Fracture Analysis Research Articles

Fracture analysis for nozzle cracks in nuclear reactor pressure vessel using FCPAS

This study addresses cracks and fracture problems in engineering structures that may cause significant challenges and safety concerns, with a focus on pressure vessels in nuclear power plants. Comprehensive parametric three-dimensional mixed mode fracture analyses for inclined and deflected nozzle corner cracks with various crack shape aspect ratios and depth ratios in nuclear reactor pressure vessels are carried out. Stress intensity factor (SIF) solutions are obtained using FRAC3D, which is part of Fracture and Crack Propagation Analysis System (FCPAS), employing enriched finite elements along the crack front. Also, improved empirical equations are developed to allow the determination of mixed mode SIFs, KI, KII, and KIII, for any values of the parameters considered in the study. This study provides practical solutions to assess the remaining life and fail-safe conditions of nuclear reactors by providing accurate SIF determination.

Fracture Analysis of Cracked Bimaterial Plate by NURBS Aided Extended Finite Element Method

Fracture Analysis of Cracked Bimaterial Plate by NURBS Aided Extended Finite Element Method

Fracture analysis of chopped carbon fiber sheet molding compound composite under tensile loading via in-situ μXCT

This paper investigated the crack initiation in a chopped carbon fiber sheet molding compound (SMC) composite under different tensile loads by integrating synchrotron micro-X-ray computed tomography (μXCT) and micromechanics analysis. It was found that the varied distribution of fiber chips in the SMC composite led to distinct fracture propagation behaviors. With the loading increasing, the crack primarily occurred within the fiber chips, and the delamination exited when the crack propagated along the interface between adjacent layers. To understand the location and sequence of crack initiation in SMC composites, the sample were divided into identical cubes. After tracking the microstructure of each cube, the corresponding interfacial debonding strength as well as Young's modulus were predicted. Predictive modeling of crack initiation characteristics was conducted assuming homogeneous material deformation under small strain. The predicted outcomes closely matched with the experimental findings.

Joining high volume fraction SiC particle reinforced aluminum matrix composites using Bi2O3-B2O3-ZnO-BaO-Na2O glass

This paper designs a bismuthate glass 58Bi2O3-25B2O3-13ZnO-2BaO-2Na2O in mol%(BBZ) and uses it to join 65 % volume fraction SiC particle reinforced aluminum matrix composites (65 vol%SiCp/ZL102) in an atmospheric environment. The thermal properties of BBZ glass were studied, and the effect of the brazing process on the mechanical properties of the joint was explored. The results show that the glass transition temperature of the glass is 344.6 °C, and the two crystallization temperatures are 464.7 °C and 544.3 °C. The oxidation of the parent material can improve the mechanical properties of the joint. The increase in welding temperature and the extension of holding time make the mechanical properties of the joint first increase and then decrease. When brazing at 490 °C for 30 min, the pre-oxidized composite material was brazed, the joint was defect-free, and the shear strength of the joint was 19.4 MPa. The analysis of the shear fracture showed that the fracture mainly occurred in the glass brazing material, which is a brittle fracture.

A unified bond–based peridynamic model without limitation of Poisson's ratio

The issue of fixed Poisson's ratio is a critical problem plaguing bond–based peridynamic (BB–PD) models. The popular approach of introducing the bond's tangential stiffness cannot completely remove Poisson's ratio limitation, but instead leads to some additional troubles, such as negative tangential stiffness and bond force density misalignment in finite rigid body rotation problems. To address the issue of fixed Poisson's ratio thoroughly, a unified bond–based peridynamics (UPD) was originally proposed. In the proposed model, a novelty pairwise force density function has been developed, in which dilatation and distortion are distinguished, and the model assigns different stiffnesses to the two deformation components. Arbitrary and reasonable values of Poisson's ratio can be achieved by adjusting the PD parameters that control the bulk and shear moduli of the material. The theoretical range of Poisson's ratio in the proposed model is (-1, 0.5], which is consistent with those in continuum mechanics. In addition, the absence of tangential stiffness prevents the proposed model from misalignment of bond force density due to rigid body rotation. Several numerical examples, including four two–dimensional and three–dimensional deformation analyses and three quasi–static fracture analyses, were implemented to verify the accuracy and reliability of the proposed model. The results show that the proposed model can accurately simulate the elastic properties of the material and obtain the deformation with high accuracy. The numerical examples also demonstrate the fracture prediction capability of the proposed model.

