Long-term aging characteristics of co-filled nano-silica and micro-ATH in HTV silicone rubber composite insulators

2020 ◽  
Vol 29 (1) ◽  
pp. 40-56 ◽  
Author(s):  
Arooj Rashid ◽  
Jawad Saleem ◽  
Muhammad Amin ◽  
Sahibzada Muhammad Ali
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Structural Changes ◽  
Erosion Resistance ◽  
Breakdown Strength ◽  
Accelerated Aging ◽  
Dielectric Strength ◽  
Superior Performance ◽  
Wave Number

Multiple environmental stresses produce complex phenomena of aging in polymeric insulators. The main aim of this research is to investigate the improved aging characteristics of silica (SiO2)/alumina trihydrate (ATH) hybrid samples (HSs) in high-temperature vulcanized rubber. For this purpose, three HSs comprising 20% micro-ATH with 2% nano-SiO2 (S2), 4% nano-SiO2 (S4), 6% nano-SiO2 (S6) along with sample-virgin (SV) are subjected to long-term accelerated aging of 9000 h. A special aging chamber is fabricated for the aging process of samples. The aging characteristics of these samples are investigated by measuring leakage current (LC) and hydrophobicity classification (HC) after every weathering cycle. Similarly, Fourier transform infrared (FTIR) spectroscopy is performed to observe the important structural changes over the entire aging time. The dielectric strength of AC is also performed after every 1000 h of aging. Tracking and erosion resistance and mechanical properties are also investigated before and after aging. From the critical investigation, it is observed that HSs possess improved results in all the conducted tests. S2 has the lowest LC and HC values throughout the aging time. Similarly, S6 described the highest breakdown strength at the end of the accelerated aging. In the case of FTIR, it is analyzed that the important wave numbers remain intact for all the HSs in the accelerated aging environment. The loss percentage in the wave number for SV is higher, compared to the HSs. After performing the tracking and erosion resistance test, HSs have superior performance. For some of the mechanical properties, HSs showed improved values. Thus, from the experimental analysis, it is deducted that the sample S2 offers the highest resistance to the aging conditions, compared to the SV and other HSs.

scholarly journals Influence of Thermally-Accelerated Aging on the Dynamic Mechanical Properties of HTPB Coating and Crosslinking Density-Modified Model for the Payne Effect

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 403 ◽  
Author(s):  
Yongqiang Du ◽  
Jian Zheng ◽  
Guibo Yu
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Loss Modulus ◽  
Accelerated Aging ◽  
Crosslinking Density ◽  
Dynamic Mechanical Properties ◽  
Maximum Elongation ◽  
Solid Rocket Motor ◽  
Payne Effect ◽  
Dynamic Mechanical

Hydroxyl terminated polybutadiene (HTPB) coating is widely used in a solid rocket motor, but an aging phenomenon exists during long-term storage, which causes irreversible damage to the performance of this HTPB coating. In order to study the effect of aging on the dynamic mechanical properties of the HTPB coating, the thermally-accelerated aging test was carried out. The variation of maximum elongation and crosslinking density with aging time was obtained, and a good linear relationship between maximum elongation and crosslinking density was found by correlation analysis. The changing regularity of dynamic mechanical properties with aging time was analyzed. It was found that with the increase of aging time, Tg of HTPB coating increased, Tα, tan β and tan α decreased, and the functional relationships between the loss factor parameters and crosslinking density were constructed. The storage modulus and loss modulus of HTPB coating increased with the increase of aging time, and decreased with the increase of pre-strain. The aging enhanced the Payne effect of HTPB coating, while the pre-strain had a weakening effect. In view of the Payne effect of HTPB coating, the crosslinking density was introduced into Kraus model as aging evaluation parameter, and the crosslinking density modified models with and without pre-strain were established. The proposed models can effectively solve the problem that the Kraus model has a poor fitting effect under the condition of small strain (generally less than 1%) and on the loss modulus, which have improved the correlations between the fitting results and the test results.

