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R Tovo - One of the best experts on this subject based on the ideXlab platform.
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mode i stress intensity factors for triangular Corner Crack nearby intersecting of cylindrical holes
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:The paper deals with the Stress Intensity Factor assessment of Cracks at the intersection of holes loaded by internal pressure. Triangular flaws are considered at the intersection of two holes inside a specific specimen. The research examines the influence of hole diameter ratio D1/D2 and the angle between their axes ?. Numerical analysis is performed to determine the Stress Intensity Factors (SIF) of mode I in many different geometric configurations. The actual shape of a real Crack nucleated at the intersection of two cylindrical holes is subject to variable internal pressure and is usually geometrically complex. The Stress Intensity Factor changes along the Crack contour and the Crack shape development is controlled by its local value, e.g. during a fatigue loading. In general, the estimation of the Stress Intensity Factors of Cracks with a complex shape is made by means of numerical methods since closed form solutions in literature are limited. However, in order to solve the problem of Crack propagation more quickly, in the case of a Crack Corner at the intersection between two cylindrical holes, we can assume, in agreement with scientific literature, a symmetrical triangular Crack shape and the Stress Intensity Factor are only calculated at the middle of the Crack. Obviously, this is a strong approximation, but this allows a reduction in the computation effort for Crack growth rate assessments and safety evaluation. In this paper, the weight function technique is used by integrating the actual stress field evaluated in the unCracked model. The method of the weight function is of general validity and the weight function is related to the displacement components close to the Crack front, as proposed by Bueckner and Rice. From a computational point of view, the use of the three-dimensional weight function is complex and in scientific literature a weight function of general validity is not available. Nevertheless, thanks to the work conducted by Petroski and Achenbach, Shen and Glinka, an efficient generalised weight function has been adopted and then developed by Sha and Yang [9], which considers a series expansion of non-singular terms. In this way, the integration of the weight function, multiplied by a nominal stress, is made along a line and not in a two-dimensional domain. In this preliminary work, according to Herz et al., we consider a weight function with three terms by assuming a priori the coefficients of the second and third non-singular terms. This contribution is essentially an extension of a previous paper by Herz et al. They only considered the case of D1/D2=1 and ?=90° (Di are the diameters of the two cylindrical holes and a is the angle between their axis). Here, we extend the analysis to D1/D2 equal to 2, 4 and 8 with an ? of 60 and 45 degrees. With the aid of three-dimensional modelling, an accurate FE model of a triangular Corner Crack at different Crack depths has been made. Subsequently, by using ANSYS finite element software, it is possible to employ the command KCAL that evaluates the Stress Intensity Factors in the middle of the Crack. Subsequently, a comparison between numerical FE results and the analytical results, giving the values of the unknown coefficients of the weight function (the unknown coefficient is indicated in the paper as M1). As reported in the tables, the accuracy of the weight functions in SIF predictions is about 5% despite the strong simplification previously introduced in the model. This result is considerable because it is possible to determine the Stress Intensity Factor of a triangular shaped Crack by a line integral of a stress profile in a model without considering the Crack.
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weight function for Corner Crack nearby intersecting cylindrical holes funzioni peso per cricche ad angolo in corrispondenza di intersezione di fori
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:Intersecting holes inside mechanical component, stressed with internal pressure, generate stress intensification; this kind of geometry detail is very common in the powertrain field. Triangular flaws has been taken into account at the intersection of two holes inside a specified specimen. Influence of bore hole D1/D2 and angle between their axes α are examined. Numerical analysis are performed to determine Stress Intensity factors (SIF) in many geometric configurations. Afterwards, fitting weight function's parameters with FEM results, new SIF analytics expression are shown. Finally, the accuracy of weight functions in SIF predictions for different inner pressure has been checked. SOMMARIO. L'intersezione di condotti cilindrici sollecitati da una pressione interna e sede di concentrazione di tensione. La memoria affronta il problema del calcolo dello Stress Intensity Factors (SIF) di cricche che nucleano in prossimita dell'intersezione di fori cilindrici ad assi complanari. Modelli FEM tridimensionali sono utilizzati per valutare, nel punto mediano, lo SIF di cricche triangolari per poi calcolare la weight function relativa a sollecitazioni di modo I. Sono presi in esame il rapporto fra i diametri dei due fori cilindrici e l'angolo formato dai loro assi. Infine, viene verificata la precisione della weight function nel calcolare lo SIF quando i due condotti sono interessati da una pressione interna.
