Showing papers on "Charpy impact test published in 2023"

Effect of quenching and tempering on structure and mechanical properties of a low-alloy 0.25C steel

Abstract: Relationships between the microstructure including the dispersed particles and the mechanical properties of a 0.25%C-1.6%Si-1.5Mn-0.5%Cr-0.3%Mo steel was examined after quenching and tempering at 200, 280, 400, and 500 °C. The lath martensite containing the dislocation and twin substructures provides a combination of 1350 MPa yield strength with 9% elongation-to-failure and Charpy V-notch impact toughness of about 60 J/cm2. The transition η-Fe2C carbide precipitates at tempering temperature of 200–400 °C, whereas cementite precipitates at tempering temperature of 500 °C. An increase in tempering temperature in the range of 200–400 °C leads to insignificant decrease in the strength and an increase in the impact toughness, while further increase in tempering temperature to 500 °C results in remarkable decrease in the yield and ultimate tensile strengths to 1090 MPa and 1180 MPa, respectively, and an increase in the impact toughness to 116 J/cm2. An attractive combination of the yield strength and the impact toughness is attributed to the large contribution of the solid solution strengthening to the overall yield strength and the high value of the fracture stress.

Effect of Reinforcement of Alkaline-Treated Sugar Palm/Bamboo/Kenaf and Fibreglass/ Kevlar with Polyester Hybrid Biocomposites: Mechanical, Morphological, and Water Absorption Properties

Abstract: In this age of globalisation, decreasing synthetic resources have exhilarated global communities to apply natural fibres as substitute materials for green technology development. The growth of products from lignocellulose fibre-reinforced composites has been a wide topic among material scientists and engineers due to their abundance, sustainability in nature, biodegradability, and availability at low cost. A series of natural/synthetic hybrid fibre-reinforced composites are prepared by reinforcing polyester resin as the matrix. Natural fibres such as sugar palm/kenaf/bamboo with fibreglass/Kevlar hybrid composite materials were used in this research to determine the mechanical and water absorption properties. The difference between the weight content of natural fibres which were 0 (control sample), 15, 45, and 60 wt% influenced their strength of mechanical properties. The Charpy impact and tensile test were performed following the ASTM D6110-10 and ASTM D3039, respectively. A water absorption test in accordance with ASTM D570-98 was also performed on three different natural fibre-reinforced hybrid composite materials to determine which composite had the best water resistance property. The results showed that hybrid fibre-reinforced composite for 45 wt% kenaf fibre possessed better tensile properties and 60 wt % sugar palm fibre performed better during the Charpy impact strength test compared to other natural/synthetic hybrid fibre-reinforced composites. It was concluded that sugar palm fibres demonstrated the best water resistance in this study.

Fracture Behavior of AlMg4.5Mn Weld Metal at Different Temperatures under Impact Loading

Abstract: This paper deals with a three-component aluminum alloy AlMg4.5Mn that was welded using a GTAW process in the shielded atmosphere of Ar+70%He+0.015%N2. The weld-metal toughness was evaluated at three different temperatures using instrumental Charpy pendulum impact testing to measure not only the total energy, but also the crack initiation energy and the crack growth energy. Fractographic analysis of the fracture surfaces and EDS analysis of large second-phase particles on fractured surfaces at each temperature were also carried out. Fractographic analysis at different temperatures indicated a clearly distinguishable fracture mechanism. It was inferred that the absorbed energy was closely correlated with the fracturing of surfaces. Moreover, it was concluded that with decrease in the amount of microscopic voids and dimples, the total energy absorbed also decreased.

Mechanical Characterization of Aluminum Sandwich Structures with Woven-Ply Pineapple Leaf/Glass Fiber-Reinforced Hybrid Composite Core

Abstract: ABSTRACT Fiber-metal laminates consisting of alternating metal and fiber-reinforced polymer layers have displayed remarkable performance in several engineering applications. This work aims to identify the feasibility of incorporating pineapple leaf fiber to partially supersede glass fiber in thermoplastic-based fiber-metal laminates. Fiber-metal laminates made of pineapple leaf/glass/polypropylene/aluminum were fabricated using the hot press molding technique. The tensile, flexural, Charpy impact and quasi-static indentation tests were performed. The findings indicated that the hybridization of glass with pineapple leaf fibers improved the mechanical properties of the laminates. The results are particularly promising in [G/P/G] laminates in which their tensile and flexural strengths are 38.98% and 20.19% higher than [P/P/P] laminates. In addition, the Charpy impact strengths of [G/P/G] laminates are also 236.66% and 175.68% greater than those of [P/P/P] laminates. In terms of indentation properties, the maximum indentation forces of [G/P/G] laminates are 16.71% and 13.76% higher than those of [P/P/P] laminates at indenter diameters of 12.7 and 20.0 mm, respectively. Interestingly, in-plane and out-of-plane properties of [G/P/G] laminates were comparable to [G/G/G] laminates. Thus, it is anticipated that the hybridization concept could escalate the utilization of natural fibers as a potential reinforcement for engineering applications.

