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Tailor weld blank (TWB) is preferred in different components of automobiles to reduce weight of the vehicle. However, TWBs have lower formability than sheets because of increased hardness and strength of weld region. Hence, in this work, detailed formability analysis of TWB of AISI304 is done and compared with as-received sheets along with microstructural correlation. Forming limit diagram for as-received sheet, TWBs are determined. Strain hardening exponent value of as-received sheet is 0.381, unweld region and weld region of TWB is observed to be 0.362 and 0.301, respectively. Numerical simulations were also done for predicting the FLC of TWB of AISI304 with the help of PAM STAMP 2 G solver. TWB showed lower formability than as-received sheets. Similarly, predicted FLD for TWB is almost coinciding with the experimental value. Similarly, optical micro-structure studies were also analysed for as-received sheet, unweld region and weld region of TWB, which showed fully austenitic structure with random grain orientations. At the same time, it was found that strain path chosen for FLD determination has a strong influence on microstructure evolution. [ABSTRACT FROM AUTHOR]

AbstractThe strain hardening behavior of friction stir welded AA7039 (Al-4.2Zn-3.1 Mg) alloy was explored in terms of dislocation density, crystallite size, hardening capacity, hardening exponent, and strain hardening rate. Strain hardening behavior was analyzed for base metal and friction stir welded specimens. Four different models were used to calculate the dislocation density viz., Scherrer model, uniform strain model (USM), uniform stress distribution model (USDM), and uniform strain energy distribution model (USDEM). Maximum dislocation density was obtained in base metal for all models (maximum for USM, 3.9 ×1015m−2) with a minimum crystallite size of 15.81 nm. The low dislocation density in FSW samples is due to the higher heat input in the FSW process. Strain hardening stages were shown by Kocks–Mecking type plots. Lower strain hardening capacity was obtained for BM, i.e. 0.427 as compared to FSW samples, due to the higher dislocation density of BM. It was determined that there is an inverse relationship between the strain hardening capacity and the strain hardening exponent. Strain hardening rate was higher for BM than FSW specimens, and similar results were obtained from mathematical relations that indicate the adequacy of the results. The ultimate tensile strength was 2.5% higher than the BM at a rotational speed of 1325 rpm, 35 mm/min of welding speed and 1.65° tilt angle. The maximum strength friction stir-welded specimen showed a more ductile fracture surface than the BM because the grain boundary phase disappeared or broke up in the thermomechanical affected zone. [ABSTRACT FROM AUTHOR]

Hydroforging is an innovative forming method used to form tubes with irregular cross-sections by using internal fluid pressure and axial force. Normally tube forming operations use solid mandrel to expand/bend the tube which does negative effect on tube or mandrel due to friction, buckling, and wrinkling. In this study, the tube material with various strain hardening exponents were hydroforged in a two-step numerical analysis with ramped fluid pressure and axial compression. The tube will be allowed to bulge with a ramped internal pressure and then shaped to a maximum expansion ratio by the axial compression in the shaping step. Some advanced materials exhibit the change in strain hardening exponent based on the plastic strain, the study focuses how the strain hardening exponent affects the deformation mechanics in tube hydroforging. It was found that the formability of tube during hydroforging is affected by the strain hardening exponent. The results show that tube can achieve a greater wall thickness reduction with increase in strain hardening exponent. Also, higher strain hardening exponent allowed tube to achieve a greater expansion ratio when axially compressed in the forging step. It was also observed that as the strain hardening exponent increases, the internal pressure requirements for the bulging and shaping steps decrease. The two model configurations of N01 and N02 failed from bursting and wrinkling, respectively, while every other model could form to the targeted disk-like shape. The forging step of the process showed that the die force for axial compression decreased as the strain hardening exponent increased for all successful models. [ABSTRACT FROM AUTHOR]

