Run-out Condition Research Articles

Bone Plates Runout Prediction Through Tensile Strength and Geometric Properties for Regulatory Mechanical Testing.

Mechanical tests on bone plates are mandatory for regulatory purposes and, typically, the ASTM F382 standard is used, which involves a four-point bending test setup to evaluate the cyclic bending fatigue performance of the bone plate. These test campaigns require a considerable financial outlay and long execution times; therefore, an accurate prediction of experimental outcomes can reduce test runtime with beneficial cost cuts for manufacturers. Hence, an analytical framework is here proposed for the direct estimation of the maximum bending moment of a bone plate under fatigue loading, to guide the identification of the runout load for regulatory testing. Eleven bone plates awaiting certification were subjected to a comprehensive testing campaign following ASTM F382 protocols to evaluate their static and fatigue bending properties. An analytical prediction of the maximum bending moment was subsequently implemented based on ultimate strength and plate geometry. The experimental loads obtained from fatigue testing were then used to verify the prediction accuracy of the analytical approach. Results showed promising predictive ability, with R2 coefficients above 0.95 in the runout condition, with potential impact in reducing the experimental tests needed for the CE marking of bone plates.

Influence of displacement sensor runout on active magnetic bearing-rotor system and control analysis

In the active magnetic bearing (AMB)-rotor system, a displacement sensor is one of the indispensable components. It detects the displacement of the rotor in real time and feeds back to the control system to realize the stable suspension of the rotor. However, due to electromagnetic interference, unstable power supply, poor grounding, and uneven rotor surface, the signal runout of the displacement sensor can often occur, resulting in rotor vibration. Given the above problems, this paper establishes the control model of the AMB-rotor system, lists three typical sensor runout signals, then analyzes the influence of different types of sensor runout on the system, and discusses the control methods under different sensor runout conditions. The research results have a specific guiding significance for vibration control of the maglev rotor under sensor runout influence.

Multiaxial high cycle fatigue of 304L stainless steel with a small defect

The influence of a small defect on the multiaxial fatigue strength of 304L stainless steel was experimentally investigated. The fatigue tests were carried out on specimens containing a cylindrical defect with area = 400 µm. Five fully reversed loading paths were employed: tension-compression, torsion, in-phase, 90° out-of-phase, and square shape. Crack orientation in the vicinity of the defect was examined at and just above 2 × 106 cycles (run-out condition). The fatigue limits and crack angles measured were used to evaluate a tensile-based critical plane criterion for small defects. Predicted and measured results were in good agreement, indicating a tensile-dominated failure mechanism in the range of experimental conditions studied.

Fully-reversed tension-compression fatigue of 2D and 3D woven polymer matrix composites at elevated temperature

High-temperature tension-compression fatigue behavior of polymer matrix composites with a 2D and a 3D fiber architecture was examined. The two composites studied in this work have the same NRPE polyimide matrix and carbon fiber reinforcement, but different fiber architectures. The 3D composite is a single-ply non-crimp 3D orthogonal weave material whereas the 2D laminated composite contains fifteen 0/90 woven plies. The study aims to evaluate the fitness of the two materials for service in aerospace thermal-protection systems. Thus mechanical testing was conducted under environmental conditions mimicking the realistic service environment: one side of the test specimen was held at 329 °C whilst the other side remained open to ambient laboratory air. The tension and compression stress-strain responses of the two composites were investigated and the basic tensile and compressive properties measured. The high-temperature properties were similar to those obtained at room temperature. Fully-reversed tension-compression cyclic tests were carried out at elevated temperature. The frequency was 1.0 Hz, the ratio of minimum to maximum stress was −1.0, and the runout condition was defined as survival of 200,000 cycles. The evolution of maximum and minimum strains with cycles as well as the progressive change in modulus were examined for each test. The 3D composite produced a higher fatigue limit, while the 2D laminated composite displayed a slightly better fatigue performance at higher stress levels. All specimens that survived 200,000 cycles without failure were tested in tension to failure to assess the retained tensile strength and stiffness. Examination of tested specimens with an optical microscope showed extensive delamination of the 2D composite. The 3D composite proffered enhanced delamination resistance.

