Point Bending Test Research Articles

Structural Behavior of Kenaf Fibre Reinforced Concrete Beams

This paper presents the effect of kenaf fibres in reinforced concrete beams. In investigating the structural behaviour of the beams, four point bending test was conducted on five beams by considering two distinct parameters (i) shear reinforcement arrangement (ii) the amount of kenaf fibres in the aforementioned beams. The beams consists of Two beams with full shear reinforcement by two amount of kenaf fibres, 10kg/m³ and 20kg/m³, respectively and two other beams with 50% increased shear spacing with two different amount of kenaf fibre 10 kg/m³ and 20 kg/m³ were examined. A control beam is made of 0 kg/m³ kenaf fibre with full shear reinforcement. The experimental results suggests that beams with the inclusion of kenaf fibres demonstrates significant increase on the load carrying capacity, ductility and shear strength. Moreover, it was observed that the mode of failure is altered from shear mode to bending mode. Furthermore, this study opines that kenaf fibres are compatible with RC which yields promising results.

Experimental evaluation of scatter in fracture stress of silicate glass and its thickness dependence

Glass is widely used in various structural application, where a transparent, durable, and stiff material is needed. Although glass is primarily not a load-bearing member in applications, however, even in common usage of glass as windows panes it is exposed to loads, such as wind loads, thermal and other mechanical loads, and may also be exposed to vibratory, impact and blast loading. However, these materials are brittle in nature and cannot withstand thermal loads beyond a certain limit. Moreover, there is a substantial scatter in their fracture stress and the median values of fracture stress is dependent upon the thickness of the specimen used in the tests. In order to study the effect of specimen thickness on fracture stress and its scatter, several experiments have been conducted on different thickness of glass material. Three point bend test was conducted on various glass specimens of 4 mm and 8 mm thickness to ascertain the scatter in the fracture strength of the glass specimen. A lot of scatter in the fracture strength of the glass specimen was observed which is attributed to the presence of micro crack on the surface of the glass specimen. Scatter in fracture stress is higher for 8 mm thickness of glass as compared to 4 mm glass specimen. It was seen that the cumulative experiment probability of fracture strength of glass follows a Weibull model. It was seen that the fracture strength of the glass reduces from 46 MPa to 40 MPa with the increase in thickness from 4 mm to 8 mm respectively indicating the decrease in fracture toughness with increasing thickness.

Earth-based building materials reinforced with flax fibers: an experimental investigation

Climate change has led to a notable shift towards sustainable design practices within the civil engineering community. In this context, earth-based building materials are particularly advantageous as they are locally sourced, easily recyclable and exhibit low levels of embodied and operational energy. Therefore, this work presents an experimental investigation of compressed earth materials reinforced with natural flax fibers. The primary objective is to investigate the influence of the embedded fibers on both the mechanical and thermal properties of the material with the aim of developing a novel type of masonry earth brick. Samples made of two types of earth (namely, a clayey silt Bouisset and a sandy silt Nagen), incorporating distinct percentages of fibers, were statically compacted at a target dry density of 1900 kg/m3 inside a metallic mould with dimensions of 40×40×160 mm3. The samples were then subjected to 3-point bending tests and compression tests, as well as thermal conductivity tests. Results indicate that the addition of fibers improves the samples’ compressive and bending strength, especially for the Nagen earth. Instead, the inclusion of fibers has a negligible effect on thermal conductivity and diffusivity. Only for the Bouisset earth, the thermal diffusivity improves with increasing fiber content, thus resulting in faster heat transfers.

