Tensile Impact Loading Research Articles

The industrial application of dynamic testing for the study of metallic strength and toughness properties

The specific type of specimens were prepared from X80 pipeline steel with perpendicular sampling orientation for the dynamic testing of impact tensile at given strain rate, 10 2 /s and instrumented pendulum impact with the given stress intensity factor rate, 5×10 5 MPa m 1/2 /s in the present paper. The comparison of the yield stress and tensile strength corresponding to quasi static and dynamic loading clearly indicates that the strength of X80 steel is sensitively dependent of the strain rate change. The correlation of σ yd and F gy obtained from instrumented impact by means of Server equation was proved to be satisfactory. Moreover tensile toughness index LST is also proposed as the plastic energy distribution throughout the cross section area under static and impact tensile loading, reveling the dependence of strength and plasticity combination of structural steel on the loading variation. In addition, dynamic crack extension resistance curve, J-Δ a , was acquired for the evaluation of toughness property, also effectively revealing the mechanism of crack initiation and growth under dynamic loading.

Dynamics of propagating phase boundaries in NiTi

Propagating boundaries of phase transformation have been generated in polycrystalline NiTi specimens under a tensile impact loading condition. Multiple strain gages were used to monitor the time evolution of the strain at different spatial locations in the specimen. Nucleation and propagation of multiple phase fronts were detected in these experiments; the phase front speed was found to be in the range between 37 and 370 m/s. The strain measurements were interpreted through the one-dimensional analysis of Abeyaratne and Knowles [1997. On the kinetics of an austenite→martensite phase transformation induced by impact in Cu–Al–Ni shape-memory alloy. Acta Mater. 45, 1671–1683] and a model of partial phase transformation in the polycrystalline specimen. The driving force for the motion of the phase front was evaluated from the measurements in order to establish the kinetic relation.

Fracture Behavior of a Brittle Polymer under Impact Tensile Loading

Brittle fracture behavior of MBS resin under impact tensile loading was studied using single-edge-cracked specimens. The dynamic load and displacement were measured using a piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e. the external work Uex applied to the specimen was used to determine the elastic energy Ee and the fracture energy Ef for creating a new fracture surface As. Energy release rates were then estimated using Gt = Uex/As and Gf=Ef/As. The values of Gt and Gf were correlated with the fracture loads and the mean crack. velocities determined from the load and time relationships.

多層ラミネートフィルムの衝撃引張挙動に及ぼす瓶口シール部形状の影響

The bottle-neck shaped seal of bags for holding liquid is particularly convenient for pouring the liquid into another container. In recent years, bags have frequently broken at the bottle-neck shaped seal because the bags were subjected to the impact during loading and unloading. Taking this into consideration, we performed impact tensile tests using two types of bags with bottle-neck shaped seals, one with barrier characteristics, i.e., laminate films of NY/alumina-evaporation PET/XA-S and NY/AL/XA-S, and one without barrier characteristics, i.e., NY/XA-S for bottle neck shaped seal diameters of 7.5, 10, 12.5, 13, 14, 15 and 20mm and flat seal bags. When the seal diameter of NY/aluminaevaporation PET/XA-S, NY/AL/XA-S or NY/XA-S is 15mm or greater, the impact tensile load at break is almost the same as that of flat seal bags.

804 衝撃及び静的引張荷重を受ける異種段付き重ね合わせ接着継手の三次元有限要素応力解析(OS-8A,OS-8 界面と接着・接合の力学)

804 衝撃及び静的引張荷重を受ける異種段付き重ね合わせ接着継手の三次元有限要素応力解析(OS-8A,OS-8 界面と接着・接合の力学)

3-D Transient Dynamic Crack Analysis by a Novel Time-Domain BEM

A novel non-hypersingular time-domain traction BEM is presented for three-dimensional (3D) transient elastodynamic crack analysis. The initialboundary value problem is formulated as a set of nonhypersingular time-domain traction boundary integral equations (BIEs). To solve the time-domain traction BIEs, a time-stepping scheme based on the convolution quadrature formula of Lubich (1988a,b; 1994) for temporal discretization and a collocation method for spatial discretization is adopted. Numerical examples are given for an unbounded solid with a penny-shaped crack under a tensile and shear impact loading. A comparison of the present time-domain BEM with the conventional one shows that the novel time-domain method is much more stable and less sensitive to the choice of the used timesteps. keyword: 3-D Time-domain boundary element method, Non-hypersingular boundary integral equations, Transient elastodynamic crack analysis, Elastodynamic stress intensity factors.

