Fracture Surface Topography Research Articles

Evaluation of Fracture Strength and Surface Topography of Interim Prosthodontics Fabricated Using 3D Printing Compared to CAD/CAM Systems (In-Vitro Study)

Evaluation of Fracture Strength and Surface Topography of Interim Prosthodontics Fabricated Using 3D Printing Compared to CAD/CAM Systems (In-Vitro Study)

Quantitative matching of forensic evidence fragments using fracture surface topography and statistical learning

The complex jagged trajectory of fractured surfaces of two pieces of forensic evidence is used to recognize a “match” by using comparative microscopy and tactile pattern analysis. The material intrinsic properties and microstructures, as well as the exposure history of external forces on a fragment of forensic evidence have the premise of uniqueness at a relevant microscopic length scale (about 2–3 grains for cleavage fracture), wherein the statistics of the fracture surface become non-self-affine. We utilize these unique features to quantitatively describe the microscopic aspects of fracture surfaces for forensic comparisons, employing spectral analysis of the topography mapped by three-dimensional microscopy. Multivariate statistical learning tools are used to classify articles and result in near-perfect identification of a “match” and “non-match” among candidate forensic specimens. The framework has the potential for forensic application across a broad range of fractured materials and toolmarks, of diverse texture and mechanical properties.

Strain rate and temperature‐dependent shear fracture mechanism of high‐energy propellant/liner interface zone

AbstractThe shear fracture of the high‐energy propellant/liner interface zone occurs in many application cases of solid rocket motors (SRMs). The shear fracture experiment development is thus a crucial issue. Here we aim to study the shear fracture mechanism of the interface zone under varying strain rates and temperatures. Shear experiments are carried out using self‐made specimens containing prefabricated cracks. Force‐displacement curves, experimental images, and fracture surface topographies are obtained at different strain rates and temperatures. The strain field of the specimen surface is analyzed using the digital image correlation (DIC) method. Additionally, the fracture surface topographies are analyzed using ImageJ software. The results show that the shear mechanical properties of the interface zone are strongly dependent on strain rates and temperatures. Specifically, the shear fracture strength and failure displacement exhibit a decrease with increasing temperature and an increase with increasing strain rate. The DIC analysis shows that the fracture strain of the interface zone typically ranges from 0.4 to 0.6. The analysis of the fracture surface topographies reveals that the shear fracture modes are predominantly mixed fractures, including propellant/liner interface fractures and propellant cohesive fractures. Since the propellant/liner interface is more sensitive to strain rate and the propellant is more sensitive to temperature, the propellant/liner interface fracture ratio increases from 1.99 % to 60.26 % with decreasing strain rate and temperature. The results show that the experimental method can effectively be used to study the shear fracture mechanism of the high‐energy propellant/liner interface zone.

The Smith-Watson-Topper parameter and fracture surface topography relationship for additively manufactured 18Ni300 steel subjected to uniaxial variable-amplitude loading

In this paper, the association between Smith-Watson-Topper (SWT) parameter and fracture surface topography is studied in additively manufactured maraging steel exposed to variable-amplitude fatigue loading. The post-failure fracture surfaces were examined using a non-contact 3D surface topography measuring system and the entire fracture surface method. The focal point is on the correspondence between fatigue characteristics, articulate by the SWT parameter, and the fracture surface topography features, represented by areal, volume, and fractal dimension parameters. A fatigue life prediction model based on SWT and fracture surface topography factors is proposed. The presented model expresses good compliance with fatigue test results. This model can be useful for post-mortem analysis of engineering elements under variable-amplitude loading fatigue, especially for materials produced by additive manufacturing (AM).

