Mechanical Fatigue Tests Research Articles

An Optimization Procedure to Convert Time‐Domain Complex Loadings to the Frequency Domain for Low‐Cost Fatigue Analysis

ABSTRACTThe time domain is the most widely chosen alternative in mechanical fatigue tests to completely represent random events. However, the main disadvantages of this approach are the long time required to complete the tests and the high cost of the complex equipment. On the other hand, fatigue test in the frequency domain is a potential alternative to overcome these disadvantages. That is, it requires less sophisticated equipment, because it uses only simple actuators instead of servo actuators. Moreover, the duration of the fatigue test is reduced, because the total length of the event is replaced by constant repetitions and constant damage. The objective of this work is to propose and develop a methodology that uses the results of structural fatigue as a starting point, and through an optimization problem solved by the genetic algorithm, it determines which loads/displacements caused them in the frequency domain. The purpose is to assist future developments in fatigue tests, supplanting tests in the time domain without losing the correlation in results.

Flammability and Mechanical Testing of Sandwich Composite for Rolling Stock Structural Applications

Components made of composite materials are being increasingly used in the construction of rolling stock. Currently, the use of components made of composite materials as train structural elements is increasingly being considered. Non-structural components made of composites are most often found inside rail vehicles (e.g., the interior lining), while structural components made of sandwich composite materials can be used for the roof, sidewalls, and underframe constructions. This article provides a description of an innovative sandwich composite developed for a metro’s underframe, as well as the production process and preparation of the composite specimens. The main parts of the work are flammability and mechanical (static and fatigue) tests of the innovative sandwich composite. The scope of the flammability tests included the testing of the fire properties using the radial plate method, the optical density of smoke, and the content of toxic gases. The mechanical strength of the sandwich composite was examined during a flexural (three-point bending) test and a fatigue strength under a given dynamic load. The results presented in the article are very significant, both in terms of flammability and the mechanical strength tests. In order to produce large-size train components, appropriately large patches of component layers of the composite are required; this may pose production problems.

In-situ pressure differential-accelerated mechanical fatigue testing and modeling of a reinforced fuel cell membrane

Modern polymer electrolyte fuel cells typically use reinforced membranes for improved mechanical durability. Due to costly experimentation, however, the fatigue properties of these membranes remain poorly understood. In this work, we employ the G'Sell-Jonas constitutive material model to investigate the mechanical fatigue response of a reinforced membrane under various environmental conditions in accelerated in-situ test settings. For fatigue evaluation, we utilize a novel pressure differential-accelerated mechanical stress test (ΔP-AMST) of shorter duration (<1 week) than previous AMSTs. The S–N curves constructed from experimental results at variable ΔP and temperature demonstrate inverse linear relationship between logarithmic fatigue lifetime and nominal stress, with greatly enhanced (∼10x) lifetime at reduced temperature. According to the results, a finite element-based fatigue model is developed and validated, which considers the impacts of hygrothermal fluctuations and strain rates. The model shows peak tensile stress during the dry phase at the center of the test section, which is consistent with the expected scenario for in-situ fuel cell membrane fatigue. Through this novel accelerated test and its modeling, it becomes possible to assess the fatigue lifetime of reinforced membranes under variable temperatures, humidity swings, pressure differentials, and swelling properties, in much shorter time than with standard protocols.

Study on the fatigue life and toughness of recycled aggregate concrete based on basalt fiber

