Crack Mouth Opening Displacement Research Articles

Fracture mechanical behavior of fine-grained carbon-bonded alumina at room and high temperature

The fracture mechanical properties of fine-grained carbon-bonded alumina (Al2O3–C) were investigated in four-point bending tests at single edged V-notched beams (SEVNB) at room and high temperature. Graphite served as a reference material. For measurement of the crack mouth opening displacement (CMOD) an optical system was used. The fracture behavior of Al2O3–C changed from brittle at room temperature to a crack resistance behavior at 1400 °C due to visco-plastic phenomena. The fracture toughness KIc was determined as 0.69 ± 0.07 MPa m1/2 at room temperature and 0.55 ± 0.21 MPa m1/2 at 1400 °C. At room temperature, the work of fracture γwof was determined as 26.3 ± 6.3 J/m2, and Hasselman's thermal shock parameters Rst and R'''' were 8.6 K m1/2 and 0.9 mm, respectively. Although a quantitative analysis of the work of fracture at 1400 °C was hindered by heat shimmer within the chamber, the results indicated significant increases of this parameter as well as Hasselman's thermal shock parameters up to 1400 °C.

Experimental study on fracture damage and seismic performance of loose through-tenon joints in ancient timber structures

A looseness is typical damage of mortise-tenon joints in ancient timber structures. Brittle fractures of loose joints are likely to occur, leading to joint failure during earthquakes. This study conducts pseudo-static tests on three groups of full-scaled through-tenon joints to examine the fracture damage and seismic behavior of the loose mortise-tenon joints and determines fracture damage modes of through-tenon joints with different looseness. It uses the acoustic emission method to measure the ring count on the tenon surface, along with each joint's critical load and critical energy release rate and then analyzes the fracture damage performance of different tenon joints. In addition, this research investigates the hysteretic and skeleton curve, stiffness degradation curve, and tenon pulling quantity of the joint under various fracture damage states. The results showed that the fracture failure mode of the through-tenon joint is a fracture in the variable cross-section and along the local tenon neck. During the loading process, the critical energy release rate initially increases and then decreases as the looseness grows. In addition, with the increase of crack mouth opening displacement (CMOD) and crack length, the bending moment of the joint firstly increases and then decreases. When the variable cross-section breaks and the tenon neck partially cracks, the joints' bending moment and stiffness reduce with increasing looseness. With the increase in local embedment compression in the lower side of the beam end and the mortise, the amount of tenon pull-out of loose joints decreases under positive and negative loading.

Evaluation of modelling parameters for AA2014-T6 in simulating dynamic fracture event

The material behavior of the aluminum alloy AA2014-T6 under different strain rates and temperatures must be examined in order to simulate their responses under extreme loading conditions like dynamic fracture and impact. In the present study, several uniaxial tensile experiments, including quasi-static, dynamic, and triaxiality, were carried out at different temperatures to evaluate the material constants for the Johnson cook constitutive and failure models of AA2014-T6. It was observed that material flow stress exhibited positive strain rate sensitivity at high strain rates and negative sensitivity when temperature increased from 25 to 250 °C. From the triaxiality experiments, it was also observed that the plastic flow increased while the ductility of the material decreased with increasing stress triaxiality. The dynamic fracture behavior of a pre-cracked 3-point bend specimen of AA2014-T6 was studied at different loading rates. Applied load and load point displacement (LPD) were measured using strain gauges. In addition, crack mouth opening displacement (CMOD) and crack initiation time were calculated using the 3D digital image correlation technique. It was found that the loading rates highly influence the dynamic fracture initiation and propagation toughness of the material. A 3D finite element simulation of dynamic 3-point bend experiments was performed in ABAQUS using the J-C damage evaluation criteria, and incident stress obtained from the dynamic experiments was used as an input load to minimize the error. In accordance, with the actual experiments conducted, the material geometry, boundary conditions, and contact circumstances were considered. The authors found good agreement between both the experimental and numerical results.

