Maximum Effective Strain Research Articles

Finite Element Analysis of the Mechanical Response for Cylindrical Lithium-Ion Batteries with the Double-Layer Windings

The plastic properties for the jellyroll of lithium-ion batteries showed different behavior in tension and compression, showing the yield strength in compression being several times higher than in tension. The crushable foam models were widely used to predict the mechanical responses to compressive loadings. However, since the compressive characteristic is dominant in this model, it is difficult to identify distributions of the yield strength in tension. In this study, a simplified jellyroll model consisting of double-layer windings was devised to reflect different plastic characteristics of a jellyroll, and the proposed model was applied to an 18650 cylindrical battery under compressive loading conditions. One winding adopted the crushable foam model for representing the compressive plastic behavior, and the other winding adopted the elastoplastic models for tracking the tensile plastic behavior. The material parameters in the crushable foam model were calibrated by comparing the simulated force–displacement curve with the experimental one for the case where the cell was crushed between two plates when the punch was displaced by 7 mm. A specific cut-off value (10 MPa) was assigned to a yield stress limit in the elastoplastic model. Further, the computational model was validated with two more loading cases, a cylindrical rod indentation and a spherical punch indentation, as the punch was displaced by 6.3 mm and 6.5 mm, respectively. For three loading cases, deformed configurations and plastic strain distributions were investigated by finite element analysis. It was found that the proposed model clearly provides the plastic behavior both in compression and tension. For the crush simulation, the maximum compressive stress approached 222 MPa in the middle of the jellyroll, and the maximum effective plastic strain approached 60% in the middle of the layered roll. For indentation with the cylindrical and the spherical punch, the maximum effective plastic strain approached 52% and 277% in the layered roll, respectively. The local crack or location of a short circuit could be predicted from the maximum effective plastic strain.

Radial clearance influence on strain and stress distribution of the polygonal shape deep-drawing operation

In the existing research, polygonal -shaped dies were manufactured based on the dimensions of the design. These dies were then assembled on the deep-drawing device to create polygonal cups (specifically heptagonal cups) for conducting experimental work tests. The process was achieved via a deep-drawing operation to create heptagonal cups with dimensions (diameter D = 40mm and height L = 31.5 mm). For both experimental work and finite element analysis, the cups of heptagonal shapes were formed from flat circular blanks of Low Carbon Steel (thickness to = 0.7 mm) and diameter D = 80mm. A commercial software program, ANSYS, was employed to perform this finite element analysis. The research aims to study the effect of different radial clearance ( RC = 1.1 to,1.2 to, and 1.3 to) between die and punch for heptagonal shape DD operations on the forming load, the height of the cup, thickness distribution, strain and stress distribution along the cup wall (side-wall and wall curvature). The analysis outcomes indicate that the maximum forming force was 51.250 kN with the wall curvature, the maximum effective strain was 0.8231, and the maximum stress was 676 MPa when the [Formula: see text]1.1 to). Additionally, the squeezing process in the mug wall occurred with [Formula: see text]1.1 to).

Dynamic Response Analysis of Airport Pavement under Impact Loading

The safety of the airport runway, as an infrastructure, is of considerable concern. The existing research has problems of hysteresis and unreasonable load application. In this paper, ANSYS is used to construct a coupled tire–pavement model to study the dynamic characteristics of airport asphalt pavements under impact loading. Taking the Boeing 737–800 as an example, the impact of an aircraft landing on an airport pavement is simulated by applying a dynamic load to the landing gear. The effects of tire pressure, landing pitch angle, and sinking speed on the dynamic response of the airport runway are investigated. The effects of each factor of the airport pavement are analyzed by comparing the maximum effective stress, effective strain, and displacement in the vertical direction at the same position of different structures. The results show that when the tire pressure is 2.0 MPa, the maximum values of effective stress, effective strain, and vertical displacement increase by 29.8%, 19.1%, and 22.2%, respectively, compared with 1.0 MPa. The maximum values of effective stress, effective strain, and vertical displacement at the 3.0 m/s sinking speed increase by 25.2%, 93.1%, and 77.1%, respectively, compared with that at the sinking speed of 1 m/s, which indicates that the effect of sinking speed on the dynamic response of the pavement is more significant. However, the change in the landing pitch angle has little impact on the response parameters of the pavement. Meanwhile, the flexural tensile stress at the bottom of the surface and the equivalent effect at the top of the soil foundation must be considered in the design of the airport pavement structure.