This paper studies the influence of basalt fibers on the mechanical properties, fatigue life, and toughness of Mechanically Recycled Aggregate Concrete (MRAC). Basalt fibers of varying volume fractions and lengths, along with quantified amounts of mineral powder and fly ash, are incorporated into MRAC to prepare Basalt Fiber Mechanically Recycled Aggregate Concrete (BFMRAC). The results of basic mechanical tests and fatigue tests showed that mineral powder and fly ash reduce cement consumption, achieve the effect of green construction, and basalt fibers improve the mechanical properties and toughness of concrete. The results of the response surface method (RSM) model indicate that the volume fraction of basalt fibers has a greater influence on the mechanical properties of BFMRAC compared to fiber length. The fatigue test results indicate that under different fiber volume fractions and lengths, the uniaxial compressive fatigue life (N) of specimens for each mix proportion is consistently improved. When the length of basalt fibers is 12 mm and the volume fraction is 0.3 %, the uniaxial compressive fatigue life of BFMRAC reaches its maximum (231638), which is twice that of MRAC. When the survival rate (P) is set to 0.5, with a basalt fibers volume content of 0.3 % and a length of 12 mm, the fatigue limit strength (Se) attains its maximum (0.8648 fc). When stress levels (S) reach 0.75 and the basalt fibers length is 12 mm, the relative CI Intensifying Coefficient achieves its maximum (1.133), resulting in optimal fatigue toughness. When the basalt fibers length is 6–12 mm, Se generally increases with the increase of fiber length, and the enhancement effect is best at 12 mm.

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.

A Methodology for the Rapid Qualification of Additively Manufactured Materials Based on Pore Defect Structures

Additive manufacturing (AM) can create net or near-net-shaped components while simultaneously building the material microstructure, therefore closely coupling forming the material and shaping the part in contrast to traditional manufacturing with distinction between the two processes. While there are well-heralded benefits to AM, the widespread adoption of AM in fatigue-limited applications is hindered by defects such as porosity resulting from off-nominal process conditions. The vast number of AM process parameters and conditions make it challenging to capture variability in porosity that drives fatigue design allowables during qualification. Furthermore, geometric features such as overhangs and thin walls influence local heat conductivity and thereby impact local defects and microstructure. Consequently, qualifying AM material within parts in terms of material properties is not always a straightforward task. This article presents an approach for rapid qualification of AM fatigue-limited parts and includes three main aspects: (1) seeding pore defects of specific size, distribution, and morphology into AM specimens, (2) combining non-destructive and destructive techniques for material characterization and mechanical fatigue testing, and (3) conducting microstructure-based simulations of fatigue behavior resulting from specific pore defect and microstructure combinations. The proposed approach enables simulated data to be generated to validate and/or augment experimental fatigue data sets with the intent to reduce the number of tests needed and promote a more rapid route to AM material qualification. Additionally, this work suggests a closer coupling between material qualification and part certification for determining material properties at distinct regions within an AM part.

Application of Microfracture Analysis to Fatigue Fractures in Materials through Non-Destructive Tests.

Fatigue fractures in materials are the main cause of approximately 80% of all material failures, and it is believed that such failures can be predicted and mathematically calculated in a reliable manner. It is possible to establish prediction modalities in cases of fatigue fractures according to three fundamental variables in fatigue, such as volume, number of fracture cycles, as well as applied stress, with the integration of Weibull constants (length characteristic). In this investigation, mechanical fatigue tests were carried out on specimens smaller than 4 mm2, made of different industrial materials. Their subsequent analysis was performed through precision computed tomography, in search for microfractures. The measurement of these microfractures, along with their metrics and classifications, was recorded. A convolutional neural network trained with deep learning was used to achieve the detection of microfractures in image processing. The detection of microfractures in images with resolutions of 480 × 854 or 960 × 960 pixels is the primary objective of this network, and its accuracy is above 95%. Images that have microfractures and those without are classified using the network. Subsequently, by means of image processing, the microfracture is isolated. Finally, the images containing this feature are interpreted using image processing to obtain their area, perimeter, characteristic length, circularity, orientation, and microfracture-type metrics. All values are obtained in pixels and converted to metric units (μm) through a conversion factor based on image resolution. The growth of microfractures will be used to define trends in the development of fatigue fractures through the studies presented.

