Nao-Aki NODA | Kyushu Institute of Technology (original) (raw)

Papers by Nao-Aki NODA

Archive of applied mechanics, Mar 5, 2024

This paper has proposed an efficient analysis method to calculate interface stress intensity fact... more This paper has proposed an efficient analysis method to calculate interface stress intensity factors (SIFs) based on a proportional stress field of a reference problem whose exact solution is available. In the previous proportional methods, the same crack length and the same element size were applied to both reference and unknown problems so that the same FEM error can be produced. Therefore, when analyzing many unknown problems, the conventional method needs to analyze many reference problems at the same time. Since this approach is time-consuming, this paper considers how to calculate many crack lengths efficiently by using only one single reference solution modeling. For this purpose, several general relations of SIFs are derived for the unknown and the reference problems when both crack length and element size are different. To analyze many unknown problems accurately by using a single reference solution modeling, how to choose the most suitable element dimension of the reference model is clarified. The proposed method is especially useful for crack propagation analysis. Keywords Stress intensity factor • Interface crack • Bimaterial plate • Finite element method • Proportional stress field List of symbols a Length of the interface crack in the unknown problem 2a* Length of the interface crack in the reference problem C 1 , C 2 Normalized factors for short interface edge crack based on the singular stress field at the interface end without the crack E Young's modulus e Minimum element size at the crack tip in the unknown problem e* Minimum element size at the crack tip in the reference problem

Key Engineering Materials, Nov 1, 2010

Adhesive joints are widely used as the joints with the same or different adherents, such as in en... more Adhesive joints are widely used as the joints with the same or different adherents, such as in engineering and electric devices. However, because of mismatch of different materials properties, failures due to crack initiation and propagation are often observed on the interface between adhesive and adherents. Therefore, it is important to analyze stress intensity factor of crack on the interface. In this paper, the effect of material combination of adhesive and adherents on stress intensity factor and effect of the thickness of adhesive on stress intensity factor are discussed. A useful method to calculate the stress intensity factor of interface crack is presented with focusing on the stresses at the crack tip calculated by finite element method. The stress intensity factors are indicated in charts under different thickness of adhesive . It is found that the intensity of singular stress first increases with increasing , then decreases from about , and keeps constant from about , when is the width of adhesive. These results are helpful to design dimensions of devices and choose appropriate materials when adhesives are used inside of them.

The composite patch repair technology can be utilized to provide upgrades, such as higher design ... more The composite patch repair technology can be utilized to provide upgrades, such as higher design requirements and life extensions. However, in this case, failures easily happen on the edge interface between the substrate material and the restorative material, because of the incompatible of different properties. Failures such as flaws or cracks lying along the interface reduce the strength of the structure significantly. In this paper, the numerical solutions of hypersingular integro-differential equations are discussed in the analysis of three dimensional interfacial cracks subjected to general internal pressure, and the problem is formulated on the basis of the body force method. The stress intensity factors are given with varying material combinations. It is found that the stress intensity factors and are determined by the bi-materials constant alone, independent of elastic modulus ratio and Poisson's ratio.

WIT transactions on engineering sciences, 1998

This paper deals with the interaction of interface cracks and arbitrarily arranged internal crack... more This paper deals with the interaction of interface cracks and arbitrarily arranged internal cracks in bonded dissimilar materials. The problem is analyzed using the singular integral equations based on the body force method. In the numerical analysis, the unknown functions of the body force densities are approximated by the products of the fundamental density functions and power series. Here, the fundamental density functions are the exact body force densities to express a single interface crack and a single internal crack. The stress intensity factors of the interface crack are systematically calculated for various crack dimensions, arrangements of the crack and elastic constants of the materials. The interaction effect of these problems is discussed by comparing the numerical results with the results of ordinary cracks in homogeneous materials.