Rolling contact fatigue deformation mechanisms of nickel-rich nickel-titanium-hafnium alloys

The deformation mechanisms that dictate the tribological performances of heat treated Ni55Ti45, Ni54Ti45Hf1 and Ni56Ti36Hf8 alloys are revealed through rolling contact fatigue (RCF) testing and transmission electron microscopy (TEM) analyses. Analysis of worn samples that passed a 5×108 cycle RCF runout condition shows that damage is primarily confined to deformation bands that propagate several hundred nanometers – to – several microns beneath the surface. These bands nucleate via localization of dislocation slip within the B2 austenite phase of the alloys. For the Ni55Ti45 and Ni54Ti45Hf1 samples, further damage and eventual spall failures occur by shearing and dissolution of the strengthening Ni4Ti3 nanoprecipitates within the deformation bands, followed by nanocrystallization that sometimes includes stress-induced nucleation of B19′ nanocrystals. Eventually, complete amorphization occurs prior to fracture. The relative 15 – 25% increase in RCF contact stress performance of the Ni56Ti36Hf8 alloy correlates with a more limited depth of damaged material beneath the wear surface; heavily damaged material beneath spall failure sites only extends 1.5 µm into the sample, compared to > 6 µm for Ni55Ti45 and Ni54Ti45Hf1 alloys. This superior RCF damage resistance of the Ni56Ti36Hf8 alloy results from a lower fraction of B2 matrix phase (≤ 13 %) that is highly confined by both cubic Ni-rich NiTiHf and H-phase nanoprecipitates. Specifically, this microstructure limits the widths of deformation bands within the B2 austenite phase to less than the size of the strengthening nanoprecipitates, which in turn inhibits precipitate shearing and dissolution processes that precede nanocrystallization and amorphization.

Fatigue properties of continuous wave and pulsed wave laser cold-wire welding of thick section AA6005-T6 aluminum alloys

The effect of laser wave modes on the fatigue behavior of laser cold-wire welding made of 4.8 mm thick AA6005-T6 aluminum alloy was investigated using continuous and pulsed wave lasers. Due to the inherent differences in these two wave laser modes, different welding parameters were used, while keeping the interaction time constant. The mechanical properties of welded joints were measured using tensile tests, while their fatigue performances were quantified using a constant amplitude force-controlled technique to obtain S-N curves. The pulsed wave laser mode produced higher fatigue resistance as compared to the continuous wave mode. The fatigue strength corresponding to the run-out condition (i.e., 107 cycles, in this study) was about 28% higher for the pulsed wave mode than for the continuous wave laser mode. At a high stress amplitude (30 MPa), the lifespan of the pulsed wave joints was about twice as high as that with continuous wave joints. These fatigue results were cross-referenced with a 3D topographic map, a 2D microhardness map, a metallographic study, and a fractographic analysis to better understand the crack nucleation and crack propagation mechanisms. A microhardness analysis performed along the cross-section of the joints did not reveal any significant difference between pulsed wave and continuous wave modes. A fractographic analysis confirmed crack propagation within the fusion zone and that 83 to 90% of cracks nucleated from the root undercuts. Topographic maps of the joints before fracture revealed that the continuous wave laser mode produces deeper and narrower (i.e., more acute) undercut defects than does the pulsed wave mode. A Weibull approach based on the biggest defects found on the fracture surfaces also confirmed that the continuous wave process produces larger defects at the root. Top defects are significantly small (55%), but they have a larger size dispersion than do root defects. Since the root undercuts act as the main stress concentrators, they are mainly responsible for the lower fatigue performance of the joints, and their sizes and shapes should be minimized during further process development of the welding process.