The Effect of Polypropylene Fibers on the Fracture Characteristics of Lightweight Aggregate Crumb Rubber Concrete Composites

The increasing use of rubber tires and their low recycling ratio have made them a serious environmental problem. This work aims to develop and investigate enhanced lightweight aggregate crumb rubber concrete (PFLWACRC) composites regarding the fracture properties of concrete. Polypropylene (PP) fibers are commonly familiar with increased crack growth endurance of concrete. On the other hand, the reuse of waste rubber in concrete plays a major role in the mitigation of the effects of climate change. Various concrete mixtures were designed with conventional Portland cement and common lightweight coarse aggregates. The variables considered in this study are PP fibers in different percentages (0.2%, 0.4%, and 0.6% volume fraction), and crumb rubber with various substitution proportions (0%, 5%, 10%, 15%, 20%, and 25% of fine aggregates). Cement with 450kg/m3 density with 10% silica fume was used. The fracture characteristics, which involve fracture toughness (KIC) and fracture energy generation (GF), of all concrete mixtures were evaluated by testing two types of samples, i.e. 54 notched concrete beams with dimensions of 10×10×52cm and 54 cylinders with diameter×height equal to 15×30cm. The results showed that the fracture toughness generation addresses the energy scattering limit of concrete mixtures. The findings showed that the existence of PP fibers increased the fracture energy and critical Crack Mouth Opening Displacement (CMOD)c. The PP fibers had a limited effect on the compressive strength and may even reduce it, but a remarkable enhancement of the energy absorption was observed.

Interfacial fracture performance of engineered cementitious composites and fire-damaged concrete

This study investigated the interfacial fracture properties of engineered cementitious composites (ECC) and fire-damaged concrete using bi-material wedge splitting specimens. The full load versus crack mouth opening displacement (CMOD) curves of the bi-material specimens were obtained using wedge splitting tests, and the fracture toughness and fracture energy were calculated. The effects of the maximum temperature experienced by the concrete (20–700 °C) and the interfacial roughness (0–5 mm) on the interfacial damage mode, fracture toughness, and fracture energy were studied. The results indicated that when the maximum temperature experienced by the concrete was lower than 400 ℃ or the interface was smooth, the damage mode of the specimens was primarily adhesive failure. However, when the maximum temperature experienced by the concrete was equal to or greater than 400 °C and the interface was rough, cohesive failure often occurred in the specimens. Owing to the change in the damage mode, the bi-material specimens had the highest values of the fracture toughness and fracture energy at 400 °C. When the maximum temperature experienced by the concrete exceeded 400 °C, both the fracture toughness and fracture energy decreased with the increasing temperature. In this study, the fracture toughness and fracture energy of the bi-material specimens first increased and subsequently decreased with the increaseing roughness, and the maximum fracture toughness and fracture energy values were obtained when the interface roughness was 3 mm. The study results would provide a reference for the surface treatment when ECC was used in the strenthening of fire damaged concrete.

Mechanical degradation of ultra-high performance concrete under flexural fatigue loading

This work investigated the behavior of pre-cracked ultra-high performance concrete (UHPC) under flexural fatigue, quantifying its mechanical deterioration during cyclic loading through crack mouth opening displacement (CMOD), stiffness and energy dissipation rate. The flexural fatigue tests were carried at a frequency of 6 Hz on notched pre-cracked prisms in four distinct maximum load levels: 90%, 80%, 70% and 50% of the material residual bending strength at 0.5 mm of CMOD. The results presented expressive gain in fatigue life and performance for UHPC compared to a 50 MPa SFRC. In addition, a linear relationship between the residual bending strength and the initial stiffness was identified. Equations were proposed to predict the fatigue life according to the upper load limit during the cyclic loading. Finally, the post-fatigue behavior of samples that did not fail after 1,000,000 cycles was evaluated under monotonic bending test. No significant damage was observed on samples subjected to load levels below the endurance limit.

Numerical study and experimental validation of the size effect of smooth and mode I cracked semi-circular bend specimens

The edge-cracked semi-circular bend (SCB) specimen subjected to three-point bending loading is used in many applications to measure the fracture behavior of quasi-brittle materials. The main objective of the present work was to study the effect of the crack length to SCB specimen radius ratio (a/R), span to specimen diameter ratio (S/D), and specimen size on its flexural and mode I crack growth behavior. The contour integral method was implemented using the 3-D finite element method to determine the mode I stress intensity factor. In addition, high-strength concrete specimens were experimentally studied to validate the numerical results. The results show that the maximum compression stress is not sensitive to the S/D value, while the tensile stress is very sensitive. The value of S/D is the main parameter controlling the crack driving force (i.e., the crack mouth opening displacement (CMOD) and the normalized stress intensity factor, YI). For the same S/D, the SCB specimen diameter value change has a marginal effect on CMOD and YI. The specimen with S/D = 0.8 showed that it is the most compatible specimen with three-point bending test conditions, regardless of the SCB specimen size. A good agreement between the numerical and experimental results was achieved.

