Tensile Strength Measurements Research Articles

Fabrication of aluminium covetic casts under different voltages and amperages of direct current

Abstract Aluminium Covetic metallurgical synthesis along with the characterization of cast material results were presented in this paper. Aluminium- 3% graphite (carbon) composites were fabricated by applying different voltages and amperages of direct current through the stir-casting process. This process, called Covetic based on patent applications of Third Millennium Metals. Obtained casts were tested for their chemical composition, density, tensile strength, hardness, microstructures, and electrical conductivity measurements using an Oxford PMI-Master Pro spark emission spectrometer, a DA-300M density measurement device, a WDW-200 universal tensile test machine, a HBA-3000S automatic Brinell Hardness Tester, a scanning electron microscope with Energy-Dispersive Spectroscopy and an AT512 Precision Ohmmeter, respectively. Moreover, increasing of amperages and/or decreasing of voltages of direct current ensured considerable increasing of electrical conductivity (≈ 34%), the notable decrement in the density (≈ 0.94%), an enhancement in the tensile strength (≈ 18%) and the hardness (≈ 15%) of aluminium Covetic casts compared to the parent metal. In summary, results show that the increasing of amperages and/or decreasing of voltages of direct current has a superior influence on improving electrical conductivity of aluminium-graphite Covetic casts with better mechanical properties.

Microstructural and mechanical properties of Cu-Ni-Mn-Mo austempered ductile iron obtained from two-step hot air austempering

In the present work, mechanical and microstructural properties of Austempered Ductile Iron (ADI) alloyed with Cu-Ni-Mn-Mo submitted to different hot air austempering cycles in a two-step mechanism were evaluated. In the first step, cooling and austempering were performed in an experimental hot air blower device. In the second step, the austempering was performed in a muffle furnace. Bars with Ø16.5 mm and 90 mm of length were austenitized in an electric resistive furnace for 90 min at 860°C. Austempering first step was performed for 10 min at 290°C, 320°C and 350°C corresponding to cycles I, II and III, respectively. Austempering second step was performed for 60 min at 380°C for all cycles. The measurements of Brinell hardness, elongation, yield strength, and ultimate tensile strength for cycle I were 288 HB, 5.0%, 840 MPa, and 988 MPa. For cycle II, the measurements were: 264 HB, 5.9%, 717 MPa, and 876 MPa. And for cycle III: 257 HB, 6.6%, 711 MPa, and 888 MPa. Microstructural analysis indicated the presence of pearlite-free ausferrite.

Optimization of Laser Sintering for Demineralized Bone/Polycaprolactone Composite Powder for Bone Tissue Scaffold

Demineralized bone matrix (DBM) is an excellent bone scaffold material, but is available in only limited sizes. An additive manufacturing (AM) method that retains these properties while enabling customized geometry fabrication would provide bone scaffolds for a larger range of geometries while maintaining the benefits of DBM. This work examines laser sintering (LS) of a blend of demineralized bone matrix (DBM) and polycaprolactone (PCL) using a CO2 laser beam. A comprehensive experimental study was carried out to find the conditions that form defect-free layers while still retaining the favorable biological features of DBM. The results identify a process setting window over which LS can be utilized to constructing complex patient-specific scaffolds. With the identified setting, first, the DBM/PCL blend was fused in the LS machine. Parts were then were further strengthened through a post-processing heat treatment. The shrinkage level, skeletal density, mechanical testing, and porosimetry of the resultant samples were compared to traditional machined DBM blocks. The maximum tensile strength of the samples and post-processing shrinkage depends on heat treatment duration. The tensile strength measurements demonstrate that the post-processing conditions can be tuned to achieve the tensile strength of the demineralized bone strips. Evaluation of the dimensional change suggests that the shrinkage along the laser paths is ~0.3% while thickness shrinks the most (up to ~20%). The porosimetry and density studies showed that the final part achieved over 40% porosity with a density comparable to blocks of DBM.

