Tensile Testing Machine Research Articles

Fracture mechanism of 316L/BNi-2 brazed joints using experiment and microstructure-based model

Compact components are prone to failure at brazed joints. To ensure the reliability of brazed joints, it is vital to have a comprehensive understanding of the fracture mechanism of brazed joints which can be attributed to highly inhomogeneous microstructures and individual phase mechanical properties. This study measured the stress-strain curve of brazed joint micro-zone of 316L austenitic stainless steel with the BNi-2 filler alloy by a tensile testing machine equipped with a CCD camera. The instrumented indentation technique was used to determine the flow properties of individual phases in joints considering the size effect. Representative volume element (RVE) technology was applied to simulate the mechanical behavior of brazed joints, which was in good agreement with the tested. The fracture of brazed joints can be divided into ductile fracture and brittle fracture which includes the decohesion of the interface between the boride and the austenite matrix and the fragmentation of the boride in terms of the analysis of the morphology of cross-section and fracture surface in brazed joints. According to the stress and strain distribution in the brazing micro-zone, the plastic strain localization cause decohesion, and the stress concentration along the loading direction cause boride fragmentation.

Effect of high energy electric pulse on microstructure and mechanical properties of pre-deformed SUS 304 ultra-thin strip

To improve the mechanical properties of the pre-deformed SUS 304 ultra-thin strip by regulating its microstructure, the paper uses high energy pulsed current to treat the pre-deformed SUS 304 ultra-thin strip. Uniaxial tensile samples with different pre-deformation (10%, 30%, 50%) are prepared by tensile testing machine and used to study the changes in microstructure and mechanical properties of the pre-deformed samples before and after the electric pulse treatment. The results show that the electric pulse treatment results in a complete recovery of plasticity and a 10% increase in elongation at break for the 10% pre-deformed sample, and leads to a 6.8% decrease in yield strength, a 13.2% increase in tensile strength and a 34.4% increase in elongation at break for the 50% pre-deformed sample. The electric pulse treatment causes recovery and static recrystallization of pre-deformed samples at lower temperatures, and some annealing twins are formed within the recrystallized grains. The electric pulse treatment reduces the dislocation density, refines the deformed grains, alleviates the {111} silk texture generated during pre-tensile deformation, and improves the anisotropy. It can be seen that the electric pulse treatment can significantly improve the mechanical properties of pre-deformed samples and promote the plastic deformation capacity of the SUS 304 ultra-thin strip.

Flexural response of 3D printed wood dust reinforced polymer composite

BackgroundThe rising environmental concern and inadequacy of conventional resources have led to increasing demand for new bio composite materials for various products and as a unique substitute for traditional and petroleum-based materials for different applications. The major constraint in most conventional bio composites manufacturing techniques is a mold or complex setup requirement, which leads to a lengthy manufacturing process. 3D printing manufacturing technique has extended a huge attention in current years because of its simplicity in manufacturing complex geometries. Problem StatementThis work is aimed to determine the flexural response of 3D printed wood –PLA composite. MethodDue to PLA's low mechanical properties, wood dust had added to enhance the properties. 22 wt% Wood dust filled PLA filament is procured with a 1.75 mm diameter. Five test samples have been printed with the fused deposited 3D printing technique. The flexural behavior – flexural strength, flexural Strain and flexural modulus, of the developed material, was tested with the help of a universal tensile testing machine. ResultsThe test results revealed the maximum flexural strength of the material is 36 MPa with a maximum Strain of 3.55% and modulus of 1.4 GPa. ConclusionWood dust acts as a filler and has improved the material’s flexibility, also, wood particles make the material porous and that affect the interfacial adhesion between wood and PLA polymer in 3D printing which reduce the strength.

