Influence Of Artificial Aging Research Articles

Influence of Artificial Aging on the Vickers Hardness of Milled and 3D Printed Provisional Materials

Influence of Artificial Aging on the Vickers Hardness of Milled and 3D Printed Provisional Materials

Mechanical and chemical analysis of structural silicone adhesives with the influence of artificial aging

Structural sealant glazing systems, or bonded glazing, refers to façades in which the glass is structurally bonded to a façade frame and which is typically used in large façades for office buildings. The structural silicone bond lines are an essential element of such façades and a variety of environmental influences and aggressive media interact with the adhesive and may affect its performance. The ETAG 002 is commonly used for the verification of the technical applicability taking these effects into account. In this study, samples of an approved standard silicone adhesive and a high-modulus silicone adhesive are artificially aged according to ETAG 002 and exposed to a climate change test. The aim of this study is to determine the essential mechanical properties and to explain the changes due to aging by means of chemical analysis. Polymer degradations are determined by evaluating the molecular structure with Fourier-transform Infrared Spectroscopy and Thermo-Gravimetric analysis. In addition, water absorption is investigated with Karl Fischer titration. Changes in the chemical structure are particularly identified after aging in SO2 atmosphere as well as after UV exposure. Increased water contents are detected for all specimens conducted to high moisture. The mechanical properties as well as their characteristic temperature ranges are determinate by the Dynamic Mechanical Analysis and Differential Scanning Calorimetry. The results of the study show significant loss of the adhesive stiffness up to 30% after artificial aging, mainly after storage in cleaning agent and after climate change test. However, there are no significant chemical effects of both aging methods on the adhesives. On the other hand UV-radiation as well as the acid attack, interact with the polysiloxane and the filler of the adhesive. This shifts the crystallization temperature a bit but it does not influence the adhesive stiffness at room temperature. Finally, tensile tests and shear tests are performed on both reference and aged bonded glass–aluminum specimens. These test confirm the good durability of silicone adhesives and the results meet the requirements of the ETAG 002.

The influence of artificial aging on tensile properties of Al 6061-T4

This paper presents an explanation related to experimental testing in the form of the tensile properties of Al 6061. Al 6061 was heat treated by the precipitation hardening method. The precipitation hardening consisted of T4 and T6 treatment. Al 6061 samples were heat-treated at a temperature of 430°C for 2 hours, then cooled slowly at room temperature. The T4 was conducted at a temperature of 530°C for 2 hours, followed by rapid cooling in a water medium and natural ageing at a temperature of 70°C for six days. Temperature T6 is the final process of applying precipitation hardening treatment to Al 6061. Temperature T6 is carried out at 530°C for 2 hours, then cooled rapidly in a water medium and continued with artificial ageing at 190°C with a variation of ageing time for 3 hours, 5 hours, and 7 hours. The effect of the applied treatment was observed to increase the maximum strength value of the tensile test of Al 6061.

Influence of Artificial Aging on Mechanical Properties of Six Resin Composite Blocks for CAD/CAM Application

(1) The interactions in the oral cavity between resin composite blocks for CAD/CAM application and saliva, biofilm, and chemicals and their influence on mechanical properties are still mostly unknown. The purpose of this study is to examine the impact of artificial aging on the flexural strength, flexural modulus, hardness, Weibull modulus, and probability of failure of six resin composite CAD/CAM materials. (2) The aging was conducted by storing the specimens in water at 37 °C for 3 months, then a 3-point bending test was applied and measured. The microhardness was measured with a Vickers microhardness tester. Weibull analysis (according to ISO) was also performed. The shape and scale parameters were calculated. (3) After aging, the flexural strength values ranged from 95.51 (SD 9.07) MPa for the aged Shofu Block HC (HC) to 160.28 (SD 10.37) MPa for non-aged Gandio blocks (GR), and the flexural modulus values ranged from 7.75 (SD 0.19) GPa for HC to 16.77 (SD 0.60) GPa for GR. The microhardness (HV01) ranged from 72.71 (SD 1.43) for the Katana Avencia Block (AV) to 140.50 (SD 5.51) for GR. After aging, the Weibull characteristic strength ranged from 99.47 MPa for HC to 169.25 MPA for Brilliant Crios (CR). (4) Water storage led to a decrease in flexural strength and characteristic strength and slightly affected the flexural modulus. Gandio Blocks, Tetric CAD, and Brilliant Crios presented higher flexural strength than others.

