity ◽  
Constitutive Law ◽  
Hadfield Steel ◽  
Flow Strength ◽  
Rate Dependent ◽  
Work Hardening Rate ◽  
The Impact

Investigation of the impact behaviour of Hadfield steel has been carried out in a broad range of strain rates from 10−3 to 9 × 103s−1 by means of a servo-hydraulic machine and a compressive split Hopkinson bar. The effects of strain rate on the impact properties, substructure evolution and fracture resistance have been evaluated. The observed stress-strain response is influenced greatly by strain rate, resulting in obvious changes of work hardening rate, strain rate sensitivity and activation volume. This rate-dependent behaviour is in good agreement with model predictions using the Zerilli-Armstrong constitutive law. Dislocation tangle and deformation twin substructures are also found to develop as a function of strain rate. Increasing dislocation and twin densities enhance the work hardening rate and flow strength. Catastrophic failure at high rates results from the formation of localized shear bands. With increasing strain rate, there is an increase in brittle cleavage microfracture, resulting in ductility loss. Microcracking initiates at grain boundaries due to the presence of carbide precipitates.

scholarly journals Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Fanlu Min ◽  
Zhanhu Yao ◽  
Teng Jiang
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Numerical Study ◽  
Material Behavior ◽  
Constitutive Law ◽  
Test Machine ◽  
Strain Rates ◽  
Dynamic Tensile Strength ◽  
Dynamic Increase Factor ◽  
Versus Strain

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1to 10−4 s−1in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates.

Dynamic Deformation Response of G33 Steel under High Temperature

2015 ◽  
Vol 782 ◽  
pp. 61-70
Author(s):  
You Jing Zhang ◽  
Hong Nian Cai ◽  
Xing Wang Cheng ◽  
Shuang Zan Zhao
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Shear Bands ◽  
Shear Zones ◽  
Adiabatic Shear ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Adiabatic Shear Bands

The high temperature deformation and fracture behavior of ultra-high strength G33 steel under high strain rate compression are investigated by means of a split Hopkinson p ressure bar. Impact tests are performed at strain rates of 1000/s and 2200/s and at temperatures ranging from 25°C to 700°C. The SEM and TEM techniques are also used to analyze the microstructure evolution of the adiabatic shear band (ASB) and fracture characteristics of the deformed specimens at high temperature. The experimental results indicate that the flow stress of G33 steel is significantly dependent on temperatures and strain rates. The flow stress of G33 steel increases with the increase of strain rates, but decreases with the increase of temperatures. The strain rate sensitivity is more pronounced at the low temperature of 25°C. In addition, G33 steel is more liable to fracture at high temperatures than at 25°C. Observations of microstructure show two well-developed symmetric parabolic adiabatic shear bands on the longitudinal cross-section of the cylindrical specimen deformed at the temperature of 700°C and at the strain rate of 2200/s. Within the ASB, the width of the fine equiaxed grain structure is about 7μm. The size of those equiaxed grains is approximately 100nm. The fracture analysis results indicate that the ASBs are the predominant deformation and the specimens fracture along adiabatic shear bands. The fracture surfaces of the deformed G33 steel specimens are characterized by two alternating zones: rough dimple zone and relatively smooth shear zone. Further observations reveal that smooth shear zones consist of severely sheared dimples.

scholarly journals The ephemeral development of C' shear bands

2021 ◽  
Author(s):  
Melanie Finch ◽  
Paul Bons ◽  
Florian Steinbach ◽  
Albert Griera ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Strain Rate ◽  
Numerical Models ◽  
Shear Bands ◽  
Shear Zones ◽  
Stress And Strain ◽  
High Mechanical Strength ◽  
Weak Phase ◽  
Ductile Shear Zones ◽  
Stress And Strain Rate ◽  
Stress And Strain Distribution

<p>C' shear bands are common structures in ductile shear zones but their development is poorly understood. They occur in rocks with a high mechanical strength contrast so we used numerical models of viscoplastic deformation to study the effect of the proportion of weak phase and the phase strength contrast on C' shear band development. We employed simple shear to a finite strain of 18 in 900 steps and recorded the microstructure, stress and strain distribution at each step. We found that C' shear bands form in models with ≥5% weak phase when there is a moderate or high phase strength contrast, and they occur in all models with weak phase proportions ≥15%. Contrary to previous research, we find that C' shear bands form when layers of weak phase parallel to the shear zone boundary rotate forwards. This occurs due to mechanical instabilities that are a result of heterogeneous distributions of stress and strain rate. C' shear bands form on planes of low strain rate and stress, not in sites of maximum strain rate as has previously been suggested. C' shear bands are ephemeral and they either rotate backwards to the C plane once they are inactive or rotate into the field of shortening and thicken to form X- and triangle- shaped structures.</p>

Influence of β phase fraction on deformation of grains in and around shear bands in machining of titanium alloys

2014 ◽  
Vol 618 ◽  
pp. 71-85 ◽  
Author(s):  
Shashikant Joshi ◽  
Pravin Pawar ◽  
Asim Tewari ◽  
Suhas S. Joshi
Keyword(s):  
Titanium Alloys ◽  
Shear Bands ◽  
Phase Fraction ◽  
Β Phase

Influence of Strain Rate on Shear Localization during Deformation and Fracture of 5754 and 5182 Aluminium Alloy

