Testing Machine Research Articles

The Effect of 3D Printing Layer Thickness and Post-Polymerization Time on the Flexural Strength and Hardness of Denture Base Resins

Purpose: This study evaluates and compares the effect of printing layer thickness (LT) and post-polymerization time (PPT) on the flexural strength and hardness of three 3D-printed resins after thermal aging. Methods: A bar shape (64 × 10 × 3.3 mm) and a disc shape (15 × 2 mm) were designed for flexural strength and hardness testing, respectively. ASIGA, NextDent, and FormLabs 3D-printed resins were used to print specimens with different LTs (25 µm, 50 µm, and 100 µm). Each thickness group was post-polymerized (PP) for different times (15, 30, 60, and 90 min). All printed specimens were thermally cycled (5000 cycles) and then tested, measuring the flexural strength and hardness using a universal testing machine and Vickers hardness tester, respectively. The data were analyzed using ANOVA and a post hoc Tukey’s test (α = 0.05). Results: A PPT of 90 min showed the highest flexural strength. In comparisons of the LTs, 25 µm and 50 µm significantly increased flexural strength compared with 100 µm, which showed the lowest value for each PPT. The hardness increased as the PPT increased for all materials. In our LT comparison, 25 µm and 50 µm significantly increased the hardness for NextDent and FormLabs resins, while only 25 µm showed high hardness compared with 50 µm and 100 µm for ASIGA. Conclusion: Both parameters (LT and PPT) impact flexural strength and hardness. Increased PPT with the minimum LT is recommended.

A novel intralamellar semi‐bioresorbable keratoprosthesis—Part B: Surface functionalization and physico‐chemical characterization toward site‐specific cellular activity

AbstractIn this article, site‐specific functionalized keratoprosthesis (KPro) was accomplished to meet epithelial on‐growth on the anterior optical surface, inhibit cell adhesion on the posterior optic surface, and promote cell ingrowth at the peripheral tissue‐haptic‐flange interface toward tissue integration. Gelatin immobilization on PC4 hydrogel surfaces was achieved through acid hydrolysis followed by EDC/NHS chemistry, and polyethylene glycol‐diacrylate (PEGDA)‐modified inter‐penetrating network (IPN) surfaces were prepared using photo‐polymerization of ethylene glycol‐diacrylate (EGDA) for enhancing and inhibiting cellular growth, respectively. The surface chemical structures of modified hydrogels were characterized using attenuated total reflectance‐infrared (ATR‐IR) spectroscopy and a bicinchoninic acid (BCA) protein adsorption assay. Further, suitable differentially functionalized surfaces were prepared and characterized using the universal testing machine (UTM), refractometer, atomic force microscopy (AFM), and contact angle measurements to understand mechanical, optical, surface morphological, and wettability properties, respectively. Finally, in vitro site‐specific cell adhesion, cell inhibition, and cell ingrowth functionalities were tested using isolated goat corneal limbal epithelial stem cells and corneal stromal fibroblast cells, respectively. Overall, the two connective articles represent a successful endeavor to develop a more esthetically pleasing, mechanically stable, tissue‐free hydrogel KPro with site‐specific surface functionality nearly mimicking the cornea's functionality. A further pre‐clinical investigation is necessary to advance this functional novel KPro to reality, especially the tissue integration aspect.

THE EFFECT OF CEMENTED FEMORAL COMPONENT DESIGN AND PROPHYLACTIC WIRE PLACEMENT AGAINST EARLY PERIPROSTHETIC FEMORAL FRACTURE IN PRIMARY TOTAL HIP ARTHROPLASTY: A BIOMECHANICAL STUDY

