Impact Energy Values Research Articles

Optimization of TIG welding process parameters using Taguchi technique for the joining of dissimilar metals of AA5083 and AA7075

This research paper aims to optimize the TIG welding parameters to join dissimilar metals of AA5083 and AA7075 using the Taguchi technique. The TIG welding current and root gap of butt geometry configuration are considered input parameters, and welding characteristics such as tensile strength, 0.2% of yield strength, hardness, and impact energy are output responses. The base metals are joined according to the Taguchi L-09 design of experiments. The welded samples were inspected using the X-ray radiography method for internal defects. Tensile properties, hardness number, and impact energy of different welding coupons were evaluated by conducting the uni-axial testing, a Brinell hardness test, and an Izod impact test, respectively. A better weld strength of 224 MPa was observed at 210 A welding current, and the root gap of 1.5 mm was maintained. Better hardness and impact energy values were observed when the root gap of 1.5 mm and welding current of 220 A were maintained. The root gap is the primary factor influencing tensile strength enhancement, which accounts for 44.78% of the effect, followed by 40.5% welding current. Root gap is the parameter that affects the tensile properties, hardness number, and impact toughness the most. The findings of this paper suggest the optimal parameters for welding AA5083 and AA7075 dissimilar base metals, which are suitable for complex structures requiring both durability and resistance to harsh environments.

Comparison of mathematical and supervised machine-learning models for ductile-to-brittle transition in bcc alloys

This study focuses on modelling Ductile-to-Brittle Transition (DBT) curves using various mathematical and supervised machine learning models. Charpy impact energy values are converted to normalized energy values to account for reductions in upper-shelf energy. The research introduces a saturation parameter in mathematical models to capture these variations and examines the influence of alloying elements, microstructure, and neutron irradiation on DBT behaviour in nuclear structural materials. Detailed analyses reveal how fitting parameters vary with these factors and demonstrate that mathematical models’ fitting parameters generally align with observed DBT curve trends. The predictive capabilities of these mathematical models are also compared with those of supervised machine learning models, highlighting the strengths and limitations of each approach in modelling DBT behaviour. An explainable approach is used for interpretation of machine learning models and it is shown that this approach can be effectively used for the influence of various independent parameters on impact energy.

Effect of chromium and molybdenum addition on the matching mechanism of strength−ductility−toughness of low carbonmedium manganese steel

Low carbon medium manganese steel with chromium and molybdenum addition (4MnCM), alongside a control group without these additions (4Mn), was developed. The quenching (860 °C) and tempering (620 °C) heat treatment process was applied to both steel groups. The influence of Cr and Mo on the microstructure evolution and mechanical properties was examined. The findings revealed that, the low−temperature impact energy values (KV2) of 4MnCM at −60 and −84 °C were enhanced by 104 and 107 J, in comparison to 4Mn. The yield and tensile strength saw an increase of 100 MPa. The higher low-temperature toughness of 4MnCM is attributed, on one hand, to the addition of Cr and Mo, which inhibiting deformation twinning through enhances the stacking fault energy (SFE) of reversed austenite. On the other hand, it is due to the absence of coarse ε−martensite (ε−m) along the crack propagation path. Additionally, the phase transformation of reversed austenite occurs at the crack nucleation stage during the impact process of both steels, which helps alleviate stress concentration and increases the energy required for crack formation. The primary reason for the higher strength of 4MnCM lies in the significant enhancement of precipitation strengthening effects through the precipitation of M6C, M23C6 and Nb/TiC co-precipitation with M6C.

