Charpy Impact Research Articles

Explosion Cracking Analysis of Sulfur Resistance Induction Heat Bend Pipe

The explosion cracking reason on induction heat bend pipe was analyzed through macroscopic analysis, chemical composition analysis, mechanical properties testing, metallographic analysis, scanning electron microscopy and XRD. The results showed that the chemical composition, tensile test, Vickers hardness results of the straight section of the bent pipe met the requirements of the technical specifications, and the metallographic structure of the straight section of the bent pipe was pearlite and ferrite. The Charpy impact test in the neutral zone of the bend section had a low shear fracture ratio, and the Vickers hardness test results were on the high side. The metallographic structure was granular bainite. The fracture surface of the failed bent pipe exhibited brittle fracture characteristics on the macro level. The metallographic analysis and hardness test results of the crack source area showed that the fracture surface had typical intergranular propagation characteristics and high hardness values. Energy spectrum analysis of the crack source area revealed the presence of S element. The XRD analysis of the product on the inner wall of the pipe contained sulfides. The comprehensive results indicated that the failed bend pipe undergoes stress corrosion and initiates corrosion cracks on the surface under the combined action of operating pressure, additional bending stress, residual stress, etc. in a sulfide corrosive medium, the cracks continued to propagate along the grain boundaries and ultimately caused the bend pipe to explode.

The anisotropy behavior of metallic foams under Charpy impact tests

Currently, the automotive industry is looking for their new products to have a density as low as possible so that CO2 emissions decrease. Metallic foams have attracted a great deal of interest in this industry because of their multiple advantages. They can be produced at a relatively low cost and have advantageous properties, especially due to their ability to absorb energy. In the framework of this study, 42 specimens were tested to determine the impact energy and Charpy impact strength according to the cutting orientation. Before being notched according to the ISO 148 standard, their specific mass was determined. For the tests, an Instron CEAST 9050 Charpy test machine was used. The impact strength was determined according to the cutting orientation, and the results obtained by the mass density groups were compared. It could be observed that the cutting orientation of the specimens does not have a clear influence on the impact strength; this is due to the irregular shape of the closed cell, however, the grouping of the specimens on specific density samples has influenced the impact strength.

The effect of reinforcement particles weight percentage on the mechanical properties and plastic flow behaviour of aluminum alloy 7075 matrix material

AbstractIn the present investigation, an aluminum 7075 based hybrid metal matrix composite has been prepared by utilizing the primary reinforcement element (boron carbide with 9 %, 7 %, 5 %, 3 %, and 1 % weight percentage) and secondary reinforcement particles (silicon carbide with 1 %, 3 %, 5 %, 7 %, and 9 % weight percentage) through the well‐known stir‐casting method. Further, the tensile, hardness and Charpy impact tests were performed on the prepared composite material for mechanical properties evaluation. In addition, an attempt has also been performed to analyze the effect of reinforcement weight percentages (primary and secondary) on the strength coefficient, strain hardening rate and strain hardening exponent of the prepared composite material compositions. The results revealed that sample 1 (aluminum 7075/9 weight percentage boron carbide/1 weight percentage silicon carbide) exhibited the maximum 14.12 percent, 14.25 percent and 19.56 percentage increase in hardness, ultimate tensile strength and yield strength respectively than the matrix material. The strain hardening exponent has been increased with the increase in the weight percentage of silicon carbide. Further, the value of the strength coefficient was decreased with the increase in the weight percentage of boron carbide particles. In addition, stage III hardening was associated with the all developed composite material compositions.

