Sub-size Specimens Research Articles

Constitutive description of distortional hardening in a TWIP steel: Addressing differential hardening under nonlinear strain paths

The present study aims to describe the in-plane differential hardening behaviour of the twinning induced plasticity sheet metal TWIP980 under various stress states, including uniaxial tension, plane strain tension, and pure shear, particularly focusing on non-proportional loading conditions. The true stress–strain curves for each stress states were inversely obtained from their corresponding load–displacement curves and modeled using a differential hardening model that can accommodate all three stress states simultaneously on plastic work (density) contours. For non-proportional loading tests, oversize specimens were initially stretched under uniaxial tension up to a 10% pre-strain along the rolling, diagonal, and transverse directions, respectively. Subsequently, the three stress states were applied to subsize specimens cut from the deformed oversize specimens along the rolling direction. To describe the hardening behaviours during non-proportional loading, a homogeneous anisotropic hardening model was adopted and calibrated using two-step uniaxial tension tests. Subsequently, the differential hardening model was successfully incorporated into the homogeneous anisotropic hardening model to describe both the differential hardening and the strain path change-induced hardening behaviours under the two-step loadings, i.e., uniaxial tension to pure shear and uniaxial tension to plane strain tension. Both experimental and simulation results underscore the necessity to consider differential hardening under non-proportional loading conditions.

Investigation on fracture resistance behaviour of dissimilar metal weld joint of modified 9Cr–1Mo steel and AISI 316LN SS

Fracture behavior of dissimilar metal weld joint consisting of mod. 9Cr–1Mo steel, AISI 316LN stainless steel, Inconel 82 butter layer and Inconel 182 weld has been investigated through experiments and FE simulations. The metallographic studies on weld joint and its interfaces have been carried out to determine the influence of microstructure on tensile and fracture properties. Tensile properties of different weld regions viz., weld metal, butter layer and HAZ have been evaluated using sub-size specimens. Fracture resistance behavior of weld joint has been studied through testing of compact type specimens with initial cracks machined at different locations. The plastic η factors for estimation of J-R curve have been obtained using FE analysis for crack in different regions viz., weld metal, butter layer and HAZ. Crack in weld metal exhibits lower fracture resistance as compared to butter layer and HAZ. Further, the constraint acting on crack and its susceptibility for deviation have been discussed in terms of stress triaxiality ahead of crack tip.

Mechanical characterization of hydrogen embrittlement in a gaseous environment: An innovative test setup using sub-size specimens

Hydrogen embrittlement (HE) of steels in the presence of gaseous hydrogen poses a challenge to the safe transportation of hydrogen through pipelines. The use of sub-size specimens machined from coupons extracted from pipes is proposed for monitoring the degradation of material properties over the entire operational life. The objective of this paper is to present a methodology based on the sub-size specimens using a machine developed to operate with a small volume of gaseous hydrogen, up to a pressure of 250 bars, and test control using Edge Tracing (ET) technique. Tensile and toughness mini-specimens extracted from a E355 mod. steel grade are employed for this study. Reliable results are obtained using tensile mini-specimens with 1.2 and 2.4 mm diameters, tested under both air and gaseous H2. Toughness tests are conducted using mini-specimens with a thickness of 5 mm. These tests monitored the Load Line Opening Displacement (LLOD) and the Opening Angle are monitored during the tests through ET technique, allowing for the determination of J−Δa and δ−Δa plots under both air and gaseous H2 conditions. The results uncover the impact of H2 pressure and specimen dimensions on hydrogen embrittlement, leading to the computation of Hydrogen Embrittlement Indexes through various methods. The insights gained from this study establish the necessary foundations for the utilization of mini-specimens in characterizing hydrogen embrittlement.

Sub-size specimen testing for near-threshold fatigue crack behaviour of additively manufactured Ti-6Al-4V

Sub-size specimen testing offers a potentially elegant solution to accompany fatigue life assessments in determining vital fatigue parameters such as effective fatigue crack growth propagation thresholds (ΔKth,eff). Additively manufactured parts stand to benefit from this in potential build-by-build fatigue validation without foregoing process-inherent material saving and low lead times. In this study, sub-size Laser Powder Bed Fusion (LPBF) produced Ti-6Al-4 V SENB specimens built in two orientations with stress relieved and annealed material states are considered. Scanning electron microscopy with electron backscatter diffraction is used to consider both meso- and microstructural features, complimented by digital image correlation (DIC) for determining local stress intensity and triaxiality around the crack tip. Results show inconsistent near-threshold fatigue behaviour linked to the microstructure of annealed material, where the fatigue threshold in sub-size specimens is reduced. Furthermore, reducing specimen size influences both in- and out-of-plane crack tip constraint, with higher constraint experienced by the sub-size specimens. Overall, this study presents and discusses the domain and suitability in using sub-size specimen FCGR threshold testing for LPBF produced Ti-6Al-4 V builds considering their unique meso- and microstructural features.

