Major Crack Research Articles

Analysis of Fracture Modes and Acoustic Emission Characteristics of Low‐Frequency Disturbed Water‐Bearing Soft Rock With Different Cyclic Initial Value

ABSTRACTIn the complex geological environment of deep mining area, water‐bearing soft rock is more prone to damage and destruction by low‐frequency disturbance. In this paper, the dynamic–static combination test was conducted on the basis of uniaxial compression test by using creep dynamic disturbance impact loading system and acoustic emission technique. The test results show that with the increase of the initial value of disturbance loading, the fracture morphology of sandstone gradually changes from a single major crack to multiple cracks coexisting, and some saturated sandstones lose the bearing capacity in the process of disturbance, presenting a cone‐shaped fracture surface. The increase of the initial value of the disturbance changes the bearing capacity of the sandstone, and the peak energy of acoustic emission reaches the maximum value when the initial value of the disturbance is 80% UCS. The results of the study can provide some reference for the stability analysis of deep water‐rich soft rock mines.

Compression-after-indentation study of alumina-based oxide/oxide ceramic matrix composite with variable damage

In this study, the damage tolerance of alumina-based Oxide/Oxide ceramic matrix composite with varying extent of quasi-static indentation damage is evaluated via compression test. Pre-existing damage in the laminates are of different sizes and exist in the form of delaminations, fiber fracture, matrix cracking, and major through-thickness cracks. Digital image correlation is used to monitor the in-test displacements and strain field. When compared to undamaged compressive strength, the strength reduction in the indented specimens range from 52 % to 57 %. This shows that the compression after indentation strength is not significantly affected by variations in the extent of indentation damage. Digital image correlation results showed out-of-plane deformation originating from the indented region that grew stably with increasing load to a critical phase, beyond which they became significantly large. This resulted in the sudden catastrophic failure of the laminate, apparently caused by delamination buckling. This was confirmed by post-test X-ray computed tomography micrographs.

A peridynamic-based reconstruction and analysis method for short-fiber reinforced composites

Abstract As the complex microstructure, predicting the effective elastic properties and damage mechanisms of Short-Fiber Reinforced Composites (SFRC) continues to pose a challenge. This study presents a new reconstruction and analysis method based on PeriDynamics (PD) for SFRC. The reconstruction of the surface profiles of short-fibers obtained from Micro-CT (Micro-Computed Tomography) scanning resulted in a PD computational model that accurately reflects the actual microstructure of SFRC. The results predicted the effective elastic modulus of SFRC while fiber volume fraction and distribution have impact. Micro-cracks emerge at stress concentration regions near the fiber-matrix-fiber interfaces between two adjacent fibers, and with increasing load, these cracks gradually propagate, interact, and merge with each other. Eventually, major cracks form, leading to material failure.

Effects of folded fissure properties on tunnel model failure: Experiments and numerical simulations

Natural folded fissures commonly exist rather than simple straight fissures in rock masses surrounding tunnels. The presence of folded fissures significantly affects the fracture processes and failure modes of tunnel structures, thereby affecting their safety and stability. However, the research in this area is limited. Given this, this study fabricates city-gate section tunnel specimens containing folded fissures of various dip angles (α) and orientation angles (β), utilising 3D sand printing with sand and furan resin as matrix materials. Uniaxial compression fracture tests were conducted at a loading rate of 0.3 mm/min on these specimens using a digital image correlation technique to assess the impact of folded fissures on the mechanical properties and failure modes of the tunnel structures. Additionally, the improved smoothed particle hydrodynamics (SPH) method was used for damage evolution simulations during interactions between folded fissures and tunnels, and the simulation results were compared with the experimental results to verify the correctness of the method. The results show that for folded fissures, wing cracks and anti-wing cracks initiate not only from the ends but also from the bends of the fissures, whereas for straight fissures, they appear only at the fissure ends. Except for β = 0°, the interaction between folded fissures and tunnels generally results in the formation of a crack connecting the folded fissure upper end with tunnel, and the connection position varies with β. Different β values of folded fissures also influence the appearance and morphologies of top major cracks, underside major cracks, side cracks, and corner cracks around tunnels. As α increases, the overlap point of the crack and the tunnel moves from the tunnel corner to the tunnel crown. Moreover, folded fissures significantly affected the peak strength of the tunnel structures. As β increases, the peak strength first decreases, then increases, and finally decreases, reaching a minimum of 3.58 MPa at β = 90°. However, the peak strength differences are not evident under different α values. Finally, the influence of folded fissures on the cracking mechanism of the tunnel models is discussed in detail. This study provides insights into the impact of folded fissures on tunnel fracture modes and offers a reference for the application of SPH to reveal the underlying failure mechanisms of tunnel structures.

