Effects Of Test Parameters Research Articles

Effect of test parameters on the recovery of underground after a Thermal Response Test and optimum waiting time between tests

Effect of test parameters on the recovery of underground after a Thermal Response Test and optimum waiting time between tests

The effect of temperature and strain rate on the grain boundary sliding in a CM247 LC Ni-based superalloy processed with laser based powder bed fusion

The current work explores the meso-scale deformation behaviour of an additively manufactured CM247 LC at room and high temperatures. In particular, the study focuses on assessing grain boundary sliding (GBS), which can play a crucial role in the high-temperature deformation of superalloys. Specific samples were produced using the Laser Based Powder Bed Fusion technique (PBF-LB), heat treated and tested under monotonic compression in a Gleeble® system. Compression tests were carried out in a wide temperature range at two strain rates and the effect of testing parameters on GBS activity was studied. A thorough microstructural characterization of the PBF-LB material using EBSD and TEM revealed a γ/γ’ microstructure consisting of columnar grains decorated with Hf-rich MC carbides without any segregations of alloying elements. Qualitative and quantitative analysis of GBS was performed using FEG-SEM and AFM, and contribution of GBS into plastic deformation was estimated. It was demonstrated that GBS is activated at 760 °C. A direct correlation between the contribution of GBS into plastic deformation and testing temperature was found, while strain rate has the opposite effect. The highest GBS contribution (∼32%) was recorded at 1093 °C/10−3 s−1. Finally, intergranular microcracking at triple junctions and along grain boundaries was observed when the material was tested at the highest temperatures (871 °C and 1093 °C). The effect of the temperature and the strain rate on the GBS activity in the PBF-LB material is discussed.

Bond behavior of concrete reinforced with high-strength and high-toughness steel bars

To investigate the bond behavior between the ordinary concrete and high-strength and high-toughness (HSHT) steel bars with special spiral grooves on the surface, twenty-one specimens were tested by pull-out tests. The effects of test parameters, including anchorage length, the diameter of HSHT steel bars, cover thickness, stirrup ratio, anchorage form, and the number of spiral grooves, on failure modes, bond-slip curves, bond strength, the relative slip, and critical anchorage length were analyzed. The results show that increasing cover thickness and end-anchorage can significantly improve bond strength. The bond strength of specimens reinforced with HSHT steel bars with six spiral grooves is higher than that of three spiral grooves, and it gradually decreases with increasing the anchorage length. In addition, the decrease of the stirrup spacing can improve bond strength. The addition of stirrups can slow down the descending branches and make the failure modes of specimens change from splitting failure to splitting-pullout failure, indicating that the energy absorption capacity and the ductility of specimens have been improved. The models for bond strength and the slip corresponding to bond strength were established based on the existing models and experimental data. At the same time, coefficients B and D were established based on Wu’s model. The evaluation shows that the proposed model can accurately calculate the bond-slip curves for ascending branches and descending branches, and it can also predict bond-slip curves corresponding to different failure modes.

Effect of Test Parameters on Tribological and Hardness Properties of UHMWPE/Reduced Graphene Oxide Nanocomposites

AbstractUltra‐high molecular weight polyethylene (UHMWPE) exhibits high wear resistance, low coefficient of friction (COF), and high impact strength. The operating conditions can influence the performance of the UHMWPE in specific applications. Graphene is applied as reinforcement to the UHMWPE matrix in order to improve the tribological and mechanical properties. In the present work, the effects of the test parameters on the hardness and tribological behavior of nanocomposites are evaluated. The Vickers microhardness of the UHMWPE/rGO nanocomposites increases by up to 25% at 0.50 wt% of rGO, regardless of the indentation applied load. Pin‐on‐disc tests are performed for the polymer at several sliding speeds and applied normal loads to get information about friction responses. Once the most suitable parameters have been defined, the pin‐on‐disc tests of the UHMWPE/rGO nanocomposites are performed, resulting in a decrease of up to 48% of the COF at 0.25 wt% of rGO.

Effects of Test Parameters on the Frictional Properties of Al/Diamond-Like Carbon Core-Shell Nanostructure-Textured Surfaces

A friction test is a beneficial means to analyze the tribological characteristics and advantages of materials and textured surfaces. However, the selected parameters of the friction test can significantly influence the outcome. In this study, several applied normal loads (10 µN, 100 µN, and 500 µN) and counterface indenter tip radii (1 µm, 5 µm, and 100 µm) were selected for testing of an Al/diamond-like carbon (DLC) core-shell nanostructure textured surface (CSNTS) and compared to a smooth DLC film deposited outside the textured area of the same surface. The effects of these friction test parameters were examined, along with the mechanisms that control these effects. It was found that the coefficients of friction (COF) were the highest under the lowest normal load due to adhesion contributions. Interlocking between the smallest tip and the core-shell nanostructures (CSNs) resulted in higher COF on the textured surface than on the smooth DLC film. Larger counterface indenter tips experienced lower COF on CSNTS than on the smooth DLC film due to reduced contact area. Surface texturing was most effective in reducing the COF when the largest tip was used as the counterface.