2006 ◽  
Vol 519-521 ◽  
pp. 1047-1052 ◽  
Author(s):  
Mohammad Jaffar Hadianfard ◽  
Michael J. Worswick
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Strain Rate ◽  
Shear Bands ◽  
Tensile Tests ◽  
Material Behavior ◽  
Damage Development ◽  
Band Formation ◽  
Deformation And Fracture ◽  
Localized Plastic Deformation

The effect of strain rate in the range of 10-4 to 10-1 s-1 on localization of deformation and fracture behavior of 5754 and 5182 aluminum alloys is investigated. For this study, tensile tests, interrupted tensile tests, shear band decoration, fractography and image analysis has been used. This investigation is based on experimental work and observation of the material behavior. Results show that strain rate has some effect on the mechanical properties and deformation stability of the alloys. The area of localized plastic deformation and thickness of the shear bands were found to be sensitive to the strain rate. It was also observed that localization of plastic deformation and shear band formation is an important step in the damage propagation and final fracture of the alloys. Detail of damage development, based upon micrographs of samples interrupted at different stages of straining is presented

Modelization and Validation of Ti-6Al-4V Alloy Material Constitutive Law for Isothermal Forging Process

2014 ◽  
Vol 622-623 ◽  
pp. 207-216 ◽  
Author(s):  
Chao Zhang ◽  
Xiao Guang Yang ◽  
Jian Hua Zhou ◽  
Ai Jun Huang
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Metal Flow ◽  
Strain Rate Range ◽  
Constitutive Law ◽  
Compression Tests ◽  
Analysis Model ◽  
Isothermal Forging ◽  
Forging Process ◽  
Material Constitutive Law

Isothermal forging is a near-net shape forming technology for manufacturing complex titanium alloy components. In order to characterize the workability of Ti-6Al-4V alloy during isothermal forging process, the material properties of Ti-6Al-4V alloy were investigated by isothermal compression tests under different strain rate-temperature, where the temperature range is 850~1000 °C and strain rate range is 0.001~0.05s−1. The obtained flow stress-strain data was used to develop the Arrhenius constitutive model of which material constants considered the compensation of strain. The developed constitutive model was used to simulate the isothermal forging process of Ti-6Al-4V alloy component by finite element (FE) based numerical method. The metal flow and potential defect locations were predicted by numerical simulation. Furthermore, the relevant simulation results were compared with the product in industrial workshop to demonstrate the validity of material constitutive model. Keywords: Isothermal forging; Ti-6Al-4V alloy; Hot compression test; Arrhenius constitutive model; FE analysis; Model validation;

Strain Rate Effect on the Mechanical Behavior of Austenitic Stainless Steel during Machining

2011 ◽  
Vol 223 ◽  
pp. 332-339
Author(s):  
Patrícia Alves Barbosa ◽  
Izabel Fernanda Machado
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Strain Rate ◽  
Strain Hardening ◽  
Shear Bands ◽  
Shear Zones ◽  
Rate Variation ◽  
Aisi 304 ◽  
Steel Aisi ◽  
Stainless Steel Aisi

Machining is characterized by a large amount of localized plastic strain on material due to chip formation; hence, there is a commitment among the strain process, strain hardening, and heat softening, generating shear bands. Understanding these shear zones is important because it contains information that can be applied to the improvement of machining techniques related to process optimization, and to materials and tools innovation. In this sense, the aim is to analyze the strain and the strain hardening with the strain rate variation as from the chip formed during the austenitic stainless steel AISI 304 turning. The results showed that the cut type, orthogonal or semi-orthogonal machining, affects the way the material strains, and that the strain rate has no significant effect on the strain and strain hardening of the austenitic stainless steel AISI 304 for the range investigated.

Evaluation of Cooling Potential and Tool Life in Turning Using Metalworking Fluids Delivered in Supercritical Carbon Dioxide

2009 ◽  
Author(s):  
Andres F. Clarens ◽  
Ye-Eun Park ◽  
Jacob Temme ◽  
Kim Hayes ◽  
Fu Zhao ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Tool Wear ◽  
Tool Life ◽  
Heat Removal ◽  
Minimum Quantity Lubrication ◽  
Metalworking Fluids ◽  
Compacted Graphite ◽  
Lower Viscosity ◽  
Cutting Zone ◽  
Machining Operations

Carbon Dioxide is an industrial byproduct that has been proposed as an alternative metalworking fluid (MWF) carrier with lower environmental impacts and better cooling potential than existing MWFs. This paper investigates the heat removal and tool life effects of rapidly expanding supercritical CO2 (scCO2)-based MWFs relative to MWFs delivered as a flood of semi-synthetic emulsion or as minimum quantity lubrication (MQL) sprays. When cutting both compacted graphite iron (CGI) and titanium, tool wear was most effectively controlled using the scCO2-based MWF compared with the other MWFs. Analysis in this paper suggests that the performance benefit imparted by rapidly expanding scCO2 appears to be related to both the cooling potential and penetration of the sprays into the cutting zone. High-pressure gas sprays have lower viscosity and higher velocity than conventional MWFs. An experiment in which the spray direction was varied clearly demonstrated the importance of spray penetration in tool wear suppression. The type of gas spray is also a significant factor in tool wear suppression. For instance, a spray of N2 delivered under similar conditions to CO2 effectively reduced tool wear relative to water based fluids, but not as much as CO2. This result is particularly relevant for MQL sprays which are shown to not cool nearly as effectively as scCO2 MWFs. These results inform development of scCO2-based MWFs in other machining operations, and provide insight into the optimization of scCO2 MWF delivery.

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