Sinusoidal Cyclic Loading Research Articles

Biomechanical performance of different cable and wire cerclage configurations

Cerclage technology is regaining interest due to the increasing number of periprosthetic fractures. Different wiring techniques have been formerly proposed and have hibernated over years. Hereby, they are compared to current cerclage technology. Seven groups (n = 6) of different cable cerclage (Ø1.7 mm, crimp closure) configurations (one single cerclage looped once around the shells, one single cerclage looped twice, two cerclages each looped once) and solid wire cerclages (Ø1.5 mm, twist closure) (same configurations as cable cerclages, and two braided wires, twisted around each other looped once) fixed two cortical half shells of human femoral shaft mounted on a testing jig. Sinusoidal cyclic loading with constantly increasing force (0.1 N/cycle) was applied starting at 50 N peak load. Cerclage pretension (P), load leading to onset of plastic deformation (D) and load at total failure (T) were identified. Statistical differences between the groups were detected by univariate ANOVA. Double looped cables (P442N ± 129; D1334N ± 319; T2734N ± 330) performed significantly better (p < 0.05) than single looped cables (P292N ± 56; D646N ± 108; T1622N ± 171) and were comparable to two single cables (P392N ± 154; D1191N ± 334; T2675N ± 361). Double looped wires (P335N ± 49; D752N ± 119; T1359N ± 80) were significantly better (p < 0.05) than single looped wires (P181N ± 16; D343N ± 33; T606N ± 109) and performed similarly to single looped cables. Braided wires (P119N ± 26; D225N ± 55; T919N ± 197) exhibited early loss of pretension and plastic deformation. Double looped cerclages provided a better fixation stability compared to a single looped cerclage. Double looped wires were comparable to a single looped cable. The use of braided wires could not be recommended mechanically.

The damage mechanism of rock fatigue and its relationship to the fracture toughness of rocks

This study presents the results of laboratory diametrical compression tests performed on Brisbane tuff disc specimens to investigate their mode-I fracture toughness response to static and cyclic loading, as a function of the applied load. Both the static and cyclic loading tests were carried out on Cracked Chevron Notched Brazilian Disc (CCNBD) rock specimens. Two different types of cyclic loading were applied: (a) cyclic loading with constant mean level and constant amplitude, termed sinusoidal cyclic loading and (b) cyclic loading with increasing mean level and constant amplitude, termed increasing cyclic loading. The fracture toughness response to cyclic loading was found to be different from that under static loading in terms of the ultimate load and the damage mechanisms in front of the chevron crack. A maximum reduction of the static fracture toughness (KIC) of 46% was obtained for the highest amplitude increasing cyclic loading test. Conversely, for sinusoidal cyclic loading, a maximum reduction of the static KIC of 29% was obtained. Detailed scanning electron microscope (SEM) examinations revealed that both loading methods cause fatigue in the CCNBD specimens. When compared with static rupture, the main difference with the cyclically loaded specimens was that intergranular cracks were formed due to particle breakage under cyclic loading, SEM images showed that fatigue damage in Brisbane tuff is strongly influenced by the failure of the matrix because of both intergranular fracturing and transgranular fracturing.

Effects of TiN and WC coating on the fatigue characteristics of dental implant

This study examined the effects of TiN (titanium nitride) and WC (tungsten carbide) coatings on the fatigue characteristics of dental implants using a sinusoidal cyclic loading machine under load between 42–420N and 58–580N according to the ISO 14801. In this study, an abutment screw was coated with a TiN and WC film by EB-PVD and sputtering, respectively. For the fatigue test, the implant fixture and abutment were tightened to a torque 32Ncm using a digital torque gauge with 0.1Ncm accuracy. Field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) were used to observe the coated surface and fracture surface of the abutment screw.The uncoated abutment screws contained scratches caused by the mechanical process, whereas the TiN and WC coated screws showed a smooth surface at the screw thread and screw valley. The mean fatigue life of the uncoated, TiN coated, and WC coated abutment screw at 420N was 5.8×105, 8.2×105 and 106cycles, respectively. At 580N, the mean fatigue life of the uncoated, TiN coated and WC coated abutment screw was 2.1×104, 4.1×104 and 2.3×104cycles, respectively. The uncoated abutment screw showed the beach mark and fatigue striation. On the other hand, in the case of TiN and WC coated abutment screws, the semi-cleavage fracture and ductile fracture appeared at 420N. Semi-cleavage fracture and massive fatigue striation with a step of 0.5μm/cycle were observed in TiN coated abutment screw, whereas a minute slip band was noted and the interval of fatigue striation increased to several μm/cycle in the WC coated screw at 580N.