Fatigue Characterization of SiC/SiC Ceramic Matrix Composites in Combustion Environment

Abstract Fatigue behavior of woven melt infiltrated (MI) SiC/SiC ceramic matrix composites (CMCs) was investigated under a tension–tension fatigue condition in a combustion environment. A special experimental facility is designed to subject the CMCs under simultaneous mechanical and combustion conditions which is more representative of some conditions experienced by the hot section components of a jet engine. The MI SiC/SiC CMCs considered in this study consists of a SiC matrix densified with liquid Si infiltration, BN interphase, and reinforced with two different fibers, namely, Hi–Nicalon type S and Tyranno SA fibers. A high velocity oxygen fuel (HVOF) gun is used to create the representative combustion condition and a horizontal hydraulic MTS machine to apply the mechanical loading. Several fatigue tests were conducted at different stress levels with a stress ratio of 0.1, frequency of 1 Hz, and the specimen surface temperature at 1200 °C. Similar tests were conducted in an isothermal furnace condition at 1200 °C for comparison. Electrical resistance (ER) was used to monitor the tests. A reduction in the fatigue life was observed for the two MI systems under combustion conditions in comparison to the isothermal furnace condition at the same applied stress level. This is attributed to the presence of harsh combustion environment present in the burner rig. ER showed some promising results in monitoring the temperature and detecting damage in the specimen. Runout condition was set as 24 H (86400 cycles) in burner rig and 100 H (360000 cycles) in furnace environment. Specimens that achieved the runout condition were subsequently tested under monotonic tension testing at room temperature after cooldown to evaluate the residual properties. Residual strength results showed a significant strength reduction in both the furnace and burner rig environments. Post-test microscopy was conducted on the fracture surfaces of the failed specimens to understand the oxidation behavior and damage mechanisms.

Analysis of cutting force coefficients in high-speed ball end milling at varying rotational speeds

ABSTRACTIn high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, tool failure, tool deflection, machine tool chatter, vibration, etc. Thus, an accurate prediction of cutting forces before actual machining is essential for a good insight into the process to produce good quality machined parts. In this article, an attempt has been made to determine specific cutting force coefficients in ball end milling based on a linear mechanistic model at a higher range of rotational speeds. The force coefficients have been determined based on average cutting force. Cutting force in one revolution of the cutter was recorded to avoid the cutter run-out condition (radial). Milling experiments have been conducted on aluminum alloy of grade Al2014-T6 at different spindle speeds and feeds. Thus, the dependence of specific cutting force coefficients on cutting speeds has been studied and analyzed. It is found that specific cutting force coefficients change with change in rotational speed while keeping other cutting parameters unchanged. Hence, simulated cutting forces at higher range of rotational speed might have considerable errors if specific cutting force coefficients evaluated at lower rotational speed are used. The specific cutting force coefficients obtained analytically have been validated through experiments.

Fatigue behavior of an advanced SiC/SiC ceramic composite with a self-healing matrix at 1300 °C in air and in steam

The fatigue behavior of a non-oxide ceramic composite with a multilayered matrix was investigated at 1300°C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated woven Hi-Nicalon™ fibers. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. Tensile stress-strain behavior and tensile properties were evaluated at 1300°C. Tension-tension fatigue behavior was studied for fatigue stresses ranging from 70 to 160MPa in air and in steam. The fatigue limit (based on a run-out condition of 2×105 cycles) was between 80 and 100MPa. Presence of steam had little influence on fatigue performance. The retained properties of all specimens that achieved fatigue run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.

Experimental study on compressive behavior of GFRP stiffened panels using digital image correlation

Stiffened composite panels are primary structural components in ship, aircraft and aerospace vehicles. The main objective of this study is to investigate the behavior of glass fiber reinforced polymer (GFRP) composite panels with stiffener runout condition and different stiffener configurations such as blade, T and hat under axial compression. A special fixture was designed and fabricated for the compressive testing of GFRP composite stiffened panels. Fabricated specimens were tested until failure and the effect of different stiffener configurations on the load–deformation behavior is compared. Digital image correlation (DIC) was used to measure the deformations and strains on the GFRP composite panels. Test results indicated that T-stiffeners performed well with higher failure load and stiffness as compared to other stiffeners. DIC results show that the presence of stiffeners reduced the out-of-plane displacement in the stiffened panels. As the load level increases, damage initiates and propagates. The surface strain and displacement are sensitive to damages and it can alter their distribution. This could be captured using DIC technique as the damage distribution takes place. The T-stiffeners were found to be effective in resisting bending strains and produced more uniform distribution of compressive strain compared to other stiffener configuration.

