Effect of strain-hardening and of heat treatment of steels on their uniform tensile strain and strain-hardening coefficient in indentation

1986 ◽  
Vol 28 (8) ◽  
pp. 572-573
Author(s):  
M. P. Markovets ◽  
V. M. Matyunin
Keyword(s):  
Heat Treatment ◽  
Strain Hardening ◽  
Tensile Strain ◽  
Hardening Coefficient

Experimental and Three-Dimensional Finite Element Study of Scratch Test of Polymers at Large Deformations

2004 ◽  
Vol 126 (2) ◽  
pp. 372-379 ◽  
Author(s):  
J. L. Bucaille ◽  
E. Felder ◽  
G. Hochstetter
Keyword(s):  
Strain Hardening ◽  
Penetration Depth ◽  
Large Deformations ◽  
Numerical Study ◽  
Scratch Test ◽  
Scratch Resistance ◽  
Plastic Strains ◽  
Thermosetting Polymer ◽  
Scratch Tests ◽  
Hardening Coefficient

An experimental and numerical study of the scratch test on polymers near their surface is presented. The elastoplastic response of three polymers is compared during scratch tests at large deformations: polycarbonate, a thermosetting polymer and a sol-gel hard coating composed of a hybrid matrix (thermosetting polymer-mineral) reinforced with oxide nanoparticles. The experiments were performed using a nanoindenter with a conical diamond tip having an included angle of 30 deg and a spherical radius of 600 nm. The observations obtained revealed that thermosetting polymers have a larger elastic recovery and a higher hardness than polycarbonate. The origin of this difference in scratch resistance was investigated with numerical modelling of the scratch test in three dimensions. Starting from results obtained by Bucaille (J. Mat. Sci., 37, pp. 3999–4011, 2002) using an inverse analysis of the indentation test, the mechanical behavior of polymers is modeled with Young’s modulus for the elastic part and with the G’sell-Jonas’ law with an exponential strain hardening for the viscoplastic part. The strain hardening coefficient is the main characteristic parameter differentiating the three studied polymers. Its value is equal to 0.5, 4.5, and 35, for polycarbonate, the thermosetting polymer and the reinforced thermosetting polymer, respectively. Firstly, simulations reveals that plastic strains are higher in scratch tests than in indentation tests, and that the magnitude of the plastic strains decreases as the strain hardening increases. For scratching on polycarbonate and for a penetration depth of 0.5 μm of the indenter mentioned above, the representative strain is equal to 124%. Secondly, in agreement with experimental results, numerical modeling shows that an increase in the strain hardening coefficient reduces the penetration depth of the indenter into the material and decreases the depth of the residual groove, which means an improvement in the scratch resistance.

Effect of Different Heat Treatments on Mechanical Properties of Laser Sintered Additive Manufactured Parts

2017 ◽  
Author(s):  
Sagar Sarkar ◽  
Cheruvu Siva Kumar ◽  
Ashish Kumar Nath
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Yield Strength ◽  
Tensile Strain ◽  
Wear Loss ◽  
Layer By Layer ◽  
Solution Annealing ◽  
Wear Properties ◽  
Sem Images ◽  
Wide Range

One of the most popular additive manufacturing processes is laser based direct metal laser sintering process which enables us to make complex three dimensional parts directly from CAD models. Due to layer by layer formation, parts built in this process tend to be anisotropic in nature. Suitable heat treatment can reduce this anisotropic behaviour by changing the microstructure. Depending upon the applications, a wide range of mechanical properties can be achieved between 482–621° C temperature for precipitation-hardened stainless steels. In the present study effect of different heat treatment processes, namely solution annealing, ageing and overaging, on tensile strength, hardness and wear properties has been studied in detail. Suitable metallurgical and mechanical characterization techniques have been applied wherever required, to support the experimental observations. Results show H900 condition gives highest yield strength and lowest tensile strain at break whereas solution annealing gives lowest yield strength and as-built condition gives highest tensile strain at break. SEM images show that H900 and H1150 condition produces brittle and ductile morphology respectively which in turn gives highest and lowest hardness value respectively.XRD analysis shows presence of austenite phases which can increase hardness at the cost of ductility. Average wear loss for H900 condition is highest whereas it is lowest for solution annealed condition. Further optical and SEM images have been taken to understand the basic wear mechanism involved.

