Maximum Impact Toughness Research Articles

Experimental studies on controlling of process parameters in dissimilar friction stir welding of DH36 shipbuilding steel–AISI 1008 steel

In the present work, DH36 steel and AISI 1008 steel sheets were joined using friction stir welding (FSW) process to investigate the influence of the rotational speed, traverse speed, and tool offset on temperature distribution, z-force, microstructure, and mechanical properties of the welded specimens. At a traverse speed (v) of 50 mm/min with a rotational speed (ω) of 600 rpm and tool offset of 2 mm, the maximum impact toughness and hardness were obtained due to higher grain refinement. The transverse tensile test specimens fractured in the weaker material (i.e., AISI 1008 steel) and exhibited the ultimate tensile strength values at least on the level of the weaker material. The impact toughness and hardness were highly dependent on the grain size variation. The effect of pitch ratio (ω/v) on grain size variation was more as compared with that on tool offset. Increasing the pitch ratio reduced the grain size and improved the impact toughness and hardness. Stir zone exhibited the acicular-shaped bainitic ferrite in DH36 steel and Widmanstatten ferrite grains in AISI 1008 steel. The higher hardness values were observed in thermo-mechanically affected zone of both steels due to significant grain refinement. Increasing the rotational speed and decreasing the traverse speed result in a higher welding temperature, which reduced the z-force.

Improved Mechanical Properties of a Quenched and Partitioned Medium-Carbon Bainitic Steel by Control of Bainitic Isothermal Transformation

A triplex microstructure of bainite, martensite and retained austenite in the 0.3C-1.4Si-1.8Mn (wt.%) steel was obtained by the bainitic isothermal transformation combined with Q&P process (B-QP process). The effects of bainite morphology and content on the mechanical properties have been studied by controlling the isothermal holding temperature and time. Results show that with isothermal holding temperature increasing from 320 to 400 °C, the bainite changes from lower bainite to upper bainite and the ultimate tensile strength and toughness decrease. Compared to the Q&T, 360 °C B-QP and 400 °C B-QP processes, the microstructure of the 320 °C B-QP-treated sample consists of lower bainite, martensite and retained austenite, and it exhibits the best combination of strength (1617 MPa), elongation (18.6%), the product of strength and elongation (PSE, 30.1 GPa%) and maximum impact toughness (103 J) when the lower bainite content is about 50%. In addition, the work hardening behaviors indicate that both the 400 °C B-QP sample with upper bainite morphology and the 320 °C B-QP sample containing 75% lower bainite exhibit the higher work hardening rate at the high strain level and larger uniform elongation.

Effect of weld groove volume on the mechanical and metallurgical performance of GTA welded martensitic stainless steel (AISI 410 SS) joints

Effect of three groove volumes on mechanical and metallurgical performance of 6 mm thick butt welded martensitic stainless steel (AISI 410 SS) joints was studied. Three weld groove geometries (using a single-V design) that resulted in the ratio of theoretical volumes (prior to welding) as 1:1.2:1.3 were made in 6 mm thick cold rolled AISI 410SS base plates. Metallurgically compatible filler was used to weld these plates using a suitable combination of gas tungsten arc welding parameters such that sound quality in these joints was achieved. The findings indicate that variation in the weld groove volume exerts a significant influence on the tensile and impact energy absorption behaviour of these joints, besides resulting into significant microstructural changes across different zones of the weldments. Amongst all welds, the smallest groove volume of 7358.7 mm3 possessed the maximum ultimate tensile strength of 758.34 MPa. Post weld heat treatment of 750˚C/70 min. followed by slow/furnace cooling enhanced the tensile strength of these joints but the ductility reduced to a marginal extent. Microhardness values decreased due to post weld heat treatment as microstructural grain coarsening occurred in these welds. Thermocouple measurements made across different welds indicate that small groove volume resulted into higher cooling rates. Maximum impact toughness of 110.6 J and 123.8 J was possessed by the joints made using the smallest groove volume in the as welded as well as the post weld heat treated condition respectively. This study establishes that smaller weld groove volume should be preferred for improved metallurgical as well as impact toughness performance of these welds.

