Tensile Fracture Mechanism Research Articles

Tribo-mechanical characterisation of MoS2 and H-BN reinforced PA66 composite

ABSTRACT This research aims to create a composite that is inexpensive and can be used in mechanical applications. The main aim is to improve the tribological performance of PA66 by reinforcements. Two fillers were utilised in the experimentation because MoS2 is a remarkably effective solid lubricant in dry conditions, but the results are not the same in high humidity. H-BN is utilised here to get the benefit in both dry and humid environments and to reduce the negative impact of humidity on the tribological performance of composite. Tensile and hardness tests were performed to identify the mechanical properties, while tribological tests on pin-on-disc were performed to analyse the COF and wear rates of materials. SEM, XRD, and DSC characterisations were utilised to analyse the tensile fracture mechanism, crystallinity, and glass-transition temperature of materials, respectively. The result shows that the strength and hardness of the composite increased in a reasonable amount compared to virgin PA66. Wear and COF tests were conducted with three different parameters, and the results showed an improvement in wear rates of composites compared to virgin PA66.

Effects of WC particles on microstructure and mechanical properties of 316L steel obtained by laser melting deposition

Stainless steel has many excellent characteristics such as high strength, weldability, corrosion resistance, easy processing and surface gloss. It has been widely applied in many industrial and architectural decoration aspects such as aerospace, chemical, and automotive. However, 316L material manufactured by Laser melting deposition has poor wear resistance and tensile strength. In this paper, WC particles are used as a strengthening phase to make up for these deficiencies of 316L. In order to comprehensively evaluate the effect of WC particles on the mechanical properties of 316L formed by laser melting deposition, 316L samples with different proportions of WC particles and different fabricating directions were prepared. The microstructure of samples was observed, and the phase composition, Vickers hardness, friction and wear properties, tensile properties were analyzed. The mechanism of the influence of WC particles on the structure and the mechanism of friction, wear and tensile fracture were studied. The results show that most of the WC particles are evenly distributed in the coating. The microhardness and wear resistance of the 316L/WC composite coating have been significantly improved with the increase in the proportion of WC. The tensile strength and elongation are the best when the WC mass fraction is 6%.

Experimental study on tensile fracture mechanism of butt joints in multi-celled CFST walls

Multi-celled concrete filled steel tubular walls (MCFSTWs) have been widely used in engineering practice. A high MCFSTW can be constructed by assembling two medium-height wall segments that are butt welded with the connector. At the connecting part between two wall segments, the connector, welding seams and steel plates of upper and lower wall segments form the butt joint. Since the butt joint is susceptible to tensile fracture, it is necessary to investigate its tensile fracture mechanism. In this paper, 12 specimens representing different parts of the butt joint are tested under tension and they include 6 types with different configurations. These specimens are designed by using connectors with different shapes and considering different welding conditions. The test results are analyzed and validated against the numerical simulation considering the ductile damage criteria. Based on the reliable finite element (FE) model, a simplified model is established to study the fracture performance of the complete butt joint. Finally, reliable design recommendations based on the experimental results and supplement FE analysis are summarized for improving the tensile performance of butt joints in MCFSTWs.

Mechanical and tribological properties of (FeCoNi)88-x(AlTi)12Mox high-entropy alloys

In this study, we designed and prepared (FeCoNi)88-x(AlTi)12Mox high-entropy alloys (HEAs) with good comprehensive properties by vacuum arc melting technology. The influence of Mo content on the microstructure, mechanical properties, and tribological properties of the HEAs were systematically studied. The results showed that all HEAs in this study are simple fcc solid solution structure, all HEAs are composed of γ + γ' phase, and they are in a coherent relationship. The tensile test results show that all the HEAs exhibit excellent strength-ductility combination, and the final tensile fracture mechanism is a ductile fracture. Mo1.0 HEA has the best comprehensive mechanical properties, with the yield strength, tensile strength, and elongation of 980 MPa, 1260 MPa, and 34.5%, respectively. The reciprocating friction and wear test results show that the HEAs have excellent friction and wear properties. Compared with the four HEAs, the order of friction and wear properties from good to poor is Mo1.0 HEA, Mo1.5 HEA, Mo0.5 HEA, and Al6Ti6 HEA. The wear mechanisms of all HEAs are abrasive wear and oxidation wear, as well as the Al6Ti6 and Mo1.0 HEAs also have delamination wear.