scholarly journals Relationship Between Rockwell C Hardness and Inelastic Material Constants

2002 ◽  
Vol 124 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Akihiko Hirano ◽  
Masao Sakane ◽  
Naomi Hamada
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Strain Hardening ◽  
Yield Stress ◽  
Plastic Material ◽  
Stress And Strain ◽  
Material Constants ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Hardening Coefficient

This paper describes the relationship between Rockwell C hardness and elastic-plastic material constants by using finite element analyses. Finite element Rockwell C hardness analyses were carried out to study the effects of friction coefficient and elastic-plastic material constants on the hardness. The friction coefficient and Young’s modulus had no influence on the hardness but the inelastic materials constants, yield stress, and strain hardening coefficient and exponent, had a significant influence on the hardness. A new equation for predicting the hardness was proposed as a function of yield stress and strain hardening coefficient and exponent. The equation evaluated the hardness within a ±5% difference for all the finite element and experimental results. The critical thickness of specimen and critical distance from specimen edge in the hardness testing was also discussed in connection with JIS and ISO standards.

Photoluminescence and Plane-View Tem Studies of Epitaxial ZnSe Layers on GaAs After H2 Gas Heat-Treatment

1989 ◽  
Vol 145 ◽  
Author(s):  
Maki Sekoguchi-pl ◽  
Takashi Murase ◽  
Tsunemasa Taguchi
Keyword(s):  
Heat Treatment ◽  
Tensile Strain ◽  
Deep Level ◽  
Annealed Film ◽  
Edge Emission ◽  
Deep Acceptor ◽  
Deviation From Stoichiometry ◽  
Microstructural Defects ◽  
Plane View ◽  
Low Temperature Photoluminescence

AbstractLow-temperature photoluminescence and plane-view TEN observations have been carried out to investigate the strain and microstructural defects in MOCVD-grown ZnSe/(100)GaAs after post- growth annealing in H2gas at temperature between 350 and 500V. A 0.35 µm thick ZnSe epitaxial layer is originally under compres- sive strain, but after annealing this receives considerably tensile strain, and the neutral deep-acceptor bound exciton () line and the edge-emission band at about 2.72 eV newly appear. The observed changes are interpreted in terms of the energy down- shift of the excitonic lines and deviation from stoichiometry. The annealed film, which deteriorated as a result of generations of dislocation tangles and small loops, results in the strong deep-level emissions around 2.25 eV.

scholarly journals Investigation of a partial, inductive short-time heat treatment of thin metal sheets integrated into the forming process

2018 ◽  
Vol 190 ◽  
pp. 12008
Author(s):  
Benjamin Clausius ◽  
Petra Maier
Keyword(s):  
Heat Treatment ◽  
Strain Hardening ◽  
Sheet Thickness ◽  
Local Strain ◽  
Single Step ◽  
Thin Metal ◽  
Recrystallization Annealing ◽  
Forming Process ◽  
Metal Sheets ◽  
Short Time

Flanging is a widespread method in the sheet metal working industry to connect same or different materials by forming. Especially the sealing technology makes high demands on the flanging process: a low sheet thickness of the inner eyelet is necessary for proper sealing. The outer edges of the neck rings are mostly manufactured by shear cutting. The quality of the cut surface and the level of the local strain hardening influence decisively the limit of the flanging process by possible cracking. This paper is focused on the dependencies of these factors regarding thin metal sheets of different materials with a thickness down to 100 μm. It could be shown that strain hardening has a stronger effect on the process limits compared to the notch effect of the sheet edges when using standard values for the clearance of the shear cutting tool. Furthermore, a process is investigated with a partial inductive short-time heat treatment of the most deformed edge area. Due to the low thickness of the material and low heat capacities related thereto, it is possible to integrate a recrystallization annealing as single step into the forming process. As a result, the strain hardening can be removed from the affected zone directly between two forming steps to increase the process limits.