Deformation behaviors of flip chip plastic ball grid array packages subjected to temperature change using moiré interferometry

When the temperature of the package assembly is changed, non-uniform deformation and local stress may occur owing to the different thermal expansion coefficients of the constituent materials, while concentrated thermal stress may cause significant failure. In this study, we carry out an experiment and analysis of the thermal deformation of a flip chip plastic ball grid array package with respect to temperature change. Interference fringe patterns representing the displacement distribution of each temperature stage are obtained using a Moiré interferometry and the bending deformation behavior and the strain of the solder ball are analyzed thereafter. We compare the deformation behavior of a single-sided package assembly and a double-sided package assembly. The effective strain, which significantly affects the failure of the solder ball, is found to be the largest in the solder ball just outside the edge of the chip in the case of the single-sided package assembly. In the case of the double-sided package assembly, the maximum effective strain is found in the solder ball just inside the edge of the chip, with a value approximately 50 % larger than in the case of the single-sided package assembly. Wenn sich die Temperatur eines Gehäuses ändert, kann es aufgrund der unterschiedlichen Wärmeausdehnungskoeffizienten der einzelnen Werkstoffe zu ungleichmäßigen Verformungen und lokalen Spannungen kommen, während konzentrierte thermische Spannungen zu erheblichen Ausfällen führen können. In dieser Studie führen wir ein Experiment und eine Analyse der thermischen Verformung einer Flip-Chip Kunststoffkugel Gitteranordnung in Abhängigkeit von der Temperaturänderung durch. Mit Hilfe der Moiré-Interferometrie werden Interferenzstreifenmuster aufgenommen, die die Verschiebungsverteilung jeder Temperaturstufe darstellen und anschließend werden das Biegeverformungsverhalten und die Dehnung der Lötkugel analysiert. Wir vergleichen das Verformungsverhalten einer einseitigen und einer doppelseitigen Gehäusebaugruppe. Es zeigt sich, dass die effektive Dehnung, die das Versagen der Lötkugel maßgeblich beeinflusst, im Fall der einseitigen Baugruppe in der Lötkugel direkt außerhalb des Chiprands am größten ist. Bei der doppelseitigen Baugruppe ist die maximale effektive Dehnung in der Lötkugel direkt innerhalb des Chiprands zu finden, mit einem Wert der etwa 50 % größer ist als bei der einseitigen Baugruppe.

A Forward Identification Method for High-Temperature Stress–Strain Curves of 7075 Aluminum Alloy Sheet Considering the Necking Stage

The necking phenomenon of metal sheet under high temperatures is serious and continues over a longer duration. It is difficult to describe the high-temperature mechanical properties of materials only on the basis of hardening behavior before necking. To obtain the high-temperature stress–strain curve considering diffuse necking stage, a forward identification method based on strain measurement is proposed in this study. Here, the strain field of the minimum cross-section in the necking region of the specimen is obtained using a DIC (digital image correlation) measurement technique, and the average axial true stress–strain curve is calculated. Then, the average axial true stress–strain curve is modified using the modified Bridgeman formula. Taking 7075 aluminum alloy as an example, the high temperature equivalent stress–strain curve considering the diffuse necking stage is obtained. Compared with the traditional method, the maximum effective strain range is expanded from 0.05 to 0.8 due to the consideration of the necking stage. The obtained curve is characterized by a coupled viscoplastic–damage constitutive model and embedded in ABAQUS through the user subroutine VUMAT to simulate the hot tensile process. The relative error of force–displacement between the simulation and the experiment was 2.4%, validating the ability of the presented method. This study provides theoretical guidance and a scientific basis for the application and forming control of hot stamping processes.