In the present investigation, an aluminum 7075 based hybrid metal matrix composite has been prepared by utilizing the primary reinforcement element (boron carbide with 9 %, 7 %, 5 %, 3 %, and 1 % weight percentage) and secondary reinforcement particles (silicon carbide with 1 %, 3 %, 5 %, 7 %, and 9 % weight percentage) through the well‐known stir‐casting method. Further, the tensile, hardness and Charpy impact tests were performed on the prepared composite material for mechanical properties evaluation. In addition, an attempt has also been performed to analyze the effect of reinforcement weight percentages (primary and secondary) on the strength coefficient, strain hardening rate and strain hardening exponent of the prepared composite material compositions. The results revealed that sample 1 (aluminum 7075/9 weight percentage boron carbide/1 weight percentage silicon carbide) exhibited the maximum 14.12 percent, 14.25 percent and 19.56 percentage increase in hardness, ultimate tensile strength and yield strength respectively than the matrix material. The strain hardening exponent has been increased with the increase in the weight percentage of silicon carbide. Further, the value of the strength coefficient was decreased with the increase in the weight percentage of boron carbide particles. In addition, stage III hardening was associated with the all developed composite material compositions. [ABSTRACT FROM AUTHOR]

Aluminum alloys are widely recognized as highly advantageous materials for various engineering applications, including pistons, valve components, brakes, engine blocks, and impellers. In this study, our objective was to investigate the mechanical characteristics and surface behavior of the Aluminum alloy (AlSi8Cu3). To achieve this, torsion tests were conducted to analyze the material's response to shear and high deformation, while mitigating instability phenomena. Specifically, torsion tests were performed on annealed aluminum alloy specimens until rupture, at 1/3 of the rupture, and at 2/3 of the rupture to evaluate crucial material properties, such as the modulus of Young and shear modulus. Through these tests, we also examined the hardness of the specimens and analyzed the microstructural state at both the center and periphery of the deformed sections. Additionally, we determined the hardness, microstructure, and values of the strength coefficient (K) and the strain hardening exponent (n) within the plastic domain of the alloy. Our experimental results demonstrated that increasing deformation on the specimens led to a reduction in grain size. Furthermore, this deformation resulted in a decrease in Young's modulus, attributed to the initiation of cavity coalescence. Based on our investigation, we conclude that the obtained results are excellent and hold significant implications for further research in this field. [ABSTRACT FROM AUTHOR]

Temperature rise of a specimen is a significant issue in drawing industries for wire, rod, and bar products, because an excessive increase in temperature during the drawing process can deteriorate the product quality and die life. The influence of the strain hardening exponent (n) of a wire on the temperature and strain distributions during wire drawing is investigated to understand its effect and to improve the quality of drawn wire. Finite element analysis and experiments are conducted to analyze the temperature and strain distributions of wires with n values of 0.0, 0.1, 0.5, and 1.0. The temperature increase of the wire augments as the n of the wire increases, despite the same amount of ideal plastic deformation, which is associated closely with the redundant work. The shear strain increases with the n of the specimen, which generates redundant work, leading to a high temperature rise. Similarly, drawing force increases with the n of the specimen, owing to the increase in redundant work with the n of the wire. In addition, the drawing force presents a linear relationship with the temperature rise of the wire. The drawing speed should be reduced and/or the cooling of wire and die should be strengthened during wire drawing, with increasing n value of the wire, because product quality and die wear are highly associated with the temperature rise of the wire in the deformation zone. [ABSTRACT FROM AUTHOR]

Artillery projectile 155mm high explosive (HE) extended range full bore boat tail (ERFB BT) and its components experience a high pressure loading of the propellant during gun launch. Mechanical properties of an engineering material are measured using quasi-static tensile test at room temperature. The materials of the projectile and its components are expected to survive time dependent propellant pressure loading inside the gun, which lasts for few microseconds. To investigate dynamic mechanical properties of the projectile and its components at medium strain rates and elevated temperature, the experimental analysis is undertaken. This research paper aims to examine the effect of medium strain rates and elevated temperatures on flow properties of the materials used in the projectile. The uniaxial tensile tests at the medium strain rates between 0.01 s-1 to 1 s-1 and at elevated temperatures ranging between 150 °C to 500 °C are performed separately. The Considére criterion was applied to evaluate strain hardening exponent of the materials. Values of strain hardening exponents of shell body and boat tail materials are less than that of driving band material. Strain rate sensitivity of the materials is observed to be very low, thus indicating a good resistance to plastic deformation. The yield strength and true yield strength of the materials fall with increase in temperature. [ABSTRACT FROM AUTHOR]