ANALISA VARIASI KUAT ARUS ELEKTRODA E6013 TERHADAP SAMBUNGAN LAS PADA PELAT BAJA UNTUK TABUNG GAS 3 KG

The quality of the welding results is influenced by the qualified welder, the appropriate type of connection, the type of welding, and the electrode. Standard electrode AWS E 6013 with trademark Nikko Steel Welding Elektodes, NK 68 with φ 2.6 mm. The type of camp used is SNI standard 1452-2007 for 3 kg LPG tube. Specimens were subjected to tensile testing, impact toughness, hardness testing, curvature testing, microstructure with current variations of 50 A and 70 A of both types of electrodes used. Welding by SMAW method with circular welding at 3 kg of gas tube blank from JIS G 3116 SG 295 materials. From the test result will be known maximum tensile strength, impact toughness, hardness, curve strength, macro and microstructure. And by comparing the samples of SNI, non SNI and samples from both types of Nikko Steel and NK 68 electrodes, there are differences in mechanical and microstructure characteristics that will significantly affect the toughness of the welding results.

Mechanical Characterization and Impact Damage Assessment of Hybrid Three-Dimensional Five-Directional Composites.

The effects of braided architecture and co-braided hybrid structure on low-velocity response of carbon-aramid hybrid three-dimensional five-directional (3D5d) braided composites were experimentally investigated in this study. Low-velocity impact was conducted on two types of hybridization and one pure carbon fiber braided reinforced composites under three velocities. Damage morphologies after low-velocity impact were detected by microscopy and ultrasonic nondestructive testing. Interior damages of composites were highly dependent on yarn type and alignment. Impact damage tolerance was introduced to evaluate the ductility of hybrid composites. Maximum impact load and toughness changed with impact velocity and constituent materials of the composites. The composite with aramid fiber as axial yarn and carbon fiber as braiding yarn showed the best impact resistance due to the synergistic effect of both materials. Wavelet transform was applied in frequency and time domain analyses to reflect the failure mode and mechanism of hybrid 3D5d braided composites. Aramid fibers were used either as axial yarns or braiding yarns, aiding in the effective decrease in the level of initial damage. In particular, when used as axial yarns, aramid fibers effectively mitigate the level of damage during damage evolution.

Synergistic enhanced yield strength, tensile ductility and impact toughness of polydicyclopentadiene nanocomposites by introducing low loadings of di-functionalized silica

Abstract One promising strategy towards the realization of synergistic enhanced strength and toughness of polymers is combining the functionalized fillers with them to produce composites, which facilitates to improve the compatibility, interfacial bonding and load transfer between filler and the matrix. In this study, the reinforced tensile and impact properties of polydicyclopentadiene (PDCPD) composites are acquired via addition of ethyl,vinyl-functionalized silica (E,V–SiO2) with reasonably small particle size of 500 nm and uniform size distribution. It is interestingly noted that the tensile ductility of E,V–SiO2/PDCPD composites is dramatically improved by 862% through incorporation of 0.2 wt% E,V–SiO2. More significantly, the maximum tensile strength and impact toughness are enhanced by 22% and 99% via addition of E,V–SiO2. Excellent dispersion of E,V–SiO2 in the matrix, efficacious load transfer from PDCPD to E,V–SiO2 and covalent bonding between vinyl groups and DCPD are responsible for the remarkable enhancements of yield strength, tensile ductility and impact toughness.

Improved static and dynamic mechanical properties of multiscale bucky paper interleaved Kevlar fiber composites

Herein, the influence of bucky paper interleaves and dispersed MWCNT network on static and dynamic mechanical properties of Kevlar-epoxy composites, subjected to different loading conditions is investigated. Multiscale hybrid laminar Kevlar composites are prepared by vacuum impregnation followed by compression moulding technique. Subsequently, these hybrid composites are subjected to tensile, flexural, dynamic mechanical and low velocity impact and directly compared with basic Kevlar composite (KE) laminate. It is found that bucky paper interleaves along with dispersed MWCNT (KEBC) improve interlaminar and interfacial properties respectively. It is found that the maximum dynamic impact energy absorption and load carrying capacity of KEBC increase to 13.8 J and 2650 N respectively which shows an overall improvement of 31% over KE. These results are further confirmed by Charpy's impact test, in which maximum impact toughness reaches to 90.4 J/mm2, which is consistent with dynamic impact test results. After conducting various lab scale mechanical tests, ballistic test is also performed over KEBC and KE. It is found that, in case of KEBC, back face signature is reduced to 30% over KE, which confirms the collective effort of bucky paper interleaves and dispersed MWCNT in enhancing the energy absorption capability of hybrid laminar composite.

