ASTM E1820 Research Articles

Effect of cenosphere and specimen crack lengths on the fracture toughness of Al6061-SiC composites

Main aim of this work is to investigate the influences of the addition of cenosphere and specimen crack length on the fracture toughness of Al6061-SiC composites. The experimental analysis was carried out for 3, 6 and 9 wt% proportions of cenosphere with the 3 wt% of SiC as reinforcements in the aluminum 6061 matrix for various crack lengths. The fracture toughness of Al6061-SiC-Cenosphere hybrid composites was estimated using compact tension (CT) specimen for the said compositions. The CT specimens were prepared, according ASTM E399 standard, for different crack length to width (a/W=0.3-0.6) ratios. From the experimental outcomes, it is identified that the fracture toughness of the hybrid composite increases upto the 6wt% of cenosphere and further increment in the cenosphere causes the decrement in the values. It is also found that the load bearing capacity and fracture toughness of the hybrid composite decreases with increment in the a/W ratios of the CT specimen.

Optical Microstructure, FESEM, Microtensile, and Microhardness Properties of LM 25-B4Cnp-Grnp Hybrid Composites Manufactured by Selective Laser Melting

The current investigation, nano-multi-powder particles, 5 and 10 wt.% boron carbide (B4C) and graphite (Gr) are utilized as a reinforcement, and aluminium LM 25 alloy is used as a matrix. These hybrid nanocomposites were fabricated by a novel additive manufacturing method—selective laser melting. The specimen was carried out in a cylindrical size having 2 circular slots of dimension 14 and length 50 mm. The diverse SLM specimens focused on tribological properties of impact, creep, tensile, and hardness were carried out for the three specimens with same weight percentage of nanoparticles. The consequence of the reinforcement has been performed through microtensile and microhardness tests. The microtensile and microhardness properties are evaluated by microtensile test machine and Vickers hardness tester, and the specimen has been prepared as per ASTM E8 and ASTM E18 standards. Microtensile strength and hardness were augmented by the addition of B4C and graphite nanoparticles. The tensile strength and hardness values are 668.93 MPa and 739.16 MPa, and 193VHN and 206.79VHN, respectively. The result of the microstructure study shows homogeneous dispersion of B4Cnp-Grnp in the matrix material of the LM25 alloy. The FESEM image results of the ruined surface illustrate the addition performance of ductile fracture, brittle fracture, and ploughing of reinforced material. The consequences of the research enhanced tensile and hardness properties of composite with reinforcement added.

Quasistatic fracture using nonlinear‐nonlocal elastostatics with explicit tangent stiffness matrix

AbstractWe apply a nonlinear‐nonlocal field theory for numerical calculation of quasistatic fracture. The model is given by a regularized nonlinear pairwise potential in a peridynamic formulation. The potential function is given by an explicit formula with an explicit first and second derivatives. This fact allows us to write the entries of the tangent stiffness matrix explicitly thereby saving computational costs during the assembly of the tangent stiffness matrix. We validate our approach against classical continuum mechanics for the linear elastic material behavior. In addition, we compare our approach to a state‐based peridynamic model that uses standard numerical derivations to assemble the tangent stiffness matrix. The numerical experiments show that for elastic material behavior our approach agrees with both classical continuum mechanics and the state‐based model. The fracture model is applied to produce a fracture simulation for a ASTM E8 like tension test. We conclude with an example of crack growth in a pre‐cracked square plate. For the pre‐cracked plate, we investigated load in force (soft loading) and load in displacement (hard loading). Our approach is novel in that only bond softening is used as opposed to bond breaking. For the fracture simulation we have shown that our approach works with and without initial damage for two common test problems.

The Effect of GTAW Welding Current on the Strength of AISI Steel 1045

Welding is a process of joining materials by melting metal at high temperatures. Gas Tungsten Arc Welding (GTAW) is one of welding method to join metals. This welding process will affect the mechanical properties of a material. So, it is necessary to conduct a study on changes in mechanical properties that occur. This study aims to determine the mechanical properties of AISI 1045 medium carbon steel using the GTAW welding process with a current variation of 80 A and 100 A. The welding was used the AWS EWTh-1 tungsten electrode and ER70S-G filler wire. The type of connection was used a butt weld joint and a single V groove seam with an angle of 60o. The standard of ASTM E8 was used for the manufacture of tensile test specimens. The results of tensile testing with welding current of 80 A was obtained an average stress of 518.463021 N/mm2 and the strain of 19.55%. For welding with a current of 100 A, the average stress was 548.814727 N/mm2 and the strain of 26.44%. Based on the fracture that occurred in the specimen, the critical area for fracture was the Heat Affecting Zone (HAZ), which the area has undergone a phase change during the cooling process. The weld area of connection part in the welding process has higher strength than the HAZ area.

