Effective Stress Distribution Research Articles

Highly Stretchable Sensitive Multiscale Hydrogel Inspired by Biological Muscles for Wearing Sensors.

Hydrogels have attracted substantial research interest for application in wearable electronics due to their stretchability, elasticity, and compliance. However, most hydrogels could not satisfy the application requirements for high-performance wearable sensors due to their poor sensitivity, low mechanical properties, and sensing detection range until this day. Inspired by the fascia in biological muscles, we propose a strategy to form entangled "clusters" through the dense entanglement between highly cross-linked elastic hydrogel microspheres and polymer segments, and prepared a multiscale hydrogel with high sensitivity and mechanical toughness. This strategy embedded highly swollen hydrogel microspheres (with different pore sizes) to act as the microregions of dense entanglement in the soft matrix to adjust the microstructure of multiscale gel. When pressure was applied, this structure could provide a fast response due to the stack layer formed by microspheres and soft matrix produced effective stress distribution, resulting in the outstanding sensitivity of the multiscale hydrogel (S = 1.1 kPa-1) in the pressure range of 0-50 kPa. The distinct microspheres functioning as microscale joint areas significantly augment energy dissipation, culminating in exceptional mechanical stability, ultrastretchability (≈1050%), and high strength of the multiscale hydrogel. The most notable progress was that the synthesized multiscale hydrogel not only combined the above advantages but also simultaneously solved multiple dilemmas of tedious synthesis steps, high cost, and poor durability. Besides, the multiscale hydrogel also had excellent antibacterial properties and biocompatibility, which enabled them to have large-scale application potential in wearable and implantable electronic devices. Our research could provide a universal approach to the creation of robust, flexible, wearable, and sensitive sensors, significantly increasing the uses of stress sensors in wearable technology.

A review of polymeric heart valves leaflet geometric configuration and structural optimization

Valvular heart disease (VHD) is a major cause of loss of physical function, quality of life and longevity, and its prevalence is growing worldwide due to increased survival rates and an aging population. The most common treatment for VHD is surgical heart valve replacement with mechanical heart valves (MHVs) and bioprosthetic heart valves (BHVs), but with different limitations. Polymeric heart valves (PHVs) exhibit promising material properties, valve dynamics and biocompatibility, representing the most feasible alternative to existing artificial heart valves. However, inadequate fatigue performance remains a critical obstacle to their clinical translation. In this case, geometry and material design are essential to obtain the best mechanical properties of the PHV. In this study, we summarized the effects of optimal design of PHVs from geometrical configuration optimization (valve height, thickness and design curve) and structural material optimization (anisotropy, fiber reinforcement, variable thickness, microstructure and asymmetric optimization), and selected the parameters including Effective Orifice Area (EOA), Regurgitant fraction (RF), and Stress Distribution to compare the performance of valves. It would provide the theoretical support for the optimal design of PHVs.

The reliability function of the case-hardened teeth of wheels of cylindrical gears