Critical Evaluation of Identified Flow Curves Using Homogeneous and Heterogeneous Solutions for Compression Test

BackgroundThe cylindrical profile model (CPM) is commonly used to convert the load–displacement measurement from the axis-symmetric compression test (ACT) to the flow curve. The model ignores the barrelling of the sample which results in serious flow curve distortion and underestimation of the effective stress and strain. To minimize these, a new solution of ACT with heterogeneous deformation is proposed in this work as an alternative to CPM.MethodRepresentative point is introduced in this new approach for better utilization of the new solution. Some key attributes of a typical flow curve are also considered to explore the sensitivity of the identified flow curve to the heterogeneous deformation. Sample flow curves are identified based on the new solution and compared with that of CPM.ResultsIt was found that CPM underestimates the maximum effective stress, strain and strain rate. Significant deviations were found between the reference flow curves and those of CPM. The model is unable to appropriately account for the rate-dependent behaviour of material and work hardening variations in the samples. Therefore, given its non-realistic homogeneous effective strain and strain rate in the sample, the CPM based flow curves are questionable. The new ACT solution provided more reliable flow curves than those of the CPM.ConclusionsConsidering the heterogeneous deformation at the centre of the sample, the new ACT solution provided flow curves that for strains bellow 0.4 closely resemble the reference curves obtained from the finite element model. Thus, the new ACT solution reduces the serious limitations of CPM and provides less error in the study of the hot deformation phenomena (e.g. recovery and recrystallization). Further recommendations were also given to limit the deviations in the identified flow curve.

Alterations in osteocyte lacunar morphology affect local bone tissue strains

Osteocytes are capable of remodeling their perilacunar bone matrix, which causes considerable variations in the shape and size of their lacunae. If these variations in lacunar morphology cause changes in the mechanical environment of the osteocytes, in particular local strains, they would subsequently affect bone mechanotransduction, since osteocytes are likely able to directly sense these strains. The purpose of this study is to quantify the effect of alterations in osteocyte lacunar morphology on peri-lacunar bone tissue strains. To this end, we related the actual lacunar shape in fibulae of six young-adult (5-month) and six old (23-month) mice, quantified by high-resolution micro-computed tomography, to microscopic strains, analyzed by micro-finite element modeling. We showed that peak effective strain increased by 12.6% in osteocyte cell bodies (OCYs), 9.6% in pericellular matrix (PCM), and 5.3% in extra cellular matrix (ECM) as the lacunae volume increased from 100-200 μm3 to 500–600 μm3. Lacunae with a larger deviation (>8°) in orientation from the longitudinal axis of the bone are exposed to 8% higher strains in OCYs, 6.5% in PCM, 4.2% in ECM than lacunae with a deviation in orientation below 8°. Moreover, increased lacuna sphericity from 0 to 0.5 to 0.7–1 led to 25%, 23%, and 13% decrease in maximum effective strains in OCYs, PCM, and ECM, respectively. We further showed that due to the presence of smaller and more round lacunae in old mice, local bone tissue strains are on average 5% lower in the vicinity of lacunae and their osteocytes of old mice compared to young. Understanding how changes in lacunar morphology affect the micromechanical environment of osteocytes presents a first step in unraveling their potential role in impaired bone mechanoresponsiveness with e.g. aging.

Effects of forming parameters on metal flow behaviour during the MDF process: taguchi and response surface methodology optimisation

ABSTRACT In this study, multidirectional forging (MDF) process parameters were optimised using Taguchi analysis and response surface methodology (RSM) for damage and effective strain. The parameters considered in the study were: temperature, friction coefficient, strain per pass, and die speed. Aluminium alloy 7075 (AA 7075) was used as a specimen for analysis during MDF processing. The output responses selected were maximum damage and effective strain. The MDF was undertaken at four levels for each input parameter. The Taguchi L16 orthogonal array was used to determine the interaction of the inputs and the contribution of the parameters. Simulations of the process were carried out on Deform 3D software. The analysis of variance demonstrated that the contribution of strain per pass was the most significant in causing damage and an increment in effective strain. Temperature and die speed were shown to have minimal effects on the outputs. The confirmation simulations demonstrated that the optimal solutions obtained by the Taguchi method had damage of 1.29, and the effective strain was 2.88. The RSM results were 0.19984 and 4.02193 for damage and effective strain, respectively.