Optimization approach of DED process to fulfil the requirements on material properties and component performance of waterjet impeller

Directed energy deposition (DED) processes have a great potential for ship building industry to reduce the lead time of ship part supply. However, ship parts such as propellers and impellers have critical requirements on material’s properties and component’s performance. To ensure the exploitation of DED manufacturing for critical parts, an optimization approach of DED process was developed and demonstrated on waterjet impeller made of duplex stainless steel. The developed approach is based on the understanding of the effects of DED process and heat treatment on the material microstructure, and the effects of the microstructure on the material properties, all optimized to fulfil the requirements on the component. The manufacturing and qualification testing were planned based on the requirements in accordance with the current standard guidance. The assessments by standard testing methods, including tensile, Charpy impact, and bending tests demonstrates that the DED material with an optimized heat treatment fulfil the standard requirements. Corrosion and cavitation tests were also performed and demonstrates the high resistances of DED material to cavitation erosion.

Heat Treatment Process, Microstructure, and Mechanical Properties of Spring Steel with Ultra-High Strength and Toughness

In this research, a new type of spring steel with ultra-high strength and toughness was designed, and its mechanical properties and microstructure under different heat treatment processes were studied. The results show that the optimal heat treatment process for the steel is oil quenching at 890 °C for 40 min, followed by tempering at 400 °C for 1 h. Its mechanical properties have an optimal combination of 1865MPa tensile strength, a yield strength of 1662 MPa, an elongation of 11.5%, a cross-sectional shrinkage of 51.5%, and a Charpy impact energy of 43.7 J at room temperature. With increasing austenitizing temperature, the austenite grain size increases, the martensite lath becomes thicker, and the strength decreases. With increasing tempering temperature, the lath boundary of martensite becomes blurred, the strength decreases, and the plasticity improves. In addition, it was found that during tempering at higher temperature (450 °C), large particle inclusions and secondary cracks appeared in the fractured surface, and a large number of carbides precipitated, leading to the brittleness of tempered martensite.

A Physically-Based Criterion for Determining the Critical Brittleness Temperature from Charpy Impact PRV Tests for Reactor Steels and Their Welds

A Physically-Based Criterion for Determining the Critical Brittleness Temperature from Charpy Impact PRV Tests for Reactor Steels and Their Welds

Assessing the master curve reference temperature T0 estimated from the Charpy impact transition curve and consequences on the correlation between Charpy DBTT- and fracture toughness T0-shifts

Integrity assessment of reactor pressure vessels of light water reactors follows well established procedures relying on the surveillance program and defined by codes, standards and nuclear regulatory requirements. These procedures were developed in times where scientific knowledge was limited increasing therefore conservative safety margins to overcome the scientific shortcomings.Taking profit from the development of a number of test techniques and evaluation, it is possible nowadays to propose an alternative interpretation of the test results that provides a complementary information to the standard regulatory approach. In this work, the focus is on the Charpy impact test as it plays a critical role in surveillance programs monitoring reactor vessel degradation induced by neutron irradiation. The development of methodologies allowing experimental determination of fracture toughness from small size specimens triggered alternative approaches of extracting fracture toughness from the Charpy impact test. One of those approaches was recently successfully developed using the instrumented Charpy impact test from which the dynamic and static fracture toughness can be estimated with a reasonably good accuracy. This paper aims to provide an equally performant but simplified procedure allowing estimation of the master curve reference temperature, T0, from the Charpy impact transition curve applied to a large variety of reactor materials and irradiated conditions.

Simultaneous improvement of strength and toughness via two-stage aging for a secondary hardening steel

A two-stage aging, involving initial low-temperature treatment followed by high-temperature treatment, was employed to induce a high number density M2C and inhibit the occurrence of chemical ordering and formation of large ellipsoidal particles at grain boundaries. The ultimate tensile strength, yield strength and Charpy impact energy increase by 233 MPa, 191 MPa and 3.3 J, respectively.

The Effect of Multi-Step Tempering and Partition Heat Treatment on 25Cr2Ni3MoV Steel's Cryogenic Strength Properties.