Previous studies have highlighted differences in the risk of periprosthetic fracture between tapered slip (TS) and composite beam (CB) stems. This biomechanical study explored periprosthetic fractures around these stems and the effect of adding a 16-gauge calcar or diaphyseal wire to TS stems on their resistance to torque.A power analysis determined a sample size of 7 specimens per group, assuming a standard deviation of 14.8 Nm in peak torque, to provide 90% power to detect a difference of at least 30 Nm between groups. Twenty-one TS stems (eight alone, six with calcar wiring, seven with diaphyseal wiring placed 2 cm distal to the lesser trochanter) and seven CB stems were cemented into standard Sawbones. A servo-hydraulic test machine applied a 1000 N load with a 1-degree rotation per second until failure. The peak torque at failure was measured, and the fracture location recorded. Comparisons were performed using two-sample t-tests.CB stems exhibited a significantly higher peak torque at failure (205.3 Nm) than TS stems (159.5 Nm, p=0.020). Calcar-wire-TS (148.2 Nm, p=0.036) and diaphyseal-wire-TS (164.9 Nm, p=0.036) were both weaker than CB stems. Wired-TS stems showed no significant difference from non-wired-TS stems. Additionally, the study could not conclude that calcar wiring is stronger than diaphyseal wiring. All TS fractures occurred at the mid-stem, simulating a B-type fracture, while the addition of the diaphyseal wire shifted the fracture location more distally in four of seven stems (p=0.0699).This biomechanical study supports the clinical evidence that CB stems have stronger resistance to torque than TS stems and may explain lower risk of periprosthetic fracture. The addition of calcar or diaphyseal wires to TS stems resulted in no significant changes in peak torque to fracture. In patients at high risk of periprosthetic fracture, CB cemented stems should be considered.

Low temperature tensile behavior and microstructure analysis of copper containing antibacterial stainless steel

Using Shimadzu AGS-100KN universal tensile testing machine, tensile tests were conducted on copper containing antibacterial stainless steel at 25 °C, −20 °C, −60 °C, −100 °C, and −140 °C. The fracture morphology and microstructure evolution of the material were then analyzed using various techniques including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. The experimental findings showed that with the decrease of deformation temperature, the ultimate tensile strength(UTS) increased by about 49.7 %, the yield strength (YS) increased by about 35.5 %, and the elongation(EI) decreased by about 27.3 %, showed obvious low temperature strengthening effect. The High-angle grain boundaries (HAGBs) increased with decreasing temperature, while low-angle grain boundaries (LAGBs) decreased. The plasticity gradually decreased and the strength gradually increased, resulting in an increase in its ability to resist deformation. The number of precipitated phases gradually increased, and the size also gradually becomes larger, and the interaction between the diffusely distributed precipitated phases and dislocations led to precipitation strengthening. With the decrease of temperature, the stacking fault energy gradually decreased, the SFE was 21.26 mJ/m2 at the temperature of −140 °C. The main plastic deformation mechanism of copper-containing austenitic stainless steel in the low-temperature tensile process was transformed from deformation twins to strain-induced martensitic phase transformation.

Comparison of Optical Properties and Fracture Loads of Multilayer Monolithic Zirconia Crowns with Different Yttria Levels.