A multi-response optimization of the multi-directional forging process for aluminium 7075 alloy using grey-based taguchi method

The multi-directional forging process of aluminium alloy 7075 (AA 7075) is studied using Deform 3D Version 11.0 simulation software. This process results in grain refinement in the bulk material. The 7075 aluminium alloy is used widely in the aerospace and automobile industries. Thermomechanical processing affects the mechanical properties of this alloy. This study focuses on optimising process parameters that affect the multi-directional forging using simulation. In the Taguchi design of experiment, four-factors and five levels are selected. The process input parameters considered are temperature, the strain per pass, the plunger speed, and the friction coefficient (μ). From Taguchi’s orthogonal array, forging simulations are undertaken and analysed. The significance of the process output parameters: material damage, stress and strain are analysed by analysis of variance. The results show that the friction coefficient and strain per pass highly affect the stress/strain distribution. Grey relational analysis is adopted to determine the optimum process parameters. The results show that the optimal combination of parameters is: temperature (200 °C), plunger speed (5 mm/s), friction coefficient (0.6), and strain per pass (0.6). Confirmation of simulation is carried out using the optimum input parameters. From the simulation results, the grey relational grade's optimal parameters have the highest maximum effective strain of 5.57, maximum effective stress of 665 MPa, and maximum damage of 0.416 compared to other simulated results.

A novel method of processing sheet metals: Electric-pulse triggered energetic materials forming

• A novel high-velocity sheet metal forming method is proposed: ETEF. The energetic materials (EMs) were introduced into the EHF system, and the electrical explosion of metal wire ignited EMs and released energy. • The EMs under the 10 wt.%Al/90 wt.%AP conditions exhibited the highest energy release efficiency, the energy grade of EMs was determined to be 3.04 kJ/g in this work. Under discharge voltage of 3 kV, the bulging height of DP600 specimen from ETEF was increased by 162 % relative to that from EHF. • Compared with that of EHF/7 kV, the strain concentration area of the sheet under the ETEF was wider (about 60 mm). The maximum major strain and maximum thinning rate of the specimen under the 2 g/3 kV/10 wt.% Al/90 wt.% AP conditions were reduced by 10.6 % and 13.1 %, respectively. • The dynamic deformation of the DP600 specimens during ETEF were presented for the first time by LS-DYNA. The EMs were ignited by electric explosion of metal wire to realize the coupling of two kinds of energy. To improve the formability of sheet metals at room temperature and overcome the limitation of the upper limit of energy storage in electrohydraulic forming (EHF), a novel sheet metal forming is proposed: electric-pulse triggered energetic materials forming (ETEF). The power to deform a metal sheet originates from the electrical explosion of a metal wire in a liquid chamber and that releasing chemical energy from the energetic materials (EMs) being triggered. Equi-biaxial stretching tests of DP600 were carried out through ETEF with different weight ratios and changing grams under a low discharge voltage. The final profiles, strain and thickness distribution of the sheet were analyzed. The energetic materials with 10 wt.%Al/90 wt.%AP had an energy level of 3.04 kJ/g, and the bulging height of the deformed specimen was 34 mm, which was higher than the energy levels obtained under other testing conditions. Compared with that of the 7 kV specimen of the same bulging height (34 mm) obtained by EHF, the strain concentration region of the specimen processed under the 2 g/3 kV/10 wt.% Al/90 wt.%AP conditions widened by 52.5 %, and the maximum major strain and maximum thinning rates were lower by 10.6 % and 13.1 %, respectively. The dynamic deformation characteristics of the DP600 specimens during ETEF were presented for the first time by LS-DYNA. The values obtained for the DP600 sheet were as follows: maximum bulging height, 32 mm; maximum effective strain rate, 1521/s; and maximum speed, 258 m/s.