In this study, the refinement of two microstructures was controlled in medium carbon 25Cr2Ni3MoV steel via multi-step tempering and partition (MTP) to achieve high cryogenic strength-ductility combinations. Microstructure evolution, the distribution of stress concentration, and microcrack formation and propagation during cryogenic Charpy impact testing were investigated. Compared with their performance in the quenching and tempering states (QT), the MTP steels showed a significant improvement in yield strength (1300 MPa), total elongation (25%), and impact toughness (>25 J) at liquid nitrogen temperature (LNT). The strengthening contributions mainly originated from the high dislocation density and refinement cementite (size: 70 nm) in the martensite lath (width: 1.5 μm) introduced by refined reversed austenite and its latter decomposition. The instrumented Charpy impact results indicated that cracks nucleated in the primary austenite grain (PAG) boundary for two steels due to the strain concentration band preferring to appear near PAGs, while cracks in the QT and MTP samples propagated along the PAGs and high-angle grain boundary (HAGB), respectively. The crystallized plasticity finite element simulation revealed that the PAG boundary with cementite precipitates of large size (>200 nm) was less able to dissipate crack propagation energy than the HAGBs by continuously forming a high strain concentration area, thus leading to the low-impact toughness of the QT steel.

Ballistic and Charpy impact performance of basalt fiber reinforced polymer composites

AbstractIn this study, the behavior of composite material produced using basalt, a natural fabric, under ballistic and Charpy impact loads was investigated. The damage resistance of target plates under ballistic loads is an important design parameter in the structures that will be exposed to these loads. Cross‐ply fiber‐reinforced composite plates were produced with different numbers of layers. The composite specimens are produced using the vacuum infusion method, cross‐ply laminated with 3, 6, 9, and 12 layers ([0/90]3, [0/90]6, [0/90]9, and [0/90]12). Carbon/Epoxy specimens were also produced in identical sequences to be used as comparison material. The study aimed to understand the absorbed energy under ballistic loads and the required energy level under the Charpy impact loads of Basalt/Epoxy composite specimens with different thicknesses. Ballistic loads are applied to the specimens using a test set‐up including the sample holder mechanism and a firing system. Charpy impact tests were conducted using a standard test machine. According to the results, for 12‐layer specimens, the residual velocity difference between Basalt/Epoxy and Carbon/Epoxy is approximately 1.5 times. For the Basalt/Epoxy plate, increasing number of layers from 3 to 12 increases the amount of energy absorbed approximately 13 times. Although this increase is approximately 19 times for the Carbon/epoxy plate, when Basalt/Epoxy and Carbon/Epoxy plates are compared, Basalt/Epoxy absorbs more energy for all layer numbers. For the Charpy impact cases, it has been observed that Basalt/Epoxy absorbs approximately 34% more energy for flat wise impact and approximately 24% more energy for edgewise impact.Highlights The behavior of composite material produced using basalt, a natural fabric. Cross‐ply fiber‐reinforced composite plates. Effect of different number of layers considered. The damage resistance of target plates under ballistic loads. Comparison of basalt and carbon‐reinforced composites.

Effect of heat input on the mechanical properties of welded Q960E ultra-high strength steel butt joints

The influence of welding heat input on the tensile properties and low-temperature impact toughness of Q960E weld metals (WMs) and butt welded joints (BWJs) was investigated. Prediction models were established to correlate the heat input range (4–17.5 kJ/cm) with the yield strength, tensile strength, and elongation of both WMs and BWJs. Impact toughness was examined at different temperatures for the WMs, heat-affected zones (HAZs), and BM. Microstructure transformations were revealed in different regions of the BWJs, and their impact on the tensile properties and toughness. The results demonstrated that the yield strength, tensile strength, and elongation of the BWJs were 0.80–0.99, 0.9–1.0, and 0.44–0.82 of the BM, respectively; this was attributed to variations in the average effective grain size and Taylor factor in different regions of the BWJs, which led to distinct strength and plastic deformation capacities. The impact toughness of both the WMs and HAZs was notably diminished when compared to the BM. For the WMs, the Charpy impact absorption energy values were only 0.24–0.34, 0.50–0.59, and 0.40–0.50 of that of the BM for heat inputs of 4, 7.4, and 11.2 kJ/cm, respectively. For the same heat inputs, in the case of the HAZs, the Charpy impact absorption energy values were only 0.71–0.90, 0.63–0.70, and 0.63–0.80 of that of the BM, respectively. The presence of martensite–austenite (M–A) islands in the HAZ contributed to the decrease in the impact toughness. Increasing the heat input resulted in larger M–A components, thus further reducing the impact toughness of the HAZ. Conversely, a higher heat input for the WMs promoted the formation of acicular ferrite, thereby enhancing its impact toughness. However, owing to the abundant lath martensite present in the WM, its impact toughness was significantly inferior to that of the BM.

