High-speed Tension Research Articles

Research on the deformation law of ultra-thin fiber metal laminates under the synergistic effect of nano-reinforcement and scale effect

At present, titanium alloy/carbon fiber reinforced polymer (TA1/CFRP) laminates, representing the latest fourth generation of fiber metal laminates (FMLs), are predominantly applied in the field of aerospace. The miniaturization of traditional FMLs in thickness or plane size to the micron level for the study of structural properties of ultra-thin laminates will further expand the application of FMLs in the field of micro-devices. Given that carbon nanotubes have a strengthening mechanism in polymers. However, most existing studies have focused on the effect of carbon nanotubes on the properties of macro-scale FMLs, while the enhancement mechanism of the interfacial and mechanical properties of ultra-thin micro-scale FMLs has not been studied, leaving the mechanism still unclear. Based on this, this paper explores the interfacial deformation mode, damage fracture and performance enhancement mechanism of the ultra-thin TA1/CFRP laminates by comparing the parameters of tensile strength and elongation under quasi-static conditions and different process parameters of multi-walled carbon nanotubes content, test temperature, geometry size and grain size. Meanwhile, the correlation law between high-speed tension and quasi-static tension is determined, a 29.3 % increase in tensile strength as the strain rate rises from 0.001 s−1 to 100 s−1, yielding the basic deformation law of ultra-thin FMLs.

Fracture Behavior of the Hot-Stamped PHS2000 Steel Based on GISSMO Failure Model

Hot-stamped steel is currently the most widely used lightweight material in automobiles, and accurately predicting its failure risk during the simulation is a bottleneck problem in the automobile industry. In this study, the fracture failure behavior of the hot-stamped PHS2000 steel manufactured by Ben Gang Group (Benxi, China) is investigated by experiments and simulation. Static tension and high-speed tension tests are conducted to obtain the elastic-plastic stress-strain relations, and a Swift + Hockett–Sherby model is proposed to describe the hardening behavior under static and high-speed loads. Tests under five kinds of stress states, namely static shear, static tensile shear, notched static tension, center-hole static tension, and static punching, are conducted to obtain the ultimate fracture strains under different stress states for establishing a failure model. The finite element method (FEM) is used to inversely achieve the fracture parameters of the material, and the GISSMO model in LS-Dyna is adopted to describe the fracture characteristics of the material. A fracture card is further established for simulation analysis by combining fracture characteristics with high-speed tension curves and simultaneously loading size effect curves of meshes. Finally, the card is applied in the simulation of the three-point bending test. High-precision results of fracture simulation matching the experimental results are obtained. This research proves that the proposed fracture card is accurate and can be widely used in the simulation of fracture behaviors of the hot-stamped PHS2000 steel.

Mechanical Properties and Fracture Microstructure of Polycarbonate under High Strain Rate Tension.

In this paper, static and dynamic tensile tests were conducted on two kinds of polycarbonate (HL6157 and A1225BK), combined with the digital image correlation (DIC), for guiding the development of the battery pack of new energy vehicles. The mechanical properties of polycarbonate at low-speed (0.01/s) and high-speed (1/s, 100/s) tension were investigated and the microstructure of the fracture for polycarbonate at different speed tensions was also investigated. The fracture microstructure of two kinds of materials was also investigated in this paper. The tension results showed that as the strain rate increased, the yield strength and modulus increased, and the yield strength of the two materials increased by 30% under high-speed tension. In addition, the fracture strain increase was greater than 10% as the strain rate increased. Meanwhile, for polycarbonate, the strain rate increased, and the fracture toughness increased.

