Peak Load Values Research Articles

Quantifying the Functional Stiffness of Pullthrough Wires Used for Endovascular Aneurysm Repairs Using Comparative Tension Dynamometry

ObjectiveThere are only few studies on the stiffness of guidewires used to deliver devices during endovascular procedures, particularly abdominal/thoracic endovascular aneurysm repair. In certain situations, tensioned pullthrough wires are also used, but no studies have examined their effective/functional stiffness. The objective of this study was to assess the radial stiffness characteristics of pullthrough wires compared with standard stiff wires.MethodsTwo types of stiff guidewires (Lunderquist Extra-Stiff and Amplatz Super Stiff; 0.035″ × 260 cm), were compared with a floppy guidewire (Radifocus Stiff M; 0.035″ × 260 cm) in two configurations: standard (non-tensioned) and pullthrough (tensioned). Radial stiffness was defined as the peak deformation force (PDF; newtons [N]) needed to deform the wires on an electromechanical dynamometer; data were logged on proprietary dynamometric software and peak load values assessed per wire. Three experimental runs were performed on three fresh sets of each wire per configuration. PDFs from straight configuration to midwire deformation at 15 mm were translated into Microsoft Excel for statistical analysis in Minitab 19 for Windows.ResultsMean ± SD PDFs were 7.83 ± 0.23 N for the Lunderquist and 9.87 ± 0.92 N for the Amplatz. This was 7.84 ± 0.52 N for the Radifocus wire in standard configuration, which increased to 15.48 ± 0.33 N when the Radifocus wire was in pullthrough configuration. This was significantly higher than both the Lunderquist and Amplatz Super Stiff wires (p < .001, one way analysis of variance).ConclusionThis study affirmed that a pullthrough wire becomes functionally more rigid than typical stiff wires used for endovascular procedures, and it is this stiffness that allows device delivery.

Weight loss and burst testing investigations of sintered silicon carbide under oxidizing environments for next generation accident tolerant fuels for SMR applications

Accident tolerant fuel (ATF) cladding is one of the most active area for research to advance the global contribution of nuclear energy since ATF will ensure and enhance the reactor safety allowing long refueling cycles and higher burnup. Silicon Carbide (SiC) is one material that can potentially be a solution to this long standing challenge. This study offers both computational reactor physics modeling and experimental investigation to examine the behavior of SiC in nuclear reactor environment. With recent interest in small modular reactors (SMR), this study selected SMR compact core as a reference assembly for Computational Burnup Modeling (CBM). Results of CBM suggest that SiC cladding will provide the highest burnup and maximum uranium utilization. Therefore, subsequent experimental investigations were focused on SiC only. Rhode Island Nuclear Science Center (RINSC)’s nuclear research reactor was used to investigate effects of irradiation on sintered tubular SiC material samples under pure steam at 1 atm, initially at 120 °C, followed by high temperatures between 850 °C and 1350 °C to simulate harsh reactor environment.Experimental analyzes of (a) weight loss and (b) burst testing are considered for SiC samples. For the weight loss experiment, we have considered both types of samples: (1) Non-irradiated and (2) Neutron-irradiated samples. Weight loss was found to be dependent on sample geometry. Irradiated samples show ∼2%–10% higher weight loss per area than that of the non-irradiated samples. Besides, considering the medium flow rate (less than 10 g/min), it has been observed that the irradiated samples exhibit ∼10%–40% higher weight loss than that of the non-irradiated samples over temperatures of 120 °C, 850 °C to 1350 °C. It is also seen that material loss rates are generally more sensitive at higher temperatures than at lower temperatures, and irradiated samples are more prone to weight loss. Furthermore, for the burst testing experimental investigations, experiments were conducted for (1) As-received samples (2) Non-irradiated samples and (3) Irradiated samples. Considering the three types of samples, it was observed that the maximum and minimum peak load values are ∼70% higher and ∼60% lower than the average peak load while fracture hoop stress is consistently ∼70%–75% higher than the internal pressure for all as-received samples. Experimental and computational investigations suggest that SiC is a viable candidate for ATF cladding material.

