Plastic Work Research Articles

Plastic temperature-dependent constitutive modeling of pure aluminum diaphragms at large strains by using bulge test

A plastic temperature-dependent constitutive model is developed for 0.05 mm thickness pure aluminum diaphragms at large strains by using bulge test method. Rupture strain of the material is recorded below two percent according to tensile tests. In order to achieve the material behavior at larger strains, an own bulge test apparatus is used to extract equi-biaxial stress–strain curves at different temperatures, i.e. from room to 150 °C. Effective stress–strain behavior is then computed via a transformation scheme using the plastic work definition as well as the room temperature uniaxial stress–strain curve. It is illustrated that the Johnson–Cook constitutive model is not able to capture this stress–strain behavior. Thus, a modified Johnson–Cook model is developed in which the strain hardening is assumed to be temperature-dependent accompanying by a novel thermal softening relation. Using the Least-square method as well as the Ant colony optimization algorithm, the material parameters of the both models are calculated. It is depicted that the new model follows the material behavior more precisely than the Johnson–Cook model. The new model is then numerically implemented into finite element software via a user subroutine. In order to compare the accuracy of both models in capturing the hot bi-axial deformation of pure aluminum, an experiment is performed and numerically simulated.

Finite-element simulation of multi-axial fatigue loading in metals based on a novel experimentally-validated microplastic hysteresis-tracking method

We propose a new approach to the prediction of multiaxial fatigue with proportional and non-proportional loading based on a recently developed three-dimensional small-strain microplasticity-based constitutive theory. The core idea of the theory is to incorporate pre-full-yield microplastic deformations in a computationally efficient way. Fatigue life is then correlated to the accumulated (micro)plastic work, which is obtained from the total plastic dissipation. The constitutive parameters required are calibrated using just a monotonic stress-strain curve determined from a simple compression test experiment together with a low cycle uniaxial fatigue experiment. The resulting three-dimensional constitutive model has also been implemented into the Abaqus/Explicit finite element program through a vectorized user-material subroutine interface with a fully-implicit, unconditionally-stable and robust time integration scheme. Using the suitably-calibrated constitutive model, a series of uniaxial and multiaxial stress- and strain-based, constant-amplitude fatigue finite element simulations have been conducted to compare with the physical experiment data from the literature. It is shown that the developed theory and its finite-element implementation (which have fewer parameters than cycle counting based methods) are able to better predict the experimental fatigue life under multiaxial proportional or non-proportional loading conditions.

Sex differences in the effect of diet, obesity, and exercise on bone quality and fracture toughness.

Bone fragility and obesity are both diseases that are multifactorial in etiology and pathology. The contributing role of high fat diet (HFD) versus energy overconsumption on bone health is controversial. Exercise is often prescribed for improving bone health, but it is unclear whether HFD or overconsumption influences skeletal adaptations to exercise. Female and male Wistar rats were fed HFD or low fat diet (LFD) for 10weeks, starting at 8weeks of age. Within HFD, rats were labeled Obesity-Resistant (OR) or Obesity-Prone (OP) based on weight and fat gain. Within each diet and phenotype group, rats were randomized to treadmill exercise or sedentary control (SED) for the final 4weeks. Femurs were assessed for fracture toughness. Cortical lamellar and nonlamellar bone microscale material behavior and chemistry were assessed using nanoindentation and Raman spectroscopy. Female bones had higher fracture toughness and mineral: matrix ratio than male bones. Diet and energy overconsumption affected bone characteristics in a sex-dependent manner, where the divergence between OP and OR in response to HFD occurred more rapidly in males. Diet composition, in general, had a stronger effect on bone quality than overconsumption. HFD dramatically decreased bone size and lamellar mineral:matrix compared to LFD. Effects of short-term exercise training on microscale tissue properties were generally more robust with LFD. Exercise enhanced the contrast between lamellar and nonlamellar bone for nanoindentation modulus but decreased this contrast for plastic work. Our data demonstrate the complexities in the relationship between diet and obesity and highlight the importance of addressing both aspects when characterizing bone quality and fracture resistance.