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mode i stress intensity factors for triangular Corner Crack nearby intersecting of cylindrical holes fattori di intensificazione delle tensioni per cricche ad angolo triangolari in corrispondenza di intersezione di fori sollecitate a modo i
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:The paper deals with the Stress Intensity Factor assessment of Cracks at the intersection of holes loaded by internal pressure. Triangular flaws are considered at the intersection of two holes inside a specific specimen. The research examines the influence of hole diameter ratio D 1 /D 2 and the angle between their axes α. Numerical analysis is performed to determine the Stress Intensity Factors (SIF) of mode I in many different geometric configurations. The actual shape of a real Crack nucleated at the intersection of two cylindrical holes is subject to variable internal pressure and is usually geometrically complex. The Stress Intensity Factor changes along the Crack contour and the Crack shape development is controlled by its local value, e.g. during a fatigue loading. In general, the estimation of the Stress Intensity Factors of Cracks with a complex shape is made by means of numerical methods since closed form solutions in literature are limited. However, in order to solve the problem of Crack propagation more quickly, in the case of a Crack Corner at the intersection between two cylindrical holes, we can assume, in agreement with scientific literature, a symmetrical triangular Crack shape and the Stress Intensity Factor are only calculated at the middle of the Crack. Obviously, this is a strong approximation, but this allows a reduction in the computation effort for Crack growth rate assessments and safety evaluation. In this paper, the weight function technique is used by integrating the actual stress field evaluated in the un- Cracked model. The method of the weight function is of general validity and the weight function is related to the displacement components close to the Crack front, as proposed by Bueckner and Rice. From a computational point of view, the use of the three-dimensional weight function is complex and in scientific literature a weight function of general validity is not available. Nevertheless, thanks to the work conducted by Petroski and Achenbach, Shen and Glinka, an efficient generalised weight function has been adopted and then developed by Sha and Yang (9), which considers a series expansion of non-singular terms. In this way, the integration of the weight function, multiplied by a nominal stress, is made along a line and not in a two-dimensional domain. In this preliminary work, according to Herz et al., we consider a weight function with three terms by assuming a priori the coefficients of the second and third non-singular terms. This contribution is essentially an extension of a previous paper by Herz et al. They only considered the case of D1/D2=1 and =90° (Di are the diameters of the two cylindrical holes and a is the angle between their axis). Here, we extend the analysis to D1/D2 equal to 2, 4 and 8 with an of 60 and 45 degrees.
Martyn J Pavier - One of the best experts on this subject based on the ideXlab platform.
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three dimensional finite element prediction of Crack closure and fatigue Crack growth rate for a Corner Crack
2006Co-Authors: S Simandjuntak, H Alizadeh, David J Smith, Martyn J PavierAbstract:Abstract The effect of plasticity induced Crack closure on fatigue Crack growth rate has been examined for the case of a 2024 aluminium alloy plate with two lateral Corner Cracks emanating from a central hole. The plate was subjected to constant amplitude loading and a combination of constant amplitude and single overload loading prior to the measurement of the opening load. The opening load was measured by comparing the strain ahead of the Crack tips with the far field strain as the load on the specimen was cycled. Measurements were also made of the growth rate of the Crack in fatigue. A three-dimensional finite element quarter model was developed of the plate with a central hole and Corner Cracks. The geometry of the model forced the Crack to assume a constant aspect ratio of bore length to surface length as the Crack grew. Two different aspect ratios of 1:1 and 1.5:1 were considered. The load on the model was cycled and the Crack extended by releasing nodes so as to predict the development of a plastic wake behind the advancing Crack. The opening load was predicted from the finite element displacement versus load results. These opening load predictions agreed favourably with the experimental measurements. The finite element model was also used to predict the fatigue Crack growth rate. This was achieved by first evaluating the effective stress intensity factor range from the stress distribution ahead of the Crack tip. A Paris law fit to high R -ratio test data was then made to allow the corresponding growth rate to be calculated. Encouraging comparisons of the finite element predictions of fatigue Crack growth rate with experimental measurement were obtained.