Multilayer monolithic zirconia, which incorporates polychromatic layers that mimic natural tooth gradients, offers enhanced aesthetics and functionality while reducing debonding risks and improving fabrication efficiency. However, uncertainties remain regarding the fracture characteristics of multilayer monolithic zirconia crowns under occlusal loading, whether composed of uniform or combined yttria levels. The current study investigated how variations in yttria levels and thicknesses affected the optical properties and fracture loads of multilayer monolithic zirconia. Samples of multilayer monolithic zirconia in the Vita A1 shade were used, while employing 3Y (SZ) and 4Y + 5Y (AZ) yttria levels. The optical properties, including the color difference (ΔEWS) and translucency parameters (TP00), were measured using a digital colorimeter. The fracture loads were analyzed using a universal testing machine, and fractured surfaces were examined under a stereomicroscope. Statistical analyses assessed the impacts of the yttria levels and sample thicknesses on the optical properties. The ΔEWS values of SZ ranged 3.6 to 4.0, while for AZ, ΔEWS at 0.5 mm was 3.9 and <2.6 for other thicknesses. The TP00 values decreased with an increased thickness, with AZ generally exhibiting greater translucency than SZ. In the fracture load investigations, SZ (>1600 N) generally exceeded AZ (>1260 N), with fracture loads notably increasing with thickness, particularly for premolars (SZ > 3270 N, AZ > 2257 N). SZ predominantly exhibited partial and complete fractures, whereas AZ showed fewer non-fracture categorizations. Complete fractures began with dense, irregular cracks that extended outward to reveal smooth surfaces, while premolars subjected to higher loads exhibited concentric ripple-like structures. Partial fractures revealed radial textures indicative of areas of stress concentration. In summary, higher yttria levels were correlated with increased translucency, while variations in the fracture loads primarily stemmed from differences in the tooth position or thickness. Overall, multilayer monolithic zirconia incorporating combined yttria levels of 4Y + 5Y (AZ) offered high translucency, precise color matching, and substantial fracture resistance, rendering it highly suitable for aesthetic and functional dental applications.

Impact of recycling on efficiency and efficacy of copper nickel titanium wire and heat activated nickel titanium wire – An invitro study

The aim of the study is to assess the feasibility of reusing copper nickel titanium wire and heat activated nickel titanium wires by evaluating the changes in efficiency and efficacy of wire after different sterilization techniques. 120 total samples were taken. 60 samples of Damon copper nickel titanium (ORMCOTM) and 60 samples of heat activated nickel titanium wires (ORMCOTM). Damon CuNiTi and HANT were divided in 4 different sub groups of 15 samples each. 15 as received wires served as controlled group. The remaining wires were placed intraorally for a period of 4 weeks in patients undergoing orthodontic treatment. After 4 weeks, these wires were taken out. Remaining 45 wires were divided on the basis of sterilization method to be used. (autoclave, 70% isopropyl alcohol, 2% glutaraldehyde solution). Maximum load and tensile strength were tested using universal testing machine. No significant difference in mechanical properties of wires after various sterilization process (p value &amp;#62; 0.05). There no such difference in mechanical properties of controlled group wires and wires those are placed intraorally for 4 weeks. Results suggested that there was no statistically significant difference in the Ultimate Tensile Strength and Maximum Load of Damon Copper Nickel-Titanium wire and Heat Activated Nickel Titanium wire following various sterilization procedures. These wires can be reused after sterilization.

Reaching for 90:90:90 in Correctional Facilities in South Africa and Zambia: Virtual Cross-Section of Coverage of HIV Testing and Antiretroviral Therapy During Universal Test and Treat Implementation.

People in correctional settings are a key population for HIV epidemic control. We sought to demonstrate scale-up of universal test and treat in correctional facilities in South Africa and Zambia through a virtual cross-sectional analysis. We used routine data on 2 dates: At the start of universal test and treat implementation (time 1, T1) and 1 year later (time 2, T2). We obtained correctional facility census lists for the selected dates and matched HIV testing and treatment data to generate virtual cross-sections of HIV care continuum indicators. In the South African site, there were 4193 and 3868 people in the facility at times T1 and T2; 43% and 36% were matched with HIV testing or treatment data, respectively. At T1 and T2, respectively, 1803 (43%) and 1386 (36%) had known HIV status, 804 (19%) and 845 (21%) were known to be living with HIV, and 60% and 56% of those with known HIV were receiving antiretroviral therapy (ART). In the Zambian site, there were 1467 and 1366 people in the facility at times T1 and T2; 58% and 92% were matched with HIV testing or treatment data, respectively. At T1 and T2, respectively, 857 (59%) and 1263 (92%) had known HIV status, 277 (19%) and 647 (47%) were known to be living with HIV, and 68% and 68% of those with known HIV were receiving ART. This virtual cross-sectional analysis identified gaps in HIV testing coverage, and ART initiation that was not clearly demonstrated by prior cohort-based studies.