Influence of interface roughness and rock type on mixed mode fracture characteristics of tunnel shotcrete-rock interface

A four-point shear (FPS) test was conducted to investigate the mixed mode fracture characteristics of the shotcrete-rock interface. Real-time monitoring of the fracture process was achieved using acoustic emission (AE) and digital image correlation (DIC) techniques. The mechanical test results indicate that residual stress increases with modal Angle or roughness under the same crack mouth opening displacement (CMOD). As the modal angle increases, the crack morphology and damage mechanism of the granite-shotcrete interface change. For large modal angles, the crack expands into the granite during the expansion process, leading to a larger range of granite damage at the interface. The results obtained through the nearest neighbor method reveal that specimens with small mode angle, low roughness or weak material properties on one side do not exhibit obvious background events, whereas the cluster characteristics of density distribution are evident. The AE events with smaller nearest neighbor distances were found to be concentrated around the macroscopic cracks. Moreover, the modal angle was observed to have a significant impact on crack opening/sliding displacement, with crack mouth sliding displacement (CMSD) and crack tip sliding displacement (CTSD) both increasing significantly as the modal angle increases.

Fracture properties of steel fibre reinforced high-volume fly ash self-compacting concrete

This paper presents an experimental investigation on the fracture mechanical properties of steel fibre-reinforced high-volume fly ash self-compacting concrete (HFSCC). Specifically, self-compacting concrete (SCC) of various toughness was designed at desired steel fibre volume fractions of 0, 0.25 v%, 0.50 v%, 0.75 v% and 1.00 v% by volume and fly ash contents of 40 wt%, 50 wt%, 60 wt% and 70 wt% by mass. The fracture mechanical properties of HFSCC (cured for one year) were studied by a three-point bending beam test. The influence of fly ash and steel fibre content on fracture parameters was systematically discussed. The research indicated that the fracture mechanical properties of HFSCC with different fly ash percentage were improved by adding steel fibres. The fullness of the force (F)-crack mouth opening displacement (CMOD) curves gradually increased with the steel fibre volume fraction (Vf). The peak load (Fp), peak CMOD (CMODP), fracture toughness (KIC) and fracture energy (GF) of the fracture parameters linearly increased with Vf. Furthermore, the correlation between them was analysed numerically. The slope of the fitting line increased with increasing fly ash content, indicating that high-volume fly ash was more conducive to improving the fracture mechanics of SCC after long-term ageing. After the hydration reaction, residual calcium hydroxide was observed only in the cross-sectional image of HFSCC-70, it helped to improve the fracture mechanical properties of HFSCC.

Data image correlation analysis of the destruction process of 3D printable layered beams subjected to the 3-point bending process

Technological processes and materials related to Additive Manufacturing (AM) are gaining popularity in civil engineering 3Dconcrete printing is aimed mainly at the process of rising the inner and outer walls of buildings. In these elements, the main load is axial compression with a low fraction of bending. The 3D-printing process of cement-based materials provides the construction elements with appropriate compressive strength. Although creating elements, which can carry the tensile loading is necessary to make the 3D-printing process used in civil engineering. Therefore, this paper aims to show the response of the 3D-printed cement-based composites to the bending process to find the effect of complex layered structures on their effective properties. Instead of the standard use of an extensometer to obtain Crack Mouth Opening Displacement results, novel Digital Image Correlation measurement technology was used during research. This technology allows for continuous real-time measurements that are extremely difficult when testing brittle materials such as concrete and avoids the additional introduction of external forces caused by the classical measuring device. The proposed AM material contains the interlayer polymeric net and smeared polymeric reinforcement to enhance flexural strength. The use of the polymeric net and smeared reinforcement introduces residual strength into the composite allowing for its further work after brittle phase failure. However, the obtained results showed that analysed layered beams had decreased interlayer resistance. The process of layer cracking occurs subsequently layer by layer and the failure in different layers developed as an independent process including cracks arresting.