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fatigue Crack closure of a Corner Crack a comparison of experimental results with finite element predictions
2005Co-Authors: S Simandjuntak, H Alizadeh, Martyn J Pavier, David J SmithAbstract:Abstract Plasticity induced Corner Crack closure has been examined for the case of a middle tension (MT) plate of 14 mm thick 2024-T351 aluminium alloy subjected to cyclic loading. The closure load has been found by comparing the strain just ahead of the Crack tip with the far field strain as the specimen was loaded and then unloaded. Special Crack detection strain gauges were placed in front of the Crack tips on the bore surface and on the free surface to allow measurement of Crack opening and closure stress as the Crack propagates. The offset observation and slope variation methods were used to determine the Crack opening and closure stress levels. A three-dimensional finite element closure model was developed for a Corner Crack emanating from a hole. Finite element analysis gives the displacement of each node around the Crack for which the opening and closure load were evaluated. The fatigue Crack closure stress levels from the finite element analysis were compared with the experimental results giving a good agreement.
David J Smith - One of the best experts on this subject based on the ideXlab platform.
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three dimensional finite element prediction of Crack closure and fatigue Crack growth rate for a Corner Crack
2006Co-Authors: S Simandjuntak, H Alizadeh, David J Smith, Martyn J PavierAbstract:Abstract The effect of plasticity induced Crack closure on fatigue Crack growth rate has been examined for the case of a 2024 aluminium alloy plate with two lateral Corner Cracks emanating from a central hole. The plate was subjected to constant amplitude loading and a combination of constant amplitude and single overload loading prior to the measurement of the opening load. The opening load was measured by comparing the strain ahead of the Crack tips with the far field strain as the load on the specimen was cycled. Measurements were also made of the growth rate of the Crack in fatigue. A three-dimensional finite element quarter model was developed of the plate with a central hole and Corner Cracks. The geometry of the model forced the Crack to assume a constant aspect ratio of bore length to surface length as the Crack grew. Two different aspect ratios of 1:1 and 1.5:1 were considered. The load on the model was cycled and the Crack extended by releasing nodes so as to predict the development of a plastic wake behind the advancing Crack. The opening load was predicted from the finite element displacement versus load results. These opening load predictions agreed favourably with the experimental measurements. The finite element model was also used to predict the fatigue Crack growth rate. This was achieved by first evaluating the effective stress intensity factor range from the stress distribution ahead of the Crack tip. A Paris law fit to high R -ratio test data was then made to allow the corresponding growth rate to be calculated. Encouraging comparisons of the finite element predictions of fatigue Crack growth rate with experimental measurement were obtained.
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fatigue Crack closure of a Corner Crack a comparison of experimental results with finite element predictions
2005Co-Authors: S Simandjuntak, H Alizadeh, Martyn J Pavier, David J SmithAbstract:Abstract Plasticity induced Corner Crack closure has been examined for the case of a middle tension (MT) plate of 14 mm thick 2024-T351 aluminium alloy subjected to cyclic loading. The closure load has been found by comparing the strain just ahead of the Crack tip with the far field strain as the specimen was loaded and then unloaded. Special Crack detection strain gauges were placed in front of the Crack tips on the bore surface and on the free surface to allow measurement of Crack opening and closure stress as the Crack propagates. The offset observation and slope variation methods were used to determine the Crack opening and closure stress levels. A three-dimensional finite element closure model was developed for a Corner Crack emanating from a hole. Finite element analysis gives the displacement of each node around the Crack for which the opening and closure load were evaluated. The fatigue Crack closure stress levels from the finite element analysis were compared with the experimental results giving a good agreement.
S Simandjuntak - One of the best experts on this subject based on the ideXlab platform.
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three dimensional finite element prediction of Crack closure and fatigue Crack growth rate for a Corner Crack
2006Co-Authors: S Simandjuntak, H Alizadeh, David J Smith, Martyn J PavierAbstract:Abstract The effect of plasticity induced Crack closure on fatigue Crack growth rate has been examined for the case of a 2024 aluminium alloy plate with two lateral Corner Cracks emanating from a central hole. The plate was subjected to constant amplitude loading and a combination of constant amplitude and single overload loading prior to the measurement of the opening load. The opening load was measured by comparing the strain ahead of the Crack tips with the far field strain as the load on the specimen was cycled. Measurements were also made of the growth rate of the Crack in fatigue. A three-dimensional finite element quarter model was developed of the plate with a central hole and Corner Cracks. The geometry of the model forced the Crack to assume a constant aspect ratio of bore length to surface length as the Crack grew. Two different aspect ratios of 1:1 and 1.5:1 were considered. The load on the model was cycled and the Crack extended by releasing nodes so as to predict the development of a plastic wake behind the advancing Crack. The opening load was predicted from the finite element displacement versus load results. These opening load predictions agreed favourably with the experimental measurements. The finite element model was also used to predict the fatigue Crack growth rate. This was achieved by first evaluating the effective stress intensity factor range from the stress distribution ahead of the Crack tip. A Paris law fit to high R -ratio test data was then made to allow the corresponding growth rate to be calculated. Encouraging comparisons of the finite element predictions of fatigue Crack growth rate with experimental measurement were obtained.