Fracture surface topography measurements analysis of low-alloyed corrosion resistant steel after bending-torsion fatigue tests

In this paper, an assessment of a topography measurement method for fracture surfaces of 10HNAP steel after bending-torsion fatigue tests was performed. Surface roughness was measured by using a non-contact Focus Variation Microscopy (FVM) technique in which the non-measured points (NMPs) and outliers (spikes) were removed by the application of general methods. The results revealed, that the optical measurement method introduced variations in the high-frequency errors, considered as noise within the selected bandwidth. Therefore, the minimization of the high-frequency noise (HFN) was proposed based on an extensive examination of ISO 25178 roughness parameters. Additionally, a general S-filter was applied, as recommended by international standards and commercial software. It was used to identify and remove noise from the measured data after pre-processing. Consequently, levelling and eliminating of NMPs and spikes was successfully performed. Subsequently, the results obtained by using various filters were compared to further assess the impact of different filtration bandwidths. Finally, the proposed procedure was validated by implementing different general functions, such as autocorrelation (ACF), power spectral densities (PSD), and texture direction (TD). It was concluded, that coupled characteristics, including profile and areal measurements, should be studied simultaneously since they are necessary to analyze the fracture surfaces comprehensively.

Role of Fracture Roughness in Fracture Surface Evolution During Acidized Corefloods of Calcareous Shales

Summary During the hydraulic fracturing process, an acidic hydraulic fracturing fluid (HFF) is injected at high flow rates to break the rock and enhance its flow potential. This rock-fluid interaction induces both physical and chemical alterations on the fracture surface, resulting in the formation of a “reaction-altered zone.” Recent research has revealed that the depth of reaction penetration is minimal, and most changes occur on the fracture surface. To gain a deeper understanding of how fracture roughness affects fracture aperture change, in this work we adopt an experimental approach. Two similar samples of carbonate-rich Wolfcamp shale with calcite-filled fractures are selected. One sample is cut through the center creating a smooth fracture (SF), while the other is fractured by parting along the calcite-filled fracture, generating a rough fracture (RF). The fracture surface topography, mineral distribution, fracture aperture, and rock hardness are characterized before a reactive coreflood using an equilibrated acidic brine is conducted. The pressure drop across the core is measured, and the effluent is periodically collected and analyzed using mass spectrometry. The temporal changes in the fracture surface are observed by conducting physicochemical surface characterization after the coreflood. The results indicate that calcite dissolution is the primary chemical reaction occurring on the fracture surface, weakening it. Furthermore, this dissolution decreases the fracture roughness, which results in fracture closure and ultimately a decrease in the fracture conductivity. The most significant change in the fracture aperture is observed near the inlet. These results highlight the potential impact of fracture roughness on the mechanism of fracture evolution during acidized corefloods. Higher fracture roughness is associated with increased fines migration and a more significant overall change in fracture aperture during injection. This research provides valuable insights into the intricate processes at play during hydraulic fracturing and aids in understanding the dynamics of fracture growth in such conditions.

Strain energy density and entire fracture surface parameters relationship for LCF life prediction of additively manufactured 18Ni300 steel

In this study, the connection between total strain energy density and fracture surface topography is investigated in additively manufactured maraging steel exposed to low-cycle fatigue loading. The specimens were fabricated using laser beam powder bed fusion (LB-PBF) and examined under fully-reversed strain-controlled setup at strain amplitudes scale from 0.3% to 1.0%. The post-mortem fracture surfaces were explored using a non-contact 3D surface topography measuring system and the entire fracture surface method. The focus is on the relationship between fatigue characteristics, expressed by the total strain energy density, and the fracture surface topography features, represented by areal, volume, and fractal dimension factors. A fatigue life prediction model based on total strain energy density and fracture surface topography parameters is proposed. The presented model shows good accordance with fatigue test results and outperforms other existing models based on the strain energy density. This model can be useful for post-failure analysis of engineering elements under low-cycle fatigue, especially for materials produced by additive manufacturing (AM).

How do different intraoral scanners and milling machines affect the fit and fatigue behavior of lithium disilicate and resin composite endocrowns?