The Effects of Thermal Aging on Microstructural and Mechanical Properties of GH3535 Alloy Welded Joint

2015 ◽  
Author(s):  
Chen Shuangjian ◽  
Li Chaowen ◽  
Yu Kun ◽  
Li Zhijun ◽  
Xintai Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Welded Joints ◽  
Welded Joint ◽  
Hardness Test ◽  
Fracture Morphology ◽  
Second Phase ◽  
Effects Of Aging ◽  
Thorium Molten Salt Reactor

Ni-Mo-Cr alloys are the main structure materials for the Thorium molten salt reactor. In order to investigate the properties of welded joints of Ni-Mo-Cr alloy under long-term elevated temperature service, mechanical behavior and microstructure of joints aged at 650°C for 250h, 500h, 1000h, 2000h and 4000h were studied. Optical microscopy and scanning electron microscopy were used to study the effects of aging time on the grain size and carbides. Meanwhile, hardness, strength and fracture morphology of welded joints were also analyzed. In this study, the eutectic was observed in the weld metal and heat affected zone. The grain sizes of base metal of welded joints under different aging time were steady at 100μm approximately. Hardness test of welded joints indicated a slight climbing trend by increasing of aging time. The results of tensile test showed that the performance of welded joints after aging was better than that of as-welded joint and increased by growth of aging time, it was stable for the mechanical properties of aged welded joints in long term aging for up to 4000h as well. Moreover, the fracture morphology and the mechanism were observed by mean of SEM, the main fracture mechanism was ductile fracture for all the joints under different aging time. The second phase precipitations with increasing of aging time were the main contributing factor to enhance of mechanical properties.

Stabilities of Microstructure and Mechanical Properties during Long-Term Aging on FGH95 Superalloy

2017 ◽  
Vol 898 ◽  
pp. 523-527
Author(s):  
Xu Qing Wang ◽  
Guo Jun Ma ◽  
Zi Chao Peng
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Residual Strain ◽  
Thermal Stabilities ◽  
Good Thermal Stability ◽  
Microstructure And Mechanical Properties ◽  
Long Time ◽  
High Temperature Tensile ◽  
Short Time

Thermal stabilities of microstructure and mechanical properties during long-term aging of 550°C/1500h, 650°C/1500h and 700°C/500h have been investigated on superalloy FGH95, in order to characterize the long-term properties of this alloy on service temperature. The results showed that the secondary and tertiary gamma-prime maintained good thermal stability at 550°C and 650°C with aging time up to 1500h. However, during 700°C aging for 500h, the secondary and tertiary γ′ both grew obviously, besides, the shape of secondary γ′ has turned from circular to square. The hardness, high-temperature tensile and creep residual strain had good stability at 550°C and 650°C with aging time up to 1500h. However, the creep residual strain apparently increased when the alloy aged at 700°C for 500h, which means that the FGH95 is suitable to be used for long time below 650°C, and short time at 700°C.

scholarly journals Accelerated Aging Effect on Mechanical Properties of Common 3D-Printing Polymers

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4132
Author(s):  
Catalin Gheorghe Amza ◽  
Aurelian Zapciu ◽  
Florin Baciu ◽  
Mihai Ion Vasile ◽  
Adrian Ionut Nicoara
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Structural Changes ◽  
Prolonged Exposure ◽  
Accelerated Aging ◽  
Aging Treatment ◽  
Aging Effect ◽  
Control Group ◽  
Outdoor Environments ◽  
3D Printed

In outdoor environments, the action of the Sun through its ultraviolet radiation has a degrading effect on most materials, with polymers being among those affected. In the past few years, 3D printing has seen an increased usage in fabricating parts for functional applications, including parts destined for outdoor use. This paper analyzes the effect of accelerated aging through prolonged exposure to UV-B on the mechanical properties of parts 3D printed from the commonly used polymers polylactic acid (PLA) and polyethylene terephthalate–glycol (PETG). Samples 3D printed from these materials went through a dry 24 h UV-B exposure aging treatment and were then tested against a control group for changes in mechanical properties. Both the tensile and compressive strengths were determined, as well as changes in material creep characteristics. After irradiation, PLA and PETG parts saw significant decreases in both tensile strength (PLA: −5.3%; PETG: −36%) and compression strength (PLA: −6.3%; PETG: −38.3%). Part stiffness did not change significantly following the UV-B exposure and creep behavior was closely connected to the decrease in mechanical properties. A scanning electron microscopy (SEM) fractographic analysis was carried out to better understand the failure mechanism and material structural changes in tensile loaded, accelerated aged parts.