Poster 286: Biomechanical Analysis Evaluating Meniscal Extrusion Following Knotless Suture Anchor Fixation for Segmental Medial Meniscus Allograft Transplantation

Objectives: Segmental medial meniscus allograft transplantation (MAT) has been shown to restore knee biomechanics, however, stable fixation of the transplant is critical to avoid extrusion and maximize healing. The purpose of this study was to evaluate the degree of meniscal extrusion and biomechanical function of segmental MAT performed with meniscocapsular sutures versus repair augmentation with knotless suture anchors. Methods: Ten fresh frozen cadaveric knees underwent central midbody medial meniscectomy (15-mm defect) and subsequently segmental medial MAT. Knees were loaded in a dynamic tensile testing machine to 1000 N for 20 seconds at 0°, 30°, 60°, and 90° of flexion. Four conditions were tested: (1) intact, (2) segmental defect, (3) inside-out segmental repair, and (4) anchors plus inside-out segmental repair of the MAT. Meniscal extrusion was measured for each test state using high-fidelity ultrasound imaging by three independent observers. Submeniscal medial and lateral pressure-mapping sensors assessed the mean contact pressure, peak contact pressure, mean contact area, and pressure mapping. Assessment of inter- and intraobserver reliability of measurements were done using intraclass correlation coefficients. A two-way repeated measures ANOVA was computed in order to evaluate whether there is a significant interaction between meniscal states and knee flexion angles on the outcome variables. If the P value was ≤ 0.05, a pairwise comparison of the means was determined using the Bonferroni method. Results: At 0° of knee flexion, the segmental defect demonstrated the statistically significant higher degree of meniscal extrusion (2.08 mm ± 0.78 mm) compared with intact (1.02 mm ± 0.86 mm, P = 0.039) and anchor plus inside-out segmental repair (1.44 mm ± 0.76 mm, P = 0.044), but not for an inside-out segmental repair (1.55 mm ± 0.49 mm, P = 0.08). The segmental defect state also showed a higher degree of meniscal extrusion compared with all other states at 90° of knee flexion (P < 0.01). There was no difference in the degree of meniscal extrusion between the intact state and the inside-out repair or anchor plus inside-out segmental repair in all knee flexion angles (P > 0.05). Three observers showed good-to-strong intra-rater and moderate-to-strong inter-rater reliabilities for extrusion measurements. There was no significant difference in the mean contact pressure and peak contact pressure among four states in all knee flexion angles for both medial and lateral compartments except for that at 0° of knee flexion, there was a significantly lower peak pressure at the medial compartment after anchor plus inside-out segmental repair compared with the segmental defect state (P = 0.048). The medial contact area of the intact state was significantly higher than the other states at 0° of knee flexion (P < 0.05). However, the lateral contact area after anchor plus inside-out repair showed no significant difference compared with the intact state (P = 0.13). Conclusions: Segmental meniscus transplantation mechanics may be improved at full extension (0° of knee flexion) with the addition of knotless anchors. However, in terms of meniscus extrusion, the knotless anchors provided limited benefit over inside-out repair. Overall, a robust repair is achieved of a segmental meniscus with sutures and knotless anchors. Although, additional work is needed to assess long-term in vivo results.

Biomechanical properties of derma materials for hernioplasty

The most common problem in the surgical treatment of hernias using tension herni-oplasty is a strong tension in the suture area, which can lead to wound dehiscence, de-formation of the hernia area, fistulas and recurrence. Therefore, at present, the technique of tension-free hernioplasty using both synthetic and natural materials is increasingly being used. Natural materials are more reliable due to biocompatibility, lack of cytotoxicity and minimal biodegradation. However, not all biomaterials have the necessary mechani-cal characteristics, such as elasticity and strength. The main goal of this study was a comparative assessment of the biomechanical properties of the acellular dermal matrix, bioplastic material obtained by the methods of detergent-enzymatic and chemical decellu-larization, respectively, and the surgical implant Permacol™. All materials were subjected to histological analysis and quantitative DNA analysis. Strength studies (stress, strain at break and initial modulus of elasticity) were carried out using an Instron 1122 universal tensile testing machine. BIoplastic material showed significantly lower values of defor-mation-strength properties and modulus of elasticity. The obtained results showed that the acellular dermal matrix and the commercial Permacol™ implant are the closest to the native dermis in strength characteristics, however, the histological structure of the acellu-lar dermal matrix is closest to the histological features of the organization of the porcine dermis, which makes this material promising for further research.