Effect of Artificial Ageing on Adhesive Bonds from Heat Treated Spruce

The influence of artificial ageing on bonded heat-treated spruce lamellas was investigated. Heat-treated spruce lamellas with different degrees of thermal modification were bonded with PVAc and MUF and then exposed to 500 artificial weathering cycles, combined with rain, UV and IR radiation. The colour change of the exposed surface, weight change, delamination of the bonded joints and adhesive bond strength were measured. Artificial weathering caused cracking and delamination of the bonded joints and reduced the bond strength of both adhesives. The results show that delamination was higher for PVAc adhesive than MUF, but increased for both adhesives with the temperature of heat treatment of wood. The shear strength of bonds on the exposed side of the samples after the artificial weathering was lower than the average strength of the whole sample.

Influence of artificial aging: mechanical and physicochemical properties of dental composites under static and dynamic compression

ObjectiveThe aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging.Materials and MethodsSpecimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F = ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C).ResultsIncorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation.ConclusionAlthough the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard.Clinical relevancePreferential use of highly filled composites for occlusal fillings is recommended.

Curvature-dependent shear bond strength of different attachment materials for orthodontic lingual indirect bonding

To evaluate the shear bond strength (SBS) of different attachment materials used for lingual bonding, the influence of artificial aging and the radii of curvature of the enamel surface on SBS, 192 third molars were photographed to determine the radius of curvature of the oral surface. After phosphoric acid etching a cylindrical test piece was bonded to the oral enamel using a mold that was filled with a chemically curing (Maximum Cure, Transbond IDB Premix) or a dual-curing (Nexus NX3, RelyX Unicem2) attachment material. SBS was tested after 24 h, 500 thermal cycles or 90 days at 37 °C with a universal testing machine. Computed tomography scans were performed to determine the bonded surface and calculate SBS. Values ranged from 8.3 to 20.9 MPa. RelyX Unicem2 showed the highest SBS values at baseline, 500 thermal cycles and after 90 days (p < 0.001). Ninety days of wet storage significantly reduced SBS of Maximum Cure (p = 0.028). The radius of curvature correlated positively with SBS (rs = 0.204, p = 0.005). The SBS of all attachment materials was sufficient for clinical use, even after artificial aging. RelyX Unicem2 showed almost twice as high SBS values as the other attachment materials.

Influence of artificial aging on corrosion of abraded Al-Zn-Mg-Cu alloys

Surface abrasion has been shown to create altered surface layers (ASLs) that are hundreds of nm thick on all types of Al alloys. Such ASLs have lower corrosion resistance than the underlying substrate of Al-Zn-Mg-Cu alloys. Here, we demonstrate how heat treatments affect the ASL microstructure on abraded Al-Zn-Mg-Cu alloys using transmission electron microscopy and atom probe tomography, and also how the corrosion properties change using electrochemical polarization. High temperature treatments on the abraded bulk samples enhance η phase precipitation in the ASL, leading to a decreased Zn content in the ASL solid solution, which ennobles the ASL breakdown potential.

Influence of Artificial Aging in Aluminum Silicon Alloy

One of the techniques to increase the hardness of aluminum alloy is by aging process. The aging process includes natural aging and artificial aging processes. This study aims to investigate the effect of artificial aging on the hardness of aluminum silicon alloys. Artificial aging is carried out at two temperature variations, namely 150 and 200 °C. Metallographic test using optical microscopy and scanning electron microscopy were performed to observe the microstructure and deposits of silicon. Investigation of the constituent elements of aluminum silicon was carried out using the Energy Dispersive X-Ray Spectroscopy technique. The mechanical properties of aluminum silicon alloys examined were hardness before aging and hardness after artificial aging at temperatures of 150 and 200 °C. Hardness testing is conducted by Rockwell B hardness testing. The hardness test results showed that the hardness before the aging process was 61.1 HRB, the hardness after artificial aging at 150 °C was 69.11 HRB and the hardness after artificial aging at 200 °C was 80.36 HRB. There was an increase in hardness after the artificial aging process was carried out.