Mechanical properties and hydrogen induced cracking behaviour of API X70 SAW weldments

Pipeline welding is an integral part of oil and gas exploration industries. Often the weld failures are observed due to lack of weld quality, improper heat treatment and poor workmanship. Further, the use of new materials in pipeline industry puts focus on a better understanding of requirements for welding and reducing the failures in future. This necessitates the need for development and design of suitable welding fluxes for joining of these materials. In this paper an attempt is made to analyse the effect of commercial submerged arc welding flux and laboratory prepared agglomerated submerged arc welding fluxes (of basic, rutile basic and rutile acidic type) on the weldability, microstructural evolution as well as the structural integrity issues in API X70 line pipe steel welds. The mechanical and microstructural behaviour of weld joints was observed for submerged arc welding fluxes. The maximum tensile strength of 613 N/mm2 was observed for weld joint prepared using commercial flux (C.F). While in case of agglomerated fluxes the maximum value of tensile strength observed was 561 N/mm2 for F15B basic flux. Impact toughness for all the weld joints was evaluated both at room temperature and at −65 °C. For the weld as well as the heat-affected zone, the maximum impact toughness (160 J and 436 J) was observed for basic flux F5B at room temperature while at −65 °C (16 J and 30 J) impact toughness was obtained which was similar to that obtained with commercial flux. Microhardness of commercial weld joint (232 HV) is maximum as compared to the other weld joints. Maximum microhardness of 222 HV was observed for weld joint fabricated with flux F15B. Flux F15B shows a maximum value of microhardness (218 HV) for the heat-affected zone. Weld joints fabricated by using F3RA and F19RA fluxes exhibit high susceptibility to hydrogen induced cracking as compared to the remaining weld joints. The crack sensitivity ratio (CSR %) is high for weld specimen F3RA (54.64%) and F19RA (50.26%) while weld specimen fabricated using (F5B and C.F) fluxes show minimum crack sensitivity ratio (27.54% & 30.97%) respectively. The high susceptibility towards hydrogen induced cracking may be attributed to the very low value of carbon equivalent as compared to the remaining weld joints.

An outlook on comparison of hybrid welds of different root pass and filler pass of FCAW and GMAW with classical welds of similar root pass and filler pass

In the present study, gas metal arc welding and flux cored arc welding were applied on SA516 Gr70 carbon steel material. Two different hybrid passes were applied, wherein flux cored wire and solid wire were applied to root pass and filler pass one by one and vice versa. Besides, two more welds of similar electrode root pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative analysis was carried out in terms of macrostructure and microstructure examination, tensile testing, hardness variations, and impact testing for these classical welds and hybrid welds. The results reveal that, hybrid welds lead to better impact properties relative to classical welds. Maximum angular distortion of 2.66° was reported with classical weld of gas metal arc welding with solid wire root pass and same filler pass. The maximum impact toughness of 49 J/m3 was reported for flux cored root pass and solid wire filler pass at the weld zone. Maximum tensile strength of 596 MPa was reported for hybrid weld of solid root pass and flux cored filler pass. Microstructures are reported with the presence of different acicular ferrite and grain boundary ferrite. Maximum acicular ferrite of 61% was reported with classical weld of flux cored arc welding.