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fatigue Crack closure of a Corner Crack a comparison of experimental results with finite element predictions
2005Co-Authors: S Simandjuntak, H Alizadeh, Martyn J Pavier, David J SmithAbstract:Abstract Plasticity induced Corner Crack closure has been examined for the case of a middle tension (MT) plate of 14 mm thick 2024-T351 aluminium alloy subjected to cyclic loading. The closure load has been found by comparing the strain just ahead of the Crack tip with the far field strain as the specimen was loaded and then unloaded. Special Crack detection strain gauges were placed in front of the Crack tips on the bore surface and on the free surface to allow measurement of Crack opening and closure stress as the Crack propagates. The offset observation and slope variation methods were used to determine the Crack opening and closure stress levels. A three-dimensional finite element closure model was developed for a Corner Crack emanating from a hole. Finite element analysis gives the displacement of each node around the Crack for which the opening and closure load were evaluated. The fatigue Crack closure stress levels from the finite element analysis were compared with the experimental results giving a good agreement.
Enrico Salvati - One of the best experts on this subject based on the ideXlab platform.
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mode i stress intensity factors for triangular Corner Crack nearby intersecting of cylindrical holes
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:The paper deals with the Stress Intensity Factor assessment of Cracks at the intersection of holes loaded by internal pressure. Triangular flaws are considered at the intersection of two holes inside a specific specimen. The research examines the influence of hole diameter ratio D1/D2 and the angle between their axes ?. Numerical analysis is performed to determine the Stress Intensity Factors (SIF) of mode I in many different geometric configurations. The actual shape of a real Crack nucleated at the intersection of two cylindrical holes is subject to variable internal pressure and is usually geometrically complex. The Stress Intensity Factor changes along the Crack contour and the Crack shape development is controlled by its local value, e.g. during a fatigue loading. In general, the estimation of the Stress Intensity Factors of Cracks with a complex shape is made by means of numerical methods since closed form solutions in literature are limited. However, in order to solve the problem of Crack propagation more quickly, in the case of a Crack Corner at the intersection between two cylindrical holes, we can assume, in agreement with scientific literature, a symmetrical triangular Crack shape and the Stress Intensity Factor are only calculated at the middle of the Crack. Obviously, this is a strong approximation, but this allows a reduction in the computation effort for Crack growth rate assessments and safety evaluation. In this paper, the weight function technique is used by integrating the actual stress field evaluated in the unCracked model. The method of the weight function is of general validity and the weight function is related to the displacement components close to the Crack front, as proposed by Bueckner and Rice. From a computational point of view, the use of the three-dimensional weight function is complex and in scientific literature a weight function of general validity is not available. Nevertheless, thanks to the work conducted by Petroski and Achenbach, Shen and Glinka, an efficient generalised weight function has been adopted and then developed by Sha and Yang [9], which considers a series expansion of non-singular terms. In this way, the integration of the weight function, multiplied by a nominal stress, is made along a line and not in a two-dimensional domain. In this preliminary work, according to Herz et al., we consider a weight function with three terms by assuming a priori the coefficients of the second and third non-singular terms. This contribution is essentially an extension of a previous paper by Herz et al. They only considered the case of D1/D2=1 and ?=90° (Di are the diameters of the two cylindrical holes and a is the angle between their axis). Here, we extend the analysis to D1/D2 equal to 2, 4 and 8 with an ? of 60 and 45 degrees. With the aid of three-dimensional modelling, an accurate FE model of a triangular Corner Crack at different Crack depths has been made. Subsequently, by using ANSYS finite element software, it is possible to employ the command KCAL that evaluates the Stress Intensity Factors in the middle of the Crack. Subsequently, a comparison between numerical FE results and the analytical results, giving the values of the unknown coefficients of the weight function (the unknown coefficient is indicated in the paper as M1). As reported in the tables, the accuracy of the weight functions in SIF predictions is about 5% despite the strong simplification previously introduced in the model. This result is considerable because it is possible to determine the Stress Intensity Factor of a triangular shaped Crack by a line integral of a stress profile in a model without considering the Crack.