The Proceedings of Conference of Kyushu Branch, 2010

The Proceedings of Conference of Kyushu Branch, 2013

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A, 1997

Journal of Applied Mechanics, 2003

In short fiber reinforced composite it is known that the singular stress at the end of fibers cau... more In short fiber reinforced composite it is known that the singular stress at the end of fibers causes crack initiation, propagation, and final failure. The singular stress field is controlled by the generalized stress intensity factors defined at the end of the inclusion. In this study the stress intensity factors are discussed for an elastic cylindrical inclusion in an infinite body under (A) asymmetric uniaxial tension in the x direction, and (B) symmetric uniaxial tension in the z direction. These problems are formulated as a system of integral equations with Cauchy-type or logarithmic-type singularities, where densities of body force distributed in infinite bodies having the same elastic constants as those of the matrix and inclusion are unknown. In the numerical analysis, the unknown body force densities are expressed as fundamental density functions and weight functions. Here, fundamental density functions are chosen to express the symmetric and skew-symmetric stress singularit...

The Proceedings of Conference of Kyushu Branch, 2007

Mechanics Based Design of Structures and Machines, 2020

It is well known that the prevailing torque for special bolt-nut connections is useful for evalua... more It is well known that the prevailing torque for special bolt-nut connections is useful for evaluating antiloosening performance. In our previous studies, several slight pitch differences were introduced between the bolt-nut connections towards realizing anti-loosening performance as well as high fatigue strength by applying axi-symmetric finite element method (FEM). In this study, by applying three-dimensional FEM, the nut screwing process is analyzed to obtain the prevailing torque Tp confirming anti-loosening. Since the nut unscrewing properties after the nut tightening is more important to prevent the nut self-loosening, the nut unscrewing is also analyzed to obtain the residual prevailing torque Tp u newly defined in this process. Both results of Tp and Tp u are in good agreement with the experimental results. With increasing the pitch difference, the residual prevailing torque Tp u increases as well as the prevailing torque Tp. Those obtained values of Tp and Tp u suggest that suitable pitch difference nuts may provide good anti-loosening performance.

IOP Conference Series: Materials Science and Engineering, 2018

Bimetallic rolls are widely used in steel rolling industries because of the excellent hardness, w... more Bimetallic rolls are widely used in steel rolling industries because of the excellent hardness, wear resistance, and high temperature properties. However, thermal stress is produced by heating-cooling thermal cycles, which is a great challenge for their practical application. Indeed, if severe thermal tensile stress is introduced into these rolls, it can assist the thermal cracks to propagate, even lead to the overall failure of rolls. In this paper, we investigated the effect of tempering treatment on the residual stress after the bimetallic rolls were subjected to quenching. Compared with the non-uniform heating-quenching process, the tempering process makes the maximum stress at the core decreased by 15% (from 275 MPa to 234 MPa) with considering martensite transformation but decreased by 26% (from 275 MPa to 201 MPa) without considering martensite transformation. For tempering process after uniform heating quenching, the maximum stress at the core decreases by 24% from 357 MPa to 273 MPa with considering martensite transformation but decreases by 30% from 357 MPa to 246 MPa without considering martensite transformation. And compared with the non-uniform heating-quenching process, the double tempering process makes the maximum stress at the core decreased by 8% (from 275 MPa to 253 MPa) with considering martensite transformation but decreased by 27% (from 275 MPa to 200 MPa) without considering martensite transformation.

IOP Conference Series: Materials Science and Engineering, 2018

In bolt-nut connection, the anti-loosening performance and high fatigue strength are always requi... more In bolt-nut connection, the anti-loosening performance and high fatigue strength are always required with low cost to ensure the connected structure's safety. In the previous study, a suitable pitch difference between the bolt-nut was obtained as α = 33 for M16 JIS boltnut through loosening experiment and FEM simulation for tightening process. However, other bolt-nut diameters have not been considered yet. In this paper, therefore, suitable pitch difference is considered for various diameters to realize anti-loosening performance. Since bolt-nut thread geometries are different depending on the diameter, they are expressed as approximate formula. Then, loosening force and anti-loosening force are considered by varying the diameter. Finally, suitable pitch difference < α < was determined from mechanical condition.