Plastic Collapse of Thin Internally Pressurized Torispherical Shells

1979 ◽  
Vol 101 (4) ◽  
pp. 311-320 ◽  
Author(s):  
S. K. Radhamohan ◽  
G. D. Galletly
Keyword(s):  
Strain Hardening ◽  
Yield Stress ◽  
Material Properties ◽  
Parametric Study ◽  
Companion Paper ◽  
Experimental Results ◽  
Plastic Collapse ◽  
Approximate Design ◽  
Mode Of Failure ◽  
Hardening Coefficient

The plastic collapse pressures of internally pressurized thin torispherical shells are given in the present paper. The influence of both the geometric parameters (i.e., r/D, RS/D and D/t) and the material properties (yield stress σyp and the strain-hardening coefficient) on the plastic collapse pressures were investigated. Both steel and aluminium shells were analyzed and, based on the present parametric study, approximate design equations for calculating the plastic collapse pressures are suggested. The asymmetric buckling pressures, pcr, for torispherical shells (obtained from a companion paper) are also compared with the plastic collapse pressures, pc, to determine which are the lower and, thus, control the mode of failure. In addition, the approximate design equations for pcr and pc are compared with some experimental results on small machined models; the agreement between theory and test was quite good.

scholarly journals Fiber-reinforced reactive magnesia-based tensile strain-hardening composites

2018 ◽  
Vol 89 ◽  
pp. 52-61 ◽  
Author(s):  
Shaoqin Ruan ◽  
Jishen Qiu ◽  
En-Hua Yang ◽  
Cise Unluer
Keyword(s):  
Strain Hardening ◽  
Tensile Strain ◽  
Fiber Reinforced ◽  
Reactive Magnesia

Strain rate sensitivity and strain hardening response of DP1000 dual phase steel

2018 ◽  
Vol 115 (5) ◽  
pp. 507
Author(s):  
Onur Çavusoglu ◽  
Hakan Gürün ◽  
Serkan Toros ◽  
Ahmet Güral
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Dual Phase Steel ◽  
Rate Sensitivity ◽  
Dual Phase ◽  
Significant Difference ◽  
Load Carrying ◽  
Hardening Coefficient

In this study, strain hardening and strain rate sensitivity behavior of commercial DP1000 dual phase steel have been examined in detail at temperatures of 25 °C, 100 °C, 200 °C and 300 °C, at strain rates of 0.0016 s−1 and 0.16 s−1. As the strain rate has increased, the yield strength has increased but no significant change in tensile strength and strain hardening coefficient has been observed. As the temperature has increased, the yield and tensile strength has decreased in between 25 and 200 °C but it has showed an increase at 300 °C. The strain hardening coefficient has increased in parallel with temperature increase. It has been seen that the strain rate sensitivity has not been affected by temperature. No significant difference in the hardening rate has appeared in between 25 and 200 °C, but the highest value has been calculated at 300 °C. It has been determined that the fracture behavior has occurred earlier and load carrying capacity on necking has reduced with the increase of strain rate and not significantly affected by temperature.

The Bauschinger Effect in a High-Strength Steel

1966 ◽  
Vol 88 (2) ◽  
pp. 480-488 ◽  
Author(s):  
R. V. Milligan ◽  
W. H. Koo ◽  
T. E. Davidson
Keyword(s):  
Heat Treatment ◽  
Yield Strength ◽  
Strain Hardening ◽  
Uniaxial Tension ◽  
High Strength Steel ◽  
Bauschinger Effect ◽  
High Strength ◽  
The Other ◽  
Material Structure ◽  
Permanent Strain

The object of this work was to evaluate quantitatively the Bauschinger effect in a 4330 modified steel as a function of strength level and structure as derived from variations in heat-treatment. Material having martensitic, pearlitic, and bainitic structures was studied utilizing a uniaxial tension-compression specimen. Various ways of defining the magnitude of the Bauschinger effect are explained. One is a conventional approach as suggested by Welter, the other a technique which takes strain-hardening into account. The results show the Bauschinger effect to be independent of yield strength for three different strength levels of the martensitic material. It is only mildly influenced by material structure and independent of the direction of overstrain. The Bauschinger effect increases with increasing permanent strain up to approximately 2 percent and thereafter remains essentially constant.

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