Comparative analysis of single- and multiple-frequency thermal wave radar imaging inspection of glass fiber reinforced polymer (GFRP)

Active infrared thermography has gained increasing popularity for nondestructive testing and evaluation in various industrial fields, especially for composite structures. In this regard, thermal wave radar (TWR) imaging is recognized as the next-generation active thermography technology to obtain great resolution and depth range over the inspected objects. A critical aspect concerns the optimal test parameter selection to guarantee reliable quality assurance required for industrial products. In this work, single- and multiple-frequency TWR was investigated in a quantitative manner with the goal of optimizing the detection parameters in terms of probing range and lateral and depth resolution. The effects of test parameters, including sampling frequency, modulation frequency, chirp duration, chirp bandwidth, etc, were investigated in detail through experiments on a glass fiber reinforced polymer specimen with multi-scale diameter-to-depth ratio defects. This paper aims to help yield a better understanding of the physical mechanism behind TWR and propose a workable scheme for testing parameter selection in practical applications.

Effects of testing parameters on the susceptibility to hydrogen embrittlement in precipitation-hardened nickel-based alloys: The role of continuous straining

The hydrogen embrittlement susceptibility of two precipitation hardened nickel-based alloys was studied. Conventional slow strain rate testing results are compared against data obtained from a modified Rising Step Loading Test with interrupted hydrogen charging to determine the role of defects in the passive layer caused by local straining. The results obtained in these tests, show that the elongation to failure for most cases was independent of the testing methodology. XPS and EIS studies indicate changes to the passive film structure caused by CP. These results imply that during hydrogen charging, the passive film is partially dissolved facilitating hydrogen uptake.

Understanding and modelling wear rates and mechanisms in fretting via the concept of rate-determining processes - Contact oxygenation, debris formation and debris ejection

A new framework which describes the role of three key processes in fretting wear of metals is proposed, with these three processes being: (i) oxygen transport into the contact; (ii) formation of oxide-based wear debris in the contact and (iii) ejection of the wear debris from the contact. Based upon a physical understanding, rate equations for the three key processes are proposed, which provide a basis for the influence of test parameters (such as contact geometry, applied load, slip amplitude, fretting frequency etc) on the three rates to be understood. To maintain system equilibrium in steady-state fretting, the three processes must operate at the same rate as each other (debris cannot be ejected from the contact faster than it is formed, and debris cannot be formed faster than it is ejected). Accordingly, the observed wear rate is the rate of the process with the lowest rate of the three processes, with this process being termed the rate-determining process. The effect of test parameters on the three key processes differs, and thus the effect of changes in any test parameter on the observed rate of wear will itself be dependent upon which of the three processes is rate-determining.A number of assumptions have been made in deriving the equations which describe the key processes and it is recognised that these equations themselves may be refined in light of future research; however, any such revised equations can simply replace those proposed as part of the rate-determining process framework.The framework can be applied to both conforming and non-conforming contact geometries. In tests with non-conforming contact geometries, the contact size increases with wear; since it is proposed that the rates of two of the three processes (oxygen transport and debris ejection) are dependent upon the size of the contact, the rate determining process can change during such a test and the rate of wear will continually fall when either of these processes are rate-determining. This complexity means that the evolution of the wear volume can only be evaluated numerically through the use of a time-marching analysis in such cases. In contrast, in tests with conforming contact geometries, the contact size does not change as wear occurs, and so there will be no changes in the rate-determining process as wear proceeds.It is recognised that this framework addresses wear under steady-state conditions and does not consider the initial period of exposure where steady-state conditions are being developed. In the case of conforming contacts where the contact size is large, the duration of the initial transient period may be substantial and may form a significant proportion of the test duration or component lifetime. This needs to be recognised both in the design of tests and in the application of this framework.