Retention force of polyetheretherketone and cobalt-chrome-molybdenum removable dental prosthesis clasps after artificial aging

ObjectivesTo examine the retention force of removable dental prosthesis (RDP) clasps made from polyetheretherketone (PEEK) and cobalt-chrome-molybdenum (CoCrMo, control group) after storage in water and artificial aging.Materials and methodsFor each material, 15 Bonwill clasps with retentive buccal and reciprocal lingual arms situated between the second pre- and first molar were manufactured by milling (Dentokeep [PEEKmilled1], NT digital implant technology; breCAM BioHPP Blank [PEEKmilled2], bredent), pressing (BioHPP Granulat for 2 press [PEEKpressed], bredent), or casting (remanium GM 800+ [CoCrMo], Dentaurum); N = 60, n = 15/subgroup. A total of 50 retention force measurements were performed for each specimen per aging level (initial; after storage [30 days, 37 °C] and 10,000 thermal cycles; after storage [60 days, 37 °C] and 20,000 thermal cycles) in a pull-off test. Data were statistically analyzed using one-way ANOVA, post hoc Scheffé and mixed models (p < 0.05).ResultsInitial, PEEKpressed (80.2 ± 35.2) and PEEKmilled1 (98.9 ± 40.3) presented the lowest results, while PEEKmilled2 (170.2 ± 51.8) showed the highest values. After artificial aging, the highest retention force was observed for the control group (131.4 ± 56.8). The influence of artificial aging was significantly higher for PEEK-based materials. While PEEKmilled2 and PEEKpressed showed an initial decline in retention force, all other groups presented no impact or an increase in retention force over a repetitive insertion and removal of the clasps.ConclusionsWithin the tested PEEK materials, PEEKmilled2 presented superior results than PEEKpressed. Although CoCrMo showed higher values after artificial aging, all materials exhibited sufficient retention to recommend usage under clinical conditions.Clinical relevanceAs RDPs are still employed for a wide range of indications, esthetic alternatives to conventional CoCrMo clasps are sought.

Influence of Artificial Aging on the Dry Sliding Wear Behavior of ADC12 Alloy-B4C-Rice Husk Ash Particulates Reinforced Hybrid Composites

The influence of artificial aging on the wear behavior of ADC12 alloy reinforced with Boron carbide (B4C) and Rice Husk Ash (RHA) composites have been investigated. Hybrid composites with 5 wt. % of B4C fortification constant and variable quantity of rice husk ash particles in steps of 9 and 12 wt. % in the ADC12 alloy prepared by melt stir process. ADC12 aluminium alloy, ADC12 alloy-5 wt. % B4C-9 wt. % RHA and ADC12 alloy-5 wt. % B4C-12 wt. % RHA Samples were solutionized at a temperature of 525˚C for 1 h. Further, these solution heat treated samples were artificially aged at the temperature of 175˚C for 10 h. Microstructural characterization was carried out by using SEM and EDS. A pin-on-disc wear testing machine was utilized to assess the wear loss of specimens, in which a solidified EN32 steel plate was utilized as the counter face. Wear tests were accompanied on ADC12 alloy, ADC12 alloy-5 wt. % B4C-9 wt. % RHA and ADC12 alloy-5 wt. % B4C-12 wt. % RHA hybrid composites at varying loads of 10 N, 20 N and 30 N with varying sliding distances of 250 rpm, 500 rpm and 750 rpm for constant sliding distance of 1000 m. The wear resistance of ADC12 alloy enriched with the accumulation of B4C and RHA particulates. Further, heat treated samples were exhibited the superior wear resistance as compared to the base alloy and un-heat treated samples.

Influence of artificial aging and ZrO2 nanoparticle-reinforced repair resin on the denture repair strength.

BackgroundThe purpose of this study was to evaluate the effect of aging process on the tensile strength (TS) of repaired acrylic denture base using ZrO2 nanoparticles (nano-ZrO2)-reinforced autopolymerized resin. Material and MethodsA total of 240 heat-polymerized acrylic resin specimens (n=10) were prepared and sectioned creating 2 mm-repair-gap. Autopolymerized acrylic resin, pure and modified with 2.5, 5, and 7.5wt% nano-ZrO2 were used for specimens repair. TS of repaired specimens were measured using the universal testing machine after water immersion at 37oC for 2, 7 and 30 days. At each time interval, half the immersed specimens underwent thermo-cycling aging process (5000 cycles at 5/55°C) before TS testing. One-way ANOVA and Tukey-Kramer multiple-comparison tests were used for data analysis at α=0.05. ResultsAging process for all groups showed significant differences in TS between unreinforced and nano-ZrO2 reinforced groups (p<0.05). Within immersed nano-ZrO2-reinforced specimens, 5% group immersed for 30-days showed the highest significant TS value (p<0.05). With regards to thermocycling, 5% group showed the highest TS values after 2-days and 30-days groups while after 7-days, significant differences were found between 2.5% group and 5% and 7.5% groups (p<0.05). SEM images analysis displayed the ductile fracture type for nano-ZrO2 reinforced groups. ConclusionsIn summary, 5.0%-nano-ZrO2 addition to repair resin showed an improvement in tensile strength of repaired acrylic resin with different aging processes. Key words:Acrylic resins, denture repair, tensile strength, thermocycling, water storage, zirconium oxide nanoparticle.