Behaviour of various framed timber joints: Capacity and improved design rules

Unlike conventional building materials like concrete, steel, aluminium, etc., timber offers a sustainable alternative due to its economy and energy efficiency and lesser carbon footprint. However, timber-framed structures possess joints as the most vulnerable elements despite their remarkable seismic resistance, having high damage susceptibility. Past studies on timber frames have mainly stressed the frame behaviour with a specific joint profile rather than the performance of various joint forms, commonly employed in timber construction. Additionally, studies to refine the joint details by optimizing the same are minimal. Thus, in the present research, using the results from the tests performed earlier on different joints (in terms of joint profile, nailed only, and nailed and with adhesive), the experimental data was used to model the observed behaviour numerically in ABAQUS. The FE models were validated and subsequently used in conducting parametric studies to obtain data over a broader domain to evaluate the effect of geometrical modifications on the joint behaviour. This facilitated in obtaining optimal joint profiles and helped in bringing out various recommendations on the same. Moreover, the numerical peak load values were compared against the design strengths evaluated using National Design Specifications (NDS)-2018 guidelines to ascertain the prediction accuracy. This comparison revealed that the predicted joint strengths varied from being unconservative to being extremely over-conservative. Thus, to improve the strength prediction using NDS-2018 guidelines, modification factors were brought out.

Quantitative Assessment of Point-of-Care 3D-Printed Patient-Specific Polyetheretherketone (PEEK) Cranial Implants.

Recent advancements in medical imaging, virtual surgical planning (VSP), and three-dimensional (3D) printing have potentially changed how today’s craniomaxillofacial surgeons use patient information for customized treatments. Over the years, polyetheretherketone (PEEK) has emerged as the biomaterial of choice to reconstruct craniofacial defects. With advancements in additive manufacturing (AM) systems, prospects for the point-of-care (POC) 3D printing of PEEK patient-specific implants (PSIs) have emerged. Consequently, investigating the clinical reliability of POC-manufactured PEEK implants has become a necessary endeavor. Therefore, this paper aims to provide a quantitative assessment of POC-manufactured, 3D-printed PEEK PSIs for cranial reconstruction through characterization of the geometrical, morphological, and biomechanical aspects of the in-hospital 3D-printed PEEK cranial implants. The study results revealed that the printed customized cranial implants had high dimensional accuracy and repeatability, displaying clinically acceptable morphologic similarity concerning fit and contours continuity. From a biomechanical standpoint, it was noticed that the tested implants had variable peak load values with discrete fracture patterns and failed at a mean (SD) peak load of 798.38 ± 211.45 N. In conclusion, the results of this preclinical study are in line with cranial implant expectations; however, specific attributes have scope for further improvements.

Investigation of the fracture energy of hot mixtures asphalt incorporating metallic wastes via semi-circular bending test

In the study, metallic wastes were evaluated in order to reduce environmental impacts and to contribute fracture energy of HMA mixtures. In this context, aluminum chips and iron powders were included in the mixtures at 0.50%, 1.00%, and 1.50% (by weight of mixtures), and the effect of HMA mixtures on fracture energy was investigated by Semi-Circular Bending (SCB) test. Experiments were performed on a total of 28 SCB test specimens from 7 different series including reference, Al-0.50, Al-1.00, Al-1.50, Fe-0.50, Fe-1.00, Fe-1.50. Basic physical properties, dissipated energy (DE), fracture energy (Gf), flexibility index (FI), and crack resistance index (CRI) values of HMA specimens were measured and compared. Based on test results, carrying load capacity and Gf values of the mixtures were increased in the use of waste iron powders. A decrease in Gf and peak load values were obtained while increasing the aluminum chips ratios. However, with the use of 0.5% waste aluminum chips were contributed Gf, peak load, CRI, and FI values compared by the reference sample. It is concluded that both aluminum chips and iron powders contributed to fracture energy of HMA mixtures.