Evaluation of dynamic tensile strength of concrete using lattice-based simulations of spalling tests

The mechanical properties and failure modes of concrete are affected by strain rate. Therefore, various experimental methods have been used to quantify the strain-rate dependency of concrete properties, such as the spalling test by using a Hopkinson bar. In the test, pullback velocity at the free-end surface of the specimen is usually measured to evaluate the dynamic tensile strength of concrete, instead of directly measuring the critical stresses at the damaged location(s) due to experimental constraints. Herein, such indirect measurements of tensile strength are compared with direct determinations of tensile strength based on lattice models of the spalling tests. To represent rate-dependent material behavior, rheological units are introduced within the lattice elements. The parameters of the rheological units are calibrated through comparisons with experimental data. The calibrated values remain unchanged in subsequent simulations, which can be regarded as virtual spalling tests at various high strain rates of loading. The separation of viscous and inertial contributions to apparent tensile strength provides insights into the dependence of actual tensile strength on high strain rates. The simulation results indicate indirectly measured dynamic tensile strength, as commonly done in practice, is sufficiently close to directly measured strength.

Demonstration of GaN/LiNbO3 Hybrid Wafer Using Room-Temperature Surface Activated Bonding

In this study, a GaN/LiNbO3 hybrid wafer was demonstrated using room-temperature bonding based on a surface activated bonding (SAB) method. The SAB using Fe-containing Ar ion beam bombardment achieved a strong bond between GaN and LiNbO3 wafers. The bonded wafer made using the modified SAB method was successfully cut into 1 × 1 mm2 dies using a dicing saw without interfacial debonding, and the measured tensile strength was estimated to be greater than approximately 26 MPa. These results show the presence of a strong bond that may be sufficient for device applications. In addition, TEM observation clearly indicated that the Fe-containing nanolayer deposited during ion beam bombardment appears to work well as an adhesive and form a strong bond between the negative surface of LiNbO3 and Ga-face of GaN. These results show the potential of this room-temperature bonding method to achieve a future GaN/LiNbO3 hybrid platform that can fully exploit the unique properties of each material.

Thermomechanical and viscoelastic properties of green composites of PLA using chitin micro-particles as fillers

Many thermoplastic biocomposites made with non-biodegradable polymers as a matrix polymer are not biodegradable. In this work, biodegradable polylactide (PLA)/chitin micro-particle composites were successfully prepared by melt blending without using any compatibilizer or processing aid. The effects of the addition of chitin micro-particles to PLA on its thermal stability, physicomechanical properties and microstructures were evaluated by thermo-gravimetric analysis, dynamic mechanical thermal analysis, differential scanning calorimetry, tensile strength measurement, and scanning electron microscopy. It was found that the addition of chitin micro-particle to PLA increased the stiffness, tensile strength, and hydrophobicity of PLA but negatively affected its thermal properties and elongation. The tensile strength exhibited by the pristine PLA was 41.5 MPa, which increased to 48.5 for the chitin loading of 3% but a further increase in the chitin loading resulted in a reduction in tensile strength. The increase in chitin loading resulted in an increase in stiffness of PLA as the storage modulus increased from 3.21 GPa for the neat PLA to 3.48 GPa for the PLA loaded with 3% chitin microparticles. The results show that chitin can be used for the reinforcement and also to enhance the moisture barrier properties of PLA.

Effect of redispersible polymer powders on selected mechanical properties of thin-bed cementitious mortars

Modern mortars are complex multi-component systems. Among the mortar components, redispersible polymer powders (RDPs) play a unique role. They improve the rheology of fresh mortar while providing flexibility and tensile strength after it has hardened. The impact of polymeric binders on mortar properties has been and is currently the subject of intensive research. This paper describes how the use of different redispersible polymer powders affects cement mortars’ selected properties, i.e., crack bridging ability, adhesion determined by measurement of tensile strength and transverse deformation. Results show that all of the RDPs tested positively affect the properties of the examined system. The most significant increase in the mortar’s tensile adhesion strength was observed for the system with vinyl acetate homopolymer, the lower one for the systems with styrene-acrylic heteropolymers and vinyl acetate and ethylene heteropolymers. All tested redispersible polymer powders in the considered system increase the ability to bridge cracks in cement mortar. However, the smallest increment is observed for the acrylic homopolymer and styrene-butadiene heteropolymer. Other RDPs similarly increase the mortar’s cracks bridging ability under test defined as the ability of the hardened material (mortar) to stop the spread of cracks without damaging it. The results obtained for thin-bed cement mortars in terms of crack bridging ability were evaluated comparing the requirements for water-impermeable products. All examined RDPs showed a similar effect on the transverse deformation value of cement mortar.

