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高速引張試験において衝撃強度を評価するためには，切欠き形状とひずみ速度集中係数の関係が重要である．そこで，切欠きを有する平板試験片の切欠き形状を変え切欠き底のひずみ速度集中係数を計算し，応力集中係数よりひずみ速度集中係数を求められることを示した．さらに，その比は開き角に依存しないこともわかった．

The high strength bolts and nuts are widely used in engineering structures. To investigate the pitch difference on the fatigue strength of bolt, a slight pitch difference is considered between the bolt and nut. Here, the pitch of the nut is α μm larger than the pitch of the bolt. The fatigue experiment is conducted with varying pitch difference. The results show that the fatigue life is extended to about 1.5 times of the one of normal bolt and nut by introducing the suitable pitch difference under the high stress amplitude. According to the detailed observation on the fractured specimens, it is found that the fractured positions and the crack distributions vary depending on the pitch difference. To clarify the improvement mechanism of the fatigue strength, the finite element method is applied to calculate the stress amplitude and mean stress at each bottom of bolt threads. It is found that the finite element analytical model considering the incomplete nut threads is useful for predicting the crack initiation under different pitch difference introduced.

The many buildings that have been built in the new seismic design method previously, seismic perform-ance is very low. These buildings was severely damaged in the earthquake. So seismic retrofitting is required. The connection of the old steel frame buildings vulnerable, reinforcement is required. However, details of the repair method is not been decided. An object of this study is the determination of the joint de-tails. Parameter to consider is the weldability and the angle of the reinforcing plate. From this result, we de-termined to 30 degrees the angle, be 40 mm the mounting position of the tab.

In this paper, the mechanism of stress concentration due to defects in honeycomb sandwich structure is studied by using finite element method. It is found that the stress concentrantion can be expressed as a function of Ectc=Eptp, where tc and tp are the thickness of core and plate, respectively, and Ec and Ep are the Young's modulus of core and plate, respectively. Also, it is found that the stress concentrantion can be evaluated by an approximation of an elliptical inclusion. The validly of this technique is verified through comparison of the evaluation values with the numerical results obtained by FEM.

Innumerable cracks and fissures caused by huge earthquakes were found on the excavated walls inside the mound of Takamatsuzuka Tumulus during archaeological investigation. The largescale excavation prior to the dismantling of the stone chamber in 2006 gave additional information about the three-dimensional distribution of those cracks and fissures. Serious ground motion due to huge subduction earthquakes hitting Japan every 100 to 140 years as well as nearfault earthquakes possibly caused the damage to the tumulus mound. Thus, seismic stability is of importance for the conservation of tumulus mounds made of soil without artificial reinforcement. In this study, a series of three-dimensional dynamic finite element analyses was conducted for the mound of Takamatsuzuka Tumulus to investigate the possibility of the occurrence of cracks and fissures induced by the outer forces of earthquakes. Based on archeological investigation, realistic modeling for the tumulus structure was conducted. Calculated performance shows that the natural period of Takamatsuzuka Tumulus that can generally be measured for near field earthquakes is 0.15 s. This means that such a small mound as Takamatsuzuka Tumulus is more fragile to near field earthquakes than subduction earthquakes. Serious amplification of acceleration can be seen in the tumulus mound. The response acceleration derived on the mound becomes much larger than the input acceleration monitored in the original ground. Calculated results also exhibit that serious stress concentration is found at the foot of the mound and at the boundary of the mound and the chamber stones, possiblycausing the occurrence of cracks in the mound of Takamatsuzuka Tumulus.

An investigation and analysis of failure accidents of Wind-lens turbine blades was presented. Due to the failure of the electric loading device, Wind-lens turbine was running under non-loading conditions for some minutes. Then, the wind velocity U around Wind-lens turbine reached U_ =19m/s and the tip velocity V_ of blades reached V_ 152m/s. Fatigue crack was easily initiated at the corner of fillets of joints connecting blades to hub where stress concentration was caused. The bolts were subjected to a large load by application of vibrational stress and torsional moment. The clearance between the head of bolts and hub was expanded. To investigate the fracture surface, the beach marks and striations characteristic of fatigue fracture were obviously observed. The number of cycles from crack initiation to final failure was calculated on the basis of fracture mechanics by observing the fatigue striation in the vicinity of fracture origin. Vibrational service stress amplitudes applied at the joint of blades and hub were much larger than the inherent fatigue strength of blade's material, ABS resin. In order to prevent such a failure accident of a small wind turbine generator, the recommended shapes of blades and hub were proposed.

