Static Cyclic Tests Research Articles

New Metallic Damper with Multiphase Behavior for Seismic Protection of Structures

This paper proposes a new metallic damper based on the plastic deformation of mild steel. It is intended to function as an energy dissipation device in structures subjected to severe or extreme earthquakes. The damper possesses a gap mechanism that prevents high-cycle fatigue damage under wind loads. Furthermore, subjected to large deformations, the damper presents a reserve of strength and energy dissipation capacity that can be mobilized in the event of extreme ground motions. An extensive experimental investigation was conducted, including static cyclic tests of the damper isolated from the structure, and dynamic shake-table tests of the dampers installed in a reinforced concrete structure. Four phases are distinguished in the response. Based on the results of the tests, a hysteretic model for predicting the force-displacement curve of the damper under arbitrary cyclic loadings is presented. The model accurately captures the increment of stiffness and strength under very large deformations. The ultimate energy dissipation capacity of the damper is found to differ depending on the phase in which it fails, and new equations are proposed for its prediction. It is concluded that the damper has a stable hysteretic response, and that the cyclic behavior, the ultimate energy dissipation capacity and failure are highly predictable with a relatively simple numerical model.

Seismic Response Analysis and Evaluation of Laminated Rubber Bearing Supported Bridge Based on the Artificial Neural Network

Laminated rubber bearings are commonly adopted in small‐to‐medium span highway bridges in earthquake‐prone areas. The accurate establishment of the mechanical model of laminated rubber bearings is one of most critical steps for the bridge seismic response analysis. A new constitutive model of bearing based on the artificial neural network (ANN) technique is established through the static cyclic test of laminated rubber bearings, considering the bearing initial stiffness, friction coefficient, and other parameters such as the bearing sectional area, height, loading velocity, vertical load, and aging time. Combined with the ANN method, the ANN‐based bridge seismic demand model is built and applied to the rapid evaluation of the bridge seismic damage. The importance of the bearing affecting design factors in the bridge seismic demands are ranked. The results demonstrated that the dimensions of the bearing and vertical load are the main factors affecting the bearings constitutive model. Based on the partial dependency analysis with the ANN‐based bridge seismic demand model, it is concluded that the height of bearing is the key design parameter which affects the bridge seismic response the most. The ANN seismic demands model can fit the complex function relationship between various factors and bridge seismic response with high precision, so as to achieve the rapid evaluation of bridge seismic damage.

Study on the Mechanical Properties of Red Clay under Drying‐Wetting Cycles

To study the mechanical properties of red clay under repeated dry and wet cycle test conditions, in this paper, the disturbed red clay in an engineering area in Liuzhou, Guangxi Province, was taken as the research object. By artificially controlling different dry and wet cycles in the laboratory, a direct shear test and triaxial consolidation drainage test were carried out on the red clay samples after different dry and wet cycles. The stress‐strain curve and change rule of corresponding c and φ values were obtained. The results showed that, in both the direct shear test and the triaxial test, the shear strength parameters of red clay decreased with an increase in the number of dry and wet cycles and the attenuation was most obvious during the first cycle. With an increase in the number of dry and wet cycles, the attenuation gradually decreased. The constitutive model of the deviatoric stress and strain curve of red clay under dry and wet cycles was a plastic‐hardening type. By analyzing the variation in parameters in the P‐H model, the relationship between c, φ, and the number of dry and wet cycles n was obtained. The results showed that the parameters had different degrees of attenuation with the action of dry and wet cycles. To explain the above rules, some samples under different drying‐wetting cycles were selected for environmental electron microscope scanning, and appropriate assumptions were made based on the microstructure.