The aim of this in vitro study was to evaluate the effect of the combinations of two different intraoral scanners (IOS), two milling machines, and two restorative materials on the marginal/internal fit and fatigue behavior of endocrowns produced by CAD-CAM. Eight groups (n= 10) were considered through the combination of TRIOS 3 (TR) or Primescan (PS) IOS; 4-axes (CR; CEREC MC XL) or 5-axes (PM; PrograMill PM7) milling machines; and lithium disilicate (LD; IPS e.max CAD) or resin composite (RC; Tetric CAD) restorative materials. Specific surface treatments were applied to each material, and the bonding to its corresponding Endocrown-shaped fiberglass-reinforced epoxy resin preparations was performed (Variolink Esthetic DC). Computed microtomography (μCT) was performed to assess the marginal/internal fit, as well as a mechanical fatigue test (20 Hz, initial load = 100 N/5000 cycles; step-size = 50 N/10,000 cycles until a threshold of 1500 N, then, the step-size was increased if needed to 100 N/10,000 cycles until failure or a threshold of 2800 N) to evaluate the restorations long-term behavior. Complementary analysis of the fracture features and surface topography in scanning electron microscopy was performed. Three-way ANOVA and Kaplan-Meier test (α = 0.05) were performed for marginal/internal fit, and fatigue behavior data, respectively. PS scanner, CR milling machine, and RC endocrowns resulted in a better marginal fit compared to their counterparts. Still, the PM machine resulted in a better pulpal space fit compared to the CR milling machine. Regardless of the scanner and milling machine, RC endocrowns exhibited superior fatigue behavior than LD ones. LD endocrowns presented margin chipping regardless of the milling machine used. Despite minor differences in terms of fit, the ‘IOS’ and ‘milling machine’ factors did not impair the fatigue behavior of endocrowns. Resin-composite restorations resulted in a higher survival rate compared to glass-ceramic ones, independently of the digital devices used in the workflow.

Hydraulic properties of stressed granite fractures with heat-induced void alteration

During the extraction of geothermal heat, the changes in temperature and pressure environments can alter the mechanical and hydraulic behavior of fractured rock masses, affecting the overall transmissivity and heat extraction efficiency accordingly. This study carried out a series of experiments, including X-ray diffraction (XRD), scanning electron microscope (SEM), uniaxial compression tests, and surface morphological scanning, to explore the influence of reservoir temperature on the mechanical behavior of granite and fracture surface topography. The results indicate that as the temperature increases, the uniaxial compressive strength, elastic modulus, and Poisson's ratio of granite show similar variation patterns that increase as the temperature approaches 200 °C and then decrease. In addition, with the increase in temperature, the overall surface elevation and roughness parameters generally decrease due to surface asperity degradation, with the maximum mean mechanical aperture found at 200 °C. Flow simulations were conducted to further explore the influence of temperature and pressure environments on fracture transmissivity and flow fields. It is found that the normalized equivalent hydraulic aperture BN of the tested fractures decreases progressively as the stress increases, and more scattered distributions of BN are observed under higher compressive stresses. Moreover, with the continuous increase in temperature, the average BN slowly increases to its peak of ~0.78 at 200 °C, then it decreases to ~0.76 at 300 °C and remains nearly constant. These findings can be important for assessing heat production performances during the geothermal extraction process with spatially and temporally varying reservoir temperatures and pressures.

Investigation on interlayer debonding behavior of unidirectional composite laminates under cyclical hygrothermal aging duration effects

AbstractThe composite interlamination is the key part of load transfer and plays a decisive role in the overall mechanical performance of composite structures. The interlaminar property is predominantly influenced by the matrix resin which is easily affected by the hygrothermal environment. This paper delved into the effect of hygrothermal aging duration on the interlayer debonding behavior of unidirectional (UD) laminates. The pre‐cracked specimens were treated by hygrothermal aging with a period of 0, 15, 30, 60, 90, and 120 days. The double cantilever beam (DCB) tests were employed to evaluate the interlaminar property. The effect of hygrothermal aging on load–displacement responses, R‐curves, crack growth speed, and fracture surface topography was analyzed. The results revealed that the load‐bearing capacity of aged specimens presented a reduction of 18.6%–29.0% compared with unaged ones. The interlaminar fracture toughness of specimens subjected to 15 days of treatment decreased significantly compared with that of unaged specimens due to the increase of water absorption caused by hygrothermal aging. With the increase in hygrothermal aging time, the interlaminar fracture toughness peaked at 60 days because of the post‐curing effect, followed by a declining trend influenced by the dominant hygrothermal aging effect. The fiber bridging of aged samples was increasingly obvious, became the most prominent at 60 days, and then gradually reduced. The fiber bridging diminished the crack propagation speed, hindered interlaminar debonding, and contributed to the interlaminar toughening.Highlights The samples underwent hygrothermal aging for 0, 15, 30, 60, 90, and 120 days. Load ability of aged samples was at least 18.6% lower than that of unaged ones. R‐curves rose before the crack length of 79 mm and then tended to stabilize. Fracture toughness first decreased, then increased and reduced with aging time. Fiber bridging could hinder crack growth and improve the interlayer property.

