Effects Of Test Parameters Research Articles

Fluid Permeability of Graded Porosity Scaffolds Architectured with Minimal Surfaces.

The natural local porosity variation in the native tissue can be replicated by graded porosity scaffolds. Scaffolds with radial porosity distribution can be a solution to improve both mechanical and biological functions of the biomimetic scaffolds. In the present study, fluid permeability as a quantitative indicator of biological performance is studied numerically and experimentally for different pore shapes and porosity distribution patterns in the scaffolds designed on the basis of triply periodic minimal surfaces (TPMSs). Among the uniform porosity scaffolds, those designed on the basis of P* (P surface) and Y** (G surface) showed the highest permeability. In the radially graded porosity scaffolds with linear porosity distribution, permeability was found to be about twice more sensitive to the peripheral porosity than the porosity at the center. The results suggest that the permeability-gradient parameter relationships can follow different trends depending on the pore shape as opposed to the conventional uniform porosity scaffolds. This implies the need for the design maps that were developed to choose appropriate scaffold pore design parameters. Finally, experimental permeability measurement was performed via a constant head permeability test, and the effect of test parameters (i.e., fluid height) was discussed.

Investigations of water-extractability of As in excavated urban soils using sequential leaching tests: Effect of testing parameters

Excavated soils with low-level As contamination obtained from construction projects during city development have been of great concern in Japan. Water-extractable As represents the most easily mobilized and ecotoxicologically relevant fraction in the soil environment. In the present study, the water-extractability of As in excavated alkaline urban soils was assessed using sequential leaching tests (SLTs) with a focus on the effects of test parameters. In addition, the potentially water-leachable As over an extremely long period was assessed using the pollution potential leaching index (PPLI), from which one can estimate the number of extractions required to reduce the As in the cumulative leachates to below the Japanese environmental standard (10 μg L−1). Total As concentrations varied from 6.75 to 79.4 mg kg−1, and As was continuously detectable among replicate SLT experiments. The water-extractable As obtained in the first step of the SLT accounted for 0.41%–7.60% of total As (average: 2.36%), while the cumulative released As in the SLTs corresponded to 1.30%–21.6% of the total (average: 10.6%). The variability of the water-soluble fractions was sensitive to the test conditions. The shaking time at each SLT step had the largest effect on the As water-extractability; followed by sample storage, shaking speed and shaking interruption. A longer shaking time in the standard leaching test of excavated soils is suggested for regulatory purposes in Japan. The use of the PPLI concept for quick estimation of the potential As leachability from excavated soils was supported by the good reproducibility of PPLI results obtained from SLTs under different test parameters.

Structural behaviour of square RC columns confined with CFRP wraps

Loading capacity and strains of square reinforced concrete (RC) columns, strengthened with external carbon fiber reinforced polymer (CFRP) sheets, were tested and evaluated. The experimental parameters include: number of wrap layers, concrete strength and the slenderness of the columns (L/a). All test specimens were loaded to failure in axial compression. Compressive stress, axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate strength, stiffness, and ductility of the specimens.Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility. The effects of test parameters are evidenced and compared.

Structural behaviour of square RC columns confined with CFRP wraps

Loading capacity and strains of square reinforced concrete (RC) columns, strengthened with external carbon fiber reinforced polymer (CFRP) sheets, were tested and evaluated. The experimental parameters include: number of wrap layers, concrete strength and the slenderness of the columns (L/a). All test specimens were loaded to failure in axial compression. Compressive stress, axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate strength, stiffness, and ductility of the specimens.Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility. The effects of test parameters are evidenced and compared.

High-stress abrasion of wear resistant steels in the cutting edges of loader buckets

Abstract To simulate the wear behavior of the cutting edge of the mining load-haul-dumper bucket, high-stress abrasion laboratory wear tests were conducted and compared to the in-service tests. The effects of test parameters and different abrasives on the wear rates and wear mechanisms of wear resistant steels were studied using the high-speed slurry-pot with a dry abrasive bed (dry-pot) and in the actual in-service use as a cutting edge. The laboratory wear tests produced results that are well comparable with the in-service case observations. Especially at the higher sample rotation speed with granite as an abrasive, the wear rates were quite similar as determined from the cutting edge of a loader bucket that had been used in a mine.