Experimental research on the fatigue crack growth behaviour of Q420C

The lack of test data on the fatigue crack growth behaviour of Q420C steel affects its application in the field of wind power engineering. To fill this gap, this paper carried out an experimental study and theoretical analysis of the fatigue crack propagation behaviour of Q420C steel under constant amplitude. Six compact tension specimens were separately tested under six loading conditions comprising two maximum loads (Fmax = 8 kN or 10 kN) and three load ratios (R = 0.1, 0.3, or 0.5). The test results show that for the two crack growth rate calculation methods given by the ASTM E647–15, the secant method provides large discrete results, while the incremental polynomial method can obtain a relatively smooth rate curve. In addition, for the incremental polynomial method, the normalisation of the number of cycles in the ASTM E647–15 should not be used to achieve acceptable results. The rate curves of Q420C steel show a clear load ratio effect. Quantitative analysis of the effect of load ratios has shown that two-parameter models based on ‘unified theory’, such as Walker's model, can accurately describe the effect of load ratios. However, the theory of plasticity-induced crack closure cannot account for the effect of load ratios, as the crack opening load Fop is less than the minimum load Fmin for load ratios greater than 0.1. Finally, a comparison is carried out against the predictions by BS7910; results verify the applicability of BS7910 to Q420C steel material and demonstrate the different degrees of conservatism of all recommended design curves in BS7910.

Effects of Fixture Configurations and Weld Strength Mismatch on J-Integral Calculation Procedure for SE(B) Specimens.

This work presents the development of a J-integral estimation procedure for deep and shallow cracked bend specimens based upon plastic ηpl factors for a butt weld made in an S690 QL high strength low alloyed steel. Experimental procedures include the characterization of average material properties by tensile testing and evaluation of base and weld metal resistance to stable tearing by fracture testing of square SE(B) specimens containing a weld centerline notch. J-integral has been estimated from plastic work using a single specimen approach and the normalization data reduction technique. A comprehensive parametric finite element study has been conducted to calibrate plastic factor ηpl and geometry factor λ for various fixture and weld configurations, while a corresponding plastic factor γpl was computed on the basis of the former two. The modified ηpl and γpl factors were then incorporated in the J computation procedure given by the ASTM E1820 standard, for evaluation of the plastic component of J and its corresponding correction due to crack growth, respectively. Two kinds of J-R curves were computed on the basis of modified and standard ηpl and γpl factors, where the latter are given by ASTM E1820. A comparison of produced J-R curves for the base material revealed that variations in specimen fixtures can lead to ≈10% overestimation of computed fracture toughness JIc. Furthermore, a comparison of J-R curves for overmatched single-material idealized welds revealed that the application of standard ηpl and γpl factors can lead to the overestimation of computed fracture toughness JIc by more than 10%. Similar observations are made for undermatched single material idealized welds, where fracture toughness JIc is overestimated by ≈5%.

Electronic Speckle Pattern Interferometry for fatigue crack monitoring

This study aims to monitor the fatigue crack tip through a contactless optical method. A Middle Tension (MT) specimen is initially prepared by submitted it to a cyclic fatigue loading, in order to generate a crack with a specified length. Then, the cracked specimen is statically loaded under a uniaxial tensile condition, and Electronic Speckle Pattern Interferometry (ESPI) is employed to monitor the crack tip. During specimen loading with incremental force values, the behavior of the cracked area is monitored, with displacement and deformation fields acquired for each load increment. The obtained data is used to calculate fracture parameters, such as the Stress Intensity Factor (SIF). For that purpose, an overdeterministic algorithm was developed to calculate SIFs for each measured crack length. The main contribution of the present work is the adoption of a high-resolution optical contactless technique to monitor the fatigue crack tip. The obtained SIF values are compared to the reference solution proposed by ASTM E647 and an acceptable agreement has been verified.