Reduced Gassing in Lithium-Ion Batteries with Organosilicon Additives

The battery industry is constantly seeking to improve battery capacity, lifetime, and safety. Electrolytes are a key development focus in achieving these goals, as traditional carbonate-based electrolytes cause capacity fade and gassing through degradation processes, as well as representing a safety risk due to flammability. The release of gasses through electrolyte decomposition is a problem of prominent concern in the battery industry, due to the negative impact of gassing on cell safety and performance. Studies on battery gassing have been reported for a wide range of battery systems,1-3 but the mechanisms and conditions of gas release are complex and not fully understood. Gaining a greater understanding of gassing mechanisms, and the specific electrolyte components that cause them, will allow for precise design of battery electrolyte formulations that optimize performance and minimize gassing.In addition to understanding traditional electrolyte blends, the investigation of new electrolytes and additives is essential in developing low-gassing batteries. Organosilicon (OS) materials have been developed by Silatronix® as critical high stability additions to conventional carbonate electrolytes to enable next-generation Li-ion batteries. This novel organosilicon chemistry involves the merging of a silane with a Li+ coordinating functionality. For example, the OS3® solvent family contains a nitrile functionality. The adoption of new Li-ion battery electrolyte materials is driven by the desire to deploy higher energy density batteries capable of performing under broader operating conditions of temperature and voltage, and the design of OS solvents results in low molecular-weight molecules that have demonstrated superior thermal and electrochemical stability,4,5 as well as good safety properties with a high flash point and low vapor pressure.Silatronix® has conducted commercially relevant performance testing and fundamental mechanistic studies to investigate gassing phenomena in advanced Li-ion chemistries under both cycling and storage test conditions. In these studies, commercially relevant electrolytes were evaluated as well as electrolytes designed to specifically isolate the effect of selected electrolyte components, including OS3® and other industry-relevant solvents. The dependence of gassing on storage and voltage conditions was investigated, and connections between gas analysis and the electrode surface chemistry are also reported. Gas component analysis was performed with a calibrated dual-column GC-TCD, a similar analytical system to that utilized in previous studies,6 which provides excellent resolution and quantification of every gaseous product. Key experimental results show that all OS3® concentrations reduce gas generation after 60°C storage and higher OS3® content provides greater benefit. Overall, we show that organosilicon additives substantially reduce gassing from carbonate-based electrolytes while maintaining good cell performance. Zhang, S.S., Insight into the Gassing Problem of Li-ion Battery. Frontiers in Energy Research 2014, 2, 59.Self, J.; Aiken, C.P.; Petibon, R.; Dahn, J.R., Survey of Gas Expansion in Li-Ion NMC Pouch Cells. Journal of the Electrochemical Society 2015, 162, A796-A802.Jung, R.; Metzger, M.; Maglia, F.; Stinner, C., Chemical vs Electrochemical Electrolyte Oxidation on NMC111, NMC622, LNMO, and Conductive Carbon. The Journal of Physical Chemistry Letters 2017, 8, 4820-4825.Guillot, S.L.; Peña-Hueso, A.; Usrey, M.; Hamers, R.J., Thermal and Hydrolytic Decomposition Mechanisms of Organosilicon Electrolytes with Enhanced Thermal Stability for Lithium-Ion batteries. Journal of the Electrochemical Society 2018, 164, A1907-A1917.Chen, X.; Usrey, M.; Peña-Hueso, A.; West, R.; Hamers, R.J., Thermal and Electrochemical Stability of Organosilicon Electrolytes for Lithium-Ion Batteries. Journal of Power Sources 2013, 241, 311-319.Xiong, D.J.; Ellis, L.D.; Petibon, R.; Hynes, T.; Liu, Q.Q.; Dahn, J.R., Studies of Gas Generation, Gas Consumption and Impedance Growth in Li-Ion Cells with Carbonate or Fluorinated Electrolytes Using the Pouch Bag Method. Journal of the Electrochemical Society 2017, 164, A340-A347.

The Influence of NiTi Alloy on the Cyclic Fatigue Resistance of Endodontic Files.

