Pub Date : 2021-07-16DOI: 10.1177/03093247211045602
Weston D Craig, Fiona B Van Leeuwen, Steven R Jarrett, R. Hansen, R. Berke
In certain applications, native surface patterns can be used in place of speckle patterns in digital image correlation (DIC). This paper explores the feasibility of using text as a native speckle pattern in DIC. Five text speckle patterns are tested in three different scenarios: a rigid body translation test, a rigid body rotation test, and an out of plane bending test. The patterns are benchmarked against a sixth, random speckle pattern applied using traditional DIC speckling methods. Rigid body translation tests are additionally performed on text patterns with varying font types and line spacings. In general, text patterns have good contrast, but low density as line spacing increases. Measurement uncertainty for the text patterns was comparable to measurement uncertainty in the random speckle pattern. Results from these tests show that while text patterns cannot be expected to perform better than a traditional DIC speckle pattern, text patterns can be effective speckle patterns in situations where already present on a specimen and applying a traditional speckle pattern is difficult.
{"title":"Using text as a native speckle pattern in digital image correlation","authors":"Weston D Craig, Fiona B Van Leeuwen, Steven R Jarrett, R. Hansen, R. Berke","doi":"10.1177/03093247211045602","DOIUrl":"https://doi.org/10.1177/03093247211045602","url":null,"abstract":"In certain applications, native surface patterns can be used in place of speckle patterns in digital image correlation (DIC). This paper explores the feasibility of using text as a native speckle pattern in DIC. Five text speckle patterns are tested in three different scenarios: a rigid body translation test, a rigid body rotation test, and an out of plane bending test. The patterns are benchmarked against a sixth, random speckle pattern applied using traditional DIC speckling methods. Rigid body translation tests are additionally performed on text patterns with varying font types and line spacings. In general, text patterns have good contrast, but low density as line spacing increases. Measurement uncertainty for the text patterns was comparable to measurement uncertainty in the random speckle pattern. Results from these tests show that while text patterns cannot be expected to perform better than a traditional DIC speckle pattern, text patterns can be effective speckle patterns in situations where already present on a specimen and applying a traditional speckle pattern is difficult.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74519308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1177/03093247211029792
Yongqiang Li, Nianzhu Wang, Wenkai Yao, Tao Wang, Mao Zhou
Improving the impact energy dissipation capacity of functionally graded brittle materials through pore design will help avoid or delay failure. In order to improve the impact energy dissipation capacity of functionally graded brittle materials, pores with specific shapes can be implanted inside them. The effect of pore shape on the impact properties of functionally graded brittle materials was investigated using a lattice-spring model that can quantitatively represent the mechanical properties of functionally graded brittle materials. The calculated results show that the pores with negative Poisson’s ratio such as inner-concave triangle, fourth-order star, and inner-concave hexagon are easy to collapse under the impact, while the square and square-hexagon pores have the strongest resistance to deformation. For all seven pore shapes, the Hugoniot elastic limit of the samples decreased gradually with increasing porosity, and the Hugoniot elastic limit did not change with the change of piston velocity. The propagation velocity of the deformation wave increases with the piston velocity and the velocity of the particle corresponding to the Hugoniot state behind the deformation wave increases accordingly. The principle that pores can enhance the macroscopic impact energy dissipation capacity of functionally graded brittle material samples revealed in this paper will contribute to the prevention of sample impact failure and provide guidance for the optimal design of impact kinetic properties of samples.