Influence of artificial aging on mechanical properties of commercially and non-commercially available zirconia dental implants

ObjectiveTo evaluate the effect of artificial aging on the mechanical resistance and micromechanical properties of commercially and noncommercially available zirconia dental implants. MethodsScanning electron microscopy (SEM) and X-ray computed tomography (X-CT) were performed on implant systems including: Z-systems®, Straumann®, Zibone® and commercially and non-commercially available TAV dental® with varying grain sizes. Accelerated aging was performed at 134 °C and 2-bar pressure for 30 hours. Before and after aging, the mechanical load to failure was investigated and the bending moments were calculated. Nanoindentation responses of the representative Zibone implant before and after aging were performed to evaluate the effects of aging on hardness (H) and Young's modulus (E). A two-sample t-test statistical analysis was used to determine significant differences of bending moments within groups. ResultsAll implants presented with compact and homogenous core structures without porosities. The bending moment was significantly increased after aging for all groups (P ≤ 0.05) except for Z-systems (significant decrease (P = 0.022)) and TAV group 3 (no significant increase (P = 0.181)). The increase in bending moment was less pronounced with increasing grain size in TAV groups (group 1: P = 0.036, group 2: P = 0.05, group 3: P = 0.18). E and H were reduced approximately 32% and 18% respectively following aging within the transformed, microcracked zone of the presentative Zibone implant. ConclusionsAging led to both increase and decrease of the mechanical properties of the implant systems analyzed. The apparent contrast amongst groups can be explained based on differences in grain sizes and surface features. Aging decreased micromechanical properties of one implant system which warrants further investigation.

Influence of Artificial Aging on Mechanical Properties and High Stress Abrasive Wear Behaviour of Al–Mg–Si Alloy

The present study evaluated hardness, tensile properties and two-body abrasive wear behaviour of Al–Mg–Si alloy specimens artificially aged at 448 K for different durations ranging from 0.5 to 504 h. In addition to the measurements of Vickers hardness and tensile properties, wear tests of differently aged alloys were conducted against SiC abrasive paper of 220 grit size under normal load of 9.81 N with the help of a pin-on-disc tribometer. Abrasive wear characteristics were assessed in terms of measurements of specific wear rate and roughness of the abraded surfaces. These were substantiated via examinations of worn surfaces, collected wear debris and subsurfaces of worn specimens to comprehend the micro-mechanisms of abrasion. The abrasive wear performance varied significantly with the duration of artificial aging and the lowest specific wear rate as well as roughness of the abraded surfaces corresponded to the peak-aged condition. An attempt was also made to correlate mechanical properties and tribological performance. It was found that the specific wear rate exhibited direct linear relation with the strain hardening exponent, and inverse linear relationships with hardness, yield strength and strength coefficient. Microplowing, microcutting and microcracking were identified as mechanisms of abrasion; the extents of these processes were found to be governed by the state of aging that determined the mechanical properties.

The collagen state within the parchment after influence of artificial aging

The collagen state within the parchment after influence of artificial aging

The influence of artificial aging on the microstructure and hardness of an Al\u2013Zn\u2013Mg\u2013Zr alloy processed by equal-channel angular pressing