Background: The aim of this study was to analyze the influence of NiTi alloy in endodontic rotary instruments on cyclic fatigue resistance. Methods: One hundred and sixty-four (164) sterile endodontic rotary files were selected and distributed into the following study groups: A: 25.08 F2 ProTaper Universal (PTU) (n = 41); B: 25.06 X2 ProTaper Next (PTN) (n = 41); C: 25.08 F2 ProTaper Gold (PTG) (n = 41), and D: 25.06 ProFile Vortex Blue (PVB) (n = 41). A cyclic fatigue device was designed to conduct the static cyclic fatigue tests with stainless steel artificial root canals systems with 250 µm apical diameter, 60° curvature angle, 5 mm radius of curvature, 20 mm length, and 6% (25.06) and 8% taper (25.08). Failure of the endodontic rotary instrument was detected by a single operator through direct observation and was also filmed to allow measurement of the exact time to failure. Results were analyzed using the ANOVA test and Weibull statistical analysis. Results: All pairwise comparisons presented statistically significant differences between the time to failure for the NiTi alloy study groups (p < 0.001), except between the PTN and PVB study groups (p = 0.379). In addition, statistically significant differences between the number of cycles to failure for the NiTi alloy study groups (p < 0.001) were also observed. Conclusions: The NiTi CM-Gold wire alloy of the ProTaper Gold endodontic rotary files resulted in greater resistance to cyclic fatigue than ProFile Vortex Blue, ProTaper Next, and ProTaper Universal endodontic rotary files.

STATIC FLEXURAL CYCLIC FATIGUE OF TWO ROTARY FILE SYSTEMS (AN IN VITRO STUDY)

INTRODUCTION: Cyclic fatigue fracture is caused by repeated compressive/tensile stresses that accumulate around the curved rotating file. Many efforts have been made to increase the fracture resistance of Nickel-titanium (NiTi) rotary instruments, such as the use of heat-treated alloy, modification of the instrument's cross section and the improvement of surface treatment. OBJECTIVES: The aim of this study was to compare the static flexural cyclic fatigue of TwoShape (Micro Mega, Besancon, France) rotary file system which is made of T-Wire heat treatment technology and OneShape (Micro Mega, Besancon, France) rotary file system which is made of conventional nickel-titanium alloy. MATERIALS AND METHODS: Eighteen files from each system were subjected to static cyclic fatigue test. Cyclic fatigue testing was performed in a device which allowed a reproducible position of the instrument inside a custom-made stainless-steel artificial canal. The artificial canal had a curvature of 60° angle and 5 mm radius. All instruments were allowed to rotate inside the artificial canal until fracture. Time to fracture (TTF) was recorded using a digital chronometer. The number of cycles to failure (NCF) was calculated. The length of separated fragments was recorded. Data were analysed. RESULTS: The NCF of TwoShape files (365.909±82.077) was statistically significantly higher when compared with the OneShape files (266.681±35.218) p < .05. While there was no significant difference in the length of separated segments between both systems. CONCLUSIONS:Within the limitations of this study, the cyclic fatigue resistance of heat treated TwoShape files was significantly higher than the OneShape files. [T-wire] heat treatment drastically enhanced the cyclic fatigue resistance of the file.

Comparison of cyclic fatigue resistance of Rotate instrument with reciprocating and continuous rotary nickel-titanium instruments at body temperature in relation to their transformation temperatures.