Assessment of Additive Manufactured IN 625's Tensile Strength Based on Nonstandard Specimens.

The study aimed to evaluate the tensile strength of additively manufactured (AMed) IN 625 using sub-sized test pieces and compare them to standard specimens. Cylindrical round coupons of varying diameters were manufactured along the Z-axis using the laser powder bed fusion technique and subjected to heat treatment. The simulation of the alloy solidification predicted the formation of several intermetallics and carbides under equilibrium conditions (slow cooling), apart from the γ phase (FCC). Sub-sized tensile specimens with different gauge diameters were machined from the coupons and tensile tested at ambient temperature. The results showed that sub-sized specimens exhibited lower tensile and yield strengths compared to standard specimens, but still higher than the minimum requirements of the relevant ASTM standard for AMed IN 625. The lower strength was attributed to the "size effect" of the test specimens. Fracture surfaces of the sub-sized test specimens exhibit a mixed character, combining cleavage and microvoid coalescence, with improved ductility compared to standard test pieces. The study highlights the importance of adapting characterization methods to the particularities of manufactured parts, including reduced thicknesses that make sampling standard-size specimens impractical. It concludes that sub-sized specimens are valuable for quality control and verifying compliance with requirements of AMed IN 625 tensile properties.

Using post-processing heat treatments to elucidate precipitate strengthening of additively manufactured superalloy 718

The poor machinability and extensive work hardening of Ni-based superalloys makes additive manufacturing an attractive option for producing geometrically complex components with distinct microstructures. Although previous studies show recovery of high strength at room temperature, very few studies demonstrate successful properties at elevated temperatures required for industrial applications. The objectives of this study are to present a post-build heat treatment for high strength across a wide temperature range, determine the strength contribution of nanoscale precipitating phases to the overall mechanical properties of superalloy 718, and from these, provide a comprehensive microstructure-property relationship for wrought and AM 718 to guide efforts to simulate the properties of AM components. Laser powder bed fusion–produced superalloy 718 was characterized at multiple length scales using scanning electron microscopy and transmission electron microscopy in the as-built condition and with multiple heat treatments designed to form combinations of γʹ, γʺ, and δ precipitates. Uniaxial tensile tests performed from room temperature to 600 °C on subsize specimens determined the yield strength, elastic modulus, ultimate tensile strength, fracture stress, and uniform elongation. Precipitates in this work proved to be weak barriers to dislocation motion through a dispersed barrier model, but they provided strength to the alloy through their consistent high density. The relative contribution to the yield strength from γʺ remained consistent between 48–57% of the total strength up to 600 °C, the primary influence on the high temperature strength of superalloy 718. The strength factors for γʺ and δ precipitates were found to trend inversely with tensile test temperature and may be attributable to the differences in precipitate coherency. A post-build heat treatment is recommended to maintain high strength at elevated temperatures. A quantitative microstructure-property relationship, dependent on precipitate size, density, and morphology, was derived and can estimate the yield strength across a wide temperature range applicable to the operational regimes for superalloy 718.

Influence of Material Thickness on the Ductile Fracture of Steel Plates for Shipbuilding

Abstract In the shipbuilding industry, the risk of brittle fractures is relatively high because some units operate in arctic or subarctic zones and use high thickness (up to 100 mm) steel plates in their structures. This risk is limited by employing certified materials with a specific impact strength, determined using the Charpy method (for a given design temperature) and by exercising control over the welding processes (technology qualification, production supervision, and non-destructive tests). However, for offshore constructions, such requirements may prove insufficient. For this reason, regulations employed in constructing offshore structures require conducting crack tip opening displacement (CTOD) tests for steel and welded joints with thicknesses exceeding 40 mm for high tensile strength steel and 50 mm for other steel types. Since classification codes do not accept the results of CTOD tests conducted on specimens of sub-sized dimensions, the problem of theoretically modelling the steel construction destruction process is of key importance, as laboratory tests for notched elements of considerable thickness (100 mm and higher) are costly and problems stemming from high loads and a wide range of recorded parameters are not uncommon. The aim of this research is to find a relationship between material thickness and CTOD value, by establishing and verifying a numerical model that allows recalculating a result obtained on a sub-size specimen to a full- size specimen for a ductile fracture mode. This work presents results and conclusions from numerical modelling and compares them with laboratory test results of the elastic-plastic properties of high thickness steel, typically used in offshore applications.