Study of Post-Spalling Reinforced Concrete Beam Repair Using Grouting and GFRP Reinforcement

Reinforced concrete beams must meet strength and durability standards, but aggressive environmental factors are the main cause of corrosion, which can affect the strength and durability of building structures. Maintenance, retrofitting, and reinforcement of structures are important to ensure safety. It is necessary to take appropriate measures to address corrosion problems in building structures early on. One way to achieve this is by repairing damaged structures using more modern and effective technologies and materials. This study aims to determine the flexural behavior of reinforced concrete (RC) beams repaired with Sikagrout-215 material and reinforced with GFRP sheets with different layer configurations. The study used three RC beams as the control group, three RC beams coated with Sikagrout-215 mortar, and six RC beams reinforced with GFRP. All beams were subjected to 4-point bending tests to determine their load capacity, crack response, ductility, and energy absorption capacity. The results showed that repair with grouting decreased the load capacity, while reinforcement with a combination of mortar grouting and GFRP increased the maximum load. Reinforcement of the support region could restore the function of the beam by 9.3%. Among the three types of reinforcement, BGRST significantly improved the first crack response, yield response, and ultimate performance of the RC beams. Beam fracture occurred more frequently with Sikagrout-215 mortar reinforcement, while reinforcement with GFRP composites partially protected the load capacity after fracture. Doi: 10.28991/CEJ-2024-010-01-08 Full Text: PDF

Monitoring of a prestressed bridge girder with integrated distributed fiber optic sensors

Several research projects carry out experiments on a newly built 45 m long research bridge, called openLAB. This contribution showcases the synergetic collaboration of the two research projects IDA-KI and smart_tendon in a joint experimental investigation on one of the openLAB’s 15 m long precast and prestressed girders, which was tested in a 4-point bending test prior to its installation into the bridge. The girder was equipped with distributed fiber optic sensors (DFOS) prior to casting, as DFOS provide detailed insights into the structure’s inner with unprecedented spatial resolution. The suitability of different installation methods for structural health monitoring applications from the beginning of the structures’ existence was studied. DFOS were either embedded in the concrete matrix, glued to the longitudinal reinforcement, included in prestressing strands in direct bond or inside strands of a post tensioned tendon. Robust DFOS with a monolithic cross-section, integrated directly into the concrete matrix, enable reliable crack monitoring and anomaly detection. DFOS integrated into tendons allow for efficient construction progress without the need for additional trades. Strain profiles in the linear elastic state can be accurately mapped. A transition to the cracked state is indicated by a disproportionate strain increase.

Artificial neural network approach to predict asphalt mixtures’ stiffness modulus based on testing frequency and temperature

To successfully guarantee the proper durability and serviceability of asphalt pavements, it is crucial to investigate asphalt mixtures’ performance and to design an accurate model to predict their mechanical behaviour. In Machine Learning, Artificial Neural Networks (ANNs) consist of a set of layered and interconnected artificial neurons capable of learning a complex function that maps the input to the target output. This study is specifically aimed at their implementation within the field of pavement engineering. The paper thoroughly discusses the development of an ANN-based methodology capable of predicting the stiffness modulus of an asphalt mixture (AM). The AM under investigation was prepared with spilite aggregate, a 50/70 penetration grade bitumen, and limestone filler. The volumetric properties of each specimen were first determined, and then the sequence of a 4-Point Bending Test was carried out under different conditions. Four testing temperatures (0, 10, 20, 30 °C) and eleven loading frequencies (0.1, 1, 2, 3, 5, 10, 15, 20, 30 and 50 Hz) were selected to investigate the asphalt mixture's mechanical behaviour. The resulting stiffness moduli represented the output of the designed neural model. Prediction accuracy was evaluated utilizing several goodness-of-fit metrics, and the results of this feasibility study proved to be very encouraging. They are certainly limited to the asphalt mixture under investigation. However, the high level of accuracy suggests that trained on a larger dataset, the developed methodology could allow the AMs’ mechanical behaviour to be predicted without the need to carry out the conventional tests that are usually expensive and time-consuming.

