Dynamic Tensile Characteristics Research Articles

Experimental investigation on the dynamic tensile characteristics and microstructure of recycled coral aggregate concrete(RCAC)

Experimental investigation on the dynamic tensile characteristics and microstructure of recycled coral aggregate concrete(RCAC)

Dynamic tensile characteristics of an artificial porous granite under various water saturation levels

Underground rocks are generally subjected to water erosion and dynamic disturbances. To exclude the effect of clay minerals on the water–rock interaction mechanism, clay-free artificial porous rock (APR) was used to investigate the coupling effect of water saturation and loading rate on tensile behavior. Dynamic Brazilian disc experiments were performed on APR with six water saturation levels (100, 80, 60, 40, 20, and 0%) using a split Hopkinson pressure bar (SHPB) combined with a high-speed camera. The results indicated that the number of cracks in the APR specimens increased with the water saturation level during the dynamic damage process, with more radial cracks at the water saturation of 80–100%. The dynamic tensile strength (DTS) and dissipated energy density exhibited different change trends with water saturation levels under different loading rates and the rate dependence was most significant in the fully saturated state (100%). At lower loading rates, DTS initially decreased rapidly and then more slowly with increasing water saturation. At higher loading rates, DTS exhibited a ‘decrease then increase’ trend. Moreover, the water-affecting factor exhibited an overall decreasing trend with the loading rate and gradually converged to 1.0. These phenomena can be attributed to the interplay between the weakening and strengthening water-effect mechanisms based on the microstructure and water distribution in the APR specimens.

Effect of strain rate on tensile characteristics and failure behavior of Al/steel welded joint producing by a laser-MIG composite heating source

Studies on dynamic tensile characteristics for Al/steel dissimilar materials are crucial to ensure the integrity and dependability of light-weight structures. In this study, the tensile characteristics and failure behaviors of Al/steel laser-MIG welded-brazed joints were studied. The dynamic fracture mechanisms of the joints are discussed. With the increase in strain rate, the fracture mode and tensile properties of Al/steel joints with reinforcement changed. The joints exhibited two failure modes of heat-affected zone failure at lower strain rates and interface failure at higher strain rates. When the strain rate was 1000 s−1, the increase in dislocation density in the weld reinforcement and diversion of cracks in the intermetallic compound layer significantly enhanced the joint’s properties. The tensile and yield strengths reached 222.6 and 166.6 MPa, 6.5 % and 17.9 % higher than those at a stain rate of 1 s−1, respectively. For Al/steel joints without reinforcement, as the strain rate increased, the crack gradually grew to the Al8Fe2Si phase, leading to a notable enhancement in the joint’s performance. At a strain rate of 500 s−1, the maximum strength of the joint reached 238.3 MPa, representing an increase of 58.9 % in comparison to the strain rate of 1 s−1.

Research on the dynamic tensile characteristics and surface crack evolution of coal under impact loading

The tensile properties of coal under dynamic loading are important mechanical characteristics of coal and are highly important for controlling coal rock stability under impact loading conditions, selecting blasting engineering parameters, and studying the mechanism of rockburst disasters. To investigate the dynamic tensile failure process of coal subjected to impact loading, this study used high-speed photography and digital image correlation technology to capture the dynamic tensile failure of coal under impact loading. The dynamic tensile evolution was quantitatively analyzed from the beginning of coal sample being loaded to failure. The captured images of the coal were processed, and the fractal dimension was used to quantitatively describe the evolution of the coal surface cracks under impact loading. The following conclusions were drawn from the experimental results: (1) An empirical formula was established to describe the dynamic tensile strength characteristics of coal under different loading rates. (2) Under impact loading, the maximum strain of a Brazilian disc coal sample first appeared at the contact end between the sample and the incident rod. (3) Under impact loading, a Brazilian disc coal sample cracked from the center of the sample outward, and the crack subsequently extended toward both ends. The fractal dimension of the crack exhibited a power function relationship with time, and the variation range of the fractal dimension of the crack was 1.05–1.39.

Dynamic tensile characteristics of elliptically shaped Ni8Ti9Cr1 rings

Thin-walled tubes with elliptically shaped annular sections are widely applied in fuel ducts and exhaust pipes. However, the tensile mechanical properties of these structures have remained elusive due to the lack of accurate testing methods. This study aims to fill this gap by establishing circumferential tensile testing methods for static and dynamic conditions by employing a split Hopkinson tensile bar and an electronic universal tensile machine. The quasistatic and dynamic tensile characteristics of two distinct elliptically shaped Ni8Ti9Cr1 rings with different aspect ratios were investigated at room temperature, revealing a significant loading rate effect. The tensile curves exhibited considerable fluctuations, which diminshed as aspect ratios decreased. These fluctuations were attributed to stress waves propagating back and forth between the specimen, the clamp, and the bars, causing superimposition. The Johnson‒Cook (JC) model was established based on the experimental results and then incorporated into the finite element model to gain deep insights into the mechanical responses of the Ni8Ti9Cr1 rings under tension. Our findings reveal that dynamic tensile testing of elliptically shaped Ni8Ti9Cr1 rings induces a complex stress state, which leads to nonuniform necking effects and structural vibrations, revealing complex behaviors previously unexplored. This investigation significantly advances the understanding of quasistatic and dynamic tensile responses in elliptically shaped ring structures, shedding light on their mechanical intricacies across varying conditions.

