Relationship between the temperature dependences of the fracture mechanics parameters and yield stress of low and medium strength steels

1987 ◽  
Vol 19 (3) ◽  
pp. 369-371
Author(s):  
G. I. Saidov
Keyword(s):  
Fracture Mechanics ◽  
Yield Stress ◽  
Medium Strength ◽  
Temperature Dependences

scholarly journals Fundamentals of cutting

2016 ◽  
Vol 6 (3) ◽  
pp. 20150108 ◽  
Author(s):  
J. G. Williams ◽  
Y. Patel
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Fracture Mechanics ◽  
Yield Stress ◽  
Material Properties ◽  
Orthogonal Cutting ◽  
Wedge Angle ◽  
Tool Geometry ◽  
Plastic Shear ◽  
Plastic Bending

The process of cutting is analysed in fracture mechanics terms with a view to quantifying the various parameters involved. The model used is that of orthogonal cutting with a wedge removing a layer of material or chip. The behaviour of the chip is governed by its thickness and for large radii of curvature the chip is elastic and smooth cutting occurs. For smaller thicknesses, there is a transition, first to plastic bending and then to plastic shear for small thicknesses and smooth chips are formed. The governing parameters are tool geometry, which is principally the wedge angle, and the material properties of elastic modulus, yield stress and fracture toughness. Friction can also be important. It is demonstrated that the cutting process may be quantified via these parameters, which could be useful in the study of cutting in biology.

scholarly journals A critical review of the influence of hydrogen on the mechanical properties of medium-strength steels

2013 ◽  
Vol 31 (3-6) ◽  
pp. 85-103 ◽  
Author(s):  
Qian Liu ◽  
Andrej Atrens
Keyword(s):  
Tensile Stress ◽  
Yield Stress ◽  
Stress Ratio ◽  
Ultimate Tensile Stress ◽  
Fatigue Properties ◽  
Lower Yield ◽  
Good Resistance ◽  
Microstructural Characteristics ◽  
Lower Yield Stress ◽  
Medium Strength

AbstractAs medium-strength steels are promising candidates for the hydrogen economy, it is important to understand their interaction with hydrogen. However, there are only a limited number of investigations on the behavior of medium-strength steels in hydrogen. The existing literature indicates that the influences of hydrogen on the tensile properties of medium-strength steels are mainly the following: (i) the steel can be hardened by hydrogen, as demonstrated by an increase in the yield stress or ultimate tensile stress; (ii) some steels can be embrittled by hydrogen, as revealed by lower yield stress or ultimate tensile stress; (iii) in most cases, these steels may experience hydrogen embrittlement (HE), as indicated by a reduction in ductility. The degree of HE mainly depends on the test conditions and the steel. The embrittlement can lead to catastrophic brittle fracture in service. The influence of hydrogen on the fatigue properties of medium-strength steels is dependent on many factors such as the stress ratio, temperature, yield stress of the steel, and test frequency. Generally, the hydrogen influence on fatigue limit is small, whereas hydrogen can accelerate the fatigue crack growth rate, leading to a shorter fatigue life. Inclusions are an important factor influencing the properties of medium-strength steels in the presence of hydrogen. However, it is not possible to predict the influence of hydrogen for any particular steel that has not been experimentally evaluated or to predict service performance. It is not known why similar steels can have different behavior, ranging from good resistance to significant embrittlement. A better understanding of the microstructural characteristics is needed.

From the Electronic Structure to the Macroscopic Behavior: A Multi-scale Analysis of Plasticity in Intermetallic Compounds

2000 ◽  
Vol 652 ◽  
Author(s):  
Manfred Fähnle ◽  
Susanne Kohlhammer ◽  
Gabriel Bester
Keyword(s):  
Yield Stress ◽  
Intermetallic Compounds ◽  
Density Functional ◽  
Strong Increase ◽  
Anomalous Temperature ◽  
Electron Theory ◽  
Multi Scale ◽  
Temperature Dependences ◽  
Crystal Interfaces ◽  
Rule Out

ABSTRACTThe influence of crystal interfaces related to stacking faults on the properties of >110< superdislocations and hence on the temperature dependences of the yield stress in intermetallic compounds is investigated. This is achieved by a combination of the ab-initio density functional electron theory (which describes the electronic scale) with the generalized Peierls-Nabarro model (which describes the atomistic scale). For Pt3Al and doped Al3Ti our data do not support the hypothesis that the strong increase of the yield stress with decreasing T at low T results from sessile SISF-bound dislocation dissociations. Alternative explanations are suggested. For Ni3Al our results do not rule out the idea that Kear-Wilsdorf locks are responsible for the experimentally observed anomalous temperature dependence of the yield stress.