Residual load-carrying performance of ECC-RC composite beam after drop hammer impact

Four types of specimens with various thicknesses of ECC layer in the tensile side of RC beam are fabricated. The influence of ECC layer on the dynamic response and residual capacity of RC beams is investigated through drop hammer impact test and post-impact static loading test. The results reveal that increasing the thickness of the ECC layer in the tensile side leads to less major cracks and more tiny cracks on the beam side under impact, and the damage of concrete in the impact zone alleviates. The incorporation of the ECC layer plays an insignificant role in displacement restitution and residual load-carrying capacity. However, ECC-RC composite beams effectively mitigate displacement ductility degradation. Compared to RC beam, ECC-RC composite beams also exhibit superior energy dissipation capacity at the post-impact loading stage. The parametric analysis indicates that a thicker ECC layer in composite beams with a low tensile reinforcement ratio effectively reduces maximum impact displacement but has a negligible influence on residual load-carrying capacity. In contrast, increasing the ECC layer in beams with a high tensile reinforcement ratio offers a limited reduction in maximum impact displacement but its residual load-carrying capacity significantly improves after impact.

Flexural behavior and serviceability of steel fiber-reinforced lightweight aggregate concrete beams reinforced with high-strength steel bars

Six beams reinforced with HRB600 bars and one reinforced with HRB400 bars fabricated using steel fiber-reinforced lightweight aggregate concrete (SFLWAC) were tested under a four-point bending load to investigate the load-carrying capacity and service performance, with different reinforcement ratios, clear span lengths, concrete strengths, and reinforcement strengths. The test results showed that cracks ran through lightweight aggregates and developed rapidly without an aggregate interlocking mechanism, and the specimens eventually failed in the mode that the compressive concrete was crushed following longitudinal bars yielded, with 3 ∼ 4 major cracks. The specimens satisfied the allowable deflection and crack width required in the codes, with a ductility coefficient exceeding 4.5, and 1/150 of the span length was recommended to be the maximum deflection at the serviceability limit state. Generally, the increasing reinforcement ratio significantly improved the flexural strength and serviceability but reduced the ductility, the linear stiffness decreased with the growing span length, and the SFLWAC strength mainly affected the cracking moment and ductility. Replacing HRB400 bars with equal strength of HRB600 bars led to a substantial drop in serviceability, while an equal area of HRB600 bars improved the ultimate moment by 38.7 %. The calculation results indicated that by neglecting the residual tensile strength, fracture characteristics, and bond properties of SFLWAC, the prediction equations in the Chinese, American, and European codes underestimated the ultimate moment and overestimated the crack width, and the Chinese code yielded the conservative deflection prediction. The analytical flexural models for HRB600-reinforced SFLWAC beams were derived by incorporating the effects of steel fibers, lightweight aggregate concrete, and bond stress, exhibiting accurate predictions.

Study on the Characteristics and Evolution Laws of Seepage Damage in Red Mud Tailings Dams

Seepage damage is a significant factor leading to red mud tailings dam failures. Laboratory tests on seepage damage were conducted to investigate the damage characteristics and distribution laws of red mud tailings dams, including soil pressure, infiltration line, pore water pressure, dam displacement, and crack evolution. The findings revealed the seepage damage mechanisms of red mud slopes, offering insights for the safe operation and seepage damage prevention of red mud tailings dams. The results showed that the higher the water level is in the red mud tailings dam, the higher position the infiltration line is when it reaches the slope face. At the highest infiltration line point of the slope surface, the increase of pore water pressure is the highest and the change of horizontal soil pressure is the highest. Consequently, increased pore water pressure leads to decreased effective stress and shear strength, increasing the susceptibility to damage. Cracks resulting from seepage damage predominantly form below the infiltration line; the higher the infiltration lines is on the slope surface, the higher the position of the main crack formations is. The displacement of the dam body primarily occurs due to the continuous expansion of major cracks; the higher the infiltration lines are on the slope surface, the larger the displacement of the dam body is.