Mechanical, thermal, and flammability properties of polyamide-6 reinforced with a combination of carbon nanotubes and titanium dioxide for under-the-hood applications

The current study aims to explore the tensile fracture mechanism and thermo-mechanical efficiency of polyamide-6 (PA6) reinforced with titanium dioxide (TiO2) and multiwalled carbon nanotubes (MWCNTs). The uniform dispersion of the MWCNTs and appreciable interfacing between PA6, TiO2, and MWCNTs were revealed in the fractography figures. The crystallization temperature and degree of crystallinity have been enhanced by the addition of nanoparticles to the PA6 matrix. Young’s modulus, tensile strength, and Charpy impact strength improved proportionally concerning reinforcement content. The essential work of fracture (EWF) method was applied to evaluate the toughening and fracture behavior of PA6 hybrid systems. Considerable improvement (+60.6%) in the EWF of PA6–TiO2–MWCNT nanocomposites was observed at 4 wt.% CNT and 2 wt.% TiO2. Limiting oxygen index (LOI) findings demonstrate that a polymer with a combination containing titanium dioxide and multiwalled carbon nanotubes has a highly substantial retardant influence. As a result, the TiO2–CNT combination acts as a synergist filler, offering versatile PA6 composite products.

The role of defects on tensile deformation and fracture mechanisms of AM AlSi10Mg alloy at room temperature and 250 °C

This paper studied the tensile deformation and fracture mechanisms of a laser powder bed fusion (L-PBF) built AlSi10Mg alloy at room temperature (RT) and 250 °C via X-ray microtomography (XCT) and fractography. The mechanical tests have shown a distinct contrast on the bulk strength and ductility between the two temperatures. It was found that the temperature influences the tensile fracture behaviour via primarily facilitating the plastic deformation, leading to the significant enlargement and elongation of the defects within the necked region. Additionally, the tensile fracture path involves less preferential propagations along the melt pool boundaries (MPBs), due to the loading direction and the less distinct solidification structure arising from the stress relief treatment. In terms of fracture mechanisms, at RT, defects coalesce to form microcracks, propagate in a quasi-zig-zag path and finally lead to a classical cup-cone fracture. While at 250 °C, defects elongate under local plastic straining and then coalesce through microvoiding as the hydrostatic constraint becomes significant due to necking, and finally lead to a ductile fracture.

Effects of Notch Radius and Thickness on the Tensile Strength and Fracture Mechanisms of Al6061-T6 Plate Specimens

Effects of Notch Radius and Thickness on the Tensile Strength and Fracture Mechanisms of Al6061-T6 Plate Specimens

Revealing the role of micron-sized in situ TiC particles on tensile properties and fracture mechanism of martensitic wear-resistant steel at elevated temperature

In order to improve the performance of the TiC ceramic reinforced wear-resistant steel at medium and high temperatures, such as slag transportation and cement production, its high-temperature tensile properties need to be well understood. In this paper, an in situ micron-sized TiC ceramic particle reinforced wear-resistant steel with 1 vol% TiC particles was fabricated. The tensile behavior and fracture mechanism of the TiC ceramic reinforced steel at 25–600 °C were investigated. The role of micron-sized TiC particles on tensile properties and fracture mechanism at elevated temperature was studied. Results indicated that the high temperature strength of TiC ceramic reinforced wear-resistant steel was enhanced by improving the thermal stability of the matrix. In the low and medium temperature range (25–500 °C), micron-sized TiC ceramic particles played a role in improving the strength, but had little effect on the elongation to failure. However, the micron-sized TiC ceramic particles greatly reduced the elongation to failure of the experimental steel when the temperature exceeded 500 °C. In the range of 25–600 °C, the fracture mechanism matched the typical ductile fracture. However, the mechanism of cavity formation varied at 500 °C. At 25–500 °C, the micro-cavities mainly formed due to fracture of the micron-sized TiC particles with sizes in the range of 1–9 μm and defects of the matrix. Above 500 °C, the interfacial debonding between the micron-sized TiC and the matrix was the main mode of crack initiation.

