Distribution Of Plastic Deformation Research Articles

Development and Implementation of Die Forging Technology Eliminating Flange Welding Operations in Conveyor Driver Forging

This article presents research results regarding the development of a new manufacturing technology for an element assigned to belt conveyor flights in the extractive industry through hot die forging (of a forging with a double-sided flange) instead of the currently realized process of producing such an element by welding two flanges onto a sleeve or one flange onto a flange forging. The studies were conducted to design an innovative and low-waste technology, mainly with the use of numerical modelling and simulations, partially based on the current technology of producing a flange forging. Additionally, during the development of the forging process, the aspect of robotization was considered, both in respect of the forging tools and the process of transportation and relocation of forging between the impressions and the forging aggregates. A thermo-mechanical model of the process of producing a belt conveyor flight forging with deformable tools was elaborated by means of the Forge 3NxT program. The results of the conducted numerical modelling made it possible, among other things, to develop models of forging tools ensuring the proper manner of material flow and filling of the impressions, as well as temperature and plastic deformation distributions in the forging and also the detection of possible forging defects. For the technology elaborated this way, the tools were built together with a special instrument for flanging in the metal, and technological tests were performed under industrial conditions. The produced forgings were verified through a measurement of the geometry, by way of 3D scanning, as well as the hardness, which definitively confirmed the properness of the developed technology. The obtained technological test results made it possible to confirm that the elaborated construction, as well as the tool impressions, ensure the possibility of implementing the designed technology with the use of robotization and automatization of the forging process.

Assessment of different agricultural soil compaction levels using shallow seismic geophysical methods

A well-developed soil structure is crucial for a fertile soil and rules its influence on the ecosystem. Slight variations in the way soil components are organized and connected can greatly impact the soil mechanical and hydraulic characteristics. However, these features are challenging to measure at a scale that is relevant for agricultural management. In this study, we assess the capability of two seismic geophysical methods, i.e. Seismic Refraction Tomography and Multichannel Analysis of Surface Waves, to monitor the effects of compaction on agricultural bare soil. The purpose is to highlight the different mechanical response caused both by soil plastic deformation and soil water distribution due to increasing compaction. Results demonstrate that both geophysical techniques provide sufficient information to capture the effects of soil compaction and distinguish its significance, while traditional direct measurements, being punctual, lack sufficient spatial coverage. P-wave velocities carry a strong imprint of soil compaction, provided by seismic refraction, incorporating the information given by the multiphase medium in its entirety. On the other hand, S-wave velocity derived from Surface Waves discriminates the effect of solid matrix structure. This work, moreover, aims to pave the way for seismic methods to spatially characterize compaction at field scale, illustrating its potential and suggesting possible developments.

Insights into thermomechanical fatigue behavior of nitrogen alloyed 316LN stainless steel under various temperature cycling ranges

Thermomechanical fatigue (TMF) failure has become one of the most important life-limiting factors of components exposure to the high temperature in the fourth-generation sodium-cooled fast reactor (SFR) nuclear power plant. Therefore, TMF tests at different temperature cycling ranges are performed to study the cyclic deformation behavior and damage mechanism of a nitrogen alloyed 316LN stainless steel. Moreover, the isothermal fatigue (IF) tests at the maximum temperature of TMF cycling are conducted for comparison. The cyclic hardening and softening response are analyzed, taking into account the phenomenon of dynamic strain aging which occurs at the temperature range of 350 °C–650 °C. Furthermore, the critical strain corresponding to the occurrence of serrated stress flow in engineering stress-strain curves keeps decreasing from 28.94% at 350 °C to 0.09% at 650 °C. The distribution of plastic deformation and the degree of strain localization are evaluated by the characterization results of kernel average misorientation map, high/low angle grain boundary map and dislocation configuration. The dominant damage mechanism and its corresponding cracking behavior in both IF and TMF tests are analyzed based on the observation of fracture surface morphology. In addition, the sequence order of fatigue life is determined as IF < IP-TMF < OP-TMF. Moreover, the maximum difference of fatigue life between IF test and TMF test occurs at the temperature range of 400 °C–600 °C, in which the IP and OP life is about 2.91 and 3.65 times larger than the IF life. The results in this work provide reliable data support and theoretical guidance for the fatigue design of high-temperature components in SFR.