Dynamic shear behaviors and microstructural deformation mechanisms in FeNiAlC dual-phase high strength alloy

Adiabatic shear band (ASB) is a common failure mechanism of metals and alloys under high strain rate dynamic loading. The hat-shaped samples of Fe-24.86Ni-5.8Al-0.38C dual-phase steel with different microstructures were impacted by the Hopkinson pressure bar device to investigate their dynamic shear behaviors and microstructural deformation mechanisms. The coarse grained (CG) structure after solution treatment was subjected to cold rolling (CR) in order to obtain various microstructures. The evolution of microstructure during dynamic shear deformation was extensively studied using transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results revealed that the FeNiAlC dual-phase steel has excellent dynamic shear properties with dynamic shear strength of 1.3 GPa and uniform dynamic shear strain of 1.5. The dual-phase steel was found to be composed of austenite phase (γ) and around 20% martensite phase (α) before deformation. The deformation process was found to be dominated by dislocations slip and twinning. Moreover, martensite transformation was found to be suppressed due to the high strain rates. ASBs were observed to be formed in all samples with various microstructures after impact, and dynamic recrystallization was found to occur with formed ultra-fined grains of about 300 nm and without transformation in ASBs. For the width of ASBs, the theoretical result (about 12.3 μm) was found to be in good agreement with the experimental value (about 14.6 μm) in CR samples. However, the measured width of ASBs was found to be about 15.8 μm, which is far smaller to the calculated value (about 30 μm) in CG samples. This may be attributed to the incompletely adiabatic conditions in CG samples. The adiabatic temperature rise due to the plastic work was found to be about 720 K (for CG sample) and 190 K (for CR sample). Through the analysis of the experimental results and the theory of the thermoplastic model, it can be concluded that the adiabatic temperature rise is not the only factor for ASB formation in the course of impact loading, and the localized deformation induced microstructure evolution in materials should also be considered.

Compaction behaviour of mannitol-cocoa powder mixtures and their resulting tablet strength and disintegration characteristics

Cocoa powder is an important ingredient in the confectionery industry and, mannitol is an alternative sugar alcohol. In this work, mannitol powder was mixed with cocoa powder and compacted into tablet form via the uniaxial die compaction process. The frictional, compaction, tablet mechanical and disintegration properties were studied due to their importance in characterizing the behaviour of the tablets during processing and its final product characteristics at varying mannitol contents. The composition of mannitol in the mannitol-cocoa tablet varied at 95% w/w, 50% w/w and 5% w/w, while pure 100% w/w mannitol and cocoa tablets were set as controls. The compaction pressures used in making the tablets varied at 37.67 MPa, 75.34 MPa, 113.01 MPa, 150.68 MPa and 188.35 MPa. The compaction behaviour of the powder during the compaction process was evaluated using the plastic work and the maximum ejection stress values. The tablet strength was determined using the tensile strength method and tablet disintegration study was also conducted. The results showed that the increase in the compaction pressures increased the plastic work, maximum ejection pressure, tablet strength and also its disintegration time. The tablet formed having 95% w/w mannitol composition exhibited the highest plastic work value of 10.32±0.01 J, highest maximum ejection pressure value of 4.4±0.06 MPa, highest tensile strength value of 1.06±0.04 MPa and shortest disintegration time of 171±51 s amongst the three different mannitol compositions studied. Meanwhile, the effects of mannitol composition in the tablet on these observed responses were also dependent upon the compaction pressures used during tablet formation. In conclusion, the addition of mannitol improved the tablet strength and shorten the disintegration time in the experimental range employed in this study.

Particle size, compaction characteristic and tablet strength of spray-dried fermented jackfruit pulp - microcrystalline cellulose binary powder mixture

The tableting properties for fermented spray dried jackfruit (FJP) and microcrystalline cellulose (MCC) powders were studied. 25% FJP + 75% MCC, 50% FJP + 50% MCC and 75% FJP + 25% MCC binary powder mixtures were compacted into tablet form at various compaction pressures ranging from 15.1 to 73.8 MPa. The properties were compared to pure FJP and MCC tablets. The addition of MCC resulted in a higher particle size and the increased in the plastic work of the tablet. The best ratio of FJP-MCC binary tablet was found to be at 25% FJP + 75% MCC where the tablet showed the highest tensile strength. In conclusion, the addition of MCC to FJP improved the compaction characteristics and the tablet mechanical strength.

The evolution of energy balance in titanium alloy Ti-0.8Al-0.8Mn in cyclic deformation mode

The present work is devoted to the experimental and numerical assessment of energy balance in titanium alloy Ti-0.8Al-0.8Mn in cyclic deformation mode. According to the thermodynamic theory of strength, the measure of damage is internal energy stored in material as a result of deformation. In this work stored energy was determined experimentally as a difference between plastic work and heat dissipation. It was shown that stored energy rate slows down when approaching the moment of damage. The numerical simulation of energy balance during cyclic deformation has shown satisfactory agreement with the experimental data.