IOP Conference Series: Materials Science and Engineering, 2018

Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese g... more Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese greenhouse design is gaining popularity because of its automated rolled-up ventilation system that is integrated into the roof. However, due to the frequent movement of the roll-up system, the plastic film deteriorates rapidly and typically lasts for only three or four months. In order to better understand the film deterioration, we studied the mechanics involved at the point of contact between the film and the metal greenhouse frame. We found that film deformation and failure were closely related to stretching and creasing, and these processes were observed at the microscope level. In this paper, the plastic film damage was investigated through the rolling contact analysis focusing on the pipe surface roughness. We found that at the inside film surface the larger strain is caused by the pipe surface roughness. This larger strain generates the wave deformation of the film, crease and line scar whose number increases with increasing the roughness of the arch pipe. The effects of pipe coating and perforated film are discussed to prevent the film damage.

IOP Conference Series: Materials Science and Engineering, 2018

The height of the bonded component of a bonded strip changes with the scope of requirements in pr... more The height of the bonded component of a bonded strip changes with the scope of requirements in practical applications. Therefore, one must understand the effect of the influence of the height of the bonded component. In this research, the stress intensity factors of an edge-cracked asymmetrically bonded strip are systematically computed using the proportional crack tip opening displacement method based on FE analysis. Then, the stress intensity factors are compared for arbitrary sets of material combinations in the whole range of Dundurs' material space with varying the height of the bonded component, and the combined effects of the relative height of the bonded component and material combinations on the stress intensity factors are discussed for the typical engineering materials.

IOP Conference Series: Materials Science and Engineering, 2018

In this study, dynamic tensile tests were conducted at the various strain rates and temperatures ... more In this study, dynamic tensile tests were conducted at the various strain rates and temperatures for traditional ductile cast iron. Then, the notch strength  B notch and the static tensile strength at room temperature  B, RT smooth were discussed in terms of the strain ratetemperature parameter R, which is known to be useful for evaluating the combined influence of strain rate and temperature. This study focuses on the notch strengthening threshold R ≧ Rth where  B notch is larger than  B, RT smooth and therefore notched components can be used safely. In other words, if R ≧ Rth,  B, RT smooth can be used to evaluate notched components in mechanical design to prevent the instantaneous fracture. In this study, it was found that the Rth value can be predicted from the static tensile property and Brinell hardness. Since the traditional ductile cast iron considered in this paper has a broad range of mechanical properties, the present approach and discussion can be applied to evaluate other materials under various temperature and strain rate.

IOP Conference Series: Materials Science and Engineering, 2018

In this study, the effect of curvature radius of the thread bottom and the pitch difference betwe... more In this study, the effect of curvature radius of the thread bottom and the pitch difference between of M16 bolt and nut on fatigue strength for bolted joint is considered experimentally. The M16 bolt-nut specimens having the two kinds of thread bottom radii and the pitch differences are prepared. The S-N curves for bolted specimens with different thread shapes are obtained by the stress-controlled fatigue test (stress ratio R>0). The experimental results are compared and discussed in terms of stress analysis. The finite element method is used to make a simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of bolt are analysed. It is found that the initiation and propagation of crack are changed by introducing the pitch difference of α=15 μm, from the crack observation in cross section of the bolt specimens after the experiment. Furthermore, the fatigue life can be extended by increasing curvature radius of thread bottom and introducing the pitch difference.

Tetsu-to-Hagane, 2019

In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the f... more In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the fatigue strength of cruciform welded joints. Here, several DCI specimens are prepared to have nearly the same fatigue strength in smooth specimens before welding and to have similar cruciform shapes in the welded joints. It is found that the fatigue strength of DCI specimen is about three times larger than that of the welded joint specimens. The fatigue strength improvement can be explained in terms of the small stress concentration factor, notch insensitivity and compressive residual stress generated by shot blasting for DCI joints.