Experimental and numerical investigations on tensile mechanical properties and fracture mechanism of granite after cyclic thermal shock

Experimental and numerical investigations on tensile mechanical properties and fracture mechanism of granite after cyclic thermal shock

Dynamic Tensile Properties of CFRP Manufactured by PCM and WCM: Effect of Strain Rate and Configurations

Carbon fiber-reinforced plastic (CFRP) is a promising material to achieve lightweight automotive components. The effects of the strain rate and configurations of CFRP on dynamic tensile properties have not yet been fully explored; thus, its lightweight benefits cannot be maximized. In this paper, the dynamic tensile properties of CFRPs, tested using two different processes with two different resins and four different configurations, were studied with a strain rate from 0.001 to 500 s−1. The tensile strength, modulus, failure strain, and fracture mechanism were analyzed. It was found that the dynamic performance enhances the strength and modulus, whereas it decreases the failure strain. The two processes demonstrated the same level of tensile strength but via different fracture mechanisms. Fiber orientation also significantly affects the fracture mode of CFRP. Resins and configurations both have an influence on strain rate sensitivity. An analytic model was proposed to examine the strain rate sensitivity of CFRPs with different processes and configurations. The proposed model agreed well with the experimental data, and it can be used in simulations to maximize the lightweight properties of CFRP.

Research on the cryogenic axial tensile fracture mechanism for 2219 aluminum alloy T-joint by dual laser-beam bilateral synchronous welding

In this paper, dual laser-beam bilateral synchronous welding (DLBSW) technology is performed to fabricate 2219 aluminum alloy T-joint. The cryogenic axial tensile strength of the DLBSW T-joint in the direction parallel to the weld at −182℃ is tested. The microstructure of T-joint, the cryogenic axial tensile strength, fracture location and tensile fracture morphology are comprehensively investigated to explore the cryogenic axial tensile mechanism. The average value of cryogenic axial tensile strength of T-joint is 415 MPa, 76.9% of base metal (BM). Under the axial tensile force, the grain deformation and intergranular cracks are respectively generated in weld seam (WS) and heat affected zone (HAZ) near the fracture location. It is found that the cryogenic axial tensile fracture mechanism of the T-joint is intergranular ductile fracture, contains cleavage fracture and microvoid coalescence fracture. The degradation of cryogenic axial tensile property is attributed to multiple factors, such as impurity phases, pores, eutectics.

Optimization of the mechanical properties of cold-mixed epoxy asphalt: effects of original asphalt, solvent, epoxy resin and additives

The influence of formulation components of cold-mixed epoxy asphalt (CMEA) on the corresponding mechanical properties was studied. For the purpose of minimising the number of experiments, the simplex-centroid design method was used as an effective tool for experimental design. Original asphalt, solvent, epoxy resin and additives were taken into consideration as important factors at different levels. Tensile strength and elongation at break at 25 ℃ and -10 ℃ were chosen as the key responses. Moreover, the workability performance and optimised CMEA were studied. Finally, the tensile cross-sectional fracture mechanism of CMEA was studied with scanning electron microscopy (SEM). The results indicated that the simplex-centroid design was an effective method for optimising the composition of the CMEA. Good agreement was found between the proposed model and experimental measurements. The CMEA pot life first increased and then decreased with increasing environmental temperature, and solvent in the CMEA could weaken the ductility.

Characterisation of Mechanical Properties, Damage Progression and Fracture Modes of Recycled Aluminium Alloys AA6061 Reinforced Alumina Oxide

Characterisation of the deformation behaviour of recycled aluminium alloy reinforced alumina oxide in terms of mechanical properties, damage progression and fracture mode is investigated via the Uniaxial Tensile Test in this manuscript. The tests are carried out at room temperature at strain rates of 6X10-3s-1, 6X10-2s-1, and 6X10-1s-1. Stress-strain curves and microstructural analysis are used to examine tensile behaviour, damage progression, and fracture mechanism. The primary form of aluminium alloy AA6061 was compared to the stress-strain curve analysis. It has been observed that when the strain rate increases, the flow stress increases. Field-Emission Scanning Electron Microscopy (FESEM) is used to analyse the damage progression, including fracture mode and continued with a close review on voids quantity and size using Image J Tooling Software. The results show that increasing strain rate increases the number of voids. In general, the recycled AA6061 reinforced Alumina Oxide exhibits strain-rate dependency behaviour. In terms of the fracture mode, an apparent necking develops around the fracture area in primary specimen. Necking, on the other hand, is less apparent in the recycled specimen. Due to alumina characteristics (ceramic), which promote fracture when necking begins to occur. The ductility of the recycled specimen is degraded after going through the recycling operations. With an increase in strain rate, the flow stress and damage evolution become more pronounced. This work contributes valuable information that can be established in various engineering applications significantly to improve the existing recycling process.