Impact energy in Heat-Treated aluminium alloy 6061 and 7075

Instrumented Charpy impact is one of the promising methods to assess the impact energy; toughness and resilience of a material. The test consists of the Charpy machine and instrumentation equipment which is the strain gauge and the data acquisition system. Impact energy evaluations are important to understand the material behaviour subjected to sudden impact loading. Aluminium 7075 has good strength strength-to-weight ratio than aluminium 6061 and hence the AL 7075 is usually used in the aerospace industry, whilst the AL 6061 is commonly used in the automotive industry. The objective of the study is to observe and analyse the impact response of the Aluminium 6061 and 7075 at different heat- treated conditions; O-anneal and T6 temper. In addition to the impact energy absorbed value, the impact strain signal is recorded too. Theoretical impact energy is calculated as well based on the information given by the Charpy machine software. Aluminium 7075 exhibits a lower value of impact energy absorbed and a smaller area under the curve compared to Aluminium 6061. The energy absorption capacity for each material grade and heat-treated condition are different from one another. O-anneal aluminium has a lesser energy absorbed value and a smaller area under the curve than the T6 temper aluminium. The outcome reveals that the heat treatment process alters the material microstructure and mechanical properties, whereas in this study the impact energy responses are influenced by these circumstances. Moreover, the chemical composition of the aluminium alloy distinguishes these two grades from one another, thus resulting in different impact responses.

The Effect of Cryogenic Treatment on W360 and E38K Hot Work Tool Steels

The present study examines the impact of cryogenic treatment (CT) on W360 and E38K hot work tool steels used in forging dies, subjected to conventional heat (HT) and CTs followed by double tempering treatment. Results reveal that CT facilitates the transformation of retained austenite from 4.9% and 2.5% for W360 and E38K steels, respectively, into martensite to an undetectable limit. Also, when compared to HT, CT at −180 °C results in about 3 times higher amount of the carbide precipitation for both steel types. In contrast, a slight increment in the hardness values with decreasing treatment temperature is observed. Notch impact test results indicate higher impact energy with lower CT temperatures, particularly notable in W360 steel. Although both steel types exhibit almost similar impact energy values at room temperature, E38K steel has ≈100% higher energy at 350 °C. DCT‐treated samples show improved wear resistance at lower cryogenic temperatures. Cryotreated W360 steel displays nearly 25% less wear rate than cryotreated E38K steel. The study underscores the suitability of W360 and E38K steels for hot work applications, with CT enhancing their mechanical and microstructural performance, particularly in W360 steel due to its higher carbide density.

Impact response of hybrid composites under varying environmental conditions: A comparative study

AbstractComposite materials are widely preferred in the aviation, automotive, construction and maritime industries due to their many superior properties. As a result of this widespread use, composite structures are inevitably subjected to various environmental conditions. Various environmental conditions may negatively affect the mechanical performance of the structure, and the structure may become unable to maintain its initial mechanical properties, especially in the face of critical loading, such as low‐velocity impacts. This research investigated the influence of various environmental conditions on the low‐velocity impact strength of composite materials. 12‐layer plate samples with epoxy matrix reinforced with woven glass fabric (GF), woven carbon fabric (CF), and hybrid fabric (HF), where the two fabrics are used together, were produced. Low‐velocity impact tests were conducted to these specimens at 20 and 40 J energy levels. Damages occurring in the material as a result of the low‐velocity impact test were interpreted using high‐resolution camera and optical microscope images. Force‐time and force‐ displacement curves were drawn and interpreted. It was concluded that as the impact energy values increased, the maximum force and displacement values also increased.Highlights The influence of various environmental conditions to which composite materials may be exposed on the dynamic response of the structure has been investigated. Various environmental conditions significantly affected the composite structure's impact behavior. While glass fabric (GF) composite samples were more affected by the seawater environment, carbon fabric (CF) composite samples were more affected by the HCl environment. Hybrid (HF) composite samples were affected by seawater and HCl in approximately equal amounts.

Study of The Microstructure and Mechanical Property Relationships of Gas Metal Arc Welded Dissimilar Protection 600T, DP450 and S275JR Steel Joints

The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties.