Anisotropic Mechanical and Microstructural Properties of a Ti-6Al-7Nb Alloy for Biomedical Applications Manufactured via Laser Powder Bed Fusion

Through tailoring the geometry and design of biomaterials, additive manufacturing is revolutionizing the production of metallic patient-specific implants, e.g., the Ti-6Al-7Nb alloy. Unfortunately, studies investigating this alloy showed that additively produced samples exhibit anisotropic microstructures. This anisotropy compromises the mechanical properties and complicates the loading state in the implant. Moreover, the minimum requirements as specified per designated standards such as ISO 5832-11 are not met. The remedy to this problem is performing a conventional heat treatment. As this route requires energy, infrastructure, labor, and expertise, which in turn mean time and money, many of the additive manufacturing benefits are negated. Thus, the goal of this work was to achieve better isotropy by applying only adapted additive manufacturing process parameters, specifically focusing on the build orientations. In this work, samples orientated in 90°, 45°, and 0° directions relative to the building platform were manufactured and tested. These tests included mechanical (tensile and fatigue tests) as well as microstructural analyses (SEM and EBSD). Subsequently, the results of these tests such as fractography were correlated with the acquired mechanical properties. These showed that 90°-aligned samples performed best under fatigue load and that all requirements specified by the standard regarding monotonic load were met.

Mechanical and fatigue resistance of restorations supported by welded-framework and realized using computer-aided designed prosthetic shells: In vitro pilot study.

Resin coating in implants rehabilitation cannot always be aesthetic, durable and comfortable for the patient mainly due to the limited dimensions of the final structure. Intraoral welding technique and computer-aided designed prosthetic shells may be a solution. This in vitro study evaluates the capacity of load and the weakest point of implant-supported provisional prosthesis using welded titanium framework. Twelve samples were produced to simulate an implant supported fixed prosthetic bridge. Two implants (Ankylos; Dentsply Sirona Implants; Germany) were inserted inside blocks of nanoceramic material produced with a stereolithographic 3D printer. A polymethylmethacrylate (PMMA) resin shell was performed with CAD/CAM and relined on welded framework. Six samples were produced with the same procedure reducing resin thickness. The samples were subjected to fatigue test (6,500,000 cycles) using ElectroForce 3310 fatigue machine (t1); subsequently a mechanical compression test using a universal Shimadzu AGS-X 10 machine (t2). The samples were analyzed with a photographic and radiographic documentation at t0, t1 and t2. The samples survived mechanical fatigue test without evidence of failure. The radiographic and photographic evaluation revealed the fracture of resin coating after the mechanical compression test. The samples with minimal resin thickness fractured first. Adequate assessment of the resin thickness is mandatory to improve the longevity of these rehabilitations. CAD-CAM digital prosthetic design allows us to optimize the thicknesses and the prosthetic shapes, allowing us to obtain good degrees of resistance even in the presence of reduced prosthetic spaces.

Fatigue-resistant NiTi micropillars with small hysteresis fabricated by micro severe plastic deformation

Through compressing polycrystalline NiTi micropillars down to a 40% height reduction by nanoindentation equipment and subsequently manufacturing them by focused ion beam, cuboidal NiTi micropillars with a nanocrystal/nanolaminate heterostructure were obtained. Mechanical behavior and fatigue tests show that the heterostructured NiTi micropillars processed by micro severe plastic deformation (MSPD) have a large recoverable strain (4.5%), small hysteresis (4.3 MPa), and ultrahigh fatigue resistance (> 106 cycles) under a maximum applied stress of 2.5 GPa. These properties were attributed to the extreme grain refinement and homogeneous phase transformation occurring in the nanocrystals. The findings suggest that the MSPD holds great potential for fabricating superior materials for applications in small-scale engineering devices.

Experimental and numerical investigation on mechanical and fatigue performance of corroded Q690D high-strength steel