Investigating the Effect of Cyclic Loading on the Indirect Tensile Strength of Rocks

This paper presents the results of laboratory experiments during the investigation of the stress-strain characteristics of Brisbane tuff disc specimens under diametral compressive cyclic loading. Two different cyclic loading methods were used: namely, sinusoidal cyclic loading and cyclic loading with increasing mean level. The first method applied the S-N curve approach to the indirect tensile strength (ITS) of rock specimens for the first time in the literature, and the second method investigated the effect of increasing cyclic loading on the ITS of rock specimens. The ITS of Brisbane tuff disc specimens was measured using the Brazilian tensile strength test. The reduction in ITS was found to be 33% with sinusoidal loading tests, whereas increasing cyclic loading caused a maximum reduction of 37%. It is believed that the fracturing under cyclic loading starts at contact points between strong grains and weak matrices, and that contact points at grain boundaries are the regions of stress concentration (i.e., indenters). Transgranular cracks emanate from these regions and intergranular cracks sometimes pass through the contact points. Once cracking begins, there is a steady progression of damage and a general 'loosening' of the rock, which is a precursor to the formation of intergranular cracks.

Fatigue Fracture of Implant System Using TiN and WC Coated Abutment Screw

Dental implant systems are subject to failure in the screw connection part which can occur due to screw loosening or fracture. For solving the problem of loosening, some researchers had carried out the TiN(titanium nitride) and WC(tungsten carbide) coating on the abutment screw, while fatigue failure may still be not researched as an issue of coating materials. In this study, fatigue test was performed to estimate the fatigue fracture of coated abutment screw for implant system according to the ISO 14801. For this purpose, TiN and WC film coating was carried out on the abutment screw using EB-PVD and sputtering, respectively. For the fatigue test, the implant fixture and abutment were tightened to a torque 32Ncm using digital torque gauge with 0.1Ncm accuracy. Each prepared samples were fixed to uniaxial sinusoidal cyclic loading machine (ADT-AV01k1, Shimadzu, Japan) under load control between 42-420N and 58-580N. Fractured surface was observed with FE-SEM and EDS. The fatigue life of implant system used TiN and WC coated abutment screw was found to be relatively longer compared to non-coated abutment screw at 420N. Also, fatigue life of TiN coated sample showed longer than that of other samples at 580N. Afterthe fatigue test at 420N, fatigue striations were showed on the fractured surface of non-coated abutment screw. The semi-cleavage surface was mainly observed on the TiN coated surface. Fatigue striations were regularly appeared at crack propagation step with striation thickness of 0.5μm/cycle.

Two- and three-dimensional micromechanical viscoelastic finite element modeling of stone-based materials with X-ray computed tomography images

This paper presents 2D and 3D micromechanical finite element (FE) models to predict the viscoelastic properties including dynamic modulus and phase angle of stone-based materials (using an example of asphalt mixtures). Heterogeneous asphalt mixtures are consisted of very irregular aggregates, asphalt matrix and a small amount of air voids. The internal microstructure of asphalt mixtures was captured with X-ray computed tomography (CT) imaging techniques. The 2D and 3D digital samples were created with the reconfiguration of the scanned horizontal surface images. The FE mesh of digital samples was generated with the locations of image pixels within each aggregate and asphalt matrix. Along the boundary of these two phases, the aggregate and matrix FEs share the nodes to connect the deformation. The micromechanical FE model was accomplished by incorporating the captured microstructure and ingredient properties (viscoelastic asphalt matrix and elastic aggregates). The generalized Maxwell model was applied for viscoelastic asphalt matrix with calibrated parameters from the nonlinear regression analysis of the lab test data. The displacement-based FE simulations were conducted for the uniaxial compression under sinusoidal cyclic loading. Overall, the predicted dynamic modulus and phase angle from 2D and 3D micromechanical models were compared favorably with lab test data of the asphalt mixture specimens. The 3D simulation with digital samples generated better prediction than the 2D models. These results indicate that the developed micromechanical FE models have the ability to accurately predict the global viscoelastic properties of the stone-based materials.