The aim of this study was to compare the cyclic fatigue resistance at body temperature and phase transformation behaviors of novel Rotate instrument (25.06) with rotating Mtwo (25.06) and reciprocating Reciproc Blue (25.08) and Reciproc (25.08) instruments. The Rotate, Reciproc Blue, Reciproc, and Mtwo instruments free of visible deformations were collected and tested in a static cyclic fatigue test method, which has a ceramic block containing an artificial canal with 60° angle of curvature and a 5-mm radius of curvature at 37 °C (n = 16). All instruments were operated until fracture occurred, and both time to fracture (TF) and the lengths of the fractured fragments were recorded. TF data was analyzed with one-way ANOVA followed by post hoc Tukey tests and Weibull analysis, and fractured fragment length data were subjected to one-way ANOVA and post hoc Tukey tests (P < 0.05). Two unused instruments from each brand were also subjected to differential scanning calorimetry (DSC) analysis to determine their phase transformation temperatures. The Reciproc Blue instruments showed significantly higher TF values and reliability than the other groups (P < 0.05). Rotate instruments exhibited greater cyclic fatigue resistance than the Reciproc and Mtwo instruments (P < 0.05). No significant difference was detected among the fractured fragment lengths (P > 0.05). The lowest austenite finish temperature was exhibited by the Mtwo, which presented a single transformation peak, followed by the Rotate, Reciproc Blue, and Reciproc instruments which all presented two peaks during transformation. Cyclic fatigue resistance of instruments manufactured from thermally treated Blue wire instruments was superior to those of the Mtwo and Reciproc, whereas reciprocating the Blue wire showed the highest resistance. The present study compared the cyclic fatigue resistance of the novel Rotate instrument with similar instruments manufactured from conventional nickel-titanium, m-wire, and Blue wire at body temperature and reported that Blue-treated instruments exhibited superior cyclic fatigue resistance.

Multi-time-scale framework for prognostic health condition of lithium battery using modified Gaussian process regression and nonlinear regression

Prognostic and health management of lithium batteries is a multi-faceted approach that can provide crucial indexes for guaranteeing the reliability and safety of the energy storage system. Herein, a novel multi-time-scale framework is proposed that focuses on short-term battery state of health estimation and long-term remaining useful lifetime prediction. The proposed method extracts four significant features through in-depth analysis of partial incremental capacity and Gaussian process regression with nonlinear regression is applied to forecasting battery health conditions. First, the advanced signal filter methods are employed to smooth initial incremental capacity curves. After that, the significant feature variables are extracted from different degrees such as intercept, slope and peak by linear fitting the partial incremental capacity curves. Second, the significant feature variables feed to Gaussian process regression to establish a short-term battery degradation model using kernel-modified Gaussian process regression. Third, an autoregressive long-term battery prediction model is established by combining the offline short-term battery model with nonlinear regression. The predictive capability, robustness and effectiveness of proposed methods are verified using four datasets with different cycling test conditions and health levels. The results show that the proposed method can give accurate battery health conditions forecasting.