Slit tear resistance of leather used in upholstery manufacturing

The paper presents experimental research on the slit tear resistance of leather used for producing upholstery. A finite element analysis is done by simulating the product's behaviour, considering different factors and parameters, and materials are classified according to the normal stress results. The maximum force exerted during the tearing of the specimen has been observed at the SATRA tensile testing machine, with STM 466ST attachment and digital software control. The load at break, the extension at break, Young's Modulus, and the load-distance graphs were registered and the medium values were calculated. The Taguchi method based on orthogonal arrays was used to maximize the material characteristics significant for this type of analysis.

Preparation and Characterization of Non-Crimping Laminated Textile Composites Reinforced with Electrospun Nanofibers.

This research investigated the use of electrospun nanofibers as reinforcing laminates in textiles to enhance their mechanical properties for use as smart and technical textile applications. Crimping plays a crucial role in textiles. Because of crimp, fabrics have extensibility, compressibility, and improved quality. Although crimping is inevitable for fabrics used in smart textiles, it is also a disadvantage as it could weaken the fibers and reduce their strength and efficiency. The study focused on preparing laminated textile composites by electrospinning a polyacrylonitrile (PAN) polymer onto textile fabric. The research examined the effect of electrospun nanofibers on the fabric by using a tensile testing machine and scanning electron microscopy. The results revealed that the prepared laminated textile was crimp-free because of the orientation of the nanofibers directly electrospun on the fabric, which exhibited perfect bonding between the laminates. Additionally, the nanofiber-reinforced composite fabrics demonstrated a 75.5% increase in the elastic moduli and a 20% increase in elongation at breaking. The study concluded that the use of electrospun nanofibers as laminates in textile composites could enhance the elastic properties, and prepared laminated composites will have the advantages of nanofibers, such as crimp-free elastic regions. Furthermore, the mechanical properties of the laminated textile composite were compared with those of the micromechanical models, providing a deeper understanding of the behavior of these laminated composites.

Adhesion of thermal oxide scale formed on silicon-containing hot-rolled steel oxidised in oxygen

Defects can be caused by the thermal oxide scale that forms on the surface of steel during the hot rolling process. The oxidation and adhesion of scale on silicon-containing hot-rolled steel were investigated in a flowing 20% O2-N2 gas mixture at 900°C. Scale spallation was observed using a tensile testing machine equipped with a CCD camera. The thickness of the scale was 3.45 μm for the higher silicon steel and 4.86 μm for the lower silicon steel. The oxide scale consists of hematite, magnetite, wustite, and iron. The strain that caused the first spallation was used to calculate the mechanical adhesion energy, which indicated the behaviour of the scale adhesion on a steel substrate. The strain initiation of the first spallation of scale on higher silicon steel was 5.57% which was higher than 4.57% for lower silicon hot-rolled steel. The calculated adhesion energy on the studied steel was shown to be in the range of 281 J.m-2 to 334 J.m-2. It can be noted that the higher amounts of silicon content in hot-rolled steel increased steel-scale interface adherence. This was due to the precipitated silicon oxide near steel-scale interface might be exhibited as a reinforcing phase.

IMPACT OF ALKALINE TREATMENT ON THE CONSTITUENTS, STRENGTH AND MORPHOLOGICAL CHARACTERISTICS OF BANANA FIBER

The readily availability of natural fibers have made them to be less expensive compared to the synthetic fibers. Hence, highest substitute for synthetic fibers in composites development today is natural fibers. In this research, banana fiber was extracted by dew retting and treated with alkaline for surface modification and possibly strengthening. Both treated and untreated fibers were tested with universal tensile testing machine and examined their surface morphology with scanning electron microscopy. The banana fiber's ultimate tensile strength (UTS) was assessed as a function of fiber diameter, test length and testing speed. It was observed from the results that chemical treatment improved the tensile strength of the fiber while surface morphology was noticed to be rough due to the removal of some fiber constituents. Hence, it was discovered that alkaline treatment improved the fiber condition, thus, making the fiber a suitable substitute for synthetic fibers in composite development

Polypropylene Blends for Highly Drawn Tapes with Improved Toughness.