The evolution mechanisms of bearing-tension-shear failure modes of FML joints under in-plane dynamic load

The quasi-static load on composite joints under normal service conditions will be transformed into in-plane impact load that is completely different from the traditional out-of-plane impact load, when the fuselage structure is threatened by dynamic impact load. The mechanical responses and damage mechanisms of bolted and hybrid (bolted/bonded) fiber metal laminate (FML) joints under high-speed tension load are investigated comprehensively. It is found that the loading velocities and adhesive layer play significant roles in determining damage pattern of bolted FML joints with specific geometric parameters. Increasing loading velocity results in the transformation of damage pattern from extended bearing-shear failure to net-tension failure in bolted joints, whose mechanisms are related to the rate dependent strength of structures. The hybrid FML joints, on the other hand, exhibit different evolution laws of damage modes due to released strain energy when the adhesive layer is damaged completely. The superposition of kinetic energy and released strain energy from adhesive layer in hybrid joints has similar effect as increasing loading velocity. The obtained conclusions provide a basis for further design of potential energy absorption joints.

Deformation and damage behavior of lightweight steels at high rate multiaxial loading

Abstract For the characterization of the deformation and damage behavior of the automotive lightweight steels ZStE340 and DP1000, high speed tension tests for various stress triaxialities with shear tensile specimens, smooth tensile specimens and notched specimens and static and dynamic Nakajima tests were performed. The deformation up to failure was recorded using high speed video cameras with high resolution in the necking zone and evaluated with 2D and in part 3D digital image correlation (DIC). The maximal achieved effective strain at the location of failure, determined by video analysis and fractography, was specified as failure strain. The results for various specimen geometries were plotted versus stress triaxiality as determined by FE simulation in order to receive failure diagrams. Overall, both materials show descending failure curves from shear loading up to tensile loading of notched specimens. Up to equibiaxial tension, failure curves are rising again. For uniaxial and equibiaxial tension, with increasing strain rate larger failure strains occured for DP1000, while no significant influence of strain rate on failure strain was observed for ZStE340. However, under shear loading with increasing strain rate, decreasing failure strains occur for both materials. This is probably due to an adiabatic temperature rise in a small localized zone which promotes shear failure. For shear crash tests a temperature rise of more than 200 K was measured by a high speed infrared camera. These results show the necessity of dynamic tests under different stress triaxialities to provide reliable input data for crash simulations and increase the ability to accurately predict failure. Especially shear failure must be investigated very carefully under crash loading, because here failure occurs at smaller failure strains than it would be expected under quasistatic loading.

Tensile and Flexural Behavior of Ultra-High Performance Concrete (UHPC) under Impact Loading

The rate-sensitive properties of ultra-high performance concrete (UHPC) subjected to flexural and direct tensile loads were investigated. Dynamic flexural tests were performed by means of a drop hammer impact machine, whereas a servo-hydraulic system was utilized to conduct direct tension tests. The absorbed energy of the UHPC specimens under flexure increased from 0.74 to 4.49 J as the input energy varied from 6.7 to 67 J. The load-bearing capacity and maximum flexural deformation exhibited identical trends as the input energy increased. The high-speed tensile properties, including strength, ductility, and energy dissipation capacity, improved upon increasing the strain rate up to 100 s-1. A nonuniform distribution of the deformation of UHPC specimens under high-speed tension was observed by identifying the zones of strain localization (near crack), uniform strain (far field), and shear lag (transition zone in between) using digital image correlation. The full-field data of displacement, strain, and strain rates were obtained and quantitatively evaluated. The results indicated that multiple mechanisms were involved in the rate-dependent behavior of the UHPC specimens.

МОДЕЛИРОВАНИЕ НАКОПЛЕНИЯ ПОВРЕЖДЕНИЙ И РАЗРУШЕНИЯ КЕРАМИЧЕСКИХ КОМПОЗИТОВ Al2O3 – ZrO2, ПОЛУЧЕННЫХ ПО АДДИТИВНЫМ ТЕХНОЛОГИЯМ, ПРИ ВЫСОКОСКОРОСТНОМ НАГРУЖЕНИИ

