Anisotropy Of Tensile Strength Research Articles

Inhomogeneity and anisotropy of Al-Zn-Mg-Cu alloy manufactured by wire arc additive manufacturing: microstructure, mechanical properties, stress corrosion cracking susceptibility

ABSTRACT In this study, Al-Zn-Mg-Cu alloy components were prepared using wire arc additive manufacturing (WAAM). Through multi-scale characterisation technology, performance testing and slow strain rate tensile (SSRT) testing, the microstructure, mechanical properties and stress corrosion cracking (SCC) susceptibility of WAAM Al-Zn-Mg-Cu components were studied, revealing the generation mechanism of inhomogeneity and anisotropy. The results show that with the increase of WAAM thermal cycles, the matrix precipitates (MPs), grain boundary precipitates (GBPs) and precipitation-free zones (PFZ) evolve in different paths and increase to varying degrees, resulting in performance decrease and increase in stress corrosion susceptibility, so the inhomogeneity is mainly attributed to differences in precipitated phases. The Inter-layer inclined to the scanning direction and the Inner-layer inclined to the building direction led to anisotropy in tensile strength and SCC behaviour, so the anisotropy is mainly attributed to the grain orientation and fracture mode.

Soluble and insoluble fractions of soy protein isolate affect the properties of its high-moisture extrudates

This research focused the impact of the variation in insoluble soy protein isolate (ISPI) and soluble soy protein isolate (SSPI) contents on the rheological properties of highly-concentrated SPI during extrusion-like conditions and the physiochemical, mechanical, and morphological characteristics of its extrudates. Results showed that increased ISPI content could resist great shear forces and increase the viscoelasticity of SPI samples. In addition, the increase of ISPI content in SPI samples also contributed to enhance the tensile strength and mechanical anisotropy, further created a distinct fibrous structures of extrudates. While higher SSPI content can form heat-induced reverseble aggregates via hydrophobic interaction and disulfide bonds, reduce the water mobility and facilitate the formation of a more uniform protein-water phase. The differences in solubility revealed the dominance of non-covalent bonds in ISS-40 extrudate (100% ISPI) and highlighted the important role of disulfide bonds in ISS-04 extrudate (100% SSPI). Possible mechanisms are proposed to explain the contrasting behavior of ISPI and SSPI under thermomechanical treatment. These insights explore the formation of protein multiphase system structures and offer valuable guidance for developing meat analogue products.

Anisotropy of Consolidation Yield Stress and Comparison with Anisotropy of Elastic Wave Velocity and Tensile Strength in Sedimentary Soft Rocks

Anisotropy of Consolidation Yield Stress and Comparison with Anisotropy of Elastic Wave Velocity and Tensile Strength in Sedimentary Soft Rocks

Mechanical characteristics of the ureter and clinical implications.

The ureteric wall is a complex multi-layered structure. The ureter shows variation in passive mechanical properties, histological morphology and insertion forces along the anatomical length. Ureter mechanical properties also vary depending on the direction of tensile testing and the anatomical region tested. Compliance is greatest in the proximal ureter and lower in the distal ureter, which contributes to the role of the ureter as a high-resistance sphincter. Similar to other human tissues, the ureteric wall remodels with age, resulting in changes to the mechanical properties. The passive mechanical properties of the ureter vary between species, and variation in tissue storage and testing methods limits comparison across some studies. Knowledge of the morphological and mechanical properties of the ureteric wall can aid in understanding urine transport and safety thresholds in surgical techniques. Indeed, various factors alter the forces required to insert access sheaths or scopes into the ureter, including sheath diameter, safety wires and medications. Future studies on human ureteric tissue both in vivo and ex vivo are required to understand the mechanical properties of the ureter and how forces influence these properties. Testing of instrument insertion forces in humans with a focus on defining safe upper limits and techniques to reduce trauma are also needed. Last, evaluation of dilatation limits in the mid and proximal ureter and clarification of tensile strength anisotropy in human specimens are necessary.