Effect of process parameters on the mechanical behavior of Ti6Al4V alloys fabricated by laser powder bed fusion method

The parameters used in the production process in laser powder bed fusion (L-PBF) technology, one of the additive manufacturing methods, have a critical effect on the mechanical behavior and density properties of the product and can change the properties of the product. Therefore, this study examined the influence of laser power, scanning speed, hatch spacing and beam rotation angle on the tensile strength, impact energy, surface roughness, and porosity levels of Ti–6Al–4V produced through the L-PBF method. It was observed that the tensile strength changes directly proportional to the laser power. In addition, the tensile strength decreases significantly with a value of 645 MPa obtained at lowest 0.07 mm hatch spacing, 190 W laser power and 900 mm scanning speed. The lowest value of impact energy, with a value of 8.7 J, was reached at a rotation angle of 180°. It has been determined that surface roughness decreases significantly with increasing laser power, while it demonstrates an increase with higher scanning speeds. Surface roughness values of 8.9 μm parallel and 8.35 μm perpendicular to the building direction were achieved at a laser power level of 220 W. Laser power was identified as the most influential factor in determining the porosity ratio, with a high porosity rate 0.48% occurring at 160 W laser power. Furthermore, an increase in scanning speed resulted in a corresponding increase in the porosity rate.

Testing the shock protection performance of Type I construction helmets using impactors of different masses.

Wearing protective helmets is an important prevention strategy to reduce work-related traumatic brain injuries. The existing standardized testing systems are used for quality control and do not provide a quantitative measure of the helmet performance. To analyze the failure characterizations of Type I industrial helmets and develop a generalized approach to quantify the shock absorption performance of Type I industrial helmets based on the existing standardized setups. A representative basic Type I construction helmet model was selected for the study. Top impact tests were performed on the helmets at different drop heights using two different impactor masses (3.6 and 5.0 kg). When the helmets were impacted with potential impact energies smaller than the critical potential impact energy values, there was a consistent relationship between the peak impact force and the potential impact energy. When the helmets were impacted under potential impact energies greater than the critical potential impact energy values, the peak impact forces increased steeply with increasing potential impact energy. A concept of safety margin for construction helmets based on potential impact energy was introduced to quantify the helmets' shock absorption performance. The proposed method will help helmet manufacturers improve their product quality.

Influence of Interfacial Interaction and Composition on Fracture Toughness and Impact Properties of Carbon Fiber-Reinforced Polyethersulfone.

In this study, the interlaminar fracture toughness and impact strength of polyethersulfone reinforced with continuous carbon fibers were studied. Interlaminar fracture toughness tests were performed using the double cantilever beam method. It was shown that surface modification using the thermal oxidation method of the carbon fibers can strongly increase the interlaminar fracture toughness of the obtained composites. Thus, the maximum value reached 1.72 kJ/m2, which was 40% higher than the fracture toughness of the composites reinforced with initial carbon fibers. Moreover, fractographic analysis using a scanning electron microscope allowed us to highlight the main reasons for the dependence of fracture toughness on fiber content and surface modification conditions of the carbon fibers. It was shown that the main factor that allowed for an increase in fracture toughness was the enhanced interfacial interaction between the fibers and polymer matrix. Additionally, it was found that expectedly, there was a good correlation between interlaminar fracture toughness and interlaminar shear strength results. However, a negative influence of surface modification on the impact properties of composites was found. Such behavior occurred because of higher structural stability and lower exposure to delamination in multiple layers of the composites reinforced with the modified carbon fibers. It was found that impact energy reached ~150 kJ/m2 for the polyethersulfone-based composites reinforced with initial fibers, while the composites reinforced with modified carbon fibers showed impact energy values of only ~80 kJ/m2. Nevertheless, surface modification of carbon fibers using the thermal oxidation method can be an effective method for improving the performance properties of polyethersulfone-based composite materials.