Effect of Tempforming Temperature on the Impact Toughness of an HSLA Steel

Abstract: The fracture behavior of a high-strength low-alloy steel subjected to tempforming at 873 K, 923 K, or 973 K was studied by means of impact and bending tests. A decrease in tempforming temperature promoted the grain refinement resulting in the ultrafine grained lamellar-type microstructure with finely dispersed particles that led to significant strengthening along with an increase in the impact toughness. The tempformed steel samples exhibited Charpy V-notch impact energy well above 100 J at temperatures of 183–293 K due to delamination along the rolling plane during bending, which was attributed to high anisotropy of cleavage fracture stress. Delamination owing to easy cleavage crosswise to the impact direction blunted the primary crack and resulted in the zigzag crack propagation, leading to high impact toughness. Depending on tempforming temperature, three types of the delamination behavior were observed in the V-notch specimens upon three-point bending tests at room temperature. Namely, the early, restrained, and late delaminations took place in the samples after tempering at 873 K, 923 K, and 973 K, respectively. On the one hand, a decrease in the test temperature promoted delamination, and on the other the strengthening by lowering tempforming temperature is accompanied by a suppression of ductile fracture. The sample tempformed at 873 K exhibited the highest impact toughness at room temperature, whereas the samples tempformed at 923–973 K were characterized by the higher impact toughness at 183–233 K.

Influence of Vanadium Micro-Alloying on the Microstructure of Structural High Strength Steels Welded Joints

Abstract: The inter-critically reheated grain coarsened heat affected zone (IC GC HAZ) has been reported as one of the most brittle section of high-strength low-alloy (HSLA) steels welds. The presence of micro-alloying elements in HSLA steels induces the formation of microstructural constituents, capable to improve the mechanical performance of welded joints. Following double welding thermal cycle, with second peak temperature in the range between Ac1 and Ac3, the IC GC HAZ undergoes a strong loss of toughness and fatigue resistance, mainly caused by the formation of residual austenite (RA). The present study aims to investigate the behavior of IC GC HAZ of a S355 steel grade, with the addition of different vanadium contents. The influence of vanadium micro-alloying on the microstructural variation, RA fraction formation and precipitation state of samples subjected to thermal cycles experienced during double-pass welding was reported. Double-pass welding thermal cycles were reproduced by heat treatment using a dilatometer at five different maximum temperatures of the secondary peak in the inter-critical area, from 720 °C to 790 °C. Although after the heat treatment it appears that the addition of V favors the formation of residual austenite, the amount of residual austenite formed is not significant for inducing detrimental effects (from the EBSD analysis the values are always less than 0.6%). Moreover, the precipitation state for the variant with 0.1 wt.% of V (high content) showed the presence of vanadium rich precipitates with size smaller than 60 nm of which, more than 50% are smaller than 15 nm.

Optimization of a structural lightweight fiber-reinforced concrete for best performance under impact loading

Abstract: Compared to normal concrete, lightweight fiber-reinforced concrete (LFRC) offers several advantages, such as a high tensile strength-to-weight ratio and high energy dissipation under impact loading. However, LFRC has a lower compressive strength and modulus of elasticity than normal concrete; finding the appropriate mix design is also essential for structural engineering. This study aims to determine the best mix proportion of LFRC by evaluating the mechanical characteristics and energy dissipation capacity under impact loading. For this purpose, an experimental study is performed to optimize the mix proportion using three types of lightweight aggregates (Leca, expanded perlite, and expanded polystyrene). Moreover, the effects of two different steel and polyvinyl alcohol fibers on LFRC properties are investigated to improve the fracture energy and tensile strength. In both phases, two Drop Weight impact and Modified Charpy impact tests are utilized in addition to the quasi-static tests (compressive, splitting tensile, and flexural tests). A quality function is proposed to achieve the best mix proportion of lightweight concrete. The results demonstrate that the mixture containing 50% expanded perlite replacement with normal weight aggregates, 20% Slag as partial replacement of cement, 0.25% PVA fiber, and 0.25% steel fiber has the best performance in the mechanical properties and energy dissipation capacity as a structural lightweight fiber reinforced concrete.