Reduced Gassing in Lithium-Ion Batteries with Organosilicon Additives

The battery industry is constantly seeking to improve battery capacity, lifetime, and safety. Electrolytes are a key development focus in achieving these goals, as traditional carbonate-based electrolytes cause capacity fade and gassing through degradation processes, as well as representing a safety risk due to flammability. The release of gasses through electrolyte decomposition is a problem of prominent concern in the battery industry, due to the negative impact of gassing on cell safety and performance. Studies on battery gassing have been reported for a wide range of battery systems,1-3 but the mechanisms and conditions of gas release are complex and not fully understood. Gaining a greater understanding of gassing mechanisms, and the specific electrolyte components that cause them, will allow for precise design of battery electrolyte formulations that optimize performance and minimize gassing.In addition to understanding traditional electrolyte blends, the investigation of new electrolytes and additives is essential in developing low-gassing batteries. Organosilicon (OS) materials have been developed by Silatronix® as critical high stability additions to conventional carbonate electrolytes to enable next-generation Li-ion batteries. This novel organosilicon chemistry involves the merging of a silane with a Li+ coordinating functionality. For example, the OS3® solvent family contains a nitrile functionality. The adoption of new Li-ion battery electrolyte materials is driven by the desire to deploy higher energy density batteries capable of performing under broader operating conditions of temperature and voltage, and the design of OS solvents results in low molecular-weight molecules that have demonstrated superior thermal and electrochemical stability,4,5 as well as good safety properties with a high flash point and low vapor pressure.Silatronix® has conducted commercially relevant performance testing and fundamental mechanistic studies to investigate gassing phenomena in advanced Li-ion chemistries under both cycling and storage test conditions. In these studies, commercially relevant electrolytes were evaluated as well as electrolytes designed to specifically isolate the effect of selected electrolyte components, including OS3® and other industry-relevant solvents. The dependence of gassing on storage and voltage conditions was investigated, and connections between gas analysis and the electrode surface chemistry are also reported. Gas component analysis was performed with a calibrated dual-column GC-TCD, a similar analytical system to that utilized in previous studies,6 which provides excellent resolution and quantification of every gaseous product. Key experimental results show that all OS3® concentrations reduce gas generation after 60°C storage and higher OS3® content provides greater benefit. Overall, we show that organosilicon additives substantially reduce gassing from carbonate-based electrolytes while maintaining good cell performance. 1. Zhang, S.S., Insight into the Gassing Problem of Li-ion Battery. Frontiers in Energy Research 2014, 2, 59.2. Self, J.; Aiken, C.P.; Petibon, R.; Dahn, J.R., Survey of Gas Expansion in Li-Ion NMC Pouch Cells. Journal of the Electrochemical Society 2015, 162, A796-A802.3. Jung, R.; Metzger, M.; Maglia, F.; Stinner, C., Chemical vs Electrochemical Electrolyte Oxidation on NMC111, NMC622, LNMO, and Conductive Carbon. The Journal of Physical Chemistry Letters 2017, 8, 4820-4825.4. Guillot, S.L.; Peña-Hueso, A.; Usrey, M.; Hamers, R.J., Thermal and Hydrolytic Decomposition Mechanisms of Organosilicon Electrolytes with Enhanced Thermal Stability for Lithium-Ion batteries. Journal of the Electrochemical Society 2018, 164, A1907-A1917.5. Chen, X.; Usrey, M.; Peña-Hueso, A.; West, R.; Hamers, R.J., Thermal and Electrochemical Stability of Organosilicon Electrolytes for Lithium-Ion Batteries. Journal of Power Sources 2013, 241, 311-319.6. Xiong, D.J.; Ellis, L.D.; Petibon, R.; Hynes, T.; Liu, Q.Q.; Dahn, J.R., Studies of Gas Generation, Gas Consumption and Impedance Growth in Li-Ion Cells with Carbonate or Fluorinated Electrolytes Using the Pouch Bag Method. Journal of the Electrochemical Society 2017, 164, A340-A347.

Assessment of Fatigue Induced Pad Cratering With a Universal Expression of Printed Circuit Board Fatigue Resistance

Abstract Repeated loading is an important reason to cause pad cratering fatigue failure in ball grid array (BGA) device in printed circuit board (PCB) assembly. For industry application, the board level drop test is commonly applied to evaluate the pad cratering fatigue strength under the repetitive drop loading. Although this testing method is consistent with the actual service condition of BGA-PCB assembly, it is extremely time consuming in the testing operation and expensive in costs. Another fatigue evaluation testing method for BGA-PCB assembly is the board level cyclic bending test. Compare with the board level drop test, this testing method can be handled by universal testing machine automatically without manual operation during the testing process. In consequence, the cyclic bending test has the merits of simple, fast, and low costs, and it is always desirable to evaluate the repeated drop life of pad cratering with cyclic bending test. This research proposes a correlation between the cyclic bending and repetitive drop test in BGA-PCB assemblies. With assistance of finite element method, the equivalent cyclic bending testing conditions of drop tests are developed. The experimental validation is also conducted to prove accuracy of the correlation. From the analysis of finite element method and experiments, both cyclic bending tests and repetitive drop tests agree with the same strain–number of cycle (S–N) curve. This means the S–N curve can be treated as a generalized failure criterion of fatigue induced pad cratering. The conclusion is crucial for reliability design phases to prevent the pad cratering fatigue failure.

Comparison of the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium rotary files at body temperature.

