Fracture Of Materials Research Articles

Unstable stress-triaxiality development and contrasting weakening in two types of high-strength transformation-induced plasticity(TRIP) steels: Insights from a new compact tensile testing method

The impact of high stress triaxiality on work hardening in transformation-induced plasticity (TRIP) steel has been widely acknowledged, particularly through measurements of the austenite fraction. Understanding this TRIP behavior is crucial for predicting material fracture in press-forming processes. However, the actual flow stresses under high-stress-triaxiality conditions remain largely undetermined. To address this gap, we developed a new tensile testing method using tiny notched round bars to investigate stress-triaxiality-induced work hardening in TRIP steels. The specimens were analyzed using two-dimensional micrometry to allow finite element analyses to identify the flow stress. Additionally, we conducted in situ tensile tests in which their crystal lattice stresses were monitored using synchrotron X-ray diffraction (XRD) to realize mechanism analyses of the unexpected work-hardening behavior identified by the developed tensile testing method. Our combined approach revealed a mutual, unstable increase in the flow stress and stress triaxiality in the TRIP-aided bainitic ferrite steel, which reduced the hardening exponent coefficients and thus induced a higher stress triaxiality. In contrast, the TRIP-aided martensitic steel exhibited a weakening behavior, characterized by a significant decrease in the hardening exponent coefficients in the case of the sharpest notch. XRD analyses showed that microstructural heterogeneity led to an extraordinarily high hydrostatic stress in the austenite phase, accounting for these contrasting behaviors. This finding challenges the established consensus on TRIP steels and suggests the need for a revised framework for their application in press-forming, taking into account stress-triaxiality conditions.

On the Manufacturing of a Cranial PEEK Implant Using SPIF

This article presents an experimental investigation of biocompatible Polyether ether ketone (PEEK) polymeric sheet deformed using Single Point Incremental Forming (SPIF) at room temperature, with the objective of manufacturing a cranial medical implant. The investigation was performed in terms of formability and failure within the principal strains space, being the material Forming Limit Diagram (FLD) assessed by means of Nakajima tests. This material characterization allowed to obtain the formability limits at necking and at fracture of PEEK polymeric material. In addition, an experimental work plan in SPIF was performed in terms of spifability (or formability in SPIF) with the aim of determining the effect of the main process parameters on the spifability, modes of failure, and temperature, among others. As a result, an optimum set of parameters along with the established methodology were used for manufacturing a cranial medical implant made of this high-performance and biocompatible polymeric material. The work primarily shows the feasibility of manufacturing PEEK medical prostheses and implants using SPIF.

Electronic strengthening mechanism of covalent Si via excess electron/hole doping

Brittle fracture of a covalent material is ultimately governed by the strength of the electronic bonds. Recently, attempts have been made to alter the mechanical properties including fracture strength by excess electron/hole doping. However, the underlying mechanics/mechanism of how these doped electrons/holes interact with the bond and changes its strength is yet to be revealed. Here, we perform first-principles density-functional theory calculations to clarify the effect of excess electrons/holes on the bonding strength of covalent Si. We demonstrate that the bond strength of Si decreases or increases monotonically in correspondence with the doping concentration. Surprisingly, change to the extent of 30–40% at the maximum feasible doping concentration could be observed. Furthermore, we demonstrated that the change in the covalent bond strength is determined by the bonding/antibonding state of the doped excess electrons/holes. In summary, this work explains the electronic strengthening mechanism of covalent Si from a quantum mechanical point of view and provides valuable insights into the electronic-level design of strength in covalent materials.

Real-time observation of compressive fracture of porous material by 10-millisecond 4D X-ray microtomography

We report on an application of 4D synchrotron radiation microtomography with a temporal resolution of 10 ms. Our device compresses a sample while rotating it at high speed, making it possible for the first time to capture the moment of a local fracture inside a porous composite material. It was visualized that the fracture was caused by local tensile shear stress, not local compressive stress.