Use of advanced composite materials in strengthening axially loaded reinforced concrete columns

The present study deals with the analysis of experimental results, regarding of load carrying capacity and strains, obtained from tests on reinforced concrete (RC) columns, strengthened with external carbon fibre reinforced polymer (CFRP) sheets. The experimental parameters include: number of wrap layers, slenderness of the columns (L/a or L/D) and section geometry (circular or square). A total of 48 specimens were subjected to axial compression. All test specimens were loaded to failure. Compressive stress, both axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate stress, stiffness, and ductility. First, the effects of test parameters are analysed and compared. Results clearly demonstrate that composite wrapping can enhance the structural performance of RC columns in terms of both maximum strength and ductility.

Effects of Test Parameters and SiCp Reinforcement on the Slurry Erosive wear response of Al-Si Alloy

The present investigation pertains to the slurry erosive wear response of Al-Si alloy reinforced with 10 and 15 wt% of SiC particle. The wear behaviour was examined by the sample rotation technique using slurry pot erosion tester. The effects of speed, slurry media and sand concentration on the slurry wear behaviour have been studied. To examine the influence of the SiC particle dispersion matrix alloy was also characterized under similar conditions. It was observed that the addition of SiC significantly improves the wear resistance of the matrix alloy in marine and mine environment and wear rate increases with sand volume content. However, slurry environment and speed has a mixed effect on the wear rate.

Optimization and predictive modeling using S/N, RSM, RA and ANNs for micro-electrical discharge drilling of AISI 304 stainless steel

In present work, micro-deep holes on AISI 304 stainless steel were drilled via electrical discharge machining (EDM) method. In the first phase of this work, the effect of test parameters on the drilling performance and the profile of drilled holes were investigated experimentally. Test parameters including discharge current, dielectric spray pressure and electrode tool rotational speed were taken and then the machining rate (MR), electrode wear rate (EWR), average over-cut (AOC) and taper angle (TA) were measured in order to assess the drillability of EDM. After experimental study, an analysis of variance was performed to identify the effect of the importance of test parameters on experiment outputs. In the second phase of this study, optimum process parameters were determined using signal-to-noise analysis and response surface methodology (RSM) for mono-optimization and multi-response optimization, respectively. In the last phase, regression analysis and artificial neural network (ANN) models for predicting the MRR, EWR, AOC and TA. As a result of experimental analysis, discharge current was the most important parameter for micro-drilling with EDM. It was found out that this parameter influenced positively MR, while it has negatively an effect on EWR, AOC and TA. Mathematical model based on ANNs exhibited a successful performance for predication of outputs. Optimum process parameters which were discharge current of 10.18 A, dielectric liquid pressure of 58.78 bar and electrode tool rotational speed of 100 rpm for multi-objective optimization were determined through RSM with desirability function analysis in micro-deep hole EDM drilling of AISI 304 stainless steel.

Activation and β-FeOOH modification of sepiolite in one-step hydrothermal reaction and its simulated solar light catalytic reduction of Cr(VI)

A simple one-step hydrothermal reaction was used to successfully activate and modify original sepiolite. The as-prepared sepiolite/β-FeOOH composites were characterized by X-ray diffractions, Fourier transform infrared spectrum, specific surface area, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the Cr(VI) reduction efficiency in the presence of tartaric acid under simulated solar light illumination. The results show that the most optimal amount of iron modification on the surface of sepiolite was 2.8mmolFe3+/g sepiolite in the reaction dispersion. The developed sepiolite/20β-FeOOH catalyst exhibited outstanding photocatalytic performance with complete Cr(VI) reduction of after irradiation of 10min under the test condition of c (Cr(VI))=100mM, catalyst dosage=400mg/L, c (tartaric acid)=40mM and initial pH=5. The XPS analysis verified that Cr(VI) adsorption also contributed to the Cr(VI) removal from the aqueous solution. The effects of test parameters, such as initial pH of suspension, catalyst dosage and tartaric acid concentration on Cr(VI) photocatalytic reduction rates were investigated. It has to be noted that the synthesized sepiolite/20β-FeOOH catalyst can be effective in a wide range of pH with quite good catalytic performance.

Sliding Wear Response of Beryl Reinforced Aluminum Composite - A Factorial Design Approach

Al-Beryl MMCs were successfully fabricated using powder metallurgy route. Processing conditions such as beryl content and particle size were varied and its influence on dry sliding wear response was studied. Effect of test parameters like applied load and sliding distance on wear performance of Al-Beryl MMCs were discussed detail. Sliding wear tests were conducted using a pin on disc machine based on the 24 (4 factors at 2 levels) factorial design. Analysis of variance (ANOVA) was performed to obtain the contribution of control parameters on wear rate. The present study shows that wear resistance of Al-beryl MMCs not only depends on the beryl content but also influenced by normal load, sliding distance and particle size. The results show that most significant variables affecting wear rate of Al - beryl MMCs are size of the beryl particles (22%), beryl content (19.60%), sliding distance (18.47%), and normal load (10.30%). The interaction effects of these parameters are less significant in influencing wear rate compared to the individual parameters. The correlation between sliding wear and its parameters was obtained by multiple regression analysis. Regression model developed in the present study can be successfully implemented to predict the wear response of Al-Beryl MMCs.