Research on nano-concrete-filled steel tubular columns with end plates after lateral impact

Abstract This paper presents thirteen square columns to study the behavior of nano-concrete-filled steel tubular columns with end plates after lateral impact. The failure modes of the square columns subjected to lateral impact damage or not subjected to lateral impact damage were compared. The lateral impact loading height, steel tubular thickness, and column height were set as the test parameters in these tests. The effects of test parameters on the ultimate capacity, initial stiffness, and ductility of columns are discussed in this paper. The bearing capacity of square columns is decreased because of the lateral impact loading which can also be concluded from the test results. And with the steel tube thickness increasing, the bearing capacity and initial stiffness of columns are increased and ductility has no obvious change. However, with the column height increasing, the bearing capacity and stiffness of columns are decreased and ductility is increased. Furthermore, the strain development of the columns under axial compressive loading is also discussed in the paper. The results indicated that the corner of the square column is more easily damaged under compressive loading. According to the test results, the calculated formula is proposed to predict the ultimate capacity of nano-concrete-filled steel tubular columns with end plates after lateral impact. The calculated results have a good agreement with the test results.

Experimental Investigation on the Static Performance of Stud Connectors in Steel-HSFRC Composite Beams.

In this research, high strength fiber reinforced concrete (HSFRC) was used to replace the normal strength concrete (NSC) in steel-concrete composite beams to improve their working performance, which might change the static performance of stud connectors. Firstly, push-out tests were conducted to investigation on the static performance of stud connectors in steel-HSFRC composite beams and compared with steel-NSC composite beams. Studs of 8 sizes, 13 mm, 16 mm, 19 mm and 22 mm in diameter and 80 mm and 120 mm in height were adopted to study the influence of stud dimension. The test phenomenon shown that the crack resistance of HSFRC was better than that of NSC, and there were some splitting cracks on NSC slabs whereas no visible cracks on HSFRC slabs when specimens failed. Next, the load-slip curves of studs were analyzed and a typical load-slip curve was proposed which was divided into four stages. In addition, the effects of test parameters were analyzed according to the characteristic points of load-slip curve. Compared with NSC slab, HSFRC slab could provide greater restraining force to the studs, which improved the shear capacity and stiffness of studs while suppressed the ductility of studs. The shear capacity, stiffness and ductility of studs would significantly increase with the increasement of stud diameter and the studs with large diameter were more suitable for steel-HSFRC composite beams. The stud height had no obvious influence on the static performance of studs. Finally, based on the test results, the empirical formulas for load-slip curve and shear capacity of stud connectors embedded in HSFRC were developed which considered the influence factors more comprehensively and had better accuracy and applicability than previous formulas.

Standardization ofhigh‐temperaturespecific heat capacity test parameters offire‐resistantgypsum board

SummaryThe specific heat capacity at the high temperature of fire‐resistant gypsum boards plays a vital role in the simulation accuracy of the thermal response for cold‐formed steel (CFS) composite structures. However, there are not given comprehensive and accurate values in the existing standard for test parameters (including heating rate, sample quality, and sample size) used in the test of the specific heat capacity of gypsum boards. This situation leads to large differences in test results. This paper aimed to provide standardized test parameters for obtaining accurate specific heat capacity curves of gypsum boards. First, the effect of test parameters was quantified by 10 groups of specific heat capacity tests of gypsum boards through the uniform design; Then, the standardized values of test parameters were proposed combined with sample composition analysis and finite element numerical analysis: the heating rate was 12°C/min, the sample mass was 18 mg, the sample particle size was 45 to 48 μm; Finally, the standardized test parameters were verified by comparing with the test results of cold‐formed steel composite floors in the literature. The results show that the specific heat capacity curve of gypsum boards measured by the standardized test parameters proposed to this paper has good accuracy for simulating the time‐temperature curve of cold‐formed steel composite floors. It is conducive to accurately assess the fire resistance of cold‐formed steel composite floors. The test parameter standardization method can also be extended to other building materials. As a result, the specific heat capacity test can follow a basic standard.

Impact of Process Parameters on Solid Particle Erosion Behavior of Waste Marble Dust-Filled Polyester Composites

The aim of this paper is to provide broad information on the solid particle erosion behavior of polymeric composites using waste marble dust as the filler. Attention is paid toward the effects of test parameters, i.e., impingement velocity, filler content, striking angle, etc., on the erosion wear rate, and their failure mechanisms are discussed. Marble dust, the filler material in this work, is an industrial/construction waste generated during the processing of marble rocks and is a known air pollutant. The possibility of incorporating waste marble dust to enhance the erosion resistance of polyester is explored in this research. The parameter combinations obtained from the Taguchi’s L25 orthogonal array are used for the erosion wear trials on the composite samples. The analysis of test results reveals that impingement velocity, filler content and striking angle in that sequence have significant effect on the erosion rate. Statistical analysis is made on the test results carried out on the composite samples using different levels within the test range of the significant parameters individually keeping all other parameters constant to explore their effect more precisely on the erosion rate. Analysis of the morphologies of worn composite surfaces reveals the predominant wear mechanisms and the erosion response (ductile/brittle) of the composites. This work shows that inclusion of various fillers into polymeric composites improves the erosion resistance which would attract the researchers to find out their application as tribo-materials.