As a prevalent environmental factor in the service process of steel structures, corrosion have a significant impact on the mechanical and fatigue properties of steel, thus deteriorating service safety. In this article, focused on corroded Q690D high-strength steel, experimental and numerical investigations have been performed. Electrolytic accelerated corrosion experiments were conducted, and 3D surface morphology measurements were employed to analyse the surface properties of specimens with various corrosion degrees. Mechanical and high-cycle fatigue tests were carried out on the corroded specimens, then degradation models between the mechanical behaviours and corrosion characteristics were established. Furthermore, the fatigue damage evolution model of Q690D high-strength steel was calibrated based on continuum damage mechanisms (CDM), and numerical simulations of the corroded specimen corresponding to the monotonic tensile tests and high cycle fatigue tests were conducted. The results show that with the increase of corrosion degree, the elastic modulus, yield stress, and tensile stress would decrease, and the fatigue performance would deteriorate. Corrosion has a greater effect on the fatigue life of long-life range and the slopes of the S-N curves after corrosion are more uniform. With the CDM parameters of non-corroded Q690D and the numerical model with consideration of surface roughness, the fatigue life of corroded Q690D could be well simulated.

Carbonitriding Effect on Fatigue Behaviour and Mechanical Properties of Steel Beam

This work deals with the influence of carbonitriding on the fatigue behavior of notched beam (v-notch) with a depth of 1mm and an angle of 45° is studded. The experimental work include mechanical tests, heat treatments and fatigue test. The heat treatment is done by using carbonitriding at a constant temperature of 800 °C, and soaking time variation 30, 60, and 90 minutes, then followed after treatment by quenching of water and tempering process. The experimental fatigue test results of this work affected by soaking time. The fatigue test has been performed on a cantilever rotating-bending samples. The result shows that the fatigue strength and lifetime increased with increasing soaking time. It is found that The Fatigue Life Improvement Factor (FLIF) at time 30, 60 and 90 minutes for notched beam (v-notch) was increasing by 11.3%, 18.6% and 20.2% respectively with respect to un-treat specimens.

Bond Wire Fatigue of Au, Cu, and PCC in Power LED Packages.

Bond wire failure, primarily wire neck breakage, in power LED devices due to thermomechanical fatigue is one of the main reliability issues in power LED devices. Currently, the standard testing methods to evaluate the device's lifetime involve time-consuming thermal cycling or thermal shock tests. While numerical or simulation methods are used as convenient and quick alternatives, obtaining data from material lifetime models with accurate reliability and without experimental fatigue has proven challenging. To address this issue, a mechanical fatigue testing system was developed with the purpose of inducing mechanical stresses in the critical region of the bond wire connection above the ball bond. The aim was to accelerate fatigue cracks at this bottleneck, inducing a similar failure mode as observed during thermal tests. Experimental investigations were conducted on Au, Cu, and Pd-coated Cu bonding wires, each with a diameter of 25 µm, using both low- and high-frequency excitation. The lifetime of the wire bond obtained from these tests ranged from 100 to 1,000,000 cycles. This proposed testing method offers material lifetime data in a significantly shorter timeframe and requires minimal sample preparation. Additionally, finite element simulations were performed to quantify the stresses at the wire neck, facilitating comparisons to conventional testing methods, fatigue test results under various operating conditions, material models, and design evaluations of the fine wire bond reliability in LED and microelectronic packages.

Fatigue failure mechanism of duplex stainless steel welded joints including role of heterogeneous cyclic hardening/softening: Experimental and modeling

This work performed experimental and modeling investigations on the fatigue failure mechanism of duplex stainless steel welded joints, and the correlation among heterogeneous microstructure, cyclic hardening/softening and fatigue failure behavior was analyzed extensively. A series of experiments including the characterization of microstructure by the electron back-scattered diffraction observation and fatigue mechanical tests assisted by digital image correlation technique were performed. The results show that at the lower stress amplitudes (approximately 520 MPa), the fatigue failure occurred in the weld metal, while it shifted to the base metal at higher amplitudes. Due to the grain refinement, the strain amplitude of weld metal was lower than that of base metal, particularly at the higher amplitudes, leading to the final failure at the base metal. However, at the lower amplitudes, due to the effect of Kurdjumov-Sachs orientation relationship at the weld metal, its cyclic softening behavior was much drastic than that of base metal, resulting in the overshoot of strain amplitude during fatigue process and finial rupture at the weld metal. A cyclic constitutive model was developed by considering the amplitude-dependent and heterogeneous cyclic hardening/softening, to accurately predict the cyclic mechanical response and fatigue failure location for both stress-controlled and strain-controlled conditions. This work can be used as guidance of structure integrity assessment and life prediction for the engineering components of duplex stainless steel.