BACKGROUND: Methods for calculating the load capacity and reliability of gears, accepted as standardized both at the national and international levels, are based on the laws of distribution of random variables, considered as the only possible ones, which is not entirely true. As a result, the developed gears have either overestimated or underestimated reliability, which leads to their low competitiveness. Therefore, the development of methods for assessing the reliability of the case-hardened gears, taking into account the actual laws of distribution of random variables, remains relevant, as it will make it possible to design competitive transmissions. AIM: Improvement of the current approach to calculating the reliability function of case-hardened gears according to their strength performance criteria. METHODS: The improved approach to calculating the reliability function is based on improved classical methods for testing the load capacity of cylindrical gears for contact and bending stresses (GOST 21354-87 and ISO 6336). The methodology for calculating the reliability function according to the criterion of deep contact durability is based on the Lebedev-Pisarenko criterion, the formulae of which have been modified for application to gears by V.I. Korotkin. The implementation of the proposed methods was carried out in MathCAD software. RESULTS: The methods for calculating the reliability function of the case-hardened gears according to the criteria of contact and bending durability, which take into account the variable value of the misalignment in the gearing caused by the deformation of the shafts, the bearing rings and the housing (force misalignment), are proposed. In addition, the dependence of the calculation results of the reliability function of cylindrical gears on the method of setting the force misalignment in the gearing of teeth (constant or variable value) is shown. Validation of the improved approach was carried out using the data available in the scientific and technical literature on failures of the case-hardened gears. The scientific novelty of the research lies in the proposed method for calculating the reliability function of the case-hardened gears according to the criterion of deep contact durability, which performs the calculation under an unknown law of distribution of effective stresses using the Parzen-Rosenblatt method (the method is also used in methods for contact and bending durability criteria), as well as in taking into account the variable value of the force misalignment in the meshing. CONCLUSION: The practical significance of the research lies in the ability of probabilistic determination of the cause of gear failure according to six criteria (pitting, tooth breakage, tooth interior flank fracture of both the pinion and the wheel), which makes it possible to adjust the design, the manufacturing technology, and the operating requirements in order to ensure the required gear performance during its design.

Parameters affecting performance of fully instrumented model testing of strip footings on geocell-reinforced soils

A thorough study was conducted to assess the performance of the strip footing reinforced with geocells in sand, focusing on understanding the enhancement effects and geocell reinforcement mechanisms. Critical factors such as geocell modulus, height, soil relative density and load eccentricity were examined through fully instrumented model tests. Measurements included surface displacement profiles, strains on the geocell layer, subsurface pressure distribution and other relevant parameters. Results revealed that the strip footing on geocell-reinforced sand beds exhibited better performance compared to those on unreinforced soil, characterized by increased load-carrying capacity and reduced settlements. Notably, stiffer geocells improved performance significantly, with a 40% higher modulus enhancing the bearing pressure by up to 25%, due to better confinement and anchorage effects. Conversely, geocells with a lower modulus demonstrated more effective vertical stress distribution. Furthermore, increased geocell height moderately enhanced footing performance by improving confinement, although wall buckling under eccentric loading limited major gains. Dense soils under centric loading exhibited up to a 20% better improvement in bearing pressure than loose soils due to higher strain mobilization within the geocell layer. These findings highlight the crucial role of geocell and soil properties, as well as loading conditions, in optimizing reinforcement effects for strip footings.

Wave–Induced Soil Dynamics and Shear Failure Potential around a Sandbar

Sandbars are commonly encountered in coastal environments, acting as natural protections during storm events. However, the sandbar response to waves and possible shear failure is poorly understood. In this research, a two–dimensional numerical model is settled to simulate the wave-induced sandbar soil dynamics and instability mechanism. The model, which is based upon the Reynolds-averaged Navier–Stokes (RANS) equations and Biot’s consolidation theory, is validated using available experiments. Parametric studies are then conducted to appraise the impact of the wave parameters and soil properties on soil dynamics. Results indicate that the vertical distribution of the maximum vertical effective stress in the sandbar is different from that in the flat seabed, which decreases rapidly along the soil depth and then increases gradually. The impact of soil permeability and saturation on the vertical effective stress distribution around the sandbar also differ from that in the flat seabed. Unlike the flat seabed, the vertical distribution of shear stress in the sandbar increases with an increasing wave period. The sandbar soil shear failure potential is discussed based upon the Mohr–Coulomb criterion. Results show that the range of shear failure around the sandbar is wider and the depth is deeper when the wave trough arrives.