Innumerable cracks and fissures caused by huge earthquakes were found inside the mound of Takamatsuzuka Tumulus. Those cracks and fissures were originally found on the excavated walls during archaeological investigation. Furthermore, the large-scale excavation prior to the dismantling of the stone chamber in 2006 gave additional information about the threedimensional distribution of those cracks and fissures. Serious ground motion due to huge subduction earthquakes hitting Japan every 100 to 140 years possibly caused the damage to the tumulus mound. The instability of the tumulus mound is one reason it was judged impossible to preserve the mural paintings in situ. This paper presents the results of a series of three-dimensional dynamic finite element analyses conducted for the mound of Takamatsuzuka Tumulus to investigate the possibility of the occurrence of cracks and fissures induced by the outer forces of earthquakes. Calculated performance shows that the natural period of Takamatsuzuka Tumulus is 0.17 s. and that this value is the one that is generally measured for near field earthquakes. This means that such a small mound as Takamatsuzuka Tumulus is more fragile to near field earthquakes than subduction earthquakes. Calculated results also show that serious stress concentration, which could have caused the occurrence of cracks and fissures in the mound of Takamatsuzuka Tumulus, is found at the foot of the mound and at the boundary of the mound and the chamber stones.

初等物理教育において,力を定量的に導入する直前の段階として,固体にかかる応力が分布する「不均一変形」を観察させる教材を示す。身の回りには,大きく変形し,壊れることによって役立つものが数多く存在している。それを学生自らが探り出し,どのようにして狙い通り壊れるのかを観察・探求するのは,物理が特別なモデルの上でのみ成り立つという意識を打破するのに有効である。また,光弾性効果を使った演示実験により,講義の中で現象を再現しながら説明することができる。さらに,有限要素法によるシミュレーションと照合する中で,実験だけで理解しようとするのは危険であることがわかった。不均一な応力場への理解は,教える側も足りないことが多いので,教材としては,課題探求・演示実験・シミュレーションの三点をセットにするのが望ましい。, The inhomogeneous distribution of deformation in stress-applied solids is one of the quite usual physical phenomena. It attracts many students, because the drastic change of the form by their force is very impressive. The homework to find it and to observe how successfully the solid is destroyed should be helpful to correct their misunderstanding that the physics only conserved in special unrealistic models. The understanding of the phenomenon is of cause so difficult that the demonstration experiment should be accompanied. Using the photoelastic experiment, the homogeneous area in the sample is now clear and the smooth shift to the physics of the stretched ropes under homogeneous stress, which is a tool of an introduction of force, becomes easy. However, the photoelastic effect with large birefringence is essentially nonlinear, and the geometrical pattern of the photoelastic image does not correspond to the distribution of deformation. Accordingly, the simulation using the finite element method in additi

This paper presents an analytical solution for an infinite strip having a circular inclusion when the strip is subjected to tension at infinity. In the analysis, the inclusion is assumed to be perfectly bonded and be allowed to slide. The analysis is based on the Papcovich Neuber stress function approach and the solution is obtained by the proper combination of harmonic function in integral forms and infinite series. The boundary conditions at the interface uniting the strip and the inclusion are satisfied using the relations between the polar and Cartesian harmonics. The numerical results obtained from the proposed method are illustrated for various stiffness ratio and sizes of the inclusion.

This paper contains an analysis of the stress and displacement distribution arising in a strip with a circular inclusion when the strip is subjected to bending at infinity. Two types of inclusion, i.e., perfect bonding and sliding inclusion are treated in this paper. The solution which is based on the Papcovich-Neuber displacement potentials is obtained by combining the harmonic potentials in integral forms and infinite series. The boundary conditions of the problem are fully satisfied using the relationships between the harmonic functions of Cartesian and polar coordinates. The effect of the inclusion on the stress and displacement are given in the form of graphs to show the availability of the present method.