Deep learning based enhanced secure emergency video streaming approach by leveraging blockchain technology for Vehicular AdHoc 5G Networks

VANET is a category of MANET that aims to provide wireless communication. It increases the safety of roads and passengers. Millions of people lose their precious lives in accidents yearly, millions are injured, and others incur disability daily. Emergency vehicles need clear roads to reach their destination faster to save lives. Video streaming can be more effective as compared to textual messages and warnings. To address this issue, we proposed a methodology to use visual sensors, cameras, and OBU to record emergency videos. Initially, the frames are detected. After re-recording, the frames detection algorithm detects the specific event from the video frames. Blockchain encrypts an emergency or specific event using hashing algorithms in the second layer of our proposed framework. In the third layer of the proposed methodology, encrypted video is broadcast with the help of 5G wireless technology to the connected nodes in the VANET. The dataset used in this research comprises up to 72 video sequences averaging about 120 seconds per video. All videos have different traffic conditions and vehicles. The ResNet-50 model is used for the feature extraction process of extracted frames. The model is trained using Tensorflow and Keras deep learning models. The Elbow method finds the optimal K number for the K Means model. This data is split into training and testing. 70% is reserved for training the support vector machine (SVM) model and test datasets, while 30%. 98% accuracy is achieved with 98% precision and 99% recall as results for the proposed methodology.

Effect of scanning strategy and laser peening on microstructure and fatigue properties of laser-directed energy deposition-built 15-5 PH stainless steel

Purpose The aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless steel with U and V notches. The study specifically concentrates on the evaluation of effect of scan strategy, machining and LSP processing on microstructural, texture evolution and fatigue behaviour of LDED-printed 15-5 PH steel. Design/methodology/approach For LSP treatment, 15-5 PH steel was printed using LDED process with bidirectional scanning strategy (XX [θ = 0°) and XY [θ = 90°]) at optimised laser power of 600 W with a scanning speed of 300 mm/min and a powder feed rate of 3 g/min. Furthermore, LSP treatment was conducted on the V- and U-notched fatigue specimens extracted from LDED-built samples at laser energy of 3.5 J with a pulse width of 10 ns using laser spot diameter of 3 mm. Post to the LSP treatment, the surface roughness, fatigue life assessment and microstructural evolution analysis is performed. For this, different advanced characterisation techniques are used, such as scanning electron microscopy attached with electron backscatter diffraction for microstructure and texture, X-ray diffraction for residual stress (RS) and structure information, Vicker’s hardness tester for microhardness and universal testing machine for low-cycle fatigue. Findings It is observed that both scanning strategies during the LDED printing of 15-5 PH steel and laser peening have played significant role in fatigue life. Specimens with the XY printing strategy shows higher fatigue life as compared to XX with both U- and V-notched conditions. Furthermore, machining and LSP treatment led to a significant improvement of fatigue life for both scanning strategies with U and V notches. The extent of increase in fatigue life for both XX and XY scanning strategy with V notch is found to be higher than U notch after LSP treatment, though without LSP samples with U notch have a higher fatigue life. As fabricated sample is found to have the lowest fatigue life as compared to machines and laser peened with both scan strategies. Originality/value This study presents an innovative method to improve the fatigue life of 15-5 PH stainless steel by changing the microstructure, texture and RS with the adoption of a suitable scanning strategy, machining and LSP treatment as post-processing. The combination of preferred microstructure and compressive RS in LDED-printed 15-5 PH stainless steel achieved with a synergy between microstructure and RS, which is responsible to improve the fatigue life. This can be adopted for the futuristic application of LDED-printed 15-5 PH stainless steel for different applications in aerospace and other industries. Graphical abstract

Effects of moisture content on the behaviour of Scots pine heartwood and sapwood under impact