RC beams externally strengthened by steel plates: experimental database and preliminary analysis

External steel plating is a popular technique for the flexural strengthening of RC beams thanks to the ease of application which does not require skilled labor, the relatively low-cost and the optimal mechanical properties of the steel material. Research on externally plated RC beams is much older than the literature related to the strengthening methods employing fiber reinforced (FRP) materials which were more recently developed. Despite this, the number of FRP applications is far greater than those available for steel applications, as also corroborated by the widespread of several international guidelines for the FRP strengthening design of RC structures. Conversely, the in-situ applications with steel plates are still very common and often preferred to FRPs, but they are not well supported by clear design indications. This paper contributes to filling this knowledge gap by presenting the results of a preliminary study on the flexural performance of steel-plated RC beams. A large experimental database was compiled from the literature, which includes three/four- point bending tests performed on RC members variably reinforced with external steel plates. The database is in-depth examined by considering the following main parameters: layout of the external steel plating, shape of beam’s cross section, mechanical percentages of both external steel plate and beam’s longitudinal steel reinforcement in tension, and failure mode. The collected data is useful for a theoretical study on beams’ flexural performance, which is under preparation.

Comparison of Mechanical Properties of Samples Fabricated by Stereolithography and Fused Deposition Modelling

Additive manufacturing (AM) technology has attracted significant attention with the rapid fabri-cation of 3D parts for various applications. With fused deposition modeling (FDM) and stereo-lithography (SLA), the most used methods in this technology, it is possible to produce functional parts with complex shapes quickly and cheaply. Determining the mechanical properties of the parts produced by these methods is important in terms of efficient operation in the relevant fields. This study, 45 test specimens were fabricated using three different polymer materials (UVR, PLA, and ABS) in SLA and FDM type 3D printers, including tensile, compression, and 3-point bending tests. Samples are printed at a 75% fill rate according to ASTM standards. Experimental studies were carried out to determine the mechanical properties of the samples. Among the samples, the highest strength values in tensile, compression and bending test samples made of UVR material were 60.39 MPa, 127.74 MPa and 118.35 MPa, respectively. In addition to mechanical properties, hardness, and SEM analyses were performed to examine the surface roughness, surface topography, and composition of the samples. As a result, the effects on the mechanical properties of the samples fabricated by the UVR-based SLA method and the PLA-ABS-based FDM method were examined and compared.

Materialising structural optimisation of reinforced concrete beams through digital fabrication

This study tackles the design, fabrication and testing of truss-like reinforced concrete beams. The paper introduces the strut optimisation method, a Eurocode 2-compliant design procedure which allows to optimise the shear strength of beams. The procedure is embedded in a numerical workflow that automates the design and fabrication of beams. Through a parametric study, potential concrete savings of 24% to 64% are estimated. A digital manufacturing workflow is presented. It is based on the 3D printing of recyclable clay moulds allowing to cast the hollowed-out parts truss-like elements. The fabrication of a 3 m-long prototype illustrates the implementation of the process. Four-point bending tests made on SOM-optimised specimens validate the compliance between the empirical behaviour and the theoretical model, paving the way for wider adoption of materially-efficient reinforced concrete beams.

Flexural strength, surface roughness, and biofilm formation of ceramic-reinforced PEEK: An in vitro comparative study.

This in vitro study aimed to compare flexural strength, surface roughness, and biofilm formation of ceramic-reinforced PEEK with conventionally heat-compressed and milled polymethylmethacrylate (PMMA) denture base materials. Thirty strips (6.4×10×3 mm) and 30 discs (10×1 mm) were fabricated from a heat-compressed PMMA, milled PMMA, and ceramic-reinforced PEEK, 10 each. One surface of each sample was polished to mimic the laboratory procedure for denture base materials. Strips were then subjected to a 3-point bend test using a universal testing machine at a crosshead speed of 5.0 mm/min. An optical profilometer was used to assess the Ra value (mm) of the discs on polished and unpolished sides. Biofilm formation behavior was analyzed by measuring the colony-forming unit (CFU)/ml of Candida albicans on the unpolished surface of the discs. One-way ANOVA followed by Tukey multiple comparison tests were used to compare the flexural strength, Ra value, and biofilm formation of the studied materials (a = 0.05). Ceramic-reinforced PEEK showed significantly higher flexural strength (178.2 ±3.2 MPa) than milled PMMA (89.6 ±0.8 MPa; P<0.001) and heat-compressed PMMA (67.3 ±5.3 MPa; P<0.001). Ceramic-reinforced PEEK exhibited a significantly higher Ra value than the other groups on unpolished sides; however, the polishing process significantly reduced the Ra values of all studied groups (P<0.05). There was no significant difference in Candida albicans adhesion among the groups (P<0.05). The flexural strength of tested materials was within acceptable limits for clinical use as a denture base material. Ceramic-reinforced PEEK had the highest surface roughness; however, its similarity in biofilm formation to other groups indicates its clinical acceptability as denture base material. This article is protected by copyright. All rights reserved.