Effects of three types of attachments in the displacements, and distribution of stress and plastic deformation, and trough finite elements (FEM)

Objectives: The aim of the study was to evaluate the effect of resin attachments on the displacement and deformation pattern of the aligner plastic, determine the center of rotation and stress distribution in the upper canine during space closure using the finite element method (FEM), and evaluate the plastic Aligner deformation. Materials and Method s: A computer-assisted design model of the superior right hemiarch was constructed with the simulation of a first premolar extraction and a canine distalization, recreating the periodontal ligament and alveolar bone. FEMs were created to analyze the behavior of stress and displacement of the upper right canine with aligners in four situations, one without attachment, and three with bonded attachments (vertical rectangular, rectangular beveled, optimized root control). In addition, the plastic deformation of the aligner was evaluated. Results: In the simulation without attachment, there was no apical movement, while with vertical rectangular and rectangular beveled the behavior was similar with crown distal displacement and mesial apex displacement. The optimized attachment had a better movement control of the canine body respecting the crown and apical movement toward the same direction. The mayor plastic deformation was shown without attachment and no deformation was evidenced with optimized attachment. Conclusion: The FEM showed that nevertheless the optimized attachment produced a distal crown and apical displacement with the use of plastic aligners during the space closure, the apex only moved ¼ of the distal crown movement. Our results suggest that to obtain a pure translation of the canine with aligners, it would be necessary the use of auxiliars which complement the needed biomechanics.

Short fatigue crack growth mechanism in Ni-Co based superalloy at elevated temperatures and in oxidative atmospheres

In this study, to elucidate the oxidation effect on the short fatigue crack growth (SFCG) characteristics of Ni-Co based TMW-4M3 superalloy, fatigue tests were conducted at room/elevated temperature in air/vacuum and three-dimensional microscopic observation of the SFCs using a plasma focused ion beam – scanning electron microscope (PFIB – SEM) system. Fatigue lives tested under vacuum at elevated temperature were comparable to those at room temperature while those tested at elevated temperatures in air showed shorter fatigue life in higher stress regions and longer fatigue life in lower stress regions than the others. In situ observation of SFCs at elevated temperatures in air revealed SFCG deceleration in the small ΔK regions and acceleration in large ΔK regions. SFCs opening/closing behaviours at elevated temperatures measured by digital image correlation (DIC) showed the crack opening stress to be higher at elevated temperature in air, possibly due to oxide-induced crack closure. However, the crack closure effect did not fully explain the difference in FCG rate between room and elevated temperatures in air. Three-dimensional investigations revealed SFCs to form at elevated temperatures in air, showing straight transgranular FCG to be insensitive to microstructure in slow growth regions, and intergranular FCG to precede that in the surrounding material in fast growth regions, in contrast to microstructural SFCs features at room temperature. It appears that slow and straight unique SFCG at elevated temperatures might occur due to intermittent brittle fracture of oxides formed at the crack tip. This suggests a possible role of the oxide layer at the crack tip in broadening the plastic deformation distribution, thus contributing to FCGR deceleration.

Electro-plastic effect on the indentation of calcium fluoride

Calcium fluoride (CaF2) possesses excellent optical properties, making it a promising material for many optical components. However, due to its brittleness, the intrinsic plasticity of CaF2 needs to be improved to enhance its machinability. The adoption of the external electric field is a feasible scheme, but the relevant electric effect on the mechanical performances of non-conductors remains little explored. This study aims to investigate the relationship between the applied electric field and the plasticity of CaF2 using both experimental and numerical approaches. Micro-indentation tests are conducted under varying electric field conditions to identify the effect of the electric field on the plasticity of CaF2. Molecular dynamics simulations are employed to investigate the deformation mechanisms under the electric effect. Specifically, the study investigates the correlated influence of the electric field direction and field intensity on plastic behavior. Combining the experimental and simulation results, it is demonstrated that the applied electric field significantly enhances the plasticity of CaF2. The field direction influences the growing direction and distribution of plastic deformations while the field intensity affects the degree. The systematic study deepens the understanding of the electro-plasticity of non-conductive ceramics, further informing the development of electric field-assisted machining techniques.