Mechanical analysis of carbon fiber reinforced polymer composite using CATIAV5 R14

High performance plastics and composites have become the substitutes for traditional materials, showing improved performance now-a-days. As compared to conventional materials, polymer matrix composites (PMCs) are well- known for their high strength and stiffness at a lower weight. The aim of this paper is to provide information on mechanical analysis of hydraulic flow pipe created utilizing carbon reinforced composites. The effects of test parameters as deformation, equivalent (von-mises) stress and principal stress tensor are discussed. The 3D model of composite cylindrical flow pipe using carbon fiber reinforced with resin epoxy and polypropylene designed, simulated and analysed using CATIA V5 R14 2017workbench. It has been found that carbon fibre reinforced with resin epoxy has shown the total deformation of 2.4788e-013 m which is lesser as compared to Polypropylene having total deformation of 4.7321e-014. Carbon fiber reinforced with resin epoxy composite sample has higher life cycle due to its less total deformation and high stress bearing capacity.

Research on the effect of test parameters on signal contrast and accuracy of determining the size of a defect

Currently, is used several non-destructive testing methods for detecting defects in the composite materials. The most potential is methods non-contact scanning for a large surface area with relative insensitivity to environmental disturbances. In this regard, are developed methods for defect detection in composites, all of which have own peculiarity. A fundamental difference concerns the overall length of time is required for non-destructive testing and analysis of thermographic data from the infrared camera, first of all, for large-scale structure. This research work has been conducted a quantitative way of analyzing data to optimizing the testing parameters in terms of testing time and signal-to-noise ratio. In particular, were carried a few tests out on stringers of carbon fiber reinforced panels. These tests included lock-in thermography technique with simulated defects, which has been used for finding parameters to correct detect dimensions of defects.

Shear Mode Damper Testing Using Flake Shape Based Magnetorheological Fluids

Use of anisotropic iron particles in the magnetorheological (MR) fluid having a high yield stress is a challenge as it increases the viscosity of the fluid in off-state. In this clause, a novel flake shaped iron powder based MR fluid with high yield stress is synthesized and used in shear mode MR damper (SMMD). MR damper design is optimized using fluid properties and Bingham model. Damping performance of newly synthesized MR fluid damper is at par with the available friction based damper used in front loaded washing machine. The unique feature of this design is minimal volume of the fluid (1.5 ml) required to achieve damping force of 50N. Effect of different volume percentage of particles in MR fluid is evaluated in terms of damping force. Effect of testing parameters like displacement and frequency of excitation on damping force was evaluated. Effect of settling of particle on damper performance is discussed in this work. It shows that the flakes shaped-based MR fluid show better stability against gravity. The smaller quantity of present flake shaped-based MR fluid will reduce the cost of shear mode damper.

Fatigue Crack Networks in the Die-Attach Joint of a Power Semiconductor Module During Power Cycling Testing and Effects of Test Parameters on the Joint Fatigue Life

The fracture mechanisms of a Sn-Ag-Cu lead-free solder joint and the effects of test parameters on power cycling life were investigated. In this study, three levels of average temperature (348, 373 and 398 K), two levels of each of current on-and-off time (2 s/10 s and 5 s/22 s), and three levels of ΔTj (75, 100 and 125 K) were used. Because the thermal expansion of the die-attach material was restrained by Si, equibiaxial tensile and compressive creep deformation occurred during power cycling. This deformation generated fatigue cracks in the central part of the die-attach joint, and the cracks connected to each other, resulting in a fatigue crack network. The fracture occupied 70% or more of the die-attach area and was the dominant factor affecting the joint’s fatigue life. As ΔTj increased, the strain energy density in the central part increased, resulting in a decrease in fatigue life. Although the strain energy density at an average temperature of 398 K decreased by about 10% compared with that at an average temperature of 348 K, the fatigue life decreased to about 40% when the average temperature increased. Continuous dynamic recrystallization occurred during power cycling, leading to fatigue failure in high-energy grain boundaries. Since continuous dynamic recrystallization tended to occur more readily at higher temperatures, the fatigue life decreased with increasing average temperature, even for the same junction temperature range ΔTj. Moreover, the area of equibiaxial tensile and compressive creep deformation in the die-attach material became larger with increasing current on-and-off times. As a result, the fracture area under long current on-and-off time conditions was increased by about 25% in comparison with that under short current on-and-off time conditions.