Effect of roll surface topography on microstructure and mechanical properties of 304 stainless steel ultra-thin strip

Since the thickness of ultra-thin strips of stainless steel is usually only at the micron level, the ratio of surface asperities to thickness significantly increases, the role of the material surface is prominent; thus, the influences of the working roll surface topography on the microstructure and mechanical properties of ultra-thin strips cannot be ignored. In this work, three kinds of rolls with different surface topographies obtained by grinding, polishing and sandblasting are used in a 20-high Sendzimir mill to roll ultra-thin strips of 304 stainless steel with thickness of 70 μm at different reduction rates. The surface morphology, microstructure, texture and mechanical properties of the steel strip are investigated. The results show that at the same reduction rate, the strip has the highest dislocation density, the smallest grain size and the highest tensile strength when rolled with a sandblasted roll; A polished roll can improve the mechanical strength while obtaining stainless steel ultra-thin strips with high elongation. In terms of roughness anisotropy, the surface roughness of steel strips rolled by a ground roll has obvious anisotropy. A sandblasted roll has the strongest influence on the diminution of the surface roughness anisotropy of steel strips. A polished roll also has a weakening function on surface roughness anisotropy, and the larger the reduction rate is, the more obvious the action. The texture intensity can be effectively minimized by weakening the surface roughness anisotropy, thus reducing the anisotropy index of mechanical properties of the ultra-thin strip, which is prominent at a small reduction rate. The tensile strength and elongation anisotropy index (IPA) of the ultra-thin strip rolled by a sandblasted roll are 55.68 % and 56.28 % of the strip rolled by a ground roll at a reduction rate of 5 %, respectively. It is suggested that the surface features, microstructure and mechanical properties of the strip can be modified by polishing and sandblasting the roll surface during the rolling process, which provides a reference for obtaining high-quality stainless steel ultra-thin strips in industrial production.

Compressive and Tensile Strength Anisotropy of Friable Sandstone and Thin-Bed Shale of the Pleistocene Erin Formation: Insights for Safe Operating Mud Weight Windows for Vertical and Horizontal Wells

Compressive and Tensile Strength Anisotropy of Friable Sandstone and Thin-Bed Shale of the Pleistocene Erin Formation: Insights for Safe Operating Mud Weight Windows for Vertical and Horizontal Wells

The Anisotropic Behavior of a Clay Shale: Strength, Hydro‐Mechanical Couplings and Failure Processes

AbstractMany rocks exhibit a structural composition, which leads to an anisotropic behavior of different properties. A proper understanding of the directional dependency of these properties is required to analyze and predict the failure behavior of the rock mass upon stress changes during many geo‐engineering applications. This study investigates the selected host rock for nuclear waste disposal in Switzerland, Opalinus Clay, for its anisotropic unconfined compressive and tensile strength, poromechanical response, and effective shear strength in an extensive laboratory testing campaign. The results show the lowest unconfined compressive strength at angles of 30°–45° between the bedding plane and the compressive load direction, whereby the lowest tensile strength is found to be normal to the bedding orientation. Triaxial consolidated‐undrained compression tests reveal an anisotropic poromechanical behavior as well as peak and residual effective strength values, which are largely controlled by the orientation of the bedding plane with respect to the maximum principal stress. The magnitude of excess pore water pressures and dilation are both functions of loading configuration. The comparison of peak strength values for different loading angles indicates that the lowest effective shear strength can be expected at a loading configuration of approximately 45° between bedding orientation and the loading axis. The variation in the hydro‐mechanical response is associated with the microstructure controlling the poroelasticity and the failure processes. The results provide a deeper understanding of failure in anisotropic rocks contributing to the development of constitutive models for predicting the rock mass response.