Centrifuge Modeling of Backfill Consolidation in Soil-bentonite Cutoff Walls

Soil-bentonite (SB) is commonly adopted for the backfill of vertical cutoff walls to contain contaminated groundwater. The permeability of SB backfill is dependent on its effective stress state, which is affected by the backfill consolidation process. This paper presents a geotechnical centrifuge model test to simulate the primary consolidation of typical SB cutoff walls with the advantages of reduced scale in time and size. The moisture content and earth pressure of the wall were monitored at varied depths. Test results showed that the rapid consolidation stage developed swiftly and various consolidation indicators exhibited significant development. Within the buried depth over the half (approximately two-thirds), the distribution of vertical effective stress was similar to the Bucknell field testing results, namely that it increased nonlinearly and then tended to stabilize. Also, the cumulative effect of lateral frictional resistance increased with depth and reached its peak value. In the deeper buried areas, lateral frictional resistance decreased sharply before increasing again with increasing depth, while vertical effective stress followed a pattern of significant increase followed by a decrease. This centrifuge test may be useful for achieving a comprehensive evaluation of the consolidation behaviour and mechanism of SB cutoff walls.

Physical field regulation of magnesium alloy wheel formed by backward extrusion process with multi-stage variable speed

To reduce the tonnage required during the forming process of magnesium (Mg) alloy wheels by backward extrusion (BE) and refine the grains at the wheel bottom, the multi-stage variable (MSV) speed process is proposed based on the characteristics of Mg alloy wheels formed by BE. A numerical model for the BE process of Mg alloy wheels using the Defrom-3D was constructed, and the effects of constant speed and MSV speed processes on the physical fields and DRXed grain size evolution during the forming of Mg alloy wheels were investigated. Lastly, the simulation results were indirectly verified by industrial trial production. The results show that constant speed extrusion has a small effect on the effective stress, but a large effect on the wheel temperature distribution, where the forming speed of the upper rim plays a decisive role in the final temperature distribution of the wheel. MSV speed process is used to regulate the physical field evolution during wheel forming based on the effect of constant speed on the physical field of the wheel. With the high-speed forming of the rim and low-speed forming of the upper wheel rim (9-9-1 mm/s), the temperature and effective stress distribution of the wheel blank are reasonable while reducing the forming tonnage and refining the grains at the wheel bottom.

Numerical study on gas production via a horizontal well from hydrate reservoirs with different slope angles in the South China Sea

AbstractIt is important to study the effect of hydrate production on the physical and mechanical properties of low‐permeability clayey–silty reservoirs for the large‐scale exploitation of hydrate reservoirs in the South China Sea. In this study, a multiphysical‐field coupling model, combined with actual exploration drilling data and the mechanical experimental data of hydrate cores in the laboratory, was established to investigate the physical and mechanical properties of low‐permeability reservoirs with different slope angles during 5‐year hydrate production by the depressurization method via a horizontal well. The result shows that the permeability of reservoirs severely affects gas production rate, and the maximum gas production amount of a 20‐m‐long horizontal well can reach 186.8 m3/day during the 5‐year hydrate production. Reservoirs with smaller slope angles show higher gas production rates. The depressurization propagation and hydrate dissociation mainly develop along the direction parallel to the slope. Besides, the mean effective stress of reservoirs is concentrated in the near‐wellbore area with the on‐going hydrate production, and gradually decreases with the increase of the slope angle. Different from the effective stress distribution law, the total reservoir settlement amount first decreases and then increases with the increase of the slope angle. The maximum settlement of reservoirs with a 0° slope angle is up to 3.4 m, and the displacement in the near‐wellbore area is as high as 2.2 m after 5 years of hydrate production. It is concluded that the pore pressure drop region of low‐permeability reservoirs in the South China Sea is limited, and various slope angles further lead to differences in effective stress and strain of reservoirs during hydrate production, resulting in severe uneven settlement of reservoirs.