Diffusion-Reaction-Deformation Coupled Modeling of Large-Deformed Germanium Thin Film Anodes

Germanium is known as a high-capacity material that reversibly stores large amounts of lithium, whereas the inevitable volume changes lead to mechanical failures and unstable reaction interfaces. According to the finite deformation theory, we establish a theoretical framework to capture the viscoplastic flow and the interfacial transfer kinetics during lithiation and delithiation under coupled diffusion-reaction-deformation environments. Many microcracks on the surface of germanium electrodes are observed by previous experiments, and we take this effect into consideration by associating the parameters of Li-Ge alloy with the degree of lithiation, such as the concentration-dependent elasticity modulus and yield stress. Subsequently, the framework is used to calculate the mechanical and electrochemical response of thin film electrodes during charge and discharge under the rigid substrate constraint. The results suggest that charge rate and electrode thickness determine the performance of thin film battery, which is in accordance with the experimentally observed phenomenon. The Cauchy stress in the thin film electrode is also subject to the effect of the inhomogeneous spatial distribution of stress, and the stress drop at the ends of the electrodes is the main source of material fracture failure.

Preface to the theme issue 'physics-informed machine learning and its structural integrity applications'.

The issue focuses on physics-informed machine learning and its applications for structural integrity and safety assessment of engineering systems/facilities. Data science and data mining are fields in fast development with a high potential in several engineering research communities; in particular, advances in machine learning (ML) are undoubtedly enabling significant breakthroughs. However, purely ML models do not necessarily carry physical meaning, nor do they generalize well to scenarios on which they have not been trained on. This is an emerging field of research that potentially will raise a huge impact in the future for designing new materials and structures, and then for their proper final assessment. This issue aims to update the current research state of the art, incorporating physics into ML models, and providing tools when dealing with material science, fatigue and fracture, including new and sophisticated algorithms based on ML techniques to treat data in real-time with high accuracy and productivity. This article is part of the theme issue 'Physics-informed machine learning and its structural integrity applications (Part 1)'.

Influence of rate-dependent damage phase-field on the limiting crack-tip velocity in dynamic fracture

This contribution explores three thermodynamically-consistent damage phase-field formulations for rate-dependent dynamic fracture in viscoelastic materials. By means of a numerical study on a uniform displacement strip benchmark, the formulations and modelling assumptions are compared, and the corresponding limiting crack-tip speeds are discussed. In essence, in addition to recalling the existing phase-field model for viscoelastic materials, a damage phase-field formulation for rate-dependent toughness is introduced as a function of the damage-rate at the crack-tip and is contrasted to existing strain-rate dependent toughness models. Dynamic fracture simulations have demonstrated the significant role of rate dependency in suppressing crack branching and accelerating the crack propagation. The rate dependency is analysed through two main mechanisms: (i) the viscous dissipation, which can promote fracture, and (ii) an increase in the energy required to evolve a crack, through rate-dependent toughness models. Depending on the specific choice of parameters, the numerical simulations show crack propagation at speeds that exceed the theoretical limit depicted by the Rayleigh wave speed. Indeed, these high speeds are attributed to the viscoelastic and viscoelastic-like (observed in the case of strain-rate dependent fracture toughness) stiffening at the crack-tip, which translates to faster running surface waves and enables supersonic crack-speeds; a never-seen-before result in damage phase-field simulations.

Effect of incorporating Lode angle into fracture criterion on predicting ballistic resistance of 6061-T651 aluminum alloy plates with different thicknesses struck by blunt projectiles

According to existing research, in addition to the second deviatoric stress invariant, Lode angle parameter (hereinafter abbreviated as Lode angle), which is related to the third deviatoric stress invariant, is also required to be taken into account when studying plastic flow and failure of metal materials. In order to study the effect of incorporating Lode angle into fracture criterion on predicting ballistic resistance of 6061-T651 aluminum alloy plates, a one-stage gas gun system was used to conduct ballistic tests of 6061-T651 aluminum alloy plates with different thicknesses when struck by the blunt projectile with a diameter of 12.66 mm and a mass of 34.0 g. Meanwhile, Abaqus/Explicit finite element software with user-defined material subroutine (VUMAT) was used to establish corresponding finite element models. Under the same constitutive model, numerical simulations were carried out by using Lode independent MJC fracture criterion and Lode dependent WMJC fracture criterion. It is found that when using MJC fracture criterion, not only the ductility of material is overestimated in low stress triaxiality state, resulting in significantly higher predicted ballistic limits; but also the predicted material fracture strain in high stress triaxiality state is negative, sometimes causing irrational predictions. Therefore, some modifications to MJC fracture criterion are needed to reasonably predict the impact process. By contrast, the predicted results of Lode dependent WMJC fracture criterion are more consistent with experiments. Besides, as the thickness of the target increases, the ballistic limit shows an “S” shaped growth trend. Overall, for ballistic tests of targets with different thicknesses, WMJC criterion has a better predictive effect than MJC criterion, indicating the importance of incorporating Lode angle into fracture criteria.