Numerical simulations of thermal fracturing in nuclear waste disposal

Regarding high-level nuclear waste (HLW) and spent fuel (SF) disposal, underground geological disposal is likely to be the most feasible and effective solution [1]. The coupled Thermo-Hydro-Mechanical (THM) behaviour of host rocks has been widely studied by laboratory tests, in-situ experiments and numerical analyses. In field experiments performed in underground laboratories, pore pressure generation and damage evolution have been observed. In this context, coupled THM numerical analyses can be an essential tool to better understand the coupled multiphysics behaviour of host rocks, buffer materials and canisters. In addition, large-scale field experiments provide a crucial opportunity to demonstrate understanding and to assess the predictive/modelling capabilities under realistic conditions.
 A number of hydromechanical (HM) numerical simulations of underground excavations have been carried out and the mechanisms of pore pressure and damage evolution have been studied [2]. Also, numerical analyses have been used to predict the observations of THM behaviour of in-situ heating tests, and there is some research on the damage evolution due to thermal loading [3], but few studies focus on the analysis of strain localization problems, in part due to specific numerical difficulties. However, thermal fracturing behaviour has indeed been observed in experiments and a better understanding of the phenomenon and of shear band evolution is crucial for a proper assessment of the stability of HLW/SF disposal.
 In this study, the coupled THM response of a generic HLW disposal facility under high-temperature has been analysed; in particular, the mechanism of thermal pressurization and the corresponding thermal fracturing behaviour have been examined. For this purpose, an advanced elastoplastic constitutive model with damage has been used to represent the mechanical behaviour of the host rock; it incorporates the following features: (1) a hyperbolic approximation to the Mohr-Coulomb yield surface to represent shear and tensile failure modes, (2) stiffness and strength anisotropy, (3) hardening and softening behaviour, (4) viscous effects and (5) a non-local integral type approach for the plasticity component of the model. The adopted overstress theory and the nonlocal formulation are capable of regularising the spatial distribution of plastic strains, eliminating mesh dependency and improving numerical efficiency. The coupling between accumulated plastic strain and hydraulic permeability has been considered in the analyses. Note that the term damage used in this study, refers to a state of the material, instead of the concept associated with damage mechanics theory; in addition, fracture represents localization phenomena in the damaged area.
 Numerical simulations have been performed using the finite element method software CODE_BRIGHT. Two-dimensional generic disposal configurations have been carried out for the two cases of unsupported and supported tunnels. The host rock is assumed to be the Callovo-Oxfordian claystone (COx). Three modelling stages have been considered: the excavation stage, the waiting stage and the heating stage, as shown in Figure 1 (a). In the heating stage, the thermal flow at the borehole wall is set as a constant power (200 W/m) and a no hydraulic flow boundary condition is prescribed. A maximum temperature of around 80 °C has been obtained on the drift wall at heating time t = 10 years.
 In addition, Figure 1 (b) shows the contours of plastic shear strains and liquid pressures at heating time t = 10 years. Near-field damage is caused by both the excavation of galleries and the effect of thermal pressurization. In the simulations presented, shear bands develop significantly during the heating stage. By comparing two cases in Figure 1 (b), it can be concluded that the installation of liners can efficiently limit the damage evolution and reduce the likelihood of thermal fracturing, significantly improving the stability of HLW disposal. Note that the scales of the two cases in Figure 1 (b) are different. Figure 1(c) shows that a lower pore pressure close to the gallery wall for the unsupported tunnel due to the higher level of damage in this case that results in a larger permeability of the rock in the damaged area.
 Apart from the analysis of the mechanism of THM behaviour in a high-temperature environment, numerical simulations have also been carried out of the large-scale PRACLAY Heater test (performed in the HADEs underground laboratory) and of the CRQ heating experiment (performed in the Meuse-Haute Marne underground laboratory). A good agreement has been observed between numerical predictions and experimental data, in terms of both temperature and pore pressure. These numerical validation exercises are, however, outside the scope of this abstract.