The material properties of sapwood and heartwood vary within various wood species and even they can show significant differences within a single tree. Scots pine (Pinus sylvestris L.), a species that plays a crucial role in timber production for joinery and building construction applications, is among those that show a notable distinction between its heartwood and sapwood. To examine the influence of moisture content (MC) on the impact behaviour of the sapwood and heartwood of pine, we tested specimens with two distinct moisture levels: a low moisture content (LMC) group with 12% MC and a high moisture content (HMC) group with 45% MC. In our study, we investigated deflection, normal strain and force development of the specimens during the short period of an impact, and also calculated the impact bending strength (IBS) of samples, using an impact testing machine equipped with a high-speed camera and digital image correlation method. Our results indicate that the differences between sapwood and heartwood at LMC were insignificant in the case of maximum deflection and normal strain, thus there is no need for differentiation; however, these differences became more pronounced, and non-negligible, with an increase in MC. We also evaluated the IBS of both heartwood and sapwood and found that, at LMC, heartwood had greater impact bending strength than sapwood, making it a preferable choice as a material subjected to impact loadings. Conversely, at HMC, both heartwood and sapwood would be equally strong against impacts, indicating that pine green wood shows no sensitivity to the ratio of sapwood to heartwood in the tree.

Numerical and experimental investigation of pre-damaged composite stiffened panel under axial compression

The purpose of this paper is to investigate the calculation method and failure mechanisms of composite stiffened panel with pre-damage. The pre-debonding specimen’s failure process is performed by a universal testing machine (UTM) and the failure mechanisms are analyzed using scanning electron microscope (SEM). Together with cohesive zone model (CZM), the finite element method (FEM) is used to simulate the damage evolution of the specimens. In addition, a novel theoretical method is proposed to calculate the bearing capacity of composite stiffened panels. It is found that the failure mode simulated by FEM is consistent with the experimental analysis. Compared with the experimental values, the maximum result error of FEM and theoretical method is 7.9 %. This paper provides a reference for the research of composite stiffened panels with debonding defect.

Are physical and mechanical properties of 3D resins dependent on the manufacturing method?

This research analyzed the effect of the manufacturing method on the flexural strength and color stability of 3D-printed resins used for producing indirect restorations. For this, two dental restorative biocompatible resin materials, OnX (OnX, SprintRay) and CB (Crown and Bridge, Dentca), were divided into 2 groups according with manufacturing method (printed with a Pro95 3D printer - SprintRay; and not printed, with samples obtained with the fluid resin being poured on PVS molds for further light activation in the post-curing process), and subdivided into 2 groups according to the post-curing method: VG (Valo Grand, Ultradent Products) for 120s and PC (Procure 2, SprintRay). Bar-shaped samples were used to evaluate the flexural strength 24h after storage in distilled water at 37°C using a universal testing machine. Disk-shaped samples were used to evaluate the color stability with a spectrophotometer at baseline, after 1-7days in dark dry storage at 37°C, and after 1day of artificial aging in water at 60°C. Data were evaluated using 3-way ANOVA (flexural strength) and 4-way repeated measures ANOVA (color stability), followed by the Tukey's HSD test (α = .05). Flexural strength showed significant results for resin (p < .001), while manufacturing and post-curing methods were not significant (p > .05). The interaction effects between resin and manufacturing method (p = .978), and between resin, manufacturing method and post-curing method (p = .659) were not significant. In general, OnX showed higher flexural strength values than CB, regardless of manufacturing method or post-curing protocol. Color stability results showed significant results for resin (p < .001), time (p < .001), resin and time (p = .029), and resin and curing method (p < .001), but no differences considering resin and manufacturing mode (p = .87), or resin, manufacturing method and curing method (p = .35). In general, OnX showed a higher color change than CB, longer storage times resulted in increased color change for both materials, and CB cured with VG showed lower color alteration than CB cured with PC2. The manufacturing method (3D printed or not 3D printed) does not seem to influence the flexural strength and color stability of 3D printed resins. This may indicate that, at least from a physical-mechanical perspective, the final properties of the material are mainly dependent on the post-curing process.