A Spline Shape Deep Drawing using Finite Element Simulation and Experimental Work Test

In the current research, an analysis study was conducted to process of design of spline cup drawing. Deep-drawing tools (dies and punches) were designed and manufactured to implement the experimental work required to produce a spline cup with inner dimensions are height h=3 mm, width W=9.64 mm, and diameter d=34 mm, drawn from a circular blank of a di ameter D b = 8 0 mm, and thicknes s t = 0 . 7 mm made of low carbon steel (1008-AISI). To simulate the spline shape deep-drawing process, a commercial finite element program code ANSYS 19.0 Workbench was employed. The research aims to produce the spline shape and study the effect of the punch wall curvature radius on the drawing force, thickness distribution, and effective strains across the sidewall, major and minor axis curvature of a completely drawn spline cup using experimental testing and finite element modeling. From the comparisons between the experimental and finite element results, it was shown that the numerical results of a spline cup deep-drawing are good agreement with the results of the experiment and lie within an average of (4% - 8%). The drawing force and thinning for the small punch wall curvature radius is higher than the large punch wall curvature radius. The maximum drawing force and maximum thinning with the smallest punch wall curvature radius (0.5) at the minor axis curvature of a completely drawn spline cup. The maximum effective strain with the smallest punch wall curvature radius (0.5) at the minor axis curvature region at the completely drawn spline cup rim.

Dynamic performance prediction and influencing factors analysis of buried polyethylene pipelines under subsurface localized explosion

Although polyethylene (PE) pipelines have been extensively used in engineering fields, very little effort has been devoted to their abilities against blast loads. In the present study, numerical method is used to predict the dynamic performance of buried small-diameter PE pipelines under subsurface localized explosion. The effectiveness of a numerical model was firstly evaluated to entirely replicate the experimental damage process of PE pipelines. Then, parametric studies are performed to show the dynamic response of PE pipelines under subsurface localized explosion. Finally, the main influencing factors are analyzed according to the grey system theory. The results show that the front and back faces, top and bottom of the pipelines, where facing explosive charge are the main failure positions of PE pipelines due to the local effect of blast load. The peak pressure, resultant displacement, peak effective strains, and peak vibration velocities of the PE pipelines increase with the explosive mass increasing. The peak pressures and peak vibration velocities decrease with the pipe size decreasing. Reducing the pipe size could increase the maximum effective strain of the pipe facing the explosive center, and reduce the vibration velocity of the pipe near the explosive center. The change law of peak pressure of PE pipelines caused by changing explosive mass and pipe size is different from that of peak vibration velocity of PE pipelines. As a sequence, the three influencing factors (explosive mass, pipe size and blasting distance) should also be considered to analyze the influence of subsurface explosion on the buried small-diameter PE pipelines.

Influence of radial forging process on strain inhomogeneity of hollow gear shaft using finite element method and orthogonal design

Due to the current trend towards lightweight design in automotive industry, hollow stepped gear shafts for automobile and its radial forging process are widely investigated. Utilizing coupled finite element thermo-mechanical model, radial forging process of a hollow stepped gear shaft for automobile was simulated. The optimal combination of three process parameters including initial temperature, rotation rate and radial reduction was also selected using orthogonal design method. To examine the strain inhomogeneity of the forging workpiece, the strain inhomogeneity factor was introduced. The results reveal that the maximum effective strain and the minimum effective strain appeared in the outermost and innermost zones of different cross sections for the hollow stepped gear shaft, respectively. Optimal forging parameters are determined as a combination of initial temperature of 780 °C, rotation rate of 21°/stroke and radial reduction of 3 mm.