This study describes a higher strength of drawn twinning-induced plasticity (TWIP) steel wire compared with its strain hardening exponent (n) and reveals that the outstanding strain hardening rate of TWIP steel was strongly related to the twinning behavior rather than dynamic strain aging based on a comparison of deformation behaviors between the tension and wire drawing in pearlitic, ferritic, and TWIP steels. The ratio of a hardening rate (h) of a drawn wire to the n in a tensile test, referred to as h/n, of ferritic, pearlitic, and stainless steels was approximately 1371 MPa, whereas that of the TWIP steel was approximately 2620 MPa. This means that the high strength of the drawn TWIP steel wire cannot be explained by n value alone. Compared with the tensile-strained specimen, the drawn wire exhibited a higher twinning rate, indicating that the high h/n value of the TWIP steel was related to the twinning behavior. The higher twinning rate of the drawn wire was attributed to the combined effects of the complex stress states owing to the die geometry and the directional nature of the deformation twinning. This means that the strength of TWIP steel can be easily improved using the general bulk forming processes, particularly complex forming processes. [ABSTRACT FROM AUTHOR]

Austenitic Stainless-Steel grade 316 L is one of the huge ASS grades used in different industry sectors, nuclear power plants and pharmaceutical applications. Because of these various applications at high temperature, it is a must to know its properties at different conditions. The present work focued on to improve the mechanical properties, like ultimate tensile strength (UTS), yield strength (YS), strain hardening exponent (n) and % elongation. These are assessed depending on the test information obtained from the uniaxial isothermal tensile tests. A total of 27 tests based on fullfactorial designed to performe temperature at 750°C, 825°C and 900°C, three orientations (0, 45, 90) degrees to the rolling direction and strain rates (0.1, 0.01 and 0.001 s−1) were chosen. From the experimental results, it is clear that temperature and strainrate has a significant effect on material properties. With the rise in temperature, % elongation increases and a considerable decline in strength was observed. The scanning electron microscope and microstructural analysis was carried out at elevated temperatures to type of fracture. From ANOVA analysis, it was observed that temperature for UTS, combine temperature * strain rate for YS and strain rate*strain rate for % elongation with 85.889%, 38.93 and 65.73% contribution respectively. [ABSTRACT FROM AUTHOR]

Temperature rise of a specimen is a significant issue in drawing industries for wire, rod, and bar products, because an excessive increase in temperature during the drawing process can deteriorate the product quality and die life. The influence of the strain hardening exponent (n) of a wire on the temperature and strain distributions during wire drawing is investigated to understand its effect and to improve the quality of drawn wire. Finite element analysis and experiments are conducted to analyze the temperature and strain distributions of wires with n values of 0.0, 0.1, 0.5, and 1.0. The temperature increase of the wire augments as the n of the wire increases, despite the same amount of ideal plastic deformation, which is associated closely with the redundant work. The shear strain increases with the n of the specimen, which generates redundant work, leading to a high temperature rise. Similarly, drawing force increases with the n of the specimen, owing to the increase in redundant work with the n of the wire. In addition, the drawing force presents a linear relationship with the temperature rise of the wire. The drawing speed should be reduced and/or the cooling of wire and die should be strengthened during wire drawing, with increasing n value of the wire, because product quality and die wear are highly associated with the temperature rise of the wire in the deformation zone.