Fracture Prediction of Aluminum Alloy Sheet AA2024-T3 Using Analytical Stress and Experimental Strain Based Failure Criteria

In this work, the fracture prediction of aluminium alloy sheet, grade AA2024-T3 was investigated using the Fracture Forming Limit Curve (FFLC) and Analytical Fracture Forming Limit Stress Curve (FFLSC) as failure criteria. Initially, the FFLC was experimentally achieved by means of the Nakajima Stretch forming test coupled with GOM strain measurement system, providing the Digital Image Correlation (DIC) technique. Subsequently, the analytical FFLSC was plastically computed using experimental FFLC data combination with Swift hardening model and anisotropic Hill’48 yield model for representing anisotropic plastic deformation behaviour on examined sheet. Finally, Fukui stretch drawing and Three point bending tests were conducted both experiment and numerical simulation to evaluate the fracture state and verifying an applicability of obtained FFLC and FFLSC. In the simulation, the ABAQUS 2017 element deletion function was employed for directly implementing the fracture criteria regarding the FFLC and FFLSC. It was concluded that the analytical FFLSC could more realistically predict fracture behaviour better than the FFLC based on strain. In term of percentage error, the analytical FFLSC generated an error less than the FFLC.

Patellar Fracture Forces Are Not Affected by Proximal Versus Distal Bone Block Anterior Cruciate Ligament Reconstruction Harvest Sites in a Cadaveric Model

To quantify the maximum load to fracture in patellae from which bone-patellar tendon-bone (BPTB) and bone-quadriceps tendon (BQT) autografts have been harvested for anterior cruciate ligament reconstruction in a cadaveric model. Forty-six fresh-frozen patellae were isolated and divided into the BPTB harvest and BQT harvest groups with matching based on donor age and sex. Computed tomography scans were obtained to calculate bone mineral density (BMD) and patellar height, width, and thickness. BPTB and BQT grafts were harvested from the inferior patella and superior patella, respectively, and then ramped to failure in a 3-point bend test configuration to simulate a postoperative fracture produced by a direct impact after a fall. The presence of fracture, fracture pattern, and maximum load to fracture were recorded. Donor demographic characteristics; patellar height, width, and thickness; and maximum load were compared by the Student t test. Pearson correlations were used to determine whether maximum load was affected by BMD or patellar morphology. The level of significance was set at P < .05. Maximum load to fracture was not significantly different (P= .91) between the BPTB (5.0 ± 2.3 kN) and BQT (5.1 ± 2.6 kN) groups. Maximum loadto fracture in the BPTB group did not correlate with BMD (P= .57) or patellar measurements (P= .57 for thickness, P= .43 for width, and P= .45 for height). Maximum load to fracture in the BQT group positively correlated with BMD and negatively correlated with patellar height. Maximum load to fracture in the BQT group did not correlate with patellar thickness or width. Fracture through the harvest site was observed in 87% of BPTB specimens and 78% of BQT specimens. The location of the BPTB or BQT autograft harvest site did not significantly affect patellar load to fracture in a cadaveric model. It is important to understand patellar morphology and the effect of BPTB and BQT graft harvest-site locations on the biomechanical strength of the patella after anterior cruciate ligament reconstruction.