{"title":"Influence of pore shape on impact dynamics characteristics of functionally graded brittle materials","authors":"Yongqiang Li, Nianzhu Wang, Wenkai Yao, Tao Wang, Mao Zhou","doi":"10.1177/03093247211029792","DOIUrl":"https://doi.org/10.1177/03093247211029792","url":null,"abstract":"Improving the impact energy dissipation capacity of functionally graded brittle materials through pore design will help avoid or delay failure. In order to improve the impact energy dissipation capacity of functionally graded brittle materials, pores with specific shapes can be implanted inside them. The effect of pore shape on the impact properties of functionally graded brittle materials was investigated using a lattice-spring model that can quantitatively represent the mechanical properties of functionally graded brittle materials. The calculated results show that the pores with negative Poisson’s ratio such as inner-concave triangle, fourth-order star, and inner-concave hexagon are easy to collapse under the impact, while the square and square-hexagon pores have the strongest resistance to deformation. For all seven pore shapes, the Hugoniot elastic limit of the samples decreased gradually with increasing porosity, and the Hugoniot elastic limit did not change with the change of piston velocity. The propagation velocity of the deformation wave increases with the piston velocity and the velocity of the particle corresponding to the Hugoniot state behind the deformation wave increases accordingly. The principle that pores can enhance the macroscopic impact energy dissipation capacity of functionally graded brittle material samples revealed in this paper will contribute to the prevention of sample impact failure and provide guidance for the optimal design of impact kinetic properties of samples.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89572628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-01DOI: 10.1177/03093247211027061
Miguel G Oliveira, S. Thuillier, A. Andrade-Campos
The accuracy of strategies combining heterogeneous mechanical tests and full-field strain measurement techniques is dependent on many factors. Recently, many heterogeneous mechanical tests with different specimen shapes have been proposed using optimization techniques or empirical knowledge. However, a comparison of heterogeneous mechanical tests is a difficult task because studies use different materials and different representations of the strain and stress states. This work discusses metrics, calculated from the stress and strain tensors, to evaluate heterogeneous mechanical tests and proposes a metric to evaluate the tests’ sensitivity to anisotropy. To illustrate the approach, four heterogeneous mechanical tests are evaluated through the use of the suggested metrics. Results show that the use of various metrics provides a good basis to evaluate heterogeneous mechanical tests. Moreover, this work identifies a heterogeneous mechanical test achieving a high range of mechanical states and high values of equivalent plastic strain.
{"title":"Evaluation of heterogeneous mechanical tests for model calibration of sheet metals","authors":"Miguel G Oliveira, S. Thuillier, A. Andrade-Campos","doi":"10.1177/03093247211027061","DOIUrl":"https://doi.org/10.1177/03093247211027061","url":null,"abstract":"The accuracy of strategies combining heterogeneous mechanical tests and full-field strain measurement techniques is dependent on many factors. Recently, many heterogeneous mechanical tests with different specimen shapes have been proposed using optimization techniques or empirical knowledge. However, a comparison of heterogeneous mechanical tests is a difficult task because studies use different materials and different representations of the strain and stress states. This work discusses metrics, calculated from the stress and strain tensors, to evaluate heterogeneous mechanical tests and proposes a metric to evaluate the tests’ sensitivity to anisotropy. To illustrate the approach, four heterogeneous mechanical tests are evaluated through the use of the suggested metrics. Results show that the use of various metrics provides a good basis to evaluate heterogeneous mechanical tests. Moreover, this work identifies a heterogeneous mechanical test achieving a high range of mechanical states and high values of equivalent plastic strain.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89401325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-26DOI: 10.1177/03093247211027085
N. Faisal, A. Fowlie, Joe Connell, Sean Mackenzie, R. Noble, Anil Prathuru
Helical Auxetic Yarns (HAYs) can be used in a variety of applications from healthcare to blast and impact resistance. This work focuses on the effect of the use of different core materials (e.g. rubber, polyurethane, polytetrafluoroethylene/teflon, polypropylene, polyetheretherketone, polycarbonate, acetal) with a nitinol wire wrap component on the maximum Negative Poisson Ratio (NPR) produced and thus the auxetic performance of Helical Auxetic Yarns (HAYs). From the analytical model, it was found that an acetal core produced the largest NPR when compared to the other six materials. The trend obtained from the experimental tensile tests (validation) correlated closely with the theoretical predictions of the NPR as axial strain was increased. The experimental method presented a maximum NPR at an average axial strain of 0.148 which was close to the strain of 0.155 predicted by theory. However, the maximum experimental NPR was significantly lower than that predicted by the analytical model.