Experimental investigation on the dynamic tensile characteristics of conglomerate based on 3D SHPB system

The mechanical properties and failure characteristics of conglomerate, main components of gravel layer, are of great significance to the study of efficient drilling methods in gravel layer. However, there are few works published previously, especially rare in terms of dynamics. While drilling in gravel layer, the bottom hole rock is subjected to complex loads, including impact loading and in-situ stress. The static and dynamic tension behaviours of conglomerate are tested by outcrop in this paper. Based on GCTS and 3D SHPB systems respectively, the static and dynamic tensile properties are analyzed, and the energy consumption while failure and the influence of axial static load on dynamic tensile characteristics are discussed. Results show that the tensile characteristics of conglomerate have a significant strain rate correlation, and the dynamic tensile strength is significantly higher than that of static; The strength in both impact direction and axial direction increase linearly with the loading strain rate, while the failure strain decreases linearly; As there is no axial load and the strain rate is 140.31–248.95 s−1, the dynamic tensile strength is 75.86–109.91 MPa, and the strength growth factor is 10.55–15.29 between the dynamic and static tensile strength. Due to the energy absorbed by the specimen increases exponentially in the dynamic test, there are a great number of cracks produced accompanied by the collapse of large debris, manifested as the volume crushing failure mainly, while in the static test, there is mainly brittle splitting failure. The dynamic tensile strength can be reduced linearly by increasing the axial static load or reducing the dynamic load. The research has an important theoretical reference for the study of drilling technology and theory in the gravel-rich stratum.

Dynamic Splitting Experimental Study on Sandstone at Actual High Temperatures under Different Loading Rates

The tensile failure of rocks is a common failure mode in rock engineering. Many studies have been conducted on the tensile strength and failure mode of rocks after high-temperature treatment under dynamic loading. However, research on the effects of high temperature on the dynamic splitting tensile characteristics of sandstone at actual high temperatures is lacking. To investigate the dynamic tensile characteristics of rocks at actual high temperatures, split Hopkinson pressure bar (SHPB) test apparatus and high-temperature environment box were used to perform dynamic splitting tensile tests under six striker velocities for sandstone specimens at 25°C–800°C. The dynamic splitting tensile strength, radial strain, average strain rate, and failure mode of sandstone under different test conditions were investigated. Test results revealed that the brittleness of sandstone specimens is enhanced at 200°C and 400°C, but slight ductility is observed at 600°C and 800°C. The strain rate effect of dynamic tensile strength is closely related to temperature. When the striker velocity exceeds 2.3 m/s, the dynamic radial strain first decreases and then increases with rising temperature. A quadratic polynomial relationship between the dynamic radial strain and temperature was observed. The temperature effect on the average strain rate is strong at low striker velocity and weak at high striker velocity. In the dynamic splitting tensile tests, high-temperature sandstone specimens are split into two semicylinders along the radial loading direction.

Microstructure and dynamic tensile characteristics of dissimilar fiber laser welded advanced high strength steels

The desire for production of anti-crash weight-optimized modern vehicles has resulted in the development of tailor welded blanks (TWBs) of 3rd-generation advanced high strength steels (3G-AHSSs). Therefore, understanding crash response (dynamic loading: strain rate of 1–100 s−1) of TWBs is essential for deploying new classes of AHSSs. The present work investigates dissimilar fiber laser joints between press-hardened 22MnB5 steel - medium manganese transformation induced plasticity (MMn-TRIP), and TRIP1100 steels. Lack of mixing within the fusion zone has been evidenced in the MMn-TRIP and TRIP1100 sides of the joints through retention of considerable austenite within the structure and the non-uniform hardness distribution, respectively. It was found that the inter-critical heat-affected zone of the MMn-TRIP side of the joints with a large volume fraction of austenite is responsible for the initiation of Lüders bands (discontinuous yield). The detailed digital image correlation technique demonstrated that the rapid decomposition of martensite in the heat-affected zone of the 22MnB5, and TRIP1100 sides of the joints localizes the plastic flow. Although the strength of the dissimilar joints showed positive strain rate sensitivity, however, under the higher applied strain rates elongation to fracture shows a transition from positive to negative strain rate sensitivity as a consequence of the suppression of the TRIP effect.