Self-Healing Potential and Post-Cracking Tensile Behavior of Polypropylene Fiber-Reinforced Cementitious Composites

The use of synthetic fibers as reinforcement in fiber-reinforced cementitious composites (FRCC) demonstrates a combination of better ductile response vis-à-vis metallic ones, enhanced durability in a high pH environment, and resistance to corrosion as well as self-healing capabilities. This study explores the effect of macro- and micro-scale polypropylene (PP) fibers on post-crack energy, ductility, and the self-healing potential of FRCC. Laboratory results indicate a significant change in fracture response, i.e., loss in ductility as curing time increases. PP fiber samples cured for 2 days demonstrated ductile fracture behavior, controllable crack growth during tensile testing, post-cracking behavior, and a regain in strength owing to FRCC’s self-healing mechanism. Different mixes of FRCC suggest an economical mixing methodology, where the strong bond between the PP fibers and cementitious matrix plays a key role in improving the tensile strength of the mortar. Additionally, the micro PP fiber samples demonstrate resistance to micro-crack propagation, observed as an increase in peak load value and shape deformation during compression and tensile tests. Notably, low volume fraction of macro-scale PP fibers in FRCC revealed higher post-crack energy than the higher dosage of micro-scale PP fibers. Lastly, few samples with a crack of &lt; 0.5 mm exhibited a self-healing mechanism, and upon testing, the healed specimens illustrated higher strain values.

Analysis of hysteresis rule of energy-saving block and invisible multi-ribbed frame composite wall

The energy-saving block and invisible multi-ribbed frame composite wall (EBIMFCW) is a new type of load-bearing wall. The study of this paper focus on it is hysteresis rule under horizontal cyclic loading. Firstly, based on the experimental data of the twelve specimens under horizontal cyclic loading, the influence of two important parameters of axial compression ratio and shear-span ratio on the restoring force model was analyzed. Secondly, a tetra-linear restoring force model considering four feature points and the degradation law of unloading stiffness was established by combining theoretical analysis and regression analysis of experimental data, and the theoretical formula of the peak load of the EBIMFCW was derived. Finally, the hysteretic path of the restoring force model was determined by analyzing the hysteresis characteristics of the typical hysteresis loop. The results show that the curves calculated by the tetra-linear restoring force model in this paper agree well with the experimental curves, especially the calculated values of the peak load of the wall are very close to the experimental values, which can provide a reference for the elastic-plastic analysis of the EBIMFCW.

Are All Wires Created the Same? A Quality Assurance Study of the Stiffness of Wires Typically Employed During Endovascular Surgery Using Tension Dynamometry

ObjectiveThere have only been a few studies on the stiffness and load bearing characteristics of guidewires used to deliver devices during endovascular procedures, particularly endovascular aneurysm repair. The aim of this study was to compare the load bearing characteristics of typical stiff and floppy wires, including in the context of consistency for each wire type.MethodsTwo sets of stiff guidewires (Lunderquist Extra-Stiff and Amplatz Super Stiff [0.035” × 260 cm]), were compared with a floppy hydrophilic guidewire (Radifocus Stiff M [0.035” × 260 cm]). Radial stiffness was defined as the force (newtons [N]) needed to deform the wires on an electromechanical dynamometer. Tests were repeated with three runs on three sets of the same wire to check for consistency. Data were logged on proprietary dynamometric software and peak load values assessed per wire. Peak deformation forces (PDFs) from straight configuration to midwire deformation at 15 mm was translated into Microsoft Excel for statistical analysis in Minitab 19 for Windows.ResultsThere was good agreement within each wire set, with no difference in PDFs from runs for each wire (p > .10). Mean ± standard deviation PDFs were 7.83 ± 0.23 N for the Lunderquist, 9.87 ± 0.92 N for the Amplatz, and 7.84 ± 0.52 N for the Radifocus wires. The Amplatz wire exhibited the greatest resistance to deformation vs. both the Lunderquist and Radifocus wires (p < .001, one way analysis of variance). Both Amplatz and Radifocus wires had non-linear deformation characteristics.ConclusionThis study confirmed that the represented hydrophilic wire is more deformable than the stiff wires. The Amplatz wire has complex construction features that yielded surprising baseline stiffness characteristics. The linear stiffness characteristics of the Lunderquist wire possibly contribute to it being the preferred choice for large endograft delivery.