In this study, we used four amorphous poly-alpha-olefin (APAO) grades to improve the toughness of drawn polypropylene (PP) tapes. The samples containing different amounts of APAOs were drawn in a heat chamber of a tensile testing machine. The APAOs reduced the work of drawing and increased the melting enthalpy of the drawn specimens, as they facilitated the movement of the PP molecules. The APAO with the highest molecular weight and with a low level of crystallinity increased both the tensile strength and the strain-at-break of the specimens, so we also produced drawn tapes from that PP/APAO blend on a continuous-operation stretching line. The continuously drawn tapes also showed improved toughness.

Shear wave elastography correlates to degeneration and stiffness of the long head of the biceps tendon in patients undergoing tenodesis with arthroscopic shoulder surgery

Tendinopathy of the long head of the biceps (LHB) tendon causes degeneration and changes its stiffness. However, a reliable means of diagnosis has not been established. Shear wave elastography (SWE) provides quantitative tissue elasticity measurements. In this study, the relationship of preoperative SWE values with biomechanically measured stiffness and degeneration of the LHB tendon tissue was investigated. LHB tendons were obtained from 18 patients who underwent arthroscopic tenodesis. SWE values were measured preoperatively at 2 sites, proximal to and within the bicipital groove of the LHB tendon. The LHB tendons were detached immediately proximal to the fixed sites and at their superior labrum insertion. Tissue degeneration was histologically quantified using the modified Bonar score. Tendon stiffness was determined using a tensile testing machine. The SWE values of the LHB tendon were 502.1±113.6kPa proximal to the groove and 439.4±123.3kPa within the groove. The stiffness was 39.3±19.2N/mm. The SWE values displayed a moderate positive correlation with the stiffness proximal to the groove (r=0.80) and within it (r=0.72). The SWE value of the LHB tendon within the groove showed a moderate negative correlation with the modified Bonar score (r=-0.74). These findings suggest that preoperative SWE values of the LHB tendon correlate moderately positively with stiffness and moderately negatively with tissue degeneration. Therefore, SWE may predict LHB tendon tissue degeneration and changes in stiffness caused by tendinopathy.

Effect of Reaction Temperature on the Microstructure and Properties of Magnesium Phosphate Chemical Conversion Coatings on Titanium.

Magnesium phosphate (MgP) has garnered growing interest in hard tissue replacement processes due to having similar biological characteristics to calcium phosphate (CaP). In this study, an MgP coating with the newberyite (MgHPO4·3H2O) was prepared on the surface of pure titanium (Ti) using the phosphate chemical conversion (PCC) method. The influence of reaction temperature on the phase composition, microstructure, and properties of coatings was systematically researched with the use of an X-ray diffractometer (XRD), a scanning electron microscope (SEM), a laser scanning confocal microscope (LSCM), a contact angle goniometer, and a tensile testing machine. The formation mechanism of MgP coating on Ti was also explored. In addition, the corrosion resistance of the coatings on Ti was researched by assessing the electrochemical behavior in 0.9% NaCl solution using an electrochemical workstation. The results showed that temperature did not obviously affect the phase composition of the MgP coatings, but affected the growth and nucleation of newberyite crystals. In addition, an increase in reaction temperature had a great impact on properties including surface roughness, thickness, bonding strength, and corrosion resistance. Higher reaction temperatures resulted in more continuous MgP, larger grain size, higher density, and better corrosion resistance.

Effects of Fe and Ni on the Microstructure and High Temperature Tensile Properties of Al-Si Aluminium Alloys

The effects of varied contents of Ni (1.2 wt.%, 1.6 wt.%) and Fe (0.6 wt.%, 0.8 wt.%) on the microstructure and high temperature mechanical properties of Al-Si alloy were studied using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and tensile testing machine. The experimental results demonstrate that Ni element plays a crucial role in modifying the Fe-rich phase type, morphology and distribution in the Al-Si alloy. The addition of 1.2 wt.% Ni and 0.6 wt.% Fe could generate a Chinese script Fe-rich strengthening phase in Al-Si alloy. Further increasing to 1.6 wt.% Ni and 0.8 wt.% Fe, the long needle-shape Fe-rich phase was detected. High temperature tensile properties of the alloy were significantly improved, because of the Chinese script Fe-rich strengthening phase in the Al-Si alloy containing 1.2 wt.% Ni and 0.6 wt.% Fe. The ultimate tensile strength (UTS) of Al-Si alloy with 1.2 wt.%Ni-0.6 wt.% Fe is up to 229 MPa, 174 MPa and 139 MPa at 250 °C, 300 °C and 350 °C, respectively.