Fatigue tests of crack propagation from a pre-crack in thin-walled tubular specimens made of a medium-carbon steel were performed under cyclic torsion with and without superposed static or cyclic axial loading. The stress ratio of cyclic loading was-1. The experimental path of fatigue crack propagation from a pre-crack was compared with the predictions based on the maximum tangential stress criterion. The direction of fatigue crack propagation was perpendicular to the direction of the maximum of the range of the tangential stress, Δσ*θmax, near the crack tip determined from the stress intensity factor which was calculated by considering the contacts of crack faces at the minimum load. The stress intensity factor calculated from the actual crack path by using the body force method showed that the mode II stress intensity factor range quickly got close to zero after a small amount of crack extension. In other words, fatigue cracks propagate to satisfy the local symmetry of the cyclic components of crack-tip deformation.

In this work, stress concentration factors (SCFs) of a round bar with a circular-arc or V-sharped notch K_t are considered on the basis of exact solutions for special cases and accurate numerical results. First, for the limiting cases of deep and shallow notches, the body force method is used to calculate the SCFs; then, the formulas are obtained as K_ and K_. On the one hand, upon comparison of K_t and K_. it is found that K_t is nearly equal to K_ if the notch is deep or blunt. On the other hand, if the notch is sharp or shallow, K_t is mainly controlled by K_ and the notch depth. The notch shape is classified into several groups according to the notch radius and notch depth; then, the least squares method is applied for calculation of K_t/K_ and K_t/K_. Finally, a set of convenient formulas useful for any shape of notch in a round test specimen is proposed. The formulas yield SCFs with less than 1% error for any shape of notch. The effect of notch opening angle on the SCF is also considered for the limiting cases of deep and shallow notches.

This paper deals with a stress concentration problem of an ellipsoidal inclusion of revolution in a bimaterial body under tension. The problem is formulated as a system of singular equations with Cauchy-type or logarithmic-type singularities, where unknowns are densities of body forces distributed in the r-and z-directions in bimaterial boodies having the same elastic constants of those of the given problem. I order to satisfy the boundary conditions along the ellipsoidal boundary, four fundamental density functions proposed in the previous paper are used. Then the body force densities are approximated by a linear combination of fundamental density functions and polynomials. The present method is found to yield rapidly converging numerical results for stress distribution along the boundaries of both the matrix and inclusion even when the inclusion is very close to the bimaterial interface. Then, the effect of bimaterial surface on the stress concentration factor is discussed with varying the distance from bimaterial interface, shape ratio, and elastic ratio.

This paper deals with a stress concentration problem of an ellipsoidal inclusion of revolution in a semi-infinite body under biaxial tension. The problem is formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where unknowns are densities of body forces distributed in the r-and z-directions in semi-infinite bodies having the same elastic constants of the matrix and inclusion. In order to satisfy the boundary conditions along the ellipsoidal boundary, four fundamental density functions proposed in the previous paper are used. Then the body force densities are approximated by a linear combination of fundamental density functions and polynomials. The present method is found to yield repidly converging numerical results for stress distribution along the boundaries of both the matrix and inclusion even when the inclusion is very close to the free boundary. Then, the effect of free surface on the stress concentration factor is discussed with varing the distance from the surface, shape ratio, and elastic ratio. Also the present results are compared with the ones of an ellipsoidal cavity in a semi-infinite body.