ObjectivesThis study aims to compare the cyclic fatigue resistance of VDW.ROTATE, TruNatomy, 2Shape, and HyFlex CM nickel-titanium (NiTi) rotary files at body temperature.Materials and MethodsIn total, 80 VDW.ROTATE (25/0.04), TruNatomy (26/0.04), 2Shape (25/0.04), and HyFlex CM (25/0.04) NiTi rotary files (n = 20 in each group) were subjected to static cyclic fatigue testing at body temperature (37°C) in stainless-steel artificial canals prepared according to the size and taper of the instruments until fracture occurred. The number of cycles to fracture (NCF) was calculated, and the lengths of the fractured fragments were measured. The data were statistically analyzed using a 1-way analysis of variance and post hoc Tamhane tests at the 5% significance level (p < 0.05).ResultsThere were significant differences in the cyclic fatigue resistance among the groups (p < 0.05), with the highest to lowest NCF values of the files as follows: VDW.ROTATE, HyFlex CM, 2Shape, and TruNatomy. There was no significant difference in the lengths of the fractured fragments among the groups. The scanning electron microscope images of the files revealed typical characteristics of fracture due to cyclic fatigue.ConclusionsThe VDW.ROTATE files had the highest cyclic fatigue resistance, and the TruNatomy and 2Shape files had the lowest cyclic fatigue resistance in artificial canals at body temperature.

CYCLIC FATIGUE RESISTANCE OF NEWLY INTRODUCED SURFACE AND THERMAL TREATED NICKEL-TITANIUM ROTARY FILES

Objectives The main objective of the present study invitro was to evaluate the cyclic fatigue resistance and metallurgic properties of newly thermal treated (CM wire) rotary Ni-Ti files with different surface treatments.Materials and Methods: A total of one hundred and twenty rotary files were used from three different rotary systems with the same thermomechanical treatment – controlled memory wire (CM Wire) and different surface treatment technique using rotation motion. Groups were set as Group 1: M3 Pro Gold (United Dental, Shanghai, China) (CM Wire) size (25/0.04), Group 2: AF F One Blue (Fanta Dental Material Co., Shanghai, China) [controlled memory wire (CM Wire)] size (25/0.04) and Group 3: Hyflex EDM (25/ 0.04). These files were tested for cyclic fatigue resistance using a custom-made static cyclic fatigue testing apparatus with various angles and radius (angle 60 radius 2.5mm and 5mm radius and angle 90 radius 2.5mm and 5mm). Each rotary file was coated with EDTA after its attachment in handpiece supported in stainless steel cylinder apparatus. M3 Pro Gold rotary files, AF F one blue and Hyflex EDM rotary files were rotated at 500rpm 2.5N/cm torque according to manufacture instructions. Digital watch was used to record the time taken until file fracture in seconds and the (NCF) number of cycles till fracture were calculated. Scanning electron microscope SEM image of the fractured surface were taken. Statistical analysis was performed using one-way analysis of variance and Tukey’s test at the 95% confidence level (P = 0.05). Results: After comparing the cyclic fatigue resistance of AF F One Blue and M3 Pro Gold by recording time till the file fracture was ranged between 670s to 1180s in all groups at angle 60 degree with different radius and 10s to 815s in all groups at angle 90 degree with different radius. There were no significant differences between the M3 Pro Gold and AF F One Blue rotary files at angle 60 degree and 90 degree in both radius 2.5mm and 5mm ( P> 0.05), while there were significant differences between the Hyflex EDM and M3 Pro Gold and AF F One Blue rotary files at angle 60 degree, radius 2.5mm ( P> 0.05). Hyflex EDM have the highly significant differences M3 Pro Gold and AF F One Blue rotary files at angle 90 degree, radius 2.5mm (P < 0.001). Conclusions: All new thermomechanical treatment technique - controlled memory CM-Wire rotary systems represented great performance and remarkable enhancement in cyclic fatigue resistance but the Hyflex EDM rotary files had the highest cyclic fatigue resistance among the M3 Pro Gold and AF F one Blue rotary files. Also surface treatment of the rotary files enhancing the cyclic fatigue resistance by decreases surface micro cracks and the tendency to fracture.