Tensile strength differences between nickel-titanium and titanium molybdenum alloy orthodontic archwire after immersion in detergent toothpaste

Background: Titanium-based alloys, such as nickel-titanium (NiTi) and titanium molybdenum alloy (TMA), have gained immense popularity in the last decades. Some toothpaste ingredients can negatively affect orthodontic procedures. Objective: The objective of this study was to examine the differences in tensile strength between NiTi and TMA orthodontic wires after immersion in detergent toothpaste. Methods: Six treatment groups were established, with NiTi and TMA wires immersed in 25 g detergent toothpaste for 4, 8, and 12 h. Tensile strength measurements were carried out using a Tensilon RTF-1350 universal testing machine. Results: The P values of the NiTi and TMA wires were as follows: 0.000 after 4 h, 0.000 after 8 h, and 0.002 after 12 h. These results showed that there were significant differences between the tensile strength of NiTi and TMA orthodontic wires after immersion in detergent toothpaste for increasing periods of time. Conclusion: The tensile strength of NiTi wire was greater than the tensile strength of TMA archwire. However, detergent toothpaste did not have a significant effect on change in tensile strength of NiTi and TMA wire.

Synthesis of hydrophobically modified guar gum film for packaging materials

Guar gum was hydrophobically modified by microwave assisted condensation with dimer acid (DA, a dimer of ricinoleic acid derived from castor oil) under “green” conditions. The condensation product (HMG) was then blended with polyvinyl alcohol and cast into films abbreviated as HMGF (hydrophobically modified guar gum film). FTIR and UV–visible spectroscopies, X-ray diffractometry, swelling, permeability and tensile strength measurements were used to evaluate the properties of HMG and HMGF. HMGF exhibits optimal mechanical strength with UV protective effect and restricted entry of chemical contaminants. HMGF could be easily disposed by burying in soil. HMGF may be a potential eco-friendly food packaging material.

Power Ultrasonic Additive Manufacturing: Process Parameters, Microstructure, and Mechanical Properties

Additive manufacturing (AM) for fabricating 3D metallic parts has recently received considerable attention. Among the emerging AM technologies is ultrasonic additive manufacturing (UAM) or ultrasonic consolidation (UC), which uses ultrasonic vibrations to bond similar or dissimilar materials to produce 3D builds. This technology has several competitive advantages over other AM technologies, which includes fabrication of dissimilar materials and complex shapes, higher deposition rate, and fabrication at lower temperatures, which results in no material transformation during processing. Although UAM process optimization and microstructure have been reported in the literature, there is still lack of standardized and satisfactory understanding of the mechanical properties of UAM builds. This could be attributed to structural defects associated with UAM processing. This article discusses the effects of UAM process parameters on the resulting microstructure and mechanical properties. Special attention is given to hardness, shear strength, tensile strength, fatigue, and creep measurements. Also, pull‐out, push‐out, and push‐pin tests commonly employed to characterize bond quality and strength have been reviewed. Finally, current challenges and drawbacks of the process and potential applications have been addressed.

Mechanical Characterization of Stir Cast Al-7075/B4C/Graphite Reinforced Hybrid Metal Matrix Composites

Abstract The modern technology requires the materials with light weight, high strength, high stiffness and superior mechanical properties. The mechanical properties of metal matrix composites (MMCs) are critical to their potential application as structural materials. A systematic examination is required to study the effect of particulate weight fraction on the mechanical properties. Aluminium based metal matrix composites find varied applications in aerospace, defence, automobile, sports equipment and electronics due to their favourable properties. Al 7075 is a light weight castable alloy with moderate hardness and strength and finds applications in automotive and aerospace. The addition of refractory reinforcement generally improves the hardness, tensile strength and high temperature properties of the material. The present investigation focuses on characterization of Stir cast Al-7075/B4C/Graphite reinforced Hybrid Metal Matrix Composites. Adding B4C with varying reinforcement of three cases, in first case 2% constant with varying graphite 1%, 3%, and 5%, in second case 4%, and in third case 6% constant with varying same graphite percentage, the aluminum matrix hybrid composites have been fabricated by stir-casting method at 650 °C. Castings for tensile testing were prepared in circular metal mold of diameter 20 mm and length 120 mm. The specimens of 55×10×10 mm with 2 mm notch for impact test, 20×10×10 mm for microscopy analysis and hardness test are cut from a cast ingot of 100×50×10 mm using CNC EDM wire cutting. Specimens are prepared as per the ASTM standards and Microstructure investigation, ultimate tensile strength, impact strength and hardness measurements have been correlated with the percentage of B4C and Graphite particles. The effects of B4C and Graphite particle content on the mechanical properties were investigated. The grain size by using the mean intercept length method, Standard deviation and 95% confidence intervals were determined at different weight fractions.