Experimental study of plastic cutting in laser-assisted machining of SiC ceramics

In this paper, the cutting process of laser-assisted machining (LAM) of SiC ceramics is studied. Three processing states of brittleness, plasticity and thermal damage are determined based on the characterization analysis of surface integrity, tool wear and chip morphology, and the surface roughness and tool wear regression model established under the plastic processing state are verified. Firstly, the surface integrity, tool wear and chip morphology are investigated by the single-factor experiment of laser power to explain the material removal mechanism according to the material fracture theory and to determine the laser power range of plastic cutting (185 W–225 W). Then the Box-Benhnken experimental scheme is designed to establish a multivariate prediction model based on the response surface methodology (RSM) to obtain the regression equation of surface roughness and tool wear and further analyze the interaction between process parameters. Finally, the experimental values of surface roughness and tool wear are compared with the predicted values through optimization analysis. The results show that the maximum error is 5 % and 7.57 % respectively, which proves that the model has good prediction ability. The surface roughness and tool wear regression prediction models provide guidance for the selection of plastic cutting process parameters for SiC ceramics.

Super plasticity of bulk metallic glasses at room temperature: A friction self-locking state

This study examines the compressive deformation and fracture characteristics of Fe74Mo6P13C7 bulk metallic glasses (BMGs) with aspect ratios ranging from 1.0 to 2.5. The compressive plastic strain of BMGs exhibits a consistent upward trend as the aspect ratio decreases. As the aspect ratio decreases, the influence of the surrounding friction becomes increasingly pronounced. The finding was made that the exceptional ability of BMGs to exhibit super plasticity at ambient temperature is attributed to the phenomenon of friction self-locking occurring within the shear planes. The deformation behavior of brittle BMGs is significantly influenced by the applied stress conditions. However, it is worth noting that even brittle BMGs can display ductile characteristics when subjected to multiaxial constraints. This finding is not only essential for comprehending the deformation and fracture of amorphous materials, but it can also serve as a valuable reference for rock mass control, structural stability, earthquake mitigation, and disaster reduction engineering.

Numerical investigation on spall fracture in metallic materials due to laser shock peening via phase field approach to fracture

Laser shock peening (LSP) is an effective surface reinforcement technique for metallic materials. However, when LSP is applied to a thin specimen, an undesirable result, spall fracture, may occur. In this work, the spall fracture generated in multiple-shock LSP processes is investigated via the phase field approach to fracture, and is validated with the experimental result. In particular, the relations between the formation of spall fracture and the shock number, the shock wave pressure, the specimen thickness and the fracture toughness of specimen are studied. The results indicate that the formation of spall fracture in multiple-shock processes is an accumulative process, and is mainly influenced by the shock wave pressure and the specimen thickness, and multiple shocks will complicate the interaction between the tensile wave tail and the compressive wave front of the shock wave, leading to an enlargement of the spall fracture region.

A cyclic GTN model for ultra-low cycle fatigue analysis of structural steels

Ultra-low cycle fatigue (ULCF) is a critical concern in the seismic design of steel structures due to its adverse effects on the ductility and energy dissipation capacity of steel connections. The Gurson-Tvergaard-Needleman (GTN) model, a well-accepted micromechanical fracture model, cannot be applied directly to ULCF analysis, as it requires proper estimation of the effects of cyclic loadings on the ductile fracture of materials. In this paper, a cyclic GTN (C-GTN) model was proposed for the ULCF prediction of materials, in which the evolution of microvoids during ULCF loadings was addressed for tensile and compressive half load cycles, respectively, and the effect of the cumulative plastic strains on the material’s resistance to ductile fracture was considered by the reduction of the critical void volume fraction for void coalescence. Then, a VUMAT subroutine was programmed for the C-GTN model, in which the cyclic hardening behavior of materials was simulated with the Voce-Chaboche model. Finally, the C-GTN model was calibrated for the G20Mn5QT cast steel based on previous tests on notched round bar specimens of the material. The applicability of the C-GTN model and the VUMAT subroutine were validated in the ULCF analysis of double-hole plate specimens of the G20Mn5QT cast steel.