High strength diffusion bonding of Ti2AlNb to GH4169 with (TiZrHfNb)95Al5 high entropy interlayer

A high entropy interlayer (TiZrHfNb)95Al5 was designed for vacuum diffusion bonding of Ti2AlNb to GH4169. The influence of bonding temperature on the interfacial microstructure morphology, mechanical properties and fracture behaviour of the resultant joints was investigated. The evolution of microstructure and fracture mechanism were revealed. The typical interface microstructure of Ti2AlNb/B2/Solid solution/(Ti, Zr, Hf)2(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)2+Solid solution/(Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe)ss/(Cr, Ni, Fe)ss/Cr-rich(Cr, Ni, Fe)ss/Ni-rich(Cr, Ni, Fe)ss/GH4169 was formed. As the bonding temperature increased, the thickness of interfacial reaction layer gradually increased, and the shear strength gradually increased until 980 °C, then decreased sharply. The highest shear strength reached 376 MPa at 980 °C for 90 min. The highest microhardness region of 11.79 GPa existed on the GH4169 side, which was mainly composed of (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe)ss phases. Meanwhile, the elastic modulus dramatically changed interface formed near this region. The fracture surface morphology indicated typical brittle fracture characteristics such as cleavage steps, transgranular fracture and intergranular fracture. According to the fracture analyses, major cracks initiated in the (Ti, Zr, Hf)(Ni, Nb) phase+(Ti, Zr, Hf)2(Ni, Nb) phase and gradually extended to the (Cr, Ni, Fe)ss phase. Thus, the major crack emerged region was located at the elastic modulus dramatically changed interface.

Predicting the Fracture Toughness of Human Cancellous Bone in Fractured Neck of Femur Patients Using Bone Volume and Micro-Architecture.

The current protocol used to determine if an individual is osteoporotic relies on assessment of the individual's bone mineral density (BMD), which allows clinicians to judge the condition of a patient with respect to their peers. This, in essence, evaluates a person's fracture risk, because BMD is a good surrogate measure for strength and stiffness. In recent studies, the authors were the first to produce fracture toughness (FT) data from osteoporotic (OP) and osteoarthritic (OA) patients, by using a testing technique which basically analyzes the prerequisite stress conditions for the onset of growth of a major crack through cancellous bone tissue. FT depends mainly on bone quantity (BV/TV, bone volume/tissue volume), but also on bone micro-architecture (mArch), the inner trabecular design of the bone. The working research hypothesis of the present study is that mArch offers added prediction power to BV/TV in determining FT parameters. Consequently, our aim was to investigate the use of predictive models for fracture toughness and also to investigate if there are any significant differences between the models produced from samples loaded across (AC, transverse to) the main trabecular orientation and along (AL, in parallel) the trabeculae. In multilinear regression analysis, we found that the strength of the relationships varied for a crack growing in these two orthogonal directions. Adding mArch variables in the Ac direction helped to increase the R2 to 0.798. However, in the AL direction, adding the mArch parameters did not add any predictive power to using BV/TV alone; BV/TV on its own could produce R2 = 0.730. The present results also imply that the anisotropic layout of the trabeculae makes it more difficult for a major crack to grow transversely across them. Cancellous bone models and remodels itself in a certain way to resist fracture in a specific direction, and thus, we should be mindful that architectural quality as well as bone quantity are needed to understand the resistance to fracture.

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature.

In order to research the residual mechanical properties of concrete shield tunnel segments after exposure to high temperatures, two types of concrete segments were designed: a self-compacting concrete segment and a mixed fiber (steel fiber and polypropylene fiber) self-compacting concrete segment. The mechanical properties of seven blocks of concrete segments (five segments after high-temperature exposure and two segments at room temperature) were tested to analyze the influence of different loading sizes and fibers on the development of cracks after high temperature, failure mode, crack width, deformation, and so on in the concrete segments. The results showed that the damage model of the segment after exposure to high temperature and the segment at room temperature were crushed in the pressurized zone, but the high temperature had little effect on the concrete in the pressurized area. The size of the preload at high temperatures had little effect on the remaining load capacity, and the effect on the number of cracks was mainly concentrated on the internal arc surface of the segment. After high-temperature exposure, the number of cracks on the sides and inner arc surface of the segment increased, and the development of cracks was concentrated as several major cracks at high temperatures. When fibers were incorporated, the cracks in the segment became obvious, where the cracks at the loading point became denser and the interval distance became smaller.