Investigation of the deleterious effects of low-temperature and hygrothermal aging conditions on the mixed-mode fracture resistance of epoxy resin using a short-beam bend specimen

The effect of different environmental aging conditions on the mixed-mode fracture behavior of epoxy resins was investigated using a sub-size specimen. The short-beam bend (SBB) specimens with different crack inclination angles were manufactured and subjected to low-temperature (-71 °C), hygrothermal (immersion in deionized water at 60 °C) and room-temperature conditions. The deleterious effect of low-temperature and hygrothermal aging conditions on the mode-I, mode-II and mixed-mode I/II fracture responses of the epoxy resin was studied by testing the aged and unaged SBB specimens under three-point bend loading. The experimental results indicated that the hygrothermal aging condition, with a reduction of 49% in the effective fracture toughness, imposed a more severe deleterious effect on the fracture response of the specimens in comparison with the low-temperature condition with a decrease of 35% in the effective fracture toughness. The generalized maximum tangential stress criterion was used to predict the fracture loads of the aged and unaged specimens. Moreover, optical microscopy and scanning electron microscopy techniques were employed to assess the fracture surfaces of the specimens aged under different conditions.

Dissimilar joining of the martensitic grade P91 and Incoloy 800HT alloy for AUSC boiler application: Microstructure, mechanical properties and residual stresses

The presented study intends to analyze the microstructure and corresponding mechanical characteristics of P91 and Incoloy 800HT dissimilar welded joint (DWJ). The thermo-physical property differences between P91 and Incoloy 800HT arise due to their complex alloying composition, making their weldability difficult. Incoloy 800HT is difficult to weld due to its high susceptibility to solidification cracking. The recommended nickel-based filler metals for welding Incoloy 800HT were employed to weld P91 and Incoloy 800HT using conventional gas tungsten arc welding (GTAW). The welded joint morphology and characteristics were analyzed in as-welded (AW) and post-weld heat treatment (PWHT) conditions. The PWHT was performed to observe changes in microstructural inhomogeneity and residual stress relaxation in weld after the heat treatment. An electron probe microanalyzer (EPMA) was utilized to observe the distribution and segregation of elements in different weld regions. The deep hole drill technique was employed to find the distribution of bi-axial residual stresses in the weld fusion zone (WFZ) and heat-affected zone (HAZ) of base metals in both AW and PWHT conditions. The two nickel-based fillers, ERNiCr-3 and ERNiCrMo-3, were employed, and their weld characteristics were compared. The mechanical strength of ERNiCr-3 filler-based DWJ was found superior to ERNiCrMo-3 filler-based DWJ. The standard AW and PWHT ERNiCr-3 filler-based DWJ tensile specimen failed from Incoloy 800HT base metal with an ultimate tensile strength (UTS) of 570 ± 4 MPa and 650 ± 4 MPa, respectively. The ERNiCrMo-3 filler-based DWJ obtained the highest UTS of 679 MPa after PWHT in a subsize specimen. The microhardness for ERNiCrMo-3 WFZ was found to be higher than ERNiCr-3 WFZ microhardness, and PWHT successfully tempered the P91 HAZ. Further, the impact toughness for the ERNiCr-3 WFZ in AW condition was 86 ± 3 J and PWHT did not provide any significant improvements, while ERNiCrMo-3 WFZ had an impact toughness of 47 ± 10 J in AW state and 41 ± 10 J in PWHT state. Thus, a successful weld characteristic study of defect-free P91 and Incoloy 800HT DWJ was completed, and ERNiCr-3 filler was concluded to be an optimum choice of filler to make the DWJ between P91 and Incoloy 800HT.