Functional ceramic composite materials are widely used in industry due to their high strength, hardness, high operating temperature, and chemical inertness. Among the most famous types of functional ceramics are the ceramic composites based on the Al2O3-20% ZrO2 system. In this work, the effect of the loading rate on the crack resistance is studied as well as the effect of the crack resistance of ceramic composites Al2O3-20% t-ZrO2 with a mass content of submicron tZrO2 particles on the high-speed compression of model specimens in shock waves and on the high-speed tension in the region of interaction of unloading waves. It is established that nonlinear effects of the mechanical behavior of ceramic composites ZrO2-Al2O3 with a transformationhardened matrix obtained by additive technologies are manifested at shock loading amplitudes close to or exceeding the Hugoniot elastic limit. Nonlinear effects under intense dynamic impacts on the considered composites are associated with the processes of self-organization of deformation regimes at a mesoscopic level, as well as with the occurrence of martensitic phase transformations in the matrix volumes, which are adjacent to strengthening particles. The modeling approach presented in this work can be used to determine the dynamic characteristics of ceramic composites up to shock loads of 1000 m/s.

Experimental study on the tension and puncture behavior of spray polyurea at high strain rates

Polyurea is widely used as a protective coating material for structures subjected to impulsive loads. In this study, the mechanical properties of polyurea were investigated experimentally over a wide range of loading rates. Firstly, quasi-static tests were performed using conventional hydraulic machine at strain rates of 7.7 × 10−4 - 7.3 × 10−3 s−1 for direct tension and at speeds of 1.67 × 10−5 - 1.67 × 10−4 m/s for puncture. Then high-speed tests were carried out using a high-speed servo-hydraulic testing machine (INSTRON VHS 160/100-20) at strain rates of 3.3–500.3 s−1 for direct tension and at speeds of 0.1–10 m/s for puncture. Deformation and failure processes of the polyurea specimens under high-speed tension were recorded with the aid of a high-speed camera. The testing results show that polyurea is a strain rate sensitive material. Under tensile loads, the initial yield stress and the strength increase with the increment of the strain rates while the fracture strain decreases. Under puncture loads, the yield force and the strength of the polyurea sheets also increase with loading rates. However, the strain rate effect on the failure deformation of the polyurea is only observed when the loading rate is less than 2 m/s. Based on the testing data, mechanism that causes the dynamic effect of polyurea material properties was discussed and some empirical relations were derived for engineering applications.

Spallation Strength of Titanium at High-Speed Tension

The motion of the rear free surface of a titanium film target of submicron thickness under the action of an ultrashort shock-compression pulse generated by a femtosecond laser was studied by spectral interferometry with a picosecond resolution. The value of the titanium spallation strength was close to the theoretical ultimate tensile strength at a strain rate of ~109 s–1.

A Study of Mechanical Properties Evaluation for Stainless Steel Under Low Temperature Region

For equipment operated in extreme weather regions such as Eastern Europe, Northern Russia, and Canada, etc. (with average temperature is colder than –20°C during winter), measures against freezing are necessary for the materials that compose plant modules and metal materials for the components of automobiles. However, only a portion of research on the effects at high temperatures have been performed in the cases of high-speed tension tests for cryogenic materials until now with the effects at low temperature being confirmed only to the extent of the presence of differences at high and low speeds. In this study, characteristics of two universal materials for stainless steel, namely TP304 and TP316, at low temperature were examined by executing comparative tests on their mechanical characteristics at both ordinary temperature and low temperature. As a result, TP304 displayed a secondary stiffening phenomenon in the low temperature range. Meanwhile, TP316 displayed a reduction in the elongation ratio in the low temperature and it was confirmed that the maximum tensile strength increased more so than at ordinary temperature. Regarding temperature dependency, the maximum tensile strength and elongation ratio were higher for TP304, while the yield strength was higher for TP316.

A novel approach for the strain rate dependent modelling of woven composites

This study proposes a new computational model for polyamid-matrix woven composites that takes into account rate effects for high speed impact applications. The rate effects are captured solely through the use of a spectral viscoelastic model, used in parallel with a conventional damage elastic-plastic model. It appears that, for very different load rates, neither plasticity nor damage kinetics need any first order rate dependency to capture the nonlinear envelope response until failure. To verify this hypothesis, a dedicated experimental setup is proposed that allows strain-controlled interruption of high speed tension loadings. Cycled loading sequences may therefore be applied to a sample even in the dynamic regime, and loss of stiffness and irreversible strains may be measured until total failure. A specific and rigorous identification procedure is proposed to that effect. Our experimental findings confirm the ability of the model to predict both the envelope response curve and the evolution of the internal mechanisms at very different strain rates.