Analytical and numerical crashworthiness uncertainty quantification of metallic thin-walled energy absorbers

Thin-walled tubular components are featured in transport structures for increased occupant protection in the event of a crash. However, when the limits of their design are sought through deterministic procedures, components often become unreliable due to uncertainties which may cause them to underperform or even fail. Seeking a deeper understanding of the effect of incertitudes on the thin-walled tubes' performance, this research focuses on the crashworthiness quantification of diverse sources of uncertainties in the progressive collapse of these components under axial loads. For a broader insight on the tubes’ behavior, diversity is considered and scrutinized on all the main fields involved in the research; studying two cross-sections, three sources of uncertainties, and the two epitomical crashworthiness metrics, namely the average and peak crushing loads. The process is undertaken via three different methods, combining analytical formulas, numerical simulations, and surrogate modeling. Results show that the best approximation is offered by the multivariate adaptive regression splines metamodel, yielding similar mean values as with the statistical propagation of the analytical formulas, while the standard deviation is overestimated by 1%–3%. The numerical noise quantified for the simulations results shows oscillation frequencies below 40% and a breadth of three-sigma under 9% for both metrics. The uncertainty quantification of both tubes offers a similar response when studying geometric uncertainties, with the plate thickness having a more relevant effect on the results than diameter or edge length. However, material uncertainties affect the absorbers in an opposite manner, as variations in the elastic modulus contribute the most to the square section metrics, while the circular tube is more affected by variations in the equivalent flow stress. Incertitudes in the operational conditions lead to reduced peak load values when the impact angle varies from a perfect axial collision, consequently delivering reduced mean values and high standard deviations.

Influence of solar drying and storage conditions on microstructure, crack propagation and nano-hardness of paddy and wheat

The influence of hybrid solar drying (HSD) and storage conditions on microstructure, crack propagation, nano-hardness and milling indices of paddy and wheat grains were investigated. Milling yield and head rice yield of dried paddy was 71.48% and 72.42%, which was further increased by 1–1.26% and 3.12–4.65%, respectively. Flour yield from dried wheat was found to be 77.30% and was reduced by 3.5–7.7% after 180 days of storage. Maximum nano-hardness of 0.15 ± 0.02 GPa was obtained for rice stored at 5 °C, whereas, for wheat, nano-hardness, elastic modulus, and peak load values gradually reduced with a storage time of 180 days. Micro-X ray computed tomography images revealed the pore size of paddy and wheat samples to be in the range of 0.01–0.8 mm3. Micrographs showed a compact paddy surface, whereas wheat endosperm witnessed cell disruption and agglomeration.

Research on Peak Load Shifting Based on Energy Storage and Air Conditioning Load in Power Grid

In order to reduce the difference between peak load and off-peak load in summer and reduce the capacity of traditional energy storage system, an optimization strategy based on the coordinated control of battery energy storage system and air conditioning load was considered. Firstly, the control strategy of energy storage system based on threshold method considering electric storage capacity is proposed, and the dynamic changing process of air conditioning system setting temperature value is established to change the electric power of air conditioning system, that is, the virtual energy storage charging and discharging process of air conditioning system, the strategy of direct reduction and early charging of air-conditioning system are proposed. Secondly, the evaluation index of peak load cutting and valley filling is established, which emphasizes the local key of peak load and valley value. Finally, based on the theoretical analysis, taking a typical daily load forecasting curve of a commercial park as an example, the optimization strategy of coordinated control of battery energy storage system and air conditioning load is compared and analysed to verify its feasibility, it provides a basis for the application of battery energy storage system and air conditioning load in peak shaving and valley filling.

Nano-Indentation Response of Ultrahigh Molecular Weight Polyethylene (UHMWPE): A Detailed Analysis.