Infrasound analysis of the 2018-Dec-18 49 kiloton Bering Sea bolide: Misassociations and celerity-range models

Automatic detections at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) are often misassociated. This occasionally leads to single events being split into multiple events. Infrasound signals generated from a large bolide over the Bering Sea on 2018-Dec-18 were recorded on more than 15 of the CTBTO International Monitoring System (IMS) stations. The bolide was also reported by the Center for Near Earth Object Studies (http://cneos.jpl.nasa.gov/fireballs) with a calculated total impact energy value of 49 kt. Signals from this bolide were automatically detected and associated at the IDC, into two different events, with the origin time differing by approximately 7.5 minutes and location by ∼125 km. To investigate why detections from this bolide event were misassociated in the automatic bulletins, we analyze infrasound observations from the IMS infrasound arrays and compare our arrival time observations to the automatic detections from the IDC. We use the Bayesian Infrasonic Source Localisation method and employ different celerity-range models, to investigate signal association for this event. Through comparison with the associations based on IDC detections, we aim to improve our understanding of the causes of misassociations and identify potential improvements to future event association algorithms.

Microstructural and mechanical properties of electron beam welded super duplex stainless steel

The electron beam welding of super duplex stainless steels is associated with challenges due to the concentrated heat input and the nitrogen loss that result in a predominantly ferritic structure after the solidification. This study presents an approach to overcome this issue by feeding nickel-based filler wire into the melt pool in welding of 2507 super duplex stainless steel. Results showed that the high-frequency beam oscillation combined with a multi-beam technique led a good mixing between the base metal and the filler wire, even at a large depth-to-width ratio. Additionally, the weld geometry was characterized by near-parallel fusion lines and a narrow heat-affected zone. The nickel addition resulted in a balanced microstructure in the weld metal with ferrite fractions of 35–55 %, despite a significant nitrogen loss, consequently leading to impact energy values of 215 ± 15 J and hardness values of 285 ± 15 HV. The findings of this investigation allow fabricators to effectively design electron beam welding processes for producing thick-walled super duplex stainless steel components.

High-velocity impact damage by projectile and tension after impact behavior at 1300 ℃ for SiC/SiC with environment barrier coating

The research on the high-speed & low-energy impact under millimetre sized projectile and residual strength under high temperature are rare for SiC/SiC with Environmental Barrier Coatings (EBC). The impact of 2 mm steel projectiles at the speed of 177.5 m/s–252.7 m/s was studied for EBC(Si/Yb2Si2O7/Yb2SiO5)-SiC/SiC with Chemical Vapor Infiltration (CVI) process. The tensile test at 1300 ℃ was conducted on an inert gas protection testing machine. The optical microscope, Scanning Electronic Microscope(SEM), μCT were used to observe the impact and tension after impact(TAI) damage. The results shows that projectile impact has strong effect on EBC peeling, SiC/SiC damage and fracture, and residual-tension strength at 1300 ℃. And the threshold values of impact velocity or energy are different for them. Furthermore, an analysis method for damage evolution by the attachment quantity of oxide was found for EBC-SiC/SiC composites.

Analisis Sifat Mekanik Komposit Serat Sabut Kelapa dengan Perlakuan Alkalisasi Etanol dan Filler Arang Tempurung Kelapa

Coconut trees are plants that are easily found in tropical areas such as Indonesia; therefore, natural products are abundant, but the use of waste from coconuts has not been processed into technological products. The aim of this study was to determine the differences in the variations in the volume fraction of fibers during tensile and impact strength testing. The variations in the volume fraction used were 5%, 10%, and 15% fiber, and the chemical treatment of the fiber was alkalized using 20% ethanol for 3 h of soaking. Composite manufacturing uses a hand layup method with random fiber orientation. The results of the research on variations in volume fraction of 5%, 10% and 15% obtained test values, in tensile testing such as maximum load obtained 32,844 kgf, 106.44 kgf and 105.59 kgf, maximum stress 6.0510 N/mm2, 16,893 N/ mm2 and 17.249 N/mm2, elongation breaking strain 0.8150, 0.3275 and 0.2617, breaking strain 1.4818 %, 0.5955 % and 0.4758 %, for the tensile test value the impact energy value was found to be 1.6 kgf, 2.3 kgf and 3.3 kgf and impact prices of 1.84 kJ/m2 , 2.45 kJ/m2 and 3.45 kJ/m2 . The high tensile and impact test results were due to mixing coconut fiber which had gone through ethanol alkalizing treatment with coconut charcoal powder to obtain high impact and tensile values.