The improved thermal and mechanical properties of polyurea nanocomposites with SiC

Polyurea as one kind of polymer is widely used in the field of protective under blast and impact loading. Polyurea matrix with nanofillers has superior mechanical properties than the pure polyurea. In this work, in order to develop polyurea with thermal stability and high mechanical properties, using Silicon carbide (SiC) as the nanofillers, polyurea nanocomposites with different content of SiC nanoparticles were prepared via in-situ polymerization method. The morphology and structure of SiC/polyurea nanocomposites were characterized by using SEM, XRD and FTIR. From the structure studies, the nanofillers of SiC had not altered the basic structure of polyurea. Thermal stability and mechanical properties were also studied by TGA and tensile testing machine, respectively. The results indicated that the incorporation of SiC nanoparticles (1.5 wt%) into polyurea could obviously improve thermal properties and mechanical properties in comparation with the pure polyurea. The enhancement of performance is relative to SiC nanoparticles reinforced polyurea matrix and high temperature properties of SiC. At higher content of SiC, the mechanical properties of SiC/polyurea nanocomposites tend to decrease. It can be inferred from the results that SiC/polyurea nanocomposites have the potential for using in protective structures.

Microstructure and Mechanical Properties of Dissimilar Friction-Welded Commercially Pure Ti and Ti–6Al–4V Alloy

Here, we investigated the microstructure and mechanical properties of dissimilar joints between grade 2 commercially pure titanium (CP-Ti-2) and Ti–6Al–4V alloy welded via friction welding. Accordingly, specimens with 15 mm diameter and 50 mm length were prepared, and friction welding was performed at a constant rotation speed (1600 rpm) and different upset lengths: 1, 2, and 3 mm. Electron backscattered diffraction (EBSD) method was introduced to systematically analyze grain boundary characteristic distributions (GBCDs), such as grain size, grain orientation, phase distribution, and misorientation angle distribution. In addition, mechanical properties of dissimilar joints were evaluated using the micro-Vickers hardness and tensile test machine. The microstructures at both sides of the CP-Ti-2 and Ti–6Al–4V alloy were refined materials, compared with each base material. These grain refinements were determined via dynamic recrystallization accompanied by frictional heat and severe plastic deformation. In addition, the increase in the upset length distinctively affected the change trend of the grain size of the CP-Ti-2 and Ti–6Al–4V alloy. The hardness values in regions around the weld interface were higher than those of base materials. Furthermore, yield and tensile strengths were maintained at a similar level to those of CP-Ti-2, and the tensile specimens were fractured at the base material zone of CP-Ti-2, not at the weld interface and its periphery. Consequently, friction welding to dissimilar joints between the CP-Ti-2 and Ti–6Al–4V alloy was successfully conducted and sound welded materials without welding defects were obtained.

Reanalysis of the Posterior Oblique Ligament: Quantitative Anatomy, Radiographic Markers, and Biomechanical Properties.