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weight function for Corner Crack nearby intersecting cylindrical holes funzioni peso per cricche ad angolo in corrispondenza di intersezione di fori
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:Intersecting holes inside mechanical component, stressed with internal pressure, generate stress intensification; this kind of geometry detail is very common in the powertrain field. Triangular flaws has been taken into account at the intersection of two holes inside a specified specimen. Influence of bore hole D1/D2 and angle between their axes α are examined. Numerical analysis are performed to determine Stress Intensity factors (SIF) in many geometric configurations. Afterwards, fitting weight function's parameters with FEM results, new SIF analytics expression are shown. Finally, the accuracy of weight functions in SIF predictions for different inner pressure has been checked. SOMMARIO. L'intersezione di condotti cilindrici sollecitati da una pressione interna e sede di concentrazione di tensione. La memoria affronta il problema del calcolo dello Stress Intensity Factors (SIF) di cricche che nucleano in prossimita dell'intersezione di fori cilindrici ad assi complanari. Modelli FEM tridimensionali sono utilizzati per valutare, nel punto mediano, lo SIF di cricche triangolari per poi calcolare la weight function relativa a sollecitazioni di modo I. Sono presi in esame il rapporto fra i diametri dei due fori cilindrici e l'angolo formato dai loro assi. Infine, viene verificata la precisione della weight function nel calcolare lo SIF quando i due condotti sono interessati da una pressione interna.
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mode i stress intensity factors for triangular Corner Crack nearby intersecting of cylindrical holes fattori di intensificazione delle tensioni per cricche ad angolo triangolari in corrispondenza di intersezione di fori sollecitate a modo i
2013Co-Authors: Enrico Salvati, Paolo Livieri, R TovoAbstract:The paper deals with the Stress Intensity Factor assessment of Cracks at the intersection of holes loaded by internal pressure. Triangular flaws are considered at the intersection of two holes inside a specific specimen. The research examines the influence of hole diameter ratio D 1 /D 2 and the angle between their axes α. Numerical analysis is performed to determine the Stress Intensity Factors (SIF) of mode I in many different geometric configurations. The actual shape of a real Crack nucleated at the intersection of two cylindrical holes is subject to variable internal pressure and is usually geometrically complex. The Stress Intensity Factor changes along the Crack contour and the Crack shape development is controlled by its local value, e.g. during a fatigue loading. In general, the estimation of the Stress Intensity Factors of Cracks with a complex shape is made by means of numerical methods since closed form solutions in literature are limited. However, in order to solve the problem of Crack propagation more quickly, in the case of a Crack Corner at the intersection between two cylindrical holes, we can assume, in agreement with scientific literature, a symmetrical triangular Crack shape and the Stress Intensity Factor are only calculated at the middle of the Crack. Obviously, this is a strong approximation, but this allows a reduction in the computation effort for Crack growth rate assessments and safety evaluation. In this paper, the weight function technique is used by integrating the actual stress field evaluated in the un- Cracked model. The method of the weight function is of general validity and the weight function is related to the displacement components close to the Crack front, as proposed by Bueckner and Rice. From a computational point of view, the use of the three-dimensional weight function is complex and in scientific literature a weight function of general validity is not available. Nevertheless, thanks to the work conducted by Petroski and Achenbach, Shen and Glinka, an efficient generalised weight function has been adopted and then developed by Sha and Yang (9), which considers a series expansion of non-singular terms. In this way, the integration of the weight function, multiplied by a nominal stress, is made along a line and not in a two-dimensional domain. In this preliminary work, according to Herz et al., we consider a weight function with three terms by assuming a priori the coefficients of the second and third non-singular terms. This contribution is essentially an extension of a previous paper by Herz et al. They only considered the case of D1/D2=1 and =90° (Di are the diameters of the two cylindrical holes and a is the angle between their axis). Here, we extend the analysis to D1/D2 equal to 2, 4 and 8 with an of 60 and 45 degrees.