An Improved Continuum Approach for Unconsolidated Formations on the Field Scale

Summary With the development of unconventional resources, such as oil sands and methane hydrate reservoirs, the importance of the mechanical performance model for underground unconsolidated rocks has increased significantly. The commonly used numerical approach for unconsolidated rocks is the discrete-element method (DEM). However, the extensive calculations required by the DEM make it inadequate for simulating unconsolidated rock behavior on a field scale. An alternative is the continuum approach, used to simulate the behavior of unconsolidated rocks on the field scale. In previous continuum approaches, unconsolidated rocks have been modeled as a visco-plastic fluid (i.e., Bingham fluid). The continuum approach based on visco-plastic fluid uses pressure (scalar) to describe the stress state of the particles. However, this approach does not account for the difference between the maximum and minimum principal stresses of the in-situ stress field when simulating the mechanical performance of unconsolidated rocks. Here, we developed an improved continuum approach for unconsolidated rocks and used the finite-element method as a numerical approach. Our improved model can consider the difference between the maximum and minimum principal stresses of the in-situ stress field and the pore pressure of the unconsolidated formation. We validated our numerical model with the angle of repose test, a benchmark problem for unconsolidated rocks. The validation results confirm the accuracy of our unconsolidated model. For the coupled model between the unconsolidated model and the flow model, we used an analytical solution to verify its reliability. Unconsolidated rock performances in an unconsolidated reservoir with fluid injection have been investigated based on our coupled model. The simulation results show that injection can activate the movement of unconsolidated rock particles, leading to changes in the distribution of effective stress and permeability. Our model has the potential to address large-scale unconsolidated rock issues and contribute to energy extraction.

Development of toughened and heat-resistant biodegradable injection-molded polylactide acid-based blend foams via enhancing interfacial bonding and PLA phase crystallization

Polylactic acid (PLA) foam is gaining increased attention as a biodegradable alternative to traditional petroleum-based plastic foams, which pose significant environmental pollution issues post-use. However, its potential application is greatly limited by inherent shortcomings such as brittleness and diminished heat resistance post-melting. Herein, high-performance biodegradable PLA/poly(butylene succinate) (PBS) blend foams with well-defined cell structure, high ductility, and enhanced heat resistance were fabricated using a core-back foam injection molding (FIM) process coupled with a straightforward annealing procedure. To enhance compatibility and tailor the dispersed phase morphology into a more fibrillar structure, an epoxy-functional chain extender (ADR) was incorporated. This addition resulted in a substantial increase in the notched impact strength, elevating it to 7.0 kJ/m2, compared to the mere 1.5 kJ/m2 of unmodified PLA foam. Moreover, with the inclusion of 1.0 phr ADR, the notched impact strength of the foam post-annealing soared to 20.7 kJ/m2, a 13.8-fold enhancement compared to pure PLA foam. The formation of a uniformly distributed and interlocked “shish-kebab" crystal structure in the blend facilitated effective stress transfer and distribution, leading to shear yield in the PLA matrix. Additionally, the heat deflection temperature of the annealed blend foam showed a significant increase significantly to 94.7 °C, in contrast to the mere 55.6 °C of pure PLA foam. This study demonstrates a viable and feasible strategy for preparing fully biodegradable PLA foams with high-toughness and heat resistance.

Design and Biomechanical Finite Element Analysis of Spatial Weaving Infracalcaneal Fixator System.

Traditional internal fixation of calcaneus fractures, involving lateral L-shaped incisions and plate fixation, has disadvantages such as increased operative exposure, eccentric plate fixation, and complications. The aim of this study was to design a Spatial Weaving Intra-calcaneal Fixator System (SWIFS) for the treatment of complex calcaneal fractures and to compare its biomechanical properties with those of traditional calcaneal plates. The computed tomography (CT) data of the normal adult calcaneus was used for modeling, and the largest trapezoidal column structure was cut and separated from the model and related parameters were measured. The SWIFS was designed within the target trapezoid, according to the characteristics of the fracture of the calcaneus. The Sanders model classification type IV calcaneal fracture was established in finite element software, and fixation with calcaneal plate and the SWIFS examined. Overall structural strength distribution and displacement in the two groups were compared. The maximum 3D trapezoidal column in the calcaneus was constructed, and the dimensions were measured. The SWIFS and the corresponding guide device were successfully designed. In the one-legged erect position state, the SWIFS group exhibited a peak von Mises equivalent stress of 96.00 MPa, a maximum displacement of 0.31 mm, and a structural stiffness of 2258.06 N/mm. The conventional calcaneal plate showed a peak von Mises equivalent stress of 228.66 Mpa, a maximum displacement of 1.26 mm, and a structural stiffness of 555.56 N/mm. The SWIFS group exhibited a 75.40% decrease in displacement and a 306.45% increase in stiffness. Compared with fixation by conventional calcaneal plate, the SWIFS provides better structural stability and effective stress distribution.