Effect of the stress level on the fatigue strengthening behavior of 2D needled C/SiC CMCs at room temperature

The fatigue behavior of 2D needled C/SiC CMCs at room temperature was studied. The residual tensile properties were determined for the run-out condition set for the fatigue testing. It is noted that the 2D needled C/SiC CMCs achieve ~20% enhancement of the ultimate tensile strength after fatigue loading with fiber pull-out present. This enhancement of residual properties is not widely observed and reported for CMCs. The increase in residual tensile properties correlates with the applied fatigue stress. The procedures for testing and the mechanics for the increased strength after fatigue testing are discussed. This is supplemented with microstructure observations. The prior fatigue loading results in more full-developed micro-damage and a more uniform stress state in the fibers of needled C/SiC CMCs, so the load capability of post-fatigue specimens is stronger than the as-received ones with extremely uneven pre-loading in fibers.

Unravelling the multiphase run-out conditions of a slide-flow mass movement

In this paper an attempt is made to unravel the run-out characteristics of a mass movement in the Sichuan Province, SW China by means of 1D numerical modelling and calibration on the topography of run-out profiles. The Dagou mass movement started as a rockslide with an initial volume of 480,000m3, which transformed into a debris flow, increasing in volume due to entrainment of loose material in the upper part of the travelling track. The rapid mass movement had a run-out distance of 1380m and a run-out time of about 50s.Numerical calculations were conducted with the depth average shallow water equation to explain the variation in thickness of the debris flow deposits along the run-out track. For the calibration of the first run-out phase, three rheological models were applied, namely the Bingham, Voellmy and Quadratic rheology. Calibration was done on 1) the run-out distance, 2) the run-out time and 3) the goodness of fit with the thickness of the deposits along the track. In addition the erosion constant in the entrainment equation was calibrated on the observed versus calculated run-out volumes. Sensitivity analyses of the resistance parameters for the different rheologies showed that the viscosity, the basal friction, the turbulence term and the resistance factor are the most sensitive ones. It appeared that the variation in thickness along the run-out track can be explained by entrainment of material in the upper part of the track and a change in parametric values during the run-out process. The three rheologies produced a reasonable fit with the observed geometry of the run-out profile, run-out time and run-out volume. It was argued that the Voellmy rheology seems to give the most appropriate explanation for the difference in resistance along the run-out path. The main problem in the simulation was to stop the debris flow on a slope with a gradient around 22°.A reactivation of the mass movement by frictional sliding of the material half way the run-out track was simulated. It occurred 30min after the first run-out phase due to an increase in pore pressure. The sliding material changed into a slow flowing mass that reached a newly built up area after about 1h and moved into Wangong Town over a distance of 80m.

Convolution spline approximations for time domain boundary integral equations

We introduce a new spline'' temporal approximation of time domain boundary integral equations (TDBIEs). It shares some properties of convolution quadrature (CQ) but, instead of being based on an underlying ODE solver, the approximation is explicitly constructed in terms of compactly supported basis functions. This results in sparse system matrices and makes it computationally more efficient than using the linear multistep version of CQ for TDBIE time-stepping. We use a Volterra integral equation (VIE) to illustrate the derivation of this new approach: at time step $t_n = n\dt$ the VIE solution is approximated in a backwards-in-time manner in terms of basis functions $\phi_j$ by $u(t_n-t) \approx \sum_{j=0}^n u_{n-j}\,\phi_j(t/\dt)$ for $t \in [0,t_n]$. We show that using isogeometric B-splines of degree $m\ge 1$ on $[0,\infty)$ in this framework gives a second order accurate scheme, but cubic splines with the parabolic runout conditions at $t=0$ are fourth order accurate. We establish a methodology for the stability analysis of VIEs and demonstrate that the new methods are stable for non-smooth kernels which are related to convergence analysis for TDBIEs, including the case of a Bessel function kernel oscillating at frequency $\oo(1/\dt)$. Numerical results for VIEs and for TDBIE problems on both open and closed surfaces confirm the theoretical predictions.