The investigation into the circumferential mechanical properties of tubular materials has been receiving increasing attention, since the tube hydroforming process has been used in the tubular materials forming field, because the circumferential mechanical properties have a significant effect on the hydroformability of the tubular materials. In the present study, a method for evaluation of the circumferential mechanical properties of the tubular materials with the flaring test was proposed. The expressions for the yield stress, strain hardening coefficient and exponent values of the tube were successfully derived based on the geometrical and mechanical relationships in the tube flaring test. To verify the reliability of this method, the calculated results of the yield stress, strain hardening coefficient and exponent values, obtained from the newly proposed method, were compared to the ones obtained with the conventional tensile tests. It was found that the method proposed in the current study is reliable, with high accuracy. The method is appropriate to evaluate the circumferential mechanical properties of the tubular materials. [ABSTRACT FROM AUTHOR]

The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10−3 s−1 and 2.1–3.3 × 103 s−1, respectively. High-strain compression was conducted using a Split Hopkinson Pressure Bar (SHPB). The details of the deformation mechanism were evaluated based on the analysis of the deformation hardening curves using the strain hardening exponent concept developed for titanium alloys in tension conditions. The used approach allowed us to identify the stages of plastic deformation observed and the controlling phase in deformation of two-phase alloy through the assessment of the strengthening index, n. It has been found that three deformation stages can be identified in quasi-static conditions. However, when the alloy is compressed at a high strain rate, the third deformation stage does not develop due to the high process rate. Further analysis of deformation curves reveals the leading role of the β-phase under the quasi-static conditions and the essential contribution of the second, α-phase, at a high compression rate. The findings on the deformation mechanism based on the analysis of hardening curves were supported by a detailed structural study. [ABSTRACT FROM AUTHOR]

The main goals of this work were to manufacture novel Al–Zn extruded alloys by varying the Zn content (0, 10, 20, 30 wt%), investigate the microstructural evolutions, hot deformation, and work hardening behaviour by hot compression test at different temperatures (25 °C, 75 °C, 150 °C, 225 °C, 300 °C). Al–20Zn alloy microstructure revealed α-Al and uniform distribution of (α + η) phases, coherent (α + η) crystals in GBs with casting defect-free surfaces, and effective interactions of pinning dislocations which led to improve mechanical performance of Al–20Zn alloy, as compared to the other alloys. The observed engineering stress–strain curve results revealed the decrease of stress with increasing of temperature due to flow softening, dynamic recovery and dynamic recrystallization. These results displayed also an increase of stress value with increasing of Zn content due to the precipitation of high density (α + η) phase in the matrix and GBs, increasing of forest and mobile dislocations density with strain fields, and the formation of fine dendrites. Work hardening rate (WHR) of extruded samples displayed three stages: stage I, WHR decreased slightly with increasing of temperature up to 75 °C and decreased drastically from 75 °C to 300 °C due to softening; stage II, WHR maintained constant due to balance between dislocation generations and dislocation annihilation; stage III, WHR slightly increased due to strain hardening of (α + η) phase. WHR was observed to increase considerably with increasing of Zn content due to the formation and dispersion of high density of (α + η) phase in the Al matrix and GBs. Deformation micro-localization in terms of different characteristics was examined and reported on the deformed samples after hot-compression test through SEM micrographs. [ABSTRACT FROM AUTHOR]

The Al-6063/Graphite composite was processed by the stir casting technique. The graphite was copper-coated using a cementation process and introduced into the matrix at 2.5, 5, and 7.5 wt%. The microstructure and the hardness of the composite were examined. The micrographs showed better particle distribution for the graphite reinforcements up to 5 wt%. Further increment resulted in inhomogeneous particle distribution and increase in % void content. The uniaxial compression test was performed to investigate the plastic flow properties. It was observed that an increase in the graphite reinforcement decreased the flow strength. However, the true fracture strain to failure increased. Furthermore, the effect of graphite reinforcement on the friction factor 'm' was analyzed by a ring compression test. The test was performed at various temperatures from 373 to 673 K in the interval of 100 K, including the ambient temperature. It was observed that the graphite reinforcement had a considerable effect on reducing the friction factor during deformation, up to 473 K. [ABSTRACT FROM AUTHOR]