Nano-indentation, a depth sensing technique, is a useful and exciting tool to investigate the surface mechanical properties of a wide range of materials, particularly polymers. Knowledge of the influence of experimental conditions employed during nano-indentation on the resultant nano-mechanical response is very important for the successful design of engineering components with appropriate surface properties. In this work, nano-indentation experiments were carried out by selecting various values of frequency, amplitude, contact depth, strain rate, holding time, and peak load. The results showed a significant effect of amplitude, frequency, and strain rate on the hardness and modulus of the considered polymer, ultrahigh molecular weight polyethylene (UHMWPE). Load-displacement curves showed a shift towards the lower indentation depths along with an increase in peak load by increasing the indentation amplitude or strain rate. The results also revealed the strong dependence of hardness and modulus on the holding time. The experimental data of creep depth as a function of holding time was successfully fitted with a logarithmic creep model (R2 ≥ 0.98). In order to remove the creeping effect and the nose problem, recommended holding times were proposed for the investigated polymer as a function of different applied loads.

Combination Design of Time-Dependent Magnetic Field and Magnetic Nanocomposites to Guide Cell Behavior.

The concept of magnetic guidance is still challenging and has opened a wide range of perspectives in the field of tissue engineering. In this context, magnetic nanocomposites consisting of a poly(ε-caprolactone) (PCL) matrix and iron oxide (Fe3O4) nanoparticles were designed and manufactured for bone tissue engineering. The mechanical properties of PCL/Fe3O4 (80/20 w/w) nanocomposites were first assessed through small punch tests. The inclusion of Fe3O4 nanoparticles improved the punching properties as the values of peak load were higher than those obtained for the neat PCL without significantly affecting the work to failure. The effect of a time-dependent magnetic field on the adhesion, proliferation, and differentiation of human mesenchymal stem cells (hMSCs) was analyzed. The Alamar Blue assay, confocal laser scanning microscopy, and image analysis (i.e., shape factor) provided information on cell adhesion and viability over time, whereas the normalized alkaline phosphatase activity (ALP/DNA) demonstrated that the combination of a time-dependent field with magnetic nanocomposites (PCL/Fe3O4 Mag) influenced cell differentiation. Furthermore, in terms of extracellular signal-regulated kinase (ERK)1/2 phosphorylation, an insight into the role of the magnetic stimulation was reported, also demonstrating a strong effect due the combination of the magnetic field with PCL/Fe3O4 nanocomposites (PCL/Fe3O4 Mag).

Effect of microcapsules addition on impact properties of carbon fiber reinforced polymer and glass fiber reinforced polymer composites

Fiber reinforced composites are ubiquitous in the aerospace and automobile industries due to their significant superior characteristics such as strength to weight ratio, corrosion resistance, fatigue resistance, specific strength and specific modulus. Impact is common kind of damage found in aircraft and automobile structures. The cause of damage may be sudden strike from a bird, falling of tool during servicing or striking of debris during transportation. Hence, predicting the behavior of composites under impact is necessary and also some mechanism to repair these damages should be found. So, this work aims at determining the effect of inclusion of microcapsules containing healing agents on impact behavior of Fiber Reinforced Polymer (FRP) composite. The resin stuffed and hardener stuffed microcapsules were prepared by in-situ polymerization. These capsules of diameter ranging from 0.19 µm to 0.30 µm were mixed in epoxy resin system during the manufacturing of FRP laminates. Experimental investigation was performed under ambient conditions to observe the variation in impact properties of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) composites. It was observed that value of peak load was boosted with addition of capsules and more energy was absorbed during elastic deformation and less during plastic deformation. Also, partial healing was observed due to addition of capsules at 2.5 wt. %.