Prediction of Dynamic Modulus and Phase Angle of Stone-Based Composites Using a Micromechanical Finite-Element Approach

This paper presents a micromechanical finite-element (FE) model for predicting the viscoelastic properties (dynamic modulus and phase angle) of asphalt mixtures, typical stone-based composites. The two-dimensional (2D) microstructure of asphalt mixtures was captured by optically scanning the surface image of sectioned specimens. FE mesh of image samples was generated within each aggregate and asphalt mastic. Along the aggregate boundary, the FEs share the nodes to connect the deformation. The micromechanical FE model was accomplished by incorporating specimen microstructure and ingredient properties (viscoelastic asphalt mastic and elastic aggregates). The generalized Maxwell model was applied for viscoelastic asphalt mastic with calibrated parameters from nonlinear regression analysis of the mastic test data on dynamic modulus and phase angle. The displacement-based FE simulations were conducted on the numerical samples under sinusoidal cyclic loading. The predicted dynamic modulus and phase angle were compared favorably with the mixture test data over a frequency range. The simulation results of the asphalt mixture samples have good correlations with the numerical calibration of asphalt mastic specimens. These results indicate that the developed micromechanical FE model can provide a computational tool for predicting the global viscoelastic properties of asphalt mixtures with captured microstructure and ingredient properties. Additionally, this study can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking their microstructure.

Stress Corrosion and Corrosion Fatigue Crack Growth of Zr-Based Bulk Metallic Glass in Aqueous Solutions

Crack-propagation tests on a bulk metallic glass (BMG), Zr55Cu30Ni5Al10, were conducted either in aqueous sodium chloride (NaCl) solutions or in high-purity water under sinusoidal cyclic loading or sustained loading. Although the crack growth rate in high-purity water was almost identical to that in air, the rate in the NaCl solution was much higher than that in air, even in a very low concentration of NaCl such as 0.01 mass pct. In a 3.5 mass pct NaCl solution, the time-based crack growth rate during cyclic loading, da/dt, was determined by the maximum stress-intensity factor, Kmax, but was almost independent of the loading frequency and the stress ratio, and the rate was close to that of stress corrosion cracking (SCC) under a sustained loading.

Cyclic plastic response and fatigue life in superduplex 2507 stainless steel

Superduplex 2507 type steel has been subjected to symmetric cyclic loading with constant strain rate and constant plastic strain amplitude or sinusoidal cyclic loading with constant stress amplitude at room temperature in a wide interval of stress and plastic strain amplitudes. Fatigue hardening/softening curves were recorded and compared for both types of loading. Cyclic stress–strain curves and fatigue life curves in the form of Coffin–Manson curve and Wöhler curve using both loading regimes were evaluated and compared. The analysis of the hysteresis loop shape was used to determine the contribution of the effective stress and to find the distribution of critical internal stresses in both phases of the steel. The typical internal dislocation structure in both phases was documented. The cyclic response of the material was discussed in relation to the dislocation structure developed in cyclic straining in austenitic and ferritic phases.

Environment Assisted Crack Propagation in Zr-Based Bulk Metallic Glass

Crack propagation tests on a bulk metallic glass, Zr55Cu30Ni5Al10, were conducted either in aqueous sodium chloride (NaCl) solutions or high purity water under sinusoidal cyclic loading or sustained loading. Although the crack growth rate in high purity water was almost identical to that in air, the rate in NaCl solution was much higher than that in air even in a very low concentration of NaCl such as 0.01%. In 3.5% NaCl solution, the time-based crack propagation rate during cyclic loading, da/dt, was determined by the maximum stress intensity factor, Kmax, but was almost independent of the loading frequency and the stress ratio, and the rate was close to that of environment-assisted cracking under a sustained load.

Fatigue cyclic loading test of an auro-galvanoforming ceramic bridge

In dental clinics, dentition defects are commonly restored with conventional porcelain-fused-to-metal fixed bridges. However, Ni-Cr alloy ceramic fixed bridges are known to have several drawbacks such as marginal coloration of the neck, low casting precision and, most seriously, poor biocompatibility. These problems could be circumvented by using noble metal ceramic bridges; however, one negative issue related to the conventional noble metal ceramic bridges is its high price due to the use of a large amount of gold for pontic. Therefore, an auro-galvanoforming ceramic bridge would be ideal to retain the advantages of a conventional material, yet reduce the amount of noble metal used. This study aimed to investigate whether any destructive changes occur to the auro-galvanoforming ceramic bridge under a fatigue cyclic loading test. On standard models which the left maxillary first premolar is lost and with the cuspid teeth and the second premolar as the fixed bridge abutment teeth, six maxillary auro-galvanoforming ceramic bridges and six corresponding nichrome ceramic jointed crowns were made as group A, six nichrome ceramic bridges and six corresponding nichrome ceramic jointed crowns were made as group B (control group). And then all specimens were fixed and tested on a fatigue cyclic loading machine; the changes occurring to the surfaces of occlusal contact with large functional area and to the porcelain-metal interfaces of the nichrome primary copings margins were observed through a scanning electron microscope (SEM). In 120 hours' continual observation, none of the specimens had porcelain coating fractures or scraping occurrence and all of the porcelain coatings had been kept intact under sinusoidal cyclic loading with the load range of 120 - 200 N and frequency of 5 Hz. Auro-galvanoforming ceramic bridges exhibited excellent fatigue strength in the fatigue cyclic loading test and may satisfy the clinical demand in theory, while the practical application shall be evaluated by observations in long-term clinical usage.