Bonding strength of plywood bonded using phenol formaldehyde mixed with wood bark powder nanofiller

This paper investigates the wettability of selected wood species from Indonesian community forests, namely (Indonesian name–Latin name) surian (Toona sinensis), jabon (Anthocephalus cadamba), gmelina (Gmelina arborea.), Manglid (Manglietia glauca), rubber wood (Hevea brasiliensis), and sengon (Paraserianthes falcataria). The study measures the contact angle and evaluates the suitability of these wood species for plywood production. Logs from a community forest were processed to convert into thin slices of veneer using the rotary cutting method at a plywood plant. Subsequently, the study analyzed the wetting behavior of the veneer samples resulting from a rotary process on tangential surfaces without smoothing treatment with distilled water. The veneer was then made into plywood using an adhesive nanofiller of phenol formaldehyde mixed with wood bark powder. Ball milling produced nanofillers from the bark of jabon, gmelina, and surian with nanoscale particle diameter size (10–1000 nm). The bonding strength of the plywood was evaluated under cyclic and dry test conditions according to Japanese Standards. The study shows that P. falcataria, H. brasiliensis, and A. cadamba have a smaller contact angle than T. sinensis, G. arborea, and M. glauca. Thus, the higher wettability of P. falcataria, H. brasiliensis, and A. cadamba results in a better adhesive spread and more intimate contact between the wood surface and the adhesive. However, the study found higher bonding strength values for H. brasiliensis and T. sinensis plywood using jabon nanofiller, followed by T. sinensis plywood using surian nanofiller and H. brasiliensis plywood using gmelina nanofiller.

Thermomechanical Analysis of Conformally Coated QFNs for High-Reliability Applications

The use of quad flat no-leads (QFNs) in high-reliability applications is receiving increased interest. To address concerns of harsh working environments, conformal coatings are used to protect the components and associated printed circuit board (PCB). However, using conformal coatings can pose a reliability risk for the components on the PCB. This paper details an investigation into the effect of conformal coatings on the reliability of QFN second-level solder interconnections. Five QFN package types and two types of conformal coatings were investigated. In the experiments, a large population of QFN assemblies coated with conformal coatings were subjected to a thermal cycling test condition. These components, designed with daisy-chain connections, were monitored during the thermal cycling tests, and the exact time for failure to occur for each component was recorded and analyzed. Detailed finite-element models for the tested QFN assemblies were developed; the inelastic strain energy density was used as the damage indicator to evaluate the impact of conformal coating on the solder joint reliability. Modeling results reveal that the conformal coating plays an intricate role in QFN solder joint reliability. The presence of conformal coating results in a reduction in the shear stress in the solder joint and plays a positive role in solder reliability. However, it also induces more stress in the solder joint in the out-of-plane direction and plays a negative role. These two mechanisms are competing, and their relative magnitude will determine the overall effect of conformal coating on solder joint reliability.

A comparative analysis of cyclic fatigue of a new preheated machined CM wire endodontic files after exposure to different irrigants

AIM: Analysis of cyclic fatigue of a new preheated machined CM wire MPro endodontic files after exposure to lycopene, curcumin and Soduim hypochlorite for two different immersion observation periods; 5 minutes and 10 minutesMethodology: Eighteen size 20 MPro files were used in this study, divided into three groups of 6 files each according to irrigant used: Group I lycopene, Group II curcumin and Group III Soduim hypochlorite. All files were immersed in irrigants for either 5 or 10 minutes. The cyclic fatigue tess were performed on all files of both immersion periods using a static cyclic fatigue testing device, which have an artificial stainless steel canal and tested using a custom-made static cyclic fatigue testing apparatus. Parameters recorded were time to fracture, number of cycles to failure (NCF) and mean length of fractured segments.Results: Results showed no statistically significant difference between the different irrigants at the two observation periods and within the same group regarding time to fracture, number of cycles to failure (NCF) and mean length of fractured segments.Conclusion: All tested irrigants lycopene, curcumin and Soduim hypochlorite had same effect on cyclic fatigue of the preheated machined CM wire Mpro endodontic files when used for 5 or 10minutes.