Ball impact responses of Sn-1Ag-0.5Cu solder joints at different temperatures and surface finishes

The purpose of this paper is to measure and analyze the Sn-1Ag-0.5Cu solder joints under high speed ball impact test (BIT) conditions. In this study, the ball impact test was conducted at impact velocity of 300 mm/s on package-level solder joints with 0.3 mm ball diameter, bonded individually on substrate pads of Ni/Au, OSP and Ni/Pd/Au surface finishes at elevated temperature of 25, 50, 75, 100 and 125 °C, respectively. The experimental results show that Ni/Pd/Au surface finish at room temperature has higher intermetallic compound (IMC) strength performance than Ni/Au and OSP. These three different substrate surface finishes, however, tend to have quite similar IMC strength performance at elevated operation temperature. The board-level drop test reliability of TFBGA 14 mm × 14 mm 409 L for these surface finishes were also performed at room temperature. The trends of BIT results are in good agreement to board-level drop test reliability. A three-dimensional finite element analysis (FEA) model was established to analyze the transient structural responses in the solder joint for determining the maximum impact toughness capacity. The effects of temperature on solder joint material yield stress and IMC strength on the impact characteristics were investigated.

Effect of Arc Welding Processes on the Weld Attributes of Type 316LN Stainless Steel Weld joint

The present study aims at understanding the effect of various arc welding processes on the evolution of microstructure, mechanical properties, residual stresses and distortion in 9 mm thick type 316LN austenitic stainless steel weld joints. Weld joints of type 316LN stainless steel were fabricated by three different arc welding processes which were commonly employed in the nuclear industry. All the weld joints passed radiographic examination. Microstructural characterization was done using optical and scanning electron microscope. Volume fraction of δ-ferrite was lowest in the A-TIG weld joint. The A-TIG welded joint exhibited adequate strength and maximum impact toughness values in comparison to that of weld joints made by SMAW and FCAW processes. The A-TIG weld joint was found to exhibit lowest residual stresses and distortion compared to that of other welding processes. This was attributed to lower weld metal volume and hence reduced shrinkage in the A-TIG weld joint compared to that of weld joints made by FCAW and SMAW processes which involved v-groove with filler metal addition. Therefore, type 316LN stainless steel A-TIG weld joint consisting of lower δ-ferrite, adequate strength, high impact toughness, lower residual stresses and distortion was suited better for elevated temperature service compared to that of SMAW and FCAW weld joints.

The role of notch tip shape and radius on deformation mechanisms of 12Cr1MoV steel under impact loading. Part 2. Influence of strain localization on fracture and numeric simulations

The fracture energy of 12Cr1MoV steel specimen with V‐shaped, U‐shaped and I‐shaped notches under impact loading was measured and analysed. The results were described using three common approaches to ductile‐brittle fracture: force‐based, energy‐based and strain‐based. Within the stage‐wise approach of physical mesomechanics of materials, the rate of increase/decrease of load at the stage of initiation and propagation of a macroscopic defect was evaluated, providing a good correlation with the work of fracture. The excitable cellular automata technique was applied to simulate the deformational behaviour of the specimens with different shape of notches. It was demonstrated that in the case of the blunted notch, the maximum impact toughness is facilitated by a more uniform distribution of the load along the notch, which hinders brittle fracture at lower testing temperature. For the specimen with the sharp I‐notch, the bands of localised shear are oriented normally to the loading axis, inhibiting macroscopic localisation of strain and crack propagation. For this reason, the impact toughness of the specimen with the I‐notch appeared to be higher than that of the V‐notched one. Using the fractographic analysis and the size of shear lips as a quantitative fracture parameter, a physical‐mechanistic scheme of fracture was suggested for the case of enhanced localised plasticity near the stress riser.

Effect of Short-Term Water Exposure on the Mechanical Properties of Halloysite Nanotube-Multi Layer Graphene Reinforced Polyester Nanocomposites.

The influence of short-term water absorption on the mechanical properties of halloysite nanotubes-multi layer graphene reinforced polyester hybrid nanocomposites has been investigated. The addition of nano-fillers significantly increased the flexural strength, tensile strength, and impact strength in dry and wet conditions. After short-term water exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed at 0.1 wt % multi-layer graphene (MLG). The microhardness increased up to 50.3%, tensile strength increased up to 40% and flexural strength increased up to 44%. Compared to dry samples, the fracture toughness and surface roughness of all types of produced nanocomposites were increased that may be attributed to the plasticization effect. Scanning electron microscopy revealed that the main failure mechanism is caused by the weakening of the nano-filler-matrix interface induced by water absorption. It was further observed that synergistic effects were not effective at a concentration of 0.1 wt % to produce considerable improvement in the mechanical properties of the produced hybrid nanocomposites.