Blasting effects of the borehole considering decoupled eccentric charge

The investigation of the blasting effects of the borehole considering decoupled eccentric charge is scarce and lacks thorough exploration. The coupled Smoothed Particle Hydrodynamics and Finite Element Method (SPH-FEM) is adopted to study the decoupled eccentric charge blasting effects. The effective stress distribution of rock around the borehole is analyzed and the damage evolution is studied quantitatively with introducing image recognition algorithm. Further, the effect of the decoupling coefficient on blasting effects is investigated. Results show that effective stress distribution presents obvious eccentric characteristics. At the bottom coupling point, the maximum effective stress is observed, and gradually reduces towards the top uncoupling point. The lower part of rock surrounding the borehole exhibits a higher damaged area ratio compared to the upper part for decoupled eccentric charge blasting. With the decoupling coefficient increases from 1.14 to 2.00, the effective stresses at monitoring points are all decreasing and the effective stress ratio first increases and then keeps relatively stable, with the decoupling coefficient of 1.6 as inflection point. As the decoupling coefficient increases to 1.6, the damage extent ratio reaches the peak. The greatest disparity in explosion energy between the coupled and uncoupled sides occurs at a decoupling coefficient of approximately 1.6.

Effects of residual effective stress and particle size distribution on reconsolidation characteristics of granular materials after undrained cyclic shear: a 3D DEM study

Effects of residual effective stress and particle size distribution on reconsolidation characteristics of granular materials after undrained cyclic shear: a 3D DEM study

Structure Design Improvement and Stiffness Reinforcement of a Machine Tool through Topology Optimization Based on Machining Characteristics

Machining characteristics were applied to topology optimization for machine tool structure design improvement in this study, and the goals of lightweight and high rigidity of the structure were achieved. Firstly, an ultrasonic-assisted grinding experiment was carried out on zirconia to investigate the surface roughness, surface morphology, grinding vibration, and forces. Then, the topology optimization analysis was conducted for structure design improvement, in which the magnitude of the grinding vibration was utilized as the reference for selecting the topology subsystems and the grinding force was used as the boundary conditions of the static analysis in the topology optimization. Hence, columns, bases, and saddles were redesigned for structure stiffness improvement, and the variations in the effective stress, natural frequency, weight, and stiffness of the whole machine tool were compared accordingly. The results showed that the deduced topological shape (model) can make the natural frequency and stiffness of the whole machine tool tend to be stable and convergent with a weight retention rate more than 75% as the design constraint. The subsystem structures with larger effective stress distributions were designated for stiffness improvement in the design. At the same time, the topological shape (model) was also employed in the design for weight reduction, focusing on minimizing redundant materials within the structure. In contrast to the consistency of the modal shapes before and after topological analysis, the sequential number of the modal mode of the machine tool model after topological analysis was advanced by two modes relative to those of the original situation, which means the original machine tool may be out of its inherently resonant frequency range. Also, the natural frequencies corresponding to each mode had an increasing tendency, and the maximum increase was 110.28%. Furthermore, the stiffness of the machine tool also increased significantly, with a maximum of 355.97%, leading to minor changes of the machine tool’s weight. These results confirm that the topology optimization based on machining characteristics proposed in this study for structure redesign improvement and stiffness enhancement is effective and feasible.