Unconventional mobility, conventional trauma: a comparative analysis of e-scooter-related fractures.

The present research aimed to compare the different types of fractures to those caused by e-scooter use as well as reveal the severity of e-scooter injuries via an epidemiological analysis of fractures over the course of 6months. This retrospective study assessed medical records of patients with fractures or dislocations admitted to a Turkish level three trauma centre emergency orthopaedic department between June 2021 and January 2022. Using a two-group design, the first group encompassed all fractures and dislocations treated, while the second focused on e-scooter-related cases. Comparative analysis covered fracture patterns and factors within the e-scooter group, like demographics, injury mechanism, and timing. Surgical need and types were explored for e-scooter injuries. Among 4481 upper extremity fractures, finger fractures (27.47%) and distal radius fractures (25.37%) were common, while e-scooter-related cases exhibited radius and ulna shaft fractures (23.07%). Of 2400 lower extremity fractures, toe fractures (30.2%) and metatarsal fractures (19.66%) predominated, with e-scooter-related injuries largely featuring metatarsal fractures (30%). The surgery rate in all patients was 8.92%, whereas the surgery rate specifically for e-scooter injuries was 48.2%. Significantly greater occurrence of lower extremity fractures was evident in e-scooter-related injuries compared to upper extremities (p = 0.011). Collisions involving stationary or moving objects were linked to injuries in the lower extremities, whereas falls were primarily associated with injuries in the upper extremities. Treatment included surgery (48.2%) and conservative management (52.8%), with ORIF (35.7%) and CRIF (10.7%) utilised. E-scooter-related fractures and dislocations are typically more severe, often requiring surgery, compared to other fractures during the same period. The study emphasises the link between injury type and increased risk of lower extremity fractures or dislocations.

Simulation-Based Investigation of Crack Formation in Forged MB15 Magnesium Alloy

In the process of riveting an MB15 forging die, cracks were discovered emerging along the longitudinaldirection and near the riveting hole. Through fracture analysis, microscopic observation, energy spectrum analysis,metallographic examination, and hardness test, the properties and causes of the cracks are discussed. The results indicatethat the cracking type is intergranular brittle cracking, occurring during the forging stage. Furthermore, the recrystallizationat the crack site is found to be incomplete, which is attributed to the low deformation temperature.

Parametrization and characterization of DED printings using recycled AISI 303 powder particles

This study investigates an upcycling solution to transform AISI 303 stainless steel chips into powder feedstock for Direct Energy Deposition (DED) printing. All the chips were transformed into particles, using a disc milling process, in a size range of 38 to 212 μm with irregular shapes. The work proceeded by parametrizing DED printings on a non-preheated AISI 1045 substrate. Then, a wall-like structure was printed and submitted to microstructure, tomography, microhardness, tensile test and fracture analyses. The printed alloy showed a hardness of 220 ± 14 HV0.1 with a reducing tendency from the heat-affected zone to the topmost region, attributed to the formation of oxides and heat accumulation. The bimetallic specimen tensile test showed failure in the substrate region, verifying a good bonding of the interface. Tomography analysis also validated this result.

Fracture analysis of orthotropic functionally graded materials using element-based peridynamics

A fracture model of orthotropic functionally graded materials (FGMs) based on element-based peridynamics (EBPD) is proposed. Two-dimensional (2D) orthotropic FGMs use three-node triangular elements to describe the force density of EBPD. Due to the gradient difference of material properties inside the element, the Gauss integral formula is used to average the node performances to the integral point of the element. The equations of motion for EBPD is established, which is also applied to orthotropic FGMs by the Gauss integral formula. The micromodulus coefficient of the EBPD is derived for orthotropic FGMs. The critical strain energy density criterion is used as the failure criterion to simulate the quasi-static and dynamic fracture problems. A series of numerical examples, including displacement analysis, stress analysis, dynamic crack propagation of FGM beam, and crack growth of orthotropic FGMs under four-point bending load, are used to validate the accuracy of the fracture model of orthotropic FGMs. The proposed model can be helpful to the material gradient design for FGMs satisfying certain requirements.

