Range Of Maximum Loads Research Articles

Measurement of Creep Stress Exponent of TC17 Titanium Alloy by Nanoindentation Method at Room Temperature.

The creep stress exponent is commonly employed to characterize the deformation mechanism during the steady-state creep stage, serving as an indicator of creep behavior. The creep phenomenon of high melting point metallic materials is not obvious at room temperature. However, the nanoindentation method proves suitable for investigating the creep properties of metallic materials under such conditions. Consequently, this paper places emphasis on measuring the creep stress exponent of TC17 titanium alloy at room temperature using the load preservation stage of the nanoindentation method with a constant loading rate. In order to investigate the effects of loading rate and maximum load on the experimental results, different loading rates were applied to the diamond Berkovich indenter to reach different maximum loads. The indenter was held under the maximum load for a duration of 360 s, and the relationship between the indentation strain rate and indentation stress during the holding process was used to obtain the creep stress exponent of the material at room temperature. The findings indicate that within the loading rate range of 1.25 to 15 mN/s and maximum load range of 50 to 300 mN, the influence on the experimental results is insignificant. Ultimately, the distribution range of the creep stress exponent for TC17 titanium alloy at room temperature was measured to be 8.524-8.687.

Characteristics of 4-Stroke Single Cylinder Ci Engine using Cotton Seed Oil Blended With Diesel

In four different compositions a cotton oil methyl ester is prepared and combine with diesel, ranging from 5% to 20% in 5% stages Tests were performed at a constant speed of 1500 rpm in a single cylinder variable compression ratio diesel engine. The highest thermal brake output and the lowest specific fuel consumption was observed for a compression ratio of 15 and 17 percent of the biodiesel blend. At a compression ratio of 17, the average emission of nitric oxide was 205 ppm and the total emission of diesel was 155 ppm. Significant decrease in emissions of smoke and carbon monoxide was observed in the maximum load range and compression ratio. For the prepared biodiesels, enhanced heat release characteristics have been noted. The results show that the biodiesels can be safely utilized without any modification of engine ..

Fatigue bending test on grouted connections for monopile offshore wind turbines

Wind and wave loadings induce stochastic bending moments in grouted connections for monopile offshore wind turbines; thus, the fatigue behavior under bending moment is extremely important. This paper presents test results on five cylindrical monopile grouted connection specimens with shear keys, which have an outer diameter of 612 mm, and different lengths of 4365 mm, 4475 mm, and 4585 mm. They were designed and tested under constant range of fatigue cyclic bending moments. The load ranges were established based on the ultimate limit state bending capacity of each specimen. It was found out that, although some local degradation exists, the whole grouted connection in the first four specimen can still survive two million load cycles with no obvious degeneracy in bending capacity. Furthermore, no obvious cracks were found at the end section of the grouted connections. Meanwhile, in the longest specimen, due to its maximum load range, the welded structures cracked after about 1.28 million load cycles indicating the end of testing. In addition, no destruction was found in the grouted connection itself. Moreover, after comparing the specimens with different lengths, the authors determined that the recommended minimum design length for grouted connections with shear keys was conservative in the commonly used design code.

STRAIN GAUGE SENSOR OF MASS MEASUREMENT USING A BRASS CANTILEVER

A study of mass measurement using strain gauge 120 which was placed in the corner of the brass cantilever has been done. This study essentially utilizes deflection phenomena on the surface. This phenomenon occurs due to the mass placed on one end of the brass cantilever. The Mass was calibrated with standard mass gauge using OHAUS PA214 Pioneer<sup>TM</sup> analytical balance. It was done a variation of mass-reduction and addition at the end of the brass cantilever with a multiple of 0.1 gram over a span interval of 1.1-7.5 grams. It obtained hysteresis curve plot for the changing strain gauge resistance (ΔR) versus mass variations on which the system has the maximum load range (7,1-7,5 gram). Moreover, The test of the system for the mass variations in the output voltage of the IC AD521JD differential amplifier was approximated as a quadratic function which was expressed in the system characteristic equation m = 2,4×V<sup>2</sup> - 0,8533×V + 1,1449, with m (gram) and V (Volt). The characteristic equation is used in the ADC conversion of the microcontroller. The measured mass value was displayed on 2 × 16 LCDs in grams.

Investigation of mechanical behavior of quenched Ti–6Al–4V alloy by microindentation

This paper investigated the micro mechanical behavior of quenched Ti–6Al–4V alloy, microindentation experiments were performed in a wide range of maximum loads: 200, 300, 500, 700, 1000, 1500, 2000, 3000, 3500 and 4900mN, and loading speeds: 10, 40 and 103mN/s. The results revealed that loading speed had little influence on measurement of hardness and Young's modulus. Microindentation hardness experiments showed strong indentation size effects. Indentation hardness as well as Young's modulus decreased with the increase of indentation load. The decrease of Young's modulus was due to the damage of materials. The analysis of plastic behavior revealed that quenching temperatures had little effect on strain hardening exponent n, but had significant influence on yield stress σy.