Acceleration of Mass Transfer under Dynamic Loading

Under dynamic loading, the interaction of unloading waves with each other and with the faces causes the deformation of the sample due to the formation of standing waves, at the nodes of which the localized- deformation bands arise (if the high-speed tension does not exceed the spall strength, so the material in the zone of interference of unloading waves preserves its continuity). A consequence of deformation localization is the mass transfer of atoms and the doping phase particles to nascent localized-deformation bands. The duration of stress oscillations in standing waves in the ultrasonic frequency range exceeds the duration of the initial impulse by at least two orders of magnitude, which ensures an increase in the distance traveled by atoms and dispersed particles during deformation in standing waves.

Failure Localization and Correlation of High-Speed Tension and Impact Tests of Strain-Hardening Cement-Based Composites

AbstractMechanical properties of strain-hardening cement-based composites (SHCC) subjected to impact and high-speed tensile loading were studied. The impact test setup was based on a free-fall drop...

On the structural behavior of ship's shell structures due to impact loading

When collision accident between ships or between ship and offshore platform occurs, a common phenomenon that occurs in structures is the plastic deformation accompanied by a large strain such as fracture. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is heated by line heating and steel plate formed by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper–Symonds model and Johnson–Cook model and the assumption that strain rate can be neglected when strain rate is less than the intermediate speed are verified through free drop test as well as comparing with numerical results in several references. This paper ends with describing the future study.

Effect of tensile speed on mechanical characteristics of preliminary rolled polyethylene terephthalate films

The effect of tensile speed on the mechanical properties of amorphous polyethylene terephthalate films is studied. The films are oriented by rolling on laboratory rollers at room temperature. In the samples with the rolling degree of two, the subsequent tension with the velocity of 5 mm/min does not afford a neck. As the tensile speed increases to 500 mm/min, a neck results from instability of the deformation process, which is caused by the polymer heating. Upon high-speed tension, the temperature of the rolled samples exceeds the glass-transition point of polyethylene terephthalate. Despite the polymer heating, the rolling completely suppresses the formation of pores. The rolling leads to the delocalization of flow over the region of polymer transfer to the neck. While in the nonrolled films the flow occurs in the zone with the length on the order of the film thickness, after the rolling, the size of the flow zone increases, and the region with the length on the order of the film width is deformed.

On the Derivation of Material Constants Associated with Dynamic Behavior of Heat Formed Plates

구조물에 충격하중이 작용하면, 그 구조물은 통상적으로 대변형을 동반하는 소성변형과 최종적으로 그에 따른 파단을 경험하게 된다. 본 연구에서는 사고적 극한 상태에 대한 합리적인 설계를 위해 열성형된 판과 냉간성형된 판의 재료상수를 고속인장시험에 대한 수치시현을 통해 정의하였다. 변형율이 중간 속도 이하인 경우에는 변형율 속도의 영향을 무시할 수 있다는 가정과 함께 Cower-Symond 모델과 John-Cook 모델에 포함되는 재료상수들의 유용성을 참고문헌들의 결과와 비교하여 입증하였다. 본 논문은 향후 연구 내용에 대한 언급을 포함하면서 마무리하였다.When impact load is applied to a plate structure, a common phenomenon that occurs in structures is plastic deformation accompanied by a large strain and eventually it will experience a fracture accordingly. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is formed by line heating and by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper-Symonds model and Johnson-Cook model with the assumption that strain rate can be neglected when strain rate is less than the intermediate speed is verified through comparing the present numerical results with those in references. This paper ends with describing the future study.