CFRP-steel composite beams with seawater sea sand concrete cores subjected to bending

A redesign was attempted for the concrete-filled double-skin tube subjected to bending, and by adjusting the core tube position and applying carbon fiber-reinforced polymer (CFRP) sheets or steel bars in the tensile region, it was hoped to delay the cracking of the concrete in the tensile region. Epoxy mortar was used to modify the interface. Seawater and sea sand has been successfully applied from reinforced concrete beams to concrete-filled steel tube beams, benefiting from the corrosion-resistant properties of CFRP and epoxy mortar. The four-point bending test parameters included the type of core tube, the number of CFRP layers, and the diameter of the steel bars. The beams with FRP sheets exhibited better flexural capacity and residual stiffness, while the brittle fracture of FRP led to major crack in concrete. The beams with steel bars exhibited better initial stiffness and the cracks in concrete were more uniform in width. When the layers of CFRP or the diameter of the steel bars was increased, the flexural capacity of the composite beams increased by 11.0%-13.6% and 7.0%-9.1%, respectively. The enhancements provided by the core tubes were small, and the design of the composite beams should be considered from various perspectives. The moment-curvature relationships, ultimate states, and flexural stiffness were defined by considering concrete cracking, FRP fracturing, and steel buckling. Several formulas for calculating flexural stiffness in the code were evaluated in combination with the test data.

Wavelet entropy-based damage characterization and material phase differentiation in concrete using acoustic emissions

Damage evolution in concrete is a complex phenomenon involving micro-cracks that originate from different material phases (mortar matrix, ITZ and aggregate), and culminate into a major crack. The information about the individual damaged material phases can provide major insights into the global failure behaviour, cracking path, and fracture processes. The evolution of damage, damage mechanisms and the material phase of origin of micro-cracks is highly influenced by the type of concrete (Normal and high strength). In order to investigate the evolution of damage in concrete of varying strength, notched beam specimens with different water-to-cement ratios have been prepared and tested under CMOD control. The evolution and growth of damage have been continuously monitored during testing through acoustic emission techniques. Based on acoustic emission results, it has been demonstrated that the damage progression in concrete can be better described as a function of the wavelet entropy of the AE events occurring during the entire loading duration, and therefore, an analytical model for the damage evolution has been proposed. The study reveals that, under the high-strength category, the level of deterioration reduces as the w/c ratio rises, while in normal-strength concrete, a reverse trend is observed. Furthermore, a novel approach has been proposed that utilizes wavelet entropy and amplitude to differentiate amongst various damaged material phases with the help of an unsupervised clustering algorithm. Normal-strength concrete with a w/c ratio of 0.4 has been used to demonstrate the proposed methodology and has been validated with the help of experiments performed on the mortar and the parent stone of aggregate. A higher occurrence of mode-I cracks compared to mode-II cracks across all material phases has been observed for the specimen. Additionally, ITZ and aggregate exhibit a greater proportion of tensile and shear cracking events than the matrix phase. In the end, a deep learning convolutional neural network (CNN) model is devised utilizing labelled scalogram images of the AE waveforms to discriminate between the various damaged material phases. A 10-fold training cross-validation of the dataset has been carried out to achieve a stable performance. The deep learning model performs well in discriminating the damaged material phases with high training, validation, and testing accuracy.

Study of the construction techniques, materials and architectural prospectives of ancient monumental structures in Allahabad City, India

This research examines the construction methodologies, materials, and architectural principles employed in creating ancient monumental structures in Allahabad (now Prayagraj), India. Despite being erected over 600 years ago, these structures stand resiliently among the evolution of modern construction techniques and seismic safety standards. The history of Prayagraj can be traced back to ancient times. The city was initially referenced in the ancient Hindu scriptures, known as the Vedas, as a sacred destination. Further, established by the Mughal Empire under Akbar’s reign in 1583, Allahabad City witnessed the construction of numerous monumental structures using robust techniques involving stone, brick masonry, and timber materials bonded together with thin mortar and plaster. Many of these ancient edifices, erected during this period, continue to serve various functions today, reflecting the enduring craftsmanship of their builders. In this study, we have identified prestigious monuments for examination, utilizing visual inspection to gain deeper insights into the emphasized construction materials and techniques. Notably, mortar is a critical component in construction and structural connections. Furthermore, our investigation reveals the diverse range of materials utilized for binding, plastering, painting, and other decorative purposes during construction. However, it is evident that some of these monuments have endured significant wear and tear over time, resulting in major cracks and damage to their structural elements and construction materials. Through this exploration, we aim to unveil the intricate craftsmanship and architectural brilliance that characterize Allahabad’s ancient monumental structures, while also highlighting the preservation challenges posed by ageing and environmental factors.