Application of Metallographic Investigation in Development of Sub-Sized Specimen Testing Techniques

Currently, there is a growing interest in testing of mechanical properties using sub-sized samples. Using these methods, it is possible to measure the current mechanical properties of the component without the necessity of shutting down the device. This is advantageous in the cases, when the residual life (especially in the energy sector) needs to be evaluated. Another advantage of this method is that due to the very small dimensions of the extracted piece of material, only the local properties of the component are tested. Thus, the miniature samples can be extracted from areas that are critical for material failure, e.g. in the transition area of welded joints and thin-walled pipes, in a direction other than axial (for axial direction standard tensile test can be used). Another small specimen application can be found in the development of new materials. Modern materials (e.g. additively processed materials) are usually highly expensive, so miniature samples are an ideal solution. It was observed that the MTT results are fully comparable with the results on standard test pieces without the need for correlation. Mini-Charpy samples (3×4×27 mm) were used to determine transition temperature FATT. In this case a correlation relationship between the Mini- Charpy and standard sample Charpy (10×10×55 mm) constant C = 60 was successfully found

Study on Intrinsic Influence Law of Specimen Size and Loading Speed on Charpy Impact Test.

Charpy impact energy/impact toughness is closely related to external factors such as specimen size. However, when the sample size is small, the linear conversion relationship between the Charpy impact energy of the sub-size and full-size Charpy specimens does not hold; the Charpy impact toughness varies with the size of the specimen and other factors. This indicates that studying the internal influence of external factors on impact energy or impact toughness is the key to accurately understanding and evaluating the toughness and brittleness of materials. In this paper, the effects of strain rate on the flow behavior and the effects of stress triaxiality on the fracture behavior of 30CrMnSiNi2A high-strength steel were investigated using quasi-static smooth bar and notched bar uniaxial tensile tests and Split Hopkinson Tensile Bar (SHTP). Based on the flow behavior and strain rate dependences of the yield behavior, a modified JC model was established to describe the flow behavior and strain rate behavior. Charpy impact tests were simulated using the modified JC model and JC failure model with the determined parameters. Reasonable agreements between the simulation and experimental results have been achieved, and the validity of the model was proved. According to the simulation results, the impact energy was divided into crack initiation energy, crack stability propagation energy and crack instability propagation energy. On this basis, the effects of striker velocity and specimen width on the energy and characteristic load of each part were studied. The results show that each part of the impact energy has a negligible dependence on the hammer velocity, but there is a significantly different positive linear relationship with the width of the sample. The energy increment of each part also showed an inverse correlation with the increase in the sample width. The findings reveal that the internal mechanism of Charpy impact toughness decreases with the increase in sample width; to a certain extent, it also reveals the internal reason why the linear transformation relationship of Charpy impact energy between sub-size specimens and standard specimens is not established when the specimens are small. The analytical method and results presented in this paper can provide a reference for the study of the dynamic behavior of high-strength steel, the relationship between material properties and sample size, and the elastic–plastic impact dynamic design.

Experimental study on cold forming process of 7075 aluminum alloy in W temper

7075 aluminum alloy (AA7075) in W temper, owning lower strength and higher elongation, demonstrates better formability at room temperature than the material in peak-aged T6 temper. In this work, post-forming artificial aging is used to restore the comprehensive mechanical properties of AA7075 in W-temper. A shortened artificial aging process with lower cost than the common peak aging process is proposed with the consideration of paint baking in automotive manufacturing. The effects of shortened artificial aging, peak aging, and paint baking on the mechanical properties of AA7075 are studied. Results show that the ultimate tensile strengths of AA7075 with peak aging (120 ℃/24 h) and shortened artificial aging (120 ℃/5 h) followed by paint baking (180 ℃/20 min) are both 540 MPa, and the fracture elongation is 15% and 16% respectively. Compared with peak aging, the overall mechanical property of AA7075 with shortened artificial aging treatment is slightly improved after paint baking, while the aging time is shortened by 79%, which greatly improves the production efficiency. A case study of W-temper forming of an anti-collision beam in vehicle side door is conducted. Cold forming experiments, post-forming heat treatments, and mechanical testing such as three-point bending and uniaxial tensile testing of sub-sized specimens are carried out. After paint baking, the tensile strength and maximum bending load of the AA7075 anti-collision door beams with peak aging and shortened artificial aging treatments are comparable, and a higher product of strength and elongation (about 7% increase) is achieved by shortened artificial aging. In addition, the related mechanism is discussed in terms of precipitation during peak aging, shortened artificial aging and paint baking.