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Austenitic Stainless Steel 316 L grade has wide applications in industries like pharmaceutical, chemical, petrochemical, medical equipment, and many specific subzero temperature products. These subzero applications are increasing in modern-day products to solve many issues like Natural gas storage and transport and many more. It is an ideal material for these applications due to its superior properties at these operating temperatures. In the present investigation tensile tests for ASS316 L material is conducted by considering the various parameters like different temperatures (room temperature(RT), 0°C, −25°C, −50°C) along with different orientation (0°,45°,90°), and crosshead speeds (3, 5 and 7 mm/min). The temperature variation was achieved by regulating the liquid CO2 cylinder connected using a pipe system to the closed furnace of the Universal Testing Machine setup is electronic controlled system. The output data were used to analyse the Mechanical Characteristics of the material. Then the fractured specimens at the room temperature and sub-zero temperatures were studied and analysed the failure modes in the material for the above changing variables. It was observed that the failure mode is changing from a ductile fracture to brittle when decreasing the temperature below zero degrees centigrade as predicted. [ABSTRACT FROM AUTHOR]

Isothermal compression tests are conducted using a thermomechanical simulator at a constant strain rate during deformation temperature range of 850 to 950 °C and strain rate range of 0.001-10 s - 1 to study the flow behavior of Ti17 alloy with initial basketweave microstructure in β forging process. The strain rate sensitivity exponent m and strain hardening exponent n are calculated, and the strain-compensated constitutive model of flow stress using hyperbolic sine-based Arrhenius model is constructed. The results show that the strain rate sensitivity exponent m is greater than 0.3 when the strain rate is low in the range of 0.001-0.01 s - 1 , and reaches its maximum at 900 °C; the component is less than 0.3 at high strain rate range of 0.1-10 s - 1 , and it is slightly lower at 850-900 °C compared with at 920-950 °C. The strain hardening exponent n monotonously decreases with the increase in true strain at strain rate of 0.001 s - 1 , while for strain rate in the range of 0.01-10 s - 1 , it decreases with the increase in strain when the true strain is less than 0.3 but does not show significant change when the true strain is greater than 0.3. The established strain-compensated flow stress constitutive model has high prediction accuracy with average absolute relative error (AARE) of 5.32% and correlation parameter R of 0.993. The model can thus be used to provide theoretical guidance for selecting β forging process parameters, and also provide the basic data for finite element simulation of β forging process of Ti17 alloy. [ABSTRACT FROM AUTHOR]

A proper understanding of material mechanical properties is important in designing and modelling of components. As a part of a study on the structural integrity, the Digital Image Correlation technique was used to obtain the full-field strain distribution during a tensile test of the specimens. The displacement maps were analyzed using Matlab scripts to compute local stress-strain variations. Consequently the local proof stress values were extracted. In this study, the local extraction of the elastic and plastic properties of Al6061 alloy has been carried out using both the uniform stress method and the virtual fields method involving digital image correlation technique. In uniform stress methodology, full range stress–strain curves are obtained using the whole field strain measurement using Digital Image Correlation. The parameters investigated are Young's modulus, Poisson's ratio, yield strength, strain hardening exponent and strength coefficient. Recently, the virtual fields method is gaining a lot of popularity in domain characterization as it is robust, accurate and faster. Young's modulus, Poisson's ratio, yield strength, strength coefficient and strain hardening exponent are the parameters extracted using both uniform stress method and virtual fields method. The parameter variation obtained by both uniform stress method and the virtual fields method compares very well. Due to various advantages associated with virtual fields method, it is generally recommended for material mechanical properties extraction.

An attempt has been made to model strain hardening parameters for sintered iron and iron-0.4% carbon steel preforms that are subjected to cold upsetting. The aspect ratios and lubricants are also considered as variables apart from the compositions. The 23 factorial design has been considered to design the experiment and subsequently Yate’s algorithm is utilized to construct the model. The model has further been refined using analysis of variance. The final model adequacy is determined through correlation coefficient which is predicted to follow near unity. Thus the mathematical model can be utilized to predict strain hardening parameters such as strength coefficient, K, and strain hardening exponent, n, subsequently to design the process parameters to inculcate the required strain hardening characteristics within the range of process parameters specifications that are considered in the present investigation.