Experimental study on seismic performance of low-yield point steel plate shear walls

This paper studies the seismic performance of the low-yield point steel plate shear wall (LSPSW) by conducting cyclic loading tests on three single-story single-span steel plate shear wall (SPSW) specimens, including a non-stiffened LSPSW (LYP) and a non-stiffened normal strength SPSW (NW). A new LSPSW with steel tube stiffeners (HSS) is then proposed to restrain the out-of-plane deformation of the infill panel. The failure modes, strain development, bearing capacity, stiffness, ductility, energy dissipation capacity, degradation characteristics, and deformation performance of the above three SPSWs are compared and analyzed. Afterwards, the corresponding numerical modeling approaches are developed and verified by the test results. Furthermore, supplementary analyses of the plate-frame interaction in terms of the shear distribution, energy dissipation behavior, and plastic damage performance are performed, and relevant suggestions are provided for the design of SPSW. The experimental and numerical results show that compared with the NW specimen, the use of low-yield point steel in the LYP specimen significantly improves the ductility and energy dissipation capacity of the SPSW, delays the tearing of the infill panels, reduces the residual deformation of the infill panels with higher ability of recovery, and achieves a more uniform distribution of cumulative plastic deformation. The application of steel tube stiffeners in the HSS specimen further enhances the energy dissipation capacity of LSPSW, effectively restrains the out-of-plane deformation of the infill panels, and reduces the impact of the tension strips on the edge columns. The analyses of the plate-frame interaction show that the boundary frame has more contribution to the shear resistance and energy dissipation after using the low-yield point steels for the infill panel. The proportion of shear force borne by the boundary frame is up to 65%–70%, which should be considered in the design procedure to optimize the geometrical dimensions of the infill panel and the boundary frame, allowing to optimize the structural performance and material utilization.

Development of AA5052/TiO2/SiC hybrid surface composites using upward material flow through multipass friction stir processing

The present study employed upward material flow during friction stir processing (FSP) to develop AA5052/TiO2/SiC hybrid surface composites rather than the downward material flow that is conventionally used. The upward material flow was generated with the help of a right-handed threaded pin tool rotating in a clockwise direction causing plastically deformed material to flow in the three-dimensional region of the stir zone. The result showed that the upward material flow pattern and multipass significantly improved the properties of composites. Substantial grain refinement was obtained after each successive pass due to the uniform distribution of fragmented reinforcement particles and intense plastic deformation during FSP. The maximum microhardness of 88.73 HV and ultimate tensile strength of 220.8 MPa were obtained after the fourth FSP pass in developed hybrid surface composites. Additionally, the tribological analysis showed that wear resistance increased with the number of passes.

Numerical and Experimental Analysis of Lap Joints Made of Grade 2 Titanium and Grade 5 Titanium Alloy by Resistance Spot Welding

The paper presents the evaluation of the load capacity of lap joints and the distribution of plastic deformations. The influence of the number and arrangement of welds on the load capacity of the joints and the method of their failure was investigated. The joints were made using resistance spot welding technology (RSW). Two combinations of joined titanium sheets were analyzed: Grade 2-Grade 5 and Grade 5-Grade 5. Non-destructive and destructive tests were carried out in order to verify the correctness of the welds within the given parameters. All types of joints were subjected to a uniaxial tensile test on a tensile testing machine, using digital image correlation and tracking (DIC). The results of the experimental tests of the lap joints were compared with the results of a numerical analysis. The numerical analysis was performed using the ADINA System 9.7.2 and was based on the finite element method (FEM). The conducted tests showed that the initiation of cracks in the lap joints occurred in the place as the maximum plastic deformations. This was determined numerically and confirmed experimentally. The number of welds and their arrangement in the joint affected the load capacity of the joints. Depending on their arrangement, Gr2-Gr5 joints with two welds reached from approximately 149 to 152% of the load capacity of joints with a single weld. The load capacity of the Gr5-Gr5 joints with two welds ranged from approximately 176 to 180% of the load capacity of joints with a single weld. Observations of the microstructure of RSW welds in the joints did not show any defects or cracks. The microhardness test in the Gr2-Gr5 joint showed that the average hardness of the weld nugget decreased by approximately 10-23% when compared to a Grade 5 titanium alloy and increased by approximately 59-92% compared to Grade 2 titanium.