{"title":"Investigating the influence of the core material on the mechanical performance of a nitinol wire wrapped helical auxetic yarn","authors":"N. Faisal, A. Fowlie, Joe Connell, Sean Mackenzie, R. Noble, Anil Prathuru","doi":"10.1177/03093247211027085","DOIUrl":"https://doi.org/10.1177/03093247211027085","url":null,"abstract":"Helical Auxetic Yarns (HAYs) can be used in a variety of applications from healthcare to blast and impact resistance. This work focuses on the effect of the use of different core materials (e.g. rubber, polyurethane, polytetrafluoroethylene/teflon, polypropylene, polyetheretherketone, polycarbonate, acetal) with a nitinol wire wrap component on the maximum Negative Poisson Ratio (NPR) produced and thus the auxetic performance of Helical Auxetic Yarns (HAYs). From the analytical model, it was found that an acetal core produced the largest NPR when compared to the other six materials. The trend obtained from the experimental tensile tests (validation) correlated closely with the theoretical predictions of the NPR as axial strain was increased. The experimental method presented a maximum NPR at an average axial strain of 0.148 which was close to the strain of 0.155 predicted by theory. However, the maximum experimental NPR was significantly lower than that predicted by the analytical model.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90425264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-26DOI: 10.1177/03093247211027077
N. Alang, Lei Zhao, K. Nikbin
Conventional strain-based numerical prediction assumes that failure occurs when ductility is exhausted or accumulation of creep strain reaches the critical failure strain. Due to instability at the onset of rupture, the failure strain value appears to be scattered and leads to the erroneousness in prediction. In this paper, a new local constraint-based damage model incorporating the Monkman–Grant ductility, as a measure of strain during uniform creep deformation stage, was implemented into a Finite Element (FE) model to predict the creep damage and rupture of Grade 92 steel under uniaxial and multiaxial stress states. The prediction was applied on plain and notched bar specimens with various notch acuities. The uniaxial stress-dependent Monkman–Grant (MG) failure strain was adopted in the FE to simulate the influence of the constraints which were induced by the creep damage. The implication of reduced failure strain in long-term creep time on the rupture prediction is discussed. The multiaxial MG failure strain of the notched bar, which has a lower value than uniaxial failure strain due to the geometrical constraint, was estimated based on the linear inverse relationship between normalised MG failure strain and normalised triaxiality factor. It was found that the results obtained from the proposed technique were in good agreement with the experimental data within the scatter band of ± factor of 2. It was shown that MG failure strain can be used as an alternative to strain at fracture. MG strain outweighed strain at fracture because the determination of its value only required short-term testing to be performed. In most cases considered in the present investigation, the rupture-type fracture was predicted, however, there was evidence that under high constraint and low stress, stable crack propagation occurred before fracture. The location of the maximum creep damage was found to be dependent on the creep time, geometry or acuity level of the specimen. For sharp notch specimen, the failure was initiated near the notch root, however, as the notch radius increased, the initiation location moved further away towards the specimen centre.