本論では，円孔ボイドスラブ構造について，曲げ剛性および応力集中の評価を行う評価係数(正確にはボイド孔直径-スラブ厚比の関数)を導入し，これらの係数によりボイドスラブを直交異方性板として解析できることを示す。続いて，この直交異方性板を等方性板として扱えることを示し，そこから導かれる解析的な式を用いて，孔の有無により生じる鉛直変位等の弾性力学的な性状の違いを述べる。また，RC規準と同等な手法によりスラブ厚の算定式を導出し，孔の大きさによる有効スパンヘの影響を調べる。確にはボイド孔直径-スラブ厚比の関数)を導入し，これらの係数によりボイドスラブを直交異方性板として解析できることを示す。続いて，この直交異方性板を等方性板として扱えることを示し，そこから導かれる解析的な式を用いて，孔の有無により生じる鉛直変位等の弾性力学的な性状の違いを述べる。また，RC規準と同等な手法によりスラブ厚の算定式を導出し，孔の大きさによる有効スパンヘの影響を調べる。, In the first part of this paper, the characteristics of the bending rigidity of the void slab and stress concentrations are confirmed and clarified by direct numerical method. These characteristics are estimated by the coefficients that are obtained in accordance with void diameter-thickness ratio. In the second part, it is shown that this ortho-tropic slab can be treated as an isotropic slab.Using the analytical equation, the difference between characteristics of elasticity by the existence of the holesuch as the vertical displacement is described. Finally, the design code of the slab thickness is deduced by the technique which is equivalent to the derivation of the RC standard, and the effect on the effective span by the size of the hole is examined.

The paper presents an axisymmetric solution for the stresses and displaements in an elastic thick plate containing an oblate spheroidal inclusion under axisymmetric bending around the z axis. The related spherical cavity and inclusion problems were solved by Tsuchida et al. in 1975. by using Papcovich-Neuber displacement potentials. We extended the method to spheroidal inclusion problem.

In the previous paper, we presented an axisymmetric solution for the stresses and displacements in an elastic thick plate containing an oblate spheroidal inclusion under axisymmetric bending around the z axis normal to the surface of the thick plate. In the present paper, we studied an asymmetric solution for an elastic thick plate containing an oblate spheroidal inclusion under transverse bending. Numerical results are given for different values of size, aspect ratio and stiffness ratio. The stress distributions around inclusion are shown graphically, and are compared with the axisymmetric results.

High-speed tensile testing is now being recognized as a standard testing method for evaluating the impact strength of engineering materials. The impact speeds of Izod and Charpy tests cannot be controlled and therefore do not correspond to the real failure of real products. The brittle-ductile transition of structural materials is affected by the temperature and loading speed. In the high-speed tensile test, it is necessary to obtain the strain rate at the notch root accurately to understand the effect of impact load. For smooth specimens, the strain rate can be determined from the tensile speed u/t and specimen length l as εsmooth = u/tl. For notched specimens, however, the strain rate at the notch root εnotch should be analyzed accurately. In this study, therefore, the strain rate concentration factor defined as Ktε = εnotch/εsmooth is studied with varying the notch geometry. To predict the strain rate concentration factor Ktε accurately, the relationship between Ktε and the stress concentration factor Kt* = σmax/σgross is investigated. Here, σgross is the remote tensile stress and P is the tensile load. It is found that the strain concentration factor Ktε can be estimeted from stress concentration factor Kt* when the relative notch depth 2t/D≦0.5 (t : notch depth, D : the specimen diameter).

In this work, stress concentration factors (SCFs) of a round bar with fillet K_t are considered on he basis of exact solutions now available for special cases and accurate numerical results. First, for he limiting cases of large and small values of the step including fillets, the body force method is used to calculate the SCFs ; then the formulas are obtained as K_ and K_. Here, K_ is a SCF of a deep shoulder fillet and K_ is a SCF of a shoulder fillet in semi-infinite plate. On the one hand, upon comparison of K_t and K_, it is found that K_t is nearly equal to K_ if the step is large or the radius of the fillet is small. On the other hand, if the step is small or the radius of the fillet is large, K_t is mainly controlled by K_ and the relative step length. The fillet shape is classified into several groups according as the fillet radius and the step length ; then, the least squares method is applied for calculation of K_t/K_ and K_t/K_. Finally, a set of convenient formulas useful for any shape of fillet in a round test specimen are proposed. The formulas yield SCFs for any shape of notch with less than 1% error in most cases.