Effect of Phytic Acid Etching and Airborne-Particle Abrasion Treatment on the Resin Bond Strength.

This study aimed to evaluate the bond strength of a universal adhesive to dentin (μTBS) using different time periods of airborne particle abrasion (APA) and two types of acid etching. Seventy-two human third molars were divided into 9 groups (n=8) according to dentin pretreatment: APA duration (0, 5, or 10s) and acid etching (no acid - NA, 37% phosphoric acid - PhoA, or 1% phytic acid - PhyA). APA was performed at a 0.5 cm distance and air pressure of 60 psi using 50 μm aluminum oxide particles. Afterwards, two coats of Single Bond Universal adhesive (3M) were applied to the dentin surface. Composite blocks were built using the incremental technique, sectioned into 1×1 mm slices and subjected to microtensile bond strength (μTBS) testing. Fracture patterns and surface topography of each dentinal pretreatment were evaluated using a Scanning electron microscope (SEM). Bond strength data were analyzed using two-way ANOVA and Bonferroni post-hoc tests. The group that received pretreatment with 5s APA and PhoA presented higher μTBS values among all groups, which was statistically different when compared with the PhoA, 10APA+PhoA, and 5APA+PhyA groups. PhyA did not significantly influence the bond strength of the air-abraded groups. Finally, adhesive failure was considered the predominant failure in all groups. Dentin pretreated by airborne particle abrasion using aluminum oxide demonstrated an increase in bond strength when abraded for 5 seconds and conditioned with phosphoric acid in a universal adhesive system.

The influence of the structural condition of high-strength steel on the fractographic characteristics of the fracture structure when testing the specimens with a falling load (VPV, DWTT)

Problem. The fracture structure of samples tested by a falling load (VPV, DWTT) of steel type 10G2FB, Х70 produced by the method of thermomechanical rolling with accelerated cooling was investigated. The DWTT fractures of high-viscosity ferrite-bainite sheet steel of thermomechanical rolling differ significantly from the fractures of ordinary hot-rolled or normalized steel. The results of a fractographic study of the topography of the DWTT samples fracture surface are presented in the paper. Metodology. The paper presents the results of a factographic study of the topography of the fracture surface of VPV sample. Steels with a ferrite-bainite structure after thermomechanical treatment were studied. Result. In the structure of fractures, elements of the "dimensional arrow" type were found. However, the current standards for the falling load test (DWTT) do not take into account the peculiarities of the structure of such fractures, which makes it difficult to identify them by the amount of viscous component. Fractures with splits and fractures of the "dimensional arrow" type can probably be recognized as a type of ductile fracture of high-viscosity thermomechanically rolled steel with a ferrite-bainite structure. Currently, the presence of splits in the fracture of VPV samples of high-viscosity steel is considered an unambiguous indicator of its generally viscous failure. Therefore, based on the similarity of the mechanisms of local destruction that form fractures with splits and fractures of the "dimensional arrow" type, the latter can probably be recognized as a specific type of viscous fracture of high-viscosity thermomechanically rolled steel with a ferrite-bainite structure. Enterprises need the creation of sample break scales for product quality control. Practical value. The conducted research made it possible to draw up scales that are used in the assessment of product quality at manufacturing plants.