The posterior oblique ligament (POL) is the largest structure of the posteromedial knee that is at risk of injury in conjunction with the medial collateral ligament (MCL). Its quantitative anatomy, biomechanical strength, and radiographic location have not been assessed in a single investigation. To evaluate the 3-dimensional and radiographic anatomy of the posteromedial knee and the biomechanical strength of the POL. Descriptive laboratory study. Ten nonpaired fresh-frozen cadaveric knees were dissected and medial structures were elevated off bone, leaving the POL. The anatomic locations of the related structures were recorded with a 3-dimensional coordinate measuring machine. Anteroposterior and lateral radiographs were taken with radiopaque pins inserted into the pertinent landmarks, and the distances between the collected structures were calculated. Each knee was then mounted to a dynamic tensile testing machine, and pull-to-failure testing was performed to record the ultimate tensile strength, stiffness, and failure mechanism. The POL femoral attachment was a mean of 15.4 mm (95% CI, 13.9-16.8 mm) posterior and 6.6 mm (95% CI, 4.4-8.8 mm) proximal to the medial epicondyle. The tibial POL attachment center was a mean of 21.4 mm (95% CI, 18.1-24.6 mm) posterior and 2.2 mm (95% CI, 0.8-3.6 mm) distal to the center of the deep MCL tibial attachment and a mean of 28.6 mm (95% CI, 24.4-32.8 mm) posterior and 41.9 mm (95% CI, 36.8-47.0 mm) proximal to the center of the superficial MCL tibial attachment. On lateral radiographs, the femoral POL was a mean of 17.56 mm (95% CI, 14.83-21.95 mm) distal to the adductor tubercle and 17.32 mm (95% CI, 14.6-21.7 mm) posterosuperior to the medial epicondyle. On the tibial side, the center of the POL attachment was a mean of 4.97 mm (95% CI, 3.85-6.79 mm) distal to the joint line on anteroposterior radiographs and 6.34 mm (95% CI, 5.01-8.48 mm) distal to the tibial joint line on lateral radiographs, at the far posterior tibial aspect. The biomechanical pull-to-failure demonstrated a mean ultimate tensile strength of 225.2 ± 71.0 N and a mean stiffness of 32.2 ± 13.1 N. The anatomic and radiographic locations of the POL and its biomechanical properties were successfully recorded. This information is useful to better understand POL anatomy and biomechanical properties as well as to clinically address an injury with repair or reconstruction.

Mechanical properties and deformation behaviour of TWIP steel at different strain rates

The mechanical properties of TWIP at different strain rates ranging from 5 s−1 to 500 s−1 were investigated by a VHS 160/100-20 high-speed tensile testing machine. The Johnson-Cook (J-C) dynamic constitutive model of TWIP steel was established based on the test results and verified by numerical simulation. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyse the microstructures of TWIP steel before and after tensile deformation. The findings demonstrate that under the tested strain rate, both the tensile strength and yield strength of TWIP steel increase with increasing strain rate, whereas the elongation decreases first and then increases. The strain rate of 100 s−1 is the turning point of the mechanical properties. The stack fault energy (SFE) is 26 mJ m−2 at room temperature, and the microstructure of TWIP steel before and after deformation is composed of single austenite, which demonstrates that only TWIP effect occurs. Dislocations accumulate along grain boundaries, forming structures such as dislocation cells and dislocation walls, causing stress concentration and promoting the formation of microcracks. With increasing strain rate, the dislocation cells are more obvious, and the thickness of the deformation twins decreases, resulting in an increase in the stress required for dislocations to cross the twin boundaries and material strengthening. The formation of nanoscale twins can not only effectively hinder the dislocation motion, but also provide space for dislocation slip and change the grain orientation, so that the slip system which is not conducive to deformation has a new orientation, resulting in a synergistic effect on strength and plasticity of TWIP steel. This work elucidates the relationship between the microscopic deformation mechanism and the macroscopic mechanical properties of TWIP steel at a specific strain rate, and a dynamic constitutive model is established, which can provide a reference for the application of TWIP steel in the design of anti-explosion and anti-impact structures.