In this work, stress concentration factors (SCFs) K_t of a flat bar with double circular-arc notches or double V-shaped notches are considered on the basis of exact solutions now available for special cases and accurate numerical results. First, for the limitting cases of deep and shallow notches, the body force method is used to calculate the SCFs ; then the formulas are obtained as K_ and K_. On the one hand, upon comparison of K_t and K_, it is found that K_t is nearly equal to K_ if the notch is deep or blunt. On the other hand, if the notch is sharp or shallow, K_t is mainly controlled by K_ and the notch depth. The notch shape is classified into several groups according as the notch radius and depth ; then, the least squares method is applied for calculation of K_t/K_ and K_t/K_. Finally, a set of convenient formulas useful for any shape of notch in a flat test specimen are proposed. The formulas yield SCFs With less than 1% error for any shape of notch.

Plastic slip deformation of a HCP bicrystal is analyzed by a crystal plasticity FE code and distribution of plastic shear strain on the primary and secondary slip systems, as well as some stress components are examined. The constituent crystal are idealized ones and slip deformation on basal, prismatic and pyramidal slip systems can take place, but twin deformation cannot. After a deformation of 1% nominal tensile strain, sharp stress concentrations are developed at the junctions of the grain boundary plane and specimen surfaces even though the crystal orientations of the two grains differ only a few degree. Results are compared with the case for FCC bicrystals and effects of the activation of secondary slip systems are discussed., 本文データは学協会の許諾に基づきCiNiiから複製したものである

In this work, stress concentration factors (SCFs) K_t of a flat bar with double circular-arc notches or double V-shaped notches are considered on the basis of exact solutions new available for special cases and accurate numerical results. First, for the limitting cases of deep and shallow notches, the body force method is used to calculate the SCFs;then the formulas are obtained as K_ and K_. On the one hand, upon comparison of K_t and K_ it is found that K_t is nearly equal to K_ if the notch is deep or blunt. On the other hand, if the notch is sharp or shallow, K_t is mainly controlled by K_ and the notch depth. The notch shape is classified into several groups according to the notch radius and depth;then, the least squares method is applied for calculation of K_t/K_ and K_t/K_. Finally, a set of convenient formulas useful for any shape of notch in a flat test specimen are proposed. The formulas yield SCFs with less than 1% error for any shape of notch.

This paper deals with interaction problems of elliptical and ellipsoidal inclusions under bending using singular integral equations of the body force method.These problems are formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where unknown functions are densities of body forces distributed in the χ, y and r, θ, z directions in infinite bodies having the same elastic constants as those of the matrix and inclusions.In order to satisfy the boundary conditions along the elliptical and the ellipsoidal boundaries, the unknown functions are approximated by a linear combination of fundamental density functions and polynominals.The present method is found to yield the exact solutions for an elliptical and spherical inclusion under bending.Also , the present method yields rapidly converging numerical results for interface stresses in the interaction of inclusions.

In this paper, a method of evaluating the static strength of a V-shaped notch based on the singular stress field at the notch tip is studied. The singular stress field is defined by two parameters, K_ and K_, which correspond to the intensities of the symmetric stress field and the skewsymmetric field, respectively. Four kinds of fracture criteria are considered ; two of them are based on the tensile strength δ_B and the other two are based on the fracture toughness K_. The usefullness of the criteria is investigated through the experiment results carried out on plane speciments of acrylic resin having a sharp notch for various notch configurations such as the opening angle, the inclined angle and the notch depth.

In this work, stress concentration factors (SCFs) of a round bar with a circular-arc or V-shaped notch K_t are considered on the basis of exact solutions for special cases and accurate numerical results. First, for the limitting cases of deep and shallow notches, the body force method is used to calculate the SCFs ; then the formulas are obtained as K_ and K_. On the one hand, upon comparison of K_t and K_, it is found that K_t is nearly equal to K_ if the notch is deep or blunt. On the other hand, if the notch is sharp or shallow, K_t is mainly controlled by K_ and the notch depth. The notch shape is classified into several groups according to the notch radius and depth ; then, the least squares method is applied for calculation of K_t/K_ and K_t/K_. Finally, a set of convenient formulas useful for any shape of notch in a round test specimen are proposed. The formulas yield SCFs with less than 1% error for any shape of notch.