Experimental study on fatigue crack propagation of octet-truss lattice

Orientation effects on fatigue crack growth rates of octet-truss lattice were studied using experimental method in this research. In order to perform the fatigue test, octet-truss lattices in different orientations were 3D printed into compact tension specimen geometry using photopolymer. The fatigue crack paths for different orientations lattices were obtained from the experiment and compared with each other. The fatigue crack growth rates of lattices in different orientations were calculated using compliance method suggested by ASTM E647. The experimental results show that orientation-Z lattice has the greatest resistance to fatigue crack propagation.

Evaluation of the T0 reference temperature for an ultra high strength martensitic steel

This work conducts an exploratory evaluation of the brittle fracture behavior for a high-strength martensitic steel using conventional three-point bend SE(B) specimens. A primary purpose of this study is to verify the effectiveness of the Master Curve methodology in providing a reliable estimate of the reference temperature (T0) derived from fracture toughness data sets measured in the ductile-to-brittle transition region (DBT) of an ultra high strength, low alloy martensitic steel. Fracture toughness testing conducted on three-point bend SE(B) specimens at different test temperatures in the DBT region provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc, and its corresponding KJc-values for the tested material. While this class of ultra high strength steel having a martensitic microstructure is currently beyond the reach of ASTM E1921, the analyses described here show that the predicted normalized curves of median fracture toughness vs. temperature are in good agreement with the experimental measurements.

Structural steel crack propagation experimental and numerical analysis

This paper presents an investigation on the crack propagation testing for three grades of structural steel material. The methodology uses experimental analysis with a test setup based on the ASTM E647 standard and a compact tension (CT) test piece, and, finite element analyses (FEA) for crack propagation based on the ANSYS separating, morphing and adaptive remeshing (SMART) tool. The FEA CT modelling is first used to develop front face compliance functions to relate the crack mouth opening displacement (CMOD) to the crack length. A set of CT test pieces were manufactured and then cyclically loaded on an Instron 8801 load frame and CMOD was measured against number of cycles. The steel material fracture mechanics based fatigue property was then estimated giving the crack growth rates for the Paris Law. The FEA models were then updated with the measured Paris Law coefficients and a SMART fatigue analysis was performed numerically and compared with the experimental results. The study showed that a hybrid numerical experimental methodology can be used to estimate fatigue crack growth material properties successfully with reasonable accuracy in a controlled laboratory environment.

Calibration and validation of extended back-face strain compliance for a wide range of crack lengths in SENB-4P specimens

Compliance equations based on back-face strain or crack mouth opening displacement, and potential drop techniques are widely used to calculate fatigue crack growth rate. Standard ASTM E647 for fatigue crack growth rate testing does not include compliance based equations for single edge notched four-point bending (SENB-4P) specimens. Equations developed based on finite element (FE) analysis have been reported in literature; however, they are limited to the long crack propagation regime (i.e., relative crack length ratios a/W > 0.15). No compliance relations for crack growth in the physically short crack regime were found in literature. This work reports on a complementary numerical-experimental study towards the development of compliance equations with an extended application range in terms of relative crack length. FE simulations have been used to calibrate a back-face strain compliance equation for calculation of relative crack length in the range 0.05 ≤ a/W ≤ 0.5 for SENB-4P specimens. Four point bending fatigue tests were performed on SENB specimens extracted from 50 mm thick welded steel plates. Direct current potential drop (DCPD) for crack monitoring was used as benchmark and validation of the crack lengths determined from a back-face strain gage.

Fracture toughness evaluation of 37CrNi3MoVE steel used for high-pressure air storage cylinder

The air storage cylinders, forming part of the impulse air system for submarine, are high-pressure steel cylinders dome-shaped at each end. To prevent the risk of cylinders rupture, the fracture toughness of cylinders is necessary to be tested. The three-point bending samples used in the fracture toughness experiment were taken from a cylinder made of 37CrNi3MoVE steel. With the consideration of the effect of the manufacturing process, both axial specimens and circumferential specimens were sampled, and the fracture toughness was compared. The effective data obtained from fracture toughness experiments were processed by different standards, such as ISO 12135 standard and ASTM E1820 standard. The fracture surface is analyzed from macroscopic and microscopic perspectives. From the test results of circumferential fracture toughness and axial fracture toughness, it can be clearly seen that under the influence of the processing technology, the circumferential fracture toughness of the cylinder of the high-pressure gas cylinder is smaller than the circumferential fracture toughness. Finally, comparing the fracture toughness values obtained by the ASTM E1820 standard with the fracture toughness values obtained by the ISO 12135 standard, it is found that the fracture toughness values obtained under the ASTM E1820 standard are all greater than the fracture toughness values obtained by the ISO 12135 standard.