Simulation of Cold Forming of Spur Gears using DEFORM 3D

In the current study, the DEFORM3D program was used to simulation of cold forming of spur gears using lead metal. Three different forms of billets were used to forming the spur gear and the choose of the size of billets was determined according to the size of suggested gear in this study. Analyzes were performed such as effect of stress, strain, average stress, total distance and speed during the formation process. Through the results of the values ​​of the average stresses for the three billets, it was observed that the lowest value is obtained when using a solid billet. As indicated by the results of the study of the maximum stress occurs when the use of hollow billet with a diameter of 4 mm. In the study of effective stress, it was observed that there was a convergence in the stress values ​​for all work pieces; these values ​​in the age zone are greater than the center area. The results obtained from numerical modeling showed that the minimum effective strain occurs when using a hollow billet with a diameter of 4 mm and the highest value when using a solid billet. The velocity of the metal flow is proportional with the shape of the billet, it is noted that the value of the velocity in the case of hollow billets (4 mm and 6 mm) was close together and higher than the value of the metal flow velocity when using a solid billet. The speed of the metal flow is proportional with the amount of the billet cavity; in the case of the hard solid billet the speed is low. Peak load is affected during the formation of the spur gear with the shape of billet; it was observed that the peak load values ​​of the 4 mm hollow billet were less than the peak load of the other two cases.

The crashworthiness performance of stacking sequence on filament wound hybrid composite energy absorption tube subjected to quasi-static compression load

This study investigates the energy absorption response of hybrid kenaf/glass fibre-reinforced epoxy when subjected to an axial quasi-static compression load with the effect of three stacking sequence of hybrid kenaf/glass reinforced epoxy. To characterise and evaluate the physical and mechanical properties, the hybrid composite tube was compared with synthetic glass fibre-reinforced epoxy. The hybrid and synthetic composites tube sampling were prepared by using automated filament winding technique which it provides the process with a proper fabricating procedure, quality control and stable process due to the mixture/ratio of the fibre and resin volume controlled by the winding speed and fibre tension. Crashworthiness mechanism of hybrid and synthetic composite tubes specimen were discussed to understand failure modes behaviour and energy absorption characteristics in term of quasi-static compressive response. Four different failure modes were observed in crushing tests as fibre/resin fracturing, local buckling, brittle fracturing and delamination. In the view of fibre stacking sequence aspect, fibre volume fraction in the hybrid specimen (HTS45-A) is a highest compared to other specimen and at the same time alleviates the capabilities in progressive failure with the significant increase 28% of initial peak load and 68% of the energy absorbed compared to the glass fibre-reinforced epoxy tube. Meanwhile, the glass fibre-reinforced tube showed the greatest specific energy absorption characteristics with the lowest initial peak load value with stability in progressive crushing behaviour. Also, experimental results have showed that kenaf fibre could be utilised as a potential reinforcement material in hybridisation with synthetic glass fibre composites as energy absorption tube application.

Energy analysis and energy planning for kindergartens based on data analysis

The aim of the study was to utilize different building data for prediction of development in energy use of a typical building type. In this study, energy use and its future development for kindergartens in Trondheim, Norway, were analyzed. The energy use data were retrieved from the energy monitoring platform of Trondheim Municipality. The total area of all the kindergartens was about 76 000 m2, where the area of each kindergarten was ranging from 100 – 4 471 m2. Firstly, typical heat and electricity duration curves per m2 of kindergartens in Trondheim within six years were identified. Secondly, the kindergartens were divided into two cohorts based on their connection to district heating (DH). The average total annual energy use was 177 kWh/m2 for kindergartens without DH, and 168 kWh/m2 for kindergartens connected to DH. The peak load values were similar for both cohorts, about 140 W/m2. Analysis of the duration curves showed a bigger electricity load variation for the kindergartens without DH connection. Within the building cohort with DH, three cases were found depending on the energy share from DH; i.e. DH high share, DH average share, and DH low share. By following different background data for CO2 factors of electricity and local DH, the kindergarten with DH high share had almost the lowest annual CO2 emission. Contrarily, the annual CO2 emission of a kindergarten with lower share of DH, or without DH, usually had a wider range of emissions due to its dependence of the electricity production mix. Finally, a prediction was made by assuming 14.2 % growth rate of kindergartens on the ground of the average six-year total kindergarten area. The result showed that if more than 50-67 % of the new building area would be connected to DH, a smaller increase of CO2 emission from the projected area could be achieved, depending on the relevant CO2 factors. This proved that buildings with DH were more robust than the one without DH concerning CO2 emission. The suggested analysis method and identified duration curves could be used to as a reference example for defining energy profiles of other building types. These profiles are necessary for diversifying and upgrading local energy supply pathways, infrastructure sizing, and improving urban energy planning.