Evaluation of Simulated Heat Affected Zone of Molybdenum- and Niobium Alloyed Ultra-High-Strength Steels

Gleeble 3800-thermomechanical simulator was used to simulate the heat affected zone of quenched and tempered 0.16 wt.% C steels with variation of molybdenum-and niobium contents. The purpose of the study was to evaluate the effect of alloying content on the properties of the coarse-grained zone of HAZ region (CGHAZ) and partially re-austenitised inter-critical zone (ICHAZ) with two different t8/5 times (5 s and 15 s). Results showed that Mo and Nb decreased the amount of softening in the HAZ-region, especially with longer t8/5 -time (15 s). 0Mo steel had mixed microstructure of bainite and martensite in the CGHAZ region with t8/5 time of 15 s, which led to higher degree of softening compared to other steels. Shorter t8/5 time of 5 s produced martensitic microstructure in CGHAZ region in all cases leading to higher hardness values. Impact energy values at-40 °C were at least 34 J/cm2 in all cases. Highest hardness values in the ICHAZ-region were achieved in the case of 0.5Mo steel. Also, at-40 °C impact energy values of ICHAZ were at least 34 J/cm2 in all cases, however Mo-free steel achieved clearly higher impact energies in ICHAZ region, which is result from softer microstructure with relatively low hardness compared to other steels. Overall, it can be concluded that longer t8/5 time can be used, which corresponds to higher heat input in welding, if Mo and/or Nb alloying is used.

Microstructural Investigation and Impact Strength of Sinter-Hardened PM Steels: Influence of Ni Content and Tempering Temperature

This study analyzed the influence of tempering treatment temperature on the microstructural and mechanical behavior of two different powder metallurgy steels containing 0 wt. % Ni and 4 wt. % Ni. The evolution of the microstructure and the macro- and microhardness of the microstructural constituents resulting from tempering treatments conducted on the sinter-hardened materials at temperatures ranging from 160 °C to 300 °C were investigated. The role of the tempering conditions in the impact behavior was assessed using Charpy tests on V-notched and unnotched samples, tempered at 180 °C, 220 °C and 280 °C. The observed macrohardness reduction with increasing tempering temperature was related to martensite transformations. At high tempering temperatures, the remarkable loss in impact energy values was attributed to microfracture modes. The contribution of Ni-rich austenite areas in enhancing impact strength was detected.

Correlation between charpy-V notch impact energy and KJIC of ferrite ductile iron in the transition-temperature region

Fracture toughness is an important index for the structural integrity assessment of ductile iron spent fuel transportation casks. Fracture toughness tests require a long test period, high cost, and difficult operation. Therefore, the Charpy V-notch impact energy value (KV) is considered to predict fracture toughness (KJIC).In this study, Charpy V-notch impact tests(−80 °C, −60 °C, −40 °C, −20 °C, 0 °C, 20 °C, 40 °C, 60 °C, 80 °C) and fracture toughness tests(−60 °C, −40 °C, −20 °C, 0 °C, 20 °C) of ferrite ductile iron(FDI) were carried out. A KJIC-KV model for FDI in the transition temperature region was proposed, taking into consideration the influence of test temperature(T) and yield strength(σ YS), then the proposed model was compared to the KIC-KV empirical equations of steel in the transition-temperature region, using the test data of FDI. The results indicate that the KJIC-KV model proposed in this work is more accurate and applicable for predicting fracture toughness values in the transition-temperature region than others, the residual between the estimated value of the KJIC-KV correlation model (KJIC-E) and the experimental value of KJIC(KJIC-T) was less than 4.1 MPa·m0.5, and the error was less than 5%.