Effect of process parameters on the mechanical properties of a Titanium alloy fabricated by Electron Beam Melting (EBM)

Electron Beam Melting is a layer-by-layer additive manufacturing technique which proved to be very efficient and versatile in the fabrication of medical devices and automotive or aerospace components. Due to the highly innovative character of the technology, its potential is not yet fully exploited and a comprehensive understanding of how the different processing parameters may affect the mechanical performance of the resulting materials still deserves to be achieved. Tensile tests on a Titanium alloy (Ti-6Al-4V-ELI) are ran at static rates for investigating the effects of different fabrication parameters on the material response, namely the speed function, the line offset, the focus offset, the number of contours and the horizontal-vertical growing direction of the specimens. A combination of such parameters is identified as a “process setup” and different setups are adopted for producing corresponding series of specimens, machined after fabrication according to ASTM F2924 and ASTM E8 regulations. The experimental procedure relies on enhanced true stress-true strain data based on the optical measurement of the neck cross section of the specimen, as an alternative to the traditional elongation-based approach to the true stress-true strain evaluation. This approach allows to better highlight the effects of the different process setups on the material performance, by focusing on the most stressed/strained material points within the overall specimen volume. The true curves allow to relate the material performance in terms of both strength and ductility to each process setup, allowing to outline the influence of single/combined fabrication parameters on the two above performance indicators.

KARAKTERISTIK ENGINE MOUNTING PADA TEMPERATUR AUSTENISASI TERHADAP SIFAT MEKANIS DAN STRUKTUR MIKRO

Engine mounting is one of the car component which is has optimize function to obtain thesystem in the car is extremely perfect. The engine mounting has to be have behavior ductile by strongestenough to support the car engine whether in rest and moving position. To obtain car engine mountingwhich has these function it has to be treated by treatment. The method was used by using Heat TreatmentSystem which we were Hardening and Tempering. Heat treatment of engine mounting is needed toanalyze the microstructure and mechanical properties of low carbon steel used. Tests carried out attemperatures of 800oC, 850oC, 900oC and normal conditions without heat treatment. Then continued withimpact charpy testing, vickers hardness testing, microstructure observation using microscope and SEM.The tests are carried out in accordance with ASTM E23, ASTM E92, ASTM A370 standards. The Vickerstest results provide the lowest HV value of 118.7Hv at 900oC, while the normal condition is at 137.409Hv.The charpy impact test results give the lowest value of 0.06 j / mm2 under normal conditions, while at900oC at 0.0962 j / mm2. The results with microscopy and SEM, the greater the temperature given to heattreatment, the less pearlite will be, while the amount of ferrite and austenite increases which makes theengine mounting more toughness.

Functionally graded materials for marine risers by additive manufacturing for high-temperature applications: Experimental investigations

In an offshore environment, marine risers are subjected to high environmental loads caused due to axial tension, wave, and current action. The hydrocarbons flowing through these marine risers put the marine riser under a continuous threat of corrosion. In this research, duplex stainless steel, a highly corrosion-resistant alloy, is functionally graded with carbon-manganese steel and the inner layer, providing structural and functional properties to the newly developed material. An experimental investigation on using functionally graded material for a marine riser application is carried out, testing its strength and durability. The mechanical properties and durability aspects are compared with that of the conventional X52 Carbon Manganese steel, a common candidate for marine risers. Wire Arc Additive Manufacturing (WAAM) is used to fabricate the FGM in the lab scale. WAAM is economical and possesses high deposition rates. ASTM E8 tensile test specimens are cut out from the FGM build to determine the mechanical properties. Based on the experimental studies carried out, it is seen that FGM shows about 11% and 25% enhanced yield strength and ultimate strength, respectively. The yield strength and elongation at a high temperature of the FGM material is close to that of X52 at room temperature. In contrast, the ultimate strength is higher, which proves its suitability for high-temperature applications. It also possesses improved durability due to the innate corrosion resistance of duplex stainless steel. The proposed FGM is seen as an effective alternate candidate for marine risers with enhanced structural properties and durability characteristics.