Simulated solarlight catalytic reduction of Cr(VI) on microwave–ultrasonication synthesized flower-like CuO in the presence of tartaric acid

In this study, flower-like CuO was successfully synthesized by a microwave–ultrasound assisted method and well characterized by X-ray diffractions, Fourier transform infrared spectrum, scanning electron microscopy, transmission electron microscopy, specific surface area, UV–vis diffused reflection spectra, X-ray photoelectron spectroscopy and point of zero charge. The photocatalytic performance of the as-prepared CuO was examined on the Cr(VI) reduction in the presence of tartaric acid under simulated solarlight irradiation. The results show that the developed CuO catalyst exhibited good photocatalytic activity with 100% reduction of Cr(VI) after irradiation of 30 min under the test condition of c(Cr(VI)) = 100 μM, catalyst loading = 400 mg/L, c(tartaric acid) = 4 mM and initial pH = 3. The reaction mechanism was proposed. The effects of test parameters, such as catalyst loading, tartaric acid concentration and initial pH, on Cr(VI) reduction efficiency were also investigated. It is worth mentioning that the developed catalyst can work at a relatively wide range of pH with quite high catalytic performance.

Investigating the effect of testing parameters on adhesive wear using Taguchi method

The aim of this study is to investigate the effect of working parameters on wear resistance of steels in terms of applied load, hardness and revolution per minute (rpm) using the Taguchi method. Pin-on-roller type of apparatus was used for adhesive wear tests. The operating parameters were investigated by employing the orthogonal array, signal-to-noise ratio and analysis of variance. The experimental wear test results show that the hardness of the materials is the major parameter among the controllable factors. After the hardness, the applied load and the rpm sequentially have influence on the wear resistance of three types of steels; AISI 1050, AISI 4140 and AISI 8620. The best wear testing parameters were determined for current conditions of the steels. A good agreement between the predicted and experimental wear amounts is observed.

Experimental evaluation of damaged rectangular reinforced concrete beams repaired with near surface mounted carbon fibre reinforced polymer

An experimental study has been carried out on damaged rectangular reinforced concrete beams, repaired with near surface mounted carbon fibre reinforced polymer materials. A total of 32 specimens were loaded to failure in a 4-point flexural test. The parameters considered are the rate of damage (20, 40 and 60%), the rate of strengthening and the type of strengthening materials (rods and strips). Concrete compressive strain, carbon fibre reinforced polymer strain, ultimate strength and load-deflection have been recorded to evaluate the response of the specimens. Results clearly demonstrate that the strengthening with near surface mounted carbon fibre reinforced polymer can enhance the structural performance of reinforced concrete beams in terms of both maximum strength and deformation. The effects of test parameters are evidenced and compared.

Effect of Test Parameters on the Friction Behaviour of Anodized Aluminium Alloy

The tribological behaviour of anodic oxide layer formed on Al5754, used in automotive applications, was investigated against test parameters. The friction coefficient under different normal loads, sliding speeds, and oxide thicknesses was studied using a pin on disc tribometer. Results show that the increase of load and sliding speed increase the friction coefficient. The rise of contact pressure and temperature seems to cause changes in wear mechanism. Glow-discharge optical emission spectroscopy (GDOES) was used to investigate the chemical composition of the oxide layer. Morphology and composition of the wear tracks were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). On the basis of these characterization techniques, a wear mechanism was proposed. The observed mechanical properties can be related to the morphology and the chemical composition of the layer.

Effects of Test Parameters on Fracture and Fatigue Characteristics of a SE(T) Steel Specimen

The understanding of crack behavior under fatigue remains a critical issue in addressing the performance of bridge structures. In this study, effects of test parameters on the stress intensity factor ( K) of a modified single edge notched tension [SE(T)] steel specimen with a through width notch was experimentally, analytically and numerically investigated. Equations were developed to include the effects of fix boundary condition on K and crack mouth opening displacement (CMOD) of the crack. Effects of axial and angular misalignments on K along the crack length were examined and a progressively decreasing influence on K was observed when the crack size increased. Two dimensional (2D) and three dimensional (3D) Finite Element Method (FEM) was used to evaluate the effect of the two end bounding conditions on K value of non-uniform crack fronts. Influence of ungripped length of the specimen on K was evaluated and showed to be more substantial for short specimens. Finally, a framework was proposed to map the crack front evolution through high cycle fatigue tests for a modified SE(T) specimen with initial crack inclination.