Dynamic interaction between a sub-interface crack and the interface in a bi-material: time-domain BEM analysis

Transient response of a sub-interface crack in a bi-material is studied with emphasis on the dynamic interaction between the crack and the interface, by combining the traditional time-domain displacement boundary element method (BEM) and the non-hypersingular traction BEM. Computations are performed for an unbounded bi-material with a crack subjected to impact tensile loading on its faces or incident impact waves and a bounded rectangular bi-material plate under remote impact tensile loading. Numerical results of the dynamic stress intensity factors (DSIFs) and dynamic interface tractions are presented for various material combinations and crack locations. It is shown that pronounced increases in DSIFs and the interface tractions may be caused in some cases because of the dynamic interaction between the crack and the interface.

Stress analysis and strength estimation of butt adhesive joints of dissimilar hollow cylinders under impact tensile loadings

The stress variations in butt adhesive joints of dissimilar hollow cylinders subjected to impact tensile loadings are analyzed in elastic and elasto-plastic deformation ranges using a finite element method (FEM). The FEM code name employed is DYNA3D. The effects of Young's modulus ratio between dissimilar adherends and the adhesive thickness on the stress variations at the interfaces are examined. In addition, the process of rupture at the interfaces of the joint is simulated. The stress distributions in the joints under static loadings are also analyzed by FEM. The characteristics of the stress variations in the joints under impact loadings are compared with those in the joints under static loadings. Also, the joint strengths under impact loadings are estimated by elasto-plastic FEM. It is found that the maximum value of the maximum principal stress σ 1 occurs at the outside edge of the lower interface. It is also found that the maximum principal stress σ 1 at the lower interface decreases as the adhesive thickness increases. The characteristics of the joints under impact loadings are found to be opposite to those under static loadings. Furthermore, differences in the characteristics of the stress variations are shown between the dissimilar joints and the similar joints. In addition, the experiments were carried out to measure the strain response and strains in the butt adhesive joints under both impact and static loadings using strain gauges. Furthermore, joint strengths under both impact and static loadings were measured. Fairly good agreements are observed between the numerical and the measured results.

Three-dimensional finite element stress analysis of single-lap adhesive joints of dissimilar adherends subjected to impact tensile loads

The stress-wave propagations and stress distributions in single-lap joints of dissimilar adherends were analyzed using an elastic three-dimensional finite-element method (DYNA3D). An impact tensile load was applied to the single-lap adhesive joint by dropping a weight. One end of the upper adherend in the single-lap adhesive joint was fixed and the other adherend (lower adherend) which was connected to a bar was impacted by the weight. The effects of Young's modulus and the thickness of each adherend on the stress wave propagations and stress distributions at the interfaces were examined. It was found that the maximum value of the maximum principal stress occurred near the edge of the interface of the fixed adherend. The maximum principal stress increased as Young's modulus of the fixed adherend increased. It was also observed that the maximum principal stress increased as the fixed adherend thickness decreased. In addition, strain responses in the single-lap adhesive joints of dissimilar adherends subjected to impact tensile loads were measured using strain gauges. Fairly good agreements were found between the FEM calculations and the experimental measurements.

620 アクリル系接着剤の繰り返し衝撃負荷に対する引張強度

The impact fatigue strength of the acrylic adhesive under impact tensile loading was evaluated by adding impact cyclic loads to a tubular butt joint. The material of adherends was aluminium alloy A5052-H34,and the acrylic adhesive Hardloc M-372-20 was used. First, the combined loading test was performed in order to evaluate the static strength of the adhesive. As a result, the value of fracture stress under shear load is stronger than the value of fracture stress under tensile load. As the adhesive layer thickness become thick, the value of fracture stress become low. In the impact fatigue test, the thickness of the adhesive layer was 0.1mm. As a result, the maximum incidence stress becomes low, the number of impact loads to a fracture will increase. In cace the insident stress is 9MPa, the specimen did't fracture even if it was subjected to the impact loads 1 million times. It was considered that the fatigue limit is 9MPa.