Determination of acrylic sheet fracture toughness using EWF approach

In characterizing the plain stress resistance, the concept of the essential fracture work (EWF) is applied for ductile polymers and associated structures. A basic specimen preparation, simple data reduction processes, and easy testing contribute to the comprehensive application of the EWF. This approach is the way of splitting the fracture-associated energy into two sections. In its internal fracture process, critical fracture works and various mechanisms consume plastic work in outward of the plastic region. The crucial function of crack propagation fractures is evaluated in the present geometry of the work test, namely the(DENT) and the SENT specimens. Where DENT is “double-edged notched tension” and SENT is “single-edged notched tension”. The novel approach is to measure the precise fracture work in profoundly double-edged samples as a function of ligament length. This sort of information is further checked empirically to eliminate the plastic fracture work and allows for the ligament-length function of the critical fracture. These claims are applied to assess the EWF by extrapolating critical fracture work to zero-ligament length.

Features of the Continuous Casting of Small-Section Billets from Copper-Based Alloys

We present a survey of the main specific features of the continuous casting of billets of copper-based alloys with small cross sections. It is possible to significantly increase the efficiency and reduce the cost of production of lengthy semifinished products made of nonferrous alloys either by replacing the process of deformation by continuous casting or by significantly decreasing the cross sections of the billets intended for plastic metal working. It is shown that, for the major part of alloys, the process of upward continuous casting has numerous technological, economic, and metallurgical advantages as compared with other procedures of drawing. We also describe the regularities of solidification of the billets and formation of defects in the course of upward continuous casting, the specific features of design of the mold, the requirements to the properties of the graphitic jacket of the mold, and the characteristics of the modes of casting depending on the properties of the alloys.

Theoretical Analysis of Bulletproof Capability of Multilayer Ceramic Composites Subjected to Impact by an Armor Piercing Projectile

Inspired by the theories of Tate and Zaera, a theoretical analysis model including the erosion of the projectile, the cracking of ceramic composites, and the deformation of metal backplate was established in this study to investigate the bulletproof capability of the ceramic composites under impact by an armor piecing projectile (AP). The analysis results were verified by ballistic tests. As for the ceramic composites, the volume of the cracked ceramic conoid and the change in the compressive strength were included. Regarding the deformation of the metal backplate, the plastic deformation work, the external work, and the conservation of kinetics were considered. Based on the thickness of the target plate, failure modes were separated into the plug type and the petal type. The ordinary differential equation solver of MATLAB, ode45, was adopted to solve relevant ordinary differential equations. In this study, the powder metallurgy was used to produce the Al2O3/ZrO2 multilayered ceramic composites of three layers; each layer was 3 mm in thickness. The ceramic composites were paired with a backplate made of 6061‐T6 aluminum alloy with a thickness of either 1 mm or 4 mm. The ballistic tests were executed by using 0.30″ AP projectiles to impact the specimens. The results from theoretical model and ballistic tests were compared and shown consistent in the field of residual velocity, residual bullet mass, and the failure modes of the metal backplate.

Improvement of nonmonotone deformation technology in plastic metal working

The production of semi-finished products made of refractory metals is considered. The advantage of parts production using combination of two types of straining with change in the straining direction: direct extrusion and equal-channel pressing is shown. The experimental investigation data of pure and simple shear for the semi-finished products processing made of tungsten and molybdenum are presented. Requirements for the tool providing diagonal flow and angular straining are formulated based on the analysis of the stress-strain state of the processes of axial symmetric extrusion and simple shear of plastically inhomogeneous body. Effectiveness evaluation of the combination of various types of fixtures and the rational sequence for using of diagonal flow and angular pressing is given. Experimental devices for practical application of the proposed technology are developed.

Development of In-plane Biaxial Compression Test Method for Thin Sheet and Investigation of SD Effect under Biaxial Stress Condition

The accuracy of the finite element simulation (FE simulation) of press forming has improved as a result of sophisticated material modelling using data of the various experiments such as uniaxial compression, biaxial tension, and in-plane cyclic loading tests. However, the biaxial compression test of sheet material has never been reported lowing to the difficulty in buckling suppression, and differences between material behavior under biaxial tension and that under biaxial compression have not yet been discussed. In this paper, the biaxial compression test of sheet material using special tools to suppress buckling and a specimen shape that leads to uniform deformation in the measurement area is proposed mainly on the basis of FE simulation. The special tool has a urethane plate where the tool come into contact with the measurement area of the specimen to prevent damage of the strain gauges. Absolute values of compressive stresses during plastic work measured by the biaxial compression test were larger than tensile stresses during the same plastic work measured by the biaxial tension test. Similar results observed in uniaxial tension and compression tests are known as the strength differential (SD) effect.