Variations of the improved characteristics on microstructure and mechanical properties of Al–Cu alloy fabricated by magnetic field assisted wire-arc additive manufacturing after heat-treated

In this investigation, Al–Cu alloy was used for wire-arc additive manufacturing experiment with and without assisted longitudinal magnetic field (ALMF) introduced, subsequently, heat treatment was conducted, aiming to investigate the variations of the improved characteristics brought by ALMF on microstructure and mechanical properties after heat-treated. The results indicated that the improved pores condition brought by ALMF was greatly weakened after heat-treated, while the promotion for the columnar to equiaxed transition and the improvement to precipitation remained. As for mechanical properties, the improvement of the uniform distribution of microhardness by the ALMF deteriorated. Moreover, the optimisation brought by ALMF on reducing the anisotropy of tensile strength was greatly weakened, and the improvement of elongation disappeared.

Anisotropy in microstructural features and tensile performance of laser powder bed fusion NiTi alloys

From the viewpoint of the poor formability and mechanical anisotropy of laser powder bed fusion (LPBF)-processed NiTi alloys, three different energy densities, i.e., minimum value, median value, and maximum value, were adopted in this work. The anisotropic behavior in the microstructural distribution and tensile properties were explored to evaluate the performance stability of NiTi components within a wide processing window. The results showed that an excellent deposition quality was acquired when the energy density was within the range of 45–75 J/mm3. The phase constitution and microstructural features were similar even under different processing parameters. In a single melting pool, the columnar grains within the body zone exhibited {110}<001> and {100}<011> textures. However, no preferred orientation was observed for the fine dot-like sub-structures within the overlapping zone. The anisotropy in tensile strength and plasticity was mainly attributed to the columnar grains with preferred crystallographic orientation in the body zone. Only a dimple-like morphology was observed on the fracture surface, indicating a ductile tensile failure mechanism. The findings demonstrated that the stable microstructural features and tensile performance of LPBF-processed NiTi components were ensured within a wide processing window (45–75 J/mm3), despite the anisotropic behavior along the transverse and longitudinal tensile directions.

Towards isotropic behaviour in Ti–6Al–4V fabricated with laser powder bed fusion and super transus hot isostatic pressing

Super β-transus hot isostatic pressing (HIPing) has been shown to be able to transfer columnar to equiaxed grains in additively manufactured Ti–6Al–4V. Although pores in the additively manufactured parts have been found to play a role in such grain transformation, it remains unclear whether super β-transus HIPing can also generate isotropic microstructure and mechanical properties in relatively high-density additively manufactured Ti–6Al–4V. In the present study, super β-transus HIPing (1030 °C, 175 MPa) was applied to high density Ti–6Al–4V manufactured by laser powder bed fusion (L-PBF). As comparison, specimens were subjected to conventional heat treatment under identical conditions to the HIPing cycle except at standard atmospheric pressure. The results showed that the conventional heat-treated sample maintained columnar grains. In contrast, the super β-transus HIPed sample showed equiaxed grains. In respect of mechanical properties, both the as-built and heat-treated samples showed anisotropic tensile strength and ductility between horizontal and vertical building directions whereas HIPed samples achieved isotropic strength and ductility.

A lightweight Fe–Mn–Al–C austenitic steel with ultra-high strength and ductility fabricated via laser powder bed fusion

Lightweight Fe–Mn–Al–C steels have become a topic of significant interest for the defense and automotive industries. These alloys can maintain high strength and ductility while also reducing weight in structural applications. Conventionally processed Fe–Mn–Al–C austenitic steels with high Al content (∼9 wt%) demonstrate greater than 1.5 GPa strength with 35% elongation. Several recent studies have demonstrated success in fabricating steel parts using laser powder bed fusion (L-PBF) additive manufacturing (AM), which can generate near-net-shape components with complex geometries and is capable of local microstructural control. However, studies on L-PBF processing of Fe–Mn–Al–C alloys have focused on low Al content (<5 wt%) compositional regimes representing alloys that undergo transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP). Here, we present the effects of L-PBF processing on the microstructure and mechanical properties of an Fe–30Mn–9Al–1Si-0.5Mo-0.9C austenitic steel. A process optimization framework is employed to determine an ideal L-PBF processing space that will result in >99% density parts. Implementing this framework resulted in near-fully dense specimens fabricated over a broad range of process parameters. Additionally, two bi-directional scan rotation strategies (90° and 67°) were applied to understand their effects on texture and anisotropy in this material. As-printed specimens displayed considerable work-hardening characteristics with average strengths of up to 1.3 GPa and 36% elongation in the build direction. However, solidification microcracks oriented in the build direction resulted in anisotropy in tensile strength and ductility resulting in average strengths of 1.1 GPa and 20% elongation perpendicular to the build direction. The successful L-PBF fabrication of Fe–30Mn–9Al–1Si-0.5Mo-0.9C presented here is expected to open new avenues for weight reduction in structural applications with a high degree of control over part topology.