A new digital image correlation method for discontinuous measurement in fracture analysis

The Digital Image Correlation (DIC) method is commonly used in fracture analysis, but it has limitations in measuring discontinuities, which is crucial in fracture analysis. To address this issue, this paper proposes the Adaptive Discontinuous Digital Image Correlation (AD-DIC) method, which is explicitly designed to measure discontinuous displacement fields effectively and accurately in fracture analysis. The AD-DIC method both overcomes the limitations of previous methods by incorporating an adaptive subset tracking technique, which adaptively adjusts the binarization threshold, and improves the traditional Reliability Guided-Digital Image Correlation algorithm to reconstruct the displacement field near cracks. According to high-precision discontinuous displacement fields measured by AD-DIC method, we can accurately identify cracks, measure crack opening, and calculate inclination angles. To validate the effectiveness of the AD-DIC method, theoretical images of type I and mixed-mode I/II cracks are analyzed, as well as four actual experiments. The results show that the AD-DIC method achieves a high level of accuracy in calculating crack opening, with an error of less than 0.1 pixels. The actual experiments presented in this study demonstrate the wide-ranging applications of the AD-DIC method in fracture analysis, including identifying cracks that are difficult to detect with the naked eye, measuring crack opening and inclination angle, and tracking crack propagation processes over time. This study provides an effective tool for brittle fracture analysis, and the relevant algorithms can serve as a reference for discontinuous measurement.

Physio-chemical, mechanical and fracture analysis of ultra-high-performance cementitious composite

The aim of this research was to develop cost-effective and environmentally friendly ultra-high-performance concrete (UHPC) using fly ash (FA) and quartz powder (QP) as sustainable cement replacements. The performance of the various constituents was examined and their influence on fresh and hardened properties was investigated in order to determine the optimum trial mix design. A cube compressive strength of 144 MPa was achieved with 20% FA and 10% QP and other ingredients without any special heat treatment. Advanced characterisation studies, such as the heat of hydration and X-ray diffraction analysis, were performed to gain understanding of the performance of FA-blended UHPC. Various fracture properties (fracture toughness, fracture energy, brittleness etc.) were investigated considering geometrically similar notched beam specimens for UHPC mixes with steel fibre contents of 1.5% and 2.5%. The optimum UHPC mix achieved good scores in terms of the strength index and the embodied carbon dioxide emissions index, indicating that the concrete is eco-friendly and sustainable.

Stress analysis of horizontal mid-root fracture managed with different intraradicular fixation protocols: A 3D-finite element study.

The current study evaluated the stress distribution in a maxillary central incisor with mid-root fracture after splinting with different intra-radicular posts using 3D-finite element analysis (FEA).Five 3D-FEA models were constructed. Model 1 was an intact tooth with no fracture, Model 2: A tooth with a horizontal mid-root fracture, with no treatment. Model 3: Same as model 2, and intraradicular splinting using fiber post. Model 4: Same as model 2 and intra-radicular splinting using Protaper Gold file F3. Model 5: Same as model 2, and with intraradicular splinting with Ribbond. The FEA of all models was done to obtain the maximum Von-Mises stress in the root canal space, the dentin, the periodontal ligament, and the bone. The highest Von Mises stresses for the root canal space and the dentin were found in Model 3, followed by models 4, 5, and 2, and least in Model 1. The Von Mises stress of the periodontal ligament was the least in model 1. The Von Mises stress of bone was higher in all experimental models than in the baseline model. The results suggest that in cases where intra-radicular splinting is indicated, fiber posts and Ribbond are better alternatives to endodontic files due to the lower stresses exerted.