The justification of interaction of fruits with the rolling-in device of a combine-harvester for harvesting cucurbit crops

The role of cucurbit crops in the life of man has been studied and presented. The process of interaction between the rolling-in device of a combine-harvester and a fruit, as well as the process of hitting water-melons into different surfaces, have been considered. The diagram of the distribution of velocities when the rolling-in device interacts with a fruit, as well as the area of expansion of plastic deformation as a result of the impact of a fruit, have been presented. The equation of work, which arises when a fruit hits into the rolling-in device, has been considered, the work being decomposed into plastic work of deformation and elastic work of deformation. The work of plastic deformation, which arises when fruits come into collision with a surface, is considered in more detail, the work being decomposed into plastic work of deformation in the volume, which is limited by a spherical segment and a cone. The absolute and allowable velocities after the impact have been theoretically determined and substantiated. The parameters of allowable velocities for the varieties "Crimson sweet" and "Kholodok" have been theoretically found and the confirmation of the theoretical analysis was carried out in experimental research, which was conducted on a laboratory installation for determining the critical speed of impact on fruits of cucurbit crops. The comparison of the theoretical and experimental values of the terminal velocities confirms the credibility of the research.

Shape optimization of preform design for minimizing plastic work of forging process

Shape optimization of preform design for minimizing plastic work of forging process

DLC/CrN or AlCrN/CrN composite films: The better candidate in terms of anti-Wear performance and lesser ion release in hip implant

The present study evaluates two composite coatings viz. DLC/CrN and AlCrN/CrN for its anti-wear performance against Ti6Al4V for application in hip implant. DLC/CrN exhibited higher strain hardening exponent and lower fraction of plastic work attributed to its elastic nature. The friction dynamics of DLC/CrN-Ti6Al4V tribopair was in lower range propounding to lower wear rate. While the primary wear mechanism of DLC/CrN was tensile cracking and abrasion, AlCrN/CrN had undergone severe material transfer and galling. Most importantly, upon EDS analysis, it was seen that release of undesirable cytotoxic vanadium content from Ti6Al4V was more on AlCrN/CrN worn out surface ascribed to high affinity between aluminum and titanium thus facilitating easy disintegration of Ti6Al4V counterbody.

Deformation mechanisms and differential work hardening behavior of AZ31 magnesium alloy during biaxial deformation

Magnesium alloys are frequently subjected to biaxial stress during manufacturing process, however, the work hardening behavior under such circumstance are not well understood. In this study, the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated. The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state, resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading, with the elastic-plastic transition part of work hardening extended and stage III hardly emerged. Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basal 〈a〉 slip during biaxial loading tests. While the thickness strain is primarily accommodated by pyramidal 〈 c + a 〉 slip at the initial stage of biaxial deformation, {10–11} contraction twinning is activated at larger plastic strain. The low activation of non-basal 〈a〉 slip also retards the dynamic recovery and cross-slip of basal and prismatic 〈a〉 slips, leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.

Parametric analysis of energy absorption capacity of thin aluminum plates impacted by rigid spherical projectiles

A finite element axisymmetric model has been developed to study the energy absorption capacity of thin Aluminum plates (0.2–20 mm thickness) in terms of the ballistic limit. The Johnson-Cook material model was used to describe the mechanical behavior of the 2024-T3 Aluminum. Numerical results were validated by comparison with experimental tests carried on similar plates using a gas gun with two high-speed cameras to measure impact velocities in the order of 100 m/s to 200 m/s. Plastic work (60%) and friction (10%) dissipate the impact energy, while the remaining energy is absorbed in the plate as elastic and kinetic energy. A parametric analysis was performed for projectile radius and plate thickness to study their influence on the perforation energy. Ballistic curves and energy balances were used to obtain the ballistic limit from numerical simulations. Ballistic limit shows a non-linear relation with plate thickness to projectile diameter ratio, while the mean perforation stress shows a linear relation with plate thickness to projectile diameter ratio. From numerical results, a semi-empirical relation is suggested to estimate mean perforation stress and consequently obtain the ballistic limit for a given plate-projectile configuration.