Proceedings of the 1992 Annual Meeting of JSME/MMD, 2006

The Proceedings of the Materials and Mechanics Conference, 2013

Archive of applied mechanics, Mar 5, 2024

This paper has proposed an efficient analysis method to calculate interface stress intensity fact... more This paper has proposed an efficient analysis method to calculate interface stress intensity factors (SIFs) based on a proportional stress field of a reference problem whose exact solution is available. In the previous proportional methods, the same crack length and the same element size were applied to both reference and unknown problems so that the same FEM error can be produced. Therefore, when analyzing many unknown problems, the conventional method needs to analyze many reference problems at the same time. Since this approach is time-consuming, this paper considers how to calculate many crack lengths efficiently by using only one single reference solution modeling. For this purpose, several general relations of SIFs are derived for the unknown and the reference problems when both crack length and element size are different. To analyze many unknown problems accurately by using a single reference solution modeling, how to choose the most suitable element dimension of the reference model is clarified. The proposed method is especially useful for crack propagation analysis. Keywords Stress intensity factor • Interface crack • Bimaterial plate • Finite element method • Proportional stress field List of symbols a Length of the interface crack in the unknown problem 2a* Length of the interface crack in the reference problem C 1 , C 2 Normalized factors for short interface edge crack based on the singular stress field at the interface end without the crack E Young's modulus e Minimum element size at the crack tip in the unknown problem e* Minimum element size at the crack tip in the reference problem

Key Engineering Materials, Nov 1, 2010

Adhesive joints are widely used as the joints with the same or different adherents, such as in en... more Adhesive joints are widely used as the joints with the same or different adherents, such as in engineering and electric devices. However, because of mismatch of different materials properties, failures due to crack initiation and propagation are often observed on the interface between adhesive and adherents. Therefore, it is important to analyze stress intensity factor of crack on the interface. In this paper, the effect of material combination of adhesive and adherents on stress intensity factor and effect of the thickness of adhesive on stress intensity factor are discussed. A useful method to calculate the stress intensity factor of interface crack is presented with focusing on the stresses at the crack tip calculated by finite element method. The stress intensity factors are indicated in charts under different thickness of adhesive . It is found that the intensity of singular stress first increases with increasing , then decreases from about , and keeps constant from about , when is the width of adhesive. These results are helpful to design dimensions of devices and choose appropriate materials when adhesives are used inside of them.

The composite patch repair technology can be utilized to provide upgrades, such as higher design ... more The composite patch repair technology can be utilized to provide upgrades, such as higher design requirements and life extensions. However, in this case, failures easily happen on the edge interface between the substrate material and the restorative material, because of the incompatible of different properties. Failures such as flaws or cracks lying along the interface reduce the strength of the structure significantly. In this paper, the numerical solutions of hypersingular integro-differential equations are discussed in the analysis of three dimensional interfacial cracks subjected to general internal pressure, and the problem is formulated on the basis of the body force method. The stress intensity factors are given with varying material combinations. It is found that the stress intensity factors and are determined by the bi-materials constant alone, independent of elastic modulus ratio and Poisson's ratio.

WIT transactions on engineering sciences, 1998

This paper deals with the interaction of interface cracks and arbitrarily arranged internal crack... more This paper deals with the interaction of interface cracks and arbitrarily arranged internal cracks in bonded dissimilar materials. The problem is analyzed using the singular integral equations based on the body force method. In the numerical analysis, the unknown functions of the body force densities are approximated by the products of the fundamental density functions and power series. Here, the fundamental density functions are the exact body force densities to express a single interface crack and a single internal crack. The stress intensity factors of the interface crack are systematically calculated for various crack dimensions, arrangements of the crack and elastic constants of the materials. The interaction effect of these problems is discussed by comparing the numerical results with the results of ordinary cracks in homogeneous materials.