Low-temperature deformation of body-centred cubic metals I. Yield and How stress measurements

1964 ◽  
Vol 281 (1385) ◽  
pp. 223-239 ◽  
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Low Temperatures ◽  
Rate Sensitivity ◽  
High Yield ◽  
Temperature Deformation ◽  
Tensile Yield Stress ◽  
Cubic Metals ◽  
Temperature Dependences ◽  
Macroscopic Deformation

Measurements of the tensile yield stress and of the temperature and strain-rate sensitivity of the flow stress are reported for single crystals of niobium and for polycrystalline speci­mens of niobium, vanadium and tantalum over the temperature range 4.2 to 373°K. The temperature dependences of yield and flow stresses are nearly identical, and the results show that the high yield stresses at low temperatures are attributable mainly to a frictional force opposing the motion of free dislocations. The yield stress is very dependent on the purity of the metal, and the temperature and strain rate sensitivities vary slightly with purity, especially at higher temperatures. At very low temperatures, the stress needed to cause macroscopic deformation at a strain rate of 10 -4 s -1 is ca . 1% of the shear modulus in all specimens examined. The relation of the results to the interpretation of the para­meters in the Hall-Petch equation for the variation of yield stress with grain size is briefly discussed.

From Dislocation Cores to high Temperature Strain rate Effects in L12 Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
V. Vitek ◽  
Y. Sodani ◽  
J. Cserti
Keyword(s):  
Strain Rate ◽  
Yield Stress ◽  
Rate Sensitivity ◽  
Physical Models ◽  
Strain Rate Effects ◽  
Screw Dislocations ◽  
The Core ◽  
Rate Effects ◽  
Temperature Dependences ◽  
Further Development

ABSTRACTIt is now generally accepted that in many L12 compounds the yielding behavior is controlled by the special features of the cores of screw dislocations. In this paper we first summarize results of the atomistic studies of the core structures of the <110> screw dislocations in these compounds. At this point we show that, depending on the atomic bonding, two distinct classes of L12 alloys exist. In the first, represented by alloys like Ni3Al, a glissile configuration of the core exists on {111} planes although a sessile configuration is energetically more favored. In the second class, represented by alloys like Pt3A1 and A13Ti modified by alloying into L12 structure, the cores of screw dislocations are always sessile. Using the results of the atomistic studies we present physical models explaining the temperature dependences of the yield stress in both classes of L12 alloys. At this point we also present a further development of the model for the anomalous temperature dependence of the yield stress in alloys like Ni3A1, originally put forward by Paidar et al. [15]. In this development strain rate effects are included and it is shown that the model explains not only the orientation dependences of the yield stress in the anomalous regime but also the very low strain rate sensitivity observed in this regime.

Study on Validity of Stress Intensity Factor in CT Specimen for Materials With Low Yield Stress

2013 ◽  
Author(s):  
Masahiro Takanashi ◽  
Yu Itabashi ◽  
Takashi Hirano
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Yield Stress ◽  
Small Scale ◽  
Low Alloy Steels ◽  
J Integral ◽  
Loading Conditions ◽  
Test Standards

This paper discusses the validity of a stress intensity factor K for compact tension (CT) specimens of stainless and low-alloy steels by computing J-integral values. In fracture mechanics testing, specimen configurations and loading conditions are strictly regulated to meet the small-scale yielding (SSY) condition and obtain valid data. For some materials, particularly those without an obvious yield point, it is hard to meet the SSY condition. The regulations specified in fracture mechanics test standards are based on experimental results. The theoretical reason for the SSY condition is not necessarily clear and the condition seems conservative. This study focuses on a correlation with the stress intensity factors K and the J-integral values under the SSY condition. J-integral values of CT specimens were analyzed by elasto-plastic finite element analysis. Subsequently, the validity of the stress intensity factor K was checked by comparing K and J–integral values to determine whether CT specimens were under the SSY condition or not. To simplify the comparison, J-integral values were converted to K values, equivalent stress intensity factor KJ values. When K values were low enough to meet the SYY condition of the specimen, they equaled KJ values. Meanwhile, KJ values exceed K values in a high K region, which means the specimen is no longer under a SSY condition. It is possible to determine whether the specimen is under the SSY condition or not by comparing the values of KJ and K. This paper evaluated the validity of K values using the correlative relationship and showed that they were valid to some extent even if loading conditions and specimen configurations were outside the scope of the specification by the test standards. The validity of K values with 0.2% offset strength or flow strength instead of yield stress is also confirmed by this method.

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