On the acoustic method of control of spatial inhomogeneity of plastic deformation of weakly anisotropic orthotropic materials

In this paper, the possibilities of using non-destructive acoustic control to determine the features of the spatial distribution of local plastic deformations during deformation of flat samples made of AMg61 alloy were investigated. The methodological features of using the acoustic anisotropy parameter to study the patterns of changes in spatial inhomogeneities of the field of local plastic deformations are analyzed. A computational and experimental method for determining the acoustic anisotropy parameter is proposed, which allows to correctly determine not only its magnitude, but also the directions of the local axes of acoustic anisotropy. The sources of errors of the proposed methodology, the limits of its applicability, as well as the requirements for hardware and software for its implementation are analyzed. The results of experimental studies carried out on samples of weakly anisotropic aluminum alloy AMg61 are compared with the representations of autowave mechanics of plasticity of metals. An engineering algorithm for determining the early localization of zones of loss of stability during plastic deformation of samples is proposed. The possibility of creating a methodology for assessing the plasticity resource of a material during its plastic shaping is shown.

Finite-time stability of any polyhedral sweeping process with uni-directional loading and application to elastoplastic models

A significant progress in the study of the dynamics of elastoplastic lattice spring models has been recently due to the development of a sweeping process framework where the dynamics of the stresses of springs is linked to a solution of the associated sweeping process. By using the sweeping process framework, a recent result by Gudoshnikov et al. (2022) ensures finite-time convergence of a lattice spring model under assumption that the vector g′(t) of the applied displacement controlled-loading lies strictly inside a suitable normal cone of the sweeping process. In this paper we drop the latter assumption by proving that g′(t) always belongs to a suitable normal cone when g′(t)=const (i.e. the loading is uni-directional) and when certain genericity condition holds. By using this result we establish that every elastoplastic lattice spring model with a generic associated polyhedron reaches a unique distribution of plastic deformations in finite time.

Research on plastic deformation transfer and distribution of large-diameter thin-walled metal ring parts in double-roll pendulum hot rotary forging process

Many key structural components in large equipment such as launch vehicles, nuclear submarines, and nuclear power equipment are composed of large thin-walled metal rings with high diameter-thickness. With the development of science and technology, the traditional manufacturing method of melon-shaped tailor welding has gradually been unable to meet the equipment requirements. Due to the advantages of a small required forming force, stable process and good forming quality, the double-roll pendulum hot rotary forging (DRPHRF) technology has great potential in the overall manufacture of large-diameter thin-walled metal ring parts. However, many issues in the DRPHRF process are still unclear, and its application has been severely hindered. Therefore, this paper firstly determines the selection range of key forming parameters for large-diameter thin-walled metal rings in the DRPHRF process. Then, a reliable 3D rigid-plastic thermo-mechanical coupled finite element model for DRPHRF machining of large-diameter thin-walled metal rings was established in the 3D dynamic finite element software 3D-DEFORM. The reliability of the model is verified by experiments. Based on a reliable finite element model, the plastic transfer and distribution in the DRPHRF process of large diameter thin-walled metal rings are studied. On this basis, by setting the process conditions and the characterization factor Q, the influence of key process factors on the plastic distribution of the ring is studied. The research results of this study provide an important basis for the selection of key parameters of the DRPHRF process and the improvement of the forming quality of the DRPHRF process.

Elimination of root kissing bond in friction stir welding of thick plates

• The root-enhanced friction stir welding was proposed to eliminate root kissing bond. • The root tolerance had been expanded from 0.1 mm to 0.6 mm. • The enlarged-tip pin increased heat input and material deformation at the bottom. • The tensile properties were increased to 345 MPa. Root kissing bond in thick-plate friction stir welded joints limits the application of plates in fuel tanks of heavy launch vehicles. Here a root-enhanced friction stir welding from aspects of the on-demand distribution of heat input and plastic deformation through an enlarged-tip pin was proposed. The pin was designed with an enlarged tip for enhanced plasticizing and forging on root materials. Root tolerance, defined by the distance between the pin tip and the lower surface of the plate without a root kissing bond, was proposed to evaluate the feasibility of the designed pin. This value increased from 0.1 mm to 0.6 mm compared to the conventional conical pin. The ultimate tensile strength and elongation reached 345±4 MPa and 11.8±0.7%, which were 11.3% and 87.3% higher than the joint by the conical pin.