The Proceedings of Conference of Kyushu Branch, 2010

The Proceedings of Conference of Kyushu Branch, 2013

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A, 1997

Journal of Applied Mechanics, 2003

In short fiber reinforced composite it is known that the singular stress at the end of fibers cau... more In short fiber reinforced composite it is known that the singular stress at the end of fibers causes crack initiation, propagation, and final failure. The singular stress field is controlled by the generalized stress intensity factors defined at the end of the inclusion. In this study the stress intensity factors are discussed for an elastic cylindrical inclusion in an infinite body under (A) asymmetric uniaxial tension in the x direction, and (B) symmetric uniaxial tension in the z direction. These problems are formulated as a system of integral equations with Cauchy-type or logarithmic-type singularities, where densities of body force distributed in infinite bodies having the same elastic constants as those of the matrix and inclusion are unknown. In the numerical analysis, the unknown body force densities are expressed as fundamental density functions and weight functions. Here, fundamental density functions are chosen to express the symmetric and skew-symmetric stress singularit...

The Proceedings of Conference of Kyushu Branch, 2007

Mechanics Based Design of Structures and Machines, 2020

It is well known that the prevailing torque for special bolt-nut connections is useful for evalua... more It is well known that the prevailing torque for special bolt-nut connections is useful for evaluating antiloosening performance. In our previous studies, several slight pitch differences were introduced between the bolt-nut connections towards realizing anti-loosening performance as well as high fatigue strength by applying axi-symmetric finite element method (FEM). In this study, by applying three-dimensional FEM, the nut screwing process is analyzed to obtain the prevailing torque Tp confirming anti-loosening. Since the nut unscrewing properties after the nut tightening is more important to prevent the nut self-loosening, the nut unscrewing is also analyzed to obtain the residual prevailing torque Tp u newly defined in this process. Both results of Tp and Tp u are in good agreement with the experimental results. With increasing the pitch difference, the residual prevailing torque Tp u increases as well as the prevailing torque Tp. Those obtained values of Tp and Tp u suggest that suitable pitch difference nuts may provide good anti-loosening performance.

IOP Conference Series: Materials Science and Engineering, 2018

Bimetallic rolls are widely used in steel rolling industries because of the excellent hardness, w... more Bimetallic rolls are widely used in steel rolling industries because of the excellent hardness, wear resistance, and high temperature properties. However, thermal stress is produced by heating-cooling thermal cycles, which is a great challenge for their practical application. Indeed, if severe thermal tensile stress is introduced into these rolls, it can assist the thermal cracks to propagate, even lead to the overall failure of rolls. In this paper, we investigated the effect of tempering treatment on the residual stress after the bimetallic rolls were subjected to quenching. Compared with the non-uniform heating-quenching process, the tempering process makes the maximum stress at the core decreased by 15% (from 275 MPa to 234 MPa) with considering martensite transformation but decreased by 26% (from 275 MPa to 201 MPa) without considering martensite transformation. For tempering process after uniform heating quenching, the maximum stress at the core decreases by 24% from 357 MPa to 273 MPa with considering martensite transformation but decreases by 30% from 357 MPa to 246 MPa without considering martensite transformation. And compared with the non-uniform heating-quenching process, the double tempering process makes the maximum stress at the core decreased by 8% (from 275 MPa to 253 MPa) with considering martensite transformation but decreased by 27% (from 275 MPa to 200 MPa) without considering martensite transformation.

IOP Conference Series: Materials Science and Engineering, 2018

In bolt-nut connection, the anti-loosening performance and high fatigue strength are always requi... more In bolt-nut connection, the anti-loosening performance and high fatigue strength are always required with low cost to ensure the connected structure's safety. In the previous study, a suitable pitch difference between the bolt-nut was obtained as α = 33 for M16 JIS boltnut through loosening experiment and FEM simulation for tightening process. However, other bolt-nut diameters have not been considered yet. In this paper, therefore, suitable pitch difference is considered for various diameters to realize anti-loosening performance. Since bolt-nut thread geometries are different depending on the diameter, they are expressed as approximate formula. Then, loosening force and anti-loosening force are considered by varying the diameter. Finally, suitable pitch difference < α < was determined from mechanical condition.