Tribological and mechanical properties of nanofilled glass fiber reinforced composites and analyzing the tribological behavior using artificial neural networks

AbstractThis study investigates the effects of filler content and type on the mechanical (tensile strength and impact resistance) and tribological properties of woven glass fiber‐reinforced composites (WGFC) produced using three different nanofillers (MgO, CuO, and Al2O3) at various loading levels (0.7, 1.4, and 2.8 wt%). Additionally, analyses of the artificial neural network algorithm were reported for the predictions of wear rate, mass loss, and coefficient of friction (COF) by given applied load, sliding distance, filler ratio, and filler type. The composites were fabricated using the hand lay‐up method. The filled composites were characterized using Fourier Transform Infrared (FTIR) spectroscopy, and the worn surfaces of the samples after the wear test were analyzed using Scanning Electron Microscopy (SEM). The wear resistance of the composite samples improved at 0.7 wt% CuO and 1.4 wt% MgO filler contents. At 200 m sliding distance and 1.4 wt% filler ratio, the highest wear ratio was determined as 55 mm3/m × 10−3 in the Al2O3‐filled composite, and the lowest was determined as 31 mm3/m × 10−3 in the MgO‐filled composite. At 1.4% filler ratio and 15 N load, the lowest friction coefficient was determined as 0.45 μ in MgO‐filled composite, and the highest was 0.56 μ in Al2O3‐filled composite. Al2O3 filler increased the mass loss and wear rate of the composite material. In Charpy impact tests, the maximum impact energy of 13.9 J/m2 was obtained with a 2.8 wt% Al2O3 filler content. Tensile tests showed an increase in tensile strength for all filler contents compared to unfilled composites. The highest tensile strength of 242.1 MPa was achieved with 0.7 wt% CuO reinforcement.Highlights In all applied wear parameters and filler ratios, the Al2O3 filler adversely affected the wear resistance of the composite, while the MgO filler showed the best performance in terms of wear resistance. All types and ratios of fillers increased the tensile strength compared to the unfilled composite. Contrary to its negative effect on wear, the Al2O3‐filled composites exhibited the highest impact resistance. The prediction analysis of the tribological behavior of composite material using ANN reveals that the Levenberg–Marquardt algorithm fits very well.

An experimental investigation of the mechanical properties and failure mode of 3D stitched composites

Mechanical behavior and failure modes of three-dimensional (3D) stitched composites were experimentally investigated. In addition, a comparative analysis between these materials and equivalent laminates (2D) was accomplished. The 3D composite plates were manufactured using sheets of glass fiber manually sewn with aramid tows and molded with epoxy resin by vacuum-assisted resin transfer molding. Three-points bending, Charpy impact, double cantilever beam (DCB), and short-beam shear (SBS) mechanical tests were carried out on both types of materials. The DCB test results revealed that the action of reinforcement tows inhibited the propagation of the delamination cracks, which led to an increase in the fracture toughness of the 3D composites. However, the damage caused by the stitching process, such as fiber breakage and misalignment as well as crimping, and resin-rich regions, was responsible for reducing the flexural and shear properties of these materials. In addition, it was revealed that the stitching did not influence the impact toughness, although it prevented delamination from quick propagation, avoiding a catastrophic failure, which enhanced the damage tolerance of these materials, mainly for aeronautical applications.