{"title":"Evaluation of Monkman–Grant strain as a key parameter in ductility exhaustion damage model to predict creep rupture of grade 92 steel","authors":"N. Alang, Lei Zhao, K. Nikbin","doi":"10.1177/03093247211027077","DOIUrl":"https://doi.org/10.1177/03093247211027077","url":null,"abstract":"Conventional strain-based numerical prediction assumes that failure occurs when ductility is exhausted or accumulation of creep strain reaches the critical failure strain. Due to instability at the onset of rupture, the failure strain value appears to be scattered and leads to the erroneousness in prediction. In this paper, a new local constraint-based damage model incorporating the Monkman–Grant ductility, as a measure of strain during uniform creep deformation stage, was implemented into a Finite Element (FE) model to predict the creep damage and rupture of Grade 92 steel under uniaxial and multiaxial stress states. The prediction was applied on plain and notched bar specimens with various notch acuities. The uniaxial stress-dependent Monkman–Grant (MG) failure strain was adopted in the FE to simulate the influence of the constraints which were induced by the creep damage. The implication of reduced failure strain in long-term creep time on the rupture prediction is discussed. The multiaxial MG failure strain of the notched bar, which has a lower value than uniaxial failure strain due to the geometrical constraint, was estimated based on the linear inverse relationship between normalised MG failure strain and normalised triaxiality factor. It was found that the results obtained from the proposed technique were in good agreement with the experimental data within the scatter band of ± factor of 2. It was shown that MG failure strain can be used as an alternative to strain at fracture. MG strain outweighed strain at fracture because the determination of its value only required short-term testing to be performed. In most cases considered in the present investigation, the rupture-type fracture was predicted, however, there was evidence that under high constraint and low stress, stable crack propagation occurred before fracture. The location of the maximum creep damage was found to be dependent on the creep time, geometry or acuity level of the specimen. For sharp notch specimen, the failure was initiated near the notch root, however, as the notch radius increased, the initiation location moved further away towards the specimen centre.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75348943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-16DOI: 10.1177/03093247211027081
Kunpeng Han, Dinghua Zhang, C. Yao, L. Tan, Zheng Zhou, Yu Zhao
The material properties of the surface layer caused by deep rolling are closely related to the degree of strain hardening. It is of great significance to establish the prediction model of strain distribution to realize the surface strain control and improve the service performance of deep rolling parts. In this study, the analytical models of elastic-plastic strain based on the Hertz contact theory were established by two different methods. The accuracy of the analytical prediction model of elastic-plastic strain was examined by deep rolling simulation. Then, the influence of deep rolling parameters, such as rolling force, the ball diameter, and material on the elastic-plastic strain along the depth was studied and validated by the microhardness profiles along the depth. The results indicate that the analytical model established by the first method is more accurate, and the error between maximum elastic-plastic strain obtained by the first method and finite element (FE) simulation is 12.6%. The elastic-plastic strain along the depth increases with the increasing rolling force and decreases with the increasing ball diameter, and its effective depth increases with the increasing rolling force. The tungsten carbide ball generates more elastic-plastic strain than balls of the other two materials (silicon nitride and steel). In addition, the elastic-plastic strain profiles are in accordance with the change of microhardness along the depth. In a word, the model can be used to predict the strain distribution along the depth induced by deep rolling.
{"title":"Analytical modeling of through depth strain induced by deep rolling","authors":"Kunpeng Han, Dinghua Zhang, C. Yao, L. Tan, Zheng Zhou, Yu Zhao","doi":"10.1177/03093247211027081","DOIUrl":"https://doi.org/10.1177/03093247211027081","url":null,"abstract":"The material properties of the surface layer caused by deep rolling are closely related to the degree of strain hardening. It is of great significance to establish the prediction model of strain distribution to realize the surface strain control and improve the service performance of deep rolling parts. In this study, the analytical models of elastic-plastic strain based on the Hertz contact theory were established by two different methods. The accuracy of the analytical prediction model of elastic-plastic strain was examined by deep rolling simulation. Then, the influence of deep rolling parameters, such as rolling force, the ball diameter, and material on the elastic-plastic strain along the depth was studied and validated by the microhardness profiles along the depth. The results indicate that the analytical model established by the first method is more accurate, and the error between maximum elastic-plastic strain obtained by the first method and finite element (FE) simulation is 12.6%. The elastic-plastic strain along the depth increases with the increasing rolling force and decreases with the increasing ball diameter, and its effective depth increases with the increasing rolling force. The tungsten carbide ball generates more elastic-plastic strain than balls of the other two materials (silicon nitride and steel). In addition, the elastic-plastic strain profiles are in accordance with the change of microhardness along the depth. In a word, the model can be used to predict the strain distribution along the depth induced by deep rolling.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79211032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-15DOI: 10.1177/03093247211025208
J. Kazakeviciute, J. Rouse, D. Focatiis, C. Hyde
Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of material. These methods are particularly useful when there is limited source material to facilitate a sufficient number of standard specimen tests, if any at all. Such situations include the development of new materials or when performing routine maintenance/inspection studies of in-service components, requiring that material conditions are updated with service exposure. The potentially more challenging loading conditions and complex stress states experienced by small specimens, in comparison with standard specimen geometries, has led to a tendency for these methods to be used in ranking studies rather than for fundamental material parameter determination. Classifying a specimen as ‘small’ can be subjective, and in the present work the focus is to review testing methods that utilise specimens with characteristic dimensions of less than 50 mm. By doing this, observations made here will be relevant to industrial service monitoring problems, wherein small samples of material are extracted and tested from operational components in such a way that structural integrity is not compromised. Whilst recently the majority of small specimen test techniques development have focused on the determination of creep behaviour/properties as well as sub-size tensile testing, attention is given here to small specimen testing methods for determining specific tensile, fatigue, fracture and crack growth properties. These areas are currently underrepresented in published reviews. The suitability of specimens and methods is discussed here, along with associated advantages and disadvantages.