Unveiling the mechanics of deep-sea sponge-inspired tubular metamaterials: Exploring bending, radial, and axial mechanical behavior

Strengthened tubular structures have had a significant impact on various industries. Advancements in aircraft, construction, medical implants, robotics, and renewable energy have improved safety, efficiency, and durability in multiple sectors. This work explores the practical applications of medical health, using nasal swabs as an example, under different loading scenarios. The study focuses on incorporating bioinspired structural elements, drawing inspiration from the skeletal lattice of sea sponges. By utilizing the sea sponge's process of trial and error in evolution, this bioinspired approach provides a promising perspective on enhancing the mechanical performance of tubular structures. To evaluate the mechanical advantages of the bioinspired design approach, we conducted 3-point bending, radial, and axial compression tests on 3D printed tubular lattice structures. The tests showed that the tubular structure, inspired by sponges, displayed improved bending properties and was approximately twice as stiff as traditional tubular designs. Furthermore, the sponge-inspired design exhibits significantly higher strength and toughness compared to traditional designs, with approximate improvements of 3 and 4 times, respectively. Numerical simulations revealed that these enhancements are attributed to the strengthening effect of diagonally double diagonal struts, which distribute stress evenly and allow for bending without excessive stress concentration. The bio-inspired design shows improved resistance to radial and axial loading, with approximately 1.3 and 3 times greater radial/axial compression stiffness compared to unreinforced designs. These improved mechanical properties of sea sponge-inspired tubular metamaterials make them suitable for a wide range of applications.

Original Research Article Effect of Radiotherapy on Flexural Strength of Luting Cementsan In Vitro Study

Aim - The aim of this study was to evaluate changes in the flexural strength of luting cements due to radiotherapy. Methodology- Total of 90 rectangular specimens of 25×2×2 mm dimension were fabricated by utilizing the putty consistency polyvinyl siloxane rubber mould. They were grouped based on their type. Group A included 30 specimens made of zinc phosphate cement, Group B included 30 specimens fabricated using glass ionomer luting cement, and Group C consisted of 30 specimen’s fabricated using resin luting cement. Once the specimens were set, they were stored in distilled water between the experiments. After 24 hours, 15 from each group of the mentioned cements were subjected to irradiation fractionally upto 60 Gy by a Cobalt-60 external beam machine. Remaining specimens from each group were used as controls. After radiotherapy, the specimens were stored in distil water for 24 hours until performing the 3 point bend test. All the specimens were subjected to 3 point bend test on universal testing machine for checking flexural strength. Statistics- Kruskal Wallis Test followed by Mann Whitney test as post hoc analysis was used to compare the mean values of different parameters between three groups of Irradiated and controlled samples. The level of significance was set at P&lt;0.05. Results- After exposure to fractional irradiation for 4 weeks, in the zinc phosphate luting cement (Group-A) and glass ionomer luting cement (Group-B), showed a slight decrease in flexural strength. The resin luting cement (Group-C) showed slight increase in flexural strength. Conclusion- Among all the groups, the resin luting cement showed a slight increase in flexural strength when compared to the other luting cement groups after fractional irradiation

The role of controlled voids shape on the flexural properties of 3D printed food: an approach for tailoring their mechanical properties

ABSTRACTThe study of the mechanical properties of 3D printed food is crucial for food personalisation. Texture impacts the sensory experience along the oral food consumption. This work aimed to investigate the mechanical properties of post-processed printed food samples with different porosity topologies (triangled-shape/squared-shape). Image analysis showed changes in the structure before and after post-processing. The mechanical properties characterised via 3-point bending tests revealed that triangle-shaped topologies presented lower strength (20% less) and higher flexural stiffness (≈20%) when compared to the square-shaped topologies. A qualitative comparison of the porosity topologies and their role in the stiffness of structures under tensile and bending loads was performed via finite element models. The flexural stiffness varied between the triangle-shaped designs (13–35%) but remained almost constant for square-shaped designs (40–43%). The results presented in this work showed that the mechanical properties of 3D-printed food could be modified by the selection of porosity topology.