Metallurgical characterization and high-temperature tensile failure of Inconel 617 alloy welded by GTAW and SMAW—a comparative study

Abstract: Two types of the weld joint of Inconel 617 alloy were produced using gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes with ERNiCrCoMo-1 filler metal and ENiCrCoMo-1 electrode, respectively. The weld metal showed the segregation of the principle alloying elements like Mo and Cr along the inter-dendritic spaces, triggering the formation of secondary phases. The microstructure characterization of the interface ensured the high dilution, which could be attributed to the closeness in melting point and chemistry of base and filler metal. Microhardness variation, tensile testing at room and high temperature, and Charpy impact test were conducted to investigate the effect of the Mo segregation in the weld zone and heterogeneity in the microstructure of weldments on the mechanical behavior of both the welded joints. The cross-weld tensile tests were conducted at room temperature and 550°C. The tensile test samples failed from the weld zone for each condition with a tensile strength value close to the base metal, which ensured the applicability of the joint for end service. The tensile strength of GTAW-RT, GTAW-HT, SMAW-RT, and SMAW-HT were measured as 766 ± 22 MPa, 570 ± 5 MPa, 760 ± 7 MPa, and 600 ± 8 MPa, respectively. A non-uniform hardness plot was witnessed with the hardness of the GTAW-weld and SMAW-weld zone of 257 ± 8 HV and 285 ± 5 HV, respectively, in the transverse direction. The impact toughness of the weld zone was 84 ± 2 J and 48 ± 4 J for GTAW and SMAW weld zone. The average impact toughness of the GTAW-weld zone was approximately 42% higher than the value of the SMAW-weld zone. In a nutshell, it can be concluded that the welded joint of Inconel 617 produced using the GTAW process with ERNiCrCoMo-1 filler had the best metallurgical and mechanical properties.

Impact Fracture Surfaces as the Indicators of Structural Steel Post-Fire Susceptibility to Brittle Cracking

Abstract: The results of experimental research on forecasting post-fire resistance to brittle failure of selected steel grades used in construction are presented and discussed in this paper. The conclusions are based on detailed analysis of fracture surfaces obtained in instrumented Charpy tests. It has been shown that the relationships formulated based on these tests agree well with conclusions drawn based on precise analysis of appropriate F–s curves. Furthermore, other relationships between lateral expansion LE and energy Wt required to break the sample constitute an additional verification in both qualitative and quantitative terms. These relationships are accompanied here by values of the SFA(n) parameter, which are different, depending on the character of the fracture. Steel grades differing in microstructure have been selected for the detailed analysis, including: S355J2+N—representative for materials of ferritic-pearlitic structure, and also stainless steels such as X20Cr13—of martensitic structure, X6CrNiTi18-10—of austenitic structure and X2CrNiMoN22-5-3 duplex steel—of austenitic-ferritic structure.

Comparison of the Charpy Resilience of Two 3D Printed Materials: A Study on the Impact Resistance of Plastic Parts

Abstract: Charpy impact testing is a widely used method for the evaluation of the toughness of materials, including 3D-printed plastic parts. This study performed Charpy test on 3D-printed samples made of PLA and ABS. Factors such as layer thickness and infill percentage varied (0.10, 0.15, and 0.20mm layer height and 50, 75, and 100% infill percentage) to investigate how they affect the mechanical properties of 3D printed parts, including their toughness.

The effect of thermal and cryogenic environments on the impact performance of aluminum-glass fibers/epoxy laminated composites

Abstract: In this research work, the effect of various environments on the impact properties of fiber metal laminates was investigated. To do so, in the first step, the 2024 aluminum layers were surface modified with the etching method. Then, the various glass fibers/epoxy composites with the configurations of (0°/0°/0°/0°, 90°/90°/90°/90°, +45°/−45°/−45°/+45° and 0°/90°/90°/0°) were sandwiched between two aluminum sheets. In the following, these samples were aged under thermal cycling (between 25 and 100 °C), isothermal aging at the temperature of 100°C, cryogenic cycling (between −196 and 25 °C), and cryogenic isothermal aging at the temperature of −196°C. To understand the effect of various aging methods on the mechanical features of these structures, the Charpy impact test was performed. Also, the failure mechanisms and related phenomena were assessed by visual observations and microstructural investigations. In the first steps of thermal aging, the impact strength of FMLs was improved, which the highest of that being 46.9%. In the higher cycles or exposing times, the impact strength showed reducing trends, due to thermal degradations of the epoxy matrix. The cryogenic cycling in the high cycles reduced the impact strength of FMLs. But in the cryogenic isothermal condition, in some cases, the improvement in the impact strength was seen, which the highest of that being about 43.4%.