{"title":"Small specimen techniques for estimation of tensile, fatigue, fracture and crack propagation material model parameters","authors":"J. Kazakeviciute, J. Rouse, D. Focatiis, C. Hyde","doi":"10.1177/03093247211025208","DOIUrl":"https://doi.org/10.1177/03093247211025208","url":null,"abstract":"Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of material. These methods are particularly useful when there is limited source material to facilitate a sufficient number of standard specimen tests, if any at all. Such situations include the development of new materials or when performing routine maintenance/inspection studies of in-service components, requiring that material conditions are updated with service exposure. The potentially more challenging loading conditions and complex stress states experienced by small specimens, in comparison with standard specimen geometries, has led to a tendency for these methods to be used in ranking studies rather than for fundamental material parameter determination. Classifying a specimen as ‘small’ can be subjective, and in the present work the focus is to review testing methods that utilise specimens with characteristic dimensions of less than 50 mm. By doing this, observations made here will be relevant to industrial service monitoring problems, wherein small samples of material are extracted and tested from operational components in such a way that structural integrity is not compromised. Whilst recently the majority of small specimen test techniques development have focused on the determination of creep behaviour/properties as well as sub-size tensile testing, attention is given here to small specimen testing methods for determining specific tensile, fatigue, fracture and crack growth properties. These areas are currently underrepresented in published reviews. The suitability of specimens and methods is discussed here, along with associated advantages and disadvantages.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82621178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-02DOI: 10.1177/03093247211020840
H. Ramezannejad Azarboni, A. Darvizeh
The effect of strain rate on the cavitation time and elastoplastic deformation of steel rectangular plate subjected to underwater explosion load is analytically and numerically investigated in this study. At the cavitation time, the total pressure of the explosion is eliminated so that the cavitation time plays a significant role in the elastoplastic deformation of underwater explosive forming of plate. Taking into account the strain rate effect, the Cowper-Symond constitutive equation of mild steel is employed. Exact linear solution using the Eigen function and numerical linear and nonlinear solution using finite difference method (FDM) of dynamic response of impulsively plate is obtained. Implementing the linear work hardening, the stress, strain, displacement, and velocity in any steps of loading are calculated. The time of cavitation can be recognized in elastic or plastic regimes by applying the Cowper-Symond constitutive equation. Considering the strain rate influence, the effects of charge mass and standoff are investigated to occur of cavitation and time dependent deflection and velocity of a rectangular plate.