Influence of wire parameters on the formability of DP600 steel sheets during wire explosion impact forming

The acoustic pulses caused by the underwater wire explosion can be used to apply work on the surrounding medium. This work designed a set of adjustable wire explosion impact forming tooling to investigate the influence of wire parameters on the formability of DP600 steel sheets. The results obtained based on the current experimental conditions showed that a longer wire length mainly played a positive role in improving the energy utilization rate; a larger lifting height weakened the disadvantage of uneven distribution of pressure caused by the explosion of metal wire, and decreased the difference between the radial pressure and the circumferential pressure of the fractured elements, causing the limit strain pair to be closer to the equi-biaxial tensile strain path and increasing the limit dome heights of the tested specimens. Under the conditions of optimal wire length of 45 mm and lifting height of 37 mm, the limit dome heights and the major strains of the tested specimens were increased by 10% and 20%, respectively, as compared with quasi-static specimens; and the energy utilization rate was improved by 30–50% as compared with other combined wire parameters. The numerical simulation reproduced the dynamic deformation process of tested specimens and showed that the maximum effective strain rate was 1740/s, which was 106 times of that during the quasi-static hydraulic bulging process. The microstructural characteristics showed that under the action of high-speed impact load, the grain size of the tested specimen was reduced by 80%, as compared with that under quasi-static condition.

Numerical simulation on the effect of sample geometry size on the metal flow behaviour during the forging process

This paper reports on the effect of sample geometry size on the metal flow behaviour using DeformTM 3D finite element simulation software. The simulation process was done at forging temperature of 1100 °C and upper die speed of 50 mm/second. The friction coefficient between the die and the sample interface was taken to be constant during the simulation process. The results of the effective stress and strain distribution in the deformed sample were reported. The results show that the effective stress and strain distribution in the deformed sample was non-uniformly distributed. The maximum effective strain occurred at the centre of the deformed sample for all the samples tested. The maximum effective stress occurred at the die-sample contact surface. At the contact surfaces, the effective stress decreased with a decrease in the sample size. The effective stress at the centre of the deformed sample increased with a decrease in the sample geometry size.

Theoretical Model and Outstanding Performance from Constructive Piezoelectric and Triboelectric Mechanism in Electrospun PVDF Fiber Film

AbstractFlexible materials with high electromechanical coupling performance are highly demanded for wide applications for electromechanical sensors and transducers, including mechanical energy harvesters. Here, outstanding electromechanical performance is obtained in electrospun‐aligned polyvinylidene fluoride (PVDF) fiber film. A theoretical model is developed from systematic theoretical analyses to clarify the underlying constructive piezoelectric‐triboelectric mechanism in the polarized PVDF fiber films that explains the experimental observations well. The electrospinning process induces polarization alignment and thus tunes the electron affinity for PVDF fibers with different polarization terminals, which results in the constructive piezoelectric and triboelectric responses in the obtained PVDF fiber films. Extremely large effective piezoelectric performance properties are achieved in the direct piezoelectric measurements, reaching the maximum effective piezoelectric strain and voltage coefficients of −1065 pm V−1 and −9178 V mm N−1, respectively, at 100 Hz. In the converse piezoelectric measurements without a significant contribution from reversible triboelectric effect, the maximum effective piezoelectric strain and voltage coefficients are −166 pm V−1 and −1499 V mm N−1, respectively. The theoretical analyses and experimental results show the great potential of the electrospun aligned polar PVDF fiber material for various electromechanical device applications, particularly for mechanical energy harvesting.

Fracture behavior of twinning-induced plasticity steel during wire drawing

The present study focuses on the effects of strain and temperature distribution on the fracture behavior in twinning-induced plasticity (TWIP) steel during wire drawing in order to understand the fracture mechanism of drawn TWIP steel wire. The deformation and fracture behaviors of a wire subjected to the reduction of area (RA) per pass of 10% (lower reduction, LR) and 20% (higher reduction, HR) were analyzed. The deformation temperature of the wire had a linear relationship with RA per pass during wire drawing, which means that the HR wire exhibited higher temperature compared to the LR wire. The maximum effective and shear strains occurred at the near surface area, i.e., at the relative distance of 0.9 from center to surface of the wire, leading to the maximum twinning rate and geometrically necessary dislocation density at the near surface area. Also, the near surface area had a lower temperature than that of the surface area. Therefore, cracks were initiated at the near surface area in TWIP steel during wire drawing, which was well observed from the fractography by scanning electron microscopy. The HR wire had a higher drawability compared to that of the LR wire because the HR wire had a lower twinning rate at the near surface area due to the higher stacking fault energy and the lower effective and shear strains. This unique fracture phenomenon of drawn wire is presented for the first time in this study since it rarely occurs in general metals during wire drawing.