Phase-shifting laser scanning confocal microscopy moiré method and its applications

The laser scanning confocal microscopy (LSCM) moiré method is an effective method for full-field displacement and strain measurement in the micrometer scale. In this study, the phase-shifting LSCM moiré method is proposed for automatic processing of the moiré fringe. A combined phase-shifting and loading system for LSCM was developed, which could offer a tensile load on the plate type sample with a maximum load range of up to 500 N. Using the PZT (piezoelectric ceramic) phase shifter in the loading system, the moiré fringe phase was shifted and measured. Full field deformation was calculated according to the phase data. With the combination of LSCM and the self-developed loading system, tensile deformation of the aluminum sample was measured by the phase-shifting LSCM moiré technique. Full-field deformations under the different loads and elastic modulus of the sample were obtained. Experimental results demonstrated the feasibility of this technique, and the accuracy for deformation measurement is clearly improved.

INDENTATION SIZE EFFECT ON THE CREEP BEHAVIOR OF A SnAgCu SOLDER

In the present study, nanoindentation studies of the 95.8 Sn -3.5 Ag -0.7 Cu lead-free solder were conducted over a range of maximum loads from 20 mN to 100 mN, under a constant ramp rate of 0.05 s-1. The indentation scale dependence of creep behavior was investigated. The results revealed that the creep rate, creep strain rate and indentation stress are all dependent on the indentation depth. As the maximum load increased, an increasing trend in the creep rate was observed, while a decreasing trend in creep strain rate and indentation stress were observed. On the contrary, for the case of stress exponent value, no trend was observed and the values were found to range from 6.16 to 7.38. Furthermore, the experimental results also showed that the creep mechanism of the lead-free solder is dominated by dislocation climb.

Creep effects in nanoindentation of hydrated phases of cement pastes

This paper focuses on the nanoindentation of cement pastes and their micromechanical response. Since cement paste is a heterogeneous material at microscale, micromechanical properties have to be assessed separately for its individual material phases, i.e. hydrated products and unhydrated phases. Our study addresses important issues concerning experimental loading paths and their effects on the evaluation of elastic properties using nanoindentation. The effect of creep is shown on a series of multicycle experiments. A wide range of maximum loads and corresponding final penetration depths (approximately 200–1200 nm) are covered in this study. Experimental measurements on both hydrated cement samples and on unhydrated clinker minerals have proved that significant creep deformation can be attributed purely to hydrated phases. Further, it has been found that cement paste exhibits a strong size effect on elastic properties measured by nanoindentation and evaluated by the standard Oliver–Pharr procedure for loading–unloading tests with no dwell period at the peak load. Such property was already reported for plastic materials like metals [Elmustafa AA., Stone DS., Indentation size effect in polycrystalline F.C.C. metals, Acta Materialia 2002; 50 (14): 3641–3650., Wei, Y., Wang, X., Zhao, M., Size effect measurement and characterization in nanoindentation test, Journal of Material Research 2004; 19 (1): 208–217.], due to various effects but creep. As shown in the paper, cyclic loading and using long dwell periods at peak load leads to minimizing of this spurious type of size effect. Moreover, comparison with results obtained for the COC/PE polymer (75% cycloolefin copolymer + 25% polyethylene) has been performed. This polymer has been found to exhibit similar time-dependent behavior as hydrated cement paste.

Berkovich indentation of diamondlike carbon coatings on silicon substrates

The deformation behavior of diamondlike carbon (DLC) coatings on silicon substrates induced by Berkovich indentation has been investigated. DLC coatings deposited by a plasma-assisted chemical vapor deposition technique were subjected to nanoindentation with a Berkovich indenter over a range of maximum loads from 100 to 300 mN. Distinct pop-ins were observed for loads greater than 150 mN. However, no pop-out was observed for the loads studied. The top surface of the indents showed annular cracks with associated fragmented material. The cross sections showed up to 20% localized reduction in thickness of the DLC coating beneath the indenter tip. Cracking, {111} slip, stacking faults, and localized phase transformations were observed in the silicon substrate. The discontinuities in the load–displacement curves at low loads are attributed to plastic deformation of the silicon substrate, whereas at higher loads they are attributed to plastic deformation as well as phase transformation.