The response of heat-treatable filler on non-heat-treatable aluminum alloy substrate against age hardening cycle for intelligent development of surface welded joints using TIG welding process

A more realistic approach is handpicked to scrutinize the weld strength of surface joints using tungsten inert gas welding for repair work. Due to the increased application of non-heat-treatable aluminum alloy (AA5182) in automobile structures, tensile weld strength is tested against heat-treatable filler (AA6061) at three age hardening temperatures (i.e., 170 °C, 200 °C, 230 °C) and times (i.e., 4, 5, 6 h). A convincing increase in peak load value is spotted by increasing the temperature and time, the highest value of 14.06 kN is witnessed at 170 °C and 6 h along with 30.42% improvement in joint strength in contrast to without age hardening state. Comparable high peak load (i.e., 13.89 kN and 13.87 kN) values were also obtained for 200 °C and 230 °C at 4 h but afterward depicted a declining trend at 5 and 6 h. An important macrocharacteristic examination of an inside fused region has represented an area of 42.71% which has comparatively shown a negligible difference of percentage with other specimens. From the regional microstructure perspective, two evidential mechanisms were involved in the strengthening, which includes the adjusted network of grain boundary morphology and the precipitation of Mg2Si which upsurge the growth during age hardening. In addition, the apprehension behind the declining behavior at high temperature is explicatively exemplified from scanning electron microscope micrographs which clinch the coalescence of small voids and the evaporation of Mg from surface as an ultimate reason.

Effect of experimental conditions on nano-indentation response of low density polyethylene (LDPE)

Nano-indentation is an interesting tool for analyzing nano-scale mechanical properties. The analysis of nano-mechanical properties as a function of experimental conditions is very critical for designing engineering components. In this study, nano-indentation experiments were performed by considering different values of amplitude (1, 5, 10 nm), frequency (11.2, 22.5, 45 Hz), strain rate (0.02, 0.05, 0.1, 0.2, 1 s−1), peak load (10, 30, 100 mN) and hold time (1, 3, 5, 10, 20, 50, 100 sec) to analyze their effect on the mechanical properties of LDPE. The results showed that the effect of amplitude and frequency on the nano-mechanical properties of LDPE were negligible. Load-displacement curves displayed a shift towards higher indentation depths along with a decrease in peak load from 20.6 to 14.8 mN by having a decrease in strain rate from 1 to 0.02 s−1. Elastic modulus and hardness values exhibited a decrease with an increase in hold time. Logarithmic creep model was used to fit the experimental data of creep as a function of holding time which showed good agreement (r2 ≥ 0.97) with the experimental values. Recommended holding times are also suggested to eliminate the creep and nose problem in order to achieve high accuracy in measurements.

An experimental and numerical study on CLT panels used as infill shear walls for RC buildings retrofit

Abstract Cross Laminated Timber (CLT) has been gaining more and more attention in research and professional fields as a sustainable and promising construction system for mid- and high-rise structures. The need of buildings higher than those usually built with CLT has pushed the research towards the development of innovative hybrid techniques in which steel framed structures incorporate CLT shear walls. This concept may be potentially extended to existing RC framed buildings, where CLT infill shear walls may constitute the base of an integrated seismic and energy retrofit. In order to investigate this potentiality, this paper presents a preliminary experimental and numerical study focused on the mechanical behavior of CLT panels used as a bracing system. In particular, diagonal compression tests on 3-ply panels have been carried out, also by reproducing a direct load transmission from the RC frame to the CLT infill. A comparison with the results of similar tests on CLT panels (with a different number of layers and thickness) and with unstrengthened and strengthened masonry infill walls has been also provided. In addition, numerical simulations have been carried out, in order to evaluate the changes in RC frame lateral response when CLT infills are added. The results have proved that CLT infills may be used as a strengthening solution, allowing RC frame to reach higher lateral stiffness and peak load values respect to masonry infills.