Tensile Impact Loading Research Articles

Measurement of phase transformation properties under moderate impact tensile loading in a NiTi alloy

Pseudoelasticity is one of the main characteristics of shape memory alloys (SMAs), allowing them to recover their initial state after undergoing large deformation. This is due to the martensitic transformation (MT) occurring in the material, turning the austenitic phase into a stress-induced martensitic phase when a mechanical load is experienced. By conducting tests in quasi-static and dynamic ranges, studies have reported the strain rate dependence of the macroscopic behavior of SMAs. This paper investigates the influence of the strain rate applied to a NiTi SMA at the level of the MT, providing experimental data of the heterogeneous strain field occurring during quasi-static and dynamic tensile loading. Experiments were conducted at three different levels of prescribed velocity: 0.01mm/s, 1mm/s and 1000mm/s, using a classical loading machine for the quasi-static cases and a Split Hopkinson Tensile Bar (SHTB) for the dynamic cases. The observations of the heterogeneous strain field during the tests were made using a digital image correlation (DIC) technique which was validated by infrared thermography (IRT) measurements, considering that MT is exothermic. The analysis of the tests shows that the velocity of growth of the transformed zone is related to the applied velocity by a constant factor. Moreover, quantitative results about the strain level in the heterogeneous strain field are analysed. This study gives complementary results to the studies already made on MT in the quasi-static case, extending the observation by 103 to 105 times regarding the applied displacement rate.

Experimental and FEM studies on mechanical properties of single-lap adhesive joint with dissimilar adherends subjected to impact tensile loadings

The rupture initiation position, the stress wave propagations and interface stress distributions of the single-lap adhesive joint with dissimilar adherends under impact tensile loadings are analyzed via experiments combined with FEM calculations taking account of the strain rate dependency property of the adhesive. It is obtained that rupture initiates at the interface of the adherend with higher Young's modulus (steel side in this study) in the joint under impact tensile loadings, which shows the opposite characteristic in the same type of joint under static loadings. A fairly good agreement is observed between the experimental measured and FEM calculated results. In addition, it is also found that the strength of the joint with dissimilar adherends is smaller than that of the joint with similar adherends when the joint is subjected to the impact tensile loadings owing to the different extent of the wave impedance mismatch which depends on the material properties. Finally, the design guideline for the single-lap adhesive joint is summarized and provided.

313 繰返し衝撃引張負荷を受ける鋳鉄の低サイクル疲労強度について(OS-4 機械材料・構造体の衝撃工学(2),オーガナイズド・セッション(OS))

313 繰返し衝撃引張負荷を受ける鋳鉄の低サイクル疲労強度について(OS-4 機械材料・構造体の衝撃工学(2),オーガナイズド・セッション(OS))

Investigation on design parameters of single-walled carbon nanotube reinforced nanocomposites under impact loads

Multi-scale material modeling is applied to investigate the effect of major design parameters of reinforcing agents in single-walled carbon nanotube (SWCNT) reinforced nanocomposites in impact loads. The influence of diameter, chirality and volume fraction (VF) of SWCNTs on impact behavior of different representative volume elements (RVEs) of nanocomposites is studied. SWCNTs are modeled through beam elements in space frame structures in finite element modeling (FEM) software based on their atomic structures in molecular mechanics. The RVEs are composed of various modeled SWCNTs embedded in an elastic medium as polymeric matrix. The various RVEs are exposed to a tensile impact load and the obtained responses are analyzed to evaluate the effective design parameters of SWCNTs in the nanocomposite structures. The results in the form of strain energy density and axial strain oscillations of RVEs in a time period after impact demonstrate a great improvement in the impact behavior of nanocomposites due to adding SWCNTs in matrix. Applying SWCNTs with smaller diameter in RVEs causes a better impact strength in nanocomposites. In design procedure of nanocomposites subject to the impact loads, it is better to concentrate on the size and the volume fraction of applied CNTs instead of their chirality.

Evaluation of the joint strength between Sn–3.0Ag–0.5Cu solders and Cu substrate at high strain rates

A lack of study on the dynamic tensile strengths of Sn-based solder joints at high strain rates was the motivation for the present study. A modified miniature Chapy impact testing machine instrumented with an impact sensor was built to quantitatively evaluate the dynamic impact strength of a solder joint under tensile impact loading. This study evaluated the tensile strength of lead-free solder ball joints at strain rates from 1.8×103s−1 and 8.5×103s−1. The maximum tensile strength of the solder ball joint decreases as the load speed increases in the testing range. This tensile strength represented that of the interface because of the interfacial fracture site. The tensile strengths of solder joints between Sn–3.0Ag–0.5Cu and copper substrate were between 196.2MPa and 72.1MPa in the high strain range. The brittle interfacial fracture was likely to occur primarily in the waist of the protuberant Cu6Sn5 intermetallic layer. The fracture toughness values of interfacial IMC (intermetallic compound) between Sn–3.0Ag–0.5Cu and copper substrate were between 1.8MPam0.5 and 1.0MPam0.5 in the speed range tested.