Effects of Steam Environment on Fatigue Behavior of Two SiC/[SiC+Si3N4] Ceramic Composites at 1300°C

The fatigue behaviors of two SiC/[SiC+Si3N4] ceramic matrix composites (CMC) were investigated at 1,300°C in laboratory air and in steam. Composites consisted of a crystalline [SiC+Si3N4] matrix reinforced with either Sylramic™ or Sylramic-iBN fibers (treated Sylramic™ fibers that possess an in situ BN coating) woven in a five-harness satin weave fabric and coated with a proprietary boron-containing dual-layer interphase. The tensile stress–strain behaviors were investigated and the tensile properties measured at 1,300°C. Tension–tension fatigue behaviors of both CMCs were studied for fatigue stresses ranging from 100 to 180 MPa. The fatigue limit (based on a run-out condition of 2 × 105 cycles) in both air and steam was 100 MPa for the CMC containing Sylramic™ fibers and 140 MPa for the CMC reinforced with Sylramic-iBN fibers. At higher fatigue stresses, the presence of steam caused noticeable degradation in fatigue performance of both composites. The retained strength and modulus of all run-out specimens were characterized. The materials tested in air retained 100% of their tensile strength, while the materials tested in steam retained only about 90% of their tensile strength.

Effects of steam environment on high-temperature mechanical behavior of NextelTM720/alumina (N720/A) continuous fiber ceramic composite

Abstract Mechanical behavior of an oxide–oxide continuous fiber ceramic composite (CFCC) consisting of a porous alumina matrix reinforced with laminated, woven mullite/alumina fibers (Nextel TM 720) was investigated at 1200 and 1330 °C in laboratory air and in 100% steam environments. CFCC has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension–tension fatigue behavior was studied for fatigue stresses ranging from 100 to 170 MPa at 1200 °C, and for fatigue stresses of 50 and 100 MPa at 1330 °C. Tensile creep behavior was examined for creep stresses ranging from 80 to 154 MPa at 1200 °C, and for creep stresses of 50 and 100 MPa at 1330 °C. At 1200 °C, the CFCC exhibited excellent fatigue resistance in laboratory air. The fatigue limit (based on a run-out condition of 10 5 cycles) was 170 MPa (88% UTS at 1200 °C). The material retained 100% of its tensile strength. Presence of steam caused noticeable degradation in fatigue performance at 1200 °C. Fatigue resistance at 1330 °C was poor. In creep tests, primary and secondary creep regimes were observed. Minimum creep rate was reached in all tests. At 1200 °C, creep rates were 10 −8 –10 −5 s −1 and maximum time to rupture was 255 h. At 1330 °C, creep rates were 10 −7 –10 −5 s −1 and maximum time to rupture was 87 h. Presence of steam accelerated creep rates and dramatically reduced creep life.

Mechanical Behavior and High‐Temperature Performance of a Woven Nicalon™/Si‐N‐C Ceramic‐Matrix Composite

A modern ceramic‐matrix composite (CMC) has been extensively characterized for a high‐temperature aerospace turbine‐engine application. The CMC system has a silicon‐nitrogen‐carbon (Si‐N‐C) matrix reinforced with Nicalon fibers woven in a balanced eight‐harness satin weave fabric. Tensile tests have demonstrated that this CMC exhibits excellent strength retention up to 1100°C. The room‐temperature fatigue limit was 160 MPa, ∼80% of the room‐temperature tensile strength. The composite reached run‐out conditions under cyclic (105 cycles at 1 Hz) and sustained tension (100 h) conditions at a stress of 110 MPa, which was ∼35 MPa above the proportional limits at temperatures up to 1100°C in air. At stress levels >110 MPa, cyclic loading at 1000°C caused a more severe reduction in life, based on time, compared with sustained tension. Further life degradation was observed in the 1000°C fatigue specimens that were exposed to a salt‐fog environment. This degradation decreased the fatigue life ∼85% at the stress levels that were tested.

A new algorithm for the detection of tool breakage in milling

In this paper a novel signal processing algorithm is presented for the detection of tool breakage using the displacement signal (RORPA). The algorithm extracts information from consecutive revolutions to decrease dependencies on runout conditions and idle noise, creating a much more robust signal for the automatic determination of tool breakage conditions. The algorithm is explained as well as the determination of dynamic thresholds. The thresholds are set using the information regarding the cutting conditions (mean displacement signal and its slope during transient milling). Examples with real data are also presented. A critique of the overall performance and future work incorporating information from x and y channels completes the discussion.