Characterization of microstructure of HAZs in as-welded and service condition of P91 pipe weldments

Steels 9-12% Cr, having the high creep rupture strength are advocated for the modern low polluting thermal power plants. In the present investigation, the P91 pipe weldments have been characterized for microstructural responses in as-welded, post-weld heat treatment (PWHT) and ageing conditions. The PWHT of welded samples were carried out at 760 °C for time of 2 h and ageing at 760 °C for 720 h and 1440 h, respectively. The effect of time has been studied on precipitates size, distribution of precipitates and grain sizes present in various zones of P91 steel weldments. The impact toughness and hardness variation of heat affected zone (HAZ) have also been studied in as-welded condition as well as at different heat treatment condition. A significant change was observed in grain size and precipitates size after each heat treatment condition. The maximum impact toughness of HAZ was obtained after PWHT at 760 °C for 2 h. The main phase observed in weld fusion zone in as-welded, PWHT and ageing conditions were M23C6, MX, M7C3, Fe-rich M3C and M2C. The unwanted Z-phase (NbCrN) was also noticed in weld fusion zone after ageing of 1440 h.

Investigations on Anisotropy Behavior of Duplex Stainless Steel AISI 2205 for Optimum Weld Properties

The present investigation aims to analyze the anisotropy behavior of 8mm thick rolled plate of duplex stainless steel AISI 2205. The study aims to connect the importance of anisotropy properties with fusion welding to achieve the optimal mechanical properties of the weldment by justifying suitable direction for welding. An outcome of the investigation implies that duplex stainless steel exhibits maximum impact toughness in the longitudinal direction i.e. rolling direction when compared to transverse and diagonal directions. Further, the existence of significant directionality was confirmed by analyzing the tensile behavior which gives greater tensile strength in the transverse direction and higher amount of elongation and better formability in the longitudinal direction. The present work was extended by fabricating the weldment using gas tungsten arc welding by keeping the welding direction perpendicular to the rolling direction of a plate. Microstructure and the mechanical properties of the weld were assessed and compared with the behavior of its parent metal.

Effect of bainitic isothermal transformation plus Q&P process on the microstructure and mechanical properties of 0.2C bainitic steel

A novel bainitic isothermal transformation plus quenching and partitioning (B-QP) process was developed for a 0.2C-1.5Si-1.8Mn bainitic steel. The microstructure and mechanical properties of the steel treated by different heat treatment process were investigated. The results show that the B3-QP (the subscript ‘3’ indicates the isothermal holding of 3min for the bainitic transformation) samples exhibit a multiphase microstructure containing carbide-free bainite, martensite, film-like retained austenite. The microstructure is much finer than that of the Q&T samples with full martensite and the B30-QP samples with a bainite microstructure. Although the Q&T sample has the highest tensile strength (1455MPa), the ductility and the product of strength and elongation (PSE) are lower. In contrast, the B3-QP and B30-QP samples exhibit better ductility and higher PSE values of 26.3GPa% and 28.2GPa%, respectively. Furthermore, the B3-QP sample exhibits maximum impact toughness value of 121 Jcm−2, which is about 20% and 55% higher than those of Q&T sample (101Jcm−2) and B30-QP sample (78Jcm−2) respectively.

The degradation of mechanical properties in halloysite nanoclay–polyester nanocomposites exposed to diluted methanol

The degradation of mechanical properties in halloysite nanoclay–polyester nanocomposites was studied after an exposure of 24 h in diluted methanol system by clamping test specimens across steel templates. The glass transition temperature ( Tg) and storage modulus increased steadily with the increase of halloysite nanoclays before and after diluted methanol exposure. The addition of nano-fillers was found to reduce liquid uptake by 0.6% in case of 1 wt% reinforcement compared to monolithic polyester. The mechanical properties of polyester-based nanocomposites were found to decrease as a result of diluted methanol absorption. After diluted methanol exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed at 1 wt% of halloysite nanoclay. The microhardness increased from 203 to 294 HV (45% increase). The Young’s modulus increased from 0.49 to 0.83 GPa (70% increase) and the tensile strength increased from 23 to 27 MPa (17.4% increase). The impact toughness increased from 0.19 to 0.54 kJ/m2 in diluted methanol system (184% increase). Surprisingly, the fracture toughness of all types of nanocomposites was found to increase after exposing to diluted methanol due to plasticization effect. Scanning electron microscope images of the fractured surfaces of tensile specimens revealed that the methanol increased the ductility of the matrix and reduced the mechanical properties of the nanocomposites.