Thermo-Mechanical Distortion of Tungsten Coated Steel During High-Heat Flux Testing Using Plasma-Arc Lamps

An experimental setup and a test section were designed and fabricated for high heat flux testing (HHFT) of neutron-irradiated specimens using water-wall plasma-arc lamps. Because of the radiological considerations and limitations of reactor irradiation, the size of the test articles was limited to disks less than 10 mm in diameter. The specimen was clamped onto an actively cooled block, and clamping allowed the insertion of several thermocouples on the back surface of the specimen through a copper (Cu) block. Five vacuum plasma sprayed tungsten (W)–coated F82H steel specimens were subjected to HHFT. Surface profilometry measurements, which were conducted after HHFT, revealed central bowing of the top W surface. This type of residual distortion occurred for all of the specimens, and the larger the specimens were, the larger was the distortion. In an attempt to understand specimen distortion and address the science questions related to the testing of subsize specimens during HHFT, a simplified thermo-mechanical model was developed. By using a measured temperature in the Cu as an isothermal boundary condition, the model eliminated the need for coupling cooling fluid flow models with stress models, greatly simplifying the analysis. The main variable in the proposed model is hC, i.e., the thermal contact conductance between the F82H and the Cu washer. Inelastic properties, including hardening properties, were considered for F82H steel and Cu. Numerical simulation results demonstrated a buildup of residual deformation during HHFT and a very complex state of stress and deformation during typical heat flux (HF) cycling. Hoop stress evolution during a high heat flux cycle reveals that F82H at an interface with W would be mainly in compression during HF application and experienced a transition to a tension state during cooldown. Also, specimen distortion evolves during each HF cycle, as the specimen bows downward during HF application and upward during the cooldown period between HF cycles. The final specimen distortion, i.e., upward bowing of the specimen center, was qualitatively predicted for hC values of 4000 to 5000 W/(m2·K). This hC range of values, for which bulging is obtained, is at the lower spectrum of the range of values for hC, consistent with the low thermal contact conductance expected from the unpolished F82H surface.

FRACture mechanics TEsting of irradiated RPV steels by means of SUb-sized Specimens: FRACTESUS PROJECT

This work presents the overall structure of the FRACTESUS project and the progress carried out so far. The project is part of the EURATOM work programme 2019-2020, topic NFRP-04: Innovation for Generation II and III reactors. The project developments will contribute to the long-term safe operation of nuclear power plants, addressing the goals of the European Union in terms of sustainable and green energy, where the decarbonisation of the energy system is a priority. FRACTESUS intends to demonstrate the reliability of measuring the fracture toughness of reactor pressure vessel steels by means of sub-sized specimens (e.g., 0.16 CT or mini CT specimens). This will allow, among others, to notably increase the number of specimens available in the surveillance programs of the nuclear power plants.

On tensile fracture of a brittle rock

Three-point bending experiments were performed to observe mode-I fracture in a series of geometrically similar, center-notched rectangular beams composed of Sioux quartzite, a stiff, hard rock with flexural tensile strength σt = 32 MPa. Acoustic emission (AE) were recorded and microcrack locations were determined to track crack growth. Digital image correlation (DIC) was used to augment the acoustic emission data. Detailed observations indicate that (i) subsize specimens of Sioux quartzite follow a size effect law, and (ii) linear elastic fracture mechanics (LEFM) can be used to explain crack growth for large specimens of Sioux quartzite, with fracture toughness KIc = 2.2 MPa m. In particular, crack lengths based on compliance from LEFM are in good agreement with those obtained from AE and DIC suggesting a small process zone for specimens with beam depth >20 times the characteristic length = (KIc/σt)2. Further, crack velocities predicted from LEFM matched those estimated from AE locations of crack tip position with time. For sufficiently sized specimens, these observations indicate that LEFM can be used to describe fracture in this stiff, hard rock.

Determining Forming Limit Diagrams Using Sub-Sized Specimen Geometry and Comparing FLD Evaluation Methods

Sheet metal forming boundaries are established using the forming limit diagram (FLD). The Nakajima and Marciniak tests, which are based on stretching a material using a punch, are the most commonly used methods for determining the FLD or fracture forming limit diagram (FFLD). The results are usually evaluated by calculating local strain, strain rates, specimen thickness reduction or fracture strain. When the amount of experimental material is insufficient, miniaturization of the testing specimens may be a solution. However, the interchangeability of the results for standard and miniaturized specimens has not been proven yet. In this study, the Nakajima tests were performed using standard and sub-sized specimens made of manganese–boron steel 22MnB5, commonly used in the automotive industry. Afterwards, four FLD/FFLD evaluation methods were applied and compared. The miniaturized specimens yielded higher strain values, which was explained by the varied ratio of material thickness/punch diameter and different bending conditions. The highest compliance of the results was recorded for the standard and miniaturized FFLD.