Fracture analysis of Brazilian circular hole disk under mixed mode loading

The paper presents an investigation into a Brazilian disk specimen featuring a concentric circular hole, accompanied by two internal edge radial cracks. By introducing rotations of the cracks relative to the vertical axis, a combination of fracture modes I and II is induced. Employing the finite element method, we compute stress intensity factors related to fracture modes I and II, alongside T-stresses, while varying geometric parameters such as inner and outer diameters, crack length-to-ring width ratio, and crack inclination angle. Experimental analyses of ebonite's fracture toughness in the mixed mode are conducted, subjecting samples to static loading until complete failure. Each test provides the angle at which crack initiation occurs and the corresponding critical load. Three distinct fracture criteria - the generalized maximum tangential stress criterion (GMTS), extended maximum tangential strain criterion (EMTSN), and generalized strain energy density (GSED) criterion - are employed to predict fracture direction and critical load. The outcomes exhibit good correspondence between experimental critical loads and theoretical predictions.

Dissimilar joining of duplex AISI 2304 stainless steel/austenitic AISI 321 stainless steel using resistance spot welding technique: Microstructural evolutions, tensile-shear properties, and fracture analysis

In this work, microstructural characteristics and mechanical performance of spot weld joints of AISI 321 austenitic stainless steel (ASS)/AISI 2304 duplex stainless steel (DSS) were experimentally assessed. The welding current and time were varied to determine their effects on the failure load/energy and mechanism of dissimilar welds. The weld metal (WM)’s microstructure had a ferritic matrix as well as a distribution of grain boundary, Widmanstätten, and transgranular austenite. Some precipitates were found in the weld. The heat-affected zone (HAZ) of the AISI 321 ASS did not experience extensive phase evolutions and only grain coarsening occurred. This led to the HAZ softening. While extensive phase transformations were identified in the HAZ of the AISI 2304 DSS. Its microstructure contained a ferrite matrix with Widmanstätten and grain boundary-type austenite. Such microstructure resulted in the HAZ strengthening. Alteration of the welding condition from 1 kA – 2 s to 3 kA – 2 s raised peak load (tensile-shear strength) from 9.7± 0.8 to 16± 1 kN and energy absorbed to fracture from 15.52 ±1 to 51.2± 2 J. Enhanced WM size was responsible for them. Finally, as welding condition reached 4 kA – 2 s, they would decrease to 14.4±1 kN and 41.76± 3 J, respectively. It arises from surface splash. Once the welding condition varied from 3 kA – 1 s to 3 kA – 3 s, the weld performance was promoted i.e., improvement of peak load from 13± 1 to 19.6± 0.5 kN and energy absorbed to fracture from 23.4±2 to 49±3 J. It results from the WM enlarged. Ultimately, welding condition of 3 kA – 4 s causes a degradation in the weld performance i.e., drop of peak load to 15.8±1 kN and energy absorbed to fracture to 33.18± 2 J. This was on account of surface splash. With reference to the fracture analysis, interfacial, single pull-out, and double pull-out fracture modes were characterized.

Influence of Loading Waveform on the Fatigue Life of 34CrNi3MoVA Steel

Mechanical components often experience fatigue loading from various waveform conditions during their operational lifespan. However, the underlying mechanisms through which variations in loading waveform affect the fatigue life of components remain unclear. Thus, this study conducted tension–compression fatigue experiments on 34CrNi3MoVA steel specimens under the same stress amplitude with different waveforms (cosine, triangular, sawtooth, and reverse sawtooth) to investigate the effects of loading waveform variations on the cyclic strain hardening behaviors, the fatigue fracture failure, and the fatigue life. The results indicated that specimens under different waveforms all exhibited cyclic strain hardening. The fatigue cyclic hardening level progressively increased in the order of cosine, triangular, and sawtooth waveforms, resulting in a continuous increase in cyclic saturation strain amplitude. The analysis of fatigue fractures demonstrated a consistent increase in both the initiation and propagation zone areas in the order of cosine, triangular, and sawtooth waveforms, and the boundary between the propagation and final fracture zones gradually shifted from a straight to a curved shape. The influence mechanisms of cyclic loading waveforms on the fatigue life of specimens were analyzed based on the energy dissipation, leading to the development of a universal fatigue life prediction model applicable to different waveform conditions, the model was then verified with the reverse sawtooth wave specimens and resulted in a prediction error less than 15%. The study is expected to serve as a significant guide for predicting and evaluating the fatigue life of mechanical components under various fatigue loading conditions.