In situ EBSD/HR-DIC-based investigation on anisotropy mechanism of a near α titanium plate with strong transverse texture

The effect of strong transverse(T) texture on anisotropy deformation mechanism of Ti60 plate was in-situ investigated using the EBSD and the high resolution-digital image correlation (HR-DIC) technique. The yield strength and the ultimate tensile strength is in descending order: TD > RD > 45°, and the ductility shows the opposite trend. The tensile anisotropy related to the discrepancy of activated slip systems in RD, 45°, and TD. In yielding stage, prism<a> slip dominated in RD, basal<a> slip dominated in the 45° direction, while pyram <c+a > slip dominated in TD. The anisotropy coefficient χ was proposed to evaluate the resistance discrepancy based on all the activated slip systems, which well explained the trend of the tensile strength anisotropy. The ductility anisotropy has been analyzed through slip transmission and slip-GB interaction using HR-DIC technology, which is determined by residual dislocation under different tensile directions. The slip transmission can be easily achieved when the Burgers vector of incoming grain is a [2‾ 110] and the Burgers vector of outcoming grain is a [112‾ 0] in 45° direction, which can effectively weaken stress concentration on the grain boundary leading to the greatest ductility among three tensile directions. The dislocation structures in three directions have been analyzed under two-beam condition and weak beam dark field (WBDF) images.

Effect of the Texture of the Ultrafine-Grained Ti-6Al-4V Titanium Alloy on Impact Toughness.

In this work, the strength properties and impact toughness of the ultrafine-grained (UFG) Ti-6Al-4V titanium alloy produced by severe plastic deformation (SPD) in combination with upsetting were studied, depending on the direction of crack propagation. In the billets processed by equal-channel angular pressing (ECAP), the presence of anisotropy of ultimate tensile strength (UTS) and ductility was observed, conditioned by the formation of a metallographic and crystallographic texture. At the same time, the ECAP-processed UFG alloy exhibited satisfactory values of impact toughness, ~0.42 MJ/m2. An additional upsetting of the ECAP-processed billet simulated the processes of shape forming/die forging and was accompanied by the development of recovery and recrystallization. This provided the "blurring" of texture and a reduction in the anisotropy of UTS and ductility, but a difference in impact toughness in several directions of fracture was still observed. It is shown that texture evolution during upsetting provided a significant increase in the crack propagation energy. The relationship between microstructure, texture and mechanical properties in different sections of the material under study is discussed.

Microstructural characteristics and its correlation to mechanical properties of additively manufactured nickel‐base superalloy upon heat treatments

AbstractThe IN718 superalloy was additively manufactured in three different heat treatment states and three loading directions (0°, 45°, 90°). The anisotropic mechanical properties were investigated based on microstructural analysis and related to the orientation and heat treatments. The differences in mechanical performances are attributed to the precipitation hardening and the impediment of dislocation motion from particles. The preferential epitaxial grain growth along the building direction and the resulting texture are considered responsible for the anisotropic tensile strength. The Weibull distribution and the area‐weighted grain diameter were presented to characterize the grain distributions. The Hall–Petch relation was established to correlate the directional grain size and the yield strength of AM IN718, which further illustrated the dominance of precipitates in strengthening mechanisms and the effects of subgrain boundaries.