On the fatigue properties of material extrusion 3D-printed biodegradable composites reinforced with continuous flax fibers

Nowadays, additive manufacturing is increasingly used for prototypes and low-volume products. Firstly, it offers great design freedom; however, the components must inevitably have certain design artifacts that cause stress concentrations. To this end, composites of biodegradable PLA (polylactic acid) matrix and continuous flax fibers were fabricated in this study using material extrusion 3D printing. Static characterization and mechanical fatigue tests between 103 and 2·106 load cycles were performed for plain specimens, three types of notches for the matrix, and two composite configurations. The notches only slightly affected the static performance of the tested materials. Accordingly, compared to the unnotched versions, the PLA matrix and composites exhibited a reduction in tensile strength of up to 8% and 19%, respectively. It was found that compared to the PLA matrix, the fatigue strength at high cycles increased by 1.8 and 2.3 times for the plain composite with a fiber volume fraction of 7.8% and 14% fibers, respectively. In the fatigue of notched composites, the notch effect is reduced by fibers in the tip. The fatigue strength is up to 1.9 and 2.9 times higher compared to the notched matrix for the composite with a smaller and larger volume fraction, respectively.

Strain-induced damage analysis of hyperelastic material through scanning electron microscopy: A statistical approach using digital image processing

In order to acquire topographic/morphological images with superior resolution and depth of focus than an ordinary optical microscope, scanning electron microscopy (SEM) is used to take photographs of a surface of materials or specimens at a desired point. In the context of polymer and rubber materials science, SEM investigations frequently try to visualize phase morphology, surface and cross-sectional topography, and surface molecular order, and clarify damage mechanisms. In the case of rubber vulcanizates, test specimens are frequently put through a variety of mechanical property assessment procedures, including tensile, flexing, fatigue, abrasion, and tear tests, in order to finalize compounding parameters for required levels of quality. The damaged surface of the test specimens exhibits distinctive topographical characteristics, which are captured as an SEM picture and associated with relevant strength properties. However, the majority of the time, the relationship between strength attributes and the type of surface topography is qualitative. Surface roughness measurement metrics such as root mean square (r.m.s) roughness, average roughness, and peak-to-valley distance are frequently determined for quantitative research using standard software accessible in an SEM. The primary goal of this research is to use a statistical/spectral-based technique for quantitatively measuring surface topography using SEM. The Mullins stress-softening phenomenon of an isotropic, incompressible, hyperelastic rubberlike material is predicted using a phenomenological model. A simple exponential damage function characterizes the model, which represents deformation-induced microstructural degradation of rubberlike material.

Development and Research of New Hybrid Composites in Order to Increase Reliability and Durability of Structural Elements

Hybrid composite materials can successfully solve the problems of reliability, durability, and extended functionality of products, components, and details, which operate under conditions of multifactorial influences (temperature, force, and deformation). The authors have developed a hybrid composite high-entropy AlCoCrCuFeNi material and ceramic cBNCoMo(B4CCoMo) layer. The formation of hybrid composites was carried out using new technology. This technology includes high-energy machining, high-velocity oxygen-fuel spraying in a protective environment, high-temperature thermomechanical treatment, and heat treatment. The use of the developed technology made it possible to increase the adhesive strength of the composite layers from 68 to 192 MPa. The authors performed an assessment of the structural parameters of the composite layers. The assessment showed that the composite layers had a nanocrystalline structure. The research included mechanical tests of the hybrid composites Hastelloy X (NiCrFeMo)—AlCoCrCuFeNi—cBNCoMo and Hastelloy X (NiCrFeMo)—AlCoCrCuFeNi—B4CCoMo for cyclic durability (fatigue mechanical tests) and friction wear. The use of surface-layered materials AlCoCrCuFeNi—cBNCoMo and AlCoCrCuFeNi—B4CCoMo in the composition of hybrid composites significantly increased cyclic durability. The use of surface-layered materials in the composition of hybrid composites made it possible to reduce wear intensity. The test results show that the developed composites are promising for use in various industries (including oil and gas), where high strength and wear resistance of materials are required.