Statične in dinamične natezne lastnosti pločevine iz S420 in IF jekla

Statične in dinamične natezne lastnosti pločevine iz S420 in IF jekla

SPRC440 강판재의 미세조직 구성이 동적 인장 특성에 미치는 영향

Abstract The behavior of metallic materials at high strain rates shows different characteristics from those in quasi-static deformation. Therefore, the strain rate should be considered when simulating crash events. The objective of this paper is to evaluate the dynamic tensile characteristics of SPRC440 as a function of the volume fraction of phases. As-received SPRC440 is composed of ferrite and pearlite phases. However, ferrite and martensite phases were observed after heat treatment at 730  and 780  for 5 minutes, as expected by calculations based on the curves from dilatometry tests. High cross-head speed tensile tests were performed to acquire strain-stress curves at various strain rates ranging from 0.001 to 300 s -1 , which are typical in real vehicle crashes. It was observed that the flow stress increases with the strain rate and this trend was more pronounced in the as-received specimens consisting of ferrite and pearlite phases. It is speculated that the dislocation density in each phase has an influence on the strain rate sensitivity.

Evaluation of Dynamic Tensile Characteristics of Polypropylene Composites with Temperature Variation

This article suggests two useful methods to obtain true stress—strain curves with the variation of the strain rate ranging from 0.001 to 200/s using a finite element technique and optimization for two typical polymers: a polypropylene; and a polypropylene composite. The polypropylene is adopted as a core material of a vehicle’s instrument panel and the polypropylene composite sustains the passenger-side air bag module (PAB module) as a structural member. Their dynamic tensile characteristics are important to predict deformation modes of the PAB module which undergoes high speed deformation during air bag expansion. Since the polymers are temperature sensitive materials, the dynamic tensile tests were performed at the three levels of temperature: the low temperature (—30°C); the room temperature (21°C); the high temperature (85°C). During tensile tests of two polypropylene composites, the gage region in the specimen of the polypropylene composite elongates uniformly while that of the polypropylene does not elongate uniformly. In the case of the polypropylene, experimental stress—strain curves were modified by enforcing the load response calculated by finite element analysis coincident with that of the experiment. In the case of the polypropylene composite, experimental stress—strain curves were scaled by applying change rate of the gage length. Stress—strain curves of both cases provide excellent performance in their numerical response with the finite element analysis. The material properties obtained are indispensible to estimate the high speed deformation mode during air bag expansion at both normal and harsh operating conditions.

Dynamic tensile characteristics of TRIP-type and DP-type steel sheets for an auto-body

This paper is concerned with the dynamic tensile characteristics of transformation-induced plasticity (TRIP)-type and dual phase (DP)-type steel sheets at intermediate strain rates ranging from 0.003 to 200 s −1. The dynamic responses of TRIP600, TRIP800, DP600 and DP800 steel sheets are investigated with the evaluation of stress–strain curves, the strain rate sensitivity, the fracture elongation and the effect of pre-strain. The dynamic responses were acquired from dynamic tensile tests at the intermediate strain rates with a high-speed material testing machine developed. Experiments were carried out with specimens whose dimensions were carefully determined by finite element analyses and experiments to induce uniform deformation in the gauge section at the intermediate strain rates. The tensile tests provide stress–strain curves and the strain rate sensitivity. Experimental results show two important aspects for TRIP-type and DP-type steel sheets quantitatively: The flow stress increases as the strain rate increases and the fracture elongation and the formability of TRIP-type sheets are better than those of DP-type sheets at the intermediate strain rates. The pre-strain effect was also investigated for two types of metals at the intermediate strain rates. TRIP600 and DP600 steel specimens pre-stained by 5% and 10% were elongated at the strain rate of 0.003 s −1 for quasi-static loading, and then tested at strain rates of 0.003, 1, 10 and 100 s −1. The results demonstrate that the mechanical properties of TRIP600 and DP600 steels are noticeably influenced by the pre-strain when the strain rate is over 1 s −1. The ultimate tensile strength as well as the yield stress increases due to the pre-strain.

Dynamic Tensile Characteristics of TRIP-Type and DP-Type Sheets for an Auto-Body

This paper investigates the dynamic tensile characteristics of TRIP600, TRIP800, DP600 and DP800 at the range of strain rate from 0.003 to 200/s. The tensile test acquires stress−strain curves and the strain rate sensitivity of each material. Experimental results show two important aspects for TRIP-type and DP-type sheets quantitatively: the flow stress increases as the strain rate increases; the elongation is not a monotonic function of the strain rate and increases at the same level of the strain rate even when the strain rate increases. In order to investigate the pre-strain effect for two types of metals at the high strain rate, TRIP600 and DP600 were elongated with the pre-strain of 5 and 10% at the strain rate of 0.003/s. Then, dynamic tensile tests were carried out at the strain rate of 0.003, 1, 10 and 100/s. The results demonstrate that the material properties of TRIP600 and DP600 are noticeably influenced by the pre-strain when the strain rate was over 1/s. The ultimate tensile strength as well as the yield stress increases due to the pre-strain effect.