The deformation behavior of the selected stainless steels (UNS S31603, UNS S32205, UNS S32550 and UNS S32760) was evaluated at strain rates ranging between 10-2 and 10-7 s-1. Microstructural evaluation was conducted using optical and scanning electron microscopy, electron backscattered diffraction and x-ray diffraction. The total strain at fracture remained approximately constant as the strain rate increased from 10-7 to 10-3 s-1. Further increase in strain rate above 10-3 s-1 resulted in relatively lower strain. The strain rate sensitivity of each steel decreased with increasing strain. Also, the strain hardening rate and exponent of the alloys increased with decreasing strain rate. Post-deformation microstructure evaluation on UNS S31603 specimens showed slip, twinning and martensitic transformation, while the duplex alloys exhibited slip, twinning with less noticeable martensitic transformation. Fractographic examination after tensile test indicates an increase in dimple diameter with strain rate and subsequent decrease in dimple density. [ABSTRACT FROM AUTHOR]

This paper discusses the various joining methods with faying surface modifications used to join AA6063 and AISI304L dissimilar alloys by Rotary Friction Welding (RFW) process at different welding conditions mainly with friction pressure (FP), upset pressure (UP) and friction time (FT). This paper also studies the tensile behavior of the welded joints. The fabricated dissimilar joints were tested using universal testing machine against tensile load, and the mechanical properties of all 30 nos. of weld joints like elongation (%), strength coefficient (K), strain hardening exponent (n), strain hardening rate (TS/YS ratio), shear strength, etc. were calculated from the tensile testing results and plotted here with a standard error bar. Hollomon's equation is considered here to study the stress and strain hardening relation and Von Mises yield criterion is considered for shear and yield stress correlation. Total elongation is also calculated from the initial and final length obtained during the tensile test. Since fracture ductility of the joints depends on the stress, strain, ' K ' and ' n ' values, it is important to study these mechanical properties and how the tensile results can be used for their estimation is detailed in this paper. The faying surfaces influence the mechanical properties as well. [ABSTRACT FROM AUTHOR]

The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10−3 s−1 and 2.1–3.3 × 103 s−1, respectively. High-strain compression was conducted using a Split Hopkinson Pressure Bar (SHPB). The details of the deformation mechanism were evaluated based on the analysis of the deformation hardening curves using the strain hardening exponent concept developed for titanium alloys in tension conditions. The used approach allowed us to identify the stages of plastic deformation observed and the controlling phase in deformation of two-phase alloy through the assessment of the strengthening index, n. It has been found that three deformation stages can be identified in quasi-static conditions. However, when the alloy is compressed at a high strain rate, the third deformation stage does not develop due to the high process rate. Further analysis of deformation curves reveals the leading role of the β-phase under the quasi-static conditions and the essential contribution of the second, α-phase, at a high compression rate. The findings on the deformation mechanism based on the analysis of hardening curves were supported by a detailed structural study.

The investigation into the circumferential mechanical properties of tubular materials has been receiving increasing attention, since the tube hydroforming process has been used in the tubular materials forming field, because the circumferential mechanical properties have a significant effect on the hydroformability of the tubular materials. In the present study, a method for evaluation of the circumferential mechanical properties of the tubular materials with the flaring test was proposed. The expressions for the yield stress, strain hardening coefficient and exponent values of the tube were successfully derived based on the geometrical and mechanical relationships in the tube flaring test. To verify the reliability of this method, the calculated results of the yield stress, strain hardening coefficient and exponent values, obtained from the newly proposed method, were compared to the ones obtained with the conventional tensile tests. It was found that the method proposed in the current study is reliable, with high accuracy. The method is appropriate to evaluate the circumferential mechanical properties of the tubular materials.