Optimization of Charpy‐impact strength of 3D ‐printed carbon fiber/polyamide composites by Taguchi method

Abstract: This study utilizes the Taguchi optimization technique to investigate the effects of FDM processing parameters on the Charpy impact strength of 3D printed CF/PA composites experimentally and statistically. The four 3D printing parameters employed in the experiment are the infill density, raster angle, extruder temperature, and printing speed, which were used to create the experimental plan with the L18 orthogonal array. Signal to noise (S/N) ratios and analysis of variance (ANOVA) were utilized to identify the optimum values and the interactions between the process parameters. SEM and thermography techniques were employed to assess the microstructural and damage status of the CF/PA composite specimens. ANOVA results determined that only three factors–infill density, raster angle, and extruder temperature–had a statistical significance, while printing speed did not. The outcomes demonstrated that the optimal 3D printing parameters are infill density (100%), raster angle (60°), extruder temperature (260°C), infill density (100%), and printing speed (30 mm/s), with the maximum contribution of 54.19% belonging to infill density, and the minimum contribution of 2.84% belonging to printing speed. The optimal combination of these 3D printing parameters yielded a Charpy impact strength of 10.54 kJ/m2, resulting in an increase of almost 150% compared to the worst-case situation. The Taguchi approach proves to be a proficient technique to boost the Charpy impact strength of 3D-printed CF/PA composites.

Mechanical characterization of hybrid biocomposites reinforced with nonwoven hemp and unidirectional flax fibers

Abstract: Fiber-reinforced polymers are widely used in many applications where high specific strength and high specific stiffness are required. Biocomposites have replaced synthetic-based fiber-reinforced polymers as a preferred option due to their environmental friendliness, ease of supply, and affordability. Comparable strength synthetic-fiber-reinforced polymers and biocomposites both have lower specific weights. This study aims to characterize hybrid biocomposites produced from unidirectional prepregs made of flax/polypropylene fibers and nonwoven mats made of hemp/polypropylene fibers. Research has also been conducted on how the number of layers and the stacking sequence affect the mechanical performance of hybrid biocomposites. Three different designs of biocomposite plates have been produced using compression molding. They were then subjected to tensile, compressive, shear, bending, Charpy impact, and drop-weight impact tests. According to the test results, it is found that each design has its own characteristics, and the characterized static and dynamic behaviors are very different from each other. Therefore, each biocomposite mentioned here may be a good candidate for engineering design based on the given engineering design criteria.

Research into Specific Mechanical Properties of Composites Produced by 3D-Printing Additive Continuous-Fiber Fabrication Technology

Abstract: This paper introduces novel research into specific mechanical properties of composites produced by 3D printing using Continuous-Fiber Fabrication (CFF). Nylon (Onyx) was used as the composite base material, while carbon constituted the reinforcement element. The carbon fiber embedment was varied in selected components taking values of 0°, 45°, 90°, and 135° for parts undergoing tensile testing, while one specific part type was produced combining all angles. Carbon-fiber-free components with 100% and 37% fillings were also produced for comparison purposes. Parts undergoing the Charpy impact test had the fibers deposited at angles of 0° and 90°, while one part type was also produced combining the four angles mentioned before. Carbon-fiber-free parts with 100% and 37% fillings were also produced for comparison purposes as with the first part. The Markforged MARK TWO 3D printer was used for printing the parts. These were subsequently scanned in the METROTOM 1500 computed tomography and submitted to the tensile and impact tests. The results showed that adding carbon fiber to the base material increased the volume of defects in the samples as a result of the porosity increase. Although the tensile testing manifested an overall increase in tensile strength Rm of up to 12 times compared to the sample without reinforcement, it was proven that an improper fiber orientation significantly diminished the strength and that combining the four selected angles did not lead to the highest strength values. Finally, the impact tests also showed that fiber-reinforced parts implied up to 2.7 times more work to fracture, and that an improved fiber orientation also led to strength reduction.