Exploring the effects of eco-friendly and biodegradable biocomposite incorporating eggshell and walnut powder as fillers

<p>Composites gain utility when filler materials are incorporated. The qualities of the material are changed when filler components are added. In recent years, the use of bio-based components in polymers and polymer composites has significantly increased. Agricultural wastes are employed in this case as filler component to create bioplastic composites since they are inexpensive, plentiful, and easily accessible. By varying the weight ratios of Eggshell (ES) powder and Walnut shell (WS) powder added to the plasticized PLA, bioplastic composite samples are created. Epoxidized soybean oil (5wt%) is used to create the plastic. The obtained bioplastic particles are then subjected to additional processing by being shaped into dog-bone-shaped samples and tested mechanically and thermally. Mechanical testing, including Tensile, Charpy Impact, and Flexural tests, revealed that the PLA possessed inferior properties to those of virgin PLA. The qualities of plasticized PLA-ES composite, however, performed better than those of plasticized PLA-WS composite.</p>

Dependence of microstructure and properties in additive manufactured 18Ni300 on heat treatment and surface enhancement

Selective laser melting (SLM) known as a rapid manufacturing technology can fabricate complex and dense metallic components of 18Ni300 with excellent properties. The performance of 18Ni300 can be improved by intermetallics using heat treatment, not including anti-corrosion property. In this study, the effects of heat and coating treatments on microstructure and properties of 18Ni300 fabricated by SLM were investigated. The characterization results indicated that grain coarsening, dislocation reduction, and texture strengthening occurred after the optimal heat treatment. The sequential processing of 820 °C for 2 h and 480 °C for 3 h can maximize the microhardness (increased by 74 %) and ultimate tensile strength (increased by 79 %), accompanying cost of Charpy impact (reduced by 43 %) and elongation (decreased by 32 %). However, excessively high or low aging temperature and time can lead to insufficient performance improvement because of austenite reversal. In addition, the great interface bonding is observed after the laser cladding coating treatment, and the wear resistance maintains well while improving the anti-corrosion property significantly with low quality loss.

Analyzing microstructural, residual stress, and mechanical characteristics in dissimilar welds of Inconel 59 and AISI 904L through double-pulsed gas metal arc welding

In this research, dissimilar welding of the nickel-based superalloy Inconel 59 and austenitic stainless steel AISI 904L steel was successfully done with double-pulsed gas metal arc welding (DP-GMAW) using the filler ERNiCrMo-13. Macroscopic analysis showed a defect-free weld with an aspect ratio of 2.4, attributed to the efficient heat delivery (0.642 kJ/mm) in DP-GMAW. The microstructure of the weld joint was examined through both optical microscopy and scanning electron microscopy. Examination of the microstructure of the weld interface exposed grain coarsening near the heat-affected zone on the AISI 904L side. In contrast, the weld fusion zone contained fine equiaxed dendrites. Microsegregation and alloying element migration across the entire weld area were assessed through energy dispersive X-ray spectroscopy point analysis and line mapping, revealing controlled microsegregation across the region. X-ray diffraction (XRD) analysis was used to ascertain the average grain size (38.41 nm) and secondary phase composition. The XRD-cosα method was used to assess the residual stress of the weld joint, revealing tensile residual stress in the weld zone and compressive residual stress in other regions. Tensile, Charpy impact, and Vickers hardness tests were conducted in the study to evaluate the strength, toughness, and hardness of a dissimilar weld. The impact of two cryogenic treatments, namely shallow and deep, on tensile and toughness characteristics was investigated in this study. The cryogenic treatments significantly enhanced the mechanical properties of weld samples compared to their as-welded condition, leading to an 11.5% increase in tensile strength and a 10% improvement in toughness.