A Computational Investigation into the Effect of Equal Channel Angular Processing on the Mechanical Properties of Severely Deformed ZK 60 Alloy Validated by Experiments

In this study, the response surface method and finite-element analysis were employed to model the ECAP processing for biodegradable magnesium alloy ZK 60 behavior at 250°C. Using Finite-Element (FE) analysis data was extracted and compared to the what was found by experimenting in order to investigate the effects of the ECAP processing parameters on the plastic deformation behavior of the ECAPed samples. The effective strain and stresses as a function of the number of passes were investigated. Hardness contour maps perpendicular to ECAP direction were plotted. Compressive properties of the billets were also examined. The FE analysis revealed that the maximum stresses were displayed at the corner and peripheral areas compared to the central areas. Moreover, straining through two passes of route Bc displayed maximum effective strain of 2.75 recorded in the top peripheral regions, whereas the central regions displayed 1.25. In addition, ECAP processing via 2-Bc correlated with rises in Hv values in the samples peripheries by 125.4% respectively, when compared with the as-annealed conditions. The compression findings showed also significant enhancement of the compressive strength compared to the as-annealed counterparts.

Effect of punch force on the upsetting deformation process using three-dimensional finite element analysis

Forging is one of the conventional shaping technologies that is widely used for the manufacture of quality products for various industrial applications. The process involves the mechanical application of a punching force to deform a material to the desired shape and improved properties. In most cases, the manufacture of quality products depends on the experience of the designer and trial and error method thus making the process wasteful and costly. The present study reports on the application of finite element method (FEM) for the analysis of the effect of punch force on the stress/strain distribution during the deformation process as a step towards the reduction of trial and error methods in practice. The results show that increase in the punch force leads to inhomogeneity in the strain/stress distribution due to change in the deformation temperature resulting from the internal heat generated during plastic deformation stage and the frictional force at the punch-workpiece interface. It is also observed that the maximum effective strain occurs at the center of the deformed sample and the maximum effective stress occurs at the low effective strain regions. Moreover, the friction parameter increases as the punch force increases.

Development, validation, and application of ligamentous cervical spinal segment C6-C7 of a six-year-old child and an adult

Background and objectiveThe cervical spine is one of the primary regions that is easily injured in traffic accidents. Although adult cervical spine finite element models have been widely adopted to investigate the cervical injury, few efforts have been made with respect to the development and application of FE models of the pediatric cervical spine, especially that of a six-year-old child. The objective of this study is to develop and validate high quality cervical spinal segment C6-C7 FE models of a six-year-old child and an adult, and to further investigate the differences of C6-C7 between the child and adult under different loading conditions. MethodsThe cervical spinal segment C6-C7 FE models were developed by a structured multiblock method, and were verified under flexion, extension, axial rotation, and lateral bending conditions. The validated models were used to investigate the differences of C6-C7 between the child and adult under different loading conditions. ResultsThe global angular displacement of C6-C7, the ligament elongation ratio, and the maximum effective strain of annulus fibrosus of the child were obviously larger than those of the adult under the same loading conditions. Regarding the loading forms, the flexion angular displacement of C6-C7 of the child was obviously larger than those of the extension and lateral bending, while for the adult cervical segment C6-C7, no obvious differences existed. The elongation ratio of different ligaments was highly dependent on the types of loadings. The maximum effective strain of annulus fibrosus under flexion, extension and lateral bending loads occurred at the compressive region of the front, rear, and one compressive lateral side, in which the annulus fibrosus was more susceptible to injury under the lateral bending condition, compared with those of the flexion and extension conditions. ConclusionsBoth the developed child and adult cervical spinal segment C6-C7 FE models exhibited high biofidelity. The responses (angular displacement, the ligament elongation ratio, and the maximum effective strain of annulus fibrosus) of the child and adult are dependent on the loading types, and the responses of the child were obviously larger than those of the adult under the same loading conditions.