Seepage Characteristics of Shale Fracture and the Effect of Filling Sand under Normal Stress

As a new type of unconventional natural gas resource, shale gas plays a vital role in energy supply. In order to deeply understand the shale fracture seepage characteristics, filled and unfilled fracture seepage tests were carried out on shale samples with different fracture surface topography with the use of self-developed shale fracture seepage testing equipment. The fitting formula that the seepage discharge decreased as a negative exponential function with the increase in normal stress was obtained in the unfilled fracture seepage test; the fitting coefficient had a good logarithmic and exponential function relationship with joint roughness coefficient JRC and surface development interface area ratio Sdr. Meanwhile, the modified cubic law was obtained by adding the correction coefficient. The correction coefficient had an exponential relationship with the anisotropy value Ka. Compared with the unfilled one, the fracture surface topography had little effect on the seepage discharge when it was filled. The experimental results show the effects of water head difference, fracture surface topography, particle size, and thickness of filling sand on shale fracture seepage characteristics under different normal stress conditions, which have a certain significance for improving the efficiency of shale gas production.

Topography measurement methods evaluation for entire bending-fatigued fracture surfaces of specimens obtained by explosive welding

In this paper, the methods of compensation of differences in the results of entire bending-fatigued fracture surface topographies were presented. The roughness evaluation was performed with a focus variation microscope and confocal surface topography measurement techniques. The differences in the ISO 25178 roughness parameters were investigated and procedures for their compensation were studied. It was found that various types of optical measurements can cause differences in the errors occurring in the measurement process, such as outliers, and noise. The reduction of differences in the various optical roughness measurements can be attained when measurement errors are compensated. For this study, the applications of general procedures available in commercial software can be suitable for improvements of the roughness measurement results, such as raw data thresholding technique, digital filtering (S-filter), power spectral density, and autocorrelation function analyses. The validation of measurement techniques was proposed for areal and profile studies, including analysis of differences in the calculation areal ISO 25178 roughness parameters.

Effects of cyclic fatigue loads on surface topography evolution and hydro-mechanical properties in natural and artificial fracture

This work investigated permeability evolution for fluid flow through natural fractures and artificial fractures in granite and the evolution of failure surface under cyclic fatigue loads condition. We revealed and compared a clear distinction between two types of fracture surfaces before and after the test, and analyzed the evolution of fracture surface roughness and other parameters which can characterize their topography feature, as well as the relationship between fracture surface topography and permeability. The studies indicated that artificial fractures show the higher roughness and subtler variations of surface topography than those of natural fractures, however, the surface topography of natural fractures was more susceptible to cyclic fatigue loads. The initial permeability and average permeability of nature fractures were both higher than those of artificial fractures during the stress-seepage coupling test and the permeability of artificially fracture was more sensitive to normal stress changes. Moreover, the experimental results were in line with theoretical predictions and the research results can provide reference for preventing the failure of rock engineering.

A brief note on entire fracture surface topography parameters for 18Ni300 maraging steel produced by LB-PBF after LCF

The concept of entire fracture surface investigation is helpful in explaining fatigue phenomena. In this paper, this method has been applied for 18Ni300 maraging steel using a 3D measurement system. Before post-mortem analysis, the specimens produced by laser beam powder bed fusion (LB-PBF) were tested under low-cycle fatigue (LCF) for eight strain amplitudes in the interval 0.3% to 1.0%. The attention was placed on the relationship between the fatigue features, represented by the strain level and the fatigue life as well as the fracture surface topography evaluated in the form of areal, volume and fractal dimension parameters. It was found that fatigue life predictions calculated using the core material volume Vmc, obtained with the entire fracture surface method were within a scatter band with factors of ±1.5. The present results can be useful for the analysis of damaged structural elements exposed to LCF, especially for materials produced by additive manufacturing (AM). The outcomes of this brief note are important for the development of other fractographic methods and validation of fatigue life evaluation procedures.