Effect of initial hydrogen distribution on the parameter extraction of the thermal desorption spectra: A finite element study

The main objective of this study was to clarify whether the commonly encountered inhomogeneous hydrogen distribution in thermal desorption tests, resulting from unsaturated hydrogen charging and hydrogen release during specimen transfer, could affect the desorption curves and parameter determination. The transient hydrogen distributions in the specimen, both in normal lattice sites and trap sites, during absorption, air exposure, and thermal aging were simulated using finite element method based on the Oriani's local equilibrium theory. Results indicated the significant effect of initial inhomogeneous hydrogen distribution on the transient hydrogen distribution and the desorption spectra. This effect could result in both the shift of peak temperature and the artifact in desorption curves, depending on the trap binding energy. The effect of testing parameters and trap parameters on the validity of Kissinger's theory was also discussed.

Experimental study on steel-plate composite wall-to-foundation connections subjected to combined axial compression and cyclic lateral-force

Nowadays, great attention has been arisen on steel-plate composite (SC) walls, but studies on SC wall-to-foundation connections were rarely reported. In this paper, eight large-scale specimens were designed and tested to investigate the in-plane and out-of-plane behavior of SC wall-to-foundation connections subjected to combined axial compression and cyclic lateral-force. Test parameters mainly included the loading direction (in-plane and out-of-plane), construction detail of the connection (lap-splice and embedding) and the aspect ratios or height-to-thickness ratios of SC walls. The effects of test parameters on SC wall-to-foundation connection performance were discussed. For test specimens subjected to in-plane loading, results showed that the specimens all failed by flexure. For specimens subjected to out-of-plane loading, the specimens with the wall height-to-thickness ratio of 1.33 and 2.5 failed by shear and flexure-splitting, respectively. The lap-splice connection could be regarded as an over-strength connection since failure usually occurs on the connection while the embedding connection could be designed as a full-strength connection where the SC wall itself fails, according to AISC N690s1-15. The lap-splice connections had better ductility than embedding connections. The specimens with larger SC-wall aspect ratios or height-to-thickness ratios had better ductility. The current expressions for the in-plane and out-of-plane load-carrying capacities of SC walls were evaluated based on the test results. The comparison showed that the current expressions generally underestimated the load-carrying capacities of the specimens. Since both construction details of lap-splice and embedding had been proven feasible for practical use in SC wall-to-foundation connections, further studies on the design of both connection types were recommended.

Cyclic creep behaviour of two-phase Ti-6Al-2Mo-2Cr alloy

One of the important criteria for selection titanium alloys for discs and blades of turbine engine compressor is their fatigue and creep strength at room and elevated temperature. Fatigue and creep properties of two-phase titanium alloys show strong dependence on microstructure, especially morphology of the α and β phases which can be controlled to certain extent by proper selection of hot working and heat treatment conditions. Quantitative description of two-phase titanium alloys behaviour under loading and environmental conditions leading to combined creep and fatigue processes has been always very challenging task due to large number of factors affecting deformation and fracture behaviour of the material. In the course of the research cyclic creep behaviour of Ti-6Al-2Mo-2Cr alloy (VT3-1) was investigated and compared to low-cycle fatigue and static creep properties at the temperature of 450°C. Microstructure of the alloy was varied by means of the heat treatment. Constant load tensile creep tests were carried out. Tension-tension cyclic loading was applied at the constant stress ratio with and without hold time at maximum load. The effect of test parameters on the creep-fatigue life at elevated temperature was estimated. Characteristic features of fracture surfaces were identified by scanning electron microscopy methods.

Study of the microhardness and erosive wear behavior of organo-modified nanoclay filled glass-epoxy composites and optimization

This research concentrates on examination and optimization of microhardness and erosion resistance of epoxy-glass-nanoclay composites (EGCN’s). The parameters considered were the weight content of Cloisite 15A (A), the volume of glass fiber (B), and the direction of glass fibers (C). Hand lay-up technique was used to make the composites and tested for microhardness and erosive wear as per ASTM standards. The L9 orthogonal array was utilized to design the microhardness tests and erosive wear test, and it was noted that the composite with high clay content, low fiber volume, and 45° orientation had shown low erosion rate (Er) even though its hardness was lesser than the optimized value. At the optimum composition corresponding to the lowest Er, further erosion studies were conducted with the L18 orthogonal array for optimizing machine testing parameters. Scanning electron microscopy (SEM) was used to explain the effect of each parameter on the output. This research gives a thought regarding the consolidated effect of A, B, and C on the erosion resistance of the EGCN’s and the effect of testing parameters.