Normalization method (NM) is a practical method for determining the J–R curves and fracture toughness of steels. There is some concern, however, about the performance of this method on steels with small strain hardening exponent and yield strength owing mainly to the assumption of infinite strain hardening exponent. This paper intends to analytically modify the NM by removing this assumption and incorporating the strain hardening in calculating the blunting corrected crack length. This modification enables the NM to be applied to steels with small strain hardening exponent and yield strength. Experiments are undertaken to verify the modified NM (CNM). A comparison of fracture toughness determined by CNM with that by the unloading compliance method and NM corroborates the improved accuracy of the developed CNM. The paper concludes that the developed CNM overcomes the deficiency of the NM for steels with small strain hardening exponent and yield strength. [ABSTRACT FROM AUTHOR]

Engineering tensile stress–strain curves for metallic materials typically show two different behaviours, namely, with Luder's strain and without Luder's strain. Luder's strain is more common for ductile materials, whereas high‐strength steels deform without Luder's strain. Usually, the stress–strain curves of ductile steels exhibit ultimate load where necking starts to develop. On the other hand, steels with low ductility exhibit monotonic increase of the applied load till failure without necking. Recently, Kamaya proposed a method to estimate the Ramberg‐Osgood relationship parameters for true stress–strain curves on the basis of conventional yield and ultimate strengths. This method can be not accurate enough for ductile materials exhibiting Luder's strain. Hence, a more general procedure for the materials exhibiting Luder's strain is proposed. In addition, an inverse method for assessing an 'apparent ultimate tensile stress' (akin to the ultimate stress of ductile materials at point of zero slope) for materials with low ductility (due to quenching or carburizing) is suggested. [ABSTRACT FROM AUTHOR]

Austenitic Stainless-Steel grade 316L is one among the significant ASS grades which is most used in various industry sectors. It has excellent corrosion resistance in ordinary atmospheric and in more arduous environments such as saltwater. Whilst performing well when exposed to relatively high temperatures, this grade of ASS also maintains its strength and toughness at sub-zero temperatures, making this an excellent choice for various applications in industrial sectors such as Marine, general construction and water treatment. Therefore, present study focused on evaluating the mechanical properties, ultimate tensile strength (UTS), yield strength (YS) and strain hardening exponent (n) are evaluated based on the experimental data obtained from the uniaxial isothermal tensile tests performed at an interval of −25°C from 0°C to −50°C and at three orientations 0, 45, 90 degrees to the rolling direction and cross-head velocity 3, 5, 7 mm/min were chosen. Total of 27 experiments have been planned based on design-of-experiments. A mathematical model for the prediction of UTS, YS and n was developed using process parameters such as temperature, orientation and cross-head velocities. Results have shown that mechanical properties can be predicted with a reasonable accuracy within the range of process parameters considered in this study. [ABSTRACT FROM AUTHOR]

The influence of room temperature flat rolling on microstructure, mechanical properties, and shape change in twinning-induced plasticity (TWIP) steel wire has been investigated to understand the deformation behaviors of flat rolled wire in TWIP steel and to apply TWIP steels to flat rolled wire products. Numerical simulation, hardness test, and EBSD techniques were used to analyze the distribution of strain, mechanical properties, and microstructure of flat rolled TWIP steel wire. The shape of flat rolled TWIP steel wire was also evaluated and compared with plain carbon steels having low strain hardening rate. A very different behavior of hardness, strain, twinning, and KAM value was observed with area of flat rolled wire due to the different stress state and strain with area of wire. The center area had the maximum twin density, KAM value, effective strain, and hardness; whereas free surface area had the minimum values. The hardness inhomogeneity factor (HIF) along the horizontal direction was much higher in comparison with that of the vertical direction. The maximum HIF value occurred at the specific reduction in height, i.e., 27%. This means HIF value gradually increased and then decreased with reduction in height, which is inconsistent with the results of plain carbon steel and Cu wire. The lateral spread and width of contact area of flat rolled TWIP steel wire were lower than those of plain carbon steels, indicating that material properties such as strain hardening exponent are crucial parameters that influence the shape of flat rolled wire products. [ABSTRACT FROM AUTHOR]