Investigation of the effects of systemic meperidine administration on fascia healing in an experimental rat model.

Purpose:To evaluate the effects of meperidine on fascial healing.Methods:Seventy adult male Sprague-Dawley rats divided into 7 groups with 10 rats in each group. One of these groups was determined as the sham group, 3 of the remaining 6 groups as meperidine groups, and 3 as control groups. These were grouped as 1st, 2nd, and 6th weeks. In the anterior abdominal wall of the rat, the skin was detached and a wound model including the peritoneum was created with a median incision. Mice in the meperidine group were injected with meperidine intraperitoneally (IP) 3 × 20 mg/kg meperidine on postoperative days 0, 1 and 2, and 2 × 20 mg/kg meperidine on postoperative days 3, 4, 5, and 6 after surgical intervention. Similar to the control group, an equal volume of saline was administered, corresponding to the doses. After sacrifice, the midline fascia was used for facial tensile strength measurement, and the other for histopathological analysis.Results:When compared, the meperidine and control groups inflammatory cell density was higher in the 1st week (p < 0.05) in the meperidine group, fibroplasia density was found to be higher at the 2nd week in the meperidine group than the control group (p < 0.05) When the tensile strength in the meperidine and control groups were compared, there was no significant difference (p > 0.05) at each of the three weeks.Conclusion:The application of postoperative systemic meperidine affects positively wound healing in the inflammatory stage and fibroplasia without changing the resistance to traction.

The Similar and Dissimilar TIG Welding of 316L and 321 Austenitic Stainless Steels

Being one the modern high quality industrial welding process especially for stainless steels and titanium alloys. TIG welding process has been has been researched for decades in order to define its parameters such as welding speed, current and arc length to improve the weld penetration. Hence it is a popular technique for joining thin materials - the thickness of the work piece is in general restricted to less than 6 mm- in manufacturing industries. In this study, AISI 321 and 316L stainless steel sheets of 4 mm of thickness were used as welding metals. Thus, AISI 321 welding metal couples, AISI 316L welding metal couples and AISI 321 and 316L welding metal couples were selected to ensure a combination of similar and dissimilar metals. The filler metal rod was made of 316L SS. The specimens were cut in dimensions of 150 x 30 x 4 mm as using an abrasive cutter, then the V weld butt joint configuration with single groove of 37.5o ± 2.5o groove angle by a lathe machine. The welding current was 200 A and TIG welding process was performed manually in single under argon shielding gas atmosphere. After TIG welding process, the separate metallographic preparations, then microscopic and macroscopic examinations of the specimens, also hardness measurements of specimens were made. The rest of them was shaped for tensile strength measurement using Instron Universal Testing Machine. The hardness of the specimens were observed being altered in the range of 145-151 HRV(average) and their tensile strength values in the scale of 345-400 MPa (average).

Underlying causes of poor mechanical properties of aluminum-lithium alloy electron beam welded joints

The measured tensile strength for the electron beam welded joint of 2195 aluminum-lithium alloy was only 60% of BM, corresponding to a drastic softening effect within the welded zone. Although hole defect worsened the tensile strength for the welded joint, the strengthening phase deficiency within welded zone, including T1 (Al2CuLi) and θ' (Al2Cu), was indeed the underlying cause for the poor mechanical properties of aluminum-lithium alloy electron beam welded joint. The primary reasons for strengthening phase deficiency were proposed. Measured by chemical testing method, the Li content within the welded zone was merely 0.71%, which was attributable to the excessive temperature up to 3573 K in melt pool, indicating that the Li evaporation loss was as high as 36%. The Li evaporation loss was the most crucial factor for the barren precipitation of strengthening phases. The high-density dislocation clusters within the welded zone suggested a too fast cooling rate during solidification process. The brittle quasi-crystal phase, T2 (Al6CuLi3), abundantly precipitated along grain boundaries, which badly overconsumed the atom of Li and Cu that were needed by T1 (Al2CuLi) and θ' (Al2Cu) precipitation, and, simultaneously, deteriorated the properties at grain boundaries.