Effect of Nano Α-Mno2 Addition on Thermal Decomposition and Compressive Properties of Epoxy

The ability of a nanocomposite material to withstand high temperatures and maintain strength is crucial for the design of products and processes. This research examined the thermal decompositionand compressive properties of α-MnO2/epoxy polymer nanocomposites. The samples were created using a simple, inexpensive solution technique. The scanning electron microscope, X-ray diffraction, and energy-dispersive X-ray analysis indicated the formation of α-MnO2 nanosheets. The thermal analysis revealed that the addition of α-MnO2 increased the glass transition temperature of the epoxy. Thermogravimetric analysis showed that the residue was left at 550°C for a sample of pure epoxy with a loading of 0.1 wt.%. 0.2 wt.%, 0.3 wt.%, and 0.5 wt.% of α-MnO2 were 9.55%, 11.05%, 16.78%, 17.37%, and 21.20%, respectively. As a result, the nanocomposites were more thermally stable than pure epoxy. The compressive characteristics were tested using a universal testing machine. Compression test results showed that the addition of α-MnO2decreased the compressive properties of the epoxy matrix. However, the brittleness of nanocomposites increased. Images captured at the microscopic level showed that the sample cracked and fractured during testing. The reduced compressive property values was associated with reduced α-MnO2dispersion in the epoxy, the shape of α-MnO2nanosheets, and the generation of air voids during the synthesis process. As a result, the α-MnO2 nanosheets reduce the compressive properties of the nanocomposites by acting as stress enhancers. The nanocomposite can be used as a thermal heat-resistant material.

Effect of Er:YAG laser surface treatment on surface properties and shear-bond strength of resin-cement to three translucent zirconia: an in-vitro study

Achieving optimal bonding to translucent zirconia poses certain challenges as there is no consensus on ideal surface treatment method. Therefore, the aim of present investigation is to evaluate effect of Er:YAG laser treatment on wettability, surface roughness and shear-bond strength of three Yttrium oxide-stabilized zirconium-oxide polycrystal translucent zirconias. 120 specimens (n = 40/zirconia type) were prepared from three commercially-available translucent zirconias (Dentsply Sirona, USA); Translucent, High-Translucent and Ultra-Translucent zirconia. Specimens were sub-divided (n = 20/surface-treatment) into control and Er:YAG laser surface-treated groups. Regarding water wettability test; goniometer was used to measure contact angle before and after laser treatment. Surface roughness was measured using atomic force microscope. For shear-bond strength (SBS) test; the control group was sandblasted. All resin-bonded zirconia specimens were thermocycled for 5000 cycle and subjected to shear force using universal testing machine with 0.5 mm/min crosshead-speed. Results were statistically analyzed using two-way-analysis-of- variance (p ≤ 0.05). There was significant decrease in average contact angles (p-value < 0.001) in all zirconia groups after laser treatment. For roughness test; insignificant difference in average Ra in Translucent zirconia group. However, significant increase in mean Ra was revealed after laser treatment for High and Ultra-Translucent zirconias. For SBS test, results revealed insignificant difference in average bond strength after laser treatment in Translucent and High-translucent zirconia groups. Significant increase in mean bond strength of Ultra-Translucent zirconia was recorded. Er: YAG laser treatment significantly affected surface properties and shear-bond strength of Ultra-Translucent zirconia. Er:YAG laser irradiation may be a promising zirconia surface treatment method.Graphical

Strain rate-dependency of thermal infrared radiation of sandstone subjected to dynamic loading: Insights from a lab testing