Assessment of a Polyamide Used in Flexible Pipes After Aging in Deoxygenated Water

2020 ◽  
Author(s):  
Danyelle Costa ◽  
Geovanio Oliveira ◽  
Leilane Cirilo ◽  
Marysilvia Costa
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
High Performance ◽  
Accelerated Aging ◽  
Volumetric Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polyamide 12 ◽  
Flexible Pipes ◽  
Indentation Tests

Abstract A high-performance polyamide grade of easy processability which presents excellent thermal and mechanical properties such as resistance to fatigue and creep is studied in this work. An accelerated aging of Polyamide 12 samples was performed in stainless steel autoclaves at 120°C in deoxygenated water at pH 8.7 in order to shorten the aging time and avoid oxidation. The samples were retrieved at distinct aging times which were enough to reach the asymptotic portion of the curve of corrected inherent viscosity (CIV) versus aging time. CIV measurements track modifications of the molecular weight due to hydrolysis. Afterwards, the samples were analyzed through their cross section in the core and edge layer in order to investigate changes due to diffusion effects. Differential scanning calorimetry (DSC) analysis assesses the degree of crystallinity and melting temperature. Thermogravimetric analysis (TGA) was employed in order to investigate changes in the thermal stability and the stage of degradation of the samples. Unlike conventional volumetric analysis techniques, the instrumented indentation tests (IIT) in micro-scale were performed to measure the mechanical properties such as elastic modulus (EIT) and hardness (HIT) along the thickness aiming to detect properties gradient between surface and core. The CIV measurements showed a decrease of 46.3% in the aged sample during the maximum aging time compared to the reference material.

Microstructures Evolution of a Ni-Base Superalloy after Long-Term Aging at 750°C

2007 ◽  
Vol 561-565 ◽  
pp. 387-390
Author(s):  
Tong Cui ◽  
Ji Jie Wang ◽  
Li Qing Chen ◽  
Guang Pu Zhao ◽  
Hong Cai Yang
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Aging Time ◽  
Aging Process ◽  
M23c6 Carbide ◽  
New Type ◽  
Base Superalloy

The microstructures evolution of a new type Ni-base superalloy has been investigated after long-term aging at 750°C for 2000h. The results indicate that TCP, a harmful phase greatly affects the mechanical properties of the alloy, is un-precipitated in the aging process. γ´ phase is precipitated in two kinds of sizes during long-term aging. The shape of larger one is transit from spherical to cubic with prolonging of aging time. The M23C6 carbide formed mainly by Cr, and other elements such as Al, Ti, Co and Mo is also precipitated in both γ matrix and grain boundaries, and the quantities of the carbide increase gradually with the increasing of aging time.

scholarly journals Effect of overload on changes in mechanical and structural properties of the annulus fibrosus of the intervertebral disc

2021 ◽  
Author(s):  
Małgorzata Żak ◽  
Celina Pezowicz
Keyword(s):  
Mechanical Properties ◽  
Intervertebral Disc ◽  
Structural Changes ◽  
Collagen Fibre ◽  
Posterior Column ◽  
Height Loss ◽  
Spinal Motion ◽  
Load Model ◽  
The Impact