Breaking behavior and stress distribution of T12A hard steel core penetrating ceramic/aluminum alloy lightweight composite armor

The armor-piercing incendiary (API) round inflicts significant damage to light armor. This article conducts penetration experiments on lightweight ceramic composite armor using 12.7 mm API rounds. The Rosin-Rammer distribution model is used to analyze the macroscopic fragmentation characteristics of the core, and the SEM is used to analyze the fracture surface of the bullet core after fragmentation at the microscopic level. Numerical simulations are also used to verify and expand the material parameters. The experimental results show that as the penetration velocity increases, the average feature size of the core decreases, indicating an increase in the degree of fragmentation of the core. The fragments generated by the fragmentation can be almost completely restored. The main fracture form is the brittle crushing fracture of the head of the projectile, while the tail and body of the projectile are basically intact, and the fracture surface is mainly a 45° shear fracture and radial platform-like tensile fracture.At the microscopic level, SEM images show that the material fracture mainly occurs in the form of radial cleavage shear fracture and river patterned tensile-shear fracture. The numerical simulation results show that as the penetration velocity increases, the energy dissipation of the core continuously increases. The main energy dissipation process of the core during penetration occurs during the contact with the ceramic cone, accounting for 66.48 % of the total energy loss, while the mass of the core remains almost unchanged during the interaction with the aluminum alloy.In addition, the experiment is verifiedusing different working conditions at different angles, confirming that the "unequal tearing" of the aluminum alloy backing plate is caused by the inclination of the penetration angle. It was also found that the penetration efficiency and destructive capability of the API round are significantly reduced when there is an angled penetration.

Instantaneous dental implant loading technique by fixed dentures: A retrospective cohort study.

In the context of dental prostheses, splinting multiple implants together may improve their stability. The approach may be especially favorable when performing immediate loading procedures, increasing the implant osseointegration rate, and reducing the risk of implant and prosthetic failure. The instantaneous loading technique (ILT) involves creating a metal framework to splint the implants by intraorally welding them pair-by-pair, using purposefully created abutments. The aim of the study was to investigate the prosthetic success when using ILT to rehabilitate partially edentulous patients through immediately loaded prostheses. Clinical records of patients treated with ILT were retrospectively assessed, and the prosthetic success rate was analyzed in terms of fractures, chipping, unscrewing, screw fracture rate, and mucositis. Furthermore, the implant success rates were evaluated by measuring marginal bone loss (MBL). A total of 55 patients (20 males and 35 females with a mean age of 59.8 ±9.4 years), corresponding to 66 prostheses, were included. A total of 160 implants were placed. At the last follow-up (39.6 ±28.4 months), 1 patient (1.8%; 1 prosthesis (1.5%)) showed the fracture of the prosthesis material. Peri-implantitis affected 4 implants (2.5%), and 4 more implants (2.5%) showed radiolucency, affecting 5 patients (9.1%). Two other patients (3.6%) suffered from mucositis. The implant success rate, according to the Albrektsson and Zarb criteria, was 94.4%. No implants were lost. The mean MBL values at the implant level, the prosthesis level and the patient level were 0.28 ±0.56 mm, 0.30 ±0.51 mm and 0.33 ±0.54 mm, respectively. The instantaneous loading technique appears to be a viable approach to rehabilitating partially edentulous patients through immediate loading.

200 Higher bone mineral density in prediabetes, diabetes and with increasing HbA1c in older Irish adults: results from the TUDA study

Abstract Background Patients with type II diabetes have higher Bone Mineral Density (BMD) but paradoxically have an increased fracture risk. However, less is known about the relationship between prediabetes and BMD or fracture risk. We aimed to evaluate the relationship between pre-diabetes, diabetes, HbA1c and BMD in older Irish adults. Methods Study participants were from a large cross-sectional study of adults aged >60 years; Trinity Ulster University Department of Agriculture (TUDA) study. Patients on treatment for osteoporosis, current or previous long-term glucocorticoids, aromatase inhibitors or androgen deprivation therapy were excluded. Diabetes was defined by self-report, use of diabetic medications or HBA1c ≥6.5% and after excluding same, prediabetes was defined as a HbA1c of 5.7–6.4%[1]. BMD was measured by DXA at the total hip and lumbar spine. The relationship between prediabetes, diabetes, HbA1c and BMD was explored in regression models. Results There were 2,127 participants and mean age was 70.0 ± 6.5 with 57.9% female. 17.7% had diabetes and 26% prediabetes. Compared to normoglycaemic participants, diabetics had higher BMD at the hip (p < 0.001) and spine (p = 0.007) and prediabetics higher BMD at the hip (p < 0.001) after adjusting for age, sex, body mass index, serum vitamin D, eGFR, smoking, alcohol intake and timed up and go. In multivariate analysis, increasing HbA1c in non-diabetics was also associated with greater BMD at the hip (p = 0.001) but not the spine. Conclusion This study demonstrates that BMD is increased in older adults with both diabetes and prediabetes and with increasing HbA1c in non-diabetics. Despite this, BMD is known to underestimate fracture risk in diabetics where a lower treatment threshold for starting osteoporosis medications is recommended. This might also hold true in prediabetes where altered BMD could affect material bone quality and fracture risk though studies are conflicting and more research is required.