Suitability of Dynamic and Relaxation Tests for the Evaluation of Moisture Susceptibility of Asphalt Mixtures

Abstract The presence of waIn ter in asphalt pavements deteriorates their condition and causes distresses that result in high maintenance costs to state and federal agencies. The objective of this research was to execute dynamic and relaxation tests and evaluate their effectiveness in assessing moisture susceptibility of asphalt mixture specimens with different air void structures determined using X-ray computed tomography (CT) and conditioned using the modified Lottman procedure. The dynamic test consisted of the application of a sinusoidal cyclic compressive load on the specimen while maintaining the strain within a specified range. The relaxation test, performed in both direct tension and compression, consisted of the application of a constant static strain. A statistical analysis was used to study the effectiveness of the tests in evaluating the moisture susceptibility of the asphalt mixtures. The results showed that none of the tests (dynamic or relaxation) were consistent in differentiating between the moisture conditioned and unconditioned specimens or between the responses of the different mixtures within each condition. In addition, the results of the dynamic and relaxation tests were compared after applying different methods to convert frequency-domain data to time-domain data.

Effect of selective dissolution on fatigue crack initiation in 2205 duplex stainless steel

The effect of selective dissolution on fatigue crack initiation of 2205 duplex stainless steel (DSS) was investigated in this study. In mixed sulfuric and hydrochloric acid aqueous solution, there existed two distinctly separated anodic peaks in the active-to-passive transition region of the polarization curve. Either ferritic or austenitic phase was selectively dissolved at each characteristic anodic peak potential. Under sinusoidal cyclic loading condition, however, selective dissolution did not assist fatigue crack initiation instead resulting in the elimination of stress concentration site in the selectively dissolving phase. As a consequence, under selective dissolution condition, fatigue crack initiated in the phase while its dissolution rate was lower with respect to the other constituent phase in the duplex stainless steel. The microstructural evolution of the corrosion fatigue crack initiation in 2205 DSS in the mixed sulfuric and hydrochloric acid solution is highlighted in this investigation.

Fatigue behavior of Ilizarov frame versus tibial interlocking nail in a comminuted tibial fracture model: a biomechanical study

BackgroundTreatment options for comminuted tibial shaft fractures include plating, intramedullary nailing, and external fixation. No biomechanical comparison between an interlocking tibia nail with external fixation by an Ilizarov frame has been reported to date. In the present study, we compared the fatigue behaviour of Ilizarov frames to interlocking intramedullary nails in a comminuted tibial fracture model under a combined loading of axial compression, bending and torsion. Our goal was to determine the biomechanical characteristics, stability and durability for each device over a clinically relevant three month testing period. The study hypothesis was that differences in the mechanical properties may account for differing clinical results and provide information applicable to clinical decision making for comminuted tibia shaft fractures.MethodsIn this biomechanical study, 12 composite tibial bone models with a comminuted fracture and a 25 mm diaphyseal gap were investigated. Of these, six models were stabilized with a 180-mm four-ring Ilizarov frame, and six models were minimally reamed and stabilized with a 10 mm statically locked Russell-Taylor Delta™ tibial nail. After measuring the pre-fatigue axial compression bending and torsion stiffness, each model was loaded under a sinusoidal cyclic combined loading of axial compression (2.8/28 lbf; 12.46/124.6 N) and torque (1.7/17 lbf-in; 0.19/1.92 Nm) at a frequency of 3 Hz. The test was performed until failure (implant breakage or ≥ 5° angulations and/or 2 cm shortening) occurred or until 252,000 cycles were completed, which corresponds to approximately three months testing period.ResultsIn all 12 models, both the Ilizarov frame and the interlocking tibia nail were able to maintain fracture stability of the tibial defect and to complete the full 252,000 cycles during the entire study period of three months. A significantly higher stiffness to axial compression and torsion was demonstrated by the tibial interlocking nail model, while the Ilizarov frame provided a significantly increased range of axial micromotion.ConclusionThis is the first study, to our knowledge, which compares the biomechanical properties of an intramedullary nail to an external Ilizarov frame to cyclic axial loading and torsion in a comminuted tibia shaft fracture model. Prospective, randomized trials comparing Ilizarov frames and interlocked tibial nails are needed to clarify the clinical impact of these biomechanical findings.