Effect of wheat straw ash as cementitious material on the mechanical characteristics and embodied carbon of concrete reinforced with coir fiber

The use of supplementary cementitious materials has been widely accepted due to increasing global carbon emissions resulting from demand and the consequent production of Portland cement. Moreover, researchers are also working on complementing the strength deficiencies of concrete; fiber reinforcement is one of those techniques. This study aims to assess the influence of recycling wheat straw ash (WSA) as cement replacement material and coir/coconut fibers (CF) as reinforcement ingredients together on the mechanical properties, permeability and embodied carbon of concrete. A total of 255 concrete samples were prepared with 1:1.5:3 mix proportions at 0.52 water-cement ratio and these all-concrete specimens were cured for 28 days. It was revealed that the addition of 10 % WSA and 2 % CF in concrete were recorded the compressive, splitting tensile and flexural strengths by 33 MPa, 3.55 MPa and 5.16 MPa which is greater than control mix concrete at 28 days respectively. Moreover, it was also observed that the permeability of concrete incorporating 4 % of coir fiber and 20 % of WSA was reduced by 63.40 % than that of the control mix after 28 days which can prevent the propagation of major and minor cracks. In addition, the embodied carbon of concrete is getting reduced when the replacement level of cement with WSA along with CF increases in concrete. Furthermore, based on the results obtained, the optimum amount of WSA was suggested to be 10 % and that of coir fiber reinforcement was suggested to be 2 % for improved results.

Evaluation of Desiccation Behavior in Basalt Microfiber–Reinforced Bentonite Clay for Geological Repositories of Nuclear Spent Fuel Using Digital Image Correlation

Abstract Secure storage of nuclear spent fuel (NSF) is of great concern for protecting public health and safety. The preferred long-term solution is underground containment in geological repositories, where one or more engineered barrier materials (EBM) encapsulate the NSF and separate it from the natural rock. Bentonite clay is commonly used as an EBM due to its many advantageous properties including low hydraulic conductivity, which ensures limitation of water infiltration to the system and the subsequent risk of corrosion in NSF canisters. However, bentonite clay subjected to heating from nuclear decay may form desiccation cracking. This study conducted disk-shaped free shrinkage tests and ring-shaped restrained shrinkage tests of bentonite clay samples reinforced with basalt microfibers. Digital image correlation was used as a noncontact full-field displacement measurement to track the time-evolving shrinkage and desiccation cracking phenomena and make quantified comparisons between plain bentonite and bentonite with varying contents of basalt microfibers (i.e., 0.0, 0.5, 1.0, and 1.5 % wt.). Results indicate that plain bentonite and basalt microfiber-reinforced samples showed similar free shrinkage behavior, while desiccation cracking behavior was significantly altered by adding basalt microfibers. Microfiber reinforcement effectively reduced major cracks through a “crack-bridging” effect while causing minor cracks to initiate earlier and at higher moisture contents than plain bentonite. Results infer that reinforcing plain bentonite with inorganic microfibers can potentially control desiccation cracking, leading to safer and improved nuclear waste management.

Fracture of all‐oxide ceramic composites: Crack path analysis by surface strain monitoring

AbstractCrack propagation in ceramic matrix composites is very difficult to observeand to quantify. To investigate crack formation in all‐oxide ceramic composites, single edge notched bending tests were performed including loading‐unloading cycles and online monitoring of surface deformation using digital image correlation. The crack length was calculated by the compliance method with the crack opening displacement determined optically using digital image correlation. Obtained crack length values were found to be too small considering the sample geometry. Secondly, surface strain monitoring was used to investigate the crack growth. Analysis of cyclic force‐crack opening displacement curves and the results from strain monitoring indicated no major crack growth for loads below maximum force but still a moderately decay of force after onset of cracking. Graphical analysis of the surfaces of broken samples showed crack flank lengths ranging from 3 to 6 mm. Due to highly individual crack deflection mechanisms throughout the thickness of the oxide ceramic composites, deviations between front and back of specimens are found. The results demonstrate the necessity to use individual crack length measurements of each specimen for quantitative fracture mechanical evaluation. Strain monitoring during testing was shown to be a valuable tool for online crack path investigation.