Failure Analysis of Fatigue Failed M20 Class 8.8 Galvanized Steel Bolt

An M20 Class 8.8 galvanized steel bolt (derrick bolt) was found to fail after five years of service in an offshore drilling station. A comprehensive failure analysis investigation was carried out to reveal the root cause of the detected failure. Visual inspection coupled with complete microstructural characterization as well as mechanical testing were performed in the investigation. The results showed that the failure was mainly caused by fatigue failure. The initiation of the fatigue crack was supposedly promoted by the existence of non-metallic inclusions that were present at both the surface and the interior of the microstructure. Furthermore, unbalanced preload forces resulted in bolt loosening which caused fretting wear of the galvanized layer thickness. The detected drop in the galvanized layer thickness by 42.20% at the primary origin of the fatigue crack along with the presence of non-metallic inclusions were thought to be the reason for the initiation of the fatigue crack. The crack was then found to propagate through a transitional complete cleavage to quasi-cleavage fracture as appeared from fracture surface topography studied by scanning electron microscopy (SEM). The final stage of the fatigue failure was found to be caused by ductile fracture of the overloaded zone.

Fractographic-fractal dimension correlation with crack initiation and fatigue life for notched aluminium alloys under bending load

In this study, fatigue fracture surfaces of aluminium alloy 2017-T4 notched specimens were investigated under cyclic bending to find an alternative failure loading index.. The surface topographies were measured on the entire fracture area with an optical profilometer for different loading conditions. Fatigue crack initiation life Ni and total fatigue life Nf were examined using standard surface topography parameters (such as, root mean square height Sq, arithmetical mean height Sa, maximum height Sz) and non-standard surface topography parameters (such as, fractal dimension Df). Fatigue life assessment was successfully performed by combining both fracture surface topography and stress state features. The results show that the fracture plane geometry, expressed by the fractographic-fractal dimension, can facilitate the estimation of post-failure loading history.

Fractographical quantitative analysis of EN-AW 2024 aluminum alloy after creep pre-strain and LCF loading

This paper explores the applicability of a new damage parameter combining both fracture surface topography and loading features to estimate the fatigue lifetime under creep pre-strain and low-cycle fatigue loading. Fractures of EN-AW 2024 aluminum alloy caused by mixed creep and low-cycle fatigue loading are experimentally characterized and quantified via surface topography analysis. The specimens were preliminary damaged in a creep process at elevated temperature (100 °C, 200 °C, or 300 °C) considering two strain levels for each temperature. The specimens with preliminary damage were then subjected to fatigue tests at room temperature. The post-failure fracture surfaces were examined with an optical profilometer, and the focus was placed on the relationship between the creep-fatigue damage and the associated fracture surface topography parameters. In addition, an original fatigue life prediction model based on both the surface topography values and the applied strains was proposed and verified. The proposed model can be helpful for post-mortem analysis of engineering components subjected to fatigue loading accounting for creep pre-strain.

Effect of graphene and MXene as 2D filler material on physico‐mechanical properties of hemp/E‐glass fibers reinforced hybrid composite: A comparative study

AbstractThe present study concentrates on the mechanical, morphological, water absorption and burning behavior of hemp/E‐glass fiber reinforced hybrid composites (FRHC). The surface adhesive characteristics of the acquired bi‐directional hemp fiber mats were enhanced by treating them with an alkali solution. Furthermore, the present work extends to identify the effects of two 2‐dimensional graphene and MXene nanoparticles as filler on the hardness, flexural and tensile behavior as well as water absorption and flammability characteristics of the FRHC. The glass fiber (G), hemp fiber (H), and hemp/glass (G/H) fiber reinforced epoxy LY556 laminates were fabricated by using the hand lay‐up method followed by the vacuum bagging approach. A 30% and 12% increase in the flexural and tensile strength of the H/G hybrid composite has been observed by adding 1% of graphene as an additional reinforcement compared with the neat FRHC. However, the use of MXene as additional reinforcements shows 45% and 10% enhancement in the flexural and tensile strength of the H/G hybrid composite. In addition, the water absorption capacity of MXene‐filled G/H hybrid composites is found to be almost half of that filled with graphene. Similarly, the flammability results reveal that the burning rate of graphene‐reinforced H/G hybrid composite is 17.44 mm/min. When comparing the mechanical, water absorption, and flammability characteristics of graphene and MXene‐reinforced G/H hybrid composites, graphene gives more intensifying results than MXene. The scanning electron microscopic studies are also incorporated to investigate the fractured surface topography of the FRHC.