An Investigation into the Densification-Affected Deformation and Fracture in Fused Silica under Contact Sliding.

Subsurface damage of fused silica optics is one of the major factors restricting the performance of optical systems. The densification-affected deformation and fracture in fused silica under a sliding contact are investigated in this study, via three-dimensional finite element analysis (FEA). The finite element models of scratching with 70.3° conical and Berkovich indenters are established. A refined elliptical constitutive model is used to consider the influence of densification. The finite element models are experimentally verified by elastic recovery, and theoretically verified by hardness ratio. Results of densification and plastic deformation distributions indicate that the accuracy of existent sliding stress field models may be improved if the spherical/cylindrical yield region is replaced by an ellipsoid/cylindroid, and the embedding of the yield region is considered. The initiation sequence, and the locations and stages of radial, median, and lateral cracks are discussed by analyzing the predicted sliding stress fields. Median and radial cracks along the sliding direction tend to be the first cracks that emerge in the sliding and unloading stages, respectively. They coalesce to form a big median–radial crack that penetrates through the entire yield region. The fracture behavior of fused silica revealed in this study is essential in the low-damage machining of fused silica optics.

Modeling of biaxial flexure tests of transport amphorae with the finite element method: Fracture strength, deformation and stress distribution

The measurement of mechanical behavior of ceramics provides essential information about the mechanical performance of ceramic vessels produced from these materials. In the present case study fragments of Hellenistic and Roman transport amphorae from the Southeast Aegean islands of Kos and Rhodes were investigated. In terms of material properties the flexural strength is of particular interest as it reflects the performance under typical mechanical loading emerging during use of these vessels. Flexural strength can be determined either in uniaxial tests, for example by three-point-bending, or more realistically, in a biaxial flexure test, for example loading with a sphere on a ring-supported ceramic disk. For the present case study ceramic disks, prepared from actual amphora wall fragments, were tested and load-displacement curves were recorded until final fracture. The flexural strength was calculated based on the maximum load at initial fracture. In order to further investigate the recorded curves in terms of elastic as well as plastic deformation and stress distribution, a three-dimensional numerical model of the biaxial flexure test was generated and evaluated using the finite element method (FEM). By adjusting the simulated behavior to the experimentally determined curves, an estimation of material properties was attempted. This approach is useful for the development of numerical models of contact loads in amphora assemblages, simulating for example storage in a cargo ship, in order to test different vessel shapes for their performance.

A Novel 2D Metal Flow Model for Hot Rolling of Aluminum Alloy Thick Plate

Considering the serious inhomogeneous distribution of plastic deformation in the rolling process of thick plate, a novel 2D metal flow model is proposed with a quadratic distribution of flow velocity in the thickness direction instead of an equal value used in traditional metal flow models. According to the energy method, this model is solved. Through comparing with the experimental data of rolling force, the accuracy of this model is validated. Then, it is found that with the increase in roll speed, the neutral point moves towards the exit of the deformation zone. However, compared with other models of metal flow in rolling process, the neutral point is distributed much closer to the entrance of the deformation zone. That is because with the quadratic distribution of flow velocity in thickness direction, flow velocity of metal at the surface increases faster than average flow velocity of metal, so that the neutral point appears earlier.

Mechanical properties and failure behavior of flow-drilling screw-bonding joining of dissimilar aluminum alloys under dynamic tensile and fatigue loading

Flow-drilling screw (FDS) is a new type of single-sided joining process that is increasingly used to join dissimilar aluminum alloys in automobile lightweight. Fatigue failure and high-speed collision may occur in automotive joints under actual service conditions. This study proposed a joining process combining FDS and adhesive bonding to join dissimilar aluminum alloy sheets commonly used in body manufacturing. The adhesive bonding improved the joint strength and increased the failure distance of FDS joint. A thorough study of the FDS-bonding joining process on the mechanical properties and failure behavior was conducted. Specifically, a finite element analysis (FEA) model was built to predict the plastic deformation and stress distribution of the joints. Microstructure and hardness tests of the joints were performed to study the effect of plastic deformation during the joining process. The comparison of the mechanical properties and failure behavior of joints in dynamic tensile and quasi-static tensile tests showed differences and strain rate sensitivity. In addition, the maximum load–fatigue life (F-N) curves of dissimilar aluminum alloy joining were obtained by fatigue tests to predict the fatigue strength and failure life of the joints. Furthermore, the relationship between failure mechanisms and mechanical properties was established. This work provides a new industrial solution and failure performance reference for the requirement of composite structure and often one-sided access connection position in automobile industry.