Behavior of Shear-Critical Recycled Aggregate Concrete Beams Containing BFRP Reinforcement

The shear performance of recycled aggregates beams reinforced with basalt fiber-reinforced polymer (BFRP) bars is evaluated and compared with that of similar beams made with natural aggregates (NA). Six beams with a shear span-to-effective depth ratio (a/d) of 3.0 were tested to failure. Test variables consisted of the recycled concrete aggregate (RCA) replacement percentage (60 and 100%) and the presence of BFRP stirrups in the shear span. Experimental results showed that a RCA replacement of 60% marginally reduced (5%) the shear capacity. However, the reduction in the shear capacity was more pronounced (17%) for the specimen made with 100% RCA. The contribution of BFRP stirrups to the shear capacity decreased with an increase in the RCA replacement percentage. The width of the major shear crack at a given value of load was higher for the beams with RCA. The deflection values at the ultimate load were greater for beams made with RCA. A codified analytical approach as well as a model published in the literature were employed to predict the shear capacity of the tested beams. Predictions of the codified analytical approach were very conservative. The analytical model published in the literature provided a more reasonable prediction for the shear capacity of the tested beams than that of the codified analytical approach.

Fatigue behaviour of Kevlar/carbon/basalt fibre-reinforced SiC nanofiller particulate hybrid epoxy composite

Abstract It is vital to conduct research on the behaviour of natural fibre composites under cyclic loading in order to have confidence in the mechanical durability. During this study, the fabrication of composite laminates will be carried out by the hybridization effect of natural and synthetic fibres. Quantifying the impact that the SiC filler (10, 20, and 30 g) has when combined with the fibre reinforcement and epoxy matrix (275 g) under cyclic loading circumstances and determining the significant sequence of hybrid composites are the goals of this research. The results of the tensile mode were used to determine the input parameters, and based on the tensile strength of the hybrid composite, 70% of the tensile strength was fixed at 3 Hz frequency as the input for fatigue analysis. The life span was then determined for the hybrid composite. The results of this fatigue test showed that increasing the amount of SiC nanofillers produced a very high potential output for the fatigue test. As a result of increasing the amount of silicon carbide fillers from 10 to 30 g, sample S3 was able to significantly tolerate 65% more life. Failure mode can be identified from scanning electron microscope analysis revealing the major porosity, matrix crack, and laminate bonding strength that causes the failure during fatigue analysis.

Shear strength determining mechanism of a +/−45 laminate under tensile loading

The shear strength of a composite material is determined as a result of a complex damage and failure process, but the detailed progression has not been clearly elucidated. Here, the mechanism of determining the strength of a ±45 laminate under tensile loading is revealed from exquisitely designed experiments in conjunction with high-fidelity numerical simulation. Synchrotron radiation computed tomography is employed for extremely high-resolution images of damage status inside the composite just before its catastrophic failure. The ex situ observations discover the unique and consistent failure progression; one major matrix crack is initiated either in the +45 or −45 layer and delamination follows after the initial crack completely grows along both the fiber and transverse directions. After the delamination failure is triggered, remaining intact layers start to fail with multiple transverse matrix cracks. The failure of the intact layers is represented as a load drop in the global stress–strain curve. This sequential and interactive failure progression determines the shear strength of the ±45 laminate. The numerical analysis finds that the location of the initial matrix crack is dependent on the microstructure. Once the matrix crack is initiated, the numerical simulation exactly reproduces the experimentally observed failure process.

An investigation of fatigue of additively manufactured commercially pure Alpha–Ti alloy at 350 °C

This work presents an elevated temperature fatigue study on additively manufactured (AM) commercially pure (CP) alpha Ti alloy with dispersed TiB particles. This study consists of both experimental and analytical investigations. Experimental data presented in this work were collected using a rotating beam fatigue (RBF) tester and a scanning electron microscope (SEM). The experimental findings presented in this work show that the AM Ti–TiB alloy lost its fatigue strength considerably at 350 °C compared to its reported room temperature fatigue strength. This loss in fatigue life is attributed to the numerous surface crack propagations. Moreover, a novel modification to the Paris’ law equation is introduced in this study. This modified equation is designed to predict fatigue life under elevated temperatures, especially in scenarios involving extensive major crack propagation. Notably, this modified equation improved the fatigue failure prediction accuracy, measured in terms of R2 value from 0.34 to 0.93.