Microstructures and Tensile Properties of ECAE-Processed and Forged AZ31 Magnesium Alloy

In order to achieve same level of high strength and high ductilityas 6061 aluminum forging alloythat is currentlyused for automobile applications, AZ31 magnesium alloyrod with a large diameter of 40 mm was subjected to ECAE-processing, and the microstructures and mechanical properties of the ECAE-processed specimens were investigated. Furthermore, automobile knuckle arm was produced byforging using the ECAE-processed material, and the mechanical properties of the forged product and their strain rate dependencies were investigated under impact tensile load conditions. 4pass-ECAE-processed specimen has fine and uniform microstructure and a texture whose basal planes are mainlyparallel to the extrusion direction with some inclined at angles up to 45 to the extrusion direction. Therefore, theyshow high ductility even if the tensile direction is parallel to the extrusion direction. The knuckle arm forged using the ECAE-processed material exhibits high elongation even in the high strain rate region. Furthermore, the tensile strength, fracture elongation and absorption energyof the forged product increase with increasing strain rate and their values are higher than those of T6-treated 6061 aluminum forging alloyspecified byJIS.

154 衝撃引張り荷重を受ける層内に充填物を有する突合せ接着継手の FEM 応力応答解析

154 衝撃引張り荷重を受ける層内に充填物を有する突合せ接着継手の FEM 応力応答解析

FEM stress analysis and strength of adhesive butt joints of similar hollow cylinders under static and impact tensile loadings

The stress wave propagations in butt adhesive joints of similar hollow cylinders subjected to static and impact tensile loadings are analyzed in elastic and elasto-plastic deformation ranges using the finite-element method (FEM). The impact loading is applied to the joint by dropping a weight. The upper end of the upper adherend is fixed and the lower adherend of which the lower end is connected to a guide bar is subjected to the impact loading. The FEM code employed is DYNA3D. The effects of the adhesive thickness and Young's modulus of the adhesive on the stress wave propagation at the interfaces are examined. In addition, the characteristics of the joints subjected to impact loadings are compared with those of the joints under static loadings and the joint strengths are estimated by using the interface stress distributions. It is found that the maximum value of the maximum principal stress, σ1 occurs at the outside edge of the interface of the lower adherend to which the impact loading is applied. The maximum value of the maximum principal stress, σ1 increases as Young's modulus of the adhesive increases when the joints are subjected to impact loadings. It is found that the characteristics of the joints subjected to impact loadings are opposite to those subjected to static loadings. In addition, experiments were carried out to measure the strain response of the butt adhesive joints subjected to impact and static tensile loadings using strain gauges and the joint strengths were also measured. Fairy good agreements are observed between the numerical and the measured results.

Deformation and Fracture of Rubber under Tensile Impact Loading

Abstract An impact experiment is designed to obtain the deformation and fracture characteristics of SBR specimens under tensile impact loading. The experimental apparatus is capable of achieving very large strains (about 300%) and high strain rates (between 10 and 1000 s−1) in the specimen. Dynamic stress-strain curves reveal that SBR goes through several phases of deformation and fracture as the strain rate increases in the specimen. In the first phase, the initial modulus, yield stress, tensile strength, and fracture strain increase, while the final modulus remains fairly constant with increasing strain rate. Increases in the initial modulus, tensile strength, and strain at fracture with increasing strain rate are due to a lack of stress relaxation in constituents that have longer relaxation times than the load duration. Local scale relaxation times are shorter than the load duration in this phase so that the final modulus is almost insensitive to strain rate. In the second phase, the initial modulus and the yield stress remain roughly constant while the final modulus increases with increasing strain rate. The tensile strength also increases, but the fracture strain decreases as the strain rate increases. Increases in the final modulus and tensile strength are due to a lack of relaxation on a local scale. The tensile fracture strain decreases because convolutions do not have sufficient time to slip completely. In the third phase, all stress-strain curves follow a master curve, but both the tensile strength and fracture strain decrease with increasing strain rate. The decrease in tensile strength as the strain rate increases could be due to stress concentration at the tip of microcracks within the SBR.