Micromechanical testing and modelling of blast furnace slag cement pastes

This work aims to understand deformation and fracture processes in blast furnace slag cement pastes made using CEM III/B which is commonly used in the Dutch infrastructure sector. First, based on our previous work on Portland cement pastes, a micromechanical model utilizing nanoindentation and X-ray computed tomography (CT) for input is created. Statistical analysis are carried out and shows that grayscale values from X-ray CT scans of slag pastes can be linearly correlated with nanoindentation measurements of elastic modulus. Simulations of uniaxial tension are then performed for varying w/c ratios using the Delft lattice model and microstructure obtained from X-ray CT. In addition, advanced micromechanical experiments for estimating the micro-scale tensile strength and elastic modulus are performed. Experimental and simulation results are then critically discussed and compared. It shows that simulation results match the measured tensile strength quite well although some discrepancy does exist at lower w/c ratios. In addition, the observations are compared to our previous findings on ordinary Portland cement pastes. It is found that tensile strength and elastic moduli of slag pastes at 28 days are higher than those of Portland cement pastes with the same w/c ratio. This study will form a basis for micromechanical testing and modelling of blended cement paste systems in the future.

Main Approaches to Cable Aging Management at Nuclear Power Plants in Ukraine

The mechanisms of cable ageing at nuclear power plants (NPPs) mainly depending on the insulation material, as well as the damaging factors affecting cables that are determined by the operating conditions are considered in the paper. The main and additional mechanisms of aging resulting from the effects of damaging factors are provided. The paper presents the main methods of cable aging management: determining the actual service life and testing using field methods and other means. The basic principles for the arrangement of cable aging management at Ukrainian NPPs, as well as the methods used to investigate the technical condition of cables, are presented. A list of mandatory lists has been defined when performing activities on cable aging management. A methodology is described for lifetime extension of cables, and conditions for extending the service life of cables that are in service are provided. A number of methods of testing cables for aging management are considered: visual inspection of insulation and measurement of crack size, discoloration, etc.; insulation hardness test; insulation chemical analysis; electrical insulation tests; tensile strength measurement; measurement of elongation at break; measurements of dielectric loss at low frequency or sweep frequency; testing by dynamic reflectometry method; AC and DC current impedance measurements. The paper presents results of separate laboratory studies for selected 1 kV representative power cables with PVC insulation of SUNPP-1, ZNPP-1 and KhNPP-2 conducted within Ukrainian NPP long-term operation, which included a stage of laboratory examination and examination of cable samples in operating conditions. The following results were obtained: dependence of VVGng 4x6 cable lifetime on operating temperature; dependence of AVVG cable lifetime on operating temperature; dependence of AVVG (a) cable lifetime on operating temperature. There are possibilities and conditions under which the use of cables within long-term operation is permissible.

Lubricant Concepts for Electrified Vehicle Transmissions and Axles

It is anticipated that many future electrified vehicle transmissions and axles will incorporate the electric motor within the unit housing. In such an arrangement, the lubricant will be in direct contact with powered motor windings, which raises new concerns regarding its electrical conductivity and its propensity to corrode copper. The heat produced at the motor windings will challenge the lubricant’s heat transfer ability and its thermal stability. Expected high temperature excursions warrant the use of new plastics, which may give rise to new compatibility concerns. In this paper we share our learnings regarding the electrical properties of lubricants and discuss new methods to characterize copper corrosion. We review the factors that affect the heat transfer characteristics of lubricants and illustrate how improving heat transfer will favor the use of lower viscosity lubricants. We also share our early efforts to quantify lubricant compatibility with higher temperature plastics using tensile strength measurements. Finally, we discuss how these new concerns will shift the perception of what is required for lubricants used in different types of electrified transmission hardware.