Characterization of fracture development in geometrical similar ultra-high-performance concrete (UHPC) beams using acoustic emission (AE) technique

The acoustic emission (AE) technique is a common method for evaluating the fracture and damage properties of materials. This study utilized the AE technique to analyze the fracture behavior of ultra-high-performance concrete (UHPC) beams. Experiments were conducted on three differently sized beam specimens that were geometrically similar. The center point bending tests were carried out under crack mouth opening displacement (CMOD) control to study the fracture properties of the UHPC beams. Based on the experimental study, the fracture properties such as crack propagation, parametric-based properties, and fracture process zone (FPZ) length and width were predicted in the present work. The AE waves generated during the cracking can readily differentiate between the concrete matrix failure and fiber bridging following the post-peak response in the UHPC beam. In this work, the AE parameters were used to detect the source location, fracture mode, the position of the crack, and strain localization near the crack tip. The presence of steel fibers in concrete provides complexity in identifying the source localization, and wave dispersion results in attenuation and distortion of the AEs. The occurrence of AE events was observed to increase in the post-peak part compared to pre-peak possibly due to fiber bridging, demonstrating the energy absorption capacity. Based on AE results, the length and width of the fracture process zone were found to increase with the specimen size.

Effects of glass fiber usage on fracture energy and mechanical behavior of concrete: An experimental approach

In this study, the fracture and mechanical behavior of glass fiber reinforced concrete (GFRC) are investigated comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using GFRC with 1, 2, and 3 kg/m3 fiber contents and the dimension of 6, 12, and 24 mm to determine the fracture energy. Fracture energy values of the GFRC specimens were calculated by analyzing load versus crack mouth opening displacement (CMOD) curves. Compressive strength was determined using cube samples with the dimension of 150x150mm. Tensile strength and Modulus of elasticity were determined using notched beams with the dimensions of 48010050 mm. Also, notched beams were produced and tested in accordance with RILEM recommendations. In addition, microstructural analyses were performed based on Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations. The results showed that the effects of fiber contents on fracture energy were very significant. However, the effect of fiber addition on the compressive strength and modulus of elasticity values was not significant.

An improved understanding of the influence of w/c ratio and interfacial transition zone on fracture mechanisms in concrete

The interfacial transition zone (ITZ) is significantly influenced by the water/cementitious materials (w/cm) ratio and governs the overall strength and fracture properties of concrete. Even though an ample number of studies on this topic are available in the literature, there is a lack of unified conclusions pertaining to the influence of w/cm ratios on various fracture characteristics and the underlying mechanisms. In this study, an attempt was made to investigate fracture characteristics (such as the size of the fracture process zone (FPZ), fracture energy, traction-free cracks (TFCs), toughening mechanisms) for varying ITZ properties and water/cement (w/c) ratios. Plain concrete beams of size 700 × 150 × 80 mm (l × d × b) with varying w/c ratios were tested under centre-point loading by controlling the crack mouth opening displacement. The acoustic emission (AE) technique was used to assess the internal damage parameters. A novel method was developed for identifying the TFC tip and the FPZ size using AE event location data at different stages of loading. The role of the ITZ on the fracture mechanisms of different types of concrete was also assessed. Evaluation of the fracture energy revealed that its relation with the w/c ratio is affected by the type of concrete.

Mixed mode I/II fracture behavior and surface morphology of hard rock under dynamic loading

To investigate the dynamic mixed mode I/II fracture properties of hard rock, split-Hopkinson pressure bar (SHPB) was utilized to conduct dynamic fracture tests on cracked straight through Brazilian disc (CSTBD) diorite specimens with different mode mixities. The dynamic fracture load and fracture toughness for different crack angles or mode mixities were determined. The dynamic fracture process and crack mouth opening displacement (CMOD) of CSTBD specimens were monitored by high-speed camera and digital image correlation (DIC) technique, and the fractal and morphology characteristics of fracture surfaces were further analyzed using laser 3D scanner and scanning electron microscope (SEM). The test results indicate that the dynamic CMOD behavior is interrelated closely to the force acting on the crack surface, and the allowable CMOD corresponding to the dynamic peak load decreases with increasing crack angle. In addition, the stress-based and strain-based fracture criteria were introduced to analyze the mixed mode fracture mechanism of diorite. It is found that the GMTS criterion with small fracture process zone (FPZ) size and the EMTSN criterion have the best prediction effect for fracture toughness and crack initiation angle respectively. Observation results show that the macro fracture trajectories of primary cracks and secondary cracks are controlled by the prefabricated crack angle, while the variation in mode mixity has little impact on the meso-roughness and micro-morphology of the fracture surface. The fracture surface of CSTBD diorite specimen under dynamic load exhibits the SEM morphology features of mixed tensile-shear cracks.