Effect of Y2O3 addition on microstructure and properties of Ti6Al4V by laser melting deposition

Y2O3 particles act as nucleation sites in the additive manufacturing (AM) process of titanium alloy, making its microstructure refined and homogeneous, which is very beneficial for improving properties. However, obtaining good properties requires a good grasp of the amount of Y2O3 addition. Excessive addition of Y2O3 particles can lead to stress concentration at the tips, increasing the probability of material fracture, so the amount of Y2O3 addition must be strictly controlled. We have attempted to add different contents of Y2O3 particles during the laser melting deposition (LMD) of Ti6Al4V. The microstructure and properties of Ti6Al4V-xY2O3 (x = 0,0.1,0.5,0.9) alloys were studied. The results show that the α-phase size of Ti6Al4V-0.1 wt% Y2O3 significantly decreases. Meanwhile, Y2O3 is activated as nucleation sites, promoting α-phase equiaxed transformation and providing excellent ductility. Compared with Ti6Al4V alloy, the yield strength and tensile strength of Ti6Al4V-0.1 wt% Y2O3 alloy are increased by 7.75% and 10.27%, respectively. What's more, the corresponding elongation increased from 5.97% to 11.53%. In addition, Y2O3 has a positive effect on improving the material's tribological properties. The friction and wear test shows that the wear resistance of Ti6Al4V-0.5 wt% Y2O3 alloy is improved by 3.6 times. This work provides a new method and abundant data for improving the mechanical properties of Ti6Al4V alloy in AM.

Mode I fracture behaviors of plain and PVA reinforced ice at Arctic low temperatures

Since the Mode I fracture of ice materials determines the safety and integrity of ice constructions, this study investigated Mode I fracture behaviorus of strengthened ice materials at Arctic low temperatures. Forty-five three-point bending (TPB) beams, including 12 plain saline water ice (PI) and 33 PVA reinforced saline water ice (PRI), were tested to investigate the mode I fracture behaviors of plain and reinforced ice at low temperatures. The investigated parameters included the low temperature (ranging from −10 °C to −80 °C), ice type (PI and PRI), and mass fraction of fibre (ωf = 0, 1, 2, and 3%), respectively. The failure modes, general P-δ and P-CMOD curves, initial cracking load, double-K fracture toughness, and fracture energy of PI and PRI at low temperatures were revealed. Meanwhile, the effects of temperature and PVA fibre content on fracture behaviors of PI and PRI were also discussed in details. Test results showed that as the temperature decreased from −10 °C to −30 °C, the increments in unstable fracture toughness of PI, PRIA, and PRIB were 414%, 757%, and 250%, respectively. Moreover, the fracture energy of PRI with 3% ωf was 113 times of PRI with 0%. Based on the results and mechanism explanation, three empirical formulae considering the influences of temperature on the unstable fracture toughness of PI, PRIA, and PRIB materials were proposed.

Study on the Deformation and Fracture Mechanisms of Plastic Metals Considering Void Damage

Fracture initiation in plastic metals is attributed to the development of voids. Analyzing the nucleation and growth processes of voids facilitates the study of plastic deformation and fracture mechanisms in metal materials. Uniaxial tensile tests were conducted on two high-quality carbon structural steels, and the microfracture surface morphology of the tensile specimens was observed by using a scanning electron microscope (SEM). From the perspective of vacancy condensation, the nucleation mechanism of voids in the absence of inclusions or particles was analyzed. Based on the continuum damage mechanics theory and the Rice–Tracy (R-T) model, a damage parameter considering the void volume fraction was derived, and a plastic potential function, hardening curve, and constitutive model for the plastic deformation process of the plastic metal material were established. Based on the uniaxial tensile test data of the two sheets of high-quality carbon steel, the strain range data in the hardening stage were converted into true stress–plastic strain data, and the established hardening curve was used to fit the true stress–plastic strain data. The results showed good agreement between the established hardening curve and the experimental results, which effectively reflected the deformation process of ductile fractures in plastic metal materials.