Determination of the deformation deceleration coefficient for calculating the initial effective length of the working part of an annular specimen made of fuel cladding

When studying the plastic properties of metallic materials under tension, the initial calculated length of the sample which affects the final results is of significant importance. In the case of determining the short-term mechanical properties of the materials of fuel cladding pipes using annular samples, calculation of the initial effective length of their working part is rather difficult since the plastic deformation of the annular sample is unevenly distributed along the perimeter. This feature is taken into account using the deformation deceleration coefficient. We present the results of determining the deformation deceleration coefficient for calculation of the initial effective length of the working part of an annular sample made of fuel cladding. An experimental method for determining the coefficient is proposed, taking into account the measurements of the distribution of plastic deformation in certain areas along the perimeter of the sample. The method consists in stretching annular and ovalized samples with marks on the end surface. It is shown that for annular and ovalized specimens from the fuel cladding of a BN-600 reactor, the values of the deformation coefficient and effective length are k = 0.50 ± 0.04 and l 0 = 6.1 ± 0.4 mm, respectively. Analysis of the actual relative deformation of the working parts and comparison with the relative elongation showed that when the ovalized specimens are stretched, the value of the relative plastic deformation is higher than that for annular specimens. The proposed method and the results obtained can be used in determination of the parameters of the materials used in the cladding pipes of the of fast neutron reactors.

Effect of various phase fractions of bainite, retained austenite, intercritical ferrite and pearlite on the wear behaviour of multiphase steels

In this study, the dry sliding wear behaviour of multiphase steels (MPS) was investigated with the help of a pin/ball-on-disc wear setup. The newly developed high strength and highly ductile MPS specimens consisting of various fractions of bainite, retained austenite, intercritical ferrite and pearlite, were obtained by a combination of continuous cooling for different times (0 s, 10 s, 20 s and 40 s) after austenitization followed by isothermal heat treatment at various temperatures (300 °C, 350 °C and 400 °C) for 10 min from a moderately high C (∼0.67 wt%) - high Si (∼1.71 wt%) steel. The worn-out surfaces and wear debris revealed that the primary material removal mechanism was of abrasive types. Wear scars were seen like a ploughed field-like structure. The depth of wear scars and amount of material collected at the periphery were affected by various phases and their fractions in the MPS specimens. The wear behaviour of the multiphase steels was affected by the distribution of plastic deformation due to continuous sliding of wear ball and application of loads on the surface of MPS specimens which was analysed by hardness variation of the sub-surfaces beneath the wear scars. At a particular austempering temperature, the wear volume loss and specific wear rate of the MPS specimens increased with the increase of continuous cooling time irrespective of the applied wear loads, and it was attributed to the formation of softer intercritical ferrite as well as pearlite formed due to longer continuous cooling. However, the bainitic structure formed by austempering without continuous cooling led to the highest wear resistance irrespective of the isothermal temperatures.

Quality reliability analysis of flash welding joint of cold-rolled 50JW800 silicon steel strip

In this study, the quality reliability of the flash butt welding (FBW) joint of a 50JW800 silicon steel strip is analyzed through metallographic observation, cupping tests, and tensile tests. It is found that the recrystallization in some areas of the joint is insufficient, as is the mechanically forced connection, owing to the plastic deformation and uneven heat distribution of the joint during the process of FBW. Insufficient recrystallization is the root cause of strip breakage during cold rolling. The quality reliability of the 50JW800 silicon steel strip FBW joint is also analyzed using eddy current nondestructive testing technology. It is found that the eddy current testing signal has a good response to different structural characteristics of the joint. Therefore, eddy current test technology can be used to ensure the quality reliability of silicon steel strip FBW joints in actual production.