Rocks are generally deformed and fractured upon various scales of strain rates. Understanding the strain rate effects on the thermal infrared radiation (IR) characteristics of rock materials is crucial for predicting and detecting rock failure. In the study, uniaxial compression experiments were conducted on sandstone samples at different strain rates using an Instron hydraulic servo testing machine and a split Hopkinson pressure bar (SHPB) system. Meanwhile, a thermal infrared camera was utilized to capture and record the changes in the IR temperature on the rock surface. The spatial and temporal evolution of thermograms, IR temperature distribution histograms, and average IR temperature (AIRT) during testing were obtained and analyzed. A quantitative correlation between strain rate and the variation in AIRT (ΔT) was established. Furthermore, the dissipation of heat energy (Q) in the sandstone samples during SHPB tests was estimated. Results indicated that at relatively lower strain rates (ranging from 10−6 to 10−2 s−1), the ΔT of rock sample exhibited slight dependence on strain rate. However, a significant rate sensitivity emerged when the strain rate exceeded a specific threshold (approximately 137.09 s−1 for the tested sandstone). The rate-dependent behavior of ΔT across the investigated range of strain rate (up to 102) can be characterized by an allometric power model. Notably, during SHPB testing, the proportion of Q was negligible despite the pronounced rate dependency of heat energy. The abrupt rises in ΔT and Q under dynamic loading conditions can be elucidated by the increasing occurrence of shear cracks and energy-level jumps stimulated by impact disturbance.

The influence of process parameters and carbon nanotubes on composite material joints

AbstractThrough resistance welding experiments, the effects of process parameters and heating elements (HE) on the welding strength of carbon fiber reinforced polyamide 6 (CF/PA6) composites were studied. Stainless steel mesh was used as the heating element for welding CF/PA6 composites. The mechanical properties of the weld were tested using a universal testing machine, and the internal structure and fracture of the joint were analyzed by scanning electron microscopy (SEM). The optimal parameters for welding CF/PA6 composites were determined. In addition, the growth of carbon nanotubes (CNTs) on the surface of the metal mesh significantly improved the welding strength, from 14.016 to 16.31 MPa. The experimental results showed that the optimal parameters included 22A current, 0.3 MPa pressure and 35 s welding time, and the optimal specification of the metal mesh heating element was 200 mesh. The burning time of the metal mesh was 10 s, and the optimum pickling time was 30 s.Highlights The matrix of the composite material is nylon 6. Improved the experimental process for growing carbon nanotubes. Explore the influence of burning time on welding effect through detection.

Pengaruh Penambahan Serat Ampas Tebu Sebagai Tulangan Micro pada Beton

Based on this research, concrete has high compressive strength but low flexural strength. There-fore, the addition of sugarcane bagasse fibers is carried out as an additive to overcome the low flexural strength issue in concrete. This study aims to determine the effect of adding sugarcane bagasse fibers on the characteristics of concrete, including compressive and flexural strength. Fiber-reinforced concrete is a composite material consisting of regular concrete and other mate-rials, such as natural or artificial fibers. The method used in this research is an experimental method, adding 1% of sugarcane bagasse fibers by weight of cement to the normal concrete with a target strength of F'c 19.3 MPa and fiber length of 5 cm. The samples used in this research are concrete cylinders and beams tested using a Universal Testing Machine. The research results show that the optimum compressive strength of normal concrete is 20.36 MPa at 28 days of age. Meanwhile, for fiber-reinforced concrete BSTC and BSTH, the compressive strengths are 17.83 MPa and 16.49 MPa, respectively, indicating a decrease compared to the normal concrete. This decrease is attributed to the addition of sugarcane bagasse fibers, which are lightweight addi-tives and not solid aggregates, resulting in some voids in the sugarcane bagasse fibers. The re-sults of the flexural strength testing show that the optimum flexural strength of BSTC is 4.44 MPa, and for BSTH, it is 4.09 MPa, while the normal concrete (BN) only achieves 3.61 MPa. This is due to the increased bonding effect in concrete caused by the addition of fibers, which helps to resist the occurrence of cracks during flexural testing

Effect of number of triggers and shape of crash box on energy absorption during experimental collision