Geomechanical Characterization of the Wufeng and Longmaxi Shales: Mechanical and Velocity Anisotropy, Static and Dynamic Moduli

Summary The Wufeng and Longmaxi shales of Sichuan Basin, Southwest China have been the primary targets for shale gas development. Because hydraulic fracturing and seismic interpretation require detailed characterization of formation mechanical properties, a sufficient understanding of anisotropy and elastic behavior in Wufeng and Longmaxi shales is necessary. In this study, we conducted Brazilian and triaxial tests and ultrasonic velocity measurements to characterize tensile and compressive strengths and P- and S-wave velocities, respectively. Shale samples were cored at a range of orientations relative to bedding and tested at multiple confining pressures, which allowed a detailed study of mechanical and velocity anisotropy, static and dynamic moduli. Our experimental work shows that Wufeng and Longmaxi shales possess similar compressive strength and associated anisotropy with other shale formations but apparently weaker tensile strength anisotropy and velocity anisotropy. These two shales also exhibit much lower static moduli than dynamic values, which are interpreted to be caused by compliant pores such as microcracks and fractures. Comparison between Wufeng and Longmaxi shales reveals distinct levels of heterogeneity. Wufeng shale shows more pronounced heterogeneity regarding measured tensile and compressive strengths as well as elastic moduli. These general characteristics of Wufeng and Longmaxi shales provide valuable first-order understanding regarding anisotropy, heterogeneity, and elastic behavior. Utilizing this understanding could help improve hydraulic fracture design and seismic data interpretation.

Fracture-initiation pressure model of inclined wells in transversely isotropic formation with anisotropic tensile strength

Fracture-initiation pressure (FIP) is closely related to lost circulation and hydraulic fracturing. However, conventional prediction models often treat formation rock as an isotropic medium, ignoring the anisotropy of rock materials, particularly, the anisotropy of tensile strength. Therefore, a universal FIP model was proposed for inclined well in transversely isotropic formations, and the combined effects of both anisotropic elasticity and tensile strength were taken into account. The proposed model was verified by indoor experiments, and the predicted FIPs of isotropic and anisotropic models were compared. Finally, the influencing factors of FIP were investigated. The results indicated that compared with the experimental results, the present model is more consistent than traditional models, and the deviation factor is concentrated between 0.8 and 1.4. Compared with the traditional isotropic model, the maximum differences of the elastic anisotropic model, strength anisotropic model, and the present model are 0.059 g/cm3, 0.262 g/cm3, 0.258 g/cm3, respectively. The dip direction has almost no effect on the FIP at a low dip angle, while it has a significant effect at a high dip angle. The FIP is the minimum when the dip direction is parallel to the azimuth of wellbore, while it is the maximum when the dip direction is perpendicular to the azimuth of wellbore. With the increase of anisotropy index, the influence of elastic anisotropy and strength anisotropy is enhanced, and the maximum difference is 0.31 g/cm3 and 0.33 g/cm3 respectively; while the Poisson's ratio only has a small effect, and the maximum difference is only 0.256 g/cm3. The spatial distribution parameter (Ω0) directly affects the variation trend of tensile strength, too high a Ω0 may overestimate the FIP, while too low a Ω0 may underestimate the FIP. The present model and analysis results can provide theoretical guidance for lost circulation prevention and hydraulic fracturing optimization.

UV-induced disulfide metathesis: Strengthening interlayer adhesion and rectifying warped 3D printed materials