IOP Conference Series: Materials Science and Engineering, 2018

Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese g... more Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese greenhouse design is gaining popularity because of its automated rolled-up ventilation system that is integrated into the roof. However, due to the frequent movement of the roll-up system, the plastic film deteriorates rapidly and typically lasts for only three or four months. In order to better understand the film deterioration, we studied the mechanics involved at the point of contact between the film and the metal greenhouse frame. We found that film deformation and failure were closely related to stretching and creasing, and these processes were observed at the microscope level. In this paper, the plastic film damage was investigated through the rolling contact analysis focusing on the pipe surface roughness. We found that at the inside film surface the larger strain is caused by the pipe surface roughness. This larger strain generates the wave deformation of the film, crease and line scar whose number increases with increasing the roughness of the arch pipe. The effects of pipe coating and perforated film are discussed to prevent the film damage.

IOP Conference Series: Materials Science and Engineering, 2018

The height of the bonded component of a bonded strip changes with the scope of requirements in pr... more The height of the bonded component of a bonded strip changes with the scope of requirements in practical applications. Therefore, one must understand the effect of the influence of the height of the bonded component. In this research, the stress intensity factors of an edge-cracked asymmetrically bonded strip are systematically computed using the proportional crack tip opening displacement method based on FE analysis. Then, the stress intensity factors are compared for arbitrary sets of material combinations in the whole range of Dundurs' material space with varying the height of the bonded component, and the combined effects of the relative height of the bonded component and material combinations on the stress intensity factors are discussed for the typical engineering materials.

IOP Conference Series: Materials Science and Engineering, 2018

In this study, dynamic tensile tests were conducted at the various strain rates and temperatures ... more In this study, dynamic tensile tests were conducted at the various strain rates and temperatures for traditional ductile cast iron. Then, the notch strength  B notch and the static tensile strength at room temperature  B, RT smooth were discussed in terms of the strain ratetemperature parameter R, which is known to be useful for evaluating the combined influence of strain rate and temperature. This study focuses on the notch strengthening threshold R ≧ Rth where  B notch is larger than  B, RT smooth and therefore notched components can be used safely. In other words, if R ≧ Rth,  B, RT smooth can be used to evaluate notched components in mechanical design to prevent the instantaneous fracture. In this study, it was found that the Rth value can be predicted from the static tensile property and Brinell hardness. Since the traditional ductile cast iron considered in this paper has a broad range of mechanical properties, the present approach and discussion can be applied to evaluate other materials under various temperature and strain rate.

IOP Conference Series: Materials Science and Engineering, 2018

In this study, the effect of curvature radius of the thread bottom and the pitch difference betwe... more In this study, the effect of curvature radius of the thread bottom and the pitch difference between of M16 bolt and nut on fatigue strength for bolted joint is considered experimentally. The M16 bolt-nut specimens having the two kinds of thread bottom radii and the pitch differences are prepared. The S-N curves for bolted specimens with different thread shapes are obtained by the stress-controlled fatigue test (stress ratio R>0). The experimental results are compared and discussed in terms of stress analysis. The finite element method is used to make a simulation of the fatigue experiment and the mean stress and stress amplitude at each thread bottom of bolt are analysed. It is found that the initiation and propagation of crack are changed by introducing the pitch difference of α=15 μm, from the crack observation in cross section of the bolt specimens after the experiment. Furthermore, the fatigue life can be extended by increasing curvature radius of thread bottom and introducing the pitch difference.

Tetsu-to-Hagane, 2019

In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the f... more In this study fatigue experiments are conducted for ductile cast iron (DCI) to compare with the fatigue strength of cruciform welded joints. Here, several DCI specimens are prepared to have nearly the same fatigue strength in smooth specimens before welding and to have similar cruciform shapes in the welded joints. It is found that the fatigue strength of DCI specimen is about three times larger than that of the welded joint specimens. The fatigue strength improvement can be explained in terms of the small stress concentration factor, notch insensitivity and compressive residual stress generated by shot blasting for DCI joints.

Proceedings of the 1992 Annual Meeting of JSME/MMD, 2006

The Proceedings of the Materials and Mechanics Conference, 2013