Fundamental understanding of the mechanical and post- cracking behaviour of ultra-high performance mortar with recycled steel fibers

The main goal of this paper was to assess the influence of recycled steel fibers sourced from end-life tires on the mechanical performance of self-compacting ultra-high performance mortars. For this purpose, mortars with different amounts of fibers, ranging from 1 to 3%, were prepared. Experimental, analytical and numerical studies were carried out in order to understand the brittle and post-cracking behaviour of the prepared mortar samples. The inspections of the fresh mortars revealed that there was a strong linear relationship between the relative slump flow and the dosage of the fibres. It was observed that mortars keep their self-compatibility when there is an addition of up to 3 % of fibre. In the mortars’ hardened state, there was an increase of their mechanical properties i.e. compressive strength and flexural strength, with an increasing content of fibres. Compared to the reference mix, the compressive strength of reinforced mortars increased by 7%, 14% and 32% (7 days) and 7%, 14% and 40% (28 days) when 1%, 2% and 3% of fiber were utilised. Moreover, it was observed that by 1%, 2% and 3% addition of fibres the flexural strength increased by 7%, 14% and 17% (7 days) and 8%, 14% and 21% (28 days).Post-cracking behaviour of mortars was evaluated using residual flexural strengths in service limit state and ultimate limit state. Statistical analysis revealed a linear trend between those strengths and dosage of fibres. Regarding to the post-cracking behaviour, it was obtained that, the mortars with the addition of 1% of fibres did not show any post-cracking responses. However, the behavior of their matrix during failure can change from being brittle to being ductile. It was observed that, the proposed models in RILEM and EN 14651 overestimated the crack mouth opening displacement responses. Accordingly, a new model was proposed in this study. The results of experimental program were validated using finite element simulations. The proposed numerical models allowed the occurrence of cracks, and their propagations, to be detected, and the obtained results were similar to those from the experimental studies.

Maximum aggregate size effects on the evolution of the FPZ and crack extensions in concrete – Experimental and numerical investigation

In this paper, an experimental/numerical investigation is proposed to study the effect of maximum aggregate size (Dmax) on the fracture process zone (FPZ) length variations and the crack extension. Experimentally, three-point bending tests have been realized on plain concrete with different maximum aggregate sizes under crack mouth opening displacement (CMOD) control. The crack growth is monitored using the acoustic emission (AE) technique. The numerical investigation is conducted at a mesoscale level. From the evolution of cohesive tangential stresses along the crack path, the variation of FPZ is explored. The crack extensions are investigated using the equivalent linear elastic fracture mechanics approach (LEFM) to investigate the R-curves. The results show a great influence of the maximum aggregate size both on the FPZ variation and on the global behavior.

Investigations into the static and dynamic fracture initiation and propagation toughness of AA2014-T6 incorporating temperatures effects

The fracture toughness of a material is an important parameter to quantify the reliability and safety of an engineering structure. In this article, the effect of loading rate and temperature on static and dynamic initiation and propagation toughness fracture behavior of AA2014-T6 is studied. Pre-crack three-point bend specimens are used in determining the static and dynamic fracture initiation and propagation toughness. Static three-point bend experiments are performed using a conventional UTM combined with the heating chamber at different displacement rates (1 mm/min, 10 mm/min, and 100 mm/min) and a wide temperature ranging from −150 °C to 200 °C. Similarly, the dynamic experiments are carried out on modified Hopkinson pressure bar (MHPB) under different loading rate and temperature. ASTM E399 was utilized in evaluating the static fracture initiation toughness, while the dynamic fracture initiation toughness is measured with the help of load point displacement (LPD) and crack initiation time. The 3D digital image correlation (DIC) in combination with ultra-high-speed imaging is used to calculate the crack initiation time and crack mouth opening displacement (CMOD). The energy conservation-based method was utilized in calculating the propagation fracture toughness in both static and dynamic loading conditions. Results show that the propagation toughness increases with temperature while the static fracture initiation toughness declines linearly. In addition, both initiation and propagation fracture toughness increases with the loading rates. Also the dynamic fracture investigation reveals that the positive rate sensitivity for dynamic propagation toughness increases with the increase in temperature. Results also show that the value of dynamic fracture initiation toughness is maximum at room temperature as the yield strength and plastic zone size are optimum in room temperature environments.