The effect of artificial aging on the microstructure and hardness of an ultrafine-grained (UFG) Al–4.8%Zn–1.2%Mg–0.14%Zr (wt%) alloy was studied. The UFG microstructure with an average grain size of about 260 nm was obtained by severe plastic deformation applying four passes of equal-channel angular pressing (ECAP) at room temperature. Then, artificial aging was performed on the ECAP-processed samples at 120 °C and 170 °C for 2 h. In the ECAP-processed sample Guinier–Preston (GP) zones, MgZn2 precipitates and a high dislocation density were observed. After aging at 120 °C, coarse MgZn2 precipitates were formed in the grain boundaries, leading to softening, while the dislocation density did not decrease. Annealing at 170 °C yielded a growth of the matrix grains to ~ 530 nm with a significant decrease in the dislocation density. In addition, GP zones disappeared and MgZn2 precipitates were formed in both the grain interiors and the boundaries. This overaging of the precipitate structure and the decrease in the dislocation density resulted in a lower hardness than after annealing at 120 °C. It was found that the hardness reduction due to the change of the precipitate structure at 170 °C was higher than that caused by the decrease in the dislocation density.

Influence of artificial aging on the lubricating ability of water miscible metalworking fluids

The understanding of the complex aging processes of water miscible metalworking fluids and their effect on the performance in machining processes is of high relevance for the metalworking industry. Nevertheless, only little knowledge is available in this context. Due to the highly dynamic interactions in the complex ecosystem “metalworking fluid”, a distinct correlating of the aging process with the performance of the fluid in metalworking processes is hardly possible. Consequences of the aging process on physical, chemical and biological properties of the fluid have been described in several research works. These consequences comprise aspects such as the decrease of the pH-value, the increase of the droplet size, the presence of bacterial cells or the modification of the metalworking fluid composition. The novel approach of the presented work aims to investigate the individual influence of isolated aging aspects on the lubricity of metalworking fluids. Therefore, selected aging aspects were artificially varied separately from each other and evaluated in tribological experiments. It could be shown that the physical presence of bacterial cells as well as extracellular polymeric substances have positive influence on the lubricating ability while the pH-value has no effect and the droplet size only a slight influence on the fluids performance. The results reveal essential knowledge for the design of future monitoring and maintenance strategies for water miscible metalworking fluids.

Influence of artificial aging on structural adhesive connections for façade applications

Contemporary architecture often requires adhesive connections as a bonding method of façade cladding elements to the supporting substructure, due to their visually smooth surface without the interruption by bolts. Low strength, elastic and durable silicone sealants have been used in façades for a long period of time, but there is a lack of information about semi-flexible and semi-rigid adhesives with higher strengths. The building façade is a very specific application for adhesive connections due to the requirements for durability, strict geometrical imperfections and joining of unconventional materials often used in the façade design. The presented paper is focused on experimental analyses of structural adhesive joints exposed to laboratory aging conditions. Due to the absence of a particular code intended for structural adhesive joints in façades, two artificial aging procedures were chosen – ETAG 002 and ISO 9142 - E4 Procedure (Exposure to neutral salt spray and elevated temperature and humidity). The joints are bonded by two different adhesives, Silane Terminated Polymer (STP), and a two-part acrylate adhesive. The joints are composed of blank aluminum with a smooth and roughened surface, anodized aluminum and galvanized steel with a smooth and roughened surface. Mechanical behavior and failure modes of a reference set of specimens are compared with the results of two specimen sets exposed to aging. The degrading effect of demineralized water immersion was more crucial for the STP adhesive than the salt spray test. On the contrary, the effect of the salt spray test was more serious for the acrylate adhesive than immersion in water. The experimental study showed that the degrading effect of a particular aging procedure can be more harmful to one adhesive than the others in dependence on the time of exposure.

Vpliv umetnega staranja na elektrokemijske lastnosti aluminijeve zlitine AA 6063

Vpliv umetnega staranja na elektrokemijske lastnosti aluminijeve zlitine AA 6063

Enhancement in Hardness and Influence of Artificial Aging on Stir Cast Al6061-B4C and Al6061-SiC Composites

Present investigation focusses on individual effect of B4C and SiC on the improvement in hardness with an average size of 35-40μm and various weight percentage of (2, 4 and 6) Al6061 alloy composite. Composites are produced by stir casting process. The precipitation hardening effect at 100, 150 and 200°C on the mechanical properties was also investigated. Optical micrographs and Brinel hardness number have been discussed. Transmission electron microscope shows precipitation of finer inter-metallic in both Al6061 alloy and its composites. Increase in percentage of both B4C and SiC reinforcement from 2-6% wt. and artificially aged at 100°C shows enhancement in hardness by 150-175% due to the precipitation of intermetallic phases of alloying elements. Al6061-B4C composites show improvement in hardness as compared to Al6061-SiC composites.