Effects of creep and cyclic loading on the mechanical properties and failure of human Achilles tendons.

The Achilles tendon is one of the most frequently injured tendons in humans, and yet the mechanisms underlying its injury are not well understood. This study examines the ex vivo mechanical behavior of excised human Achilles tendons to elucidate the relationships between mechanical loading and Achilles tendon injury. Eighteen tendons underwent creep testing at constant stresses from 35 to 75 MPa. Another 25 tendons underwent sinusoidal cyclic loading at 1 Hz between a minimum stress of 10 MPa and maximum stresses of 30-80 MPa. For the creep specimens, there was no significant relationship between applied stress and time to failure, but time to failure decreased exponentially with increasing initial strain (strain when target stress is first reached) and decreasing failure strain. For the cyclically loaded specimens, secant modulus decreased and cyclic energy dissipation increased over time. Time and cycles to failure decreased exponentially with increasing applied stress, increasing initial strain (peak strain from first loading cycle), and decreasing failure strain. For both creep and cyclic loading, initial strain was the best predictor of time or cycles to failure, supporting the hypothesis that strain is the primary mechanical parameter governing tendon damage accumulation and injury. The cyclically loaded specimens failed faster than would be expected if only time-dependent damage occurred, suggesting that repetitive loading also contributes to Achilles tendon injuries.

The effect of surface treatments on interfacial fatigue crack initiation in aluminum/epoxy bonds

The effect of different substrate surface pre-treatments on the initiation of interfacial fatigue cracks was studied for adhesive bonds. Aluminum-epoxy bimaterial specimens were used to investigate how surface pre-treatment affects resistance to fatigue crack initiation at the interface corner. A stress singularity approach was utilized to assess the effect of four different treatments; P2 etch, phosphoric acid anodization (PAA), sulfuric acid anodization (SAA), and sol-gel. A bimaterial system with a 90° epoxy wedge was tested under sinusoidal cyclic loading. The surface treatment effect was rather significant on the resistance to fatigue crack initiation at the interface. Results show that PAA generated the strongest interface, while SAA led to the weakest for the material system studied here.

Estimating Creep Rates During Tensile Cyclic Loading

Abstract A new form is formulated and presented graphically for estimating creep rates during sinusoidal cyclic loading of materials which obey Norton's creep power law. Also, a new closed form expression is derived and presented graphically for the average creep strain rate during ramp-type cyclic loading.

Three-dimensional primary stability of cementless femoral stems

Objective. This study investigates by means of a new bone-prosthesis interface motion detector whether conceptual design differences of femoral stems are reflected in their primary stability pattern. Design. An in vitro experiment using a biaxial materials testing machine in combination with three-dimensional motion measurement devices was performed. Background. Primary stability of uncemented total hip replacements is considered to be a prerequisite for the quality of bony ongrowth to the femoral stem. Dynamic motion as a response to loading as well as total motion of the prosthesis have to be considered under quasi-physiological cyclic loading conditions. Methods. Seven paired fresh cadaveric femora were used for the testing of two types of uncemented femoral stems with different anchoring concepts: CLS stem (Spotorno) and Cone Prosthesis (Wagner). Under sinusoidal cyclic loading mimicking in vivo hip joint forces a new measurement technique was applied allowing for the analysis of the three-dimensional interface motion. Results. Considerable differences between the two prostheses could be detected both in their dynamic motion and total motion behaviour. Whereas the CLS stem, due to the wedge-shaped concept, provides smaller total motions, the longitudinal ribs of the Cone prostheses result in a substantially smaller dynamic motion. Conclusions. The measuring technique provided reliable and accurate data illustrating the three-dimensional interface motion of uncemented femoral stems.

常圧焼結窒化ケイ素の高温繰返し荷重下におけるき裂進展挙動（応力比の影響）

Crack propagation tests of sintered silicon nitrode were carried out under sinusoidal cyclic load at elevated temperatures. The stress ratios used were 0.5 and 0.1, while the test temperature ranged from 1073K to 1273K. The main results obtained are as follows:(1) Although the crack propagation rate with R=0.1 was higher than that with R=0.5 at 1073K, this tendency faded out at 1223K.(2) The crack propagation rate at R=0.5 increased with temperature, while that at R=0.1 did not change with temperature.(3) When the maximum stress intensity factor KImax decreased stepwise with R=0.1, the crack propagation rate decreased gradually, although KImax increased with crack length at each KImax revel.(4) Slight oxidation started at 1073K. The grain boundary glassy phase softened at 1173K and Si3N4 crystal was attacked severely by oxygen in the atmosphere at 1273K.