In order to derive a method for estimating the strength coefficient and strain hardening exponent of steel, the performance parameters of 86 kinds of steel taken from American Iron and Steel Institute (AISI) Bar Steel Fatigue Database were examined and equations that related the strength coefficient and strain hardening exponent to the ultimate tensile strength and yield strength were developed. Correlations from the literature among the strength coefficient, strain hardening exponent and other monotonic tensile properties were also examined and compared to the relationships proposed in this study using the data of 86 kinds of steel. The proposed method was shown to be better used to estimate the strength coefficient and strain hardening exponent. [ABSTRACT FROM AUTHOR]

This paper presents an experimental estimation of the ductile behavior and low-cycle fatigue life for widely used structural steels AISI 1020 and AISI 1030 based on continuum damage mechanics approach. This method identifies the deterioration in stiffness of a material arising from micromechanisms of formation, growth, and coalescence of microvoids. This helps the characterization of the ductile flow behavior of metals through a damage variable D, evaluated via load–unload cyclic tensile test. The influence of strain hardening exponent, commonly treated as a constant in ductile flow characterization, is also explored in the current investigation. Its determination uses the Hollomon constitutive relation. Estimated D at different strain levels defines the corresponding effective stress. Application of this stress to the strain equivalence theory then enables the prediction of the stress–strain curve. The model-based results closely approximate the experimental stress–strain curve up to the onset of necking. The agreement of experimental results for fatigue life of the materials from low-cycle fatigue tests with damage-based low-cycle fatigue model demonstrates the correctness of the experimental findings. The damage-based model additionally helps in the prediction of microcrack nucleation and crack propagation life separately. Fractographic examinations of test specimen exhibit usually observed morphology of involved failure mechanisms. The present study emphasizes the experimental means of damage-based ductile flow assessment involving strain hardening exponent term and also the low-cycle fatigue life estimation. The significance of varying strain hardening exponent is further expressed in terms of the corresponding damage magnitude. The material data obtained from this study depicts the damage state at different levels of plastic strain that may serve as a useful information for metal-forming process design. [ABSTRACT FROM AUTHOR]

A proper understanding of material mechanical properties is important in designing and modelling of components. As a part of a study on the structural integrity, the Digital Image Correlation technique was used to obtain the full-field strain distribution during a tensile test of the specimens. In this study, the elastic and plastic properties of Al6061 alloy has been carried out using both the uniform stress method and the virtual fields method involving digital image correlation technique. In uniform stress methodology, full range stress-strain curves are obtained using the whole field strain measurement using Digital Image Correlation. Recently, the virtual fields method is gaining a lot of popularity in domain characterization as it is robust, accurate and faster. Young's modulus, Poisson's ratio, yield strength, strength coefficient and strain hardening exponent are the parameters extracted using both uniform stress method and virtual fields method. The parameter variation obtained by both uniform stress method and the virtual fields method are compared very well. The Virtual Fields Method provides a theoretically sound basis for developing robust optimization constructs to estimate local material properties, including spatial variations in hardening exponent and strength coefficient. Due to various advantages associated with virtual fields method, it is generally recommended for material mechanical properties extraction. [ABSTRACT FROM AUTHOR]

A Fe-0.20C-1.49Mn-1.52Si-0.58Cr-0.05Nb (wt%) steel was treated by a novel quenching-partitioning-tempering (Q-P-T) process and traditional quenching and tempering (Q&T) for comparison, respectively. The researches of the mechanical properties and forming limit diagrams reveal that Q-P-T martensitic steel has more retained austenite (10.8%) than the Q&T martensitic steel (less than 3%), which makes Q-P-T martensitc steel possess higher strain hardening exponent and true uniform elongation than the Q&T martensitic steel. The high value of hardening exponent (n) and true uniform elongation (εu) stem from the low initial dislocation density in martensitic matrix in Q-P-T martensitic steel before deformation and the high strain hardening rate and dislocation absorption by retained austenite (DARA) effect of retained austenite during deformation. Moreover, the n, or the εu, is a most important parameter in all the apparent parameters affecting the formability of metal sheets, and this conclusion is of practical importance in the comparison of several steels' formability. [ABSTRACT FROM AUTHOR]