AbstractThe research focussed on analysing structural and mechanical properties in the intervertebral disc (IVD), caused by long-term cyclic loading. Spinal motion segments were divided into two groups: the control (C), and the group in which it was analysed the impact of posterior column in the load-bearing system of the spine—specimens with intact posterior column (IPC) and without posterior column (WPC). To evaluate the structural and mechanical changes, the specimens were tested with simulation of 100,000 compression-flexion load cycles after which it was performed macroscopic analysis. Mechanical properties of the annulus fibrosis (AF) from the anterior and posterior regions of the IVD were tested at the uniaxial tension test. The stiffness coefficient values were statistically 32% higher in the WPC group (110 N/mm) than in the IPC (79 N/mm). The dynamics of increase in this parameter does not correspond with the course of decrease in height loss. WPC segments revealed clear structural changes that mainly involve the posterior regions of the IVD (bulging and delamination with the effect of separation of collagen fibre bundles). Pathological changes also caused decreases in the value of stress in the AF. The greatest changes in the stress value about group C (7.43 ± 4.49 MPa) were observed in the front part of the fibrous ring, where this value was for IPC 4.49 ± 4.78 MPa and WPC 2.56 ± 1.01 MPa. The research indicates that the applied load model allows simulating damage that occurs in pathological IVD. And the posterior column’s presence affects this change’s dynamics, structural and mechanical properties of AF.

Extra-Fibrilar Matrix Properties of Human Annulus Fibrosus are Location and Age Dependent

2012 ◽  
Author(s):  
Daniel H. Cortes ◽  
Woojin M. Han ◽  
Lachlan J. Smith ◽  
Dawn M. Elliott
Keyword(s):  
Mechanical Properties ◽  
Structural Changes ◽  
Accelerated Aging ◽  
Intervertebral Discs ◽  
Cross Linking ◽  
Matrix Properties ◽  
Age Dependent ◽  
Compositional Changes ◽  
Opposing Effects ◽  
Protein Cross Linking

Aging and degeneration of the intervertebral discs are cell mediated processes that include biochemical, mechanical and structural changes. Although these processes are similar, disc degeneration is defined as an accelerated aging process that results in a detriment in the function of the disc. Biochemical changes include protein cross-linking, proteoglycan depletion and changes on collagen type. These compositional changes are related to changes in the mechanical properties of the disc and its tissues. For instance, it has been shown that an increase of protein cross-linking by glycation or genipin treatment causes an increase of the stiffness in disc tissues [1,2]. On the other hand, a decrease on the amount of proteoglycan has been shown to cause a decrease on tissue stiffness due to a reduction of the osmotic pressure [3,4]. However, during aging and degeneration, these two processes occur simultaneously with opposing effects on the mechanical properties of the tissue. Consequently, it is important to analyze these effects separately. Additionally, many multiphasic models for soft charged tissues, such articular cartilage and intervertebral disc, also consider the ionic phases separately from non-charged solids. Although multiphasic models for the disc have been used in the past, the mechanical properties of the non-charged extra-fibrillar matrix (EFM) have not been measured directly.

Evaluation of the Degradation Characteristics of CF-8A Cast Stainless Steel Using Indentation Techniques and EDS

2006 ◽  
Vol 306-308 ◽  
pp. 869-874 ◽  
Author(s):  
Seung Baek ◽  
Jae Mean Koo ◽  
Chang Sung Seok
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Structural Changes ◽  
Accelerated Aging ◽  
Ball Indentation ◽  
Indentation Tests ◽  
Pump Valve ◽  
Cast Stainless Steel

Cast austenitic stainless steel piping pump, valve casings and elbows are susceptible to reductions in toughness and ductility because of long term exposure at the operating temperatures in the LWR (light water reactor). In this study, the three classes of thermally aged CF-8A cast austenitic stainless steel specimens were prepared using an artificially accelerated aging method for 0, 2,679 and 3,572 hours at 400oC. An indentation technique was applied to evaluate of the thermal aging of CF-8A cast austenitic stainless steel. We have performed indentation tests (automated ball indentation and nano-indentation) and EDS (energy dispersive spectroscopy) in order to characterize the micro-structural changes of the phase with aging. The fracture toughness of aged CF-8A cast stainless steel was determined by standard fracture toughness tests and automated ball indentation techniques.

Sign in / Sign up

Export Citation Format

Share Document