On The Role of Environment on Tensile Response and Fracture Behavior of A High Strength Alloy Steel

In this paper, the influence of exposure to an aggressive environment and concomitant degradation due to corrosion on tensile properties and fracture behavior of a high strength alloy steel in the fully annealed condition is presented and discussed. Cylindrical specimens, conforming to the specifications detailed in American Society for Testing and Materials standard (ASTM E8), were prepared for purpose of this study. A test method (GMW14872), developed by General Motors (Michigan, USA), for purpose of inducing controlled corrosion on the exposed surface, using a spray technique, was used for stimulating accelerated corrosion in an environmental chamber. This was done with the intent of establishing the influence of damage resulting from an exposure to aggressive environment on short-term mechanical properties of the chosen alloy steel. The deformed and failed samples of the chosen alloy steel were examined in a scanning electron microscope with the objective of establishing the conjoint influence of severity of environment, exposure time, nature of loading and intrinsic microstructural effects on tensile response and fracture behavior.

Critical assessment of the Rolfe-Novak CVN-KIC upper shelf correlation

The Rolfe-Novak correlation, was the first attempt to relate Charpy-V impact energy to a fracture mechanical material parameter. They tested 11 materials with variable yield strength, mainly in the range 1000–1300 MPa. This data was used to develop a correlation between Charpy-V notch energy and linear elastic fracture toughness KIc. The correlation is considered as base for high strength steel CVN-KIc correlations still today. The historic Rolfe – Novak fracture toughness data are here re-analyzed based on present understanding of fracture mechanics. It is shown that the original results were affected by different specimen sizes, shallow flaw effects, varying degree of plasticity and a non-systematic and non-standard engineering definition of fracture toughness KIc. The data has been re-evaluated in terms of the new size-independent fracture toughness definition KIsi, now described in ASTM E399. Based on the re-evaluation a new physically sound correlation between CVN and KIsi is determined. KIsi is shown to be close to KJIc according to ASTM E1820 for high strength steels.

Data‐driven approach to construct a fracture toughness master curve for ferritic steels based on tensile properties

Data‐driven approach to construct a fracture toughness master curve for ferritic steels based on tensile properties

Impact of Crack Growth Behavior on High Strength Steel and Sandwich Metal Panel Using the Constant Stress Ratio, Frequency and Thickness

The armoured vehicle uses a special solid steel that has a heavy vehicle ratio which causes the performance to decrease after being triggered by high velocity impact bullet on rescue missions thus experiencing the phenomenon of fatigue and unstable crack growth flow. In this study, an investigation on crack growth behaviour was carried out for sandwich metal panel and solid High Strength Steel (HSS) which has high ability in terms of residual life. Meanwhile, sandwiched metal panel contains HSS as face sheets and lightweight material as a solid core. The main objective of this study was to determine the crack growth behaviour on two types of structural material by applied frequency (f=10 Hz), stress ratio (R=0.1), and thickness (10 mm) as a constant parameter. The crack growth experiment used compact tension (CT) specimen as followed the ASTM E647 standard. The benchmark for establishing the crack growth behaviour is the (a-N) graph and the Paris law regime, da/dN against stress intensity in order to determine Paris constant (C and m). Based on the results, the sandwich metal panel is more applicable with the number cycle of N = 23300 with an increase in about 27% compared to solid HSS. It can be concluded that the sandwich metal is most practicable and affordable for using higher level of threat for hard armour vehicle panel.

Application of an Artificial Neural Network to Develop Fracture Toughness Predictor of Ferritic Steels Based on Tensile Test Results

Analyzing the structural integrity of ferritic steel structures subjected to large temperature variations requires the collection of the fracture toughness (KJc) of ferritic steels in the ductile-to-brittle transition region. Consequently, predicting KJc from minimal testing has been of interest for a long time. In this study, a Windows-ready KJc predictor based on tensile properties (specifically, yield stress σYSRT and tensile strength σBRT at room temperature (RT) and σYS at KJc prediction temperature) was developed by applying an artificial neural network (ANN) to 531 KJc data points. If the σYS temperature dependence can be adequately described using the Zerilli–Armstrong σYS master curve (MC), the necessary data for KJc prediction are reduced to σYSRT and σBRT. The developed KJc predictor successfully predicted KJc under arbitrary conditions. Compared with the existing ASTM E1921 KJc MC, the developed KJc predictor was especially effective in cases where σB/σYS of the material was larger than that of RPV steel.