The effect of quenching/double quenching and tempering heat treatment cycles on the microstructure, impact energy and hardness of AISI H13 tool steel

ABSTRACT In this study, microstructure modifications of AISI H13 steel were studied with different heat treatments such as conventional quenching, quenching + tempering/double tempering and double quenching + tempering/double tempering. Carbide volume ratio analyses were performed. The XRD analysis was used to determine the type of carbide, the average crystallite size, and the dislocation density in the samples. Charpy impact tests were performed. The hardness values of the samples were measured with the Rockwell C scale. The presence of MC, M23C6, and M7C3 type carbides was determined in the microstructures. Heat treatment cycles caused a high dislocation density in martensite laths. The dislocation density of martensite laths decreased with double quenching. The tempering process caused the formation of fine carbide particles in the microstructure. In addition, tempering processes gave rise to an increase in the volume ratio of M23C6-type strip carbides. The length/width ratio of the strip-type carbides increased with the effect of double tempering. As a result of the applied heat treatments, the impact energies of the samples decreased. The tempering process caused a secondary hardening of the samples. While the double quenching process increased the impact energy value by approximately 2%, it caused a decrease in hardness by 24%.

On the importance of nano-oxide control in laser powder bed fusion manufactured Ni-based alloys to enhance fracture properties

In this study, a series of Ni-Cr-Mo based alloys (IN625, C22 and NA282), sourced from various powder suppliers and having varying oxygen concentrations (200 ppm to 800 ppm), were printed under similar conditions using laser powder bed fusion (LPBF). Nano-oxides in the range of 20–50 nm were observed in each alloy in the as-printed state, albeit with different number densities. Room temperature tensile tests and liquid nitrogen (LN2, -196 °C) Charpy impact tests were performed to assess the mechanical response of each alloy. The IN625 and C22 samples showed considerably lower impact energy values than the NA282, as well as lower room temperature post-necking tensile elongations, despite showing similar yield strengths and strain hardening behaviours. Fracture surface dimple sizes were shown to correlate with nano-oxide particle spacings. Nano-oxides were found in the middle of most dimples on fracture surfaces suggesting that the nano-oxides are the sites of void nucleation during fracture, despite being only 20–50 nm in size. The precursor metal powders were identified as the primary origin of the nano-oxide particles. This study highlights the critical, detrimental role that nano-oxides, typically present in LPBF metals, have on the fracture properties of these materials. In the case of the Ni-Cr-Mo alloys examined here, limiting oxide formation is critical to achieving optimal fracture properties.

Comparison of low‐velocity impact behavior of thick laminated composite structure with experimental and modeling technique

AbstractIn this study, the dynamic behavior under low‐veloctiy impact of E‐glass epoxy unidirectional thick laminated composite structure was investigated by numerical methods and compared with experimental results. Thereby, it was aimed to detect the impact behavior of the composite structures with numerical analysis program for reducing experimental tests on these composite structures. LS‐DYNA finite element method (FEM) software was used for numerical modeling. The material model MAT055, which is based on the Tsai–Wu matrix failure modeling on damage mechanics, was selected for the analyses in LS‐DYNA. Low‐velocity impact analyses have been carried out on composite structures at various impact energies as a range of 15–250 J as similar to experiments. From the analysis of the plots, it can be seen that the values of absorption energy provided by the FEM analyses are close to the experimental values at all impact energy levels. It can be determined that the mean difference between the absorption energy levels provided from the experimental and numerical studies is 1.81%. In the same studies, matrix cracking was observed at 50 J impact energy value and full penetration was observed at 250 J impact energy. The error rate between the values obtained using the derived impact energy prediction equation and the values obtained as a result of numerical analysis was maximum 5.26%. Thus, derived equation was found to be reasonable for use in predicting the absorption energy. As a result, these values indicate that the experimental results are agreed well with the numerical results.Highlights Dynamic behavior under impact of thick laminated composite was investigated. Impact analyses were performed at impact energies as a range of 15–250 J. At 250 J impact energy, the composite deformed with full penetration damage. Impact damage areas were calculated according to impact energy levels. It would be useful to use numerical analysis method in terms of cost and time.