High strain rate visco-damageable behavior of Advanced Sheet Molding Compound (A-SMC) under tension

Advanced Sheet Molding Compound (A-SMC) is a serious composite material candidate for structural automotive parts. It has a thermoset matrix and consists of high weight content of glass fibers (50% in mass) compared to standard SMC with less than 30% weight fiber content. During crash events, structural parts are heavily exposed to high rates of loading and straining. This work is concerned with the development of an advanced experimental approach devoted to the micro and macroscopic characterization of A-SMC mechanical behavior under high-speed tension. High speed tensile tests are achieved using servo-hydraulic test equipment in order to get required high strain rates up to 100 s−1. Local deformation is measured through a contactless technique using a high speed camera. Numerical computations have led to an optimal design of the specimen geometry and the experimental damping systems have been optimized in terms of thickness and material properties. These simulations were achieved using ABAQUS explicit finite element code. The developed experimental methodology is applied for two types of A-SMC: Randomly Oriented (RO) and Highly Oriented (HO) plates. In the case of HO samples, two tensile directions were chosen: HO-0° (parallel to the Mold Flow Direction (MFD)) and HO-90° (perpendicular to the MFD). High speed tensile tests results show that A-SMC behavior is strongly strain-rate dependent although the Young's modulus remains constant with increasing strain rate. In the case of HO-0°, the stress damage threshold is shown an increase of 63%, when the strain rate varies from quasi-static (0.001 s−1) to 100 s−1. The experimental methodology was coupled to microscopic observations using SEM. Damage mechanisms investigation of HO and RO specimens showed a competition between two mechanisms: fiber-matrix interface debonding and pseudo-delamination between neighboring bundles of fibers. It is shown that pseudo-delamination cannot be neglected. In fact, this mechanism can greatly participate to energy absorption during crash. Moreover, the influence of fiber orientation and imposed velocity is studied. It is shown that high strain rate and oriented fiber in the tensile direction favor the pseudo-delamination.

Influence of weaving on the mechanical response of aramid yarns subjected to high-speed loading

Aramid fibres are used in high performance fabrics and yarns for dynamic loading applications, because of their high strength and stiffness, and good energy absorption. This investigation explores the influence of the weaving process on the mechanical response of aramid yarns. The quasi-static and dynamic properties of virgin T1040 Twaron® yarns and their woven counterparts, extracted from plain-woven T717 Twaron® fabric, are characterized and compared, to examine the effect of the weaving process. In particular, the phenomenon of yarn uncrimping is examined. A Split Hopkinson Tensile Bar device, with a specially-designed fixture to attach specimens to the loading bars, is used to apply high-speed tension to yarn specimens. High-speed photography is employed to observe deformation and failure, and to measure specimen strain. Experimental results show that virgin and woven yarns exhibit similar rate sensitivity – an increase in strain rate makes both stiffer, increases their tensile strength, and decreases the failure strain. Virgin yarns possess a lower failure strain compared to woven yarns, but a higher strength and stiffness. Observation of broken fibres shows this may be due to the damage of the fibre during the weaving process, which affects the cohesion of the fibrils at the micro-level. Consequently, the yarn strength and stiffness are degraded, and this decreases the overall energy absorption capacity.

A Study on High Speed Tension Property of C-Grade Bullet Proof Steel Plate

In this paper, the high speed tension experiments have been performed on ultra high strength bullet proof steel. The samples were cut from the bullet proof steel plate after hard-module quenching with thickness of 3.7 mm. The mechanical properties at strain rates of 0.001 s-1, 0.01 s-1, 0.1 s-1 and 1 s-1 were carried out on MTS810, while those at higher strain rates of 200 s-1, 500s-1 and 1000s-1 were tested on HTM5020 high speed tension tester and Hopkinson bar. The data from the high-speed tension experiments were fitted via Johnson-Cook constitutive equation, and the fracture surface of each sample was analyzed by SEM. The results indicate that, the shoot-resistance capability of bullet proof steel is closely related to its strength, thickness and flow behaviors under high strain rate. The shoot-resistance will be improved in the case of higher strength and better matching between strength and elongation. The Johnson-Cook equation fitted via experimental data provides fundament to numerical simulation. With the increase of strain rate, the size and depth of dimple trend to decrease and the depth of dimple changes less in steel with lower strength and higher elongation. The SEM analysis of fracture is benefit for further understanding of deformation and fracture mode under high strain rate.

Study on high speed tension property of B-grade bulletproof steel

Study on high speed tension property of B-grade bulletproof steel