UV-curing 3D printing technology has greatly facilitated the development of manufacturing industry. However, there still are some crucial drawbacks to UV-curing 3D printed materials, i.e., the anisotropic mechanical strength, curing shrinkage and warpage. Herein, UV-induced disulfide metathesis able to rearrange the crosslinked network is adopted to overcome these difficulties. A disulfide bond-containing acrylate (MA-SS) is synthesized and incorporated into a 3D printing photosensitive resin. The photopolymerization kinetics indicate that the moderate amount of MA-SS can promote the photopolymerization conversion, while excessive MA-SS will decrease the conversion. The MA-SS can also greatly improve the tensile strength of 3D printed materials, owing to the more homogenous crosslinked networks and higher crosslinking density. Moreover, the anisotropic tensile strength between x- and z- axis is greatly reduced by the MA-SS, since disulfide metathesis can enhance the adhesion between printing layers. Furthermore, the 3D printed materials can be reversibly transformed from one shape to another by virtue of UV-induced disulfide metathesis. More importantly, the seriously warped 3D printed materials can be effectively rectified under the action of UV irradiation, where the warpage is significantly decreased from 6% to 1–2%. Therefore, this facile strategy of rearranging the crosslinked networks can conquer the drawbacks within UV-curing 3D printing materials to fulfill high-precision 3D printed materials. • UV-induced disulfide metathesis is conducive to better 3D printed materials. • UV-induced disulfide metathesis enhances interface adhesion among printing layers. • The warped 3D printed materials can be rectified by UV-induced disulfide metathesis. • The 3D printed materials can be reversibly transformed under UV irradiation.

Mechanical properties and microstructural characteristics of wire arc additive manufactured 308 L stainless steel cylindrical components made by gas metal arc and cold metal transfer arc welding processes

Wire arc additive manufacturing (WAAM) is suitable for manufacturing large-scale complex parts due to many advantages, including high disposition rate and low cost and thus become a viable advanced manufacturing technique. In the present study, two different arc welding processes were used to fabricate 308 L austenitic stainless steel (SS) cylindrical components. The mechanism and impact of the processes on the microstructure and mechanical characteristics were analysed. The results indicated that the component produced by the cold metal transfer (CMT) arc welding process exhibits finer grains and higher amount of ferrite than conventional gas metal arc welding (GMAW) process. Furthermore, the percentage of anisotropy in tensile strength was reduced from 8.07% to 6.21% for cylinders built by the GMAW process to the CMT process. In addition, the average ultimate tensile strength (UTS), elongation (EL) and hardness of the CMT cylinder are 5.17–7.0%, 4.029–7.80% and 4.02–5.88% higher than the GMAW cylinder, irrespective of orientations. The tensile properties are higher than those of the 308 L welding wire and other arc-welding based additively manufactured 308 L stainless steel parts. The produced WAAM 308 L SS cylinders exhibited superior performance than the stainless steel made by industrial forging standards. Therefore, the 308 L SS cylindrical components made by WAAM technique are found to be suitable for industrial application.

Insight into spontaneous water-based working fluid imbibition on the dynamic tensile behavior of anisotropic shale

Shale gas is becoming a new energy development focus worldwide with advances in horizontal wells and hydraulic fracturing, and spontaneous water-based working fluid imbibition is one of the strongest phenomena that can impact borehole stability and the gas extraction rate. Our present experimental work was carried out on shale Brazilian discs with 5 different bedding orientations (0°, 30°, 45°, 60° and 90°) after air-drying and spontaneous water imbibition using a split Hopkinson pressure bar. The results illustrate that under the same loading rate (100–900 GPa/s), spontaneous water imbibition obviously weakens the dynamic tensile strength of shale discs, except for shale discs with a bedding orientation of 90° when the loading rate exceeds 400 GPa/s, and does not change the anisotropic dynamic tensile strength variation trend versus bedding orientations. Models that can well fit test data and reveal the coupling effects of bedding orientation and loading rate on the dynamic tensile strength of shale after air-drying and spontaneous water imbibition are proposed. The rate-dependent failure mode only appears among shale discs with bedding orientations of 30°, 45° and 60°, and this phenomenon is exacerbated and more complex after spontaneous water imbibition. Bedding planes of shale discs after air-drying and spontaneous water imbibition both play three different roles in affecting the failure crack propagation, i.e., intersecting propagation, promoting propagation and promoting turning. Finally, the dynamic tensile strength responses of shale after spontaneous water imbibition are analyzed and discussed, and potential field applications in borehole stability, perforation design and hydraulic fracturing are suggested.