Features of the analytical solution of the problem of displacement cantilever steel beams with variable flange depth

The article is devoted to the problem of generalization of the influence of the variability of stiffness of elastic steel elements on thedisplacement and angles of rotation in the Cartesian coordinate system when placing the origin ofthe coordinates in the center of gravity of the largest cross section. Cantilever elastic I-beam steelbeam with variable flange depth is considered.The obtained formulas are shows the influenceof the variability of the I-beam cross-section on themoment of inertia in two main axis. This made itpossible to write the differential equation of beambending as a linear equation with variable coefficients.The solution of the differential equation makesit possible to obtain analytical formulae for determining the displacements and angles of rotation ofthe cross section of cantilever I-beams with variable flange depth. To confirm the obtained analytical expressions in the transition to the definition ofdeflections and angles of rotation of the I-beamswith a constant cross-section, the Lopital-Bernoullirule was used. A variant of the formula for theconsequences of the second remarkable (special)boundary in the disclosure of uncertainty is obtained.This makes it possible to prove by an analyticalapproach the coincidence of the obtained solutionswith the solutions for constant cross-section Ibeams. Numerical studies also confirmed the obtained result. This approach can be applied to Ibeams with variable flange depth under differentsupport conditions.The obtained displacement formulas make itpossible to check the stiffness of cantilever steel Ibeams with a linear change in their stiffness of thebeams according to the deflection limits. The obtained results can also be used for research of Ibeams with variable flange depth under differentsupport conditions. The obtained displacementformulas make it possible to check the stiffness ofcantilever steel I-beams with a linear change intheir stiffness of the beams according to the deflection limits. The obtained results can also be usedfor research of I-beams at linear change of stiffness, including a change of the modulus of deformation of steel at limited plastic work deformations on different sections of a beam.

Визначення придатності пористих пресовок з алюмінію та алюмінієвих сплавів для використання в якості енергопоглинаючих елементів

This work reports the results of experimental studies on the applicability of porous pressings of aluminum alloys to passive safety systems. The porous pressings were made from aluminum and aluminum alloy powders with a particle size up to 200 ?m using a hydraulic press. The porosity was varied by varying the pressure in the press hydrosystem and the pressing force. The specimens were not sintered, and no plasticizer was added. To determine which specimen characteristic, the mass or the porosity, is more important, specimens of the same mass (0.01 kg) were used [the deviation did not exceed (2.7 ? 2.8) % ]. To determine the impact absorption ability of the porous pressings of aluminum and aluminum alloy powders, a vertical impact testing machine was used. The ram mass was 22.5 kg (weight 220 N), the fall speed was 5 m/s, and the fall energy was 300 J. The impact absorption ability of the porous pressings was determined by comparing the accelerations and rebound height of the ram in the presence of a porous pressing with their calculated free-fall values. The experiments showed that the use of specimens of maximum porosity decreases the impact energy by the value of the plastic work of deformation and the fracture energy. A comparison of the performance of different specimens showed that the energy absorption ability increases with porosity. As demonstrated by the experiments, porous pressings of aluminum and aluminum alloys can be used as energy -absorbing elements of passive safety systems for commercial and armored combat vehicles, and the impact absorption ability of porous fillers, in particular porous pressings of aluminum and aluminum alloys, can be determined using vertical impact testing machines. Using porous pressings of aluminum and aluminum alloys as an energy-absorbing material decreases the impact acceleration by a factor of 30 to 85 at an impact speed up to 5 m/s. The ability of a pressing to reduce the impact acceleration depends on its dimensions and porosity to a greater extent than on its mass. The greatest decrease in impact acceleration is provided by porous pressings of maximum porosity, in which the impact energy is converted to the plastic work of deformation and the fracture energy.

Ballistic performance of monolithic and double layered thin-metallic hemispherical shells at normal and oblique impact

The present study discusses experimental and numerical investigations on the ballistic performance of aluminum 1100-H12 hemispherical shell targets of 150 mm diameter against 19 mm diameter cylindrical steel projectiles. The influence of nose profile of the projectiles on the impact resistance of the targets, was observed by varying the nose geometry to ogive, blunt, conical and hemispherical shapes. Effect of normal as well as oblique impact on the failure mechanisms and perforation process of shells was studied at 0 (normal), 15 and 30° angle from the normal incidence path. Further, the ballistic performance of two target configurations, viz. 2 mm thick monolithic and double layered in-contact shell targets was investigated and compared within the configurations. The finite element analysis of the ballistic impact on shell targets was done in ABAQUS/Explicit solver by employing the Johnson – Cook constitutive strength and damage model for deformable target material, whereas all the projectiles were assumed as rigid body. The ballistic performance of both shell target configurations against oblique impacts with different projectiles was evaluated and compared in terms of ballistic limit, local and global deformations, failure mechanisms and plastic work done in radial, polar, meridional and shear deformations. The obtained experimental results were then compared with numerical simulations and found in good corroboration. It was observed that both monolithic and layered shell targets showed highest ballistic resistance against hemispherical nosed projectile. For all the projectiles, layered shell targets displayed higher energy dissipation than monolithic targets.