Experimental and simulation analysis on the effect of vibratory stress relief on impact toughness of Q345/316 L dissimilar steel welded joints

Vibratory stress relief (VSR) is residual stress relieving technology with the characteristics of green, energy-saving, and environmentally friendly. In response to the lack of research on the impact toughness of dissimilar steel welded joints under VSR, In this study, the law of the impact toughness of Q345/316 L dissimilar steel welded joints under VSR treatment is studied. Firstly, a platform-type VSR system is used to perform VSR treatment on the Q345/316 L dissimilar steel welded specimens. Secondly, Charpy impact tests are conducted on the specimens before and after VSR treatment, and the fracture morphology of the Q345/316 L dissimilar steel welded joints is observed based on scanning electron microscopy. Then, a numerical model of Q345/316 L dissimilar steel welding is established using ABAQUS finite element software, and the effect of VSR on the residual stress is analyzed based on the Hole-drilling method. Finally, based on the fracture morphology and residual stress evolution law, the mechanism of improving the impact toughness of Q345/316 L dissimilar steel welded joints under VSR is analyzed. The results show that VSR can effectively improve the impact toughness of dissimilar steel welded joints. The impact toughness of the welded joints after VSR increased by 26.2% compared to the untreated specimens. The residual stress of the specimens generally decreases, and the stress concentration phenomenon is alleviated. The fracture morphology exhibits a significant increase in toughness and an overall reduction in residual stress levels. Based on the comprehensive analysis of fracture morphology and residual stress state, it can be concluded that the reduction and homogenization of residual stress are the main reasons for the improvement of impact toughness.

An Overview of Estimations for the High-Cycle Fatigue Strength of Conventionally Manufactured Steels Based on Other Mechanical Properties

Due to the time-consuming and costly nature of high-cycle fatigue experiments, correlations between fatigue strength and mechanical properties obtained through more simple and fast experiments can be interesting from an economic perspective. This review article aims to provide an overview of such relations established in the open literature from the 1980s to 2023 for conventionally manufactured steel grades. The majority of these models relate fatigue strength at a given fatigue life (often termed “fatigue limit” or “endurance limit”) to ultimate tensile strength, yield strength (both static and cyclic), hardness, elongation, reduction in area, and Charpy impact energy. Relations taking flaws such as nonmetallic inclusions into account are also discussed. Additionally, models predicting S–N curves are provided. The various estimations are presented in tables, together with the materials and test conditions for which they were established.

Experimental analysis of the effects of different production directions on the mechanical characteristics of ABS, PLA, and PETG materials produced by FDM

Abstract One of the most researched technologies among technologies used for producing complex and diverse parts today is additive manufacturing. In additive manufacturing, production can be carried out using thermoplastic and metal materials without requiring an additional process. Among the additive manufacturing technologies, the Fused Filament Fabrication (FFF) method is the most widely used method worldwide due to its affordability and broad application area. FFF is a method in which part formation is achieved by depositing melted materials on each other. In recent years, polymer materials such as polylactic acid (PLA), polyethylene terephthalate glycol (PETG), and acrylonitrile butadiene styrene (ABS) have been frequently used in many industrial areas in the FFF method because they are lightweight, inexpensive, sustainable, and provide sufficient strength for engineering applications. This study conducted tensile, three-point bending, Charpy, and compression tests on PLA, PETG, and ABS materials at angles of 15°–75° and 30°–60°, and the results were compared.

Effect of gradual thermoforming pressure on the mechanical properties of jute/polypropylene commingled composites

The present work presents a new approach to the parameters of the thermoforming process for jute fiber commingled thermoplastic composites based on pressure control. Effect of gradual pressure on the microstructures of jute fiber and their mechanical properties has been investigated. The singeing of Jute yarn and subsequent co-twisting with Polypropylene (PP) was done to make reinforcement. Jute/PP composites were developed using Jute/PP commingled reinforcement. Flexural and Charpy impact tests were conducted to analyze the mechanical performance of composites made using gradual and instant loading on the compression hot press. It is found that application of gradual pressure not only decreases fiber damages, but also increase flexural strength by 82%, impact strength by 43% and impact energy by 93% as compared to composite fabricated using instant pressure. Further, the complete analysis of microstructure of fibers of both type of composites is done to compare the effect of both fabrication techniques.