Relationship between mechanical properties in 42SiCr and 42SiMn medium-carbon steels and austempering temperatures

Sheet metal forming boundaries are established using the forming limit diagram (FLD). The Nakajima and Marciniak tests, which are based on stretching a material using a punch, are the most commonly used methods for determining the FLD or fracture forming limit diagram (FFLD). The results are usually evaluated by calculating local strain, strain rates, specimen thickness reduction or fracture strain. When the amount of experimental material is insufficient, miniaturization of the testing specimens may be a solution. However, the interchangeability of the results for standard and miniaturized specimens has not been proven yet. In this study, the Nakajima tests were performed using standard and sub-sized specimens made of manganese–boron steel 22MnB5, commonly used in the automotive industry. Afterwards, four FLD/FFLD evaluation methods were applied and compared. The miniaturized specimens yielded higher strain values, which was explained by the varied ratio of material thickness/punch diameter and different bending conditions. The highest compliance of the results was recorded for the standard and miniaturized FFLD

Microstructural Influence on Mechanical Properties of a Lightweight Ultrahigh Strength Fe-18Mn-10Al-0.9C-5Ni (wt%) Steel

This study evaluates the role of thermomechanical processing and heat treatment on the microstructure and mechanical properties of a hot rolled, annealed, and aged Fe-18Mn-10Al-0.9C-5Ni (wt%) steel. The steel exhibited rapid age hardening kinetics when aged in the temperature range of 500–600 °C for up to 50 h, which has been shown in other work to be the result of B2 ordering in the ferrite and κ-carbide precipitation within the austenite matrix. The ultimate tensile strength increased from 1120 MPa in the annealed condition to 1230 MPa after 2 h of aging at 570 °C. Charpy V-notch toughness was evaluated at −40 °C in sub-sized specimens with a maximum in the annealed and quenched condition of 28.5 J in the L-T orientation.

Sub-sized and miniature CVN specimen conversion methodology

Presently most structural integrity assessment procedures still allow the use of Charpy-V notch impact tests as a measure of fracture toughness. The use is generally made through some more or less reliable correlations between standard Charpy-V notch energy and fracture toughness or tearing resistance. A problem arises if the structure has such a geometry that standard size Charpy-V notch specimens cannot be used. Application standards contain some guides on how to convert sub-sized specimen data to correspond to full size specimens, but these are often inaccurate and limited in their application range. Procedures like ASTM A370, BS7910 and API 579 give some advice on the use of sub-sized Charpy-V specimens but none of them cover the whole Charpy-V transition curve, nor all possible specimen dimensions. Here, a new simple procedure is presented. It is shown that it is applicable over the whole transition curve, thus enabling a point-wise conversion of sub-sized and miniature Charpy-V data to correspond to full size specimens. The new procedure is applicable for steel strengths ranging from 200 MPa to 1400 MPa.

Determination of Johnson–Cook parameters and evaluation of Charpy impact test performance for X80 pipeline steel

Controlling the Charpy impact toughness of materials is the key to the ductile fracture arrest design of pipelines. The finite element method based on Johnson–Cook (J-C) model has become an effective method to assist the experimental study of material impact toughness. In this paper, model parameters of J-C constitutive relation and damage parameters of J-C failure model for X80 pipeline steel have been determined experimentally from quasi-static uniaxial tension tests and Split Hopkinson Pressure Bar (SHPB) tests. Charpy impact test has been simulated using J-C constitutive and failure models with the determined parameters. Reasonable agreements between the simulation and experimental results have been achieved. On this basis, the effects of the pendulum velocity, specimen width and striker radius on Charpy impact test results are studied. The results show that pendulum velocity has negligible influence on Charpy impact test results; the maximum force and impact absorbed energy both have a highly linear relationship to specimen width; Charpy impact test is sensitive to striker geometry, the results measured by 2 mm-striker are obviously smaller than those of 8 mm-striker. Based on the above researches, the impact absorbed energy correlation model between sub-size specimens and standard full-size specimens, the test results transformation rules of the two strikers are established. The methods and results presented in this paper will provide references for dynamic behavior study, impact dynamic design, pipeline safety operation and risk assessment of high-grade pipeline steel.