Dissimilar welding of A7075-T651 and AZ31B alloys by gas metal arc plug welding method

Innovative welding techniques allow for the fabrication of light, high-specific-strength, and fuel-saving Al and Mg alloys for use in transportation industries. Furthermore, these techniques have minimal detrimental impact on the environment. However, the poor mechanical properties of joints resulting from the formation of brittle Al m Mg n intermetallic compounds are key barriers to joining Al and Mg alloys. To date, a proper solution to this problem has not yet been provided. The aim of this research was to investigate the mechanical and metallurgical properties of the joint between AZ31B and A7075-T651 alloys welded by a new technique called gas metal arc plug welding method. ER5356 aluminum wire was used as a filler. The yield and ultimate tensile strengths as well as impact toughness of the joints were measured. The fracture surface was investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The maximum ultimate tensile strength and impact toughness of the joints were 89 and 84 % of those of the AZ31B parent alloy, respectively. Generally, the joints failed in the ER5356 nugget, whereas some failed in the AZ31B alloy. No fracture was observed in the A7075-T65 alloy. Brittle fracture mechanism was observed for all the joints. In conclusion, the proposed welding technique can allow for better mechanical properties of joints for dissimilar welding of aluminum and magnesium alloys.

Microstructure and mechanical properties of a medium-carbon bainitic steel by a novel quenching and dynamic partitioning (Q-DP) process

A novel Quenching and Dynamic Partitioning (Q-DP) process for a 0.3C-1.4Si-1.8Mn-1.3Cr-0.3Mo (wt%) bainitic steel was developed and the microstructure and mechanical properties were investigated. The results show that the microstructure of the Q-DP treated steel consists of bainite, martensite and retained austenite, and it exhibit a better combination of tensile strength (above 1500MPa), total elongation (above 17%) and impact toughness (above 90J). Among the different Q-DP process, the sample treated by 250°C Q-DP process exhibits the best combination of strength (1519MPa), ductility (21.3%), the product of strength and elongation (PSE, 32.4GPa%) and maximum impact toughness (108J) compared to the quenching and partitioning (Q&P) process and other Q-DP processes. In addition, the work hardening behaviors of the Q&P and Q-DP samples were investigated. The stress-strain curves show that the Q&P and 250°C Q-DP treated samples exhibit the larger uniform elongation and the value of n calculated for samples is 0.109 and 0.101 respectively.

Effect of chill formation on the mechanical properties and microstructure of grey and nodular cast irons used in automotive industry

Cam shafts used in automobiles are produced by cast iron (grey cast iron, nodular cast iron) or steel. In this study, effect of chill formation on the surface of grey and nodular cast irons is investigated on the wear behavior, hardness, impact toughness and microstructure of grey and nodular cast irons. For this purpose, four types cam shaft made of grey cast iron with and without chill on the surfaces and nodular cast iron with and without chill on the surfaces, were casted. Mechanical tests were conducted after the camshafts have been produced by casting method. Surface hardness and wear resistance of grey and nodular cast irons have been improved by chill formation on the surfaces and it is concluded that the amount of wear on the surfaces of grey cast iron with chill and nodular cast iron with chill is almost the same. Maximum hardness value was obtained on the surface of grey cast iron with chill. The impact toughness has been found to decrease by chill formation. Maximum impact toughness value was obtained on nodular cast iron. Microstructures of grey cast iron with and without chill and nodular cast iron with and without chill were examined under optical microscope and worn surfaces of cast irons were examined by scanning electron microscopy (SEM). Wear mechanisms of the four types of cast iron were evaluated by SEM examination. Keywords: Cam shafts, Cast irons, Chill formation, Mechanical properties, Microstructure