High C-Factor Cavities: How Do "Snowplow Technique", Adhesive Application Mode and Aging Influence the Microtensile Bond Strength to Dentin?

To investigate the microtensile bond strength (µTBS) to dentin in class-I cavities using different layering techniques, adhesive application modes, and aging. 150 caries-free human molars were randomly assigned to 8 experimental and 2 control groups (n=15 teeth/ group). For each tooth, a standardized class-I cavity was prepared (4x4x4 mm) and pretreated with a universal adhesive (self-etch or etch-and-rinse mode). Incrementally layered restorations served as the control. In the experimental groups, either lining with bulk-fill flowable composite and a layering technique, bulk filling, or the snowplow technique with one or two layers of viscous composite were applied. Four microsticks were obtained from each cavity. Half were tested initially and the other half after aging (thermocycling, 15,000 cycles, 5-55°C, n=30 sticks/group). Tobit regression was used for analyzing group differences, including analysis of interactions, Pearson's chi-squared test or Fishers's exact test for fracture analyses (significance level 0.05). Regression analysis showed significant differences in µTBS between groups initially and after aging. In both etching modes, lining with a bulk-fill flowable composite and layering technique achieved the highest µTBS both initially and after aging. In contrast to the etching mode (self-etch < etch-and-rinse), aging did not influence µTBS significantly. The predominant failure types were adhesive and mixed, with a significantly lower number of pre-test failures in the etch-and-rinse groups. The etch-and-rinse mode achieves higher µTBS in class-I cavities compared to the self-etch mode. The lining technique with bulk-fill flowable composite as well as the snowplow technique yielded the highest µTBS after aging, whereas bulk filling and its combination with the snowplow technique resulted in lower µTBS.

Bonding of Composite Cements Containing 10-MDP to Zirconia Ceramics Without Dedicated Ceramic Primer.

To measure zirconia-to-zirconia microtensile bond strength (µTBS) using composite cements with and without primer. Two Initial Zirconia UHT (GC) sticks (1.8x1.8x5.0 mm) were bonded using four cements with and without their respective manufacturer's primer/adhesive (G-CEM ONE [GOne] and G-Multi Primer, GC; Panavia V5 [Pv5]), and Panavia SA Cement Universal [PSAu], and Clearfil Ceramic Plus, Kuraray Noritake; RelyX Universal (RXu) and Scotchbond Universal Plus [SBUp], 3M Oral Care). Specimens were trimmed to an hour-glass shaped specimen whose isthmus is circular in cross-section. After 1-week water storage, the specimens were either tested immediately (1-week μTBS) or first subjected to 50,000 thermocycles (50kTC-aged μTBS). The fracture mode was categorized as either adhesive interfacial failure, cohesive failure in composite cement, or mixed failure, followed by SEM fracture analysis of selected specimens. Data were analyzed using linear mixed-effects statistics (α = 0.05; variables: composite cement, primer/adhesive application, aging). The statistical analysis revealed no significant differences with aging (p = 0.3662). No significant difference in µTBS with/without primer and aging was recorded for GOne and PSAu. A significantly higher µTBS was recorded for Pv5 and RXu when applied with their respective primer/adhesive. Comparing the four composite cements when they were applied in the manner that resulted in their best performance, a significant difference in 50kTC-aged μTBS was found for PSAu compared to Pv5 and RXu. A significant decrease in µTBS upon 50kTC aging was only recorded for RXu in combination with SBUp. Adequate bonding to zirconia requires the functional monomer 10-MDP either contained in the composite cement, in which case a separate 10-MDP primer is no longer needed, or in the separately applied primer/adhesive.