Strain Rate Dependence of Hot Tensile Behavior, Microstructure Evolution, and Fracture Mechanism of Lean Duplex Stainless Steel 2101

To improve the hot workability of lean duplex stainless steel 2101 (LDX 2101), the effects of strain rate on the hot tensile behavior, microstructure evolution, and fracture mechanism of LDX 2101 are systematically studied. Results indicate that ferrite is softened by continuous dynamic recrystallization (CDRX) and austenite may start through a mechanism analogous to CDRX at the low strain rate of 0.1 s−1. A softening mechanism similar to the discontinuous dynamic recrystallization (DDRX) is observed both in ferrite and in austenite at the strain rate of 5 s−1. The main fracture mechanism is a void accumulation fracture mode. Cracks form and propagate into the ferrite due to the low softening degree of austenite at the strain rate of 0.1 s−1. As the strain rate increases to 5 s−1, the dynamic recrystallization behavior of austenite increases due to the accelerated accumulation of dislocations and the high storage energy. The microhardness and strain distribution difference between ferrite and austenite decreases, and the crack propagation trend weakens, thus improving the thermoplasticity. The findings are of great significance for understanding the thermoplasticity of LDX 2101 and other two‐phase alloys.

Tensile Strength and Fracture Behavior of Single Abaca Fiber

ABSTRACT A novel experiment device was employed to investigate the tensile strength and fracture mechanism of single abaca fibers. Twenty specimens of untreated single fibers with a gauge length of 30 mm were subjected to tensile force with a loading rate of 0.46 N/s. Results show that the tensile strength of the fiber ranges from 417 MPa to 1548 MPa. The tensile strength was calculated using the measured value of cross-sectional area of each fiber, evaluated by using a three-dimensional microscopic observation. The observation conducted for all specimens reveals the fracture mechanism of the single fiber classified into three types, i.e. shear, tension, and combined of shear and tension. The considerably high tensile strength of the single fiber and fracture mechanism of the single fiber provide a possibility for designing high strength abaca fiber reinforced composite for various engineering applications.

Tensile Properties and Fracture Mechanism of Strain Rate Brittleness on Quenched Cold‐Rolled Carbon Steel

For metal materials, the corresponding mechanical indicators obtained by tensile experiments at different strain rates are different. Herein, after the quenching and cold‐rolling process, a deformed lath martensite structure is obtained in low‐carbon steel. A scanning electron microscope (SEM), transmission electron microscope (TEM), and 3D atom probe (3DAP) analyses are used in this research. The results show that measurement uncertainty exists and when the strain rate is 0.0021 s−1 at room temperature, the elongation is at its minimum value, which gets into an extreme point. C atoms segregate into the martensite boundary when the strain rate brittleness occurs from 3DAP analysis. This phenomenon indicates that the supersaturated C atoms in the steel undergo nonequilibrium segregation at the lath boundary during the elastic phase of stretching, which results in strain rate brittleness.

Tensile Properties and Fracture Mechanisms of Corn Bract for Corn Peeling Device Design

This paper describes the physical and tensile properties of corn bracts during a whole harvest period by using two corn cultivars, aiming to realize efficient peeling with minimum energy performance and decrease the incidence of ear damage. The value range and change rule of tensile properties were obtained by combining mechanical experiments and numerical statistics. Meanwhile, mathematical models were established for tensile properties depending on bract moisture content and bract thickness. The experimental results show that the tensile properties of leaf blade were affected by the orientation between pulling force and longitudinal vein, and that parallel orientation was greater than perpendicular. Further, the tensile properties of leaf sheaths depended on the angle between pulling force and natural growth direction of the bract in the following order: 0° > 90° > 180°. A larger pulling force angle can improve the probability of bract fracturing at the root of leaf sheaths, which helps reduce bract residue on the peduncle. In addition, the fracture mechanisms of leaf blades and sheaths were expressed from physiological and morphological perspectives. The experimental results are believed to be able to provide theoretical guidance by which to design and optimize corn-peeling devices.