Stress‐strain characteristics of S15C carbon steel friction‐welded butt joints under impact tensile loading

Stress-strain characteristics of S15C carbon steel friction welded butt joints under impact tensile loading are evaluated using the split Hopkinson bar. Round tensile specimens machined from as-welded butt joints of 13 mm diameter are used in both static and impact tension tests. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. The effect of strain rate up to e≅700/s on the tensile stress-strain characteristics of both friction welded butt joints and a base material (S15C carbon steel) is studied. It is shown that the flow stress for friction welded butt joints is always higher than that for the base material at low and high rates of strain, but the former are less sensitive to strain rate than the latter. Microhardness measurements are conducted to examine the extent of the heat-affected zone (HAZ) across the weld interface. Metallographic examination reveals that there are zones of different grain structure through the weld region. The increase in the flow stress for friction welded butt joints is attributed to the presence of a locally-hardened region within the HAZ.

334 Stress analysis of butt adhesive joints of dissimilar hollow cylinders under impact tensile loadings

334 Stress analysis of butt adhesive joints of dissimilar hollow cylinders under impact tensile loadings

221 瓶口シール部の形状による多層ラミネートフィルムの衝撃引張挙動に及ぼす影響

The bottle-neck shaped seal of bags for holding liquid is particularly convenient for pouring the liquid into another container. In recent years, bags have frequently broken at the bottle-neck shaped seal because the bags were subjected to the impact during loading and unloading. Taking this into consideration, we performed impact tensile tests using two types of bags with bottle-neck shaped seals, one with barrier characteristics, i.e., laminate films of NY/alumina-evaporation PET/XA-S and NY/AL/XA-S, and one without barrier characteristics, i.e., NY/XA-S for bottle neck shaped seal diameters of 7.5, 10, 12.5, 13, 14, 15 and 20mm and flat seal bags. When the seal diameter of NY/aluminaevaporation PET/XA-S, NY/AL/XA-S or NY/XA-S is 15mm or greater, the impact tensile load at break is almost the same as that of flat seal bags.

604 The Effect of Initial Tightening Force on the Impact Strength for Bolted Joints

The behavior of bolted joints tightened with steel bolts under the impact tensile load are studied experimentally, changing the mechanical properties classes and length of straightportion of reduced diameter of bolts. The effects of the initial tightening force on the steel bolt strength is clarified through experiment. The result obtained are as follows : (1) As the initial tightening force is increased, the maximum stress and Φ-value (additional force/external impact load) decrease. (2) Without the initial tightening force, the higher the property class, the higher the maximum impact load. (3) Regardless of the property class, increasing the initial tightening force results in lowered impact absorbed energy. (4) Load capacity of the joints tightened in yield point is a little lower than that in elastic region. (5) Permitting the decrease of initial tightening force by 10%, the allowable load is about 85% of the yield strength of the bolt. (6) The allowable load estimated in the joint (load cell) whose stiffness is lower than actual condition is in safety zone.

1201 軸引張荷重を受けるねじ締結体の衝撃応力の推定法

1201 軸引張荷重を受けるねじ締結体の衝撃応力の推定法

Three-dimensional finite element analysis of single-lap adhesive joints under impact loads

This paper deals with the stress wave propagation and stress distribution in single-lap adhesive joints subjected to impact tensile loads with small strain rate. The stress wave propagations and stress distributions in single-lap joints have been analyzed using an elastic three-dimensional finite-element method (DYNA3D). An impact load was applied to the single-lap adhesive joint by dropping a weight. One end of one of the adherends in the single-lap adhesive joint was fixed and the other adherend to which a bar was connected was impacted by the weight. The effects of Young's modulus of the adherends, the overlap length, the adhesive thickness and the adherend thickness on the stress wave propagations and stress distributions at the interfaces have been examined. It was found that the maximum stress occurred near the edge of the interface and that it increased with an increase of Young's modulus of the adherends. It was also seen that the maximum stress increased as the overlap length, the adhesive thickness and the adherend thickness decreased. In addition, strain response of single-lap adhesive joints subjected to impact tensile loads was measured using strain gauges. Fairly good agreements were observed between the numerical and experimental results.