Experimental investigation of bond characteristics between CFRP fabrics and steel plate joints under impact tensile loads

In recent years, the use of adhesively-bonded fibre-reinforced composite materials has attracted widespread attention as a viable alternative for the retrofitting of civil infrastructure such as buildings and bridges. This has been particularly the case for concrete structures. The retrofitting of metallic bridges and buildings with FRP materials, however, is still in its early stages. In real life, these structures are subjected to dynamic loads. Therefore, it is necessary to understand the bond behaviour between steel and the strengthening materials for both static and dynamic loads. To examine the bond between steel plates and carbon fibre-reinforced polymers (CFRP) fabrics, this paper describes the experimental procedures and results of double strap steel joints loaded at different loading rates (2 mm/min, 3.35, 4.43 and 5 m/s). In this test program, ultimate load-carrying capacity, effective bond length, failure mechanism and strain distribution were examined for all loading rates. Different numbers of CFRP layers with different bond lengths were investigated. Experimental findings reveal that the maximum improvement in joint capacity occurs at a rate of 3.35 m/s. It was observed that the effective bond length is insensitive to loading rate for both joints. The failure modes and strain distributions, however, exhibit little difference between static and dynamic conditions.

3-D FEM stress analysis and strength evaluation of single-lap adhesive joints subjected to impact tensile loads

The stress wave propagations and interface stress distributions in the single-lap adhesive joint under impact tensile loads are analyzed using the three-dimensional finite element method (3D-FEM) taking into account the strain rate sensitive of the adhesive using Cowper–Symonds constitutive model. It is found that the rupture of the joint initiates near the middle area of the edges of the interfaces along the width direction. In addition, the effects of Young's modulus of the adherend, the overlap length and the thickness of the adhesive layer, and the initial impact velocity of the impacted mass on the stress wave propagations and the interface stress distributions are examined. The characteristics are compared with those of the joint under static loads, which show the different properties. Furthermore, experiments are also carried out for measuring the strain responses and the joint strength. A fairly good agreement is observed between the numerical and the measured results. The strength of the single-lap adhesive joint, which is described using impact energy, is obtained between 5.439 and 5.620 J for the present joint.

Effect of Impact Tensile Load on Strength of CFRP Bonded Steel Plate Joints

This paper reports an experimental investigation into the effect of impact tensile loads on the bond strength, effective bond length and failure modes of double strap joints. Unidirectional normal modulus carbon fibre reinforced polymer (CFRP) sheet with one and three layers (plies) and Araldite 420 adhesive are used in this investigation. Dynamic results were compared with those subjected to static tension to highlight the influence of loading rate. It was found that the impact loading has significant influence on joint strength but little influence on effective bond length.

Mechanical Behaviour of Normal Modulus Carbon Fibre Reinforced Polymer (CFRP) and Epoxy under Impact Tensile Loads

This paper is concerned with experimental investigations of the mechanical properties of unidirectional normal modulus carbon fibre reinforced polymer (CFRP) sheet and Araldite 420 epoxy under quasi-static and medium impact tensile loads. It is found that both the CFRP sheet and Araldite resin were strain rate dependent. For CFRP the increase in tensile stress is about 20 to 40% whereas the increase in modulus of elasticity and strain at failure is about 20%. For Araldite the increase in tensile stress and modulus of elasticity is about 220% and 100% respectively, whereas a 50% reduction in strain at failure was observed.

Deformation response and constitutive modeling of PC, ABS and PC/ABS alloys under impact tensile loading

The objective of this paper is to experimentally study the tensile deformation behavior of the polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and PC/ABS alloys (with the blending ratio of PC to ABS being 80:20, 60:40, 50:50 and 40:60) at strain rates 6.0 × 10 2 s −1, 1.2 × 10 3 s −1 and 2.2 × 10 3 s −1, respectively. The Split Hopkinson Tension Bar (SHTB) tests are carried out at room temperature (300 K) to characterize the strain rate-dependent elastic, yielding and post-yielding deformation behavior. The curves of engineering stress and engineering strain and true stress and true strain are obtained for the PC, ABS and PC/ABS alloys at different strain rates. The effects of strain rate and the ABS fraction on the deformation behavior of PC, ABS and PC/ABS alloys are discussed in details, and then a strain rate-dependent phenomenological constitutive model for PC, ABS and PC/ABS alloys is developed.