Evaluation of Mechanical Properties and Corrosion Protection Performance of Surface Modified Nano-alumina Encapsulated Epoxy Coated Mild Steel

The incorporation of imidazole-modified nano-alumina on the corrosion protection properties of epoxy coating on mild steel was studied by electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) in 3.5% NaCl solution. The dispersability of the alumina nanoparticles was greatly improved by the surface modification using imidazole in the epoxy matrix. The imidazole-modified nanoparticle was analyzed by Fourier transform infrared spectroscopy. Both EIS and SECM studies confirmed that the corrosion resistance is higher for the alumina–epoxy nanocomposite coated steel than that of the pure epoxy-coated steel. It is evidenced that alumina–epoxy nanocomposite coated mild steel has higher charge transfer resistance values, 156,344 Ω cm2, compared to pure epoxy coated mild steel, 79,546 Ω cm2, at 40 days of immersion. The modified nanoparticles enhanced the adhesive properties of the coatings. Possible chemical interactions between epoxy matrix and surface-modified alumina nanoparticles in nanocomposites cause high protection properties and ionic resistances. FE-SEM/EDX analysis showed the presence of Fe, Al, and O in the corrosion products. Hardness and tensile strength measurements showed that the improved mechanical properties were noticed for alumina–epoxy nanocomposite coated mild steel.

A study of tensile stress with suction by restrained ring method

Abstract In expansive soils, tensile strength and tensile stress are two main factors that control the development of cracks due to drying shrinkage. Numerous experimental methods and theoretical models have been proposed for the measurement and prediction of tensile strength. However, there are only few studies that focus on the measurement and prediction of tensile stresses in expansive soils. Understanding the mechanism behind the crack initiation due to an increase in suction in expansive soils is of paramount importance in geotechnical engineering. In this study, the restrained ring method was modified for studying the variation of tensile stress with suction. Strain gauges were installed in the restrained ring to measure tensile strain, and a tensiometer and filter paper method were utilized to measure the suction. The experimental test results indicate that the change of tensile tress with suction can be generally simulated by the model proposed by Chen and Bulut (2017). It is noted that tensile stress increases nearly linearly with suction expressed in pF units (i.e., suction in logarithmic scale, pF = log10 (suction in cm of water as a positive number). Soil suction is also currently represented in log10 (kPa) unit system (i.e., log10 (kPa) = log10 (suction in kPa units as a positive number). In addition, it is found that the maximum tensile stress measured from the specimens initially at optimum water content is approximately twice the value of the maximum tensile stress measured from the specimens at near-saturation state. The test results also indicate that the suction change from the initial moisture state to crack initiation is about 0.2–0.3 pF for the specimens at optimum water content, and is about 0.5–0.7 pF for the specimens at near-saturation moisture state.

NEW METAL-CONTAINING POLY(URETHANE-SEMICARBAZIDES) ON THE BASIS OF PYRIDINE DERIVATIVES

The growth of science and technology of polyurethanes leads to the development of new materials with more desirable properties. Modification of polyurethane (PU) by incorporating metal and functional groups are used extensively to improve various properties, such as enhanced thermal stability, fire retardancy, flexibility and solubility. In this investigation, a new metal-containing poly(urethane-semicarbazides) bearing a pyridine moiety have been synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA/TG) and tensile strength measurements. The results showed that the incorporation of metal ions into the polymer chain greatly influenced their mechanical and thermal properties. The tensile strength measurements on the PU films showed a marked difference in the elongation and tensile strength for compositions with various metal salts. The nature of the anion of the salt also affects the properties of the polymers, since the anions are able to form complexes with hydrogen atoms of urethane-semicarbazide PU segments. According to the results of DTA, introduction of metal ions leads to the increase of the thermal stability of metal-containing PU, as compared to the original PU. FTIR spectra data confirmed that the metal ions Cu2+, Co2+ are coordinated in the polymer metal chelates with hydrazide and urethane groups. The research results can be used to develop the new materials and methods for the preparation and designing of metal-containing polymers required in various areas, such as development of medical equipment, functional films and other related areas.