Tensile Performance Test Research of Hybrid Steel Fiber-Reinforced Self-Compacting Concrete.

Notched beam specimens were loaded by the three-point bending test device, and the effects of different volume contents and combinations of steel fibers on the tensile properties of hybrid steel fiber-reinforced self-compacting concrete (HSFRSCC) were studied. The failure law and strain field distribution of the specimens were studied by digital image correlation (DIC) technology. Moreover, the curves between the load and crack mouth opening displacement (CMOD) of 18 groups of hybrid steel fiber-reinforced concrete specimens were obtained, and the stress-strain curves of 18 groups of specimens were derived from the load-CMOD curves. The results show that both single and hybrid steel fibers can improve the crack deformation resistance and tensile properties of concrete, but hybrid steel fibers have a more significant improvement effect. Only when the content of steel fiber is more than 0.6% can it have a more obvious postpeak descending section, and hybrid steel fiber has higher postpeak deformation capacity and flexural toughness. The fundamental reason why concrete with hybrid steel fibers has better tensile properties is that micro and macro steel fibers cooperate with each other to resist cracks, improving the toughness of concrete after cracking. Finally, the mechanism of different size and volume content of steel fiber was analyzed from the micro level, which can be used as a reference for the engineering design of HSFRSCC in the future.

Dynamic fracture behaviour of AA7475-T7351 alloy at different strain rates and temperatures

The fracture behaviour of the aluminium alloy AA7475-T7351 at different loading rates and temperatures (-150 °C to 200 °C) is investigated here. The three-point bend experiments are conducted at Zwick/Roell-50 UTM (crosshead speed up to 100 mm/min), MTS-250 machine (crosshead speed upto 1000 mm/min) and modified Hopkinson pressure bar (striker velocity 11–19 m/s) to understand the initiation and propagation fracture toughness of AA7475-T7351 aluminium alloy along the rolling (L-T) and transverse (T-L) directions. The digital image correlation (DIC) technique is used to obtain the load point displacement (LPD) and crack mouth opening displacement (CMOD) and the same is used to calculate the stress intensity factor (SIF). The fracture surface is studied using a digital stereo microscope (DVM6) and scanning electron microscope (SEM). The fracture toughness of AA7475-T7351 is found to depend on the loading rates and temperatures and found to vary between 50 and 66 MPm1/2 along the L-T direction, whereas the corresponding value along the T-L direction is comparatively less.

Analysis of fractures in linear viscoelastic media using a generalized finite element method and the elastic–viscoelastic correspondence principle

A methodology for an efficient analysis of 3-D fracture mechanics problems in linear viscoelastic media is presented. It combines the Elastic–Viscoelastic Correspondence Principle (EVCP), a Generalized Finite Element Method (GFEM), and an inverse Laplace transform (ILT) method to compute Energy Release Rate (ERR) and Crack Mouth Opening Displacement (CMOD) for viscoelastic fracture problems in the time domain. The method is denoted EVCP-GFEM-ILT and consists of solving a reference elastic problem in the Laplace domain using a quadratic p-hierarchical GFEM, computing quantities of interest in this domain, and transforming them to the time domain with the aid of a numerical ILT method. One of the key features of the method is that a single elastic solution is required, regardless of the time interval of the target viscoelastic problem. A detailed verification of the methodology against analytical and reference numerical solutions is performed. Problems subjected to either non-homogeneous Neumann or Dirichlet boundary conditions of increasing complexity are considered. Two ILT methods are studied and the one based on Fourier series is shown to deliver accurate results for all tested boundary conditions, as well as non-trivial viscoelastic material models. The computational cost of the method applied to a 3-D problem is compared with the one for Abaqus which solves the problem directly in the time domain using a FEM mesh with quarter-point elements. A fully 3-D mixed-mode fracture problem with a non-trivial viscoelastic material model is solved to highlight the applicability of the proposed methodology. Finally, a problem of practical interest is analyzed in order to show how the methodology proposed in this work can be applied to efficiently handle large-scale simulations.