Effect of test parameters on the micro-abrasion behavior of PVD CrN coatings

Micro-abrasion wear test is a widely used method in measurement of abrasive wear resistance of thin hard coatings. During the test, selection of test parameters has great importance in determination of the wear behavior of the material under investigation correctly. Therefore, in this study, the effect of test parameters on the micro-abrasion behavior of CrN coating was investigated by the fixed-ball micro-scale abrasion test and modeled by response surface methodology. The coating was deposited on AISI D2 cold work tool steel using industrial cathodic arc evaporation system. The wear tests have been performed using SiC abrasive slurry. Analysis of worn craters was conducted by scanning electron microscope (SEM). It was found that the models obtained from ANOVA tables for wear volume and wear rate of CrN coating are significant and have high correlation coefficients. The rotation speed has higher influence on the wear volume of CrN coating, whereas the normal load has higher influence on the wear rate. The higher normal load increases the wear volume and decreases the wear rate. The effect of rotation speed changes according to the value of applied speed. Grooves take place by two-body abrasion in all of the craters obtained at different rotation speed and normal load values. Depth of parallel grooves in CrN coating and AISI D2 substrate decreases with the normal load and with the rotation speed.

Effect of test parameters on large particle high speed slurry erosion testing

A high speed slurry-pot wear tester was developed for close-to-reality heavy-duty wear testing of materials used in mineral applications. The samples are attached on four levels in a pin mill configuration. The tester and the developed sample rotation test method deliver reproducible results. This study focuses on the effects of testing parameters in large particle slurry testing. Parameters such as the speed, particle size and slurry concentration were varied. The effect of test duration was also examined. Round steel samples and slurry of water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for particle size, up to 23 wt-% for concentration and up to 20 m s−1 for the sample tip speed. The relationships between the parameters are discussed. The kinetic energy of the large abrasive particles is also considered. Wear surfaces studied with optical and electron microscopy are also presented and discussed.

Stress relaxation behaviour of high acyl gellan gels

Summary Stress relaxation behaviour of high acyl gellan gels has been investigated, and data were fitted successfully by a seven elements empirical model and a four term modified Maxwell model with three fixed relaxation times (20, 200 and 2000 s). In addition, the effect of testing parameters on stress relaxation characteristics and the relationship between those characteristics and intrinsic gel properties were studied. High acyl gellan gels were tested in stress relaxation with different cross-head speeds (0.1–10 mm s−1) to applied strains (3–30%). The results showed that the cross-head speed had little effect on stress relaxation behaviour of gels. With increasing the applied strain, the initial stress and the equilibrium stress increased. The equilibrium stresses from relaxation measurement were positively related to the hardness from TPA tests (R2 = 0.991). Relaxation appeared to be associated with the shifting of cross-links in the gel matrix.

Thermal Cycling Reliability of Sn-Ag-Cu Solder Interconnections. Part 1: Effects of Test Parameters

The work presented in part 1 of this study focuses on identifying the effects of thermal cycling test parameters on the lifetime of ball grid array (BGA) component boards. Detailed understanding about the effects of the thermal cycling parameters is essential because it provides means to develop more efficient and meaningful methods of reliability assessment for electronic products. The study was carried out with a single package type (BGA with 144 solder balls), printed wiring board (eight-layer build-up FR4 structure), and solder interconnection composition (Sn-3.1Ag-0.5Cu) to ensure that individual test results would be comparable with each other. The effects of (i) temperature difference (ΔT), (ii) lower dwell temperature and lower dwell time, (iii) mean temperature, (iv) dwell time, and (v) ramp rate were evaluated. Based on the characteristic lifetimes, the thermal cycling profiles were categorized into three lifetime groups: (i) highly accelerated conditions, (ii) moderately accelerated conditions, and (iii) mildly/nonaccelerated conditions. Thus, one might be tempted to use the highly accelerated conditions to produce lifetime statistics as quickly as possible. However, to do this one needs to know that the failure mechanisms do not change from one lifetime group to another and that the failure mechanisms correlate with real-use failures. Therefore, in part 2 the observed differences in component board lifetimes will be explained by studying the failure mechanisms that take place in the three lifetime groups.

Structural Performance of Square Concrete Columns Wrapped with CFRP Sheets

An experimental study has been carried out on square reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 48 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains have been recorded to evaluate the stress-strain relationship, ultimate strength, stiffness, and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square RC columns in terms of both maximum strength and ductility. The effects of test parameters are evidenced and compared