Revealing tensile behaviors and fracture mechanism of Ti–6Al–4V titanium alloy electron-beam-welded joints using microstructure evolution and in situ tension observation

This study aimed to systematically investigate the microstructure evolution of the nail-shaped weld on electron beam welded joint of Ti–6Al–4V alloy. The microstructure evolution demonstrated that the needle martensitic α′ phases constituted the microstructure in the fusion zone, in which the grain size decreased in the depth direction, and the Widmannstätten structure lamellar α phases covered the base metal. The fusion zone got the strongest tensile strength that reached 980 MPa due to the smallest grain size and the largest number of low angle grain boundary, whereas the tensile strength of the base metal was the lowest in the whole butt joint. The best plastic deformation capacity in the base metal in which the strain approached 13 % was attributed to the largest number of high angle grain boundary in the Widmannstätten structure. Moreover, there were many deformation twins and faults in fusion zone to enhance the resistance to deformation. The tip of the nail-shaped weld was the brittlest location in the entire joint. The experiment also explored the fracture mechanism by in situ observation of tension and fractography, which involved the following three processes: the nucleation and growth of microvoids, the formation of microcracks produced by microvoids, and the occurrence of fracture caused by the growth and propagation of microcracks.

Using Continuum-Discontinuum Element Method to Model the Foliation-Affected Fracturing in Rock Brazilian Test

In this study, the continuum-discontinuum element method (CDEM) was used to investigate the tensile fracture mechanism of rock materials. An isotropic rock disk model and models considering different foliation inclinations were established, and three schemes were used to simulate the rock fracturing in Brazilian test. Then, the influences of the rock matrix and foliation strengths on anisotropy rock fracturing were investigated. Furtherly, simulation results were verified, and the rock fracture mechanisms were discussed. The results show that the rock fracturing in Brazilian test can be accurately simulated by CDEM, which is in accordance with the experimental results. For isotropic and horizontal foliation rock, the stress concentration in loading positions causes a local fracture of rock sample, and application of a local strengthening scheme can simulate the integral tension fracture of sample middle. As the foliation angle varies from 15° to 45°, the rock fracturing is affected by the stress concentration and foliation distribution. In splitting simulation, a strengthening scheme should be adopted to overcome this influence. As a result, the rock sample generates the sliding and compression-shear fracture. As the foliation angle changes from 45° to 75°, the foliation, rather than the matrix, dominates the fracture behavior of rock sample. For vertical foliations’ rock, as the middle foliation thickness is appropriately broadened, the simulation results are reasonable. In general, the tensile strength of anisotropic rock entirely decreases with an increase of foliation angle, and the effect of foliation strength on the tensile strength rock sample is larger than that of the rock matrix.

Studies on the Modification of Commercial Bisphenol-A-Based Epoxy Resin Using Different Multifunctional Epoxy Systems

The tensile fracture mechanics and thermo-mechanical properties of mixtures composed of two kinds of epoxy resins of different chemical structures and functional groups were studied. The base resin was a bi-functional epoxy resin based on diglycidyl ether of bisphenol-A (DGEBA) and the other resins were (a) distilled triglycidylether of meta-amino phenol (b) 1, 6–naphthalene di epoxy and (c) fluorene di epoxy. This research shows that a small number of multifunctional epoxy systems, both di- and tri-functional, can significantly increase tensile strength (14%) over neat DGEBA while having no negative impact on other mechanical properties including glass transition temperature and elastic modulus. In fact, when compared to unmodified DGEBA, the tri-functional epoxy shows a slight increase (5%) in glass transition temperature at 10 wt.% concentration. The enhanced crosslinking of DGEBA (90 wt.%)/distilled triglycidylether of meta-amino phenol (10 wt.%) blends may be the possible reason for the improved glass transition. Finally, the influence of strain rate, temperature and moisture were investigated for both the neat DGEBA and the best performing modified system. The neat DGEBA was steadily outperformed by its modified counterpart in every condition.