{"title":"The influence of strain rate on the cavitation time and deformation of an underwater impulsively rectangular plate","authors":"H. Ramezannejad Azarboni, A. Darvizeh","doi":"10.1177/03093247211020840","DOIUrl":"https://doi.org/10.1177/03093247211020840","url":null,"abstract":"The effect of strain rate on the cavitation time and elastoplastic deformation of steel rectangular plate subjected to underwater explosion load is analytically and numerically investigated in this study. At the cavitation time, the total pressure of the explosion is eliminated so that the cavitation time plays a significant role in the elastoplastic deformation of underwater explosive forming of plate. Taking into account the strain rate effect, the Cowper-Symond constitutive equation of mild steel is employed. Exact linear solution using the Eigen function and numerical linear and nonlinear solution using finite difference method (FDM) of dynamic response of impulsively plate is obtained. Implementing the linear work hardening, the stress, strain, displacement, and velocity in any steps of loading are calculated. The time of cavitation can be recognized in elastic or plastic regimes by applying the Cowper-Symond constitutive equation. Considering the strain rate influence, the effects of charge mass and standoff are investigated to occur of cavitation and time dependent deflection and velocity of a rectangular plate.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77898997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-27DOI: 10.1177/03093247211021257
M. M. Kasaei, M. Oliveira
This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.
{"title":"Influence of the contact with friction on the deformation behavior of advanced high strength steels in the Nakajima test","authors":"M. M. Kasaei, M. Oliveira","doi":"10.1177/03093247211021257","DOIUrl":"https://doi.org/10.1177/03093247211021257","url":null,"abstract":"This work presents a new understanding on the deformation mechanics involved in the Nakajima test, which is commonly used to determine the forming limit curve of sheet metals, and is focused on the interaction between the friction conditions and the deformation behaviour of a dual phase steel. The methodology is based on the finite element analysis of the Nakajima test, considering different values of the classic Coulomb friction coefficient, including a pressure-dependent model. The validity of the finite element model is examined through a comparison with experimental data. The results show that friction affects the location and strain path of the necking point by changing the strain rate distribution in the specimen. The strain localization alters the contact status from slip to stick at a portion of the contact area from the pole to the necking zone. This leads to the sharp increase of the strain rate at the necking point, as the punch rises further. The influence of the pressure-dependent friction coefficient on the deformation behaviour is very small, due to the uniform distribution of the contact pressure in the Nakajima test. Moreover, the low contact pressure range attained cannot properly replicate real contact condition in sheet metal forming processes of advanced high strength steels.","PeriodicalId":50038,"journal":{"name":"Journal of Strain Analysis for Engineering Design","volume":null,"pages":null},"PeriodicalIF":1.6,"publicationDate":"2021-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1177/03093247211021257","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72534189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-26DOI: 10.1177/03093247211021240
R. Yildiz
The paper computationally investigates the explosive forming of the oxygen-free high thermal conductivity (OFHC) copper tube subjected to five different explosives. To investigate the effect of explosive type on the formability of OFHC copper tube, commonly used explosives, including C-4, TNT, HMX, Comp-B, and PBXN, was compared by using the finite element method. To verify the developed finite element model (FEM), the explosive forming experiments were carried out by using C-4. In the simulations, Coupled-Eulerian-Lagrangian (CEL) method to model the large deformations, Jones-Wilkins-Lee (JWL) equations of state (EOS) to define the explosive properties and Johnson-Cook (J-C) strength and damage models to specify the metal’s mechanical behavior were utilized. Besides, Hillerborg’s fracture energy was calculated with the Charpy impact test results and given as input to the FEM. The results of FEM were compared and verified using the results of explosive forming tests considering the mesh density and friction coefficient. The simulations revealed that the explosive type affected both the final shape and also the strain rate of the copper tube. When the simulation results for C-4 was taken as reference, HMX and PBX-N increased the strain rate as 110%, roughly. However, Comp-B and TNT reduced the strain rate by nearly 10% and 22%, respectively. Also, the explosive type changed the final hardness of the metal. OFHC Copper had the lowest hardness (112.7 HV) when the simulations were conducted with TNT. In contrast, the highest hardness value (129.5 HV) was reached when HMX was used in the simulations. In addition, simulations put forth that Hillerborg’s fracture energy criteria could be used in the explosive simulations to predict the damage on the metals.
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