Improvement of Transient Operation Controllability in Engine Test Bench for Heavy-Duty Vehicles

In this study, two kinds of control methods for the transient operation of an engine test bench for heavy-duty vehicles were applied in the JE05 test cycle and World Harmonized Transient Cycle (WHTC) test conditions in order to evaluate the controllability of transient operations and the effect on emissions. One control method uses dynamometer torque with its inertia correction as the feedback signal (dyno torque F/B control); the other method uses axial torque measured by a flange-type high-response torque meter as the feedback signal (axial torque F/B control). The transient operation controllability using the axial torque F/B control improved compared with the dyno torque F/B control. The results influence NOx emissions in the emissions test cycle, such as JE05 and WHTC, with the engine test bench. Axial torque F/B control could become a more useful technique when it is required to improve the reproducibility of real driving conditions.

Effects of power cycling test condition and test strategy on lifetime estimation of power modules in power electronic systems

One of the main purposes of an accelerated power cycling test is to develop a lifetime model for the lifetime prediction of power modules. It is important to select proper test conditions when the power cycling test is performed since it is closely related to the lifetime model parameters and also to the testing time. In this paper, the effects of power cycling test condition and test strategy on the lifetime estimation of power modules are studied. The lifetime models of the IGBT module are developed by the accelerated power cycling tests with different test conditions and also by calibrated accelerated power cycling test. As a case study, the lifetime of IGBT module in motor drive system is estimated with different lifetime models and the results are compared.

Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions.

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

Investigation and analysis of finger breakages in commercial crystalline silicon photovoltaic modules under standard thermal cycling test

The front grid fingers play a major role in the conduction of current in crystalline silicon photovoltaic (PV) modules. These fingers generally break with time during the field exposure which affects the modules mechanical and electrical integrity and causes reduction in its performance. In this paper, a systematic methodology has been presented for investigation of the nature and evolution of finger breakages observed in crystalline silicon PV technology modules under standard thermal cycling tests as specified under IEC 61215 standard. Illuminated current-voltage (I-V) analysis and electroluminescence (EL) imaging techniques have been exploited in tandem for investigation of the cause, types and progression of the finger breakages. The results obtained from the study identified various faulty solder configurations which are sensitive to thermal fatigue and subsequently cause finger breakages. A generalized method to quantify the finger breakages from EL images has been introduced. The different finger breakage patterns have been classified according to their appearance in the EL images originating from the breakage of the busbar-finger junctions. Distributed diode modelling and simulation have also been performed for the quantification of severity of different finger breakage patterns. In addition, a finger breakage constant has been proposed for comparative assessment of durability of fingers in PV modules under thermal cycling test conditions. The present investigation and analysis of finger breakages can be instrumental in prevention of failures thereby enhancing performance and durability of PV modules.

Prognostic health condition for lithium battery using the partial incremental capacity and Gaussian process regression

Precisely battery state of health estimation and remaining useful lifetime prediction are crucial factors in ensuring the reliability and safety for system operation. This paper thus focuses on the short-term battery state of health estimation and long-term battery remaining useful lifetime prediction. A novel hybrid method by fusion of partial incremental capacity and Gaussian process regression is proposed and dual Gaussian process regression models are employed to forecast battery health conditions. First, the initial incremental capacity curves are filtered by using the advanced signal process technology. Second, the important health feature variables are extracted from partial incremental capacity curves using correlation analysis method. Third, the Gaussian process regression is applied to model the short-term battery SOH estimation using the feature variables. Forth, an autoregressive long-term battery remaining useful lifetime model is established using the results of battery SOH values and previous output. The predictive capability and effectiveness of two models are demonstrated by four battery datasets under different cycling test conditions. Otherwise, the robustness of the two models is verified using four datasets with different health levels. The experimental results show that the proposed method can provide accurate battery state of health estimation and remaining useful lifetime.