Study on the member fracture and collapse performance of single-layer grid structures using discrete solid element method

In this study, the discrete solid element method (DSEM) incorporating a softening model is proposed, to accurately simulate the dynamic crack propagation and the member fracture of the single-layer grid structure. Firstly, based on the fracture criteria of strain energy release rate, the bilinear softening model and the trilinear softening model are proposed to simulate the fracture in both elastic and elastic-plastic materials. Secondly, the validity of the proposed approach is assessed through a comparison with empirical results. Furthermore, the fracture of the rectangular beam, dynamic crack propagation of the circular tube and member fracture of the hexagonal spatial rigid frame are simulated and compared with other numerical methods. Finally, the DSEM with the softening model is employed to investigate the collapse performance of single-layer grid structures, and the whole process of member fracture is captured by the DSEM. A thorough analysis is conducted to evaluate the influence of material parameters, loading methods, and rise-span ratios on the bearing capacity and fracture occurrence of single-layer grid structures. The results show that the material property of steel is superior to aluminum for single-layer grid structures. Moreover, the single-layer grid structures adopting full node loading or high rise-span ratios are shown to exhibit premature member fracture and rapid structural collapse. The obtained results exhibit remarkable agreement with the experimental results and are superior to the finite particle method (FPM) and the extended finite element method (XFEM). Therefore, DSEM with the softening model possesses the potential to evolve into an effective numerical tool capable of solving complex problems such as dynamic crack propagation and structural collapse.

Fracture Resistance of Laboratory Composite Versus All-Ceramic Restorations in Class II Inlay Cavity Preparations: An In Vitro Study.

A posterior tooth's occlusal surfaces and the proximal surface can be restored by using an inlay, which is an intra-crown cast reconstruction without affecting the cusps of the tooth. When an inlay is prepared using an indirect approach, issues with traditional filling approaches, including poor morphology of the occlusal aspect or proximal aspect, inadequate resistance to wear, or subpar mechanical qualities of the directly inserted filler substance, are overcome. The current study was conducted in order to compare and assess the resistance to fracture of dental materials used in the preparation of inlay restorations indirectly, like composite restorations prepared by laboratories indirectly, inlays formed indirectly of monolithic translucent ceramic derived from zirconia, and inlays formed indirectly of traditional monolithic ceramic derived from zirconia. For the investigation, 100 human premolars of the maxilla that were extracted recently were chosen. A self-polymerizing acrylic resin was used to incorporate the tooth roots in a band made up of polyvinyl chloride up to 2 mm below the cement-enamel junction. The dimension of the band was 1.3 cm by 1.9 cm. Five categories of 20 specimens of such teeth were formed. Category one, featuring teeth in good condition, acted as the positive control category. The remaining four categories of teeth received inlay tooth preparation. The research samples underwent thermocycling after having been preserved for a full week following the cementation of inlay replacements. Then, in a universal testing apparatus, every sample endured axial compressive force with a metal globe delivered vertically at a crosshead rate of 1 mm/minute. The amount of force necessary to cause a fracture was measured in Newtons (N). The mean values of resistance against fracture in specimens in categories 1-5 were 1208.87 N, 614.89 N, 733.05 N, 1179.14 N, and 1148.49 N, respectively. The values of fracture resistance in specimens where an inlay cavity preparation was done but not filled were lower than those in traditional monolithic ceramic derived from zirconia and tooth specimens with inlays formed of monolithic translucent ceramic derived from zirconia, and the difference was significant statistically (p=0.001). The values of fracture resistance in composite inlay restorations prepared by laboratories were indirectly lower than those of monolithic ceramic derived from zirconia and tooth specimens with inlays formed of monolithic translucent ceramic derived from zirconia, and the difference was significant statistically (p=0.004). Within the constraints of the current investigation, we can state that indirect zirconia-based ceramic products offer adequate fracture resistance, but additional research is needed to determine how well these materials hold up under different types of pressures before employing them in clinical tooth restoration.