OS1102 衝撃引張負荷を受ける光重合型コンポジットレジンの破壊計測(実験力学における最近の進歩,オーガナイズドセッション)

The fracture behavior of a light cure composite resin under impact tensile loading was studied using single-edge-cracked specimens. The impact load and displacement were measured with a Piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e. the external work applied to the specimen was partitioned into three parts: the elastic energy left in the fractured specimen, the nonelastic energy due to viscoplastic deformation and the fracture energy for creating new surfaces. These energies were then determined and correlated with the fracture load. Energy release rates were also evaluated, and the results were discussed.

光重合型コンポジットレジンの衝撃引張り破壊計測

光重合型コンポジットレジンの衝撃引張り破壊計測

851 衝撃引張り荷重作用下におけるCFRP積層板二重重ね合せ/突合せ接着継手の三次元有限要素応力解析(接着接合の力学I)

851 衝撃引張り荷重作用下におけるCFRP積層板二重重ね合せ/突合せ接着継手の三次元有限要素応力解析(接着接合の力学I)

Failure analysis on connection components of turbo-disk and main-shaft used in a locomotive turbocharger

Three bolts, three pins connecting turbo-disk and main-shaft and the navel of turbo-disk fractured during servicing, which were used in a locomotive turbocharger. Examination and analysis results show that one of location pins was not riveted into the pin hole on the plate of the main-shaft due to dislocation. The pin encountered greater hammering force and resistance to moving downward when being riveted into the hole, so corresponding impact tensile load was exerted on opposite bolt and the navel. The cracks initiated at the last engaged thread root of the bolt and the root fillet of navel and propagated in fatigue mode under the action of alternative loads. The bolt and the navel fractured first. Other components fractured in succession. Defective operation of riveting is responsible for the fracture of connection components.

High deformation rate and failure characteristics of amorphous polymers and their blends

This paper presents a study on deformation and failure characteristics of polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS) and their blends under a constant impact tensile loading rate. The test results showed that blending PC with weaker ABS produced a tougher PC/ABS blend but it demonstrated higher amplitude of oscillation and immediately fractured after yielding. Scanning electron microscopy on the fracture surface revealed that such behavior might be induced by developing voids because of the weakness of the interface between PC and ABS.

602 静的及び衝撃引張り荷重を受ける層内に円形弾性充填物を有する突合せ接着継手の応力解析(接着接合の力学)

602 静的及び衝撃引張り荷重を受ける層内に円形弾性充填物を有する突合せ接着継手の応力解析(接着接合の力学)

Effect of Rubber Particle Size on Impact Tensile Fracture Behavior of MBS Resin

The single-edge-cracked specimens of MBS resin with two different sizes of rubber particles were fractured under impact tensile loading. 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 rate was then estimated using Gf = Ef/As. The values of Gf were correlated with the fracture loads and the mean crack velocities determined from the load and time relationships. The effect of the particle size on the impact tensile fracture behavior was then examined. The results showed that the particle size plays an important role in changing the impact fracture behavior of MBS resin.

Mechanical Behavior and Deformation Modes of Commercially Pure Titanium under Impact Tensile Load

Abstract The impact tensile test was carried out on hot-rolled commercially pure titanium at temperature from 293 K to 77 K. The microstructures after fracture were examined by transmission electron microscope to determine the deformation modes. Strength and ductility increase with decreasing temperature from 293 K to 77 K. The investigation on the microstructure shows that slip cooperates with twinning in the deformation, and twinning becomes more active at lower temperature. At high strain rate titanium exhibits obvious strain hardening and twinning plays an important role in strain hardening. {1012} twin is identified in the microstructure at room temperature and three types of twins were identified at 77 K, which are {1011}, {1012}, {1121} twins.

Axial Dynamic Tensile Strength of Concrete under Static Lateral Compression

The rate effect on concrete tensile strength can be modeled by the description of crack extension in a fictitious fracture plane [1,2].The plane represents the initial, internal damage and the geometry of the final fracture plane. In the paper, the same approach is applied to model the failure envelope for the biaxial loading condition of static lateral compression and axial impact tensile load. The predicted failure envelope is compared with data from experimental work.

Impact tensile fracture testing of a brittle polymer

The fracture behavior of a brittle polymer, methylmethacrylate–butadiene–styrene resin, under impact tensile loading was studied using single-edge-cracked specimens. The dynamic load and displacement were measured with a Piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e., the external work, U ex, applied to the specimen was used to determine the elastic energy, E e, and non-elastic energy, E n, due to viscoelastic and plastic deformation, and the fracture energy, E f, for creating new fracture surface, A s. The energy-release rates were then estimated using G t= U ex/ A s and G f= E f/ A s. The values of G t and G f were correlated with the fracture loads and the mean crack velocities determined from the load and time relationships.