The capacity of passenger car crash boxes to absorb energy during crashes has been the subject of extensive research, which started with the creation of multiple crash box models, changes in crash box filling, and the inclusion of crash box triggers. On the other hand, no research has been done on the combination of axle trigger holes, nine-cell columns, and crash box models. The results of the experiment on the energy-absorbing capacity of AA6061-T4 crash box specimens under compressive loads are presented in this paper. The compression tests were conducted on a Universal Testing Machine with a maximum force capability of 1000 kN and a speed capability of 5 mm/s. Three models are used in crash box modeling. A cross-section of the model with a round hole-shaped trigger variation is included in these three versions. It is established that the hexagonal Frusta type with two holes absorbs the highest energy at 33.30 kJ, and has a displacement of 4.12 mm and a maximum force of 348.5 kN. The energy absorption capacity of the crash box was found to be increased by combining frusta versions of the hexagon model with two holes and nine-cell column filling.

Influence of Gamma-Phase Aluminum Oxide Nanopowder and Polyester-Glass Recyclate Filler on the Destruction Process of Composite Materials Reinforced by Glass Fiber.

Recycling of composite materials is an important global issue due to the wide use of these materials in many industries. Waste management options are being explored. Mechanical recycling is one of the methods that allows obtaining polyester-glass recyclate in powder form as a result of appropriate crushing and grinding of waste. Due to the fact that the properties of composites can be easily modified by adding various types of fillers and nanofillers, this is one of the ways to improve the properties of such complex composite materials. This article presents the strength parameters of composites with the addition of fillers in the form of polyester-glass recyclate and a nanofiller in the form of gamma-phase aluminum nanopowder. To analyze the obtained results, Kolmogorov-Sinai (K-S) metric entropy was used to determine the transition from the elastic to the viscoelastic state in materials without and with the addition of nanoaluminum, during a static tensile test. The tests included samples with the addition of fillers and nanofillers, as well as a base sample without any additives. The article presents the strength parameters obtained from a testing machine during a static tensile test. Additionally, the acoustic emission method was used during the research. Thanks to which, graphs of the effective value of the electrical signal (RMS) were prepared as a function of time, the parameters were previously identified as extremely useful for analyzing the destruction process of composite materials. The values obtained from the K-S metric entropy method and the acoustic emission method were plotted on sample stretching graphs. The influence of the nanofiller and filler on these parameters was also analyzed. The presented results showed that the aluminum nanoadditive did not increase the strength parameters of the composite with recyclate as a result of the addition of aluminum nanofiller; however, its addition influenced the operational parameters, which is reflected in a 5% increase in the UTS value (from 55% to 60%).

Comparison of the flexural strength of printed and milled denture base materials

BackgroundTo evaluate the flexural strength of digitally milled and printed denture base materials.MethodsThe materials tested were Lucitone 199 denture base disc (Dentsply Sirona), AvaDent denture base puck (AvaDent), KeyMill denture base disc (Keystone), Lucitone digital print denture base resin (Dentsply Sirona), Formlab denture base resin (Formlabs), and Dentca base resin II (Dentca). Sixty bar-shaped specimens of each material were prepared for flexural strength testing and were divided into five groups: control, thermocycled, fatigue cycled, and repair using two different materials. The flexural strength and modulus were tested using a 3-point bend test performed on an Instron Universal Testing Machine with a 1kN load cell. The specimens were centered under a loading apparatus with a perpendicular alignment. The loading rate was a crosshead speed of 0.5 mm/min. Each specimen was loaded with a force until failure occurred. A one-way ANOVA test was used to analyze the data, followed by Tukey’s HSD test (α = 0.05).ResultsThe milled materials exhibited higher flexural strength than the printed materials. Thermocycling and fatigue reduce the flexural strengths of printed and milled materials. The repaired groups exhibited flexural strengths of 32.80% and 30.67% of the original flexural strengths of printed and milled materials, respectively. Nevertheless, the type of repair material affected the flexural strength of the printed materials; the composite resin exhibited higher flexural strength values than the acrylic resin.ConclusionsThe milled denture base materials showed higher flexural strength than the printed ones.