Comparison of tensile properties and porcelain bond strength in metal frameworks fabricated by selective laser melting using three different Co-Cr alloy powders

Statement of problemThe selective laser melting (SLM) manufacturing technique has been widely employed to produce Co-Cr dental metal frameworks. The selection of Co-Cr alloy powders has the potential to influence the microstructure and tensile properties, consequently impacting the bond strength of the metal-porcelain. However, limited information is available regarding the effect of Co-Cr alloy powder on these properties when all other factors remain consistent. PurposeThe purpose of this in vitro study was to assess how the choice of Co-Cr alloys during SLM manufacturing influences the microstructure, tensile properties, and bond strength of metal-ceramic combinations. Material and methodsThree different Co-Cr alloy powders, Co-Cr-Mo, Co-Cr-Mo-W, and Co-Cr-W were selected in this study. The powder characteristics and chemical compositions were analyzed using a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis, respectively. Subsequently, 12×12×15-mm cube specimens, cylindrical tensile test specimens, and 25×3×0.5-mm metal strips were fabricated using the SLM technique. Microstructural investigations of the cube specimens were conducted after metallographic preparation using SEM. The cylindrical tensile specimens (n=8) from each composition were subjected to tensile tests at a deformation rate of 0.5 mm/min. Following the application of ceramic to the metal specimens (n=10) in each group, the strength of the metal-ceramic bond was evaluated through a 3-point bend test conducted at a crosshead speed of 1 mm/min. Mechanical properties obtained from the tensile tests and bond strength values were statistically analyzed using a one-way ANOVA and Tukey post hoc comparison tests (α=.05). ResultsMelt pool boundaries, columnar and equiaxed grains, and precipitates were observed in the microstructures of 3 different alloys produced by SLM. The Co-Cr-Mo-W alloy had more uniformly dispersed and finely distributed precipitates compared with other alloy compositions. The Co-Cr-Mo-W alloy had exhibited the highest yield strength (1068.0 ±41.2 MPa) and ultimate tensile strength (1263.4 ±10.7 MPa) while showing the lowest ductility under the tensile tests (6.1 ±0.9%) among all 3 alloys. Significant differences in the tensile mechanical properties were observed in the alloys except between the yield strength of the Co-Cr-Mo and Co-Cr-W alloys. The highest elongation (8.9 ±1.2%) was seen in the Co-Cr-Mo alloy. However, no significant differences were detected regarding the bond strength of all 3 groups (P>.05). The mean bond strength values were approximately 42 MPa for all the alloys. ConclusionsThe results indicate that the selection of different Co-Cr alloy powders used in SLM production may influence both microstructure and tensile properties. However, the strength of the metal-ceramic bond of Co-Cr alloys remained unaffected by this selection.

The Challenges and Advantages of Distributed Fiber Optic Strain Monitoring in and on the Cementitious Matrix of Concrete Beams

Distributed fiber optic strain measurement techniques have become increasingly important in recent years, especially in the field of structural health monitoring of reinforced concrete structures. Numerous publications show the various monitoring possibilities from bridges to special heavy structures. The present study is intended to demonstrate the possibilities, but also the challenges, of distributed fiber optic strain measurement in reinforced concrete structures. For this purpose, concrete beams for 3-point bending tests were equipped with optical fibers on the reinforcement and concrete surface as well as in the concrete matrix in order to record the strains in the compression and tension zone. In parallel, an analytical approach based on the maximum strains in the uncracked and cracked states was performed using the Eurocode 2 interpolation coefficient. In principle, the structural design correlates with the measured values, but the strains are underestimated, especially in the cracked zone. During load increase, structural distortions in the compression zone affected the strain signal, making reliable evaluation in this zone difficult. The information content of distributed fiber optic strain measurement in reinforced concrete structures can offer tremendous opportunities. Future research should consider all aspects of the bond, sensor selection and positioning. In addition, there is a lack of information on the long-term stability of the joint and the fiber coating, as well as the effects of dynamic loading.