A novel extended integrated radial basis functions meshfree method for crack analysis in plate problem

In this paper, a novel extended meshfree method is presented based on the integrated radial basis functions (iRBF) for crack analysis in bending plate problems. The new method is named XiRBF. The First-order Shear Deformation Theory (FSDT) is adopted to describe the deformation and stresses in cracked plate structures. The advantage of the iRBF approach is that it starts the approximation process with the highest-order derivative of the primary function first and then the lower-order derivatives are obtained by integration. This approximation style can give more accurate results for derivative values that appear a lot in governing equations of boundary value problems. In addition, the iRBF shape function also satisfies the Kronecker delta property, so essential boundary conditions can be applied as simply as the finite element method. In fracture analysis, to model the discontinuous behavior of crack surfaces, the Heaviside function is used, and to capture the singularity at the crack tip, the enriched functions are selected suitably based on the asymptotic analysis from the analytical solution. Various numerical tests are performed in which the stress resultant intensity factors (SRIFs) are calculated and the crack paths are visualized for crack propagation in the plate problems. The accuracy and efficiency of the proposed method are confirmed by comparing the present results with those obtained by other existing methods.

Therapeutic Effects of a Placental Tissue-Derived Allograft on Fracture Healing

Background:As 5-10% of fractures will not heal without medical intervention, there is an ongoing need for effective treatments to promote fracture healing. CTM Biomedical produces human placental tissue-derived allografts that are used clinically and may assist in healing; however, no pre-clinical studies assessing these products have been performed. Our study investigating the impact of CTM products on the healing of a standard femoral fracture and a critical sized femoral defect (CSD) aims to fill this gap. We hypothesize that CTM product application will improve fracture healing and reduce pain-related behaviors.&#x0D; Methods:Femoral fractures were induced in 45 mice. CTM membrane, CTM paste, a combination of CTM membrane and paste, or saline was applied to each fracture. X-rays were taken twice weekly over 22 days, and blinded modified Radiological Union Scale for Tibia (mRUST) fracture scoring was performed. Complete blood analysis was conducted weekly. Following euthanasia 23 days post-surgery, μCT and histomorphometric analyses were conducted. CSDs have also been surgically induced in the femurs of 95 mice, with plans for similar fracture analyses.&#x0D; Results:CTM product application did not significantly alter the levels of inflammatory cells, suggesting that the mice did not undergo immunological reactions. mRUST scoring indicated that CTM products may not alter fracture healing rates. However, combined application of CTM membrane and paste significantly increased the fracture callus’s mineralized volume (by ~90%) and the percent of the callus that was bone. CTM membrane and paste application also led to an increased threshold for hind paw withdrawal, suggesting that CTM products may decrease pain-related behaviors.&#x0D; Future Directions:We hypothesize that in our CSD model, mice treated with the combination of CTM membrane and paste will display improved fracture healing and decreased pain-related behaviors. If shown to be effective, CTM product use may decrease fracture nonunion risk and increase comfort.

Isolated traumatic orbital floor fracture: An analysis of the National Trauma Data Bank.

To date, no study provides a comprehensive analysis of traumatic orbital floor fractures across the United States. We aimed to characterize patient demographics, injury-related variables, and operative management in this population. The National Trauma Data Bank was queried for open or closed orbital floor fractures from 2008 to 2016. Clinical data were extracted. Overall, 148,592 orbital floor fractures were identified, with 142,577 (95.9%) closed- and 6158 (4.1%) open-type fractures. A total of 106,243 (71.5%) patients were male and the median patient age was 41 years. The majority of patients (79.2%) had abbreviated injury scale scores of ≤2, indicating minor/moderate injury. Fracture mechanism of injury (MOI) differed by gender, with the most frequent being unarmed fights in men (34.3%) and falls in women (14.0%). There were 29,600 patients (19.9%) with isolated orbital floor (I-OF) fractures. The MOI most strongly associated with operative intervention of with I-OF fractures were penetrating injuries caused by a firearm (odds ratio [OR]: 2.91; 95% confidence interval [CI]: 1.62-5.20) and cuttings/piercings (OR: 2.17; 95% CI: 1.29-3.65). This large epidemiological study reveals that orbital floor fractures tend to present with minor or moderate injuries and are more likely to require operative intervention in setting of firearm or cut/pierce injuries.