Nanoindentation-induced deformation behaviour of diamond-like carbon coatings on silicon substrates

The deformation behaviour of diamond-like carbon (DLC) coatings on silicon substrates induced by indentation has been investigated. DLC coatings, deposited by a plasma-assisted chemical vapour deposition technique, were subjected to nanoindentation over a range of maximum loads from 100 mN to 300 mN. The resulting load-displacement plots displayed pop-ins for maximum loads of 200 mN and above, with no distinct pop-out for any of the loads studied. Compressive deformation of the coating, up to a strain of ∼ 9%, was observed. The coating–substrate composite was devoid of cracks at lower loads, but at the maximum load of 300 mN, ring cracks in the coating and a median crack in the substrate were observed. Furthermore, cracking, {111} slip and localized phase transformations were observed in the silicon substrate. The onset of these structural changes was correlated to the mechanical behaviour during indentation.

Indentation-Induced Damage Mechanisms in Germanium

AbstractThe response of crystalline Ge to indentation has been studied over a range of maximum loads. At a certain load, an unusual ‘giant pop-in’ event occurs, in which a discontinuous extension of >1 μm is observed in the force-displacement curve. In such cases, load release curves show a pronounced ‘elbowing’ response, leading to increased depth recovery. TEM and Raman microspectroscopy revealed the presence of amorphous material in the residual impression. To examine cracking, a sequence of cross-sections was milled through the indent and images taken using an automated method (the ‘slice-and-view’ method). Using 3-D reconstruction software, the data was segmented and reconstructed into a 3-dimensional representation of the cracks around the indent. Applying this technique to indents featuring a giant pop-in, it was deduced that the inelastic elbowing observed was a bending response of material detached by lateral cracking. The giant pop-in is attributable to material removal, caused by lateral cracks formed during loading.

Effect of Repetitions and Gender on Acceleration Range of Motion During Knee Extension on an Isokinetic Device

Assuming velocity attainment, acceleration range of motion (AccROM) determines the amount of ROM spent under load range. This study sought to determine if gender, repetition type, and number affect knee extension AccROM. Subjects (15 M, 20 F; age 27.5 ± 6.5 yrs) performed 3 maximal concentric knee extension repetitions at isokinetic velocities between 60 and 450°/sec and 50 reps at 180°/sec. AccROM was defined as the ROM needed to attain the preselected velocity. The first repetition, starting from a dead stop, was identified as single while Repetitions 2 and 3 were identified as reciprocal. Results revealed that reciprocal repetitions had significantly (p < 0.05) less AccROM than single at all speeds. Men had significantly less AccROM than women during reciprocal repetitions at 120–450°/sec and during single reps at 240-450°/ sec. AccROM during 50 repetitions significantly increased every 10 reps from 20 through 50. To ensure maximum load range, knee extension exercise protocols on an isokinetic device should be specific to gender, repetition type, and number.

Development of an on-board fatigue processor for helicopters

An on-board fatigue processor was developed for helicopters. This processor can provide a continuous monitoring of fatigue usage of rotating mechanical components during flight using only standard flight control data as input. The monitoring methodology used in the fatigue processor reduces a complex load time-history into two parameters: load-cycle spectrum type and maximum load range. Correlations between the two parameters and the flight control data from various maneuvers are developed using flight load survey data. Pattern recognition method is used to identify (or correlate) the load-cycle spectrum type. Flight load models for the maximum load range are developed using multiple linear regression technique. Once the correlations are developed, only the flight control data are used by the fatigue processor to identify the load-cycle spectrum type, the corresponding component load range, and ultimately to compute the cumulative fatigue usage for the monitored components. Validation of the on-board fatigue processor was performed using flight load survey data and simulated flight conditions. The fatigue usages calculated by the fatigue processor compare well with the component fatigue usages computed directly from the measured component loads of the flight tests. Computation time for the fatigue usage calculation was done well below the processing time needed for real-time monitoring, on a small, personal computer platform. The method thus represents an efficient and practical monitoring approach for the on-board implementation in helicopters.

Irradiation studies of magnet insulator materials

Recent magnet insulator studies at the Idaho National Engineering Laboratory have included work applicable to quite different magnet configurations, both the conventional wrapped conductor and the Bitter plate. These investigations have emphasized irradiation effects work in support of the Princeton Plasma Physics Laboratory (PPPL) for the Tokamak Fusion Test Reactor (TFTR) and of Massachusetts Institute of Technology (MIT) for the ZEPHYR program. Postirradiation testing included shear bond testing of specimens prepared at Princeton and compressive fatigue tests of fiberglass-epoxy disks, principally G-10, for MIT. The fatigue tests included both room temperature and liquid nitrogen temperature over a range of maximum loads. The method for determining disk failure during the fatigue test is emphasized in this report.