THE INFLUENCE OF WELDING TYPE ON THE STRENGTH CHARACTERISTICS OF CONNECTIONS OF REINFORCING BARS WITH A METAL PLATE

Introduction. In reinforced concrete structures, the ends of reinforcing bars are anchored in the concrete by launching the reinforcement beyond the considered section for the length of the force transfer zone from the reinforcement to the concrete as well as by using anchoring devices. If the required design length of the reinforcement cannot be ensured, special measures to anchor the reinforcement bars are applied [1, p. 5.36]. One of these measures is to install special anchoring devices in the form of plates at the ends of the longitudinal bars. When anchoring devices in the form of plates, special attention is paid to the welding type of the plate with the bar, which should prevent the bar from being pulled out when longitudinal forces from external load are applied. Materials and methodology. The material to be investigated was reinforcing bars of class A500C with diameters of 25 and 32 mm, connected at the ends to metal plates by means of contact welding. Holes with a diameter equal to the diameter of the reinforcement were drilled in the metal plates. The bars were inserted into the holes flush with the surface of the plates and welded to the plates by one and double sided welding. A total of two bars were used per welded joint. The strength of welded connection of reinforcing bars with plates was determined on the tensile testing machine HMS-100 by applying maximum tensile force to reinforcing bars. The fracture pattern of each reinforcing bar to plate joint was noted. The results of the experiment. As a result of the experiment, it was found that the destruction of the connection between the two reinforcing bars of 25 mm and 32 mm diameter and the metal plate during one-sided welding occurred by destroying the welding connection and pulling the bars out of the plate. When the bars were joined on both sides, there was no pulling out of the plate. In this case, one 25-mm-diameter bar joint is out of service due to bar breakage in the area of contact with the weld and the other is due to the exhaustion of its physical yield strength. The destruction of the 32mm diameter bars and metal plate joint in the two-sided welding process was due to the rupture of one bar in the area of its contact with the weld and the cracking of the other bar's contact with the weld. Conclusions. As a result of the experiment, it was found that the strength values of the welded connection between reinforcing bars 25 mm and 32 mm in diameter and a metal plate at bilateral welding were 1,33−1,36 times higher than those at one-sided welding.

Preparation and Characterization of a Silk Fibroin/Polyurethane Fiber Blend Membrane Containing Actinomycin X2 with Excellent Mechanical Properties and Enhanced Antibacterial Activities.

Development of suitable antimicrobial biomaterials for hygienic wound dressing and healing is an important requirement for medical application. Durable mechanical properties increase the application range of biomaterial in different environmental and biological conditions. Due to the inherent brittleness of silk fibroin (SF), polyurethane fiber (PUF) was used to modify SF containing actinomycin X2 (Ac.X2) to prepare silk fibroin@actinomycin X2 /polyurethane fiber (ASF/PUF) blend membranes. The ASF/PUF blend membrane was developed by solution casting method. Incorporation of PUF improved the flexibility of material and introduction of Ac.X2 has increased antibacterial activity of materials. Excellent mechanical properties (tensile strength up to 25.7 MPa and elongation at break up to 946.5 %) of 50 % SF+50 % PUF blend membrane were proved by tensile testing machine. FT-IR spectra, TGA, contact angle and DMA were tested to prove the blend membrane's physico-chemical characteristics. ASF/PUF blend membrane displayed satisfactory antibacterial activity against S. aureus, and the cytotoxicity tests showed that the blend membrane has better biosafety compared to directly applied Ac.X2 in soluble form. These results suggest that the modification of SF through PUF for development of flexible antibacterial membranes has great potential application value in the field of silk-like material fabrication.

Study of work of PVC membranes for engineering waterproofing under increased seismic conditions

Objective. At present, increased requirements are imposed on waterproofing materials used in seismic hazard zones. The aim of the study is to assess the possibility of using LOGICBASE™ polymer membranes in regions of increased seismic activity in the Russian Federation.Method. The mechanism of operation of polymeric membranes in foundation structures under conditions of constant displacement and friction is considered. Experiments were carried out to determine the coefficient of friction according to the method of state standards on a tensile testing machine MIRK-1000K. Samples of a round shape made of polymeric membranes were studied on a special multiaxial stretching device in accordance with the requirements of state standards.Result. Multiaxial tensile testing of LOGICBASE™ V-SL polymeric membranes revealed that the maximum tensile strength of the samples was 6948.22 kPa (~ 6.95 MPa), and the elongation of the samples at break was 113.89%. The coefficient of friction in the system "polymer waterproofing material - concrete structure" was determined under conditions of increased seismic activity according to the MSK-64 scale.Conclusion. According to the studies, it was concluded that PVC membranes for engineering waterproofing can be used in construction areas with seismicity up to 9 points inclusive on the MSK-64 scale.