Macroscopic material degradation model of Norway spruce clear wood for XFEM

The study aims at investigating the failure behavior of Norway spruce clear wood specimens using XFEM by modeling earlywood and latewood growth rings. The growth ring pattern in the specimens are determined using a photo-analytical processing program. For the simulations, 6 damage initiation mechanisms were considered and the subroutines were implemented in the finite element solver ABAQUS. A normal vector to the crack surface is calculated for each damage mode, taking into account the orientation of the maximum and minimum principal stresses. The XFEM model and the material properties are calibrated based on experiments, where the edge-notched specimens were subjected to 3-point bending, tensile and compression tests. The goal is to determine the ultimate load, locate structural weakpoints and obtaining a realistic crack propagation path by means of XFEM.

Impact bending strength of thermally-modified timber

Abstract The article offers a perspective on how thermal-modification affects the impact bending strength of five different wood species, an aspect that has not received as much attention as the well-studied static load behavior of thermally-modified timber (TMT). Since the TMTs are mainly employed as outdoor materials, where they may encounter impact forces, a comparative investigation into the flexibility and strength of these materials under impact is useful. This article evaluates different aspects of the TMT, such as deflection, strain in the impact region, the maximum force needed to initiate cracks, and the energy required for rupture. Wood planks from ash, beech, larch, oak, and spruce were thermally modified at 180 and 220 °C. They were cut into test specimens, while a separate set of unmodified specimens from each wood species served as the reference group. The specimens were subjected to an impact 3-point bending test, and an ultra-high-speed camera meticulously recorded the results. The images were processed by the digital image correlation (DIC) method to determine the deflection and strain distribution of the beams during the impact test. The deflection, maximum force, maximum longitudinal strain, and required work for rupture of each group were determined. The results showed that thermal-modification decreases the wood deflection and maximum longitudinal strain by approximately 50 %. In addition, the impact bending strength decreased by nearly 60 %. However, the impact bending strength did not exhibit a statistically significant decrease at 180 °C; in some cases, it even increased.

Failure of Porcelain Coating on Milled and SLM Fabricated Titanium Alloy with Different Surface Treatment

The present paper aimed at investigating the influence of surface treatment on the failure of porcelain coating on Ti6Al4V alloy fabricated by milling and selective laser melting (SLM). The titanium alloy surface was treated by three different ways: sandblasting, application of a layer of bonding agent and combined (sandblasting and subsequent bond layer). A coating of ultra-low fusing ceramic was fabricated on one surface of the samples. The adhesion of the porcelain to the titanium alloy was investigated by standard 3-point bending test and the failure of the coating was evaluated by optical microscopy. It was found that the type of surface treatment of the titanium alloy affects the failure mechanism of porcelain coating on its surface. In case of all samples, the fracture of the ceramics was observed to occur by a mixed adhesion-cohesion mechanism with a difference in the layer of adhesive or cohesive failures. These differences are greater for the milled alloy compared to its SLM-treated counterpart. In the milled sample, adhesive failure occurs along the metal/oxide layer interface and cohesion through the oxide layer. After sandblasting, both adhesion and cohesion fractures were observed between the oxide layer and the porcelain. In the bond-treated samples, adhesive and cohesive failures were found to occur mainly between the oxide layer and the bond. Most of the specimens treated in a combined way failed cohesively by cracking the ceramic coating. In the control and sandblasted subgroups of the SLM-processed alloy, the porcelain coating was destroyed through adhesive-cohesive route: adhesive along the metal/oxide layer interface, and cohesive through the porcelain. Ceramic fracture in the bond- and combined treated subgroups was observed to occur adhesively along the bond/porcelain interface, and cohesively through the bond and porcelain.