Hybrid Printing of Silver-Based Inks for Application in Flexible Printed Sensors

This study explores the potential benefits of combining different printing techniques to improve the production of flexible printed sensors, which is a relevant application for modern coating and surface design. The demand for cheap, flexible, precise, and scalable sensors for wearable electronics is increasing, and printed electronics techniques have shown great potential in meeting these requirements. To achieve higher performance and synergy, the paper introduces the concept of hybrid printing of electronics by combining aerosol jet printing and screen printing. This multi-process approach allows for large-scale production with high printing precision. The study prepares hybrid connections on a flexible substrate foil for use in flexible printed sensor manufacturing. The research team tests different combinations of printed layers and annealing processes and finds that all prepared samples exhibit high durability during mechanical fatigue tests. Surface morphology, SEM images, and cross-section profiles demonstrate the high quality of printed layers. The lowest resistance among the tested hybrid connections obtained was 1.47 Ω. The study’s findings show that the hybrid printing approach offers a novel and promising solution for the future production of flexible sensors. Overall, this research represents an interdisciplinary approach to modern coating and surface design that addresses the need for improved production of wearable electronics. By combining different printing techniques, the study demonstrates the potential for achieving high-volume production, miniaturization, and high precision, which are essential for the ever-growing market of wearable sensors.

High‐performance hierarchical composites based on polyamide 6, carbon fiber and graphene oxide

AbstractThis study reports the effect of graphene oxide (GO) coating on carbon fiber (CF) surface on the mechanical and thermal properties and morphology of CF‐reinforced polyamide 6 (PA6) composites containing 7.5 wt% of short CFs. GO was coated on the CF surface by a physical absorption method with concentrations ranging from 0.05 to 0.5 wt% GO. The PA6/CF composites were prepared by extrusion, and the specimens were obtained by injection molding. Their morphology (SEM, XRD tests), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (DSC, TG and HDT tests) were analyzed. A significant change in the preferential (growth) crystal planes of PA6 was observed upon the incorporation of CFs containing GO, favoring the formation of α crystals in PA6. GO coating on CFs was effective and provided an increase in tensile strength and Young's modulus up to 12% and 24%, flexural strength and flexural modulus up to 22% and 25%, and a decrease in impact strength and fatigue life up to 30% and 23%, respectively, when compared to unmodified PA6/CF composites. Fracture micrographs indicated an increase in the PA6/CF interaction and the effectiveness of GO as a coupling agent for the composite.

Different Conical Angle Connection of Implant and Abutment Behavior: A Static and Dynamic Load Test and Finite Element Analysis Study.

Dental implants are artificial dental roots anchoring prosthetic restorations to replace natural teeth. Dental implant systems may have different tapered conical connections. Our research focused on the mechanical examination of implant-superstructure connections. Thirty-five samples with 5 different cone angles (24°, 35°, 55°, 75°, and 90°) were tested for static and dynamic loads, carried out by a mechanical fatigue testing machine. Fixing screws were fixed with a torque of 35 Ncm before measurements. For static loading, samples were loaded with a force of 500 N in 20 s. For dynamic loading, the samples were loaded for 15,000 cycles with a force of 250 ± 150 N. In both cases, the compression resulting from load and reverse torque was examined. At the highest compression load of the static tests, a significant difference (p = 0.021) was found for each cone angle group. Following dynamic loading, significant differences (p < 0.001) for the reverse torques of the fixing screw were also shown. Static and dynamic results showed a similar trend: under the same loading conditions, changing the cone angle-which determines the relationship between the implant and the abutment-had led to significant differences in the loosening of the fixing screw. In conclusion, the greater the angle of the implant-superstructure connection, the smaller the screw loosening due to loading, which may have considerable effects on the long-term, safe operation of the dental prosthesis.