Predicting monotonic lateral load-displacement behavior of offshore flexible piles in saturated MCC soils: An application of the cavity expansion theory

This paper proposes an application of the cavity expansion theory to predict the load-displacement response of monotonically laterally loaded piles and the effective stress distribution of saturated modified Cam-clay (MCC) soil surrounding the pile. This approach incorporates geometric relationship, equilibrium equation, and boundary conditions to derive governing equations. These equations are subsequently solved to obtain monotonic p-y curves, which encompass the elastic, elastoplastic, and critical processes. To determine the load-displacement behavior and effective stress distribution of the soil, the proposed approach combines the deflection equilibrium differential equation with the finite-difference method. The accuracy and effectiveness of the approach are validated through a comparison with a Finite Element Method (FEM) simulation. Parametric studies are also presented to investigate the effects of overconsolidation ratio, in-situ coefficient, and mean effective stress. The validity and capacity of the proposed model are further demonstrated using model pile tests. The results affirm that this approach can well predict the monotonic load-displacement response of the pile and effectively captures important phenomena observed in pile tests.

MYflow - A simple computer program for rheological modelling of mylonites

In this study, we present a new Matlab-derived software, MYflow, developed to perform rheological modelling of high-strain rocks and mylonites. The software handles both monomineralic and compositionally heterogeneous rocks made of various proportions of the most common minerals such as quartz, feldspar, calcite, olivine, plagioclase, micas, pyroxene, amphibole and garnet. The rheology of composite mylonites is evaluated using a suite of mixing models combined with two complementary mechanical constraints derived from the assumption of either uniform stress or strain-rate. Various compositions can be used to run either 0th dimensional rheological models corresponding to classical strength profiles, or 2D maps showing the grain-scale spatial variability of stress and strain rate as a function of composition, grain size and effective deformation mechanism. The applicability of the code, along with its main functionalities, is demonstrated using a model of composite mylonite that reproduces the typical microstructure of rocks deformed in high-strain zones. The software is further benchmarked by modelling the grain-scale distribution of effective deformation mechanism, stress, and strain-rate of three natural mylonite developed under different pressure, temperature, and strain-rate conditions. The outcomes of our modelling approach are compared to the results obtained from classical paleopiezometry studies and evaluated in relation to the processes that yield to partitioning of stress and strain rate in shear zones. Finally, we discuss the significance of mean stress and strain rate in mylonites addressing the applicability of recrystallized grain-size paleopiezometry.

Investigation of casing stress distribution and parameter optimization during the transient impact process of multi-hole perforation operations

Perforation operation is critical in bridging completion and production enhancement operations. At the same time, the perforation parameters also affect the structural integrity of the casing. Still, there are fewer studies on the stress distribution of the casing under the blast transient impact loading of multi-hole perforation. To address this, considering the engineering application of helical perforation in unconventional oil and gas reservoirs, a three-dimensional numerical model of perforating charge-casing-cement sheath-formation is established, and the Holmquist-Johnson-Cook (HJC) rock dynamics material model, as well as the fluid–solid coupling and Arbitrary Lagrange-Euler (ALE) algorithms. On this basis, the variation rule and distribution characteristics of the effective stress in the double-perforation holes stress superposition area under different perforation density, phase angle, and geostress conditions are analyzed with the casing strength safety threshold as the optimization judgment condition of perforation parameters. The research results show that the numerical simulation result has good consistency in the results of engineering practice, perforation aperture diameter error is 3.04%, and jet head velocity error is 6.85%. The variation rule of perforation density and phase angle has a significant effect on the effective stress distribution in the stress superposition area around the hole: with the decreasing perforation density or increasing phase angle, the casing stress superposition area in the middle part of the neighboring perforation holes is gradually narrowed down, and when the perforation density is more than 9 P/m and 51°, the casing stress in the stress superposition area between the perforated holes is lower than the safety threshold value. With the increasing ground stress, the stress in the middle of the neighboring perforated holes increases continuously, showing a quadratic function change trend. The perforation density should be appropriately reduced, and the phase angle should be increased when the geostress is high to ensure the integrity of the casing structure after the perforation operation. The research results can provide a practical reference for conducting perforation engineering operations and optimizing perforation parameters.