Dependence of Charpy Impact Properties of Fe-30Mn-0.05C Steel on Microstructure

Abstract: Fe-30Mn-0.05C steel specimens with cold-rolled, partially recrystallized, fine-grained, and coarse-grained microstructures were fabricated by means of 80% cold rolling followed by annealing at 550–1000 °C. The initial and deformed microstructures were characterized, and the Charpy impact properties were tested at room temperature (RT) and liquid nitrogen temperature (LNT). It was found that the Charpy absorbed energy increased with the annealing temperature, while the specimens showed different trends: parabolic increase at RT and exponential increase at LNT, respectively. Compared with the fully recrystallized specimens, those with a partially recrystallized microstructure exhibited lower impact energy, especially at LNT. This was because cracks tended to nucleate and propagate along the recovery microstructure where stress concentration existed. The grain size played an important role in the twinning behavior and impact properties. High Charpy impact energy (~320 J) was obtained in the coarse-grained specimen having the grain size of 42.1 μm at both RT and LNT, which was attributed to the activation of high-density deformation twinning. However, deformation twinning was inhibited in the specimen with the average grain size of 3.1 μm, resulting in limited work hardening and lower impact energy.

Investigations on microstructural and mechanical properties of BSK 46 steel weldments

Abstract: BSK 46 is a low alloy structural steel with excellent mechanical and corrosion properties and is widely used in many applications, including tipper bodies of heavy-duty trucks. Optimizing the welding parameters to reduce defects and improve productivity is critical for the users. The present work addresses optimizing the welding process parameters to improve productivity with adequate weld quality during the pulsed gas metal arc welding (P-GMAW) process. Three BSK 46 weldments (weld-1, weld-2 and weld-3) were fabricated by varying the root gap, root face, filler pass and heat input. The metallographic and mechanical characterization of P-GMAW weldments were done through microstructures, Vickers micro-hardness, transverse tensile strength, Charpy toughness and three-point bend test. Subsequently, a correlation has been developed between the microstructural features and mechanical properties of the weld joints. The hardness was found to be incremental in nature from the base metal to the fusion zone. Maximum hardness of 215.81 ± 10 HV was observed in the weld-3 fusion zone. Tensile test results reveal that weld-3 weldments exhibit a higher tensile strength of 547.48 ± 2 MPa than weld-1 (537.46 ± 7 MPa) and weld-2 (533.67 ± 9 MPa) weldments. Maximum impact toughness of 136.33 ± 14 J was observed in the weld-3 weldments. Post-bend testing showed no cracks on the weld surfaces, indicating defect-free weld joints with good ductility. It is observed that weld-3 showed relatively better mechanical properties than weld-1 and weld-2 in lesser welding time and lower welding cost

Quantitative Characterization of Impact‐Induced Energy Harvesting: A Case Study on Stretchable Piezoelectric Thin Films on Different Substrates

Abstract: Piezoelectric materials represent a great alternative to power small electronic devices with a lower environmental impact than conventional power sources. Despite significant progress on the subject, most studies focus on energy harvesting from vibrating systems. Other publications focus on the design of the piezoelectric devices, but they are hardly comparable in terms of the amount of energy collected. In this paper a new method is presented to quantitatively characterize piezoelectric energy harvesters under a single mechanical impact using a custom Charpy‐like test bench. The method is illustrated by studying screen‐printed piezoelectric thin films of poly(vinylidenefluoride‐co‐trifluoroethylene) P(VDF‐TrFE), with different substrates acting as mechanical support. Devices printed on stretchable substrates allowing large deformation lead to overall better energy harvesting performance. However it is also demonstrated that the nature of the substrate influences the material properties of the piezoelectric film despite identical fabrication process.

Mechanical properties and corrosion behaviour of developed high nitrogen high manganese stainless steels

Abstract: Influence of composition, specifically manganese and nitrogen content, on the microstructure associated corrosion resistance property of newly developed stainless steel has been studied. The developed steels have been characterised for their microstructure, mechanical and electrochemical properties. The results indicate that the addition of manganese and nitrogen as a substitute for nickel favours the austenite microstructure, higher yield strength (>350 MPa), tensile strength (>700 MPa), elongation and superior Charpy V‐notch impact toughness properties. The results obtained from electrochemical tests such as potentiodynamic polarisation and electrochemical impedance spectroscopy of manganese stainless steel show remarkable improvement (about 4 times) in corrosion resistance exhibiting passivity behaviour like that of commercial stainless steel (316L).