A novel method for ball forming by cross wedge rolling

In this paper, a novel method for ball forming by cross wedge rolling (CWR) was proposed, and the finite element (FE) simulation and experimental verification were carried out with the 26 mm diameter steel ball as an example. First of all, the die parameters including spreading angle β and forming angle α were selected and the 3D models of the die and guide plate were designed. Then, the FE model was established and preliminary simulation was carried out using the Simufact 16.0 software. The preliminary simulation results showed that the pushing empty defect occurred in the process due to lack of transition from spreading stage to sizing stage and conical die section. Modifying the die design by adopting the method of adding transition spreading angle θ and forming angle α´ increasing with the increase of rolling depth to, the defect could be eliminated and the full filling can be obtained. In addition, the simulation analysis after modified also included effective strain and stress distribution, the kinematic analysis of metal flow, the damage distribution based on the Cockcroft-Latham criterion, the temperature evolution and force parameters in the CWR process. Finally, the rolling experiments and radial rolling force testing experiments were carried out to verify the numerical results. The results indicated that the FE simulation results were consistent with the experimental results through quantitative analysis, which proved that the novel method for ball forming by CWR was feasible simultaneously.

Effects of equal channel angular rolling process on the mechanical properties of Al-Cu two-layer sheets: experimental and numerical approaches

Abstract This study investigates the mechanical properties and microstructural characteristics of explosion-welded Al/Cu two-layer strips during the ECAR process using finite element simulations and experiments. Furthermore, the explosion-welded Al/Cu two-layer strip was examined with various configurations to determine the effects of die angle and friction coefficient on the distributions of effective strain and stress. In addition, the experimental and computational approaches were utilized to explore the ECAR process in two routes, RA and RC, for three directions. Finite element simulations were run and validated using experimental data. The findings show that the ECAR method is effective to enhance the mechanical characteristics of the strips. Moreover, the obtained results represent that the ECAR process reduced the size of the grains. Furthermore, it was shown that by increasing the number of routes in the ECAR process, the stress values were increased. However, the ductility of the two-layer strip was decreased. According to the current study, the route and the number of routes used in the ECAR process have a considerable effect on the strength of the two-layer strip.

The Cold Forming Analysis of Eccentric Parts

In this study, a multi-stage cold forming process for the manufacture of eccentric parts is studied numerically with low carbon steel AISI 1022. The forming processes through five stages and four stages include two-step forward extrusion, eccentric upsetting, and backward extrusion over a moving punch. The numerical simulations of cold forming are conducted using the code of DEFORM-3D. The formability of the workpiece is studied numerically, such as the effect on forging load responses, maximum forging loads, effective stress and effective strain distributions and metal flow pattern. The maximum effective stress of 819 MPa at the third stage is the largest among the stages. The maximum effective stresses of the last stages for the four-stage forming and five-stage forming are almost the same. The effective strain distributions of the last stages for the four-stage forming and five-stage forming are very similar. The flow line distributions of the last stages both for the four-stage forming and five-stage forming are also very similar. For the maximum axial forging force and forming energy, the third stage of eccentric upsetting at the upper end is the largest among the stages. The total maximum axial forging loads from the first to the last stages are 795.8kN for the five-stage forming and 590.4kN for the four-stage forming; and the total forming energies are about 0.751kJ for the five-stage forming and 0.671kJ for the four-stage forming. Although the total maximum axial forging loads and total forming energy of the four-stage forming are smaller than those of the five-stage forming, the maximum lateral forging force in the last stage of the four-stage forming is almost five times that of the last stage of the five-stage forming. Increasing lateral forging force may lead to wear and damage of the punch. Moreover, the inner surfaces of the hexagonal cavity at the upper end are relatively uneven because of simultaneous eccentric upsetting and backward extrusion in the last stage of the four-stage forming.